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macho: add routine for creating lazy pointer for stub

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This commit is contained in:
Jakub Konka 2021-08-23 23:01:14 +02:00
parent 799c5bb955
commit 9e7b2fb894
1 changed files with 37 additions and 30 deletions
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67
src/link/MachO.zig
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@ -808,8 +808,14 @@ pub fn flush(self: *MachO, comp: *Compilation) !void {
sect.size -= atom.size;
}
for (self.stubs.items) |_| {
const atom = try self.createStubHelperAtom();
try self.allocateAtomStage1(atom, .{
const stub_atom = try self.createStubHelperAtom();
try self.allocateAtomStage1(stub_atom, .{
.seg = self.text_segment_cmd_index.?,
.sect = self.stub_helper_section_index.?,
});
const laptr_atom = try self.createLazyPointerAtom(stub_atom.local_sym_index);
try self.allocateAtomStage1(laptr_atom, .{
.seg = self.text_segment_cmd_index.?,
.sect = self.stub_helper_section_index.?,
});
@ -1767,16 +1773,9 @@ fn allocateDataConstSegment(self: *MachO) !void {
fn allocateDataSegment(self: *MachO) !void {
const seg = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
const nstubs = @intCast(u32, self.stubs.items.len);
const data_const_seg = self.load_commands.items[self.data_const_segment_cmd_index.?].Segment;
seg.inner.fileoff = data_const_seg.inner.fileoff + data_const_seg.inner.filesize;
seg.inner.vmaddr = data_const_seg.inner.vmaddr + data_const_seg.inner.vmsize;
// Set la_symbol_ptr
const la_symbol_ptr = &seg.sections.items[self.la_symbol_ptr_section_index.?];
la_symbol_ptr.size += nstubs * @sizeOf(u64);
try self.allocateSegment(self.data_segment_cmd_index.?, 0);
}
@ -2241,6 +2240,35 @@ fn createStubHelperAtom(self: *MachO) !*TextBlock {
return atom;
}
fn createLazyPointerAtom(self: *MachO, stub_sym_index: u32) !*TextBlock {
const local_sym_index = @intCast(u32, self.locals.items.len);
try self.locals.append(self.base.allocator, .{
.n_strx = try self.makeString("lazy_ptr"),
.n_type = macho.N_SECT,
.n_sect = 0,
.n_desc = 0,
.n_value = 0,
});
const atom = try self.createEmptyAtom(.{
.seg = self.data_segment_cmd_index.?,
.sect = self.la_symbol_ptr_section_index.?,
}, local_sym_index, @sizeOf(u64), 3);
try atom.relocs.append(self.base.allocator, .{
.offset = 0,
.where = .local,
.where_index = stub_sym_index,
.payload = .{
.unsigned = .{
.subtractor = null,
.addend = 0,
.is_64bit = true,
},
},
});
self.lazy_binding_info_dirty = true;
return atom;
}
fn resolveSymbolsInObject(
self: *MachO,
object_id: u16,
@ -2731,7 +2759,6 @@ fn flushZld(self: *MachO) !void {
for (self.stubs.items) |_, i| {
const index = @intCast(u32, i);
// TODO weak bound pointers
try self.writeLazySymbolPointer(index);
try self.writeStub(index);
}
@ -4633,26 +4660,6 @@ fn writeGotEntry(self: *MachO, index: usize) !void {
try self.base.file.?.pwriteAll(mem.asBytes(&sym.n_value), off);
}
fn writeLazySymbolPointer(self: *MachO, index: u32) !void {
const text_segment = self.load_commands.items[self.text_segment_cmd_index.?].Segment;
const stub_helper = text_segment.sections.items[self.stub_helper_section_index.?];
const data_segment = self.load_commands.items[self.data_segment_cmd_index.?].Segment;
const la_symbol_ptr = data_segment.sections.items[self.la_symbol_ptr_section_index.?];
const stub_size: u4 = switch (self.base.options.target.cpu.arch) {
.x86_64 => 10,
.aarch64 => 3 * @sizeOf(u32),
else => unreachable,
};
const stub_off = self.stub_helper_stubs_start_off.? + index * stub_size;
const end = stub_helper.addr + stub_off - stub_helper.offset;
var buf: [@sizeOf(u64)]u8 = undefined;
mem.writeIntLittle(u64, &buf, end);
const off = la_symbol_ptr.offset + index * @sizeOf(u64);
log.debug("writing lazy symbol pointer entry 0x{x} at 0x{x}", .{ end, off });
try self.base.file.?.pwriteAll(&buf, off);
}
fn writeStub(self: *MachO, index: u32) !void {
const text_segment = self.load_commands.items[self.text_segment_cmd_index.?].Segment;
const stubs = text_segment.sections.items[self.stubs_section_index.?];