From 2875a7335aa5363303019dae8b837036ed547d53 Mon Sep 17 00:00:00 2001 From: Jakub Konka Date: Tue, 29 Dec 2020 22:43:07 +0100 Subject: [PATCH] macho: add Elf dwarf sections --- src/link/MachO.zig | 310 ++++++++++++- src/link/MachO/DebugSymbols.zig | 744 +++++++++++++++++++++++++++++++- src/link/MachO/commands.zig | 6 +- 3 files changed, 1035 insertions(+), 25 deletions(-) diff --git a/src/link/MachO.zig b/src/link/MachO.zig index 6c94df7286..131d06df49 100644 --- a/src/link/MachO.zig +++ b/src/link/MachO.zig @@ -11,9 +11,10 @@ const codegen = @import("../codegen.zig"); const aarch64 = @import("../codegen/aarch64.zig"); const math = std.math; const mem = std.mem; +const DW = std.dwarf; +const leb = std.leb; const trace = @import("../tracy.zig").trace; -const Type = @import("../type.zig").Type; const build_options = @import("build_options"); const Module = @import("../Module.zig"); const Compilation = @import("../Compilation.zig"); @@ -108,9 +109,6 @@ dyld_stub_binder_index: ?u16 = null, /// Table of symbol names aka the string table. string_table: std.ArrayListUnmanaged(u8) = .{}, -/// Table of debug symbol names aka the debug string table. -debug_string_table: std.ArrayListUnmanaged(u8) = .{}, - /// Table of trampolines to the actual symbols in __text section. offset_table: std.ArrayListUnmanaged(u64) = .{}, @@ -207,12 +205,25 @@ pub const TextBlock = struct { prev: ?*TextBlock, next: ?*TextBlock, + /// Previous/next linked list pointers. This value is `next ^ prev`. + /// This is the linked list node for this Decl's corresponding .debug_info tag. + dbg_info_prev: ?*TextBlock, + dbg_info_next: ?*TextBlock, + /// Offset into .debug_info pointing to the tag for this Decl. + dbg_info_off: u32, + /// Size of the .debug_info tag for this Decl, not including padding. + dbg_info_len: u32, + pub const empty = TextBlock{ .local_sym_index = 0, .offset_table_index = undefined, .size = 0, .prev = null, .next = null, + .dbg_info_prev = null, + .dbg_info_next = null, + .dbg_info_off = undefined, + .dbg_info_len = undefined, }; /// Returns how much room there is to grow in virtual address space. @@ -248,7 +259,23 @@ pub const Export = struct { }; pub const SrcFn = struct { - pub const empty = SrcFn{}; + /// Offset from the beginning of the Debug Line Program header that contains this function. + off: u32, + /// Size of the line number program component belonging to this function, not + /// including padding. + len: u32, + + /// Points to the previous and next neighbors, based on the offset from .debug_line. + /// This can be used to find, for example, the capacity of this `SrcFn`. + prev: ?*SrcFn, + next: ?*SrcFn, + + pub const empty: SrcFn = .{ + .off = 0, + .len = 0, + .prev = null, + .next = null, + }; }; pub fn openPath(allocator: *Allocator, sub_path: []const u8, options: link.Options) !*MachO { @@ -361,7 +388,7 @@ pub fn flushModule(self: *MachO, comp: *Compilation) !void { if (self.d_sym) |*ds| { // Flush debug symbols bundle. - try ds.flush(self.base.allocator); + try ds.flushModule(self.base.allocator, self.base.options); } if (target.cpu.arch == .aarch64) { @@ -983,7 +1010,6 @@ pub fn deinit(self: *MachO) void { self.text_block_free_list.deinit(self.base.allocator); self.offset_table.deinit(self.base.allocator); self.offset_table_free_list.deinit(self.base.allocator); - self.debug_string_table.deinit(self.base.allocator); self.string_table.deinit(self.base.allocator); self.undef_symbols.deinit(self.base.allocator); self.global_symbols.deinit(self.base.allocator); @@ -1091,8 +1117,126 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void { var code_buffer = std.ArrayList(u8).init(self.base.allocator); defer code_buffer.deinit(); + var dbg_line_buffer = std.ArrayList(u8).init(self.base.allocator); + defer dbg_line_buffer.deinit(); + + var dbg_info_buffer = std.ArrayList(u8).init(self.base.allocator); + defer dbg_info_buffer.deinit(); + + var dbg_info_type_relocs: File.DbgInfoTypeRelocsTable = .{}; + defer { + var it = dbg_info_type_relocs.iterator(); + while (it.next()) |entry| { + entry.value.relocs.deinit(self.base.allocator); + } + dbg_info_type_relocs.deinit(self.base.allocator); + } + const typed_value = decl.typed_value.most_recent.typed_value; - const res = try codegen.generateSymbol(&self.base, decl.src(), typed_value, &code_buffer, .none); + const is_fn: bool = switch (typed_value.ty.zigTypeTag()) { + .Fn => true, + else => false, + }; + if (is_fn) { + const zir_dumps = if (std.builtin.is_test) &[0][]const u8{} else build_options.zir_dumps; + if (zir_dumps.len != 0) { + for (zir_dumps) |fn_name| { + if (mem.eql(u8, mem.spanZ(decl.name), fn_name)) { + std.debug.print("\n{}\n", .{decl.name}); + typed_value.val.cast(Value.Payload.Function).?.func.dump(module.*); + } + } + } + + // For functions we need to add a prologue to the debug line program. + try dbg_line_buffer.ensureCapacity(26); + + const line_off: u28 = blk: { + if (decl.scope.cast(Module.Scope.Container)) |container_scope| { + const tree = container_scope.file_scope.contents.tree; + const file_ast_decls = tree.root_node.decls(); + // TODO Look into improving the performance here by adding a token-index-to-line + // lookup table. Currently this involves scanning over the source code for newlines. + const fn_proto = file_ast_decls[decl.src_index].castTag(.FnProto).?; + const block = fn_proto.getBodyNode().?.castTag(.Block).?; + const line_delta = std.zig.lineDelta(tree.source, 0, tree.token_locs[block.lbrace].start); + break :blk @intCast(u28, line_delta); + } else if (decl.scope.cast(Module.Scope.ZIRModule)) |zir_module| { + const byte_off = zir_module.contents.module.decls[decl.src_index].inst.src; + const line_delta = std.zig.lineDelta(zir_module.source.bytes, 0, byte_off); + break :blk @intCast(u28, line_delta); + } else { + unreachable; + } + }; + + dbg_line_buffer.appendSliceAssumeCapacity(&[_]u8{ + DW.LNS_extended_op, + @sizeOf(u64) + 1, + DW.LNE_set_address, + }); + // This is the "relocatable" vaddr, corresponding to `code_buffer` index `0`. + assert(DebugSymbols.dbg_line_vaddr_reloc_index == dbg_line_buffer.items.len); + dbg_line_buffer.items.len += @sizeOf(u64); + + dbg_line_buffer.appendAssumeCapacity(DW.LNS_advance_line); + // This is the "relocatable" relative line offset from the previous function's end curly + // to this function's begin curly. + assert(DebugSymbols.getRelocDbgLineOff() == dbg_line_buffer.items.len); + // Here we use a ULEB128-fixed-4 to make sure this field can be overwritten later. + leb.writeUnsignedFixed(4, dbg_line_buffer.addManyAsArrayAssumeCapacity(4), line_off); + + dbg_line_buffer.appendAssumeCapacity(DW.LNS_set_file); + assert(DebugSymbols.getRelocDbgFileIndex() == dbg_line_buffer.items.len); + // Once we support more than one source file, this will have the ability to be more + // than one possible value. + const file_index = 1; + leb.writeUnsignedFixed(4, dbg_line_buffer.addManyAsArrayAssumeCapacity(4), file_index); + + // Emit a line for the begin curly with prologue_end=false. The codegen will + // do the work of setting prologue_end=true and epilogue_begin=true. + dbg_line_buffer.appendAssumeCapacity(DW.LNS_copy); + + // .debug_info subprogram + const decl_name_with_null = decl.name[0 .. mem.lenZ(decl.name) + 1]; + try dbg_info_buffer.ensureCapacity(dbg_info_buffer.items.len + 25 + decl_name_with_null.len); + + const fn_ret_type = typed_value.ty.fnReturnType(); + const fn_ret_has_bits = fn_ret_type.hasCodeGenBits(); + if (fn_ret_has_bits) { + dbg_info_buffer.appendAssumeCapacity(DebugSymbols.abbrev_subprogram); + } else { + dbg_info_buffer.appendAssumeCapacity(DebugSymbols.abbrev_subprogram_retvoid); + } + // These get overwritten after generating the machine code. These values are + // "relocations" and have to be in this fixed place so that functions can be + // moved in virtual address space. + assert(DebugSymbols.dbg_info_low_pc_reloc_index == dbg_info_buffer.items.len); + dbg_info_buffer.items.len += @sizeOf(u64); // DW.AT_low_pc, DW.FORM_addr + assert(DebugSymbols.getRelocDbgInfoSubprogramHighPC() == dbg_info_buffer.items.len); + dbg_info_buffer.items.len += 4; // DW.AT_high_pc, DW.FORM_data4 + if (fn_ret_has_bits) { + const gop = try dbg_info_type_relocs.getOrPut(self.base.allocator, fn_ret_type); + if (!gop.found_existing) { + gop.entry.value = .{ + .off = undefined, + .relocs = .{}, + }; + } + try gop.entry.value.relocs.append(self.base.allocator, @intCast(u32, dbg_info_buffer.items.len)); + dbg_info_buffer.items.len += 4; // DW.AT_type, DW.FORM_ref4 + } + dbg_info_buffer.appendSliceAssumeCapacity(decl_name_with_null); // DW.AT_name, DW.FORM_string + } else { + // TODO implement .debug_info for global variables + } + const res = try codegen.generateSymbol(&self.base, decl.src(), typed_value, &code_buffer, .{ + .dwarf = .{ + .dbg_line = &dbg_line_buffer, + .dbg_info = &dbg_info_buffer, + .dbg_info_type_relocs = &dbg_info_type_relocs, + }, + }); const code = switch (res) { .externally_managed => |x| x, @@ -1178,12 +1322,160 @@ pub fn updateDecl(self: *MachO, module: *Module, decl: *Module.Decl) !void { const file_offset = text_section.offset + section_offset; try self.base.file.?.pwriteAll(code, file_offset); + const text_block = &decl.link.macho; + // If the Decl is a function, we need to update the __debug_line program. + if (is_fn) { + // Perform the relocations based on vaddr. + { + const ptr = dbg_line_buffer.items[DebugSymbols.dbg_line_vaddr_reloc_index..][0..8]; + mem.writeIntLittle(u64, ptr, symbol.n_value); + } + { + const ptr = dbg_info_buffer.items[DebugSymbols.dbg_info_low_pc_reloc_index..][0..8]; + mem.writeIntLittle(u64, ptr, symbol.n_value); + } + { + const ptr = dbg_info_buffer.items[DebugSymbols.getRelocDbgInfoSubprogramHighPC()..][0..4]; + mem.writeIntLittle(u32, ptr, @intCast(u32, text_block.size)); + } + + try dbg_line_buffer.appendSlice(&[_]u8{ DW.LNS_extended_op, 1, DW.LNE_end_sequence }); + + // Now we have the full contents and may allocate a region to store it. + + // This logic is nearly identical to the logic below in `updateDeclDebugInfo` for + // `TextBlock` and the .debug_info. If you are editing this logic, you + // probably need to edit that logic too. + + const dwarf_segment = &self.d_sym.?.load_commands.items[self.d_sym.?.dwarf_segment_cmd_index.?].Segment; + const debug_line_sect = &dwarf_segment.sections.items[self.d_sym.?.debug_line_section_index.?]; + const src_fn = &decl.fn_link.macho; + src_fn.len = @intCast(u32, dbg_line_buffer.items.len); + if (self.d_sym.?.dbg_line_fn_last) |last| { + if (src_fn.next) |next| { + // Update existing function - non-last item. + if (src_fn.off + src_fn.len + DebugSymbols.min_nop_size > next.off) { + // It grew too big, so we move it to a new location. + if (src_fn.prev) |prev| { + _ = self.d_sym.?.dbg_line_fn_free_list.put(self.base.allocator, prev, {}) catch {}; + prev.next = src_fn.next; + } + next.prev = src_fn.prev; + src_fn.next = null; + // Populate where it used to be with NOPs. + const file_pos = debug_line_sect.offset + src_fn.off; + try self.d_sym.?.pwriteDbgLineNops(0, &[0]u8{}, src_fn.len, file_pos); + // TODO Look at the free list before appending at the end. + src_fn.prev = last; + last.next = src_fn; + self.d_sym.?.dbg_line_fn_last = src_fn; + + src_fn.off = last.off + (last.len * alloc_num / alloc_den); + } + } else if (src_fn.prev == null) { + // Append new function. + // TODO Look at the free list before appending at the end. + src_fn.prev = last; + last.next = src_fn; + self.d_sym.?.dbg_line_fn_last = src_fn; + + src_fn.off = last.off + (last.len * alloc_num / alloc_den); + } + } else { + // This is the first function of the Line Number Program. + self.d_sym.?.dbg_line_fn_first = src_fn; + self.d_sym.?.dbg_line_fn_last = src_fn; + + src_fn.off = self.d_sym.?.dbgLineNeededHeaderBytes(module) * alloc_num / alloc_den; + } + + const last_src_fn = self.d_sym.?.dbg_line_fn_last.?; + const needed_size = last_src_fn.off + last_src_fn.len; + if (needed_size != debug_line_sect.size) { + if (needed_size > dwarf_segment.allocatedSize(debug_line_sect.offset)) { + const new_offset = dwarf_segment.findFreeSpace(needed_size, 1, null); + const existing_size = last_src_fn.off; + + assert(dwarf_segment.inner.fileoff + dwarf_segment.inner.filesize >= new_offset + needed_size); + + log.debug("moving __zdebug_line section: {} bytes from 0x{x} to 0x{x}", .{ + existing_size, + debug_line_sect.offset, + new_offset, + }); + + const amt = try self.d_sym.?.file.copyRangeAll(debug_line_sect.offset, self.d_sym.?.file, new_offset, existing_size); + if (amt != existing_size) return error.InputOutput; + debug_line_sect.offset = @intCast(u32, new_offset); + debug_line_sect.addr = dwarf_segment.inner.vmaddr + new_offset - dwarf_segment.inner.fileoff; + } + debug_line_sect.size = needed_size; + self.d_sym.?.load_commands_dirty = true; // TODO look into making only the one section dirty + self.d_sym.?.debug_line_header_dirty = true; + } + const prev_padding_size: u32 = if (src_fn.prev) |prev| src_fn.off - (prev.off + prev.len) else 0; + const next_padding_size: u32 = if (src_fn.next) |next| next.off - (src_fn.off + src_fn.len) else 0; + + // We only have support for one compilation unit so far, so the offsets are directly + // from the .debug_line section. + const file_pos = debug_line_sect.offset + src_fn.off; + try self.d_sym.?.pwriteDbgLineNops(prev_padding_size, dbg_line_buffer.items, next_padding_size, file_pos); + + // .debug_info - End the TAG_subprogram children. + try dbg_info_buffer.append(0); + } + + // Now we emit the .debug_info types of the Decl. These will count towards the size of + // the buffer, so we have to do it before computing the offset, and we can't perform the actual + // relocations yet. + var it = dbg_info_type_relocs.iterator(); + while (it.next()) |entry| { + entry.value.off = @intCast(u32, dbg_info_buffer.items.len); + try self.d_sym.?.addDbgInfoType(entry.key, &dbg_info_buffer, self.base.options.target); + } + + try self.d_sym.?.updateDeclDebugInfoAllocation(self.base.allocator, text_block, @intCast(u32, dbg_info_buffer.items.len)); + + // Now that we have the offset assigned we can finally perform type relocations. + it = dbg_info_type_relocs.iterator(); + while (it.next()) |entry| { + for (entry.value.relocs.items) |off| { + mem.writeIntLittle( + u32, + dbg_info_buffer.items[off..][0..4], + text_block.dbg_info_off + entry.value.off, + ); + } + } + + try self.d_sym.?.writeDeclDebugInfo(text_block, dbg_info_buffer.items); + // Since we updated the vaddr and the size, each corresponding export symbol also needs to be updated. const decl_exports = module.decl_exports.get(decl) orelse &[0]*Module.Export{}; try self.updateDeclExports(module, decl, decl_exports); } -pub fn updateDeclLineNumber(self: *MachO, module: *Module, decl: *const Module.Decl) !void {} +pub fn updateDeclLineNumber(self: *MachO, module: *Module, decl: *const Module.Decl) !void { + const tracy = trace(@src()); + defer tracy.end(); + + const container_scope = decl.scope.cast(Module.Scope.Container).?; + const tree = container_scope.file_scope.contents.tree; + const file_ast_decls = tree.root_node.decls(); + // TODO Look into improving the performance here by adding a token-index-to-line + // lookup table. Currently this involves scanning over the source code for newlines. + const fn_proto = file_ast_decls[decl.src_index].castTag(.FnProto).?; + const block = fn_proto.getBodyNode().?.castTag(.Block).?; + const line_delta = std.zig.lineDelta(tree.source, 0, tree.token_locs[block.lbrace].start); + const casted_line_off = @intCast(u28, line_delta); + + const dwarf_segment = &self.d_sym.?.load_commands.items[self.d_sym.?.dwarf_segment_cmd_index.?].Segment; + const shdr = &dwarf_segment.sections.items[self.d_sym.?.debug_line_section_index.?]; + const file_pos = shdr.offset + decl.fn_link.macho.off + DebugSymbols.getRelocDbgLineOff(); + var data: [4]u8 = undefined; + leb.writeUnsignedFixed(4, &data, casted_line_off); + try self.d_sym.?.file.pwriteAll(&data, file_pos); +} pub fn updateDeclExports( self: *MachO, diff --git a/src/link/MachO/DebugSymbols.zig b/src/link/MachO/DebugSymbols.zig index c08c1b9bec..349ecd9d30 100644 --- a/src/link/MachO/DebugSymbols.zig +++ b/src/link/MachO/DebugSymbols.zig @@ -11,7 +11,12 @@ const leb = std.leb; const Allocator = mem.Allocator; const trace = @import("../../tracy.zig").trace; +const Module = @import("../../Module.zig"); +const Type = @import("../../type.zig").Type; +const link = @import("../../link.zig"); const MachO = @import("../MachO.zig"); +const SrcFn = MachO.SrcFn; +const TextBlock = MachO.TextBlock; const satMul = MachO.satMul; const alloc_num = MachO.alloc_num; const alloc_den = MachO.alloc_den; @@ -58,6 +63,21 @@ debug_line_section_index: ?u16 = null, debug_abbrev_table_offset: ?u64 = null, +/// A list of `SrcFn` whose Line Number Programs have surplus capacity. +/// This is the same concept as `text_block_free_list`; see those doc comments. +dbg_line_fn_free_list: std.AutoHashMapUnmanaged(*SrcFn, void) = .{}, +dbg_line_fn_first: ?*SrcFn = null, +dbg_line_fn_last: ?*SrcFn = null, + +/// A list of `TextBlock` whose corresponding .debug_info tags have surplus capacity. +/// This is the same concept as `text_block_free_list`; see those doc comments. +dbg_info_decl_free_list: std.AutoHashMapUnmanaged(*TextBlock, void) = .{}, +dbg_info_decl_first: ?*TextBlock = null, +dbg_info_decl_last: ?*TextBlock = null, + +/// Table of debug symbol names aka the debug string table. +debug_string_table: std.ArrayListUnmanaged(u8) = .{}, + header_dirty: bool = false, load_commands_dirty: bool = false, string_table_dirty: bool = false, @@ -67,6 +87,13 @@ debug_aranges_section_dirty: bool = false, debug_info_header_dirty: bool = false, debug_line_header_dirty: bool = false, +pub const abbrev_compile_unit = 1; +pub const abbrev_subprogram = 2; +pub const abbrev_subprogram_retvoid = 3; +pub const abbrev_base_type = 4; +pub const abbrev_pad1 = 5; +pub const abbrev_parameter = 6; + /// You must call this function *after* `MachO.populateMissingMetadata()` /// has been called to get a viable debug symbols output. pub fn populateMissingMetadata(self: *DebugSymbols, allocator: *Allocator) !void { @@ -186,20 +213,14 @@ pub fn populateMissingMetadata(self: *DebugSymbols, allocator: *Allocator) !void if (self.debug_str_section_index == null) { const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; self.debug_str_section_index = @intCast(u16, dwarf_segment.sections.items.len); - assert(self.base.debug_string_table.items.len == 0); - - const file_size_hint = 200; - const p_align = 1; - const off = dwarf_segment.findFreeSpace(file_size_hint, p_align, null); - - log.debug("found dSym __debug_strtab free space 0x{x} to 0x{x}", .{ off, off + file_size_hint }); + assert(self.debug_string_table.items.len == 0); try dwarf_segment.addSection(allocator, .{ .sectname = makeStaticString("__debug_str"), .segname = makeStaticString("__DWARF"), - .addr = dwarf_segment.inner.vmaddr + off, - .size = @intCast(u32, self.base.debug_string_table.items.len), - .offset = @intCast(u32, off), + .addr = dwarf_segment.inner.vmaddr, + .size = @intCast(u32, self.debug_string_table.items.len), + .offset = @intCast(u32, dwarf_segment.inner.fileoff), .@"align" = 1, .reloff = 0, .nreloc = 0, @@ -225,7 +246,7 @@ pub fn populateMissingMetadata(self: *DebugSymbols, allocator: *Allocator) !void try dwarf_segment.addSection(allocator, .{ .sectname = makeStaticString("__debug_info"), .segname = makeStaticString("__DWARF"), - .addr = dwarf_segment.inner.vmaddr + off, + .addr = dwarf_segment.inner.vmaddr + off - dwarf_segment.inner.fileoff, .size = file_size_hint, .offset = @intCast(u32, off), .@"align" = p_align, @@ -253,7 +274,7 @@ pub fn populateMissingMetadata(self: *DebugSymbols, allocator: *Allocator) !void try dwarf_segment.addSection(allocator, .{ .sectname = makeStaticString("__debug_abbrev"), .segname = makeStaticString("__DWARF"), - .addr = dwarf_segment.inner.vmaddr + off, + .addr = dwarf_segment.inner.vmaddr + off - dwarf_segment.inner.fileoff, .size = file_size_hint, .offset = @intCast(u32, off), .@"align" = p_align, @@ -281,7 +302,7 @@ pub fn populateMissingMetadata(self: *DebugSymbols, allocator: *Allocator) !void try dwarf_segment.addSection(allocator, .{ .sectname = makeStaticString("__debug_aranges"), .segname = makeStaticString("__DWARF"), - .addr = dwarf_segment.inner.vmaddr + off, + .addr = dwarf_segment.inner.vmaddr + off - dwarf_segment.inner.fileoff, .size = file_size_hint, .offset = @intCast(u32, off), .@"align" = p_align, @@ -309,7 +330,7 @@ pub fn populateMissingMetadata(self: *DebugSymbols, allocator: *Allocator) !void try dwarf_segment.addSection(allocator, .{ .sectname = makeStaticString("__debug_line"), .segname = makeStaticString("__DWARF"), - .addr = dwarf_segment.inner.vmaddr + off, + .addr = dwarf_segment.inner.vmaddr + off - dwarf_segment.inner.fileoff, .size = file_size_hint, .offset = @intCast(u32, off), .@"align" = p_align, @@ -326,17 +347,346 @@ pub fn populateMissingMetadata(self: *DebugSymbols, allocator: *Allocator) !void } } -pub fn flush(self: *DebugSymbols, allocator: *Allocator) !void { +pub fn flushModule(self: *DebugSymbols, allocator: *Allocator, options: link.Options) !void { + // TODO This linker code currently assumes there is only 1 compilation unit and it corresponds to the + // Zig source code. + const module = options.module orelse return error.LinkingWithoutZigSourceUnimplemented; + const init_len_size: usize = 12; + + if (self.debug_abbrev_section_dirty) { + const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; + const debug_abbrev_sect = &dwarf_segment.sections.items[self.debug_abbrev_section_index.?]; + + // These are LEB encoded but since the values are all less than 127 + // we can simply append these bytes. + const abbrev_buf = [_]u8{ + abbrev_compile_unit, DW.TAG_compile_unit, DW.CHILDREN_yes, // header + DW.AT_stmt_list, DW.FORM_sec_offset, DW.AT_low_pc, + DW.FORM_addr, DW.AT_high_pc, DW.FORM_addr, + DW.AT_name, DW.FORM_strp, DW.AT_comp_dir, + DW.FORM_strp, DW.AT_producer, DW.FORM_strp, + DW.AT_language, DW.FORM_data2, 0, + 0, // table sentinel + abbrev_subprogram, + DW.TAG_subprogram, + DW.CHILDREN_yes, // header + DW.AT_low_pc, + DW.FORM_addr, + DW.AT_high_pc, + DW.FORM_data4, + DW.AT_type, + DW.FORM_ref4, + DW.AT_name, + DW.FORM_string, + 0, 0, // table sentinel + abbrev_subprogram_retvoid, + DW.TAG_subprogram, DW.CHILDREN_yes, // header + DW.AT_low_pc, DW.FORM_addr, + DW.AT_high_pc, DW.FORM_data4, + DW.AT_name, DW.FORM_string, + 0, + 0, // table sentinel + abbrev_base_type, + DW.TAG_base_type, + DW.CHILDREN_no, // header + DW.AT_encoding, + DW.FORM_data1, + DW.AT_byte_size, + DW.FORM_data1, + DW.AT_name, + DW.FORM_string, 0, 0, // table sentinel + abbrev_pad1, DW.TAG_unspecified_type, DW.CHILDREN_no, // header + 0, 0, // table sentinel + abbrev_parameter, + DW.TAG_formal_parameter, DW.CHILDREN_no, // header + DW.AT_location, DW.FORM_exprloc, + DW.AT_type, DW.FORM_ref4, + DW.AT_name, DW.FORM_string, + 0, + 0, // table sentinel + 0, + 0, + 0, // section sentinel + }; + + const needed_size = abbrev_buf.len; + const allocated_size = dwarf_segment.allocatedSize(debug_abbrev_sect.offset); + if (needed_size > allocated_size) { + debug_abbrev_sect.size = 0; // free the space + debug_abbrev_sect.offset = @intCast(u32, dwarf_segment.findFreeSpace(needed_size, 1, null)); + } + debug_abbrev_sect.size = needed_size; + log.debug("__debug_abbrev start=0x{x} end=0x{x}", .{ + debug_abbrev_sect.offset, + debug_abbrev_sect.offset + needed_size, + }); + + const abbrev_offset = 0; + self.debug_abbrev_table_offset = abbrev_offset; + try self.file.pwriteAll(&abbrev_buf, debug_abbrev_sect.offset + abbrev_offset); + self.load_commands_dirty = true; + self.debug_abbrev_section_dirty = false; + } + + if (self.debug_info_header_dirty) debug_info: { + // If this value is null it means there is an error in the module; + // leave debug_info_header_dirty=true. + const first_dbg_info_decl = self.dbg_info_decl_first orelse break :debug_info; + const last_dbg_info_decl = self.dbg_info_decl_last.?; + const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; + const debug_info_sect = &dwarf_segment.sections.items[self.debug_info_section_index.?]; + + var di_buf = std.ArrayList(u8).init(allocator); + defer di_buf.deinit(); + + // We have a function to compute the upper bound size, because it's needed + // for determining where to put the offset of the first `LinkBlock`. + try di_buf.ensureCapacity(self.dbgInfoNeededHeaderBytes()); + + // initial length - length of the .debug_info contribution for this compilation unit, + // not including the initial length itself. + // We have to come back and write it later after we know the size. + const after_init_len = di_buf.items.len + init_len_size; + // +1 for the final 0 that ends the compilation unit children. + const dbg_info_end = last_dbg_info_decl.dbg_info_off + last_dbg_info_decl.dbg_info_len + 1; + const init_len = dbg_info_end - after_init_len; + di_buf.appendNTimesAssumeCapacity(0xff, 4); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), init_len); + mem.writeIntLittle(u16, di_buf.addManyAsArrayAssumeCapacity(2), 4); // DWARF version + const abbrev_offset = self.debug_abbrev_table_offset.?; + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), abbrev_offset); + di_buf.appendAssumeCapacity(8); // address size + // Write the form for the compile unit, which must match the abbrev table above. + const name_strp = try self.makeDebugString(allocator, module.root_pkg.root_src_path); + const comp_dir_strp = try self.makeDebugString(allocator, module.root_pkg.root_src_directory.path orelse "."); + const producer_strp = try self.makeDebugString(allocator, link.producer_string); + // Currently only one compilation unit is supported, so the address range is simply + // identical to the main program header virtual address and memory size. + const text_segment = self.load_commands.items[self.text_segment_cmd_index.?].Segment; + const text_section = text_segment.sections.items[self.text_section_index.?]; + const low_pc = text_section.addr; + const high_pc = text_section.addr + text_section.size; + + di_buf.appendAssumeCapacity(abbrev_compile_unit); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), 0); // DW.AT_stmt_list, DW.FORM_sec_offset + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), low_pc); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), high_pc); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), name_strp); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), comp_dir_strp); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), producer_strp); + // We are still waiting on dwarf-std.org to assign DW_LANG_Zig a number: + // http://dwarfstd.org/ShowIssue.php?issue=171115.1 + // Until then we say it is C99. + mem.writeIntLittle(u16, di_buf.addManyAsArrayAssumeCapacity(2), DW.LANG_C99); + + if (di_buf.items.len > first_dbg_info_decl.dbg_info_off) { + // Move the first N decls to the end to make more padding for the header. + @panic("TODO: handle __zdebug_info header exceeding its padding"); + } + const jmp_amt = first_dbg_info_decl.dbg_info_off - di_buf.items.len; + try self.pwriteDbgInfoNops(0, di_buf.items, jmp_amt, false, debug_info_sect.offset); + self.debug_info_header_dirty = false; + } + + if (self.debug_aranges_section_dirty) { + const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; + const debug_aranges_sect = &dwarf_segment.sections.items[self.debug_aranges_section_index.?]; + const debug_info_sect = dwarf_segment.sections.items[self.debug_info_section_index.?]; + + var di_buf = std.ArrayList(u8).init(allocator); + defer di_buf.deinit(); + + // Enough for all the data without resizing. When support for more compilation units + // is added, the size of this section will become more variable. + try di_buf.ensureCapacity(100); + + // initial length - length of the .debug_aranges contribution for this compilation unit, + // not including the initial length itself. + // We have to come back and write it later after we know the size. + const init_len_index = di_buf.items.len; + di_buf.items.len += init_len_size; + const after_init_len = di_buf.items.len; + mem.writeIntLittle(u16, di_buf.addManyAsArrayAssumeCapacity(2), 2); // version + // When more than one compilation unit is supported, this will be the offset to it. + // For now it is always at offset 0 in .debug_info. + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), debug_info_sect.addr); // __debug_info offset + di_buf.appendAssumeCapacity(@sizeOf(u64)); // address_size + di_buf.appendAssumeCapacity(0); // segment_selector_size + + const end_header_offset = di_buf.items.len; + const begin_entries_offset = mem.alignForward(end_header_offset, @sizeOf(u64) * 2); + di_buf.appendNTimesAssumeCapacity(0, begin_entries_offset - end_header_offset); + + // Currently only one compilation unit is supported, so the address range is simply + // identical to the main program header virtual address and memory size. + const text_segment = self.load_commands.items[self.text_segment_cmd_index.?].Segment; + const text_section = text_segment.sections.items[self.text_section_index.?]; + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), text_section.addr); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), text_section.size); + + // Sentinel. + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), 0); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), 0); + + // Go back and populate the initial length. + const init_len = di_buf.items.len - after_init_len; + // initial length - length of the .debug_aranges contribution for this compilation unit, + // not including the initial length itself. + di_buf.items[init_len_index..][0..4].* = [_]u8{ 0xff, 0xff, 0xff, 0xff }; + mem.writeIntLittle(u64, di_buf.items[init_len_index + 4 ..][0..8], init_len); + + const needed_size = di_buf.items.len; + const allocated_size = dwarf_segment.allocatedSize(debug_aranges_sect.offset); + if (needed_size > allocated_size) { + debug_aranges_sect.size = 0; // free the space + const offset = dwarf_segment.findFreeSpace(needed_size, 16, null); + debug_aranges_sect.offset = @intCast(u32, offset); + debug_aranges_sect.addr = dwarf_segment.inner.vmaddr + offset - dwarf_segment.inner.fileoff; + } + debug_aranges_sect.size = needed_size; + log.debug("__debug_aranges start=0x{x} end=0x{x}", .{ + debug_aranges_sect.offset, + debug_aranges_sect.offset + needed_size, + }); + + try self.file.pwriteAll(di_buf.items, debug_aranges_sect.offset); + self.load_commands_dirty = true; + self.debug_aranges_section_dirty = false; + } + if (self.debug_line_header_dirty) debug_line: { + if (self.dbg_line_fn_first == null) { + break :debug_line; // Error in module; leave debug_line_header_dirty=true. + } + const dbg_line_prg_off = self.getDebugLineProgramOff(); + const dbg_line_prg_end = self.getDebugLineProgramEnd(); + assert(dbg_line_prg_end != 0); + + const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; + const debug_line_sect = &dwarf_segment.sections.items[self.debug_line_section_index.?]; + + var di_buf = std.ArrayList(u8).init(allocator); + defer di_buf.deinit(); + + // The size of this header is variable, depending on the number of directories, + // files, and padding. We have a function to compute the upper bound size, however, + // because it's needed for determining where to put the offset of the first `SrcFn`. + try di_buf.ensureCapacity(self.dbgLineNeededHeaderBytes(module)); + + // initial length - length of the .debug_line contribution for this compilation unit, + // not including the initial length itself. + const after_init_len = di_buf.items.len + init_len_size; + const init_len = dbg_line_prg_end - after_init_len; + di_buf.appendNTimesAssumeCapacity(0xff, 4); + mem.writeIntLittle(u64, di_buf.addManyAsArrayAssumeCapacity(8), init_len); + mem.writeIntLittle(u16, di_buf.addManyAsArrayAssumeCapacity(2), 4); // version + + // Empirically, debug info consumers do not respect this field, or otherwise + // consider it to be an error when it does not point exactly to the end of the header. + // Therefore we rely on the NOP jump at the beginning of the Line Number Program for + // padding rather than this field. + const before_header_len = di_buf.items.len; + di_buf.items.len += @sizeOf(u64); // We will come back and write this. + const after_header_len = di_buf.items.len; + + const opcode_base = DW.LNS_set_isa + 1; + di_buf.appendSliceAssumeCapacity(&[_]u8{ + 1, // minimum_instruction_length + 1, // maximum_operations_per_instruction + 1, // default_is_stmt + 1, // line_base (signed) + 1, // line_range + opcode_base, + + // Standard opcode lengths. The number of items here is based on `opcode_base`. + // The value is the number of LEB128 operands the instruction takes. + 0, // `DW.LNS_copy` + 1, // `DW.LNS_advance_pc` + 1, // `DW.LNS_advance_line` + 1, // `DW.LNS_set_file` + 1, // `DW.LNS_set_column` + 0, // `DW.LNS_negate_stmt` + 0, // `DW.LNS_set_basic_block` + 0, // `DW.LNS_const_add_pc` + 1, // `DW.LNS_fixed_advance_pc` + 0, // `DW.LNS_set_prologue_end` + 0, // `DW.LNS_set_epilogue_begin` + 1, // `DW.LNS_set_isa` + 0, // include_directories (none except the compilation unit cwd) + }); + // file_names[0] + di_buf.appendSliceAssumeCapacity(module.root_pkg.root_src_path); // relative path name + di_buf.appendSliceAssumeCapacity(&[_]u8{ + 0, // null byte for the relative path name + 0, // directory_index + 0, // mtime (TODO supply this) + 0, // file size bytes (TODO supply this) + 0, // file_names sentinel + }); + + const header_len = di_buf.items.len - after_header_len; + mem.writeIntLittle(u64, di_buf.items[before_header_len..][0..8], header_len); + + // We use NOPs because consumers empirically do not respect the header length field. + if (di_buf.items.len > dbg_line_prg_off) { + // Move the first N files to the end to make more padding for the header. + @panic("TODO: handle __debug_line header exceeding its padding"); + } + const jmp_amt = dbg_line_prg_off - di_buf.items.len; + try self.pwriteDbgLineNops(0, di_buf.items, jmp_amt, debug_line_sect.offset); + self.debug_line_header_dirty = false; + } + { + const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; + const debug_strtab_sect = &dwarf_segment.sections.items[self.debug_str_section_index.?]; + if (self.debug_string_table_dirty or self.debug_string_table.items.len != debug_strtab_sect.size) { + const allocated_size = dwarf_segment.allocatedSize(debug_strtab_sect.offset); + const needed_size = self.debug_string_table.items.len; + + if (needed_size > allocated_size) { + debug_strtab_sect.size = 0; // free the space + const new_offset = dwarf_segment.findFreeSpace(needed_size, 1, null); + debug_strtab_sect.addr = dwarf_segment.inner.vmaddr + new_offset - dwarf_segment.inner.fileoff; + debug_strtab_sect.offset = @intCast(u32, new_offset); + } + debug_strtab_sect.size = @intCast(u32, needed_size); + + log.debug("__debug_strtab start=0x{x} end=0x{x}", .{ + debug_strtab_sect.offset, + debug_strtab_sect.offset + needed_size, + }); + + try self.file.pwriteAll(self.debug_string_table.items, debug_strtab_sect.offset); + self.load_commands_dirty = true; + self.debug_string_table_dirty = false; + } + } + try self.writeStringTable(); + + { + const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; + var file_size: u64 = 0; + for (dwarf_segment.sections.items) |sect| { + file_size += sect.size; + } + dwarf_segment.inner.filesize = file_size; + } + try self.writeLoadCommands(allocator); try self.writeHeader(); assert(!self.header_dirty); assert(!self.load_commands_dirty); assert(!self.string_table_dirty); + assert(!self.debug_abbrev_section_dirty); + assert(!self.debug_aranges_section_dirty); + assert(!self.debug_string_table_dirty); } pub fn deinit(self: *DebugSymbols, allocator: *Allocator) void { + self.dbg_info_decl_free_list.deinit(allocator); + self.dbg_line_fn_free_list.deinit(allocator); + self.debug_string_table.deinit(allocator); for (self.load_commands.items) |*lc| { lc.deinit(allocator); } @@ -535,3 +885,367 @@ pub fn writeStringTable(self: *DebugSymbols) !void { self.load_commands_dirty = true; self.string_table_dirty = false; } + +/// Asserts the type has codegen bits. +pub fn addDbgInfoType( + self: *DebugSymbols, + ty: Type, + dbg_info_buffer: *std.ArrayList(u8), + target: std.Target, +) !void { + switch (ty.zigTypeTag()) { + .Void => unreachable, + .NoReturn => unreachable, + .Bool => { + try dbg_info_buffer.appendSlice(&[_]u8{ + abbrev_base_type, + DW.ATE_boolean, // DW.AT_encoding , DW.FORM_data1 + 1, // DW.AT_byte_size, DW.FORM_data1 + 'b', + 'o', + 'o', + 'l', + 0, // DW.AT_name, DW.FORM_string + }); + }, + .Int => { + const info = ty.intInfo(target); + try dbg_info_buffer.ensureCapacity(dbg_info_buffer.items.len + 12); + dbg_info_buffer.appendAssumeCapacity(abbrev_base_type); + // DW.AT_encoding, DW.FORM_data1 + dbg_info_buffer.appendAssumeCapacity(switch (info.signedness) { + .signed => DW.ATE_signed, + .unsigned => DW.ATE_unsigned, + }); + // DW.AT_byte_size, DW.FORM_data1 + dbg_info_buffer.appendAssumeCapacity(@intCast(u8, ty.abiSize(target))); + // DW.AT_name, DW.FORM_string + try dbg_info_buffer.writer().print("{}\x00", .{ty}); + }, + else => { + std.log.scoped(.compiler).err("TODO implement .debug_info for type '{}'", .{ty}); + try dbg_info_buffer.append(abbrev_pad1); + }, + } +} + +pub fn updateDeclDebugInfoAllocation( + self: *DebugSymbols, + allocator: *Allocator, + text_block: *TextBlock, + len: u32, +) !void { + const tracy = trace(@src()); + defer tracy.end(); + + // This logic is nearly identical to the logic above in `updateDecl` for + // `SrcFn` and the line number programs. If you are editing this logic, you + // probably need to edit that logic too. + + const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; + const debug_info_sect = &dwarf_segment.sections.items[self.debug_info_section_index.?]; + text_block.dbg_info_len = len; + if (self.dbg_info_decl_last) |last| { + if (text_block.dbg_info_next) |next| { + // Update existing Decl - non-last item. + if (text_block.dbg_info_off + text_block.dbg_info_len + min_nop_size > next.dbg_info_off) { + // It grew too big, so we move it to a new location. + if (text_block.dbg_info_prev) |prev| { + _ = self.dbg_info_decl_free_list.put(allocator, prev, {}) catch {}; + prev.dbg_info_next = text_block.dbg_info_next; + } + next.dbg_info_prev = text_block.dbg_info_prev; + text_block.dbg_info_next = null; + // Populate where it used to be with NOPs. + const file_pos = debug_info_sect.offset + text_block.dbg_info_off; + try self.pwriteDbgInfoNops(0, &[0]u8{}, text_block.dbg_info_len, false, file_pos); + // TODO Look at the free list before appending at the end. + text_block.dbg_info_prev = last; + last.dbg_info_next = text_block; + self.dbg_info_decl_last = text_block; + + text_block.dbg_info_off = last.dbg_info_off + (last.dbg_info_len * alloc_num / alloc_den); + } + } else if (text_block.dbg_info_prev == null) { + // Append new Decl. + // TODO Look at the free list before appending at the end. + text_block.dbg_info_prev = last; + last.dbg_info_next = text_block; + self.dbg_info_decl_last = text_block; + + text_block.dbg_info_off = last.dbg_info_off + (last.dbg_info_len * alloc_num / alloc_den); + } + } else { + // This is the first Decl of the .debug_info + self.dbg_info_decl_first = text_block; + self.dbg_info_decl_last = text_block; + + text_block.dbg_info_off = self.dbgInfoNeededHeaderBytes() * alloc_num / alloc_den; + } +} + +pub fn writeDeclDebugInfo(self: *DebugSymbols, text_block: *TextBlock, dbg_info_buf: []const u8) !void { + const tracy = trace(@src()); + defer tracy.end(); + + // This logic is nearly identical to the logic above in `updateDecl` for + // `SrcFn` and the line number programs. If you are editing this logic, you + // probably need to edit that logic too. + + const dwarf_segment = &self.load_commands.items[self.dwarf_segment_cmd_index.?].Segment; + const debug_info_sect = &dwarf_segment.sections.items[self.debug_info_section_index.?]; + + const last_decl = self.dbg_info_decl_last.?; + // +1 for a trailing zero to end the children of the decl tag. + const needed_size = last_decl.dbg_info_off + last_decl.dbg_info_len + 1; + if (needed_size != debug_info_sect.size) { + if (needed_size > dwarf_segment.allocatedSize(debug_info_sect.offset)) { + const new_offset = dwarf_segment.findFreeSpace(needed_size, 1, null); + const existing_size = last_decl.dbg_info_off; + + // TODO + assert(dwarf_segment.inner.fileoff + dwarf_segment.inner.filesize >= new_offset + needed_size); + + log.debug("moving _debug_info section: {} bytes from 0x{x} to 0x{x}", .{ + existing_size, + debug_info_sect.offset, + new_offset, + }); + + const amt = try self.file.copyRangeAll(debug_info_sect.offset, self.file, new_offset, existing_size); + if (amt != existing_size) return error.InputOutput; + debug_info_sect.offset = @intCast(u32, new_offset); + debug_info_sect.addr = dwarf_segment.inner.vmaddr + new_offset - dwarf_segment.inner.fileoff; + } + debug_info_sect.size = needed_size; + self.load_commands_dirty = true; // TODO look into making only the one section dirty + self.debug_info_header_dirty = true; + } + const prev_padding_size: u32 = if (text_block.dbg_info_prev) |prev| + text_block.dbg_info_off - (prev.dbg_info_off + prev.dbg_info_len) + else + 0; + const next_padding_size: u32 = if (text_block.dbg_info_next) |next| + next.dbg_info_off - (text_block.dbg_info_off + text_block.dbg_info_len) + else + 0; + + // To end the children of the decl tag. + const trailing_zero = text_block.dbg_info_next == null; + + // We only have support for one compilation unit so far, so the offsets are directly + // from the .debug_info section. + const file_pos = debug_info_sect.offset + text_block.dbg_info_off; + try self.pwriteDbgInfoNops(prev_padding_size, dbg_info_buf, next_padding_size, trailing_zero, file_pos); +} + +fn getDebugLineProgramOff(self: DebugSymbols) u32 { + return self.dbg_line_fn_first.?.off; +} + +fn getDebugLineProgramEnd(self: DebugSymbols) u32 { + return self.dbg_line_fn_last.?.off + self.dbg_line_fn_last.?.len; +} + +/// TODO Improve this to use a table. +fn makeDebugString(self: *DebugSymbols, allocator: *Allocator, bytes: []const u8) !u32 { + try self.debug_string_table.ensureCapacity(allocator, self.debug_string_table.items.len + bytes.len + 1); + const result = self.debug_string_table.items.len; + self.debug_string_table.appendSliceAssumeCapacity(bytes); + self.debug_string_table.appendAssumeCapacity(0); + return @intCast(u32, result); +} + +/// The reloc offset for the virtual address of a function in its Line Number Program. +/// Size is a virtual address integer. +pub const dbg_line_vaddr_reloc_index = 3; +/// The reloc offset for the virtual address of a function in its .debug_info TAG_subprogram. +/// Size is a virtual address integer. +pub const dbg_info_low_pc_reloc_index = 1; + +/// The reloc offset for the line offset of a function from the previous function's line. +/// It's a fixed-size 4-byte ULEB128. +pub fn getRelocDbgLineOff() usize { + return dbg_line_vaddr_reloc_index + @sizeOf(u64) + 1; +} + +pub fn getRelocDbgFileIndex() usize { + return getRelocDbgLineOff() + 5; +} + +pub fn getRelocDbgInfoSubprogramHighPC() u32 { + return dbg_info_low_pc_reloc_index + @sizeOf(u64); +} + +pub fn dbgLineNeededHeaderBytes(self: DebugSymbols, module: *Module) u32 { + const directory_entry_format_count = 1; + const file_name_entry_format_count = 1; + const directory_count = 1; + const file_name_count = 1; + const root_src_dir_path_len = if (module.root_pkg.root_src_directory.path) |p| p.len else 1; // "." + return @intCast(u32, 53 + directory_entry_format_count * 2 + file_name_entry_format_count * 2 + + directory_count * 8 + file_name_count * 8 + + // These are encoded as DW.FORM_string rather than DW.FORM_strp as we would like + // because of a workaround for readelf and gdb failing to understand DWARFv5 correctly. + root_src_dir_path_len + + module.root_pkg.root_src_path.len); +} + +fn dbgInfoNeededHeaderBytes(self: DebugSymbols) u32 { + return 120; +} + +pub const min_nop_size = 2; + +/// Writes to the file a buffer, prefixed and suffixed by the specified number of +/// bytes of NOPs. Asserts each padding size is at least `min_nop_size` and total padding bytes +/// are less than 126,976 bytes (if this limit is ever reached, this function can be +/// improved to make more than one pwritev call, or the limit can be raised by a fixed +/// amount by increasing the length of `vecs`). +pub fn pwriteDbgLineNops( + self: *DebugSymbols, + prev_padding_size: usize, + buf: []const u8, + next_padding_size: usize, + offset: u64, +) !void { + const tracy = trace(@src()); + defer tracy.end(); + + const page_of_nops = [1]u8{DW.LNS_negate_stmt} ** 4096; + const three_byte_nop = [3]u8{ DW.LNS_advance_pc, 0b1000_0000, 0 }; + var vecs: [32]std.os.iovec_const = undefined; + var vec_index: usize = 0; + { + var padding_left = prev_padding_size; + if (padding_left % 2 != 0) { + vecs[vec_index] = .{ + .iov_base = &three_byte_nop, + .iov_len = three_byte_nop.len, + }; + vec_index += 1; + padding_left -= three_byte_nop.len; + } + while (padding_left > page_of_nops.len) { + vecs[vec_index] = .{ + .iov_base = &page_of_nops, + .iov_len = page_of_nops.len, + }; + vec_index += 1; + padding_left -= page_of_nops.len; + } + if (padding_left > 0) { + vecs[vec_index] = .{ + .iov_base = &page_of_nops, + .iov_len = padding_left, + }; + vec_index += 1; + } + } + + vecs[vec_index] = .{ + .iov_base = buf.ptr, + .iov_len = buf.len, + }; + vec_index += 1; + + { + var padding_left = next_padding_size; + if (padding_left % 2 != 0) { + vecs[vec_index] = .{ + .iov_base = &three_byte_nop, + .iov_len = three_byte_nop.len, + }; + vec_index += 1; + padding_left -= three_byte_nop.len; + } + while (padding_left > page_of_nops.len) { + vecs[vec_index] = .{ + .iov_base = &page_of_nops, + .iov_len = page_of_nops.len, + }; + vec_index += 1; + padding_left -= page_of_nops.len; + } + if (padding_left > 0) { + vecs[vec_index] = .{ + .iov_base = &page_of_nops, + .iov_len = padding_left, + }; + vec_index += 1; + } + } + try self.file.pwritevAll(vecs[0..vec_index], offset - prev_padding_size); +} + +/// Writes to the file a buffer, prefixed and suffixed by the specified number of +/// bytes of padding. +pub fn pwriteDbgInfoNops( + self: *DebugSymbols, + prev_padding_size: usize, + buf: []const u8, + next_padding_size: usize, + trailing_zero: bool, + offset: u64, +) !void { + const tracy = trace(@src()); + defer tracy.end(); + + const page_of_nops = [1]u8{abbrev_pad1} ** 4096; + var vecs: [32]std.os.iovec_const = undefined; + var vec_index: usize = 0; + { + var padding_left = prev_padding_size; + while (padding_left > page_of_nops.len) { + vecs[vec_index] = .{ + .iov_base = &page_of_nops, + .iov_len = page_of_nops.len, + }; + vec_index += 1; + padding_left -= page_of_nops.len; + } + if (padding_left > 0) { + vecs[vec_index] = .{ + .iov_base = &page_of_nops, + .iov_len = padding_left, + }; + vec_index += 1; + } + } + + vecs[vec_index] = .{ + .iov_base = buf.ptr, + .iov_len = buf.len, + }; + vec_index += 1; + + { + var padding_left = next_padding_size; + while (padding_left > page_of_nops.len) { + vecs[vec_index] = .{ + .iov_base = &page_of_nops, + .iov_len = page_of_nops.len, + }; + vec_index += 1; + padding_left -= page_of_nops.len; + } + if (padding_left > 0) { + vecs[vec_index] = .{ + .iov_base = &page_of_nops, + .iov_len = padding_left, + }; + vec_index += 1; + } + } + + if (trailing_zero) { + var zbuf = [1]u8{0}; + vecs[vec_index] = .{ + .iov_base = &zbuf, + .iov_len = zbuf.len, + }; + vec_index += 1; + } + + try self.file.pwritevAll(vecs[0..vec_index], offset - prev_padding_size); +} diff --git a/src/link/MachO/commands.zig b/src/link/MachO/commands.zig index d0b0e76ec2..e94ca1c8e5 100644 --- a/src/link/MachO/commands.zig +++ b/src/link/MachO/commands.zig @@ -5,6 +5,7 @@ const mem = std.mem; const meta = std.meta; const macho = std.macho; const testing = std.testing; +const assert = std.debug.assert; const Allocator = std.mem.Allocator; const MachO = @import("../MachO.zig"); @@ -202,9 +203,12 @@ pub const SegmentCommand = struct { pub fn allocatedSize(self: SegmentCommand, start: u64) u64 { assert(start > 0); + if (start == self.inner.fileoff) + return 0; var min_pos: u64 = std.math.maxInt(u64); for (self.sections.items) |section| { - if (section.offset > start and section.offset < min_pos) min_pos = section.offset; + if (section.offset <= start) continue; + if (section.offset < min_pos) min_pos = section.offset; } return min_pos - start; }