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dwbug/elf: support old-style compressed DWARF

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GCC and LLVM support zlib-compressing DWARF debug sections (and
there's some evidence that this may be happening by default in some
circumstances now).

Add support for reading compressed DWARF sections. Since ELF
relocations apply to the decompressed data, decompression is done
before applying relocations. Since relcations are applied by
debug/elf, decompression must also be handled there.

Note that this is different from compressed ELF sections, which is a
more general mechanism used by very recent versions of GCC.

Updates #11773.

Change-Id: I3f4bf1b04d0802cc1e8fcb7c2a5fcf6c467c5089
Reviewed-on: https://go-review.googlesource.com/17340
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
This commit is contained in:
Austin Clements 2015-12-01 22:55:28 -05:00
parent 606d9a7e18
commit e1544d3bb6
5 changed files with 60 additions and 6 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
src/cmd/dist/deps.go vendored
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@ -5,11 +5,13 @@ package main
var builddeps = map[string][]string{
"bufio": {"bytes", "errors", "internal/race", "io", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sync", "sync/atomic", "unicode", "unicode/utf8"},
"bytes": {"errors", "internal/race", "io", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sync", "sync/atomic", "unicode", "unicode/utf8"},
"compress/flate": {"bufio", "bytes", "errors", "fmt", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "math", "os", "reflect", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "sync", "sync/atomic", "syscall", "time", "unicode", "unicode/utf16", "unicode/utf8"},
"compress/zlib": {"bufio", "bytes", "compress/flate", "errors", "fmt", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "math", "os", "reflect", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "sync", "sync/atomic", "syscall", "time", "unicode", "unicode/utf16", "unicode/utf8"},
"container/heap": {"runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort"},
"crypto": {"errors", "hash", "internal/race", "io", "math", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "strconv", "sync", "sync/atomic", "unicode/utf8"},
"crypto/sha1": {"crypto", "errors", "hash", "internal/race", "io", "math", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "strconv", "sync", "sync/atomic", "unicode/utf8"},
"debug/dwarf": {"encoding/binary", "errors", "fmt", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "math", "os", "path", "reflect", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "time", "unicode", "unicode/utf16", "unicode/utf8"},
"debug/elf": {"bytes", "debug/dwarf", "encoding/binary", "errors", "fmt", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "math", "os", "path", "reflect", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "time", "unicode", "unicode/utf16", "unicode/utf8"},
"debug/elf": {"bufio", "bytes", "compress/flate", "compress/zlib", "debug/dwarf", "encoding/binary", "errors", "fmt", "hash", "hash/adler32", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "math", "os", "path", "reflect", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "time", "unicode", "unicode/utf16", "unicode/utf8"},
"debug/macho": {"bytes", "debug/dwarf", "encoding/binary", "errors", "fmt", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "math", "os", "path", "reflect", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "time", "unicode", "unicode/utf16", "unicode/utf8"},
"encoding": {"runtime", "runtime/internal/atomic", "runtime/internal/sys"},
"encoding/base64": {"errors", "internal/race", "io", "math", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "strconv", "sync", "sync/atomic", "unicode/utf8"},
@ -25,6 +27,7 @@ var builddeps = map[string][]string{
"go/scanner": {"bytes", "errors", "fmt", "go/token", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "math", "os", "path/filepath", "reflect", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "time", "unicode", "unicode/utf16", "unicode/utf8"},
"go/token": {"errors", "fmt", "internal/race", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "math", "os", "reflect", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "sync", "sync/atomic", "syscall", "time", "unicode/utf16", "unicode/utf8"},
"hash": {"errors", "internal/race", "io", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sync", "sync/atomic"},
"hash/adler32": {"errors", "hash", "internal/race", "io", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sync", "sync/atomic"},
"internal/race": {"runtime", "runtime/internal/atomic", "runtime/internal/sys"},
"internal/singleflight": {"internal/race", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sync", "sync/atomic"},
"internal/syscall/windows": {"errors", "internal/race", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sync", "sync/atomic", "syscall", "unicode/utf16"},
@ -57,5 +60,5 @@ var builddeps = map[string][]string{
"unicode": {"runtime", "runtime/internal/atomic", "runtime/internal/sys"},
"unicode/utf16": {"runtime", "runtime/internal/atomic", "runtime/internal/sys"},
"unicode/utf8": {"runtime", "runtime/internal/atomic", "runtime/internal/sys"},
"cmd/go": {"bufio", "bytes", "container/heap", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding", "encoding/base64", "encoding/binary", "encoding/json", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "internal/race", "internal/singleflight", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
"cmd/go": {"bufio", "bytes", "compress/flate", "compress/zlib", "container/heap", "crypto", "crypto/sha1", "debug/dwarf", "debug/elf", "debug/macho", "encoding", "encoding/base64", "encoding/binary", "encoding/json", "errors", "flag", "fmt", "go/ast", "go/build", "go/doc", "go/parser", "go/scanner", "go/token", "hash", "hash/adler32", "internal/race", "internal/singleflight", "internal/syscall/windows", "internal/syscall/windows/registry", "io", "io/ioutil", "log", "math", "net/url", "os", "os/exec", "os/signal", "path", "path/filepath", "reflect", "regexp", "regexp/syntax", "runtime", "runtime/internal/atomic", "runtime/internal/sys", "sort", "strconv", "strings", "sync", "sync/atomic", "syscall", "text/template", "text/template/parse", "time", "unicode", "unicode/utf16", "unicode/utf8"},
}

29
src/debug/elf/file.go
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@ -7,6 +7,7 @@ package elf
import (
"bytes"
"compress/zlib"
"debug/dwarf"
"encoding/binary"
"errors"
@ -863,6 +864,22 @@ func (f *File) DWARF() (*dwarf.Data, error) {
return nil, err
}
if len(b) >= 12 && string(b[:4]) == "ZLIB" {
dlen := binary.BigEndian.Uint64(b[4:12])
dbuf := make([]byte, dlen)
r, err := zlib.NewReader(bytes.NewBuffer(b[12:]))
if err != nil {
return nil, err
}
if _, err := io.ReadFull(r, dbuf); err != nil {
return nil, err
}
if err := r.Close(); err != nil {
return nil, err
}
b = dbuf
}
for _, r := range f.Sections {
if r.Type != SHT_RELA && r.Type != SHT_REL {
continue
@ -887,17 +904,23 @@ func (f *File) DWARF() (*dwarf.Data, error) {
// Don't bother loading others.
var dat = map[string][]byte{"abbrev": nil, "info": nil, "str": nil, "line": nil}
for i, s := range f.Sections {
if !strings.HasPrefix(s.Name, ".debug_") {
suffix := ""
switch {
case strings.HasPrefix(s.Name, ".debug_"):
suffix = s.Name[7:]
case strings.HasPrefix(s.Name, ".zdebug_"):
suffix = s.Name[8:]
default:
continue
}
if _, ok := dat[s.Name[7:]]; !ok {
if _, ok := dat[suffix]; !ok {
continue
}
b, err := sectionData(i, s)
if err != nil {
return nil, err
}
dat[s.Name[7:]] = b
dat[suffix] = b
}
d, err := dwarf.New(dat["abbrev"], nil, nil, dat["info"], dat["line"], nil, nil, dat["str"])

28
src/debug/elf/file_test.go
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@ -514,6 +514,34 @@ func TestDWARFRelocations(t *testing.T) {
}
}
func TestCompressedDWARF(t *testing.T) {
// Test file built with GCC 4.8.4 and as 2.24 using:
// gcc -Wa,--compress-debug-sections -g -c -o zdebug-test-gcc484-x86-64.obj hello.c
f, err := Open("testdata/zdebug-test-gcc484-x86-64.obj")
if err != nil {
t.Fatal(err)
}
dwarf, err := f.DWARF()
if err != nil {
t.Fatal(err)
}
reader := dwarf.Reader()
n := 0
for {
entry, err := reader.Next()
if err != nil {
t.Fatal(err)
}
if entry == nil {
break
}
n++
}
if n != 18 {
t.Fatalf("want %d DWARF entries, got %d", 18, n)
}
}
func TestNoSectionOverlaps(t *testing.T) {
// Ensure 6l outputs sections without overlaps.
if runtime.GOOS != "linux" && runtime.GOOS != "freebsd" {

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src/debug/elf/testdata/zdebug-test-gcc484-x86-64.obj vendored Normal file
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2
src/go/build/deps_test.go
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@ -218,7 +218,7 @@ var pkgDeps = map[string][]string{
"database/sql": {"L4", "container/list", "database/sql/driver"},
"database/sql/driver": {"L4", "time"},
"debug/dwarf": {"L4"},
"debug/elf": {"L4", "OS", "debug/dwarf"},
"debug/elf": {"L4", "OS", "debug/dwarf", "compress/zlib"},
"debug/gosym": {"L4"},
"debug/macho": {"L4", "OS", "debug/dwarf"},
"debug/pe": {"L4", "OS", "debug/dwarf"},