src/cmd/link/elf_test.go

// 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 dragonfly freebsd linux netbsd openbsd

package main

import (
	"fmt"
	"internal/testenv"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"
)

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, err := ioutil.TempDir("", "go-link-TestSectionsWithSameName")
	if err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(dir)

	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)'
func TestMinusRSymsWithSameName(t *testing.T) {
	testenv.MustHaveGoBuild(t)
	testenv.MustHaveCGO(t)
	t.Parallel()

	dir, err := ioutil.TempDir("", "go-link-TestMinusRSymsWithSameName")
	if err != nil {
		t.Fatal(err)
	}
	defer os.RemoveAll(dir)

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