src/cmd/link/elf_test.go - go - Git at Google

 // 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.

 //go:build dragonfly || freebsd || linux || netbsd || openbsd
 // +build dragonfly freebsd linux netbsd openbsd

 package main

 import (
 	"cmd/internal/sys"
 	"debug/elf"
 	"fmt"
 	"internal/testenv"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
 	"runtime"
 	"strings"
 	"sync"
 	"testing"
 	"text/template"
 )

 func getCCAndCCFLAGS(t *testing.T, env []string) (string, []string) {
 	goTool := testenv.GoToolPath(t)
 	cmd := exec.Command(goTool, "env", "CC")
 	cmd.Env = env
 	ccb, err := cmd.Output()
 	if err != nil {
 		t.Fatal(err)
 	}
 	cc := strings.TrimSpace(string(ccb))

 	cmd = exec.Command(goTool, "env", "GOGCCFLAGS")
 	cmd.Env = env
 	cflagsb, err := cmd.Output()
 	if err != nil {
 		t.Fatal(err)
 	}
 	cflags := strings.Fields(string(cflagsb))

 	return cc, cflags
 }

 var asmSource = `
 	.section .text1,"ax"
 s1:
 	.byte 0
 	.section .text2,"ax"
 s2:
 	.byte 0
 `

 var goSource = `
 package main
 func main() {}
 `

 // The linker used to crash if an ELF input file had multiple text sections
 // with the same name.
 func TestSectionsWithSameName(t *testing.T) {
 	testenv.MustHaveGoBuild(t)
 	testenv.MustHaveCGO(t)
 	t.Parallel()

 	objcopy, err := exec.LookPath("objcopy")
 	if err != nil {
 		t.Skipf("can't find objcopy: %v", err)
 	}

 	dir := t.TempDir()

 	gopath := filepath.Join(dir, "GOPATH")
 	env := append(os.Environ(), "GOPATH="+gopath)

 	if err := ioutil.WriteFile(filepath.Join(dir, "go.mod"), []byte("module elf_test\n"), 0666); err != nil {
 		t.Fatal(err)
 	}

 	asmFile := filepath.Join(dir, "x.s")
 	if err := ioutil.WriteFile(asmFile, []byte(asmSource), 0444); err != nil {
 		t.Fatal(err)
 	}

 	goTool := testenv.GoToolPath(t)
 	cc, cflags := getCCAndCCFLAGS(t, env)

 	asmObj := filepath.Join(dir, "x.o")
 	t.Logf("%s %v -c -o %s %s", cc, cflags, asmObj, asmFile)
 	if out, err := exec.Command(cc, append(cflags, "-c", "-o", asmObj, asmFile)...).CombinedOutput(); err != nil {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}

 	asm2Obj := filepath.Join(dir, "x2.syso")
 	t.Logf("%s --rename-section .text2=.text1 %s %s", objcopy, asmObj, asm2Obj)
 	if out, err := exec.Command(objcopy, "--rename-section", ".text2=.text1", asmObj, asm2Obj).CombinedOutput(); err != nil {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}

 	for _, s := range []string{asmFile, asmObj} {
 		if err := os.Remove(s); err != nil {
 			t.Fatal(err)
 		}
 	}

 	goFile := filepath.Join(dir, "main.go")
 	if err := ioutil.WriteFile(goFile, []byte(goSource), 0444); err != nil {
 		t.Fatal(err)
 	}

 	cmd := exec.Command(goTool, "build")
 	cmd.Dir = dir
 	cmd.Env = env
 	t.Logf("%s build", goTool)
 	if out, err := cmd.CombinedOutput(); err != nil {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}
 }

 var cSources35779 = []string{`
 static int blah() { return 42; }
 int Cfunc1() { return blah(); }
 `, `
 static int blah() { return 42; }
 int Cfunc2() { return blah(); }
 `,
 }

 // TestMinusRSymsWithSameName tests a corner case in the new
 // loader. Prior to the fix this failed with the error 'loadelf:
 // $WORK/b001/_pkg_.a(ldr.syso): duplicate symbol reference: blah in
 // both main(.text) and main(.text)'. See issue #35779.
 func TestMinusRSymsWithSameName(t *testing.T) {
 	testenv.MustHaveGoBuild(t)
 	testenv.MustHaveCGO(t)
 	t.Parallel()

 	dir := t.TempDir()

 	gopath := filepath.Join(dir, "GOPATH")
 	env := append(os.Environ(), "GOPATH="+gopath)

 	if err := ioutil.WriteFile(filepath.Join(dir, "go.mod"), []byte("module elf_test\n"), 0666); err != nil {
 		t.Fatal(err)
 	}

 	goTool := testenv.GoToolPath(t)
 	cc, cflags := getCCAndCCFLAGS(t, env)

 	objs := []string{}
 	csrcs := []string{}
 	for i, content := range cSources35779 {
 		csrcFile := filepath.Join(dir, fmt.Sprintf("x%d.c", i))
 		csrcs = append(csrcs, csrcFile)
 		if err := ioutil.WriteFile(csrcFile, []byte(content), 0444); err != nil {
 			t.Fatal(err)
 		}

 		obj := filepath.Join(dir, fmt.Sprintf("x%d.o", i))
 		objs = append(objs, obj)
 		t.Logf("%s %v -c -o %s %s", cc, cflags, obj, csrcFile)
 		if out, err := exec.Command(cc, append(cflags, "-c", "-o", obj, csrcFile)...).CombinedOutput(); err != nil {
 			t.Logf("%s", out)
 			t.Fatal(err)
 		}
 	}

 	sysoObj := filepath.Join(dir, "ldr.syso")
 	t.Logf("%s %v -nostdlib -r -o %s %v", cc, cflags, sysoObj, objs)
 	if out, err := exec.Command(cc, append(cflags, "-nostdlib", "-r", "-o", sysoObj, objs[0], objs[1])...).CombinedOutput(); err != nil {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}

 	cruft := [][]string{objs, csrcs}
 	for _, sl := range cruft {
 		for _, s := range sl {
 			if err := os.Remove(s); err != nil {
 				t.Fatal(err)
 			}
 		}
 	}

 	goFile := filepath.Join(dir, "main.go")
 	if err := ioutil.WriteFile(goFile, []byte(goSource), 0444); err != nil {
 		t.Fatal(err)
 	}

 	t.Logf("%s build", goTool)
 	cmd := exec.Command(goTool, "build")
 	cmd.Dir = dir
 	cmd.Env = env
 	if out, err := cmd.CombinedOutput(); err != nil {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}
 }

 func TestMergeNoteSections(t *testing.T) {
 	testenv.MustHaveGoBuild(t)
 	expected := 1

 	switch runtime.GOOS {
 	case "linux", "freebsd", "dragonfly":
 	case "openbsd", "netbsd":
 		// These OSes require independent segment
 		expected = 2
 	default:
 		t.Skip("We should only test on elf output.")
 	}
 	t.Parallel()

 	goFile := filepath.Join(t.TempDir(), "notes.go")
 	if err := ioutil.WriteFile(goFile, []byte(goSource), 0444); err != nil {
 		t.Fatal(err)
 	}
 	outFile := filepath.Join(t.TempDir(), "notes.exe")
 	goTool := testenv.GoToolPath(t)
 	// sha1sum of "gopher"
 	id := "0xf4e8cd51ce8bae2996dc3b74639cdeaa1f7fee5f"
 	cmd := exec.Command(goTool, "build", "-o", outFile, "-ldflags",
 		"-B "+id, goFile)
 	cmd.Dir = t.TempDir()
 	if out, err := cmd.CombinedOutput(); err != nil {
 		t.Logf("%s", out)
 		t.Fatal(err)
 	}

 	ef, err := elf.Open(outFile)
 	if err != nil {
 		t.Fatalf("open elf file failed:%v", err)
 	}
 	defer ef.Close()
 	sec := ef.Section(".note.gnu.build-id")
 	if sec == nil {
 		t.Fatalf("can't find gnu build id")
 	}

 	sec = ef.Section(".note.go.buildid")
 	if sec == nil {
 		t.Fatalf("can't find go build id")
 	}
 	cnt := 0
 	for _, ph := range ef.Progs {
 		if ph.Type == elf.PT_NOTE {
 			cnt += 1
 		}
 	}
 	if cnt != expected {
 		t.Fatalf("want %d PT_NOTE segment, got %d", expected, cnt)
 	}
 }

 const pieSourceTemplate = `
 package main

 import "fmt"

 // Force the creation of a lot of type descriptors that will go into
 // the .data.rel.ro section.
 {{range $index, $element := .}}var V{{$index}} interface{} = [{{$index}}]int{}
 {{end}}

 func main() {
 {{range $index, $element := .}}	fmt.Println(V{{$index}})
 {{end}}
 }
 `

 func TestPIESize(t *testing.T) {
 	testenv.MustHaveGoBuild(t)

 	// We don't want to test -linkmode=external if cgo is not supported.
 	// On some systems -buildmode=pie implies -linkmode=external, so just
 	// always skip the test if cgo is not supported.
 	testenv.MustHaveCGO(t)

 	if !sys.BuildModeSupported(runtime.Compiler, "pie", runtime.GOOS, runtime.GOARCH) {
 		t.Skip("-buildmode=pie not supported")
 	}

 	t.Parallel()

 	tmpl := template.Must(template.New("pie").Parse(pieSourceTemplate))

 	writeGo := func(t *testing.T, dir string) {
 		f, err := os.Create(filepath.Join(dir, "pie.go"))
 		if err != nil {
 			t.Fatal(err)
 		}

 		// Passing a 100-element slice here will cause
 		// pieSourceTemplate to create 100 variables with
 		// different types.
 		if err := tmpl.Execute(f, make([]byte, 100)); err != nil {
 			t.Fatal(err)
 		}

 		if err := f.Close(); err != nil {
 			t.Fatal(err)
 		}
 	}

 	for _, external := range []bool{false, true} {
 		external := external

 		name := "TestPieSize-"
 		if external {
 			name += "external"
 		} else {
 			name += "internal"
 		}
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()

 			dir := t.TempDir()

 			writeGo(t, dir)

 			binexe := filepath.Join(dir, "exe")
 			binpie := filepath.Join(dir, "pie")
 			if external {
 				binexe += "external"
 				binpie += "external"
 			}

 			build := func(bin, mode string) error {
 				cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", bin, "-buildmode="+mode)
 				if external {
 					cmd.Args = append(cmd.Args, "-ldflags=-linkmode=external")
 				}
 				cmd.Args = append(cmd.Args, "pie.go")
 				cmd.Dir = dir
 				t.Logf("%v", cmd.Args)
 				out, err := cmd.CombinedOutput()
 				if len(out) > 0 {
 					t.Logf("%s", out)
 				}
 				if err != nil {
 					t.Error(err)
 				}
 				return err
 			}

 			var errexe, errpie error
 			var wg sync.WaitGroup
 			wg.Add(2)
 			go func() {
 				defer wg.Done()
 				errexe = build(binexe, "exe")
 			}()
 			go func() {
 				defer wg.Done()
 				errpie = build(binpie, "pie")
 			}()
 			wg.Wait()
 			if errexe != nil || errpie != nil {
 				t.Fatal("link failed")
 			}

 			var sizeexe, sizepie uint64
 			if fi, err := os.Stat(binexe); err != nil {
 				t.Fatal(err)
 			} else {
 				sizeexe = uint64(fi.Size())
 			}
 			if fi, err := os.Stat(binpie); err != nil {
 				t.Fatal(err)
 			} else {
 				sizepie = uint64(fi.Size())
 			}

 			elfexe, err := elf.Open(binexe)
 			if err != nil {
 				t.Fatal(err)
 			}
 			defer elfexe.Close()

 			elfpie, err := elf.Open(binpie)
 			if err != nil {
 				t.Fatal(err)
 			}
 			defer elfpie.Close()

 			// The difference in size between exe and PIE
 			// should be approximately the difference in
 			// size of the .text section plus the size of
 			// the PIE dynamic data sections plus the
 			// difference in size of the .got and .plt
 			// sections if they exist.
 			// We ignore unallocated sections.
 			// There may be gaps between non-writeable and
 			// writable PT_LOAD segments. We also skip those
 			// gaps (see issue #36023).

 			textsize := func(ef *elf.File, name string) uint64 {
 				for _, s := range ef.Sections {
 					if s.Name == ".text" {
 						return s.Size
 					}
 				}
 				t.Fatalf("%s: no .text section", name)
 				return 0
 			}
 			textexe := textsize(elfexe, binexe)
 			textpie := textsize(elfpie, binpie)

 			dynsize := func(ef *elf.File) uint64 {
 				var ret uint64
 				for _, s := range ef.Sections {
 					if s.Flags&elf.SHF_ALLOC == 0 {
 						continue
 					}
 					switch s.Type {
 					case elf.SHT_DYNSYM, elf.SHT_STRTAB, elf.SHT_REL, elf.SHT_RELA, elf.SHT_HASH, elf.SHT_GNU_HASH, elf.SHT_GNU_VERDEF, elf.SHT_GNU_VERNEED, elf.SHT_GNU_VERSYM:
 						ret += s.Size
 					}
 					if s.Flags&elf.SHF_WRITE != 0 && (strings.Contains(s.Name, ".got") || strings.Contains(s.Name, ".plt")) {
 						ret += s.Size
 					}
 				}
 				return ret
 			}

 			dynexe := dynsize(elfexe)
 			dynpie := dynsize(elfpie)

 			extrasize := func(ef *elf.File) uint64 {
 				var ret uint64
 				// skip unallocated sections
 				for _, s := range ef.Sections {
 					if s.Flags&elf.SHF_ALLOC == 0 {
 						ret += s.Size
 					}
 				}
 				// also skip gaps between PT_LOAD segments
 				var prev *elf.Prog
 				for _, seg := range ef.Progs {
 					if seg.Type != elf.PT_LOAD {
 						continue
 					}
 					if prev != nil {
 						ret += seg.Off - prev.Off - prev.Filesz
 					}
 					prev = seg
 				}
 				return ret
 			}

 			extraexe := extrasize(elfexe)
 			extrapie := extrasize(elfpie)

 			diffReal := (sizepie - extrapie) - (sizeexe - extraexe)
 			diffExpected := (textpie + dynpie) - (textexe + dynexe)

 			t.Logf("real size difference %#x, expected %#x", diffReal, diffExpected)

 			if diffReal > (diffExpected + diffExpected/10) {
 				t.Errorf("PIE unexpectedly large: got difference of %d (%d - %d), expected difference %d", diffReal, sizepie, sizeexe, diffExpected)
 			}
 		})
 	}
 }
	// 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.

	//go:build dragonfly \|\| freebsd \|\| linux \|\| netbsd \|\| openbsd
	// +build dragonfly freebsd linux netbsd openbsd

	package main

	import (
	"cmd/internal/sys"
	"debug/elf"
	"fmt"
	"internal/testenv"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"sync"
	"testing"
	"text/template"
	)

	func getCCAndCCFLAGS(t *testing.T, env []string) (string, []string) {
	goTool := testenv.GoToolPath(t)
	cmd := exec.Command(goTool, "env", "CC")
	cmd.Env = env
	ccb, err := cmd.Output()
	if err != nil {
	t.Fatal(err)
	}
	cc := strings.TrimSpace(string(ccb))

	cmd = exec.Command(goTool, "env", "GOGCCFLAGS")
	cmd.Env = env
	cflagsb, err := cmd.Output()
	if err != nil {
	t.Fatal(err)
	}
	cflags := strings.Fields(string(cflagsb))

	return cc, cflags
	}

	var asmSource = `
	.section .text1,"ax"
	s1:
	.byte 0
	.section .text2,"ax"
	s2:
	.byte 0
	`

	var goSource = `
	package main
	func main() {}
	`

	// The linker used to crash if an ELF input file had multiple text sections
	// with the same name.
	func TestSectionsWithSameName(t *testing.T) {
	testenv.MustHaveGoBuild(t)
	testenv.MustHaveCGO(t)
	t.Parallel()

	objcopy, err := exec.LookPath("objcopy")
	if err != nil {
	t.Skipf("can't find objcopy: %v", err)
	}

	dir := t.TempDir()

	gopath := filepath.Join(dir, "GOPATH")
	env := append(os.Environ(), "GOPATH="+gopath)

	if err := ioutil.WriteFile(filepath.Join(dir, "go.mod"), []byte("module elf_test\n"), 0666); err != nil {
	t.Fatal(err)
	}

	asmFile := filepath.Join(dir, "x.s")
	if err := ioutil.WriteFile(asmFile, []byte(asmSource), 0444); err != nil {
	t.Fatal(err)
	}

	goTool := testenv.GoToolPath(t)
	cc, cflags := getCCAndCCFLAGS(t, env)

	asmObj := filepath.Join(dir, "x.o")
	t.Logf("%s %v -c -o %s %s", cc, cflags, asmObj, asmFile)
	if out, err := exec.Command(cc, append(cflags, "-c", "-o", asmObj, asmFile)...).CombinedOutput(); err != nil {
	t.Logf("%s", out)
	t.Fatal(err)
	}

	asm2Obj := filepath.Join(dir, "x2.syso")
	t.Logf("%s --rename-section .text2=.text1 %s %s", objcopy, asmObj, asm2Obj)
	if out, err := exec.Command(objcopy, "--rename-section", ".text2=.text1", asmObj, asm2Obj).CombinedOutput(); err != nil {
	t.Logf("%s", out)
	t.Fatal(err)
	}

	for _, s := range []string{asmFile, asmObj} {
	if err := os.Remove(s); err != nil {
	t.Fatal(err)
	}
	}

	goFile := filepath.Join(dir, "main.go")
	if err := ioutil.WriteFile(goFile, []byte(goSource), 0444); err != nil {
	t.Fatal(err)
	}

	cmd := exec.Command(goTool, "build")
	cmd.Dir = dir
	cmd.Env = env
	t.Logf("%s build", goTool)
	if out, err := cmd.CombinedOutput(); err != nil {
	t.Logf("%s", out)
	t.Fatal(err)
	}
	}

	var cSources35779 = []string{`
	static int blah() { return 42; }
	int Cfunc1() { return blah(); }
	`, `
	static int blah() { return 42; }
	int Cfunc2() { return blah(); }
	`,
	}

	// TestMinusRSymsWithSameName tests a corner case in the new
	// loader. Prior to the fix this failed with the error 'loadelf:
	// $WORK/b001/_pkg_.a(ldr.syso): duplicate symbol reference: blah in
	// both main(.text) and main(.text)'. See issue #35779.
	func TestMinusRSymsWithSameName(t *testing.T) {
	testenv.MustHaveGoBuild(t)
	testenv.MustHaveCGO(t)
	t.Parallel()

	dir := t.TempDir()

	gopath := filepath.Join(dir, "GOPATH")
	env := append(os.Environ(), "GOPATH="+gopath)

	if err := ioutil.WriteFile(filepath.Join(dir, "go.mod"), []byte("module elf_test\n"), 0666); err != nil {
	t.Fatal(err)
	}

	goTool := testenv.GoToolPath(t)
	cc, cflags := getCCAndCCFLAGS(t, env)

	objs := []string{}
	csrcs := []string{}
	for i, content := range cSources35779 {
	csrcFile := filepath.Join(dir, fmt.Sprintf("x%d.c", i))
	csrcs = append(csrcs, csrcFile)
	if err := ioutil.WriteFile(csrcFile, []byte(content), 0444); err != nil {
	t.Fatal(err)
	}

	obj := filepath.Join(dir, fmt.Sprintf("x%d.o", i))
	objs = append(objs, obj)
	t.Logf("%s %v -c -o %s %s", cc, cflags, obj, csrcFile)
	if out, err := exec.Command(cc, append(cflags, "-c", "-o", obj, csrcFile)...).CombinedOutput(); err != nil {
	t.Logf("%s", out)
	t.Fatal(err)
	}
	}

	sysoObj := filepath.Join(dir, "ldr.syso")
	t.Logf("%s %v -nostdlib -r -o %s %v", cc, cflags, sysoObj, objs)
	if out, err := exec.Command(cc, append(cflags, "-nostdlib", "-r", "-o", sysoObj, objs[0], objs[1])...).CombinedOutput(); err != nil {
	t.Logf("%s", out)
	t.Fatal(err)
	}

	cruft := [][]string{objs, csrcs}
	for _, sl := range cruft {
	for _, s := range sl {
	if err := os.Remove(s); err != nil {
	t.Fatal(err)
	}
	}
	}

	goFile := filepath.Join(dir, "main.go")
	if err := ioutil.WriteFile(goFile, []byte(goSource), 0444); err != nil {
	t.Fatal(err)
	}

	t.Logf("%s build", goTool)
	cmd := exec.Command(goTool, "build")
	cmd.Dir = dir
	cmd.Env = env
	if out, err := cmd.CombinedOutput(); err != nil {
	t.Logf("%s", out)
	t.Fatal(err)
	}
	}

	func TestMergeNoteSections(t *testing.T) {
	testenv.MustHaveGoBuild(t)
	expected := 1

	switch runtime.GOOS {
	case "linux", "freebsd", "dragonfly":
	case "openbsd", "netbsd":
	// These OSes require independent segment
	expected = 2
	default:
	t.Skip("We should only test on elf output.")
	}
	t.Parallel()

	goFile := filepath.Join(t.TempDir(), "notes.go")
	if err := ioutil.WriteFile(goFile, []byte(goSource), 0444); err != nil {
	t.Fatal(err)
	}
	outFile := filepath.Join(t.TempDir(), "notes.exe")
	goTool := testenv.GoToolPath(t)
	// sha1sum of "gopher"
	id := "0xf4e8cd51ce8bae2996dc3b74639cdeaa1f7fee5f"
	cmd := exec.Command(goTool, "build", "-o", outFile, "-ldflags",
	"-B "+id, goFile)
	cmd.Dir = t.TempDir()
	if out, err := cmd.CombinedOutput(); err != nil {
	t.Logf("%s", out)
	t.Fatal(err)
	}

	ef, err := elf.Open(outFile)
	if err != nil {
	t.Fatalf("open elf file failed:%v", err)
	}
	defer ef.Close()
	sec := ef.Section(".note.gnu.build-id")
	if sec == nil {
	t.Fatalf("can't find gnu build id")
	}

	sec = ef.Section(".note.go.buildid")
	if sec == nil {
	t.Fatalf("can't find go build id")
	}
	cnt := 0
	for _, ph := range ef.Progs {
	if ph.Type == elf.PT_NOTE {
	cnt += 1
	}
	}
	if cnt != expected {
	t.Fatalf("want %d PT_NOTE segment, got %d", expected, cnt)
	}
	}

	const pieSourceTemplate = `
	package main

	import "fmt"

	// Force the creation of a lot of type descriptors that will go into
	// the .data.rel.ro section.
	{{range $index, $element := .}}var V{{$index}} interface{} = [{{$index}}]int{}
	{{end}}

	func main() {
	{{range $index, $element := .}} fmt.Println(V{{$index}})
	{{end}}
	}
	`

	func TestPIESize(t *testing.T) {
	testenv.MustHaveGoBuild(t)

	// We don't want to test -linkmode=external if cgo is not supported.
	// On some systems -buildmode=pie implies -linkmode=external, so just
	// always skip the test if cgo is not supported.
	testenv.MustHaveCGO(t)

	if !sys.BuildModeSupported(runtime.Compiler, "pie", runtime.GOOS, runtime.GOARCH) {
	t.Skip("-buildmode=pie not supported")
	}

	t.Parallel()

	tmpl := template.Must(template.New("pie").Parse(pieSourceTemplate))

	writeGo := func(t *testing.T, dir string) {
	f, err := os.Create(filepath.Join(dir, "pie.go"))
	if err != nil {
	t.Fatal(err)
	}

	// Passing a 100-element slice here will cause
	// pieSourceTemplate to create 100 variables with
	// different types.
	if err := tmpl.Execute(f, make([]byte, 100)); err != nil {
	t.Fatal(err)
	}

	if err := f.Close(); err != nil {
	t.Fatal(err)
	}
	}

	for _, external := range []bool{false, true} {
	external := external

	name := "TestPieSize-"
	if external {
	name += "external"
	} else {
	name += "internal"
	}
	t.Run(name, func(t *testing.T) {
	t.Parallel()

	dir := t.TempDir()

	writeGo(t, dir)

	binexe := filepath.Join(dir, "exe")
	binpie := filepath.Join(dir, "pie")
	if external {
	binexe += "external"
	binpie += "external"
	}

	build := func(bin, mode string) error {
	cmd := exec.Command(testenv.GoToolPath(t), "build", "-o", bin, "-buildmode="+mode)
	if external {
	cmd.Args = append(cmd.Args, "-ldflags=-linkmode=external")
	}
	cmd.Args = append(cmd.Args, "pie.go")
	cmd.Dir = dir
	t.Logf("%v", cmd.Args)
	out, err := cmd.CombinedOutput()
	if len(out) > 0 {
	t.Logf("%s", out)
	}
	if err != nil {
	t.Error(err)
	}
	return err
	}

	var errexe, errpie error
	var wg sync.WaitGroup
	wg.Add(2)
	go func() {
	defer wg.Done()
	errexe = build(binexe, "exe")
	}()
	go func() {
	defer wg.Done()
	errpie = build(binpie, "pie")
	}()
	wg.Wait()
	if errexe != nil \|\| errpie != nil {
	t.Fatal("link failed")
	}

	var sizeexe, sizepie uint64
	if fi, err := os.Stat(binexe); err != nil {
	t.Fatal(err)
	} else {
	sizeexe = uint64(fi.Size())
	}
	if fi, err := os.Stat(binpie); err != nil {
	t.Fatal(err)
	} else {
	sizepie = uint64(fi.Size())
	}

	elfexe, err := elf.Open(binexe)
	if err != nil {
	t.Fatal(err)
	}
	defer elfexe.Close()

	elfpie, err := elf.Open(binpie)
	if err != nil {
	t.Fatal(err)
	}
	defer elfpie.Close()

	// The difference in size between exe and PIE
	// should be approximately the difference in
	// size of the .text section plus the size of
	// the PIE dynamic data sections plus the
	// difference in size of the .got and .plt
	// sections if they exist.
	// We ignore unallocated sections.
	// There may be gaps between non-writeable and
	// writable PT_LOAD segments. We also skip those
	// gaps (see issue #36023).

	textsize := func(ef *elf.File, name string) uint64 {
	for _, s := range ef.Sections {
	if s.Name == ".text" {
	return s.Size
	}
	}
	t.Fatalf("%s: no .text section", name)
	return 0
	}
	textexe := textsize(elfexe, binexe)
	textpie := textsize(elfpie, binpie)

	dynsize := func(ef *elf.File) uint64 {
	var ret uint64
	for _, s := range ef.Sections {
	if s.Flags&elf.SHF_ALLOC == 0 {
	continue
	}
	switch s.Type {
	case elf.SHT_DYNSYM, elf.SHT_STRTAB, elf.SHT_REL, elf.SHT_RELA, elf.SHT_HASH, elf.SHT_GNU_HASH, elf.SHT_GNU_VERDEF, elf.SHT_GNU_VERNEED, elf.SHT_GNU_VERSYM:
	ret += s.Size
	}
	if s.Flags&elf.SHF_WRITE != 0 && (strings.Contains(s.Name, ".got") \|\| strings.Contains(s.Name, ".plt")) {
	ret += s.Size
	}
	}
	return ret
	}

	dynexe := dynsize(elfexe)
	dynpie := dynsize(elfpie)

	extrasize := func(ef *elf.File) uint64 {
	var ret uint64
	// skip unallocated sections
	for _, s := range ef.Sections {
	if s.Flags&elf.SHF_ALLOC == 0 {
	ret += s.Size
	}
	}
	// also skip gaps between PT_LOAD segments
	var prev *elf.Prog
	for _, seg := range ef.Progs {
	if seg.Type != elf.PT_LOAD {
	continue
	}
	if prev != nil {
	ret += seg.Off - prev.Off - prev.Filesz
	}
	prev = seg
	}
	return ret
	}

	extraexe := extrasize(elfexe)
	extrapie := extrasize(elfpie)

	diffReal := (sizepie - extrapie) - (sizeexe - extraexe)
	diffExpected := (textpie + dynpie) - (textexe + dynexe)

	t.Logf("real size difference %#x, expected %#x", diffReal, diffExpected)

	if diffReal > (diffExpected + diffExpected/10) {
	t.Errorf("PIE unexpectedly large: got difference of %d (%d - %d), expected difference %d", diffReal, sizepie, sizeexe, diffExpected)
	}
	})
	}
	}