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macho: add routine for creating stubs in __stubs section
This commit is contained in:
Jakub Konka
parent
876071b50b
commit
91c0552cfc
@ -808,17 +808,23 @@ pub fn flush(self: *MachO, comp: *Compilation) !void {
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sect.size -= atom.size;
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}
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for (self.stubs.items) |_| {
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const stub_atom = try self.createStubHelperAtom();
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try self.allocateAtomStage1(stub_atom, .{
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const stub_helper_atom = try self.createStubHelperAtom();
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try self.allocateAtomStage1(stub_helper_atom, .{
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.seg = self.text_segment_cmd_index.?,
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.sect = self.stub_helper_section_index.?,
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});
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const laptr_atom = try self.createLazyPointerAtom(stub_atom.local_sym_index);
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const laptr_atom = try self.createLazyPointerAtom(stub_helper_atom.local_sym_index);
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try self.allocateAtomStage1(laptr_atom, .{
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.seg = self.data_segment_cmd_index.?,
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.sect = self.la_symbol_ptr_section_index.?,
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});
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const stub_atom = try self.createStubAtom(laptr_atom.local_sym_index);
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try self.allocateAtomStage1(stub_atom, .{
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.seg = self.text_segment_cmd_index.?,
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.sect = self.stubs_section_index.?,
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});
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}
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try self.allocateTextSegment();
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try self.allocateDataConstSegment();
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@ -1715,16 +1721,10 @@ fn sortSections(self: *MachO) !void {
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fn allocateTextSegment(self: *MachO) !void {
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const seg = &self.load_commands.items[self.text_segment_cmd_index.?].Segment;
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const nstubs = @intCast(u32, self.stubs.items.len);
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const base_vmaddr = self.load_commands.items[self.pagezero_segment_cmd_index.?].Segment.inner.vmsize;
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seg.inner.fileoff = 0;
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seg.inner.vmaddr = base_vmaddr;
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// Set stubs sizes
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const stubs = &seg.sections.items[self.stubs_section_index.?];
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stubs.size += nstubs * stubs.reserved2;
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var sizeofcmds: u64 = 0;
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for (self.load_commands.items) |lc| {
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sizeofcmds += lc.cmdsize();
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@ -2274,6 +2274,86 @@ fn createLazyPointerAtom(self: *MachO, stub_sym_index: u32) !*TextBlock {
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return atom;
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}
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fn createStubAtom(self: *MachO, laptr_sym_index: u32) !*TextBlock {
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const arch = self.base.options.target.cpu.arch;
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const alignment: u2 = switch (arch) {
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.x86_64 => 0,
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.aarch64 => 2,
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else => unreachable, // unhandled architecture type
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};
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const stub_size: u4 = switch (arch) {
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.x86_64 => 6,
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.aarch64 => 3 * @sizeOf(u32),
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else => unreachable, // unhandled architecture type
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};
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const local_sym_index = @intCast(u32, self.locals.items.len);
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try self.locals.append(self.base.allocator, .{
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.n_strx = try self.makeString("stub"),
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.n_type = macho.N_SECT,
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.n_sect = 0,
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.n_desc = 0,
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.n_value = 0,
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});
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const atom = try self.createEmptyAtom(.{
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.seg = self.text_segment_cmd_index.?,
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.sect = self.stubs_section_index.?,
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}, local_sym_index, stub_size, alignment);
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switch (arch) {
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.x86_64 => {
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// jmp
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atom.code.items[0] = 0xff;
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atom.code.items[1] = 0x25;
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try atom.relocs.append(self.base.allocator, .{
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.offset = 2,
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.where = .local,
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.where_index = laptr_sym_index,
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.payload = .{
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.branch = .{ .arch = arch },
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},
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});
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},
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.aarch64 => {
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try atom.relocs.ensureTotalCapacity(self.base.allocator, 2);
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// adrp x16, pages
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mem.writeIntLittle(u32, atom.code.items[0..4], aarch64.Instruction.adrp(.x16, 0).toU32());
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atom.relocs.appendAssumeCapacity(.{
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.offset = 0,
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.where = .local,
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.where_index = laptr_sym_index,
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.payload = .{
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.page = .{
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.kind = .page,
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.addend = 0,
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},
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},
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});
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// ldr x16, x16, offset
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mem.writeIntLittle(u32, atom.code.items[4..8], aarch64.Instruction.ldr(.x16, .{
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.register = .{
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.rn = .x16,
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.offset = aarch64.Instruction.LoadStoreOffset.imm(0),
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},
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}).toU32());
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atom.relocs.appendAssumeCapacity(.{
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.offset = 4,
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.where = .local,
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.where_index = laptr_sym_index,
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.payload = .{
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.page_off = .{
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.kind = .page,
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.addend = 0,
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.op_kind = .load,
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},
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},
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});
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// br x16
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mem.writeIntLittle(u32, atom.code.items[8..12], aarch64.Instruction.br(.x16).toU32());
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},
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else => unreachable,
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}
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return atom;
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}
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fn resolveSymbolsInObject(
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self: *MachO,
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object_id: u16,
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@ -2761,12 +2841,6 @@ fn addLoadDylibLCs(self: *MachO) !void {
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fn flushZld(self: *MachO) !void {
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try self.writeTextBlocks();
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for (self.stubs.items) |_, i| {
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const index = @intCast(u32, i);
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// TODO weak bound pointers
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try self.writeStub(index);
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}
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if (self.common_section_index) |index| {
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const seg = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
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const sect = &seg.sections.items[index];
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@ -4665,82 +4739,6 @@ fn writeGotEntry(self: *MachO, index: usize) !void {
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try self.base.file.?.pwriteAll(mem.asBytes(&sym.n_value), off);
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}
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fn writeStub(self: *MachO, index: u32) !void {
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const text_segment = self.load_commands.items[self.text_segment_cmd_index.?].Segment;
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const stubs = text_segment.sections.items[self.stubs_section_index.?];
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const data_segment = self.load_commands.items[self.data_segment_cmd_index.?].Segment;
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const la_symbol_ptr = data_segment.sections.items[self.la_symbol_ptr_section_index.?];
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const stub_off = stubs.offset + index * stubs.reserved2;
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const stub_addr = stubs.addr + index * stubs.reserved2;
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const la_ptr_addr = la_symbol_ptr.addr + index * @sizeOf(u64);
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log.debug("writing stub at 0x{x}", .{stub_off});
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var code = try self.base.allocator.alloc(u8, stubs.reserved2);
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defer self.base.allocator.free(code);
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switch (self.base.options.target.cpu.arch) {
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.x86_64 => {
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assert(la_ptr_addr >= stub_addr + stubs.reserved2);
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const displacement = try math.cast(u32, la_ptr_addr - stub_addr - stubs.reserved2);
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// jmp
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code[0] = 0xff;
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code[1] = 0x25;
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mem.writeIntLittle(u32, code[2..][0..4], displacement);
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},
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.aarch64 => {
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assert(la_ptr_addr >= stub_addr);
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outer: {
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const this_addr = stub_addr;
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const target_addr = la_ptr_addr;
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inner: {
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const displacement = math.divExact(u64, target_addr - this_addr, 4) catch break :inner;
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const literal = math.cast(u18, displacement) catch break :inner;
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// ldr x16, literal
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mem.writeIntLittle(u32, code[0..4], aarch64.Instruction.ldr(.x16, .{
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.literal = literal,
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}).toU32());
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// nop
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mem.writeIntLittle(u32, code[4..8], aarch64.Instruction.nop().toU32());
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break :outer;
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}
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inner: {
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const new_this_addr = this_addr + @sizeOf(u32);
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const displacement = math.divExact(u64, target_addr - new_this_addr, 4) catch break :inner;
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const literal = math.cast(u18, displacement) catch break :inner;
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// nop
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mem.writeIntLittle(u32, code[0..4], aarch64.Instruction.nop().toU32());
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// ldr x16, literal
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mem.writeIntLittle(u32, code[4..8], aarch64.Instruction.ldr(.x16, .{
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.literal = literal,
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}).toU32());
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break :outer;
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}
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// Use adrp followed by ldr(register).
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const this_page = @intCast(i32, this_addr >> 12);
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const target_page = @intCast(i32, target_addr >> 12);
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const pages = @intCast(i21, target_page - this_page);
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// adrp x16, pages
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mem.writeIntLittle(u32, code[0..4], aarch64.Instruction.adrp(.x16, pages).toU32());
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const narrowed = @truncate(u12, target_addr);
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const offset = try math.divExact(u12, narrowed, 8);
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// ldr x16, x16, offset
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mem.writeIntLittle(u32, code[4..8], aarch64.Instruction.ldr(.x16, .{
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.register = .{
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.rn = .x16,
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.offset = aarch64.Instruction.LoadStoreOffset.imm(offset),
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},
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}).toU32());
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}
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// br x16
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mem.writeIntLittle(u32, code[8..12], aarch64.Instruction.br(.x16).toU32());
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},
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else => unreachable,
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}
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try self.base.file.?.pwriteAll(code, stub_off);
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}
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fn relocateSymbolTable(self: *MachO) !void {
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const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
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const nlocals = self.locals.items.len;
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