diff --git a/src/cmd/asm/internal/asm/endtoend_test.go b/src/cmd/asm/internal/asm/endtoend_test.go
index 1307c42..8986281 100644
--- a/src/cmd/asm/internal/asm/endtoend_test.go
+++ b/src/cmd/asm/internal/asm/endtoend_test.go
@@ -17,6 +17,7 @@
 	"testing"
 
 	"cmd/asm/internal/lex"
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 )
 
@@ -33,7 +34,7 @@
 	pList := obj.Linknewplist(ctxt)
 	var ok bool
 	testOut = new(bytes.Buffer) // The assembler writes test output to this buffer.
-	ctxt.Bso = obj.Binitw(os.Stdout)
+	ctxt.Bso = bio.BufWriter(os.Stdout)
 	defer ctxt.Bso.Flush()
 	failed := false
 	ctxt.DiagFunc = func(format string, args ...interface{}) {
@@ -271,7 +272,7 @@
 	pList := obj.Linknewplist(ctxt)
 	var ok bool
 	testOut = new(bytes.Buffer) // The assembler writes test output to this buffer.
-	ctxt.Bso = obj.Binitw(os.Stdout)
+	ctxt.Bso = bio.BufWriter(os.Stdout)
 	defer ctxt.Bso.Flush()
 	failed := false
 	var errBuf bytes.Buffer
diff --git a/src/cmd/asm/main.go b/src/cmd/asm/main.go
index 4e450be..75cb8f7 100644
--- a/src/cmd/asm/main.go
+++ b/src/cmd/asm/main.go
@@ -15,6 +15,7 @@
 	"cmd/asm/internal/flags"
 	"cmd/asm/internal/lex"
 
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 )
 
@@ -45,9 +46,9 @@
 	if *flags.Shared || *flags.Dynlink {
 		ctxt.Flag_shared = 1
 	}
-	ctxt.Bso = obj.Binitw(os.Stdout)
+	ctxt.Bso = bio.BufWriter(os.Stdout)
 	defer ctxt.Bso.Flush()
-	output := obj.Binitw(fd)
+	output := bio.BufWriter(fd)
 	fmt.Fprintf(output, "go object %s %s %s\n", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion())
 	fmt.Fprintf(output, "!\n")
 
diff --git a/src/cmd/compile/internal/gc/bexport.go b/src/cmd/compile/internal/gc/bexport.go
index 092cdac..7020902 100644
--- a/src/cmd/compile/internal/gc/bexport.go
+++ b/src/cmd/compile/internal/gc/bexport.go
@@ -92,7 +92,7 @@
 import (
 	"bytes"
 	"cmd/compile/internal/big"
-	"cmd/internal/obj"
+	"cmd/internal/bio"
 	"encoding/binary"
 	"fmt"
 	"sort"
@@ -124,7 +124,7 @@
 const exportInlined = true // default: true
 
 type exporter struct {
-	out      *obj.Biobuf
+	out      *bio.Buf
 	pkgIndex map[*Pkg]int
 	typIndex map[*Type]int
 	inlined  []*Func
@@ -136,7 +136,7 @@
 }
 
 // Export writes the exportlist for localpkg to out and returns the number of bytes written.
-func Export(out *obj.Biobuf, trace bool) int {
+func Export(out *bio.Buf, trace bool) int {
 	p := exporter{
 		out:      out,
 		pkgIndex: make(map[*Pkg]int),
@@ -1531,10 +1531,10 @@
 		fallthrough
 	case '|':
 		// write '|' as '|' '|'
-		obj.Bputc(p.out, '|')
+		p.out.WriteByte('|')
 		p.written++
 	}
-	obj.Bputc(p.out, b)
+	p.out.WriteByte(b)
 	p.written++
 }
 
diff --git a/src/cmd/compile/internal/gc/export.go b/src/cmd/compile/internal/gc/export.go
index 17311cf..5d4add8 100644
--- a/src/cmd/compile/internal/gc/export.go
+++ b/src/cmd/compile/internal/gc/export.go
@@ -7,7 +7,7 @@
 import (
 	"bufio"
 	"bytes"
-	"cmd/internal/obj"
+	"cmd/internal/bio"
 	"fmt"
 	"sort"
 	"unicode"
@@ -384,7 +384,7 @@
 		if debugFormat {
 			// save a copy of the export data
 			var copy bytes.Buffer
-			bcopy := obj.Binitw(&copy)
+			bcopy := bio.BufWriter(&copy)
 			size = Export(bcopy, Debug_export != 0)
 			bcopy.Flush() // flushing to bytes.Buffer cannot fail
 			if n, err := bout.Write(copy.Bytes()); n != size || err != nil {
@@ -577,7 +577,7 @@
 }
 
 func dumpasmhdr() {
-	b, err := obj.Bopenw(asmhdr)
+	b, err := bio.Create(asmhdr)
 	if err != nil {
 		Fatalf("%v", err)
 	}
@@ -604,5 +604,5 @@
 		}
 	}
 
-	obj.Bterm(b)
+	b.Close()
 }
diff --git a/src/cmd/compile/internal/gc/go.go b/src/cmd/compile/internal/gc/go.go
index ef8b516..cd9db38 100644
--- a/src/cmd/compile/internal/gc/go.go
+++ b/src/cmd/compile/internal/gc/go.go
@@ -6,6 +6,7 @@
 
 import (
 	"cmd/compile/internal/ssa"
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 )
 
@@ -132,7 +133,7 @@
 
 var outfile string
 
-var bout *obj.Biobuf
+var bout *bio.Buf
 
 var nerrors int
 
@@ -287,7 +288,7 @@
 
 var writearchive int
 
-var bstdout obj.Biobuf
+var bstdout *bio.Buf
 
 var Nacl bool
 
diff --git a/src/cmd/compile/internal/gc/main.go b/src/cmd/compile/internal/gc/main.go
index 079f491..c8a778c 100644
--- a/src/cmd/compile/internal/gc/main.go
+++ b/src/cmd/compile/internal/gc/main.go
@@ -9,6 +9,7 @@
 import (
 	"bufio"
 	"cmd/compile/internal/ssa"
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"cmd/internal/sys"
 	"flag"
@@ -97,8 +98,8 @@
 
 	Ctxt = obj.Linknew(Thearch.LinkArch)
 	Ctxt.DiagFunc = Yyerror
-	Ctxt.Bso = &bstdout
-	bstdout = *obj.Binitw(os.Stdout)
+	bstdout = bio.BufWriter(os.Stdout)
+	Ctxt.Bso = bstdout
 
 	localpkg = mkpkg("")
 	localpkg.Prefix = "\"\""
diff --git a/src/cmd/compile/internal/gc/obj.go b/src/cmd/compile/internal/gc/obj.go
index 99eb73b..3920e25 100644
--- a/src/cmd/compile/internal/gc/obj.go
+++ b/src/cmd/compile/internal/gc/obj.go
@@ -5,6 +5,7 @@
 package gc
 
 import (
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"crypto/sha256"
 	"fmt"
@@ -23,7 +24,7 @@
 
 func dumpobj() {
 	var err error
-	bout, err = obj.Bopenw(outfile)
+	bout, err = bio.Create(outfile)
 	if err != nil {
 		Flusherrors()
 		fmt.Printf("can't create %s: %v\n", outfile, err)
@@ -33,10 +34,10 @@
 	startobj := int64(0)
 	var arhdr [ArhdrSize]byte
 	if writearchive != 0 {
-		obj.Bwritestring(bout, "!<arch>\n")
+		bout.WriteString("!<arch>\n")
 		arhdr = [ArhdrSize]byte{}
 		bout.Write(arhdr[:])
-		startobj = obj.Boffset(bout)
+		startobj = bio.Boffset(bout)
 	}
 
 	fmt.Fprintf(bout, "go object %s %s %s %s\n", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion(), obj.Expstring())
@@ -44,19 +45,19 @@
 
 	if writearchive != 0 {
 		bout.Flush()
-		size := obj.Boffset(bout) - startobj
+		size := bio.Boffset(bout) - startobj
 		if size&1 != 0 {
-			obj.Bputc(bout, 0)
+			bout.WriteByte(0)
 		}
-		obj.Bseek(bout, startobj-ArhdrSize, 0)
+		bio.Bseek(bout, startobj-ArhdrSize, 0)
 		formathdr(arhdr[:], "__.PKGDEF", size)
 		bout.Write(arhdr[:])
 		bout.Flush()
 
-		obj.Bseek(bout, startobj+size+(size&1), 0)
+		bio.Bseek(bout, startobj+size+(size&1), 0)
 		arhdr = [ArhdrSize]byte{}
 		bout.Write(arhdr[:])
-		startobj = obj.Boffset(bout)
+		startobj = bio.Boffset(bout)
 		fmt.Fprintf(bout, "go object %s %s %s %s\n", obj.Getgoos(), obj.Getgoarch(), obj.Getgoversion(), obj.Expstring())
 	}
 
@@ -91,16 +92,16 @@
 
 	if writearchive != 0 {
 		bout.Flush()
-		size := obj.Boffset(bout) - startobj
+		size := bio.Boffset(bout) - startobj
 		if size&1 != 0 {
-			obj.Bputc(bout, 0)
+			bout.WriteByte(0)
 		}
-		obj.Bseek(bout, startobj-ArhdrSize, 0)
+		bio.Bseek(bout, startobj-ArhdrSize, 0)
 		formathdr(arhdr[:], "_go_.o", size)
 		bout.Write(arhdr[:])
 	}
 
-	obj.Bterm(bout)
+	bout.Close()
 }
 
 func dumpglobls() {
@@ -132,9 +133,9 @@
 	funcsyms = nil
 }
 
-func Bputname(b *obj.Biobuf, s *obj.LSym) {
-	obj.Bwritestring(b, s.Name)
-	obj.Bputc(b, 0)
+func Bputname(b *bio.Buf, s *obj.LSym) {
+	b.WriteString(s.Name)
+	b.WriteByte(0)
 }
 
 func Linksym(s *Sym) *obj.LSym {
diff --git a/src/cmd/dist/buildtool.go b/src/cmd/dist/buildtool.go
index 123d5cc..777c92c 100644
--- a/src/cmd/dist/buildtool.go
+++ b/src/cmd/dist/buildtool.go
@@ -38,6 +38,7 @@
 	"compile/internal/ppc64",
 	"compile/internal/ssa",
 	"compile/internal/x86",
+	"internal/bio",
 	"internal/gcprog",
 	"internal/obj",
 	"internal/obj/arm",
diff --git a/src/cmd/internal/bio/buf.go b/src/cmd/internal/bio/buf.go
new file mode 100644
index 0000000..a1df26c
--- /dev/null
+++ b/src/cmd/internal/bio/buf.go
@@ -0,0 +1,150 @@
+// Copyright 2015 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 bio implements seekable buffered I/O.
+package bio
+
+import (
+	"bufio"
+	"io"
+	"log"
+	"os"
+)
+
+const EOF = -1
+
+// Buf implements a seekable buffered I/O abstraction.
+type Buf struct {
+	f *os.File
+	r *bufio.Reader
+	w *bufio.Writer
+}
+
+func (b *Buf) Reader() *bufio.Reader { return b.r }
+func (b *Buf) Writer() *bufio.Writer { return b.w }
+
+func Create(name string) (*Buf, error) {
+	f, err := os.Create(name)
+	if err != nil {
+		return nil, err
+	}
+	return &Buf{f: f, w: bufio.NewWriter(f)}, nil
+}
+
+func Open(name string) (*Buf, error) {
+	f, err := os.Open(name)
+	if err != nil {
+		return nil, err
+	}
+	return &Buf{f: f, r: bufio.NewReader(f)}, nil
+}
+
+func BufWriter(w io.Writer) *Buf {
+	return &Buf{w: bufio.NewWriter(w)}
+}
+
+func BufReader(r io.Reader) *Buf {
+	return &Buf{r: bufio.NewReader(r)}
+}
+
+func (b *Buf) Write(p []byte) (int, error) {
+	return b.w.Write(p)
+}
+
+func (b *Buf) WriteString(p string) (int, error) {
+	return b.w.WriteString(p)
+}
+
+func Bseek(b *Buf, offset int64, whence int) int64 {
+	if b.w != nil {
+		if err := b.w.Flush(); err != nil {
+			log.Fatalf("writing output: %v", err)
+		}
+	} else if b.r != nil {
+		if whence == 1 {
+			offset -= int64(b.r.Buffered())
+		}
+	}
+	off, err := b.f.Seek(offset, whence)
+	if err != nil {
+		log.Fatalf("seeking in output: %v", err)
+	}
+	if b.r != nil {
+		b.r.Reset(b.f)
+	}
+	return off
+}
+
+func Boffset(b *Buf) int64 {
+	if b.w != nil {
+		if err := b.w.Flush(); err != nil {
+			log.Fatalf("writing output: %v", err)
+		}
+	}
+	off, err := b.f.Seek(0, 1)
+	if err != nil {
+		log.Fatalf("seeking in output [0, 1]: %v", err)
+	}
+	if b.r != nil {
+		off -= int64(b.r.Buffered())
+	}
+	return off
+}
+
+func (b *Buf) Flush() error {
+	return b.w.Flush()
+}
+
+func (b *Buf) WriteByte(c byte) error {
+	return b.w.WriteByte(c)
+}
+
+func Bread(b *Buf, p []byte) int {
+	n, err := io.ReadFull(b.r, p)
+	if n == 0 {
+		if err != nil && err != io.EOF {
+			n = -1
+		}
+	}
+	return n
+}
+
+func Bgetc(b *Buf) int {
+	c, err := b.r.ReadByte()
+	if err != nil {
+		if err != io.EOF {
+			log.Fatalf("reading input: %v", err)
+		}
+		return EOF
+	}
+	return int(c)
+}
+
+func (b *Buf) Read(p []byte) (int, error) {
+	return b.r.Read(p)
+}
+
+func (b *Buf) Peek(n int) ([]byte, error) {
+	return b.r.Peek(n)
+}
+
+func Brdline(b *Buf, delim int) string {
+	s, err := b.r.ReadBytes(byte(delim))
+	if err != nil {
+		log.Fatalf("reading input: %v", err)
+	}
+	return string(s)
+}
+
+func (b *Buf) Close() error {
+	var err error
+	if b.w != nil {
+		err = b.w.Flush()
+	}
+	err1 := b.f.Close()
+	if err == nil {
+		err = err1
+	}
+	return err
+}
diff --git a/src/cmd/internal/obj/link.go b/src/cmd/internal/obj/link.go
index 81a5689..2c81ca2f 100644
--- a/src/cmd/internal/obj/link.go
+++ b/src/cmd/internal/obj/link.go
@@ -30,7 +30,10 @@
 
 package obj
 
-import "cmd/internal/sys"
+import (
+	"cmd/internal/bio"
+	"cmd/internal/sys"
+)
 
 // An Addr is an argument to an instruction.
 // The general forms and their encodings are:
@@ -626,7 +629,7 @@
 	Flag_shared   int32
 	Flag_dynlink  bool
 	Flag_optimize bool
-	Bso           *Biobuf
+	Bso           *bio.Buf
 	Pathname      string
 	Goroot        string
 	Goroot_final  string
diff --git a/src/cmd/internal/obj/objfile.go b/src/cmd/internal/obj/objfile.go
index bdd3bfc..405cbf4 100644
--- a/src/cmd/internal/obj/objfile.go
+++ b/src/cmd/internal/obj/objfile.go
@@ -109,6 +109,7 @@
 
 import (
 	"bufio"
+	"cmd/internal/bio"
 	"cmd/internal/sys"
 	"fmt"
 	"log"
@@ -120,7 +121,7 @@
 // The Go and C compilers, and the assembler, call writeobj to write
 // out a Go object file. The linker does not call this; the linker
 // does not write out object files.
-func Writeobjdirect(ctxt *Link, b *Biobuf) {
+func Writeobjdirect(ctxt *Link, b *bio.Buf) {
 	Flushplist(ctxt)
 	WriteObjFile(ctxt, b)
 }
@@ -373,16 +374,16 @@
 	w.writeInt(int64(w.nFile))
 }
 
-func newObjWriter(ctxt *Link, b *Biobuf) *objWriter {
+func newObjWriter(ctxt *Link, b *bio.Buf) *objWriter {
 	return &objWriter{
 		ctxt:    ctxt,
-		wr:      b.w,
+		wr:      b.Writer(),
 		vrefIdx: make(map[string]int),
 		refIdx:  make(map[string]int),
 	}
 }
 
-func WriteObjFile(ctxt *Link, b *Biobuf) {
+func WriteObjFile(ctxt *Link, b *bio.Buf) {
 	w := newObjWriter(ctxt, b)
 
 	// Magic header
diff --git a/src/cmd/internal/obj/util.go b/src/cmd/internal/obj/util.go
index 245fab9..04e6a76 100644
--- a/src/cmd/internal/obj/util.go
+++ b/src/cmd/internal/obj/util.go
@@ -5,10 +5,8 @@
 package obj
 
 import (
-	"bufio"
 	"bytes"
 	"fmt"
-	"io"
 	"log"
 	"os"
 	"strings"
@@ -26,144 +24,6 @@
 	return time.Since(start).Seconds()
 }
 
-type Biobuf struct {
-	f       *os.File
-	r       *bufio.Reader
-	w       *bufio.Writer
-	linelen int
-}
-
-func (b *Biobuf) Reader() *bufio.Reader { return b.r }
-
-func Bopenw(name string) (*Biobuf, error) {
-	f, err := os.Create(name)
-	if err != nil {
-		return nil, err
-	}
-	return &Biobuf{f: f, w: bufio.NewWriter(f)}, nil
-}
-
-func Bopenr(name string) (*Biobuf, error) {
-	f, err := os.Open(name)
-	if err != nil {
-		return nil, err
-	}
-	return &Biobuf{f: f, r: bufio.NewReader(f)}, nil
-}
-
-func Binitw(w io.Writer) *Biobuf {
-	return &Biobuf{w: bufio.NewWriter(w)}
-}
-
-func Binitr(r io.Reader) *Biobuf {
-	return &Biobuf{r: bufio.NewReader(r)}
-}
-
-func (b *Biobuf) Write(p []byte) (int, error) {
-	return b.w.Write(p)
-}
-
-func Bwritestring(b *Biobuf, p string) (int, error) {
-	return b.w.WriteString(p)
-}
-
-func Bseek(b *Biobuf, offset int64, whence int) int64 {
-	if b.w != nil {
-		if err := b.w.Flush(); err != nil {
-			log.Fatalf("writing output: %v", err)
-		}
-	} else if b.r != nil {
-		if whence == 1 {
-			offset -= int64(b.r.Buffered())
-		}
-	}
-	off, err := b.f.Seek(offset, whence)
-	if err != nil {
-		log.Fatalf("seeking in output: %v", err)
-	}
-	if b.r != nil {
-		b.r.Reset(b.f)
-	}
-	return off
-}
-
-func Boffset(b *Biobuf) int64 {
-	if b.w != nil {
-		if err := b.w.Flush(); err != nil {
-			log.Fatalf("writing output: %v", err)
-		}
-	}
-	off, err := b.f.Seek(0, 1)
-	if err != nil {
-		log.Fatalf("seeking in output [0, 1]: %v", err)
-	}
-	if b.r != nil {
-		off -= int64(b.r.Buffered())
-	}
-	return off
-}
-
-func (b *Biobuf) Flush() error {
-	return b.w.Flush()
-}
-
-func Bputc(b *Biobuf, c byte) {
-	b.w.WriteByte(c)
-}
-
-const Beof = -1
-
-func Bread(b *Biobuf, p []byte) int {
-	n, err := io.ReadFull(b.r, p)
-	if n == 0 {
-		if err != nil && err != io.EOF {
-			n = -1
-		}
-	}
-	return n
-}
-
-func Bgetc(b *Biobuf) int {
-	c, err := b.r.ReadByte()
-	if err != nil {
-		return -1
-	}
-	return int(c)
-}
-
-func (b *Biobuf) Read(p []byte) (int, error) {
-	return b.r.Read(p)
-}
-
-func (b *Biobuf) Peek(n int) ([]byte, error) {
-	return b.r.Peek(n)
-}
-
-func Brdline(b *Biobuf, delim int) string {
-	s, err := b.r.ReadBytes(byte(delim))
-	if err != nil {
-		log.Fatalf("reading input: %v", err)
-	}
-	b.linelen = len(s)
-	return string(s)
-}
-
-func Blinelen(b *Biobuf) int {
-	return b.linelen
-}
-
-func Bterm(b *Biobuf) error {
-	var err error
-	if b.w != nil {
-		err = b.w.Flush()
-	}
-	err1 := b.f.Close()
-	if err == nil {
-		err = err1
-	}
-	return err
-}
-
 func envOr(key, value string) string {
 	if x := os.Getenv(key); x != "" {
 		return x
diff --git a/src/cmd/link/internal/ld/ar.go b/src/cmd/link/internal/ld/ar.go
index d077560..205773c 100644
--- a/src/cmd/link/internal/ld/ar.go
+++ b/src/cmd/link/internal/ld/ar.go
@@ -31,6 +31,7 @@
 package ld
 
 import (
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"encoding/binary"
 	"fmt"
@@ -62,7 +63,7 @@
 // define them. This is used for the compiler support library
 // libgcc.a.
 func hostArchive(name string) {
-	f, err := obj.Bopenr(name)
+	f, err := bio.Open(name)
 	if err != nil {
 		if os.IsNotExist(err) {
 			// It's OK if we don't have a libgcc file at all.
@@ -73,15 +74,15 @@
 		}
 		Exitf("cannot open file %s: %v", name, err)
 	}
-	defer obj.Bterm(f)
+	defer f.Close()
 
 	magbuf := make([]byte, len(ARMAG))
-	if obj.Bread(f, magbuf) != len(magbuf) {
+	if bio.Bread(f, magbuf) != len(magbuf) {
 		Exitf("file %s too short", name)
 	}
 
 	var arhdr ArHdr
-	l := nextar(f, obj.Boffset(f), &arhdr)
+	l := nextar(f, bio.Boffset(f), &arhdr)
 	if l <= 0 {
 		Exitf("%s missing armap", name)
 	}
@@ -117,7 +118,7 @@
 			l = atolwhex(arhdr.size)
 
 			h := ldobj(f, "libgcc", l, pname, name, ArchiveObj)
-			obj.Bseek(f, h.off, 0)
+			bio.Bseek(f, h.off, 0)
 			h.ld(f, h.pkg, h.length, h.pn)
 		}
 
@@ -130,7 +131,7 @@
 type archiveMap map[string]uint64
 
 // readArmap reads the archive symbol map.
-func readArmap(filename string, f *obj.Biobuf, arhdr ArHdr) archiveMap {
+func readArmap(filename string, f *bio.Buf, arhdr ArHdr) archiveMap {
 	is64 := arhdr.name == "/SYM64/"
 	wordSize := 4
 	if is64 {
@@ -139,7 +140,7 @@
 
 	l := atolwhex(arhdr.size)
 	contents := make([]byte, l)
-	if obj.Bread(f, contents) != int(l) {
+	if bio.Bread(f, contents) != int(l) {
 		Exitf("short read from %s", filename)
 	}
 
diff --git a/src/cmd/link/internal/ld/go.go b/src/cmd/link/internal/ld/go.go
index 027e05d..8bafaff 100644
--- a/src/cmd/link/internal/ld/go.go
+++ b/src/cmd/link/internal/ld/go.go
@@ -8,6 +8,7 @@
 
 import (
 	"bytes"
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"fmt"
 	"os"
@@ -26,7 +27,7 @@
 //	once the dust settles, try to move some code to
 //		libmach, so that other linkers and ar can share.
 
-func ldpkg(f *obj.Biobuf, pkg string, length int64, filename string, whence int) {
+func ldpkg(f *bio.Buf, pkg string, length int64, filename string, whence int) {
 	var p0, p1 int
 
 	if Debug['g'] != 0 {
@@ -48,7 +49,7 @@
 	}
 
 	bdata := make([]byte, length)
-	if int64(obj.Bread(f, bdata)) != length {
+	if int64(bio.Bread(f, bdata)) != length {
 		fmt.Fprintf(os.Stderr, "%s: short pkg read %s\n", os.Args[0], filename)
 		if Debug['u'] != 0 {
 			errorexit()
diff --git a/src/cmd/link/internal/ld/ldelf.go b/src/cmd/link/internal/ld/ldelf.go
index 485599b..eafc693 100644
--- a/src/cmd/link/internal/ld/ldelf.go
+++ b/src/cmd/link/internal/ld/ldelf.go
@@ -2,6 +2,7 @@
 
 import (
 	"bytes"
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"cmd/internal/sys"
 	"encoding/binary"
@@ -267,7 +268,7 @@
 }
 
 type ElfObj struct {
-	f         *obj.Biobuf
+	f         *bio.Buf
 	base      int64 // offset in f where ELF begins
 	length    int64 // length of ELF
 	is64      int
@@ -446,13 +447,13 @@
 	}
 }
 
-func ldelf(f *obj.Biobuf, pkg string, length int64, pn string) {
+func ldelf(f *bio.Buf, pkg string, length int64, pn string) {
 	if Debug['v'] != 0 {
 		fmt.Fprintf(&Bso, "%5.2f ldelf %s\n", obj.Cputime(), pn)
 	}
 
 	Ctxt.IncVersion()
-	base := int32(obj.Boffset(f))
+	base := int32(bio.Boffset(f))
 
 	var add uint64
 	var e binary.ByteOrder
@@ -475,7 +476,7 @@
 	var sect *ElfSect
 	var sym ElfSym
 	var symbols []*LSym
-	if obj.Bread(f, hdrbuf[:]) != len(hdrbuf) {
+	if bio.Bread(f, hdrbuf[:]) != len(hdrbuf) {
 		goto bad
 	}
 	hdr = new(ElfHdrBytes)
@@ -600,7 +601,7 @@
 
 	elfobj.nsect = uint(elfobj.shnum)
 	for i := 0; uint(i) < elfobj.nsect; i++ {
-		if obj.Bseek(f, int64(uint64(base)+elfobj.shoff+uint64(int64(i)*int64(elfobj.shentsize))), 0) < 0 {
+		if bio.Bseek(f, int64(uint64(base)+elfobj.shoff+uint64(int64(i)*int64(elfobj.shentsize))), 0) < 0 {
 			goto bad
 		}
 		sect = &elfobj.sect[i]
@@ -986,7 +987,7 @@
 
 	sect.base = make([]byte, sect.size)
 	err = fmt.Errorf("short read")
-	if obj.Bseek(elfobj.f, int64(uint64(elfobj.base)+sect.off), 0) < 0 || obj.Bread(elfobj.f, sect.base) != len(sect.base) {
+	if bio.Bseek(elfobj.f, int64(uint64(elfobj.base)+sect.off), 0) < 0 || bio.Bread(elfobj.f, sect.base) != len(sect.base) {
 		return err
 	}
 
diff --git a/src/cmd/link/internal/ld/ldmacho.go b/src/cmd/link/internal/ld/ldmacho.go
index 9fbb212..6376116 100644
--- a/src/cmd/link/internal/ld/ldmacho.go
+++ b/src/cmd/link/internal/ld/ldmacho.go
@@ -1,6 +1,7 @@
 package ld
 
 import (
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"cmd/internal/sys"
 	"encoding/binary"
@@ -42,7 +43,7 @@
 )
 
 type LdMachoObj struct {
-	f          *obj.Biobuf
+	f          *bio.Buf
 	base       int64 // off in f where Mach-O begins
 	length     int64 // length of Mach-O
 	is64       bool
@@ -298,7 +299,7 @@
 	rel := make([]LdMachoRel, sect.nreloc)
 	n := int(sect.nreloc * 8)
 	buf := make([]byte, n)
-	if obj.Bseek(m.f, m.base+int64(sect.reloff), 0) < 0 || obj.Bread(m.f, buf) != n {
+	if bio.Bseek(m.f, m.base+int64(sect.reloff), 0) < 0 || bio.Bread(m.f, buf) != n {
 		return -1
 	}
 	var p []byte
@@ -344,7 +345,7 @@
 	n := int(d.nindirectsyms)
 
 	p := make([]byte, n*4)
-	if obj.Bseek(m.f, m.base+int64(d.indirectsymoff), 0) < 0 || obj.Bread(m.f, p) != len(p) {
+	if bio.Bseek(m.f, m.base+int64(d.indirectsymoff), 0) < 0 || bio.Bread(m.f, p) != len(p) {
 		return -1
 	}
 
@@ -361,7 +362,7 @@
 	}
 
 	strbuf := make([]byte, symtab.strsize)
-	if obj.Bseek(m.f, m.base+int64(symtab.stroff), 0) < 0 || obj.Bread(m.f, strbuf) != len(strbuf) {
+	if bio.Bseek(m.f, m.base+int64(symtab.stroff), 0) < 0 || bio.Bread(m.f, strbuf) != len(strbuf) {
 		return -1
 	}
 
@@ -371,7 +372,7 @@
 	}
 	n := int(symtab.nsym * uint32(symsize))
 	symbuf := make([]byte, n)
-	if obj.Bseek(m.f, m.base+int64(symtab.symoff), 0) < 0 || obj.Bread(m.f, symbuf) != len(symbuf) {
+	if bio.Bseek(m.f, m.base+int64(symtab.symoff), 0) < 0 || bio.Bread(m.f, symbuf) != len(symbuf) {
 		return -1
 	}
 	sym := make([]LdMachoSym, symtab.nsym)
@@ -401,7 +402,7 @@
 	return 0
 }
 
-func ldmacho(f *obj.Biobuf, pkg string, length int64, pn string) {
+func ldmacho(f *bio.Buf, pkg string, length int64, pn string) {
 	var err error
 	var j int
 	var is64 bool
@@ -431,8 +432,8 @@
 	var name string
 
 	Ctxt.IncVersion()
-	base := obj.Boffset(f)
-	if obj.Bread(f, hdr[:]) != len(hdr) {
+	base := bio.Boffset(f)
+	if bio.Bread(f, hdr[:]) != len(hdr) {
 		goto bad
 	}
 
@@ -455,7 +456,7 @@
 
 	if is64 {
 		var tmp [4]uint8
-		obj.Bread(f, tmp[:4]) // skip reserved word in header
+		bio.Bread(f, tmp[:4]) // skip reserved word in header
 	}
 
 	m = new(LdMachoObj)
@@ -493,7 +494,7 @@
 	m.cmd = make([]LdMachoCmd, ncmd)
 	off = uint32(len(hdr))
 	cmdp = make([]byte, cmdsz)
-	if obj.Bread(f, cmdp) != len(cmdp) {
+	if bio.Bread(f, cmdp) != len(cmdp) {
 		err = fmt.Errorf("reading cmds: %v", err)
 		goto bad
 	}
@@ -556,7 +557,7 @@
 	}
 
 	dat = make([]byte, c.seg.filesz)
-	if obj.Bseek(f, m.base+int64(c.seg.fileoff), 0) < 0 || obj.Bread(f, dat) != len(dat) {
+	if bio.Bseek(f, m.base+int64(c.seg.fileoff), 0) < 0 || bio.Bread(f, dat) != len(dat) {
 		err = fmt.Errorf("cannot load object data: %v", err)
 		goto bad
 	}
diff --git a/src/cmd/link/internal/ld/ldpe.go b/src/cmd/link/internal/ld/ldpe.go
index ea0c482..e97e842 100644
--- a/src/cmd/link/internal/ld/ldpe.go
+++ b/src/cmd/link/internal/ld/ldpe.go
@@ -5,6 +5,7 @@
 package ld
 
 import (
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"cmd/internal/sys"
 	"encoding/binary"
@@ -117,7 +118,7 @@
 }
 
 type PeObj struct {
-	f      *obj.Biobuf
+	f      *bio.Buf
 	name   string
 	base   uint32
 	sect   []PeSect
@@ -128,14 +129,14 @@
 	snames []byte
 }
 
-func ldpe(f *obj.Biobuf, pkg string, length int64, pn string) {
+func ldpe(f *bio.Buf, pkg string, length int64, pn string) {
 	if Debug['v'] != 0 {
 		fmt.Fprintf(&Bso, "%5.2f ldpe %s\n", obj.Cputime(), pn)
 	}
 
 	var sect *PeSect
 	Ctxt.IncVersion()
-	base := int32(obj.Boffset(f))
+	base := int32(bio.Boffset(f))
 
 	peobj := new(PeObj)
 	peobj.f = f
@@ -173,15 +174,15 @@
 	// TODO return error if found .cormeta
 
 	// load string table
-	obj.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(peobj.fh.NumberOfSymbols), 0)
+	bio.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(peobj.fh.NumberOfSymbols), 0)
 
-	if obj.Bread(f, symbuf[:4]) != 4 {
+	if bio.Bread(f, symbuf[:4]) != 4 {
 		goto bad
 	}
 	l = Le32(symbuf[:])
 	peobj.snames = make([]byte, l)
-	obj.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(peobj.fh.NumberOfSymbols), 0)
-	if obj.Bread(f, peobj.snames) != len(peobj.snames) {
+	bio.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(peobj.fh.NumberOfSymbols), 0)
+	if bio.Bread(f, peobj.snames) != len(peobj.snames) {
 		goto bad
 	}
 
@@ -201,10 +202,10 @@
 	peobj.pesym = make([]PeSym, peobj.fh.NumberOfSymbols)
 
 	peobj.npesym = uint(peobj.fh.NumberOfSymbols)
-	obj.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable), 0)
+	bio.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable), 0)
 	for i := 0; uint32(i) < peobj.fh.NumberOfSymbols; i += numaux + 1 {
-		obj.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(i), 0)
-		if obj.Bread(f, symbuf[:]) != len(symbuf) {
+		bio.Bseek(f, int64(base)+int64(peobj.fh.PointerToSymbolTable)+int64(len(symbuf))*int64(i), 0)
+		if bio.Bread(f, symbuf[:]) != len(symbuf) {
 			goto bad
 		}
 
@@ -289,10 +290,10 @@
 		}
 
 		r = make([]Reloc, rsect.sh.NumberOfRelocations)
-		obj.Bseek(f, int64(peobj.base)+int64(rsect.sh.PointerToRelocations), 0)
+		bio.Bseek(f, int64(peobj.base)+int64(rsect.sh.PointerToRelocations), 0)
 		for j = 0; j < int(rsect.sh.NumberOfRelocations); j++ {
 			rp = &r[j]
-			if obj.Bread(f, symbuf[:10]) != 10 {
+			if bio.Bread(f, symbuf[:10]) != 10 {
 				goto bad
 			}
 			rva := Le32(symbuf[0:])
@@ -465,7 +466,7 @@
 	if sect.sh.PointerToRawData == 0 { // .bss doesn't have data in object file
 		return 0
 	}
-	if obj.Bseek(peobj.f, int64(peobj.base)+int64(sect.sh.PointerToRawData), 0) < 0 || obj.Bread(peobj.f, sect.base) != len(sect.base) {
+	if bio.Bseek(peobj.f, int64(peobj.base)+int64(sect.sh.PointerToRawData), 0) < 0 || bio.Bread(peobj.f, sect.base) != len(sect.base) {
 		return -1
 	}
 
diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 305a3bc..789eaef 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -33,6 +33,7 @@
 import (
 	"bufio"
 	"bytes"
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"cmd/internal/sys"
 	"crypto/sha1"
@@ -240,7 +241,7 @@
 var (
 	headstring string
 	// buffered output
-	Bso obj.Biobuf
+	Bso bio.Buf
 )
 
 type outBuf struct {
@@ -738,13 +739,13 @@
  * look for the next file in an archive.
  * adapted from libmach.
  */
-func nextar(bp *obj.Biobuf, off int64, a *ArHdr) int64 {
+func nextar(bp *bio.Buf, off int64, a *ArHdr) int64 {
 	if off&1 != 0 {
 		off++
 	}
-	obj.Bseek(bp, off, 0)
+	bio.Bseek(bp, off, 0)
 	buf := make([]byte, SAR_HDR)
-	if n := obj.Bread(bp, buf); n < len(buf) {
+	if n := bio.Bread(bp, buf); n < len(buf) {
 		if n >= 0 {
 			return 0
 		}
@@ -773,25 +774,25 @@
 		fmt.Fprintf(&Bso, "%5.2f ldobj: %s (%s)\n", obj.Cputime(), lib.File, pkg)
 	}
 	Bso.Flush()
-	f, err := obj.Bopenr(lib.File)
+	f, err := bio.Open(lib.File)
 	if err != nil {
 		Exitf("cannot open file %s: %v", lib.File, err)
 	}
 
 	magbuf := make([]byte, len(ARMAG))
-	if obj.Bread(f, magbuf) != len(magbuf) || !strings.HasPrefix(string(magbuf), ARMAG) {
+	if bio.Bread(f, magbuf) != len(magbuf) || !strings.HasPrefix(string(magbuf), ARMAG) {
 		/* load it as a regular file */
-		l := obj.Bseek(f, 0, 2)
+		l := bio.Bseek(f, 0, 2)
 
-		obj.Bseek(f, 0, 0)
+		bio.Bseek(f, 0, 0)
 		ldobj(f, pkg, l, lib.File, lib.File, FileObj)
-		obj.Bterm(f)
+		f.Close()
 
 		return
 	}
 
 	/* process __.PKGDEF */
-	off := obj.Boffset(f)
+	off := bio.Boffset(f)
 
 	var arhdr ArHdr
 	l := nextar(f, off, &arhdr)
@@ -807,12 +808,12 @@
 	}
 
 	if Buildmode == BuildmodeShared {
-		before := obj.Boffset(f)
+		before := bio.Boffset(f)
 		pkgdefBytes := make([]byte, atolwhex(arhdr.size))
-		obj.Bread(f, pkgdefBytes)
+		bio.Bread(f, pkgdefBytes)
 		hash := sha1.Sum(pkgdefBytes)
 		lib.hash = hash[:]
-		obj.Bseek(f, before, 0)
+		bio.Bseek(f, before, 0)
 	}
 
 	off += l
@@ -848,11 +849,11 @@
 	}
 
 out:
-	obj.Bterm(f)
+	f.Close()
 }
 
 type Hostobj struct {
-	ld     func(*obj.Biobuf, string, int64, string)
+	ld     func(*bio.Buf, string, int64, string)
 	pkg    string
 	pn     string
 	file   string
@@ -873,7 +874,7 @@
 	"runtime/msan",
 }
 
-func ldhostobj(ld func(*obj.Biobuf, string, int64, string), f *obj.Biobuf, pkg string, length int64, pn string, file string) *Hostobj {
+func ldhostobj(ld func(*bio.Buf, string, int64, string), f *bio.Buf, pkg string, length int64, pn string, file string) *Hostobj {
 	isinternal := false
 	for i := 0; i < len(internalpkg); i++ {
 		if pkg == internalpkg[i] {
@@ -904,26 +905,26 @@
 	h.pkg = pkg
 	h.pn = pn
 	h.file = file
-	h.off = obj.Boffset(f)
+	h.off = bio.Boffset(f)
 	h.length = length
 	return h
 }
 
 func hostobjs() {
-	var f *obj.Biobuf
+	var f *bio.Buf
 	var h *Hostobj
 
 	for i := 0; i < len(hostobj); i++ {
 		h = &hostobj[i]
 		var err error
-		f, err = obj.Bopenr(h.file)
+		f, err = bio.Open(h.file)
 		if f == nil {
 			Exitf("cannot reopen %s: %v", h.pn, err)
 		}
 
-		obj.Bseek(f, h.off, 0)
+		bio.Bseek(f, h.off, 0)
 		h.ld(f, h.pkg, h.length, h.pn)
-		obj.Bterm(f)
+		f.Close()
 	}
 }
 
@@ -1265,15 +1266,15 @@
 // ldobj loads an input object. If it is a host object (an object
 // compiled by a non-Go compiler) it returns the Hostobj pointer. If
 // it is a Go object, it returns nil.
-func ldobj(f *obj.Biobuf, pkg string, length int64, pn string, file string, whence int) *Hostobj {
-	eof := obj.Boffset(f) + length
+func ldobj(f *bio.Buf, pkg string, length int64, pn string, file string, whence int) *Hostobj {
+	eof := bio.Boffset(f) + length
 
-	start := obj.Boffset(f)
-	c1 := obj.Bgetc(f)
-	c2 := obj.Bgetc(f)
-	c3 := obj.Bgetc(f)
-	c4 := obj.Bgetc(f)
-	obj.Bseek(f, start, 0)
+	start := bio.Boffset(f)
+	c1 := bio.Bgetc(f)
+	c2 := bio.Bgetc(f)
+	c3 := bio.Bgetc(f)
+	c4 := bio.Bgetc(f)
+	bio.Bseek(f, start, 0)
 
 	magic := uint32(c1)<<24 | uint32(c2)<<16 | uint32(c3)<<8 | uint32(c4)
 	if magic == 0x7f454c46 { // \x7F E L F
@@ -1289,12 +1290,8 @@
 	}
 
 	/* check the header */
-	line := obj.Brdline(f, '\n')
+	line := bio.Brdline(f, '\n')
 	if line == "" {
-		if obj.Blinelen(f) > 0 {
-			Diag("%s: not an object file", pn)
-			return nil
-		}
 		Diag("truncated object file: %s", pn)
 		return nil
 	}
@@ -1337,28 +1334,28 @@
 	}
 
 	/* skip over exports and other info -- ends with \n!\n */
-	import0 := obj.Boffset(f)
+	import0 := bio.Boffset(f)
 
 	c1 = '\n' // the last line ended in \n
-	c2 = obj.Bgetc(f)
-	c3 = obj.Bgetc(f)
+	c2 = bio.Bgetc(f)
+	c3 = bio.Bgetc(f)
 	for c1 != '\n' || c2 != '!' || c3 != '\n' {
 		c1 = c2
 		c2 = c3
-		c3 = obj.Bgetc(f)
-		if c3 == obj.Beof {
+		c3 = bio.Bgetc(f)
+		if c3 == bio.EOF {
 			Diag("truncated object file: %s", pn)
 			return nil
 		}
 	}
 
-	import1 := obj.Boffset(f)
+	import1 := bio.Boffset(f)
 
-	obj.Bseek(f, import0, 0)
+	bio.Bseek(f, import0, 0)
 	ldpkg(f, pkg, import1-import0-2, pn, whence) // -2 for !\n
-	obj.Bseek(f, import1, 0)
+	bio.Bseek(f, import1, 0)
 
-	LoadObjFile(Ctxt, f, pkg, eof-obj.Boffset(f), pn)
+	LoadObjFile(Ctxt, f, pkg, eof-bio.Boffset(f), pn)
 	return nil
 }
 
diff --git a/src/cmd/link/internal/ld/link.go b/src/cmd/link/internal/ld/link.go
index f081138..d3f9ed3 100644
--- a/src/cmd/link/internal/ld/link.go
+++ b/src/cmd/link/internal/ld/link.go
@@ -31,7 +31,7 @@
 package ld
 
 import (
-	"cmd/internal/obj"
+	"cmd/internal/bio"
 	"cmd/internal/sys"
 	"debug/elf"
 	"fmt"
@@ -165,7 +165,7 @@
 	Headtype  int
 	Arch      *sys.Arch
 	Debugvlog int32
-	Bso       *obj.Biobuf
+	Bso       *bio.Buf
 	Windows   int32
 	Goroot    string
 
diff --git a/src/cmd/link/internal/ld/objfile.go b/src/cmd/link/internal/ld/objfile.go
index 8a406d1..6f17786 100644
--- a/src/cmd/link/internal/ld/objfile.go
+++ b/src/cmd/link/internal/ld/objfile.go
@@ -110,6 +110,7 @@
 import (
 	"bufio"
 	"bytes"
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"io"
 	"log"
@@ -146,8 +147,8 @@
 	file        []*LSym
 }
 
-func LoadObjFile(ctxt *Link, f *obj.Biobuf, pkg string, length int64, pn string) {
-	start := obj.Boffset(f)
+func LoadObjFile(ctxt *Link, f *bio.Buf, pkg string, length int64, pn string) {
+	start := bio.Boffset(f)
 	r := &objReader{
 		rd:     f.Reader(),
 		pkg:    pkg,
@@ -156,8 +157,8 @@
 		dupSym: &LSym{Name: ".dup"},
 	}
 	r.loadObjFile()
-	if obj.Boffset(f) != start+length {
-		log.Fatalf("%s: unexpected end at %d, want %d", pn, int64(obj.Boffset(f)), int64(start+length))
+	if bio.Boffset(f) != start+length {
+		log.Fatalf("%s: unexpected end at %d, want %d", pn, int64(bio.Boffset(f)), int64(start+length))
 	}
 }
 
diff --git a/src/cmd/link/internal/ld/pobj.go b/src/cmd/link/internal/ld/pobj.go
index b9902a5..bb48f13 100644
--- a/src/cmd/link/internal/ld/pobj.go
+++ b/src/cmd/link/internal/ld/pobj.go
@@ -31,6 +31,7 @@
 package ld
 
 import (
+	"cmd/internal/bio"
 	"cmd/internal/obj"
 	"cmd/internal/sys"
 	"flag"
@@ -49,7 +50,7 @@
 	Ctxt.Diag = Diag
 	Ctxt.Bso = &Bso
 
-	Bso = *obj.Binitw(os.Stdout)
+	Bso = *bio.BufWriter(os.Stdout)
 	Debug = [128]int{}
 	nerrors = 0
 	outfile = ""