Merge pull request #17146 from ziglang/elf-linker

elf: upstream zld/ELF functionality, part 2

14 files changed, 952 insertions, 47 deletions

diff --git a/src/arch/aarch64/CodeGen.zig b/src/arch/aarch64/CodeGen.zig
index 2c6e3f5a7b..2788bb4055 100644
--- a/src/arch/aarch64/CodeGen.zig
+++ b/src/arch/aarch64/CodeGen.zig
@@ -4316,7 +4316,7 @@ fn airCall(self: *Self, inst: Air.Inst.Index, modifier: std.builtin.CallModifier
             if (self.bin_file.cast(link.File.Elf)) |elf_file| {
                 const sym_index = try elf_file.getOrCreateMetadataForDecl(func.owner_decl);
                 const sym = elf_file.symbol(sym_index);
-                _ = try sym.getOrCreateGotEntry(elf_file);
+                _ = try sym.getOrCreateGotEntry(sym_index, elf_file);
                 const got_addr = @as(u32, @intCast(sym.gotAddress(elf_file)));
                 try self.genSetReg(Type.usize, .x30, .{ .memory = got_addr });
             } else if (self.bin_file.cast(link.File.MachO)) |macho_file| {
diff --git a/src/arch/arm/CodeGen.zig b/src/arch/arm/CodeGen.zig
index 937d4aa1dd..3e15b544a7 100644
--- a/src/arch/arm/CodeGen.zig
+++ b/src/arch/arm/CodeGen.zig
@@ -4296,7 +4296,7 @@ fn airCall(self: *Self, inst: Air.Inst.Index, modifier: std.builtin.CallModifier
             if (self.bin_file.cast(link.File.Elf)) |elf_file| {
                 const sym_index = try elf_file.getOrCreateMetadataForDecl(func.owner_decl);
                 const sym = elf_file.symbol(sym_index);
-                _ = try sym.getOrCreateGotEntry(elf_file);
+                _ = try sym.getOrCreateGotEntry(sym_index, elf_file);
                 const got_addr = @as(u32, @intCast(sym.gotAddress(elf_file)));
                 try self.genSetReg(Type.usize, .lr, .{ .memory = got_addr });
             } else if (self.bin_file.cast(link.File.MachO)) |_| {
diff --git a/src/arch/riscv64/CodeGen.zig b/src/arch/riscv64/CodeGen.zig
index d3f162ae0f..66e5d5d965 100644
--- a/src/arch/riscv64/CodeGen.zig
+++ b/src/arch/riscv64/CodeGen.zig
@@ -1749,7 +1749,7 @@ fn airCall(self: *Self, inst: Air.Inst.Index, modifier: std.builtin.CallModifier
                 .func => |func| {
                     const sym_index = try elf_file.getOrCreateMetadataForDecl(func.owner_decl);
                     const sym = elf_file.symbol(sym_index);
-                    _ = try sym.getOrCreateGotEntry(elf_file);
+                    _ = try sym.getOrCreateGotEntry(sym_index, elf_file);
                     const got_addr = @as(u32, @intCast(sym.gotAddress(elf_file)));
                     try self.genSetReg(Type.usize, .ra, .{ .memory = got_addr });
                     _ = try self.addInst(.{
diff --git a/src/arch/sparc64/CodeGen.zig b/src/arch/sparc64/CodeGen.zig
index df1a7cf970..e6da6d24bb 100644
--- a/src/arch/sparc64/CodeGen.zig
+++ b/src/arch/sparc64/CodeGen.zig
@@ -1351,7 +1351,7 @@ fn airCall(self: *Self, inst: Air.Inst.Index, modifier: std.builtin.CallModifier
                     const got_addr = if (self.bin_file.cast(link.File.Elf)) |elf_file| blk: {
                         const sym_index = try elf_file.getOrCreateMetadataForDecl(func.owner_decl);
                         const sym = elf_file.symbol(sym_index);
-                        _ = try sym.getOrCreateGotEntry(elf_file);
+                        _ = try sym.getOrCreateGotEntry(sym_index, elf_file);
                         break :blk @as(u32, @intCast(sym.gotAddress(elf_file)));
                     } else unreachable;
 
diff --git a/src/arch/x86_64/CodeGen.zig b/src/arch/x86_64/CodeGen.zig
index e535894604..15bf51489a 100644
--- a/src/arch/x86_64/CodeGen.zig
+++ b/src/arch/x86_64/CodeGen.zig
@@ -8157,7 +8157,7 @@ fn airCall(self: *Self, inst: Air.Inst.Index, modifier: std.builtin.CallModifier
                 const sym_index = try elf_file.getOrCreateMetadataForDecl(owner_decl);
                 const sym = elf_file.symbol(sym_index);
                 sym.flags.needs_got = true;
-                _ = try sym.getOrCreateGotEntry(elf_file);
+                _ = try sym.getOrCreateGotEntry(sym_index, elf_file);
                 const got_addr = sym.gotAddress(elf_file);
                 try self.asmMemory(.{ ._, .call }, Memory.sib(.qword, .{
                     .base = .{ .reg = .ds },
@@ -10236,7 +10236,7 @@ fn genLazySymbolRef(
             return self.fail("{s} creating lazy symbol", .{@errorName(err)});
         const sym = elf_file.symbol(sym_index);
         sym.flags.needs_got = true;
-        _ = try sym.getOrCreateGotEntry(elf_file);
+        _ = try sym.getOrCreateGotEntry(sym_index, elf_file);
         const got_addr = sym.gotAddress(elf_file);
         const got_mem =
             Memory.sib(.qword, .{ .base = .{ .reg = .ds }, .disp = @intCast(got_addr) });
diff --git a/src/arch/x86_64/Disassembler.zig b/src/arch/x86_64/Disassembler.zig
new file mode 100644
index 0000000000..a0d5dea29c
--- /dev/null
+++ b/src/arch/x86_64/Disassembler.zig
@@ -0,0 +1,475 @@
+const Disassembler = @This();
+
+const std = @import("std");
+const assert = std.debug.assert;
+const math = std.math;
+
+const bits = @import("bits.zig");
+const encoder = @import("encoder.zig");
+
+const Encoding = @import("Encoding.zig");
+const Immediate = bits.Immediate;
+const Instruction = encoder.Instruction;
+const LegacyPrefixes = encoder.LegacyPrefixes;
+const Memory = bits.Memory;
+const Register = bits.Register;
+const Rex = encoder.Rex;
+
+pub const Error = error{
+    EndOfStream,
+    LegacyPrefixAfterRex,
+    UnknownOpcode,
+    Overflow,
+    Todo,
+};
+
+code: []const u8,
+pos: usize = 0,
+
+pub fn init(code: []const u8) Disassembler {
+    return .{ .code = code };
+}
+
+pub fn next(dis: *Disassembler) Error!?Instruction {
+    const prefixes = dis.parsePrefixes() catch |err| switch (err) {
+        error.EndOfStream => return null,
+        else => |e| return e,
+    };
+
+    const enc = try dis.parseEncoding(prefixes) orelse return error.UnknownOpcode;
+    switch (enc.data.op_en) {
+        .np => return inst(enc, .{}),
+        .d, .i => {
+            const imm = try dis.parseImm(enc.data.ops[0]);
+            return inst(enc, .{
+                .op1 = .{ .imm = imm },
+            });
+        },
+        .zi => {
+            const imm = try dis.parseImm(enc.data.ops[1]);
+            return inst(enc, .{
+                .op1 = .{ .reg = Register.rax.toBitSize(enc.data.ops[0].regBitSize()) },
+                .op2 = .{ .imm = imm },
+            });
+        },
+        .o, .oi => {
+            const reg_low_enc = @as(u3, @truncate(dis.code[dis.pos - 1]));
+            const op2: Instruction.Operand = if (enc.data.op_en == .oi) .{
+                .imm = try dis.parseImm(enc.data.ops[1]),
+            } else .none;
+            return inst(enc, .{
+                .op1 = .{ .reg = parseGpRegister(reg_low_enc, prefixes.rex.b, prefixes.rex, enc.data.ops[0].regBitSize()) },
+                .op2 = op2,
+            });
+        },
+        .m, .mi, .m1, .mc => {
+            const modrm = try dis.parseModRmByte();
+            const act_enc = Encoding.findByOpcode(enc.opcode(), .{
+                .legacy = prefixes.legacy,
+                .rex = prefixes.rex,
+            }, modrm.op1) orelse return error.UnknownOpcode;
+            const sib = if (modrm.sib()) try dis.parseSibByte() else null;
+
+            if (modrm.direct()) {
+                const op2: Instruction.Operand = switch (act_enc.data.op_en) {
+                    .mi => .{ .imm = try dis.parseImm(act_enc.data.ops[1]) },
+                    .m1 => .{ .imm = Immediate.u(1) },
+                    .mc => .{ .reg = .cl },
+                    .m => .none,
+                    else => unreachable,
+                };
+                return inst(act_enc, .{
+                    .op1 = .{ .reg = parseGpRegister(modrm.op2, prefixes.rex.b, prefixes.rex, act_enc.data.ops[0].regBitSize()) },
+                    .op2 = op2,
+                });
+            }
+
+            const disp = try dis.parseDisplacement(modrm, sib);
+            const op2: Instruction.Operand = switch (act_enc.data.op_en) {
+                .mi => .{ .imm = try dis.parseImm(act_enc.data.ops[1]) },
+                .m1 => .{ .imm = Immediate.u(1) },
+                .mc => .{ .reg = .cl },
+                .m => .none,
+                else => unreachable,
+            };
+
+            if (modrm.rip()) {
+                return inst(act_enc, .{
+                    .op1 = .{ .mem = Memory.rip(Memory.PtrSize.fromBitSize(act_enc.data.ops[0].memBitSize()), disp) },
+                    .op2 = op2,
+                });
+            }
+
+            const scale_index = if (sib) |info| info.scaleIndex(prefixes.rex) else null;
+            const base = if (sib) |info|
+                info.baseReg(modrm, prefixes)
+            else
+                parseGpRegister(modrm.op2, prefixes.rex.b, prefixes.rex, 64);
+            return inst(act_enc, .{
+                .op1 = .{ .mem = Memory.sib(Memory.PtrSize.fromBitSize(act_enc.data.ops[0].memBitSize()), .{
+                    .base = if (base) |base_reg| .{ .reg = base_reg } else .none,
+                    .scale_index = scale_index,
+                    .disp = disp,
+                }) },
+                .op2 = op2,
+            });
+        },
+        .fd => {
+            const seg = segmentRegister(prefixes.legacy);
+            const offset = try dis.parseOffset();
+            return inst(enc, .{
+                .op1 = .{ .reg = Register.rax.toBitSize(enc.data.ops[0].regBitSize()) },
+                .op2 = .{ .mem = Memory.moffs(seg, offset) },
+            });
+        },
+        .td => {
+            const seg = segmentRegister(prefixes.legacy);
+            const offset = try dis.parseOffset();
+            return inst(enc, .{
+                .op1 = .{ .mem = Memory.moffs(seg, offset) },
+                .op2 = .{ .reg = Register.rax.toBitSize(enc.data.ops[1].regBitSize()) },
+            });
+        },
+        .mr, .mri, .mrc => {
+            const modrm = try dis.parseModRmByte();
+            const sib = if (modrm.sib()) try dis.parseSibByte() else null;
+            const src_bit_size = enc.data.ops[1].regBitSize();
+
+            if (modrm.direct()) {
+                return inst(enc, .{
+                    .op1 = .{ .reg = parseGpRegister(modrm.op2, prefixes.rex.b, prefixes.rex, enc.data.ops[0].regBitSize()) },
+                    .op2 = .{ .reg = parseGpRegister(modrm.op1, prefixes.rex.x, prefixes.rex, src_bit_size) },
+                });
+            }
+
+            const dst_bit_size = enc.data.ops[0].memBitSize();
+            const disp = try dis.parseDisplacement(modrm, sib);
+            const op3: Instruction.Operand = switch (enc.data.op_en) {
+                .mri => .{ .imm = try dis.parseImm(enc.data.ops[2]) },
+                .mrc => .{ .reg = .cl },
+                .mr => .none,
+                else => unreachable,
+            };
+
+            if (modrm.rip()) {
+                return inst(enc, .{
+                    .op1 = .{ .mem = Memory.rip(Memory.PtrSize.fromBitSize(dst_bit_size), disp) },
+                    .op2 = .{ .reg = parseGpRegister(modrm.op1, prefixes.rex.r, prefixes.rex, src_bit_size) },
+                    .op3 = op3,
+                });
+            }
+
+            const scale_index = if (sib) |info| info.scaleIndex(prefixes.rex) else null;
+            const base = if (sib) |info|
+                info.baseReg(modrm, prefixes)
+            else
+                parseGpRegister(modrm.op2, prefixes.rex.b, prefixes.rex, 64);
+            return inst(enc, .{
+                .op1 = .{ .mem = Memory.sib(Memory.PtrSize.fromBitSize(dst_bit_size), .{
+                    .base = if (base) |base_reg| .{ .reg = base_reg } else .none,
+                    .scale_index = scale_index,
+                    .disp = disp,
+                }) },
+                .op2 = .{ .reg = parseGpRegister(modrm.op1, prefixes.rex.r, prefixes.rex, src_bit_size) },
+                .op3 = op3,
+            });
+        },
+        .rm, .rmi => {
+            const modrm = try dis.parseModRmByte();
+            const sib = if (modrm.sib()) try dis.parseSibByte() else null;
+            const dst_bit_size = enc.data.ops[0].regBitSize();
+
+            if (modrm.direct()) {
+                const op3: Instruction.Operand = switch (enc.data.op_en) {
+                    .rm => .none,
+                    .rmi => .{ .imm = try dis.parseImm(enc.data.ops[2]) },
+                    else => unreachable,
+                };
+                return inst(enc, .{
+                    .op1 = .{ .reg = parseGpRegister(modrm.op1, prefixes.rex.x, prefixes.rex, dst_bit_size) },
+                    .op2 = .{ .reg = parseGpRegister(modrm.op2, prefixes.rex.b, prefixes.rex, enc.data.ops[1].regBitSize()) },
+                    .op3 = op3,
+                });
+            }
+
+            const src_bit_size = if (enc.data.ops[1] == .m) dst_bit_size else enc.data.ops[1].memBitSize();
+            const disp = try dis.parseDisplacement(modrm, sib);
+            const op3: Instruction.Operand = switch (enc.data.op_en) {
+                .rmi => .{ .imm = try dis.parseImm(enc.data.ops[2]) },
+                .rm => .none,
+                else => unreachable,
+            };
+
+            if (modrm.rip()) {
+                return inst(enc, .{
+                    .op1 = .{ .reg = parseGpRegister(modrm.op1, prefixes.rex.r, prefixes.rex, dst_bit_size) },
+                    .op2 = .{ .mem = Memory.rip(Memory.PtrSize.fromBitSize(src_bit_size), disp) },
+                    .op3 = op3,
+                });
+            }
+
+            const scale_index = if (sib) |info| info.scaleIndex(prefixes.rex) else null;
+            const base = if (sib) |info|
+                info.baseReg(modrm, prefixes)
+            else
+                parseGpRegister(modrm.op2, prefixes.rex.b, prefixes.rex, 64);
+            return inst(enc, .{
+                .op1 = .{ .reg = parseGpRegister(modrm.op1, prefixes.rex.r, prefixes.rex, dst_bit_size) },
+                .op2 = .{ .mem = Memory.sib(Memory.PtrSize.fromBitSize(src_bit_size), .{
+                    .base = if (base) |base_reg| .{ .reg = base_reg } else .none,
+                    .scale_index = scale_index,
+                    .disp = disp,
+                }) },
+                .op3 = op3,
+            });
+        },
+        .rm0, .vmi, .rvm, .rvmr, .rvmi, .mvr => unreachable, // TODO
+    }
+}
+
+fn inst(encoding: Encoding, args: struct {
+    prefix: Instruction.Prefix = .none,
+    op1: Instruction.Operand = .none,
+    op2: Instruction.Operand = .none,
+    op3: Instruction.Operand = .none,
+    op4: Instruction.Operand = .none,
+}) Instruction {
+    var i = Instruction{ .encoding = encoding, .prefix = args.prefix, .ops = .{
+        args.op1,
+        args.op2,
+        args.op3,
+        args.op4,
+    } };
+    return i;
+}
+
+const Prefixes = struct {
+    legacy: LegacyPrefixes = .{},
+    rex: Rex = .{},
+    // TODO add support for VEX prefix
+};
+
+fn parsePrefixes(dis: *Disassembler) !Prefixes {
+    const rex_prefix_mask: u4 = 0b0100;
+    var stream = std.io.fixedBufferStream(dis.code[dis.pos..]);
+    const reader = stream.reader();
+
+    var res: Prefixes = .{};
+
+    while (true) {
+        const next_byte = try reader.readByte();
+        dis.pos += 1;
+
+        switch (next_byte) {
+            0xf0, 0xf2, 0xf3, 0x2e, 0x36, 0x26, 0x64, 0x65, 0x3e, 0x66, 0x67 => {
+                // Legacy prefix
+                if (res.rex.present) return error.LegacyPrefixAfterRex;
+                switch (next_byte) {
+                    0xf0 => res.legacy.prefix_f0 = true,
+                    0xf2 => res.legacy.prefix_f2 = true,
+                    0xf3 => res.legacy.prefix_f3 = true,
+                    0x2e => res.legacy.prefix_2e = true,
+                    0x36 => res.legacy.prefix_36 = true,
+                    0x26 => res.legacy.prefix_26 = true,
+                    0x64 => res.legacy.prefix_64 = true,
+                    0x65 => res.legacy.prefix_65 = true,
+                    0x3e => res.legacy.prefix_3e = true,
+                    0x66 => res.legacy.prefix_66 = true,
+                    0x67 => res.legacy.prefix_67 = true,
+                    else => unreachable,
+                }
+            },
+            else => {
+                if (rex_prefix_mask == @as(u4, @truncate(next_byte >> 4))) {
+                    // REX prefix
+                    res.rex.w = next_byte & 0b1000 != 0;
+                    res.rex.r = next_byte & 0b100 != 0;
+                    res.rex.x = next_byte & 0b10 != 0;
+                    res.rex.b = next_byte & 0b1 != 0;
+                    res.rex.present = true;
+                    continue;
+                }
+
+                // TODO VEX prefix
+
+                dis.pos -= 1;
+                break;
+            },
+        }
+    }
+
+    return res;
+}
+
+fn parseEncoding(dis: *Disassembler, prefixes: Prefixes) !?Encoding {
+    const o_mask: u8 = 0b1111_1000;
+
+    var opcode: [3]u8 = .{ 0, 0, 0 };
+    var stream = std.io.fixedBufferStream(dis.code[dis.pos..]);
+    const reader = stream.reader();
+
+    comptime var opc_count = 0;
+    inline while (opc_count < 3) : (opc_count += 1) {
+        const byte = try reader.readByte();
+        opcode[opc_count] = byte;
+        dis.pos += 1;
+
+        if (byte == 0x0f) {
+            // Multi-byte opcode
+        } else if (opc_count > 0) {
+            // Multi-byte opcode
+            if (Encoding.findByOpcode(opcode[0 .. opc_count + 1], .{
+                .legacy = prefixes.legacy,
+                .rex = prefixes.rex,
+            }, null)) |mnemonic| {
+                return mnemonic;
+            }
+        } else {
+            // Single-byte opcode
+            if (Encoding.findByOpcode(opcode[0..1], .{
+                .legacy = prefixes.legacy,
+                .rex = prefixes.rex,
+            }, null)) |mnemonic| {
+                return mnemonic;
+            } else {
+                // Try O* encoding
+                return Encoding.findByOpcode(&.{opcode[0] & o_mask}, .{
+                    .legacy = prefixes.legacy,
+                    .rex = prefixes.rex,
+                }, null);
+            }
+        }
+    }
+    return null;
+}
+
+fn parseGpRegister(low_enc: u3, is_extended: bool, rex: Rex, bit_size: u64) Register {
+    const reg_id: u4 = @as(u4, @intCast(@intFromBool(is_extended))) << 3 | low_enc;
+    const reg = @as(Register, @enumFromInt(reg_id)).toBitSize(bit_size);
+    return switch (reg) {
+        .spl => if (rex.present or rex.isSet()) .spl else .ah,
+        .dil => if (rex.present or rex.isSet()) .dil else .bh,
+        .bpl => if (rex.present or rex.isSet()) .bpl else .ch,
+        .sil => if (rex.present or rex.isSet()) .sil else .dh,
+        else => reg,
+    };
+}
+
+fn parseImm(dis: *Disassembler, kind: Encoding.Op) !Immediate {
+    var stream = std.io.fixedBufferStream(dis.code[dis.pos..]);
+    var creader = std.io.countingReader(stream.reader());
+    const reader = creader.reader();
+    const imm = switch (kind) {
+        .imm8s, .rel8 => Immediate.s(try reader.readInt(i8, .Little)),
+        .imm16s, .rel16 => Immediate.s(try reader.readInt(i16, .Little)),
+        .imm32s, .rel32 => Immediate.s(try reader.readInt(i32, .Little)),
+        .imm8 => Immediate.u(try reader.readInt(u8, .Little)),
+        .imm16 => Immediate.u(try reader.readInt(u16, .Little)),
+        .imm32 => Immediate.u(try reader.readInt(u32, .Little)),
+        .imm64 => Immediate.u(try reader.readInt(u64, .Little)),
+        else => unreachable,
+    };
+    dis.pos += std.math.cast(usize, creader.bytes_read) orelse return error.Overflow;
+    return imm;
+}
+
+fn parseOffset(dis: *Disassembler) !u64 {
+    var stream = std.io.fixedBufferStream(dis.code[dis.pos..]);
+    const reader = stream.reader();
+    const offset = try reader.readInt(u64, .Little);
+    dis.pos += 8;
+    return offset;
+}
+
+const ModRm = packed struct {
+    mod: u2,
+    op1: u3,
+    op2: u3,
+
+    inline fn direct(self: ModRm) bool {
+        return self.mod == 0b11;
+    }
+
+    inline fn rip(self: ModRm) bool {
+        return self.mod == 0 and self.op2 == 0b101;
+    }
+
+    inline fn sib(self: ModRm) bool {
+        return !self.direct() and self.op2 == 0b100;
+    }
+};
+
+fn parseModRmByte(dis: *Disassembler) !ModRm {
+    if (dis.code[dis.pos..].len == 0) return error.EndOfStream;
+    const modrm_byte = dis.code[dis.pos];
+    dis.pos += 1;
+    const mod: u2 = @as(u2, @truncate(modrm_byte >> 6));
+    const op1: u3 = @as(u3, @truncate(modrm_byte >> 3));
+    const op2: u3 = @as(u3, @truncate(modrm_byte));
+    return ModRm{ .mod = mod, .op1 = op1, .op2 = op2 };
+}
+
+fn segmentRegister(prefixes: LegacyPrefixes) Register {
+    if (prefixes.prefix_2e) return .cs;
+    if (prefixes.prefix_36) return .ss;
+    if (prefixes.prefix_26) return .es;
+    if (prefixes.prefix_64) return .fs;
+    if (prefixes.prefix_65) return .gs;
+    return .ds;
+}
+
+const Sib = packed struct {
+    scale: u2,
+    index: u3,
+    base: u3,
+
+    fn scaleIndex(self: Sib, rex: Rex) ?Memory.ScaleIndex {
+        if (self.index == 0b100 and !rex.x) return null;
+        return .{
+            .scale = @as(u4, 1) << self.scale,
+            .index = parseGpRegister(self.index, rex.x, rex, 64),
+        };
+    }
+
+    fn baseReg(self: Sib, modrm: ModRm, prefixes: Prefixes) ?Register {
+        if (self.base == 0b101 and modrm.mod == 0) {
+            if (self.scaleIndex(prefixes.rex)) |_| return null;
+            return segmentRegister(prefixes.legacy);
+        }
+        return parseGpRegister(self.base, prefixes.rex.b, prefixes.rex, 64);
+    }
+};
+
+fn parseSibByte(dis: *Disassembler) !Sib {
+    if (dis.code[dis.pos..].len == 0) return error.EndOfStream;
+    const sib_byte = dis.code[dis.pos];
+    dis.pos += 1;
+    const scale: u2 = @as(u2, @truncate(sib_byte >> 6));
+    const index: u3 = @as(u3, @truncate(sib_byte >> 3));
+    const base: u3 = @as(u3, @truncate(sib_byte));
+    return Sib{ .scale = scale, .index = index, .base = base };
+}
+
+fn parseDisplacement(dis: *Disassembler, modrm: ModRm, sib: ?Sib) !i32 {
+    var stream = std.io.fixedBufferStream(dis.code[dis.pos..]);
+    var creader = std.io.countingReader(stream.reader());
+    const reader = creader.reader();
+    const disp = disp: {
+        if (sib) |info| {
+            if (info.base == 0b101 and modrm.mod == 0) {
+                break :disp try reader.readInt(i32, .Little);
+            }
+        }
+        if (modrm.rip()) {
+            break :disp try reader.readInt(i32, .Little);
+        }
+        break :disp switch (modrm.mod) {
+            0b00 => 0,
+            0b01 => try reader.readInt(i8, .Little),
+            0b10 => try reader.readInt(i32, .Little),
+            0b11 => unreachable,
+        };
+    };
+    dis.pos += std.math.cast(usize, creader.bytes_read) orelse return error.Overflow;
+    return disp;
+}
diff --git a/src/codegen.zig b/src/codegen.zig
index 3d86e4b6bc..a2d0f225bc 100644
--- a/src/codegen.zig
+++ b/src/codegen.zig
@@ -861,7 +861,7 @@ fn genDeclRef(
         const sym_index = try elf_file.getOrCreateMetadataForDecl(decl_index);
         const sym = elf_file.symbol(sym_index);
         sym.flags.needs_got = true;
-        _ = try sym.getOrCreateGotEntry(elf_file);
+        _ = try sym.getOrCreateGotEntry(sym_index, elf_file);
         return GenResult.mcv(.{ .memory = sym.gotAddress(elf_file) });
     } else if (bin_file.cast(link.File.MachO)) |macho_file| {
         const atom_index = try macho_file.getOrCreateAtomForDecl(decl_index);
diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index 16b7706f7a..b12d24745b 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -40,6 +40,8 @@ phdr_got_index: ?u16 = null,
 phdr_load_ro_index: ?u16 = null,
 /// The index into the program headers of a PT_LOAD program header with Write flag
 phdr_load_rw_index: ?u16 = null,
+/// The index into the program headers of a PT_LOAD program header with zerofill data.
+phdr_load_zerofill_index: ?u16 = null,
 
 entry_addr: ?u64 = null,
 page_size: u32,
@@ -56,6 +58,7 @@ got: GotSection = .{},
 text_section_index: ?u16 = null,
 rodata_section_index: ?u16 = null,
 data_section_index: ?u16 = null,
+bss_section_index: ?u16 = null,
 eh_frame_section_index: ?u16 = null,
 eh_frame_hdr_section_index: ?u16 = null,
 dynamic_section_index: ?u16 = null,
@@ -532,6 +535,26 @@ pub fn populateMissingMetadata(self: *Elf) !void {
         self.phdr_table_dirty = true;
     }
 
+    if (self.phdr_load_zerofill_index == null) {
+        self.phdr_load_zerofill_index = @as(u16, @intCast(self.phdrs.items.len));
+        const p_align = if (self.base.options.target.os.tag == .linux) self.page_size else @as(u16, ptr_size);
+        const off = self.phdrs.items[self.phdr_load_rw_index.?].p_offset;
+        log.debug("found PT_LOAD zerofill free space 0x{x} to 0x{x}", .{ off, off });
+        // TODO Same as for GOT
+        const addr: u32 = if (self.base.options.target.ptrBitWidth() >= 32) 0x14000000 else 0xf000;
+        try self.phdrs.append(gpa, .{
+            .p_type = elf.PT_LOAD,
+            .p_offset = off,
+            .p_filesz = 0,
+            .p_vaddr = addr,
+            .p_paddr = addr,
+            .p_memsz = 0,
+            .p_align = p_align,
+            .p_flags = elf.PF_R | elf.PF_W,
+        });
+        self.phdr_table_dirty = true;
+    }
+
     if (self.shstrtab_section_index == null) {
         self.shstrtab_section_index = @as(u16, @intCast(self.shdrs.items.len));
         assert(self.shstrtab.buffer.items.len == 0);
@@ -655,6 +678,26 @@ pub fn populateMissingMetadata(self: *Elf) !void {
         self.shdr_table_dirty = true;
     }
 
+    if (self.bss_section_index == null) {
+        self.bss_section_index = @as(u16, @intCast(self.shdrs.items.len));
+        const phdr = &self.phdrs.items[self.phdr_load_zerofill_index.?];
+        try self.shdrs.append(gpa, .{
+            .sh_name = try self.shstrtab.insert(gpa, ".bss"),
+            .sh_type = elf.SHT_NOBITS,
+            .sh_flags = elf.SHF_WRITE | elf.SHF_ALLOC,
+            .sh_addr = phdr.p_vaddr,
+            .sh_offset = phdr.p_offset,
+            .sh_size = phdr.p_filesz,
+            .sh_link = 0,
+            .sh_info = 0,
+            .sh_addralign = @as(u16, ptr_size),
+            .sh_entsize = 0,
+        });
+        try self.phdr_to_shdr_table.putNoClobber(gpa, self.bss_section_index.?, self.phdr_load_zerofill_index.?);
+        try self.last_atom_and_free_list_table.putNoClobber(gpa, self.bss_section_index.?, .{});
+        self.shdr_table_dirty = true;
+    }
+
     if (self.symtab_section_index == null) {
         self.symtab_section_index = @as(u16, @intCast(self.shdrs.items.len));
         const min_align: u16 = if (small_ptr) @alignOf(elf.Elf32_Sym) else @alignOf(elf.Elf64_Sym);
@@ -868,8 +911,9 @@ 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 phdr = &self.phdrs.items[phdr_index];
+    const is_zerofill = shdr.sh_type == elf.SHT_NOBITS;
 
-    if (needed_size > self.allocatedSize(shdr.sh_offset)) {
+    if (needed_size > self.allocatedSize(shdr.sh_offset) and !is_zerofill) {
         // Must move the entire section.
         const new_offset = self.findFreeSpace(needed_size, self.page_size);
         const existing_size = if (self.last_atom_and_free_list_table.get(shdr_index)) |meta| blk: {
@@ -893,7 +937,10 @@ pub fn growAllocSection(self: *Elf, shdr_index: u16, needed_size: u64) !void {
 
     shdr.sh_size = needed_size;
     phdr.p_memsz = needed_size;
-    phdr.p_filesz = needed_size;
+
+    if (!is_zerofill) {
+        phdr.p_filesz = needed_size;
+    }
 
     self.markDirty(shdr_index, phdr_index);
 }
@@ -1005,13 +1052,6 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
     const directory = self.base.options.emit.?.directory; // Just an alias to make it shorter to type.
     const full_out_path = try directory.join(arena, &[_][]const u8{self.base.options.emit.?.sub_path});
 
-    const compiler_rt_path: ?[]const u8 = blk: {
-        if (comp.compiler_rt_lib) |x| break :blk x.full_object_path;
-        if (comp.compiler_rt_obj) |x| break :blk x.full_object_path;
-        break :blk null;
-    };
-    _ = compiler_rt_path;
-
     // Here we will parse input positional and library files (if referenced).
     // This will roughly match in any linker backend we support.
     var positionals = std.ArrayList(Compilation.LinkObject).init(arena);
@@ -1037,6 +1077,15 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
         try positionals.append(.{ .path = key.status.success.object_path });
     }
 
+    const compiler_rt_path: ?[]const u8 = blk: {
+        if (comp.compiler_rt_lib) |x| break :blk x.full_object_path;
+        if (comp.compiler_rt_obj) |x| break :blk x.full_object_path;
+        break :blk null;
+    };
+    if (compiler_rt_path) |path| {
+        try positionals.append(.{ .path = path });
+    }
+
     for (positionals.items) |obj| {
         const in_file = try std.fs.cwd().openFile(obj.path, .{});
         defer in_file.close();
@@ -1093,7 +1142,7 @@ pub fn flushModule(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node
     // input Object files.
     // Any qualifing unresolved symbol will be upgraded to an absolute, weak
     // symbol for potential resolution at load-time.
-    self.resolveSymbols();
+    try self.resolveSymbols();
     self.markImportsExports();
     self.claimUnresolved();
 
@@ -1356,6 +1405,7 @@ const ParseError = error{
     EndOfStream,
     FileSystem,
     NotSupported,
+    InvalidCharacter,
 } || std.os.SeekError || std.fs.File.OpenError || std.fs.File.ReadError;
 
 fn parsePositional(
@@ -1367,10 +1417,32 @@ fn parsePositional(
 ) ParseError!void {
     const tracy = trace(@src());
     defer tracy.end();
-    _ = must_link;
 
     if (Object.isObject(in_file)) {
         try self.parseObject(in_file, path, ctx);
+    } else {
+        try self.parseLibrary(in_file, path, .{
+            .path = null,
+            .needed = false,
+            .weak = false,
+        }, must_link, ctx);
+    }
+}
+
+fn parseLibrary(
+    self: *Elf,
+    in_file: std.fs.File,
+    path: []const u8,
+    lib: link.SystemLib,
+    must_link: bool,
+    ctx: *ParseErrorCtx,
+) ParseError!void {
+    const tracy = trace(@src());
+    defer tracy.end();
+    _ = lib;
+
+    if (Archive.isArchive(in_file)) {
+        try self.parseArchive(in_file, path, must_link, ctx);
     } else return error.UnknownFileType;
 }
 
@@ -1395,15 +1467,109 @@ fn parseObject(self: *Elf, in_file: std.fs.File, path: []const u8, ctx: *ParseEr
     if (ctx.detected_cpu_arch != self.base.options.target.cpu.arch) return error.InvalidCpuArch;
 }
 
-fn resolveSymbols(self: *Elf) void {
-    if (self.zig_module_index) |index| {
-        const zig_module = self.file(index).?.zig_module;
-        zig_module.resolveSymbols(self);
+fn parseArchive(
+    self: *Elf,
+    in_file: std.fs.File,
+    path: []const u8,
+    must_link: bool,
+    ctx: *ParseErrorCtx,
+) ParseError!void {
+    const tracy = trace(@src());
+    defer tracy.end();
+
+    const gpa = self.base.allocator;
+    const data = try in_file.readToEndAlloc(gpa, std.math.maxInt(u32));
+    var archive = Archive{ .path = path, .data = data };
+    defer archive.deinit(gpa);
+    try archive.parse(self);
+
+    for (archive.objects.items) |extracted| {
+        const index = @as(File.Index, @intCast(try self.files.addOne(gpa)));
+        self.files.set(index, .{ .object = extracted });
+        const object = &self.files.items(.data)[index].object;
+        object.index = index;
+        object.alive = must_link;
+        try object.parse(self);
+        try self.objects.append(gpa, index);
+
+        ctx.detected_cpu_arch = object.header.?.e_machine.toTargetCpuArch().?;
+        if (ctx.detected_cpu_arch != self.base.options.target.cpu.arch) return error.InvalidCpuArch;
+    }
+}
+
+/// When resolving symbols, we approach the problem similarly to `mold`.
+/// 1. Resolve symbols across all objects (including those preemptively extracted archives).
+/// 2. Resolve symbols across all shared objects.
+/// 3. Mark live objects (see `Elf.markLive`)
+/// 4. Reset state of all resolved globals since we will redo this bit on the pruned set.
+/// 5. Remove references to dead objects/shared objects
+/// 6. Re-run symbol resolution on pruned objects and shared objects sets.
+fn resolveSymbols(self: *Elf) error{Overflow}!void {
+    // Resolve symbols in the ZigModule. For now, we assume that it's always live.
+    if (self.zig_module_index) |index| self.file(index).?.resolveSymbols(self);
+    // Resolve symbols on the set of all objects and shared objects (even if some are unneeded).
+    for (self.objects.items) |index| self.file(index).?.resolveSymbols(self);
+
+    // Mark live objects.
+    self.markLive();
+
+    // Reset state of all globals after marking live objects.
+    if (self.zig_module_index) |index| self.file(index).?.resetGlobals(self);
+    for (self.objects.items) |index| self.file(index).?.resetGlobals(self);
+
+    // Prune dead objects and shared objects.
+    var i: usize = 0;
+    while (i < self.objects.items.len) {
+        const index = self.objects.items[i];
+        if (!self.file(index).?.isAlive()) {
+            _ = self.objects.orderedRemove(i);
+        } else i += 1;
+    }
+
+    // Dedup comdat groups.
+    for (self.objects.items) |index| {
+        const object = self.file(index).?.object;
+        for (object.comdat_groups.items) |cg_index| {
+            const cg = self.comdatGroup(cg_index);
+            const cg_owner = self.comdatGroupOwner(cg.owner);
+            const owner_file_index = if (self.file(cg_owner.file)) |file_ptr|
+                file_ptr.object.index
+            else
+                std.math.maxInt(File.Index);
+            cg_owner.file = @min(owner_file_index, index);
+        }
     }
 
     for (self.objects.items) |index| {
         const object = self.file(index).?.object;
-        object.resolveSymbols(self);
+        for (object.comdat_groups.items) |cg_index| {
+            const cg = self.comdatGroup(cg_index);
+            const cg_owner = self.comdatGroupOwner(cg.owner);
+            if (cg_owner.file != index) {
+                for (try object.comdatGroupMembers(cg.shndx)) |shndx| {
+                    const atom_index = object.atoms.items[shndx];
+                    if (self.atom(atom_index)) |atom_ptr| {
+                        atom_ptr.alive = false;
+                        // atom_ptr.markFdesDead(self);
+                    }
+                }
+            }
+        }
+    }
+
+    // Re-resolve the symbols.
+    if (self.zig_module_index) |index| self.file(index).?.resolveSymbols(self);
+    for (self.objects.items) |index| self.file(index).?.resolveSymbols(self);
+}
+
+/// Traverses all objects and shared objects marking any object referenced by
+/// a live object/shared object as alive itself.
+/// This routine will prune unneeded objects extracted from archives and
+/// unneeded shared objects.
+fn markLive(self: *Elf) void {
+    for (self.objects.items) |index| {
+        const file_ptr = self.file(index).?;
+        if (file_ptr.isAlive()) file_ptr.markLive(self);
     }
 }
 
@@ -1477,11 +1643,11 @@ fn scanRelocs(self: *Elf) !void {
 
     try self.reportUndefined(&undefs);
 
-    for (self.symbols.items) |*sym| {
+    for (self.symbols.items, 0..) |*sym, sym_index| {
         if (sym.flags.needs_got) {
             log.debug("'{s}' needs GOT", .{sym.name(self)});
             // TODO how can we tell we need to write it again, aka the entry is dirty?
-            const gop = try sym.getOrCreateGotEntry(self);
+            const gop = try sym.getOrCreateGotEntry(@intCast(sym_index), self);
             try self.got.writeEntry(self, gop.index);
         }
     }
@@ -1500,7 +1666,7 @@ fn allocateObjects(self: *Elf) !void {
             const local = self.symbol(local_index);
             const atom_ptr = local.atom(self) orelse continue;
             if (!atom_ptr.alive) continue;
-            local.value = atom_ptr.value;
+            local.value += atom_ptr.value;
         }
 
         for (object.globals()) |global_index| {
@@ -1508,7 +1674,7 @@ fn allocateObjects(self: *Elf) !void {
             const atom_ptr = global.atom(self) orelse continue;
             if (!atom_ptr.alive) continue;
             if (global.file_index == index) {
-                global.value = atom_ptr.value;
+                global.value += atom_ptr.value;
             }
         }
     }
@@ -1524,7 +1690,11 @@ fn writeObjects(self: *Elf) !void {
             if (!atom_ptr.alive) continue;
 
             const shdr = &self.shdrs.items[atom_ptr.output_section_index];
+            if (shdr.sh_type == elf.SHT_NOBITS) continue;
+            if (shdr.sh_flags & elf.SHF_ALLOC == 0) continue; // TODO we don't yet know how to handle non-alloc sections
+
             const file_offset = shdr.sh_offset + atom_ptr.value - shdr.sh_addr;
+            log.debug("writing atom({d}) at 0x{x}", .{ atom_ptr.atom_index, file_offset });
             const code = try atom_ptr.codeInObjectUncompressAlloc(self);
             defer gpa.free(code);
 
@@ -2529,7 +2699,7 @@ fn updateDeclCode(
         esym.st_value = atom_ptr.value;
 
         sym.flags.needs_got = true;
-        const gop = try sym.getOrCreateGotEntry(self);
+        const gop = try sym.getOrCreateGotEntry(sym_index, self);
         try self.got.writeEntry(self, gop.index);
     }
 
@@ -2764,7 +2934,7 @@ fn updateLazySymbol(self: *Elf, sym: link.File.LazySymbol, symbol_index: Symbol.
     local_esym.st_value = atom_ptr.value;
 
     local_sym.flags.needs_got = true;
-    const gop = try local_sym.getOrCreateGotEntry(self);
+    const gop = try local_sym.getOrCreateGotEntry(symbol_index, self);
     try self.got.writeEntry(self, gop.index);
 
     const section_offset = atom_ptr.value - self.phdrs.items[phdr_index].p_vaddr;
@@ -3635,7 +3805,7 @@ pub fn addSymbol(self: *Elf) !Symbol.Index {
             break :blk index;
         }
     };
-    self.symbols.items[index] = .{ .index = index };
+    self.symbols.items[index] = .{};
     return index;
 }
 
@@ -4012,6 +4182,7 @@ const synthetic_sections = @import("Elf/synthetic_sections.zig");
 
 const Air = @import("../Air.zig");
 const Allocator = std.mem.Allocator;
+const Archive = @import("Elf/Archive.zig");
 pub const Atom = @import("Elf/Atom.zig");
 const Cache = std.Build.Cache;
 const Compilation = @import("../Compilation.zig");
diff --git a/src/link/Elf/Archive.zig b/src/link/Elf/Archive.zig
new file mode 100644
index 0000000000..f34b323206
--- /dev/null
+++ b/src/link/Elf/Archive.zig
@@ -0,0 +1,153 @@
+path: []const u8,
+data: []const u8,
+
+objects: std.ArrayListUnmanaged(Object) = .{},
+strtab: []const u8 = &[0]u8{},
+
+// Archive files start with the ARMAG identifying string.  Then follows a
+// `struct ar_hdr', and as many bytes of member file data as its `ar_size'
+// member indicates, for each member file.
+/// String that begins an archive file.
+pub const ARMAG: *const [SARMAG:0]u8 = "!<arch>\n";
+/// Size of that string.
+pub const SARMAG: u4 = 8;
+
+/// String in ar_fmag at the end of each header.
+const ARFMAG: *const [2:0]u8 = "`\n";
+
+const SYM64NAME: *const [7:0]u8 = "/SYM64/";
+
+const ar_hdr = extern struct {
+    /// Member file name, sometimes / terminated.
+    ar_name: [16]u8,
+
+    /// File date, decimal seconds since Epoch.
+    ar_date: [12]u8,
+
+    /// User ID, in ASCII format.
+    ar_uid: [6]u8,
+
+    /// Group ID, in ASCII format.
+    ar_gid: [6]u8,
+
+    /// File mode, in ASCII octal.
+    ar_mode: [8]u8,
+
+    /// File size, in ASCII decimal.
+    ar_size: [10]u8,
+
+    /// Always contains ARFMAG.
+    ar_fmag: [2]u8,
+
+    fn date(self: ar_hdr) !u64 {
+        const value = getValue(&self.ar_date);
+        return std.fmt.parseInt(u64, value, 10);
+    }
+
+    fn size(self: ar_hdr) !u32 {
+        const value = getValue(&self.ar_size);
+        return std.fmt.parseInt(u32, value, 10);
+    }
+
+    fn getValue(raw: []const u8) []const u8 {
+        return mem.trimRight(u8, raw, &[_]u8{@as(u8, 0x20)});
+    }
+
+    fn isStrtab(self: ar_hdr) bool {
+        return mem.eql(u8, getValue(&self.ar_name), "//");
+    }
+
+    fn isSymtab(self: ar_hdr) bool {
+        return mem.eql(u8, getValue(&self.ar_name), "/");
+    }
+};
+
+pub fn isArchive(file: std.fs.File) bool {
+    const reader = file.reader();
+    const magic = reader.readBytesNoEof(Archive.SARMAG) catch return false;
+    defer file.seekTo(0) catch {};
+    if (!mem.eql(u8, &magic, ARMAG)) return false;
+    return true;
+}
+
+pub fn deinit(self: *Archive, allocator: Allocator) void {
+    allocator.free(self.data);
+    self.objects.deinit(allocator);
+}
+
+pub fn parse(self: *Archive, elf_file: *Elf) !void {
+    const gpa = elf_file.base.allocator;
+
+    var stream = std.io.fixedBufferStream(self.data);
+    const reader = stream.reader();
+    _ = try reader.readBytesNoEof(SARMAG);
+
+    while (true) {
+        if (stream.pos % 2 != 0) {
+            stream.pos += 1;
+        }
+
+        const hdr = reader.readStruct(ar_hdr) catch break;
+
+        if (!mem.eql(u8, &hdr.ar_fmag, ARFMAG)) {
+            // TODO convert into an error
+            log.debug(
+                "{s}: invalid header delimiter: expected '{s}', found '{s}'",
+                .{ self.path, std.fmt.fmtSliceEscapeLower(ARFMAG), std.fmt.fmtSliceEscapeLower(&hdr.ar_fmag) },
+            );
+            return;
+        }
+
+        const size = try hdr.size();
+        defer {
+            _ = stream.seekBy(size) catch {};
+        }
+
+        if (hdr.isSymtab()) continue;
+        if (hdr.isStrtab()) {
+            self.strtab = self.data[stream.pos..][0..size];
+            continue;
+        }
+
+        const name = ar_hdr.getValue(&hdr.ar_name);
+
+        if (mem.eql(u8, name, "__.SYMDEF") or mem.eql(u8, name, "__.SYMDEF SORTED")) continue;
+
+        const object_name = blk: {
+            if (name[0] == '/') {
+                const off = try std.fmt.parseInt(u32, name[1..], 10);
+                break :blk self.getString(off);
+            }
+            break :blk name;
+        };
+
+        const object = Object{
+            .archive = self.path,
+            .path = try gpa.dupe(u8, object_name[0 .. object_name.len - 1]), // To account for trailing '/'
+            .data = try gpa.dupe(u8, self.data[stream.pos..][0..size]),
+            .index = undefined,
+            .alive = false,
+        };
+
+        log.debug("extracting object '{s}' from archive '{s}'", .{ object.path, self.path });
+
+        try self.objects.append(gpa, object);
+    }
+}
+
+fn getString(self: Archive, off: u32) []const u8 {
+    assert(off < self.strtab.len);
+    return mem.sliceTo(@as([*:'\n']const u8, @ptrCast(self.strtab.ptr + off)), 0);
+}
+
+const std = @import("std");
+const assert = std.debug.assert;
+const elf = std.elf;
+const fs = std.fs;
+const log = std.log.scoped(.link);
+const mem = std.mem;
+
+const Allocator = mem.Allocator;
+const Archive = @This();
+const Elf = @import("../Elf.zig");
+const Object = @import("Object.zig");
diff --git a/src/link/Elf/Atom.zig b/src/link/Elf/Atom.zig
index 82c2b46d1d..073536fbaa 100644
--- a/src/link/Elf/Atom.zig
+++ b/src/link/Elf/Atom.zig
@@ -322,11 +322,12 @@ pub fn scanRelocs(self: Atom, elf_file: *Elf, undefs: anytype) !void {
 
         if (rel.r_type() == elf.R_X86_64_NONE) continue;
 
-        const symbol = switch (file_ptr) {
-            .zig_module => |x| elf_file.symbol(x.symbol(rel.r_sym())),
-            .object => |x| elf_file.symbol(x.symbols.items[rel.r_sym()]),
+        const symbol_index = switch (file_ptr) {
+            .zig_module => |x| x.symbol(rel.r_sym()),
+            .object => |x| x.symbols.items[rel.r_sym()],
             else => unreachable,
         };
+        const symbol = elf_file.symbol(symbol_index);
 
         // Check for violation of One Definition Rule for COMDATs.
         if (symbol.file(elf_file) == null) {
@@ -340,7 +341,7 @@ pub fn scanRelocs(self: Atom, elf_file: *Elf, undefs: anytype) !void {
         }
 
         // Report an undefined symbol.
-        try self.reportUndefined(elf_file, symbol, rel, undefs);
+        try self.reportUndefined(elf_file, symbol, symbol_index, rel, undefs);
 
         // While traversing relocations, mark symbols that require special handling such as
         // pointer indirection via GOT, or a stub trampoline via PLT.
@@ -379,7 +380,14 @@ pub fn scanRelocs(self: Atom, elf_file: *Elf, undefs: anytype) !void {
 }
 
 // This function will report any undefined non-weak symbols that are not imports.
-fn reportUndefined(self: Atom, elf_file: *Elf, sym: *const Symbol, rel: elf.Elf64_Rela, undefs: anytype) !void {
+fn reportUndefined(
+    self: Atom,
+    elf_file: *Elf,
+    sym: *const Symbol,
+    sym_index: Symbol.Index,
+    rel: elf.Elf64_Rela,
+    undefs: anytype,
+) !void {
     const rel_esym = switch (elf_file.file(self.file_index).?) {
         .zig_module => |x| x.elfSym(rel.r_sym()).*,
         .object => |x| x.symtab[rel.r_sym()],
@@ -392,7 +400,7 @@ fn reportUndefined(self: Atom, elf_file: *Elf, sym: *const Symbol, rel: elf.Elf6
         !sym.flags.import and
         esym.st_shndx == elf.SHN_UNDEF)
     {
-        const gop = try undefs.getOrPut(sym.index);
+        const gop = try undefs.getOrPut(sym_index);
         if (!gop.found_existing) {
             gop.value_ptr.* = std.ArrayList(Atom.Index).init(elf_file.base.allocator);
         }
@@ -417,6 +425,7 @@ pub fn resolveRelocs(self: Atom, elf_file: *Elf, code: []u8) !void {
             .object => |x| elf_file.symbol(x.symbols.items[rel.r_sym()]),
             else => unreachable,
         };
+        const r_offset = std.math.cast(usize, rel.r_offset) orelse return error.Overflow;
 
         // We will use equation format to resolve relocations:
         // https://intezer.com/blog/malware-analysis/executable-and-linkable-format-101-part-3-relocations/
@@ -446,24 +455,49 @@ pub fn resolveRelocs(self: Atom, elf_file: *Elf, code: []u8) !void {
 
         relocs_log.debug("  {s}: {x}: [{x} => {x}] G({x}) ({s})", .{
             fmtRelocType(r_type),
-            rel.r_offset,
+            r_offset,
             P,
             S + A,
             G + GOT + A,
             target.name(elf_file),
         });
 
-        try stream.seekTo(rel.r_offset);
+        try stream.seekTo(r_offset);
 
         switch (rel.r_type()) {
             elf.R_X86_64_NONE => unreachable,
 
             elf.R_X86_64_64 => try cwriter.writeIntLittle(i64, S + A),
 
+            elf.R_X86_64_32 => try cwriter.writeIntLittle(u32, @as(u32, @truncate(@as(u64, @intCast(S + A))))),
+            elf.R_X86_64_32S => try cwriter.writeIntLittle(i32, @as(i32, @truncate(S + A))),
+
             elf.R_X86_64_PLT32,
             elf.R_X86_64_PC32,
             => try cwriter.writeIntLittle(i32, @as(i32, @intCast(S + A - P))),
 
+            elf.R_X86_64_GOTPCREL => try cwriter.writeIntLittle(i32, @as(i32, @intCast(G + GOT + A - P))),
+            elf.R_X86_64_GOTPC32 => try cwriter.writeIntLittle(i32, @as(i32, @intCast(GOT + A - P))),
+            elf.R_X86_64_GOTPC64 => try cwriter.writeIntLittle(i64, GOT + A - P),
+
+            elf.R_X86_64_GOTPCRELX => {
+                if (!target.flags.import and !target.isIFunc(elf_file) and !target.isAbs(elf_file)) blk: {
+                    x86_64.relaxGotpcrelx(code[r_offset - 2 ..]) catch break :blk;
+                    try cwriter.writeIntLittle(i32, @as(i32, @intCast(S + A - P)));
+                    continue;
+                }
+                try cwriter.writeIntLittle(i32, @as(i32, @intCast(G + GOT + A - P)));
+            },
+
+            elf.R_X86_64_REX_GOTPCRELX => {
+                if (!target.flags.import and !target.isIFunc(elf_file) and !target.isAbs(elf_file)) blk: {
+                    x86_64.relaxRexGotpcrelx(code[r_offset - 3 ..]) catch break :blk;
+                    try cwriter.writeIntLittle(i32, @as(i32, @intCast(S + A - P)));
+                    continue;
+                }
+                try cwriter.writeIntLittle(i32, @as(i32, @intCast(G + GOT + A - P)));
+            },
+
             else => {
                 log.err("TODO: unhandled relocation type {}", .{fmtRelocType(rel.r_type())});
                 @panic("TODO unhandled relocation type");
@@ -591,6 +625,58 @@ fn format2(
 // future.
 pub const Index = u16;
 
+const x86_64 = struct {
+    pub fn relaxGotpcrelx(code: []u8) !void {
+        const old_inst = disassemble(code) orelse return error.RelaxFail;
+        const inst = switch (old_inst.encoding.mnemonic) {
+            .call => try Instruction.new(old_inst.prefix, .call, &.{
+                // TODO: hack to force imm32s in the assembler
+                .{ .imm = Immediate.s(-129) },
+            }),
+            .jmp => try Instruction.new(old_inst.prefix, .jmp, &.{
+                // TODO: hack to force imm32s in the assembler
+                .{ .imm = Immediate.s(-129) },
+            }),
+            else => return error.RelaxFail,
+        };
+        relocs_log.debug("    relaxing {} => {}", .{ old_inst.encoding, inst.encoding });
+        const nop = try Instruction.new(.none, .nop, &.{});
+        encode(&.{ nop, inst }, code) catch return error.RelaxFail;
+    }
+
+    pub fn relaxRexGotpcrelx(code: []u8) !void {
+        const old_inst = disassemble(code) orelse return error.RelaxFail;
+        switch (old_inst.encoding.mnemonic) {
+            .mov => {
+                const inst = try Instruction.new(old_inst.prefix, .lea, &old_inst.ops);
+                relocs_log.debug("    relaxing {} => {}", .{ old_inst.encoding, inst.encoding });
+                encode(&.{inst}, code) catch return error.RelaxFail;
+            },
+            else => return error.RelaxFail,
+        }
+    }
+
+    fn disassemble(code: []const u8) ?Instruction {
+        var disas = Disassembler.init(code);
+        const inst = disas.next() catch return null;
+        return inst;
+    }
+
+    fn encode(insts: []const Instruction, code: []u8) !void {
+        var stream = std.io.fixedBufferStream(code);
+        const writer = stream.writer();
+        for (insts) |inst| {
+            try inst.encode(writer, .{});
+        }
+    }
+
+    const bits = @import("../../arch/x86_64/bits.zig");
+    const encoder = @import("../../arch/x86_64/encoder.zig");
+    const Disassembler = @import("../../arch/x86_64/Disassembler.zig");
+    const Immediate = bits.Immediate;
+    const Instruction = encoder.Instruction;
+};
+
 const std = @import("std");
 const assert = std.debug.assert;
 const elf = std.elf;
diff --git a/src/link/Elf/Object.zig b/src/link/Elf/Object.zig
index b0a6ef2a1c..32c96b8d95 100644
--- a/src/link/Elf/Object.zig
+++ b/src/link/Elf/Object.zig
@@ -485,9 +485,9 @@ pub fn claimUnresolved(self: *Object, elf_file: *Elf) void {
 pub fn resetGlobals(self: *Object, elf_file: *Elf) void {
     for (self.globals()) |index| {
         const global = elf_file.symbol(index);
-        const name = global.name;
+        const off = global.name_offset;
         global.* = .{};
-        global.name = name;
+        global.name_offset = off;
     }
 }
 
@@ -499,7 +499,7 @@ pub fn markLive(self: *Object, elf_file: *Elf) void {
         if (sym.st_bind() == elf.STB_WEAK) continue;
 
         const global = elf_file.symbol(index);
-        const file = global.getFile(elf_file) orelse continue;
+        const file = global.file(elf_file) orelse continue;
         const should_keep = sym.st_shndx == elf.SHN_UNDEF or
             (sym.st_shndx == elf.SHN_COMMON and global.elfSym(elf_file).st_shndx != elf.SHN_COMMON);
         if (should_keep and !file.isAlive()) {
diff --git a/src/link/Elf/Symbol.zig b/src/link/Elf/Symbol.zig
index 42b9b81ef9..c70d0b8229 100644
--- a/src/link/Elf/Symbol.zig
+++ b/src/link/Elf/Symbol.zig
@@ -1,7 +1,5 @@
 //! Represents a defined symbol.
 
-index: Index = 0,
-
 /// Allocated address value of this symbol.
 value: u64 = 0,
 
@@ -117,10 +115,10 @@ const GetOrCreateGotEntryResult = struct {
     index: GotSection.Index,
 };
 
-pub fn getOrCreateGotEntry(symbol: *Symbol, elf_file: *Elf) !GetOrCreateGotEntryResult {
+pub fn getOrCreateGotEntry(symbol: *Symbol, symbol_index: Index, elf_file: *Elf) !GetOrCreateGotEntryResult {
     assert(symbol.flags.needs_got);
     if (symbol.flags.has_got) return .{ .found_existing = true, .index = symbol.extra(elf_file).?.got };
-    const index = try elf_file.got.addGotSymbol(symbol.index, elf_file);
+    const index = try elf_file.got.addGotSymbol(symbol_index, elf_file);
     symbol.flags.has_got = true;
     return .{ .found_existing = false, .index = index };
 }
@@ -270,7 +268,7 @@ fn format2(
     _ = options;
     _ = unused_fmt_string;
     const symbol = ctx.symbol;
-    try writer.print("%{d} : {s} : @{x}", .{ symbol.index, symbol.fmtName(ctx.elf_file), symbol.value });
+    try writer.print("%{d} : {s} : @{x}", .{ symbol.esym_index, symbol.fmtName(ctx.elf_file), symbol.value });
     if (symbol.file(ctx.elf_file)) |file_ptr| {
         if (symbol.isAbs(ctx.elf_file)) {
             if (symbol.elfSym(ctx.elf_file).st_shndx == elf.SHN_UNDEF) {
diff --git a/src/link/Elf/ZigModule.zig b/src/link/Elf/ZigModule.zig
index 46a382abf9..98496a2c38 100644
--- a/src/link/Elf/ZigModule.zig
+++ b/src/link/Elf/ZigModule.zig
@@ -148,6 +148,15 @@ pub fn scanRelocs(self: *ZigModule, elf_file: *Elf, undefs: anytype) !void {
     }
 }
 
+pub fn resetGlobals(self: *ZigModule, elf_file: *Elf) void {
+    for (self.globals()) |index| {
+        const global = elf_file.symbol(index);
+        const off = global.name_offset;
+        global.* = .{};
+        global.name_offset = off;
+    }
+}
+
 pub fn updateSymtabSize(self: *ZigModule, elf_file: *Elf) void {
     for (self.locals()) |local_index| {
         const local = elf_file.symbol(local_index);
diff --git a/src/link/Elf/file.zig b/src/link/Elf/file.zig
index 2b49f43bf1..3b9790dffa 100644
--- a/src/link/Elf/file.zig
+++ b/src/link/Elf/file.zig
@@ -62,6 +62,19 @@ pub const File = union(enum) {
         return (@as(u32, base) << 24) + file.index();
     }
 
+    pub fn resolveSymbols(file: File, elf_file: *Elf) void {
+        switch (file) {
+            inline else => |x| x.resolveSymbols(elf_file),
+        }
+    }
+
+    pub fn resetGlobals(file: File, elf_file: *Elf) void {
+        switch (file) {
+            .linker_defined => unreachable,
+            inline else => |x| x.resetGlobals(elf_file),
+        }
+    }
+
     pub fn setAlive(file: File) void {
         switch (file) {
             .zig_module, .linker_defined => {},
@@ -71,7 +84,7 @@ pub const File = union(enum) {
 
     pub fn markLive(file: File, elf_file: *Elf) void {
         switch (file) {
-            .zig_module, .linker_defined => {},
+            .zig_module, .linker_defined => unreachable,
             inline else => |x| x.markLive(elf_file),
         }
     }