diff options
| -rw-r--r-- | cmd/symbols_map/elf.go | 25 | ||||
| -rw-r--r-- | cmd/symbols_map/elf_test.go | 68 |
2 files changed, 92 insertions, 1 deletions
diff --git a/cmd/symbols_map/elf.go b/cmd/symbols_map/elf.go index b38896a32..3c8b1e42b 100644 --- a/cmd/symbols_map/elf.go +++ b/cmd/symbols_map/elf.go @@ -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 { diff --git a/cmd/symbols_map/elf_test.go b/cmd/symbols_map/elf_test.go index e6162280c..b96ea592c 100644 --- a/cmd/symbols_map/elf_test.go +++ b/cmd/symbols_map/elf_test.go @@ -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() +} |