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macho: fix reloc generation for stubs and GOT entries

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The current approach is somewhat hacky, however, works well for
one-off self-hosted linking.
This commit is contained in:
Jakub Konka 2021-07-21 23:05:03 +02:00
parent 845c906e6a
commit e05b1e0e07
1 changed files with 44 additions and 19 deletions
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63
src/codegen.zig
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@ -2523,21 +2523,25 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
} else if (func_value.castTag(.extern_fn)) |func_payload| {
const decl = func_payload.data;
const where_index = try macho_file.addExternFn(mem.spanZ(decl.name));
const offset = @intCast(u32, self.code.items.len);
switch (arch) {
.x86_64 => {
// callq
try self.code.ensureCapacity(self.code.items.len + 5);
self.code.appendSliceAssumeCapacity(&[5]u8{ 0xe8, 0x0, 0x0, 0x0, 0x0 });
},
.aarch64 => {
// bl
writeInt(u32, try self.code.addManyAsArray(4), Instruction.bl(0).toU32());
},
else => unreachable, // unsupported architecture on MachO
}
const offset = blk: {
switch (arch) {
.x86_64 => {
// callq
try self.code.ensureCapacity(self.code.items.len + 5);
self.code.appendSliceAssumeCapacity(&[5]u8{ 0xe8, 0x0, 0x0, 0x0, 0x0 });
break :blk @intCast(u32, self.code.items.len) - 4;
},
.aarch64 => {
const offset = @intCast(u32, self.code.items.len);
// bl
writeInt(u32, try self.code.addManyAsArray(4), Instruction.bl(0).toU32());
break :blk offset;
},
else => unreachable, // unsupported architecture on MachO
}
};
// Add relocation to the decl.
try decl.link.macho.relocs.append(self.bin_file.allocator, .{
try macho_file.active_decl.?.link.macho.relocs.append(self.bin_file.allocator, .{
.offset = offset,
.where = .import,
.where_index = where_index,
@ -3879,19 +3883,29 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
}).toU32());
if (self.bin_file.cast(link.File.MachO)) |macho_file| {
// TODO this is super awkward. We are reversing the address of the GOT entry here.
// We should probably have it cached or move the reloc adding somewhere else.
const got_addr = blk: {
const seg = macho_file.load_commands.items[macho_file.data_const_segment_cmd_index.?].Segment;
const got = seg.sections.items[macho_file.got_section_index.?];
break :blk got.addr;
};
const where_index = blk: for (macho_file.got_entries.items) |key, id| {
if (got_addr + id * @sizeOf(u64) == addr) break :blk key.where_index;
} else unreachable;
const decl = macho_file.active_decl.?;
// Page reloc for adrp instruction.
try decl.link.macho.relocs.append(self.bin_file.allocator, .{
.offset = offset,
.where = .local,
.where_index = decl.link.macho.local_sym_index,
.where_index = where_index,
.payload = .{ .page = .{ .kind = .got } },
});
// Pageoff reloc for adrp instruction.
try decl.link.macho.relocs.append(self.bin_file.allocator, .{
.offset = offset + 4,
.where = .local,
.where_index = decl.link.macho.local_sym_index,
.where_index = where_index,
.payload = .{ .page_off = .{ .kind = .got } },
});
} else {
@ -4136,7 +4150,6 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
const abi_size = ty.abiSize(self.target.*);
const encoder = try X8664Encoder.init(self.code, 10);
const offset = @intCast(u32, self.code.items.len);
// LEA reg, [<offset>]
// We encode the instruction FIRST because prefixes may or may not appear.
@ -4150,13 +4163,25 @@ fn Function(comptime arch: std.Target.Cpu.Arch) type {
encoder.modRm_RIPDisp32(reg.low_id());
encoder.disp32(0);
const offset = @intCast(u32, self.code.items.len);
if (self.bin_file.cast(link.File.MachO)) |macho_file| {
// TODO this is super awkward. We are reversing the address of the GOT entry here.
// We should probably have it cached or move the reloc adding somewhere else.
const got_addr = blk: {
const seg = macho_file.load_commands.items[macho_file.data_const_segment_cmd_index.?].Segment;
const got = seg.sections.items[macho_file.got_section_index.?];
break :blk got.addr;
};
const where_index = blk: for (macho_file.got_entries.items) |key, id| {
if (got_addr + id * @sizeOf(u64) == x) break :blk key.where_index;
} else unreachable;
const decl = macho_file.active_decl.?;
// Load reloc for LEA instruction.
try decl.link.macho.relocs.append(self.bin_file.allocator, .{
.offset = offset,
.offset = offset - 4,
.where = .local,
.where_index = decl.link.macho.local_sym_index,
.where_index = where_index,
.payload = .{ .load = .{ .kind = .got } },
});
} else {