| // Copyright 2017 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 loadmacho implements a Mach-O file reader. |
| package loadmacho |
| |
| import ( |
| "bytes" |
| "cmd/internal/bio" |
| "cmd/internal/objabi" |
| "cmd/internal/sys" |
| "cmd/link/internal/sym" |
| "encoding/binary" |
| "fmt" |
| "io" |
| "sort" |
| ) |
| |
| /* |
| Derived from Plan 9 from User Space's src/libmach/elf.h, elf.c |
| http://code.swtch.com/plan9port/src/tip/src/libmach/ |
| |
| Copyright © 2004 Russ Cox. |
| Portions Copyright © 2008-2010 Google Inc. |
| Portions Copyright © 2010 The Go Authors. |
| |
| Permission is hereby granted, free of charge, to any person obtaining a copy |
| of this software and associated documentation files (the "Software"), to deal |
| in the Software without restriction, including without limitation the rights |
| to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| copies of the Software, and to permit persons to whom the Software is |
| furnished to do so, subject to the following conditions: |
| |
| The above copyright notice and this permission notice shall be included in |
| all copies or substantial portions of the Software. |
| |
| THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
| THE SOFTWARE. |
| */ |
| const ( |
| N_EXT = 0x01 |
| N_TYPE = 0x1e |
| N_STAB = 0xe0 |
| ) |
| |
| // TODO(crawshaw): de-duplicate these symbols with cmd/internal/ld |
| const ( |
| MACHO_X86_64_RELOC_UNSIGNED = 0 |
| MACHO_X86_64_RELOC_SIGNED = 1 |
| MACHO_FAKE_GOTPCREL = 100 |
| ) |
| |
| type ldMachoObj struct { |
| f *bio.Reader |
| base int64 // off in f where Mach-O begins |
| length int64 // length of Mach-O |
| is64 bool |
| name string |
| e binary.ByteOrder |
| cputype uint |
| subcputype uint |
| filetype uint32 |
| flags uint32 |
| cmd []ldMachoCmd |
| ncmd uint |
| } |
| |
| type ldMachoCmd struct { |
| type_ int |
| off uint32 |
| size uint32 |
| seg ldMachoSeg |
| sym ldMachoSymtab |
| dsym ldMachoDysymtab |
| } |
| |
| type ldMachoSeg struct { |
| name string |
| vmaddr uint64 |
| vmsize uint64 |
| fileoff uint32 |
| filesz uint32 |
| maxprot uint32 |
| initprot uint32 |
| nsect uint32 |
| flags uint32 |
| sect []ldMachoSect |
| } |
| |
| type ldMachoSect struct { |
| name string |
| segname string |
| addr uint64 |
| size uint64 |
| off uint32 |
| align uint32 |
| reloff uint32 |
| nreloc uint32 |
| flags uint32 |
| res1 uint32 |
| res2 uint32 |
| sym *sym.Symbol |
| rel []ldMachoRel |
| } |
| |
| type ldMachoRel struct { |
| addr uint32 |
| symnum uint32 |
| pcrel uint8 |
| length uint8 |
| extrn uint8 |
| type_ uint8 |
| scattered uint8 |
| value uint32 |
| } |
| |
| type ldMachoSymtab struct { |
| symoff uint32 |
| nsym uint32 |
| stroff uint32 |
| strsize uint32 |
| str []byte |
| sym []ldMachoSym |
| } |
| |
| type ldMachoSym struct { |
| name string |
| type_ uint8 |
| sectnum uint8 |
| desc uint16 |
| kind int8 |
| value uint64 |
| sym *sym.Symbol |
| } |
| |
| type ldMachoDysymtab struct { |
| ilocalsym uint32 |
| nlocalsym uint32 |
| iextdefsym uint32 |
| nextdefsym uint32 |
| iundefsym uint32 |
| nundefsym uint32 |
| tocoff uint32 |
| ntoc uint32 |
| modtaboff uint32 |
| nmodtab uint32 |
| extrefsymoff uint32 |
| nextrefsyms uint32 |
| indirectsymoff uint32 |
| nindirectsyms uint32 |
| extreloff uint32 |
| nextrel uint32 |
| locreloff uint32 |
| nlocrel uint32 |
| indir []uint32 |
| } |
| |
| const ( |
| LdMachoCpuVax = 1 |
| LdMachoCpu68000 = 6 |
| LdMachoCpu386 = 7 |
| LdMachoCpuAmd64 = 0x1000007 |
| LdMachoCpuMips = 8 |
| LdMachoCpu98000 = 10 |
| LdMachoCpuHppa = 11 |
| LdMachoCpuArm = 12 |
| LdMachoCpu88000 = 13 |
| LdMachoCpuSparc = 14 |
| LdMachoCpu860 = 15 |
| LdMachoCpuAlpha = 16 |
| LdMachoCpuPower = 18 |
| LdMachoCmdSegment = 1 |
| LdMachoCmdSymtab = 2 |
| LdMachoCmdSymseg = 3 |
| LdMachoCmdThread = 4 |
| LdMachoCmdDysymtab = 11 |
| LdMachoCmdSegment64 = 25 |
| LdMachoFileObject = 1 |
| LdMachoFileExecutable = 2 |
| LdMachoFileFvmlib = 3 |
| LdMachoFileCore = 4 |
| LdMachoFilePreload = 5 |
| ) |
| |
| func unpackcmd(p []byte, m *ldMachoObj, c *ldMachoCmd, type_ uint, sz uint) int { |
| e4 := m.e.Uint32 |
| e8 := m.e.Uint64 |
| |
| c.type_ = int(type_) |
| c.size = uint32(sz) |
| switch type_ { |
| default: |
| return -1 |
| |
| case LdMachoCmdSegment: |
| if sz < 56 { |
| return -1 |
| } |
| c.seg.name = cstring(p[8:24]) |
| c.seg.vmaddr = uint64(e4(p[24:])) |
| c.seg.vmsize = uint64(e4(p[28:])) |
| c.seg.fileoff = e4(p[32:]) |
| c.seg.filesz = e4(p[36:]) |
| c.seg.maxprot = e4(p[40:]) |
| c.seg.initprot = e4(p[44:]) |
| c.seg.nsect = e4(p[48:]) |
| c.seg.flags = e4(p[52:]) |
| c.seg.sect = make([]ldMachoSect, c.seg.nsect) |
| if uint32(sz) < 56+c.seg.nsect*68 { |
| return -1 |
| } |
| p = p[56:] |
| var s *ldMachoSect |
| for i := 0; uint32(i) < c.seg.nsect; i++ { |
| s = &c.seg.sect[i] |
| s.name = cstring(p[0:16]) |
| s.segname = cstring(p[16:32]) |
| s.addr = uint64(e4(p[32:])) |
| s.size = uint64(e4(p[36:])) |
| s.off = e4(p[40:]) |
| s.align = e4(p[44:]) |
| s.reloff = e4(p[48:]) |
| s.nreloc = e4(p[52:]) |
| s.flags = e4(p[56:]) |
| s.res1 = e4(p[60:]) |
| s.res2 = e4(p[64:]) |
| p = p[68:] |
| } |
| |
| case LdMachoCmdSegment64: |
| if sz < 72 { |
| return -1 |
| } |
| c.seg.name = cstring(p[8:24]) |
| c.seg.vmaddr = e8(p[24:]) |
| c.seg.vmsize = e8(p[32:]) |
| c.seg.fileoff = uint32(e8(p[40:])) |
| c.seg.filesz = uint32(e8(p[48:])) |
| c.seg.maxprot = e4(p[56:]) |
| c.seg.initprot = e4(p[60:]) |
| c.seg.nsect = e4(p[64:]) |
| c.seg.flags = e4(p[68:]) |
| c.seg.sect = make([]ldMachoSect, c.seg.nsect) |
| if uint32(sz) < 72+c.seg.nsect*80 { |
| return -1 |
| } |
| p = p[72:] |
| var s *ldMachoSect |
| for i := 0; uint32(i) < c.seg.nsect; i++ { |
| s = &c.seg.sect[i] |
| s.name = cstring(p[0:16]) |
| s.segname = cstring(p[16:32]) |
| s.addr = e8(p[32:]) |
| s.size = e8(p[40:]) |
| s.off = e4(p[48:]) |
| s.align = e4(p[52:]) |
| s.reloff = e4(p[56:]) |
| s.nreloc = e4(p[60:]) |
| s.flags = e4(p[64:]) |
| s.res1 = e4(p[68:]) |
| s.res2 = e4(p[72:]) |
| |
| // p+76 is reserved |
| p = p[80:] |
| } |
| |
| case LdMachoCmdSymtab: |
| if sz < 24 { |
| return -1 |
| } |
| c.sym.symoff = e4(p[8:]) |
| c.sym.nsym = e4(p[12:]) |
| c.sym.stroff = e4(p[16:]) |
| c.sym.strsize = e4(p[20:]) |
| |
| case LdMachoCmdDysymtab: |
| if sz < 80 { |
| return -1 |
| } |
| c.dsym.ilocalsym = e4(p[8:]) |
| c.dsym.nlocalsym = e4(p[12:]) |
| c.dsym.iextdefsym = e4(p[16:]) |
| c.dsym.nextdefsym = e4(p[20:]) |
| c.dsym.iundefsym = e4(p[24:]) |
| c.dsym.nundefsym = e4(p[28:]) |
| c.dsym.tocoff = e4(p[32:]) |
| c.dsym.ntoc = e4(p[36:]) |
| c.dsym.modtaboff = e4(p[40:]) |
| c.dsym.nmodtab = e4(p[44:]) |
| c.dsym.extrefsymoff = e4(p[48:]) |
| c.dsym.nextrefsyms = e4(p[52:]) |
| c.dsym.indirectsymoff = e4(p[56:]) |
| c.dsym.nindirectsyms = e4(p[60:]) |
| c.dsym.extreloff = e4(p[64:]) |
| c.dsym.nextrel = e4(p[68:]) |
| c.dsym.locreloff = e4(p[72:]) |
| c.dsym.nlocrel = e4(p[76:]) |
| } |
| |
| return 0 |
| } |
| |
| func macholoadrel(m *ldMachoObj, sect *ldMachoSect) int { |
| if sect.rel != nil || sect.nreloc == 0 { |
| return 0 |
| } |
| rel := make([]ldMachoRel, sect.nreloc) |
| n := int(sect.nreloc * 8) |
| buf := make([]byte, n) |
| if m.f.Seek(m.base+int64(sect.reloff), 0) < 0 { |
| return -1 |
| } |
| if _, err := io.ReadFull(m.f, buf); err != nil { |
| return -1 |
| } |
| for i := uint32(0); i < sect.nreloc; i++ { |
| r := &rel[i] |
| p := buf[i*8:] |
| r.addr = m.e.Uint32(p) |
| |
| // TODO(rsc): Wrong interpretation for big-endian bitfields? |
| if r.addr&0x80000000 != 0 { |
| // scatterbrained relocation |
| r.scattered = 1 |
| |
| v := r.addr >> 24 |
| r.addr &= 0xFFFFFF |
| r.type_ = uint8(v & 0xF) |
| v >>= 4 |
| r.length = 1 << (v & 3) |
| v >>= 2 |
| r.pcrel = uint8(v & 1) |
| r.value = m.e.Uint32(p[4:]) |
| } else { |
| v := m.e.Uint32(p[4:]) |
| r.symnum = v & 0xFFFFFF |
| v >>= 24 |
| r.pcrel = uint8(v & 1) |
| v >>= 1 |
| r.length = 1 << (v & 3) |
| v >>= 2 |
| r.extrn = uint8(v & 1) |
| v >>= 1 |
| r.type_ = uint8(v) |
| } |
| } |
| |
| sect.rel = rel |
| return 0 |
| } |
| |
| func macholoaddsym(m *ldMachoObj, d *ldMachoDysymtab) int { |
| n := int(d.nindirectsyms) |
| |
| p := make([]byte, n*4) |
| if m.f.Seek(m.base+int64(d.indirectsymoff), 0) < 0 { |
| return -1 |
| } |
| if _, err := io.ReadFull(m.f, p); err != nil { |
| return -1 |
| } |
| |
| d.indir = make([]uint32, n) |
| for i := 0; i < n; i++ { |
| d.indir[i] = m.e.Uint32(p[4*i:]) |
| } |
| return 0 |
| } |
| |
| func macholoadsym(m *ldMachoObj, symtab *ldMachoSymtab) int { |
| if symtab.sym != nil { |
| return 0 |
| } |
| |
| strbuf := make([]byte, symtab.strsize) |
| if m.f.Seek(m.base+int64(symtab.stroff), 0) < 0 { |
| return -1 |
| } |
| if _, err := io.ReadFull(m.f, strbuf); err != nil { |
| return -1 |
| } |
| |
| symsize := 12 |
| if m.is64 { |
| symsize = 16 |
| } |
| n := int(symtab.nsym * uint32(symsize)) |
| symbuf := make([]byte, n) |
| if m.f.Seek(m.base+int64(symtab.symoff), 0) < 0 { |
| return -1 |
| } |
| if _, err := io.ReadFull(m.f, symbuf); err != nil { |
| return -1 |
| } |
| sym := make([]ldMachoSym, symtab.nsym) |
| p := symbuf |
| for i := uint32(0); i < symtab.nsym; i++ { |
| s := &sym[i] |
| v := m.e.Uint32(p) |
| if v >= symtab.strsize { |
| return -1 |
| } |
| s.name = cstring(strbuf[v:]) |
| s.type_ = p[4] |
| s.sectnum = p[5] |
| s.desc = m.e.Uint16(p[6:]) |
| if m.is64 { |
| s.value = m.e.Uint64(p[8:]) |
| } else { |
| s.value = uint64(m.e.Uint32(p[8:])) |
| } |
| p = p[symsize:] |
| } |
| |
| symtab.str = strbuf |
| symtab.sym = sym |
| return 0 |
| } |
| |
| // Load loads the Mach-O file pn from f. |
| // Symbols are written into syms, and a slice of the text symbols is returned. |
| func Load(arch *sys.Arch, syms *sym.Symbols, f *bio.Reader, pkg string, length int64, pn string) (textp []*sym.Symbol, err error) { |
| errorf := func(str string, args ...interface{}) ([]*sym.Symbol, error) { |
| return nil, fmt.Errorf("loadmacho: %v: %v", pn, fmt.Sprintf(str, args...)) |
| } |
| |
| localSymVersion := syms.IncVersion() |
| base := f.Offset() |
| |
| var hdr [7 * 4]uint8 |
| if _, err := io.ReadFull(f, hdr[:]); err != nil { |
| return errorf("reading hdr: %v", err) |
| } |
| |
| var e binary.ByteOrder |
| if binary.BigEndian.Uint32(hdr[:])&^1 == 0xFEEDFACE { |
| e = binary.BigEndian |
| } else if binary.LittleEndian.Uint32(hdr[:])&^1 == 0xFEEDFACE { |
| e = binary.LittleEndian |
| } else { |
| return errorf("bad magic - not mach-o file") |
| } |
| |
| is64 := e.Uint32(hdr[:]) == 0xFEEDFACF |
| ncmd := e.Uint32(hdr[4*4:]) |
| cmdsz := e.Uint32(hdr[5*4:]) |
| if ncmd > 0x10000 || cmdsz >= 0x01000000 { |
| return errorf("implausible mach-o header ncmd=%d cmdsz=%d", ncmd, cmdsz) |
| } |
| |
| if is64 { |
| f.Seek(4, 1) // skip reserved word in header |
| } |
| |
| m := &ldMachoObj{ |
| f: f, |
| e: e, |
| cputype: uint(e.Uint32(hdr[1*4:])), |
| subcputype: uint(e.Uint32(hdr[2*4:])), |
| filetype: e.Uint32(hdr[3*4:]), |
| ncmd: uint(ncmd), |
| flags: e.Uint32(hdr[6*4:]), |
| is64: is64, |
| base: base, |
| length: length, |
| name: pn, |
| } |
| |
| switch arch.Family { |
| default: |
| return errorf("mach-o %s unimplemented", arch.Name) |
| |
| case sys.AMD64: |
| if e != binary.LittleEndian || m.cputype != LdMachoCpuAmd64 { |
| return errorf("mach-o object but not amd64") |
| } |
| |
| case sys.I386: |
| if e != binary.LittleEndian || m.cputype != LdMachoCpu386 { |
| return errorf("mach-o object but not 386") |
| } |
| } |
| |
| m.cmd = make([]ldMachoCmd, ncmd) |
| cmdp := make([]byte, cmdsz) |
| if _, err := io.ReadFull(f, cmdp); err != nil { |
| return errorf("reading cmds: %v", err) |
| } |
| |
| // read and parse load commands |
| var c *ldMachoCmd |
| |
| var symtab *ldMachoSymtab |
| var dsymtab *ldMachoDysymtab |
| |
| off := uint32(len(hdr)) |
| for i := uint32(0); i < ncmd; i++ { |
| ty := e.Uint32(cmdp) |
| sz := e.Uint32(cmdp[4:]) |
| m.cmd[i].off = off |
| unpackcmd(cmdp, m, &m.cmd[i], uint(ty), uint(sz)) |
| cmdp = cmdp[sz:] |
| off += sz |
| if ty == LdMachoCmdSymtab { |
| if symtab != nil { |
| return errorf("multiple symbol tables") |
| } |
| |
| symtab = &m.cmd[i].sym |
| macholoadsym(m, symtab) |
| } |
| |
| if ty == LdMachoCmdDysymtab { |
| dsymtab = &m.cmd[i].dsym |
| macholoaddsym(m, dsymtab) |
| } |
| |
| if (is64 && ty == LdMachoCmdSegment64) || (!is64 && ty == LdMachoCmdSegment) { |
| if c != nil { |
| return errorf("multiple load commands") |
| } |
| |
| c = &m.cmd[i] |
| } |
| } |
| |
| // load text and data segments into memory. |
| // they are not as small as the load commands, but we'll need |
| // the memory anyway for the symbol images, so we might |
| // as well use one large chunk. |
| if c == nil { |
| return errorf("no load command") |
| } |
| |
| if symtab == nil { |
| // our work is done here - no symbols means nothing can refer to this file |
| return |
| } |
| |
| if int64(c.seg.fileoff+c.seg.filesz) >= length { |
| return errorf("load segment out of range") |
| } |
| |
| if f.Seek(m.base+int64(c.seg.fileoff), 0) < 0 { |
| return errorf("cannot load object data: seek failed") |
| } |
| dat := make([]byte, c.seg.filesz) |
| if _, err := io.ReadFull(f, dat); err != nil { |
| return errorf("cannot load object data: %v", err) |
| } |
| |
| for i := uint32(0); i < c.seg.nsect; i++ { |
| sect := &c.seg.sect[i] |
| if sect.segname != "__TEXT" && sect.segname != "__DATA" { |
| continue |
| } |
| if sect.name == "__eh_frame" { |
| continue |
| } |
| name := fmt.Sprintf("%s(%s/%s)", pkg, sect.segname, sect.name) |
| s := syms.Lookup(name, localSymVersion) |
| if s.Type != 0 { |
| return errorf("duplicate %s/%s", sect.segname, sect.name) |
| } |
| |
| if sect.flags&0xff == 1 { // S_ZEROFILL |
| s.P = make([]byte, sect.size) |
| } else { |
| s.P = dat[sect.addr-c.seg.vmaddr:][:sect.size] |
| } |
| s.Size = int64(len(s.P)) |
| |
| if sect.segname == "__TEXT" { |
| if sect.name == "__text" { |
| s.Type = sym.STEXT |
| } else { |
| s.Type = sym.SRODATA |
| } |
| } else { |
| if sect.name == "__bss" { |
| s.Type = sym.SNOPTRBSS |
| s.P = s.P[:0] |
| } else { |
| s.Type = sym.SNOPTRDATA |
| } |
| } |
| |
| sect.sym = s |
| } |
| |
| // enter sub-symbols into symbol table. |
| // have to guess sizes from next symbol. |
| for i := uint32(0); i < symtab.nsym; i++ { |
| machsym := &symtab.sym[i] |
| if machsym.type_&N_STAB != 0 { |
| continue |
| } |
| |
| // TODO: check sym->type against outer->type. |
| name := machsym.name |
| |
| if name[0] == '_' && name[1] != '\x00' { |
| name = name[1:] |
| } |
| v := 0 |
| if machsym.type_&N_EXT == 0 { |
| v = localSymVersion |
| } |
| s := syms.Lookup(name, v) |
| if machsym.type_&N_EXT == 0 { |
| s.Attr |= sym.AttrDuplicateOK |
| } |
| machsym.sym = s |
| if machsym.sectnum == 0 { // undefined |
| continue |
| } |
| if uint32(machsym.sectnum) > c.seg.nsect { |
| return errorf("reference to invalid section %d", machsym.sectnum) |
| } |
| |
| sect := &c.seg.sect[machsym.sectnum-1] |
| outer := sect.sym |
| if outer == nil { |
| continue // ignore reference to invalid section |
| } |
| |
| if s.Outer != nil { |
| if s.Attr.DuplicateOK() { |
| continue |
| } |
| return errorf("duplicate symbol reference: %s in both %s and %s", s.Name, s.Outer.Name, sect.sym.Name) |
| } |
| |
| s.Type = outer.Type |
| s.Attr |= sym.AttrSubSymbol |
| s.Sub = outer.Sub |
| outer.Sub = s |
| s.Outer = outer |
| s.Value = int64(machsym.value - sect.addr) |
| if !s.Attr.CgoExportDynamic() { |
| s.SetDynimplib("") // satisfy dynimport |
| } |
| if outer.Type == sym.STEXT { |
| if s.Attr.External() && !s.Attr.DuplicateOK() { |
| return errorf("%v: duplicate symbol definition", s) |
| } |
| s.Attr |= sym.AttrExternal |
| } |
| |
| machsym.sym = s |
| } |
| |
| // Sort outer lists by address, adding to textp. |
| // This keeps textp in increasing address order. |
| for i := 0; uint32(i) < c.seg.nsect; i++ { |
| sect := &c.seg.sect[i] |
| s := sect.sym |
| if s == nil { |
| continue |
| } |
| if s.Sub != nil { |
| s.Sub = sym.SortSub(s.Sub) |
| |
| // assign sizes, now that we know symbols in sorted order. |
| for s1 := s.Sub; s1 != nil; s1 = s1.Sub { |
| if s1.Sub != nil { |
| s1.Size = s1.Sub.Value - s1.Value |
| } else { |
| s1.Size = s.Value + s.Size - s1.Value |
| } |
| } |
| } |
| |
| if s.Type == sym.STEXT { |
| if s.Attr.OnList() { |
| return errorf("symbol %s listed multiple times", s.Name) |
| } |
| s.Attr |= sym.AttrOnList |
| textp = append(textp, s) |
| for s1 := s.Sub; s1 != nil; s1 = s1.Sub { |
| if s1.Attr.OnList() { |
| return errorf("symbol %s listed multiple times", s1.Name) |
| } |
| s1.Attr |= sym.AttrOnList |
| textp = append(textp, s1) |
| } |
| } |
| } |
| |
| // load relocations |
| for i := 0; uint32(i) < c.seg.nsect; i++ { |
| sect := &c.seg.sect[i] |
| s := sect.sym |
| if s == nil { |
| continue |
| } |
| macholoadrel(m, sect) |
| if sect.rel == nil { |
| continue |
| } |
| r := make([]sym.Reloc, sect.nreloc) |
| rpi := 0 |
| Reloc: |
| for j := uint32(0); j < sect.nreloc; j++ { |
| rp := &r[rpi] |
| rel := §.rel[j] |
| if rel.scattered != 0 { |
| if arch.Family != sys.I386 { |
| // mach-o only uses scattered relocation on 32-bit platforms |
| return errorf("%v: unexpected scattered relocation", s) |
| } |
| |
| // on 386, rewrite scattered 4/1 relocation and some |
| // scattered 2/1 relocation into the pseudo-pc-relative |
| // reference that it is. |
| // assume that the second in the pair is in this section |
| // and use that as the pc-relative base. |
| if j+1 >= sect.nreloc { |
| return errorf("unsupported scattered relocation %d", int(rel.type_)) |
| } |
| |
| if sect.rel[j+1].scattered == 0 || sect.rel[j+1].type_ != 1 || (rel.type_ != 4 && rel.type_ != 2) || uint64(sect.rel[j+1].value) < sect.addr || uint64(sect.rel[j+1].value) >= sect.addr+sect.size { |
| return errorf("unsupported scattered relocation %d/%d", int(rel.type_), int(sect.rel[j+1].type_)) |
| } |
| |
| rp.Siz = rel.length |
| rp.Off = int32(rel.addr) |
| |
| // NOTE(rsc): I haven't worked out why (really when) |
| // we should ignore the addend on a |
| // scattered relocation, but it seems that the |
| // common case is we ignore it. |
| // It's likely that this is not strictly correct |
| // and that the math should look something |
| // like the non-scattered case below. |
| rp.Add = 0 |
| |
| // want to make it pc-relative aka relative to rp->off+4 |
| // but the scatter asks for relative to off = sect->rel[j+1].value - sect->addr. |
| // adjust rp->add accordingly. |
| rp.Type = objabi.R_PCREL |
| |
| rp.Add += int64(uint64(int64(rp.Off)+4) - (uint64(sect.rel[j+1].value) - sect.addr)) |
| |
| // now consider the desired symbol. |
| // find the section where it lives. |
| for k := 0; uint32(k) < c.seg.nsect; k++ { |
| ks := &c.seg.sect[k] |
| if ks.addr <= uint64(rel.value) && uint64(rel.value) < ks.addr+ks.size { |
| if ks.sym != nil { |
| rp.Sym = ks.sym |
| rp.Add += int64(uint64(rel.value) - ks.addr) |
| } else if ks.segname == "__IMPORT" && ks.name == "__pointers" { |
| // handle reference to __IMPORT/__pointers. |
| // how much worse can this get? |
| // why are we supporting 386 on the mac anyway? |
| rp.Type = 512 + MACHO_FAKE_GOTPCREL |
| |
| // figure out which pointer this is a reference to. |
| k = int(uint64(ks.res1) + (uint64(rel.value)-ks.addr)/4) |
| |
| // load indirect table for __pointers |
| // fetch symbol number |
| if dsymtab == nil || k < 0 || uint32(k) >= dsymtab.nindirectsyms || dsymtab.indir == nil { |
| return errorf("invalid scattered relocation: indirect symbol reference out of range") |
| } |
| |
| k = int(dsymtab.indir[k]) |
| if k < 0 || uint32(k) >= symtab.nsym { |
| return errorf("invalid scattered relocation: symbol reference out of range") |
| } |
| |
| rp.Sym = symtab.sym[k].sym |
| } else { |
| return errorf("unsupported scattered relocation: reference to %s/%s", ks.segname, ks.name) |
| } |
| |
| rpi++ |
| |
| // skip #1 of 2 rel; continue skips #2 of 2. |
| j++ |
| |
| continue Reloc |
| } |
| } |
| |
| return errorf("unsupported scattered relocation: invalid address %#x", rel.addr) |
| } |
| |
| rp.Siz = rel.length |
| rp.Type = 512 + (objabi.RelocType(rel.type_) << 1) + objabi.RelocType(rel.pcrel) |
| rp.Off = int32(rel.addr) |
| |
| // Handle X86_64_RELOC_SIGNED referencing a section (rel->extrn == 0). |
| if arch.Family == sys.AMD64 && rel.extrn == 0 && rel.type_ == MACHO_X86_64_RELOC_SIGNED { |
| // Calculate the addend as the offset into the section. |
| // |
| // The rip-relative offset stored in the object file is encoded |
| // as follows: |
| // |
| // movsd 0x00000360(%rip),%xmm0 |
| // |
| // To get the absolute address of the value this rip-relative address is pointing |
| // to, we must add the address of the next instruction to it. This is done by |
| // taking the address of the relocation and adding 4 to it (since the rip-relative |
| // offset can at most be 32 bits long). To calculate the offset into the section the |
| // relocation is referencing, we subtract the vaddr of the start of the referenced |
| // section found in the original object file. |
| // |
| // [For future reference, see Darwin's /usr/include/mach-o/x86_64/reloc.h] |
| secaddr := c.seg.sect[rel.symnum-1].addr |
| |
| rp.Add = int64(uint64(int64(int32(e.Uint32(s.P[rp.Off:])))+int64(rp.Off)+4) - secaddr) |
| } else { |
| rp.Add = int64(int32(e.Uint32(s.P[rp.Off:]))) |
| } |
| |
| // An unsigned internal relocation has a value offset |
| // by the section address. |
| if arch.Family == sys.AMD64 && rel.extrn == 0 && rel.type_ == MACHO_X86_64_RELOC_UNSIGNED { |
| secaddr := c.seg.sect[rel.symnum-1].addr |
| rp.Add -= int64(secaddr) |
| } |
| |
| // For i386 Mach-O PC-relative, the addend is written such that |
| // it *is* the PC being subtracted. Use that to make |
| // it match our version of PC-relative. |
| if rel.pcrel != 0 && arch.Family == sys.I386 { |
| rp.Add += int64(rp.Off) + int64(rp.Siz) |
| } |
| if rel.extrn == 0 { |
| if rel.symnum < 1 || rel.symnum > c.seg.nsect { |
| return errorf("invalid relocation: section reference out of range %d vs %d", rel.symnum, c.seg.nsect) |
| } |
| |
| rp.Sym = c.seg.sect[rel.symnum-1].sym |
| if rp.Sym == nil { |
| return errorf("invalid relocation: %s", c.seg.sect[rel.symnum-1].name) |
| } |
| |
| // References to symbols in other sections |
| // include that information in the addend. |
| // We only care about the delta from the |
| // section base. |
| if arch.Family == sys.I386 { |
| rp.Add -= int64(c.seg.sect[rel.symnum-1].addr) |
| } |
| } else { |
| if rel.symnum >= symtab.nsym { |
| return errorf("invalid relocation: symbol reference out of range") |
| } |
| |
| rp.Sym = symtab.sym[rel.symnum].sym |
| } |
| |
| rpi++ |
| } |
| |
| sort.Sort(sym.RelocByOff(r[:rpi])) |
| s.R = r |
| s.R = s.R[:rpi] |
| } |
| |
| return textp, nil |
| } |
| |
| func cstring(x []byte) string { |
| i := bytes.IndexByte(x, '\x00') |
| if i >= 0 { |
| x = x[:i] |
| } |
| return string(x) |
| } |
