Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

6 files changed, 1633 insertions, 0 deletions

diff --git a/src/cmd/internal/goobj/builtin.go b/src/cmd/internal/goobj/builtin.go
new file mode 100644
index 0000000..e7d612a
--- /dev/null
+++ b/src/cmd/internal/goobj/builtin.go
@@ -0,0 +1,45 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package goobj
+
+// Builtin (compiler-generated) function references appear
+// frequently. We assign special indices for them, so they
+// don't need to be referenced by name.
+
+// NBuiltin returns the number of listed builtin
+// symbols.
+func NBuiltin() int {
+	return len(builtins)
+}
+
+// BuiltinName returns the name and ABI of the i-th
+// builtin symbol.
+func BuiltinName(i int) (string, int) {
+	return builtins[i].name, builtins[i].abi
+}
+
+// BuiltinIdx returns the index of the builtin with the
+// given name and abi, or -1 if it is not a builtin.
+func BuiltinIdx(name string, abi int) int {
+	i, ok := builtinMap[name]
+	if !ok {
+		return -1
+	}
+	if builtins[i].abi != abi {
+		return -1
+	}
+	return i
+}
+
+//go:generate go run mkbuiltin.go
+
+var builtinMap map[string]int
+
+func init() {
+	builtinMap = make(map[string]int, len(builtins))
+	for i, b := range builtins {
+		builtinMap[b.name] = i
+	}
+}
diff --git a/src/cmd/internal/goobj/builtinlist.go b/src/cmd/internal/goobj/builtinlist.go
new file mode 100644
index 0000000..0cca752
--- /dev/null
+++ b/src/cmd/internal/goobj/builtinlist.go
@@ -0,0 +1,245 @@
+// Code generated by mkbuiltin.go. DO NOT EDIT.
+
+package goobj
+
+var builtins = [...]struct {
+	name string
+	abi  int
+}{
+	{"runtime.newobject", 1},
+	{"runtime.mallocgc", 1},
+	{"runtime.panicdivide", 1},
+	{"runtime.panicshift", 1},
+	{"runtime.panicmakeslicelen", 1},
+	{"runtime.panicmakeslicecap", 1},
+	{"runtime.throwinit", 1},
+	{"runtime.panicwrap", 1},
+	{"runtime.gopanic", 1},
+	{"runtime.gorecover", 1},
+	{"runtime.goschedguarded", 1},
+	{"runtime.goPanicIndex", 1},
+	{"runtime.goPanicIndexU", 1},
+	{"runtime.goPanicSliceAlen", 1},
+	{"runtime.goPanicSliceAlenU", 1},
+	{"runtime.goPanicSliceAcap", 1},
+	{"runtime.goPanicSliceAcapU", 1},
+	{"runtime.goPanicSliceB", 1},
+	{"runtime.goPanicSliceBU", 1},
+	{"runtime.goPanicSlice3Alen", 1},
+	{"runtime.goPanicSlice3AlenU", 1},
+	{"runtime.goPanicSlice3Acap", 1},
+	{"runtime.goPanicSlice3AcapU", 1},
+	{"runtime.goPanicSlice3B", 1},
+	{"runtime.goPanicSlice3BU", 1},
+	{"runtime.goPanicSlice3C", 1},
+	{"runtime.goPanicSlice3CU", 1},
+	{"runtime.printbool", 1},
+	{"runtime.printfloat", 1},
+	{"runtime.printint", 1},
+	{"runtime.printhex", 1},
+	{"runtime.printuint", 1},
+	{"runtime.printcomplex", 1},
+	{"runtime.printstring", 1},
+	{"runtime.printpointer", 1},
+	{"runtime.printiface", 1},
+	{"runtime.printeface", 1},
+	{"runtime.printslice", 1},
+	{"runtime.printnl", 1},
+	{"runtime.printsp", 1},
+	{"runtime.printlock", 1},
+	{"runtime.printunlock", 1},
+	{"runtime.concatstring2", 1},
+	{"runtime.concatstring3", 1},
+	{"runtime.concatstring4", 1},
+	{"runtime.concatstring5", 1},
+	{"runtime.concatstrings", 1},
+	{"runtime.cmpstring", 1},
+	{"runtime.intstring", 1},
+	{"runtime.slicebytetostring", 1},
+	{"runtime.slicebytetostringtmp", 1},
+	{"runtime.slicerunetostring", 1},
+	{"runtime.stringtoslicebyte", 1},
+	{"runtime.stringtoslicerune", 1},
+	{"runtime.slicecopy", 1},
+	{"runtime.slicestringcopy", 1},
+	{"runtime.decoderune", 1},
+	{"runtime.countrunes", 1},
+	{"runtime.convI2I", 1},
+	{"runtime.convT16", 1},
+	{"runtime.convT32", 1},
+	{"runtime.convT64", 1},
+	{"runtime.convTstring", 1},
+	{"runtime.convTslice", 1},
+	{"runtime.convT2E", 1},
+	{"runtime.convT2Enoptr", 1},
+	{"runtime.convT2I", 1},
+	{"runtime.convT2Inoptr", 1},
+	{"runtime.assertE2I", 1},
+	{"runtime.assertE2I2", 1},
+	{"runtime.assertI2I", 1},
+	{"runtime.assertI2I2", 1},
+	{"runtime.panicdottypeE", 1},
+	{"runtime.panicdottypeI", 1},
+	{"runtime.panicnildottype", 1},
+	{"runtime.ifaceeq", 1},
+	{"runtime.efaceeq", 1},
+	{"runtime.fastrand", 1},
+	{"runtime.makemap64", 1},
+	{"runtime.makemap", 1},
+	{"runtime.makemap_small", 1},
+	{"runtime.mapaccess1", 1},
+	{"runtime.mapaccess1_fast32", 1},
+	{"runtime.mapaccess1_fast64", 1},
+	{"runtime.mapaccess1_faststr", 1},
+	{"runtime.mapaccess1_fat", 1},
+	{"runtime.mapaccess2", 1},
+	{"runtime.mapaccess2_fast32", 1},
+	{"runtime.mapaccess2_fast64", 1},
+	{"runtime.mapaccess2_faststr", 1},
+	{"runtime.mapaccess2_fat", 1},
+	{"runtime.mapassign", 1},
+	{"runtime.mapassign_fast32", 1},
+	{"runtime.mapassign_fast32ptr", 1},
+	{"runtime.mapassign_fast64", 1},
+	{"runtime.mapassign_fast64ptr", 1},
+	{"runtime.mapassign_faststr", 1},
+	{"runtime.mapiterinit", 1},
+	{"runtime.mapdelete", 1},
+	{"runtime.mapdelete_fast32", 1},
+	{"runtime.mapdelete_fast64", 1},
+	{"runtime.mapdelete_faststr", 1},
+	{"runtime.mapiternext", 1},
+	{"runtime.mapclear", 1},
+	{"runtime.makechan64", 1},
+	{"runtime.makechan", 1},
+	{"runtime.chanrecv1", 1},
+	{"runtime.chanrecv2", 1},
+	{"runtime.chansend1", 1},
+	{"runtime.closechan", 1},
+	{"runtime.writeBarrier", 0},
+	{"runtime.typedmemmove", 1},
+	{"runtime.typedmemclr", 1},
+	{"runtime.typedslicecopy", 1},
+	{"runtime.selectnbsend", 1},
+	{"runtime.selectnbrecv", 1},
+	{"runtime.selectnbrecv2", 1},
+	{"runtime.selectsetpc", 1},
+	{"runtime.selectgo", 1},
+	{"runtime.block", 1},
+	{"runtime.makeslice", 1},
+	{"runtime.makeslice64", 1},
+	{"runtime.makeslicecopy", 1},
+	{"runtime.growslice", 1},
+	{"runtime.memmove", 1},
+	{"runtime.memclrNoHeapPointers", 1},
+	{"runtime.memclrHasPointers", 1},
+	{"runtime.memequal", 1},
+	{"runtime.memequal0", 1},
+	{"runtime.memequal8", 1},
+	{"runtime.memequal16", 1},
+	{"runtime.memequal32", 1},
+	{"runtime.memequal64", 1},
+	{"runtime.memequal128", 1},
+	{"runtime.f32equal", 1},
+	{"runtime.f64equal", 1},
+	{"runtime.c64equal", 1},
+	{"runtime.c128equal", 1},
+	{"runtime.strequal", 1},
+	{"runtime.interequal", 1},
+	{"runtime.nilinterequal", 1},
+	{"runtime.memhash", 1},
+	{"runtime.memhash0", 1},
+	{"runtime.memhash8", 1},
+	{"runtime.memhash16", 1},
+	{"runtime.memhash32", 1},
+	{"runtime.memhash64", 1},
+	{"runtime.memhash128", 1},
+	{"runtime.f32hash", 1},
+	{"runtime.f64hash", 1},
+	{"runtime.c64hash", 1},
+	{"runtime.c128hash", 1},
+	{"runtime.strhash", 1},
+	{"runtime.interhash", 1},
+	{"runtime.nilinterhash", 1},
+	{"runtime.int64div", 1},
+	{"runtime.uint64div", 1},
+	{"runtime.int64mod", 1},
+	{"runtime.uint64mod", 1},
+	{"runtime.float64toint64", 1},
+	{"runtime.float64touint64", 1},
+	{"runtime.float64touint32", 1},
+	{"runtime.int64tofloat64", 1},
+	{"runtime.uint64tofloat64", 1},
+	{"runtime.uint32tofloat64", 1},
+	{"runtime.complex128div", 1},
+	{"runtime.racefuncenter", 1},
+	{"runtime.racefuncenterfp", 1},
+	{"runtime.racefuncexit", 1},
+	{"runtime.raceread", 1},
+	{"runtime.racewrite", 1},
+	{"runtime.racereadrange", 1},
+	{"runtime.racewriterange", 1},
+	{"runtime.msanread", 1},
+	{"runtime.msanwrite", 1},
+	{"runtime.checkptrAlignment", 1},
+	{"runtime.checkptrArithmetic", 1},
+	{"runtime.libfuzzerTraceCmp1", 1},
+	{"runtime.libfuzzerTraceCmp2", 1},
+	{"runtime.libfuzzerTraceCmp4", 1},
+	{"runtime.libfuzzerTraceCmp8", 1},
+	{"runtime.libfuzzerTraceConstCmp1", 1},
+	{"runtime.libfuzzerTraceConstCmp2", 1},
+	{"runtime.libfuzzerTraceConstCmp4", 1},
+	{"runtime.libfuzzerTraceConstCmp8", 1},
+	{"runtime.x86HasPOPCNT", 0},
+	{"runtime.x86HasSSE41", 0},
+	{"runtime.x86HasFMA", 0},
+	{"runtime.armHasVFPv4", 0},
+	{"runtime.arm64HasATOMICS", 0},
+	{"runtime.deferproc", 1},
+	{"runtime.deferprocStack", 1},
+	{"runtime.deferreturn", 1},
+	{"runtime.newproc", 1},
+	{"runtime.panicoverflow", 1},
+	{"runtime.sigpanic", 1},
+	{"runtime.gcWriteBarrier", 0},
+	{"runtime.morestack", 0},
+	{"runtime.morestackc", 0},
+	{"runtime.morestack_noctxt", 0},
+	{"type.int8", 0},
+	{"type.*int8", 0},
+	{"type.uint8", 0},
+	{"type.*uint8", 0},
+	{"type.int16", 0},
+	{"type.*int16", 0},
+	{"type.uint16", 0},
+	{"type.*uint16", 0},
+	{"type.int32", 0},
+	{"type.*int32", 0},
+	{"type.uint32", 0},
+	{"type.*uint32", 0},
+	{"type.int64", 0},
+	{"type.*int64", 0},
+	{"type.uint64", 0},
+	{"type.*uint64", 0},
+	{"type.float32", 0},
+	{"type.*float32", 0},
+	{"type.float64", 0},
+	{"type.*float64", 0},
+	{"type.complex64", 0},
+	{"type.*complex64", 0},
+	{"type.complex128", 0},
+	{"type.*complex128", 0},
+	{"type.unsafe.Pointer", 0},
+	{"type.*unsafe.Pointer", 0},
+	{"type.uintptr", 0},
+	{"type.*uintptr", 0},
+	{"type.bool", 0},
+	{"type.*bool", 0},
+	{"type.string", 0},
+	{"type.*string", 0},
+	{"type.error", 0},
+	{"type.*error", 0},
+	{"type.func(error) string", 0},
+	{"type.*func(error) string", 0},
+}
diff --git a/src/cmd/internal/goobj/funcinfo.go b/src/cmd/internal/goobj/funcinfo.go
new file mode 100644
index 0000000..2cca8f6
--- /dev/null
+++ b/src/cmd/internal/goobj/funcinfo.go
@@ -0,0 +1,239 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package goobj
+
+import (
+	"bytes"
+	"cmd/internal/objabi"
+	"encoding/binary"
+)
+
+// CUFileIndex is used to index the filenames that are stored in the
+// per-package/per-CU FileList.
+type CUFileIndex uint32
+
+// FuncInfo is serialized as a symbol (aux symbol). The symbol data is
+// the binary encoding of the struct below.
+//
+// TODO: make each pcdata a separate symbol?
+type FuncInfo struct {
+	Args   uint32
+	Locals uint32
+	FuncID objabi.FuncID
+
+	Pcsp        SymRef
+	Pcfile      SymRef
+	Pcline      SymRef
+	Pcinline    SymRef
+	Pcdata      []SymRef
+	Funcdataoff []uint32
+	File        []CUFileIndex
+
+	InlTree []InlTreeNode
+}
+
+func (a *FuncInfo) Write(w *bytes.Buffer) {
+	var b [4]byte
+	writeUint32 := func(x uint32) {
+		binary.LittleEndian.PutUint32(b[:], x)
+		w.Write(b[:])
+	}
+	writeSymRef := func(s SymRef) {
+		writeUint32(s.PkgIdx)
+		writeUint32(s.SymIdx)
+	}
+
+	writeUint32(a.Args)
+	writeUint32(a.Locals)
+	writeUint32(uint32(a.FuncID))
+
+	writeSymRef(a.Pcsp)
+	writeSymRef(a.Pcfile)
+	writeSymRef(a.Pcline)
+	writeSymRef(a.Pcinline)
+	writeUint32(uint32(len(a.Pcdata)))
+	for _, sym := range a.Pcdata {
+		writeSymRef(sym)
+	}
+
+	writeUint32(uint32(len(a.Funcdataoff)))
+	for _, x := range a.Funcdataoff {
+		writeUint32(x)
+	}
+	writeUint32(uint32(len(a.File)))
+	for _, f := range a.File {
+		writeUint32(uint32(f))
+	}
+	writeUint32(uint32(len(a.InlTree)))
+	for i := range a.InlTree {
+		a.InlTree[i].Write(w)
+	}
+}
+
+func (a *FuncInfo) Read(b []byte) {
+	readUint32 := func() uint32 {
+		x := binary.LittleEndian.Uint32(b)
+		b = b[4:]
+		return x
+	}
+	readSymIdx := func() SymRef {
+		return SymRef{readUint32(), readUint32()}
+	}
+
+	a.Args = readUint32()
+	a.Locals = readUint32()
+	a.FuncID = objabi.FuncID(readUint32())
+
+	a.Pcsp = readSymIdx()
+	a.Pcfile = readSymIdx()
+	a.Pcline = readSymIdx()
+	a.Pcinline = readSymIdx()
+	a.Pcdata = make([]SymRef, readUint32())
+	for i := range a.Pcdata {
+		a.Pcdata[i] = readSymIdx()
+	}
+
+	funcdataofflen := readUint32()
+	a.Funcdataoff = make([]uint32, funcdataofflen)
+	for i := range a.Funcdataoff {
+		a.Funcdataoff[i] = readUint32()
+	}
+	filelen := readUint32()
+	a.File = make([]CUFileIndex, filelen)
+	for i := range a.File {
+		a.File[i] = CUFileIndex(readUint32())
+	}
+	inltreelen := readUint32()
+	a.InlTree = make([]InlTreeNode, inltreelen)
+	for i := range a.InlTree {
+		b = a.InlTree[i].Read(b)
+	}
+}
+
+// FuncInfoLengths is a cache containing a roadmap of offsets and
+// lengths for things within a serialized FuncInfo. Each length field
+// stores the number of items (e.g. files, inltree nodes, etc), and the
+// corresponding "off" field stores the byte offset of the start of
+// the items in question.
+type FuncInfoLengths struct {
+	NumPcdata      uint32
+	PcdataOff      uint32
+	NumFuncdataoff uint32
+	FuncdataoffOff uint32
+	NumFile        uint32
+	FileOff        uint32
+	NumInlTree     uint32
+	InlTreeOff     uint32
+	Initialized    bool
+}
+
+func (*FuncInfo) ReadFuncInfoLengths(b []byte) FuncInfoLengths {
+	var result FuncInfoLengths
+
+	// Offset to the number of pcdata values. This value is determined by counting
+	// the number of bytes until we write pcdata to the file.
+	const numpcdataOff = 44
+	result.NumPcdata = binary.LittleEndian.Uint32(b[numpcdataOff:])
+	result.PcdataOff = numpcdataOff + 4
+
+	numfuncdataoffOff := result.PcdataOff + 8*result.NumPcdata
+	result.NumFuncdataoff = binary.LittleEndian.Uint32(b[numfuncdataoffOff:])
+	result.FuncdataoffOff = numfuncdataoffOff + 4
+
+	numfileOff := result.FuncdataoffOff + 4*result.NumFuncdataoff
+	result.NumFile = binary.LittleEndian.Uint32(b[numfileOff:])
+	result.FileOff = numfileOff + 4
+
+	numinltreeOff := result.FileOff + 4*result.NumFile
+	result.NumInlTree = binary.LittleEndian.Uint32(b[numinltreeOff:])
+	result.InlTreeOff = numinltreeOff + 4
+
+	result.Initialized = true
+
+	return result
+}
+
+func (*FuncInfo) ReadArgs(b []byte) uint32 { return binary.LittleEndian.Uint32(b) }
+
+func (*FuncInfo) ReadLocals(b []byte) uint32 { return binary.LittleEndian.Uint32(b[4:]) }
+
+func (*FuncInfo) ReadFuncID(b []byte) uint32 { return binary.LittleEndian.Uint32(b[8:]) }
+
+func (*FuncInfo) ReadPcsp(b []byte) SymRef {
+	return SymRef{binary.LittleEndian.Uint32(b[12:]), binary.LittleEndian.Uint32(b[16:])}
+}
+
+func (*FuncInfo) ReadPcfile(b []byte) SymRef {
+	return SymRef{binary.LittleEndian.Uint32(b[20:]), binary.LittleEndian.Uint32(b[24:])}
+}
+
+func (*FuncInfo) ReadPcline(b []byte) SymRef {
+	return SymRef{binary.LittleEndian.Uint32(b[28:]), binary.LittleEndian.Uint32(b[32:])}
+}
+
+func (*FuncInfo) ReadPcinline(b []byte) SymRef {
+	return SymRef{binary.LittleEndian.Uint32(b[36:]), binary.LittleEndian.Uint32(b[40:])}
+}
+
+func (*FuncInfo) ReadPcdata(b []byte) []SymRef {
+	syms := make([]SymRef, binary.LittleEndian.Uint32(b[44:]))
+	for i := range syms {
+		syms[i] = SymRef{binary.LittleEndian.Uint32(b[48+i*8:]), binary.LittleEndian.Uint32(b[52+i*8:])}
+	}
+	return syms
+}
+
+func (*FuncInfo) ReadFuncdataoff(b []byte, funcdataofffoff uint32, k uint32) int64 {
+	return int64(binary.LittleEndian.Uint32(b[funcdataofffoff+4*k:]))
+}
+
+func (*FuncInfo) ReadFile(b []byte, filesoff uint32, k uint32) CUFileIndex {
+	return CUFileIndex(binary.LittleEndian.Uint32(b[filesoff+4*k:]))
+}
+
+func (*FuncInfo) ReadInlTree(b []byte, inltreeoff uint32, k uint32) InlTreeNode {
+	const inlTreeNodeSize = 4 * 6
+	var result InlTreeNode
+	result.Read(b[inltreeoff+k*inlTreeNodeSize:])
+	return result
+}
+
+// InlTreeNode is the serialized form of FileInfo.InlTree.
+type InlTreeNode struct {
+	Parent   int32
+	File     CUFileIndex
+	Line     int32
+	Func     SymRef
+	ParentPC int32
+}
+
+func (inl *InlTreeNode) Write(w *bytes.Buffer) {
+	var b [4]byte
+	writeUint32 := func(x uint32) {
+		binary.LittleEndian.PutUint32(b[:], x)
+		w.Write(b[:])
+	}
+	writeUint32(uint32(inl.Parent))
+	writeUint32(uint32(inl.File))
+	writeUint32(uint32(inl.Line))
+	writeUint32(inl.Func.PkgIdx)
+	writeUint32(inl.Func.SymIdx)
+	writeUint32(uint32(inl.ParentPC))
+}
+
+// Read an InlTreeNode from b, return the remaining bytes.
+func (inl *InlTreeNode) Read(b []byte) []byte {
+	readUint32 := func() uint32 {
+		x := binary.LittleEndian.Uint32(b)
+		b = b[4:]
+		return x
+	}
+	inl.Parent = int32(readUint32())
+	inl.File = CUFileIndex(readUint32())
+	inl.Line = int32(readUint32())
+	inl.Func = SymRef{readUint32(), readUint32()}
+	inl.ParentPC = int32(readUint32())
+	return b
+}
diff --git a/src/cmd/internal/goobj/mkbuiltin.go b/src/cmd/internal/goobj/mkbuiltin.go
new file mode 100644
index 0000000..07c3406
--- /dev/null
+++ b/src/cmd/internal/goobj/mkbuiltin.go
@@ -0,0 +1,159 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+// Generate builtinlist.go from cmd/compile/internal/gc/builtin/runtime.go.
+
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"io"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+var stdout = flag.Bool("stdout", false, "write to stdout instead of builtinlist.go")
+
+func main() {
+	flag.Parse()
+
+	var b bytes.Buffer
+	fmt.Fprintln(&b, "// Code generated by mkbuiltin.go. DO NOT EDIT.")
+	fmt.Fprintln(&b)
+	fmt.Fprintln(&b, "package goobj")
+
+	mkbuiltin(&b)
+
+	out, err := format.Source(b.Bytes())
+	if err != nil {
+		log.Fatal(err)
+	}
+	if *stdout {
+		_, err = os.Stdout.Write(out)
+	} else {
+		err = ioutil.WriteFile("builtinlist.go", out, 0666)
+	}
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func mkbuiltin(w io.Writer) {
+	pkg := "runtime"
+	fset := token.NewFileSet()
+	path := filepath.Join("..", "..", "compile", "internal", "gc", "builtin", "runtime.go")
+	f, err := parser.ParseFile(fset, path, nil, 0)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	decls := make(map[string]bool)
+
+	fmt.Fprintf(w, "var builtins = [...]struct{ name string; abi int }{\n")
+	for _, decl := range f.Decls {
+		switch decl := decl.(type) {
+		case *ast.FuncDecl:
+			if decl.Recv != nil {
+				log.Fatal("methods unsupported")
+			}
+			if decl.Body != nil {
+				log.Fatal("unexpected function body")
+			}
+			declName := pkg + "." + decl.Name.Name
+			decls[declName] = true
+			fmt.Fprintf(w, "{%q, 1},\n", declName) // functions are ABIInternal (1)
+		case *ast.GenDecl:
+			if decl.Tok == token.IMPORT {
+				continue
+			}
+			if decl.Tok != token.VAR {
+				log.Fatal("unhandled declaration kind", decl.Tok)
+			}
+			for _, spec := range decl.Specs {
+				spec := spec.(*ast.ValueSpec)
+				if len(spec.Values) != 0 {
+					log.Fatal("unexpected values")
+				}
+				for _, name := range spec.Names {
+					declName := pkg + "." + name.Name
+					decls[declName] = true
+					fmt.Fprintf(w, "{%q, 0},\n", declName) // variables are ABI0
+				}
+			}
+		default:
+			log.Fatal("unhandled decl type", decl)
+		}
+	}
+
+	// The list above only contains ones that are used by the frontend.
+	// The backend may create more references of builtin functions.
+	// We also want to include predefined types.
+	// Add them.
+	extras := append(fextras[:], enumerateBasicTypes()...)
+	for _, b := range extras {
+		prefix := ""
+		if !strings.HasPrefix(b.name, "type.") {
+			prefix = pkg + "."
+		}
+		name := prefix + b.name
+		if decls[name] {
+			log.Fatalf("%q already added -- mkbuiltin.go out of sync?", name)
+		}
+		fmt.Fprintf(w, "{%q, %d},\n", name, b.abi)
+	}
+	fmt.Fprintln(w, "}")
+}
+
+// addBasicTypes returns the symbol names for basic types that are
+// defined in the runtime and referenced in other packages.
+// Needs to be kept in sync with reflect.go:dumpbasictypes() and
+// reflect.go:dtypesym() in the compiler.
+func enumerateBasicTypes() []extra {
+	names := [...]string{
+		"int8", "uint8", "int16", "uint16",
+		"int32", "uint32", "int64", "uint64",
+		"float32", "float64", "complex64", "complex128",
+		"unsafe.Pointer", "uintptr", "bool", "string", "error",
+		"func(error) string"}
+	result := []extra{}
+	for _, n := range names {
+		result = append(result, extra{"type." + n, 0})
+		result = append(result, extra{"type.*" + n, 0})
+	}
+	return result
+}
+
+type extra struct {
+	name string
+	abi  int
+}
+
+var fextras = [...]extra{
+	// compiler frontend inserted calls (sysfunc)
+	{"deferproc", 1},
+	{"deferprocStack", 1},
+	{"deferreturn", 1},
+	{"newproc", 1},
+	{"panicoverflow", 1},
+	{"sigpanic", 1},
+
+	// compiler backend inserted calls
+	{"gcWriteBarrier", 0}, // asm function, ABI0
+
+	// assembler backend inserted calls
+	{"morestack", 0},        // asm function, ABI0
+	{"morestackc", 0},       // asm function, ABI0
+	{"morestack_noctxt", 0}, // asm function, ABI0
+}
diff --git a/src/cmd/internal/goobj/objfile.go b/src/cmd/internal/goobj/objfile.go
new file mode 100644
index 0000000..e6447e4
--- /dev/null
+++ b/src/cmd/internal/goobj/objfile.go
@@ -0,0 +1,874 @@
+// Copyright 2019 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// This package defines the Go object file format, and provide "low-level" functions
+// for reading and writing object files.
+
+// The object file is understood by the compiler, assembler, linker, and tools. They
+// have "high level" code that operates on object files, handling application-specific
+// logics, and use this package for the actual reading and writing. Specifically, the
+// code below:
+//
+// - cmd/internal/obj/objfile.go (used by cmd/asm and cmd/compile)
+// - cmd/internal/objfile/goobj.go (used cmd/nm, cmd/objdump)
+// - cmd/link/internal/loader package (used by cmd/link)
+//
+// If the object file format changes, they may (or may not) need to change.
+
+package goobj
+
+import (
+	"bytes"
+	"cmd/internal/bio"
+	"crypto/sha1"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"internal/unsafeheader"
+	"io"
+	"unsafe"
+)
+
+// New object file format.
+//
+//    Header struct {
+//       Magic       [...]byte   // "\x00go116ld"
+//       Fingerprint [8]byte
+//       Flags       uint32
+//       Offsets     [...]uint32 // byte offset of each block below
+//    }
+//
+//    Strings [...]struct {
+//       Data [...]byte
+//    }
+//
+//    Autolib  [...]struct { // imported packages (for file loading)
+//       Pkg         string
+//       Fingerprint [8]byte
+//    }
+//
+//    PkgIndex [...]string // referenced packages by index
+//
+//    Files [...]string
+//
+//    SymbolDefs [...]struct {
+//       Name  string
+//       ABI   uint16
+//       Type  uint8
+//       Flag  uint8
+//       Flag2 uint8
+//       Size  uint32
+//    }
+//    Hashed64Defs [...]struct { // short hashed (content-addressable) symbol definitions
+//       ... // same as SymbolDefs
+//    }
+//    HashedDefs [...]struct { // hashed (content-addressable) symbol definitions
+//       ... // same as SymbolDefs
+//    }
+//    NonPkgDefs [...]struct { // non-pkg symbol definitions
+//       ... // same as SymbolDefs
+//    }
+//    NonPkgRefs [...]struct { // non-pkg symbol references
+//       ... // same as SymbolDefs
+//    }
+//
+//    RefFlags [...]struct { // referenced symbol flags
+//       Sym   symRef
+//       Flag  uint8
+//       Flag2 uint8
+//    }
+//
+//    Hash64 [...][8]byte
+//    Hash   [...][N]byte
+//
+//    RelocIndex [...]uint32 // index to Relocs
+//    AuxIndex   [...]uint32 // index to Aux
+//    DataIndex  [...]uint32 // offset to Data
+//
+//    Relocs [...]struct {
+//       Off  int32
+//       Size uint8
+//       Type uint8
+//       Add  int64
+//       Sym  symRef
+//    }
+//
+//    Aux [...]struct {
+//       Type uint8
+//       Sym  symRef
+//    }
+//
+//    Data   [...]byte
+//    Pcdata [...]byte
+//
+//    // blocks only used by tools (objdump, nm)
+//
+//    RefNames [...]struct { // referenced symbol names
+//       Sym  symRef
+//       Name string
+//       // TODO: include ABI version as well?
+//    }
+//
+// string is encoded as is a uint32 length followed by a uint32 offset
+// that points to the corresponding string bytes.
+//
+// symRef is struct { PkgIdx, SymIdx uint32 }.
+//
+// Slice type (e.g. []symRef) is encoded as a length prefix (uint32)
+// followed by that number of elements.
+//
+// The types below correspond to the encoded data structure in the
+// object file.
+
+// Symbol indexing.
+//
+// Each symbol is referenced with a pair of indices, { PkgIdx, SymIdx },
+// as the symRef struct above.
+//
+// PkgIdx is either a predeclared index (see PkgIdxNone below) or
+// an index of an imported package. For the latter case, PkgIdx is the
+// index of the package in the PkgIndex array. 0 is an invalid index.
+//
+// SymIdx is the index of the symbol in the given package.
+// - If PkgIdx is PkgIdxSelf, SymIdx is the index of the symbol in the
+//   SymbolDefs array.
+// - If PkgIdx is PkgIdxHashed64, SymIdx is the index of the symbol in the
+//   Hashed64Defs array.
+// - If PkgIdx is PkgIdxHashed, SymIdx is the index of the symbol in the
+//   HashedDefs array.
+// - If PkgIdx is PkgIdxNone, SymIdx is the index of the symbol in the
+//   NonPkgDefs array (could natually overflow to NonPkgRefs array).
+// - Otherwise, SymIdx is the index of the symbol in some other package's
+//   SymbolDefs array.
+//
+// {0, 0} represents a nil symbol. Otherwise PkgIdx should not be 0.
+//
+// Hash contains the content hashes of content-addressable symbols, of
+// which PkgIdx is PkgIdxHashed, in the same order of HashedDefs array.
+// Hash64 is similar, for PkgIdxHashed64 symbols.
+//
+// RelocIndex, AuxIndex, and DataIndex contains indices/offsets to
+// Relocs/Aux/Data blocks, one element per symbol, first for all the
+// defined symbols, then all the defined hashed and non-package symbols,
+// in the same order of SymbolDefs/Hashed64Defs/HashedDefs/NonPkgDefs
+// arrays. For N total defined symbols, the array is of length N+1. The
+// last element is the total number of relocations (aux symbols, data
+// blocks, etc.).
+//
+// They can be accessed by index. For the i-th symbol, its relocations
+// are the RelocIndex[i]-th (inclusive) to RelocIndex[i+1]-th (exclusive)
+// elements in the Relocs array. Aux/Data are likewise. (The index is
+// 0-based.)
+
+// Auxiliary symbols.
+//
+// Each symbol may (or may not) be associated with a number of auxiliary
+// symbols. They are described in the Aux block. See Aux struct below.
+// Currently a symbol's Gotype, FuncInfo, and associated DWARF symbols
+// are auxiliary symbols.
+
+const stringRefSize = 8 // two uint32s
+
+type FingerprintType [8]byte
+
+func (fp FingerprintType) IsZero() bool { return fp == FingerprintType{} }
+
+// Package Index.
+const (
+	PkgIdxNone     = (1<<31 - 1) - iota // Non-package symbols
+	PkgIdxHashed64                      // Short hashed (content-addressable) symbols
+	PkgIdxHashed                        // Hashed (content-addressable) symbols
+	PkgIdxBuiltin                       // Predefined runtime symbols (ex: runtime.newobject)
+	PkgIdxSelf                          // Symbols defined in the current package
+	PkgIdxInvalid  = 0
+	// The index of other referenced packages starts from 1.
+)
+
+// Blocks
+const (
+	BlkAutolib = iota
+	BlkPkgIdx
+	BlkFile
+	BlkSymdef
+	BlkHashed64def
+	BlkHasheddef
+	BlkNonpkgdef
+	BlkNonpkgref
+	BlkRefFlags
+	BlkHash64
+	BlkHash
+	BlkRelocIdx
+	BlkAuxIdx
+	BlkDataIdx
+	BlkReloc
+	BlkAux
+	BlkData
+	BlkPcdata
+	BlkRefName
+	BlkEnd
+	NBlk
+)
+
+// File header.
+// TODO: probably no need to export this.
+type Header struct {
+	Magic       string
+	Fingerprint FingerprintType
+	Flags       uint32
+	Offsets     [NBlk]uint32
+}
+
+const Magic = "\x00go116ld"
+
+func (h *Header) Write(w *Writer) {
+	w.RawString(h.Magic)
+	w.Bytes(h.Fingerprint[:])
+	w.Uint32(h.Flags)
+	for _, x := range h.Offsets {
+		w.Uint32(x)
+	}
+}
+
+func (h *Header) Read(r *Reader) error {
+	b := r.BytesAt(0, len(Magic))
+	h.Magic = string(b)
+	if h.Magic != Magic {
+		return errors.New("wrong magic, not a Go object file")
+	}
+	off := uint32(len(h.Magic))
+	copy(h.Fingerprint[:], r.BytesAt(off, len(h.Fingerprint)))
+	off += 8
+	h.Flags = r.uint32At(off)
+	off += 4
+	for i := range h.Offsets {
+		h.Offsets[i] = r.uint32At(off)
+		off += 4
+	}
+	return nil
+}
+
+func (h *Header) Size() int {
+	return len(h.Magic) + 4 + 4*len(h.Offsets)
+}
+
+// Autolib
+type ImportedPkg struct {
+	Pkg         string
+	Fingerprint FingerprintType
+}
+
+const importedPkgSize = stringRefSize + 8
+
+func (p *ImportedPkg) Write(w *Writer) {
+	w.StringRef(p.Pkg)
+	w.Bytes(p.Fingerprint[:])
+}
+
+// Symbol definition.
+//
+// Serialized format:
+// Sym struct {
+//    Name  string
+//    ABI   uint16
+//    Type  uint8
+//    Flag  uint8
+//    Flag2 uint8
+//    Siz   uint32
+//    Align uint32
+// }
+type Sym [SymSize]byte
+
+const SymSize = stringRefSize + 2 + 1 + 1 + 1 + 4 + 4
+
+const SymABIstatic = ^uint16(0)
+
+const (
+	ObjFlagShared            = 1 << iota // this object is built with -shared
+	ObjFlagNeedNameExpansion             // the linker needs to expand `"".` to package path in symbol names
+	ObjFlagFromAssembly                  // object is from asm src, not go
+)
+
+// Sym.Flag
+const (
+	SymFlagDupok = 1 << iota
+	SymFlagLocal
+	SymFlagTypelink
+	SymFlagLeaf
+	SymFlagNoSplit
+	SymFlagReflectMethod
+	SymFlagGoType
+	SymFlagTopFrame
+)
+
+// Sym.Flag2
+const (
+	SymFlagUsedInIface = 1 << iota
+	SymFlagItab
+)
+
+// Returns the length of the name of the symbol.
+func (s *Sym) NameLen(r *Reader) int {
+	return int(binary.LittleEndian.Uint32(s[:]))
+}
+
+func (s *Sym) Name(r *Reader) string {
+	len := binary.LittleEndian.Uint32(s[:])
+	off := binary.LittleEndian.Uint32(s[4:])
+	return r.StringAt(off, len)
+}
+
+func (s *Sym) ABI() uint16   { return binary.LittleEndian.Uint16(s[8:]) }
+func (s *Sym) Type() uint8   { return s[10] }
+func (s *Sym) Flag() uint8   { return s[11] }
+func (s *Sym) Flag2() uint8  { return s[12] }
+func (s *Sym) Siz() uint32   { return binary.LittleEndian.Uint32(s[13:]) }
+func (s *Sym) Align() uint32 { return binary.LittleEndian.Uint32(s[17:]) }
+
+func (s *Sym) Dupok() bool         { return s.Flag()&SymFlagDupok != 0 }
+func (s *Sym) Local() bool         { return s.Flag()&SymFlagLocal != 0 }
+func (s *Sym) Typelink() bool      { return s.Flag()&SymFlagTypelink != 0 }
+func (s *Sym) Leaf() bool          { return s.Flag()&SymFlagLeaf != 0 }
+func (s *Sym) NoSplit() bool       { return s.Flag()&SymFlagNoSplit != 0 }
+func (s *Sym) ReflectMethod() bool { return s.Flag()&SymFlagReflectMethod != 0 }
+func (s *Sym) IsGoType() bool      { return s.Flag()&SymFlagGoType != 0 }
+func (s *Sym) TopFrame() bool      { return s.Flag()&SymFlagTopFrame != 0 }
+func (s *Sym) UsedInIface() bool   { return s.Flag2()&SymFlagUsedInIface != 0 }
+func (s *Sym) IsItab() bool        { return s.Flag2()&SymFlagItab != 0 }
+
+func (s *Sym) SetName(x string, w *Writer) {
+	binary.LittleEndian.PutUint32(s[:], uint32(len(x)))
+	binary.LittleEndian.PutUint32(s[4:], w.stringOff(x))
+}
+
+func (s *Sym) SetABI(x uint16)   { binary.LittleEndian.PutUint16(s[8:], x) }
+func (s *Sym) SetType(x uint8)   { s[10] = x }
+func (s *Sym) SetFlag(x uint8)   { s[11] = x }
+func (s *Sym) SetFlag2(x uint8)  { s[12] = x }
+func (s *Sym) SetSiz(x uint32)   { binary.LittleEndian.PutUint32(s[13:], x) }
+func (s *Sym) SetAlign(x uint32) { binary.LittleEndian.PutUint32(s[17:], x) }
+
+func (s *Sym) Write(w *Writer) { w.Bytes(s[:]) }
+
+// for testing
+func (s *Sym) fromBytes(b []byte) { copy(s[:], b) }
+
+// Symbol reference.
+type SymRef struct {
+	PkgIdx uint32
+	SymIdx uint32
+}
+
+// Hash64
+type Hash64Type [Hash64Size]byte
+
+const Hash64Size = 8
+
+// Hash
+type HashType [HashSize]byte
+
+const HashSize = sha1.Size
+
+// Relocation.
+//
+// Serialized format:
+// Reloc struct {
+//    Off  int32
+//    Siz  uint8
+//    Type uint8
+//    Add  int64
+//    Sym  SymRef
+// }
+type Reloc [RelocSize]byte
+
+const RelocSize = 4 + 1 + 1 + 8 + 8
+
+func (r *Reloc) Off() int32  { return int32(binary.LittleEndian.Uint32(r[:])) }
+func (r *Reloc) Siz() uint8  { return r[4] }
+func (r *Reloc) Type() uint8 { return r[5] }
+func (r *Reloc) Add() int64  { return int64(binary.LittleEndian.Uint64(r[6:])) }
+func (r *Reloc) Sym() SymRef {
+	return SymRef{binary.LittleEndian.Uint32(r[14:]), binary.LittleEndian.Uint32(r[18:])}
+}
+
+func (r *Reloc) SetOff(x int32)  { binary.LittleEndian.PutUint32(r[:], uint32(x)) }
+func (r *Reloc) SetSiz(x uint8)  { r[4] = x }
+func (r *Reloc) SetType(x uint8) { r[5] = x }
+func (r *Reloc) SetAdd(x int64)  { binary.LittleEndian.PutUint64(r[6:], uint64(x)) }
+func (r *Reloc) SetSym(x SymRef) {
+	binary.LittleEndian.PutUint32(r[14:], x.PkgIdx)
+	binary.LittleEndian.PutUint32(r[18:], x.SymIdx)
+}
+
+func (r *Reloc) Set(off int32, size uint8, typ uint8, add int64, sym SymRef) {
+	r.SetOff(off)
+	r.SetSiz(size)
+	r.SetType(typ)
+	r.SetAdd(add)
+	r.SetSym(sym)
+}
+
+func (r *Reloc) Write(w *Writer) { w.Bytes(r[:]) }
+
+// for testing
+func (r *Reloc) fromBytes(b []byte) { copy(r[:], b) }
+
+// Aux symbol info.
+//
+// Serialized format:
+// Aux struct {
+//    Type uint8
+//    Sym  SymRef
+// }
+type Aux [AuxSize]byte
+
+const AuxSize = 1 + 8
+
+// Aux Type
+const (
+	AuxGotype = iota
+	AuxFuncInfo
+	AuxFuncdata
+	AuxDwarfInfo
+	AuxDwarfLoc
+	AuxDwarfRanges
+	AuxDwarfLines
+	AuxPcsp
+	AuxPcfile
+	AuxPcline
+	AuxPcinline
+	AuxPcdata
+)
+
+func (a *Aux) Type() uint8 { return a[0] }
+func (a *Aux) Sym() SymRef {
+	return SymRef{binary.LittleEndian.Uint32(a[1:]), binary.LittleEndian.Uint32(a[5:])}
+}
+
+func (a *Aux) SetType(x uint8) { a[0] = x }
+func (a *Aux) SetSym(x SymRef) {
+	binary.LittleEndian.PutUint32(a[1:], x.PkgIdx)
+	binary.LittleEndian.PutUint32(a[5:], x.SymIdx)
+}
+
+func (a *Aux) Write(w *Writer) { w.Bytes(a[:]) }
+
+// for testing
+func (a *Aux) fromBytes(b []byte) { copy(a[:], b) }
+
+// Referenced symbol flags.
+//
+// Serialized format:
+// RefFlags struct {
+//    Sym   symRef
+//    Flag  uint8
+//    Flag2 uint8
+// }
+type RefFlags [RefFlagsSize]byte
+
+const RefFlagsSize = 8 + 1 + 1
+
+func (r *RefFlags) Sym() SymRef {
+	return SymRef{binary.LittleEndian.Uint32(r[:]), binary.LittleEndian.Uint32(r[4:])}
+}
+func (r *RefFlags) Flag() uint8  { return r[8] }
+func (r *RefFlags) Flag2() uint8 { return r[9] }
+
+func (r *RefFlags) SetSym(x SymRef) {
+	binary.LittleEndian.PutUint32(r[:], x.PkgIdx)
+	binary.LittleEndian.PutUint32(r[4:], x.SymIdx)
+}
+func (r *RefFlags) SetFlag(x uint8)  { r[8] = x }
+func (r *RefFlags) SetFlag2(x uint8) { r[9] = x }
+
+func (r *RefFlags) Write(w *Writer) { w.Bytes(r[:]) }
+
+// Used to construct an artifically large array type when reading an
+// item from the object file relocs section or aux sym section (needs
+// to work on 32-bit as well as 64-bit). See issue 41621.
+const huge = (1<<31 - 1) / RelocSize
+
+// Referenced symbol name.
+//
+// Serialized format:
+// RefName struct {
+//    Sym  symRef
+//    Name string
+// }
+type RefName [RefNameSize]byte
+
+const RefNameSize = 8 + stringRefSize
+
+func (n *RefName) Sym() SymRef {
+	return SymRef{binary.LittleEndian.Uint32(n[:]), binary.LittleEndian.Uint32(n[4:])}
+}
+func (n *RefName) Name(r *Reader) string {
+	len := binary.LittleEndian.Uint32(n[8:])
+	off := binary.LittleEndian.Uint32(n[12:])
+	return r.StringAt(off, len)
+}
+
+func (n *RefName) SetSym(x SymRef) {
+	binary.LittleEndian.PutUint32(n[:], x.PkgIdx)
+	binary.LittleEndian.PutUint32(n[4:], x.SymIdx)
+}
+func (n *RefName) SetName(x string, w *Writer) {
+	binary.LittleEndian.PutUint32(n[8:], uint32(len(x)))
+	binary.LittleEndian.PutUint32(n[12:], w.stringOff(x))
+}
+
+func (n *RefName) Write(w *Writer) { w.Bytes(n[:]) }
+
+type Writer struct {
+	wr        *bio.Writer
+	stringMap map[string]uint32
+	off       uint32 // running offset
+}
+
+func NewWriter(wr *bio.Writer) *Writer {
+	return &Writer{wr: wr, stringMap: make(map[string]uint32)}
+}
+
+func (w *Writer) AddString(s string) {
+	if _, ok := w.stringMap[s]; ok {
+		return
+	}
+	w.stringMap[s] = w.off
+	w.RawString(s)
+}
+
+func (w *Writer) stringOff(s string) uint32 {
+	off, ok := w.stringMap[s]
+	if !ok {
+		panic(fmt.Sprintf("writeStringRef: string not added: %q", s))
+	}
+	return off
+}
+
+func (w *Writer) StringRef(s string) {
+	w.Uint32(uint32(len(s)))
+	w.Uint32(w.stringOff(s))
+}
+
+func (w *Writer) RawString(s string) {
+	w.wr.WriteString(s)
+	w.off += uint32(len(s))
+}
+
+func (w *Writer) Bytes(s []byte) {
+	w.wr.Write(s)
+	w.off += uint32(len(s))
+}
+
+func (w *Writer) Uint64(x uint64) {
+	var b [8]byte
+	binary.LittleEndian.PutUint64(b[:], x)
+	w.wr.Write(b[:])
+	w.off += 8
+}
+
+func (w *Writer) Uint32(x uint32) {
+	var b [4]byte
+	binary.LittleEndian.PutUint32(b[:], x)
+	w.wr.Write(b[:])
+	w.off += 4
+}
+
+func (w *Writer) Uint16(x uint16) {
+	var b [2]byte
+	binary.LittleEndian.PutUint16(b[:], x)
+	w.wr.Write(b[:])
+	w.off += 2
+}
+
+func (w *Writer) Uint8(x uint8) {
+	w.wr.WriteByte(x)
+	w.off++
+}
+
+func (w *Writer) Offset() uint32 {
+	return w.off
+}
+
+type Reader struct {
+	b        []byte // mmapped bytes, if not nil
+	readonly bool   // whether b is backed with read-only memory
+
+	rd    io.ReaderAt
+	start uint32
+	h     Header // keep block offsets
+}
+
+func NewReaderFromBytes(b []byte, readonly bool) *Reader {
+	r := &Reader{b: b, readonly: readonly, rd: bytes.NewReader(b), start: 0}
+	err := r.h.Read(r)
+	if err != nil {
+		return nil
+	}
+	return r
+}
+
+func (r *Reader) BytesAt(off uint32, len int) []byte {
+	if len == 0 {
+		return nil
+	}
+	end := int(off) + len
+	return r.b[int(off):end:end]
+}
+
+func (r *Reader) uint64At(off uint32) uint64 {
+	b := r.BytesAt(off, 8)
+	return binary.LittleEndian.Uint64(b)
+}
+
+func (r *Reader) int64At(off uint32) int64 {
+	return int64(r.uint64At(off))
+}
+
+func (r *Reader) uint32At(off uint32) uint32 {
+	b := r.BytesAt(off, 4)
+	return binary.LittleEndian.Uint32(b)
+}
+
+func (r *Reader) int32At(off uint32) int32 {
+	return int32(r.uint32At(off))
+}
+
+func (r *Reader) uint16At(off uint32) uint16 {
+	b := r.BytesAt(off, 2)
+	return binary.LittleEndian.Uint16(b)
+}
+
+func (r *Reader) uint8At(off uint32) uint8 {
+	b := r.BytesAt(off, 1)
+	return b[0]
+}
+
+func (r *Reader) StringAt(off uint32, len uint32) string {
+	b := r.b[off : off+len]
+	if r.readonly {
+		return toString(b) // backed by RO memory, ok to make unsafe string
+	}
+	return string(b)
+}
+
+func toString(b []byte) string {
+	if len(b) == 0 {
+		return ""
+	}
+
+	var s string
+	hdr := (*unsafeheader.String)(unsafe.Pointer(&s))
+	hdr.Data = unsafe.Pointer(&b[0])
+	hdr.Len = len(b)
+
+	return s
+}
+
+func (r *Reader) StringRef(off uint32) string {
+	l := r.uint32At(off)
+	return r.StringAt(r.uint32At(off+4), l)
+}
+
+func (r *Reader) Fingerprint() FingerprintType {
+	return r.h.Fingerprint
+}
+
+func (r *Reader) Autolib() []ImportedPkg {
+	n := (r.h.Offsets[BlkAutolib+1] - r.h.Offsets[BlkAutolib]) / importedPkgSize
+	s := make([]ImportedPkg, n)
+	off := r.h.Offsets[BlkAutolib]
+	for i := range s {
+		s[i].Pkg = r.StringRef(off)
+		copy(s[i].Fingerprint[:], r.BytesAt(off+stringRefSize, len(s[i].Fingerprint)))
+		off += importedPkgSize
+	}
+	return s
+}
+
+func (r *Reader) Pkglist() []string {
+	n := (r.h.Offsets[BlkPkgIdx+1] - r.h.Offsets[BlkPkgIdx]) / stringRefSize
+	s := make([]string, n)
+	off := r.h.Offsets[BlkPkgIdx]
+	for i := range s {
+		s[i] = r.StringRef(off)
+		off += stringRefSize
+	}
+	return s
+}
+
+func (r *Reader) NPkg() int {
+	return int(r.h.Offsets[BlkPkgIdx+1]-r.h.Offsets[BlkPkgIdx]) / stringRefSize
+}
+
+func (r *Reader) Pkg(i int) string {
+	off := r.h.Offsets[BlkPkgIdx] + uint32(i)*stringRefSize
+	return r.StringRef(off)
+}
+
+func (r *Reader) NFile() int {
+	return int(r.h.Offsets[BlkFile+1]-r.h.Offsets[BlkFile]) / stringRefSize
+}
+
+func (r *Reader) File(i int) string {
+	off := r.h.Offsets[BlkFile] + uint32(i)*stringRefSize
+	return r.StringRef(off)
+}
+
+func (r *Reader) NSym() int {
+	return int(r.h.Offsets[BlkSymdef+1]-r.h.Offsets[BlkSymdef]) / SymSize
+}
+
+func (r *Reader) NHashed64def() int {
+	return int(r.h.Offsets[BlkHashed64def+1]-r.h.Offsets[BlkHashed64def]) / SymSize
+}
+
+func (r *Reader) NHasheddef() int {
+	return int(r.h.Offsets[BlkHasheddef+1]-r.h.Offsets[BlkHasheddef]) / SymSize
+}
+
+func (r *Reader) NNonpkgdef() int {
+	return int(r.h.Offsets[BlkNonpkgdef+1]-r.h.Offsets[BlkNonpkgdef]) / SymSize
+}
+
+func (r *Reader) NNonpkgref() int {
+	return int(r.h.Offsets[BlkNonpkgref+1]-r.h.Offsets[BlkNonpkgref]) / SymSize
+}
+
+// SymOff returns the offset of the i-th symbol.
+func (r *Reader) SymOff(i uint32) uint32 {
+	return r.h.Offsets[BlkSymdef] + uint32(i*SymSize)
+}
+
+// Sym returns a pointer to the i-th symbol.
+func (r *Reader) Sym(i uint32) *Sym {
+	off := r.SymOff(i)
+	return (*Sym)(unsafe.Pointer(&r.b[off]))
+}
+
+// NRefFlags returns the number of referenced symbol flags.
+func (r *Reader) NRefFlags() int {
+	return int(r.h.Offsets[BlkRefFlags+1]-r.h.Offsets[BlkRefFlags]) / RefFlagsSize
+}
+
+// RefFlags returns a pointer to the i-th referenced symbol flags.
+// Note: here i is not a local symbol index, just a counter.
+func (r *Reader) RefFlags(i int) *RefFlags {
+	off := r.h.Offsets[BlkRefFlags] + uint32(i*RefFlagsSize)
+	return (*RefFlags)(unsafe.Pointer(&r.b[off]))
+}
+
+// Hash64 returns the i-th short hashed symbol's hash.
+// Note: here i is the index of short hashed symbols, not all symbols
+// (unlike other accessors).
+func (r *Reader) Hash64(i uint32) uint64 {
+	off := r.h.Offsets[BlkHash64] + uint32(i*Hash64Size)
+	return r.uint64At(off)
+}
+
+// Hash returns a pointer to the i-th hashed symbol's hash.
+// Note: here i is the index of hashed symbols, not all symbols
+// (unlike other accessors).
+func (r *Reader) Hash(i uint32) *HashType {
+	off := r.h.Offsets[BlkHash] + uint32(i*HashSize)
+	return (*HashType)(unsafe.Pointer(&r.b[off]))
+}
+
+// NReloc returns the number of relocations of the i-th symbol.
+func (r *Reader) NReloc(i uint32) int {
+	relocIdxOff := r.h.Offsets[BlkRelocIdx] + uint32(i*4)
+	return int(r.uint32At(relocIdxOff+4) - r.uint32At(relocIdxOff))
+}
+
+// RelocOff returns the offset of the j-th relocation of the i-th symbol.
+func (r *Reader) RelocOff(i uint32, j int) uint32 {
+	relocIdxOff := r.h.Offsets[BlkRelocIdx] + uint32(i*4)
+	relocIdx := r.uint32At(relocIdxOff)
+	return r.h.Offsets[BlkReloc] + (relocIdx+uint32(j))*uint32(RelocSize)
+}
+
+// Reloc returns a pointer to the j-th relocation of the i-th symbol.
+func (r *Reader) Reloc(i uint32, j int) *Reloc {
+	off := r.RelocOff(i, j)
+	return (*Reloc)(unsafe.Pointer(&r.b[off]))
+}
+
+// Relocs returns a pointer to the relocations of the i-th symbol.
+func (r *Reader) Relocs(i uint32) []Reloc {
+	off := r.RelocOff(i, 0)
+	n := r.NReloc(i)
+	return (*[huge]Reloc)(unsafe.Pointer(&r.b[off]))[:n:n]
+}
+
+// NAux returns the number of aux symbols of the i-th symbol.
+func (r *Reader) NAux(i uint32) int {
+	auxIdxOff := r.h.Offsets[BlkAuxIdx] + i*4
+	return int(r.uint32At(auxIdxOff+4) - r.uint32At(auxIdxOff))
+}
+
+// AuxOff returns the offset of the j-th aux symbol of the i-th symbol.
+func (r *Reader) AuxOff(i uint32, j int) uint32 {
+	auxIdxOff := r.h.Offsets[BlkAuxIdx] + i*4
+	auxIdx := r.uint32At(auxIdxOff)
+	return r.h.Offsets[BlkAux] + (auxIdx+uint32(j))*uint32(AuxSize)
+}
+
+// Aux returns a pointer to the j-th aux symbol of the i-th symbol.
+func (r *Reader) Aux(i uint32, j int) *Aux {
+	off := r.AuxOff(i, j)
+	return (*Aux)(unsafe.Pointer(&r.b[off]))
+}
+
+// Auxs returns the aux symbols of the i-th symbol.
+func (r *Reader) Auxs(i uint32) []Aux {
+	off := r.AuxOff(i, 0)
+	n := r.NAux(i)
+	return (*[huge]Aux)(unsafe.Pointer(&r.b[off]))[:n:n]
+}
+
+// DataOff returns the offset of the i-th symbol's data.
+func (r *Reader) DataOff(i uint32) uint32 {
+	dataIdxOff := r.h.Offsets[BlkDataIdx] + i*4
+	return r.h.Offsets[BlkData] + r.uint32At(dataIdxOff)
+}
+
+// DataSize returns the size of the i-th symbol's data.
+func (r *Reader) DataSize(i uint32) int {
+	dataIdxOff := r.h.Offsets[BlkDataIdx] + i*4
+	return int(r.uint32At(dataIdxOff+4) - r.uint32At(dataIdxOff))
+}
+
+// Data returns the i-th symbol's data.
+func (r *Reader) Data(i uint32) []byte {
+	dataIdxOff := r.h.Offsets[BlkDataIdx] + i*4
+	base := r.h.Offsets[BlkData]
+	off := r.uint32At(dataIdxOff)
+	end := r.uint32At(dataIdxOff + 4)
+	return r.BytesAt(base+off, int(end-off))
+}
+
+// NRefName returns the number of referenced symbol names.
+func (r *Reader) NRefName() int {
+	return int(r.h.Offsets[BlkRefName+1]-r.h.Offsets[BlkRefName]) / RefNameSize
+}
+
+// RefName returns a pointer to the i-th referenced symbol name.
+// Note: here i is not a local symbol index, just a counter.
+func (r *Reader) RefName(i int) *RefName {
+	off := r.h.Offsets[BlkRefName] + uint32(i*RefNameSize)
+	return (*RefName)(unsafe.Pointer(&r.b[off]))
+}
+
+// ReadOnly returns whether r.BytesAt returns read-only bytes.
+func (r *Reader) ReadOnly() bool {
+	return r.readonly
+}
+
+// Flags returns the flag bits read from the object file header.
+func (r *Reader) Flags() uint32 {
+	return r.h.Flags
+}
+
+func (r *Reader) Shared() bool            { return r.Flags()&ObjFlagShared != 0 }
+func (r *Reader) NeedNameExpansion() bool { return r.Flags()&ObjFlagNeedNameExpansion != 0 }
+func (r *Reader) FromAssembly() bool      { return r.Flags()&ObjFlagFromAssembly != 0 }
diff --git a/src/cmd/internal/goobj/objfile_test.go b/src/cmd/internal/goobj/objfile_test.go
new file mode 100644
index 0000000..c6fd427
--- /dev/null
+++ b/src/cmd/internal/goobj/objfile_test.go
@@ -0,0 +1,71 @@
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package goobj
+
+import (
+	"bufio"
+	"bytes"
+	"cmd/internal/bio"
+	"cmd/internal/objabi"
+	"testing"
+)
+
+func dummyWriter(buf *bytes.Buffer) *Writer {
+	wr := &bio.Writer{Writer: bufio.NewWriter(buf)} // hacky: no file, so cannot seek
+	return NewWriter(wr)
+}
+
+func TestReadWrite(t *testing.T) {
+	// Test that we get the same data in a write-read roundtrip.
+
+	// Write a symbol, a relocation, and an aux info.
+	var buf bytes.Buffer
+	w := dummyWriter(&buf)
+
+	var s Sym
+	s.SetABI(1)
+	s.SetType(uint8(objabi.STEXT))
+	s.SetFlag(0x12)
+	s.SetSiz(12345)
+	s.SetAlign(8)
+	s.Write(w)
+
+	var r Reloc
+	r.SetOff(12)
+	r.SetSiz(4)
+	r.SetType(uint8(objabi.R_ADDR))
+	r.SetAdd(54321)
+	r.SetSym(SymRef{11, 22})
+	r.Write(w)
+
+	var a Aux
+	a.SetType(AuxFuncInfo)
+	a.SetSym(SymRef{33, 44})
+	a.Write(w)
+
+	w.wr.Flush()
+
+	// Read them back and check.
+	b := buf.Bytes()
+	var s2 Sym
+	s2.fromBytes(b)
+	if s2.ABI() != 1 || s2.Type() != uint8(objabi.STEXT) || s2.Flag() != 0x12 || s2.Siz() != 12345 || s2.Align() != 8 {
+		t.Errorf("read Sym2 mismatch: got %v %v %v %v %v", s2.ABI(), s2.Type(), s2.Flag(), s2.Siz(), s2.Align())
+	}
+
+	b = b[SymSize:]
+	var r2 Reloc
+	r2.fromBytes(b)
+	if r2.Off() != 12 || r2.Siz() != 4 || r2.Type() != uint8(objabi.R_ADDR) || r2.Add() != 54321 || r2.Sym() != (SymRef{11, 22}) {
+		t.Errorf("read Reloc2 mismatch: got %v %v %v %v %v", r2.Off(), r2.Siz(), r2.Type(), r2.Add(), r2.Sym())
+	}
+
+	b = b[RelocSize:]
+	var a2 Aux
+	a2.fromBytes(b)
+	if a2.Type() != AuxFuncInfo || a2.Sym() != (SymRef{33, 44}) {
+		t.Errorf("read Aux2 mismatch: got %v %v", a2.Type(), a2.Sym())
+	}
+}