From b2f94d3e88775fae4cf19d34c87a61efa814d079 Mon Sep 17 00:00:00 2001
From: Cherry Zhang <cherryyz@google.com>
Date: Wed, 3 Apr 2019 22:41:48 -0400
Subject: [PATCH] cmd/link: mmap output file
Use mmap for writing most of the output file content,
specifically, the sections and segments. After layout, we
already know the sizes and file offsets for the sections and
segments. So we can just write the bytes by copying to a mmap'd
backing store.
The writing of the output file is split into two parts. The first
part writes the sections and segments to the mmap'd region. The
second part writes some extra content, for which we don't know
the size, so we use direct file IO.
This is in preparation for mmap'ing input files read-only.
Change-Id: I9f3b4616a9f96bfd5c940d74c50aacd6d330f7d2
Reviewed-on: https://go-review.googlesource.com/c/go/+/170738
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
---
src/cmd/link/internal/amd64/asm.go | 2 ++
src/cmd/link/internal/amd64/obj.go | 1 +
src/cmd/link/internal/arm/asm.go | 2 ++
src/cmd/link/internal/arm/obj.go | 1 +
src/cmd/link/internal/arm64/asm.go | 2 ++
src/cmd/link/internal/arm64/obj.go | 1 +
src/cmd/link/internal/ld/data.go | 6 ++--
src/cmd/link/internal/ld/lib.go | 15 +++++---
src/cmd/link/internal/ld/main.go | 25 +++++++++++--
src/cmd/link/internal/ld/outbuf.go | 43 +++++++++++++++++++---
src/cmd/link/internal/ld/outbuf_mmap.go | 44 +++++++++++++++++++++++
src/cmd/link/internal/ld/outbuf_nommap.go | 15 ++++++++
src/cmd/link/internal/mips/asm.go | 2 ++
src/cmd/link/internal/mips/obj.go | 1 +
src/cmd/link/internal/mips64/asm.go | 2 ++
src/cmd/link/internal/mips64/obj.go | 1 +
src/cmd/link/internal/ppc64/asm.go | 2 ++
src/cmd/link/internal/ppc64/obj.go | 1 +
src/cmd/link/internal/s390x/asm.go | 2 ++
src/cmd/link/internal/s390x/obj.go | 3 +-
src/cmd/link/internal/wasm/asm.go | 4 ++-
src/cmd/link/internal/wasm/obj.go | 1 +
src/cmd/link/internal/x86/asm.go | 2 ++
src/cmd/link/internal/x86/obj.go | 1 +
24 files changed, 165 insertions(+), 14 deletions(-)
create mode 100644 src/cmd/link/internal/ld/outbuf_mmap.go
create mode 100644 src/cmd/link/internal/ld/outbuf_nommap.go
diff --git a/src/cmd/link/internal/amd64/asm.go b/src/cmd/link/internal/amd64/asm.go
index fca4877a45a..7dbe99c581d 100644
--- a/src/cmd/link/internal/amd64/asm.go
+++ b/src/cmd/link/internal/amd64/asm.go
@@ -704,7 +704,9 @@ func asmb(ctxt *ld.Link) {
ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+func asmb2(ctxt *ld.Link) {
machlink := int64(0)
if ctxt.HeadType == objabi.Hdarwin {
machlink = ld.Domacholink(ctxt)
diff --git a/src/cmd/link/internal/amd64/obj.go b/src/cmd/link/internal/amd64/obj.go
index eeeed1ab1a7..23741eb4f65 100644
--- a/src/cmd/link/internal/amd64/obj.go
+++ b/src/cmd/link/internal/amd64/obj.go
@@ -54,6 +54,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archreloc: archreloc,
Archrelocvariant: archrelocvariant,
Asmb: asmb,
+ Asmb2: asmb2,
Elfreloc1: elfreloc1,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
diff --git a/src/cmd/link/internal/arm/asm.go b/src/cmd/link/internal/arm/asm.go
index 7ea1fe5f8f9..43d387c862d 100644
--- a/src/cmd/link/internal/arm/asm.go
+++ b/src/cmd/link/internal/arm/asm.go
@@ -800,7 +800,9 @@ func asmb(ctxt *ld.Link) {
ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+func asmb2(ctxt *ld.Link) {
machlink := uint32(0)
if ctxt.HeadType == objabi.Hdarwin {
machlink = uint32(ld.Domacholink(ctxt))
diff --git a/src/cmd/link/internal/arm/obj.go b/src/cmd/link/internal/arm/obj.go
index ea91711df01..45a406ec063 100644
--- a/src/cmd/link/internal/arm/obj.go
+++ b/src/cmd/link/internal/arm/obj.go
@@ -52,6 +52,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archrelocvariant: archrelocvariant,
Trampoline: trampoline,
Asmb: asmb,
+ Asmb2: asmb2,
Elfreloc1: elfreloc1,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
diff --git a/src/cmd/link/internal/arm64/asm.go b/src/cmd/link/internal/arm64/asm.go
index 5ba038d1477..c8320997268 100644
--- a/src/cmd/link/internal/arm64/asm.go
+++ b/src/cmd/link/internal/arm64/asm.go
@@ -426,7 +426,9 @@ func asmb(ctxt *ld.Link) {
ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+func asmb2(ctxt *ld.Link) {
machlink := uint32(0)
if ctxt.HeadType == objabi.Hdarwin {
machlink = uint32(ld.Domacholink(ctxt))
diff --git a/src/cmd/link/internal/arm64/obj.go b/src/cmd/link/internal/arm64/obj.go
index 04202012ee2..2f8a1411390 100644
--- a/src/cmd/link/internal/arm64/obj.go
+++ b/src/cmd/link/internal/arm64/obj.go
@@ -51,6 +51,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archreloc: archreloc,
Archrelocvariant: archrelocvariant,
Asmb: asmb,
+ Asmb2: asmb2,
Elfreloc1: elfreloc1,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
diff --git a/src/cmd/link/internal/ld/data.go b/src/cmd/link/internal/ld/data.go
index cb74b9a723d..a6f75b74e1f 100644
--- a/src/cmd/link/internal/ld/data.go
+++ b/src/cmd/link/internal/ld/data.go
@@ -792,6 +792,7 @@ func Datblk(ctxt *Link, addr int64, size int64) {
writeDatblkToOutBuf(ctxt, ctxt.Out, addr, size)
}
+// Used only on Wasm for now.
func DatblkBytes(ctxt *Link, addr int64, size int64) []byte {
buf := bytes.NewBuffer(make([]byte, 0, size))
out := &OutBuf{w: bufio.NewWriter(buf)}
@@ -2319,7 +2320,8 @@ func (ctxt *Link) address() []*sym.Segment {
}
// layout assigns file offsets and lengths to the segments in order.
-func (ctxt *Link) layout(order []*sym.Segment) {
+// Returns the file size containing all the segments.
+func (ctxt *Link) layout(order []*sym.Segment) uint64 {
var prev *sym.Segment
for _, seg := range order {
if prev == nil {
@@ -2348,7 +2350,7 @@ func (ctxt *Link) layout(order []*sym.Segment) {
}
prev = seg
}
-
+ return prev.Fileoff + prev.Filelen
}
// add a trampoline with symbol s (to be laid down after the current function)
diff --git a/src/cmd/link/internal/ld/lib.go b/src/cmd/link/internal/ld/lib.go
index 62f24533584..c4748781911 100644
--- a/src/cmd/link/internal/ld/lib.go
+++ b/src/cmd/link/internal/ld/lib.go
@@ -127,8 +127,15 @@ type Arch struct {
// offset value.
Archrelocvariant func(link *Link, rel *sym.Reloc, sym *sym.Symbol,
offset int64) (relocatedOffset int64)
- Trampoline func(*Link, *sym.Reloc, *sym.Symbol)
- Asmb func(*Link)
+ Trampoline func(*Link, *sym.Reloc, *sym.Symbol)
+
+ // Asmb and Asmb2 are arch-specific routines that write the output
+ // file. Typically, Asmb writes most of the content (sections and
+ // segments), for which we have computed the size and offset. Asmb2
+ // writes the rest.
+ Asmb func(*Link)
+ Asmb2 func(*Link)
+
Elfreloc1 func(*Link, *sym.Reloc, int64) bool
Elfsetupplt func(*Link)
Gentext func(*Link)
@@ -261,7 +268,7 @@ func libinit(ctxt *Link) {
Lflag(ctxt, filepath.Join(objabi.GOROOT, "pkg", fmt.Sprintf("%s_%s%s%s", objabi.GOOS, objabi.GOARCH, suffixsep, suffix)))
mayberemoveoutfile()
- f, err := os.OpenFile(*flagOutfile, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0775)
+ f, err := os.OpenFile(*flagOutfile, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0775)
if err != nil {
Exitf("cannot create %s: %v", *flagOutfile, err)
}
@@ -1014,7 +1021,7 @@ func hostlinksetup(ctxt *Link) {
p := filepath.Join(*flagTmpdir, "go.o")
var err error
- f, err := os.OpenFile(p, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0775)
+ f, err := os.OpenFile(p, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0775)
if err != nil {
Exitf("cannot create %s: %v", p, err)
}
diff --git a/src/cmd/link/internal/ld/main.go b/src/cmd/link/internal/ld/main.go
index 48a99538937..1b2d376fd4a 100644
--- a/src/cmd/link/internal/ld/main.go
+++ b/src/cmd/link/internal/ld/main.go
@@ -241,8 +241,29 @@ func Main(arch *sys.Arch, theArch Arch) {
order := ctxt.address()
ctxt.reloc()
dwarfcompress(ctxt)
- ctxt.layout(order)
- thearch.Asmb(ctxt)
+ filesize := ctxt.layout(order)
+
+ // Write out the output file.
+ // It is split into two parts (Asmb and Asmb2). The first
+ // part writes most of the content (sections and segments),
+ // for which we have computed the size and offset, in a
+ // mmap'd region. The second part writes more content, for
+ // which we don't know the size.
+ var outputMmapped bool
+ if ctxt.Arch.Family != sys.Wasm {
+ // Don't mmap if we're building for Wasm. Wasm file
+ // layout is very different so filesize is meaningless.
+ err := ctxt.Out.Mmap(filesize)
+ outputMmapped = err == nil
+ }
+ if outputMmapped {
+ thearch.Asmb(ctxt)
+ ctxt.Out.Munmap()
+ } else {
+ thearch.Asmb(ctxt)
+ }
+ thearch.Asmb2(ctxt)
+
ctxt.undef()
ctxt.hostlink()
ctxt.archive()
diff --git a/src/cmd/link/internal/ld/outbuf.go b/src/cmd/link/internal/ld/outbuf.go
index 5df2be43014..f1b5d7495c5 100644
--- a/src/cmd/link/internal/ld/outbuf.go
+++ b/src/cmd/link/internal/ld/outbuf.go
@@ -8,6 +8,7 @@ import (
"bufio"
"cmd/internal/sys"
"encoding/binary"
+ "log"
"os"
)
@@ -20,10 +21,18 @@ import (
//
// Second, it provides a very cheap offset counter that doesn't require
// any system calls to read the value.
+//
+// It also mmaps the output file (if available). The intended usage is:
+// - Mmap the output file
+// - Write the content
+// - possibly apply any edits in the output buffer
+// - Munmap the output file
+// - possibly write more content to the file, which will not be edited later.
type OutBuf struct {
arch *sys.Arch
off int64
w *bufio.Writer
+ buf []byte // backing store of mmap'd output file
f *os.File
encbuf [8]byte // temp buffer used by WriteN methods
}
@@ -32,9 +41,11 @@ func (out *OutBuf) SeekSet(p int64) {
if p == out.off {
return
}
- out.Flush()
- if _, err := out.f.Seek(p, 0); err != nil {
- Exitf("seeking to %d in %s: %v", p, out.f.Name(), err)
+ if out.buf == nil {
+ out.Flush()
+ if _, err := out.f.Seek(p, 0); err != nil {
+ Exitf("seeking to %d in %s: %v", p, out.f.Name(), err)
+ }
}
out.off = p
}
@@ -49,12 +60,22 @@ func (out *OutBuf) Offset() int64 {
// to explicitly handle the returned error as long as Flush is
// eventually called.
func (out *OutBuf) Write(v []byte) (int, error) {
+ if out.buf != nil {
+ n := copy(out.buf[out.off:], v)
+ out.off += int64(n)
+ return n, nil
+ }
n, err := out.w.Write(v)
out.off += int64(n)
return n, err
}
func (out *OutBuf) Write8(v uint8) {
+ if out.buf != nil {
+ out.buf[out.off] = v
+ out.off++
+ return
+ }
if err := out.w.WriteByte(v); err == nil {
out.off++
}
@@ -92,6 +113,14 @@ func (out *OutBuf) Write64b(v uint64) {
}
func (out *OutBuf) WriteString(s string) {
+ if out.buf != nil {
+ n := copy(out.buf[out.off:], s)
+ if n != len(s) {
+ log.Fatalf("WriteString truncated. buffer size: %d, offset: %d, len(s)=%d", len(out.buf), out.off, len(s))
+ }
+ out.off += int64(n)
+ return
+ }
n, _ := out.w.WriteString(s)
out.off += int64(n)
}
@@ -120,7 +149,13 @@ func (out *OutBuf) WriteStringPad(s string, n int, pad []byte) {
}
func (out *OutBuf) Flush() {
- if err := out.w.Flush(); err != nil {
+ var err error
+ if out.buf != nil {
+ err = out.Msync()
+ } else {
+ err = out.w.Flush()
+ }
+ if err != nil {
Exitf("flushing %s: %v", out.f.Name(), err)
}
}
diff --git a/src/cmd/link/internal/ld/outbuf_mmap.go b/src/cmd/link/internal/ld/outbuf_mmap.go
new file mode 100644
index 00000000000..4075141171d
--- /dev/null
+++ b/src/cmd/link/internal/ld/outbuf_mmap.go
@@ -0,0 +1,44 @@
+// 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 darwin dragonfly freebsd linux openbsd
+
+package ld
+
+import (
+ "syscall"
+ "unsafe"
+)
+
+func (out *OutBuf) Mmap(filesize uint64) error {
+ err := out.f.Truncate(int64(filesize))
+ if err != nil {
+ Exitf("resize output file failed: %v", err)
+ }
+ out.buf, err = syscall.Mmap(int(out.f.Fd()), 0, int(filesize), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED|syscall.MAP_FILE)
+ return err
+}
+
+func (out *OutBuf) Munmap() {
+ err := out.Msync()
+ if err != nil {
+ Exitf("msync output file failed: %v", err)
+ }
+ syscall.Munmap(out.buf)
+ out.buf = nil
+ _, err = out.f.Seek(out.off, 0)
+ if err != nil {
+ Exitf("seek output file failed: %v", err)
+ }
+}
+
+func (out *OutBuf) Msync() error {
+ // TODO: netbsd supports mmap and msync, but the syscall package doesn't define MSYNC.
+ // It is excluded from the build tag for now.
+ _, _, errno := syscall.Syscall(syscall.SYS_MSYNC, uintptr(unsafe.Pointer(&out.buf[0])), uintptr(len(out.buf)), syscall.MS_SYNC)
+ if errno != 0 {
+ return errno
+ }
+ return nil
+}
diff --git a/src/cmd/link/internal/ld/outbuf_nommap.go b/src/cmd/link/internal/ld/outbuf_nommap.go
new file mode 100644
index 00000000000..36a32860992
--- /dev/null
+++ b/src/cmd/link/internal/ld/outbuf_nommap.go
@@ -0,0 +1,15 @@
+// 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 !darwin,!dragonfly,!freebsd,!linux,!openbsd
+
+package ld
+
+import "errors"
+
+var errNotSupported = errors.New("mmap not supported")
+
+func (out *OutBuf) Mmap(filesize uint64) error { return errNotSupported }
+func (out *OutBuf) Munmap() { panic("unreachable") }
+func (out *OutBuf) Msync() error { panic("unreachable") }
diff --git a/src/cmd/link/internal/mips/asm.go b/src/cmd/link/internal/mips/asm.go
index 8409e43afcb..f05455e5200 100644
--- a/src/cmd/link/internal/mips/asm.go
+++ b/src/cmd/link/internal/mips/asm.go
@@ -197,7 +197,9 @@ func asmb(ctxt *ld.Link) {
ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+func asmb2(ctxt *ld.Link) {
/* output symbol table */
ld.Symsize = 0
diff --git a/src/cmd/link/internal/mips/obj.go b/src/cmd/link/internal/mips/obj.go
index 3c71e23497e..231e1ff322a 100644
--- a/src/cmd/link/internal/mips/obj.go
+++ b/src/cmd/link/internal/mips/obj.go
@@ -54,6 +54,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archreloc: archreloc,
Archrelocvariant: archrelocvariant,
Asmb: asmb,
+ Asmb2: asmb2,
Elfreloc1: elfreloc1,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
diff --git a/src/cmd/link/internal/mips64/asm.go b/src/cmd/link/internal/mips64/asm.go
index 51eba596dc7..25a1d94dcc0 100644
--- a/src/cmd/link/internal/mips64/asm.go
+++ b/src/cmd/link/internal/mips64/asm.go
@@ -209,7 +209,9 @@ func asmb(ctxt *ld.Link) {
ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+func asmb2(ctxt *ld.Link) {
/* output symbol table */
ld.Symsize = 0
diff --git a/src/cmd/link/internal/mips64/obj.go b/src/cmd/link/internal/mips64/obj.go
index b01746e59ac..96042083f6f 100644
--- a/src/cmd/link/internal/mips64/obj.go
+++ b/src/cmd/link/internal/mips64/obj.go
@@ -53,6 +53,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archreloc: archreloc,
Archrelocvariant: archrelocvariant,
Asmb: asmb,
+ Asmb2: asmb2,
Elfreloc1: elfreloc1,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
diff --git a/src/cmd/link/internal/ppc64/asm.go b/src/cmd/link/internal/ppc64/asm.go
index d376c4de587..365a45ec135 100644
--- a/src/cmd/link/internal/ppc64/asm.go
+++ b/src/cmd/link/internal/ppc64/asm.go
@@ -1103,7 +1103,9 @@ func asmb(ctxt *ld.Link) {
ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+func asmb2(ctxt *ld.Link) {
/* output symbol table */
ld.Symsize = 0
diff --git a/src/cmd/link/internal/ppc64/obj.go b/src/cmd/link/internal/ppc64/obj.go
index bd85856c97c..51d1791f21a 100644
--- a/src/cmd/link/internal/ppc64/obj.go
+++ b/src/cmd/link/internal/ppc64/obj.go
@@ -54,6 +54,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archreloc: archreloc,
Archrelocvariant: archrelocvariant,
Asmb: asmb,
+ Asmb2: asmb2,
Elfreloc1: elfreloc1,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
diff --git a/src/cmd/link/internal/s390x/asm.go b/src/cmd/link/internal/s390x/asm.go
index 46a6ffef828..85403774004 100644
--- a/src/cmd/link/internal/s390x/asm.go
+++ b/src/cmd/link/internal/s390x/asm.go
@@ -540,7 +540,9 @@ func asmb(ctxt *ld.Link) {
ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+func asmb2(ctxt *ld.Link) {
/* output symbol table */
ld.Symsize = 0
diff --git a/src/cmd/link/internal/s390x/obj.go b/src/cmd/link/internal/s390x/obj.go
index a7e30e2d657..3454476b0f6 100644
--- a/src/cmd/link/internal/s390x/obj.go
+++ b/src/cmd/link/internal/s390x/obj.go
@@ -50,7 +50,8 @@ func Init() (*sys.Arch, ld.Arch) {
Archinit: archinit,
Archreloc: archreloc,
Archrelocvariant: archrelocvariant,
- Asmb: asmb, // in asm.go
+ Asmb: asmb, // in asm.go
+ Asmb2: asmb2, // in asm.go
Elfreloc1: elfreloc1,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
diff --git a/src/cmd/link/internal/wasm/asm.go b/src/cmd/link/internal/wasm/asm.go
index ea6b406c7e2..8ab58b200f3 100644
--- a/src/cmd/link/internal/wasm/asm.go
+++ b/src/cmd/link/internal/wasm/asm.go
@@ -92,9 +92,11 @@ func assignAddress(ctxt *ld.Link, sect *sym.Section, n int, s *sym.Symbol, va ui
return sect, n, va
}
+func asmb(ctxt *ld.Link) {} // dummy
+
// asmb writes the final WebAssembly module binary.
// Spec: https://webassembly.github.io/spec/core/binary/modules.html
-func asmb(ctxt *ld.Link) {
+func asmb2(ctxt *ld.Link) {
if ctxt.Debugvlog != 0 {
ctxt.Logf("%5.2f asmb\n", ld.Cputime())
}
diff --git a/src/cmd/link/internal/wasm/obj.go b/src/cmd/link/internal/wasm/obj.go
index 55f34e335b6..f8090a3551c 100644
--- a/src/cmd/link/internal/wasm/obj.go
+++ b/src/cmd/link/internal/wasm/obj.go
@@ -18,6 +18,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archinit: archinit,
AssignAddress: assignAddress,
Asmb: asmb,
+ Asmb2: asmb2,
Gentext: gentext,
}
diff --git a/src/cmd/link/internal/x86/asm.go b/src/cmd/link/internal/x86/asm.go
index 9472f5516d0..427ccaf6297 100644
--- a/src/cmd/link/internal/x86/asm.go
+++ b/src/cmd/link/internal/x86/asm.go
@@ -662,7 +662,9 @@ func asmb(ctxt *ld.Link) {
ctxt.Out.SeekSet(int64(ld.Segdwarf.Fileoff))
ld.Dwarfblk(ctxt, int64(ld.Segdwarf.Vaddr), int64(ld.Segdwarf.Filelen))
+}
+func asmb2(ctxt *ld.Link) {
machlink := uint32(0)
if ctxt.HeadType == objabi.Hdarwin {
machlink = uint32(ld.Domacholink(ctxt))
diff --git a/src/cmd/link/internal/x86/obj.go b/src/cmd/link/internal/x86/obj.go
index dbb31263a89..f1fad20081b 100644
--- a/src/cmd/link/internal/x86/obj.go
+++ b/src/cmd/link/internal/x86/obj.go
@@ -51,6 +51,7 @@ func Init() (*sys.Arch, ld.Arch) {
Archreloc: archreloc,
Archrelocvariant: archrelocvariant,
Asmb: asmb,
+ Asmb2: asmb2,
Elfreloc1: elfreloc1,
Elfsetupplt: elfsetupplt,
Gentext: gentext,
--
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