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macho: exclude linkedit and symtab/dysymtab load commands from the uuid calc

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This commit is contained in:
Jakub Konka 2022-12-15 16:04:10 +01:00
parent 660270b7a9
commit b323e14b1c
1 changed files with 64 additions and 21 deletions
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85
src/link/MachO/zld.zig
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@ -2675,7 +2675,11 @@ pub const Zld = struct {
self.dysymtab_cmd.nindirectsyms = nindirectsyms;
}
fn writeUuid(self: *Zld, comp: *const Compilation, offset: u32) !void {
fn writeUuid(self: *Zld, comp: *const Compilation, args: struct {
linkedit_cmd_offset: u32,
symtab_cmd_offset: u32,
uuid_cmd_offset: u32,
}) !void {
switch (self.options.optimize_mode) {
.Debug => {
// In Debug we don't really care about reproducibility, so put in a random value
@ -2691,8 +2695,24 @@ pub const Zld = struct {
var hashes = std.ArrayList([Md5.digest_length]u8).init(self.gpa);
defer hashes.deinit();
var subsections: [4]FileSubsection = undefined;
var count: usize = 2;
// Exclude LINKEDIT segment command as it contains file size that includes stabs contribution
// and code signature.
subsections[0] = .{
.start = 0,
.end = args.linkedit_cmd_offset,
};
// Exclude SYMTAB and DYSYMTAB commands for the same reason.
subsections[1] = .{
.start = args.linkedit_cmd_offset + @sizeOf(macho.segment_command_64),
.end = args.symtab_cmd_offset,
};
if (!self.options.strip) {
// First exclusion region will comprise all symbol stabs.
// Exclude region comprising all symbol stabs.
const nlocals = self.dysymtab_cmd.nlocalsym;
const locals_buf = try self.gpa.alloc(u8, nlocals * @sizeOf(macho.nlist_64));
@ -2706,26 +2726,40 @@ pub const Zld = struct {
if (local.stab()) break i;
} else locals.len;
const nstabs = locals.len - istab;
if (nstabs == 0) {
subsections[2] = .{
.start = args.symtab_cmd_offset + @sizeOf(macho.symtab_command) + @sizeOf(macho.dysymtab_command),
.end = max_file_size,
};
count += 1;
} else {
// Exclude a subsection of the strtab with names of the stabs.
// We do not care about anything succeeding strtab as it is the code signature data which is
// not part of the UUID calculation anyway.
const stab_stroff = locals[istab].n_strx;
// Next, a subsection of the strtab.
// We do not care about anything succeeding strtab as it is the code signature data which is
// not part of the UUID calculation anyway.
const stab_stroff = locals[istab].n_strx;
subsections[2] = .{
.start = args.symtab_cmd_offset + @sizeOf(macho.symtab_command) + @sizeOf(macho.dysymtab_command),
.end = @intCast(u32, self.symtab_cmd.symoff + istab * @sizeOf(macho.nlist_64)),
};
subsections[3] = .{
.start = subsections[2].end + @intCast(u32, nstabs * @sizeOf(macho.nlist_64)),
.end = self.symtab_cmd.stroff + stab_stroff,
};
const first_cut = FileSubsection{
.start = 0,
.end = @intCast(u32, self.symtab_cmd.symoff + istab * @sizeOf(macho.nlist_64)),
};
const second_cut = FileSubsection{
.start = first_cut.end + @intCast(u32, nstabs * @sizeOf(macho.nlist_64)),
.end = self.symtab_cmd.stroff + stab_stroff,
};
for (&[_]FileSubsection{ first_cut, second_cut }) |cut| {
try self.calcUuidHashes(comp, cut, &hashes);
count += 2;
}
} else {
try self.calcUuidHashes(comp, .{ .start = 0, .end = max_file_size }, &hashes);
subsections[2] = .{
.start = args.symtab_cmd_offset + @sizeOf(macho.symtab_command) + @sizeOf(macho.dysymtab_command),
.end = max_file_size,
};
count += 1;
}
for (subsections[0..count]) |cut| {
std.debug.print("{x} - {x}\n", .{ cut.start, cut.end });
try self.calcUuidHashes(comp, cut, &hashes);
}
const final_buffer = try self.gpa.alloc(u8, hashes.items.len * Md5.digest_length);
@ -2740,7 +2774,7 @@ pub const Zld = struct {
},
}
const in_file = @sizeOf(macho.mach_header_64) + offset + @sizeOf(macho.load_command);
const in_file = args.uuid_cmd_offset + @sizeOf(macho.load_command);
try self.file.pwriteAll(&self.uuid_cmd.uuid, in_file);
}
@ -4057,11 +4091,16 @@ pub fn linkWithZld(macho_file: *MachO, comp: *Compilation, prog_node: *std.Progr
const lc_writer = lc_buffer.writer();
try zld.writeSegmentHeaders(lc_writer);
const linkedit_cmd_offset = @sizeOf(macho.mach_header_64) + @intCast(u32, lc_buffer.items.len - @sizeOf(macho.segment_command_64));
try lc_writer.writeStruct(zld.dyld_info_cmd);
try lc_writer.writeStruct(zld.function_starts_cmd);
try lc_writer.writeStruct(zld.data_in_code_cmd);
const symtab_cmd_offset = @sizeOf(macho.mach_header_64) + @intCast(u32, lc_buffer.items.len);
try lc_writer.writeStruct(zld.symtab_cmd);
try lc_writer.writeStruct(zld.dysymtab_cmd);
try load_commands.writeDylinkerLC(lc_writer);
if (zld.options.output_mode == .Exe) {
@ -4084,7 +4123,7 @@ pub fn linkWithZld(macho_file: *MachO, comp: *Compilation, prog_node: *std.Progr
});
try load_commands.writeBuildVersionLC(zld.options, lc_writer);
const uuid_offset = @intCast(u32, lc_buffer.items.len);
const uuid_cmd_offset = @sizeOf(macho.mach_header_64) + @intCast(u32, lc_buffer.items.len);
try lc_writer.writeStruct(zld.uuid_cmd);
try load_commands.writeLoadDylibLCs(zld.dylibs.items, zld.referenced_dylibs.keys(), lc_writer);
@ -4115,7 +4154,11 @@ pub fn linkWithZld(macho_file: *MachO, comp: *Compilation, prog_node: *std.Progr
try zld.file.pwriteAll(lc_buffer.items, @sizeOf(macho.mach_header_64));
try zld.writeHeader(ncmds, @intCast(u32, lc_buffer.items.len));
try zld.writeUuid(comp, uuid_offset);
try zld.writeUuid(comp, .{
.linkedit_cmd_offset = linkedit_cmd_offset,
.symtab_cmd_offset = symtab_cmd_offset,
.uuid_cmd_offset = uuid_cmd_offset,
});
if (codesig) |*csig| {
try zld.writeCodeSignature(comp, csig); // code signing always comes last