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[MachO] add -pagezero_size

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Pass `-pagezero_size` to the MachO linker. This is the final
"unsupported linker arg" that I could chase that CGo uses. After this
and #11874 we may be able to fail on an "unsupported linker arg" instead
of emiting a warning.

Test case:

    zig=/code/zig/build/zig
    CGO_ENABLED=1 GOOS=darwin GOARCH=amd64 CC="$zig cc -target x86_64-macos" CXX="$zig c++ -target x86_64-macos" go build -a -ldflags "-s -w" cgo.go

I compiled a trivial CGo program and executed it on an amd64 Darwin
host.

To be honest, I am not entirely sure what this is doing. This feels
right after reading what this argument does in LLVM sources, but I am by
no means qualified to make MachO pull requests. Will take feedback.
This commit is contained in:
Motiejus Jakštys 2022-06-16 15:42:35 +03:00 committed by Jakub Konka
parent a97a39bea6
commit 98138ba78c
7 changed files with 29 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
src/Compilation.zig
View File

@ -903,6 +903,8 @@ pub const InitOptions = struct {
install_name: ?[]const u8 = null,
/// (Darwin) Path to entitlements file
entitlements: ?[]const u8 = null,
/// (Darwin) size of the __PAGEZERO segment
pagezero_size: ?u64 = null,
};
fn addPackageTableToCacheHash(
@ -2359,7 +2361,7 @@ fn prepareWholeEmitSubPath(arena: Allocator, opt_emit: ?EmitLoc) error{OutOfMemo
/// to remind the programmer to update multiple related pieces of code that
/// are in different locations. Bump this number when adding or deleting
/// anything from the link cache manifest.
pub const link_hash_implementation_version = 3;
pub const link_hash_implementation_version = 4;
fn addNonIncrementalStuffToCacheManifest(comp: *Compilation, man: *Cache.Manifest) !void {
const gpa = comp.gpa;
@ -2369,7 +2371,7 @@ fn addNonIncrementalStuffToCacheManifest(comp: *Compilation, man: *Cache.Manifes
defer arena_allocator.deinit();
const arena = arena_allocator.allocator();
comptime assert(link_hash_implementation_version == 3);
comptime assert(link_hash_implementation_version == 4);
if (comp.bin_file.options.module) |mod| {
const main_zig_file = try mod.main_pkg.root_src_directory.join(arena, &[_][]const u8{
@ -2474,6 +2476,7 @@ fn addNonIncrementalStuffToCacheManifest(comp: *Compilation, man: *Cache.Manifes
man.hash.addListOfBytes(comp.bin_file.options.framework_dirs);
man.hash.addListOfBytes(comp.bin_file.options.frameworks);
try man.addOptionalFile(comp.bin_file.options.entitlements);
if (comp.bin_file.options.pagezero_size) |value| man.hash.add(value);
// COFF specific stuff
man.hash.addOptional(comp.bin_file.options.subsystem);

3
src/link.zig
View File

@ -187,6 +187,9 @@ pub const Options = struct {
/// (Darwin) Path to entitlements file
entitlements: ?[]const u8 = null,
/// (Darwin) size of the __PAGEZERO segment
pagezero_size: ?u64 = null,
pub fn effectiveOutputMode(options: Options) std.builtin.OutputMode {
return if (options.use_lld) .Obj else options.output_mode;
}

2
src/link/Coff.zig
View File

@ -969,7 +969,7 @@ fn linkWithLLD(self: *Coff, comp: *Compilation, prog_node: *std.Progress.Node) !
man = comp.cache_parent.obtain();
self.base.releaseLock();
comptime assert(Compilation.link_hash_implementation_version == 3);
comptime assert(Compilation.link_hash_implementation_version == 4);
for (self.base.options.objects) |obj| {
_ = try man.addFile(obj.path, null);

2
src/link/Elf.zig
View File

@ -1298,7 +1298,7 @@ fn linkWithLLD(self: *Elf, comp: *Compilation, prog_node: *std.Progress.Node) !v
// We are about to obtain this lock, so here we give other processes a chance first.
self.base.releaseLock();
comptime assert(Compilation.link_hash_implementation_version == 3);
comptime assert(Compilation.link_hash_implementation_version == 4);
try man.addOptionalFile(self.base.options.linker_script);
try man.addOptionalFile(self.base.options.version_script);

11
src/link/MachO.zig
View File

@ -286,8 +286,8 @@ const default_dyld_path: [*:0]const u8 = "/usr/lib/dyld";
const minimum_text_block_size = 64;
pub const min_text_capacity = padToIdeal(minimum_text_block_size);
/// Virtual memory offset corresponds to the size of __PAGEZERO segment and start of
/// __TEXT segment.
/// Virtual memory offset corresponds to the size of __PAGEZERO segment and
/// start of __TEXT segment.
const pagezero_vmsize: u64 = 0x100000000;
pub const Export = struct {
@ -536,7 +536,7 @@ pub fn flushModule(self: *MachO, comp: *Compilation, prog_node: *std.Progress.No
// We are about to obtain this lock, so here we give other processes a chance first.
self.base.releaseLock();
comptime assert(Compilation.link_hash_implementation_version == 3);
comptime assert(Compilation.link_hash_implementation_version == 4);
for (self.base.options.objects) |obj| {
_ = try man.addFile(obj.path, null);
@ -549,6 +549,7 @@ pub fn flushModule(self: *MachO, comp: *Compilation, prog_node: *std.Progress.No
// We can skip hashing libc and libc++ components that we are in charge of building from Zig
// installation sources because they are always a product of the compiler version + target information.
man.hash.add(stack_size);
if (self.base.options.pagezero_size) |value| man.hash.add(value);
man.hash.addListOfBytes(self.base.options.lib_dirs);
man.hash.addListOfBytes(self.base.options.framework_dirs);
man.hash.addListOfBytes(self.base.options.frameworks);
@ -4372,7 +4373,7 @@ fn populateMissingMetadata(self: *MachO) !void {
.segment = .{
.inner = .{
.segname = makeStaticString("__PAGEZERO"),
.vmsize = pagezero_vmsize,
.vmsize = self.base.options.pagezero_size orelse pagezero_vmsize,
.cmdsize = @sizeOf(macho.segment_command_64),
},
},
@ -4394,7 +4395,7 @@ fn populateMissingMetadata(self: *MachO) !void {
.segment = .{
.inner = .{
.segname = makeStaticString("__TEXT"),
.vmaddr = pagezero_vmsize,
.vmaddr = self.base.options.pagezero_size orelse pagezero_vmsize,
.vmsize = needed_size,
.filesize = needed_size,
.maxprot = macho.PROT.READ | macho.PROT.EXEC,

2
src/link/Wasm.zig
View File

@ -2274,7 +2274,7 @@ fn linkWithLLD(self: *Wasm, comp: *Compilation, prog_node: *std.Progress.Node) !
// We are about to obtain this lock, so here we give other processes a chance first.
self.base.releaseLock();
comptime assert(Compilation.link_hash_implementation_version == 3);
comptime assert(Compilation.link_hash_implementation_version == 4);
for (self.base.options.objects) |obj| {
_ = try man.addFile(obj.path, null);

12
src/main.zig
View File

@ -447,6 +447,7 @@ const usage_build_generic =
\\ -F[dir] (Darwin) add search path for frameworks
\\ -install_name=[value] (Darwin) add dylib's install name
\\ --entitlements [path] (Darwin) add path to entitlements file for embedding in code signature
\\ -pagezero_size [value] (Darwin) size of the __PAGEZERO segment
\\ --import-memory (WebAssembly) import memory from the environment
\\ --import-table (WebAssembly) import function table from the host environment
\\ --export-table (WebAssembly) export function table to the host environment
@ -694,6 +695,7 @@ fn buildOutputType(
var install_name: ?[]const u8 = null;
var hash_style: link.HashStyle = .both;
var entitlements: ?[]const u8 = null;
var pagezero_size: ?u64 = null;
// e.g. -m3dnow or -mno-outline-atomics. They correspond to std.Target llvm cpu feature names.
// This array is populated by zig cc frontend and then has to be converted to zig-style
@ -1647,6 +1649,15 @@ fn buildOutputType(
linker_optimization = std.fmt.parseUnsigned(u8, arg["-O".len..], 10) catch |err| {
fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
};
} else if (mem.eql(u8, arg, "-pagezero_size")) {
i += 1;
if (i >= linker_args.items.len) {
fatal("expected linker arg after '{s}'", .{arg});
}
const next_arg = linker_args.items[i];
pagezero_size = std.fmt.parseUnsigned(u64, next_arg, 0) catch |err| {
fatal("unable to parse '{s}': {s}", .{ arg, @errorName(err) });
};
} else if (mem.eql(u8, arg, "--gc-sections")) {
linker_gc_sections = true;
} else if (mem.eql(u8, arg, "--no-gc-sections")) {
@ -2763,6 +2774,7 @@ fn buildOutputType(
.native_darwin_sdk = native_darwin_sdk,
.install_name = install_name,
.entitlements = entitlements,
.pagezero_size = pagezero_size,
}) catch |err| switch (err) {
error.LibCUnavailable => {
const target = target_info.target;