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macho: backport fixes from upstreaming MachO to Zig #102

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merged 2 commits into from
Jan 13, 2024
Merged

macho: backport fixes from upstreaming MachO to Zig #102

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f2ecb4a
macho: fix encoding LSDA/personality in __eh_frame via __unwind_info
kubkon Jan 13, 2024
e2d6026
macho: test -dead_strip with __DWARF sections present
kubkon Jan 13, 2024
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2 changes: 2 additions & 0 deletions src/MachO/Object.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,8 @@ pub fn parse(self: *Object, macho_file: *MachO) !void {
const tracy = trace(@src());
defer tracy.end();

log.debug("parsing input object file {}", .{self.fmtPath()});

const gpa = macho_file.base.allocator;
var stream = std.io.fixedBufferStream(self.data);
const reader = stream.reader();
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33 changes: 26 additions & 7 deletions src/MachO/UnwindInfo.zig
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Expand Up @@ -65,6 +65,16 @@ pub fn generate(info: *UnwindInfo, macho_file: *MachO) !void {
const rec = macho_file.getUnwindRecord(index);
if (rec.getFde(macho_file)) |fde| {
rec.enc.setDwarfSectionOffset(@intCast(fde.out_offset));
if (fde.getLsdaAtom(macho_file)) |lsda| {
rec.lsda = lsda.atom_index;
rec.lsda_offset = fde.lsda_offset;
rec.enc.setHasLsda(true);
}
const cie = fde.getCie(macho_file);
if (cie.getPersonality(macho_file)) |_| {
const personality_index = try info.getOrPutPersonalityFunction(cie.personality.?.index); // TODO handle error
rec.enc.setPersonalityIndex(personality_index + 1);
}
} else if (rec.getPersonality(macho_file)) |_| {
const personality_index = try info.getOrPutPersonalityFunction(rec.personality.?); // TODO handle error
rec.enc.setPersonalityIndex(personality_index + 1);
Expand Down Expand Up @@ -232,11 +242,13 @@ pub fn generate(info: *UnwindInfo, macho_file: *MachO) !void {
}

// Save records having an LSDA pointer
log.debug("LSDA pointers:", .{});
try info.lsdas_lookup.ensureTotalCapacityPrecise(gpa, info.records.items.len);
for (info.records.items, 0..) |index, i| {
const rec = macho_file.getUnwindRecord(index);
info.lsdas_lookup.appendAssumeCapacity(@intCast(info.lsdas.items.len));
if (rec.getLsdaAtom(macho_file)) |_| {
if (rec.getLsdaAtom(macho_file)) |lsda| {
log.debug(" @{x} => lsda({d})", .{ rec.getAtomAddress(macho_file), lsda.atom_index });
try info.lsdas.append(gpa, @intCast(i));
}
}
Expand Down Expand Up @@ -367,7 +379,8 @@ pub const Encoding = extern struct {

pub fn getMode(enc: Encoding) u4 {
comptime assert(macho.UNWIND_ARM64_MODE_MASK == macho.UNWIND_X86_64_MODE_MASK);
return @as(u4, @truncate((enc.enc & macho.UNWIND_ARM64_MODE_MASK) >> 24));
const shift = comptime @ctz(macho.UNWIND_ARM64_MODE_MASK);
return @as(u4, @truncate((enc.enc & macho.UNWIND_ARM64_MODE_MASK) >> shift));
}

pub fn isDwarf(enc: Encoding, macho_file: *MachO) bool {
Expand All @@ -380,26 +393,32 @@ pub const Encoding = extern struct {
}

pub fn setMode(enc: *Encoding, mode: anytype) void {
enc.enc |= @as(u32, @intCast(@intFromEnum(mode))) << 24;
comptime assert(macho.UNWIND_ARM64_MODE_MASK == macho.UNWIND_X86_64_MODE_MASK);
const shift = comptime @ctz(macho.UNWIND_ARM64_MODE_MASK);
enc.enc |= @as(u32, @intCast(@intFromEnum(mode))) << shift;
}

pub fn hasLsda(enc: Encoding) bool {
const has_lsda = @as(u1, @truncate((enc.enc & macho.UNWIND_HAS_LSDA) >> 31));
const shift = comptime @ctz(macho.UNWIND_HAS_LSDA);
const has_lsda = @as(u1, @truncate((enc.enc & macho.UNWIND_HAS_LSDA) >> shift));
return has_lsda == 1;
}

pub fn setHasLsda(enc: *Encoding, has_lsda: bool) void {
const mask = @as(u32, @intCast(@intFromBool(has_lsda))) << 31;
const shift = comptime @ctz(macho.UNWIND_HAS_LSDA);
const mask = @as(u32, @intCast(@intFromBool(has_lsda))) << shift;
enc.enc |= mask;
}

pub fn getPersonalityIndex(enc: Encoding) u2 {
const index = @as(u2, @truncate((enc.enc & macho.UNWIND_PERSONALITY_MASK) >> 28));
const shift = comptime @ctz(macho.UNWIND_PERSONALITY_MASK);
const index = @as(u2, @truncate((enc.enc & macho.UNWIND_PERSONALITY_MASK) >> shift));
return index;
}

pub fn setPersonalityIndex(enc: *Encoding, index: u2) void {
const mask = @as(u32, @intCast(index)) << 28;
const shift = comptime @ctz(macho.UNWIND_PERSONALITY_MASK);
const mask = @as(u32, @intCast(index)) << shift;
enc.enc |= mask;
}

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7 changes: 6 additions & 1 deletion src/MachO/dead_strip.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -91,7 +91,12 @@ fn mark(roots: []*Atom, objects: []const File.Index, macho_file: *MachO) void {
for (macho_file.getFile(index).?.getAtoms()) |atom_index| {
const atom = macho_file.getAtom(atom_index).?;
const isec = atom.getInputSection(macho_file);
if (isec.isDontDeadStripIfReferencesLive() and !atom.flags.alive and refersLive(atom, macho_file)) {
if (isec.isDontDeadStripIfReferencesLive() and
!(mem.eql(u8, isec.sectName(), "__eh_frame") or
mem.eql(u8, isec.sectName(), "__compact_unwind") or
isec.attrs() & macho.S_ATTR_DEBUG != 0) and
!atom.flags.alive and refersLive(atom, macho_file))
{
markLive(atom, macho_file);
loop = true;
}
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4 changes: 2 additions & 2 deletions src/MachO/eh_frame.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -427,9 +427,9 @@ pub fn write(macho_file: *MachO, buffer: []u8) void {
}

if (fde.getLsdaAtom(macho_file)) |atom| {
const offset = fde.out_offset + fde.lsda_offset;
const offset = fde.out_offset + fde.lsda_ptr_offset;
const saddr = sect.addr + offset;
const taddr = atom.value;
const taddr = atom.value + fde.lsda_offset;
switch (fde.getCie(macho_file).lsda_size.?) {
.p32 => std.mem.writeInt(
i32,
Expand Down
102 changes: 70 additions & 32 deletions test/macho.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -2416,40 +2416,78 @@ fn testSymbolStabs(b: *Build, opts: Options) *Step {
else => unreachable,
}

const exe = cc(b, "a.out", opts);
exe.addCSource(
\\#include <stdio.h>
\\int get_x();
\\void incr_x();
\\int bar();
\\void print_x() {
\\ printf("x=%d\n", get_x());
\\}
\\void print_bar() {
\\ printf("bar=%d\n", bar());
\\}
\\int main() {
\\ print_x();
\\ incr_x();
\\ print_x();
\\ print_bar();
\\ return 0;
\\}
);
exe.addFileSource(a_o.getFile());
exe.addFileSource(b_o.getFile());
exe.addArg("-g");
{
const exe = cc(b, "a.out", opts);
exe.addCSource(
\\#include <stdio.h>
\\int get_x();
\\void incr_x();
\\int bar();
\\void print_x() {
\\ printf("x=%d\n", get_x());
\\}
\\void print_bar() {
\\ printf("bar=%d\n", bar());
\\}
\\int main() {
\\ print_x();
\\ incr_x();
\\ print_x();
\\ print_bar();
\\ return 0;
\\}
);
exe.addFileSource(a_o.getFile());
exe.addFileSource(b_o.getFile());
exe.addArg("-g");

const run = exe.run();
run.expectStdOutEqual(
\\x=0
\\x=1
\\bar=42
\\
);
test_step.dependOn(run.step());
const run = exe.run();
run.expectStdOutEqual(
\\x=0
\\x=1
\\bar=42
\\
);
test_step.dependOn(run.step());

// TODO check for _foo and _bar having set sizes in stabs

}

{
const exe = cc(b, "a.out", opts);
exe.addCSource(
\\#include <stdio.h>
\\int get_x();
\\void incr_x();
\\int bar();
\\void print_x() {
\\ printf("x=%d\n", get_x());
\\}
\\void print_bar() {
\\ printf("bar=%d\n", bar());
\\}
\\int main() {
\\ print_x();
\\ incr_x();
\\ print_x();
\\ print_bar();
\\ return 0;
\\}
);
exe.addFileSource(a_o.getFile());
exe.addFileSource(b_o.getFile());
exe.addArgs(&.{ "-g", "-Wl,-dead_strip" });

// TODO check for _foo and _bar having set sizes in stabs
const run = exe.run();
run.expectStdOutEqual(
\\x=0
\\x=1
\\bar=42
\\
);
test_step.dependOn(run.step());
}

return test_step;
}
Expand Down