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macho: sanitize Zig sections segment names before emitting a relocatable

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As reported by jacobly, the Apple system linker matches sections to
segments by name and not by flags causing Zig's executable section
ending up in a segment with incorrect permission flags.
This commit is contained in:
Jakub Konka 2024-02-04 11:23:17 +01:00
parent 3c7970dc4e
commit a1b607acb5
1 changed files with 29 additions and 0 deletions
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29
src/link/MachO/relocatable.zig
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@ -78,6 +78,10 @@ pub fn flush(macho_file: *MachO, comp: *Compilation, module_obj_path: ?[]const u
off = mem.alignForward(u32, off, @alignOf(u64));
off = try macho_file.writeStrtab(off);
// In order to please Apple ld (and possibly other MachO linkers in the wild),
// we will now sanitize segment names of Zig-specific segments.
sanitizeZigSections(macho_file);
const ncmds, const sizeofcmds = try writeLoadCommands(macho_file);
try writeHeader(macho_file, ncmds, sizeofcmds);
}
@ -245,6 +249,31 @@ fn allocateSections(macho_file: *MachO) !void {
}
}
/// Renames segment names in Zig sections to standard MachO segment names such as
/// `__TEXT`, `__DATA_CONST` and `__DATA`.
/// TODO: I think I may be able to get rid of this if I rework section/segment
/// allocation mechanism to not rely so much on having `_ZIG` sections always
/// pushed to the back. For instance, this is not a problem in ELF linker.
/// Then, we can create sections with the correct name from the start in `MachO.initMetadata`.
fn sanitizeZigSections(macho_file: *MachO) void {
if (macho_file.zig_text_sect_index) |index| {
const header = &macho_file.sections.items(.header)[index];
header.segname = MachO.makeStaticString("__TEXT");
}
if (macho_file.zig_const_sect_index) |index| {
const header = &macho_file.sections.items(.header)[index];
header.segname = MachO.makeStaticString("__DATA_CONST");
}
if (macho_file.zig_data_sect_index) |index| {
const header = &macho_file.sections.items(.header)[index];
header.segname = MachO.makeStaticString("__DATA");
}
if (macho_file.zig_bss_sect_index) |index| {
const header = &macho_file.sections.items(.header)[index];
header.segname = MachO.makeStaticString("__DATA");
}
}
fn createSegment(macho_file: *MachO) !void {
const gpa = macho_file.base.comp.gpa;