| // Copyright 2009 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package ld |
| |
| import ( |
| "bytes" |
| "cmd/internal/objabi" |
| "cmd/internal/sys" |
| "cmd/link/internal/loader" |
| "cmd/link/internal/sym" |
| "debug/macho" |
| "encoding/binary" |
| "fmt" |
| "io" |
| "os" |
| "sort" |
| "strings" |
| ) |
| |
| type MachoHdr struct { |
| cpu uint32 |
| subcpu uint32 |
| } |
| |
| type MachoSect struct { |
| name string |
| segname string |
| addr uint64 |
| size uint64 |
| off uint32 |
| align uint32 |
| reloc uint32 |
| nreloc uint32 |
| flag uint32 |
| res1 uint32 |
| res2 uint32 |
| } |
| |
| type MachoSeg struct { |
| name string |
| vsize uint64 |
| vaddr uint64 |
| fileoffset uint64 |
| filesize uint64 |
| prot1 uint32 |
| prot2 uint32 |
| nsect uint32 |
| msect uint32 |
| sect []MachoSect |
| flag uint32 |
| } |
| |
| // MachoPlatformLoad represents a LC_VERSION_MIN_* or |
| // LC_BUILD_VERSION load command. |
| type MachoPlatformLoad struct { |
| platform MachoPlatform // One of PLATFORM_* constants. |
| cmd MachoLoad |
| } |
| |
| type MachoLoad struct { |
| type_ uint32 |
| data []uint32 |
| } |
| |
| type MachoPlatform int |
| |
| /* |
| * Total amount of space to reserve at the start of the file |
| * for Header, PHeaders, and SHeaders. |
| * May waste some. |
| */ |
| const ( |
| INITIAL_MACHO_HEADR = 4 * 1024 |
| ) |
| |
| 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_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 ( |
| MH_MAGIC = 0xfeedface |
| MH_MAGIC_64 = 0xfeedfacf |
| |
| MH_OBJECT = 0x1 |
| MH_EXECUTE = 0x2 |
| |
| MH_NOUNDEFS = 0x1 |
| MH_DYLDLINK = 0x4 |
| MH_PIE = 0x200000 |
| ) |
| |
| const ( |
| LC_SEGMENT = 0x1 |
| LC_SYMTAB = 0x2 |
| LC_SYMSEG = 0x3 |
| LC_THREAD = 0x4 |
| LC_UNIXTHREAD = 0x5 |
| LC_LOADFVMLIB = 0x6 |
| LC_IDFVMLIB = 0x7 |
| LC_IDENT = 0x8 |
| LC_FVMFILE = 0x9 |
| LC_PREPAGE = 0xa |
| LC_DYSYMTAB = 0xb |
| LC_LOAD_DYLIB = 0xc |
| LC_ID_DYLIB = 0xd |
| LC_LOAD_DYLINKER = 0xe |
| LC_ID_DYLINKER = 0xf |
| LC_PREBOUND_DYLIB = 0x10 |
| LC_ROUTINES = 0x11 |
| LC_SUB_FRAMEWORK = 0x12 |
| LC_SUB_UMBRELLA = 0x13 |
| LC_SUB_CLIENT = 0x14 |
| LC_SUB_LIBRARY = 0x15 |
| LC_TWOLEVEL_HINTS = 0x16 |
| LC_PREBIND_CKSUM = 0x17 |
| LC_LOAD_WEAK_DYLIB = 0x80000018 |
| LC_SEGMENT_64 = 0x19 |
| LC_ROUTINES_64 = 0x1a |
| LC_UUID = 0x1b |
| LC_RPATH = 0x8000001c |
| LC_CODE_SIGNATURE = 0x1d |
| LC_SEGMENT_SPLIT_INFO = 0x1e |
| LC_REEXPORT_DYLIB = 0x8000001f |
| LC_LAZY_LOAD_DYLIB = 0x20 |
| LC_ENCRYPTION_INFO = 0x21 |
| LC_DYLD_INFO = 0x22 |
| LC_DYLD_INFO_ONLY = 0x80000022 |
| LC_LOAD_UPWARD_DYLIB = 0x80000023 |
| LC_VERSION_MIN_MACOSX = 0x24 |
| LC_VERSION_MIN_IPHONEOS = 0x25 |
| LC_FUNCTION_STARTS = 0x26 |
| LC_DYLD_ENVIRONMENT = 0x27 |
| LC_MAIN = 0x80000028 |
| LC_DATA_IN_CODE = 0x29 |
| LC_SOURCE_VERSION = 0x2A |
| LC_DYLIB_CODE_SIGN_DRS = 0x2B |
| LC_ENCRYPTION_INFO_64 = 0x2C |
| LC_LINKER_OPTION = 0x2D |
| LC_LINKER_OPTIMIZATION_HINT = 0x2E |
| LC_VERSION_MIN_TVOS = 0x2F |
| LC_VERSION_MIN_WATCHOS = 0x30 |
| LC_VERSION_NOTE = 0x31 |
| LC_BUILD_VERSION = 0x32 |
| ) |
| |
| const ( |
| S_REGULAR = 0x0 |
| S_ZEROFILL = 0x1 |
| S_NON_LAZY_SYMBOL_POINTERS = 0x6 |
| S_SYMBOL_STUBS = 0x8 |
| S_MOD_INIT_FUNC_POINTERS = 0x9 |
| S_ATTR_PURE_INSTRUCTIONS = 0x80000000 |
| S_ATTR_DEBUG = 0x02000000 |
| S_ATTR_SOME_INSTRUCTIONS = 0x00000400 |
| ) |
| |
| const ( |
| PLATFORM_MACOS MachoPlatform = 1 |
| PLATFORM_IOS MachoPlatform = 2 |
| PLATFORM_TVOS MachoPlatform = 3 |
| PLATFORM_WATCHOS MachoPlatform = 4 |
| 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 |
| ) |
| |
| // Mach-O file writing |
| // https://developer.apple.com/mac/library/DOCUMENTATION/DeveloperTools/Conceptual/MachORuntime/Reference/reference.html |
| |
| var machohdr MachoHdr |
| |
| var load []MachoLoad |
| |
| var machoPlatform MachoPlatform |
| |
| var seg [16]MachoSeg |
| |
| var nseg int |
| |
| var ndebug int |
| |
| var nsect int |
| |
| const ( |
| SymKindLocal = 0 + iota |
| SymKindExtdef |
| SymKindUndef |
| NumSymKind |
| ) |
| |
| var nkind [NumSymKind]int |
| |
| var sortsym []loader.Sym |
| |
| var nsortsym int |
| |
| // Amount of space left for adding load commands |
| // that refer to dynamic libraries. Because these have |
| // to go in the Mach-O header, we can't just pick a |
| // "big enough" header size. The initial header is |
| // one page, the non-dynamic library stuff takes |
| // up about 1300 bytes; we overestimate that as 2k. |
| var loadBudget = INITIAL_MACHO_HEADR - 2*1024 |
| |
| func getMachoHdr() *MachoHdr { |
| return &machohdr |
| } |
| |
| func newMachoLoad(arch *sys.Arch, type_ uint32, ndata uint32) *MachoLoad { |
| if arch.PtrSize == 8 && (ndata&1 != 0) { |
| ndata++ |
| } |
| |
| load = append(load, MachoLoad{}) |
| l := &load[len(load)-1] |
| l.type_ = type_ |
| l.data = make([]uint32, ndata) |
| return l |
| } |
| |
| func newMachoSeg(name string, msect int) *MachoSeg { |
| if nseg >= len(seg) { |
| Exitf("too many segs") |
| } |
| |
| s := &seg[nseg] |
| nseg++ |
| s.name = name |
| s.msect = uint32(msect) |
| s.sect = make([]MachoSect, msect) |
| return s |
| } |
| |
| func newMachoSect(seg *MachoSeg, name string, segname string) *MachoSect { |
| if seg.nsect >= seg.msect { |
| Exitf("too many sects in segment %s", seg.name) |
| } |
| |
| s := &seg.sect[seg.nsect] |
| seg.nsect++ |
| s.name = name |
| s.segname = segname |
| nsect++ |
| return s |
| } |
| |
| // Generic linking code. |
| |
| var dylib []string |
| |
| var linkoff int64 |
| |
| func machowrite(ctxt *Link, arch *sys.Arch, out *OutBuf, linkmode LinkMode) int { |
| o1 := out.Offset() |
| |
| loadsize := 4 * 4 * ndebug |
| for i := range load { |
| loadsize += 4 * (len(load[i].data) + 2) |
| } |
| if arch.PtrSize == 8 { |
| loadsize += 18 * 4 * nseg |
| loadsize += 20 * 4 * nsect |
| } else { |
| loadsize += 14 * 4 * nseg |
| loadsize += 17 * 4 * nsect |
| } |
| |
| if arch.PtrSize == 8 { |
| out.Write32(MH_MAGIC_64) |
| } else { |
| out.Write32(MH_MAGIC) |
| } |
| out.Write32(machohdr.cpu) |
| out.Write32(machohdr.subcpu) |
| if linkmode == LinkExternal { |
| out.Write32(MH_OBJECT) /* file type - mach object */ |
| } else { |
| out.Write32(MH_EXECUTE) /* file type - mach executable */ |
| } |
| out.Write32(uint32(len(load)) + uint32(nseg) + uint32(ndebug)) |
| out.Write32(uint32(loadsize)) |
| flags := uint32(0) |
| if nkind[SymKindUndef] == 0 { |
| 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 */ |
| } |
| |
| for i := 0; i < nseg; i++ { |
| s := &seg[i] |
| if arch.PtrSize == 8 { |
| out.Write32(LC_SEGMENT_64) |
| out.Write32(72 + 80*s.nsect) |
| out.WriteStringN(s.name, 16) |
| out.Write64(s.vaddr) |
| out.Write64(s.vsize) |
| out.Write64(s.fileoffset) |
| out.Write64(s.filesize) |
| out.Write32(s.prot1) |
| out.Write32(s.prot2) |
| out.Write32(s.nsect) |
| out.Write32(s.flag) |
| } else { |
| out.Write32(LC_SEGMENT) |
| out.Write32(56 + 68*s.nsect) |
| out.WriteStringN(s.name, 16) |
| out.Write32(uint32(s.vaddr)) |
| out.Write32(uint32(s.vsize)) |
| out.Write32(uint32(s.fileoffset)) |
| out.Write32(uint32(s.filesize)) |
| out.Write32(s.prot1) |
| out.Write32(s.prot2) |
| out.Write32(s.nsect) |
| out.Write32(s.flag) |
| } |
| |
| for j := uint32(0); j < s.nsect; j++ { |
| t := &s.sect[j] |
| if arch.PtrSize == 8 { |
| out.WriteStringN(t.name, 16) |
| out.WriteStringN(t.segname, 16) |
| out.Write64(t.addr) |
| out.Write64(t.size) |
| out.Write32(t.off) |
| out.Write32(t.align) |
| out.Write32(t.reloc) |
| out.Write32(t.nreloc) |
| out.Write32(t.flag) |
| out.Write32(t.res1) /* reserved */ |
| out.Write32(t.res2) /* reserved */ |
| out.Write32(0) /* reserved */ |
| } else { |
| out.WriteStringN(t.name, 16) |
| out.WriteStringN(t.segname, 16) |
| out.Write32(uint32(t.addr)) |
| out.Write32(uint32(t.size)) |
| out.Write32(t.off) |
| out.Write32(t.align) |
| out.Write32(t.reloc) |
| out.Write32(t.nreloc) |
| out.Write32(t.flag) |
| out.Write32(t.res1) /* reserved */ |
| out.Write32(t.res2) /* reserved */ |
| } |
| } |
| } |
| |
| for i := range load { |
| l := &load[i] |
| out.Write32(l.type_) |
| out.Write32(4 * (uint32(len(l.data)) + 2)) |
| for j := 0; j < len(l.data); j++ { |
| out.Write32(l.data[j]) |
| } |
| } |
| |
| return int(out.Offset() - o1) |
| } |
| |
| func (ctxt *Link) domacho() { |
| if *FlagD { |
| return |
| } |
| |
| // Copy platform load command. |
| for _, h := range hostobj { |
| load, err := hostobjMachoPlatform(&h) |
| if err != nil { |
| Exitf("%v", err) |
| } |
| if load != nil { |
| machoPlatform = load.platform |
| ml := newMachoLoad(ctxt.Arch, load.cmd.type_, uint32(len(load.cmd.data))) |
| copy(ml.data, load.cmd.data) |
| break |
| } |
| } |
| if machoPlatform == 0 { |
| switch ctxt.Arch.Family { |
| default: |
| machoPlatform = PLATFORM_MACOS |
| if ctxt.LinkMode == LinkInternal { |
| // For lldb, must say LC_VERSION_MIN_MACOSX or else |
| // it won't know that this Mach-O binary is from OS X |
| // (could be iOS or WatchOS instead). |
| // Go on iOS uses linkmode=external, and linkmode=external |
| // adds this itself. So we only need this code for linkmode=internal |
| // and we can assume OS X. |
| // |
| // See golang.org/issues/12941. |
| // |
| // The version must be at least 10.9; see golang.org/issues/30488. |
| ml := newMachoLoad(ctxt.Arch, LC_VERSION_MIN_MACOSX, 2) |
| ml.data[0] = 10<<16 | 9<<8 | 0<<0 // OS X version 10.9.0 |
| ml.data[1] = 10<<16 | 9<<8 | 0<<0 // SDK 10.9.0 |
| } |
| case sys.ARM, sys.ARM64: |
| machoPlatform = PLATFORM_IOS |
| } |
| } |
| |
| // empirically, string table must begin with " \x00". |
| s := ctxt.loader.LookupOrCreateSym(".machosymstr", 0) |
| sb := ctxt.loader.MakeSymbolUpdater(s) |
| |
| sb.SetType(sym.SMACHOSYMSTR) |
| sb.SetReachable(true) |
| sb.AddUint8(' ') |
| sb.AddUint8('\x00') |
| |
| s = ctxt.loader.LookupOrCreateSym(".machosymtab", 0) |
| sb = ctxt.loader.MakeSymbolUpdater(s) |
| sb.SetType(sym.SMACHOSYMTAB) |
| sb.SetReachable(true) |
| |
| if ctxt.IsInternal() { |
| s = ctxt.loader.LookupOrCreateSym(".plt", 0) // will be __symbol_stub |
| sb = ctxt.loader.MakeSymbolUpdater(s) |
| sb.SetType(sym.SMACHOPLT) |
| sb.SetReachable(true) |
| |
| s = ctxt.loader.LookupOrCreateSym(".got", 0) // will be __nl_symbol_ptr |
| sb = ctxt.loader.MakeSymbolUpdater(s) |
| sb.SetType(sym.SMACHOGOT) |
| sb.SetReachable(true) |
| sb.SetAlign(4) |
| |
| s = ctxt.loader.LookupOrCreateSym(".linkedit.plt", 0) // indirect table for .plt |
| sb = ctxt.loader.MakeSymbolUpdater(s) |
| sb.SetType(sym.SMACHOINDIRECTPLT) |
| sb.SetReachable(true) |
| |
| s = ctxt.loader.LookupOrCreateSym(".linkedit.got", 0) // indirect table for .got |
| sb = ctxt.loader.MakeSymbolUpdater(s) |
| sb.SetType(sym.SMACHOINDIRECTGOT) |
| sb.SetReachable(true) |
| } |
| |
| // Add a dummy symbol that will become the __asm marker section. |
| if ctxt.IsExternal() { |
| s = ctxt.loader.LookupOrCreateSym(".llvmasm", 0) |
| sb = ctxt.loader.MakeSymbolUpdater(s) |
| sb.SetType(sym.SMACHO) |
| 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) { |
| if seenlib[lib] || linkmode == LinkExternal { |
| return |
| } |
| seenlib[lib] = true |
| |
| // Will need to store the library name rounded up |
| // and 24 bytes of header metadata. If not enough |
| // space, grab another page of initial space at the |
| // beginning of the output file. |
| loadBudget -= (len(lib)+7)/8*8 + 24 |
| |
| if loadBudget < 0 { |
| HEADR += 4096 |
| *FlagTextAddr += 4096 |
| loadBudget += 4096 |
| } |
| |
| dylib = append(dylib, lib) |
| } |
| |
| func machoshbits(ctxt *Link, mseg *MachoSeg, sect *sym.Section, segname string) { |
| buf := "__" + strings.Replace(sect.Name[1:], ".", "_", -1) |
| |
| msect := newMachoSect(mseg, buf, segname) |
| |
| if sect.Rellen > 0 { |
| msect.reloc = uint32(sect.Reloff) |
| msect.nreloc = uint32(sect.Rellen / 8) |
| } |
| |
| for 1<<msect.align < sect.Align { |
| msect.align++ |
| } |
| msect.addr = sect.Vaddr |
| msect.size = sect.Length |
| |
| if sect.Vaddr < sect.Seg.Vaddr+sect.Seg.Filelen { |
| // data in file |
| if sect.Length > sect.Seg.Vaddr+sect.Seg.Filelen-sect.Vaddr { |
| Errorf(nil, "macho cannot represent section %s crossing data and bss", sect.Name) |
| } |
| msect.off = uint32(sect.Seg.Fileoff + sect.Vaddr - sect.Seg.Vaddr) |
| } else { |
| msect.off = 0 |
| msect.flag |= S_ZEROFILL |
| } |
| |
| if sect.Rwx&1 != 0 { |
| msect.flag |= S_ATTR_SOME_INSTRUCTIONS |
| } |
| |
| if sect.Name == ".text" { |
| msect.flag |= S_ATTR_PURE_INSTRUCTIONS |
| } |
| |
| if sect.Name == ".plt" { |
| msect.name = "__symbol_stub1" |
| msect.flag = S_ATTR_PURE_INSTRUCTIONS | S_ATTR_SOME_INSTRUCTIONS | S_SYMBOL_STUBS |
| msect.res1 = 0 //nkind[SymKindLocal]; |
| msect.res2 = 6 |
| } |
| |
| if sect.Name == ".got" { |
| msect.name = "__nl_symbol_ptr" |
| msect.flag = S_NON_LAZY_SYMBOL_POINTERS |
| msect.res1 = uint32(ctxt.loader.SymSize(ctxt.ArchSyms.LinkEditPLT) / 4) /* offset into indirect symbol table */ |
| } |
| |
| if sect.Name == ".init_array" { |
| msect.name = "__mod_init_func" |
| msect.flag = S_MOD_INIT_FUNC_POINTERS |
| } |
| |
| // Some platforms such as watchOS and tvOS require binaries with |
| // bitcode enabled. The Go toolchain can't output bitcode, so use |
| // a marker section in the __LLVM segment, "__asm", to tell the Apple |
| // toolchain that the Go text came from assembler and thus has no |
| // bitcode. This is not true, but Kotlin/Native, Rust and Flutter |
| // are also using this trick. |
| if sect.Name == ".llvmasm" { |
| msect.name = "__asm" |
| msect.segname = "__LLVM" |
| } |
| |
| if segname == "__DWARF" { |
| msect.flag |= S_ATTR_DEBUG |
| } |
| } |
| |
| func asmbMacho(ctxt *Link) { |
| machlink := doMachoLink(ctxt) |
| if !*FlagS && ctxt.IsExternal() { |
| symo := int64(Segdwarf.Fileoff + uint64(Rnd(int64(Segdwarf.Filelen), int64(*FlagRound))) + uint64(machlink)) |
| ctxt.Out.SeekSet(symo) |
| machoEmitReloc(ctxt) |
| } |
| ctxt.Out.SeekSet(0) |
| |
| /* apple MACH */ |
| va := *FlagTextAddr - int64(HEADR) |
| |
| mh := getMachoHdr() |
| switch ctxt.Arch.Family { |
| default: |
| Exitf("unknown macho architecture: %v", ctxt.Arch.Family) |
| |
| case sys.AMD64: |
| mh.cpu = MACHO_CPU_AMD64 |
| mh.subcpu = MACHO_SUBCPU_X86 |
| |
| case sys.ARM64: |
| mh.cpu = MACHO_CPU_ARM64 |
| mh.subcpu = MACHO_SUBCPU_ARM64_ALL |
| } |
| |
| var ms *MachoSeg |
| if ctxt.LinkMode == LinkExternal { |
| /* segment for entire file */ |
| ms = newMachoSeg("", 40) |
| |
| ms.fileoffset = Segtext.Fileoff |
| ms.filesize = Segdwarf.Fileoff + Segdwarf.Filelen - Segtext.Fileoff |
| ms.vsize = Segdwarf.Vaddr + Segdwarf.Length - Segtext.Vaddr |
| } |
| |
| /* segment for zero page */ |
| if ctxt.LinkMode != LinkExternal { |
| ms = newMachoSeg("__PAGEZERO", 0) |
| ms.vsize = uint64(va) |
| } |
| |
| /* text */ |
| v := Rnd(int64(uint64(HEADR)+Segtext.Length), int64(*FlagRound)) |
| |
| if ctxt.LinkMode != LinkExternal { |
| ms = newMachoSeg("__TEXT", 20) |
| ms.vaddr = uint64(va) |
| ms.vsize = uint64(v) |
| ms.fileoffset = 0 |
| ms.filesize = uint64(v) |
| ms.prot1 = 7 |
| ms.prot2 = 5 |
| } |
| |
| for _, sect := range Segtext.Sections { |
| 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 { |
| ms = newMachoSeg("__DATA", 20) |
| ms.vaddr = Segdata.Vaddr |
| ms.vsize = Segdata.Length |
| ms.fileoffset = Segdata.Fileoff |
| ms.filesize = Segdata.Filelen |
| ms.prot1 = 3 |
| ms.prot2 = 3 |
| } |
| |
| for _, sect := range Segdata.Sections { |
| machoshbits(ctxt, ms, sect, "__DATA") |
| } |
| |
| /* dwarf */ |
| if !*FlagW { |
| if ctxt.LinkMode != LinkExternal { |
| ms = newMachoSeg("__DWARF", 20) |
| ms.vaddr = Segdwarf.Vaddr |
| ms.vsize = 0 |
| ms.fileoffset = Segdwarf.Fileoff |
| ms.filesize = Segdwarf.Filelen |
| } |
| for _, sect := range Segdwarf.Sections { |
| machoshbits(ctxt, ms, sect, "__DWARF") |
| } |
| } |
| |
| if ctxt.LinkMode != LinkExternal { |
| switch ctxt.Arch.Family { |
| default: |
| Exitf("unknown macho architecture: %v", ctxt.Arch.Family) |
| |
| case sys.AMD64: |
| ml := newMachoLoad(ctxt.Arch, LC_UNIXTHREAD, 42+2) |
| ml.data[0] = 4 /* thread type */ |
| ml.data[1] = 42 /* word count */ |
| ml.data[2+32] = uint32(Entryvalue(ctxt)) /* start pc */ |
| ml.data[2+32+1] = uint32(Entryvalue(ctxt) >> 32) |
| |
| case sys.ARM64: |
| 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) |
| } |
| } |
| |
| if !*FlagD { |
| ldr := ctxt.loader |
| |
| // 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)) |
| |
| if ctxt.LinkMode != LinkExternal { |
| ms := newMachoSeg("__LINKEDIT", 0) |
| ms.vaddr = uint64(Rnd(int64(Segdata.Vaddr+Segdata.Length), int64(*FlagRound))) |
| ms.vsize = uint64(s1 + s2 + s3 + s4 + s5 + s6) |
| ms.fileoffset = uint64(linkoff) |
| ms.filesize = ms.vsize |
| ms.prot1 = 1 |
| ms.prot2 = 1 |
| } |
| |
| 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 + 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, linkoff+s1+s2) |
| |
| if ctxt.LinkMode != LinkExternal { |
| ml := newMachoLoad(ctxt.Arch, LC_LOAD_DYLINKER, 6) |
| ml.data[0] = 12 /* offset to string */ |
| stringtouint32(ml.data[1:], "/usr/lib/dyld") |
| |
| for _, lib := range dylib { |
| ml = newMachoLoad(ctxt.Arch, LC_LOAD_DYLIB, 4+(uint32(len(lib))+1+7)/8*2) |
| ml.data[0] = 24 /* offset of string from beginning of load */ |
| ml.data[1] = 0 /* time stamp */ |
| ml.data[2] = 0 /* version */ |
| ml.data[3] = 0 /* compatibility version */ |
| stringtouint32(ml.data[4:], lib) |
| } |
| } |
| } |
| |
| a := machowrite(ctxt, ctxt.Arch, ctxt.Out, ctxt.LinkMode) |
| if int32(a) > HEADR { |
| Exitf("HEADR too small: %d > %d", a, HEADR) |
| } |
| } |
| |
| func symkind(ldr *loader.Loader, s loader.Sym) int { |
| if ldr.SymType(s) == sym.SDYNIMPORT { |
| return SymKindUndef |
| } |
| if ldr.AttrCgoExport(s) { |
| return SymKindExtdef |
| } |
| return SymKindLocal |
| } |
| |
| func collectmachosyms(ctxt *Link) { |
| ldr := ctxt.loader |
| |
| addsym := func(s loader.Sym) { |
| sortsym = append(sortsym, s) |
| nkind[symkind(ldr, s)]++ |
| } |
| |
| // Add special runtime.text and runtime.etext symbols. |
| // We've already included this symbol in Textp on darwin if ctxt.DynlinkingGo(). |
| // See data.go:/textaddress |
| if !ctxt.DynlinkingGo() { |
| s := ldr.Lookup("runtime.text", 0) |
| if ldr.SymType(s) == sym.STEXT { |
| addsym(s) |
| } |
| s = ldr.Lookup("runtime.etext", 0) |
| if ldr.SymType(s) == sym.STEXT { |
| addsym(s) |
| } |
| } |
| |
| // Add text symbols. |
| for _, s := range ctxt.Textp { |
| addsym(s) |
| } |
| |
| shouldBeInSymbolTable := func(s loader.Sym) bool { |
| if ldr.AttrNotInSymbolTable(s) { |
| return false |
| } |
| name := ldr.RawSymName(s) // TODO: try not to read the name |
| if name == "" || name[0] == '.' { |
| return false |
| } |
| return true |
| } |
| |
| // Add data symbols and external references. |
| for s := loader.Sym(1); s < loader.Sym(ldr.NSym()); s++ { |
| if !ldr.AttrReachable(s) { |
| continue |
| } |
| t := ldr.SymType(s) |
| if t >= sym.SELFRXSECT && t < sym.SXREF { // data sections handled in dodata |
| if t == sym.STLSBSS { |
| // TLSBSS is not used on darwin. See data.go:allocateDataSections |
| continue |
| } |
| if !shouldBeInSymbolTable(s) { |
| continue |
| } |
| addsym(s) |
| } |
| |
| switch t { |
| case sym.SDYNIMPORT, sym.SHOSTOBJ, sym.SUNDEFEXT: |
| addsym(s) |
| } |
| |
| // Some 64-bit functions have a "$INODE64" or "$INODE64$UNIX2003" suffix. |
| if t == sym.SDYNIMPORT && ldr.SymDynimplib(s) == "/usr/lib/libSystem.B.dylib" { |
| // But only on macOS. |
| if machoPlatform == PLATFORM_MACOS { |
| switch n := ldr.SymExtname(s); n { |
| case "fdopendir": |
| switch objabi.GOARCH { |
| case "amd64": |
| ldr.SetSymExtname(s, n+"$INODE64") |
| } |
| case "readdir_r", "getfsstat": |
| switch objabi.GOARCH { |
| case "amd64": |
| ldr.SetSymExtname(s, n+"$INODE64") |
| } |
| } |
| } |
| } |
| } |
| |
| nsortsym = len(sortsym) |
| } |
| |
| func machosymorder(ctxt *Link) { |
| ldr := ctxt.loader |
| |
| // On Mac OS X Mountain Lion, we must sort exported symbols |
| // So we sort them here and pre-allocate dynid for them |
| // See https://golang.org/issue/4029 |
| for _, s := range ctxt.dynexp { |
| if !ldr.AttrReachable(s) { |
| panic("dynexp symbol is not reachable") |
| } |
| } |
| collectmachosyms(ctxt) |
| sort.Slice(sortsym[:nsortsym], func(i, j int) bool { |
| s1 := sortsym[i] |
| s2 := sortsym[j] |
| k1 := symkind(ldr, s1) |
| k2 := symkind(ldr, s2) |
| if k1 != k2 { |
| return k1 < k2 |
| } |
| return ldr.SymExtname(s1) < ldr.SymExtname(s2) // Note: unnamed symbols are not added in collectmachosyms |
| }) |
| for i, s := range sortsym { |
| ldr.SetSymDynid(s, int32(i)) |
| } |
| } |
| |
| // machoShouldExport reports whether a symbol needs to be exported. |
| // |
| // When dynamically linking, all non-local variables and plugin-exported |
| // symbols need to be exported. |
| func machoShouldExport(ctxt *Link, ldr *loader.Loader, s loader.Sym) bool { |
| if !ctxt.DynlinkingGo() || ldr.AttrLocal(s) { |
| return false |
| } |
| if ctxt.BuildMode == BuildModePlugin && strings.HasPrefix(ldr.SymExtname(s), objabi.PathToPrefix(*flagPluginPath)) { |
| return true |
| } |
| name := ldr.RawSymName(s) |
| if strings.HasPrefix(name, "go.itab.") { |
| return true |
| } |
| if strings.HasPrefix(name, "type.") && !strings.HasPrefix(name, "type..") { |
| // reduce runtime typemap pressure, but do not |
| // export alg functions (type..*), as these |
| // appear in pclntable. |
| return true |
| } |
| if strings.HasPrefix(name, "go.link.pkghash") { |
| return true |
| } |
| return ldr.SymType(s) >= sym.SFirstWritable // only writable sections |
| } |
| |
| func machosymtab(ctxt *Link) { |
| ldr := ctxt.loader |
| symtab := ldr.CreateSymForUpdate(".machosymtab", 0) |
| symstr := ldr.CreateSymForUpdate(".machosymstr", 0) |
| |
| for _, s := range sortsym[:nsortsym] { |
| symtab.AddUint32(ctxt.Arch, uint32(symstr.Size())) |
| |
| export := machoShouldExport(ctxt, ldr, s) |
| |
| // 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)) |
| |
| if t := ldr.SymType(s); t == sym.SDYNIMPORT || t == sym.SHOSTOBJ || t == sym.SUNDEFEXT { |
| symtab.AddUint8(0x01) // type N_EXT, external symbol |
| symtab.AddUint8(0) // no section |
| symtab.AddUint16(ctxt.Arch, 0) // desc |
| symtab.AddUintXX(ctxt.Arch, 0, ctxt.Arch.PtrSize) // no value |
| } else { |
| 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) // N_SECT |
| } |
| o := s |
| if outer := ldr.OuterSym(o); outer != 0 { |
| o = outer |
| } |
| if ldr.SymSect(o) == nil { |
| ldr.Errorf(s, "missing section for symbol") |
| symtab.AddUint8(0) |
| } else { |
| symtab.AddUint8(uint8(ldr.SymSect(o).Extnum)) |
| } |
| symtab.AddUint16(ctxt.Arch, 0) // desc |
| symtab.AddUintXX(ctxt.Arch, uint64(ldr.SymAddr(s)), ctxt.Arch.PtrSize) |
| } |
| } |
| } |
| |
| func machodysymtab(ctxt *Link, base int64) { |
| ml := newMachoLoad(ctxt.Arch, LC_DYSYMTAB, 18) |
| |
| n := 0 |
| ml.data[0] = uint32(n) /* ilocalsym */ |
| ml.data[1] = uint32(nkind[SymKindLocal]) /* nlocalsym */ |
| n += nkind[SymKindLocal] |
| |
| ml.data[2] = uint32(n) /* iextdefsym */ |
| ml.data[3] = uint32(nkind[SymKindExtdef]) /* nextdefsym */ |
| n += nkind[SymKindExtdef] |
| |
| ml.data[4] = uint32(n) /* iundefsym */ |
| ml.data[5] = uint32(nkind[SymKindUndef]) /* nundefsym */ |
| |
| ml.data[6] = 0 /* tocoffset */ |
| ml.data[7] = 0 /* ntoc */ |
| ml.data[8] = 0 /* modtaboff */ |
| ml.data[9] = 0 /* nmodtab */ |
| ml.data[10] = 0 /* extrefsymoff */ |
| ml.data[11] = 0 /* nextrefsyms */ |
| |
| 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) |
| ml.data[12] = uint32(base + s1) /* indirectsymoff */ |
| ml.data[13] = uint32((s2 + s3) / 4) /* nindirectsyms */ |
| |
| ml.data[14] = 0 /* extreloff */ |
| ml.data[15] = 0 /* nextrel */ |
| ml.data[16] = 0 /* locreloff */ |
| ml.data[17] = 0 /* nlocrel */ |
| } |
| |
| func doMachoLink(ctxt *Link) int64 { |
| machosymtab(ctxt) |
| |
| machoDyldInfo(ctxt) |
| |
| ldr := ctxt.loader |
| |
| // write data that will be linkedit section |
| 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) |
| |
| // Force the linkedit section to end on a 16-byte |
| // boundary. This allows pure (non-cgo) Go binaries |
| // to be code signed correctly. |
| // |
| // Apple's codesign_allocate (a helper utility for |
| // the codesign utility) can do this fine itself if |
| // it is run on a dynamic Mach-O binary. However, |
| // when it is run on a pure (non-cgo) Go binary, where |
| // the linkedit section is mostly empty, it fails to |
| // account for the extra padding that it itself adds |
| // when adding the LC_CODE_SIGNATURE load command |
| // (which must be aligned on a 16-byte boundary). |
| // |
| // By forcing the linkedit section to end on a 16-byte |
| // boundary, codesign_allocate will not need to apply |
| // any alignment padding itself, working around the |
| // issue. |
| s6b := ldr.MakeSymbolUpdater(s6) |
| for s6b.Size()%16 != 0 { |
| s6b.AddUint8(0) |
| } |
| |
| size := int(ldr.SymSize(s1) + ldr.SymSize(s2) + ldr.SymSize(s3) + ldr.SymSize(s4) + ldr.SymSize(s5) + ldr.SymSize(s6)) |
| |
| if size > 0 { |
| 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)) |
| } |
| |
| return Rnd(int64(size), int64(*FlagRound)) |
| } |
| |
| func machorelocsect(ctxt *Link, out *OutBuf, sect *sym.Section, syms []loader.Sym) { |
| // If main section has no bits, nothing to relocate. |
| if sect.Vaddr >= sect.Seg.Vaddr+sect.Seg.Filelen { |
| return |
| } |
| ldr := ctxt.loader |
| |
| for i, s := range syms { |
| if !ldr.AttrReachable(s) { |
| continue |
| } |
| if uint64(ldr.SymValue(s)) >= sect.Vaddr { |
| syms = syms[i:] |
| break |
| } |
| } |
| |
| eaddr := int32(sect.Vaddr + sect.Length) |
| for _, s := range syms { |
| if !ldr.AttrReachable(s) { |
| continue |
| } |
| if ldr.SymValue(s) >= int64(eaddr) { |
| break |
| } |
| |
| // Compute external relocations on the go, and pass to Machoreloc1 |
| // to stream out. |
| relocs := ldr.Relocs(s) |
| for ri := 0; ri < relocs.Count(); ri++ { |
| r := relocs.At(ri) |
| rr, ok := extreloc(ctxt, ldr, s, r) |
| if !ok { |
| continue |
| } |
| if rr.Xsym == 0 { |
| ldr.Errorf(s, "missing xsym in relocation") |
| continue |
| } |
| if !ldr.AttrReachable(rr.Xsym) { |
| ldr.Errorf(s, "unreachable reloc %d (%s) target %v", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), ldr.SymName(rr.Xsym)) |
| } |
| if !thearch.Machoreloc1(ctxt.Arch, out, ldr, s, rr, int64(uint64(ldr.SymValue(s)+int64(r.Off()))-sect.Vaddr)) { |
| ldr.Errorf(s, "unsupported obj reloc %d (%s)/%d to %s", r.Type(), sym.RelocName(ctxt.Arch, r.Type()), r.Siz(), ldr.SymName(r.Sym())) |
| } |
| } |
| } |
| |
| // sanity check |
| if uint64(out.Offset()) != sect.Reloff+sect.Rellen { |
| panic("machorelocsect: size mismatch") |
| } |
| } |
| |
| func machoEmitReloc(ctxt *Link) { |
| for ctxt.Out.Offset()&7 != 0 { |
| ctxt.Out.Write8(0) |
| } |
| |
| sizeExtRelocs(ctxt, thearch.MachorelocSize) |
| relocSect, wg := relocSectFn(ctxt, machorelocsect) |
| |
| relocSect(ctxt, Segtext.Sections[0], ctxt.Textp) |
| 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) |
| } |
| for i := 0; i < len(Segdwarf.Sections); i++ { |
| sect := Segdwarf.Sections[i] |
| si := dwarfp[i] |
| if si.secSym() != loader.Sym(sect.Sym) || |
| ctxt.loader.SymSect(si.secSym()) != sect { |
| panic("inconsistency between dwarfp and Segdwarf") |
| } |
| relocSect(ctxt, sect, si.syms) |
| } |
| wg.Wait() |
| } |
| |
| // hostobjMachoPlatform returns the first platform load command found |
| // in the host object, if any. |
| func hostobjMachoPlatform(h *Hostobj) (*MachoPlatformLoad, error) { |
| f, err := os.Open(h.file) |
| if err != nil { |
| return nil, fmt.Errorf("%s: failed to open host object: %v\n", h.file, err) |
| } |
| defer f.Close() |
| sr := io.NewSectionReader(f, h.off, h.length) |
| m, err := macho.NewFile(sr) |
| if err != nil { |
| // Not a valid Mach-O file. |
| return nil, nil |
| } |
| return peekMachoPlatform(m) |
| } |
| |
| // peekMachoPlatform returns the first LC_VERSION_MIN_* or LC_BUILD_VERSION |
| // load command found in the Mach-O file, if any. |
| func peekMachoPlatform(m *macho.File) (*MachoPlatformLoad, error) { |
| for _, cmd := range m.Loads { |
| raw := cmd.Raw() |
| ml := MachoLoad{ |
| type_: m.ByteOrder.Uint32(raw), |
| } |
| // Skip the type and command length. |
| data := raw[8:] |
| var p MachoPlatform |
| switch ml.type_ { |
| case LC_VERSION_MIN_IPHONEOS: |
| p = PLATFORM_IOS |
| case LC_VERSION_MIN_MACOSX: |
| p = PLATFORM_MACOS |
| case LC_VERSION_MIN_WATCHOS: |
| p = PLATFORM_WATCHOS |
| case LC_VERSION_MIN_TVOS: |
| p = PLATFORM_TVOS |
| case LC_BUILD_VERSION: |
| p = MachoPlatform(m.ByteOrder.Uint32(data)) |
| default: |
| continue |
| } |
| ml.data = make([]uint32, len(data)/4) |
| r := bytes.NewReader(data) |
| if err := binary.Read(r, m.ByteOrder, &ml.data); err != nil { |
| return nil, err |
| } |
| return &MachoPlatformLoad{ |
| platform: p, |
| cmd: ml, |
| }, nil |
| } |
| 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. |
| } |
