diff options
Diffstat (limited to 'src/cmd/link/internal/ld/macho.go')
| -rw-r--r-- | src/cmd/link/internal/ld/macho.go | 564 |
1 files changed, 463 insertions, 101 deletions
diff --git a/src/cmd/link/internal/ld/macho.go b/src/cmd/link/internal/ld/macho.go index f6356729a6..4605644767 100644 --- a/src/cmd/link/internal/ld/macho.go +++ b/src/cmd/link/internal/ld/macho.go @@ -6,6 +6,7 @@ package ld import ( "bytes" + "cmd/internal/codesign" "cmd/internal/objabi" "cmd/internal/sys" "cmd/link/internal/loader" @@ -17,6 +18,7 @@ import ( "os" "sort" "strings" + "unsafe" ) type MachoHdr struct { @@ -76,36 +78,38 @@ const ( ) const ( - MACHO_CPU_AMD64 = 1<<24 | 7 - MACHO_CPU_386 = 7 - MACHO_SUBCPU_X86 = 3 - MACHO_CPU_ARM = 12 - MACHO_SUBCPU_ARM = 0 - MACHO_SUBCPU_ARMV7 = 9 - MACHO_CPU_ARM64 = 1<<24 | 12 - MACHO_SUBCPU_ARM64_ALL = 0 - MACHO32SYMSIZE = 12 - MACHO64SYMSIZE = 16 - MACHO_X86_64_RELOC_UNSIGNED = 0 - MACHO_X86_64_RELOC_SIGNED = 1 - MACHO_X86_64_RELOC_BRANCH = 2 - MACHO_X86_64_RELOC_GOT_LOAD = 3 - MACHO_X86_64_RELOC_GOT = 4 - MACHO_X86_64_RELOC_SUBTRACTOR = 5 - MACHO_X86_64_RELOC_SIGNED_1 = 6 - MACHO_X86_64_RELOC_SIGNED_2 = 7 - MACHO_X86_64_RELOC_SIGNED_4 = 8 - MACHO_ARM_RELOC_VANILLA = 0 - MACHO_ARM_RELOC_PAIR = 1 - MACHO_ARM_RELOC_SECTDIFF = 2 - MACHO_ARM_RELOC_BR24 = 5 - MACHO_ARM64_RELOC_UNSIGNED = 0 - MACHO_ARM64_RELOC_BRANCH26 = 2 - MACHO_ARM64_RELOC_PAGE21 = 3 - MACHO_ARM64_RELOC_PAGEOFF12 = 4 - MACHO_ARM64_RELOC_ADDEND = 10 - MACHO_GENERIC_RELOC_VANILLA = 0 - MACHO_FAKE_GOTPCREL = 100 + MACHO_CPU_AMD64 = 1<<24 | 7 + MACHO_CPU_386 = 7 + MACHO_SUBCPU_X86 = 3 + MACHO_CPU_ARM = 12 + MACHO_SUBCPU_ARM = 0 + MACHO_SUBCPU_ARMV7 = 9 + MACHO_CPU_ARM64 = 1<<24 | 12 + MACHO_SUBCPU_ARM64_ALL = 0 + MACHO32SYMSIZE = 12 + MACHO64SYMSIZE = 16 + MACHO_X86_64_RELOC_UNSIGNED = 0 + MACHO_X86_64_RELOC_SIGNED = 1 + MACHO_X86_64_RELOC_BRANCH = 2 + MACHO_X86_64_RELOC_GOT_LOAD = 3 + MACHO_X86_64_RELOC_GOT = 4 + MACHO_X86_64_RELOC_SUBTRACTOR = 5 + MACHO_X86_64_RELOC_SIGNED_1 = 6 + MACHO_X86_64_RELOC_SIGNED_2 = 7 + MACHO_X86_64_RELOC_SIGNED_4 = 8 + MACHO_ARM_RELOC_VANILLA = 0 + MACHO_ARM_RELOC_PAIR = 1 + MACHO_ARM_RELOC_SECTDIFF = 2 + MACHO_ARM_RELOC_BR24 = 5 + MACHO_ARM64_RELOC_UNSIGNED = 0 + MACHO_ARM64_RELOC_BRANCH26 = 2 + MACHO_ARM64_RELOC_PAGE21 = 3 + MACHO_ARM64_RELOC_PAGEOFF12 = 4 + MACHO_ARM64_RELOC_GOT_LOAD_PAGE21 = 5 + MACHO_ARM64_RELOC_GOT_LOAD_PAGEOFF12 = 6 + MACHO_ARM64_RELOC_ADDEND = 10 + MACHO_GENERIC_RELOC_VANILLA = 0 + MACHO_FAKE_GOTPCREL = 100 ) const ( @@ -116,6 +120,8 @@ const ( MH_EXECUTE = 0x2 MH_NOUNDEFS = 0x1 + MH_DYLDLINK = 0x4 + MH_PIE = 0x200000 ) const ( @@ -191,6 +197,58 @@ const ( PLATFORM_BRIDGEOS MachoPlatform = 5 ) +// rebase table opcode +const ( + REBASE_TYPE_POINTER = 1 + REBASE_TYPE_TEXT_ABSOLUTE32 = 2 + REBASE_TYPE_TEXT_PCREL32 = 3 + + REBASE_OPCODE_MASK = 0xF0 + REBASE_IMMEDIATE_MASK = 0x0F + REBASE_OPCODE_DONE = 0x00 + REBASE_OPCODE_SET_TYPE_IMM = 0x10 + REBASE_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB = 0x20 + REBASE_OPCODE_ADD_ADDR_ULEB = 0x30 + REBASE_OPCODE_ADD_ADDR_IMM_SCALED = 0x40 + REBASE_OPCODE_DO_REBASE_IMM_TIMES = 0x50 + REBASE_OPCODE_DO_REBASE_ULEB_TIMES = 0x60 + REBASE_OPCODE_DO_REBASE_ADD_ADDR_ULEB = 0x70 + REBASE_OPCODE_DO_REBASE_ULEB_TIMES_SKIPPING_ULEB = 0x80 +) + +// bind table opcode +const ( + BIND_TYPE_POINTER = 1 + BIND_TYPE_TEXT_ABSOLUTE32 = 2 + BIND_TYPE_TEXT_PCREL32 = 3 + + BIND_SPECIAL_DYLIB_SELF = 0 + BIND_SPECIAL_DYLIB_MAIN_EXECUTABLE = -1 + BIND_SPECIAL_DYLIB_FLAT_LOOKUP = -2 + BIND_SPECIAL_DYLIB_WEAK_LOOKUP = -3 + + BIND_OPCODE_MASK = 0xF0 + BIND_IMMEDIATE_MASK = 0x0F + BIND_OPCODE_DONE = 0x00 + BIND_OPCODE_SET_DYLIB_ORDINAL_IMM = 0x10 + BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB = 0x20 + BIND_OPCODE_SET_DYLIB_SPECIAL_IMM = 0x30 + BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM = 0x40 + BIND_OPCODE_SET_TYPE_IMM = 0x50 + BIND_OPCODE_SET_ADDEND_SLEB = 0x60 + BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB = 0x70 + BIND_OPCODE_ADD_ADDR_ULEB = 0x80 + BIND_OPCODE_DO_BIND = 0x90 + BIND_OPCODE_DO_BIND_ADD_ADDR_ULEB = 0xA0 + BIND_OPCODE_DO_BIND_ADD_ADDR_IMM_SCALED = 0xB0 + BIND_OPCODE_DO_BIND_ULEB_TIMES_SKIPPING_ULEB = 0xC0 + BIND_OPCODE_THREADED = 0xD0 + BIND_SUBOPCODE_THREADED_SET_BIND_ORDINAL_TABLE_SIZE_ULEB = 0x00 + BIND_SUBOPCODE_THREADED_APPLY = 0x01 +) + +const machoHeaderSize64 = 8 * 4 // size of 64-bit Mach-O header + // Mach-O file writing // https://developer.apple.com/mac/library/DOCUMENTATION/DeveloperTools/Conceptual/MachORuntime/Reference/reference.html @@ -277,7 +335,7 @@ var dylib []string var linkoff int64 -func machowrite(arch *sys.Arch, out *OutBuf, linkmode LinkMode) int { +func machowrite(ctxt *Link, arch *sys.Arch, out *OutBuf, linkmode LinkMode) int { o1 := out.Offset() loadsize := 4 * 4 * ndebug @@ -306,11 +364,14 @@ func machowrite(arch *sys.Arch, out *OutBuf, linkmode LinkMode) int { } out.Write32(uint32(len(load)) + uint32(nseg) + uint32(ndebug)) out.Write32(uint32(loadsize)) + flags := uint32(0) if nkind[SymKindUndef] == 0 { - out.Write32(MH_NOUNDEFS) /* flags - no undefines */ - } else { - out.Write32(0) /* flags */ + flags |= MH_NOUNDEFS } + if ctxt.IsPIE() && linkmode == LinkInternal { + flags |= MH_PIE | MH_DYLDLINK + } + out.Write32(flags) /* flags */ if arch.PtrSize == 8 { out.Write32(0) /* reserved */ } @@ -473,6 +534,18 @@ func (ctxt *Link) domacho() { sb.SetReachable(true) sb.AddUint8(0) } + + // Do not export C symbols dynamically in plugins, as runtime C symbols like crosscall2 + // are in pclntab and end up pointing at the host binary, breaking unwinding. + // See Issue #18190. + if ctxt.BuildMode == BuildModePlugin { + for _, name := range []string{"_cgo_topofstack", "__cgo_topofstack", "_cgo_panic", "crosscall2"} { + s := ctxt.loader.Lookup(name, 0) + if s != 0 { + ctxt.loader.SetAttrCgoExportDynamic(s, false) + } + } + } } func machoadddynlib(lib string, linkmode LinkMode) { @@ -499,16 +572,7 @@ func machoadddynlib(lib string, linkmode LinkMode) { func machoshbits(ctxt *Link, mseg *MachoSeg, sect *sym.Section, segname string) { buf := "__" + strings.Replace(sect.Name[1:], ".", "_", -1) - var msect *MachoSect - if sect.Rwx&1 == 0 && segname != "__DWARF" && (ctxt.Arch.Family == sys.ARM64 || - (ctxt.Arch.Family == sys.AMD64 && ctxt.BuildMode != BuildModeExe)) { - // Darwin external linker on arm64, and on amd64 in c-shared/c-archive buildmode - // complains about absolute relocs in __TEXT, so if the section is not - // executable, put it in __DATA segment. - msect = newMachoSect(mseg, buf, "__DATA") - } else { - msect = newMachoSect(mseg, buf, segname) - } + msect := newMachoSect(mseg, buf, segname) if sect.Rellen > 0 { msect.reloc = uint32(sect.Reloff) @@ -583,6 +647,8 @@ func asmbMacho(ctxt *Link) { } ctxt.Out.SeekSet(0) + ldr := ctxt.loader + /* apple MACH */ va := *FlagTextAddr - int64(HEADR) @@ -633,13 +699,28 @@ func asmbMacho(ctxt *Link) { machoshbits(ctxt, ms, sect, "__TEXT") } + /* rodata */ + if ctxt.LinkMode != LinkExternal && Segrelrodata.Length > 0 { + ms = newMachoSeg("__DATA_CONST", 20) + ms.vaddr = Segrelrodata.Vaddr + ms.vsize = Segrelrodata.Length + ms.fileoffset = Segrelrodata.Fileoff + ms.filesize = Segrelrodata.Filelen + ms.prot1 = 3 + ms.prot2 = 3 + ms.flag = 0x10 // SG_READ_ONLY + } + + for _, sect := range Segrelrodata.Sections { + machoshbits(ctxt, ms, sect, "__DATA_CONST") + } + /* data */ if ctxt.LinkMode != LinkExternal { - w := int64(Segdata.Length) ms = newMachoSeg("__DATA", 20) - ms.vaddr = uint64(va) + uint64(v) - ms.vsize = uint64(w) - ms.fileoffset = uint64(v) + ms.vaddr = Segdata.Vaddr + ms.vsize = Segdata.Length + ms.fileoffset = Segdata.Fileoff ms.filesize = Segdata.Filelen ms.prot1 = 3 ms.prot2 = 3 @@ -676,40 +757,56 @@ func asmbMacho(ctxt *Link) { ml.data[2+32+1] = uint32(Entryvalue(ctxt) >> 32) case sys.ARM64: - ml := newMachoLoad(ctxt.Arch, LC_UNIXTHREAD, 68+2) - ml.data[0] = 6 /* thread type */ - ml.data[1] = 68 /* word count */ - ml.data[2+64] = uint32(Entryvalue(ctxt)) /* start pc */ - ml.data[2+64+1] = uint32(Entryvalue(ctxt) >> 32) + ml := newMachoLoad(ctxt.Arch, LC_MAIN, 4) + ml.data[0] = uint32(uint64(Entryvalue(ctxt)) - (Segtext.Vaddr - uint64(HEADR))) + ml.data[1] = uint32((uint64(Entryvalue(ctxt)) - (Segtext.Vaddr - uint64(HEADR))) >> 32) } } + var codesigOff int64 if !*FlagD { - ldr := ctxt.loader - - // must match domacholink below - s1 := ldr.SymSize(ldr.Lookup(".machosymtab", 0)) - s2 := ldr.SymSize(ctxt.ArchSyms.LinkEditPLT) - s3 := ldr.SymSize(ctxt.ArchSyms.LinkEditGOT) - s4 := ldr.SymSize(ldr.Lookup(".machosymstr", 0)) + // must match doMachoLink below + s1 := ldr.SymSize(ldr.Lookup(".machorebase", 0)) + s2 := ldr.SymSize(ldr.Lookup(".machobind", 0)) + s3 := ldr.SymSize(ldr.Lookup(".machosymtab", 0)) + s4 := ldr.SymSize(ctxt.ArchSyms.LinkEditPLT) + s5 := ldr.SymSize(ctxt.ArchSyms.LinkEditGOT) + s6 := ldr.SymSize(ldr.Lookup(".machosymstr", 0)) + s7 := ldr.SymSize(ldr.Lookup(".machocodesig", 0)) if ctxt.LinkMode != LinkExternal { ms := newMachoSeg("__LINKEDIT", 0) - ms.vaddr = uint64(va) + uint64(v) + uint64(Rnd(int64(Segdata.Length), int64(*FlagRound))) - ms.vsize = uint64(s1) + uint64(s2) + uint64(s3) + uint64(s4) + ms.vaddr = uint64(Rnd(int64(Segdata.Vaddr+Segdata.Length), int64(*FlagRound))) + ms.vsize = uint64(s1 + s2 + s3 + s4 + s5 + s6 + s7) ms.fileoffset = uint64(linkoff) ms.filesize = ms.vsize - ms.prot1 = 7 - ms.prot2 = 3 + ms.prot1 = 1 + ms.prot2 = 1 + + codesigOff = linkoff + s1 + s2 + s3 + s4 + s5 + s6 + } + + if ctxt.LinkMode != LinkExternal && ctxt.IsPIE() { + ml := newMachoLoad(ctxt.Arch, LC_DYLD_INFO_ONLY, 10) + ml.data[0] = uint32(linkoff) // rebase off + ml.data[1] = uint32(s1) // rebase size + ml.data[2] = uint32(linkoff + s1) // bind off + ml.data[3] = uint32(s2) // bind size + ml.data[4] = 0 // weak bind off + ml.data[5] = 0 // weak bind size + ml.data[6] = 0 // lazy bind off + ml.data[7] = 0 // lazy bind size + ml.data[8] = 0 // export + ml.data[9] = 0 // export size } ml := newMachoLoad(ctxt.Arch, LC_SYMTAB, 4) - ml.data[0] = uint32(linkoff) /* symoff */ - ml.data[1] = uint32(nsortsym) /* nsyms */ - ml.data[2] = uint32(linkoff + s1 + s2 + s3) /* stroff */ - ml.data[3] = uint32(s4) /* strsize */ + ml.data[0] = uint32(linkoff + s1 + s2) /* symoff */ + ml.data[1] = uint32(nsortsym) /* nsyms */ + ml.data[2] = uint32(linkoff + s1 + s2 + s3 + s4 + s5) /* stroff */ + ml.data[3] = uint32(s6) /* strsize */ - machodysymtab(ctxt) + machodysymtab(ctxt, linkoff+s1+s2) if ctxt.LinkMode != LinkExternal { ml := newMachoLoad(ctxt.Arch, LC_LOAD_DYLINKER, 6) @@ -725,12 +822,31 @@ func asmbMacho(ctxt *Link) { stringtouint32(ml.data[4:], lib) } } + + if ctxt.IsInternal() && ctxt.NeedCodeSign() { + ml := newMachoLoad(ctxt.Arch, LC_CODE_SIGNATURE, 2) + ml.data[0] = uint32(codesigOff) + ml.data[1] = uint32(s7) + } } - a := machowrite(ctxt.Arch, ctxt.Out, ctxt.LinkMode) + a := machowrite(ctxt, ctxt.Arch, ctxt.Out, ctxt.LinkMode) if int32(a) > HEADR { Exitf("HEADR too small: %d > %d", a, HEADR) } + + // Now we have written everything. Compute the code signature (which + // is a hash of the file content, so it must be done at last.) + if ctxt.IsInternal() && ctxt.NeedCodeSign() { + cs := ldr.Lookup(".machocodesig", 0) + data := ctxt.Out.Data() + if int64(len(data)) != codesigOff { + panic("wrong size") + } + codesign.Sign(ldr.Data(cs), bytes.NewReader(data), "a.out", codesigOff, int64(Segtext.Fileoff), int64(Segtext.Filelen), ctxt.IsExe() || ctxt.IsPIE()) + ctxt.Out.SeekSet(codesigOff) + ctxt.Out.Write(ldr.Data(cs)) + } } func symkind(ldr *loader.Loader, s loader.Sym) int { @@ -812,12 +928,10 @@ func collectmachosyms(ctxt *Link) { switch objabi.GOARCH { case "amd64": ldr.SetSymExtname(s, n+"$INODE64") - case "386": - ldr.SetSymExtname(s, n+"$INODE64$UNIX2003") } case "readdir_r", "getfsstat": switch objabi.GOARCH { - case "amd64", "386": + case "amd64": ldr.SetSymExtname(s, n+"$INODE64") } } @@ -891,19 +1005,12 @@ func machosymtab(ctxt *Link) { symtab.AddUint32(ctxt.Arch, uint32(symstr.Size())) export := machoShouldExport(ctxt, ldr, s) - isGoSymbol := strings.Contains(ldr.SymExtname(s), ".") - // In normal buildmodes, only add _ to C symbols, as - // Go symbols have dot in the name. - // - // Do not export C symbols in plugins, as runtime C - // symbols like crosscall2 are in pclntab and end up - // pointing at the host binary, breaking unwinding. - // See Issue #18190. - cexport := !isGoSymbol && (ctxt.BuildMode != BuildModePlugin || onlycsymbol(ldr.SymName(s))) - if cexport || export || isGoSymbol { - symstr.AddUint8('_') - } + // Prefix symbol names with "_" to match the system toolchain. + // (We used to only prefix C symbols, which is all required for the build. + // But some tools don't recognize Go symbols as symbols, so we prefix them + // as well.) + symstr.AddUint8('_') // replace "·" as ".", because DTrace cannot handle it. symstr.Addstring(strings.Replace(ldr.SymExtname(s), "·", ".", -1)) @@ -914,10 +1021,13 @@ func machosymtab(ctxt *Link) { symtab.AddUint16(ctxt.Arch, 0) // desc symtab.AddUintXX(ctxt.Arch, 0, ctxt.Arch.PtrSize) // no value } else { - if ldr.AttrCgoExport(s) || export { - symtab.AddUint8(0x0f) + if export || ldr.AttrCgoExportDynamic(s) { + symtab.AddUint8(0x0f) // N_SECT | N_EXT + } else if ldr.AttrCgoExportStatic(s) { + // Only export statically, not dynamically. (N_PEXT is like hidden visibility) + symtab.AddUint8(0x1f) // N_SECT | N_EXT | N_PEXT } else { - symtab.AddUint8(0x0e) + symtab.AddUint8(0x0e) // N_SECT } o := s if outer := ldr.OuterSym(o); outer != 0 { @@ -935,7 +1045,7 @@ func machosymtab(ctxt *Link) { } } -func machodysymtab(ctxt *Link) { +func machodysymtab(ctxt *Link, base int64) { ml := newMachoLoad(ctxt.Arch, LC_DYSYMTAB, 18) n := 0 @@ -963,7 +1073,7 @@ func machodysymtab(ctxt *Link) { s1 := ldr.SymSize(ldr.Lookup(".machosymtab", 0)) s2 := ldr.SymSize(ctxt.ArchSyms.LinkEditPLT) s3 := ldr.SymSize(ctxt.ArchSyms.LinkEditGOT) - ml.data[12] = uint32(linkoff + s1) /* indirectsymoff */ + ml.data[12] = uint32(base + s1) /* indirectsymoff */ ml.data[13] = uint32((s2 + s3) / 4) /* nindirectsyms */ ml.data[14] = 0 /* extreloff */ @@ -974,14 +1084,19 @@ func machodysymtab(ctxt *Link) { func doMachoLink(ctxt *Link) int64 { machosymtab(ctxt) + machoDyldInfo(ctxt) ldr := ctxt.loader // write data that will be linkedit section - s1 := ldr.Lookup(".machosymtab", 0) - s2 := ctxt.ArchSyms.LinkEditPLT - s3 := ctxt.ArchSyms.LinkEditGOT - s4 := ldr.Lookup(".machosymstr", 0) + s1 := ldr.Lookup(".machorebase", 0) + s2 := ldr.Lookup(".machobind", 0) + s3 := ldr.Lookup(".machosymtab", 0) + s4 := ctxt.ArchSyms.LinkEditPLT + s5 := ctxt.ArchSyms.LinkEditGOT + s6 := ldr.Lookup(".machosymstr", 0) + + size := ldr.SymSize(s1) + ldr.SymSize(s2) + ldr.SymSize(s3) + ldr.SymSize(s4) + ldr.SymSize(s5) + ldr.SymSize(s6) // Force the linkedit section to end on a 16-byte // boundary. This allows pure (non-cgo) Go binaries @@ -1000,24 +1115,31 @@ func doMachoLink(ctxt *Link) int64 { // boundary, codesign_allocate will not need to apply // any alignment padding itself, working around the // issue. - s4b := ldr.MakeSymbolUpdater(s4) - for s4b.Size()%16 != 0 { - s4b.AddUint8(0) + if size%16 != 0 { + n := 16 - size%16 + s6b := ldr.MakeSymbolUpdater(s6) + s6b.Grow(s6b.Size() + n) + s6b.SetSize(s6b.Size() + n) + size += n } - size := int(ldr.SymSize(s1) + ldr.SymSize(s2) + ldr.SymSize(s3) + ldr.SymSize(s4)) - if size > 0 { - linkoff = Rnd(int64(uint64(HEADR)+Segtext.Length), int64(*FlagRound)) + Rnd(int64(Segdata.Filelen), int64(*FlagRound)) + Rnd(int64(Segdwarf.Filelen), int64(*FlagRound)) + linkoff = Rnd(int64(uint64(HEADR)+Segtext.Length), int64(*FlagRound)) + Rnd(int64(Segrelrodata.Filelen), int64(*FlagRound)) + Rnd(int64(Segdata.Filelen), int64(*FlagRound)) + Rnd(int64(Segdwarf.Filelen), int64(*FlagRound)) ctxt.Out.SeekSet(linkoff) ctxt.Out.Write(ldr.Data(s1)) ctxt.Out.Write(ldr.Data(s2)) ctxt.Out.Write(ldr.Data(s3)) ctxt.Out.Write(ldr.Data(s4)) + ctxt.Out.Write(ldr.Data(s5)) + ctxt.Out.Write(ldr.Data(s6)) + + // Add code signature if necessary. This must be the last. + s7 := machoCodeSigSym(ctxt, linkoff+size) + size += ldr.SymSize(s7) } - return Rnd(int64(size), int64(*FlagRound)) + return Rnd(size, int64(*FlagRound)) } func machorelocsect(ctxt *Link, out *OutBuf, sect *sym.Section, syms []loader.Sym) { @@ -1086,6 +1208,9 @@ func machoEmitReloc(ctxt *Link) { for _, sect := range Segtext.Sections[1:] { relocSect(ctxt, sect, ctxt.datap) } + for _, sect := range Segrelrodata.Sections { + relocSect(ctxt, sect, ctxt.datap) + } for _, sect := range Segdata.Sections { relocSect(ctxt, sect, ctxt.datap) } @@ -1155,3 +1280,240 @@ func peekMachoPlatform(m *macho.File) (*MachoPlatformLoad, error) { } return nil, nil } + +// A rebase entry tells the dynamic linker the data at sym+off needs to be +// relocated when the in-memory image moves. (This is somewhat like, say, +// ELF R_X86_64_RELATIVE). +// For now, the only kind of entry we support is that the data is an absolute +// address. That seems all we need. +// In the binary it uses a compact stateful bytecode encoding. So we record +// entries as we go and build the table at the end. +type machoRebaseRecord struct { + sym loader.Sym + off int64 +} + +var machorebase []machoRebaseRecord + +func MachoAddRebase(s loader.Sym, off int64) { + machorebase = append(machorebase, machoRebaseRecord{s, off}) +} + +// A bind entry tells the dynamic linker the data at GOT+off should be bound +// to the address of the target symbol, which is a dynamic import. +// For now, the only kind of entry we support is that the data is an absolute +// address, and the source symbol is always the GOT. That seems all we need. +// In the binary it uses a compact stateful bytecode encoding. So we record +// entries as we go and build the table at the end. +type machoBindRecord struct { + off int64 + targ loader.Sym +} + +var machobind []machoBindRecord + +func MachoAddBind(off int64, targ loader.Sym) { + machobind = append(machobind, machoBindRecord{off, targ}) +} + +// Generate data for the dynamic linker, used in LC_DYLD_INFO_ONLY load command. +// See mach-o/loader.h, struct dyld_info_command, for the encoding. +// e.g. https://opensource.apple.com/source/xnu/xnu-6153.81.5/EXTERNAL_HEADERS/mach-o/loader.h +func machoDyldInfo(ctxt *Link) { + ldr := ctxt.loader + rebase := ldr.CreateSymForUpdate(".machorebase", 0) + bind := ldr.CreateSymForUpdate(".machobind", 0) + + if !(ctxt.IsPIE() && ctxt.IsInternal()) { + return + } + + segId := func(seg *sym.Segment) uint8 { + switch seg { + case &Segtext: + return 1 + case &Segrelrodata: + return 2 + case &Segdata: + if Segrelrodata.Length > 0 { + return 3 + } + return 2 + } + panic("unknown segment") + } + + dylibId := func(s loader.Sym) int { + slib := ldr.SymDynimplib(s) + for i, lib := range dylib { + if lib == slib { + return i + 1 + } + } + return BIND_SPECIAL_DYLIB_FLAT_LOOKUP // don't know where it is from + } + + // Rebase table. + // TODO: use more compact encoding. The encoding is stateful, and + // we can use delta encoding. + rebase.AddUint8(REBASE_OPCODE_SET_TYPE_IMM | REBASE_TYPE_POINTER) + for _, r := range machorebase { + seg := ldr.SymSect(r.sym).Seg + off := uint64(ldr.SymValue(r.sym)+r.off) - seg.Vaddr + rebase.AddUint8(REBASE_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB | segId(seg)) + rebase.AddUleb(off) + + rebase.AddUint8(REBASE_OPCODE_DO_REBASE_IMM_TIMES | 1) + } + rebase.AddUint8(REBASE_OPCODE_DONE) + sz := Rnd(rebase.Size(), 8) + rebase.Grow(sz) + rebase.SetSize(sz) + + // Bind table. + // TODO: compact encoding, as above. + // TODO: lazy binding? + got := ctxt.GOT + seg := ldr.SymSect(got).Seg + gotAddr := ldr.SymValue(got) + bind.AddUint8(BIND_OPCODE_SET_TYPE_IMM | BIND_TYPE_POINTER) + for _, r := range machobind { + off := uint64(gotAddr+r.off) - seg.Vaddr + bind.AddUint8(BIND_OPCODE_SET_SEGMENT_AND_OFFSET_ULEB | segId(seg)) + bind.AddUleb(off) + + d := dylibId(r.targ) + if d > 0 && d < 128 { + bind.AddUint8(BIND_OPCODE_SET_DYLIB_ORDINAL_IMM | uint8(d)&0xf) + } else if d >= 128 { + bind.AddUint8(BIND_OPCODE_SET_DYLIB_ORDINAL_ULEB) + bind.AddUleb(uint64(d)) + } else { // d <= 0 + bind.AddUint8(BIND_OPCODE_SET_DYLIB_SPECIAL_IMM | uint8(d)&0xf) + } + + bind.AddUint8(BIND_OPCODE_SET_SYMBOL_TRAILING_FLAGS_IMM) + // target symbol name as a C string, with _ prefix + bind.AddUint8('_') + bind.Addstring(ldr.SymExtname(r.targ)) + + bind.AddUint8(BIND_OPCODE_DO_BIND) + } + bind.AddUint8(BIND_OPCODE_DONE) + sz = Rnd(bind.Size(), 16) // make it 16-byte aligned, see the comment in doMachoLink + bind.Grow(sz) + bind.SetSize(sz) + + // TODO: export table. + // The symbols names are encoded as a trie. I'm really too lazy to do that + // for now. + // Without it, the symbols are not dynamically exported, so they cannot be + // e.g. dlsym'd. But internal linking is not the default in that case, so + // it is fine. +} + +// machoCodeSigSym creates and returns a symbol for code signature. +// The symbol context is left as zeros, which will be generated at the end +// (as it depends on the rest of the file). +func machoCodeSigSym(ctxt *Link, codeSize int64) loader.Sym { + ldr := ctxt.loader + cs := ldr.CreateSymForUpdate(".machocodesig", 0) + if !ctxt.NeedCodeSign() || ctxt.IsExternal() { + return cs.Sym() + } + sz := codesign.Size(codeSize, "a.out") + cs.Grow(sz) + cs.SetSize(sz) + return cs.Sym() +} + +// machoCodeSign code-signs Mach-O file fname with an ad-hoc signature. +// This is used for updating an external linker generated binary. +func machoCodeSign(ctxt *Link, fname string) error { + f, err := os.OpenFile(fname, os.O_RDWR, 0) + if err != nil { + return err + } + defer f.Close() + + mf, err := macho.NewFile(f) + if err != nil { + return err + } + if mf.Magic != macho.Magic64 { + Exitf("not 64-bit Mach-O file: %s", fname) + } + + // Find existing LC_CODE_SIGNATURE and __LINKEDIT segment + var sigOff, sigSz, csCmdOff, linkeditOff int64 + var linkeditSeg, textSeg *macho.Segment + loadOff := int64(machoHeaderSize64) + get32 := mf.ByteOrder.Uint32 + for _, l := range mf.Loads { + data := l.Raw() + cmd, sz := get32(data), get32(data[4:]) + if cmd == LC_CODE_SIGNATURE { + sigOff = int64(get32(data[8:])) + sigSz = int64(get32(data[12:])) + csCmdOff = loadOff + } + if seg, ok := l.(*macho.Segment); ok { + switch seg.Name { + case "__LINKEDIT": + linkeditSeg = seg + linkeditOff = loadOff + case "__TEXT": + textSeg = seg + } + } + loadOff += int64(sz) + } + + if sigOff == 0 { + // The C linker doesn't generate a signed binary, for some reason. + // Skip. + return nil + } + + fi, err := f.Stat() + if err != nil { + return err + } + if sigOff+sigSz != fi.Size() { + // We don't expect anything after the signature (this will invalidate + // the signature anyway.) + return fmt.Errorf("unexpected content after code signature") + } + + sz := codesign.Size(sigOff, "a.out") + if sz != sigSz { + // Update the load command, + var tmp [8]byte + mf.ByteOrder.PutUint32(tmp[:4], uint32(sz)) + _, err = f.WriteAt(tmp[:4], csCmdOff+12) + if err != nil { + return err + } + + // Uodate the __LINKEDIT segment. + segSz := sigOff + sz - int64(linkeditSeg.Offset) + mf.ByteOrder.PutUint64(tmp[:8], uint64(segSz)) + _, err = f.WriteAt(tmp[:8], int64(linkeditOff)+int64(unsafe.Offsetof(macho.Segment64{}.Memsz))) + if err != nil { + return err + } + _, err = f.WriteAt(tmp[:8], int64(linkeditOff)+int64(unsafe.Offsetof(macho.Segment64{}.Filesz))) + if err != nil { + return err + } + } + + cs := make([]byte, sz) + codesign.Sign(cs, f, "a.out", sigOff, int64(textSeg.Offset), int64(textSeg.Filesz), ctxt.IsExe() || ctxt.IsPIE()) + _, err = f.WriteAt(cs, sigOff) + if err != nil { + return err + } + err = f.Truncate(sigOff + sz) + return err +} |