debug/dwarf, debug/elf: support DWARF 5

Change-Id: I6e9d47865c198299d497911c58235cd40f775e34
Reviewed-on: https://go-review.googlesource.com/c/go/+/175138
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>

7 files changed, 470 insertions, 51 deletions

diff --git a/src/debug/dwarf/buf.go b/src/debug/dwarf/buf.go
index 24d266db10..3e6ce293fd 100644
--- a/src/debug/dwarf/buf.go
+++ b/src/debug/dwarf/buf.go
@@ -99,6 +99,18 @@ func (b *buf) uint16() uint16 {
 	return b.order.Uint16(a)
 }
 
+func (b *buf) uint24() uint32 {
+	a := b.bytes(3)
+	if a == nil {
+		return 0
+	}
+	if b.dwarf.bigEndian {
+		return uint32(a[2]) | uint32(a[1])<<8 | uint32(a[0])<<16
+	} else {
+		return uint32(a[0]) | uint32(a[1])<<8 | uint32(a[2])<<16
+	}
+}
+
 func (b *buf) uint32() uint32 {
 	a := b.bytes(4)
 	if a == nil {
diff --git a/src/debug/dwarf/entry.go b/src/debug/dwarf/entry.go
index 6be0700b7e..dfc2f44abc 100644
--- a/src/debug/dwarf/entry.go
+++ b/src/debug/dwarf/entry.go
@@ -26,6 +26,7 @@ type afield struct {
 	attr  Attr
 	fmt   format
 	class Class
+	val   int64 // for formImplicitConst
 }
 
 // a map from entry format ids to their descriptions
@@ -67,6 +68,9 @@ func (d *Data) parseAbbrev(off uint64, vers int) (abbrevTable, error) {
 			if tag == 0 && fmt == 0 {
 				break
 			}
+			if format(fmt) == formImplicitConst {
+				b1.int()
+			}
 			n++
 		}
 		if b1.err != nil {
@@ -82,6 +86,9 @@ func (d *Data) parseAbbrev(off uint64, vers int) (abbrevTable, error) {
 			a.field[i].attr = Attr(b.uint())
 			a.field[i].fmt = format(b.uint())
 			a.field[i].class = formToClass(a.field[i].fmt, a.field[i].attr, vers, &b)
+			if a.field[i].fmt == formImplicitConst {
+				a.field[i].val = b.int()
+			}
 		}
 		b.uint()
 		b.uint()
@@ -137,6 +144,11 @@ var attrPtrClass = map[Attr]Class{
 	AttrUseLocation:   ClassLocListPtr,
 	AttrVtableElemLoc: ClassLocListPtr,
 	AttrRanges:        ClassRangeListPtr,
+	// The following are new in DWARF 5.
+	AttrStrOffsetsBase: ClassStrOffsetsPtr,
+	AttrAddrBase:       ClassAddrPtr,
+	AttrRnglistsBase:   ClassRngListsPtr,
+	AttrLoclistsBase:   ClassLocListPtr,
 }
 
 // formToClass returns the DWARF 4 Class for the given form. If the
@@ -148,7 +160,7 @@ func formToClass(form format, attr Attr, vers int, b *buf) Class {
 		b.error("cannot determine class of unknown attribute form")
 		return 0
 
-	case formAddr:
+	case formAddr, formAddrx, formAddrx1, formAddrx2, formAddrx3, formAddrx4:
 		return ClassAddress
 
 	case formDwarfBlock1, formDwarfBlock2, formDwarfBlock4, formDwarfBlock:
@@ -163,7 +175,7 @@ func formToClass(form format, attr Attr, vers int, b *buf) Class {
 		}
 		return ClassBlock
 
-	case formData1, formData2, formData4, formData8, formSdata, formUdata:
+	case formData1, formData2, formData4, formData8, formSdata, formUdata, formData16, formImplicitConst:
 		// In DWARF 2 and 3, ClassPtr was encoded as a
 		// constant. Unlike ClassExprLoc/ClassBlock, some
 		// DWARF 4 attributes need to distinguish Class*Ptr
@@ -177,13 +189,13 @@ func formToClass(form format, attr Attr, vers int, b *buf) Class {
 	case formFlag, formFlagPresent:
 		return ClassFlag
 
-	case formRefAddr, formRef1, formRef2, formRef4, formRef8, formRefUdata:
+	case formRefAddr, formRef1, formRef2, formRef4, formRef8, formRefUdata, formRefSup4, formRefSup8:
 		return ClassReference
 
 	case formRefSig8:
 		return ClassReferenceSig
 
-	case formString, formStrp:
+	case formString, formStrp, formStrx, formStrpSup, formLineStrp, formStrx1, formStrx2, formStrx3, formStrx4:
 		return ClassString
 
 	case formSecOffset:
@@ -203,6 +215,12 @@ func formToClass(form format, attr Attr, vers int, b *buf) Class {
 
 	case formGnuStrpAlt:
 		return ClassStringAlt
+
+	case formLoclistx:
+		return ClassLocList
+
+	case formRnglistx:
+		return ClassRngList
 	}
 }
 
@@ -324,6 +342,27 @@ const (
 	// offset into the DWARF string section of an alternate object
 	// file.
 	ClassStringAlt
+
+	// ClassAddrPtr represents values that are an int64 offset
+	// into the "addr" section.
+	ClassAddrPtr
+
+	// ClassLocList represents values that are an int64 offset
+	// into the "loclists" section.
+	ClassLocList
+
+	// ClassRngList represents values that are an int64 offset
+	// from the base of the "rnglists" section.
+	ClassRngList
+
+	// ClassRngListsPtr represents values that are an int64 offset
+	// into the "rnglists" section. These are used as the base for
+	// ClassRngList values.
+	ClassRngListsPtr
+
+	// ClassStrOffsetsPtr represents values that are an int64
+	// offset into the "str_offsets" section.
+	ClassStrOffsetsPtr
 )
 
 //go:generate stringer -type=Class
@@ -363,7 +402,7 @@ type Offset uint32
 
 // Entry reads a single entry from buf, decoding
 // according to the given abbreviation table.
-func (b *buf) entry(atab abbrevTable, ubase Offset) *Entry {
+func (b *buf) entry(cu *Entry, atab abbrevTable, ubase Offset) *Entry {
 	off := b.off
 	id := uint32(b.uint())
 	if id == 0 {
@@ -395,6 +434,54 @@ func (b *buf) entry(atab abbrevTable, ubase Offset) *Entry {
 		// address
 		case formAddr:
 			val = b.addr()
+		case formAddrx, formAddrx1, formAddrx2, formAddrx3, formAddrx4:
+			var off uint64
+			switch fmt {
+			case formAddrx:
+				off = b.uint()
+			case formAddrx1:
+				off = uint64(b.uint8())
+			case formAddrx2:
+				off = uint64(b.uint16())
+			case formAddrx3:
+				off = uint64(b.uint24())
+			case formAddrx4:
+				off = uint64(b.uint32())
+			}
+			if len(b.dwarf.addr) == 0 {
+				b.error("DW_FORM_addrx with no .debug_addr section")
+			}
+			if b.err != nil {
+				return nil
+			}
+			addrsize := b.format.addrsize()
+			if addrsize == 0 {
+				b.error("unknown address size for DW_FORM_addrx")
+			}
+			off *= uint64(addrsize)
+
+			// We have to adjust by the offset of the
+			// compilation unit. This won't work if the
+			// program uses Reader.Seek to skip over the
+			// unit. Not much we can do about that.
+			if cu != nil {
+				cuOff, ok := cu.Val(AttrAddrBase).(int64)
+				if ok {
+					off += uint64(cuOff)
+				}
+			}
+
+			if uint64(int(off)) != off {
+				b.error("DW_FORM_addrx offset out of range")
+			}
+
+			b1 := makeBuf(b.dwarf, b.format, "addr", 0, b.dwarf.addr)
+			b1.skip(int(off))
+			val = b1.addr()
+			if b1.err != nil {
+				b.err = b1.err
+				return nil
+			}
 
 		// block
 		case formDwarfBlock1:
@@ -415,10 +502,14 @@ func (b *buf) entry(atab abbrevTable, ubase Offset) *Entry {
 			val = int64(b.uint32())
 		case formData8:
 			val = int64(b.uint64())
+		case formData16:
+			val = b.bytes(16)
 		case formSdata:
 			val = int64(b.int())
 		case formUdata:
 			val = int64(b.uint())
+		case formImplicitConst:
+			val = a.field[i].val
 
 		// flag
 		case formFlag:
@@ -460,29 +551,112 @@ func (b *buf) entry(atab abbrevTable, ubase Offset) *Entry {
 		// string
 		case formString:
 			val = b.string()
-		case formStrp:
+		case formStrp, formLineStrp:
 			var off uint64 // offset into .debug_str
 			is64, known := b.format.dwarf64()
 			if !known {
-				b.error("unknown size for DW_FORM_strp")
+				b.error("unknown size for DW_FORM_strp/line_strp")
 			} else if is64 {
 				off = b.uint64()
 			} else {
 				off = uint64(b.uint32())
 			}
 			if uint64(int(off)) != off {
-				b.error("DW_FORM_strp offset out of range")
+				b.error("DW_FORM_strp/line_strp offset out of range")
 			}
 			if b.err != nil {
 				return nil
 			}
-			b1 := makeBuf(b.dwarf, unknownFormat{}, "str", 0, b.dwarf.str)
+			var b1 buf
+			if fmt == formStrp {
+				b1 = makeBuf(b.dwarf, b.format, "str", 0, b.dwarf.str)
+			} else {
+				if len(b.dwarf.lineStr) == 0 {
+					b.error("DW_FORM_line_strp with no .debug_line_str section")
+				}
+				b1 = makeBuf(b.dwarf, b.format, "line_str", 0, b.dwarf.lineStr)
+			}
 			b1.skip(int(off))
 			val = b1.string()
 			if b1.err != nil {
 				b.err = b1.err
 				return nil
 			}
+		case formStrx, formStrx1, formStrx2, formStrx3, formStrx4:
+			var off uint64
+			switch fmt {
+			case formStrx:
+				off = b.uint()
+			case formStrx1:
+				off = uint64(b.uint8())
+			case formStrx2:
+				off = uint64(b.uint16())
+			case formStrx3:
+				off = uint64(b.uint24())
+			case formStrx4:
+				off = uint64(b.uint32())
+			}
+			if len(b.dwarf.strOffsets) == 0 {
+				b.error("DW_FORM_strx with no .debug_str_offsets section")
+			}
+			is64, known := b.format.dwarf64()
+			if !known {
+				b.error("unknown offset size for DW_FORM_strx")
+			}
+			if b.err != nil {
+				return nil
+			}
+			if is64 {
+				off *= 8
+			} else {
+				off *= 4
+			}
+
+			// We have to adjust by the offset of the
+			// compilation unit. This won't work if the
+			// program uses Reader.Seek to skip over the
+			// unit. Not much we can do about that.
+			if cu != nil {
+				cuOff, ok := cu.Val(AttrStrOffsetsBase).(int64)
+				if ok {
+					off += uint64(cuOff)
+				}
+			}
+
+			if uint64(int(off)) != off {
+				b.error("DW_FORM_strx offset out of range")
+			}
+
+			b1 := makeBuf(b.dwarf, b.format, "str_offsets", 0, b.dwarf.strOffsets)
+			b1.skip(int(off))
+			if is64 {
+				off = b1.uint64()
+			} else {
+				off = uint64(b1.uint32())
+			}
+			if b1.err != nil {
+				b.err = b1.err
+				return nil
+			}
+			if uint64(int(off)) != off {
+				b.error("DW_FORM_strx indirect offset out of range")
+			}
+			b1 = makeBuf(b.dwarf, b.format, "str", 0, b.dwarf.str)
+			b1.skip(int(off))
+			val = b1.string()
+			if b1.err != nil {
+				b.err = b1.err
+				return nil
+			}
+		case formStrpSup:
+			is64, known := b.format.dwarf64()
+			if !known {
+				b.error("unknown size for DW_FORM_strp_sup")
+			} else if is64 {
+				val = b.uint64()
+			} else {
+				val = b.uint32()
+			}
 
 		// lineptr, loclistptr, macptr, rangelistptr
 		// New in DWARF 4, but clang can generate them with -gdwarf-2.
@@ -507,6 +681,18 @@ func (b *buf) entry(atab abbrevTable, ubase Offset) *Entry {
 		case formRefSig8:
 			// 64-bit type signature.
 			val = b.uint64()
+		case formRefSup4:
+			val = b.uint32()
+		case formRefSup8:
+			val = b.uint64()
+
+		// loclist
+		case formLoclistx:
+			val = b.uint()
+
+		// rnglist
+		case formRnglistx:
+			val = b.uint()
 		}
 		e.Field[i].Val = val
 	}
@@ -528,6 +714,7 @@ type Reader struct {
 	unit         int
 	lastChildren bool   // .Children of last entry returned by Next
 	lastSibling  Offset // .Val(AttrSibling) of last entry returned by Next
+	cu           *Entry // current compilation unit
 }
 
 // Reader returns a new Reader for Data.
@@ -557,6 +744,7 @@ func (r *Reader) Seek(off Offset) {
 		u := &d.unit[0]
 		r.unit = 0
 		r.b = makeBuf(r.d, u, "info", u.off, u.data)
+		r.cu = nil
 		return
 	}
 
@@ -565,6 +753,9 @@ func (r *Reader) Seek(off Offset) {
 		r.err = errors.New("offset out of range")
 		return
 	}
+	if i != r.unit {
+		r.cu = nil
+	}
 	u := &d.unit[i]
 	r.unit = i
 	r.b = makeBuf(r.d, u, "info", off, u.data[off-u.off:])
@@ -576,6 +767,7 @@ func (r *Reader) maybeNextUnit() {
 		r.unit++
 		u := &r.d.unit[r.unit]
 		r.b = makeBuf(r.d, u, "info", u.off, u.data)
+		r.cu = nil
 	}
 }
 
@@ -592,7 +784,7 @@ func (r *Reader) Next() (*Entry, error) {
 		return nil, nil
 	}
 	u := &r.d.unit[r.unit]
-	e := r.b.entry(u.atable, u.base)
+	e := r.b.entry(r.cu, u.atable, u.base)
 	if r.b.err != nil {
 		r.err = r.b.err
 		return nil, r.err
@@ -602,6 +794,9 @@ func (r *Reader) Next() (*Entry, error) {
 		if r.lastChildren {
 			r.lastSibling, _ = e.Val(AttrSibling).(Offset)
 		}
+		if e.Tag == TagCompileUnit || e.Tag == TagPartialUnit {
+			r.cu = e
+		}
 	} else {
 		r.lastChildren = false
 	}
@@ -734,7 +929,7 @@ func (d *Data) Ranges(e *Entry) ([][2]uint64, error) {
 			}
 			u := &d.unit[i]
 			b := makeBuf(d, u, "info", u.off, u.data)
-			cu = b.entry(u.atable, u.base)
+			cu = b.entry(nil, u.atable, u.base)
 			if b.err != nil {
 				return nil, b.err
 			}
diff --git a/src/debug/dwarf/line.go b/src/debug/dwarf/line.go
index b862b49d62..4fc1896dbc 100644
--- a/src/debug/dwarf/line.go
+++ b/src/debug/dwarf/line.go
@@ -23,8 +23,13 @@ type LineReader struct {
 	// Original .debug_line section data. Used by Seek.
 	section []byte
 
+	str     []byte // .debug_str
+	lineStr []byte // .debug_line_str
+
 	// Header information
 	version              uint16
+	addrsize             int
+	segmentSelectorSize  int
 	minInstructionLength int
 	maxOpsPerInstruction int
 	defaultIsStmt        bool
@@ -158,10 +163,15 @@ func (d *Data) LineReader(cu *Entry) (*LineReader, error) {
 	u := &d.unit[d.offsetToUnit(cu.Offset)]
 	buf := makeBuf(d, u, "line", Offset(off), d.line[off:])
 	// The compilation directory is implicitly directories[0].
-	r := LineReader{buf: buf, section: d.line, directories: []string{compDir}}
+	r := LineReader{
+		buf:     buf,
+		section: d.line,
+		str:     d.str,
+		lineStr: d.lineStr,
+	}
 
 	// Read the header.
-	if err := r.readHeader(); err != nil {
+	if err := r.readHeader(compDir); err != nil {
 		return nil, err
 	}
 
@@ -173,7 +183,7 @@ func (d *Data) LineReader(cu *Entry) (*LineReader, error) {
 
 // readHeader reads the line number program header from r.buf and sets
 // all of the header fields in r.
-func (r *LineReader) readHeader() error {
+func (r *LineReader) readHeader(compDir string) error {
 	buf := &r.buf
 
 	// Read basic header fields [DWARF2 6.2.4].
@@ -184,7 +194,7 @@ func (r *LineReader) readHeader() error {
 		return DecodeError{"line", hdrOffset, fmt.Sprintf("line table end %d exceeds section size %d", r.endOffset, buf.off+Offset(len(buf.data)))}
 	}
 	r.version = buf.uint16()
-	if buf.err == nil && (r.version < 2 || r.version > 4) {
+	if buf.err == nil && (r.version < 2 || r.version > 5) {
 		// DWARF goes to all this effort to make new opcodes
 		// backward-compatible, and then adds fields right in
 		// the middle of the header in new versions, so we're
@@ -192,6 +202,13 @@ func (r *LineReader) readHeader() error {
 		// versions.
 		return DecodeError{"line", hdrOffset, fmt.Sprintf("unknown line table version %d", r.version)}
 	}
+	if r.version >= 5 {
+		r.addrsize = int(buf.uint8())
+		r.segmentSelectorSize = int(buf.uint8())
+	} else {
+		r.addrsize = buf.format.addrsize()
+		r.segmentSelectorSize = 0
+	}
 	var headerLength Offset
 	if dwarf64 {
 		headerLength = Offset(buf.uint64())
@@ -238,39 +255,170 @@ func (r *LineReader) readHeader() error {
 		}
 	}
 
-	// Read include directories table. The caller already set
-	// directories[0] to the compilation directory.
-	for {
-		directory := buf.string()
-		if buf.err != nil {
-			return buf.err
+	if r.version < 5 {
+		// Read include directories table.
+		r.directories = []string{compDir}
+		for {
+			directory := buf.string()
+			if buf.err != nil {
+				return buf.err
+			}
+			if len(directory) == 0 {
+				break
+			}
+			if !pathIsAbs(directory) {
+				// Relative paths are implicitly relative to
+				// the compilation directory.
+				directory = pathJoin(compDir, directory)
+			}
+			r.directories = append(r.directories, directory)
 		}
-		if len(directory) == 0 {
-			break
+
+		// Read file name list. File numbering starts with 1,
+		// so leave the first entry nil.
+		r.fileEntries = make([]*LineFile, 1)
+		for {
+			if done, err := r.readFileEntry(); err != nil {
+				return err
+			} else if done {
+				break
+			}
 		}
-		if !pathIsAbs(directory) {
-			// Relative paths are implicitly relative to
-			// the compilation directory.
-			directory = pathJoin(r.directories[0], directory)
+	} else {
+		dirFormat := r.readLNCTFormat()
+		c := buf.uint()
+		r.directories = make([]string, c)
+		for i := range r.directories {
+			dir, _, _, err := r.readLNCT(dirFormat, dwarf64)
+			if err != nil {
+				return err
+			}
+			r.directories[i] = dir
 		}
-		r.directories = append(r.directories, directory)
-	}
-
-	// Read file name list. File numbering starts with 1, so leave
-	// the first entry nil.
-	r.fileEntries = make([]*LineFile, 1)
-	for {
-		if done, err := r.readFileEntry(); err != nil {
-			return err
-		} else if done {
-			break
+		fileFormat := r.readLNCTFormat()
+		c = buf.uint()
+		r.fileEntries = make([]*LineFile, c)
+		for i := range r.fileEntries {
+			name, mtime, size, err := r.readLNCT(fileFormat, dwarf64)
+			if err != nil {
+				return err
+			}
+			r.fileEntries[i] = &LineFile{name, mtime, int(size)}
 		}
 	}
+
 	r.initialFileEntries = len(r.fileEntries)
 
 	return buf.err
 }
 
+// lnctForm is a pair of an LNCT code and a form. This represents an
+// entry in the directory name or file name description in the DWARF 5
+// line number program header.
+type lnctForm struct {
+	lnct int
+	form format
+}
+
+// readLNCTFormat reads an LNCT format description.
+func (r *LineReader) readLNCTFormat() []lnctForm {
+	c := r.buf.uint8()
+	ret := make([]lnctForm, c)
+	for i := range ret {
+		ret[i].lnct = int(r.buf.uint())
+		ret[i].form = format(r.buf.uint())
+	}
+	return ret
+}
+
+// readLNCT reads a sequence of LNCT entries and returns path information.
+func (r *LineReader) readLNCT(s []lnctForm, dwarf64 bool) (path string, mtime uint64, size uint64, err error) {
+	var dir string
+	for _, lf := range s {
+		var str string
+		var val uint64
+		switch lf.form {
+		case formString:
+			str = r.buf.string()
+		case formStrp, formLineStrp:
+			var off uint64
+			if dwarf64 {
+				off = r.buf.uint64()
+			} else {
+				off = uint64(r.buf.uint32())
+			}
+			if uint64(int(off)) != off {
+				return "", 0, 0, DecodeError{"line", r.buf.off, "strp/line_strp offset out of range"}
+			}
+			var b1 buf
+			if lf.form == formStrp {
+				b1 = makeBuf(r.buf.dwarf, r.buf.format, "str", 0, r.str)
+			} else {
+				b1 = makeBuf(r.buf.dwarf, r.buf.format, "line_str", 0, r.lineStr)
+			}
+			b1.skip(int(off))
+			str = b1.string()
+			if b1.err != nil {
+				return "", 0, 0, DecodeError{"line", r.buf.off, b1.err.Error()}
+			}
+		case formStrpSup:
+			// Supplemental sections not yet supported.
+			if dwarf64 {
+				r.buf.uint64()
+			} else {
+				r.buf.uint32()
+			}
+		case formStrx:
+			// .debug_line.dwo sections not yet supported.
+			r.buf.uint()
+		case formStrx1:
+			r.buf.uint8()
+		case formStrx2:
+			r.buf.uint16()
+		case formStrx3:
+			r.buf.uint24()
+		case formStrx4:
+			r.buf.uint32()
+		case formData1:
+			val = uint64(r.buf.uint8())
+		case formData2:
+			val = uint64(r.buf.uint16())
+		case formData4:
+			val = uint64(r.buf.uint32())
+		case formData8:
+			val = r.buf.uint64()
+		case formData16:
+			r.buf.bytes(16)
+		case formDwarfBlock:
+			r.buf.bytes(int(r.buf.uint()))
+		case formUdata:
+			val = r.buf.uint()
+		}
+
+		switch lf.lnct {
+		case lnctPath:
+			path = str
+		case lnctDirectoryIndex:
+			if val >= uint64(len(r.directories)) {
+				return "", 0, 0, DecodeError{"line", r.buf.off, "directory index out of range"}
+			}
+			dir = r.directories[val]
+		case lnctTimestamp:
+			mtime = val
+		case lnctSize:
+			size = val
+		case lnctMD5:
+			// Ignored.
+		}
+	}
+
+	if dir != "" && path != "" {
+		path = pathJoin(dir, path)
+	}
+
+	return path, mtime, size, nil
+}
+
 // readFileEntry reads a file entry from either the header or a
 // DW_LNE_define_file extended opcode and adds it to r.fileEntries. A
 // true return value indicates that there are no more entries to read.
@@ -381,7 +529,18 @@ func (r *LineReader) step(entry *LineEntry) bool {
 			r.resetState()
 
 		case lneSetAddress:
-			r.state.Address = r.buf.addr()
+			switch r.addrsize {
+			case 1:
+				r.state.Address = uint64(r.buf.uint8())
+			case 2:
+				r.state.Address = uint64(r.buf.uint16())
+			case 4:
+				r.state.Address = uint64(r.buf.uint32())
+			case 8:
+				r.state.Address = r.buf.uint64()
+			default:
+				r.buf.error("unknown address size")
+			}
 
 		case lneDefineFile:
 			if done, err := r.readFileEntry(); err != nil {
diff --git a/src/debug/dwarf/open.go b/src/debug/dwarf/open.go
index 57344d82b4..72ee64d558 100644
--- a/src/debug/dwarf/open.go
+++ b/src/debug/dwarf/open.go
@@ -22,8 +22,14 @@ type Data struct {
 	ranges   []byte
 	str      []byte
 
+	// New sections added in DWARF 5.
+	addr       []byte
+	lineStr    []byte
+	strOffsets []byte
+
 	// parsed data
 	abbrevCache map[uint64]abbrevTable
+	bigEndian   bool
 	order       binary.ByteOrder
 	typeCache   map[Offset]Type
 	typeSigs    map[uint64]*typeUnit
@@ -72,8 +78,10 @@ func New(abbrev, aranges, frame, info, line, pubnames, ranges, str []byte) (*Dat
 	case x == 0 && y == 0:
 		return nil, DecodeError{"info", 4, "unsupported version 0"}
 	case x == 0:
+		d.bigEndian = true
 		d.order = binary.BigEndian
 	case y == 0:
+		d.bigEndian = false
 		d.order = binary.LittleEndian
 	default:
 		return nil, DecodeError{"info", 4, "cannot determine byte order"}
@@ -94,3 +102,20 @@ func New(abbrev, aranges, frame, info, line, pubnames, ranges, str []byte) (*Dat
 func (d *Data) AddTypes(name string, types []byte) error {
 	return d.parseTypes(name, types)
 }
+
+// AddSection adds another DWARF section by name. The name should be a
+// DWARF section name such as ".debug_addr", ".debug_str_offsets", and
+// so forth. This approach is used for new DWARF sections added in
+// DWARF 5 and later.
+func (d *Data) AddSection(name string, contents []byte) error {
+	switch name {
+	case ".debug_addr":
+		d.addr = contents
+	case ".debug_line_str":
+		d.lineStr = contents
+	case ".debug_str_offsets":
+		d.strOffsets = contents
+	}
+	// Just ignore names that we don't yet support.
+	return nil
+}
diff --git a/src/debug/dwarf/typeunit.go b/src/debug/dwarf/typeunit.go
index 76b357ce28..a03dc84c83 100644
--- a/src/debug/dwarf/typeunit.go
+++ b/src/debug/dwarf/typeunit.go
@@ -137,7 +137,7 @@ func (tur *typeUnitReader) Next() (*Entry, error) {
 	if len(tur.tu.data) == 0 {
 		return nil, nil
 	}
-	e := tur.b.entry(tur.tu.atable, tur.tu.base)
+	e := tur.b.entry(nil, tur.tu.atable, tur.tu.base)
 	if tur.b.err != nil {
 		tur.err = tur.b.err
 		return nil, tur.err
diff --git a/src/debug/dwarf/unit.go b/src/debug/dwarf/unit.go
index 98024ca1f8..29a744fd18 100644
--- a/src/debug/dwarf/unit.go
+++ b/src/debug/dwarf/unit.go
@@ -19,7 +19,8 @@ type unit struct {
 	atable abbrevTable
 	asize  int
 	vers   int
-	is64   bool // True for 64-bit DWARF format
+	utype  uint8 // DWARF 5 unit type
+	is64   bool  // True for 64-bit DWARF format
 }
 
 // Implement the dataFormat interface.
@@ -63,11 +64,15 @@ func (d *Data) parseUnits() ([]unit, error) {
 		n, u.is64 = b.unitLength()
 		dataOff := b.off
 		vers := b.uint16()
-		if vers != 2 && vers != 3 && vers != 4 {
+		if vers < 2 || vers > 5 {
 			b.error("unsupported DWARF version " + strconv.Itoa(int(vers)))
 			break
 		}
 		u.vers = int(vers)
+		if vers >= 5 {
+			u.utype = b.uint8()
+			u.asize = int(b.uint8())
+		}
 		var abbrevOff uint64
 		if u.is64 {
 			abbrevOff = b.uint64()
@@ -82,7 +87,22 @@ func (d *Data) parseUnits() ([]unit, error) {
 			break
 		}
 		u.atable = atable
-		u.asize = int(b.uint8())
+		if vers < 5 {
+			u.asize = int(b.uint8())
+		}
+
+		switch u.utype {
+		case utSkeleton, utSplitCompile:
+			b.uint64() // unit ID
+		case utType, utSplitType:
+			b.uint64()  // type signature
+			if u.is64 { // type offset
+				b.uint64()
+			} else {
+				b.uint32()
+			}
+		}
+
 		u.off = b.off
 		u.data = b.bytes(int(n - (b.off - dataOff)))
 	}
diff --git a/src/debug/elf/file.go b/src/debug/elf/file.go
index 79ef467145..0f59fa4c32 100644
--- a/src/debug/elf/file.go
+++ b/src/debug/elf/file.go
@@ -1174,9 +1174,8 @@ func (f *File) DWARF() (*dwarf.Data, error) {
 		return b, nil
 	}
 
-	// There are many other DWARF sections, but these
-	// are the ones the debug/dwarf package uses.
-	// Don't bother loading others.
+	// There are many DWARf sections, but these are the ones
+	// the debug/dwarf package started with.
 	var dat = map[string][]byte{"abbrev": nil, "info": nil, "str": nil, "line": nil, "ranges": nil}
 	for i, s := range f.Sections {
 		suffix := dwarfSuffix(s)
@@ -1198,10 +1197,14 @@ func (f *File) DWARF() (*dwarf.Data, error) {
 		return nil, err
 	}
 
-	// Look for DWARF4 .debug_types sections.
+	// Look for DWARF4 .debug_types sections and DWARF5 sections.
 	for i, s := range f.Sections {
 		suffix := dwarfSuffix(s)
-		if suffix != "types" {
+		if suffix == "" {
+			continue
+		}
+		if _, ok := dat[suffix]; ok {
+			// Already handled.
 			continue
 		}
 
@@ -1210,9 +1213,14 @@ func (f *File) DWARF() (*dwarf.Data, error) {
 			return nil, err
 		}
 
-		err = d.AddTypes(fmt.Sprintf("types-%d", i), b)
-		if err != nil {
-			return nil, err
+		if suffix == "types" {
+			if err := d.AddTypes(fmt.Sprintf("types-%d", i), b); err != nil {
+				return nil, err
+			}
+		} else {
+			if err := d.AddSection(".debug_"+suffix, b); err != nil {
+				return nil, err
+			}
 		}
 	}