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// Copyright 2013 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.
// Writing of Go object files.
package obj
import (
"bufio"
"cmd/internal/dwarf"
"cmd/internal/objabi"
"cmd/internal/sys"
"fmt"
"log"
"path/filepath"
"sort"
)
// objWriter writes Go object files.
type objWriter struct {
wr *bufio.Writer
ctxt *Link
// Temporary buffer for zigzag int writing.
varintbuf [10]uint8
// Provide the index of a symbol reference by symbol name.
// One map for versioned symbols and one for unversioned symbols.
// Used for deduplicating the symbol reference list.
refIdx map[string]int
vrefIdx map[string]int
// Number of objects written of each type.
nRefs int
nData int
nReloc int
nPcdata int
nAutom int
nFuncdata int
nFile int
}
func (w *objWriter) addLengths(s *LSym) {
w.nData += len(s.P)
w.nReloc += len(s.R)
if s.Type != objabi.STEXT {
return
}
pc := &s.Func.Pcln
data := 0
data += len(pc.Pcsp.P)
data += len(pc.Pcfile.P)
data += len(pc.Pcline.P)
data += len(pc.Pcinline.P)
for i := 0; i < len(pc.Pcdata); i++ {
data += len(pc.Pcdata[i].P)
}
w.nData += data
w.nPcdata += len(pc.Pcdata)
w.nAutom += len(s.Func.Autom)
w.nFuncdata += len(pc.Funcdataoff)
w.nFile += len(pc.File)
}
func (w *objWriter) writeLengths() {
w.writeInt(int64(w.nData))
w.writeInt(int64(w.nReloc))
w.writeInt(int64(w.nPcdata))
w.writeInt(int64(w.nAutom))
w.writeInt(int64(w.nFuncdata))
w.writeInt(int64(w.nFile))
}
func newObjWriter(ctxt *Link, b *bufio.Writer) *objWriter {
return &objWriter{
ctxt: ctxt,
wr: b,
vrefIdx: make(map[string]int),
refIdx: make(map[string]int),
}
}
func WriteObjFile(ctxt *Link, b *bufio.Writer) {
w := newObjWriter(ctxt, b)
// Magic header
w.wr.WriteString("\x00\x00go19ld")
// Version
w.wr.WriteByte(1)
// Autolib
for _, pkg := range ctxt.Imports {
w.writeString(pkg)
}
w.writeString("")
// Symbol references
for _, s := range ctxt.Text {
w.writeRefs(s)
w.addLengths(s)
}
for _, s := range ctxt.Data {
w.writeRefs(s)
w.addLengths(s)
}
// End symbol references
w.wr.WriteByte(0xff)
// Lengths
w.writeLengths()
// Data block
for _, s := range ctxt.Text {
w.wr.Write(s.P)
pc := &s.Func.Pcln
w.wr.Write(pc.Pcsp.P)
w.wr.Write(pc.Pcfile.P)
w.wr.Write(pc.Pcline.P)
w.wr.Write(pc.Pcinline.P)
for i := 0; i < len(pc.Pcdata); i++ {
w.wr.Write(pc.Pcdata[i].P)
}
}
for _, s := range ctxt.Data {
if len(s.P) > 0 {
switch s.Type {
case objabi.SBSS, objabi.SNOPTRBSS, objabi.STLSBSS:
ctxt.Diag("cannot provide data for %v sym %v", s.Type, s.Name)
}
}
w.wr.Write(s.P)
}
// Symbols
for _, s := range ctxt.Text {
w.writeSym(s)
}
for _, s := range ctxt.Data {
w.writeSym(s)
}
// Magic footer
w.wr.WriteString("\xff\xffgo19ld")
}
// Symbols are prefixed so their content doesn't get confused with the magic footer.
const symPrefix = 0xfe
func (w *objWriter) writeRef(s *LSym, isPath bool) {
if s == nil || s.RefIdx != 0 {
return
}
var m map[string]int
if !s.Static() {
m = w.refIdx
} else {
m = w.vrefIdx
}
if idx := m[s.Name]; idx != 0 {
s.RefIdx = idx
return
}
w.wr.WriteByte(symPrefix)
if isPath {
w.writeString(filepath.ToSlash(s.Name))
} else {
w.writeString(s.Name)
}
// Write "version".
if s.Static() {
w.writeInt(1)
} else {
w.writeInt(0)
}
w.nRefs++
s.RefIdx = w.nRefs
m[s.Name] = w.nRefs
}
func (w *objWriter) writeRefs(s *LSym) {
w.writeRef(s, false)
w.writeRef(s.Gotype, false)
for i := range s.R {
w.writeRef(s.R[i].Sym, false)
}
if s.Type == objabi.STEXT {
for _, a := range s.Func.Autom {
w.writeRef(a.Asym, false)
w.writeRef(a.Gotype, false)
}
pc := &s.Func.Pcln
for _, d := range pc.Funcdata {
w.writeRef(d, false)
}
for _, f := range pc.File {
fsym := w.ctxt.Lookup(f)
w.writeRef(fsym, true)
}
for _, call := range pc.InlTree.nodes {
w.writeRef(call.Func, false)
f, _ := linkgetlineFromPos(w.ctxt, call.Pos)
fsym := w.ctxt.Lookup(f)
w.writeRef(fsym, true)
}
}
}
func (w *objWriter) writeSymDebug(s *LSym) {
ctxt := w.ctxt
fmt.Fprintf(ctxt.Bso, "%s ", s.Name)
if s.Type != 0 {
fmt.Fprintf(ctxt.Bso, "%v ", s.Type)
}
if s.Static() {
fmt.Fprint(ctxt.Bso, "static ")
}
if s.DuplicateOK() {
fmt.Fprintf(ctxt.Bso, "dupok ")
}
if s.CFunc() {
fmt.Fprintf(ctxt.Bso, "cfunc ")
}
if s.NoSplit() {
fmt.Fprintf(ctxt.Bso, "nosplit ")
}
fmt.Fprintf(ctxt.Bso, "size=%d", s.Size)
if s.Type == objabi.STEXT {
fmt.Fprintf(ctxt.Bso, " args=%#x locals=%#x", uint64(s.Func.Args), uint64(s.Func.Locals))
if s.Leaf() {
fmt.Fprintf(ctxt.Bso, " leaf")
}
}
fmt.Fprintf(ctxt.Bso, "\n")
if s.Type == objabi.STEXT {
for p := s.Func.Text; p != nil; p = p.Link {
fmt.Fprintf(ctxt.Bso, "\t%#04x %v\n", uint(int(p.Pc)), p)
}
}
for i := 0; i < len(s.P); i += 16 {
fmt.Fprintf(ctxt.Bso, "\t%#04x", uint(i))
j := i
for j = i; j < i+16 && j < len(s.P); j++ {
fmt.Fprintf(ctxt.Bso, " %02x", s.P[j])
}
for ; j < i+16; j++ {
fmt.Fprintf(ctxt.Bso, " ")
}
fmt.Fprintf(ctxt.Bso, " ")
for j = i; j < i+16 && j < len(s.P); j++ {
c := int(s.P[j])
if ' ' <= c && c <= 0x7e {
fmt.Fprintf(ctxt.Bso, "%c", c)
} else {
fmt.Fprintf(ctxt.Bso, ".")
}
}
fmt.Fprintf(ctxt.Bso, "\n")
}
sort.Sort(relocByOff(s.R)) // generate stable output
for _, r := range s.R {
name := ""
if r.Sym != nil {
name = r.Sym.Name
} else if r.Type == objabi.R_TLS_LE {
name = "TLS"
}
if ctxt.Arch.InFamily(sys.ARM, sys.PPC64) {
fmt.Fprintf(ctxt.Bso, "\trel %d+%d t=%d %s+%x\n", int(r.Off), r.Siz, r.Type, name, uint64(r.Add))
} else {
fmt.Fprintf(ctxt.Bso, "\trel %d+%d t=%d %s+%d\n", int(r.Off), r.Siz, r.Type, name, r.Add)
}
}
}
func (w *objWriter) writeSym(s *LSym) {
ctxt := w.ctxt
if ctxt.Debugasm {
w.writeSymDebug(s)
}
w.wr.WriteByte(symPrefix)
w.wr.WriteByte(byte(s.Type))
w.writeRefIndex(s)
flags := int64(0)
if s.DuplicateOK() {
flags |= 1
}
if s.Local() {
flags |= 1 << 1
}
if s.MakeTypelink() {
flags |= 1 << 2
}
w.writeInt(flags)
w.writeInt(s.Size)
w.writeRefIndex(s.Gotype)
w.writeInt(int64(len(s.P)))
w.writeInt(int64(len(s.R)))
var r *Reloc
for i := 0; i < len(s.R); i++ {
r = &s.R[i]
w.writeInt(int64(r.Off))
w.writeInt(int64(r.Siz))
w.writeInt(int64(r.Type))
w.writeInt(r.Add)
w.writeRefIndex(r.Sym)
}
if s.Type != objabi.STEXT {
return
}
w.writeInt(int64(s.Func.Args))
w.writeInt(int64(s.Func.Locals))
if s.NoSplit() {
w.writeInt(1)
} else {
w.writeInt(0)
}
flags = int64(0)
if s.Leaf() {
flags |= 1
}
if s.CFunc() {
flags |= 1 << 1
}
if s.ReflectMethod() {
flags |= 1 << 2
}
if ctxt.Flag_shared {
flags |= 1 << 3
}
w.writeInt(flags)
w.writeInt(int64(len(s.Func.Autom)))
for _, a := range s.Func.Autom {
w.writeRefIndex(a.Asym)
w.writeInt(int64(a.Aoffset))
if a.Name == NAME_AUTO {
w.writeInt(objabi.A_AUTO)
} else if a.Name == NAME_PARAM {
w.writeInt(objabi.A_PARAM)
} else {
log.Fatalf("%s: invalid local variable type %d", s.Name, a.Name)
}
w.writeRefIndex(a.Gotype)
}
pc := &s.Func.Pcln
w.writeInt(int64(len(pc.Pcsp.P)))
w.writeInt(int64(len(pc.Pcfile.P)))
w.writeInt(int64(len(pc.Pcline.P)))
w.writeInt(int64(len(pc.Pcinline.P)))
w.writeInt(int64(len(pc.Pcdata)))
for i := 0; i < len(pc.Pcdata); i++ {
w.writeInt(int64(len(pc.Pcdata[i].P)))
}
w.writeInt(int64(len(pc.Funcdataoff)))
for i := 0; i < len(pc.Funcdataoff); i++ {
w.writeRefIndex(pc.Funcdata[i])
}
for i := 0; i < len(pc.Funcdataoff); i++ {
w.writeInt(pc.Funcdataoff[i])
}
w.writeInt(int64(len(pc.File)))
for _, f := range pc.File {
fsym := ctxt.Lookup(f)
w.writeRefIndex(fsym)
}
w.writeInt(int64(len(pc.InlTree.nodes)))
for _, call := range pc.InlTree.nodes {
w.writeInt(int64(call.Parent))
f, l := linkgetlineFromPos(w.ctxt, call.Pos)
fsym := ctxt.Lookup(f)
w.writeRefIndex(fsym)
w.writeInt(int64(l))
w.writeRefIndex(call.Func)
}
}
func (w *objWriter) writeInt(sval int64) {
var v uint64
uv := (uint64(sval) << 1) ^ uint64(sval>>63)
p := w.varintbuf[:]
for v = uv; v >= 0x80; v >>= 7 {
p[0] = uint8(v | 0x80)
p = p[1:]
}
p[0] = uint8(v)
p = p[1:]
w.wr.Write(w.varintbuf[:len(w.varintbuf)-len(p)])
}
func (w *objWriter) writeString(s string) {
w.writeInt(int64(len(s)))
w.wr.WriteString(s)
}
func (w *objWriter) writeRefIndex(s *LSym) {
if s == nil {
w.writeInt(0)
return
}
if s.RefIdx == 0 {
log.Fatalln("writing an unreferenced symbol", s.Name)
}
w.writeInt(int64(s.RefIdx))
}
// relocByOff sorts relocations by their offsets.
type relocByOff []Reloc
func (x relocByOff) Len() int { return len(x) }
func (x relocByOff) Less(i, j int) bool { return x[i].Off < x[j].Off }
func (x relocByOff) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
// implement dwarf.Context
type dwCtxt struct{ *Link }
func (c dwCtxt) PtrSize() int {
return c.Arch.PtrSize
}
func (c dwCtxt) AddInt(s dwarf.Sym, size int, i int64) {
ls := s.(*LSym)
ls.WriteInt(c.Link, ls.Size, size, i)
}
func (c dwCtxt) AddBytes(s dwarf.Sym, b []byte) {
ls := s.(*LSym)
ls.WriteBytes(c.Link, ls.Size, b)
}
func (c dwCtxt) AddString(s dwarf.Sym, v string) {
ls := s.(*LSym)
ls.WriteString(c.Link, ls.Size, len(v), v)
ls.WriteInt(c.Link, ls.Size, 1, 0)
}
func (c dwCtxt) SymValue(s dwarf.Sym) int64 {
return 0
}
func (c dwCtxt) AddAddress(s dwarf.Sym, data interface{}, value int64) {
ls := s.(*LSym)
size := c.PtrSize()
if data != nil {
rsym := data.(*LSym)
ls.WriteAddr(c.Link, ls.Size, size, rsym, value)
} else {
ls.WriteInt(c.Link, ls.Size, size, value)
}
}
func (c dwCtxt) AddSectionOffset(s dwarf.Sym, size int, t interface{}, ofs int64) {
ls := s.(*LSym)
rsym := t.(*LSym)
ls.WriteAddr(c.Link, ls.Size, size, rsym, ofs)
r := &ls.R[len(ls.R)-1]
r.Type = objabi.R_DWARFREF
}
// dwarfSym returns the DWARF symbols for TEXT symbol.
func (ctxt *Link) dwarfSym(s *LSym) (dwarfInfoSym, dwarfLocSym, dwarfRangesSym *LSym) {
if s.Type != objabi.STEXT {
ctxt.Diag("dwarfSym of non-TEXT %v", s)
}
if s.Func.dwarfInfoSym == nil {
s.Func.dwarfInfoSym = ctxt.LookupDerived(s, dwarf.InfoPrefix+s.Name)
if ctxt.Flag_locationlists {
s.Func.dwarfLocSym = ctxt.LookupDerived(s, dwarf.LocPrefix+s.Name)
}
s.Func.dwarfRangesSym = ctxt.LookupDerived(s, dwarf.RangePrefix+s.Name)
}
return s.Func.dwarfInfoSym, s.Func.dwarfLocSym, s.Func.dwarfRangesSym
}
func (s *LSym) Len() int64 {
return s.Size
}
// populateDWARF fills in the DWARF Debugging Information Entries for TEXT symbol s.
// The DWARFs symbol must already have been initialized in InitTextSym.
func (ctxt *Link) populateDWARF(curfn interface{}, s *LSym) {
info, loc, ranges := ctxt.dwarfSym(s)
if info.Size != 0 {
ctxt.Diag("makeFuncDebugEntry double process %v", s)
}
var scopes []dwarf.Scope
if ctxt.DebugInfo != nil {
scopes = ctxt.DebugInfo(s, curfn)
}
err := dwarf.PutFunc(dwCtxt{ctxt}, info, loc, ranges, s.Name, !s.Static(), s, s.Size, scopes)
if err != nil {
ctxt.Diag("emitting DWARF for %s failed: %v", s.Name, err)
}
}