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macho: separate reloc parsing logic by cpu arch
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@kubkon
kubkon committed Dec 17, 2023
1 parent eeeddbb commit 020df24
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Showing 2 changed files with 153 additions and 71 deletions.
193 changes: 153 additions & 40 deletions src/MachO/Object.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -419,7 +419,6 @@ fn sortAtoms(self: *Object, macho_file: *MachO) !void {
}

fn initRelocs(self: *Object, macho_file: *MachO) !void {
const gpa = macho_file.base.allocator;
const cpu_arch = macho_file.options.cpu_arch.?;
const slice = self.sections.slice();

Expand All @@ -428,42 +427,164 @@ fn initRelocs(self: *Object, macho_file: *MachO) !void {
if (sect.attrs() & macho.S_ATTR_DEBUG != 0 and
!mem.eql(u8, sect.sectName(), "__compact_unwind")) continue;

const relocs = @as([*]align(1) const macho.relocation_info, @ptrCast(self.data.ptr + sect.reloff))[0..sect.nreloc];
switch (cpu_arch) {
.x86_64 => try x86_64.parseRelocs(self, @intCast(n_sect), sect, out, macho_file),
.aarch64 => try aarch64.parseRelocs(self, @intCast(n_sect), sect, out, macho_file),
else => unreachable,
}

mem.sort(Relocation, out.items, {}, Relocation.lessThan);
}

for (slice.items(.header), slice.items(.relocs), slice.items(.subsections)) |sect, relocs, subsections| {
if (sect.isZerofill()) continue;

var next_reloc: usize = 0;
for (subsections.items) |subsection| {
const atom = macho_file.getAtom(subsection.atom).?;
if (!atom.flags.alive) continue;
if (next_reloc >= relocs.items.len) break;
const end_addr = atom.off + atom.size;
atom.relocs.pos = next_reloc;

while (next_reloc < relocs.items.len and relocs.items[next_reloc].offset < end_addr) : (next_reloc += 1) {}

atom.relocs.len = next_reloc - atom.relocs.pos;
}
}
}

const x86_64 = struct {
fn parseRelocs(
self: *const Object,
n_sect: u8,
sect: macho.section_64,
out: *std.ArrayListUnmanaged(Relocation),
macho_file: *MachO,
) !void {
const gpa = macho_file.base.allocator;

const relocs = @as(
[*]align(1) const macho.relocation_info,
@ptrCast(self.data.ptr + sect.reloff),
)[0..sect.nreloc];
const code = self.getSectionData(@intCast(n_sect));

try out.ensureTotalCapacityPrecise(gpa, relocs.len);

var i: usize = 0;
while (i < relocs.len) : (i += 1) {
const rel = relocs[i];
const rel_type: macho.reloc_type_x86_64 = @enumFromInt(rel.r_type);
const rel_offset = @as(u32, @intCast(rel.r_address));

var addend = switch (rel.r_length) {
0 => code[rel_offset],
1 => mem.readInt(i16, code[rel_offset..][0..2], .little),
2 => mem.readInt(i32, code[rel_offset..][0..4], .little),
3 => mem.readInt(i64, code[rel_offset..][0..8], .little),
};
addend += switch (@as(macho.reloc_type_x86_64, @enumFromInt(rel.r_type))) {
.X86_64_RELOC_SIGNED_1 => 1,
.X86_64_RELOC_SIGNED_2 => 2,
.X86_64_RELOC_SIGNED_4 => 4,
else => 0,
};

const target = if (rel.r_extern == 0) blk: {
const nsect = rel.r_symbolnum - 1;
const taddr: i64 = if (rel.r_pcrel == 1)
@as(i64, @intCast(sect.addr)) + rel.r_address + addend + 4
else
addend;
const target = self.findAtomInSection(@intCast(taddr), @intCast(nsect)) orelse {
macho_file.base.fatal("{}: {s},{s}: 0x{x}: bad relocation", .{
self.fmtPath(), sect.segName(), sect.sectName(), rel.r_address,
});
return error.ParseFailed;
};
addend = taddr - @as(i64, @intCast(macho_file.getAtom(target).?.getInputSection(macho_file).addr));
break :blk target;
} else self.symbols.items[rel.r_symbolnum];

const has_subtractor = if (i > 0)
@as(macho.reloc_type_x86_64, @enumFromInt(relocs[i - 1].r_type)) == .X86_64_RELOC_SUBTRACTOR
else
false;

out.appendAssumeCapacity(.{
.tag = if (rel.r_extern == 1) .@"extern" else .local,
.offset = @as(u32, @intCast(rel.r_address)),
.target = target,
.addend = addend,
.type = switch (rel_type) {
.X86_64_RELOC_UNSIGNED => .unsigned,
.X86_64_RELOC_SIGNED => .signed,
.X86_64_RELOC_SIGNED_1 => .signed1,
.X86_64_RELOC_SIGNED_2 => .signed2,
.X86_64_RELOC_SIGNED_4 => .signed4,
.X86_64_RELOC_BRANCH => .branch,
.X86_64_RELOC_GOT_LOAD => .got_load,
.X86_64_RELOC_GOT => .got,
.X86_64_RELOC_SUBTRACTOR => .subtractor,
.X86_64_RELOC_TLV => .tlv,
},
.meta = .{
.pcrel = rel.r_pcrel == 1,
.has_subtractor = has_subtractor,
.length = rel.r_length,
.symbolnum = rel.r_symbolnum,
},
});
}
}
};

const aarch64 = struct {
fn parseRelocs(
self: *const Object,
n_sect: u8,
sect: macho.section_64,
out: *std.ArrayListUnmanaged(Relocation),
macho_file: *MachO,
) !void {
const gpa = macho_file.base.allocator;

const relocs = @as(
[*]align(1) const macho.relocation_info,
@ptrCast(self.data.ptr + sect.reloff),
)[0..sect.nreloc];
const code = self.getSectionData(@intCast(n_sect));

try out.ensureTotalCapacityPrecise(gpa, relocs.len);

var i: usize = 0;
while (i < relocs.len) : (i += 1) {
var rel = relocs[i];
const rel_offset = @as(u32, @intCast(rel.r_address));

var addend: i64 = 0;

switch (cpu_arch) {
.aarch64 => if (@as(macho.reloc_type_arm64, @enumFromInt(rel.r_type)) == .ARM64_RELOC_ADDEND) {
switch (@as(macho.reloc_type_arm64, @enumFromInt(rel.r_type))) {
.ARM64_RELOC_ADDEND => {
// TODO validate it is followed by either page or pageoff variety
addend = rel.r_address;
i += 1;
rel = relocs[i];
},
.x86_64 => {
const rel_offset = @as(u32, @intCast(rel.r_address));
.ARM64_RELOC_UNSIGNED => {
addend = switch (rel.r_length) {
0 => code[rel_offset],
1 => mem.readInt(i16, code[rel_offset..][0..2], .little),
2 => mem.readInt(i32, code[rel_offset..][0..4], .little),
3 => mem.readInt(i64, code[rel_offset..][0..8], .little),
};
addend += switch (@as(macho.reloc_type_x86_64, @enumFromInt(rel.r_type))) {
.X86_64_RELOC_SIGNED_1 => 1,
.X86_64_RELOC_SIGNED_2 => 2,
.X86_64_RELOC_SIGNED_4 => 4,
else => 0,
};
},
else => unreachable,
else => {},
}

const rel_type = Relocation.Type.fromInt(rel.r_type, cpu_arch);
const rel_type: macho.reloc_type_arm64 = @enumFromInt(rel.r_type);

const target = if (rel.r_extern == 0) blk: {
const nsect = rel.r_symbolnum - 1;
const taddr: i64 = if (rel.r_pcrel == 1)
Expand All @@ -480,18 +601,29 @@ fn initRelocs(self: *Object, macho_file: *MachO) !void {
break :blk target;
} else self.symbols.items[rel.r_symbolnum];

const has_subtractor = if (i > 0) switch (cpu_arch) {
.x86_64 => @as(macho.reloc_type_x86_64, @enumFromInt(relocs[i - 1].r_type)) == .X86_64_RELOC_SUBTRACTOR,
.aarch64 => @as(macho.reloc_type_arm64, @enumFromInt(relocs[i - 1].r_type)) == .ARM64_RELOC_SUBTRACTOR,
else => unreachable,
} else false;
const has_subtractor = if (i > 0)
@as(macho.reloc_type_arm64, @enumFromInt(relocs[i - 1].r_type)) == .ARM64_RELOC_SUBTRACTOR
else
false;

out.appendAssumeCapacity(.{
.tag = if (rel.r_extern == 1) .@"extern" else .local,
.offset = @as(u32, @intCast(rel.r_address)),
.target = target,
.addend = addend,
.type = rel_type,
.type = switch (rel_type) {
.ARM64_RELOC_UNSIGNED => .unsigned,
.ARM64_RELOC_SUBTRACTOR => .subtractor,
.ARM64_RELOC_BRANCH26 => .branch,
.ARM64_RELOC_PAGE21 => .page,
.ARM64_RELOC_PAGEOFF12 => .pageoff,
.ARM64_RELOC_GOT_LOAD_PAGE21 => .got_load_page,
.ARM64_RELOC_GOT_LOAD_PAGEOFF12 => .got_load_pageoff,
.ARM64_RELOC_TLVP_LOAD_PAGE21 => .tlvp_page,
.ARM64_RELOC_TLVP_LOAD_PAGEOFF12 => .tlvp_pageoff,
.ARM64_RELOC_POINTER_TO_GOT => .got,
.ARM64_RELOC_ADDEND => unreachable, // We make it part of the addend field
},
.meta = .{
.pcrel = rel.r_pcrel == 1,
.has_subtractor = has_subtractor,
Expand All @@ -500,27 +632,8 @@ fn initRelocs(self: *Object, macho_file: *MachO) !void {
},
});
}

mem.sort(Relocation, out.items, {}, Relocation.lessThan);
}

for (slice.items(.header), slice.items(.relocs), slice.items(.subsections)) |sect, relocs, subsections| {
if (sect.isZerofill()) continue;

var next_reloc: usize = 0;
for (subsections.items) |subsection| {
const atom = macho_file.getAtom(subsection.atom).?;
if (!atom.flags.alive) continue;
if (next_reloc >= relocs.items.len) break;
const end_addr = atom.off + atom.size;
atom.relocs.pos = next_reloc;

while (next_reloc < relocs.items.len and relocs.items[next_reloc].offset < end_addr) : (next_reloc += 1) {}

atom.relocs.len = next_reloc - atom.relocs.pos;
}
}
}
};

fn initEhFrameRecords(self: *Object, sect_id: u8, macho_file: *MachO) !void {
const gpa = macho_file.base.allocator;
Expand Down
31 changes: 0 additions & 31 deletions src/MachO/Relocation.zig
View file
Original file line number Diff line number Diff line change
Expand Up @@ -82,37 +82,6 @@ pub const Type = enum {
tlvp_page,
/// Represents .ARM64_RELOC_TLVP_PAGEOFF12
tlvp_pageoff,

pub fn fromInt(raw: u4, arch: std.Target.Cpu.Arch) Type {
return switch (arch) {
.x86_64 => switch (@as(macho.reloc_type_x86_64, @enumFromInt(raw))) {
.X86_64_RELOC_UNSIGNED => .unsigned,
.X86_64_RELOC_SIGNED => .signed,
.X86_64_RELOC_SIGNED_1 => .signed1,
.X86_64_RELOC_SIGNED_2 => .signed2,
.X86_64_RELOC_SIGNED_4 => .signed4,
.X86_64_RELOC_BRANCH => .branch,
.X86_64_RELOC_GOT_LOAD => .got_load,
.X86_64_RELOC_GOT => .got,
.X86_64_RELOC_SUBTRACTOR => .subtractor,
.X86_64_RELOC_TLV => .tlv,
},
.aarch64 => switch (@as(macho.reloc_type_arm64, @enumFromInt(raw))) {
.ARM64_RELOC_UNSIGNED => .unsigned,
.ARM64_RELOC_SUBTRACTOR => .subtractor,
.ARM64_RELOC_BRANCH26 => .branch,
.ARM64_RELOC_PAGE21 => .page,
.ARM64_RELOC_PAGEOFF12 => .pageoff,
.ARM64_RELOC_GOT_LOAD_PAGE21 => .got_load_page,
.ARM64_RELOC_GOT_LOAD_PAGEOFF12 => .got_load_pageoff,
.ARM64_RELOC_TLVP_LOAD_PAGE21 => .tlvp_page,
.ARM64_RELOC_TLVP_LOAD_PAGEOFF12 => .tlvp_pageoff,
.ARM64_RELOC_POINTER_TO_GOT => .got,
.ARM64_RELOC_ADDEND => unreachable, // We make it part of addend field
},
else => unreachable,
};
}
};

const assert = std.debug.assert;
Expand Down

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