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// -*- Mode: Go; indent-tabs-mode: t -*-
/*
* Copyright (C) 2017 Canonical Ltd
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package osutil
import (
"debug/elf"
"encoding/binary"
"encoding/hex"
"errors"
"os"
)
var osReadlink = os.Readlink
// ErrNoBuildID is returned when an executable does not contain a Build-ID
var ErrNoBuildID = errors.New("executable does not contain a build ID")
type elfNoteHeader struct {
Namesz uint32
Descsz uint32
Type uint32
}
const (
gnuElfNote = "GNU\x00"
gnuHdrType = 3
goElfNote = "Go\x00\x00"
goHdrType = 4
)
// ReadBuildID returns the build ID of a given binary. GNU BuildID is is
// preferred over Go BuildID. Returns an error when neither is found.
func ReadBuildID(fname string) (string, error) {
if buildId, err := readGenericBuildID(fname, gnuElfNote, gnuHdrType); err == nil {
return buildId, nil
}
return readGenericBuildID(fname, goElfNote, goHdrType)
}
func readGenericBuildID(fname, elfNote string, hdrType uint32) (string, error) {
// Open the designated ELF file
f, err := elf.Open(fname)
if err != nil {
return "", err
}
defer f.Close()
for _, section := range f.Sections {
// We are looking for note sections
if section.Type != elf.SHT_NOTE {
continue
}
// NOTE: this is a ReadSeeker so no need to close it
sr := section.Open()
sr.Seek(0, os.SEEK_SET)
// Read the ELF Note header
nHdr := new(elfNoteHeader)
if err := binary.Read(sr, f.ByteOrder, nHdr); err != nil {
return "", err
}
// We are looking for a specific type of note
if nHdr.Type != hdrType {
continue
}
// Read note name
noteName := make([]byte, nHdr.Namesz)
if err := binary.Read(sr, f.ByteOrder, noteName); err != nil {
return "", err
}
// We are only in a specific note
if string(noteName) != elfNote {
continue
}
// Read note data
noteData := make([]byte, nHdr.Descsz)
if err := binary.Read(sr, f.ByteOrder, noteData); err != nil {
return "", err
}
// Return the first build-id we manage to find
return hex.EncodeToString(noteData), nil
}
return "", ErrNoBuildID
}
// MyBuildID return the build-id of the currently running executable
func MyBuildID() (string, error) {
exe, err := osReadlink("/proc/self/exe")
if err != nil {
return "", err
}
return ReadBuildID(exe)
}
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