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macho: add routine for creating a dynamic stub_helper atom
With this routine, we are now able to freely shift stub_helper section in memory and in file since the VM addressing is now dynamically dependent on the positioning of `__stub_helper` preamble and other sections generated by the linker.
This commit is contained in:
Jakub Konka
parent
ea499203fe
commit
799c5bb955
@ -177,8 +177,6 @@ has_stabs: bool = false,
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section_ordinals: std.AutoArrayHashMapUnmanaged(MatchingSection, void) = .{},
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pending_updates: std.ArrayListUnmanaged(PendingUpdate) = .{},
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/// A list of text blocks that have surplus capacity. This list can have false
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/// positives, as functions grow and shrink over time, only sometimes being added
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/// or removed from the freelist.
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@ -384,6 +382,26 @@ pub fn openPath(allocator: *Allocator, sub_path: []const u8, options: link.Optio
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try ds.writeLocalSymbol(0);
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}
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{
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const atom = try self.createDyldPrivateAtom();
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const match = MatchingSection{
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.seg = self.data_segment_cmd_index.?,
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.sect = self.data_section_index.?,
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};
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const vaddr = try self.allocateAtom(atom, match);
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try self.writeAtom(atom, match);
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}
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{
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const atom = try self.createStubHelperPreambleAtom();
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const match = MatchingSection{
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.seg = self.text_segment_cmd_index.?,
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.sect = self.stub_helper_section_index.?,
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};
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const vaddr = try self.allocateAtom(atom, match);
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try self.writeAtom(atom, match);
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}
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return self;
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}
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@ -760,50 +778,42 @@ pub fn flush(self: *MachO, comp: *Compilation) !void {
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try self.parseLibs(libs.items, self.base.options.sysroot);
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try self.resolveSymbols();
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try self.resolveDyldStubBinder();
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try self.createDyldPrivateAtom();
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try self.createStubHelperPreambleAtom();
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if (!use_stage1) {
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// TODO just a temp
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const seg = self.load_commands.items[self.text_segment_cmd_index.?].Segment;
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const sect = seg.sections.items[self.stub_helper_section_index.?];
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self.stub_helper_stubs_start_off = sect.offset + switch (self.base.options.target.cpu.arch) {
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.x86_64 => @intCast(u64, 15),
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.aarch64 => @intCast(u64, 6 * @sizeOf(u32)),
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else => unreachable,
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};
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}
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// Apply pending updates
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var still_pending = std.ArrayList(PendingUpdate).init(self.base.allocator);
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defer still_pending.deinit();
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for (self.pending_updates.items) |update| {
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switch (update) {
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.add_stub_entry => |stub_index| {
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try self.writeStub(stub_index);
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try self.writeStubInStubHelper(stub_index);
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try self.writeLazySymbolPointer(stub_index);
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self.rebase_info_dirty = true;
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self.lazy_binding_info_dirty = true;
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},
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else => unreachable,
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}
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}
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self.pending_updates.clearRetainingCapacity();
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for (still_pending.items) |update| {
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self.pending_updates.appendAssumeCapacity(update);
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}
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try self.parseTextBlocks();
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try self.addRpathLCs(rpath_table.keys());
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try self.addLoadDylibLCs();
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try self.addDataInCodeLC();
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try self.addCodeSignatureLC();
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if (use_stage1) {
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try self.parseTextBlocks();
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try self.sortSections();
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{
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const atom = try self.createDyldPrivateAtom();
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try self.allocateAtomStage1(atom, .{
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.seg = self.data_segment_cmd_index.?,
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.sect = self.data_section_index.?,
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});
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}
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{
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const atom = try self.createStubHelperPreambleAtom();
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try self.allocateAtomStage1(atom, .{
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.seg = self.text_segment_cmd_index.?,
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.sect = self.stub_helper_section_index.?,
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});
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// TODO this is just a temp
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// We already prealloc stub helper size in populateMissingMetadata(), but
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// perhaps it's not needed after all?
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const seg = &self.load_commands.items[self.text_segment_cmd_index.?].Segment;
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const sect = &seg.sections.items[self.stub_helper_section_index.?];
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sect.size -= atom.size;
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}
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for (self.stubs.items) |_| {
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const atom = try self.createStubHelperAtom();
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try self.allocateAtomStage1(atom, .{
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.seg = self.text_segment_cmd_index.?,
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.sect = self.stub_helper_section_index.?,
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});
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}
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try self.allocateTextSegment();
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try self.allocateDataConstSegment();
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try self.allocateDataSegment();
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@ -1705,18 +1715,10 @@ fn allocateTextSegment(self: *MachO) !void {
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seg.inner.fileoff = 0;
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seg.inner.vmaddr = base_vmaddr;
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// Set stubs and stub_helper sizes
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// Set stubs sizes
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const stubs = &seg.sections.items[self.stubs_section_index.?];
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const stub_helper = &seg.sections.items[self.stub_helper_section_index.?];
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stubs.size += nstubs * stubs.reserved2;
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const stub_size: u4 = switch (self.base.options.target.cpu.arch) {
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.x86_64 => 10,
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.aarch64 => 3 * @sizeOf(u32),
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else => unreachable,
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};
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stub_helper.size += nstubs * stub_size;
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var sizeofcmds: u64 = 0;
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for (self.load_commands.items) |lc| {
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sizeofcmds += lc.cmdsize();
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@ -1947,41 +1949,81 @@ fn createEmptyAtom(
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defer self.base.allocator.free(code);
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mem.set(u8, code, 0);
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const block = try self.base.allocator.create(TextBlock);
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errdefer self.base.allocator.destroy(block);
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block.* = TextBlock.empty;
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block.local_sym_index = local_sym_index;
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block.size = size;
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block.alignment = alignment;
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try block.code.appendSlice(self.base.allocator, code);
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const atom = try self.base.allocator.create(TextBlock);
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errdefer self.base.allocator.destroy(atom);
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atom.* = TextBlock.empty;
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atom.local_sym_index = local_sym_index;
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atom.size = size;
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atom.alignment = alignment;
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try atom.code.appendSlice(self.base.allocator, code);
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try self.managed_blocks.append(self.base.allocator, atom);
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try self.managed_blocks.append(self.base.allocator, block);
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return atom;
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}
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fn allocateAtom(self: *MachO, atom: *TextBlock, match: MatchingSection) !u64 {
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// TODO converge with `allocateTextBlock`
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const seg = self.load_commands.items[match.seg].Segment;
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const sect = seg.sections.items[match.sect];
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const base_addr = if (atom.prev) |prev| blk: {
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const prev_atom_sym = self.locals.items[prev.local_sym_index];
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break :blk prev_atom_sym.n_value;
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} else sect.addr;
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const atom_alignment = try math.powi(u32, 2, atom.alignment);
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const vaddr = mem.alignForwardGeneric(u64, base_addr, atom_alignment);
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// TODO we should check if we need to expand the section or not like we
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// do in `allocateTextBlock`.
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if (self.blocks.getPtr(match)) |last| {
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last.*.next = atom;
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atom.prev = last.*;
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last.* = atom;
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} else {
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try self.blocks.putNoClobber(self.base.allocator, match, atom);
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}
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return vaddr;
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}
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fn writeAtom(self: *MachO, atom: *TextBlock, match: MatchingSection) !void {
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const seg = self.load_commands.items[match.seg].Segment;
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const sect = seg.sections.items[match.sect];
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const vaddr = try self.allocateAtom(atom, match);
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const sym = &self.locals.items[atom.local_sym_index];
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sym.n_value = vaddr;
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sym.n_sect = @intCast(u8, self.section_ordinals.getIndex(match).? + 1);
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try atom.resolveRelocs(self);
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const file_offset = sect.offset + vaddr - sect.addr;
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log.debug("writing atom for symbol {s} at file offset 0x{x}", .{ self.getString(sym.n_strx), file_offset });
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try self.base.file.?.pwriteAll(atom.code.items, file_offset);
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try self.writeLocalSymbol(atom.local_sym_index);
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}
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fn allocateAtomStage1(self: *MachO, atom: *TextBlock, match: MatchingSection) !void {
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// Update target section's metadata
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// TODO should we update segment's size here too?
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// How does it tie with incremental space allocs?
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const tseg = &self.load_commands.items[match.seg].Segment;
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const tsect = &tseg.sections.items[match.sect];
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const new_alignment = math.max(tsect.@"align", alignment);
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const new_alignment = math.max(tsect.@"align", atom.alignment);
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const new_alignment_pow_2 = try math.powi(u32, 2, new_alignment);
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const new_size = mem.alignForwardGeneric(u64, tsect.size, new_alignment_pow_2) + size;
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const new_size = mem.alignForwardGeneric(u64, tsect.size, new_alignment_pow_2) + atom.size;
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tsect.size = new_size;
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tsect.@"align" = new_alignment;
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if (self.blocks.getPtr(match)) |last| {
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last.*.next = block;
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block.prev = last.*;
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last.* = block;
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last.*.next = atom;
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atom.prev = last.*;
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last.* = atom;
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} else {
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try self.blocks.putNoClobber(self.base.allocator, match, block);
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try self.blocks.putNoClobber(self.base.allocator, match, atom);
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}
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return block;
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}
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fn createDyldPrivateAtom(self: *MachO) !void {
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if (self.dyld_private_sym_index != null) return;
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fn createDyldPrivateAtom(self: *MachO) !*TextBlock {
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const match = MatchingSection{
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.seg = self.data_segment_cmd_index.?,
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.sect = self.data_section_index.?,
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@ -1994,35 +2036,11 @@ fn createDyldPrivateAtom(self: *MachO) !void {
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.n_desc = 0,
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.n_value = 0,
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});
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const last = self.blocks.get(match);
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const atom = try self.createEmptyAtom(match, local_sym_index, @sizeOf(u64), 3);
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if (!(build_options.is_stage1 and self.base.options.use_stage1)) {
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const seg = self.load_commands.items[match.seg].Segment;
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const sect = seg.sections.items[match.sect];
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const base_addr = if (last) |last_atom| blk: {
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const last_atom_sym = self.locals.items[last_atom.local_sym_index];
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break :blk last_atom_sym.n_value;
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} else sect.addr;
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const n_sect = @intCast(u8, self.section_ordinals.getIndex(match).? + 1);
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const atom_alignment = try math.powi(u32, 2, atom.alignment);
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const vaddr = mem.alignForwardGeneric(u64, base_addr, atom_alignment);
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const sym = &self.locals.items[local_sym_index];
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sym.n_value = vaddr;
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sym.n_sect = n_sect;
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const file_offset = sect.offset + vaddr - sect.addr;
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log.debug("writing code for symbol {s} at file offset 0x{x}", .{ self.getString(sym.n_strx), file_offset });
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try self.base.file.?.pwriteAll(atom.code.items, file_offset);
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try self.writeLocalSymbol(local_sym_index);
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}
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self.dyld_private_sym_index = local_sym_index;
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return self.createEmptyAtom(match, local_sym_index, @sizeOf(u64), 3);
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}
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fn createStubHelperPreambleAtom(self: *MachO) !void {
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if (self.stub_preamble_sym_index != null) return;
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fn createStubHelperPreambleAtom(self: *MachO) !*TextBlock {
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const arch = self.base.options.target.cpu.arch;
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const match = MatchingSection{
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.seg = self.text_segment_cmd_index.?,
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@ -2046,7 +2064,6 @@ fn createStubHelperPreambleAtom(self: *MachO) !void {
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.n_desc = 0,
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.n_value = 0,
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});
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const last = self.blocks.get(match);
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const atom = try self.createEmptyAtom(match, local_sym_index, size, alignment);
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switch (arch) {
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.x86_64 => {
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@ -2157,36 +2174,71 @@ fn createStubHelperPreambleAtom(self: *MachO) !void {
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else => unreachable,
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}
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self.stub_preamble_sym_index = local_sym_index;
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return atom;
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}
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if (!(build_options.is_stage1 and self.base.options.use_stage1)) {
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const seg = self.load_commands.items[match.seg].Segment;
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const sect = seg.sections.items[match.sect];
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const base_addr = if (last) |last_atom| blk: {
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const last_atom_sym = self.locals.items[last_atom.local_sym_index];
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break :blk last_atom_sym.n_value;
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} else sect.addr;
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const n_sect = @intCast(u8, self.section_ordinals.getIndex(match).? + 1);
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const atom_alignment = try math.powi(u32, 2, atom.alignment);
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const vaddr = mem.alignForwardGeneric(u64, base_addr, atom_alignment);
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fn createStubHelperAtom(self: *MachO) !*TextBlock {
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const arch = self.base.options.target.cpu.arch;
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const stub_size: u4 = switch (arch) {
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.x86_64 => 10,
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.aarch64 => 3 * @sizeOf(u32),
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else => unreachable,
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};
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const local_sym_index = @intCast(u32, self.locals.items.len);
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try self.locals.append(self.base.allocator, .{
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.n_strx = try self.makeString("stub_in_stub_helper"),
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.n_type = macho.N_SECT,
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.n_sect = 0,
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.n_desc = 0,
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.n_value = 0,
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});
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const atom = try self.createEmptyAtom(.{
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.seg = self.text_segment_cmd_index.?,
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.sect = self.stub_helper_section_index.?,
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}, local_sym_index, stub_size, 2);
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try atom.relocs.ensureTotalCapacity(self.base.allocator, 1);
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const sym = &self.locals.items[local_sym_index];
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sym.n_value = vaddr;
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sym.n_sect = n_sect;
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try atom.resolveRelocs(self);
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const file_offset = sect.offset + vaddr - sect.addr;
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log.debug("writing code for symbol {s} at file offset 0x{x}", .{ self.getString(sym.n_strx), file_offset });
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try self.base.file.?.pwriteAll(atom.code.items, file_offset);
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try self.writeLocalSymbol(local_sym_index);
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switch (arch) {
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.x86_64 => {
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// pushq
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atom.code.items[0] = 0x68;
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// Next 4 bytes 1..4 are just a placeholder populated in `populateLazyBindOffsetsInStubHelper`.
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// jmpq
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atom.code.items[5] = 0xe9;
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atom.relocs.appendAssumeCapacity(.{
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.offset = 6,
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.where = .local,
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.where_index = self.stub_preamble_sym_index.?,
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.payload = .{
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.branch = .{ .arch = arch },
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},
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});
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},
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.aarch64 => {
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const literal = blk: {
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const div_res = try math.divExact(u64, stub_size - @sizeOf(u32), 4);
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break :blk try math.cast(u18, div_res);
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};
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// ldr w16, literal
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mem.writeIntLittle(u32, atom.code.items[0..4], aarch64.Instruction.ldr(.w16, .{
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.literal = literal,
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}).toU32());
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// b disp
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mem.writeIntLittle(u32, atom.code.items[4..8], aarch64.Instruction.b(0).toU32());
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atom.relocs.appendAssumeCapacity(.{
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.offset = 4,
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.where = .local,
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.where_index = self.stub_preamble_sym_index.?,
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.payload = .{
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.branch = .{ .arch = arch },
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},
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});
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// Next 4 bytes 8..12 are just a placeholder populated in `populateLazyBindOffsetsInStubHelper`.
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},
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else => unreachable,
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}
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// TODO this needs to be fixed
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// We already prealloc stub helper size in populateMissingMetadata(), but
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// perhaps it's not needed after all?
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const seg = &self.load_commands.items[self.text_segment_cmd_index.?].Segment;
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const sect = &seg.sections.items[self.stub_helper_section_index.?];
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sect.size -= size;
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return atom;
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}
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fn resolveSymbolsInObject(
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@ -2681,7 +2733,6 @@ fn flushZld(self: *MachO) !void {
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// TODO weak bound pointers
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try self.writeLazySymbolPointer(index);
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try self.writeStub(index);
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try self.writeStubInStubHelper(index);
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}
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if (self.common_section_index) |index| {
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@ -3173,7 +3224,6 @@ pub fn deinit(self: *MachO) void {
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}
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self.section_ordinals.deinit(self.base.allocator);
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self.pending_updates.deinit(self.base.allocator);
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self.got_entries.deinit(self.base.allocator);
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self.got_entries_map.deinit(self.base.allocator);
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self.got_entries_free_list.deinit(self.base.allocator);
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@ -4404,11 +4454,7 @@ pub fn addExternFn(self: *MachO, name: []const u8) !u32 {
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try self.stubs.append(self.base.allocator, sym_index);
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try self.stubs_map.putNoClobber(self.base.allocator, sym_index, stubs_index);
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// TODO discuss this. The caller context expects codegen.InnerError{ OutOfMemory, CodegenFail },
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// which obviously doesn't include file writing op errors. So instead of trying to write the stub
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// entry right here and now, queue it up and dispose of when updating decl.
|
||||
try self.pending_updates.ensureUnusedCapacity(self.base.allocator, 1);
|
||||
self.pending_updates.appendAssumeCapacity(.{ .add_stub_entry = stubs_index });
|
||||
// TODO create and write stub, stub_helper and lazy_ptr atoms
|
||||
|
||||
return sym_index;
|
||||
}
|
||||
@ -4683,53 +4729,6 @@ fn writeStub(self: *MachO, index: u32) !void {
|
||||
try self.base.file.?.pwriteAll(code, stub_off);
|
||||
}
|
||||
|
||||
fn writeStubInStubHelper(self: *MachO, index: u32) !void {
|
||||
const text_segment = self.load_commands.items[self.text_segment_cmd_index.?].Segment;
|
||||
const stub_helper = text_segment.sections.items[self.stub_helper_section_index.?];
|
||||
|
||||
const stub_size: u4 = switch (self.base.options.target.cpu.arch) {
|
||||
.x86_64 => 10,
|
||||
.aarch64 => 3 * @sizeOf(u32),
|
||||
else => unreachable,
|
||||
};
|
||||
const stub_off = self.stub_helper_stubs_start_off.? + index * stub_size;
|
||||
|
||||
var code = try self.base.allocator.alloc(u8, stub_size);
|
||||
defer self.base.allocator.free(code);
|
||||
|
||||
switch (self.base.options.target.cpu.arch) {
|
||||
.x86_64 => {
|
||||
const displacement = try math.cast(
|
||||
i32,
|
||||
@intCast(i64, stub_helper.offset) - @intCast(i64, stub_off) - stub_size,
|
||||
);
|
||||
// pushq
|
||||
code[0] = 0x68;
|
||||
mem.writeIntLittle(u32, code[1..][0..4], 0x0); // Just a placeholder populated in `populateLazyBindOffsetsInStubHelper`.
|
||||
// jmpq
|
||||
code[5] = 0xe9;
|
||||
mem.writeIntLittle(u32, code[6..][0..4], @bitCast(u32, displacement));
|
||||
},
|
||||
.aarch64 => {
|
||||
const literal = blk: {
|
||||
const div_res = try math.divExact(u64, stub_size - @sizeOf(u32), 4);
|
||||
break :blk try math.cast(u18, div_res);
|
||||
};
|
||||
// ldr w16, literal
|
||||
mem.writeIntLittle(u32, code[0..4], aarch64.Instruction.ldr(.w16, .{
|
||||
.literal = literal,
|
||||
}).toU32());
|
||||
const displacement = try math.cast(i28, @intCast(i64, stub_helper.offset) - @intCast(i64, stub_off) - 4);
|
||||
// b disp
|
||||
mem.writeIntLittle(u32, code[4..8], aarch64.Instruction.b(displacement).toU32());
|
||||
// Just a placeholder populated in `populateLazyBindOffsetsInStubHelper`.
|
||||
mem.writeIntLittle(u32, code[8..12], 0x0);
|
||||
},
|
||||
else => unreachable,
|
||||
}
|
||||
try self.base.file.?.pwriteAll(code, stub_off);
|
||||
}
|
||||
|
||||
fn relocateSymbolTable(self: *MachO) !void {
|
||||
const symtab = &self.load_commands.items[self.symtab_cmd_index.?].Symtab;
|
||||
const nlocals = self.locals.items.len;
|
||||
|
||||
Loading…
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Reference in New Issue
Block a user