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elf: handle more relocs with GOT relaxation

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Jakub Konka 2023-09-13 17:54:57 +02:00
parent 7a16a97671
commit 5eef7577d1
1 changed files with 77 additions and 0 deletions
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77
src/link/Elf/Atom.zig
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@ -460,10 +460,35 @@ pub fn resolveRelocs(self: Atom, elf_file: *Elf, code: []u8) !void {
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[rel.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[rel.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 +616,58 @@ 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;