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// Copyright 2019 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 Go object files.
package obj
import (
"bytes"
"cmd/internal/bio"
"cmd/internal/goobj2"
"cmd/internal/objabi"
"fmt"
"path/filepath"
"strings"
)
// Entry point of writing new object file.
func WriteObjFile2(ctxt *Link, b *bio.Writer, pkgpath string) {
debugAsmEmit(ctxt)
genFuncInfoSyms(ctxt)
w := writer{
Writer: goobj2.NewWriter(b),
ctxt: ctxt,
pkgpath: objabi.PathToPrefix(pkgpath),
}
start := b.Offset()
w.init()
// Header
// We just reserve the space. We'll fill in the offsets later.
flags := uint32(0)
if ctxt.Flag_shared {
flags |= goobj2.ObjFlagShared
}
h := goobj2.Header{
Magic: goobj2.Magic,
Fingerprint: ctxt.Fingerprint,
Flags: flags,
}
h.Write(w.Writer)
// String table
w.StringTable()
// Autolib
h.Offsets[goobj2.BlkAutolib] = w.Offset()
for i := range ctxt.Imports {
ctxt.Imports[i].Write(w.Writer)
}
// Package references
h.Offsets[goobj2.BlkPkgIdx] = w.Offset()
for _, pkg := range w.pkglist {
w.StringRef(pkg)
}
// DWARF file table
h.Offsets[goobj2.BlkDwarfFile] = w.Offset()
for _, f := range ctxt.PosTable.DebugLinesFileTable() {
w.StringRef(filepath.ToSlash(f))
}
// Symbol definitions
h.Offsets[goobj2.BlkSymdef] = w.Offset()
for _, s := range ctxt.defs {
w.Sym(s)
}
// Non-pkg symbol definitions
h.Offsets[goobj2.BlkNonpkgdef] = w.Offset()
for _, s := range ctxt.nonpkgdefs {
w.Sym(s)
}
// Non-pkg symbol references
h.Offsets[goobj2.BlkNonpkgref] = w.Offset()
for _, s := range ctxt.nonpkgrefs {
w.Sym(s)
}
// Reloc indexes
h.Offsets[goobj2.BlkRelocIdx] = w.Offset()
nreloc := uint32(0)
lists := [][]*LSym{ctxt.defs, ctxt.nonpkgdefs}
for _, list := range lists {
for _, s := range list {
w.Uint32(nreloc)
nreloc += uint32(len(s.R))
}
}
w.Uint32(nreloc)
// Symbol Info indexes
h.Offsets[goobj2.BlkAuxIdx] = w.Offset()
naux := uint32(0)
for _, list := range lists {
for _, s := range list {
w.Uint32(naux)
naux += uint32(nAuxSym(s))
}
}
w.Uint32(naux)
// Data indexes
h.Offsets[goobj2.BlkDataIdx] = w.Offset()
dataOff := uint32(0)
for _, list := range lists {
for _, s := range list {
w.Uint32(dataOff)
dataOff += uint32(len(s.P))
}
}
w.Uint32(dataOff)
// Relocs
h.Offsets[goobj2.BlkReloc] = w.Offset()
for _, list := range lists {
for _, s := range list {
for i := range s.R {
w.Reloc(&s.R[i])
}
}
}
// Aux symbol info
h.Offsets[goobj2.BlkAux] = w.Offset()
for _, list := range lists {
for _, s := range list {
w.Aux(s)
}
}
// Data
h.Offsets[goobj2.BlkData] = w.Offset()
for _, list := range lists {
for _, s := range list {
w.Bytes(s.P)
}
}
// Pcdata
h.Offsets[goobj2.BlkPcdata] = w.Offset()
for _, s := range ctxt.Text { // iteration order must match genFuncInfoSyms
if s.Func != nil {
pc := &s.Func.Pcln
w.Bytes(pc.Pcsp.P)
w.Bytes(pc.Pcfile.P)
w.Bytes(pc.Pcline.P)
w.Bytes(pc.Pcinline.P)
for i := range pc.Pcdata {
w.Bytes(pc.Pcdata[i].P)
}
}
}
// Fix up block offsets in the header
end := start + int64(w.Offset())
b.MustSeek(start, 0)
h.Write(w.Writer)
b.MustSeek(end, 0)
}
type writer struct {
*goobj2.Writer
ctxt *Link
pkgpath string // the package import path (escaped), "" if unknown
pkglist []string // list of packages referenced, indexed by ctxt.pkgIdx
}
// prepare package index list
func (w *writer) init() {
w.pkglist = make([]string, len(w.ctxt.pkgIdx)+1)
w.pkglist[0] = "" // dummy invalid package for index 0
for pkg, i := range w.ctxt.pkgIdx {
w.pkglist[i] = pkg
}
}
func (w *writer) StringTable() {
w.AddString("")
for _, p := range w.ctxt.Imports {
w.AddString(p.Pkg)
}
for _, pkg := range w.pkglist {
w.AddString(pkg)
}
w.ctxt.traverseSyms(traverseAll, func(s *LSym) {
if w.pkgpath != "" {
s.Name = strings.Replace(s.Name, "\"\".", w.pkgpath+".", -1)
}
w.AddString(s.Name)
})
w.ctxt.traverseSyms(traverseDefs, func(s *LSym) {
if s.Type != objabi.STEXT {
return
}
pc := &s.Func.Pcln
for _, f := range pc.File {
w.AddString(filepath.ToSlash(f))
}
for _, call := range pc.InlTree.nodes {
f, _ := linkgetlineFromPos(w.ctxt, call.Pos)
w.AddString(filepath.ToSlash(f))
}
})
for _, f := range w.ctxt.PosTable.DebugLinesFileTable() {
w.AddString(filepath.ToSlash(f))
}
}
func (w *writer) Sym(s *LSym) {
abi := uint16(s.ABI())
if s.Static() {
abi = goobj2.SymABIstatic
}
flag := uint8(0)
if s.DuplicateOK() {
flag |= goobj2.SymFlagDupok
}
if s.Local() {
flag |= goobj2.SymFlagLocal
}
if s.MakeTypelink() {
flag |= goobj2.SymFlagTypelink
}
if s.Leaf() {
flag |= goobj2.SymFlagLeaf
}
if s.NoSplit() {
flag |= goobj2.SymFlagNoSplit
}
if s.ReflectMethod() {
flag |= goobj2.SymFlagReflectMethod
}
if s.TopFrame() {
flag |= goobj2.SymFlagTopFrame
}
if strings.HasPrefix(s.Name, "type.") && s.Name[5] != '.' && s.Type == objabi.SRODATA {
flag |= goobj2.SymFlagGoType
}
name := s.Name
if strings.HasPrefix(name, "gofile..") {
name = filepath.ToSlash(name)
}
var align uint32
if s.Func != nil {
align = uint32(s.Func.Align)
}
var o goobj2.Sym
o.SetName(name, w.Writer)
o.SetABI(abi)
o.SetType(uint8(s.Type))
o.SetFlag(flag)
o.SetSiz(uint32(s.Size))
o.SetAlign(align)
o.Write(w.Writer)
}
func makeSymRef(s *LSym) goobj2.SymRef {
if s == nil {
return goobj2.SymRef{}
}
if s.PkgIdx == 0 || !s.Indexed() {
fmt.Printf("unindexed symbol reference: %v\n", s)
panic("unindexed symbol reference")
}
return goobj2.SymRef{PkgIdx: uint32(s.PkgIdx), SymIdx: uint32(s.SymIdx)}
}
func (w *writer) Reloc(r *Reloc) {
var o goobj2.Reloc
o.SetOff(r.Off)
o.SetSiz(r.Siz)
o.SetType(uint8(r.Type))
o.SetAdd(r.Add)
o.SetSym(makeSymRef(r.Sym))
o.Write(w.Writer)
}
func (w *writer) aux1(typ uint8, rs *LSym) {
var o goobj2.Aux
o.SetType(typ)
o.SetSym(makeSymRef(rs))
o.Write(w.Writer)
}
func (w *writer) Aux(s *LSym) {
if s.Gotype != nil {
w.aux1(goobj2.AuxGotype, s.Gotype)
}
if s.Func != nil {
w.aux1(goobj2.AuxFuncInfo, s.Func.FuncInfoSym)
for _, d := range s.Func.Pcln.Funcdata {
w.aux1(goobj2.AuxFuncdata, d)
}
if s.Func.dwarfInfoSym != nil && s.Func.dwarfInfoSym.Size != 0 {
w.aux1(goobj2.AuxDwarfInfo, s.Func.dwarfInfoSym)
}
if s.Func.dwarfLocSym != nil && s.Func.dwarfLocSym.Size != 0 {
w.aux1(goobj2.AuxDwarfLoc, s.Func.dwarfLocSym)
}
if s.Func.dwarfRangesSym != nil && s.Func.dwarfRangesSym.Size != 0 {
w.aux1(goobj2.AuxDwarfRanges, s.Func.dwarfRangesSym)
}
if s.Func.dwarfDebugLinesSym != nil && s.Func.dwarfDebugLinesSym.Size != 0 {
w.aux1(goobj2.AuxDwarfLines, s.Func.dwarfDebugLinesSym)
}
}
}
// return the number of aux symbols s have.
func nAuxSym(s *LSym) int {
n := 0
if s.Gotype != nil {
n++
}
if s.Func != nil {
// FuncInfo is an aux symbol, each Funcdata is an aux symbol
n += 1 + len(s.Func.Pcln.Funcdata)
if s.Func.dwarfInfoSym != nil && s.Func.dwarfInfoSym.Size != 0 {
n++
}
if s.Func.dwarfLocSym != nil && s.Func.dwarfLocSym.Size != 0 {
n++
}
if s.Func.dwarfRangesSym != nil && s.Func.dwarfRangesSym.Size != 0 {
n++
}
if s.Func.dwarfDebugLinesSym != nil && s.Func.dwarfDebugLinesSym.Size != 0 {
n++
}
}
return n
}
// generate symbols for FuncInfo.
func genFuncInfoSyms(ctxt *Link) {
infosyms := make([]*LSym, 0, len(ctxt.Text))
var pcdataoff uint32
var b bytes.Buffer
symidx := int32(len(ctxt.defs))
for _, s := range ctxt.Text {
if s.Func == nil {
continue
}
o := goobj2.FuncInfo{
Args: uint32(s.Func.Args),
Locals: uint32(s.Func.Locals),
}
pc := &s.Func.Pcln
o.Pcsp = pcdataoff
pcdataoff += uint32(len(pc.Pcsp.P))
o.Pcfile = pcdataoff
pcdataoff += uint32(len(pc.Pcfile.P))
o.Pcline = pcdataoff
pcdataoff += uint32(len(pc.Pcline.P))
o.Pcinline = pcdataoff
pcdataoff += uint32(len(pc.Pcinline.P))
o.Pcdata = make([]uint32, len(pc.Pcdata))
for i, pcd := range pc.Pcdata {
o.Pcdata[i] = pcdataoff
pcdataoff += uint32(len(pcd.P))
}
o.PcdataEnd = pcdataoff
o.Funcdataoff = make([]uint32, len(pc.Funcdataoff))
for i, x := range pc.Funcdataoff {
o.Funcdataoff[i] = uint32(x)
}
o.File = make([]goobj2.SymRef, len(pc.File))
for i, f := range pc.File {
fsym := ctxt.Lookup(f)
o.File[i] = makeSymRef(fsym)
}
o.InlTree = make([]goobj2.InlTreeNode, len(pc.InlTree.nodes))
for i, inl := range pc.InlTree.nodes {
f, l := linkgetlineFromPos(ctxt, inl.Pos)
fsym := ctxt.Lookup(f)
o.InlTree[i] = goobj2.InlTreeNode{
Parent: int32(inl.Parent),
File: makeSymRef(fsym),
Line: l,
Func: makeSymRef(inl.Func),
ParentPC: inl.ParentPC,
}
}
o.Write(&b)
isym := &LSym{
Type: objabi.SDATA, // for now, I don't think it matters
PkgIdx: goobj2.PkgIdxSelf,
SymIdx: symidx,
P: append([]byte(nil), b.Bytes()...),
}
isym.Set(AttrIndexed, true)
symidx++
infosyms = append(infosyms, isym)
s.Func.FuncInfoSym = isym
b.Reset()
dwsyms := []*LSym{s.Func.dwarfRangesSym, s.Func.dwarfLocSym, s.Func.dwarfDebugLinesSym, s.Func.dwarfInfoSym}
for _, s := range dwsyms {
if s == nil || s.Size == 0 {
continue
}
s.PkgIdx = goobj2.PkgIdxSelf
s.SymIdx = symidx
s.Set(AttrIndexed, true)
symidx++
infosyms = append(infosyms, s)
}
}
ctxt.defs = append(ctxt.defs, infosyms...)
}
// debugDumpAux is a dumper for selected aux symbols.
func writeAuxSymDebug(ctxt *Link, par *LSym, aux *LSym) {
// Most aux symbols (ex: funcdata) are not interesting--
// pick out just the DWARF ones for now.
if aux.Type != objabi.SDWARFLOC &&
aux.Type != objabi.SDWARFINFO &&
aux.Type != objabi.SDWARFLINES &&
aux.Type != objabi.SDWARFRANGE {
return
}
ctxt.writeSymDebugNamed(aux, "aux for "+par.Name)
}
func debugAsmEmit(ctxt *Link) {
if ctxt.Debugasm > 0 {
ctxt.traverseSyms(traverseDefs, ctxt.writeSymDebug)
if ctxt.Debugasm > 1 {
fn := func(par *LSym, aux *LSym) {
writeAuxSymDebug(ctxt, par, aux)
}
ctxt.traverseAuxSyms(traverseAux, fn)
}
}
}