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elf+aarch64: implement .plt.got

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This commit is contained in:
Jakub Konka 2024-03-07 22:46:07 +01:00
parent 1cf45fb209
commit 0af5d2e9b6
3 changed files with 64 additions and 17 deletions
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4
src/link/Elf.zig
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@ -4062,7 +4062,7 @@ fn updateSectionSizes(self: *Elf) !void {
}
if (self.plt_got_section_index) |index| {
self.shdrs.items[index].sh_size = self.plt_got.size();
self.shdrs.items[index].sh_size = self.plt_got.size(self);
}
if (self.rela_dyn_section_index) |shndx| {
@ -4747,7 +4747,7 @@ fn writeSyntheticSections(self: *Elf) !void {
if (self.plt_got_section_index) |shndx| {
const shdr = self.shdrs.items[shndx];
var buffer = try std.ArrayList(u8).initCapacity(gpa, self.plt_got.size());
var buffer = try std.ArrayList(u8).initCapacity(gpa, self.plt_got.size(self));
defer buffer.deinit();
try self.plt_got.write(self, buffer.writer());
try self.base.file.?.pwriteAll(buffer.items, shdr.sh_offset);

4
src/link/Elf/Symbol.zig
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@ -139,7 +139,8 @@ pub fn pltGotAddress(symbol: Symbol, elf_file: *Elf) u64 {
if (!(symbol.flags.has_plt and symbol.flags.has_got)) return 0;
const extras = symbol.extra(elf_file).?;
const shdr = elf_file.shdrs.items[elf_file.plt_got_section_index.?];
return shdr.sh_addr + extras.plt_got * 16;
const cpu_arch = elf_file.getTarget().cpu.arch;
return shdr.sh_addr + extras.plt_got * PltGotSection.entrySize(cpu_arch);
}
pub fn pltAddress(symbol: Symbol, elf_file: *Elf) u64 {
@ -442,6 +443,7 @@ const GotPltSection = synthetic_sections.GotPltSection;
const LinkerDefined = @import("LinkerDefined.zig");
const Object = @import("Object.zig");
const PltSection = synthetic_sections.PltSection;
const PltGotSection = synthetic_sections.PltGotSection;
const SharedObject = @import("SharedObject.zig");
const Symbol = @This();
const ZigGotSection = synthetic_sections.ZigGotSection;

73
src/link/Elf/synthetic_sections.zig
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@ -1130,23 +1130,24 @@ pub const PltGotSection = struct {
try plt_got.symbols.append(gpa, sym_index);
}
pub fn size(plt_got: PltGotSection) usize {
return plt_got.symbols.items.len * 16;
pub fn size(plt_got: PltGotSection, elf_file: *Elf) usize {
return plt_got.symbols.items.len * entrySize(elf_file.getTarget().cpu.arch);
}
pub fn entrySize(cpu_arch: std.Target.Cpu.Arch) usize {
return switch (cpu_arch) {
.x86_64 => 16,
.aarch64 => 4 * @sizeOf(u32),
else => @panic("TODO implement PltGotSection.entrySize for this arch"),
};
}
pub fn write(plt_got: PltGotSection, elf_file: *Elf, writer: anytype) !void {
for (plt_got.symbols.items) |sym_index| {
const sym = elf_file.symbol(sym_index);
const target_addr = sym.gotAddress(elf_file);
const source_addr = sym.pltGotAddress(elf_file);
const disp = @as(i64, @intCast(target_addr)) - @as(i64, @intCast(source_addr + 6)) - 4;
var entry = [_]u8{
0xf3, 0x0f, 0x1e, 0xfa, // endbr64
0xff, 0x25, 0x00, 0x00, 0x00, 0x00, // jmp qword ptr [rip] -> .got[N]
0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc,
};
mem.writeInt(i32, entry[6..][0..4], @as(i32, @intCast(disp)), .little);
try writer.writeAll(&entry);
const cpu_arch = elf_file.getTarget().cpu.arch;
switch (cpu_arch) {
.x86_64 => try x86_64.write(plt_got, elf_file, writer),
.aarch64 => try aarch64.write(plt_got, elf_file, writer),
else => return error.UnsupportedCpuArch,
}
}
@ -1175,6 +1176,50 @@ pub const PltGotSection = struct {
};
}
}
const x86_64 = struct {
pub fn write(plt_got: PltGotSection, elf_file: *Elf, writer: anytype) !void {
for (plt_got.symbols.items) |sym_index| {
const sym = elf_file.symbol(sym_index);
const target_addr = sym.gotAddress(elf_file);
const source_addr = sym.pltGotAddress(elf_file);
const disp = @as(i64, @intCast(target_addr)) - @as(i64, @intCast(source_addr + 6)) - 4;
var entry = [_]u8{
0xf3, 0x0f, 0x1e, 0xfa, // endbr64
0xff, 0x25, 0x00, 0x00, 0x00, 0x00, // jmp qword ptr [rip] -> .got[N]
0xcc, 0xcc, 0xcc, 0xcc, 0xcc, 0xcc,
};
mem.writeInt(i32, entry[6..][0..4], @as(i32, @intCast(disp)), .little);
try writer.writeAll(&entry);
}
}
};
const aarch64 = struct {
fn write(plt_got: PltGotSection, elf_file: *Elf, writer: anytype) !void {
for (plt_got.symbols.items) |sym_index| {
const sym = elf_file.symbol(sym_index);
const target_addr = sym.gotAddress(elf_file);
const source_addr = sym.pltGotAddress(elf_file);
const pages = try aarch64_util.calcNumberOfPages(source_addr, target_addr);
const off = try aarch64_util.calcPageOffset(.load_store_64, target_addr);
const insts = &[_]Instruction{
Instruction.adrp(.x16, pages),
Instruction.ldr(.x17, .x16, Instruction.LoadStoreOffset.imm(off)),
Instruction.br(.x17),
Instruction.nop(),
};
comptime assert(insts.len == 4);
for (insts) |inst| {
try writer.writeInt(u32, inst.toU32(), .little);
}
}
}
const aarch64_util = @import("../aarch64.zig");
const Instruction = aarch64_util.Instruction;
const Register = aarch64_util.Register;
};
};
pub const CopyRelSection = struct {