Merge "symbols_map: don't error on bad elf files" (07907127) · Commits · e / os / android_build_soong

cmd/symbols_map/elf.go

+24 −1

Original line number	Diff line number	Diff line
		@@ -18,8 +18,10 @@ import (
		"debug/elf"
		"encoding/binary"
		"encoding/hex"
		"errors"
		"fmt"
		"io"
		"os"
		)

		const gnuBuildID = "GNU\x00"
		@@ -27,12 +29,33 @@ const gnuBuildID = "GNU\x00"
		// elfIdentifier extracts the elf build ID from an elf file. If allowMissing is true it returns
		// an empty identifier if the file exists but the build ID note does not.
		func elfIdentifier(filename string, allowMissing bool) (string, error) {
		f, err := elf.Open(filename)
		f, err := os.Open(filename)
		if err != nil {
		return "", fmt.Errorf("failed to open %s: %w", filename, err)
		}
		defer f.Close()

		return elfIdentifierFromReaderAt(f, filename, allowMissing)
		}

		// elfIdentifier extracts the elf build ID from a ReaderAt. If allowMissing is true it returns
		// an empty identifier if the file exists but the build ID note does not.
		func elfIdentifierFromReaderAt(r io.ReaderAt, filename string, allowMissing bool) (string, error) {
		f, err := elf.NewFile(r)
		if err != nil {
		if allowMissing {
		if errors.Is(err, io.EOF) {
		return "", nil
		}
		if _, ok := err.(*elf.FormatError); ok {
		// The file was not an elf file.
		return "", nil
		}
		}
		return "", fmt.Errorf("failed to parse elf file %s: %w", filename, err)
		}
		defer f.Close()

		buildIDNote := f.Section(".note.gnu.build-id")
		if buildIDNote == nil {
		if allowMissing {

cmd/symbols_map/elf_test.go

+68 −0

Original line number	Diff line number	Diff line
		@@ -16,11 +16,46 @@ package main

		import (
		"bytes"
		"debug/elf"
		"encoding/binary"
		"reflect"
		"testing"
		)

		func Test_elfIdentifierFromReaderAt_BadElfFile(t *testing.T) {
		tests := []struct {
		name string
		contents string
		}{
		{
		name: "empty",
		contents: "",
		},
		{
		name: "text",
		contents: "#!/bin/bash\necho foobar",
		},
		{
		name: "empty elf",
		contents: emptyElfFile(),
		},
		}

		for _, tt := range tests {
		t.Run(tt.name, func(t *testing.T) {
		buf := bytes.NewReader([]byte(tt.contents))
		_, err := elfIdentifierFromReaderAt(buf, "<>", false)
		if err == nil {
		t.Errorf("expected error reading bad elf file without allowMissing")
		}
		_, err = elfIdentifierFromReaderAt(buf, "<>", true)
		if err != nil {
		t.Errorf("expected no error reading bad elf file with allowMissing, got %q", err.Error())
		}
		})
		}
		}

		func Test_readNote(t *testing.T) {
		note := []byte{
		0x04, 0x00, 0x00, 0x00,
		@@ -43,3 +78,36 @@ func Test_readNote(t *testing.T) {
		t.Errorf("incorrect return, want %#v got %#v", expectedDescs, descs)
		}
		}

		// emptyElfFile returns an elf file header with no program headers or sections.
		func emptyElfFile() string {
		ident := [elf.EI_NIDENT]byte{}
		identBuf := bytes.NewBuffer(ident[0:0:elf.EI_NIDENT])
		binary.Write(identBuf, binary.LittleEndian, []byte("\x7fELF"))
		binary.Write(identBuf, binary.LittleEndian, elf.ELFCLASS64)
		binary.Write(identBuf, binary.LittleEndian, elf.ELFDATA2LSB)
		binary.Write(identBuf, binary.LittleEndian, elf.EV_CURRENT)
		binary.Write(identBuf, binary.LittleEndian, elf.ELFOSABI_LINUX)
		binary.Write(identBuf, binary.LittleEndian, make([]byte, 8))

		header := elf.Header64{
		Ident: ident,
		Type: uint16(elf.ET_EXEC),
		Machine: uint16(elf.EM_X86_64),
		Version: uint32(elf.EV_CURRENT),
		Entry: 0,
		Phoff: uint64(binary.Size(elf.Header64{})),
		Shoff: uint64(binary.Size(elf.Header64{})),
		Flags: 0,
		Ehsize: uint16(binary.Size(elf.Header64{})),
		Phentsize: 0x38,
		Phnum: 0,
		Shentsize: 0x40,
		Shnum: 0,
		Shstrndx: 0,
		}

		buf := &bytes.Buffer{}
		binary.Write(buf, binary.LittleEndian, header)
		return buf.String()
		}