Commit 3dff040ca5
Changed files (3)
src
link
src/link/MachO/dead_strip.zig
@@ -238,16 +238,10 @@ fn mark(zld: *Zld, roots: AtomTable, alive: *AtomTable) !void {
}
}
- for (zld.objects.items) |object, object_id| {
+ for (zld.objects.items) |_, object_id| {
// Traverse unwind and eh_frame records noting if the source symbol has been marked, and if so,
// marking all references as live.
- // TODO I am currently assuming there will always be __unwind_info section emitted which implies
- // we will not traverse __eh_frame in isolation. This however is only true for more recent versions
- // of macOS so if there is a feature request to handle earlier versions of macOS, the following
- // bit code needs updating as well.
- if (object.hasUnwindRecords()) {
- try markUnwindRecords(zld, @intCast(u32, object_id), alive);
- }
+ try markUnwindRecords(zld, @intCast(u32, object_id), alive);
}
}
@@ -256,9 +250,23 @@ fn markUnwindRecords(zld: *Zld, object_id: u32, alive: *AtomTable) !void {
const cpu_arch = zld.options.target.cpu.arch;
const unwind_records = object.getUnwindRecords();
- var it = object.getEhFrameRecordsIterator();
for (object.exec_atoms.items) |atom_index| {
+ if (!object.hasUnwindRecords()) {
+ if (object.eh_frame_records_lookup.get(atom_index)) |fde_offset| {
+ const ptr = object.eh_frame_relocs_lookup.getPtr(fde_offset).?;
+ if (ptr.dead) continue; // already marked
+ if (!alive.contains(atom_index)) {
+ // Mark dead and continue.
+ ptr.dead = true;
+ } else {
+ // Mark references live and continue.
+ try markEhFrameRecord(zld, object_id, atom_index, alive);
+ }
+ continue;
+ }
+ }
+
const record_id = object.unwind_records_lookup.get(atom_index) orelse continue;
if (object.unwind_relocs_lookup[record_id].dead) continue; // already marked, nothing to do
if (!alive.contains(atom_index)) {
@@ -272,61 +280,7 @@ fn markUnwindRecords(zld: *Zld, object_id: u32, alive: *AtomTable) !void {
const record = unwind_records[record_id];
if (UnwindInfo.UnwindEncoding.isDwarf(record.compactUnwindEncoding, cpu_arch)) {
- const fde_offset = object.eh_frame_records_lookup.get(atom_index).?;
- it.seekTo(fde_offset);
- const fde = (try it.next()).?;
-
- const cie_ptr = fde.getCiePointer();
- const cie_offset = fde_offset + 4 - cie_ptr;
- it.seekTo(cie_offset);
- const cie = (try it.next()).?;
-
- switch (cpu_arch) {
- .aarch64 => {
- // Mark FDE references which should include any referenced LSDA record
- const relocs = eh_frame.getRelocs(zld, object_id, fde_offset);
- for (relocs) |rel| {
- const target = UnwindInfo.parseRelocTarget(
- zld,
- object_id,
- rel,
- fde.data,
- @intCast(i32, fde_offset) + 4,
- );
- const target_sym = zld.getSymbol(target);
- if (!target_sym.undf()) blk: {
- const target_object = zld.objects.items[target.getFile().?];
- const target_atom_index = target_object.getAtomIndexForSymbol(target.sym_index) orelse
- break :blk;
- markLive(zld, target_atom_index, alive);
- }
- }
- },
- .x86_64 => {
- const lsda_ptr = try fde.getLsdaPointer(cie, .{
- .base_addr = object.eh_frame_sect.?.addr,
- .base_offset = fde_offset,
- });
- if (lsda_ptr) |lsda_address| {
- // Mark LSDA record as live
- const sym_index = object.getSymbolByAddress(lsda_address, null);
- const target_atom_index = object.getAtomIndexForSymbol(sym_index).?;
- markLive(zld, target_atom_index, alive);
- }
- },
- else => unreachable,
- }
-
- // Mark CIE references which should include any referenced personalities
- // that are defined locally.
- if (cie.getPersonalityPointerReloc(zld, object_id, cie_offset)) |target| {
- const target_sym = zld.getSymbol(target);
- if (!target_sym.undf()) {
- const target_object = zld.objects.items[target.getFile().?];
- const target_atom_index = target_object.getAtomIndexForSymbol(target.sym_index).?;
- markLive(zld, target_atom_index, alive);
- }
- }
+ try markEhFrameRecord(zld, object_id, atom_index, alive);
} else {
if (UnwindInfo.getPersonalityFunctionReloc(zld, object_id, record_id)) |rel| {
const target = UnwindInfo.parseRelocTarget(
@@ -360,6 +314,68 @@ fn markUnwindRecords(zld: *Zld, object_id: u32, alive: *AtomTable) !void {
}
}
+fn markEhFrameRecord(zld: *Zld, object_id: u32, atom_index: AtomIndex, alive: *AtomTable) !void {
+ const cpu_arch = zld.options.target.cpu.arch;
+ const object = &zld.objects.items[object_id];
+ var it = object.getEhFrameRecordsIterator();
+
+ const fde_offset = object.eh_frame_records_lookup.get(atom_index).?;
+ it.seekTo(fde_offset);
+ const fde = (try it.next()).?;
+
+ const cie_ptr = fde.getCiePointer();
+ const cie_offset = fde_offset + 4 - cie_ptr;
+ it.seekTo(cie_offset);
+ const cie = (try it.next()).?;
+
+ switch (cpu_arch) {
+ .aarch64 => {
+ // Mark FDE references which should include any referenced LSDA record
+ const relocs = eh_frame.getRelocs(zld, object_id, fde_offset);
+ for (relocs) |rel| {
+ const target = UnwindInfo.parseRelocTarget(
+ zld,
+ object_id,
+ rel,
+ fde.data,
+ @intCast(i32, fde_offset) + 4,
+ );
+ const target_sym = zld.getSymbol(target);
+ if (!target_sym.undf()) blk: {
+ const target_object = zld.objects.items[target.getFile().?];
+ const target_atom_index = target_object.getAtomIndexForSymbol(target.sym_index) orelse
+ break :blk;
+ markLive(zld, target_atom_index, alive);
+ }
+ }
+ },
+ .x86_64 => {
+ const lsda_ptr = try fde.getLsdaPointer(cie, .{
+ .base_addr = object.eh_frame_sect.?.addr,
+ .base_offset = fde_offset,
+ });
+ if (lsda_ptr) |lsda_address| {
+ // Mark LSDA record as live
+ const sym_index = object.getSymbolByAddress(lsda_address, null);
+ const target_atom_index = object.getAtomIndexForSymbol(sym_index).?;
+ markLive(zld, target_atom_index, alive);
+ }
+ },
+ else => unreachable,
+ }
+
+ // Mark CIE references which should include any referenced personalities
+ // that are defined locally.
+ if (cie.getPersonalityPointerReloc(zld, object_id, cie_offset)) |target| {
+ const target_sym = zld.getSymbol(target);
+ if (!target_sym.undf()) {
+ const target_object = zld.objects.items[target.getFile().?];
+ const target_atom_index = target_object.getAtomIndexForSymbol(target.sym_index).?;
+ markLive(zld, target_atom_index, alive);
+ }
+ }
+}
+
fn prune(zld: *Zld, alive: AtomTable) void {
log.debug("pruning dead atoms", .{});
for (zld.objects.items) |*object| {
src/link/MachO/Object.zig
@@ -725,7 +725,18 @@ fn parseEhFrameSection(self: *Object, zld: *Zld, object_id: u32) !void {
}
fn parseUnwindInfo(self: *Object, zld: *Zld, object_id: u32) !void {
- const sect = self.unwind_info_sect orelse return;
+ const sect = self.unwind_info_sect orelse {
+ // If it so happens that the object had `__eh_frame` section defined but no `__compact_unwind`,
+ // we will try fully synthesising unwind info records to somewhat match Apple ld's
+ // approach. However, we will only synthesise DWARF records and nothing more. For this reason,
+ // we still create the output `__TEXT,__unwind_info` section.
+ if (self.eh_frame_sect != null) {
+ if (zld.getSectionByName("__TEXT", "__unwind_info") == null) {
+ _ = try zld.initSection("__TEXT", "__unwind_info", .{});
+ }
+ }
+ return;
+ };
log.debug("parsing unwind info in {s}", .{self.name});
src/link/MachO/UnwindInfo.zig
@@ -253,37 +253,13 @@ pub fn collect(info: *UnwindInfo, zld: *Zld) !void {
try records.ensureUnusedCapacity(object.exec_atoms.items.len);
try atom_indexes.ensureUnusedCapacity(object.exec_atoms.items.len);
- var it = object.getEhFrameRecordsIterator();
-
for (object.exec_atoms.items) |atom_index| {
var record = if (object.unwind_records_lookup.get(atom_index)) |record_id| blk: {
if (object.unwind_relocs_lookup[record_id].dead) continue;
var record = unwind_records[record_id];
if (UnwindEncoding.isDwarf(record.compactUnwindEncoding, cpu_arch)) {
- const fde_offset = object.eh_frame_records_lookup.get(atom_index).?;
- it.seekTo(fde_offset);
- const fde = (try it.next()).?;
- const cie_ptr = fde.getCiePointer();
- const cie_offset = fde_offset + 4 - cie_ptr;
- it.seekTo(cie_offset);
- const cie = (try it.next()).?;
-
- if (cie.getPersonalityPointerReloc(
- zld,
- @intCast(u32, object_id),
- cie_offset,
- )) |target| {
- const personality_index = info.getPersonalityFunction(target) orelse inner: {
- const personality_index = info.personalities_count;
- info.personalities[personality_index] = target;
- info.personalities_count += 1;
- break :inner personality_index;
- };
-
- record.personalityFunction = personality_index + 1;
- UnwindEncoding.setPersonalityIndex(&record.compactUnwindEncoding, personality_index + 1);
- }
+ try info.collectPersonalityFromDwarf(zld, @intCast(u32, object_id), atom_index, &record);
} else {
if (getPersonalityFunctionReloc(
zld,
@@ -324,6 +300,21 @@ pub fn collect(info: *UnwindInfo, zld: *Zld) !void {
const atom = zld.getAtom(atom_index);
const sym = zld.getSymbol(atom.getSymbolWithLoc());
if (sym.n_desc == N_DEAD) continue;
+
+ if (!object.hasUnwindRecords()) {
+ if (object.eh_frame_records_lookup.get(atom_index)) |fde_offset| {
+ if (object.eh_frame_relocs_lookup.get(fde_offset).?.dead) continue;
+ var record = nullRecord();
+ try info.collectPersonalityFromDwarf(zld, @intCast(u32, object_id), atom_index, &record);
+ switch (cpu_arch) {
+ .aarch64 => UnwindEncoding.setMode(&record.compactUnwindEncoding, macho.UNWIND_ARM64_MODE.DWARF),
+ .x86_64 => UnwindEncoding.setMode(&record.compactUnwindEncoding, macho.UNWIND_X86_64_MODE.DWARF),
+ else => unreachable,
+ }
+ break :blk record;
+ }
+ }
+
break :blk nullRecord();
};
@@ -499,6 +490,40 @@ pub fn collect(info: *UnwindInfo, zld: *Zld) !void {
}
}
+fn collectPersonalityFromDwarf(
+ info: *UnwindInfo,
+ zld: *Zld,
+ object_id: u32,
+ atom_index: u32,
+ record: *macho.compact_unwind_entry,
+) !void {
+ const object = &zld.objects.items[object_id];
+ var it = object.getEhFrameRecordsIterator();
+ const fde_offset = object.eh_frame_records_lookup.get(atom_index).?;
+ it.seekTo(fde_offset);
+ const fde = (try it.next()).?;
+ const cie_ptr = fde.getCiePointer();
+ const cie_offset = fde_offset + 4 - cie_ptr;
+ it.seekTo(cie_offset);
+ const cie = (try it.next()).?;
+
+ if (cie.getPersonalityPointerReloc(
+ zld,
+ @intCast(u32, object_id),
+ cie_offset,
+ )) |target| {
+ const personality_index = info.getPersonalityFunction(target) orelse inner: {
+ const personality_index = info.personalities_count;
+ info.personalities[personality_index] = target;
+ info.personalities_count += 1;
+ break :inner personality_index;
+ };
+
+ record.personalityFunction = personality_index + 1;
+ UnwindEncoding.setPersonalityIndex(&record.compactUnwindEncoding, personality_index + 1);
+ }
+}
+
pub fn calcSectionSize(info: UnwindInfo, zld: *Zld) !void {
const sect_id = zld.getSectionByName("__TEXT", "__unwind_info") orelse return;
const sect = &zld.sections.items(.header)[sect_id];
@@ -766,40 +791,26 @@ fn getCommonEncoding(info: UnwindInfo, enc: macho.compact_unwind_encoding_t) ?u7
}
pub const UnwindEncoding = struct {
- pub const UNWIND_X86_64_MODE = enum(u4) {
- none = 0,
- ebp_frame = 1,
- stack_immd = 2,
- stack_ind = 3,
- dwarf = 4,
- };
-
- pub const UNWIND_ARM64_MODE = enum(u4) {
- none = 0,
- frameless = 2,
- dwarf = 3,
- frame = 4,
- };
-
- pub const UNWIND_MODE_MASK: u32 = 0x0F000000;
- pub const UNWIND_PERSONALITY_INDEX_MASK: u32 = 0x30000000;
- pub const UNWIND_HAS_LSDA_MASK: u32 = 0x40000000;
-
pub fn getMode(enc: macho.compact_unwind_encoding_t) u4 {
- const mode = @truncate(u4, (enc & UNWIND_MODE_MASK) >> 24);
- return mode;
+ comptime assert(macho.UNWIND_ARM64_MODE_MASK == macho.UNWIND_X86_64_MODE_MASK);
+ return @truncate(u4, (enc & macho.UNWIND_ARM64_MODE_MASK) >> 24);
}
pub fn isDwarf(enc: macho.compact_unwind_encoding_t, cpu_arch: std.Target.Cpu.Arch) bool {
- switch (cpu_arch) {
- .aarch64 => return @intToEnum(UNWIND_ARM64_MODE, getMode(enc)) == .dwarf,
- .x86_64 => return @intToEnum(UNWIND_X86_64_MODE, getMode(enc)) == .dwarf,
+ const mode = getMode(enc);
+ return switch (cpu_arch) {
+ .aarch64 => @intToEnum(macho.UNWIND_ARM64_MODE, mode) == .DWARF,
+ .x86_64 => @intToEnum(macho.UNWIND_X86_64_MODE, mode) == .DWARF,
else => unreachable,
- }
+ };
+ }
+
+ pub fn setMode(enc: *macho.compact_unwind_encoding_t, mode: anytype) void {
+ enc.* |= @intCast(u32, @enumToInt(mode)) << 24;
}
pub fn hasLsda(enc: macho.compact_unwind_encoding_t) bool {
- const has_lsda = @truncate(u1, (enc & UNWIND_HAS_LSDA_MASK) >> 31);
+ const has_lsda = @truncate(u1, (enc & macho.UNWIND_HAS_LSDA) >> 31);
return has_lsda == 1;
}
@@ -809,7 +820,7 @@ pub const UnwindEncoding = struct {
}
pub fn getPersonalityIndex(enc: macho.compact_unwind_encoding_t) u2 {
- const index = @truncate(u2, (enc & UNWIND_PERSONALITY_INDEX_MASK) >> 28);
+ const index = @truncate(u2, (enc & macho.UNWIND_PERSONALITY_MASK) >> 28);
return index;
}