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Merge pull request #17057 from ziglang/elf-symtab
elf: write all symbols in bulk in flush
This commit is contained in:
Jakub Konka
GitHub
commit
e265dc61e6
137
src/link/Elf.zig
137
src/link/Elf.zig
@ -750,7 +750,6 @@ pub fn populateMissingMetadata(self: *Elf) !void {
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.phdr_index = undefined,
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});
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self.shdr_table_dirty = true;
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try self.writeSymbol(0);
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}
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if (self.dwarf) |*dw| {
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@ -1134,9 +1133,7 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
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}
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}
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// Unfortunately these have to be buffered and done at the end because ELF does not allow
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// mixing local and global symbols within a symbol table.
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try self.writeAllGlobalSymbols();
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try self.writeSymbols();
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if (build_options.enable_logging) {
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self.logSymtab();
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@ -2551,9 +2548,6 @@ fn updateDeclCode(self: *Elf, decl_index: Module.Decl.Index, code: []const u8, s
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self.shrinkAtom(atom_index, code.len);
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}
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local_sym.st_size = code.len;
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// TODO this write could be avoided if no fields of the symbol were changed.
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try self.writeSymbol(local_sym_index);
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} else {
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const local_sym = atom.getSymbolPtr(self);
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local_sym.* = .{
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@ -2571,7 +2565,6 @@ fn updateDeclCode(self: *Elf, decl_index: Module.Decl.Index, code: []const u8, s
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local_sym.st_value = vaddr;
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local_sym.st_size = code.len;
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try self.writeSymbol(local_sym_index);
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const got_entry_index = try atom.getOrCreateOffsetTableEntry(self);
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try self.writeOffsetTableEntry(got_entry_index);
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}
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@ -2807,7 +2800,6 @@ fn updateLazySymbolAtom(
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local_sym.st_value = vaddr;
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local_sym.st_size = code.len;
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try self.writeSymbol(local_sym_index);
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const got_entry_index = try atom.getOrCreateOffsetTableEntry(self);
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try self.writeOffsetTableEntry(got_entry_index);
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@ -2870,7 +2862,6 @@ pub fn lowerUnnamedConst(self: *Elf, typed_value: TypedValue, decl_index: Module
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log.debug("allocated text block for {s} at 0x{x}", .{ name, local_sym.st_value });
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try self.writeSymbol(self.getAtom(atom_index).getSymbolIndex().?);
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try unnamed_consts.append(gpa, atom_index);
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const section_offset = local_sym.st_value - self.program_headers.items[phdr_index].p_vaddr;
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@ -3096,63 +3087,19 @@ fn writeOffsetTableEntry(self: *Elf, index: @TypeOf(self.got_table).Index) !void
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}
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}
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fn writeSymbol(self: *Elf, index: usize) !void {
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const tracy = trace(@src());
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defer tracy.end();
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const syms_sect = &self.sections.items(.shdr)[self.symtab_section_index.?];
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// Make sure we are not pointlessly writing symbol data that will have to get relocated
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// due to running out of space.
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if (self.local_symbols.items.len != syms_sect.sh_info) {
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const sym_size: u64 = switch (self.ptr_width) {
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.p32 => @sizeOf(elf.Elf32_Sym),
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.p64 => @sizeOf(elf.Elf64_Sym),
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};
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const sym_align: u16 = switch (self.ptr_width) {
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.p32 => @alignOf(elf.Elf32_Sym),
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.p64 => @alignOf(elf.Elf64_Sym),
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};
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const needed_size = (self.local_symbols.items.len + self.global_symbols.items.len) * sym_size;
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try self.growNonAllocSection(self.symtab_section_index.?, needed_size, sym_align, true);
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syms_sect.sh_info = @as(u32, @intCast(self.local_symbols.items.len));
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}
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const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
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const off = switch (self.ptr_width) {
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.p32 => syms_sect.sh_offset + @sizeOf(elf.Elf32_Sym) * index,
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.p64 => syms_sect.sh_offset + @sizeOf(elf.Elf64_Sym) * index,
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fn elf32SymFromSym(sym: elf.Elf64_Sym, out: *elf.Elf32_Sym) void {
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out.* = .{
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.st_name = sym.st_name,
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.st_value = @as(u32, @intCast(sym.st_value)),
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.st_size = @as(u32, @intCast(sym.st_size)),
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.st_info = sym.st_info,
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.st_other = sym.st_other,
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.st_shndx = sym.st_shndx,
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};
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const local = self.local_symbols.items[index];
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log.debug("writing symbol {d}, '{?s}' at 0x{x}", .{ index, self.strtab.get(local.st_name), off });
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log.debug(" ({})", .{local});
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switch (self.ptr_width) {
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.p32 => {
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var sym = [1]elf.Elf32_Sym{
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.{
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.st_name = local.st_name,
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.st_value = @as(u32, @intCast(local.st_value)),
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.st_size = @as(u32, @intCast(local.st_size)),
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.st_info = local.st_info,
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.st_other = local.st_other,
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.st_shndx = local.st_shndx,
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},
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};
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if (foreign_endian) {
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mem.byteSwapAllFields(elf.Elf32_Sym, &sym[0]);
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}
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try self.base.file.?.pwriteAll(mem.sliceAsBytes(sym[0..1]), off);
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},
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.p64 => {
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var sym = [1]elf.Elf64_Sym{local};
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if (foreign_endian) {
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mem.byteSwapAllFields(elf.Elf64_Sym, &sym[0]);
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}
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try self.base.file.?.pwriteAll(mem.sliceAsBytes(sym[0..1]), off);
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},
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}
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}
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fn writeAllGlobalSymbols(self: *Elf) !void {
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const syms_sect = &self.sections.items(.shdr)[self.symtab_section_index.?];
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fn writeSymbols(self: *Elf) !void {
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const gpa = self.base.allocator;
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const sym_size: u64 = switch (self.ptr_width) {
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.p32 => @sizeOf(elf.Elf32_Sym),
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.p64 => @sizeOf(elf.Elf64_Sym),
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@ -3161,52 +3108,54 @@ fn writeAllGlobalSymbols(self: *Elf) !void {
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.p32 => @alignOf(elf.Elf32_Sym),
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.p64 => @alignOf(elf.Elf64_Sym),
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};
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const needed_size = (self.local_symbols.items.len + self.global_symbols.items.len) * sym_size;
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const shdr = &self.sections.items(.shdr)[self.symtab_section_index.?];
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shdr.sh_info = @intCast(self.local_symbols.items.len);
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self.markDirty(self.symtab_section_index.?, null);
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const nsyms = self.local_symbols.items.len + self.global_symbols.items.len;
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const needed_size = nsyms * sym_size;
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try self.growNonAllocSection(self.symtab_section_index.?, needed_size, sym_align, true);
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const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
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const global_syms_off = syms_sect.sh_offset + self.local_symbols.items.len * sym_size;
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log.debug("writing {d} global symbols at 0x{x}", .{ self.global_symbols.items.len, global_syms_off });
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log.debug("writing {d} symbols at 0x{x}", .{ nsyms, shdr.sh_offset });
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switch (self.ptr_width) {
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.p32 => {
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const buf = try self.base.allocator.alloc(elf.Elf32_Sym, self.global_symbols.items.len);
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defer self.base.allocator.free(buf);
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const buf = try gpa.alloc(elf.Elf32_Sym, nsyms);
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defer gpa.free(buf);
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for (buf, 0..) |*sym, i| {
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const global = self.global_symbols.items[i];
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sym.* = .{
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.st_name = global.st_name,
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.st_value = @as(u32, @intCast(global.st_value)),
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.st_size = @as(u32, @intCast(global.st_size)),
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.st_info = global.st_info,
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.st_other = global.st_other,
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.st_shndx = global.st_shndx,
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};
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for (buf[0..self.local_symbols.items.len], self.local_symbols.items) |*sym, local| {
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elf32SymFromSym(local, sym);
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if (foreign_endian) {
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mem.byteSwapAllFields(elf.Elf32_Sym, sym);
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}
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}
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try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), global_syms_off);
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for (buf[self.local_symbols.items.len..], self.global_symbols.items) |*sym, global| {
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elf32SymFromSym(global, sym);
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if (foreign_endian) {
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mem.byteSwapAllFields(elf.Elf32_Sym, sym);
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}
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}
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try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), shdr.sh_offset);
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},
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.p64 => {
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const buf = try self.base.allocator.alloc(elf.Elf64_Sym, self.global_symbols.items.len);
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defer self.base.allocator.free(buf);
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for (buf, 0..) |*sym, i| {
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const global = self.global_symbols.items[i];
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sym.* = .{
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.st_name = global.st_name,
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.st_value = global.st_value,
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.st_size = global.st_size,
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.st_info = global.st_info,
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.st_other = global.st_other,
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.st_shndx = global.st_shndx,
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};
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const buf = try gpa.alloc(elf.Elf64_Sym, nsyms);
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defer gpa.free(buf);
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for (buf[0..self.local_symbols.items.len], self.local_symbols.items) |*sym, local| {
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sym.* = local;
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if (foreign_endian) {
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mem.byteSwapAllFields(elf.Elf64_Sym, sym);
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}
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}
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try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), global_syms_off);
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for (buf[self.local_symbols.items.len..], self.global_symbols.items) |*sym, global| {
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sym.* = global;
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if (foreign_endian) {
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mem.byteSwapAllFields(elf.Elf64_Sym, sym);
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}
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}
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try self.base.file.?.pwriteAll(mem.sliceAsBytes(buf), shdr.sh_offset);
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},
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}
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}
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