Meg's Mirrors

zig

1	pub const Atom = @import("Elf/Atom.zig");
2
3	base: link.File,
4	zig_object: ?*ZigObject,
5	rpath_table: std.array_hash_map.String(void),
6	image_base: u64,
7	z_nodelete: bool,
8	z_notext: bool,
9	z_defs: bool,
10	z_origin: bool,
11	z_nocopyreloc: bool,
12	z_now: bool,
13	z_relro: bool,
14	/// TODO make this non optional and resolve the default in open()
15	z_common_page_size: ?u64,
16	/// TODO make this non optional and resolve the default in open()
17	z_max_page_size: ?u64,
18	soname: ?[]const u8,
19	entry_name: ?[]const u8,
20
21	ptr_width: PtrWidth,
22
23	/// A list of all input files.
24	/// First index is a special "null file". Order is otherwise not observed.
25	files: std.MultiArrayList(File.Entry) = .{},
26	/// Long-lived list of all file descriptors.
27	/// We store them globally rather than per actual File so that we can re-use
28	/// one file handle per every object file within an archive.
29	file_handles: std.ArrayList(File.Handle) = .empty,
30	zig_object_index: ?File.Index = null,
31	linker_defined_index: ?File.Index = null,
32	objects: std.ArrayList(File.Index) = .empty,
33	shared_objects: std.array_hash_map.String(File.Index) = .empty,
34
35	/// List of all output sections and their associated metadata.
36	sections: std.MultiArrayList(Section) = .{},
37	/// File offset into the shdr table.
38	shdr_table_offset: ?u64 = null,
39
40	/// Stored in native-endian format, depending on target endianness needs to be bswapped on read/write.
41	/// Same order as in the file.
42	phdrs: ProgramHeaderList = .empty,
43
44	/// Special program headers.
45	phdr_indexes: ProgramHeaderIndexes = .{},
46	section_indexes: SectionIndexes = .{},
47
48	page_size: u32,
49	default_sym_version: elf.Versym,
50
51	/// .shstrtab buffer
52	shstrtab: std.ArrayList(u8) = .empty,
53	/// .symtab buffer
54	symtab: std.ArrayList(elf.Elf64_Sym) = .empty,
55	/// .strtab buffer
56	strtab: std.ArrayList(u8) = .empty,
57	/// Dynamic symbol table. Only populated and emitted when linking dynamically.
58	dynsym: DynsymSection = .{},
59	/// .dynstrtab buffer
60	dynstrtab: std.ArrayList(u8) = .empty,
61	/// Version symbol table. Only populated and emitted when linking dynamically.
62	versym: std.ArrayList(elf.Versym) = .empty,
63	/// .verneed section
64	verneed: VerneedSection = .{},
65	/// .got section
66	got: GotSection = .{},
67	/// .rela.dyn section
68	rela_dyn: std.ArrayList(elf.Elf64_Rela) = .empty,
69	/// .dynamic section
70	dynamic: DynamicSection = .{},
71	/// .hash section
72	hash: HashSection = .{},
73	/// .gnu.hash section
74	gnu_hash: GnuHashSection = .{},
75	/// .plt section
76	plt: PltSection = .{},
77	/// .got.plt section
78	got_plt: GotPltSection = .{},
79	/// .plt.got section
80	plt_got: PltGotSection = .{},
81	/// .copyrel section
82	copy_rel: CopyRelSection = .{},
83	/// .rela.plt section
84	rela_plt: std.ArrayList(elf.Elf64_Rela) = .empty,
85	/// SHT_GROUP sections
86	/// Applies only to a relocatable.
87	group_sections: std.ArrayList(GroupSection) = .empty,
88
89	resolver: SymbolResolver = .{},
90
91	has_text_reloc: bool = false,
92	num_ifunc_dynrelocs: usize = 0,
93
94	/// List of range extension thunks.
95	thunks: std.ArrayList(Thunk) = .empty,
96
97	/// List of output merge sections with deduped contents.
98	merge_sections: std.ArrayList(Merge.Section) = .empty,
99	comment_merge_section_index: ?Merge.Section.Index = null,
100
101	/// `--verbose-link` output.
102	/// Initialized on creation, appended to as inputs are added, printed during `flush`.
103	dump_argv_list: std.ArrayList([]const u8),
104
105	const SectionIndexes = struct {
106	copy_rel: ?u32 = null,
107	dynamic: ?u32 = null,
108	dynstrtab: ?u32 = null,
109	dynsymtab: ?u32 = null,
110	eh_frame: ?u32 = null,
111	eh_frame_rela: ?u32 = null,
112	eh_frame_hdr: ?u32 = null,
113	hash: ?u32 = null,
114	gnu_hash: ?u32 = null,
115	got: ?u32 = null,
116	got_plt: ?u32 = null,
117	interp: ?u32 = null,
118	plt: ?u32 = null,
119	plt_got: ?u32 = null,
120	rela_dyn: ?u32 = null,
121	rela_plt: ?u32 = null,
122	versym: ?u32 = null,
123	verneed: ?u32 = null,
124
125	shstrtab: ?u32 = null,
126	strtab: ?u32 = null,
127	symtab: ?u32 = null,
128	};
129
130	const ProgramHeaderList = std.ArrayList(elf.Elf64.Phdr);
131
132	const OptionalProgramHeaderIndex = enum(u16) {
133	none = std.math.maxInt(u16),
134	_,
135
136	fn unwrap(i: OptionalProgramHeaderIndex) ?ProgramHeaderIndex {
137	if (i == .none) return null;
138	return @fromBackingInt(@intCast(@backingInt(i)));
139	}
140
141	fn int(i: OptionalProgramHeaderIndex) ?u16 {
142	if (i == .none) return null;
143	return @backingInt(i);
144	}
145	};
146
147	const ProgramHeaderIndex = enum(u16) {
148	_,
149
150	fn toOptional(i: ProgramHeaderIndex) OptionalProgramHeaderIndex {
151	const result: OptionalProgramHeaderIndex = @fromBackingInt(@intCast(@backingInt(i)));
152	assert(result != .none);
153	return result;
154	}
155
156	fn int(i: ProgramHeaderIndex) u16 {
157	return @backingInt(i);
158	}
159	};
160
161	const ProgramHeaderIndexes = struct {
162	/// PT.PHDR
163	table: OptionalProgramHeaderIndex = .none,
164	/// PT.LOAD for PHDR table
165	/// We add this special load segment to ensure the EHDR and PHDR table are always
166	/// loaded into memory.
167	table_load: OptionalProgramHeaderIndex = .none,
168	/// PT.INTERP
169	interp: OptionalProgramHeaderIndex = .none,
170	/// PT.DYNAMIC
171	dynamic: OptionalProgramHeaderIndex = .none,
172	/// PT.GNU_EH_FRAME
173	gnu_eh_frame: OptionalProgramHeaderIndex = .none,
174	/// PT.GNU_STACK
175	gnu_stack: OptionalProgramHeaderIndex = .none,
176	/// PT.TLS
177	/// TODO I think ELF permits multiple TLS segments but for now, assume one per file.
178	tls: OptionalProgramHeaderIndex = .none,
179	};
180
181	/// When allocating, the ideal_capacity is calculated by
182	/// actual_capacity + (actual_capacity / ideal_factor)
183	const ideal_factor = 3;
184
185	/// In order for a slice of bytes to be considered eligible to keep metadata pointing at
186	/// it as a possible place to put new symbols, it must have enough room for this many bytes
187	/// (plus extra for reserved capacity).
188	const minimum_atom_size = 64;
189	pub const min_text_capacity = padToIdeal(minimum_atom_size);
190
191	pub const PtrWidth = enum { p32, p64 };
192
193	pub fn createEmpty(
194	arena: Allocator,
195	comp: *Compilation,
196	emit: Path,
197	options: link.File.OpenOptions,
198	) !*Elf {
199	const target = &comp.root_mod.resolved_target.result;
200	assert(target.ofmt == .elf);
201
202	const use_llvm = comp.config.use_llvm;
203	const opt_zcu = comp.zcu;
204	const output_mode = comp.config.output_mode;
205	const link_mode = comp.config.link_mode;
206	const optimize_mode = comp.root_mod.optimize_mode;
207	const is_native_os = comp.root_mod.resolved_target.is_native_os;
208	const ptr_width: PtrWidth = switch (target.ptrBitWidth()) {
209	0...32 => .p32,
210	33...64 => .p64,
211	else => return error.UnsupportedELFArchitecture,
212	};
213
214	// This is the max page size that the target system can run with, aka the ABI page size. Not to
215	// be confused with the common page size, which is the page size that's used in practice on most
216	// systems.
217	const page_size: u32 = switch (target.cpu.arch) {
218	.bpfel,
219	.bpfeb,
220	.sparc64,
221	=> 0x100000,
222	.aarch64,
223	.aarch64_be,
224	.amdgcn,
225	.hexagon,
226	.mips,
227	.mipsel,
228	.mips64,
229	.mips64el,
230	.powerpc,
231	.powerpcle,
232	.powerpc64,
233	.powerpc64le,
234	.sparc,
235	=> 0x10000,
236	.loongarch32,
237	.loongarch64,
238	=> 0x4000,
239	.arc,
240	.m68k,
241	=> 0x2000,
242	.msp430,
243	=> 0x4,
244	.avr,
245	=> 0x1,
246	else => 0x1000,
247	};
248
249	const is_dyn_lib = output_mode == .Lib and link_mode == .dynamic;
250	const default_sym_version: elf.Versym = if (is_dyn_lib or comp.config.rdynamic) .GLOBAL else .LOCAL;
251
252	var rpath_table: std.array_hash_map.String(void) = .empty;
253	try rpath_table.entries.resize(arena, options.rpath_list.len);
254	@memcpy(rpath_table.entries.items(.key), options.rpath_list);
255	try rpath_table.reIndex(arena);
256
257	const self = try arena.create(Elf);
258	self.* = .{
259	.base = .{
260	.tag = .elf,
261	.comp = comp,
262	.emit = emit,
263	.gc_sections = options.gc_sections orelse (optimize_mode != .debug and output_mode != .Obj),
264	.print_gc_sections = options.print_gc_sections,
265	.stack_size = options.stack_size orelse 16777216,
266	.allow_shlib_undefined = options.allow_shlib_undefined orelse !is_native_os,
267	.file = null,
268	.build_id = options.build_id,
269	},
270	.zig_object = null,
271	.rpath_table = rpath_table,
272	.ptr_width = ptr_width,
273	.page_size = page_size,
274	.default_sym_version = default_sym_version,
275
276	.entry_name = switch (options.entry) {
277	.disabled => null,
278	.default => if (output_mode != .Exe) null else defaultEntrySymbolName(target.cpu.arch),
279	.enabled => defaultEntrySymbolName(target.cpu.arch),
280	.named => |name| name,
281	},
282
283	.image_base = b: {
284	if (is_dyn_lib) break :b 0;
285	if (output_mode == .Exe and (comp.config.pie or target.os.tag == .haiku)) break :b 0;
286	break :b options.image_base orelse switch (ptr_width) {
287	.p32 => 0x10000,
288	.p64 => 0x1000000,
289	};
290	},
291
292	.z_nodelete = options.z_nodelete,
293	.z_notext = options.z_notext,
294	.z_defs = options.z_defs,
295	.z_origin = options.z_origin,
296	.z_nocopyreloc = options.z_nocopyreloc,
297	.z_now = options.z_now,
298	.z_relro = options.z_relro,
299	.z_common_page_size = options.z_common_page_size,
300	.z_max_page_size = options.z_max_page_size,
301	.soname = options.soname,
302	.dump_argv_list = .empty,
303	};
304	errdefer self.base.destroy();
305
306	// --verbose-link
307	if (comp.verbose_link) try dumpArgvInit(self, arena);
308
309	const is_obj = output_mode == .Obj;
310	const is_obj_or_ar = is_obj or (output_mode == .Lib and link_mode == .static);
311
312	const io = comp.io;
313
314	// What path should this ELF linker code output to?
315	const sub_path = emit.sub_path;
316	self.base.file = try emit.root_dir.handle.createFile(io, sub_path, .{
317	.truncate = true,
318	.read = true,
319	.permissions = link.File.determinePermissions(output_mode, link_mode),
320	});
321
322	const gpa = comp.gpa;
323
324	// Append null file at index 0
325	try self.files.append(gpa, .null);
326	// Append null byte to string tables
327	try self.shstrtab.append(gpa, 0);
328	try self.strtab.append(gpa, 0);
329	// There must always be a null shdr in index 0
330	_ = try self.addSection(.{});
331	// Append null symbol in output symtab
332	try self.symtab.append(gpa, null_sym);
333
334	if (!is_obj_or_ar) {
335	try self.dynstrtab.append(gpa, 0);
336
337	// Initialize PT.PHDR program header
338	const p_align: u16 = switch (self.ptr_width) {
339	.p32 => @alignOf(elf.Elf32.Phdr),
340	.p64 => @alignOf(elf.Elf64.Phdr),
341	};
342	const ehsize: u64 = switch (self.ptr_width) {
343	.p32 => @sizeOf(elf.Elf32_Ehdr),
344	.p64 => @sizeOf(elf.Elf64_Ehdr),
345	};
346	const phsize: u64 = switch (self.ptr_width) {
347	.p32 => @sizeOf(elf.Elf32.Phdr),
348	.p64 => @sizeOf(elf.Elf64.Phdr),
349	};
350	const max_nphdrs = comptime getMaxNumberOfPhdrs();
351	const reserved: u64 = mem.alignForward(u64, padToIdeal(max_nphdrs * phsize), self.page_size);
352	self.phdr_indexes.table = (try self.addPhdr(.{
353	.type = @backingInt(elf.PT.PHDR),
354	.flags = elf.PF_R,
355	.@"align" = p_align,
356	.addr = self.image_base + ehsize,
357	.offset = ehsize,
358	.filesz = reserved,
359	.memsz = reserved,
360	})).toOptional();
361	self.phdr_indexes.table_load = (try self.addPhdr(.{
362	.type = @backingInt(elf.PT.LOAD),
363	.flags = elf.PF_R,
364	.@"align" = self.page_size,
365	.addr = self.image_base,
366	.offset = 0,
367	.filesz = reserved + ehsize,
368	.memsz = reserved + ehsize,
369	})).toOptional();
370	}
371
372	if (opt_zcu) |zcu| {
373	if (!use_llvm) {
374	const index: File.Index = @intCast(try self.files.addOne(gpa));
375	self.files.set(index, .zig_object);
376	self.zig_object_index = index;
377	const zig_object = try arena.create(ZigObject);
378	self.zig_object = zig_object;
379	zig_object.* = .{
380	.index = index,
381	.basename = try std.fmt.allocPrint(arena, "{s}.o", .{
382	fs.path.stem(zcu.main_mod.root_src_path),
383	}),
384	};
385	try zig_object.init(self, .{
386	.symbol_count_hint = options.symbol_count_hint,
387	.program_code_size_hint = options.program_code_size_hint,
388	});
389	}
390	}
391
392	return self;
393	}
394
395	pub fn open(
396	arena: Allocator,
397	comp: *Compilation,
398	emit: Path,
399	options: link.File.OpenOptions,
400	) !*Elf {
401	// TODO: restore saved linker state, don't truncate the file, and
402	// participate in incremental compilation.
403	return createEmpty(arena, comp, emit, options);
404	}
405
406	pub fn deinit(self: *Elf) void {
407	const comp = self.base.comp;
408	const gpa = comp.gpa;
409	const io = comp.io;
410
411	for (self.file_handles.items) |fh| {
412	fh.close(io);
413	}
414	self.file_handles.deinit(gpa);
415
416	for (self.files.items(.tags), self.files.items(.data)) |tag, *data| switch (tag) {
417	.null, .zig_object => {},
418	.linker_defined => data.linker_defined.deinit(gpa),
419	.object => data.object.deinit(gpa),
420	.shared_object => data.shared_object.deinit(gpa),
421	};
422	if (self.zig_object) |zig_object| {
423	zig_object.deinit(gpa);
424	}
425	self.files.deinit(gpa);
426	self.objects.deinit(gpa);
427	self.shared_objects.deinit(gpa);
428
429	for (self.sections.items(.atom_list_2), self.sections.items(.atom_list), self.sections.items(.free_list)) |*atom_list, *atoms, *free_list| {
430	atom_list.deinit(gpa);
431	atoms.deinit(gpa);
432	free_list.deinit(gpa);
433	}
434	self.sections.deinit(gpa);
435	self.phdrs.deinit(gpa);
436	self.shstrtab.deinit(gpa);
437	self.symtab.deinit(gpa);
438	self.strtab.deinit(gpa);
439	self.resolver.deinit(gpa);
440
441	for (self.thunks.items) |*th| {
442	th.deinit(gpa);
443	}
444	self.thunks.deinit(gpa);
445	for (self.merge_sections.items) |*sect| {
446	sect.deinit(gpa);
447	}
448	self.merge_sections.deinit(gpa);
449
450	self.got.deinit(gpa);
451	self.plt.deinit(gpa);
452	self.plt_got.deinit(gpa);
453	self.dynsym.deinit(gpa);
454	self.dynstrtab.deinit(gpa);
455	self.dynamic.deinit(gpa);
456	self.hash.deinit(gpa);
457	self.versym.deinit(gpa);
458	self.verneed.deinit(gpa);
459	self.copy_rel.deinit(gpa);
460	self.rela_dyn.deinit(gpa);
461	self.rela_plt.deinit(gpa);
462	self.group_sections.deinit(gpa);
463	self.dump_argv_list.deinit(gpa);
464	}
465
466	pub fn getNavVAddr(self: *Elf, pt: Zcu.PerThread, nav_index: InternPool.Nav.Index, reloc_info: link.File.RelocInfo) !u64 {
467	return self.zigObjectPtr().?.getNavVAddr(self, pt, nav_index, reloc_info);
468	}
469
470	pub fn lowerUav(
471	self: *Elf,
472	pt: Zcu.PerThread,
473	uav: InternPool.Index,
474	explicit_alignment: InternPool.Alignment,
475	) !link.File.SymbolId {
476	return self.zigObjectPtr().?.lowerUav(self, pt, uav, explicit_alignment);
477	}
478
479	pub fn getUavVAddr(self: *Elf, uav: InternPool.Index, reloc_info: link.File.RelocInfo) !u64 {
480	return self.zigObjectPtr().?.getUavVAddr(self, uav, reloc_info);
481	}
482
483	/// Returns end pos of collision, if any.
484	fn detectAllocCollision(self: *Elf, start: u64, size: u64) !?u64 {
485	const comp = self.base.comp;
486	const io = comp.io;
487	const small_ptr = self.ptr_width == .p32;
488	const ehdr_size: u64 = if (small_ptr) @sizeOf(elf.Elf32_Ehdr) else @sizeOf(elf.Elf64_Ehdr);
489	if (start < ehdr_size)
490	return ehdr_size;
491
492	var at_end = true;
493	const end = start + padToIdeal(size);
494
495	if (self.shdr_table_offset) |off| {
496	const shdr_size: u64 = if (small_ptr) @sizeOf(elf.Elf32_Shdr) else @sizeOf(elf.Elf64_Shdr);
497	const tight_size = self.sections.items(.shdr).len * shdr_size;
498	const increased_size = padToIdeal(tight_size);
499	const test_end = off +| increased_size;
500	if (start < test_end) {
501	if (end > off) return test_end;
502	if (test_end < std.math.maxInt(u64)) at_end = false;
503	}
504	}
505
506	for (self.sections.items(.shdr)) |shdr| {
507	if (shdr.sh_type == elf.SHT_NOBITS) continue;
508	const increased_size = padToIdeal(shdr.sh_size);
509	const test_end = shdr.sh_offset +| increased_size;
510	if (start < test_end) {
511	if (end > shdr.sh_offset) return test_end;
512	if (test_end < std.math.maxInt(u64)) at_end = false;
513	}
514	}
515
516	for (self.phdrs.items) |phdr| {
517	if (phdr.type != .LOAD) continue;
518	const increased_size = padToIdeal(phdr.filesz);
519	const test_end = phdr.offset +| increased_size;
520	if (start < test_end) {
521	if (end > phdr.offset) return test_end;
522	if (test_end < std.math.maxInt(u64)) at_end = false;
523	}
524	}
525
526	if (at_end) try self.base.file.?.setLength(io, end);
527	return null;
528	}
529
530	pub fn allocatedSize(self: *Elf, start: u64) u64 {
531	if (start == 0) return 0;
532	var min_pos: u64 = std.math.maxInt(u64);
533	if (self.shdr_table_offset) |off| {
534	if (off > start and off < min_pos) min_pos = off;
535	}
536	for (self.sections.items(.shdr)) |section| {
537	if (section.sh_offset <= start) continue;
538	if (section.sh_offset < min_pos) min_pos = section.sh_offset;
539	}
540	for (self.phdrs.items) |phdr| {
541	if (phdr.offset <= start) continue;
542	if (phdr.offset < min_pos) min_pos = phdr.offset;
543	}
544	return min_pos - start;
545	}
546
547	pub fn findFreeSpace(self: *Elf, object_size: u64, min_alignment: u64) !u64 {
548	var start: u64 = 0;
549	while (try self.detectAllocCollision(start, object_size)) |item_end| {
550	start = mem.alignForward(u64, item_end, min_alignment);
551	}
552	return start;
553	}
554
555	pub fn growSection(self: *Elf, shdr_index: u32, needed_size: u64, min_alignment: u64) !void {
556	const comp = self.base.comp;
557	const io = comp.io;
558	const shdr = &self.sections.items(.shdr)[shdr_index];
559
560	if (shdr.sh_type != elf.SHT_NOBITS) {
561	const allocated_size = self.allocatedSize(shdr.sh_offset);
562	log.debug("allocated size {x} of '{s}', needed size {x}", .{
563	allocated_size,
564	self.getShString(shdr.sh_name),
565	needed_size,
566	});
567
568	if (needed_size > allocated_size) {
569	const existing_size = shdr.sh_size;
570	shdr.sh_size = 0;
571	// Must move the entire section.
572	const new_offset = try self.findFreeSpace(needed_size, min_alignment);
573
574	log.debug("moving '{s}' from 0x{x} to 0x{x}", .{
575	self.getShString(shdr.sh_name),
576	shdr.sh_offset,
577	new_offset,
578	});
579
580	try self.base.copyRangeAll(shdr.sh_offset, new_offset, existing_size);
581
582	shdr.sh_offset = new_offset;
583	} else if (shdr.sh_offset + allocated_size == std.math.maxInt(u64)) {
584	try self.base.file.?.setLength(io, shdr.sh_offset + needed_size);
585	}
586	}
587
588	shdr.sh_size = needed_size;
589	self.markDirty(shdr_index);
590	}
591
592	fn markDirty(self: *Elf, shdr_index: u32) void {
593	if (self.zigObjectPtr()) |zo| {
594	for ([_]?Symbol.Index{
595	zo.debug_info_index,
596	zo.debug_abbrev_index,
597	zo.debug_aranges_index,
598	zo.debug_str_index,
599	zo.debug_line_index,
600	zo.debug_line_str_index,
601	zo.debug_loclists_index,
602	zo.debug_rnglists_index,
603	}, [_]*bool{
604	&zo.debug_info_section_dirty,
605	&zo.debug_abbrev_section_dirty,
606	&zo.debug_aranges_section_dirty,
607	&zo.debug_str_section_dirty,
608	&zo.debug_line_section_dirty,
609	&zo.debug_line_str_section_dirty,
610	&zo.debug_loclists_section_dirty,
611	&zo.debug_rnglists_section_dirty,
612	}) |maybe_sym_index, dirty| {
613	const sym_index = maybe_sym_index orelse continue;
614	if (zo.symbol(sym_index).atom(self).?.output_section_index == shdr_index) {
615	dirty.* = true;
616	break;
617	}
618	}
619	}
620	}
621
622	const AllocateChunkResult = struct {
623	value: u64,
624	placement: Ref,
625	};
626
627	pub fn allocateChunk(self: *Elf, args: struct {
628	size: u64,
629	shndx: u32,
630	alignment: Atom.Alignment,
631	requires_padding: bool = true,
632	}) !AllocateChunkResult {
633	const slice = self.sections.slice();
634	const shdr = &slice.items(.shdr)[args.shndx];
635	const free_list = &slice.items(.free_list)[args.shndx];
636	const last_atom_ref = &slice.items(.last_atom)[args.shndx];
637	const new_atom_ideal_capacity = if (args.requires_padding) padToIdeal(args.size) else args.size;
638
639	// First we look for an appropriately sized free list node.
640	// The list is unordered. We'll just take the first thing that works.
641	const res: AllocateChunkResult = blk: {
642	var i: usize = if (self.base.child_pid == null) 0 else free_list.items.len;
643	while (i < free_list.items.len) {
644	const big_atom_ref = free_list.items[i];
645	const big_atom = self.atom(big_atom_ref).?;
646	// We now have a pointer to a live atom that has too much capacity.
647	// Is it enough that we could fit this new atom?
648	const cap = big_atom.capacity(self);
649	const ideal_capacity = if (args.requires_padding) padToIdeal(cap) else cap;
650	const ideal_capacity_end_vaddr = std.math.add(u64, @intCast(big_atom.value), ideal_capacity) catch ideal_capacity;
651	const capacity_end_vaddr = @as(u64, @intCast(big_atom.value)) + cap;
652	const new_start_vaddr_unaligned = capacity_end_vaddr - new_atom_ideal_capacity;
653	const new_start_vaddr = args.alignment.backward(new_start_vaddr_unaligned);
654	if (new_start_vaddr < ideal_capacity_end_vaddr) {
655	// Additional bookkeeping here to notice if this free list node
656	// should be deleted because the block that it points to has grown to take up
657	// more of the extra capacity.
658	if (!big_atom.freeListEligible(self)) {
659	_ = free_list.swapRemove(i);
660	} else {
661	i += 1;
662	}
663	continue;
664	}
665	// At this point we know that we will place the new block here. But the
666	// remaining question is whether there is still yet enough capacity left
667	// over for there to still be a free list node.
668	const remaining_capacity = new_start_vaddr - ideal_capacity_end_vaddr;
669	const keep_free_list_node = remaining_capacity >= min_text_capacity;
670
671	if (!keep_free_list_node) {
672	_ = free_list.swapRemove(i);
673	}
674	break :blk .{ .value = new_start_vaddr, .placement = big_atom_ref };
675	} else if (self.atom(last_atom_ref.*)) |last_atom| {
676	const ideal_capacity = if (args.requires_padding) padToIdeal(last_atom.size) else last_atom.size;
677	const ideal_capacity_end_vaddr = @as(u64, @intCast(last_atom.value)) + ideal_capacity;
678	const new_start_vaddr = args.alignment.forward(ideal_capacity_end_vaddr);
679	break :blk .{ .value = new_start_vaddr, .placement = last_atom.ref() };
680	} else {
681	break :blk .{ .value = 0, .placement = .{} };
682	}
683	};
684
685	const expand_section = if (self.atom(res.placement)) |placement_atom|
686	placement_atom.nextAtom(self) == null
687	else
688	true;
689	if (expand_section) {
690	const needed_size = res.value + args.size;
691	try self.growSection(args.shndx, needed_size, args.alignment.toByteUnits().?);
692	}
693
694	log.debug("allocated chunk (size({x}),align({x})) in {s} at 0x{x} (file(0x{x}))", .{
695	args.size,
696	args.alignment.toByteUnits().?,
697	self.getShString(shdr.sh_name),
698	shdr.sh_addr + res.value,
699	shdr.sh_offset + res.value,
700	});
701	log.debug(" placement {f}, {s}", .{
702	res.placement,
703	if (self.atom(res.placement)) |atom_ptr| atom_ptr.name(self) else "",
704	});
705
706	return res;
707	}
708
709	pub fn loadInput(self: *Elf, input: link.Input) !void {
710	const comp = self.base.comp;
711	const gpa = comp.gpa;
712	const io = comp.io;
713	const diags = &comp.link_diags;
714	const target = self.getTarget();
715	const debug_fmt_strip = comp.config.debug_format == .strip;
716	const default_sym_version = self.default_sym_version;
717
718	if (comp.verbose_link) {
719	comp.mutex.lockUncancelable(io); // protect comp.arena
720	defer comp.mutex.unlock(io);
721
722	const argv = &self.dump_argv_list;
723	switch (input) {
724	.res => unreachable,
725	.dso_exact => |dso_exact| try argv.appendSlice(gpa, &.{ "-l", dso_exact.name }),
726	.object, .archive => |obj| try argv.append(gpa, try obj.path.toString(comp.arena)),
727	.dso => |dso| try argv.append(gpa, try dso.path.toString(comp.arena)),
728	}
729	}
730
731	switch (input) {
732	.res => unreachable,
733	.dso_exact => @panic("TODO"),
734	.object => |obj| try parseObject(self, obj),
735	.archive => |obj| if (self.base.isStaticLib()) {
736	// Ignore static library inputs when generating a static library.
737	} else {
738	try parseArchive(gpa, io, diags, &self.file_handles, &self.files, target, debug_fmt_strip, default_sym_version, &self.objects, obj);
739	},
740	.dso => |dso| try parseDso(gpa, io, diags, dso, &self.shared_objects, &self.files, target),
741	}
742	}
743
744	pub fn flush(self: *Elf, arena: Allocator, tid: Zcu.PerThread.Id, prog_node: std.Progress.Node) link.Error!void {
745	const tracy = trace(@src());
746	defer tracy.end();
747
748	const comp = self.base.comp;
749	const io = comp.io;
750	const diags = &comp.link_diags;
751
752	if (comp.verbose_link) try Compilation.dumpArgv(io, self.dump_argv_list.items);
753
754	const sub_prog_node = prog_node.start("ELF Flush", 0);
755	defer sub_prog_node.end();
756
757	return flushInner(self, arena, tid) catch |err| switch (err) {
758	error.OutOfMemory, error.AlreadyReported => |e| return e,
759	else => |e| return diags.fail("ELF flush failed: {t}", .{e}),
760	};
761	}
762
763	fn flushInner(self: *Elf, arena: Allocator, tid: Zcu.PerThread.Id) !void {
764	_ = arena;
765
766	const comp = self.base.comp;
767	const gpa = comp.gpa;
768	const diags = &comp.link_diags;
769
770	if (self.zigObjectPtr()) |zig_object| try zig_object.flush(self, tid);
771
772	switch (comp.config.output_mode) {
773	.Obj => return relocatable.flushObject(self, comp),
774	.Lib => switch (comp.config.link_mode) {
775	.dynamic => {},
776	.static => return relocatable.flushStaticLib(self, comp),
777	},
778	.Exe => {},
779	}
780
781	if (diags.hasErrors()) return error.AlreadyReported;
782
783	// If we haven't already, create a linker-generated input file comprising of
784	// linker-defined synthetic symbols only such as `_DYNAMIC`, etc.
785	if (self.linker_defined_index == null) {
786	const index: File.Index = @intCast(try self.files.addOne(gpa));
787	self.files.set(index, .{ .linker_defined = .{ .index = index } });
788	self.linker_defined_index = index;
789	const object = self.linkerDefinedPtr().?;
790	try object.init(gpa);
791	try object.initSymbols(self);
792	}
793
794	// Now, we are ready to resolve the symbols across all input files.
795	// We will first resolve the files in the ZigObject, next in the parsed
796	// input Object files.
797	// Any qualifing unresolved symbol will be upgraded to an absolute, weak
798	// symbol for potential resolution at load-time.
799	try self.resolveSymbols();
800	self.markEhFrameAtomsDead();
801	try self.resolveMergeSections();
802
803	for (self.objects.items) |index| {
804	try self.file(index).?.object.convertCommonSymbols(self);
805	}
806	self.markImportsExports();
807
808	if (self.base.gc_sections) {
809	try gc.gcAtoms(self);
810	}
811
812	self.checkDuplicates() catch |err| switch (err) {
813	error.HasDuplicates => return error.AlreadyReported,
814	else => |e| return e,
815	};
816
817	try self.addCommentString();
818	try self.finalizeMergeSections();
819	try self.initOutputSections();
820	if (self.linkerDefinedPtr()) |obj| {
821	try obj.initStartStopSymbols(self);
822	}
823	self.claimUnresolved();
824
825	// Scan and create missing synthetic entries such as GOT indirection.
826	try self.scanRelocs();
827
828	// Generate and emit synthetic sections.
829	try self.initSyntheticSections();
830	try self.initSpecialPhdrs();
831	try sortShdrs(
832	gpa,
833	&self.section_indexes,
834	&self.sections,
835	self.shstrtab.items,
836	self.merge_sections.items,
837	self.group_sections.items,
838	self.zigObjectPtr(),
839	self.files,
840	);
841
842	try self.setDynamicSection(self.rpath_table.keys());
843	self.sortDynamicSymtab();
844	try self.setHashSections();
845	try self.setVersionSymtab();
846
847	try self.sortInitFini();
848	try self.updateMergeSectionSizes();
849	try self.updateSectionSizes();
850
851	try self.addLoadPhdrs();
852	try self.allocatePhdrTable();
853	try self.allocateAllocSections();
854	try sortPhdrs(gpa, &self.phdrs, &self.phdr_indexes, self.sections.items(.phndx));
855	try self.allocateNonAllocSections();
856	self.allocateSpecialPhdrs();
857	if (self.linkerDefinedPtr()) |obj| {
858	obj.allocateSymbols(self);
859	}
860
861	// Dump the state for easy debugging.
862	// State can be dumped via `--debug-log link_state`.
863	if (build_options.enable_logging) {
864	state_log.debug("{f}", .{self.dumpState()});
865	}
866
867	// Beyond this point, everything has been allocated a virtual address and we can resolve
868	// the relocations, and commit objects to file.
869	for (self.objects.items) |index| {
870	self.file(index).?.object.dirty = false;
871	}
872	// TODO: would state tracking be more appropriate here? perhaps even custom relocation type?
873	self.rela_dyn.clearRetainingCapacity();
874	self.rela_plt.clearRetainingCapacity();
875
876	if (self.zigObjectPtr()) |zo| {
877	var undefs: std.array_hash_map.Auto(SymbolResolver.Index, std.array_list.Managed(Ref)) = .empty;
878	defer {
879	for (undefs.values()) |*refs| refs.deinit();
880	undefs.deinit(gpa);
881	}
882
883	var has_reloc_errors = false;
884	for (zo.atoms_indexes.items) |atom_index| {
885	const atom_ptr = zo.atom(atom_index) orelse continue;
886	if (!atom_ptr.alive) continue;
887	const out_shndx = atom_ptr.output_section_index;
888	const shdr = &self.sections.items(.shdr)[out_shndx];
889	if (shdr.sh_type == elf.SHT_NOBITS) continue;
890	const code = try zo.codeAlloc(self, atom_index);
891	defer gpa.free(code);
892	const file_offset = atom_ptr.offset(self);
893	(if (shdr.sh_flags & elf.SHF_ALLOC == 0)
894	atom_ptr.resolveRelocsNonAlloc(self, code, &undefs)
895	else
896	atom_ptr.resolveRelocsAlloc(self, code)) catch |err| switch (err) {
897	error.RelocFailure, error.RelaxFailure => has_reloc_errors = true,
898	error.UnsupportedCpuArch => {
899	try self.reportUnsupportedCpuArch();
900	return error.AlreadyReported;
901	},
902	else => |e| return e,
903	};
904	try self.pwriteAll(code, file_offset);
905	}
906
907	try self.reportUndefinedSymbols(&undefs);
908
909	if (has_reloc_errors) return error.AlreadyReported;
910	}
911
912	try self.writePhdrTable();
913	try self.writeShdrTable();
914	try self.writeAtoms();
915	try self.writeMergeSections();
916
917	self.writeSyntheticSections() catch |err| switch (err) {
918	error.RelocFailure => return error.AlreadyReported,
919	error.UnsupportedCpuArch => {
920	try self.reportUnsupportedCpuArch();
921	return error.AlreadyReported;
922	},
923	else => |e| return e,
924	};
925
926	if (self.base.isExe() and self.linkerDefinedPtr().?.entry_index == null) {
927	log.debug("flushing. no_entry_point_found = true", .{});
928	diags.flags.no_entry_point_found = true;
929	} else {
930	log.debug("flushing. no_entry_point_found = false", .{});
931	diags.flags.no_entry_point_found = false;
932	try self.writeElfHeader();
933	}
934
935	if (diags.hasErrors()) return error.AlreadyReported;
936	}
937
938	fn dumpArgvInit(self: *Elf, arena: Allocator) !void {
939	const comp = self.base.comp;
940	const gpa = comp.gpa;
941	const target = self.getTarget();
942	const full_out_path = try self.base.emit.root_dir.join(arena, &[_][]const u8{self.base.emit.sub_path});
943
944	const argv = &self.dump_argv_list;
945
946	try argv.append(gpa, "zig");
947
948	if (self.base.isStaticLib()) {
949	try argv.append(gpa, "ar");
950	} else {
951	try argv.append(gpa, "ld");
952	}
953
954	if (self.base.isObject()) {
955	try argv.append(gpa, "-r");
956	}
957
958	try argv.append(gpa, "-o");
959	try argv.append(gpa, full_out_path);
960
961	if (!self.base.isRelocatable()) {
962	if (!self.base.isStatic()) {
963	if (target.dynamic_linker.get()) |path| {
964	try argv.appendSlice(gpa, &.{ "-dynamic-linker", try arena.dupe(u8, path) });
965	}
966	}
967
968	if (self.base.isDynLib()) {
969	if (self.soname) |name| {
970	try argv.append(gpa, "-soname");
971	try argv.append(gpa, name);
972	}
973	}
974
975	if (self.entry_name) |name| {
976	try argv.appendSlice(gpa, &.{ "--entry", name });
977	}
978
979	for (self.rpath_table.keys()) |rpath| {
980	try argv.appendSlice(gpa, &.{ "-rpath", rpath });
981	}
982
983	try argv.appendSlice(gpa, &.{
984	"-z",
985	try std.fmt.allocPrint(arena, "stack-size={d}", .{self.base.stack_size}),
986	});
987
988	try argv.append(gpa, try std.fmt.allocPrint(arena, "--image-base={d}", .{self.image_base}));
989
990	if (self.base.gc_sections) {
991	try argv.append(gpa, "--gc-sections");
992	}
993
994	if (self.base.print_gc_sections) {
995	try argv.append(gpa, "--print-gc-sections");
996	}
997
998	if (comp.link_eh_frame_hdr) {
999	try argv.append(gpa, "--eh-frame-hdr");
1000	}
1001
1002	if (comp.config.rdynamic) {
1003	try argv.append(gpa, "--export-dynamic");
1004	}
1005
1006	if (self.z_notext) {
1007	try argv.append(gpa, "-z");
1008	try argv.append(gpa, "notext");
1009	}
1010
1011	if (self.z_nocopyreloc) {
1012	try argv.append(gpa, "-z");
1013	try argv.append(gpa, "nocopyreloc");
1014	}
1015
1016	if (self.z_now) {
1017	try argv.append(gpa, "-z");
1018	try argv.append(gpa, "now");
1019	}
1020
1021	if (self.base.isStatic()) {
1022	try argv.append(gpa, "-static");
1023	} else if (self.isEffectivelyDynLib()) {
1024	try argv.append(gpa, "-shared");
1025	}
1026
1027	if (comp.config.pie and self.base.isExe()) {
1028	try argv.append(gpa, "-pie");
1029	}
1030
1031	if (comp.config.debug_format == .strip) {
1032	try argv.append(gpa, "-s");
1033	}
1034
1035	if (comp.config.link_libc) {
1036	if (self.base.comp.libc_installation) |lci| {
1037	try argv.append(gpa, "-L");
1038	try argv.append(gpa, lci.crt_dir.?);
1039	}
1040	}
1041	}
1042	}
1043
1044	fn parseObject(self: *Elf, obj: link.Input.Object) !void {
1045	const tracy = trace(@src());
1046	defer tracy.end();
1047
1048	const comp = self.base.comp;
1049	const io = comp.io;
1050	const gpa = comp.gpa;
1051	const diags = &comp.link_diags;
1052	const target = &comp.root_mod.resolved_target.result;
1053	const debug_fmt_strip = comp.config.debug_format == .strip;
1054	const default_sym_version = self.default_sym_version;
1055	const file_handles = &self.file_handles;
1056
1057	const handle = obj.file;
1058	const fh = try addFileHandle(gpa, file_handles, handle);
1059
1060	const index: File.Index = @intCast(try self.files.addOne(gpa));
1061	self.files.set(index, .{ .object = .{
1062	.path = .{
1063	.root_dir = obj.path.root_dir,
1064	.sub_path = try gpa.dupe(u8, obj.path.sub_path),
1065	},
1066	.file_handle = fh,
1067	.index = index,
1068	} });
1069	try self.objects.append(gpa, index);
1070
1071	const object = self.file(index).?.object;
1072	try object.parseCommon(gpa, io, diags, obj.path, handle, target);
1073	if (!self.base.isStaticLib()) {
1074	try object.parse(gpa, io, diags, obj.path, handle, target, debug_fmt_strip, default_sym_version);
1075	}
1076	}
1077
1078	fn parseArchive(
1079	gpa: Allocator,
1080	io: Io,
1081	diags: *Diags,
1082	file_handles: *std.ArrayList(File.Handle),
1083	files: *std.MultiArrayList(File.Entry),
1084	target: *const std.Target,
1085	debug_fmt_strip: bool,
1086	default_sym_version: elf.Versym,
1087	objects: *std.ArrayList(File.Index),
1088	obj: link.Input.Object,
1089	) !void {
1090	const tracy = trace(@src());
1091	defer tracy.end();
1092
1093	const fh = try addFileHandle(gpa, file_handles, obj.file);
1094	var archive = try Archive.parse(gpa, io, diags, file_handles, obj.path, fh);
1095	defer archive.deinit(gpa);
1096
1097	for (archive.objects) |extracted| {
1098	const index: File.Index = @intCast(try files.addOne(gpa));
1099	files.set(index, .{ .object = extracted });
1100	const object = &files.items(.data)[index].object;
1101	object.index = index;
1102	object.alive = obj.must_link;
1103	try object.parseCommon(gpa, io, diags, obj.path, obj.file, target);
1104	try object.parse(gpa, io, diags, obj.path, obj.file, target, debug_fmt_strip, default_sym_version);
1105	try objects.append(gpa, index);
1106	}
1107	}
1108
1109	fn parseDso(
1110	gpa: Allocator,
1111	io: Io,
1112	diags: *Diags,
1113	dso: link.Input.Dso,
1114	shared_objects: *std.array_hash_map.String(File.Index),
1115	files: *std.MultiArrayList(File.Entry),
1116	target: *const std.Target,
1117	) !void {
1118	const tracy = trace(@src());
1119	defer tracy.end();
1120
1121	const handle = dso.file;
1122
1123	const stat = Stat.fromFs(try handle.stat(io));
1124	var header = try SharedObject.parseHeader(gpa, io, diags, dso.path, handle, stat, target);
1125	defer header.deinit(gpa);
1126
1127	const soname = header.soname() orelse dso.path.basename();
1128
1129	const gop = try shared_objects.getOrPut(gpa, soname);
1130	if (gop.found_existing) return;
1131	errdefer _ = shared_objects.pop();
1132
1133	const index: File.Index = @intCast(try files.addOne(gpa));
1134	errdefer _ = files.pop();
1135
1136	gop.value_ptr.* = index;
1137
1138	var parsed = try SharedObject.parse(gpa, io, &header, handle);
1139	errdefer parsed.deinit(gpa);
1140
1141	const duped_path: Path = .{
1142	.root_dir = dso.path.root_dir,
1143	.sub_path = try gpa.dupe(u8, dso.path.sub_path),
1144	};
1145	errdefer gpa.free(duped_path.sub_path);
1146
1147	files.set(index, .{
1148	.shared_object = .{
1149	.parsed = parsed,
1150	.path = duped_path,
1151	.index = index,
1152	.needed = dso.needed,
1153	.alive = dso.needed,
1154	.aliases = null,
1155	.symbols = .empty,
1156	.symbols_extra = .empty,
1157	.symbols_resolver = .empty,
1158	.output_symtab_ctx = .{},
1159	},
1160	});
1161	const so = fileLookup(files.*, index, null).?.shared_object;
1162
1163	// TODO: save this work for later
1164	const nsyms = parsed.symbols.len;
1165	try so.symbols.ensureTotalCapacityPrecise(gpa, nsyms);
1166	try so.symbols_extra.ensureTotalCapacityPrecise(gpa, nsyms * @typeInfo(Symbol.Extra).@"struct".field_names.len);
1167	try so.symbols_resolver.ensureTotalCapacityPrecise(gpa, nsyms);
1168	so.symbols_resolver.appendNTimesAssumeCapacity(0, nsyms);
1169
1170	for (parsed.symtab, parsed.symbols, parsed.versyms, 0..) |esym, sym, versym, i| {
1171	const out_sym_index = so.addSymbolAssumeCapacity();
1172	const out_sym = &so.symbols.items[out_sym_index];
1173	out_sym.value = @intCast(esym.st_value);
1174	out_sym.name_offset = sym.mangled_name;
1175	out_sym.ref = .{ .index = 0, .file = 0 };
1176	out_sym.esym_index = @intCast(i);
1177	out_sym.version_index = versym;
1178	out_sym.extra_index = so.addSymbolExtraAssumeCapacity(.{});
1179	}
1180	}
1181
1182	/// When resolving symbols, we approach the problem similarly to `mold`.
1183	/// 1. Resolve symbols across all objects (including those preemptively extracted archives).
1184	/// 2. Resolve symbols across all shared objects.
1185	/// 3. Mark live objects (see `Elf.markLive`)
1186	/// 4. Reset state of all resolved globals since we will redo this bit on the pruned set.
1187	/// 5. Remove references to dead objects/shared objects
1188	/// 6. Re-run symbol resolution on pruned objects and shared objects sets.
1189	pub fn resolveSymbols(self: *Elf) !void {
1190	// This function mutates `shared_objects`.
1191	const shared_objects = &self.shared_objects;
1192
1193	// Resolve symbols in the ZigObject. For now, we assume that it's always live.
1194	if (self.zigObjectPtr()) |zo| try zo.asFile().resolveSymbols(self);
1195	// Resolve symbols on the set of all objects and shared objects (even if some are unneeded).
1196	for (self.objects.items) |index| try self.file(index).?.resolveSymbols(self);
1197	for (shared_objects.values()) |index| try self.file(index).?.resolveSymbols(self);
1198	if (self.linkerDefinedPtr()) |obj| try obj.asFile().resolveSymbols(self);
1199
1200	// Mark live objects.
1201	self.markLive();
1202
1203	// Reset state of all globals after marking live objects.
1204	self.resolver.reset();
1205
1206	// Prune dead objects and shared objects.
1207	var i: usize = 0;
1208	while (i < self.objects.items.len) {
1209	const index = self.objects.items[i];
1210	if (!self.file(index).?.isAlive()) {
1211	_ = self.objects.orderedRemove(i);
1212	} else i += 1;
1213	}
1214	// TODO This loop has 2 major flaws:
1215	// 1. It is O(N^2) which is never allowed in the codebase.
1216	// 2. It mutates shared_objects, which is a non-starter for incremental compilation.
1217	i = 0;
1218	while (i < shared_objects.values().len) {
1219	const index = shared_objects.values()[i];
1220	if (!self.file(index).?.isAlive()) {
1221	_ = shared_objects.orderedRemoveAt(i);
1222	} else i += 1;
1223	}
1224
1225	{
1226	// Dedup groups.
1227	var table = std.StringHashMap(Ref).init(self.base.comp.gpa);
1228	defer table.deinit();
1229
1230	for (self.objects.items) |index| {
1231	try self.file(index).?.object.resolveGroups(self, &table);
1232	}
1233
1234	for (self.objects.items) |index| {
1235	self.file(index).?.object.markGroupsDead(self);
1236	}
1237	}
1238
1239	// Re-resolve the symbols.
1240	if (self.zigObjectPtr()) |zo| try zo.asFile().resolveSymbols(self);
1241	for (self.objects.items) |index| try self.file(index).?.resolveSymbols(self);
1242	for (shared_objects.values()) |index| try self.file(index).?.resolveSymbols(self);
1243	if (self.linkerDefinedPtr()) |obj| try obj.asFile().resolveSymbols(self);
1244	}
1245
1246	/// Traverses all objects and shared objects marking any object referenced by
1247	/// a live object/shared object as alive itself.
1248	/// This routine will prune unneeded objects extracted from archives and
1249	/// unneeded shared objects.
1250	fn markLive(self: *Elf) void {
1251	const shared_objects = self.shared_objects.values();
1252	if (self.zigObjectPtr()) |zig_object| zig_object.asFile().markLive(self);
1253	for (self.objects.items) |index| {
1254	const file_ptr = self.file(index).?;
1255	if (file_ptr.isAlive()) file_ptr.markLive(self);
1256	}
1257	for (shared_objects) |index| {
1258	const file_ptr = self.file(index).?;
1259	if (file_ptr.isAlive()) file_ptr.markLive(self);
1260	}
1261	}
1262
1263	pub fn markEhFrameAtomsDead(self: *Elf) void {
1264	for (self.objects.items) |index| {
1265	const file_ptr = self.file(index).?;
1266	if (!file_ptr.isAlive()) continue;
1267	file_ptr.object.markEhFrameAtomsDead(self);
1268	}
1269	}
1270
1271	fn markImportsExports(self: *Elf) void {
1272	const shared_objects = self.shared_objects.values();
1273	if (self.zigObjectPtr()) |zo| {
1274	zo.markImportsExports(self);
1275	}
1276	for (self.objects.items) |index| {
1277	self.file(index).?.object.markImportsExports(self);
1278	}
1279	if (!self.isEffectivelyDynLib()) {
1280	for (shared_objects) |index| {
1281	self.file(index).?.shared_object.markImportExports(self);
1282	}
1283	}
1284	}
1285
1286	fn claimUnresolved(self: *Elf) void {
1287	if (self.zigObjectPtr()) |zig_object| {
1288	zig_object.claimUnresolved(self);
1289	}
1290	for (self.objects.items) |index| {
1291	self.file(index).?.object.claimUnresolved(self);
1292	}
1293	}
1294
1295	/// In scanRelocs we will go over all live atoms and scan their relocs.
1296	/// This will help us work out what synthetics to emit, GOT indirection, etc.
1297	/// This is also the point where we will report undefined symbols for any
1298	/// alloc sections.
1299	fn scanRelocs(self: *Elf) !void {
1300	const gpa = self.base.comp.gpa;
1301	const shared_objects = self.shared_objects.values();
1302
1303	var undefs: std.array_hash_map.Auto(SymbolResolver.Index, std.array_list.Managed(Ref)) = .empty;
1304	defer {
1305	for (undefs.values()) |*refs| refs.deinit();
1306	undefs.deinit(gpa);
1307	}
1308
1309	var has_reloc_errors = false;
1310	if (self.zigObjectPtr()) |zo| {
1311	zo.asFile().scanRelocs(self, &undefs) catch |err| switch (err) {
1312	error.RelaxFailure => unreachable,
1313	error.UnsupportedCpuArch => {
1314	try self.reportUnsupportedCpuArch();
1315	return error.AlreadyReported;
1316	},
1317	error.RelocFailure => has_reloc_errors = true,
1318	else => |e| return e,
1319	};
1320	}
1321	for (self.objects.items) |index| {
1322	self.file(index).?.scanRelocs(self, &undefs) catch |err| switch (err) {
1323	error.RelaxFailure => unreachable,
1324	error.UnsupportedCpuArch => {
1325	try self.reportUnsupportedCpuArch();
1326	return error.AlreadyReported;
1327	},
1328	error.RelocFailure => has_reloc_errors = true,
1329	else => |e| return e,
1330	};
1331	}
1332
1333	try self.reportUndefinedSymbols(&undefs);
1334
1335	if (has_reloc_errors) return error.AlreadyReported;
1336
1337	if (self.zigObjectPtr()) |zo| {
1338	try zo.asFile().createSymbolIndirection(self);
1339	}
1340	for (self.objects.items) |index| {
1341	try self.file(index).?.createSymbolIndirection(self);
1342	}
1343	for (shared_objects) |index| {
1344	try self.file(index).?.createSymbolIndirection(self);
1345	}
1346	if (self.linkerDefinedPtr()) |obj| {
1347	try obj.asFile().createSymbolIndirection(self);
1348	}
1349	if (self.got.flags.needs_tlsld) {
1350	log.debug("program needs TLSLD", .{});
1351	try self.got.addTlsLdSymbol(self);
1352	}
1353	}
1354
1355	pub fn initOutputSection(self: *Elf, args: struct {
1356	name: [:0]const u8,
1357	flags: u64,
1358	type: u32,
1359	}) error{OutOfMemory}!u32 {
1360	const name = blk: {
1361	if (self.base.isRelocatable()) break :blk args.name;
1362	if (args.flags & elf.SHF_MERGE != 0) break :blk args.name;
1363	const name_prefixes: []const [:0]const u8 = &.{
1364	".text", ".data.rel.ro", ".data", ".rodata", ".bss.rel.ro", ".bss",
1365	".preinit_array", ".init_array", ".fini_array", ".tbss", ".tdata", ".gcc_except_table",
1366	".ctors", ".dtors", ".gnu.warning",
1367	};
1368	inline for (name_prefixes) |prefix| {
1369	if (mem.eql(u8, args.name, prefix) or mem.startsWith(u8, args.name, prefix ++ ".")) {
1370	break :blk prefix;
1371	}
1372	}
1373	break :blk args.name;
1374	};
1375	const @"type" = tt: {
1376	if (self.getTarget().cpu.arch == .x86_64 and args.type == elf.SHT_X86_64_UNWIND)
1377	break :tt elf.SHT_PROGBITS;
1378	switch (args.type) {
1379	elf.SHT_NULL => unreachable,
1380	elf.SHT_PROGBITS => {
1381	if (mem.eql(u8, args.name, ".preinit_array") or mem.startsWith(u8, args.name, ".preinit_array."))
1382	break :tt elf.SHT_PREINIT_ARRAY;
1383	if (mem.eql(u8, args.name, ".init_array") or mem.startsWith(u8, args.name, ".init_array."))
1384	break :tt elf.SHT_INIT_ARRAY;
1385	if (mem.eql(u8, args.name, ".fini_array") or mem.startsWith(u8, args.name, ".fini_array."))
1386	break :tt elf.SHT_FINI_ARRAY;
1387	break :tt args.type;
1388	},
1389	else => break :tt args.type,
1390	}
1391	};
1392	const flags = blk: {
1393	var flags = args.flags;
1394	if (!self.base.isRelocatable()) {
1395	flags &= ~@as(u64, elf.SHF_COMPRESSED | elf.SHF_GROUP | elf.SHF_GNU_RETAIN);
1396	}
1397	break :blk switch (@"type") {
1398	elf.SHT_INIT_ARRAY, elf.SHT_FINI_ARRAY => flags | elf.SHF_WRITE,
1399	else => flags,
1400	};
1401	};
1402	const out_shndx = self.sectionByName(name) orelse try self.addSection(.{
1403	.type = @"type",
1404	.flags = flags,
1405	.name = try self.insertShString(name),
1406	});
1407	return out_shndx;
1408	}
1409
1410	pub fn writeShdrTable(self: *Elf) !void {
1411	const gpa = self.base.comp.gpa;
1412	const target_endian = self.getTarget().cpu.arch.endian();
1413	const foreign_endian = target_endian != builtin.cpu.arch.endian();
1414	const shsize: u64 = switch (self.ptr_width) {
1415	.p32 => @sizeOf(elf.Elf32_Shdr),
1416	.p64 => @sizeOf(elf.Elf64_Shdr),
1417	};
1418	const shalign: u16 = switch (self.ptr_width) {
1419	.p32 => @alignOf(elf.Elf32_Shdr),
1420	.p64 => @alignOf(elf.Elf64_Shdr),
1421	};
1422
1423	const shoff = self.shdr_table_offset orelse 0;
1424	const needed_size = self.sections.items(.shdr).len * shsize;
1425
1426	if (needed_size > self.allocatedSize(shoff)) {
1427	self.shdr_table_offset = null;
1428	self.shdr_table_offset = try self.findFreeSpace(needed_size, shalign);
1429	}
1430
1431	log.debug("writing section headers from 0x{x} to 0x{x}", .{
1432	self.shdr_table_offset.?,
1433	self.shdr_table_offset.? + needed_size,
1434	});
1435
1436	switch (self.ptr_width) {
1437	.p32 => {
1438	const buf = try gpa.alloc(elf.Elf32_Shdr, self.sections.items(.shdr).len);
1439	defer gpa.free(buf);
1440
1441	for (buf, 0..) |*shdr, i| {
1442	assert(self.sections.items(.shdr)[i].sh_offset != math.maxInt(u64));
1443	shdr.* = shdrTo32(self.sections.items(.shdr)[i]);
1444	if (foreign_endian) {
1445	mem.byteSwapAllFields(elf.Elf32_Shdr, shdr);
1446	}
1447	}
1448	try self.pwriteAll(@ptrCast(buf), self.shdr_table_offset.?);
1449	},
1450	.p64 => {
1451	const buf = try gpa.alloc(elf.Elf64_Shdr, self.sections.items(.shdr).len);
1452	defer gpa.free(buf);
1453
1454	for (buf, 0..) |*shdr, i| {
1455	assert(self.sections.items(.shdr)[i].sh_offset != math.maxInt(u64));
1456	shdr.* = self.sections.items(.shdr)[i];
1457	if (foreign_endian) {
1458	mem.byteSwapAllFields(elf.Elf64_Shdr, shdr);
1459	}
1460	}
1461	try self.pwriteAll(@ptrCast(buf), self.shdr_table_offset.?);
1462	},
1463	}
1464	}
1465
1466	fn writePhdrTable(self: *Elf) !void {
1467	const gpa = self.base.comp.gpa;
1468	const target_endian = self.getTarget().cpu.arch.endian();
1469	const foreign_endian = target_endian != builtin.cpu.arch.endian();
1470	const phdr_table = &self.phdrs.items[self.phdr_indexes.table.int().?];
1471
1472	log.debug("writing program headers from 0x{x} to 0x{x}", .{
1473	phdr_table.offset,
1474	phdr_table.offset + phdr_table.filesz,
1475	});
1476
1477	switch (self.ptr_width) {
1478	.p32 => {
1479	const buf = try gpa.alloc(elf.Elf32.Phdr, self.phdrs.items.len);
1480	defer gpa.free(buf);
1481
1482	for (buf, 0..) |*phdr, i| {
1483	phdr.* = phdrTo32(self.phdrs.items[i]);
1484	if (foreign_endian) {
1485	mem.byteSwapAllFields(elf.Elf32.Phdr, phdr);
1486	}
1487	}
1488	try self.pwriteAll(@ptrCast(buf), phdr_table.offset);
1489	},
1490	.p64 => {
1491	const buf = try gpa.alloc(elf.Elf64.Phdr, self.phdrs.items.len);
1492	defer gpa.free(buf);
1493
1494	for (buf, 0..) |*phdr, i| {
1495	phdr.* = self.phdrs.items[i];
1496	if (foreign_endian) {
1497	mem.byteSwapAllFields(elf.Elf64.Phdr, phdr);
1498	}
1499	}
1500	try self.pwriteAll(@ptrCast(buf), phdr_table.offset);
1501	},
1502	}
1503	}
1504
1505	pub fn writeElfHeader(self: *Elf) !void {
1506	const diags = &self.base.comp.link_diags;
1507	if (diags.hasErrors()) return; // We had errors, so skip flushing to render the output unusable
1508
1509	const comp = self.base.comp;
1510	var hdr_buf: [@sizeOf(elf.Elf64_Ehdr)]u8 = undefined;
1511
1512	var index: usize = 0;
1513	hdr_buf[0..4].* = elf.MAGIC.*;
1514	index += 4;
1515
1516	hdr_buf[index] = switch (self.ptr_width) {
1517	.p32 => elf.ELFCLASS32,
1518	.p64 => elf.ELFCLASS64,
1519	};
1520	index += 1;
1521
1522	const target = self.getTarget();
1523	const endian = target.cpu.arch.endian();
1524	hdr_buf[index] = switch (endian) {
1525	.little => elf.ELFDATA2LSB,
1526	.big => elf.ELFDATA2MSB,
1527	};
1528	index += 1;
1529
1530	hdr_buf[index] = 1; // ELF version
1531	index += 1;
1532
1533	hdr_buf[index] = @backingInt(@as(elf.OSABI, switch (target.cpu.arch) {
1534	.amdgcn => switch (target.os.tag) {
1535	.amdhsa => .AMDGPU_HSA,
1536	.amdpal => .AMDGPU_PAL,
1537	.mesa3d => .AMDGPU_MESA3D,
1538	else => .NONE,
1539	},
1540	.msp430 => .STANDALONE,
1541	else => switch (target.os.tag) {
1542	.freebsd, .ps4 => .FREEBSD,
1543	.hermit => .STANDALONE,
1544	.illumos => .SOLARIS,
1545	.openbsd => .OPENBSD,
1546	else => .NONE,
1547	},
1548	}));
1549	index += 1;
1550
1551	// ABI Version, possibly used by glibc but not by static executables
1552	// padding
1553	@memset(hdr_buf[index..][0..8], 0);
1554	index += 8;
1555
1556	assert(index == 16);
1557
1558	const output_mode = comp.config.output_mode;
1559	const link_mode = comp.config.link_mode;
1560	const elf_type: elf.ET = switch (output_mode) {
1561	.Exe => if (comp.config.pie or target.os.tag == .haiku) .DYN else .EXEC,
1562	.Obj => .REL,
1563	.Lib => switch (link_mode) {
1564	.static => @as(elf.ET, .REL),
1565	.dynamic => .DYN,
1566	},
1567	};
1568	mem.writeInt(u16, hdr_buf[index..][0..2], @backingInt(elf_type), endian);
1569	index += 2;
1570
1571	const machine = target.toElfMachine();
1572	mem.writeInt(u16, hdr_buf[index..][0..2], @backingInt(machine), endian);
1573	index += 2;
1574
1575	// ELF Version, again
1576	mem.writeInt(u32, hdr_buf[index..][0..4], 1, endian);
1577	index += 4;
1578
1579	const e_entry: u64 = if (self.linkerDefinedPtr()) |obj| blk: {
1580	const entry_sym = obj.entrySymbol(self) orelse break :blk 0;
1581	break :blk @intCast(entry_sym.address(.{}, self));
1582	} else 0;
1583	const phdr_table_offset = if (self.phdr_indexes.table.int()) |phndx| self.phdrs.items[phndx].offset else 0;
1584	switch (self.ptr_width) {
1585	.p32 => {
1586	mem.writeInt(u32, hdr_buf[index..][0..4], @intCast(e_entry), endian);
1587	index += 4;
1588
1589	// e_phoff
1590	mem.writeInt(u32, hdr_buf[index..][0..4], @intCast(phdr_table_offset), endian);
1591	index += 4;
1592
1593	// e_shoff
1594	mem.writeInt(u32, hdr_buf[index..][0..4], @intCast(self.shdr_table_offset.?), endian);
1595	index += 4;
1596	},
1597	.p64 => {
1598	// e_entry
1599	mem.writeInt(u64, hdr_buf[index..][0..8], e_entry, endian);
1600	index += 8;
1601
1602	// e_phoff
1603	mem.writeInt(u64, hdr_buf[index..][0..8], phdr_table_offset, endian);
1604	index += 8;
1605
1606	// e_shoff
1607	mem.writeInt(u64, hdr_buf[index..][0..8], self.shdr_table_offset.?, endian);
1608	index += 8;
1609	},
1610	}
1611
1612	const e_flags = 0;
1613	mem.writeInt(u32, hdr_buf[index..][0..4], e_flags, endian);
1614	index += 4;
1615
1616	const e_ehsize: u16 = switch (self.ptr_width) {
1617	.p32 => @sizeOf(elf.Elf32_Ehdr),
1618	.p64 => @sizeOf(elf.Elf64_Ehdr),
1619	};
1620	mem.writeInt(u16, hdr_buf[index..][0..2], e_ehsize, endian);
1621	index += 2;
1622
1623	const e_phentsize: u16 = switch (self.ptr_width) {
1624	.p32 => @sizeOf(elf.Elf32.Phdr),
1625	.p64 => @sizeOf(elf.Elf64.Phdr),
1626	};
1627	mem.writeInt(u16, hdr_buf[index..][0..2], e_phentsize, endian);
1628	index += 2;
1629
1630	const e_phnum = @as(u16, @intCast(self.phdrs.items.len));
1631	mem.writeInt(u16, hdr_buf[index..][0..2], e_phnum, endian);
1632	index += 2;
1633
1634	const e_shentsize: u16 = switch (self.ptr_width) {
1635	.p32 => @sizeOf(elf.Elf32_Shdr),
1636	.p64 => @sizeOf(elf.Elf64_Shdr),
1637	};
1638	mem.writeInt(u16, hdr_buf[index..][0..2], e_shentsize, endian);
1639	index += 2;
1640
1641	const e_shnum: u16 = @intCast(self.sections.items(.shdr).len);
1642	mem.writeInt(u16, hdr_buf[index..][0..2], e_shnum, endian);
1643	index += 2;
1644
1645	mem.writeInt(u16, hdr_buf[index..][0..2], @intCast(self.section_indexes.shstrtab.?), endian);
1646	index += 2;
1647
1648	assert(index == e_ehsize);
1649
1650	try self.pwriteAll(hdr_buf[0..index], 0);
1651	}
1652
1653	pub fn freeNav(self: *Elf, nav: InternPool.Nav.Index) void {
1654	return self.zigObjectPtr().?.freeNav(self, nav);
1655	}
1656
1657	pub fn updateFunc(
1658	self: *Elf,
1659	pt: Zcu.PerThread,
1660	func_index: InternPool.Index,
1661	mir: *const codegen.AnyMir,
1662	) link.Error!void {
1663	return self.zigObjectPtr().?.updateFunc(self, pt, func_index, mir);
1664	}
1665
1666	pub fn updateNav(
1667	self: *Elf,
1668	pt: Zcu.PerThread,
1669	nav: InternPool.Nav.Index,
1670	) link.Error!void {
1671	return self.zigObjectPtr().?.updateNav(self, pt, nav);
1672	}
1673
1674	pub fn updateContainerType(
1675	self: *Elf,
1676	pt: Zcu.PerThread,
1677	ty: InternPool.Index,
1678	success: bool,
1679	) link.Error!void {
1680	try self.zigObjectPtr().?.updateContainerType(pt, ty, success);
1681	}
1682
1683	pub fn updateExports(
1684	self: *Elf,
1685	pt: Zcu.PerThread,
1686	export_indices: []const Zcu.Export.Index,
1687	) link.Error!void {
1688	return self.zigObjectPtr().?.updateExports(self, pt, export_indices);
1689	}
1690
1691	pub fn updateLineNumber(self: *Elf, pt: Zcu.PerThread, inst: InternPool.TrackedInst.Index, line: u32) link.Error!void {
1692	return self.zigObjectPtr().?.updateLineNumber(pt, inst, line);
1693	}
1694
1695	fn checkDuplicates(self: *Elf) !void {
1696	const gpa = self.base.comp.gpa;
1697
1698	var dupes: std.array_hash_map.Auto(SymbolResolver.Index, std.ArrayList(File.Index)) = .empty;
1699	defer {
1700	for (dupes.values()) |*list| {
1701	list.deinit(gpa);
1702	}
1703	dupes.deinit(gpa);
1704	}
1705
1706	if (self.zigObjectPtr()) |zig_object| {
1707	try zig_object.checkDuplicates(&dupes, self);
1708	}
1709	for (self.objects.items) |index| {
1710	try self.file(index).?.object.checkDuplicates(&dupes, self);
1711	}
1712
1713	try self.reportDuplicates(dupes);
1714	}
1715
1716	pub fn addCommentString(self: *Elf) !void {
1717	const gpa = self.base.comp.gpa;
1718	if (self.comment_merge_section_index != null) return;
1719	const msec_index = try self.getOrCreateMergeSection(".comment", elf.SHF_MERGE | elf.SHF_STRINGS, elf.SHT_PROGBITS);
1720	const msec = self.mergeSection(msec_index);
1721	const res = try msec.insertZ(gpa, "zig " ++ builtin.zig_version_string);
1722	if (res.found_existing) return;
1723	const msub_index = try msec.addMergeSubsection(gpa);
1724	const msub = msec.mergeSubsection(msub_index);
1725	msub.merge_section_index = msec_index;
1726	msub.string_index = res.key.pos;
1727	msub.alignment = .@"1";
1728	msub.size = res.key.len;
1729	msub.entsize = 1;
1730	msub.alive = true;
1731	res.sub.* = msub_index;
1732	self.comment_merge_section_index = msec_index;
1733	}
1734
1735	pub fn resolveMergeSections(self: *Elf) !void {
1736	const tracy = trace(@src());
1737	defer tracy.end();
1738
1739	var has_errors = false;
1740	for (self.objects.items) |index| {
1741	const object = self.file(index).?.object;
1742	if (!object.alive) continue;
1743	if (!object.dirty) continue;
1744	object.initInputMergeSections(self) catch |err| switch (err) {
1745	error.AlreadyReported => has_errors = true,
1746	else => |e| return e,
1747	};
1748	}
1749
1750	if (has_errors) return error.AlreadyReported;
1751
1752	for (self.objects.items) |index| {
1753	const object = self.file(index).?.object;
1754	if (!object.alive) continue;
1755	if (!object.dirty) continue;
1756	try object.initOutputMergeSections(self);
1757	}
1758
1759	for (self.objects.items) |index| {
1760	const object = self.file(index).?.object;
1761	if (!object.alive) continue;
1762	if (!object.dirty) continue;
1763	object.resolveMergeSubsections(self) catch |err| switch (err) {
1764	error.AlreadyReported => has_errors = true,
1765	else => |e| return e,
1766	};
1767	}
1768
1769	if (has_errors) return error.AlreadyReported;
1770	}
1771
1772	pub fn finalizeMergeSections(self: *Elf) !void {
1773	for (self.merge_sections.items) |*msec| {
1774	try msec.finalize(self.base.comp.gpa);
1775	}
1776	}
1777
1778	pub fn updateMergeSectionSizes(self: *Elf) !void {
1779	for (self.merge_sections.items) |*msec| {
1780	msec.updateSize();
1781	}
1782	for (self.merge_sections.items) |*msec| {
1783	const shdr = &self.sections.items(.shdr)[msec.output_section_index];
1784	const offset = msec.alignment.forward(shdr.sh_size);
1785	const padding = offset - shdr.sh_size;
1786	msec.value = @intCast(offset);
1787	shdr.sh_size += padding + msec.size;
1788	shdr.sh_addralign = @max(shdr.sh_addralign, msec.alignment.toByteUnits() orelse 1);
1789	shdr.sh_entsize = if (shdr.sh_entsize == 0) msec.entsize else @min(shdr.sh_entsize, msec.entsize);
1790	}
1791	}
1792
1793	pub fn writeMergeSections(self: *Elf) !void {
1794	const gpa = self.base.comp.gpa;
1795	var buffer = std.array_list.Managed(u8).init(gpa);
1796	defer buffer.deinit();
1797
1798	for (self.merge_sections.items) |*msec| {
1799	const shdr = self.sections.items(.shdr)[msec.output_section_index];
1800	const fileoff = try self.cast(usize, msec.value + shdr.sh_offset);
1801	const size = try self.cast(usize, msec.size);
1802	try buffer.ensureTotalCapacity(size);
1803	buffer.appendNTimesAssumeCapacity(0, size);
1804
1805	for (msec.finalized_subsections.items) |msub_index| {
1806	const msub = msec.mergeSubsection(msub_index);
1807	assert(msub.alive);
1808	const string = msub.getString(self);
1809	const off = try self.cast(usize, msub.value);
1810	@memcpy(buffer.items[off..][0..string.len], string);
1811	}
1812
1813	try self.pwriteAll(buffer.items, fileoff);
1814	buffer.clearRetainingCapacity();
1815	}
1816	}
1817
1818	fn initOutputSections(self: *Elf) !void {
1819	for (self.objects.items) |index| {
1820	try self.file(index).?.object.initOutputSections(self);
1821	}
1822	for (self.merge_sections.items) |*msec| {
1823	if (msec.finalized_subsections.items.len == 0) continue;
1824	try msec.initOutputSection(self);
1825	}
1826	}
1827
1828	fn initSyntheticSections(self: *Elf) !void {
1829	const comp = self.base.comp;
1830	const target = self.getTarget();
1831	const ptr_size = self.ptrWidthBytes();
1832
1833	const is_exe_or_dyn_lib = switch (comp.config.output_mode) {
1834	.Exe => true,
1835	.Lib => comp.config.link_mode == .dynamic,
1836	.Obj => false,
1837	};
1838	const have_dynamic_linker = comp.config.link_mode == .dynamic and is_exe_or_dyn_lib;
1839
1840	const needs_eh_frame = blk: {
1841	if (self.zigObjectPtr()) |zo|
1842	if (zo.eh_frame_index != null) break :blk true;
1843	break :blk for (self.objects.items) |index| {
1844	if (self.file(index).?.object.cies.items.len > 0) break true;
1845	} else false;
1846	};
1847
1848	if (needs_eh_frame) {
1849	if (self.section_indexes.eh_frame == null) {
1850	self.section_indexes.eh_frame = self.sectionByName(".eh_frame") orelse try self.addSection(.{
1851	.name = try self.insertShString(".eh_frame"),
1852	.type = if (target.cpu.arch == .x86_64)
1853	elf.SHT_X86_64_UNWIND
1854	else
1855	elf.SHT_PROGBITS,
1856	.flags = elf.SHF_ALLOC,
1857	.addralign = ptr_size,
1858	});
1859	}
1860	if (comp.link_eh_frame_hdr and self.section_indexes.eh_frame_hdr == null) {
1861	self.section_indexes.eh_frame_hdr = try self.addSection(.{
1862	.name = try self.insertShString(".eh_frame_hdr"),
1863	.type = elf.SHT_PROGBITS,
1864	.flags = elf.SHF_ALLOC,
1865	.addralign = 4,
1866	});
1867	}
1868	}
1869
1870	if (self.got.entries.items.len > 0 and self.section_indexes.got == null) {
1871	self.section_indexes.got = try self.addSection(.{
1872	.name = try self.insertShString(".got"),
1873	.type = elf.SHT_PROGBITS,
1874	.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
1875	.addralign = ptr_size,
1876	});
1877	}
1878
1879	if (have_dynamic_linker) {
1880	if (self.section_indexes.got_plt == null) {
1881	self.section_indexes.got_plt = try self.addSection(.{
1882	.name = try self.insertShString(".got.plt"),
1883	.type = elf.SHT_PROGBITS,
1884	.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
1885	.addralign = @alignOf(u64),
1886	});
1887	}
1888	} else {
1889	assert(self.plt.symbols.items.len == 0);
1890	}
1891
1892	const needs_rela_dyn = blk: {
1893	if (self.got.flags.needs_rela or self.got.flags.needs_tlsld or self.copy_rel.symbols.items.len > 0)
1894	break :blk true;
1895	if (self.zigObjectPtr()) |zig_object| {
1896	if (zig_object.num_dynrelocs > 0) break :blk true;
1897	}
1898	for (self.objects.items) |index| {
1899	if (self.file(index).?.object.num_dynrelocs > 0) break :blk true;
1900	}
1901	break :blk false;
1902	};
1903	if (needs_rela_dyn and self.section_indexes.rela_dyn == null) {
1904	self.section_indexes.rela_dyn = try self.addSection(.{
1905	.name = try self.insertShString(".rela.dyn"),
1906	.type = elf.SHT_RELA,
1907	.flags = elf.SHF_ALLOC,
1908	.addralign = @alignOf(elf.Elf64_Rela),
1909	.entsize = @sizeOf(elf.Elf64_Rela),
1910	});
1911	}
1912
1913	if (self.plt.symbols.items.len > 0) {
1914	if (self.section_indexes.plt == null) {
1915	self.section_indexes.plt = try self.addSection(.{
1916	.name = try self.insertShString(".plt"),
1917	.type = elf.SHT_PROGBITS,
1918	.flags = elf.SHF_ALLOC | elf.SHF_EXECINSTR,
1919	.addralign = 16,
1920	});
1921	}
1922	if (self.section_indexes.rela_plt == null) {
1923	self.section_indexes.rela_plt = try self.addSection(.{
1924	.name = try self.insertShString(".rela.plt"),
1925	.type = elf.SHT_RELA,
1926	.flags = elf.SHF_ALLOC,
1927	.addralign = @alignOf(elf.Elf64_Rela),
1928	.entsize = @sizeOf(elf.Elf64_Rela),
1929	});
1930	}
1931	}
1932
1933	if (self.plt_got.symbols.items.len > 0 and self.section_indexes.plt_got == null) {
1934	self.section_indexes.plt_got = try self.addSection(.{
1935	.name = try self.insertShString(".plt.got"),
1936	.type = elf.SHT_PROGBITS,
1937	.flags = elf.SHF_ALLOC | elf.SHF_EXECINSTR,
1938	.addralign = 16,
1939	});
1940	}
1941
1942	if (self.copy_rel.symbols.items.len > 0 and self.section_indexes.copy_rel == null) {
1943	self.section_indexes.copy_rel = try self.addSection(.{
1944	.name = try self.insertShString(".copyrel"),
1945	.type = elf.SHT_NOBITS,
1946	.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
1947	});
1948	}
1949
1950	if (needs_interp: {
1951	if (comp.config.link_mode == .static) break :needs_interp false;
1952	if (target.dynamic_linker.get() == null) break :needs_interp false;
1953	break :needs_interp switch (comp.config.output_mode) {
1954	.Exe => true,
1955	.Lib => comp.root_mod.resolved_target.is_explicit_dynamic_linker,
1956	.Obj => false,
1957	};
1958	} and self.section_indexes.interp == null) {
1959	self.section_indexes.interp = try self.addSection(.{
1960	.name = try self.insertShString(".interp"),
1961	.type = elf.SHT_PROGBITS,
1962	.flags = elf.SHF_ALLOC,
1963	.addralign = 1,
1964	});
1965	}
1966
1967	if (have_dynamic_linker or comp.config.pie or self.isEffectivelyDynLib()) {
1968	if (self.section_indexes.dynstrtab == null) {
1969	self.section_indexes.dynstrtab = try self.addSection(.{
1970	.name = try self.insertShString(".dynstr"),
1971	.flags = elf.SHF_ALLOC,
1972	.type = elf.SHT_STRTAB,
1973	.entsize = 1,
1974	.addralign = 1,
1975	});
1976	}
1977	if (self.section_indexes.dynamic == null) {
1978	self.section_indexes.dynamic = try self.addSection(.{
1979	.name = try self.insertShString(".dynamic"),
1980	.flags = elf.SHF_ALLOC | elf.SHF_WRITE,
1981	.type = elf.SHT_DYNAMIC,
1982	.entsize = @sizeOf(elf.Elf64_Dyn),
1983	.addralign = @alignOf(elf.Elf64_Dyn),
1984	});
1985	}
1986	if (self.section_indexes.dynsymtab == null) {
1987	self.section_indexes.dynsymtab = try self.addSection(.{
1988	.name = try self.insertShString(".dynsym"),
1989	.flags = elf.SHF_ALLOC,
1990	.type = elf.SHT_DYNSYM,
1991	.addralign = @alignOf(elf.Elf64_Sym),
1992	.entsize = @sizeOf(elf.Elf64_Sym),
1993	.info = 1,
1994	});
1995	}
1996	if (self.section_indexes.hash == null) {
1997	self.section_indexes.hash = try self.addSection(.{
1998	.name = try self.insertShString(".hash"),
1999	.flags = elf.SHF_ALLOC,
2000	.type = elf.SHT_HASH,
2001	.addralign = 4,
2002	.entsize = 4,
2003	});
2004	}
2005	if (self.section_indexes.gnu_hash == null) {
2006	self.section_indexes.gnu_hash = try self.addSection(.{
2007	.name = try self.insertShString(".gnu.hash"),
2008	.flags = elf.SHF_ALLOC,
2009	.type = elf.SHT_GNU_HASH,
2010	.addralign = 8,
2011	});
2012	}
2013
2014	const needs_versions = for (self.dynsym.entries.items) |entry| {
2015	const sym = self.symbol(entry.ref).?;
2016	if (sym.flags.import and sym.version_index.VERSION > elf.Versym.GLOBAL.VERSION) break true;
2017	} else false;
2018	if (needs_versions) {
2019	if (self.section_indexes.versym == null) {
2020	self.section_indexes.versym = try self.addSection(.{
2021	.name = try self.insertShString(".gnu.version"),
2022	.flags = elf.SHF_ALLOC,
2023	.type = elf.SHT_GNU_VERSYM,
2024	.addralign = @alignOf(elf.Versym),
2025	.entsize = @sizeOf(elf.Versym),
2026	});
2027	}
2028	if (self.section_indexes.verneed == null) {
2029	self.section_indexes.verneed = try self.addSection(.{
2030	.name = try self.insertShString(".gnu.version_r"),
2031	.flags = elf.SHF_ALLOC,
2032	.type = elf.SHT_GNU_VERNEED,
2033	.addralign = @alignOf(elf.Elf64_Verneed),
2034	});
2035	}
2036	}
2037	}
2038
2039	try self.initSymtab();
2040	try self.initShStrtab();
2041	}
2042
2043	pub fn initSymtab(self: *Elf) !void {
2044	const small_ptr = switch (self.ptr_width) {
2045	.p32 => true,
2046	.p64 => false,
2047	};
2048	if (self.section_indexes.symtab == null) {
2049	self.section_indexes.symtab = try self.addSection(.{
2050	.name = try self.insertShString(".symtab"),
2051	.type = elf.SHT_SYMTAB,
2052	.addralign = if (small_ptr) @alignOf(elf.Elf32_Sym) else @alignOf(elf.Elf64_Sym),
2053	.entsize = if (small_ptr) @sizeOf(elf.Elf32_Sym) else @sizeOf(elf.Elf64_Sym),
2054	});
2055	}
2056	if (self.section_indexes.strtab == null) {
2057	self.section_indexes.strtab = try self.addSection(.{
2058	.name = try self.insertShString(".strtab"),
2059	.type = elf.SHT_STRTAB,
2060	.entsize = 1,
2061	.addralign = 1,
2062	});
2063	}
2064	}
2065
2066	pub fn initShStrtab(self: *Elf) !void {
2067	if (self.section_indexes.shstrtab == null) {
2068	self.section_indexes.shstrtab = try self.addSection(.{
2069	.name = try self.insertShString(".shstrtab"),
2070	.type = elf.SHT_STRTAB,
2071	.entsize = 1,
2072	.addralign = 1,
2073	});
2074	}
2075	}
2076
2077	fn initSpecialPhdrs(self: *Elf) !void {
2078	comptime assert(max_number_of_special_phdrs == 5);
2079
2080	if (self.section_indexes.interp != null and self.phdr_indexes.interp == .none) {
2081	self.phdr_indexes.interp = (try self.addPhdr(.{
2082	.type = @backingInt(elf.PT.INTERP),
2083	.flags = elf.PF_R,
2084	.@"align" = 1,
2085	})).toOptional();
2086	}
2087	if (self.section_indexes.dynamic != null and self.phdr_indexes.dynamic == .none) {
2088	self.phdr_indexes.dynamic = (try self.addPhdr(.{
2089	.type = @backingInt(elf.PT.DYNAMIC),
2090	.flags = elf.PF_R | elf.PF_W,
2091	})).toOptional();
2092	}
2093	if (self.section_indexes.eh_frame_hdr != null and self.phdr_indexes.gnu_eh_frame == .none) {
2094	self.phdr_indexes.gnu_eh_frame = (try self.addPhdr(.{
2095	.type = @backingInt(elf.PT.GNU_EH_FRAME),
2096	.flags = elf.PF_R,
2097	})).toOptional();
2098	}
2099	if (self.phdr_indexes.gnu_stack == .none) {
2100	self.phdr_indexes.gnu_stack = (try self.addPhdr(.{
2101	.type = @backingInt(elf.PT.GNU_STACK),
2102	.flags = elf.PF_W | elf.PF_R,
2103	.memsz = self.base.stack_size,
2104	.@"align" = 1,
2105	})).toOptional();
2106	}
2107
2108	const has_tls = for (self.sections.items(.shdr)) |shdr| {
2109	if (shdr.sh_flags & elf.SHF_TLS != 0) break true;
2110	} else false;
2111	if (has_tls and self.phdr_indexes.tls == .none) {
2112	self.phdr_indexes.tls = (try self.addPhdr(.{
2113	.type = @backingInt(elf.PT.TLS),
2114	.flags = elf.PF_R,
2115	.@"align" = 1,
2116	})).toOptional();
2117	}
2118	}
2119
2120	/// We need to sort constructors/destuctors in the following sections:
2121	/// * .init_array
2122	/// * .fini_array
2123	/// * .preinit_array
2124	/// * .ctors
2125	/// * .dtors
2126	/// The prority of inclusion is defined as part of the input section's name. For example, .init_array.10000.
2127	/// If no priority value has been specified,
2128	/// * for .init_array, .fini_array and .preinit_array, we automatically assign that section max value of maxInt(i32)
2129	/// and push it to the back of the queue,
2130	/// * for .ctors and .dtors, we automatically assign that section min value of -1
2131	/// and push it to the front of the queue,
2132	/// crtbegin and ctrend are assigned minInt(i32) and maxInt(i32) respectively.
2133	/// Ties are broken by the file prority which corresponds to the inclusion of input sections in this output section
2134	/// we are about to sort.
2135	fn sortInitFini(self: *Elf) !void {
2136	const gpa = self.base.comp.gpa;
2137	const slice = self.sections.slice();
2138
2139	const Entry = struct {
2140	priority: i32,
2141	atom_ref: Ref,
2142
2143	pub fn lessThan(ctx: *Elf, lhs: @This(), rhs: @This()) bool {
2144	if (lhs.priority == rhs.priority) {
2145	return ctx.atom(lhs.atom_ref).?.priority(ctx) < ctx.atom(rhs.atom_ref).?.priority(ctx);
2146	}
2147	return lhs.priority < rhs.priority;
2148	}
2149	};
2150
2151	for (slice.items(.shdr), slice.items(.atom_list_2)) |shdr, *atom_list| {
2152	if (shdr.sh_flags & elf.SHF_ALLOC == 0) continue;
2153	if (atom_list.atoms.keys().len == 0) continue;
2154
2155	var is_init_fini = false;
2156	var is_ctor_dtor = false;
2157	switch (shdr.sh_type) {
2158	elf.SHT_PREINIT_ARRAY,
2159	elf.SHT_INIT_ARRAY,
2160	elf.SHT_FINI_ARRAY,
2161	=> is_init_fini = true,
2162	else => {
2163	const name = self.getShString(shdr.sh_name);
2164	is_ctor_dtor = mem.find(u8, name, ".ctors") != null or mem.find(u8, name, ".dtors") != null;
2165	},
2166	}
2167	if (!is_init_fini and !is_ctor_dtor) continue;
2168
2169	var entries = std.array_list.Managed(Entry).init(gpa);
2170	try entries.ensureTotalCapacityPrecise(atom_list.atoms.keys().len);
2171	defer entries.deinit();
2172
2173	for (atom_list.atoms.keys()) |ref| {
2174	const atom_ptr = self.atom(ref).?;
2175	const object = atom_ptr.file(self).?.object;
2176	const priority = blk: {
2177	if (is_ctor_dtor) {
2178	const basename = object.path.basename();
2179	if (mem.eql(u8, basename, "crtbegin.o")) break :blk std.math.minInt(i32);
2180	if (mem.eql(u8, basename, "crtend.o")) break :blk std.math.maxInt(i32);
2181	}
2182	const default: i32 = if (is_ctor_dtor) -1 else std.math.maxInt(i32);
2183	const name = atom_ptr.name(self);
2184	var it = mem.splitBackwardsScalar(u8, name, '.');
2185	const priority = std.fmt.parseUnsigned(u16, it.first(), 10) catch default;
2186	break :blk priority;
2187	};
2188	entries.appendAssumeCapacity(.{ .priority = priority, .atom_ref = ref });
2189	}
2190
2191	mem.sort(Entry, entries.items, self, Entry.lessThan);
2192
2193	atom_list.atoms.clearRetainingCapacity();
2194	for (entries.items) |entry| {
2195	_ = atom_list.atoms.getOrPutAssumeCapacity(entry.atom_ref);
2196	}
2197	}
2198	}
2199
2200	fn setDynamicSection(self: *Elf, rpaths: []const []const u8) !void {
2201	if (self.section_indexes.dynamic == null) return;
2202
2203	const shared_objects = self.shared_objects.values();
2204
2205	for (shared_objects) |index| {
2206	const shared_object = self.file(index).?.shared_object;
2207	if (!shared_object.alive) continue;
2208	try self.dynamic.addNeeded(shared_object, self);
2209	}
2210
2211	if (self.isEffectivelyDynLib()) {
2212	if (self.soname) |soname| {
2213	try self.dynamic.setSoname(soname, self);
2214	}
2215	}
2216
2217	try self.dynamic.setRpath(rpaths, self);
2218	}
2219
2220	fn sortDynamicSymtab(self: *Elf) void {
2221	if (self.section_indexes.gnu_hash == null) return;
2222	self.dynsym.sort(self);
2223	}
2224
2225	fn setVersionSymtab(self: *Elf) !void {
2226	const gpa = self.base.comp.gpa;
2227	if (self.section_indexes.versym == null) return;
2228	try self.versym.resize(gpa, self.dynsym.count());
2229	self.versym.items[0] = .LOCAL;
2230	for (self.dynsym.entries.items, 1..) |entry, i| {
2231	const sym = self.symbol(entry.ref).?;
2232	self.versym.items[i] = sym.version_index;
2233	}
2234
2235	if (self.section_indexes.verneed) |shndx| {
2236	try self.verneed.generate(self);
2237	const shdr = &self.sections.items(.shdr)[shndx];
2238	shdr.sh_info = @as(u32, @intCast(self.verneed.verneed.items.len));
2239	}
2240	}
2241
2242	fn setHashSections(self: *Elf) !void {
2243	if (self.section_indexes.hash != null) {
2244	try self.hash.generate(self);
2245	}
2246	if (self.section_indexes.gnu_hash != null) {
2247	try self.gnu_hash.calcSize(self);
2248	}
2249	}
2250
2251	fn phdrRank(phdr: elf.Elf64.Phdr) u8 {
2252	return switch (phdr.type) {
2253	.NULL => 0,
2254	.PHDR => 1,
2255	.INTERP => 2,
2256	.LOAD => 3,
2257	.DYNAMIC, .TLS => 4,
2258	.GNU_EH_FRAME => 5,
2259	.GNU_STACK => 6,
2260	else => 7,
2261	};
2262	}
2263
2264	fn sortPhdrs(
2265	gpa: Allocator,
2266	phdrs: *ProgramHeaderList,
2267	special_indexes: *ProgramHeaderIndexes,
2268	section_indexes: []OptionalProgramHeaderIndex,
2269	) error{OutOfMemory}!void {
2270	const Entry = struct {
2271	phndx: u16,
2272
2273	pub fn lessThan(program_headers: []const elf.Elf64.Phdr, lhs: @This(), rhs: @This()) bool {
2274	const lhs_phdr = program_headers[lhs.phndx];
2275	const rhs_phdr = program_headers[rhs.phndx];
2276	const lhs_rank = phdrRank(lhs_phdr);
2277	const rhs_rank = phdrRank(rhs_phdr);
2278	if (lhs_rank == rhs_rank) return lhs_phdr.vaddr < rhs_phdr.vaddr;
2279	return lhs_rank < rhs_rank;
2280	}
2281	};
2282
2283	const entries = try gpa.alloc(Entry, phdrs.items.len);
2284	defer gpa.free(entries);
2285	for (entries, 0..) |*entry, phndx| {
2286	entry.* = .{ .phndx = @intCast(phndx) };
2287	}
2288
2289	// The `@as` here works around a bug in the C backend.
2290	mem.sort(Entry, entries, @as([]const elf.Elf64.Phdr, phdrs.items), Entry.lessThan);
2291
2292	const backlinks = try gpa.alloc(u16, entries.len);
2293	defer gpa.free(backlinks);
2294	const slice = try phdrs.toOwnedSlice(gpa);
2295	defer gpa.free(slice);
2296	try phdrs.resize(gpa, slice.len);
2297
2298	for (entries, phdrs.items, 0..) |entry, *phdr, i| {
2299	backlinks[entry.phndx] = @intCast(i);
2300	phdr.* = slice[entry.phndx];
2301	}
2302
2303	inline for (@typeInfo(ProgramHeaderIndexes).@"struct".field_names) |field_name| {
2304	if (@field(special_indexes, field_name).int()) |special_index| {
2305	@field(special_indexes, field_name) = @fromBackingInt(@intCast(backlinks[special_index]));
2306	}
2307	}
2308
2309	for (section_indexes) |*opt_phndx| {
2310	if (opt_phndx.int()) |index| {
2311	opt_phndx.* = @fromBackingInt(@intCast(backlinks[index]));
2312	}
2313	}
2314	}
2315
2316	fn shdrRank(shdr: elf.Elf64_Shdr, shstrtab: []const u8) u8 {
2317	const name = shString(shstrtab, shdr.sh_name);
2318	const flags = shdr.sh_flags;
2319
2320	switch (shdr.sh_type) {
2321	elf.SHT_NULL => return 0,
2322	elf.SHT_DYNSYM => return 2,
2323	elf.SHT_HASH => return 3,
2324	elf.SHT_GNU_HASH => return 3,
2325	elf.SHT_GNU_VERSYM => return 4,
2326	elf.SHT_GNU_VERDEF => return 4,
2327	elf.SHT_GNU_VERNEED => return 4,
2328
2329	elf.SHT_PREINIT_ARRAY,
2330	elf.SHT_INIT_ARRAY,
2331	elf.SHT_FINI_ARRAY,
2332	=> return 0xf1,
2333
2334	elf.SHT_DYNAMIC => return 0xf2,
2335
2336	elf.SHT_RELA, elf.SHT_GROUP => return 0xf,
2337
2338	elf.SHT_PROGBITS => if (flags & elf.SHF_ALLOC != 0) {
2339	if (flags & elf.SHF_EXECINSTR != 0) {
2340	return 0xf0;
2341	} else if (flags & elf.SHF_WRITE != 0) {
2342	return if (flags & elf.SHF_TLS != 0) 0xf3 else 0xf5;
2343	} else if (mem.eql(u8, name, ".interp")) {
2344	return 1;
2345	} else if (mem.startsWith(u8, name, ".eh_frame")) {
2346	return 0xe1;
2347	} else {
2348	return 0xe0;
2349	}
2350	} else {
2351	if (mem.startsWith(u8, name, ".debug")) {
2352	return 0xf7;
2353	} else {
2354	return 0xf8;
2355	}
2356	},
2357	elf.SHT_X86_64_UNWIND => return 0xe1,
2358
2359	elf.SHT_NOBITS => return if (flags & elf.SHF_TLS != 0) 0xf4 else 0xf6,
2360	elf.SHT_SYMTAB => return 0xf9,
2361	elf.SHT_STRTAB => return if (mem.eql(u8, name, ".dynstr")) 0x4 else 0xfa,
2362	else => return 0xff,
2363	}
2364	}
2365
2366	pub fn sortShdrs(
2367	gpa: Allocator,
2368	section_indexes: *SectionIndexes,
2369	sections: *std.MultiArrayList(Section),
2370	shstrtab: []const u8,
2371	merge_sections: []Merge.Section,
2372	comdat_group_sections: []GroupSection,
2373	zig_object_ptr: ?*ZigObject,
2374	files: std.MultiArrayList(File.Entry),
2375	) !void {
2376	const Entry = struct {
2377	shndx: u32,
2378
2379	const Context = struct {
2380	shdrs: []const elf.Elf64_Shdr,
2381	shstrtab: []const u8,
2382	};
2383
2384	pub fn lessThan(ctx: Context, lhs: @This(), rhs: @This()) bool {
2385	const lhs_rank = shdrRank(ctx.shdrs[lhs.shndx], ctx.shstrtab);
2386	const rhs_rank = shdrRank(ctx.shdrs[rhs.shndx], ctx.shstrtab);
2387	if (lhs_rank == rhs_rank) {
2388	const lhs_name = shString(ctx.shstrtab, ctx.shdrs[lhs.shndx].sh_name);
2389	const rhs_name = shString(ctx.shstrtab, ctx.shdrs[rhs.shndx].sh_name);
2390	return std.mem.lessThan(u8, lhs_name, rhs_name);
2391	}
2392	return lhs_rank < rhs_rank;
2393	}
2394	};
2395
2396	const shdrs = sections.items(.shdr);
2397
2398	const entries = try gpa.alloc(Entry, shdrs.len);
2399	defer gpa.free(entries);
2400	for (entries, 0..shdrs.len) |*entry, shndx| {
2401	entry.* = .{ .shndx = @intCast(shndx) };
2402	}
2403
2404	const sort_context: Entry.Context = .{
2405	.shdrs = shdrs,
2406	.shstrtab = shstrtab,
2407	};
2408	mem.sortUnstable(Entry, entries, sort_context, Entry.lessThan);
2409
2410	const backlinks = try gpa.alloc(u32, entries.len);
2411	defer gpa.free(backlinks);
2412	{
2413	var slice = sections.toOwnedSlice();
2414	defer slice.deinit(gpa);
2415	try sections.resize(gpa, slice.len);
2416
2417	for (entries, 0..) |entry, i| {
2418	backlinks[entry.shndx] = @intCast(i);
2419	sections.set(i, slice.get(entry.shndx));
2420	}
2421	}
2422
2423	inline for (@typeInfo(SectionIndexes).@"struct".field_names) |field_name| {
2424	if (@field(section_indexes, field_name)) |special_index| {
2425	@field(section_indexes, field_name) = backlinks[special_index];
2426	}
2427	}
2428
2429	for (merge_sections) |*msec| {
2430	msec.output_section_index = backlinks[msec.output_section_index];
2431	}
2432
2433	const slice = sections.slice();
2434	for (slice.items(.shdr), slice.items(.atom_list_2)) |*shdr, *atom_list| {
2435	atom_list.output_section_index = backlinks[atom_list.output_section_index];
2436	for (atom_list.atoms.keys()) |ref| {
2437	fileLookup(files, ref.file, zig_object_ptr).?.atom(ref.index).?.output_section_index = atom_list.output_section_index;
2438	}
2439	if (shdr.sh_type == elf.SHT_RELA) {
2440	shdr.sh_link = section_indexes.symtab.?;
2441	shdr.sh_info = backlinks[shdr.sh_info];
2442	}
2443	}
2444
2445	if (zig_object_ptr) |zo| zo.resetShdrIndexes(backlinks);
2446
2447	for (comdat_group_sections) |*cg| {
2448	cg.shndx = backlinks[cg.shndx];
2449	}
2450
2451	if (section_indexes.symtab) |index| {
2452	const shdr = &slice.items(.shdr)[index];
2453	shdr.sh_link = section_indexes.strtab.?;
2454	}
2455
2456	if (section_indexes.dynamic) |index| {
2457	const shdr = &slice.items(.shdr)[index];
2458	shdr.sh_link = section_indexes.dynstrtab.?;
2459	}
2460
2461	if (section_indexes.dynsymtab) |index| {
2462	const shdr = &slice.items(.shdr)[index];
2463	shdr.sh_link = section_indexes.dynstrtab.?;
2464	}
2465
2466	if (section_indexes.hash) |index| {
2467	const shdr = &slice.items(.shdr)[index];
2468	shdr.sh_link = section_indexes.dynsymtab.?;
2469	}
2470
2471	if (section_indexes.gnu_hash) |index| {
2472	const shdr = &slice.items(.shdr)[index];
2473	shdr.sh_link = section_indexes.dynsymtab.?;
2474	}
2475
2476	if (section_indexes.versym) |index| {
2477	const shdr = &slice.items(.shdr)[index];
2478	shdr.sh_link = section_indexes.dynsymtab.?;
2479	}
2480
2481	if (section_indexes.verneed) |index| {
2482	const shdr = &slice.items(.shdr)[index];
2483	shdr.sh_link = section_indexes.dynstrtab.?;
2484	}
2485
2486	if (section_indexes.rela_dyn) |index| {
2487	const shdr = &slice.items(.shdr)[index];
2488	shdr.sh_link = section_indexes.dynsymtab orelse 0;
2489	}
2490
2491	if (section_indexes.rela_plt) |index| {
2492	const shdr = &slice.items(.shdr)[index];
2493	shdr.sh_link = section_indexes.dynsymtab.?;
2494	shdr.sh_info = section_indexes.plt.?;
2495	}
2496
2497	if (section_indexes.eh_frame_rela) |index| {
2498	const shdr = &slice.items(.shdr)[index];
2499	shdr.sh_link = section_indexes.symtab.?;
2500	shdr.sh_info = section_indexes.eh_frame.?;
2501	}
2502	}
2503
2504	fn updateSectionSizes(self: *Elf) !void {
2505	const slice = self.sections.slice();
2506	for (slice.items(.shdr), slice.items(.atom_list_2)) |shdr, *atom_list| {
2507	if (atom_list.atoms.keys().len == 0) continue;
2508	if (!atom_list.dirty) continue;
2509	if (self.requiresThunks() and shdr.sh_flags & elf.SHF_EXECINSTR != 0) continue;
2510	atom_list.updateSize(self);
2511	try atom_list.allocate(self);
2512	atom_list.dirty = false;
2513	}
2514
2515	if (self.requiresThunks()) {
2516	for (slice.items(.shdr), slice.items(.atom_list_2)) |shdr, *atom_list| {
2517	if (shdr.sh_flags & elf.SHF_EXECINSTR == 0) continue;
2518	if (atom_list.atoms.keys().len == 0) continue;
2519	if (!atom_list.dirty) continue;
2520
2521	// Create jump/branch range extenders if needed.
2522	try self.createThunks(atom_list);
2523	try atom_list.allocate(self);
2524	atom_list.dirty = false;
2525	}
2526
2527	// This might not be needed if there was a link from Atom/Thunk to AtomList.
2528	for (self.thunks.items) |*th| {
2529	th.value += slice.items(.atom_list_2)[th.output_section_index].value;
2530	}
2531	}
2532
2533	const shdrs = slice.items(.shdr);
2534	if (self.section_indexes.eh_frame) |index| {
2535	shdrs[index].sh_size = try eh_frame.calcEhFrameSize(self);
2536	}
2537
2538	if (self.section_indexes.eh_frame_hdr) |index| {
2539	shdrs[index].sh_size = eh_frame.calcEhFrameHdrSize(self);
2540	}
2541
2542	if (self.section_indexes.got) |index| {
2543	shdrs[index].sh_size = self.got.size(self);
2544	}
2545
2546	if (self.section_indexes.plt) |index| {
2547	shdrs[index].sh_size = self.plt.size(self);
2548	}
2549
2550	if (self.section_indexes.got_plt) |index| {
2551	shdrs[index].sh_size = self.got_plt.size(self);
2552	}
2553
2554	if (self.section_indexes.plt_got) |index| {
2555	shdrs[index].sh_size = self.plt_got.size(self);
2556	}
2557
2558	if (self.section_indexes.rela_dyn) |shndx| {
2559	var num = self.got.numRela(self) + self.copy_rel.numRela();
2560	if (self.zigObjectPtr()) |zig_object| {
2561	num += zig_object.num_dynrelocs;
2562	}
2563	for (self.objects.items) |index| {
2564	num += self.file(index).?.object.num_dynrelocs;
2565	}
2566	shdrs[shndx].sh_size = num * @sizeOf(elf.Elf64_Rela);
2567	}
2568
2569	if (self.section_indexes.rela_plt) |index| {
2570	shdrs[index].sh_size = self.plt.numRela() * @sizeOf(elf.Elf64_Rela);
2571	}
2572
2573	if (self.section_indexes.copy_rel) |index| {
2574	try self.copy_rel.updateSectionSize(index, self);
2575	}
2576
2577	if (self.section_indexes.interp) |index| {
2578	shdrs[index].sh_size = self.getTarget().dynamic_linker.get().?.len + 1;
2579	}
2580
2581	if (self.section_indexes.hash) |index| {
2582	shdrs[index].sh_size = self.hash.size();
2583	}
2584
2585	if (self.section_indexes.gnu_hash) |index| {
2586	shdrs[index].sh_size = self.gnu_hash.size();
2587	}
2588
2589	if (self.section_indexes.dynamic) |index| {
2590	shdrs[index].sh_size = self.dynamic.size(self);
2591	}
2592
2593	if (self.section_indexes.dynsymtab) |index| {
2594	shdrs[index].sh_size = self.dynsym.size();
2595	}
2596
2597	if (self.section_indexes.dynstrtab) |index| {
2598	shdrs[index].sh_size = self.dynstrtab.items.len;
2599	}
2600
2601	if (self.section_indexes.versym) |index| {
2602	shdrs[index].sh_size = self.versym.items.len * @sizeOf(elf.Versym);
2603	}
2604
2605	if (self.section_indexes.verneed) |index| {
2606	shdrs[index].sh_size = self.verneed.size();
2607	}
2608
2609	try self.updateSymtabSize();
2610	self.updateShStrtabSize();
2611	}
2612
2613	pub fn updateShStrtabSize(self: *Elf) void {
2614	if (self.section_indexes.shstrtab) |index| {
2615	self.sections.items(.shdr)[index].sh_size = self.shstrtab.items.len;
2616	}
2617	}
2618
2619	fn shdrToPhdrFlags(sh_flags: u64) u32 {
2620	const write = sh_flags & elf.SHF_WRITE != 0;
2621	const exec = sh_flags & elf.SHF_EXECINSTR != 0;
2622	var out_flags: u32 = elf.PF_R;
2623	if (write) out_flags |= elf.PF_W;
2624	if (exec) out_flags |= elf.PF_X;
2625	return out_flags;
2626	}
2627
2628	/// Returns maximum number of program headers that may be emitted by the linker.
2629	/// (This is an upper bound so that we can reserve enough space for the header and progam header
2630	/// table without running out of space and being forced to move things around.)
2631	fn getMaxNumberOfPhdrs() u64 {
2632	// The estimated maximum number of segments the linker can emit for input sections are:
2633	var num: u64 = max_number_of_object_segments;
2634	// Any other non-loadable program headers, including TLS, DYNAMIC, GNU_STACK, GNU_EH_FRAME, INTERP:
2635	num += max_number_of_special_phdrs;
2636	// PHDR program header and corresponding read-only load segment:
2637	num += 2;
2638	return num;
2639	}
2640
2641	fn addLoadPhdrs(self: *Elf) error{OutOfMemory}!void {
2642	for (self.sections.items(.shdr)) |shdr| {
2643	if (shdr.sh_type == elf.SHT_NULL) continue;
2644	if (shdr.sh_flags & elf.SHF_ALLOC == 0) continue;
2645	const flags = shdrToPhdrFlags(shdr.sh_flags);
2646	if (self.getPhdr(.{ .flags = flags, .type = @backingInt(elf.PT.LOAD) }) == .none) {
2647	_ = try self.addPhdr(.{ .flags = flags, .type = @backingInt(elf.PT.LOAD) });
2648	}
2649	}
2650	}
2651
2652	/// Allocates PHDR table in virtual memory and in file.
2653	fn allocatePhdrTable(self: *Elf) error{OutOfMemory}!void {
2654	const diags = &self.base.comp.link_diags;
2655	const phdr_table = &self.phdrs.items[self.phdr_indexes.table.int().?];
2656	const phdr_table_load = &self.phdrs.items[self.phdr_indexes.table_load.int().?];
2657
2658	const ehsize: u64 = switch (self.ptr_width) {
2659	.p32 => @sizeOf(elf.Elf32_Ehdr),
2660	.p64 => @sizeOf(elf.Elf64_Ehdr),
2661	};
2662	const phsize: u64 = switch (self.ptr_width) {
2663	.p32 => @sizeOf(elf.Elf32.Phdr),
2664	.p64 => @sizeOf(elf.Elf64.Phdr),
2665	};
2666	const needed_size = self.phdrs.items.len * phsize;
2667	const available_space = self.allocatedSize(phdr_table.offset);
2668
2669	if (needed_size > available_space) {
2670	// In this case, we have two options:
2671	// 1. increase the available padding for EHDR + PHDR table so that we don't overflow it
2672	// (revisit getMaxNumberOfPhdrs())
2673	// 2. shift everything in file to free more space for EHDR + PHDR table
2674	// TODO verify `getMaxNumberOfPhdrs()` is accurate and convert this into no-op
2675	var err = try diags.addErrorWithNotes(1);
2676	try err.addMsg("fatal linker error: not enough space reserved for EHDR and PHDR table", .{});
2677	err.addNote("required 0x{x}, available 0x{x}", .{ needed_size, available_space });
2678	}
2679
2680	phdr_table_load.filesz = needed_size + ehsize;
2681	phdr_table_load.memsz = needed_size + ehsize;
2682	phdr_table.filesz = needed_size;
2683	phdr_table.memsz = needed_size;
2684	}
2685
2686	/// Allocates alloc sections and creates load segments for sections
2687	/// extracted from input object files.
2688	pub fn allocateAllocSections(self: *Elf) !void {
2689	// We use this struct to track maximum alignment of all TLS sections.
2690	// According to https://github.com/rui314/mold/commit/bd46edf3f0fe9e1a787ea453c4657d535622e61f in mold,
2691	// in-file offsets have to be aligned against the start of TLS program header.
2692	// If that's not ensured, then in a multi-threaded context, TLS variables across a shared object
2693	// boundary may not get correctly loaded at an aligned address.
2694	const Align = struct {
2695	tls_start_align: u64 = 1,
2696	first_tls_index: ?usize = null,
2697
2698	fn isFirstTlsShdr(this: @This(), other: usize) bool {
2699	if (this.first_tls_index) |index| return index == other;
2700	return false;
2701	}
2702
2703	fn @"align"(this: @This(), index: usize, sh_addralign: u64, addr: u64) u64 {
2704	const alignment = if (this.isFirstTlsShdr(index)) this.tls_start_align else sh_addralign;
2705	return mem.alignForward(u64, addr, alignment);
2706	}
2707	};
2708
2709	const slice = self.sections.slice();
2710	var alignment = Align{};
2711	for (slice.items(.shdr), 0..) |shdr, i| {
2712	if (shdr.sh_type == elf.SHT_NULL) continue;
2713	if (shdr.sh_flags & elf.SHF_TLS == 0) continue;
2714	if (alignment.first_tls_index == null) alignment.first_tls_index = i;
2715	alignment.tls_start_align = @max(alignment.tls_start_align, shdr.sh_addralign);
2716	}
2717
2718	// Next, calculate segment covers by scanning all alloc sections.
2719	// If a section matches segment flags with the preceeding section,
2720	// we put it in the same segment. Otherwise, we create a new cover.
2721	// This algorithm is simple but suboptimal in terms of space re-use:
2722	// normally we would also take into account any gaps in allocated
2723	// virtual and file offsets. However, the simple one will do for one
2724	// as we are more interested in quick turnaround and compatibility
2725	// with `findFreeSpace` mechanics than anything else.
2726	const Cover = std.array_list.Managed(u32);
2727	const gpa = self.base.comp.gpa;
2728	var covers: [max_number_of_object_segments]Cover = undefined;
2729	for (&covers) |*cover| {
2730	cover.* = Cover.init(gpa);
2731	}
2732	defer for (&covers) |*cover| {
2733	cover.deinit();
2734	};
2735
2736	for (slice.items(.shdr), 0..) |shdr, shndx| {
2737	if (shdr.sh_type == elf.SHT_NULL) continue;
2738	if (shdr.sh_flags & elf.SHF_ALLOC == 0) continue;
2739	const flags = shdrToPhdrFlags(shdr.sh_flags);
2740	try covers[flags - 1].append(@intCast(shndx));
2741	}
2742
2743	// Now we can proceed with allocating the sections in virtual memory.
2744	// As the base address we take the end address of the PHDR table.
2745	// When allocating we first find the largest required alignment
2746	// of any section that is contained in a cover and use it to align
2747	// the start address of the segement (and first section).
2748	const phdr_table = &self.phdrs.items[self.phdr_indexes.table_load.int().?];
2749	var addr = phdr_table.vaddr + phdr_table.memsz;
2750
2751	for (covers) |cover| {
2752	if (cover.items.len == 0) continue;
2753
2754	var @"align": u64 = self.page_size;
2755	for (cover.items) |shndx| {
2756	const shdr = slice.items(.shdr)[shndx];
2757	if (shdr.sh_type == elf.SHT_NOBITS and shdr.sh_flags & elf.SHF_TLS != 0) continue;
2758	@"align" = @max(@"align", shdr.sh_addralign);
2759	}
2760
2761	addr = mem.alignForward(u64, addr, @"align");
2762
2763	var memsz: u64 = 0;
2764	var filesz: u64 = 0;
2765	var i: usize = 0;
2766	while (i < cover.items.len) : (i += 1) {
2767	const shndx = cover.items[i];
2768	const shdr = &slice.items(.shdr)[shndx];
2769	if (shdr.sh_type == elf.SHT_NOBITS and shdr.sh_flags & elf.SHF_TLS != 0) {
2770	// .tbss is a little special as it's used only by the loader meaning it doesn't
2771	// need to be actually mmap'ed at runtime. We still need to correctly increment
2772	// the addresses of every TLS zerofill section tho. Thus, we hack it so that
2773	// we increment the start address like normal, however, after we are done,
2774	// the next ALLOC section will get its start address allocated within the same
2775	// range as the .tbss sections. We will get something like this:
2776	//
2777	// ...
2778	// .tbss 0x10
2779	// .tcommon 0x20
2780	// .data 0x10
2781	// ...
2782	var tbss_addr = addr;
2783	while (i < cover.items.len and
2784	slice.items(.shdr)[cover.items[i]].sh_type == elf.SHT_NOBITS and
2785	slice.items(.shdr)[cover.items[i]].sh_flags & elf.SHF_TLS != 0) : (i += 1)
2786	{
2787	const tbss_shndx = cover.items[i];
2788	const tbss_shdr = &slice.items(.shdr)[tbss_shndx];
2789	tbss_addr = alignment.@"align"(tbss_shndx, tbss_shdr.sh_addralign, tbss_addr);
2790	tbss_shdr.sh_addr = tbss_addr;
2791	tbss_addr += tbss_shdr.sh_size;
2792	}
2793	i -= 1;
2794	continue;
2795	}
2796	const next = alignment.@"align"(shndx, shdr.sh_addralign, addr);
2797	const padding = next - addr;
2798	addr = next;
2799	shdr.sh_addr = addr;
2800	if (shdr.sh_type != elf.SHT_NOBITS) {
2801	filesz += padding + shdr.sh_size;
2802	}
2803	memsz += padding + shdr.sh_size;
2804	addr += shdr.sh_size;
2805	}
2806
2807	const first = slice.items(.shdr)[cover.items[0]];
2808	const phndx = self.getPhdr(.{ .type = @backingInt(elf.PT.LOAD), .flags = shdrToPhdrFlags(first.sh_flags) }).unwrap().?;
2809	const phdr = &self.phdrs.items[phndx.int()];
2810	const allocated_size = self.allocatedSize(phdr.offset);
2811	if (filesz > allocated_size) {
2812	const old_offset = phdr.offset;
2813	phdr.offset = 0;
2814	var new_offset = try self.findFreeSpace(filesz, @"align");
2815	phdr.offset = new_offset;
2816
2817	log.debug("moving phdr({d}) from 0x{x} to 0x{x}", .{ phndx, old_offset, new_offset });
2818
2819	for (cover.items) |shndx| {
2820	const shdr = &slice.items(.shdr)[shndx];
2821	slice.items(.phndx)[shndx] = phndx.toOptional();
2822	if (shdr.sh_type == elf.SHT_NOBITS) {
2823	shdr.sh_offset = 0;
2824	continue;
2825	}
2826	new_offset = alignment.@"align"(shndx, shdr.sh_addralign, new_offset);
2827
2828	log.debug("moving {s} from 0x{x} to 0x{x}", .{
2829	self.getShString(shdr.sh_name),
2830	shdr.sh_offset,
2831	new_offset,
2832	});
2833
2834	if (shdr.sh_offset > 0) {
2835	// Get size actually commited to the output file.
2836	const existing_size = self.sectionSize(shndx);
2837	try self.base.copyRangeAll(shdr.sh_offset, new_offset, existing_size);
2838	}
2839
2840	shdr.sh_offset = new_offset;
2841	new_offset += shdr.sh_size;
2842	}
2843	}
2844
2845	phdr.vaddr = first.sh_addr;
2846	phdr.paddr = first.sh_addr;
2847	phdr.memsz = memsz;
2848	phdr.filesz = filesz;
2849	phdr.@"align" = @"align";
2850
2851	addr = mem.alignForward(u64, addr, self.page_size);
2852	}
2853	}
2854
2855	/// Allocates non-alloc sections (debug info, symtabs, etc.).
2856	pub fn allocateNonAllocSections(self: *Elf) !void {
2857	for (self.sections.items(.shdr), 0..) |*shdr, shndx| {
2858	if (shdr.sh_type == elf.SHT_NULL) continue;
2859	if (shdr.sh_flags & elf.SHF_ALLOC != 0) continue;
2860	const needed_size = shdr.sh_size;
2861	if (needed_size > self.allocatedSize(shdr.sh_offset)) {
2862	shdr.sh_size = 0;
2863	const new_offset = try self.findFreeSpace(needed_size, shdr.sh_addralign);
2864
2865	log.debug("moving {s} from 0x{x} to 0x{x}", .{
2866	self.getShString(shdr.sh_name),
2867	shdr.sh_offset,
2868	new_offset,
2869	});
2870
2871	if (shdr.sh_offset > 0) {
2872	const existing_size = self.sectionSize(@intCast(shndx));
2873	try self.base.copyRangeAll(shdr.sh_offset, new_offset, existing_size);
2874	}
2875
2876	shdr.sh_offset = new_offset;
2877	shdr.sh_size = needed_size;
2878	}
2879	}
2880	}
2881
2882	fn allocateSpecialPhdrs(self: *Elf) void {
2883	const slice = self.sections.slice();
2884
2885	for (&[_]struct { OptionalProgramHeaderIndex, ?u32 }{
2886	.{ self.phdr_indexes.interp, self.section_indexes.interp },
2887	.{ self.phdr_indexes.dynamic, self.section_indexes.dynamic },
2888	.{ self.phdr_indexes.gnu_eh_frame, self.section_indexes.eh_frame_hdr },
2889	}) |pair| {
2890	if (pair[0].int()) |index| {
2891	const shdr = slice.items(.shdr)[pair[1].?];
2892	const phdr = &self.phdrs.items[index];
2893	phdr.@"align" = shdr.sh_addralign;
2894	phdr.offset = shdr.sh_offset;
2895	phdr.vaddr = shdr.sh_addr;
2896	phdr.paddr = shdr.sh_addr;
2897	phdr.filesz = shdr.sh_size;
2898	phdr.memsz = shdr.sh_size;
2899	}
2900	}
2901
2902	// Set the TLS segment boundaries.
2903	// We assume TLS sections are laid out contiguously and that there is
2904	// a single TLS segment.
2905	if (self.phdr_indexes.tls.int()) |index| {
2906	const shdrs = slice.items(.shdr);
2907	const phdr = &self.phdrs.items[index];
2908	var shndx: u32 = 0;
2909	while (shndx < shdrs.len) {
2910	const shdr = shdrs[shndx];
2911	if (shdr.sh_flags & elf.SHF_TLS == 0) {
2912	shndx += 1;
2913	continue;
2914	}
2915	phdr.offset = shdr.sh_offset;
2916	phdr.vaddr = shdr.sh_addr;
2917	phdr.paddr = shdr.sh_addr;
2918	phdr.@"align" = shdr.sh_addralign;
2919	shndx += 1;
2920	phdr.@"align" = @max(phdr.@"align", shdr.sh_addralign);
2921	if (shdr.sh_type != elf.SHT_NOBITS) {
2922	phdr.filesz = shdr.sh_offset + shdr.sh_size - phdr.offset;
2923	}
2924	phdr.memsz = shdr.sh_addr + shdr.sh_size - phdr.vaddr;
2925
2926	while (shndx < shdrs.len) : (shndx += 1) {
2927	const next = shdrs[shndx];
2928	if (next.sh_flags & elf.SHF_TLS == 0) break;
2929	phdr.@"align" = @max(phdr.@"align", next.sh_addralign);
2930	if (next.sh_type != elf.SHT_NOBITS) {
2931	phdr.filesz = next.sh_offset + next.sh_size - phdr.offset;
2932	}
2933	phdr.memsz = next.sh_addr + next.sh_size - phdr.vaddr;
2934	}
2935	}
2936	}
2937	}
2938
2939	fn writeAtoms(self: *Elf) !void {
2940	const gpa = self.base.comp.gpa;
2941
2942	var undefs: std.array_hash_map.Auto(SymbolResolver.Index, std.array_list.Managed(Ref)) = .empty;
2943	defer {
2944	for (undefs.values()) |*refs| refs.deinit();
2945	undefs.deinit(gpa);
2946	}
2947
2948	var buffer: std.Io.Writer.Allocating = .init(gpa);
2949	defer buffer.deinit();
2950
2951	const slice = self.sections.slice();
2952	var has_reloc_errors = false;
2953	for (slice.items(.shdr), slice.items(.atom_list_2)) |shdr, atom_list| {
2954	if (shdr.sh_type == elf.SHT_NOBITS) continue;
2955	if (atom_list.atoms.keys().len == 0) continue;
2956	atom_list.write(&buffer, &undefs, self) catch |err| switch (err) {
2957	error.UnsupportedCpuArch => {
2958	try self.reportUnsupportedCpuArch();
2959	return error.AlreadyReported;
2960	},
2961	error.RelocFailure, error.RelaxFailure => has_reloc_errors = true,
2962	else => |e| return e,
2963	};
2964	}
2965
2966	try self.reportUndefinedSymbols(&undefs);
2967	if (has_reloc_errors) return error.AlreadyReported;
2968
2969	if (self.requiresThunks()) {
2970	for (self.thunks.items) |th| {
2971	const thunk_size = th.size(self);
2972	try buffer.ensureUnusedCapacity(thunk_size);
2973	const shdr = slice.items(.shdr)[th.output_section_index];
2974	const offset = @as(u64, @intCast(th.value)) + shdr.sh_offset;
2975	try th.write(self, &buffer.writer);
2976	assert(buffer.written().len == thunk_size);
2977	try self.pwriteAll(buffer.written(), offset);
2978	buffer.clearRetainingCapacity();
2979	}
2980	}
2981	}
2982
2983	pub fn updateSymtabSize(self: *Elf) !void {
2984	var nlocals: u32 = 0;
2985	var nglobals: u32 = 0;
2986	var strsize: u32 = 0;
2987
2988	const gpa = self.base.comp.gpa;
2989	const shared_objects = self.shared_objects.values();
2990
2991	var files = std.array_list.Managed(File.Index).init(gpa);
2992	defer files.deinit();
2993	try files.ensureTotalCapacityPrecise(self.objects.items.len + shared_objects.len + 2);
2994
2995	if (self.zig_object_index) |index| files.appendAssumeCapacity(index);
2996	for (self.objects.items) |index| files.appendAssumeCapacity(index);
2997	for (shared_objects) |index| files.appendAssumeCapacity(index);
2998	if (self.linker_defined_index) |index| files.appendAssumeCapacity(index);
2999
3000	// Section symbols
3001	nlocals += @intCast(self.sections.slice().len);
3002
3003	if (self.requiresThunks()) for (self.thunks.items) |*th| {
3004	th.output_symtab_ctx.reset();
3005	th.output_symtab_ctx.ilocal = nlocals;
3006	th.calcSymtabSize(self);
3007	nlocals += th.output_symtab_ctx.nlocals;
3008	strsize += th.output_symtab_ctx.strsize;
3009	};
3010
3011	for (files.items) |index| {
3012	const file_ptr = self.file(index).?;
3013	const ctx = switch (file_ptr) {
3014	inline else => |x| &x.output_symtab_ctx,
3015	};
3016	ctx.reset();
3017	ctx.ilocal = nlocals;
3018	ctx.iglobal = nglobals;
3019	try file_ptr.updateSymtabSize(self);
3020	nlocals += ctx.nlocals;
3021	nglobals += ctx.nglobals;
3022	strsize += ctx.strsize;
3023	}
3024
3025	if (self.section_indexes.got) |_| {
3026	self.got.output_symtab_ctx.reset();
3027	self.got.output_symtab_ctx.ilocal = nlocals;
3028	self.got.updateSymtabSize(self);
3029	nlocals += self.got.output_symtab_ctx.nlocals;
3030	strsize += self.got.output_symtab_ctx.strsize;
3031	}
3032
3033	if (self.section_indexes.plt) |_| {
3034	self.plt.output_symtab_ctx.reset();
3035	self.plt.output_symtab_ctx.ilocal = nlocals;
3036	self.plt.updateSymtabSize(self);
3037	nlocals += self.plt.output_symtab_ctx.nlocals;
3038	strsize += self.plt.output_symtab_ctx.strsize;
3039	}
3040
3041	if (self.section_indexes.plt_got) |_| {
3042	self.plt_got.output_symtab_ctx.reset();
3043	self.plt_got.output_symtab_ctx.ilocal = nlocals;
3044	self.plt_got.updateSymtabSize(self);
3045	nlocals += self.plt_got.output_symtab_ctx.nlocals;
3046	strsize += self.plt_got.output_symtab_ctx.strsize;
3047	}
3048
3049	for (files.items) |index| {
3050	const file_ptr = self.file(index).?;
3051	const ctx = switch (file_ptr) {
3052	inline else => |x| &x.output_symtab_ctx,
3053	};
3054	ctx.iglobal += nlocals;
3055	}
3056
3057	const slice = self.sections.slice();
3058	const symtab_shdr = &slice.items(.shdr)[self.section_indexes.symtab.?];
3059	symtab_shdr.sh_info = nlocals;
3060	symtab_shdr.sh_link = self.section_indexes.strtab.?;
3061
3062	const sym_size: u64 = switch (self.ptr_width) {
3063	.p32 => @sizeOf(elf.Elf32_Sym),
3064	.p64 => @sizeOf(elf.Elf64_Sym),
3065	};
3066	const needed_size = (nlocals + nglobals) * sym_size;
3067	symtab_shdr.sh_size = needed_size;
3068
3069	const strtab = &slice.items(.shdr)[self.section_indexes.strtab.?];
3070	strtab.sh_size = strsize + 1;
3071	}
3072
3073	fn writeSyntheticSections(self: *Elf) !void {
3074	const gpa = self.base.comp.gpa;
3075	const slice = self.sections.slice();
3076
3077	if (self.section_indexes.interp) |shndx| {
3078	var buffer: [256]u8 = undefined;
3079	const interp = self.getTarget().dynamic_linker.get().?;
3080	@memcpy(buffer[0..interp.len], interp);
3081	buffer[interp.len] = 0;
3082	const contents = buffer[0 .. interp.len + 1];
3083	const shdr = slice.items(.shdr)[shndx];
3084	assert(shdr.sh_size == contents.len);
3085	try self.pwriteAll(contents, shdr.sh_offset);
3086	}
3087
3088	if (self.section_indexes.hash) |shndx| {
3089	const shdr = slice.items(.shdr)[shndx];
3090	try self.pwriteAll(self.hash.buffer.items, shdr.sh_offset);
3091	}
3092
3093	if (self.section_indexes.gnu_hash) |shndx| {
3094	const shdr = slice.items(.shdr)[shndx];
3095	var aw: std.Io.Writer.Allocating = .init(gpa);
3096	try aw.ensureUnusedCapacity(self.gnu_hash.size());
3097	defer aw.deinit();
3098	try self.gnu_hash.write(self, &aw.writer);
3099	try self.pwriteAll(aw.written(), shdr.sh_offset);
3100	}
3101
3102	if (self.section_indexes.versym) |shndx| {
3103	const shdr = slice.items(.shdr)[shndx];
3104	try self.pwriteAll(@ptrCast(self.versym.items), shdr.sh_offset);
3105	}
3106
3107	if (self.section_indexes.verneed) |shndx| {
3108	const shdr = slice.items(.shdr)[shndx];
3109	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, self.verneed.size());
3110	defer buffer.deinit();
3111	try self.verneed.write(&buffer.writer);
3112	try self.pwriteAll(buffer.written(), shdr.sh_offset);
3113	}
3114
3115	if (self.section_indexes.dynamic) |shndx| {
3116	const shdr = slice.items(.shdr)[shndx];
3117	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, self.dynamic.size(self));
3118	defer buffer.deinit();
3119	try self.dynamic.write(self, &buffer.writer);
3120	try self.pwriteAll(buffer.written(), shdr.sh_offset);
3121	}
3122
3123	if (self.section_indexes.dynsymtab) |shndx| {
3124	const shdr = slice.items(.shdr)[shndx];
3125	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, self.dynsym.size());
3126	defer buffer.deinit();
3127	try self.dynsym.write(self, &buffer.writer);
3128	try self.pwriteAll(buffer.written(), shdr.sh_offset);
3129	}
3130
3131	if (self.section_indexes.dynstrtab) |shndx| {
3132	const shdr = slice.items(.shdr)[shndx];
3133	try self.pwriteAll(self.dynstrtab.items, shdr.sh_offset);
3134	}
3135
3136	if (self.section_indexes.eh_frame) |shndx| {
3137	const existing_size = existing_size: {
3138	const zo = self.zigObjectPtr() orelse break :existing_size 0;
3139	const sym = zo.symbol(zo.eh_frame_index orelse break :existing_size 0);
3140	break :existing_size sym.atom(self).?.size;
3141	};
3142	const shdr = slice.items(.shdr)[shndx];
3143	const sh_size = try self.cast(usize, shdr.sh_size);
3144	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, @intCast(sh_size - existing_size));
3145	defer buffer.deinit();
3146	try eh_frame.writeEhFrame(self, &buffer.writer);
3147	assert(buffer.written().len == sh_size - existing_size);
3148	try self.pwriteAll(buffer.written(), shdr.sh_offset + existing_size);
3149	}
3150
3151	if (self.section_indexes.eh_frame_hdr) |shndx| {
3152	const shdr = slice.items(.shdr)[shndx];
3153	const sh_size = try self.cast(usize, shdr.sh_size);
3154	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, sh_size);
3155	defer buffer.deinit();
3156	try eh_frame.writeEhFrameHdr(self, &buffer.writer);
3157	try self.pwriteAll(buffer.written(), shdr.sh_offset);
3158	}
3159
3160	if (self.section_indexes.got) |index| {
3161	const shdr = slice.items(.shdr)[index];
3162	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, self.got.size(self));
3163	defer buffer.deinit();
3164	try self.got.write(self, &buffer.writer);
3165	try self.pwriteAll(buffer.written(), shdr.sh_offset);
3166	}
3167
3168	if (self.section_indexes.rela_dyn) |shndx| {
3169	const shdr = slice.items(.shdr)[shndx];
3170	try self.got.addRela(self);
3171	try self.copy_rel.addRela(self);
3172	self.sortRelaDyn();
3173	try self.pwriteAll(@ptrCast(self.rela_dyn.items), shdr.sh_offset);
3174	}
3175
3176	if (self.section_indexes.plt) |shndx| {
3177	const shdr = slice.items(.shdr)[shndx];
3178	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, self.plt.size(self));
3179	defer buffer.deinit();
3180	try self.plt.write(self, &buffer.writer);
3181	try self.pwriteAll(buffer.written(), shdr.sh_offset);
3182	}
3183
3184	if (self.section_indexes.got_plt) |shndx| {
3185	const shdr = slice.items(.shdr)[shndx];
3186	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, self.got_plt.size(self));
3187	defer buffer.deinit();
3188	try self.got_plt.write(self, &buffer.writer);
3189	try self.pwriteAll(buffer.written(), shdr.sh_offset);
3190	}
3191
3192	if (self.section_indexes.plt_got) |shndx| {
3193	const shdr = slice.items(.shdr)[shndx];
3194	var buffer = try std.Io.Writer.Allocating.initCapacity(gpa, self.plt_got.size(self));
3195	defer buffer.deinit();
3196	try self.plt_got.write(self, &buffer.writer);
3197	try self.pwriteAll(buffer.written(), shdr.sh_offset);
3198	}
3199
3200	if (self.section_indexes.rela_plt) |shndx| {
3201	const shdr = slice.items(.shdr)[shndx];
3202	try self.plt.addRela(self);
3203	try self.pwriteAll(@ptrCast(self.rela_plt.items), shdr.sh_offset);
3204	}
3205
3206	try self.writeSymtab();
3207	try self.writeShStrtab();
3208	}
3209
3210	pub fn writeShStrtab(self: *Elf) !void {
3211	if (self.section_indexes.shstrtab) |index| {
3212	const shdr = self.sections.items(.shdr)[index];
3213	log.debug("writing .shstrtab from 0x{x} to 0x{x}", .{ shdr.sh_offset, shdr.sh_offset + shdr.sh_size });
3214	try self.pwriteAll(self.shstrtab.items, shdr.sh_offset);
3215	}
3216	}
3217
3218	pub fn writeSymtab(self: *Elf) !void {
3219	const gpa = self.base.comp.gpa;
3220	const shared_objects = self.shared_objects.values();
3221
3222	const slice = self.sections.slice();
3223	const symtab_shdr = slice.items(.shdr)[self.section_indexes.symtab.?];
3224	const strtab_shdr = slice.items(.shdr)[self.section_indexes.strtab.?];
3225	const sym_size: u64 = switch (self.ptr_width) {
3226	.p32 => @sizeOf(elf.Elf32_Sym),
3227	.p64 => @sizeOf(elf.Elf64_Sym),
3228	};
3229	const nsyms = try self.cast(usize, @divExact(symtab_shdr.sh_size, sym_size));
3230
3231	log.debug("writing {d} symbols in .symtab from 0x{x} to 0x{x}", .{
3232	nsyms,
3233	symtab_shdr.sh_offset,
3234	symtab_shdr.sh_offset + symtab_shdr.sh_size,
3235	});
3236	log.debug("writing .strtab from 0x{x} to 0x{x}", .{
3237	strtab_shdr.sh_offset,
3238	strtab_shdr.sh_offset + strtab_shdr.sh_size,
3239	});
3240
3241	try self.symtab.resize(gpa, nsyms);
3242	const needed_strtab_size = try self.cast(usize, strtab_shdr.sh_size - 1);
3243	// TODO we could resize instead and in ZigObject/Object always access as slice
3244	self.strtab.clearRetainingCapacity();
3245	self.strtab.appendAssumeCapacity(0);
3246	try self.strtab.ensureUnusedCapacity(gpa, needed_strtab_size);
3247
3248	for (slice.items(.shdr), 0..) |shdr, shndx| {
3249	const out_sym = &self.symtab.items[shndx];
3250	out_sym.* = .{
3251	.st_name = 0,
3252	.st_value = shdr.sh_addr,
3253	.st_info = if (shdr.sh_type == elf.SHT_NULL) elf.STT_NOTYPE else elf.STT_SECTION,
3254	.st_shndx = @intCast(shndx),
3255	.st_size = 0,
3256	.st_other = 0,
3257	};
3258	}
3259
3260	if (self.requiresThunks()) for (self.thunks.items) |th| {
3261	th.writeSymtab(self);
3262	};
3263
3264	if (self.zigObjectPtr()) |zig_object| {
3265	zig_object.asFile().writeSymtab(self);
3266	}
3267
3268	for (self.objects.items) |index| {
3269	const file_ptr = self.file(index).?;
3270	file_ptr.writeSymtab(self);
3271	}
3272
3273	for (shared_objects) |index| {
3274	const file_ptr = self.file(index).?;
3275	file_ptr.writeSymtab(self);
3276	}
3277
3278	if (self.linkerDefinedPtr()) |obj| {
3279	obj.asFile().writeSymtab(self);
3280	}
3281
3282	if (self.section_indexes.got) |_| {
3283	self.got.writeSymtab(self);
3284	}
3285
3286	if (self.section_indexes.plt) |_| {
3287	self.plt.writeSymtab(self);
3288	}
3289
3290	if (self.section_indexes.plt_got) |_| {
3291	self.plt_got.writeSymtab(self);
3292	}
3293
3294	const foreign_endian = self.getTarget().cpu.arch.endian() != builtin.cpu.arch.endian();
3295	switch (self.ptr_width) {
3296	.p32 => {
3297	const buf = try gpa.alloc(elf.Elf32_Sym, self.symtab.items.len);
3298	defer gpa.free(buf);
3299
3300	for (buf, self.symtab.items) |*out, sym| {
3301	out.* = .{
3302	.st_name = sym.st_name,
3303	.st_info = sym.st_info,
3304	.st_other = sym.st_other,
3305	.st_shndx = sym.st_shndx,
3306	.st_value = @intCast(sym.st_value),
3307	.st_size = @intCast(sym.st_size),
3308	};
3309	if (foreign_endian) mem.byteSwapAllFields(elf.Elf32_Sym, out);
3310	}
3311	try self.pwriteAll(@ptrCast(buf), symtab_shdr.sh_offset);
3312	},
3313	.p64 => {
3314	if (foreign_endian) {
3315	for (self.symtab.items) |*sym| mem.byteSwapAllFields(elf.Elf64_Sym, sym);
3316	}
3317	try self.pwriteAll(@ptrCast(self.symtab.items), symtab_shdr.sh_offset);
3318	},
3319	}
3320
3321	try self.pwriteAll(self.strtab.items, strtab_shdr.sh_offset);
3322	}
3323
3324	/// Always 4 or 8 depending on whether this is 32-bit ELF or 64-bit ELF.
3325	pub fn ptrWidthBytes(self: Elf) u8 {
3326	return switch (self.ptr_width) {
3327	.p32 => 4,
3328	.p64 => 8,
3329	};
3330	}
3331
3332	/// Does not necessarily match `ptrWidthBytes` for example can be 2 bytes
3333	/// in a 32-bit ELF file.
3334	pub fn archPtrWidthBytes(self: Elf) u8 {
3335	return @intCast(@divExact(self.getTarget().ptrBitWidth(), 8));
3336	}
3337
3338	fn phdrTo32(phdr: elf.Elf64.Phdr) elf.Elf32.Phdr {
3339	return .{
3340	.type = phdr.type,
3341	.flags = phdr.flags,
3342	.offset = @intCast(phdr.offset),
3343	.vaddr = @intCast(phdr.vaddr),
3344	.paddr = @intCast(phdr.paddr),
3345	.filesz = @intCast(phdr.filesz),
3346	.memsz = @intCast(phdr.memsz),
3347	.@"align" = @intCast(phdr.@"align"),
3348	};
3349	}
3350
3351	fn shdrTo32(shdr: elf.Elf64_Shdr) elf.Elf32_Shdr {
3352	return .{
3353	.sh_name = shdr.sh_name,
3354	.sh_type = shdr.sh_type,
3355	.sh_flags = @as(u32, @intCast(shdr.sh_flags)),
3356	.sh_addr = @as(u32, @intCast(shdr.sh_addr)),
3357	.sh_offset = @as(u32, @intCast(shdr.sh_offset)),
3358	.sh_size = @as(u32, @intCast(shdr.sh_size)),
3359	.sh_link = shdr.sh_link,
3360	.sh_info = shdr.sh_info,
3361	.sh_addralign = @as(u32, @intCast(shdr.sh_addralign)),
3362	.sh_entsize = @as(u32, @intCast(shdr.sh_entsize)),
3363	};
3364	}
3365
3366	pub fn padToIdeal(actual_size: anytype) @TypeOf(actual_size) {
3367	return actual_size +| (actual_size / ideal_factor);
3368	}
3369
3370	/// If a target compiles other output modes as dynamic libraries,
3371	/// this function returns true for those too.
3372	pub fn isEffectivelyDynLib(self: Elf) bool {
3373	if (self.base.isDynLib()) return true;
3374	return switch (self.getTarget().os.tag) {
3375	.haiku => self.base.isExe(),
3376	else => false,
3377	};
3378	}
3379
3380	fn getPhdr(self: *Elf, opts: struct {
3381	type: u32 = 0,
3382	flags: u32 = 0,
3383	}) OptionalProgramHeaderIndex {
3384	for (self.phdrs.items, 0..) |phdr, phndx| {
3385	if (self.phdr_indexes.table_load.int()) |index| {
3386	if (phndx == index) continue;
3387	}
3388	if (@backingInt(phdr.type) == opts.type and @backingInt(phdr.flags) == opts.flags)
3389	return @fromBackingInt(@intCast(phndx));
3390	}
3391	return .none;
3392	}
3393
3394	fn addPhdr(self: *Elf, opts: struct {
3395	type: u32 = 0,
3396	flags: u32 = 0,
3397	@"align": u64 = 0,
3398	offset: u64 = 0,
3399	addr: u64 = 0,
3400	filesz: u64 = 0,
3401	memsz: u64 = 0,
3402	}) error{OutOfMemory}!ProgramHeaderIndex {
3403	const gpa = self.base.comp.gpa;
3404	const index: ProgramHeaderIndex = @fromBackingInt(@intCast(self.phdrs.items.len));
3405	try self.phdrs.append(gpa, .{
3406	.type = @fromBackingInt(opts.type),
3407	.flags = @fromBackingInt(opts.flags),
3408	.offset = opts.offset,
3409	.vaddr = opts.addr,
3410	.paddr = opts.addr,
3411	.filesz = opts.filesz,
3412	.memsz = opts.memsz,
3413	.@"align" = opts.@"align",
3414	});
3415	return index;
3416	}
3417
3418	pub fn addRelaShdr(self: *Elf, name: u32, shndx: u32) !u32 {
3419	const entsize: u64 = switch (self.ptr_width) {
3420	.p32 => @sizeOf(elf.Elf32_Rela),
3421	.p64 => @sizeOf(elf.Elf64_Rela),
3422	};
3423	const addralign: u64 = switch (self.ptr_width) {
3424	.p32 => @alignOf(elf.Elf32_Rela),
3425	.p64 => @alignOf(elf.Elf64_Rela),
3426	};
3427	return self.addSection(.{
3428	.name = name,
3429	.type = elf.SHT_RELA,
3430	.flags = elf.SHF_INFO_LINK,
3431	.entsize = entsize,
3432	.info = shndx,
3433	.addralign = addralign,
3434	});
3435	}
3436
3437	pub const AddSectionOpts = struct {
3438	name: u32 = 0,
3439	type: u32 = elf.SHT_NULL,
3440	flags: u64 = 0,
3441	link: u32 = 0,
3442	info: u32 = 0,
3443	addralign: u64 = 0,
3444	entsize: u64 = 0,
3445	};
3446
3447	pub fn addSection(self: *Elf, opts: AddSectionOpts) !u32 {
3448	const gpa = self.base.comp.gpa;
3449	const index: u32 = @intCast(try self.sections.addOne(gpa));
3450	self.sections.set(index, .{
3451	.shdr = .{
3452	.sh_name = opts.name,
3453	.sh_type = opts.type,
3454	.sh_flags = opts.flags,
3455	.sh_addr = 0,
3456	.sh_offset = 0,
3457	.sh_size = 0,
3458	.sh_link = opts.link,
3459	.sh_info = opts.info,
3460	.sh_addralign = opts.addralign,
3461	.sh_entsize = opts.entsize,
3462	},
3463	});
3464	return index;
3465	}
3466
3467	pub fn sectionByName(self: *Elf, name: [:0]const u8) ?u32 {
3468	for (self.sections.items(.shdr), 0..) |*shdr, i| {
3469	const this_name = self.getShString(shdr.sh_name);
3470	if (mem.eql(u8, this_name, name)) return @intCast(i);
3471	} else return null;
3472	}
3473
3474	const RelaDyn = struct {
3475	offset: u64,
3476	sym: u64 = 0,
3477	type: u32,
3478	addend: i64 = 0,
3479	target: ?*const Symbol = null,
3480	};
3481
3482	pub fn addRelaDyn(self: *Elf, opts: RelaDyn) !void {
3483	try self.rela_dyn.ensureUnusedCapacity(self.base.alloctor, 1);
3484	self.addRelaDynAssumeCapacity(opts);
3485	}
3486
3487	pub fn addRelaDynAssumeCapacity(self: *Elf, opts: RelaDyn) void {
3488	relocs_log.debug(" {f}: [{x} => {d}({s})] + {x}", .{
3489	relocation.fmtRelocType(opts.type, self.getTarget().cpu.arch),
3490	opts.offset,
3491	opts.sym,
3492	if (opts.target) |sym| sym.name(self) else "",
3493	opts.addend,
3494	});
3495	self.rela_dyn.appendAssumeCapacity(.{
3496	.r_offset = opts.offset,
3497	.r_info = (opts.sym << 32) | opts.type,
3498	.r_addend = opts.addend,
3499	});
3500	}
3501
3502	fn sortRelaDyn(self: *Elf) void {
3503	const Sort = struct {
3504	fn rank(rel: elf.Elf64_Rela, ctx: *Elf) u2 {
3505	const cpu_arch = ctx.getTarget().cpu.arch;
3506	const r_type = rel.r_type();
3507	const r_kind = relocation.decode(r_type, cpu_arch).?;
3508	return switch (r_kind) {
3509	.rel => 0,
3510	.irel => 2,
3511	else => 1,
3512	};
3513	}
3514
3515	pub fn lessThan(ctx: *Elf, lhs: elf.Elf64_Rela, rhs: elf.Elf64_Rela) bool {
3516	if (rank(lhs, ctx) == rank(rhs, ctx)) {
3517	if (lhs.r_sym() == rhs.r_sym()) return lhs.r_offset < rhs.r_offset;
3518	return lhs.r_sym() < rhs.r_sym();
3519	}
3520	return rank(lhs, ctx) < rank(rhs, ctx);
3521	}
3522	};
3523	mem.sort(elf.Elf64_Rela, self.rela_dyn.items, self, Sort.lessThan);
3524	}
3525
3526	pub fn calcNumIRelativeRelocs(self: *Elf) usize {
3527	var count: usize = self.num_ifunc_dynrelocs;
3528
3529	for (self.got.entries.items) |entry| {
3530	if (entry.tag != .got) continue;
3531	const sym = self.symbol(entry.ref).?;
3532	if (sym.isIFunc(self)) count += 1;
3533	}
3534
3535	return count;
3536	}
3537
3538	pub fn getStartStopBasename(self: Elf, shdr: elf.Elf64_Shdr) ?[]const u8 {
3539	const name = self.getShString(shdr.sh_name);
3540	if (shdr.sh_flags & elf.SHF_ALLOC != 0 and name.len > 0) {
3541	if (Elf.isCIdentifier(name)) return name;
3542	}
3543	return null;
3544	}
3545
3546	pub fn isCIdentifier(name: []const u8) bool {
3547	if (name.len == 0) return false;
3548	const first_c = name[0];
3549	if (!std.ascii.isAlphabetic(first_c) and first_c != '_') return false;
3550	for (name[1..]) |c| {
3551	if (!std.ascii.isAlphanumeric(c) and c != '_') return false;
3552	}
3553	return true;
3554	}
3555
3556	pub fn addThunk(self: *Elf) !Thunk.Index {
3557	const index = @as(Thunk.Index, @intCast(self.thunks.items.len));
3558	const th = try self.thunks.addOne(self.base.comp.gpa);
3559	th.* = .{};
3560	return index;
3561	}
3562
3563	pub fn thunk(self: *Elf, index: Thunk.Index) *Thunk {
3564	assert(index < self.thunks.items.len);
3565	return &self.thunks.items[index];
3566	}
3567
3568	pub fn file(self: *Elf, index: File.Index) ?File {
3569	return fileLookup(self.files, index, self.zig_object);
3570	}
3571
3572	fn fileLookup(files: std.MultiArrayList(File.Entry), index: File.Index, zig_object: ?*ZigObject) ?File {
3573	const tag = files.items(.tags)[index];
3574	return switch (tag) {
3575	.null => null,
3576	.linker_defined => .{ .linker_defined = &files.items(.data)[index].linker_defined },
3577	.zig_object => .{ .zig_object = zig_object.? },
3578	.object => .{ .object = &files.items(.data)[index].object },
3579	.shared_object => .{ .shared_object = &files.items(.data)[index].shared_object },
3580	};
3581	}
3582
3583	pub fn addFileHandle(
3584	gpa: Allocator,
3585	file_handles: *std.ArrayList(File.Handle),
3586	handle: Io.File,
3587	) Allocator.Error!File.HandleIndex {
3588	try file_handles.append(gpa, handle);
3589	return @intCast(file_handles.items.len - 1);
3590	}
3591
3592	pub fn fileHandle(self: Elf, index: File.HandleIndex) File.Handle {
3593	return self.file_handles.items[index];
3594	}
3595
3596	pub fn atom(self: *Elf, ref: Ref) ?*Atom {
3597	const file_ptr = self.file(ref.file) orelse return null;
3598	return file_ptr.atom(ref.index);
3599	}
3600
3601	pub fn group(self: *Elf, ref: Ref) *Group {
3602	return self.file(ref.file).?.group(ref.index);
3603	}
3604
3605	pub fn symbol(self: *Elf, ref: Ref) ?*Symbol {
3606	const file_ptr = self.file(ref.file) orelse return null;
3607	return file_ptr.symbol(ref.index);
3608	}
3609
3610	pub fn getGlobalSymbol(self: *Elf, name: []const u8, lib_name: ?[]const u8) !u32 {
3611	return self.zigObjectPtr().?.getGlobalSymbol(self, name, lib_name);
3612	}
3613
3614	pub fn zigObjectPtr(self: *Elf) ?*ZigObject {
3615	return self.zig_object;
3616	}
3617
3618	pub fn linkerDefinedPtr(self: *Elf) ?*LinkerDefined {
3619	const index = self.linker_defined_index orelse return null;
3620	return self.file(index).?.linker_defined;
3621	}
3622
3623	pub fn getOrCreateMergeSection(self: *Elf, name: [:0]const u8, flags: u64, @"type": u32) !Merge.Section.Index {
3624	const gpa = self.base.comp.gpa;
3625	const out_name = name: {
3626	if (self.base.isRelocatable()) break :name name;
3627	if (mem.eql(u8, name, ".rodata") or mem.startsWith(u8, name, ".rodata"))
3628	break :name if (flags & elf.SHF_STRINGS != 0) ".rodata.str" else ".rodata.cst";
3629	break :name name;
3630	};
3631	for (self.merge_sections.items, 0..) |msec, index| {
3632	if (mem.eql(u8, msec.name(self), out_name)) return @intCast(index);
3633	}
3634	const out_off = try self.insertShString(out_name);
3635	const out_flags = flags & ~@as(u64, elf.SHF_COMPRESSED | elf.SHF_GROUP);
3636	const index: Merge.Section.Index = @intCast(self.merge_sections.items.len);
3637	const msec = try self.merge_sections.addOne(gpa);
3638	msec.* = .{
3639	.name_offset = out_off,
3640	.flags = out_flags,
3641	.type = @"type",
3642	};
3643	return index;
3644	}
3645
3646	pub fn mergeSection(self: *Elf, index: Merge.Section.Index) *Merge.Section {
3647	assert(index < self.merge_sections.items.len);
3648	return &self.merge_sections.items[index];
3649	}
3650
3651	pub fn gotAddress(self: *Elf) i64 {
3652	const shndx = blk: {
3653	if (self.getTarget().cpu.arch == .x86_64 and self.section_indexes.got_plt != null)
3654	break :blk self.section_indexes.got_plt.?;
3655	break :blk if (self.section_indexes.got) |shndx| shndx else null;
3656	};
3657	return if (shndx) |index| @intCast(self.sections.items(.shdr)[index].sh_addr) else 0;
3658	}
3659
3660	pub fn tpAddress(self: *Elf) i64 {
3661	const index = self.phdr_indexes.tls.int() orelse return 0;
3662	const phdr = self.phdrs.items[index];
3663	const addr = switch (self.getTarget().cpu.arch) {
3664	.x86_64 => mem.alignForward(u64, phdr.vaddr + phdr.memsz, phdr.@"align"),
3665	.aarch64, .aarch64_be => mem.alignBackward(u64, phdr.vaddr - 16, phdr.@"align"),
3666	.riscv64, .riscv64be => phdr.vaddr,
3667	else => |arch| std.debug.panic("TODO implement getTpAddress for {s}", .{@tagName(arch)}),
3668	};
3669	return @intCast(addr);
3670	}
3671
3672	pub fn dtpAddress(self: *Elf) i64 {
3673	const index = self.phdr_indexes.tls.int() orelse return 0;
3674	const phdr = self.phdrs.items[index];
3675	return @intCast(phdr.vaddr);
3676	}
3677
3678	pub fn tlsAddress(self: *Elf) i64 {
3679	const index = self.phdr_indexes.tls.int() orelse return 0;
3680	const phdr = self.phdrs.items[index];
3681	return @intCast(phdr.vaddr);
3682	}
3683
3684	pub fn getShString(self: Elf, off: u32) [:0]const u8 {
3685	return shString(self.shstrtab.items, off);
3686	}
3687
3688	fn shString(
3689	shstrtab: []const u8,
3690	off: u32,
3691	) [:0]const u8 {
3692	const slice = shstrtab[off..];
3693	return slice[0..mem.findScalar(u8, slice, 0).? :0];
3694	}
3695
3696	pub fn insertShString(self: *Elf, name: [:0]const u8) error{OutOfMemory}!u32 {
3697	const gpa = self.base.comp.gpa;
3698	const off = @as(u32, @intCast(self.shstrtab.items.len));
3699	try self.shstrtab.ensureUnusedCapacity(gpa, name.len + 1);
3700	self.shstrtab.print(gpa, "{s}\x00", .{name}) catch unreachable;
3701	return off;
3702	}
3703
3704	pub fn getDynString(self: Elf, off: u32) [:0]const u8 {
3705	assert(off < self.dynstrtab.items.len);
3706	return mem.sliceTo(@as([*:0]const u8, @ptrCast(self.dynstrtab.items.ptr + off)), 0);
3707	}
3708
3709	pub fn insertDynString(self: *Elf, name: []const u8) error{OutOfMemory}!u32 {
3710	const gpa = self.base.comp.gpa;
3711	const off = @as(u32, @intCast(self.dynstrtab.items.len));
3712	try self.dynstrtab.ensureUnusedCapacity(gpa, name.len + 1);
3713	self.dynstrtab.print(gpa, "{s}\x00", .{name}) catch unreachable;
3714	return off;
3715	}
3716
3717	fn reportUndefinedSymbols(self: *Elf, undefs: anytype) !void {
3718	const gpa = self.base.comp.gpa;
3719	const diags = &self.base.comp.link_diags;
3720	const max_notes = 4;
3721
3722	try diags.msgs.ensureUnusedCapacity(gpa, undefs.count());
3723
3724	for (undefs.keys(), undefs.values()) |key, refs| {
3725	const undef_sym = self.resolver.keys.items[key - 1];
3726	const nrefs = @min(refs.items.len, max_notes);
3727	const nnotes = nrefs + @intFromBool(refs.items.len > max_notes);
3728
3729	var err = try diags.addErrorWithNotesAssumeCapacity(nnotes);
3730	try err.addMsg("undefined symbol: {s}", .{undef_sym.name(self)});
3731
3732	for (refs.items[0..nrefs]) |ref| {
3733	const atom_ptr = self.atom(ref).?;
3734	const file_ptr = atom_ptr.file(self).?;
3735	err.addNote("referenced by {f}:{s}", .{ file_ptr.fmtPath(), atom_ptr.name(self) });
3736	}
3737
3738	if (refs.items.len > max_notes) {
3739	const remaining = refs.items.len - max_notes;
3740	err.addNote("referenced {d} more times", .{remaining});
3741	}
3742	}
3743	}
3744
3745	fn reportDuplicates(self: *Elf, dupes: anytype) error{ HasDuplicates, OutOfMemory }!void {
3746	if (dupes.keys().len == 0) return; // Nothing to do
3747	const diags = &self.base.comp.link_diags;
3748
3749	const max_notes = 3;
3750
3751	for (dupes.keys(), dupes.values()) |key, notes| {
3752	const sym = self.resolver.keys.items[key - 1];
3753	const nnotes = @min(notes.items.len, max_notes) + @intFromBool(notes.items.len > max_notes);
3754
3755	var err = try diags.addErrorWithNotes(nnotes + 1);
3756	try err.addMsg("duplicate symbol definition: {s}", .{sym.name(self)});
3757	err.addNote("defined by {f}", .{sym.file(self).?.fmtPath()});
3758
3759	var inote: usize = 0;
3760	while (inote < @min(notes.items.len, max_notes)) : (inote += 1) {
3761	const file_ptr = self.file(notes.items[inote]).?;
3762	err.addNote("defined by {f}", .{file_ptr.fmtPath()});
3763	}
3764
3765	if (notes.items.len > max_notes) {
3766	const remaining = notes.items.len - max_notes;
3767	err.addNote("defined {d} more times", .{remaining});
3768	}
3769	}
3770
3771	return error.HasDuplicates;
3772	}
3773
3774	fn reportUnsupportedCpuArch(self: *Elf) error{OutOfMemory}!void {
3775	const diags = &self.base.comp.link_diags;
3776	var err = try diags.addErrorWithNotes(0);
3777	try err.addMsg("fatal linker error: unsupported CPU architecture {s}", .{
3778	@tagName(self.getTarget().cpu.arch),
3779	});
3780	}
3781
3782	pub fn addFileError(
3783	self: *Elf,
3784	file_index: File.Index,
3785	comptime format: []const u8,
3786	args: anytype,
3787	) error{OutOfMemory}!void {
3788	const diags = &self.base.comp.link_diags;
3789	var err = try diags.addErrorWithNotes(1);
3790	try err.addMsg(format, args);
3791	err.addNote("while parsing {f}", .{self.file(file_index).?.fmtPath()});
3792	}
3793
3794	pub fn failFile(
3795	self: *Elf,
3796	file_index: File.Index,
3797	comptime format: []const u8,
3798	args: anytype,
3799	) error{ OutOfMemory, AlreadyReported } {
3800	try addFileError(self, file_index, format, args);
3801	return error.AlreadyReported;
3802	}
3803
3804	const FormatShdr = struct {
3805	elf_file: *Elf,
3806	shdr: elf.Elf64_Shdr,
3807	};
3808
3809	fn fmtShdr(self: *Elf, shdr: elf.Elf64_Shdr) std.fmt.Alt(FormatShdr, formatShdr) {
3810	return .{ .data = .{
3811	.shdr = shdr,
3812	.elf_file = self,
3813	} };
3814	}
3815
3816	fn formatShdr(ctx: FormatShdr, writer: *std.Io.Writer) std.Io.Writer.Error!void {
3817	const shdr = ctx.shdr;
3818	try writer.print("{s} : @{x} ({x}) : align({x}) : size({x}) : entsize({x}) : flags({f})", .{
3819	ctx.elf_file.getShString(shdr.sh_name), shdr.sh_offset,
3820	shdr.sh_addr, shdr.sh_addralign,
3821	shdr.sh_size, shdr.sh_entsize,
3822	fmtShdrFlags(shdr.sh_flags),
3823	});
3824	}
3825
3826	pub fn fmtShdrFlags(sh_flags: u64) std.fmt.Alt(u64, formatShdrFlags) {
3827	return .{ .data = sh_flags };
3828	}
3829
3830	fn formatShdrFlags(sh_flags: u64, writer: *std.Io.Writer) std.Io.Writer.Error!void {
3831	if (elf.SHF_WRITE & sh_flags != 0) {
3832	try writer.writeAll("W");
3833	}
3834	if (elf.SHF_ALLOC & sh_flags != 0) {
3835	try writer.writeAll("A");
3836	}
3837	if (elf.SHF_EXECINSTR & sh_flags != 0) {
3838	try writer.writeAll("X");
3839	}
3840	if (elf.SHF_MERGE & sh_flags != 0) {
3841	try writer.writeAll("M");
3842	}
3843	if (elf.SHF_STRINGS & sh_flags != 0) {
3844	try writer.writeAll("S");
3845	}
3846	if (elf.SHF_INFO_LINK & sh_flags != 0) {
3847	try writer.writeAll("I");
3848	}
3849	if (elf.SHF_LINK_ORDER & sh_flags != 0) {
3850	try writer.writeAll("L");
3851	}
3852	if (elf.SHF_EXCLUDE & sh_flags != 0) {
3853	try writer.writeAll("E");
3854	}
3855	if (elf.SHF_COMPRESSED & sh_flags != 0) {
3856	try writer.writeAll("C");
3857	}
3858	if (elf.SHF_GROUP & sh_flags != 0) {
3859	try writer.writeAll("G");
3860	}
3861	if (elf.SHF_OS_NONCONFORMING & sh_flags != 0) {
3862	try writer.writeAll("O");
3863	}
3864	if (elf.SHF_TLS & sh_flags != 0) {
3865	try writer.writeAll("T");
3866	}
3867	if (elf.SHF_X86_64_LARGE & sh_flags != 0) {
3868	try writer.writeAll("l");
3869	}
3870	if (elf.SHF_MIPS_ADDR & sh_flags != 0 or elf.SHF_ARM_PURECODE & sh_flags != 0) {
3871	try writer.writeAll("p");
3872	}
3873	}
3874
3875	const FormatPhdr = struct {
3876	elf_file: *Elf,
3877	phdr: elf.Elf64.Phdr,
3878	};
3879
3880	fn fmtPhdr(self: *Elf, phdr: elf.Elf64.Phdr) std.fmt.Alt(FormatPhdr, formatPhdr) {
3881	return .{ .data = .{
3882	.phdr = phdr,
3883	.elf_file = self,
3884	} };
3885	}
3886
3887	fn formatPhdr(ctx: FormatPhdr, writer: *std.Io.Writer) std.Io.Writer.Error!void {
3888	const phdr = ctx.phdr;
3889	const write = phdr.flags.W;
3890	const read = phdr.flags.R;
3891	const exec = phdr.flags.X;
3892	var flags: [3]u8 = @splat('_');
3893	if (exec) flags[0] = 'X';
3894	if (write) flags[1] = 'W';
3895	if (read) flags[2] = 'R';
3896	const p_type = switch (phdr.type) {
3897	.LOAD => "LOAD",
3898	.TLS => "TLS",
3899	.GNU_EH_FRAME => "GNU_EH_FRAME",
3900	.GNU_STACK => "GNU_STACK",
3901	.DYNAMIC => "DYNAMIC",
3902	.INTERP => "INTERP",
3903	.NULL => "NULL",
3904	.PHDR => "PHDR",
3905	.NOTE => "NOTE",
3906	else => "UNKNOWN",
3907	};
3908	try writer.print("{s} : {s} : @{x} ({x}) : align({x}) : filesz({x}) : memsz({x})", .{
3909	p_type, flags, phdr.offset, phdr.vaddr,
3910	phdr.@"align", phdr.filesz, phdr.memsz,
3911	});
3912	}
3913
3914	pub fn dumpState(self: *Elf) std.fmt.Alt(*Elf, fmtDumpState) {
3915	return .{ .data = self };
3916	}
3917
3918	fn fmtDumpState(self: *Elf, writer: *std.Io.Writer) std.Io.Writer.Error!void {
3919	const shared_objects = self.shared_objects.values();
3920
3921	if (self.zigObjectPtr()) |zig_object| {
3922	try writer.print("zig_object({d}) : {s}\n", .{ zig_object.index, zig_object.basename });
3923	try writer.print("{f}{f}", .{
3924	zig_object.fmtAtoms(self),
3925	zig_object.fmtSymtab(self),
3926	});
3927	try writer.writeByte('\n');
3928	}
3929
3930	for (self.objects.items) |index| {
3931	const object = self.file(index).?.object;
3932	try writer.print("object({d}) : {f}", .{ index, object.fmtPath() });
3933	if (!object.alive) try writer.writeAll(" : [*]");
3934	try writer.writeByte('\n');
3935	try writer.print("{f}{f}{f}{f}{f}\n", .{
3936	object.fmtAtoms(self),
3937	object.fmtCies(self),
3938	object.fmtFdes(self),
3939	object.fmtSymtab(self),
3940	object.fmtGroups(self),
3941	});
3942	}
3943
3944	for (shared_objects) |index| {
3945	const shared_object = self.file(index).?.shared_object;
3946	try writer.print("shared_object({d}) : {f} : needed({})", .{
3947	index, shared_object.path, shared_object.needed,
3948	});
3949	if (!shared_object.alive) try writer.writeAll(" : [*]");
3950	try writer.writeByte('\n');
3951	try writer.print("{f}\n", .{shared_object.fmtSymtab(self)});
3952	}
3953
3954	if (self.linker_defined_index) |index| {
3955	const linker_defined = self.file(index).?.linker_defined;
3956	try writer.print("linker_defined({d}) : (linker defined)\n", .{index});
3957	try writer.print("{f}\n", .{linker_defined.fmtSymtab(self)});
3958	}
3959
3960	const slice = self.sections.slice();
3961	{
3962	try writer.writeAll("atom lists\n");
3963	for (slice.items(.shdr), slice.items(.atom_list_2), 0..) |shdr, atom_list, shndx| {
3964	try writer.print("shdr({d}) : {s} : {f}\n", .{ shndx, self.getShString(shdr.sh_name), atom_list.fmt(self) });
3965	}
3966	}
3967
3968	if (self.requiresThunks()) {
3969	try writer.writeAll("thunks\n");
3970	for (self.thunks.items, 0..) |th, index| {
3971	try writer.print("thunk({d}) : {f}\n", .{ index, th.fmt(self) });
3972	}
3973	}
3974
3975	try writer.print("{f}\n", .{self.got.fmt(self)});
3976	try writer.print("{f}\n", .{self.plt.fmt(self)});
3977
3978	try writer.writeAll("Output groups\n");
3979	for (self.group_sections.items) |cg| {
3980	try writer.print(" shdr({d}) : GROUP({f})\n", .{ cg.shndx, cg.cg_ref });
3981	}
3982
3983	try writer.writeAll("\nOutput merge sections\n");
3984	for (self.merge_sections.items) |msec| {
3985	try writer.print(" shdr({d}) : {f}\n", .{ msec.output_section_index, msec.fmt(self) });
3986	}
3987
3988	try writer.writeAll("\nOutput shdrs\n");
3989	for (slice.items(.shdr), slice.items(.phndx), 0..) |shdr, phndx, shndx| {
3990	try writer.print(" shdr({d}) : phdr({d}) : {f}\n", .{
3991	shndx,
3992	phndx,
3993	self.fmtShdr(shdr),
3994	});
3995	}
3996	try writer.writeAll("\nOutput phdrs\n");
3997	for (self.phdrs.items, 0..) |phdr, phndx| {
3998	try writer.print(" phdr({d}) : {f}\n", .{ phndx, self.fmtPhdr(phdr) });
3999	}
4000	}
4001
4002	/// Caller owns the memory.
4003	pub fn preadAllAlloc(allocator: Allocator, io: Io, io_file: Io.File, offset: u64, size: u64) ![]u8 {
4004	const buffer = try allocator.alloc(u8, math.cast(usize, size) orelse return error.Overflow);
4005	errdefer allocator.free(buffer);
4006	const amt = try io_file.readPositionalAll(io, buffer, offset);
4007	if (amt != size) return error.InputOutput;
4008	return buffer;
4009	}
4010
4011	/// Binary search
4012	pub fn bsearch(comptime T: type, haystack: []const T, predicate: anytype) usize {
4013	var min: usize = 0;
4014	var max: usize = haystack.len;
4015	while (min < max) {
4016	const index = (min + max) / 2;
4017	const curr = haystack[index];
4018	if (predicate.predicate(curr)) {
4019	min = index + 1;
4020	} else {
4021	max = index;
4022	}
4023	}
4024	return min;
4025	}
4026
4027	/// Linear search
4028	pub fn lsearch(comptime T: type, haystack: []const T, predicate: anytype) usize {
4029	var i: usize = 0;
4030	while (i < haystack.len) : (i += 1) {
4031	if (predicate.predicate(haystack[i])) break;
4032	}
4033	return i;
4034	}
4035
4036	pub fn getTarget(self: *const Elf) *const std.Target {
4037	return &self.base.comp.root_mod.resolved_target.result;
4038	}
4039
4040	fn requiresThunks(self: Elf) bool {
4041	return switch (self.getTarget().cpu.arch) {
4042	.aarch64, .aarch64_be => true,
4043	.x86_64, .riscv64, .riscv64be => false,
4044	else => @panic("TODO unimplemented architecture"),
4045	};
4046	}
4047
4048	/// The following three values are only observed at compile-time and used to emit a compile error
4049	/// to remind the programmer to update expected maximum numbers of different program header types
4050	/// so that we reserve enough space for the program header table up-front.
4051	/// Bump these numbers when adding or deleting a Zig specific pre-allocated segment, or adding
4052	/// more special-purpose program headers.
4053	const max_number_of_object_segments = 9;
4054	const max_number_of_special_phdrs = 5;
4055
4056	const default_entry_addr = 0x8000000;
4057
4058	pub const base_tag: link.File.Tag = .elf;
4059
4060	pub const Group = struct {
4061	signature_off: u32,
4062	file_index: File.Index,
4063	shndx: u32,
4064	members_start: u32,
4065	members_len: u32,
4066	is_comdat: bool,
4067	alive: bool = true,
4068
4069	pub fn file(cg: Group, elf_file: *Elf) File {
4070	return elf_file.file(cg.file_index).?;
4071	}
4072
4073	pub fn signature(cg: Group, elf_file: *Elf) [:0]const u8 {
4074	return cg.file(elf_file).object.getString(cg.signature_off);
4075	}
4076
4077	pub fn members(cg: Group, elf_file: *Elf) []const u32 {
4078	const object = cg.file(elf_file).object;
4079	return object.group_data.items[cg.members_start..][0..cg.members_len];
4080	}
4081
4082	pub const Index = u32;
4083	};
4084
4085	pub const SymtabCtx = struct {
4086	ilocal: u32 = 0,
4087	iglobal: u32 = 0,
4088	nlocals: u32 = 0,
4089	nglobals: u32 = 0,
4090	strsize: u32 = 0,
4091
4092	pub fn reset(ctx: *SymtabCtx) void {
4093	ctx.ilocal = 0;
4094	ctx.iglobal = 0;
4095	ctx.nlocals = 0;
4096	ctx.nglobals = 0;
4097	ctx.strsize = 0;
4098	}
4099	};
4100
4101	pub const null_sym = elf.Elf64_Sym{
4102	.st_name = 0,
4103	.st_info = 0,
4104	.st_other = 0,
4105	.st_shndx = 0,
4106	.st_value = 0,
4107	.st_size = 0,
4108	};
4109
4110	pub const null_shdr = elf.Elf64_Shdr{
4111	.sh_name = 0,
4112	.sh_type = 0,
4113	.sh_flags = 0,
4114	.sh_addr = 0,
4115	.sh_offset = 0,
4116	.sh_size = 0,
4117	.sh_link = 0,
4118	.sh_info = 0,
4119	.sh_addralign = 0,
4120	.sh_entsize = 0,
4121	};
4122
4123	pub const SystemLib = struct {
4124	needed: bool = false,
4125	path: Path,
4126	};
4127
4128	pub const Ref = struct {
4129	index: u32 = 0,
4130	file: u32 = 0,
4131
4132	pub fn eql(ref: Ref, other: Ref) bool {
4133	return ref.index == other.index and ref.file == other.file;
4134	}
4135
4136	pub fn format(ref: Ref, writer: *std.Io.Writer) std.Io.Writer.Error!void {
4137	try writer.print("ref({d},{d})", .{ ref.index, ref.file });
4138	}
4139	};
4140
4141	pub const SymbolResolver = struct {
4142	keys: std.ArrayList(Key) = .empty,
4143	values: std.ArrayList(Ref) = .empty,
4144	table: std.array_hash_map.Auto(void, void) = .empty,
4145
4146	const Result = struct {
4147	found_existing: bool,
4148	index: Index,
4149	ref: *Ref,
4150	};
4151
4152	pub fn deinit(resolver: *SymbolResolver, allocator: Allocator) void {
4153	resolver.keys.deinit(allocator);
4154	resolver.values.deinit(allocator);
4155	resolver.table.deinit(allocator);
4156	}
4157
4158	pub fn getOrPut(
4159	resolver: *SymbolResolver,
4160	allocator: Allocator,
4161	ref: Ref,
4162	elf_file: *Elf,
4163	) !Result {
4164	const adapter = Adapter{ .keys = resolver.keys.items, .elf_file = elf_file };
4165	const key = Key{ .index = ref.index, .file_index = ref.file };
4166	const gop = try resolver.table.getOrPutAdapted(allocator, key, adapter);
4167	if (!gop.found_existing) {
4168	try resolver.keys.append(allocator, key);
4169	_ = try resolver.values.addOne(allocator);
4170	}
4171	return .{
4172	.found_existing = gop.found_existing,
4173	.index = @intCast(gop.index + 1),
4174	.ref = &resolver.values.items[gop.index],
4175	};
4176	}
4177
4178	pub fn get(resolver: SymbolResolver, index: Index) ?Ref {
4179	if (index == 0) return null;
4180	return resolver.values.items[index - 1];
4181	}
4182
4183	pub fn reset(resolver: *SymbolResolver) void {
4184	resolver.keys.clearRetainingCapacity();
4185	resolver.values.clearRetainingCapacity();
4186	resolver.table.clearRetainingCapacity();
4187	}
4188
4189	const Key = struct {
4190	index: Symbol.Index,
4191	file_index: File.Index,
4192
4193	fn name(key: Key, elf_file: *Elf) [:0]const u8 {
4194	const ref = Ref{ .index = key.index, .file = key.file_index };
4195	return elf_file.symbol(ref).?.name(elf_file);
4196	}
4197
4198	fn file(key: Key, elf_file: *Elf) ?File {
4199	return elf_file.file(key.file_index);
4200	}
4201
4202	fn eql(key: Key, other: Key, elf_file: *Elf) bool {
4203	const key_name = key.name(elf_file);
4204	const other_name = other.name(elf_file);
4205	return mem.eql(u8, key_name, other_name);
4206	}
4207
4208	fn hash(key: Key, elf_file: *Elf) u32 {
4209	return @truncate(Hash.hash(0, key.name(elf_file)));
4210	}
4211	};
4212
4213	const Adapter = struct {
4214	keys: []const Key,
4215	elf_file: *Elf,
4216
4217	pub fn eql(ctx: @This(), key: Key, b_void: void, b_map_index: usize) bool {
4218	_ = b_void;
4219	const other = ctx.keys[b_map_index];
4220	return key.eql(other, ctx.elf_file);
4221	}
4222
4223	pub fn hash(ctx: @This(), key: Key) u32 {
4224	return key.hash(ctx.elf_file);
4225	}
4226	};
4227
4228	pub const Index = u32;
4229	};
4230
4231	const Section = struct {
4232	/// Section header.
4233	shdr: elf.Elf64_Shdr,
4234
4235	/// Assigned program header index if any.
4236	phndx: OptionalProgramHeaderIndex = .none,
4237
4238	/// List of atoms contributing to this section.
4239	/// TODO currently this is only used for relocations tracking in relocatable mode
4240	/// but will be merged with atom_list_2.
4241	atom_list: std.ArrayList(Ref) = .empty,
4242
4243	/// List of atoms contributing to this section.
4244	/// This can be used by sections that require special handling such as init/fini array, etc.
4245	atom_list_2: AtomList = .{},
4246
4247	/// Index of the last allocated atom in this section.
4248	last_atom: Ref = .{ .index = 0, .file = 0 },
4249
4250	/// A list of atoms that have surplus capacity. This list can have false
4251	/// positives, as functions grow and shrink over time, only sometimes being added
4252	/// or removed from the freelist.
4253	///
4254	/// An atom has surplus capacity when its overcapacity value is greater than
4255	/// padToIdeal(minimum_atom_size). That is, when it has so
4256	/// much extra capacity, that we could fit a small new symbol in it, itself with
4257	/// ideal_capacity or more.
4258	///
4259	/// Ideal capacity is defined by size + (size / ideal_factor)
4260	///
4261	/// Overcapacity is measured by actual_capacity - ideal_capacity. Note that
4262	/// overcapacity can be negative. A simple way to have negative overcapacity is to
4263	/// allocate a fresh text block, which will have ideal capacity, and then grow it
4264	/// by 1 byte. It will then have -1 overcapacity.
4265	free_list: std.ArrayList(Ref) = .empty,
4266	};
4267
4268	pub fn sectionSize(self: *Elf, shndx: u32) u64 {
4269	const last_atom_ref = self.sections.items(.last_atom)[shndx];
4270	const atom_ptr = self.atom(last_atom_ref) orelse return 0;
4271	return @as(u64, @intCast(atom_ptr.value)) + atom_ptr.size;
4272	}
4273
4274	fn defaultEntrySymbolName(cpu_arch: std.Target.Cpu.Arch) []const u8 {
4275	return switch (cpu_arch) {
4276	.mips, .mipsel, .mips64, .mips64el => "__start",
4277	else => "_start",
4278	};
4279	}
4280
4281	fn createThunks(elf_file: *Elf, atom_list: *AtomList) !void {
4282	const gpa = elf_file.base.comp.gpa;
4283	const cpu_arch = elf_file.getTarget().cpu.arch;
4284
4285	// A branch will need an extender if its target is larger than
4286	// `2^(jump_bits - 1) - margin` where margin is some arbitrary number.
4287	const max_distance = switch (cpu_arch) {
4288	.aarch64, .aarch64_be => 0x500_000,
4289	.x86_64, .riscv64, .riscv64be => unreachable,
4290	else => @panic("unhandled arch"),
4291	};
4292
4293	const advance = struct {
4294	fn advance(list: *AtomList, size: u64, alignment: Atom.Alignment) !i64 {
4295	const offset = alignment.forward(list.size);
4296	const padding = offset - list.size;
4297	list.size += padding + size;
4298	list.alignment = list.alignment.max(alignment);
4299	return @intCast(offset);
4300	}
4301	}.advance;
4302
4303	for (atom_list.atoms.keys()) |ref| {
4304	elf_file.atom(ref).?.value = -1;
4305	}
4306
4307	var i: usize = 0;
4308	while (i < atom_list.atoms.keys().len) {
4309	const start = i;
4310	const start_atom = elf_file.atom(atom_list.atoms.keys()[start]).?;
4311	assert(start_atom.alive);
4312	start_atom.value = try advance(atom_list, start_atom.size, start_atom.alignment);
4313	i += 1;
4314
4315	while (i < atom_list.atoms.keys().len) : (i += 1) {
4316	const atom_ptr = elf_file.atom(atom_list.atoms.keys()[i]).?;
4317	assert(atom_ptr.alive);
4318	if (@as(i64, @intCast(atom_ptr.alignment.forward(atom_list.size))) - start_atom.value >= max_distance)
4319	break;
4320	atom_ptr.value = try advance(atom_list, atom_ptr.size, atom_ptr.alignment);
4321	}
4322
4323	// Insert a thunk at the group end
4324	const thunk_index = try elf_file.addThunk();
4325	const thunk_ptr = elf_file.thunk(thunk_index);
4326	thunk_ptr.output_section_index = atom_list.output_section_index;
4327
4328	// Scan relocs in the group and create trampolines for any unreachable callsite
4329	for (atom_list.atoms.keys()[start..i]) |ref| {
4330	const atom_ptr = elf_file.atom(ref).?;
4331	const file_ptr = atom_ptr.file(elf_file).?;
4332	log.debug("atom({f}) {s}", .{ ref, atom_ptr.name(elf_file) });
4333	for (atom_ptr.relocs(elf_file)) |rel| {
4334	const is_reachable = switch (cpu_arch) {
4335	.aarch64, .aarch64_be => r: {
4336	const r_type: elf.R_AARCH64 = @fromBackingInt(@intCast(rel.r_type()));
4337	if (r_type != .CALL26 and r_type != .JUMP26) break :r true;
4338	const target_ref = file_ptr.resolveSymbol(rel.r_sym(), elf_file);
4339	const target = elf_file.symbol(target_ref).?;
4340	if (target.flags.has_plt) break :r false;
4341	if (atom_ptr.output_section_index != target.output_section_index) break :r false;
4342	const target_atom = target.atom(elf_file).?;
4343	if (target_atom.value == -1) break :r false;
4344	const saddr = atom_ptr.address(elf_file) + @as(i64, @intCast(rel.r_offset));
4345	const taddr = target.address(.{}, elf_file);
4346	_ = math.cast(i28, taddr + rel.r_addend - saddr) orelse break :r false;
4347	break :r true;
4348	},
4349	.x86_64, .riscv64, .riscv64be => unreachable,
4350	else => @panic("unsupported arch"),
4351	};
4352	if (is_reachable) continue;
4353	const target = file_ptr.resolveSymbol(rel.r_sym(), elf_file);
4354	try thunk_ptr.symbols.put(gpa, target, {});
4355	}
4356	atom_ptr.addExtra(.{ .thunk = thunk_index }, elf_file);
4357	}
4358
4359	thunk_ptr.value = try advance(atom_list, thunk_ptr.size(elf_file), Atom.Alignment.fromNonzeroByteUnits(2));
4360
4361	log.debug("thunk({d}) : {f}", .{ thunk_index, thunk_ptr.fmt(elf_file) });
4362	}
4363	}
4364
4365	pub fn stringTableLookup(strtab: []const u8, off: u32) [:0]const u8 {
4366	const slice = strtab[off..];
4367	return slice[0..mem.findScalar(u8, slice, 0).? :0];
4368	}
4369
4370	pub fn pwriteAll(elf_file: *Elf, bytes: []const u8, offset: u64) error{AlreadyReported}!void {
4371	const comp = elf_file.base.comp;
4372	const io = comp.io;
4373	const diags = &comp.link_diags;
4374	elf_file.base.file.?.writePositionalAll(io, bytes, offset) catch |err|
4375	return diags.fail("failed to write: {t}", .{err});
4376	}
4377
4378	pub fn setLength(elf_file: *Elf, length: u64) error{AlreadyReported}!void {
4379	const comp = elf_file.base.comp;
4380	const io = comp.i;
4381	const diags = &comp.link_diags;
4382	elf_file.base.file.?.setLength(io, length) catch |err| {
4383	return diags.fail("failed to set file end pos: {s}", .{@errorName(err)});
4384	};
4385	}
4386
4387	pub fn cast(elf_file: *Elf, comptime T: type, x: anytype) error{AlreadyReported}!T {
4388	return std.math.cast(T, x) orelse {
4389	const comp = elf_file.base.comp;
4390	const diags = &comp.link_diags;
4391	return diags.fail("encountered {d}, overflowing {d}-bit value", .{ x, @bitSizeOf(T) });
4392	};
4393	}
4394
4395	const std = @import("std");
4396	const Io = std.Io;
4397	const build_options = @import("build_options");
4398	const builtin = @import("builtin");
4399	const assert = std.debug.assert;
4400	const elf = std.elf;
4401	const fs = std.fs;
4402	const log = std.log.scoped(.link);
4403	const relocs_log = std.log.scoped(.link_relocs);
4404	const state_log = std.log.scoped(.link_state);
4405	const math = std.math;
4406	const mem = std.mem;
4407	const Allocator = std.mem.Allocator;
4408	const Hash = std.hash.Wyhash;
4409	const Path = std.Build.Cache.Path;
4410	const Stat = std.Build.Cache.File.Stat;
4411
4412	const codegen = @import("../codegen.zig");
4413	const eh_frame = @import("Elf/eh_frame.zig");
4414	const gc = @import("Elf/gc.zig");
4415	const musl = @import("../libs/musl.zig");
4416	const link = @import("../link.zig");
4417	const relocatable = @import("Elf/relocatable.zig");
4418	const relocation = @import("Elf/relocation.zig");
4419	const target_util = @import("../target.zig");
4420	const trace = @import("../tracy.zig").trace;
4421	const synthetic_sections = @import("Elf/synthetic_sections.zig");
4422
4423	const Merge = @import("Elf/Merge.zig");
4424	const Archive = @import("Elf/Archive.zig");
4425	const AtomList = @import("Elf/AtomList.zig");
4426	const Compilation = @import("../Compilation.zig");
4427	const GroupSection = synthetic_sections.GroupSection;
4428	const CopyRelSection = synthetic_sections.CopyRelSection;
4429	const Diags = @import("../link.zig").Diags;
4430	const DynamicSection = synthetic_sections.DynamicSection;
4431	const DynsymSection = synthetic_sections.DynsymSection;
4432	const Dwarf = @import("Dwarf.zig");
4433	const Elf = @This();
4434	const File = @import("Elf/file.zig").File;
4435	const GnuHashSection = synthetic_sections.GnuHashSection;
4436	const GotSection = synthetic_sections.GotSection;
4437	const GotPltSection = synthetic_sections.GotPltSection;
4438	const HashSection = synthetic_sections.HashSection;
4439	const LinkerDefined = @import("Elf/LinkerDefined.zig");
4440	const Zcu = @import("../Zcu.zig");
4441	const Object = @import("Elf/Object.zig");
4442	const InternPool = @import("../InternPool.zig");
4443	const PltSection = synthetic_sections.PltSection;
4444	const PltGotSection = synthetic_sections.PltGotSection;
4445	const SharedObject = @import("Elf/SharedObject.zig");
4446	const Symbol = @import("Elf/Symbol.zig");
4447	const StringTable = @import("StringTable.zig");
4448	const Thunk = @import("Elf/Thunk.zig");
4449	const Value = @import("../Value.zig");
4450	const VerneedSection = synthetic_sections.VerneedSection;
4451	const ZigObject = @import("Elf/ZigObject.zig");