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cmd/objdump: implement objdump of .o files

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Update goobj reader so it can provide all the information
necessary to disassemble .o (and .a) files.

Grab architecture of .o files from header.

.o files have relocations in them.  This CL also contains a simple
mechanism to disassemble relocations and add relocation info as an extra
column in the output.

Fixes #13862

Change-Id: I608fd253ff1522ea47f18be650b38d528dae9054
Reviewed-on: https://go-review.googlesource.com/24818
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Keith Randall 2016-07-02 17:19:25 -07:00
parent 873dca4c17
commit a99f812cba
14 changed files with 187 additions and 42 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
src/cmd/internal/goobj/read.go
View File

@ -163,7 +163,7 @@ type Data struct {
// A Reloc describes a relocation applied to a memory image to refer
// to an address within a particular symbol.
type Reloc struct {
// The bytes at [Offset, Offset+Size) within the memory image
// The bytes at [Offset, Offset+Size) within the containing Sym
// should be updated to refer to the address Add bytes after the start
// of the symbol Sym.
Offset int
@ -174,7 +174,7 @@ type Reloc struct {
// The Type records the form of address expected in the bytes
// described by the previous fields: absolute, PC-relative, and so on.
// TODO(rsc): The interpretation of Type is not exposed by this package.
Type int
Type obj.RelocType
}
// A Var describes a variable in a function stack frame: a declared
@ -220,6 +220,7 @@ type Package struct {
SymRefs []SymID // list of symbol names and versions referred to by this pack
Syms []*Sym // symbols defined by this package
MaxVersion int // maximum Version in any SymID in Syms
Arch string // architecture
}
var (
@ -561,14 +562,13 @@ func (r *objReader) parseArchive() error {
// The format of that part is defined in a comment at the top
// of src/liblink/objfile.c.
func (r *objReader) parseObject(prefix []byte) error {
// TODO(rsc): Maybe use prefix and the initial input to
// record the header line from the file, which would
// give the architecture and other version information.
r.p.MaxVersion++
h := make([]byte, 0, 256)
h = append(h, prefix...)
var c1, c2, c3 byte
for {
c1, c2, c3 = c2, c3, r.readByte()
h = append(h, c3)
// The new export format can contain 0 bytes.
// Don't consider them errors, only look for r.err != nil.
if r.err != nil {
@ -579,6 +579,12 @@ func (r *objReader) parseObject(prefix []byte) error {
}
}
hs := strings.Fields(string(h))
if len(hs) >= 4 {
r.p.Arch = hs[3]
}
// TODO: extract OS + build ID if/when we need it
r.readFull(r.tmp[:8])
if !bytes.Equal(r.tmp[:8], []byte("\x00\x00go17ld")) {
return r.error(errCorruptObject)
@ -643,7 +649,7 @@ func (r *objReader) parseObject(prefix []byte) error {
rel := &s.Reloc[i]
rel.Offset = r.readInt()
rel.Size = r.readInt()
rel.Type = r.readInt()
rel.Type = obj.RelocType(r.readInt())
rel.Add = r.readInt()
rel.Sym = r.readSymID()
}
@ -693,3 +699,18 @@ func (r *objReader) parseObject(prefix []byte) error {
return nil
}
func (r *Reloc) String(insnOffset uint64) string {
delta := r.Offset - int(insnOffset)
s := fmt.Sprintf("[%d:%d]%s", delta, delta+r.Size, r.Type)
if r.Sym.Name != "" {
if r.Add != 0 {
return fmt.Sprintf("%s:%s+%d", s, r.Sym.Name, r.Add)
}
return fmt.Sprintf("%s:%s", s, r.Sym.Name)
}
if r.Add != 0 {
return fmt.Sprintf("%s:%d", s, r.Add)
}
return s
}

8
src/cmd/internal/obj/link.go
View File

@ -442,14 +442,16 @@ const (
type Reloc struct {
Off int32
Siz uint8
Type int32
Type RelocType
Add int64
Sym *LSym
}
// Reloc.type
type RelocType int32
//go:generate stringer -type=RelocType
const (
R_ADDR = 1 + iota
R_ADDR RelocType = 1 + iota
// R_ADDRPOWER relocates a pair of "D-form" instructions (instructions with 16-bit
// immediates in the low half of the instruction word), usually addis followed by
// another add or a load, inserting the "high adjusted" 16 bits of the address of

17
src/cmd/internal/obj/reloctype_string.go Normal file
View File

@ -0,0 +1,17 @@
// Code generated by "stringer -type=RelocType"; DO NOT EDIT
package obj
import "fmt"
const _RelocType_name = "R_ADDRR_ADDRPOWERR_ADDRARM64R_ADDRMIPSR_ADDROFFR_SIZER_CALLR_CALLARMR_CALLARM64R_CALLINDR_CALLPOWERR_CALLMIPSR_CONSTR_PCRELR_TLS_LER_TLS_IER_GOTOFFR_PLT0R_PLT1R_PLT2R_USEFIELDR_USETYPER_METHODOFFR_POWER_TOCR_GOTPCRELR_JMPMIPSR_DWARFREFR_ARM64_TLS_LER_ARM64_TLS_IER_ARM64_GOTPCRELR_POWER_TLS_LER_POWER_TLS_IER_POWER_TLSR_ADDRPOWER_DSR_ADDRPOWER_GOTR_ADDRPOWER_PCRELR_ADDRPOWER_TOCRELR_ADDRPOWER_TOCREL_DSR_PCRELDBLR_ADDRMIPSUR_ADDRMIPSTLS"
var _RelocType_index = [...]uint16{0, 6, 17, 28, 38, 47, 53, 59, 68, 79, 88, 99, 109, 116, 123, 131, 139, 147, 153, 159, 165, 175, 184, 195, 206, 216, 225, 235, 249, 263, 279, 293, 307, 318, 332, 347, 364, 382, 403, 413, 424, 437}
func (i RelocType) String() string {
i -= 1
if i < 0 || i >= RelocType(len(_RelocType_index)-1) {
return fmt.Sprintf("RelocType(%d)", i+1)
}
return _RelocType_name[_RelocType_index[i]:_RelocType_index[i+1]]
}

24
src/cmd/internal/objfile/disasm.go
View File

@ -22,7 +22,7 @@ import (
// Disasm is a disassembler for a given File.
type Disasm struct {
syms []Sym //symbols in file, sorted by address
pcln *gosym.Table // pcln table
pcln Liner // pcln table
text []byte // bytes of text segment (actual instructions)
textStart uint64 // start PC of text
textEnd uint64 // end PC of text
@ -116,6 +116,7 @@ func (d *Disasm) Print(w io.Writer, filter *regexp.Regexp, start, end uint64) {
for _, sym := range d.syms {
symStart := sym.Addr
symEnd := sym.Addr + uint64(sym.Size)
relocs := sym.Relocs
if sym.Code != 'T' && sym.Code != 't' ||
symStart < d.textStart ||
symEnd <= start || end <= symStart ||
@ -135,7 +136,7 @@ func (d *Disasm) Print(w io.Writer, filter *regexp.Regexp, start, end uint64) {
symEnd = end
}
code := d.text[:end-d.textStart]
d.Decode(symStart, symEnd, func(pc, size uint64, file string, line int, text string) {
d.Decode(symStart, symEnd, relocs, func(pc, size uint64, file string, line int, text string) {
i := pc - d.textStart
fmt.Fprintf(tw, "\t%s:%d\t%#x\t", base(file), line, pc)
if size%4 != 0 || d.goarch == "386" || d.goarch == "amd64" {
@ -158,7 +159,7 @@ func (d *Disasm) Print(w io.Writer, filter *regexp.Regexp, start, end uint64) {
}
// Decode disassembles the text segment range [start, end), calling f for each instruction.
func (d *Disasm) Decode(start, end uint64, f func(pc, size uint64, file string, line int, text string)) {
func (d *Disasm) Decode(start, end uint64, relocs []Reloc, f func(pc, size uint64, file string, line int, text string)) {
if start < d.textStart {
start = d.textStart
}
@ -171,6 +172,17 @@ func (d *Disasm) Decode(start, end uint64, f func(pc, size uint64, file string,
i := pc - d.textStart
text, size := d.disasm(code[i:], pc, lookup)
file, line, _ := d.pcln.PCToLine(pc)
text += "\t"
first := true
for len(relocs) > 0 && relocs[0].Addr < i+uint64(size) {
if first {
first = false
} else {
text += " "
}
text += relocs[0].Stringer.String(pc - start)
relocs = relocs[1:]
}
f(pc, uint64(size), file, line, text)
pc += uint64(size)
}
@ -247,3 +259,9 @@ var byteOrders = map[string]binary.ByteOrder{
"ppc64le": binary.LittleEndian,
"s390x": binary.BigEndian,
}
type Liner interface {
// Given a pc, returns the corresponding file, line, and function data.
// If unknown, returns "",0,nil.
PCToLine(uint64) (string, int, *gosym.Func)
}

73
src/cmd/internal/objfile/goobj.go
View File

@ -8,7 +8,9 @@ package objfile
import (
"cmd/internal/goobj"
"cmd/internal/sys"
"debug/dwarf"
"debug/gosym"
"errors"
"fmt"
"os"
@ -16,6 +18,7 @@ import (
type goobjFile struct {
goobj *goobj.Package
f *os.File // the underlying .o or .a file
}
func openGoobj(r *os.File) (rawFile, error) {
@ -23,7 +26,7 @@ func openGoobj(r *os.File) (rawFile, error) {
if err != nil {
return nil, err
}
return &goobjFile{f}, nil
return &goobjFile{goobj: f, f: r}, nil
}
func goobjName(id goobj.SymID) string {
@ -55,6 +58,9 @@ func (f *goobjFile) symbols() ([]Sym, error) {
if s.Version != 0 {
sym.Code += 'a' - 'A'
}
for i, r := range s.Reloc {
sym.Relocs = append(sym.Relocs, Reloc{Addr: uint64(s.Data.Offset) + uint64(r.Offset), Size: uint64(r.Size), Stringer: &s.Reloc[i]})
}
syms = append(syms, sym)
}
@ -75,23 +81,68 @@ func (f *goobjFile) symbols() ([]Sym, error) {
return syms, nil
}
// pcln does not make sense for Go object files, because each
// symbol has its own individual pcln table, so there is no global
// space of addresses to map.
func (f *goobjFile) pcln() (textStart uint64, symtab, pclntab []byte, err error) {
// Should never be called. We implement Liner below, callers
// should use that instead.
return 0, nil, nil, fmt.Errorf("pcln not available in go object file")
}
// text does not make sense for Go object files, because
// each function has a separate section.
func (f *goobjFile) text() (textStart uint64, text []byte, err error) {
return 0, nil, fmt.Errorf("text not available in go object file")
// Find returns the file name, line, and function data for the given pc.
// Returns "",0,nil if unknown.
// This function implements the Liner interface in preference to pcln() above.
func (f *goobjFile) PCToLine(pc uint64) (string, int, *gosym.Func) {
// TODO: this is really inefficient. Binary search? Memoize last result?
var arch *sys.Arch
for _, a := range sys.Archs {
if a.Name == f.goobj.Arch {
arch = a
break
}
}
if arch == nil {
return "", 0, nil
}
for _, s := range f.goobj.Syms {
if pc < uint64(s.Data.Offset) || pc >= uint64(s.Data.Offset+s.Data.Size) {
continue
}
if s.Func == nil {
return "", 0, nil
}
pcfile := make([]byte, s.Func.PCFile.Size)
_, err := f.f.ReadAt(pcfile, s.Func.PCFile.Offset)
if err != nil {
return "", 0, nil
}
fileID := gosym.PCValue(pcfile, pc-uint64(s.Data.Offset), arch.MinLC)
fileName := s.Func.File[fileID]
pcline := make([]byte, s.Func.PCLine.Size)
_, err = f.f.ReadAt(pcline, s.Func.PCLine.Offset)
if err != nil {
return "", 0, nil
}
line := gosym.PCValue(pcline, pc-uint64(s.Data.Offset), arch.MinLC)
// Note: we provide only the name in the Func structure.
// We could provide more if needed.
return fileName, line, &gosym.Func{Sym: &gosym.Sym{Name: s.Name}}
}
return "", 0, nil
}
// We treat the whole object file as the text section.
func (f *goobjFile) text() (textStart uint64, text []byte, err error) {
var info os.FileInfo
info, err = f.f.Stat()
if err != nil {
return
}
text = make([]byte, info.Size())
_, err = f.f.ReadAt(text, 0)
return
}
// goarch makes sense but is not exposed in debug/goobj's API,
// and we don't need it yet for any users of internal/objfile.
func (f *goobjFile) goarch() string {
return "GOARCH unimplemented for debug/goobj files"
return f.goobj.Arch
}
func (f *goobjFile) loadAddress() (uint64, error) {

31
src/cmd/internal/objfile/objfile.go
View File

@ -30,11 +30,24 @@ type File struct {
// A Sym is a symbol defined in an executable file.
type Sym struct {
Name string // symbol name
Addr uint64 // virtual address of symbol
Size int64 // size in bytes
Code rune // nm code (T for text, D for data, and so on)
Type string // XXX?
Name string // symbol name
Addr uint64 // virtual address of symbol
Size int64 // size in bytes
Code rune // nm code (T for text, D for data, and so on)
Type string // XXX?
Relocs []Reloc // in increasing Addr order
}
type Reloc struct {
Addr uint64 // Address of first byte that reloc applies to.
Size uint64 // Number of bytes
Stringer RelocStringer
}
type RelocStringer interface {
// insnOffset is the offset of the instruction containing the relocation
// from the start of the symbol containing the relocation.
String(insnOffset uint64) string
}
var openers = []func(*os.File) (rawFile, error){
@ -80,7 +93,13 @@ func (x byAddr) Less(i, j int) bool { return x[i].Addr < x[j].Addr }
func (x byAddr) Len() int { return len(x) }
func (x byAddr) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
func (f *File) PCLineTable() (*gosym.Table, error) {
func (f *File) PCLineTable() (Liner, error) {
// If the raw file implements Liner directly, use that.
// Currently, only Go intermediate objects and archives (goobj) use this path.
if pcln, ok := f.raw.(Liner); ok {
return pcln, nil
}
// Otherwise, read the pcln tables and build a Liner out of that.
textStart, symtab, pclntab, err := f.raw.pcln()
if err != nil {
return nil, err

13
src/cmd/internal/sys/arch.go
View File

@ -146,3 +146,16 @@ var ArchS390X = &Arch{
RegSize: 8,
MinLC: 2,
}
var Archs = [...]*Arch{
Arch386,
ArchAMD64,
ArchAMD64P32,
ArchARM,
ArchARM64,
ArchMIPS64,
ArchMIPS64LE,
ArchPPC64,
ArchPPC64LE,
ArchS390X,
}

4
src/cmd/link/internal/arm/asm.go
View File

@ -492,12 +492,12 @@ func archrelocvariant(ctxt *ld.Link, r *ld.Reloc, s *ld.Symbol, t int64) int64 {
return t
}
func addpltreloc(ctxt *ld.Link, plt *ld.Symbol, got *ld.Symbol, sym *ld.Symbol, typ int) *ld.Reloc {
func addpltreloc(ctxt *ld.Link, plt *ld.Symbol, got *ld.Symbol, sym *ld.Symbol, typ obj.RelocType) *ld.Reloc {
r := ld.Addrel(plt)
r.Sym = got
r.Off = int32(plt.Size)
r.Siz = 4
r.Type = int32(typ)
r.Type = typ
r.Add = int64(sym.Got) - 8
plt.Attr |= ld.AttrReachable

2
src/cmd/link/internal/ld/ldelf.go
View File

@ -912,7 +912,7 @@ func ldelf(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
rp.Sym = sym.sym
}
rp.Type = 256 + int32(info)
rp.Type = 256 + obj.RelocType(info)
rp.Siz = relSize(ctxt, pn, uint32(info))
if rela != 0 {
rp.Add = int64(add)

2
src/cmd/link/internal/ld/ldmacho.go
View File

@ -828,7 +828,7 @@ func ldmacho(ctxt *Link, f *bio.Reader, pkg string, length int64, pn string) {
}
rp.Siz = rel.length
rp.Type = 512 + (int32(rel.type_) << 1) + int32(rel.pcrel)
rp.Type = 512 + (obj.RelocType(rel.type_) << 1) + obj.RelocType(rel.pcrel)
rp.Off = int32(rel.addr)
// Handle X86_64_RELOC_SIGNED referencing a section (rel->extrn == 0).

3
src/cmd/link/internal/ld/link.go
View File

@ -32,6 +32,7 @@ package ld
import (
"bufio"
"cmd/internal/obj"
"cmd/internal/sys"
"debug/elf"
"fmt"
@ -135,7 +136,7 @@ type Reloc struct {
Off int32
Siz uint8
Done uint8
Type int32
Type obj.RelocType
Variant int32
Add int64
Xadd int64

2
src/cmd/link/internal/ld/objfile.go
View File

@ -326,7 +326,7 @@ overwrite:
s.R[i] = Reloc{
Off: r.readInt32(),
Siz: r.readUint8(),
Type: r.readInt32(),
Type: obj.RelocType(r.readInt32()),
Add: r.readInt64(),
Sym: r.readSymIndex(),
}

5
src/cmd/pprof/pprof.go
View File

@ -6,7 +6,6 @@ package main
import (
"debug/dwarf"
"debug/gosym"
"flag"
"fmt"
"net/url"
@ -161,7 +160,7 @@ func (t *objTool) Disasm(file string, start, end uint64) ([]plugin.Inst, error)
return nil, err
}
var asm []plugin.Inst
d.Decode(start, end, func(pc, size uint64, file string, line int, text string) {
d.Decode(start, end, nil, func(pc, size uint64, file string, line int, text string) {
asm = append(asm, plugin.Inst{Addr: pc, File: file, Line: line, Text: text})
})
return asm, nil
@ -203,7 +202,7 @@ type file struct {
offset uint64
sym []objfile.Sym
file *objfile.File
pcln *gosym.Table
pcln objfile.Liner
triedDwarf bool
dwarf *dwarf.Data

10
src/debug/gosym/pclntab.go
View File

@ -291,13 +291,17 @@ func (t *LineTable) step(p *[]byte, pc *uint64, val *int32, first bool) bool {
return true
}
// PCValue looks up the given PC in a pc value table. target is the
// offset of the pc from the entry point.
func PCValue(tab []byte, target uint64, quantum int) int {
t := LineTable{Data: tab, quantum: uint32(quantum)}
return int(t.pcvalue(0, 0, target))
}
// pcvalue reports the value associated with the target pc.
// off is the offset to the beginning of the pc-value table,
// and entry is the start PC for the corresponding function.
func (t *LineTable) pcvalue(off uint32, entry, targetpc uint64) int32 {
if off == 0 {
return -1
}
p := t.Data[off:]
val := int32(-1)