authorgravatar for kubkon@jakubkonka.comJakub Konka <kubkon@jakubkonka.com> 2024-09-03 13:28:01+02:00
committergravatar for kubkon@jakubkonka.comJakub Konka <kubkon@jakubkonka.com> 2024-09-04 13:34:26+02:00
log2ef3e30e2d04f16510d0953e6d266a97bcb4eb49
tree2d4fd8e6fd36449939b254f99408370b3884cc86
parent5cb51c10debd3e9542e35e22648bca2a8b59259e

elf: emit relocs for self-hosted generated .eh_frame section

5 files changed, 61 insertions(+), 25 deletions(-)

src/link/Elf.zig+13-11
......@@ -3388,34 +3388,36 @@ fn shdrRank(self: *Elf, shndx: u32) u8 {
33883388 elf.SHT_PREINIT_ARRAY,
33893389 elf.SHT_INIT_ARRAY,
33903390 elf.SHT_FINI_ARRAY,
3391 => return 0xf2,
3391 => return 0xf1,
33923392
3393 elf.SHT_DYNAMIC => return 0xf3,
3393 elf.SHT_DYNAMIC => return 0xf2,
33943394
33953395 elf.SHT_RELA, elf.SHT_GROUP => return 0xf,
33963396
33973397 elf.SHT_PROGBITS => if (flags & elf.SHF_ALLOC != 0) {
33983398 if (flags & elf.SHF_EXECINSTR != 0) {
3399 return 0xf1;
3399 return 0xf0;
34003400 } else if (flags & elf.SHF_WRITE != 0) {
3401 return if (flags & elf.SHF_TLS != 0) 0xf4 else 0xf6;
3401 return if (flags & elf.SHF_TLS != 0) 0xf3 else 0xf5;
34023402 } else if (mem.eql(u8, name, ".interp")) {
34033403 return 1;
3404 } else if (mem.startsWith(u8, name, ".eh_frame")) {
3405 return 0xe1;
34043406 } else {
3405 return 0xf0;
3407 return 0xe0;
34063408 }
34073409 } else {
34083410 if (mem.startsWith(u8, name, ".debug")) {
3409 return 0xf8;
3411 return 0xf7;
34103412 } else {
3411 return 0xf9;
3413 return 0xf8;
34123414 }
34133415 },
3414 elf.SHT_X86_64_UNWIND => return 0xf0,
3416 elf.SHT_X86_64_UNWIND => return 0xe1,
34153417
3416 elf.SHT_NOBITS => return if (flags & elf.SHF_TLS != 0) 0xf5 else 0xf7,
3417 elf.SHT_SYMTAB => return 0xfa,
3418 elf.SHT_STRTAB => return if (mem.eql(u8, name, ".dynstr")) 0x4 else 0xfb,
3418 elf.SHT_NOBITS => return if (flags & elf.SHF_TLS != 0) 0xf4 else 0xf6,
3419 elf.SHT_SYMTAB => return 0xf9,
3420 elf.SHT_STRTAB => return if (mem.eql(u8, name, ".dynstr")) 0x4 else 0xfa,
34193421 else => return 0xff,
34203422 }
34213423}
src/link/Elf/Object.zig+19-9
......@@ -391,15 +391,24 @@ fn parseEhFrame(self: *Object, allocator: Allocator, handle: std.fs.File, shndx:
391391 .input_section_index = shndx,
392392 .file_index = self.index,
393393 }),
394 .fde => try self.fdes.append(allocator, .{
395 .offset = data_start + rec.offset,
396 .size = rec.size,
397 .cie_index = undefined,
398 .rel_index = rel_start + @as(u32, @intCast(rel_range.start)),
399 .rel_num = @as(u32, @intCast(rel_range.len)),
400 .input_section_index = shndx,
401 .file_index = self.index,
402 }),
394 .fde => {
395 if (rel_range.len == 0) {
396 // No relocs for an FDE means we cannot associate this FDE to an Atom
397 // so we skip it. According to mold source code
398 // (https://github.com/rui314/mold/blob/a3e69502b0eaf1126d6093e8ea5e6fdb95219811/src/input-files.cc#L525-L528)
399 // this can happen for object files built with -r flag by the linker.
400 continue;
401 }
402 try self.fdes.append(allocator, .{
403 .offset = data_start + rec.offset,
404 .size = rec.size,
405 .cie_index = undefined,
406 .rel_index = rel_start + @as(u32, @intCast(rel_range.start)),
407 .rel_num = @as(u32, @intCast(rel_range.len)),
408 .input_section_index = shndx,
409 .file_index = self.index,
410 });
411 },
403412 }
404413 }
405414
......@@ -1106,6 +1115,7 @@ pub fn addAtomsToRelaSections(self: *Object, elf_file: *Elf) !void {
11061115 for (self.atoms_indexes.items) |atom_index| {
11071116 const atom_ptr = self.atom(atom_index) orelse continue;
11081117 if (!atom_ptr.alive) continue;
1118 if (atom_ptr.output_section_index == elf_file.eh_frame_section_index) continue;
11091119 const shndx = blk: {
11101120 const shndx = atom_ptr.relocsShndx() orelse continue;
11111121 const shdr = self.shdrs.items[shndx];
src/link/Elf/ZigObject.zig+1
......@@ -808,6 +808,7 @@ pub fn addAtomsToRelaSections(self: *ZigObject, elf_file: *Elf) !void {
808808 for (self.atoms_indexes.items) |atom_index| {
809809 const atom_ptr = self.atom(atom_index) orelse continue;
810810 if (!atom_ptr.alive) continue;
811 if (atom_ptr.output_section_index == elf_file.eh_frame_section_index) continue;
811812 const rela_shndx = atom_ptr.relocsShndx() orelse continue;
812813 // TODO this check will become obsolete when we rework our relocs mechanism at the ZigObject level
813814 if (self.relocs.items[rela_shndx].items.len == 0) continue;
src/link/Elf/eh_frame.zig+26-4
......@@ -288,6 +288,13 @@ pub fn calcEhFrameHdrSize(elf_file: *Elf) usize {
288288
289289pub fn calcEhFrameRelocs(elf_file: *Elf) usize {
290290 var count: usize = 0;
291 if (elf_file.zigObjectPtr()) |zo| zo: {
292 const sym_index = zo.eh_frame_index orelse break :zo;
293 const sym = zo.symbol(sym_index);
294 const atom_ptr = zo.atom(sym.ref.index).?;
295 if (!atom_ptr.alive) break :zo;
296 count += atom_ptr.relocs(elf_file).len;
297 }
291298 for (elf_file.objects.items) |index| {
292299 const object = elf_file.file(index).?.object;
293300 for (object.cies.items) |cie| {
......@@ -416,9 +423,9 @@ pub fn writeEhFrameRelocatable(elf_file: *Elf, writer: anytype) !void {
416423 }
417424}
418425
419fn emitReloc(elf_file: *Elf, rec: anytype, sym: *const Symbol, rel: elf.Elf64_Rela) elf.Elf64_Rela {
426fn emitReloc(elf_file: *Elf, base_offset: u64, sym: *const Symbol, rel: elf.Elf64_Rela) elf.Elf64_Rela {
420427 const cpu_arch = elf_file.getTarget().cpu.arch;
421 const r_offset = rec.address(elf_file) + rel.r_offset - rec.offset;
428 const r_offset = base_offset + rel.r_offset;
422429 const r_type = rel.r_type();
423430 var r_addend = rel.r_addend;
424431 var r_sym: u32 = 0;
......@@ -452,6 +459,19 @@ pub fn writeEhFrameRelocs(elf_file: *Elf, writer: anytype) !void {
452459 elf_file.sections.items(.shdr)[elf_file.eh_frame_section_index.?].sh_addr,
453460 });
454461
462 if (elf_file.zigObjectPtr()) |zo| zo: {
463 const sym_index = zo.eh_frame_index orelse break :zo;
464 const sym = zo.symbol(sym_index);
465 const atom_ptr = zo.atom(sym.ref.index).?;
466 if (!atom_ptr.alive) break :zo;
467 for (atom_ptr.relocs(elf_file)) |rel| {
468 const ref = zo.resolveSymbol(rel.r_sym(), elf_file);
469 const target = elf_file.symbol(ref).?;
470 const out_rel = emitReloc(elf_file, 0, target, rel);
471 try writer.writeStruct(out_rel);
472 }
473 }
474
455475 for (elf_file.objects.items) |index| {
456476 const object = elf_file.file(index).?.object;
457477
......@@ -460,7 +480,8 @@ pub fn writeEhFrameRelocs(elf_file: *Elf, writer: anytype) !void {
460480 for (cie.relocs(elf_file)) |rel| {
461481 const ref = object.resolveSymbol(rel.r_sym(), elf_file);
462482 const sym = elf_file.symbol(ref).?;
463 const out_rel = emitReloc(elf_file, cie, sym, rel);
483 const offset = cie.address(elf_file) - cie.offset;
484 const out_rel = emitReloc(elf_file, offset, sym, rel);
464485 try writer.writeStruct(out_rel);
465486 }
466487 }
......@@ -470,7 +491,8 @@ pub fn writeEhFrameRelocs(elf_file: *Elf, writer: anytype) !void {
470491 for (fde.relocs(elf_file)) |rel| {
471492 const ref = object.resolveSymbol(rel.r_sym(), elf_file);
472493 const sym = elf_file.symbol(ref).?;
473 const out_rel = emitReloc(elf_file, fde, sym, rel);
494 const offset = fde.address(elf_file) - fde.offset;
495 const out_rel = emitReloc(elf_file, offset, sym, rel);
474496 try writer.writeStruct(out_rel);
475497 }
476498 }
src/link/Elf/relocatable.zig+2-1
......@@ -424,8 +424,9 @@ fn writeSyntheticSections(elf_file: *Elf) !void {
424424 const gpa = elf_file.base.comp.gpa;
425425 const slice = elf_file.sections.slice();
426426
427 for (slice.items(.shdr), slice.items(.atom_list)) |shdr, atom_list| {
427 for (slice.items(.shdr), slice.items(.atom_list), 0..) |shdr, atom_list, shndx| {
428428 if (shdr.sh_type != elf.SHT_RELA) continue;
429 if (@as(u32, @intCast(shndx)) == elf_file.eh_frame_rela_section_index) continue;
429430 if (atom_list.items.len == 0) continue;
430431
431432 const num_relocs = math.cast(usize, @divExact(shdr.sh_size, shdr.sh_entsize)) orelse