-
Notifications
You must be signed in to change notification settings - Fork 0
/
symtab.go
782 lines (715 loc) · 18.2 KB
/
symtab.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
// 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 gosym implements access to the Go symbol
// and line number tables embedded in Go binaries generated
// by the gc compilers.
package gosym
import (
"bytes"
"encoding/binary"
"fmt"
"strconv"
"strings"
)
/*
* Symbols
*/
// A Sym represents a single symbol table entry.
type Sym struct {
Value uint64
Type byte
Name string
GoType uint64
// If this symbol is a function symbol, the corresponding Func
Func *Func
GoVersion Version
}
// Static reports whether this symbol is static (not visible outside its file).
func (s *Sym) Static() bool { return s.Type >= 'a' }
// nameWithoutInst returns s.Name if s.Name has no brackets (does not reference an
// instantiated type, function, or method). If s.Name contains brackets, then it
// returns s.Name with all the contents between (and including) the outermost left
// and right bracket removed. This is useful to ignore any extra slashes or dots
// inside the brackets from the string searches below, where needed.
func (s *Sym) nameWithoutInst() string {
start := strings.Index(s.Name, "[")
if start < 0 {
return s.Name
}
end := strings.LastIndex(s.Name, "]")
if end < 0 {
// Malformed name, should contain closing bracket too.
return s.Name
}
return s.Name[0:start] + s.Name[end+1:]
}
// PackageName returns the package part of the symbol name,
// or the empty string if there is none.
func (s *Sym) PackageName() string {
name := s.nameWithoutInst()
// Since go1.20, a prefix of "type:" and "go:" is a compiler-generated symbol,
// they do not belong to any package.
//
// See cmd/compile/internal/base/link.go:ReservedImports variable.
if s.GoVersion >= Ver120 && (strings.HasPrefix(name, "go:") || strings.HasPrefix(name, "type:")) {
return ""
}
// For go1.18 and below, the prefix are "type." and "go." instead.
if s.GoVersion <= Ver118 && (strings.HasPrefix(name, "go.") || strings.HasPrefix(name, "type.")) {
return ""
}
pathend := strings.LastIndex(name, "/")
if pathend < 0 {
pathend = 0
}
if i := strings.Index(name[pathend:], "."); i != -1 {
return name[:pathend+i]
}
return ""
}
// ReceiverName returns the receiver type name of this symbol,
// or the empty string if there is none. A receiver name is only detected in
// the case that s.Name is fully-specified with a package name.
func (s *Sym) ReceiverName() string {
name := s.nameWithoutInst()
// If we find a slash in name, it should precede any bracketed expression
// that was removed, so pathend will apply correctly to name and s.Name.
pathend := strings.LastIndex(name, "/")
if pathend < 0 {
pathend = 0
}
// Find the first dot after pathend (or from the beginning, if there was
// no slash in name).
l := strings.Index(name[pathend:], ".")
// Find the last dot after pathend (or the beginning).
r := strings.LastIndex(name[pathend:], ".")
if l == -1 || r == -1 || l == r {
// There is no receiver if we didn't find two distinct dots after pathend.
return ""
}
// Given there is a trailing '.' that is in name, find it now in s.Name.
// pathend+l should apply to s.Name, because it should be the dot in the
// package name.
r = strings.LastIndex(s.Name[pathend:], ".")
return s.Name[pathend+l+1 : pathend+r]
}
// BaseName returns the symbol name without the package or receiver name.
func (s *Sym) BaseName() string {
name := s.nameWithoutInst()
if i := strings.LastIndex(name, "."); i != -1 {
if s.Name != name {
brack := strings.Index(s.Name, "[")
if i > brack {
// BaseName is a method name after the brackets, so
// recalculate for s.Name. Otherwise, i applies
// correctly to s.Name, since it is before the
// brackets.
i = strings.LastIndex(s.Name, ".")
}
}
return s.Name[i+1:]
}
return s.Name
}
// A Func collects information about a single function.
type Func struct {
Entry uint64
*Sym
End uint64
Params []*Sym // nil for Go 1.3 and later binaries
Locals []*Sym // nil for Go 1.3 and later binaries
FrameSize int
LineTable *LineTable
Obj *Obj
// from shotizam
OffPCSP uint32 // pcsp table (offset from pcvalue table)
OffPCFile uint32 // pcfile table (offset from pcvalue table)
OffPCLn uint32 // pcln table (offset from pcvalue table)
NumPCData int // number of entries in pcdata list
NumFuncData int // number of entries in funcdata list
funcDataBytes []byte
}
// An Obj represents a collection of functions in a symbol table.
//
// The exact method of division of a binary into separate Objs is an internal detail
// of the symbol table format.
//
// In early versions of Go each source file became a different Obj.
//
// In Go 1 and Go 1.1, each package produced one Obj for all Go sources
// and one Obj per C source file.
//
// In Go 1.2, there is a single Obj for the entire program.
type Obj struct {
// Funcs is a list of functions in the Obj.
Funcs []Func
// In Go 1.1 and earlier, Paths is a list of symbols corresponding
// to the source file names that produced the Obj.
// In Go 1.2, Paths is nil.
// Use the keys of Table.Files to obtain a list of source files.
Paths []Sym // meta
}
/*
* Symbol tables
*/
// Table represents a Go symbol table. It stores all of the
// symbols decoded from the program and provides methods to translate
// between symbols, names, and addresses.
type Table struct {
Syms []Sym // nil for Go 1.3 and later binaries
Funcs []Func
Files map[string]*Obj // for Go 1.2 and later all files map to one Obj
Objs []Obj // for Go 1.2 and later only one Obj in slice
go12line *LineTable // Go 1.2 line number table
}
type sym struct {
value uint64
gotype uint64
typ byte
name []byte
}
var (
littleEndianSymtab = []byte{0xFD, 0xFF, 0xFF, 0xFF, 0x00, 0x00, 0x00}
bigEndianSymtab = []byte{0xFF, 0xFF, 0xFF, 0xFD, 0x00, 0x00, 0x00}
oldLittleEndianSymtab = []byte{0xFE, 0xFF, 0xFF, 0xFF, 0x00, 0x00}
)
func walksymtab(data []byte, fn func(sym) error) error {
if len(data) == 0 { // missing symtab is okay
return nil
}
var order binary.ByteOrder = binary.BigEndian
newTable := false
switch {
case bytes.HasPrefix(data, oldLittleEndianSymtab):
// Same as Go 1.0, but little endian.
// Format was used during interim development between Go 1.0 and Go 1.1.
// Should not be widespread, but easy to support.
data = data[6:]
order = binary.LittleEndian
case bytes.HasPrefix(data, bigEndianSymtab):
newTable = true
case bytes.HasPrefix(data, littleEndianSymtab):
newTable = true
order = binary.LittleEndian
}
var ptrsz int
if newTable {
if len(data) < 8 {
return &DecodingError{len(data), "unexpected EOF", nil}
}
ptrsz = int(data[7])
if ptrsz != 4 && ptrsz != 8 {
return &DecodingError{7, "invalid pointer size", ptrsz}
}
data = data[8:]
}
var s sym
p := data
for len(p) >= 4 {
var typ byte
if newTable {
// Symbol type, value, Go type.
typ = p[0] & 0x3F
wideValue := p[0]&0x40 != 0
goType := p[0]&0x80 != 0
if typ < 26 {
typ += 'A'
} else {
typ += 'a' - 26
}
s.typ = typ
p = p[1:]
if wideValue {
if len(p) < ptrsz {
return &DecodingError{len(data), "unexpected EOF", nil}
}
// fixed-width value
if ptrsz == 8 {
s.value = order.Uint64(p[0:8])
p = p[8:]
} else {
s.value = uint64(order.Uint32(p[0:4]))
p = p[4:]
}
} else {
// varint value
s.value = 0
shift := uint(0)
for len(p) > 0 && p[0]&0x80 != 0 {
s.value |= uint64(p[0]&0x7F) << shift
shift += 7
p = p[1:]
}
if len(p) == 0 {
return &DecodingError{len(data), "unexpected EOF", nil}
}
s.value |= uint64(p[0]) << shift
p = p[1:]
}
if goType {
if len(p) < ptrsz {
return &DecodingError{len(data), "unexpected EOF", nil}
}
// fixed-width go type
if ptrsz == 8 {
s.gotype = order.Uint64(p[0:8])
p = p[8:]
} else {
s.gotype = uint64(order.Uint32(p[0:4]))
p = p[4:]
}
}
} else {
// Value, symbol type.
s.value = uint64(order.Uint32(p[0:4]))
if len(p) < 5 {
return &DecodingError{len(data), "unexpected EOF", nil}
}
typ = p[4]
if typ&0x80 == 0 {
return &DecodingError{len(data) - len(p) + 4, "bad symbol type", typ}
}
typ &^= 0x80
s.typ = typ
p = p[5:]
}
// Name.
var i int
var nnul int
for i = 0; i < len(p); i++ {
if p[i] == 0 {
nnul = 1
break
}
}
switch typ {
case 'z', 'Z':
p = p[i+nnul:]
for i = 0; i+2 <= len(p); i += 2 {
if p[i] == 0 && p[i+1] == 0 {
nnul = 2
break
}
}
}
if len(p) < i+nnul {
return &DecodingError{len(data), "unexpected EOF", nil}
}
s.name = p[0:i]
i += nnul
p = p[i:]
if !newTable {
if len(p) < 4 {
return &DecodingError{len(data), "unexpected EOF", nil}
}
// Go type.
s.gotype = uint64(order.Uint32(p[:4]))
p = p[4:]
}
fn(s)
}
return nil
}
// NewTable decodes the Go symbol table (the ".gosymtab" section in ELF),
// returning an in-memory representation.
// Starting with Go 1.3, the Go symbol table no longer includes symbol data.
func NewTable(symtab []byte, pcln *LineTable) (*Table, error) {
var n int
err := walksymtab(symtab, func(s sym) error {
n++
return nil
})
if err != nil {
return nil, err
}
var t Table
if pcln.isGo12() {
t.go12line = pcln
}
fname := make(map[uint16]string)
t.Syms = make([]Sym, 0, n)
nf := 0
nz := 0
lasttyp := uint8(0)
err = walksymtab(symtab, func(s sym) error {
n := len(t.Syms)
t.Syms = t.Syms[0 : n+1]
ts := &t.Syms[n]
ts.Type = s.typ
ts.Value = s.value
ts.GoType = s.gotype
ts.GoVersion = pcln.version
switch s.typ {
default:
// rewrite name to use . instead of · (c2 b7)
w := 0
b := s.name
for i := 0; i < len(b); i++ {
if b[i] == 0xc2 && i+1 < len(b) && b[i+1] == 0xb7 {
i++
b[i] = '.'
}
b[w] = b[i]
w++
}
ts.Name = string(s.name[0:w])
case 'z', 'Z':
if lasttyp != 'z' && lasttyp != 'Z' {
nz++
}
for i := 0; i < len(s.name); i += 2 {
eltIdx := binary.BigEndian.Uint16(s.name[i : i+2])
elt, ok := fname[eltIdx]
if !ok {
return &DecodingError{-1, "bad filename code", eltIdx}
}
if n := len(ts.Name); n > 0 && ts.Name[n-1] != '/' {
ts.Name += "/"
}
ts.Name += elt
}
}
switch s.typ {
case 'T', 't', 'L', 'l':
nf++
case 'f':
fname[uint16(s.value)] = ts.Name
}
lasttyp = s.typ
return nil
})
if err != nil {
return nil, err
}
t.Funcs = make([]Func, 0, nf)
t.Files = make(map[string]*Obj)
var obj *Obj
if t.go12line != nil {
// Put all functions into one Obj.
t.Objs = make([]Obj, 1)
obj = &t.Objs[0]
t.go12line.go12MapFiles(t.Files, obj)
} else {
t.Objs = make([]Obj, 0, nz)
}
// Count text symbols and attach frame sizes, parameters, and
// locals to them. Also, find object file boundaries.
lastf := 0
for i := 0; i < len(t.Syms); i++ {
sym := &t.Syms[i]
switch sym.Type {
case 'Z', 'z': // path symbol
if t.go12line != nil {
// Go 1.2 binaries have the file information elsewhere. Ignore.
break
}
// Finish the current object
if obj != nil {
obj.Funcs = t.Funcs[lastf:]
}
lastf = len(t.Funcs)
// Start new object
n := len(t.Objs)
t.Objs = t.Objs[0 : n+1]
obj = &t.Objs[n]
// Count & copy path symbols
var end int
for end = i + 1; end < len(t.Syms); end++ {
if c := t.Syms[end].Type; c != 'Z' && c != 'z' {
break
}
}
obj.Paths = t.Syms[i:end]
i = end - 1 // loop will i++
// Record file names
depth := 0
for j := range obj.Paths {
s := &obj.Paths[j]
if s.Name == "" {
depth--
} else {
if depth == 0 {
t.Files[s.Name] = obj
}
depth++
}
}
case 'T', 't', 'L', 'l': // text symbol
if n := len(t.Funcs); n > 0 {
t.Funcs[n-1].End = sym.Value
}
if sym.Name == "runtime.etext" || sym.Name == "etext" {
continue
}
// Count parameter and local (auto) syms
var np, na int
var end int
countloop:
for end = i + 1; end < len(t.Syms); end++ {
switch t.Syms[end].Type {
case 'T', 't', 'L', 'l', 'Z', 'z':
break countloop
case 'p':
np++
case 'a':
na++
}
}
// Fill in the function symbol
n := len(t.Funcs)
t.Funcs = t.Funcs[0 : n+1]
fn := &t.Funcs[n]
sym.Func = fn
fn.Params = make([]*Sym, 0, np)
fn.Locals = make([]*Sym, 0, na)
fn.Sym = sym
fn.Entry = sym.Value
fn.Obj = obj
if t.go12line != nil {
// All functions share the same line table.
// It knows how to narrow down to a specific
// function quickly.
fn.LineTable = t.go12line
} else if pcln != nil {
fn.LineTable = pcln.slice(fn.Entry)
pcln = fn.LineTable
}
for j := i; j < end; j++ {
s := &t.Syms[j]
switch s.Type {
case 'm':
fn.FrameSize = int(s.Value)
case 'p':
n := len(fn.Params)
fn.Params = fn.Params[0 : n+1]
fn.Params[n] = s
case 'a':
n := len(fn.Locals)
fn.Locals = fn.Locals[0 : n+1]
fn.Locals[n] = s
}
}
i = end - 1 // loop will i++
}
}
if t.go12line != nil && nf == 0 {
t.Funcs = t.go12line.go12Funcs()
}
if obj != nil {
obj.Funcs = t.Funcs[lastf:]
}
return &t, nil
}
// PCToFunc returns the function containing the program counter pc,
// or nil if there is no such function.
func (t *Table) PCToFunc(pc uint64) *Func {
funcs := t.Funcs
for len(funcs) > 0 {
m := len(funcs) / 2
fn := &funcs[m]
switch {
case pc < fn.Entry:
funcs = funcs[0:m]
case fn.Entry <= pc && pc < fn.End:
return fn
default:
funcs = funcs[m+1:]
}
}
return nil
}
// PCToLine looks up line number information for a program counter.
// If there is no information, it returns fn == nil.
func (t *Table) PCToLine(pc uint64) (file string, line int, fn *Func) {
if fn = t.PCToFunc(pc); fn == nil {
return
}
if t.go12line != nil {
file = t.go12line.go12PCToFile(pc)
line = t.go12line.go12PCToLine(pc)
} else {
file, line = fn.Obj.lineFromAline(fn.LineTable.PCToLine(pc))
}
return
}
// LineToPC looks up the first program counter on the given line in
// the named file. It returns [UnknownFileError] or [UnknownLineError] if
// there is an error looking up this line.
func (t *Table) LineToPC(file string, line int) (pc uint64, fn *Func, err error) {
obj, ok := t.Files[file]
if !ok {
return 0, nil, UnknownFileError(file)
}
if t.go12line != nil {
pc := t.go12line.go12LineToPC(file, line)
if pc == 0 {
return 0, nil, &UnknownLineError{file, line}
}
return pc, t.PCToFunc(pc), nil
}
abs, err := obj.alineFromLine(file, line)
if err != nil {
return
}
for i := range obj.Funcs {
f := &obj.Funcs[i]
pc := f.LineTable.LineToPC(abs, f.End)
if pc != 0 {
return pc, f, nil
}
}
return 0, nil, &UnknownLineError{file, line}
}
// LookupSym returns the text, data, or bss symbol with the given name,
// or nil if no such symbol is found.
func (t *Table) LookupSym(name string) *Sym {
// TODO(austin) Maybe make a map
for i := range t.Syms {
s := &t.Syms[i]
switch s.Type {
case 'T', 't', 'L', 'l', 'D', 'd', 'B', 'b':
if s.Name == name {
return s
}
}
}
return nil
}
// LookupFunc returns the text, data, or bss symbol with the given name,
// or nil if no such symbol is found.
func (t *Table) LookupFunc(name string) *Func {
for i := range t.Funcs {
f := &t.Funcs[i]
if f.Sym.Name == name {
return f
}
}
return nil
}
// SymByAddr returns the text, data, or bss symbol starting at the given address.
func (t *Table) SymByAddr(addr uint64) *Sym {
for i := range t.Syms {
s := &t.Syms[i]
switch s.Type {
case 'T', 't', 'L', 'l', 'D', 'd', 'B', 'b':
if s.Value == addr {
return s
}
}
}
return nil
}
/*
* Object files
*/
// This is legacy code for Go 1.1 and earlier, which used the
// Plan 9 format for pc-line tables. This code was never quite
// correct. It's probably very close, and it's usually correct, but
// we never quite found all the corner cases.
//
// Go 1.2 and later use a simpler format, documented at golang.org/s/go12symtab.
func (o *Obj) lineFromAline(aline int) (string, int) {
type stackEnt struct {
path string
start int
offset int
prev *stackEnt
}
noPath := &stackEnt{"", 0, 0, nil}
tos := noPath
pathloop:
for _, s := range o.Paths {
val := int(s.Value)
switch {
case val > aline:
break pathloop
case val == 1:
// Start a new stack
tos = &stackEnt{s.Name, val, 0, noPath}
case s.Name == "":
// Pop
if tos == noPath {
return "<malformed symbol table>", 0
}
tos.prev.offset += val - tos.start
tos = tos.prev
default:
// Push
tos = &stackEnt{s.Name, val, 0, tos}
}
}
if tos == noPath {
return "", 0
}
return tos.path, aline - tos.start - tos.offset + 1
}
func (o *Obj) alineFromLine(path string, line int) (int, error) {
if line < 1 {
return 0, &UnknownLineError{path, line}
}
for i, s := range o.Paths {
// Find this path
if s.Name != path {
continue
}
// Find this line at this stack level
depth := 0
var incstart int
line += int(s.Value)
pathloop:
for _, s := range o.Paths[i:] {
val := int(s.Value)
switch {
case depth == 1 && val >= line:
return line - 1, nil
case s.Name == "":
depth--
if depth == 0 {
break pathloop
} else if depth == 1 {
line += val - incstart
}
default:
if depth == 1 {
incstart = val
}
depth++
}
}
return 0, &UnknownLineError{path, line}
}
return 0, UnknownFileError(path)
}
/*
* Errors
*/
// UnknownFileError represents a failure to find the specific file in
// the symbol table.
type UnknownFileError string
func (e UnknownFileError) Error() string { return "unknown file: " + string(e) }
// UnknownLineError represents a failure to map a line to a program
// counter, either because the line is beyond the bounds of the file
// or because there is no code on the given line.
type UnknownLineError struct {
File string
Line int
}
func (e *UnknownLineError) Error() string {
return "no code at " + e.File + ":" + strconv.Itoa(e.Line)
}
// DecodingError represents an error during the decoding of
// the symbol table.
type DecodingError struct {
off int
msg string
val any
}
func (e *DecodingError) Error() string {
msg := e.msg
if e.val != nil {
msg += fmt.Sprintf(" '%v'", e.val)
}
msg += fmt.Sprintf(" at byte %#x", e.off)
return msg
}