Commit 5e78600f0f

Jakub Konka <kubkon@jakubkonka.com>
2023-11-07 22:48:02
elf: actually track output symtab index of symbols
1 parent ecf6ed7
src/link/Elf/Atom.zig
@@ -293,6 +293,32 @@ pub fn relocs(self: Atom, elf_file: *Elf) []align(1) const elf.Elf64_Rela {
     };
 }
 
+pub fn writeRelocs(self: Atom, elf_file: *Elf, out_relocs: *std.ArrayList(elf.Elf64_Rela)) !void {
+    const file_ptr = self.file(elf_file).?;
+    for (self.relocs(elf_file)) |rel| {
+        const target_index = switch (file_ptr) {
+            .zig_object => |x| x.symbol(rel.r_sym()),
+            .object => |x| x.symbols.items[rel.r_sym()],
+            else => unreachable,
+        };
+        const target = elf_file.symbol(target_index);
+        const r_sym = target.outputSymtabIndex(elf_file);
+        const r_offset = self.value + rel.r_offset;
+        const r_addend = rel.r_addend;
+        const r_type = switch (rel.r_type()) {
+            Elf.R_X86_64_ZIG_GOT32,
+            Elf.R_X86_64_ZIG_GOTPCREL,
+            => unreachable, // Sanity check if we accidentally emitted those.
+            else => |r_type| r_type,
+        };
+        out_relocs.appendAssumeCapacity(.{
+            .r_offset = r_offset,
+            .r_addend = r_addend,
+            .r_info = (@as(u64, @intCast(r_sym)) << 32) | r_type,
+        });
+    }
+}
+
 pub fn fdes(self: Atom, elf_file: *Elf) []Fde {
     if (self.fde_start == self.fde_end) return &[0]Fde{};
     const object = self.file(elf_file).?.object;
src/link/Elf/file.zig
@@ -127,9 +127,9 @@ pub const File = union(enum) {
         };
     }
 
-    pub fn updateSymtabSize(file: File, elf_file: *Elf) void {
-        const output_symtab_size = switch (file) {
-            inline else => |x| &x.output_symtab_size,
+    pub fn updateSymtabSize(file: File, elf_file: *Elf) !void {
+        const output_symtab_ctx = switch (file) {
+            inline else => |x| &x.output_symtab_ctx,
         };
         for (file.locals()) |local_index| {
             const local = elf_file.symbol(local_index);
@@ -140,8 +140,9 @@ pub const File = union(enum) {
                 else => {},
             }
             local.flags.output_symtab = true;
-            output_symtab_size.nlocals += 1;
-            output_symtab_size.strsize += @as(u32, @intCast(local.name(elf_file).len)) + 1;
+            try local.setOutputSymtabIndex(output_symtab_ctx.nlocals, elf_file);
+            output_symtab_ctx.nlocals += 1;
+            output_symtab_ctx.strsize += @as(u32, @intCast(local.name(elf_file).len)) + 1;
         }
 
         for (file.globals()) |global_index| {
@@ -151,28 +152,28 @@ pub const File = union(enum) {
             if (global.atom(elf_file)) |atom| if (!atom.flags.alive) continue;
             global.flags.output_symtab = true;
             if (global.isLocal(elf_file)) {
-                output_symtab_size.nlocals += 1;
+                try global.setOutputSymtabIndex(output_symtab_ctx.nlocals, elf_file);
+                output_symtab_ctx.nlocals += 1;
             } else {
-                output_symtab_size.nglobals += 1;
+                try global.setOutputSymtabIndex(output_symtab_ctx.nglobals, elf_file);
+                output_symtab_ctx.nglobals += 1;
             }
-            output_symtab_size.strsize += @as(u32, @intCast(global.name(elf_file).len)) + 1;
+            output_symtab_ctx.strsize += @as(u32, @intCast(global.name(elf_file).len)) + 1;
         }
     }
 
-    pub fn writeSymtab(file: File, elf_file: *Elf, ctx: anytype) void {
-        var ilocal: usize = ctx.ilocal;
+    pub fn writeSymtab(file: File, elf_file: *Elf) void {
         for (file.locals()) |local_index| {
             const local = elf_file.symbol(local_index);
             if (!local.flags.output_symtab) continue;
-            const out_sym = &elf_file.symtab.items[ilocal];
+            const idx = local.outputSymtabIndex(elf_file);
+            const out_sym = &elf_file.symtab.items[idx];
             out_sym.st_name = @intCast(elf_file.strtab.items.len);
             elf_file.strtab.appendSliceAssumeCapacity(local.name(elf_file));
             elf_file.strtab.appendAssumeCapacity(0);
             local.setOutputSym(elf_file, out_sym);
-            ilocal += 1;
         }
 
-        var iglobal: usize = ctx.iglobal;
         for (file.globals()) |global_index| {
             const global = elf_file.symbol(global_index);
             const file_ptr = global.file(elf_file) orelse continue;
@@ -181,17 +182,10 @@ pub const File = union(enum) {
             const st_name = @as(u32, @intCast(elf_file.strtab.items.len));
             elf_file.strtab.appendSliceAssumeCapacity(global.name(elf_file));
             elf_file.strtab.appendAssumeCapacity(0);
-            if (global.isLocal(elf_file)) {
-                const out_sym = &elf_file.symtab.items[ilocal];
-                out_sym.st_name = st_name;
-                global.setOutputSym(elf_file, out_sym);
-                ilocal += 1;
-            } else {
-                const out_sym = &elf_file.symtab.items[iglobal];
-                out_sym.st_name = st_name;
-                global.setOutputSym(elf_file, out_sym);
-                iglobal += 1;
-            }
+            const idx = global.outputSymtabIndex(elf_file);
+            const out_sym = &elf_file.symtab.items[idx];
+            out_sym.st_name = st_name;
+            global.setOutputSym(elf_file, out_sym);
         }
     }
 
src/link/Elf/LinkerDefined.zig
@@ -3,7 +3,7 @@ symtab: std.ArrayListUnmanaged(elf.Elf64_Sym) = .{},
 strtab: std.ArrayListUnmanaged(u8) = .{},
 symbols: std.ArrayListUnmanaged(Symbol.Index) = .{},
 
-output_symtab_size: Elf.SymtabSize = .{},
+output_symtab_ctx: Elf.SymtabCtx = .{},
 
 pub fn deinit(self: *LinkerDefined, allocator: Allocator) void {
     self.symtab.deinit(allocator);
src/link/Elf/Object.zig
@@ -19,7 +19,7 @@ cies: std.ArrayListUnmanaged(Cie) = .{},
 alive: bool = true,
 num_dynrelocs: u32 = 0,
 
-output_symtab_size: Elf.SymtabSize = .{},
+output_symtab_ctx: Elf.SymtabCtx = .{},
 output_ar_state: Archive.ArState = .{},
 
 pub fn isObject(path: []const u8) !bool {
@@ -672,22 +672,19 @@ pub fn initRelaSections(self: Object, elf_file: *Elf) !void {
     }
 }
 
-pub fn updateRelaSectionsSizes(self: Object, elf_file: *Elf) void {
+pub fn addAtomsToRelaSections(self: Object, elf_file: *Elf) !void {
     for (self.atoms.items) |atom_index| {
         const atom = elf_file.atom(atom_index) orelse continue;
         if (!atom.flags.alive) continue;
         const shndx = atom.relocsShndx() orelse continue;
         const shdr = self.shdrs.items[shndx];
         const out_shndx = self.initOutputSection(elf_file, shdr) catch unreachable;
-        const out_shdr = &elf_file.shdrs.items[out_shndx];
-        const relocs = atom.relocs(elf_file);
-        out_shdr.sh_size += out_shdr.sh_entsize * relocs.len;
-    }
-}
 
-pub fn writeRelaSections(self: Object, elf_file: *Elf) !void {
-    _ = self;
-    _ = elf_file;
+        const gpa = elf_file.base.allocator;
+        const gop = try elf_file.output_rela_sections.getOrPut(gpa, out_shndx);
+        if (!gop.found_existing) gop.value_ptr.* = .{};
+        try gop.value_ptr.append(gpa, atom_index);
+    }
 }
 
 pub fn updateArSymtab(self: Object, ar_symtab: *Archive.ArSymtab, elf_file: *Elf) !void {
src/link/Elf/SharedObject.zig
@@ -21,7 +21,7 @@ verdef_sect_index: ?u16 = null,
 needed: bool,
 alive: bool,
 
-output_symtab_size: Elf.SymtabSize = .{},
+output_symtab_ctx: Elf.SymtabCtx = .{},
 
 pub fn isSharedObject(path: []const u8) !bool {
     const file = try std.fs.cwd().openFile(path, .{});
src/link/Elf/Symbol.zig
@@ -107,6 +107,24 @@ pub fn address(symbol: Symbol, opts: struct { plt: bool = true }, elf_file: *Elf
     return symbol.value;
 }
 
+pub fn outputSymtabIndex(symbol: Symbol, elf_file: *Elf) u32 {
+    assert(symbol.flags.output_symtab);
+    const file_ptr = symbol.file(elf_file).?;
+    const symtab_ctx = switch (file_ptr) {
+        inline else => |x| x.output_symtab_ctx,
+    };
+    const idx = symbol.extra(elf_file).?.symtab;
+    return if (symbol.isLocal(elf_file)) idx + symtab_ctx.ilocal else idx + symtab_ctx.iglobal;
+}
+
+pub fn setOutputSymtabIndex(symbol: *Symbol, index: u32, elf_file: *Elf) !void {
+    if (symbol.extra(elf_file)) |extras| {
+        var new_extras = extras;
+        new_extras.symtab = index;
+        symbol.setExtra(new_extras, elf_file);
+    } else try symbol.addExtra(.{ .symtab = index }, elf_file);
+}
+
 pub fn gotAddress(symbol: Symbol, elf_file: *Elf) u64 {
     if (!symbol.flags.has_got) return 0;
     const extras = symbol.extra(elf_file).?;
@@ -388,6 +406,7 @@ pub const Extra = struct {
     plt: u32 = 0,
     plt_got: u32 = 0,
     dynamic: u32 = 0,
+    symtab: u32 = 0,
     copy_rel: u32 = 0,
     tlsgd: u32 = 0,
     gottp: u32 = 0,
src/link/Elf/synthetic_sections.zig
@@ -222,7 +222,7 @@ pub const DynamicSection = struct {
 
 pub const ZigGotSection = struct {
     entries: std.ArrayListUnmanaged(Symbol.Index) = .{},
-    output_symtab_size: Elf.SymtabSize = .{},
+    output_symtab_ctx: Elf.SymtabCtx = .{},
     flags: Flags = .{},
 
     const Flags = packed struct {
@@ -359,15 +359,15 @@ pub const ZigGotSection = struct {
     }
 
     pub fn updateSymtabSize(zig_got: *ZigGotSection, elf_file: *Elf) void {
-        zig_got.output_symtab_size.nlocals = @as(u32, @intCast(zig_got.entries.items.len));
+        zig_got.output_symtab_ctx.nlocals = @as(u32, @intCast(zig_got.entries.items.len));
         for (zig_got.entries.items) |entry| {
             const name = elf_file.symbol(entry).name(elf_file);
-            zig_got.output_symtab_size.strsize += @as(u32, @intCast(name.len + "$ziggot".len)) + 1;
+            zig_got.output_symtab_ctx.strsize += @as(u32, @intCast(name.len + "$ziggot".len)) + 1;
         }
     }
 
-    pub fn writeSymtab(zig_got: ZigGotSection, elf_file: *Elf, ctx: anytype) void {
-        for (zig_got.entries.items, ctx.ilocal.., 0..) |entry, ilocal, index| {
+    pub fn writeSymtab(zig_got: ZigGotSection, elf_file: *Elf) void {
+        for (zig_got.entries.items, zig_got.output_symtab_ctx.ilocal.., 0..) |entry, ilocal, index| {
             const symbol = elf_file.symbol(entry);
             const symbol_name = symbol.name(elf_file);
             const st_name = @as(u32, @intCast(elf_file.strtab.items.len));
@@ -420,7 +420,7 @@ pub const ZigGotSection = struct {
 
 pub const GotSection = struct {
     entries: std.ArrayListUnmanaged(Entry) = .{},
-    output_symtab_size: Elf.SymtabSize = .{},
+    output_symtab_ctx: Elf.SymtabCtx = .{},
     tlsld_index: ?u32 = null,
     flags: Flags = .{},
 
@@ -760,18 +760,18 @@ pub const GotSection = struct {
     }
 
     pub fn updateSymtabSize(got: *GotSection, elf_file: *Elf) void {
-        got.output_symtab_size.nlocals = @as(u32, @intCast(got.entries.items.len));
+        got.output_symtab_ctx.nlocals = @as(u32, @intCast(got.entries.items.len));
         for (got.entries.items) |entry| {
             const symbol_name = switch (entry.tag) {
                 .tlsld => "",
                 inline else => elf_file.symbol(entry.symbol_index).name(elf_file),
             };
-            got.output_symtab_size.strsize += @as(u32, @intCast(symbol_name.len + @tagName(entry.tag).len)) + 1 + 1;
+            got.output_symtab_ctx.strsize += @as(u32, @intCast(symbol_name.len + @tagName(entry.tag).len)) + 1 + 1;
         }
     }
 
-    pub fn writeSymtab(got: GotSection, elf_file: *Elf, ctx: anytype) void {
-        for (got.entries.items, ctx.ilocal..) |entry, ilocal| {
+    pub fn writeSymtab(got: GotSection, elf_file: *Elf) void {
+        for (got.entries.items, got.output_symtab_ctx.ilocal..) |entry, ilocal| {
             const symbol = switch (entry.tag) {
                 .tlsld => null,
                 inline else => elf_file.symbol(entry.symbol_index),
@@ -831,7 +831,7 @@ pub const GotSection = struct {
 
 pub const PltSection = struct {
     symbols: std.ArrayListUnmanaged(Symbol.Index) = .{},
-    output_symtab_size: Elf.SymtabSize = .{},
+    output_symtab_ctx: Elf.SymtabCtx = .{},
 
     pub const preamble_size = 32;
 
@@ -909,15 +909,15 @@ pub const PltSection = struct {
     }
 
     pub fn updateSymtabSize(plt: *PltSection, elf_file: *Elf) void {
-        plt.output_symtab_size.nlocals = @as(u32, @intCast(plt.symbols.items.len));
+        plt.output_symtab_ctx.nlocals = @as(u32, @intCast(plt.symbols.items.len));
         for (plt.symbols.items) |sym_index| {
             const name = elf_file.symbol(sym_index).name(elf_file);
-            plt.output_symtab_size.strsize += @as(u32, @intCast(name.len + "$plt".len)) + 1;
+            plt.output_symtab_ctx.strsize += @as(u32, @intCast(name.len + "$plt".len)) + 1;
         }
     }
 
-    pub fn writeSymtab(plt: PltSection, elf_file: *Elf, ctx: anytype) void {
-        var ilocal = ctx.ilocal;
+    pub fn writeSymtab(plt: PltSection, elf_file: *Elf) void {
+        var ilocal = plt.output_symtab_ctx.ilocal;
         for (plt.symbols.items) |sym_index| {
             const sym = elf_file.symbol(sym_index);
             const st_name = @as(u32, @intCast(elf_file.strtab.items.len));
@@ -968,7 +968,7 @@ pub const GotPltSection = struct {
 
 pub const PltGotSection = struct {
     symbols: std.ArrayListUnmanaged(Symbol.Index) = .{},
-    output_symtab_size: Elf.SymtabSize = .{},
+    output_symtab_ctx: Elf.SymtabCtx = .{},
 
     pub fn deinit(plt_got: *PltGotSection, allocator: Allocator) void {
         plt_got.symbols.deinit(allocator);
@@ -1008,15 +1008,15 @@ pub const PltGotSection = struct {
     }
 
     pub fn updateSymtabSize(plt_got: *PltGotSection, elf_file: *Elf) void {
-        plt_got.output_symtab_size.nlocals = @as(u32, @intCast(plt_got.symbols.items.len));
+        plt_got.output_symtab_ctx.nlocals = @as(u32, @intCast(plt_got.symbols.items.len));
         for (plt_got.symbols.items) |sym_index| {
             const name = elf_file.symbol(sym_index).name(elf_file);
-            plt_got.output_symtab_size.strsize += @as(u32, @intCast(name.len + "$pltgot".len)) + 1;
+            plt_got.output_symtab_ctx.strsize += @as(u32, @intCast(name.len + "$pltgot".len)) + 1;
         }
     }
 
-    pub fn writeSymtab(plt_got: PltGotSection, elf_file: *Elf, ctx: anytype) void {
-        var ilocal = ctx.ilocal;
+    pub fn writeSymtab(plt_got: PltGotSection, elf_file: *Elf) void {
+        var ilocal = plt_got.output_symtab_ctx.ilocal;
         for (plt_got.symbols.items) |sym_index| {
             const sym = elf_file.symbol(sym_index);
             const st_name = @as(u32, @intCast(elf_file.strtab.items.len));
src/link/Elf/ZigObject.zig
@@ -18,7 +18,7 @@ relocs: std.ArrayListUnmanaged(std.ArrayListUnmanaged(elf.Elf64_Rela)) = .{},
 
 num_dynrelocs: u32 = 0,
 
-output_symtab_size: Elf.SymtabSize = .{},
+output_symtab_ctx: Elf.SymtabCtx = .{},
 output_ar_state: Archive.ArState = .{},
 
 dwarf: ?Dwarf = null,
@@ -533,94 +533,17 @@ pub fn writeAr(self: ZigObject, elf_file: *Elf, writer: anytype) !void {
     try writer.writeAll(contents);
 }
 
-pub fn updateRelaSectionsSizes(self: ZigObject, elf_file: *Elf) void {
-    _ = self;
-
-    for (&[_]?u16{
-        elf_file.zig_text_rela_section_index,
-        elf_file.zig_data_rel_ro_rela_section_index,
-        elf_file.zig_data_rela_section_index,
-    }) |maybe_index| {
-        const index = maybe_index orelse continue;
-        const shdr = &elf_file.shdrs.items[index];
-        const meta = elf_file.last_atom_and_free_list_table.get(@intCast(shdr.sh_info)).?;
-        const last_atom_index = meta.last_atom_index;
-
-        var atom = elf_file.atom(last_atom_index) orelse continue;
-        while (true) {
-            const relocs = atom.relocs(elf_file);
-            shdr.sh_size += relocs.len * shdr.sh_entsize;
-            if (elf_file.atom(atom.prev_index)) |prev| {
-                atom = prev;
-            } else break;
-        }
-    }
-
-    for (&[_]?u16{
-        elf_file.zig_text_rela_section_index,
-        elf_file.zig_data_rel_ro_rela_section_index,
-        elf_file.zig_data_rela_section_index,
-    }) |maybe_index| {
-        const index = maybe_index orelse continue;
-        const shdr = &elf_file.shdrs.items[index];
-        if (shdr.sh_size == 0) shdr.sh_offset = 0;
-    }
-}
-
-pub fn writeRelaSections(self: ZigObject, elf_file: *Elf) !void {
-    const gpa = elf_file.base.allocator;
-
-    for (&[_]?u16{
-        elf_file.zig_text_rela_section_index,
-        elf_file.zig_data_rel_ro_rela_section_index,
-        elf_file.zig_data_rela_section_index,
-    }) |maybe_index| {
-        const index = maybe_index orelse continue;
-        const shdr = elf_file.shdrs.items[index];
-        const meta = elf_file.last_atom_and_free_list_table.get(@intCast(shdr.sh_info)).?;
-        const last_atom_index = meta.last_atom_index;
-
-        var atom = elf_file.atom(last_atom_index) orelse continue;
-
-        var relocs = std.ArrayList(elf.Elf64_Rela).init(gpa);
-        defer relocs.deinit();
-        try relocs.ensureTotalCapacityPrecise(@intCast(@divExact(shdr.sh_size, shdr.sh_entsize)));
-
-        while (true) {
-            for (atom.relocs(elf_file)) |rel| {
-                const target = elf_file.symbol(self.symbol(rel.r_sym()));
-                const r_offset = atom.value + rel.r_offset;
-                const r_sym: u32 = if (target.flags.global)
-                    (target.esym_index & symbol_mask) + @as(u32, @intCast(self.local_esyms.slice().len))
-                else
-                    target.esym_index;
-                const r_type = switch (rel.r_type()) {
-                    Elf.R_X86_64_ZIG_GOT32,
-                    Elf.R_X86_64_ZIG_GOTPCREL,
-                    => unreachable, // Sanity check if we accidentally emitted those.
-                    else => |r_type| r_type,
-                };
-                relocs.appendAssumeCapacity(.{
-                    .r_offset = r_offset,
-                    .r_addend = rel.r_addend,
-                    .r_info = (@as(u64, @intCast(r_sym + 1)) << 32) | r_type,
-                });
-            }
-            if (elf_file.atom(atom.prev_index)) |prev| {
-                atom = prev;
-            } else break;
-        }
-
-        const SortRelocs = struct {
-            pub fn lessThan(ctx: void, lhs: elf.Elf64_Rela, rhs: elf.Elf64_Rela) bool {
-                _ = ctx;
-                return lhs.r_offset < rhs.r_offset;
-            }
-        };
-
-        mem.sort(elf.Elf64_Rela, relocs.items, {}, SortRelocs.lessThan);
+pub fn addAtomsToRelaSections(self: ZigObject, elf_file: *Elf) !void {
+    for (self.atoms.items) |atom_index| {
+        const atom = elf_file.atom(atom_index) orelse continue;
+        if (!atom.flags.alive) continue;
+        _ = atom.relocsShndx() orelse continue;
+        const out_shndx = atom.outputShndx().?;
 
-        try elf_file.base.file.?.pwriteAll(mem.sliceAsBytes(relocs.items), shdr.sh_offset);
+        const gpa = elf_file.base.allocator;
+        const gop = try elf_file.output_rela_sections.getOrPut(gpa, out_shndx);
+        if (!gop.found_existing) gop.value_ptr.* = .{};
+        try gop.value_ptr.append(gpa, atom_index);
     }
 }
 
src/link/Elf.zig
@@ -24,6 +24,7 @@ shdr_table_offset: ?u64 = null,
 /// Table of lists of atoms per output section.
 /// This table is not used to track incrementally generated atoms.
 output_sections: std.AutoArrayHashMapUnmanaged(u16, std.ArrayListUnmanaged(Atom.Index)) = .{},
+output_rela_sections: std.AutoArrayHashMapUnmanaged(u16, std.ArrayListUnmanaged(Atom.Index)) = .{},
 
 /// Stored in native-endian format, depending on target endianness needs to be bswapped on read/write.
 /// Same order as in the file.
@@ -105,11 +106,8 @@ zig_got: ZigGotSection = .{},
 /// Tracked section headers with incremental updates to Zig object.
 /// .rela.* sections are only used when emitting a relocatable object file.
 zig_text_section_index: ?u16 = null,
-zig_text_rela_section_index: ?u16 = null,
 zig_data_rel_ro_section_index: ?u16 = null,
-zig_data_rel_ro_rela_section_index: ?u16 = null,
 zig_data_section_index: ?u16 = null,
-zig_data_rela_section_index: ?u16 = null,
 zig_bss_section_index: ?u16 = null,
 zig_got_section_index: ?u16 = null,
 
@@ -357,6 +355,10 @@ pub fn deinit(self: *Elf) void {
         list.deinit(gpa);
     }
     self.output_sections.deinit(gpa);
+    for (self.output_rela_sections.values()) |*list| {
+        list.deinit(gpa);
+    }
+    self.output_rela_sections.deinit(gpa);
     self.shstrtab.deinit(gpa);
     self.symtab.deinit(gpa);
     self.strtab.deinit(gpa);
@@ -597,10 +599,8 @@ pub fn initMetadata(self: *Elf) !void {
         const shdr = &self.shdrs.items[self.zig_text_section_index.?];
         fillSection(self, shdr, self.base.options.program_code_size_hint, self.phdr_zig_load_re_index);
         if (self.isRelocatable()) {
-            self.zig_text_rela_section_index = try self.addRelaShdr(
-                ".rela.text.zig",
-                self.zig_text_section_index.?,
-            );
+            const rela_shndx = try self.addRelaShdr(".rela.text.zig", self.zig_text_section_index.?);
+            try self.output_rela_sections.putNoClobber(gpa, rela_shndx, .{});
         } else {
             try self.phdr_to_shdr_table.putNoClobber(
                 gpa,
@@ -644,10 +644,11 @@ pub fn initMetadata(self: *Elf) !void {
         const shdr = &self.shdrs.items[self.zig_data_rel_ro_section_index.?];
         fillSection(self, shdr, 1024, self.phdr_zig_load_ro_index);
         if (self.isRelocatable()) {
-            self.zig_data_rel_ro_rela_section_index = try self.addRelaShdr(
+            const rela_shndx = try self.addRelaShdr(
                 ".rela.data.rel.ro.zig",
                 self.zig_data_rel_ro_section_index.?,
             );
+            try self.output_rela_sections.putNoClobber(gpa, rela_shndx, .{});
         } else {
             try self.phdr_to_shdr_table.putNoClobber(
                 gpa,
@@ -670,10 +671,11 @@ pub fn initMetadata(self: *Elf) !void {
         const shdr = &self.shdrs.items[self.zig_data_section_index.?];
         fillSection(self, shdr, 1024, self.phdr_zig_load_rw_index);
         if (self.isRelocatable()) {
-            self.zig_data_rela_section_index = try self.addRelaShdr(
+            const rela_shndx = try self.addRelaShdr(
                 ".rela.data.zig",
                 self.zig_data_section_index.?,
             );
+            try self.output_rela_sections.putNoClobber(gpa, rela_shndx, .{});
         } else {
             try self.phdr_to_shdr_table.putNoClobber(
                 gpa,
@@ -1514,16 +1516,13 @@ pub fn flushStaticLib(self: *Elf) link.File.FlushError!void {
         try self.initSymtab();
         try self.initShStrtab();
         try self.sortShdrs();
-        zig_object.updateRelaSectionsSizes(self);
-        self.updateSymtabSizeZigObject(zig_object);
-        self.updateShStrtabSize();
+        try zig_object.addAtomsToRelaSections(self);
+        try self.updateSectionSizesObject();
 
         try self.allocateNonAllocSections();
 
         try self.writeShdrTable();
-        try zig_object.writeRelaSections(self);
-        try self.writeSymtabZigObject(zig_object);
-        try self.writeShStrtab();
+        try self.writeSyntheticSectionsObject();
         try self.writeElfHeader();
     }
 
@@ -1620,7 +1619,9 @@ pub fn flushObject(self: *Elf) link.File.FlushError!void {
     try self.initSectionsObject();
     try self.sortShdrs();
     for (self.objects.items) |index| {
-        try self.file(index).?.object.addAtomsToOutputSections(self);
+        const object = self.file(index).?.object;
+        try object.addAtomsToOutputSections(self);
+        try object.addAtomsToRelaSections(self);
     }
     try self.updateSectionSizesObject();
 
@@ -3452,7 +3453,7 @@ fn initSectionsObject(self: *Elf) !void {
             .addralign = ptr_size,
             .offset = std.math.maxInt(u64),
         });
-        _ = try self.addRelaShdr(".rela.eh_frame", self.eh_frame_section_index.?);
+        // _ = try self.addRelaShdr(".rela.eh_frame", self.eh_frame_section_index.?);
     }
 
     try self.initSymtab();
@@ -3841,12 +3842,9 @@ fn sortShdrs(self: *Elf) !void {
         &self.versym_section_index,
         &self.verneed_section_index,
         &self.zig_text_section_index,
-        &self.zig_text_rela_section_index,
         &self.zig_got_section_index,
         &self.zig_data_rel_ro_section_index,
-        &self.zig_data_rel_ro_rela_section_index,
         &self.zig_data_section_index,
-        &self.zig_data_rela_section_index,
         &self.zig_bss_section_index,
         &self.debug_str_section_index,
         &self.debug_info_section_index,
@@ -4066,7 +4064,7 @@ fn updateSectionSizes(self: *Elf) !void {
         self.shdrs.items[index].sh_size = self.verneed.size();
     }
 
-    self.updateSymtabSize();
+    try self.updateSymtabSize();
     self.updateShStrtabSize();
 }
 
@@ -4084,19 +4082,21 @@ fn updateSectionSizesObject(self: *Elf) !void {
         }
     }
 
-    if (self.zigObjectPtr()) |zig_object| {
-        zig_object.updateRelaSectionsSizes(self);
-    }
-
-    for (self.objects.items) |index| {
-        self.file(index).?.object.updateRelaSectionsSizes(self);
+    for (self.output_rela_sections.keys(), self.output_rela_sections.values()) |shndx, atom_list| {
+        const shdr = &self.shdrs.items[shndx];
+        for (atom_list.items) |atom_index| {
+            const atom_ptr = self.atom(atom_index) orelse continue;
+            if (!atom_ptr.flags.alive) continue;
+            const relocs = atom_ptr.relocs(self);
+            shdr.sh_size += shdr.sh_entsize * relocs.len;
+        }
     }
 
     if (self.eh_frame_section_index) |index| {
         self.shdrs.items[index].sh_size = try eh_frame.calcEhFrameSize(self);
     }
 
-    self.updateSymtabSize();
+    try self.updateSymtabSize();
     self.updateShStrtabSize();
 }
 
@@ -4597,96 +4597,123 @@ fn writeAtomsObject(self: *Elf) !void {
     }
 }
 
-fn updateSymtabSize(self: *Elf) void {
-    var sizes = SymtabSize{};
+fn updateSymtabSize(self: *Elf) !void {
+    var nlocals: u32 = 0;
+    var nglobals: u32 = 0;
+    var strsize: u32 = 0;
 
-    if (self.zigObjectPtr()) |zig_object| {
-        zig_object.asFile().updateSymtabSize(self);
-        sizes.add(zig_object.output_symtab_size);
-    }
+    const gpa = self.base.allocator;
+    var files = std.ArrayList(File.Index).init(gpa);
+    defer files.deinit();
+    try files.ensureTotalCapacityPrecise(self.objects.items.len + self.shared_objects.items.len + 1);
 
+    if (self.zig_object_index) |index| files.appendAssumeCapacity(index);
     for (self.objects.items) |index| {
-        const file_ptr = self.file(index).?;
-        file_ptr.updateSymtabSize(self);
-        sizes.add(file_ptr.object.output_symtab_size);
+        files.appendAssumeCapacity(index);
     }
-
     for (self.shared_objects.items) |index| {
+        files.appendAssumeCapacity(index);
+    }
+
+    // Section symbols
+    for (self.output_sections.keys()) |_| {
+        nlocals += 1;
+    }
+
+    for (files.items) |index| {
         const file_ptr = self.file(index).?;
-        file_ptr.updateSymtabSize(self);
-        sizes.add(file_ptr.shared_object.output_symtab_size);
+        const ctx = switch (file_ptr) {
+            inline else => |x| &x.output_symtab_ctx,
+        };
+        ctx.ilocal = nlocals + 1;
+        ctx.iglobal = nglobals + 1;
+        try file_ptr.updateSymtabSize(self);
+        nlocals += ctx.nlocals;
+        nglobals += ctx.nglobals;
+        strsize += ctx.strsize;
     }
 
     if (self.zig_got_section_index) |_| {
+        self.zig_got.output_symtab_ctx.ilocal = nlocals + 1;
         self.zig_got.updateSymtabSize(self);
-        sizes.add(self.zig_got.output_symtab_size);
+        nlocals += self.zig_got.output_symtab_ctx.nlocals;
+        strsize += self.zig_got.output_symtab_ctx.strsize;
     }
 
     if (self.got_section_index) |_| {
+        self.got.output_symtab_ctx.ilocal = nlocals + 1;
         self.got.updateSymtabSize(self);
-        sizes.add(self.got.output_symtab_size);
+        nlocals += self.got.output_symtab_ctx.nlocals;
+        strsize += self.got.output_symtab_ctx.strsize;
     }
 
     if (self.plt_section_index) |_| {
+        self.plt.output_symtab_ctx.ilocal = nlocals + 1;
         self.plt.updateSymtabSize(self);
-        sizes.add(self.plt.output_symtab_size);
+        nlocals += self.plt.output_symtab_ctx.nlocals;
+        strsize += self.plt.output_symtab_ctx.strsize;
     }
 
     if (self.plt_got_section_index) |_| {
+        self.plt_got.output_symtab_ctx.ilocal = nlocals + 1;
         self.plt_got.updateSymtabSize(self);
-        sizes.add(self.plt_got.output_symtab_size);
+        nlocals += self.plt_got.output_symtab_ctx.nlocals;
+        strsize += self.plt_got.output_symtab_ctx.strsize;
     }
 
-    if (self.linker_defined_index) |index| {
+    for (files.items) |index| {
         const file_ptr = self.file(index).?;
-        file_ptr.updateSymtabSize(self);
-        sizes.add(file_ptr.linker_defined.output_symtab_size);
-    }
-
-    // Section symbols
-    for (self.output_sections.keys()) |_| {
-        sizes.nlocals += 1;
+        const ctx = switch (file_ptr) {
+            inline else => |x| &x.output_symtab_ctx,
+        };
+        ctx.iglobal += nlocals;
     }
 
     const symtab_shdr = &self.shdrs.items[self.symtab_section_index.?];
-    symtab_shdr.sh_info = sizes.nlocals + 1;
+    symtab_shdr.sh_info = nlocals + 1;
     symtab_shdr.sh_link = self.strtab_section_index.?;
 
     const sym_size: u64 = switch (self.ptr_width) {
         .p32 => @sizeOf(elf.Elf32_Sym),
         .p64 => @sizeOf(elf.Elf64_Sym),
     };
-    const needed_size = (sizes.nlocals + sizes.nglobals + 1) * sym_size;
+    const needed_size = (nlocals + nglobals + 1) * sym_size;
     symtab_shdr.sh_size = needed_size;
 
     const strtab = &self.shdrs.items[self.strtab_section_index.?];
-    strtab.sh_size = sizes.strsize + 1;
+    strtab.sh_size = strsize + 1;
 }
 
 fn updateSymtabSizeZigObject(self: *Elf, zig_object: *ZigObject) void {
-    var sizes = SymtabSize{};
-
-    zig_object.asFile().updateSymtabSize(self);
-    sizes.add(zig_object.output_symtab_size);
+    var nlocals: u32 = 0;
+    var nglobals: u32 = 0;
+    var strsize: u32 = 0;
 
     // Section symbols
     for (self.output_sections.keys()) |_| {
-        sizes.nlocals += 1;
+        nlocals += 1;
     }
 
+    zig_object.output_symtab_ctx.ilocal = nlocals + 1;
+    try zig_object.asFile().updateSymtabSize(self);
+    nlocals += zig_object.output_symtab_ctx.nlocals;
+    nglobals += zig_object.output_symtab_ctx.nglobals;
+    strsize += zig_object.output_symtab_ctx.strsize;
+    zig_object.output_symtab_ctx.iglobal = nlocals + 1;
+
     const symtab_shdr = &self.shdrs.items[self.symtab_section_index.?];
-    symtab_shdr.sh_info = sizes.nlocals + 1;
+    symtab_shdr.sh_info = nlocals + 1;
     symtab_shdr.sh_link = self.strtab_section_index.?;
 
     const sym_size: u64 = switch (self.ptr_width) {
         .p32 => @sizeOf(elf.Elf32_Sym),
         .p64 => @sizeOf(elf.Elf64_Sym),
     };
-    const needed_size = (sizes.nlocals + sizes.nglobals + 1) * sym_size;
+    const needed_size = (nlocals + nglobals + 1) * sym_size;
     symtab_shdr.sh_size = needed_size;
 
     const strtab = &self.shdrs.items[self.strtab_section_index.?];
-    strtab.sh_size = sizes.strsize + 1;
+    strtab.sh_size = strsize + 1;
 }
 
 fn writeSyntheticSections(self: *Elf) !void {
@@ -4822,12 +4849,31 @@ fn writeSyntheticSections(self: *Elf) !void {
 fn writeSyntheticSectionsObject(self: *Elf) !void {
     const gpa = self.base.allocator;
 
-    if (self.zigObjectPtr()) |zig_object| {
-        try zig_object.writeRelaSections(self);
-    }
+    for (self.output_rela_sections.keys(), self.output_rela_sections.values()) |shndx, atom_list| {
+        if (atom_list.items.len == 0) continue;
 
-    for (self.objects.items) |index| {
-        try self.file(index).?.object.writeRelaSections(self);
+        const shdr = self.shdrs.items[shndx];
+
+        const num_relocs = @divExact(shdr.sh_size, shdr.sh_entsize);
+        var relocs = try std.ArrayList(elf.Elf64_Rela).initCapacity(gpa, num_relocs);
+        defer relocs.deinit();
+
+        for (atom_list.items) |atom_index| {
+            const atom_ptr = self.atom(atom_index) orelse continue;
+            if (!atom_ptr.flags.alive) continue;
+            try atom_ptr.writeRelocs(self, &relocs);
+        }
+
+        const SortRelocs = struct {
+            pub fn lessThan(ctx: void, lhs: elf.Elf64_Rela, rhs: elf.Elf64_Rela) bool {
+                _ = ctx;
+                return lhs.r_offset < rhs.r_offset;
+            }
+        };
+
+        mem.sort(elf.Elf64_Rela, relocs.items, {}, SortRelocs.lessThan);
+
+        try self.base.file.?.pwriteAll(mem.sliceAsBytes(relocs.items), shdr.sh_offset);
     }
 
     if (self.eh_frame_section_index) |shndx| {
@@ -4836,7 +4882,7 @@ fn writeSyntheticSectionsObject(self: *Elf) !void {
         var buffer = try std.ArrayList(u8).initCapacity(gpa, sh_size);
         defer buffer.deinit();
         try eh_frame.writeEhFrame(self, buffer.writer());
-        // try self.base.file.?.pwriteAll(buffer.items, shdr.sh_offset);
+        try self.base.file.?.pwriteAll(buffer.items, shdr.sh_offset);
     }
 
     try self.writeSymtab();
@@ -4850,16 +4896,6 @@ fn writeShStrtab(self: *Elf) !void {
     }
 }
 
-const WriteSymtabCtx = struct {
-    ilocal: usize,
-    iglobal: usize,
-
-    fn incr(this: *@This(), ss: SymtabSize) void {
-        this.ilocal += ss.nlocals;
-        this.iglobal += ss.nglobals;
-    }
-};
-
 fn writeSymtab(self: *Elf) !void {
     const gpa = self.base.allocator;
     const symtab_shdr = self.shdrs.items[self.symtab_section_index.?];
@@ -4876,54 +4912,41 @@ fn writeSymtab(self: *Elf) !void {
     const needed_strtab_size = math.cast(usize, strtab_shdr.sh_size - 1) orelse return error.Overflow;
     try self.strtab.ensureUnusedCapacity(gpa, needed_strtab_size);
 
-    var ctx: WriteSymtabCtx = .{
-        .ilocal = 1,
-        .iglobal = symtab_shdr.sh_info,
-    };
-
-    ctx.incr(self.writeSectionSymbols(ctx));
+    self.writeSectionSymbols();
 
     if (self.zigObjectPtr()) |zig_object| {
-        zig_object.asFile().writeSymtab(self, ctx);
-        ctx.incr(zig_object.output_symtab_size);
+        zig_object.asFile().writeSymtab(self);
     }
 
     for (self.objects.items) |index| {
         const file_ptr = self.file(index).?;
-        file_ptr.writeSymtab(self, ctx);
-        ctx.incr(file_ptr.object.output_symtab_size);
+        file_ptr.writeSymtab(self);
     }
 
     for (self.shared_objects.items) |index| {
         const file_ptr = self.file(index).?;
-        file_ptr.writeSymtab(self, ctx);
-        ctx.incr(file_ptr.shared_object.output_symtab_size);
+        file_ptr.writeSymtab(self);
     }
 
     if (self.zig_got_section_index) |_| {
-        self.zig_got.writeSymtab(self, ctx);
-        ctx.incr(self.zig_got.output_symtab_size);
+        self.zig_got.writeSymtab(self);
     }
 
     if (self.got_section_index) |_| {
-        self.got.writeSymtab(self, ctx);
-        ctx.incr(self.got.output_symtab_size);
+        self.got.writeSymtab(self);
     }
 
     if (self.plt_section_index) |_| {
-        self.plt.writeSymtab(self, ctx);
-        ctx.incr(self.plt.output_symtab_size);
+        self.plt.writeSymtab(self);
     }
 
     if (self.plt_got_section_index) |_| {
-        self.plt_got.writeSymtab(self, ctx);
-        ctx.incr(self.plt_got.output_symtab_size);
+        self.plt_got.writeSymtab(self);
     }
 
     if (self.linker_defined_index) |index| {
         const file_ptr = self.file(index).?;
-        file_ptr.writeSymtab(self, ctx);
-        ctx.incr(file_ptr.linker_defined.output_symtab_size);
+        file_ptr.writeSymtab(self);
     }
 
     const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
@@ -4972,15 +4995,8 @@ fn writeSymtabZigObject(self: *Elf, zig_object: *ZigObject) !void {
     const needed_strtab_size = math.cast(usize, strtab_shdr.sh_size - 1) orelse return error.Overflow;
     try self.strtab.ensureUnusedCapacity(gpa, needed_strtab_size);
 
-    var ctx: WriteSymtabCtx = .{
-        .ilocal = 1,
-        .iglobal = symtab_shdr.sh_info,
-    };
-
-    ctx.incr(self.writeSectionSymbols(ctx));
-
-    zig_object.asFile().writeSymtab(self, ctx);
-    ctx.incr(zig_object.output_symtab_size);
+    self.writeSectionSymbols();
+    zig_object.asFile().writeSymtab(self);
 
     const foreign_endian = self.base.options.target.cpu.arch.endian() != builtin.cpu.arch.endian();
     switch (self.ptr_width) {
@@ -5012,8 +5028,8 @@ fn writeSymtabZigObject(self: *Elf, zig_object: *ZigObject) !void {
     try self.base.file.?.pwriteAll(self.strtab.items, strtab_shdr.sh_offset);
 }
 
-fn writeSectionSymbols(self: *Elf, ctx: WriteSymtabCtx) SymtabSize {
-    var ilocal = ctx.ilocal;
+fn writeSectionSymbols(self: *Elf) void {
+    var ilocal: u32 = 1;
     for (self.output_sections.keys()) |shndx| {
         const shdr = self.shdrs.items[shndx];
         const out_sym = &self.symtab.items[ilocal];
@@ -5027,7 +5043,6 @@ fn writeSectionSymbols(self: *Elf, ctx: WriteSymtabCtx) SymtabSize {
         };
         ilocal += 1;
     }
-    return .{ .nlocals = @intCast(ilocal - ctx.ilocal) };
 }
 
 /// Always 4 or 8 depending on whether this is 32-bit ELF or 64-bit ELF.
@@ -6056,16 +6071,12 @@ pub const ComdatGroup = struct {
     pub const Index = u32;
 };
 
-pub const SymtabSize = struct {
+pub const SymtabCtx = struct {
+    ilocal: u32 = 0,
+    iglobal: u32 = 0,
     nlocals: u32 = 0,
     nglobals: u32 = 0,
     strsize: u32 = 0,
-
-    fn add(ss: *SymtabSize, other: SymtabSize) void {
-        ss.nlocals += other.nlocals;
-        ss.nglobals += other.nglobals;
-        ss.strsize += other.strsize;
-    }
 };
 
 pub const null_sym = elf.Elf64_Sym{