96 lines
2.6 KiB
Go
96 lines
2.6 KiB
Go
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// Copyright 2022 Google Inc. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package main
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import (
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"debug/elf"
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"encoding/binary"
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"encoding/hex"
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"fmt"
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"io"
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)
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const gnuBuildID = "GNU\x00"
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// elfIdentifier extracts the elf build ID from an elf file. If allowMissing is true it returns
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// an empty identifier if the file exists but the build ID note does not.
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func elfIdentifier(filename string, allowMissing bool) (string, error) {
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f, err := elf.Open(filename)
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if err != nil {
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return "", fmt.Errorf("failed to open %s: %w", filename, err)
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}
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defer f.Close()
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buildIDNote := f.Section(".note.gnu.build-id")
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if buildIDNote == nil {
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if allowMissing {
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return "", nil
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}
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return "", fmt.Errorf("failed to find .note.gnu.build-id in %s", filename)
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}
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buildIDs, err := readNote(buildIDNote.Open(), f.ByteOrder)
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if err != nil {
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return "", fmt.Errorf("failed to read .note.gnu.build-id: %w", err)
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}
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for name, desc := range buildIDs {
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if name == gnuBuildID {
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return hex.EncodeToString(desc), nil
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}
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}
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return "", nil
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}
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// readNote reads the contents of a note section, returning it as a map from name to descriptor.
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func readNote(note io.Reader, byteOrder binary.ByteOrder) (map[string][]byte, error) {
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var noteHeader struct {
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Namesz uint32
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Descsz uint32
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Type uint32
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}
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notes := make(map[string][]byte)
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for {
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err := binary.Read(note, byteOrder, ¬eHeader)
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if err != nil {
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if err == io.EOF {
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return notes, nil
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}
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return nil, fmt.Errorf("failed to read note header: %w", err)
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}
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nameBuf := make([]byte, align4(noteHeader.Namesz))
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err = binary.Read(note, byteOrder, &nameBuf)
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if err != nil {
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return nil, fmt.Errorf("failed to read note name: %w", err)
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}
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name := string(nameBuf[:noteHeader.Namesz])
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descBuf := make([]byte, align4(noteHeader.Descsz))
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err = binary.Read(note, byteOrder, &descBuf)
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if err != nil {
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return nil, fmt.Errorf("failed to read note desc: %w", err)
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}
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notes[name] = descBuf[:noteHeader.Descsz]
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}
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}
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// align4 rounds the input up to the next multiple of 4.
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func align4(i uint32) uint32 {
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return (i + 3) &^ 3
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}
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