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macho: remove redundant writeStubHelperCommon codepath

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This commit is contained in:
Jakub Konka 2021-08-18 11:46:45 +02:00
parent 8167456c58
commit 30247fbb6a
1 changed files with 15 additions and 141 deletions
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156
src/link/MachO.zig
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@ -376,10 +376,6 @@ pub fn openPath(allocator: *Allocator, sub_path: []const u8, options: link.Optio
try self.populateMissingMetadata();
try self.writeLocalSymbol(0);
if (self.stub_helper_stubs_start_off == null) {
try self.writeStubHelperPreamble();
}
if (self.d_sym) |*ds| {
try ds.populateMissingMetadata(allocator);
try ds.writeLocalSymbol(0);
@ -762,6 +758,11 @@ pub fn flush(self: *MachO, comp: *Compilation) !void {
try self.resolveSymbols();
try self.resolveDyldStubBinder();
if (!use_stage1) {
// TODO this should be made common when I figure out how to prealloc space for traditional linker path.
try self.writeStubHelperPreamble();
}
// Apply pending updates
var still_pending = std.ArrayList(PendingUpdate).init(self.base.allocator);
defer still_pending.deinit();
@ -824,6 +825,7 @@ pub fn flush(self: *MachO, comp: *Compilation) !void {
try self.allocateDataSegment();
self.allocateLinkeditSegment();
try self.allocateTextBlocks();
try self.writeStubHelperPreamble();
try self.flushZld();
} else {
try self.flushModule(comp);
@ -1943,7 +1945,7 @@ fn writeTextBlocks(self: *MachO) !void {
}
}
fn writeStubHelperCommon(self: *MachO) !void {
fn writeStubHelperPreamble(self: *MachO) !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_const_segment = &self.load_commands.items[self.data_const_segment_cmd_index.?].Segment;
@ -2074,14 +2076,6 @@ fn writeStubHelperCommon(self: *MachO) !void {
else => unreachable,
}
};
for (self.stubs.items) |_, i| {
const index = @intCast(u32, i);
// TODO weak bound pointers
try self.writeLazySymbolPointer(index);
try self.writeStub(index);
try self.writeStubInStubHelper(index);
}
}
fn resolveSymbolsInObject(
@ -2616,7 +2610,14 @@ fn addLoadDylibLCs(self: *MachO) !void {
fn flushZld(self: *MachO) !void {
try self.writeTextBlocks();
try self.writeStubHelperCommon();
for (self.stubs.items) |_, i| {
const index = @intCast(u32, i);
// TODO weak bound pointers
try self.writeLazySymbolPointer(index);
try self.writeStub(index);
try self.writeStubInStubHelper(index);
}
if (self.common_section_index) |index| {
const seg = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
@ -4540,133 +4541,6 @@ fn writeLazySymbolPointer(self: *MachO, index: u32) !void {
try self.base.file.?.pwriteAll(&buf, off);
}
fn writeStubHelperPreamble(self: *MachO) !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_const_segment = &self.load_commands.items[self.data_const_segment_cmd_index.?].Segment;
const got = &data_const_segment.sections.items[self.got_section_index.?];
const data_segment = &self.load_commands.items[self.data_segment_cmd_index.?].Segment;
const data = &data_segment.sections.items[self.data_section_index.?];
switch (self.base.options.target.cpu.arch) {
.x86_64 => {
const code_size = 15;
var code: [code_size]u8 = undefined;
// lea %r11, [rip + disp]
code[0] = 0x4c;
code[1] = 0x8d;
code[2] = 0x1d;
{
const target_addr = data.addr;
const displacement = try math.cast(u32, target_addr - stub_helper.addr - 7);
mem.writeIntLittle(u32, code[3..7], displacement);
}
// push %r11
code[7] = 0x41;
code[8] = 0x53;
// jmp [rip + disp]
code[9] = 0xff;
code[10] = 0x25;
{
const displacement = try math.cast(u32, got.addr - stub_helper.addr - code_size);
mem.writeIntLittle(u32, code[11..], displacement);
}
try self.base.file.?.pwriteAll(&code, stub_helper.offset);
self.stub_helper_stubs_start_off = stub_helper.offset + code_size;
},
.aarch64 => {
var code: [6 * @sizeOf(u32)]u8 = undefined;
data_blk_outer: {
const this_addr = stub_helper.addr;
const target_addr = data.addr;
data_blk: {
const displacement = math.cast(i21, target_addr - this_addr) catch break :data_blk;
// adr x17, disp
mem.writeIntLittle(u32, code[0..4], aarch64.Instruction.adr(.x17, displacement).toU32());
// nop
mem.writeIntLittle(u32, code[4..8], aarch64.Instruction.nop().toU32());
break :data_blk_outer;
}
data_blk: {
const new_this_addr = this_addr + @sizeOf(u32);
const displacement = math.cast(i21, target_addr - new_this_addr) catch break :data_blk;
// nop
mem.writeIntLittle(u32, code[0..4], aarch64.Instruction.nop().toU32());
// adr x17, disp
mem.writeIntLittle(u32, code[4..8], aarch64.Instruction.adr(.x17, displacement).toU32());
break :data_blk_outer;
}
// Jump is too big, replace adr with adrp and add.
const this_page = @intCast(i32, this_addr >> 12);
const target_page = @intCast(i32, target_addr >> 12);
const pages = @intCast(i21, target_page - this_page);
// adrp x17, pages
mem.writeIntLittle(u32, code[0..4], aarch64.Instruction.adrp(.x17, pages).toU32());
const narrowed = @truncate(u12, target_addr);
mem.writeIntLittle(u32, code[4..8], aarch64.Instruction.add(.x17, .x17, narrowed, false).toU32());
}
// stp x16, x17, [sp, #-16]!
mem.writeIntLittle(u32, code[8..12], aarch64.Instruction.stp(
.x16,
.x17,
aarch64.Register.sp,
aarch64.Instruction.LoadStorePairOffset.pre_index(-16),
).toU32());
binder_blk_outer: {
const this_addr = stub_helper.addr + 3 * @sizeOf(u32);
const target_addr = got.addr;
binder_blk: {
const displacement = math.divExact(u64, target_addr - this_addr, 4) catch break :binder_blk;
const literal = math.cast(u18, displacement) catch break :binder_blk;
// ldr x16, label
mem.writeIntLittle(u32, code[12..16], aarch64.Instruction.ldr(.x16, .{
.literal = literal,
}).toU32());
// nop
mem.writeIntLittle(u32, code[16..20], aarch64.Instruction.nop().toU32());
break :binder_blk_outer;
}
binder_blk: {
const new_this_addr = this_addr + @sizeOf(u32);
const displacement = math.divExact(u64, target_addr - new_this_addr, 4) catch break :binder_blk;
const literal = math.cast(u18, displacement) catch break :binder_blk;
// nop
mem.writeIntLittle(u32, code[12..16], aarch64.Instruction.nop().toU32());
// ldr x16, label
mem.writeIntLittle(u32, code[16..20], aarch64.Instruction.ldr(.x16, .{
.literal = literal,
}).toU32());
break :binder_blk_outer;
}
// Jump is too big, replace ldr with adrp and ldr(register).
const this_page = @intCast(i32, this_addr >> 12);
const target_page = @intCast(i32, target_addr >> 12);
const pages = @intCast(i21, target_page - this_page);
// adrp x16, pages
mem.writeIntLittle(u32, code[12..16], aarch64.Instruction.adrp(.x16, pages).toU32());
const narrowed = @truncate(u12, target_addr);
const offset = try math.divExact(u12, narrowed, 8);
// ldr x16, x16, offset
mem.writeIntLittle(u32, code[16..20], aarch64.Instruction.ldr(.x16, .{
.register = .{
.rn = .x16,
.offset = aarch64.Instruction.LoadStoreOffset.imm(offset),
},
}).toU32());
}
// br x16
mem.writeIntLittle(u32, code[20..24], aarch64.Instruction.br(.x16).toU32());
try self.base.file.?.pwriteAll(&code, stub_helper.offset);
self.stub_helper_stubs_start_off = stub_helper.offset + code.len;
},
else => unreachable,
}
}
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.?];