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macho: do not GC local symbols unless reference dead symbols

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If a local references another local, we keep it. If it doesn't
reference anything, we keep it. Otherwise, we dead strip it.
This commit is contained in:
Jakub Konka 2022-07-19 15:55:49 +02:00
parent a089a6dc4f
commit 39df241df4
4 changed files with 298 additions and 201 deletions
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425
src/link/MachO.zig
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@ -171,17 +171,19 @@ stub_helper_preamble_atom: ?*Atom = null,
strtab: StringTable(.strtab) = .{},
// TODO I think synthetic tables are a perfect match for some generic refactoring,
// and probably reusable between linker backends too.
tlv_ptr_entries: std.ArrayListUnmanaged(Entry) = .{},
tlv_ptr_entries_free_list: std.ArrayListUnmanaged(u32) = .{},
tlv_ptr_entries_table: std.AutoArrayHashMapUnmanaged(SymbolWithLoc, u32) = .{},
tlv_ptr_entries_table: std.AutoHashMapUnmanaged(SymbolWithLoc, u32) = .{},
got_entries: std.ArrayListUnmanaged(Entry) = .{},
got_entries_free_list: std.ArrayListUnmanaged(u32) = .{},
got_entries_table: std.AutoArrayHashMapUnmanaged(SymbolWithLoc, u32) = .{},
got_entries_table: std.AutoHashMapUnmanaged(SymbolWithLoc, u32) = .{},
stubs: std.ArrayListUnmanaged(Entry) = .{},
stubs_free_list: std.ArrayListUnmanaged(u32) = .{},
stubs_table: std.AutoArrayHashMapUnmanaged(SymbolWithLoc, u32) = .{},
stubs_table: std.AutoHashMapUnmanaged(SymbolWithLoc, u32) = .{},
error_flags: File.ErrorFlags = File.ErrorFlags{},
@ -251,7 +253,24 @@ decls: std.AutoArrayHashMapUnmanaged(Module.Decl.Index, ?MatchingSection) = .{},
const Entry = struct {
target: SymbolWithLoc,
atom: *Atom,
// Index into the synthetic symbol table (i.e., file == null).
sym_index: u32,
pub fn getSymbol(entry: Entry, macho_file: *MachO) macho.nlist_64 {
return macho_file.getSymbol(.{ .sym_index = entry.sym_index, .file = null });
}
pub fn getSymbolPtr(entry: Entry, macho_file: *MachO) *macho.nlist_64 {
return macho_file.getSymbolPtr(.{ .sym_index = entry.sym_index, .file = null });
}
pub fn getAtom(entry: Entry, macho_file: *MachO) *Atom {
return macho_file.getAtomForSymbol(.{ .sym_index = entry.sym_index, .file = null }).?;
}
pub fn getName(entry: Entry, macho_file: *MachO) []const u8 {
return macho_file.getSymbolName(.{ .sym_index = entry.sym_index, .file = null });
}
};
const UnnamedConstTable = std.AutoHashMapUnmanaged(Module.Decl.Index, std.ArrayListUnmanaged(*Atom));
@ -1652,6 +1671,15 @@ fn parseDependentLibs(self: *MachO, syslibroot: ?[]const u8, dependent_libs: any
pub const MatchingSection = struct {
seg: u16,
sect: u16,
pub fn eql(this: MatchingSection, other: struct {
seg: ?u16,
sect: ?u16,
}) bool {
const seg = other.seg orelse return false;
const sect = other.sect orelse return false;
return this.seg == seg and this.sect == sect;
}
};
pub fn getMatchingSection(self: *MachO, sect: macho.section_64) !?MatchingSection {
@ -3153,8 +3181,7 @@ fn resolveSymbolsInDylibs(self: *MachO) !void {
const stub_helper_atom = try self.createStubHelperAtom();
const laptr_atom = try self.createLazyPointerAtom(stub_helper_atom.sym_index, global);
const stub_atom = try self.createStubAtom(laptr_atom.sym_index);
self.stubs.items[stub_index].atom = stub_atom;
self.stubs.items[stub_index].sym_index = stub_atom.sym_index;
}
continue :loop;
@ -3251,7 +3278,7 @@ fn resolveDyldStubBinder(self: *MachO) !void {
// Add dyld_stub_binder as the final GOT entry.
const got_index = try self.allocateGotEntry(global);
const got_atom = try self.createGotAtom(global);
self.got_entries.items[got_index].atom = got_atom;
self.got_entries.items[got_index].sym_index = got_atom.sym_index;
}
fn addLoadDylibLC(self: *MachO, id: u16) !void {
@ -3288,11 +3315,7 @@ fn setEntryPoint(self: *MachO) !void {
if (self.base.options.output_mode != .Exe) return;
const seg = self.load_commands.items[self.text_segment_cmd_index.?].segment;
const global = self.getEntryPoint() orelse {
const name = self.base.options.entry orelse "_main";
log.err("entrypoint '{s}' not found", .{name});
return error.MissingMainEntrypoint;
};
const global = try self.getEntryPoint();
const sym = self.getSymbol(global);
const ec = &self.load_commands.items[self.main_cmd_index.?].main;
ec.entryoff = @intCast(u32, sym.n_value - seg.inner.vmaddr);
@ -3508,7 +3531,8 @@ fn allocateSymbol(self: *MachO) !u32 {
}
pub fn allocateGotEntry(self: *MachO, target: SymbolWithLoc) !u32 {
try self.got_entries.ensureUnusedCapacity(self.base.allocator, 1);
const gpa = self.base.allocator;
try self.got_entries.ensureUnusedCapacity(gpa, 1);
const index = blk: {
if (self.got_entries_free_list.popOrNull()) |index| {
@ -3522,8 +3546,8 @@ pub fn allocateGotEntry(self: *MachO, target: SymbolWithLoc) !u32 {
}
};
self.got_entries.items[index] = .{ .target = target, .atom = undefined };
try self.got_entries_table.putNoClobber(self.base.allocator, target, index);
self.got_entries.items[index] = .{ .target = target, .sym_index = 0 };
try self.got_entries_table.putNoClobber(gpa, target, index);
return index;
}
@ -3543,7 +3567,7 @@ pub fn allocateStubEntry(self: *MachO, target: SymbolWithLoc) !u32 {
}
};
self.stubs.items[index] = .{ .target = target, .atom = undefined };
self.stubs.items[index] = .{ .target = target, .sym_index = 0 };
try self.stubs_table.putNoClobber(self.base.allocator, target, index);
return index;
@ -3564,7 +3588,7 @@ pub fn allocateTlvPtrEntry(self: *MachO, target: SymbolWithLoc) !u32 {
}
};
self.tlv_ptr_entries.items[index] = .{ .target = target, .atom = undefined };
self.tlv_ptr_entries.items[index] = .{ .target = target, .sym_index = 0 };
try self.tlv_ptr_entries_table.putNoClobber(self.base.allocator, target, index);
return index;
@ -4029,7 +4053,7 @@ fn placeDecl(self: *MachO, decl_index: Module.Decl.Index, code_len: usize) !*mac
const got_target = SymbolWithLoc{ .sym_index = decl.link.macho.sym_index, .file = null };
const got_index = try self.allocateGotEntry(got_target);
const got_atom = try self.createGotAtom(got_target);
self.got_entries.items[got_index].atom = got_atom;
self.got_entries.items[got_index].sym_index = got_atom.sym_index;
}
return symbol;
@ -4219,9 +4243,9 @@ pub fn freeDecl(self: *MachO, decl_index: Module.Decl.Index) void {
self.got_entries_free_list.append(self.base.allocator, @intCast(u32, got_index)) catch {};
self.got_entries.items[got_index] = .{
.target = .{ .sym_index = 0, .file = null },
.atom = undefined,
.sym_index = 0,
};
_ = self.got_entries_table.swapRemove(got_target);
_ = self.got_entries_table.remove(got_target);
if (self.d_sym) |*d_sym| {
d_sym.swapRemoveRelocs(decl.link.macho.sym_index);
@ -5493,46 +5517,26 @@ fn gcAtoms(self: *MachO, gc_roots: *std.AutoHashMap(*Atom, void)) !void {
if (self.base.options.output_mode == .Exe) {
// Add entrypoint as GC root
if (self.getEntryPoint()) |global| {
if (self.getAtomForSymbol(global)) |gc_root| {
_ = try gc_roots.getOrPut(gc_root);
} else {
log.debug("skipping {s}", .{self.getSymbolName(global)});
}
}
const global = try self.getEntryPoint();
const atom = self.getAtomForSymbol(global).?; // panic here means fatal error
_ = try gc_roots.getOrPut(atom);
} else {
assert(self.base.options.output_mode == .Lib);
// Add exports as GC roots
for (self.globals.values()) |global| {
const sym = self.getSymbol(global);
if (!sym.sect()) continue;
const gc_root = self.getAtomForSymbol(global) orelse {
const atom = self.getAtomForSymbol(global) orelse {
log.debug("skipping {s}", .{self.getSymbolName(global)});
continue;
};
_ = try gc_roots.getOrPut(gc_root);
_ = try gc_roots.getOrPut(atom);
}
}
// Add any atom targeting an import as GC root
var atoms_it = self.atoms.iterator();
while (atoms_it.next()) |entry| {
var atom = entry.value_ptr.*;
while (true) {
for (atom.relocs.items) |rel| {
if ((try rel.getTargetAtom(self)) == null) {
const target_sym = self.getSymbol(rel.target);
if (target_sym.undf()) {
_ = try gc_roots.getOrPut(atom);
break;
}
}
}
if (atom.prev) |prev| {
atom = prev;
} else break;
// TODO just a temp until we learn how to parse unwind records
if (self.globals.get("___gxx_personality_v0")) |global| {
if (self.getAtomForSymbol(global)) |atom| {
_ = try gc_roots.getOrPut(atom);
}
}
@ -5540,80 +5544,80 @@ fn gcAtoms(self: *MachO, gc_roots: *std.AutoHashMap(*Atom, void)) !void {
defer stack.deinit();
try stack.ensureUnusedCapacity(gc_roots.count());
var retained = std.AutoHashMap(*Atom, void).init(gpa);
defer retained.deinit();
try retained.ensureUnusedCapacity(gc_roots.count());
var alive = std.AutoHashMap(*Atom, void).init(gpa);
defer alive.deinit();
try alive.ensureUnusedCapacity(gc_roots.count());
log.debug("GC roots:", .{});
var gc_roots_it = gc_roots.keyIterator();
while (gc_roots_it.next()) |gc_root| {
self.logAtom(gc_root.*);
stack.appendAssumeCapacity(gc_root.*);
retained.putAssumeCapacityNoClobber(gc_root.*, {});
alive.putAssumeCapacity(gc_root.*, {});
}
log.debug("walking tree...", .{});
while (stack.popOrNull()) |source_atom| {
for (source_atom.relocs.items) |rel| {
if (try rel.getTargetAtom(self)) |target_atom| {
const gop = try retained.getOrPut(target_atom);
if (rel.getTargetAtom(self)) |target_atom| {
const gop = try alive.getOrPut(target_atom);
if (!gop.found_existing) {
log.debug(" RETAINED ATOM(%{d}) -> ATOM(%{d})", .{
source_atom.sym_index,
log.debug(" retained ATOM(%{d}, '{s}') in object({d})", .{
target_atom.sym_index,
target_atom.getName(self),
target_atom.file,
});
log.debug(" referenced by ATOM(%{d}, '{s}') in object({d})", .{
source_atom.sym_index,
source_atom.getName(self),
source_atom.file,
});
try stack.append(target_atom);
}
}
}
}
// TODO live support
// Any section that ends up here will be updated, that is,
// its size and alignment recalculated.
var gc_sections = std.AutoHashMap(MatchingSection, void).init(gpa);
defer gc_sections.deinit();
atoms_it = self.atoms.iterator();
while (atoms_it.next()) |entry| {
const match = entry.key_ptr.*;
var loop: bool = true;
while (loop) {
loop = false;
if (self.text_segment_cmd_index) |seg| {
if (seg == match.seg) {
if (self.eh_frame_section_index) |sect| {
if (sect == match.sect) continue;
}
}
}
if (self.data_segment_cmd_index) |seg| {
if (seg == match.seg) {
if (self.rustc_section_index) |sect| {
if (sect == match.sect) continue;
}
}
}
const sect = self.getSectionPtr(match);
var atom = entry.value_ptr.*;
log.debug("GCing atoms in {s},{s}", .{ sect.segName(), sect.sectName() });
while (true) {
const orig_prev = atom.prev;
if (!retained.contains(atom)) {
// Dead atom; remove.
log.debug(" DEAD ATOM(%{d})", .{atom.sym_index});
for (self.objects.items) |object| {
for (object.getSourceSymtab()) |_, source_index| {
const atom = object.getAtomForSymbol(@intCast(u32, source_index)) orelse continue;
if (alive.contains(atom)) continue;
const global = atom.getSymbolWithLoc();
const sym = atom.getSymbolPtr(self);
sym.n_desc = N_DESC_GCED;
// TODO add full bookkeeping here
const global = SymbolWithLoc{ .sym_index = atom.sym_index, .file = atom.file };
_ = self.got_entries_table.swapRemove(global);
_ = self.stubs_table.swapRemove(global);
_ = self.tlv_ptr_entries_table.swapRemove(global);
if (sym.n_desc == N_DESC_GCED) continue;
if (!sym.ext()) {
for (atom.relocs.items) |rel| {
if (rel.getTargetAtom(self)) |target_atom| {
const target_sym = target_atom.getSymbol(self);
if (target_sym.n_desc == N_DESC_GCED) break;
}
} else continue;
}
loop = true;
const match = self.getMatchingSectionFromOrdinal(sym.n_sect);
// TODO don't dedup eh_frame info yet until we actually implement parsing unwind records
if (match.eql(.{
.seg = self.text_segment_cmd_index,
.sect = self.eh_frame_section_index,
})) continue;
self.logAtom(atom);
sym.n_desc = N_DESC_GCED;
self.removeAtomFromSection(atom, match);
_ = try gc_sections.put(match, {});
for (atom.contained.items) |sym_off| {
const inner = self.getSymbolPtr(.{
@ -5622,34 +5626,64 @@ fn gcAtoms(self: *MachO, gc_roots: *std.AutoHashMap(*Atom, void)) !void {
});
inner.n_desc = N_DESC_GCED;
}
// If we want to enable GC for incremental codepath, we need to take into
// account any padding that might have been left here.
sect.size -= atom.size;
_ = try gc_sections.put(match, {});
if (atom.prev) |prev| {
prev.next = atom.next;
if (self.got_entries_table.contains(global)) {
const got_atom = self.getGotAtomForSymbol(global).?;
const got_sym = got_atom.getSymbolPtr(self);
got_sym.n_desc = N_DESC_GCED;
}
if (atom.next) |next| {
next.prev = atom.prev;
} else {
if (atom.prev) |prev| {
entry.value_ptr.* = prev;
} else {
// The section will be GCed in the next step.
entry.value_ptr.* = undefined;
sect.size = 0;
}
if (self.stubs_table.contains(global)) {
const stubs_atom = self.getStubsAtomForSymbol(global).?;
const stubs_sym = stubs_atom.getSymbolPtr(self);
stubs_sym.n_desc = N_DESC_GCED;
}
if (self.tlv_ptr_entries_table.contains(global)) {
const tlv_ptr_atom = self.getTlvPtrAtomForSymbol(global).?;
const tlv_ptr_sym = tlv_ptr_atom.getSymbolPtr(self);
tlv_ptr_sym.n_desc = N_DESC_GCED;
}
}
if (orig_prev) |prev| {
atom = prev;
} else break;
}
}
for (self.got_entries.items) |entry| {
const sym = entry.getSymbol(self);
if (sym.n_desc != N_DESC_GCED) continue;
// TODO tombstone
const atom = entry.getAtom(self);
const match = self.getMatchingSectionFromOrdinal(sym.n_sect);
self.removeAtomFromSection(atom, match);
_ = try gc_sections.put(match, {});
_ = self.got_entries_table.remove(entry.target);
}
for (self.stubs.items) |entry| {
const sym = entry.getSymbol(self);
if (sym.n_desc != N_DESC_GCED) continue;
// TODO tombstone
const atom = entry.getAtom(self);
const match = self.getMatchingSectionFromOrdinal(sym.n_sect);
self.removeAtomFromSection(atom, match);
_ = try gc_sections.put(match, {});
_ = self.stubs_table.remove(entry.target);
}
for (self.tlv_ptr_entries.items) |entry| {
const sym = entry.getSymbol(self);
if (sym.n_desc != N_DESC_GCED) continue;
// TODO tombstone
const atom = entry.getAtom(self);
const match = self.getMatchingSectionFromOrdinal(sym.n_sect);
self.removeAtomFromSection(atom, match);
_ = try gc_sections.put(match, {});
_ = self.tlv_ptr_entries_table.remove(entry.target);
}
var gc_sections_it = gc_sections.iterator();
while (gc_sections_it.next()) |entry| {
const match = entry.key_ptr.*;
@ -5679,6 +5713,30 @@ fn gcAtoms(self: *MachO, gc_roots: *std.AutoHashMap(*Atom, void)) !void {
}
}
fn removeAtomFromSection(self: *MachO, atom: *Atom, match: MatchingSection) void {
const sect = self.getSectionPtr(match);
// If we want to enable GC for incremental codepath, we need to take into
// account any padding that might have been left here.
sect.size -= atom.size;
if (atom.prev) |prev| {
prev.next = atom.next;
}
if (atom.next) |next| {
next.prev = atom.prev;
} else {
const last = self.atoms.getPtr(match).?;
if (atom.prev) |prev| {
last.* = prev;
} else {
// The section will be GCed in the next step.
last.* = undefined;
sect.size = 0;
}
}
}
fn updateSectionOrdinals(self: *MachO) !void {
if (!self.sections_order_dirty) return;
@ -5849,7 +5907,7 @@ fn writeDyldInfoData(self: *MachO) !void {
if (self.base.options.output_mode == .Exe) {
for (&[_]SymbolWithLoc{
self.getEntryPoint().?, // We would already errored out if no entrypoint was found.
try self.getEntryPoint(),
self.globals.get("__mh_execute_header").?,
}) |global| {
const sym = self.getSymbol(global);
@ -6337,10 +6395,13 @@ fn writeSymtab(self: *MachO) !void {
.sect = stubs_section_index,
});
stubs.reserved1 = 0;
for (self.stubs_table.keys()) |target| {
const sym = self.getSymbol(target);
assert(sym.undf());
try writer.writeIntLittle(u32, dysymtab.iundefsym + imports_table.get(target).?);
for (self.stubs.items) |entry| {
if (entry.sym_index == 0) continue;
const atom_sym = entry.getSymbol(self);
if (atom_sym.n_desc == N_DESC_GCED) continue;
const target_sym = self.getSymbol(entry.target);
assert(target_sym.undf());
try writer.writeIntLittle(u32, dysymtab.iundefsym + imports_table.get(entry.target).?);
}
}
@ -6351,10 +6412,13 @@ fn writeSymtab(self: *MachO) !void {
.sect = got_section_index,
});
got.reserved1 = nstubs;
for (self.got_entries_table.keys()) |target| {
const sym = self.getSymbol(target);
if (sym.undf()) {
try writer.writeIntLittle(u32, dysymtab.iundefsym + imports_table.get(target).?);
for (self.got_entries.items) |entry| {
if (entry.sym_index == 0) continue;
const atom_sym = entry.getSymbol(self);
if (atom_sym.n_desc == N_DESC_GCED) continue;
const target_sym = self.getSymbol(entry.target);
if (target_sym.undf()) {
try writer.writeIntLittle(u32, dysymtab.iundefsym + imports_table.get(entry.target).?);
} else {
try writer.writeIntLittle(u32, macho.INDIRECT_SYMBOL_LOCAL);
}
@ -6368,10 +6432,13 @@ fn writeSymtab(self: *MachO) !void {
.sect = la_symbol_ptr_section_index,
});
la_symbol_ptr.reserved1 = nstubs + ngot_entries;
for (self.stubs_table.keys()) |target| {
const sym = self.getSymbol(target);
assert(sym.undf());
try writer.writeIntLittle(u32, dysymtab.iundefsym + imports_table.get(target).?);
for (self.stubs.items) |entry| {
if (entry.sym_index == 0) continue;
const atom_sym = entry.getSymbol(self);
if (atom_sym.n_desc == N_DESC_GCED) continue;
const target_sym = self.getSymbol(entry.target);
assert(target_sym.undf());
try writer.writeIntLittle(u32, dysymtab.iundefsym + imports_table.get(entry.target).?);
}
}
@ -6623,7 +6690,7 @@ pub fn getSymbolName(self: *MachO, sym_with_loc: SymbolWithLoc) []const u8 {
pub fn getAtomForSymbol(self: *MachO, sym_with_loc: SymbolWithLoc) ?*Atom {
if (sym_with_loc.file) |file| {
const object = self.objects.items[file];
return object.atom_by_index_table.get(sym_with_loc.sym_index);
return object.getAtomForSymbol(sym_with_loc.sym_index);
} else {
return self.atom_by_index_table.get(sym_with_loc.sym_index);
}
@ -6633,28 +6700,32 @@ pub fn getAtomForSymbol(self: *MachO, sym_with_loc: SymbolWithLoc) ?*Atom {
/// Returns null otherwise.
pub fn getGotAtomForSymbol(self: *MachO, sym_with_loc: SymbolWithLoc) ?*Atom {
const got_index = self.got_entries_table.get(sym_with_loc) orelse return null;
return self.got_entries.items[got_index].atom;
return self.got_entries.items[got_index].getAtom(self);
}
/// Returns stubs atom that references `sym_with_loc` if one exists.
/// Returns null otherwise.
pub fn getStubsAtomForSymbol(self: *MachO, sym_with_loc: SymbolWithLoc) ?*Atom {
const stubs_index = self.stubs_table.get(sym_with_loc) orelse return null;
return self.stubs.items[stubs_index].atom;
return self.stubs.items[stubs_index].getAtom(self);
}
/// Returns TLV pointer atom that references `sym_with_loc` if one exists.
/// Returns null otherwise.
pub fn getTlvPtrAtomForSymbol(self: *MachO, sym_with_loc: SymbolWithLoc) ?*Atom {
const tlv_ptr_index = self.tlv_ptr_entries_table.get(sym_with_loc) orelse return null;
return self.tlv_ptr_entries.items[tlv_ptr_index].atom;
return self.tlv_ptr_entries.items[tlv_ptr_index].getAtom(self);
}
/// Returns symbol location corresponding to the set entrypoint.
/// Asserts output mode is executable.
pub fn getEntryPoint(self: MachO) ?SymbolWithLoc {
pub fn getEntryPoint(self: MachO) error{MissingMainEntrypoint}!SymbolWithLoc {
const entry_name = self.base.options.entry orelse "_main";
return self.globals.get(entry_name);
const global = self.globals.get(entry_name) orelse {
log.err("entrypoint '{s}' not found", .{entry_name});
return error.MissingMainEntrypoint;
};
return global;
}
pub fn findFirst(comptime T: type, haystack: []const T, start: usize, predicate: anytype) usize {
@ -6986,7 +7057,7 @@ fn snapshotState(self: *MachO) !void {
break :blk source_sym.n_value + rel.offset;
};
const target_addr = blk: {
const target_atom = (try rel.getTargetAtom(self)) orelse {
const target_atom = rel.getTargetAtom(self) orelse {
// If there is no atom for target, we still need to check for special, atom-less
// symbols such as `___dso_handle`.
const target_name = self.getSymbolName(rel.target);
@ -7119,8 +7190,9 @@ fn snapshotState(self: *MachO) !void {
try writer.writeByte(']');
}
pub fn logSymAttributes(sym: macho.nlist_64, buf: *[4]u8) []const u8 {
mem.set(u8, buf, '_');
fn logSymAttributes(sym: macho.nlist_64, buf: *[9]u8) []const u8 {
mem.set(u8, buf[0..4], '_');
mem.set(u8, buf[4..], ' ');
if (sym.sect()) {
buf[0] = 's';
}
@ -7137,11 +7209,14 @@ pub fn logSymAttributes(sym: macho.nlist_64, buf: *[4]u8) []const u8 {
if (sym.undf()) {
buf[3] = 'u';
}
if (sym.n_desc == N_DESC_GCED) {
mem.copy(u8, buf[5..], "DEAD");
}
return buf[0..];
}
fn logSymtab(self: *MachO) void {
var buf: [4]u8 = undefined;
var buf: [9]u8 = undefined;
log.debug("symtab:", .{});
for (self.objects.items) |object, id| {
@ -7186,42 +7261,50 @@ fn logSymtab(self: *MachO) void {
}
log.debug("GOT entries:", .{});
for (self.got_entries_table.values()) |value| {
const target = self.got_entries.items[value].target;
const target_sym = self.getSymbol(target);
const atom = self.got_entries.items[value].atom;
const atom_sym = atom.getSymbol(self);
for (self.got_entries.items) |entry, i| {
const atom_sym = entry.getSymbol(self);
if (atom_sym.n_desc == N_DESC_GCED) continue;
const target_sym = self.getSymbol(entry.target);
if (target_sym.undf()) {
log.debug(" {d}@{x} => import('{s}')", .{ value, atom_sym.n_value, self.getSymbolName(target) });
} else {
log.debug(" {d}@{x} => local(%{d}) in object({d})", .{
value,
log.debug(" {d}@{x} => import('{s}')", .{
i,
atom_sym.n_value,
target.sym_index,
target.file,
self.getSymbolName(entry.target),
});
} else {
log.debug(" {d}@{x} => local(%{d}) in object({d}) {s}", .{
i,
atom_sym.n_value,
entry.target.sym_index,
entry.target.file,
logSymAttributes(target_sym, &buf),
});
}
}
log.debug("__thread_ptrs entries:", .{});
for (self.tlv_ptr_entries_table.values()) |value| {
const target = self.tlv_ptr_entries.items[value].target;
const target_sym = self.getSymbol(target);
const atom = self.tlv_ptr_entries.items[value].atom;
const atom_sym = atom.getSymbol(self);
for (self.tlv_ptr_entries.items) |entry, i| {
const atom_sym = entry.getSymbol(self);
if (atom_sym.n_desc == N_DESC_GCED) continue;
const target_sym = self.getSymbol(entry.target);
assert(target_sym.undf());
log.debug(" {d}@{x} => import('{s}')", .{ value, atom_sym.n_value, self.getSymbolName(target) });
log.debug(" {d}@{x} => import('{s}')", .{
i,
atom_sym.n_value,
self.getSymbolName(entry.target),
});
}
log.debug("stubs entries:", .{});
for (self.stubs_table.values()) |value| {
const target = self.stubs.items[value].target;
const target_sym = self.getSymbol(target);
const atom = self.stubs.items[value].atom;
const atom_sym = atom.getSymbol(self);
for (self.stubs.items) |entry, i| {
const target_sym = self.getSymbol(entry.target);
const atom_sym = entry.getSymbol(self);
assert(target_sym.undf());
log.debug(" {d}@{x} => import('{s}')", .{ value, atom_sym.n_value, self.getSymbolName(target) });
log.debug(" {d}@{x} => import('{s}')", .{
i,
atom_sym.n_value,
self.getSymbolName(entry.target),
});
}
}
@ -7248,7 +7331,6 @@ fn logAtoms(self: *MachO) void {
while (true) {
self.logAtom(atom);
if (atom.next) |next| {
atom = next;
} else break;
@ -7256,14 +7338,17 @@ fn logAtoms(self: *MachO) void {
}
}
pub fn logAtom(self: *MachO, atom: *const Atom) void {
fn logAtom(self: *MachO, atom: *const Atom) void {
const sym = atom.getSymbol(self);
const sym_name = atom.getName(self);
log.debug(" ATOM(%{d}, '{s}') @ {x} in object({d})", .{
log.debug(" ATOM(%{d}, '{s}') @ {x} (sizeof({x}), alignof({x})) in object({d}) in sect({d})", .{
atom.sym_index,
sym_name,
sym.n_value,
atom.size,
atom.alignment,
atom.file,
sym.n_sect,
});
for (atom.contained.items) |sym_off| {
@ -7271,13 +7356,15 @@ pub fn logAtom(self: *MachO, atom: *const Atom) void {
.sym_index = sym_off.sym_index,
.file = atom.file,
});
const inner_sym_name = self.getSymbolName(.{ .sym_index = sym_off.sym_index, .file = atom.file });
log.debug(" (%{d}, '{s}') @ {x} ({x}) in object({d})", .{
const inner_sym_name = self.getSymbolName(.{
.sym_index = sym_off.sym_index,
.file = atom.file,
});
log.debug(" (%{d}, '{s}') @ {x} ({x})", .{
sym_off.sym_index,
inner_sym_name,
inner_sym.n_value,
sym_off.offset,
atom.file,
});
}
}

42
src/link/MachO/Atom.zig
View File

@ -94,7 +94,7 @@ pub const Relocation = struct {
@"type": u4,
pub fn getTargetAtom(self: Relocation, macho_file: *MachO) !?*Atom {
pub fn getTargetAtom(self: Relocation, macho_file: *MachO) ?*Atom {
const is_via_got = got: {
switch (macho_file.base.options.target.cpu.arch) {
.aarch64 => break :got switch (@intToEnum(macho.reloc_type_arm64, self.@"type")) {
@ -112,21 +112,9 @@ pub const Relocation = struct {
}
};
const target_sym = macho_file.getSymbol(self.target);
if (is_via_got) {
const got_atom = macho_file.getGotAtomForSymbol(self.target) orelse {
log.err("expected GOT entry for symbol", .{});
if (target_sym.undf()) {
log.err(" import('{s}')", .{macho_file.getSymbolName(self.target)});
} else {
log.err(" local(%{d}) in object({d})", .{ self.target.sym_index, self.target.file });
}
log.err(" this is an internal linker error", .{});
return error.FailedToResolveRelocationTarget;
};
return got_atom;
return macho_file.getGotAtomForSymbol(self.target).?; // panic means fatal error
}
if (macho_file.getStubsAtomForSymbol(self.target)) |stubs_atom| return stubs_atom;
if (macho_file.getTlvPtrAtomForSymbol(self.target)) |tlv_ptr_atom| return tlv_ptr_atom;
return macho_file.getAtomForSymbol(self.target);
@ -174,6 +162,10 @@ pub fn getSymbolPtr(self: Atom, macho_file: *MachO) *macho.nlist_64 {
});
}
pub fn getSymbolWithLoc(self: Atom) SymbolWithLoc {
return .{ .sym_index = self.sym_index, .file = self.file };
}
/// Returns true if the symbol pointed at with `sym_loc` is contained within this atom.
/// WARNING this function assumes all atoms have been allocated in the virtual memory.
/// Calling it without allocating with `MachO.allocateSymbols` (or equivalent) will
@ -515,7 +507,7 @@ fn addTlvPtrEntry(target: MachO.SymbolWithLoc, context: RelocContext) !void {
const index = try context.macho_file.allocateTlvPtrEntry(target);
const atom = try context.macho_file.createTlvPtrAtom(target);
context.macho_file.tlv_ptr_entries.items[index].atom = atom;
context.macho_file.tlv_ptr_entries.items[index].sym_index = atom.sym_index;
}
fn addGotEntry(target: MachO.SymbolWithLoc, context: RelocContext) !void {
@ -523,7 +515,7 @@ fn addGotEntry(target: MachO.SymbolWithLoc, context: RelocContext) !void {
const index = try context.macho_file.allocateGotEntry(target);
const atom = try context.macho_file.createGotAtom(target);
context.macho_file.got_entries.items[index].atom = atom;
context.macho_file.got_entries.items[index].sym_index = atom.sym_index;
}
fn addStub(target: MachO.SymbolWithLoc, context: RelocContext) !void {
@ -536,7 +528,7 @@ fn addStub(target: MachO.SymbolWithLoc, context: RelocContext) !void {
const laptr_atom = try context.macho_file.createLazyPointerAtom(stub_helper_atom.sym_index, target);
const stub_atom = try context.macho_file.createStubAtom(laptr_atom.sym_index);
context.macho_file.stubs.items[stub_index].atom = stub_atom;
context.macho_file.stubs.items[stub_index].sym_index = stub_atom.sym_index;
}
pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
@ -578,7 +570,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
break :is_tlv sect.type_() == macho.S_THREAD_LOCAL_VARIABLES;
};
const target_addr = blk: {
const target_atom = (try rel.getTargetAtom(macho_file)) orelse {
const target_atom = rel.getTargetAtom(macho_file) orelse {
// If there is no atom for target, we still need to check for special, atom-less
// symbols such as `___dso_handle`.
const target_name = macho_file.getSymbolName(rel.target);
@ -597,6 +589,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
macho_file.getSymbol(rel.target)
else
target_atom.getSymbol(macho_file);
assert(target_sym.n_desc != MachO.N_DESC_GCED);
const base_address: u64 = if (is_tlv) base_address: {
// For TLV relocations, the value specified as a relocation is the displacement from the
// TLV initializer (either value in __thread_data or zero-init in __thread_bss) to the first
@ -624,12 +617,12 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
};
log.debug(" | source_addr = 0x{x}", .{source_addr});
log.debug(" | target_addr = 0x{x}", .{target_addr});
switch (arch) {
.aarch64 => {
switch (@intToEnum(macho.reloc_type_arm64, rel.@"type")) {
.ARM64_RELOC_BRANCH26 => {
log.debug(" | target_addr = 0x{x}", .{target_addr});
const displacement = math.cast(
i28,
@intCast(i64, target_addr) - @intCast(i64, source_addr),
@ -658,6 +651,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
.ARM64_RELOC_TLVP_LOAD_PAGE21,
=> {
const actual_target_addr = @intCast(i64, target_addr) + rel.addend;
log.debug(" | target_addr = 0x{x}", .{actual_target_addr});
const source_page = @intCast(i32, source_addr >> 12);
const target_page = @intCast(i32, actual_target_addr >> 12);
const pages = @bitCast(u21, @intCast(i21, target_page - source_page));
@ -675,6 +669,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
.ARM64_RELOC_PAGEOFF12 => {
const code = self.code.items[rel.offset..][0..4];
const actual_target_addr = @intCast(i64, target_addr) + rel.addend;
log.debug(" | target_addr = 0x{x}", .{actual_target_addr});
const narrowed = @truncate(u12, @intCast(u64, actual_target_addr));
if (isArithmeticOp(self.code.items[rel.offset..][0..4])) {
var inst = aarch64.Instruction{
@ -712,6 +707,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
.ARM64_RELOC_GOT_LOAD_PAGEOFF12 => {
const code = self.code.items[rel.offset..][0..4];
const actual_target_addr = @intCast(i64, target_addr) + rel.addend;
log.debug(" | target_addr = 0x{x}", .{actual_target_addr});
const narrowed = @truncate(u12, @intCast(u64, actual_target_addr));
var inst: aarch64.Instruction = .{
.load_store_register = mem.bytesToValue(meta.TagPayload(
@ -726,6 +722,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
.ARM64_RELOC_TLVP_LOAD_PAGEOFF12 => {
const code = self.code.items[rel.offset..][0..4];
const actual_target_addr = @intCast(i64, target_addr) + rel.addend;
log.debug(" | target_addr = 0x{x}", .{actual_target_addr});
const RegInfo = struct {
rd: u5,
@ -783,6 +780,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
mem.writeIntLittle(u32, code, inst.toU32());
},
.ARM64_RELOC_POINTER_TO_GOT => {
log.debug(" | target_addr = 0x{x}", .{target_addr});
const result = math.cast(i32, @intCast(i64, target_addr) - @intCast(i64, source_addr)) orelse return error.Overflow;
mem.writeIntLittle(u32, self.code.items[rel.offset..][0..4], @bitCast(u32, result));
},
@ -795,6 +793,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
break :blk @intCast(i64, target_addr) + rel.addend;
}
};
log.debug(" | target_addr = 0x{x}", .{result});
if (rel.length == 3) {
mem.writeIntLittle(u64, self.code.items[rel.offset..][0..8], @bitCast(u64, result));
@ -813,6 +812,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
.x86_64 => {
switch (@intToEnum(macho.reloc_type_x86_64, rel.@"type")) {
.X86_64_RELOC_BRANCH => {
log.debug(" | target_addr = 0x{x}", .{target_addr});
const displacement = math.cast(
i32,
@intCast(i64, target_addr) - @intCast(i64, source_addr) - 4 + rel.addend,
@ -820,6 +820,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
mem.writeIntLittle(u32, self.code.items[rel.offset..][0..4], @bitCast(u32, displacement));
},
.X86_64_RELOC_GOT, .X86_64_RELOC_GOT_LOAD => {
log.debug(" | target_addr = 0x{x}", .{target_addr});
const displacement = math.cast(
i32,
@intCast(i64, target_addr) - @intCast(i64, source_addr) - 4 + rel.addend,
@ -827,6 +828,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
mem.writeIntLittle(u32, self.code.items[rel.offset..][0..4], @bitCast(u32, displacement));
},
.X86_64_RELOC_TLV => {
log.debug(" | target_addr = 0x{x}", .{target_addr});
if (!macho_file.tlv_ptr_entries_table.contains(rel.target)) {
// We need to rewrite the opcode from movq to leaq.
self.code.items[rel.offset - 2] = 0x8d;
@ -850,6 +852,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
else => unreachable,
};
const actual_target_addr = @intCast(i64, target_addr) + rel.addend;
log.debug(" | target_addr = 0x{x}", .{actual_target_addr});
const displacement = math.cast(
i32,
actual_target_addr - @intCast(i64, source_addr + correction + 4),
@ -865,6 +868,7 @@ pub fn resolveRelocs(self: *Atom, macho_file: *MachO) !void {
break :blk @intCast(i64, target_addr) + rel.addend;
}
};
log.debug(" | target_addr = 0x{x}", .{result});
if (rel.length == 3) {
mem.writeIntLittle(u64, self.code.items[rel.offset..][0..8], @bitCast(u64, result));

18
src/link/MachO/DebugSymbols.zig
View File

@ -275,9 +275,12 @@ pub fn flushModule(self: *DebugSymbols, allocator: Allocator, options: link.Opti
const sym = switch (reloc.@"type") {
.direct_load => self.base.getSymbol(.{ .sym_index = reloc.target, .file = null }),
.got_load => blk: {
const got_index = self.base.got_entries_table.get(.{ .sym_index = reloc.target, .file = null }).?;
const got_atom = self.base.got_entries.items[got_index].atom;
break :blk got_atom.getSymbol(self.base);
const got_index = self.base.got_entries_table.get(.{
.sym_index = reloc.target,
.file = null,
}).?;
const got_entry = self.base.got_entries.items[got_index];
break :blk got_entry.getSymbol(self.base);
},
};
if (sym.n_value == reloc.prev_vaddr) continue;
@ -285,9 +288,12 @@ pub fn flushModule(self: *DebugSymbols, allocator: Allocator, options: link.Opti
const sym_name = switch (reloc.@"type") {
.direct_load => self.base.getSymbolName(.{ .sym_index = reloc.target, .file = null }),
.got_load => blk: {
const got_index = self.base.got_entries_table.get(.{ .sym_index = reloc.target, .file = null }).?;
const got_atom = self.base.got_entries.items[got_index].atom;
break :blk got_atom.getName(self.base);
const got_index = self.base.got_entries_table.get(.{
.sym_index = reloc.target,
.file = null,
}).?;
const got_entry = self.base.got_entries.items[got_index];
break :blk got_entry.getName(self.base);
},
};
const seg = &self.load_commands.items[self.dwarf_segment_cmd_index.?].segment;

14
src/link/MachO/Object.zig
View File

@ -410,7 +410,9 @@ pub fn splitIntoAtomsOneShot(
next_sym_count += atom_syms.len;
assert(atom_syms.len > 0);
const sym_index = atom_syms[0].index;
const sym_index = for (atom_syms) |atom_sym| {
if (atom_sym.getSymbol(context).ext()) break atom_sym.index;
} else atom_syms[0].index;
const atom_size = blk: {
const end_addr = if (next_sym_count < filtered_syms.len)
filtered_syms[next_sym_count].getSymbol(context).n_value
@ -570,12 +572,6 @@ fn createAtomFromSubsection(
if (gc_roots) |gcr| {
const is_gc_root = blk: {
if (sect.isDontDeadStrip()) break :blk true;
if (sect.isDontDeadStripIfReferencesLive()) {
// TODO if isDontDeadStripIfReferencesLive we should analyse the edges
// before making it a GC root
break :blk true;
}
if (mem.eql(u8, "__StaticInit", sect.sectName())) break :blk true;
switch (sect.type_()) {
macho.S_MOD_INIT_FUNC_POINTERS,
macho.S_MOD_TERM_FUNC_POINTERS,
@ -641,3 +637,7 @@ pub fn getSection(self: Object, n_sect: u16) macho.section_64 {
assert(n_sect < seg.sections.items.len);
return seg.sections.items[n_sect];
}
pub fn getAtomForSymbol(self: Object, sym_index: u32) ?*Atom {
return self.atom_by_index_table.get(sym_index);
}