Adding upstream version 1.22.1.upstream/1.22.1

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

1 files changed, 882 insertions, 0 deletions

diff --git a/src/cmd/internal/goobj/objfile.go b/src/cmd/internal/goobj/objfile.go
new file mode 100644
index 0000000..6c0f5e6
--- /dev/null
+++ b/src/cmd/internal/goobj/objfile.go
@@ -0,0 +1,882 @@
+// 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 (
+	"cmd/internal/bio"
+	"encoding/binary"
+	"errors"
+	"fmt"
+	"unsafe"
+)
+
+// New object file format.
+//
+//    Header struct {
+//       Magic       [...]byte   // "\x00go120ld"
+//       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 uint16
+//       Add  int64
+//       Sym  symRef
+//    }
+//
+//    Aux [...]struct {
+//       Type uint8
+//       Sym  symRef
+//    }
+//
+//    Data   [...]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 naturally 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
+	PkgIdxSpecial  = PkgIdxSelf         // Indices above it has special meanings
+	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
+	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 = "\x00go120ld"
+
+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) + len(h.Fingerprint) + 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
+	_                               // was ObjFlagNeedNameExpansion
+	ObjFlagFromAssembly             // object is from asm src, not go
+	ObjFlagUnlinkable               // unlinkable package (linker will emit an error)
+)
+
+// Sym.Flag
+const (
+	SymFlagDupok = 1 << iota
+	SymFlagLocal
+	SymFlagTypelink
+	SymFlagLeaf
+	SymFlagNoSplit
+	SymFlagReflectMethod
+	SymFlagGoType
+)
+
+// Sym.Flag2
+const (
+	SymFlagUsedInIface = 1 << iota
+	SymFlagItab
+	SymFlagDict
+	SymFlagPkgInit
+)
+
+// 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) UsedInIface() bool   { return s.Flag2()&SymFlagUsedInIface != 0 }
+func (s *Sym) IsItab() bool        { return s.Flag2()&SymFlagItab != 0 }
+func (s *Sym) IsDict() bool        { return s.Flag2()&SymFlagDict != 0 }
+func (s *Sym) IsPkgInit() bool     { return s.Flag2()&SymFlagPkgInit != 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
+}
+
+func (s SymRef) IsZero() bool { return s == SymRef{} }
+
+// Hash64
+type Hash64Type [Hash64Size]byte
+
+const Hash64Size = 8
+
+// Hash
+type HashType [HashSize]byte
+
+const HashSize = 16 // truncated SHA256
+
+// Relocation.
+//
+// Serialized format:
+//
+//	Reloc struct {
+//	   Off  int32
+//	   Siz  uint8
+//	   Type uint16
+//	   Add  int64
+//	   Sym  SymRef
+//	}
+type Reloc [RelocSize]byte
+
+const RelocSize = 4 + 1 + 2 + 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() uint16 { return binary.LittleEndian.Uint16(r[5:]) }
+func (r *Reloc) Add() int64   { return int64(binary.LittleEndian.Uint64(r[7:])) }
+func (r *Reloc) Sym() SymRef {
+	return SymRef{binary.LittleEndian.Uint32(r[15:]), binary.LittleEndian.Uint32(r[19:])}
+}
+
+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 uint16) { binary.LittleEndian.PutUint16(r[5:], x) }
+func (r *Reloc) SetAdd(x int64)   { binary.LittleEndian.PutUint64(r[7:], uint64(x)) }
+func (r *Reloc) SetSym(x SymRef) {
+	binary.LittleEndian.PutUint32(r[15:], x.PkgIdx)
+	binary.LittleEndian.PutUint32(r[19:], x.SymIdx)
+}
+
+func (r *Reloc) Set(off int32, size uint8, typ uint16, 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
+	AuxWasmImport
+	AuxSehUnwindInfo
+)
+
+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 artificially 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
+
+	b [8]byte // scratch space for writing bytes
+}
+
+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) {
+	binary.LittleEndian.PutUint64(w.b[:], x)
+	w.wr.Write(w.b[:])
+	w.off += 8
+}
+
+func (w *Writer) Uint32(x uint32) {
+	binary.LittleEndian.PutUint32(w.b[:4], x)
+	w.wr.Write(w.b[:4])
+	w.off += 4
+}
+
+func (w *Writer) Uint16(x uint16) {
+	binary.LittleEndian.PutUint16(w.b[:2], x)
+	w.wr.Write(w.b[:2])
+	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
+
+	start uint32
+	h     Header // keep block offsets
+}
+
+func NewReaderFromBytes(b []byte, readonly bool) *Reader {
+	r := &Reader{b: b, readonly: readonly, 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 ""
+	}
+	return unsafe.String(&b[0], len(b))
+}
+
+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))
+}
+
+// DataString returns the i-th symbol's data as a string.
+func (r *Reader) DataString(i uint32) string {
+	dataIdxOff := r.h.Offsets[BlkDataIdx] + i*4
+	base := r.h.Offsets[BlkData]
+	off := r.uint32At(dataIdxOff)
+	end := r.uint32At(dataIdxOff + 4)
+	return r.StringAt(base+off, 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) FromAssembly() bool { return r.Flags()&ObjFlagFromAssembly != 0 }
+func (r *Reader) Unlinkable() bool   { return r.Flags()&ObjFlagUnlinkable != 0 }