cmd/internal/obj/x86: fix relocation offset for VEX encoded instructions

VEX encoded instructions don't have a REX byte, so for PC relative
addressing we don't need to recalculate relocation offset.

Fixes #19518

Change-Id: Icf5414962de4350d76fd220817498337f90614fc
Reviewed-on: https://go-review.googlesource.com/38138
Run-TryBot: Ilya Tocar <ilya.tocar@intel.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/internal/obj/x86/asm6.go b/src/cmd/internal/obj/x86/asm6.go
index cee1a6516dc42559fc892847916eefcecb0abfa6..721768a18585af809d2fd7b4b031036f3802ad30 100644 (file)
--- a/src/cmd/internal/obj/x86/asm6.go
+++ b/src/cmd/internal/obj/x86/asm6.go
@@ -4565,7 +4565,7 @@ func (asmbuf *AsmBuf) asmins(ctxt *obj.Link, cursym *obj.LSym, p *obj.Prog) {
                if int64(r.Off) < p.Pc {
                        break
                }
-               if asmbuf.rexflag != 0 {
+               if asmbuf.rexflag != 0 && asmbuf.vexflag == 0 {
                        r.Off++
                }
                if r.Type == objabi.R_PCREL {

diff --git a/src/cmd/internal/obj/x86/issue19518_test.go b/src/cmd/internal/obj/x86/issue19518_test.go
new file mode 100644 (file)
index 0000000..2fe227e
--- /dev/null
+++ b/src/cmd/internal/obj/x86/issue19518_test.go
@@ -0,0 +1,110 @@
+// Copyright 2017 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 x86_test
+
+import (
+       "bytes"
+       "internal/testenv"
+       "io/ioutil"
+       "os"
+       "os/exec"
+       "path/filepath"
+       "strings"
+       "testing"
+)
+
+const asmData = `
+GLOBL zeros<>(SB),8,$64
+TEXT ·testASM(SB),4,$0
+VMOVDQU zeros<>(SB), Y8 // PC relative relocation is off by 1, for Y8-15
+RET
+`
+
+const goData = `
+package main
+
+func testASM()
+
+func main() {
+       testASM()
+}
+`
+
+func objdumpOutput(t *testing.T) []byte {
+       cwd, err := os.Getwd()
+       if err != nil {
+               t.Fatal(err)
+       }
+       tmpdir, err := ioutil.TempDir("", "19518")
+       if err != nil {
+               t.Fatal(err)
+       }
+       defer os.RemoveAll(tmpdir)
+       tmpfile, err := os.Create(filepath.Join(tmpdir, "input.s"))
+       if err != nil {
+               t.Fatal(err)
+       }
+       defer tmpfile.Close()
+       _, err = tmpfile.WriteString(asmData)
+       if err != nil {
+               t.Fatal(err)
+       }
+       tmpfile2, err := os.Create(filepath.Join(tmpdir, "input.go"))
+       if err != nil {
+               t.Fatal(err)
+       }
+       defer tmpfile2.Close()
+       _, err = tmpfile2.WriteString(goData)
+       if err != nil {
+               t.Fatal(err)
+       }
+       err = os.Chdir(tmpdir)
+       if err != nil {
+               t.Fatal(err)
+       }
+       cmd := exec.Command(
+               testenv.GoToolPath(t), "build", "-o",
+               filepath.Join(tmpdir, "output"))
+
+       var env []string
+       for _, v := range os.Environ() {
+               if !strings.HasPrefix(v, "GOARCH=") {
+                       env = append(env, v)
+               }
+       }
+       cmd.Env = append(env, "GOARCH=amd64")
+       out, err := cmd.CombinedOutput()
+       if err != nil {
+               t.Fatalf("error %s output %s", err, out)
+       }
+       cmd2 := exec.Command(
+               testenv.GoToolPath(t), "tool", "objdump", "-s", "testASM",
+               filepath.Join(tmpdir, "output"))
+       cmd2.Env = cmd.Env
+       objout, err := cmd2.CombinedOutput()
+       if err != nil {
+               t.Fatalf("error %s output %s", err, objout)
+       }
+       err = os.Chdir(cwd)
+       if err != nil {
+               t.Fatal(err)
+       }
+       return objout
+}
+
+func TestVexPCrelative(t *testing.T) {
+       testenv.MustHaveGoBuild(t)
+       objout := objdumpOutput(t)
+       data := bytes.Split(objout, []byte("\n"))
+       for idx := len(data) - 1; idx >= 0; idx-- {
+               // OBJDUMP doesn't know about VMOVDQU,
+               // so instead of checking that it was assembled correctly,
+               // check that RET wasn't overwritten.
+               if bytes.Index(data[idx], []byte("RET")) != -1 {
+                       return
+               }
+       }
+       t.Fatal("RET was overwritten")
+}