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proc: support gnu_debuglink section (#3073)

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Load separate debug info using gnu_debuglink.

Fixes #2150
This commit is contained in:
Alessandro Arzilli 2022-07-25 19:01:41 +02:00 committed by GitHub
parent e72d9b3372
commit 2900418e78
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 217 additions and 15 deletions
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187
pkg/proc/bininfo.go
View File

@ -13,6 +13,7 @@ import (
"go/ast"
"go/token"
"io"
"io/ioutil"
"os"
"path/filepath"
"sort"
@ -1207,34 +1208,98 @@ func (bi *BinaryInfo) parseDebugFrameGeneral(image *Image, debugFrameBytes []byt
// Alternatively, if the debug file cannot be found be the build-id, Delve
// will look in directories specified by the debug-info-directories config value.
func (bi *BinaryInfo) openSeparateDebugInfo(image *Image, exe *elf.File, debugInfoDirectories []string) (*os.File, *elf.File, error) {
var debugFilePath string
var err error
for _, dir := range debugInfoDirectories {
var potentialDebugFilePath string
if strings.Contains(dir, "build-id") && len(bi.BuildID) > 2 {
potentialDebugFilePath = fmt.Sprintf("%s/%s/%s.debug", dir, bi.BuildID[:2], bi.BuildID[2:])
} else if strings.HasPrefix(image.Path, "/proc") {
path, err := filepath.EvalSymlinks(image.Path)
if err == nil {
potentialDebugFilePath = fmt.Sprintf("%s/%s.debug", dir, filepath.Base(path))
}
} else {
potentialDebugFilePath = fmt.Sprintf("%s/%s.debug", dir, filepath.Base(image.Path))
exePath := image.Path
exeName := filepath.Base(image.Path)
if strings.HasPrefix(image.Path, "/proc") {
var err error
exePath, err = filepath.EvalSymlinks(image.Path)
if err == nil {
exeName = filepath.Base(exePath)
}
}
var debugFilePath string
check := func(potentialDebugFilePath string) bool {
_, err := os.Stat(potentialDebugFilePath)
if err == nil {
debugFilePath = potentialDebugFilePath
break
return true
}
return false
}
find := func(f func(string) bool, suffix string) {
for _, dir := range debugInfoDirectories {
if f != nil && !f(dir) {
continue
}
if check(fmt.Sprintf("%s/%s", dir, suffix)) {
break
}
}
}
if debugFilePath == "" && len(bi.BuildID) > 2 {
// Build ID method: look for a file named .build-id/nn/nnnnnnnn.debug in
// every debug info directory.
find(nil, fmt.Sprintf(".build-id/%s/%s.debug", bi.BuildID[:2], bi.BuildID[2:]))
}
if debugFilePath == "" {
// Debug link: method if the executable contains a .gnu_debuglink section
// it will look for the file named in the same directory of the
// executable, then in a subdirectory named .debug and finally in each
// debug info directory in a subdirectory with the same path as the
// directory of the executable
debugLink, crc := bi.getDebugLink(exe)
if debugLink != "" {
check(filepath.Join(filepath.Dir(exePath), debugLink))
if debugFilePath == "" {
check(filepath.Join(filepath.Dir(exePath), ".debug", debugLink))
}
if debugFilePath == "" {
suffix := filepath.Join(filepath.Dir(exePath)[1:], debugLink)
find(nil, suffix)
}
}
if debugFilePath != "" {
// CRC check
computedCRC, ok := gnuDebugLinkCRC(debugFilePath)
if ok && crc != computedCRC {
bi.logger.Errorf("gnu_debuglink CRC check failed for %s (want %x got %x)", debugFilePath, crc, computedCRC)
debugFilePath = ""
}
}
}
if debugFilePath == "" && len(bi.BuildID) > 2 {
// Previous verrsions of delve looked for the build id in every debug info
// directory that contained the build-id substring. This behavior deviates
// from the ones specified by GDB but we keep it for backwards compatibility.
find(func(dir string) bool { return strings.Contains(dir, "build-id") }, fmt.Sprintf(".build-id/%s/%s.debug", bi.BuildID[:2], bi.BuildID[2:]))
}
if debugFilePath == "" {
// Previous versions of delve looked for the executable filename (with
// .debug extension) in every debug info directory. This behavior also
// deviates from the ones specified by GDB, but we keep it for backwards
// compatibility.
find(func(dir string) bool { return !strings.Contains(dir, "build-id") }, fmt.Sprintf("%s.debug", exeName))
}
// We cannot find the debug information locally on the system. Try and see if we're on a system that
// has debuginfod so that we can use that in order to find any relevant debug information.
if debugFilePath == "" {
var err error
debugFilePath, err = debuginfod.GetDebuginfo(bi.BuildID)
if err != nil {
return nil, nil, ErrNoDebugInfoFound
}
}
sepFile, err := os.OpenFile(debugFilePath, 0, os.ModePerm)
if err != nil {
return nil, nil, errors.New("can't open separate debug file: " + err.Error())
@ -1254,6 +1319,77 @@ func (bi *BinaryInfo) openSeparateDebugInfo(image *Image, exe *elf.File, debugIn
return sepFile, elfFile, nil
}
var gnuDebugLinkCRCTable = [256]uint32{
0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
0x2d02ef8d,
}
// gnuDebugLinkCRC calculates the CRC for gnu_debuglink as specified in:
//
// https://sourceware.org/gdb/onlinedocs/gdb/Separate-Debug-Files.html
func gnuDebugLinkCRC(debugFilePath string) (uint32, bool) {
buf, err := ioutil.ReadFile(debugFilePath)
if err != nil {
return 0, false
}
crc := uint32(0)
crc = ^crc & 0xffffffff
for _, ch := range buf {
crc = gnuDebugLinkCRCTable[(crc^uint32(ch))&0xff] ^ (crc >> 8)
}
return ^crc & 0xffffffff, true
}
// loadBinaryInfoElf specifically loads information from an ELF binary.
func loadBinaryInfoElf(bi *BinaryInfo, image *Image, path string, addr uint64, wg *sync.WaitGroup) error {
exe, err := os.OpenFile(path, 0, os.ModePerm)
@ -1359,7 +1495,6 @@ func (bi *BinaryInfo) loadSymbolName(image *Image, file *elf.File, wg *sync.Wait
func (bi *BinaryInfo) loadBuildID(image *Image, file *elf.File) {
buildid := file.Section(".note.gnu.build-id")
if buildid == nil {
bi.logger.Warn("can't find build-id note on binary")
return
}
@ -1389,6 +1524,28 @@ func (bi *BinaryInfo) loadBuildID(image *Image, file *elf.File) {
bi.BuildID = hex.EncodeToString(descBinary)
}
func (bi *BinaryInfo) getDebugLink(exe *elf.File) (debugLink string, crc uint32) {
gnuDebugLink := exe.Section(".gnu_debuglink")
if gnuDebugLink == nil {
return
}
br := gnuDebugLink.Open()
buf, err := ioutil.ReadAll(br)
if err != nil {
bi.logger.Warnf("can't read .gnu_debuglink: %v", err)
return
}
zero := bytes.Index(buf, []byte{0})
if zero <= 0 || len(buf[zero+1:]) < 4 {
bi.logger.Warnf("wrong .gnu_debuglink format: %q", buf)
return
}
debugLink = string(buf[:zero])
crc = binary.LittleEndian.Uint32(buf[len(buf)-4:])
return
}
func (bi *BinaryInfo) parseDebugFrameElf(image *Image, dwarfFile, exeFile *elf.File, debugInfoBytes []byte, wg *sync.WaitGroup) {
defer wg.Done()

45
pkg/proc/proc_test.go
View File

@ -5921,3 +5921,48 @@ func TestCallInjectionFlagCorruption(t *testing.T) {
assertLineNumber(p, t, 17, "expected line :17") // since we passed "0" as argument we should be going into the false branch at line :17
})
}
func TestGnuDebuglink(t *testing.T) {
skipUnlessOn(t, "N/A", "linux")
// build math.go and make a copy of the executable
fixture := protest.BuildFixture("math", 0)
buf, err := ioutil.ReadFile(fixture.Path)
assertNoError(err, t, "ReadFile")
debuglinkPath := fixture.Path + "-gnu_debuglink"
assertNoError(ioutil.WriteFile(debuglinkPath, buf, 0666), t, "WriteFile")
defer os.Remove(debuglinkPath)
run := func(exe string, args ...string) {
cmd := exec.Command(exe, args...)
out, err := cmd.CombinedOutput()
assertNoError(err, t, fmt.Sprintf("%s %q: %s", cmd, strings.Join(args, " "), out))
}
// convert the executable copy to use .gnu_debuglink
debuglinkDwoPath := debuglinkPath + ".dwo"
run("objcopy", "--only-keep-debug", debuglinkPath, debuglinkDwoPath)
defer os.Remove(debuglinkDwoPath)
run("objcopy", "--strip-debug", debuglinkPath)
run("objcopy", "--add-gnu-debuglink="+debuglinkDwoPath, debuglinkPath)
// open original executable
normalBinInfo := proc.NewBinaryInfo(runtime.GOOS, runtime.GOARCH)
assertNoError(normalBinInfo.LoadBinaryInfo(fixture.Path, 0, []string{"/debugdir"}), t, "LoadBinaryInfo (normal exe)")
// open .gnu_debuglink executable
debuglinkBinInfo := proc.NewBinaryInfo(runtime.GOOS, runtime.GOARCH)
assertNoError(debuglinkBinInfo.LoadBinaryInfo(debuglinkPath, 0, []string{"/debugdir"}), t, "LoadBinaryInfo (gnu_debuglink exe)")
if len(normalBinInfo.Functions) != len(debuglinkBinInfo.Functions) {
t.Fatalf("function list mismatch")
}
for i := range normalBinInfo.Functions {
normalFn := normalBinInfo.Functions[i]
debuglinkFn := debuglinkBinInfo.Functions[i]
if normalFn.Entry != debuglinkFn.Entry || normalFn.Name != normalFn.Name {
t.Fatalf("function definition mismatch")
}
}
}