1 files changed, 33 insertions, 20 deletions

diff --git a/src/pkg/debug/elf/file.go b/src/pkg/debug/elf/file.go
index 184ca8375..acb9817af 100644
--- a/src/pkg/debug/elf/file.go
+++ b/src/pkg/debug/elf/file.go
@@ -31,6 +31,7 @@ type FileHeader struct {
 	ByteOrder  binary.ByteOrder
 	Type       Type
 	Machine    Machine
+	Entry      uint64
 }
 
 // A File represents an open ELF file.
@@ -240,6 +241,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
 		}
 		f.Type = Type(hdr.Type)
 		f.Machine = Machine(hdr.Machine)
+		f.Entry = uint64(hdr.Entry)
 		if v := Version(hdr.Version); v != f.Version {
 			return nil, &FormatError{0, "mismatched ELF version", v}
 		}
@@ -258,6 +260,7 @@ func NewFile(r io.ReaderAt) (*File, error) {
 		}
 		f.Type = Type(hdr.Type)
 		f.Machine = Machine(hdr.Machine)
+		f.Entry = uint64(hdr.Entry)
 		if v := Version(hdr.Version); v != f.Version {
 			return nil, &FormatError{0, "mismatched ELF version", v}
 		}
@@ -269,7 +272,8 @@ func NewFile(r io.ReaderAt) (*File, error) {
 		shnum = int(hdr.Shnum)
 		shstrndx = int(hdr.Shstrndx)
 	}
-	if shstrndx < 0 || shstrndx >= shnum {
+
+	if shnum > 0 && shoff > 0 && (shstrndx < 0 || shstrndx >= shnum) {
 		return nil, &FormatError{0, "invalid ELF shstrndx", shstrndx}
 	}
 
@@ -364,6 +368,10 @@ func NewFile(r io.ReaderAt) (*File, error) {
 		f.Sections[i] = s
 	}
 
+	if len(f.Sections) == 0 {
+		return f, nil
+	}
+
 	// Load section header string table.
 	shstrtab, err := f.Sections[shstrndx].Data()
 	if err != nil {
@@ -414,10 +422,6 @@ func (f *File) getSymbols32(typ SectionType) ([]Symbol, []byte, error) {
 		return nil, nil, errors.New("cannot load string table section")
 	}
 
-	// The first entry is all zeros.
-	var skip [Sym32Size]byte
-	symtab.Read(skip[0:])
-
 	symbols := make([]Symbol, symtab.Len()/Sym32Size)
 
 	i := 0
@@ -457,10 +461,6 @@ func (f *File) getSymbols64(typ SectionType) ([]Symbol, []byte, error) {
 		return nil, nil, errors.New("cannot load string table section")
 	}
 
-	// The first entry is all zeros.
-	var skip [Sym64Size]byte
-	symtab.Read(skip[0:])
-
 	symbols := make([]Symbol, symtab.Len()/Sym64Size)
 
 	i := 0
@@ -705,8 +705,8 @@ func (f *File) gnuVersionInit(str []byte) {
 // gnuVersion adds Library and Version information to sym,
 // which came from offset i of the symbol table.
 func (f *File) gnuVersion(i int, sym *ImportedSymbol) {
-	// Each entry is two bytes; skip undef entry at beginning.
-	i = (i + 1) * 2
+	// Each entry is two bytes.
+	i = i * 2
 	if i >= len(f.gnuVersym) {
 		return
 	}
@@ -723,6 +723,20 @@ func (f *File) gnuVersion(i int, sym *ImportedSymbol) {
 // referred to by the binary f that are expected to be
 // linked with the binary at dynamic link time.
 func (f *File) ImportedLibraries() ([]string, error) {
+	return f.DynString(DT_NEEDED)
+}
+
+// DynString returns the strings listed for the given tag in the file's dynamic
+// section.
+//
+// The tag must be one that takes string values: DT_NEEDED, DT_SONAME, DT_RPATH, or
+// DT_RUNPATH.
+func (f *File) DynString(tag DynTag) ([]string, error) {
+	switch tag {
+	case DT_NEEDED, DT_SONAME, DT_RPATH, DT_RUNPATH:
+	default:
+		return nil, fmt.Errorf("non-string-valued tag %v", tag)
+	}
 	ds := f.SectionByType(SHT_DYNAMIC)
 	if ds == nil {
 		// not dynamic, so no libraries
@@ -738,25 +752,24 @@ func (f *File) ImportedLibraries() ([]string, error) {
 	}
 	var all []string
 	for len(d) > 0 {
-		var tag DynTag
-		var value uint64
+		var t DynTag
+		var v uint64
 		switch f.Class {
 		case ELFCLASS32:
-			tag = DynTag(f.ByteOrder.Uint32(d[0:4]))
-			value = uint64(f.ByteOrder.Uint32(d[4:8]))
+			t = DynTag(f.ByteOrder.Uint32(d[0:4]))
+			v = uint64(f.ByteOrder.Uint32(d[4:8]))
 			d = d[8:]
 		case ELFCLASS64:
-			tag = DynTag(f.ByteOrder.Uint64(d[0:8]))
-			value = f.ByteOrder.Uint64(d[8:16])
+			t = DynTag(f.ByteOrder.Uint64(d[0:8]))
+			v = f.ByteOrder.Uint64(d[8:16])
 			d = d[16:]
 		}
-		if tag == DT_NEEDED {
-			s, ok := getString(str, int(value))
+		if t == tag {
+			s, ok := getString(str, int(v))
 			if ok {
 				all = append(all, s)
 			}
 		}
 	}
-
 	return all, nil
 }