Commit 0ee2ab413fd0370a8ced8d433c71d1d951dab41c | zig

author	Jakub Konka <kubkon@jakubkonka.com> 2023-11-01 18:01:29+01:00
committer	Jakub Konka <kubkon@jakubkonka.com> 2023-11-04 09:09:26+01:00
log	0ee2ab413fd0370a8ced8d433c71d1d951dab41c
tree	ae75278dcaa46cc1413e300e3f373c60a36fbf08
parent	74f12d0691292e9730327971bbf6c27a78095ae8

elf: emit valid section headers table when building an object file

2 files changed, 37 insertions(+), 29 deletions(-)

src
- link
  - Elf.zig
  - Elf
    ZigObject.zig

src/link/Elf.zig+27-15

 @@ -768,15 +768,15 @@ pub fn initMetadata(self: *Elf) !void {
 pub fn growAllocSection(self: *Elf, shdr_index: u16, needed_size: u64) !void {
     const shdr = &self.shdrs.items[shdr_index];
-    const phdr_index = self.phdr_to_shdr_table.get(shdr_index).?;
+    const maybe_phdr = if (self.phdr_to_shdr_table.get(shdr_index)) |phndx| &self.phdrs.items[phndx] else null;
-    const phdr = &self.phdrs.items[phdr_index];
     const is_zerofill = shdr.sh_type == elf.SHT_NOBITS;
     if (needed_size > self.allocatedSize(shdr.sh_offset) and !is_zerofill) {
         const existing_size = shdr.sh_size;
         shdr.sh_size = 0;
         // Must move the entire section.
-        const new_offset = self.findFreeSpace(needed_size, self.page_size);
+        const alignment = if (maybe_phdr) |phdr| phdr.p_align else shdr.sh_addralign;
+        const new_offset = self.findFreeSpace(needed_size, alignment);
         log.debug("new '{s}' file offset 0x{x} to 0x{x}", .{
             self.getShString(shdr.sh_name),
 @@ -789,25 +789,27 @@ pub fn growAllocSection(self: *Elf, shdr_index: u16, needed_size: u64) !void {
         if (amt != existing_size) return error.InputOutput;
         shdr.sh_offset = new_offset;
-        phdr.p_offset = new_offset;
+        if (maybe_phdr) |phdr| phdr.p_offset = new_offset;
     }
     shdr.sh_size = needed_size;
     if (!is_zerofill) {
-        phdr.p_filesz = needed_size;
+        if (maybe_phdr) |phdr| phdr.p_filesz = needed_size;
     }
-    const mem_capacity = self.allocatedVirtualSize(phdr.p_vaddr);
+    if (maybe_phdr) |phdr| {
-    if (needed_size > mem_capacity) {
+        const mem_capacity = self.allocatedVirtualSize(phdr.p_vaddr);
-        var err = try self.addErrorWithNotes(2);
+        if (needed_size > mem_capacity) {
-        try err.addMsg(self, "fatal linker error: cannot expand load segment phdr({d}) in virtual memory", .{
+            var err = try self.addErrorWithNotes(2);
-            phdr_index,
+            try err.addMsg(self, "fatal linker error: cannot expand load segment phdr({d}) in virtual memory", .{
-        });
+                self.phdr_to_shdr_table.get(shdr_index).?,
-        try err.addNote(self, "TODO: emit relocations to memory locations in self-hosted backends", .{});
+            });
-        try err.addNote(self, "as a workaround, try increasing pre-allocated virtual memory of each segment", .{});
+            try err.addNote(self, "TODO: emit relocations to memory locations in self-hosted backends", .{});
-    }
+            try err.addNote(self, "as a workaround, try increasing pre-allocated virtual memory of each segment", .{});
+        }
-    phdr.p_memsz = needed_size;
+        phdr.p_memsz = needed_size;
+    }
     self.markDirty(shdr_index);
 }
 @@ -1499,7 +1501,17 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
 pub fn flushObject(self: *Elf, comp: *Compilation) link.File.FlushError!void {
     _ = comp;
     try self.initSections();
+    try self.sortShdrs();
+    try self.updateSectionSizes();
+    try self.allocateNonAllocSections();
+    if (build_options.enable_logging) {
+        state_log.debug("{}", .{self.dumpState()});
+    }
     try self.writeShdrTable();
+    try self.writeSyntheticSections();
     try self.writeHeader();
 }

src/link/Elf/ZigObject.zig+10-14

 @@ -180,16 +180,16 @@ pub fn flushModule(self: *ZigObject, elf_file: *Elf) !void {
         }
         if (self.debug_info_header_dirty) {
-            const text_phdr = &elf_file.phdrs.items[elf_file.phdr_zig_load_re_index.?];
+            const text_shdr = elf_file.shdrs.items[elf_file.zig_text_section_index.?];
-            const low_pc = text_phdr.p_vaddr;
+            const low_pc = text_shdr.sh_addr;
-            const high_pc = text_phdr.p_vaddr + text_phdr.p_memsz;
+            const high_pc = text_shdr.sh_addr + text_shdr.sh_size;
             try dw.writeDbgInfoHeader(elf_file.base.options.module.?, low_pc, high_pc);
             self.debug_info_header_dirty = false;
         }
         if (self.debug_aranges_section_dirty) {
-            const text_phdr = &elf_file.phdrs.items[elf_file.phdr_zig_load_re_index.?];
+            const text_shdr = elf_file.shdrs.items[elf_file.zig_text_section_index.?];
-            try dw.writeDbgAranges(text_phdr.p_vaddr, text_phdr.p_memsz);
+            try dw.writeDbgAranges(text_shdr.sh_addr, text_shdr.sh_size);
             self.debug_aranges_section_dirty = false;
         }
 @@ -731,9 +731,7 @@ fn updateDeclCode(
     const shdr = elf_file.shdrs.items[shdr_index];
     if (shdr.sh_type != elf.SHT_NOBITS) {
-        const phdr_index = elf_file.phdr_to_shdr_table.get(shdr_index).?;
+        const file_offset = shdr.sh_offset + sym.value - shdr.sh_addr;
-        const section_offset = sym.value - elf_file.phdrs.items[phdr_index].p_vaddr;
-        const file_offset = shdr.sh_offset + section_offset;
         try elf_file.base.file.?.pwriteAll(code, file_offset);
     }
 }
 @@ -940,7 +938,6 @@ fn updateLazySymbol(
         .const_data => elf_file.zig_data_rel_ro_section_index.?,
     };
     const local_sym = elf_file.symbol(symbol_index);
-    const phdr_index = elf_file.phdr_to_shdr_table.get(output_section_index).?;
     local_sym.name_offset = name_str_index;
     local_sym.output_section_index = output_section_index;
     const local_esym = &self.local_esyms.items(.elf_sym)[local_sym.esym_index];
 @@ -963,8 +960,8 @@ fn updateLazySymbol(
     const gop = try local_sym.getOrCreateZigGotEntry(symbol_index, elf_file);
     try elf_file.zig_got.writeOne(elf_file, gop.index);
-    const section_offset = atom_ptr.value - elf_file.phdrs.items[phdr_index].p_vaddr;
+    const shdr = elf_file.shdrs.items[output_section_index];
-    const file_offset = elf_file.shdrs.items[output_section_index].sh_offset + section_offset;
+    const file_offset = shdr.sh_offset + atom_ptr.value - shdr.sh_addr;
     try elf_file.base.file.?.pwriteAll(code, file_offset);
 }
 @@ -1038,7 +1035,6 @@ fn lowerConst(
         .fail => |em| return .{ .fail = em },
     };
-    const phdr_index = elf_file.phdr_to_shdr_table.get(output_section_index).?;
     const local_sym = elf_file.symbol(sym_index);
     const name_str_index = try self.insertString(gpa, name);
     local_sym.name_offset = name_str_index;
 @@ -1061,8 +1057,8 @@ fn lowerConst(
     local_sym.value = atom_ptr.value;
     local_esym.st_value = atom_ptr.value;
-    const section_offset = atom_ptr.value - elf_file.phdrs.items[phdr_index].p_vaddr;
+    const shdr = elf_file.shdrs.items[output_section_index];
-    const file_offset = elf_file.shdrs.items[output_section_index].sh_offset + section_offset;
+    const file_offset = shdr.sh_offset + atom_ptr.value - shdr.sh_addr;
     try elf_file.base.file.?.pwriteAll(code, file_offset);
     return .{ .ok = sym_index };