support mach-o overlay

debug/elf/file.go

@@ -1479,7 +1479,7 @@ func (f *File) Overlay() ([]byte, error) {
 	}
 	overlayEnd, err := sr.Seek(0, io.SeekEnd)
 	if err != nil {
-		return nil, fmt.Errorf("pe: seek %v", err)
+		return nil, fmt.Errorf("elf: seek %v", err)
 	}
 	overlayLen := overlayEnd - int64(f.OverlayOffset)
 	overlay := make([]byte, overlayLen)

debug/macho/file.go

@@ -12,21 +12,29 @@ import (
 	"compress/zlib"
 	"debug/dwarf"
 	"encoding/binary"
+	"errors"
 	"fmt"
 	"io"
 	"os"
 	"strings"
 )
 
+// error
+var (
+	ErrNoOverlayFound = errors.New("macho: not have overlay data")
+)
+
 // A File represents an open Mach-O file.
 type File struct {
 	FileHeader
 	ByteOrder binary.ByteOrder
 	Loads     []Load
 	Sections  []*Section
 
-	Symtab   *Symtab
-	Dysymtab *Dysymtab
+	Symtab        *Symtab
+	Dysymtab      *Dysymtab
+	OverlayOffset uint64
+	r             io.ReaderAt
 
 	closer io.Closer
 }
@@ -227,6 +235,7 @@ func (f *File) Close() error {
 // The Mach-O binary is expected to start at position 0 in the ReaderAt.
 func NewFile(r io.ReaderAt) (*File, error) {
 	f := new(File)
+	f.r = r
 	sr := io.NewSectionReader(r, 0, 1<<63-1)
 
 	// Read and decode Mach magic to determine byte order, size.
@@ -375,6 +384,9 @@ func NewFile(r io.ReaderAt) (*File, error) {
 			s.Memsz = uint64(seg32.Memsz)
 			s.Offset = uint64(seg32.Offset)
 			s.Filesz = uint64(seg32.Filesz)
+			if sectionEnd := uint64(s.Offset) + s.Filesz; sectionEnd > f.OverlayOffset {
+				f.OverlayOffset = sectionEnd
+			}
 			s.Maxprot = seg32.Maxprot
 			s.Prot = seg32.Prot
 			s.Nsect = seg32.Nsect
@@ -415,6 +427,9 @@ func NewFile(r io.ReaderAt) (*File, error) {
 			s.Memsz = seg64.Memsz
 			s.Offset = seg64.Offset
 			s.Filesz = seg64.Filesz
+			if sectionEnd := uint64(s.Offset) + s.Filesz; sectionEnd > f.OverlayOffset {
+				f.OverlayOffset = sectionEnd
+			}
 			s.Maxprot = seg64.Maxprot
 			s.Prot = seg64.Prot
 			s.Nsect = seg64.Nsect
@@ -445,6 +460,11 @@ func NewFile(r io.ReaderAt) (*File, error) {
 			s.ReaderAt = s.sr
 		}
 	}
+	for _, sec := range f.Sections {
+		if sectionEnd := uint64(sec.Offset) + sec.Size; sectionEnd > f.OverlayOffset {
+			f.OverlayOffset = sectionEnd
+		}
+	}
 	return f, nil
 }
 
@@ -691,3 +711,34 @@ func (f *File) ImportedLibraries() ([]string, error) {
 	}
 	return all, nil
 }
+
+// NewOverlayReader create a new ReaderAt for read PE overlay data
+func (f *File) NewOverlayReader() (io.ReaderAt, error) {
+	if f.r == nil {
+		return nil, errors.New("elf: file reader is nil")
+	}
+	if f.OverlayOffset == 0 {
+		return nil, ErrNoOverlayFound
+	}
+	return io.NewSectionReader(f.r, int64(f.OverlayOffset), 1<<63-1), nil
+}
+
+// Overlay returns the overlay of the ELF fil (i.e. any optional bytes directly
+// succeeding the image).
+func (f *File) Overlay() ([]byte, error) {
+	sr, ok := f.r.(io.Seeker)
+	if !ok {
+		return nil, errors.New("macho: reader not a io.Seeker")
+	}
+	overlayEnd, err := sr.Seek(0, io.SeekEnd)
+	if err != nil {
+		return nil, fmt.Errorf("macho: seek %v", err)
+	}
+	overlayLen := overlayEnd - int64(f.OverlayOffset)
+	overlay := make([]byte, overlayLen)
+	ser := io.NewSectionReader(f.r, int64(f.OverlayOffset), overlayLen)
+	if _, err := io.ReadFull(ser, overlay); err != nil {
+		return nil, err
+	}
+	return overlay, nil
+}

debug/pe/overlay.go

@@ -14,7 +14,7 @@ var (
 // NewOverlayReader create a new ReaderAt for read PE overlay data
 func (f *File) NewOverlayReader() (io.ReaderAt, error) {
 	if f.r == nil {
-		return nil, errors.New("PE file reader is nil")
+		return nil, errors.New("pe: file reader is nil")
 	}
 	return io.NewSectionReader(f.r, f.OverlayOffset, 1<<63-1), nil
 }

test/elfreader/main.go

@@ -26,7 +26,7 @@ func main() {
 	if st.Size() > int64(fd.OverlayOffset) {
 		overlay, err := fd.Overlay()
 		if err != nil && err != elf.ErrNoOverlayFound {
-			fmt.Fprintf(os.Stderr, "unable LookupExports: %s %v\n", os.Args[1], err)
+			fmt.Fprintf(os.Stderr, "unable lookup elf overlay data: %s %v\n", os.Args[1], err)
 			os.Exit(1)
 		}
 		fmt.Fprintf(os.Stderr, "Overlay: %v\n", string(overlay))

test/machoreader/main.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/fcharlie/buna/debug/macho"
+)
+
+func main() {
+	if len(os.Args) < 2 {
+		fmt.Fprintf(os.Stderr, "usage: %s pefile\n", os.Args[0])
+		os.Exit(1)
+	}
+	st, err := os.Stat(os.Args[1])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "unable state: %v\n", err)
+		os.Exit(1)
+	}
+	size := st.Size()
+	fmt.Fprintf(os.Stderr, "FileSize: %d\n", size)
+	fd, err := macho.Open(os.Args[1])
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "unable open file: %s %v\n", os.Args[1], err)
+		os.Exit(1)
+	}
+	defer fd.Close()
+	if size > int64(fd.OverlayOffset) {
+		overlay, err := fd.Overlay()
+		if err != nil && err != macho.ErrNoOverlayFound {
+			fmt.Fprintf(os.Stderr, "unable lookuo overlay data: %s %v\n", os.Args[1], err)
+			os.Exit(1)
+		}
+		fmt.Fprintf(os.Stderr, "Overlay: %v\n", string(overlay))
+	}
+
+}