1// Copyright 2016 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// This program generates a test to verify that a program can be
6// successfully linked even when there are very large text
7// sections present.
8
9package main
10
11import (
12	"bytes"
13	"fmt"
14	"internal/buildcfg"
15	"internal/testenv"
16	"os"
17	"testing"
18)
19
20func TestLargeText(t *testing.T) {
21	if testing.Short() || (buildcfg.GOARCH != "ppc64le" && buildcfg.GOARCH != "ppc64" && buildcfg.GOARCH != "arm") {
22		t.Skipf("Skipping large text section test in short mode or on %s", buildcfg.GOARCH)
23	}
24	testenv.MustHaveGoBuild(t)
25
26	var w bytes.Buffer
27	const FN = 4
28	tmpdir := t.TempDir()
29
30	if err := os.WriteFile(tmpdir+"/go.mod", []byte("module big_test\n"), 0666); err != nil {
31		t.Fatal(err)
32	}
33
34	// Generate the scenario where the total amount of text exceeds the
35	// limit for the jmp/call instruction, on RISC architectures like ppc64le,
36	// which is 2^26.  When that happens the call requires special trampolines or
37	// long branches inserted by the linker where supported.
38	// Multiple .s files are generated instead of one.
39	instOnArch := map[string]string{
40		"ppc64":   "\tMOVD\tR0,R3\n",
41		"ppc64le": "\tMOVD\tR0,R3\n",
42		"arm":     "\tMOVW\tR0,R1\n",
43	}
44	inst := instOnArch[buildcfg.GOARCH]
45	for j := 0; j < FN; j++ {
46		testname := fmt.Sprintf("bigfn%d", j)
47		fmt.Fprintf(&w, "TEXT ·%s(SB),$0\n", testname)
48		for i := 0; i < 2200000; i++ {
49			fmt.Fprintf(&w, inst)
50		}
51		fmt.Fprintf(&w, "\tRET\n")
52		err := os.WriteFile(tmpdir+"/"+testname+".s", w.Bytes(), 0666)
53		if err != nil {
54			t.Fatalf("can't write output: %v\n", err)
55		}
56		w.Reset()
57	}
58	fmt.Fprintf(&w, "package main\n")
59	fmt.Fprintf(&w, "\nimport (\n")
60	fmt.Fprintf(&w, "\t\"os\"\n")
61	fmt.Fprintf(&w, "\t\"fmt\"\n")
62	fmt.Fprintf(&w, ")\n\n")
63
64	for i := 0; i < FN; i++ {
65		fmt.Fprintf(&w, "func bigfn%d()\n", i)
66	}
67	fmt.Fprintf(&w, "\nfunc main() {\n")
68
69	// There are lots of dummy code generated in the .s files just to generate a lot
70	// of text. Link them in but guard their call so their code is not executed but
71	// the main part of the program can be run.
72	fmt.Fprintf(&w, "\tif os.Getenv(\"LINKTESTARG\") != \"\" {\n")
73	for i := 0; i < FN; i++ {
74		fmt.Fprintf(&w, "\t\tbigfn%d()\n", i)
75	}
76	fmt.Fprintf(&w, "\t}\n")
77	fmt.Fprintf(&w, "\tfmt.Printf(\"PASS\\n\")\n")
78	fmt.Fprintf(&w, "}")
79	err := os.WriteFile(tmpdir+"/bigfn.go", w.Bytes(), 0666)
80	if err != nil {
81		t.Fatalf("can't write output: %v\n", err)
82	}
83
84	// Build and run with internal linking.
85	cmd := testenv.Command(t, testenv.GoToolPath(t), "build", "-o", "bigtext")
86	cmd.Dir = tmpdir
87	out, err := cmd.CombinedOutput()
88	if err != nil {
89		t.Fatalf("Build failed for big text program with internal linking: %v, output: %s", err, out)
90	}
91	cmd = testenv.Command(t, "./bigtext")
92	cmd.Dir = tmpdir
93	out, err = cmd.CombinedOutput()
94	if err != nil {
95		t.Fatalf("Program built with internal linking failed to run with err %v, output: %s", err, out)
96	}
97
98	// Build and run with external linking
99	cmd = testenv.Command(t, testenv.GoToolPath(t), "build", "-o", "bigtext", "-ldflags", "-linkmode=external")
100	cmd.Dir = tmpdir
101	out, err = cmd.CombinedOutput()
102	if err != nil {
103		t.Fatalf("Build failed for big text program with external linking: %v, output: %s", err, out)
104	}
105	cmd = testenv.Command(t, "./bigtext")
106	cmd.Dir = tmpdir
107	out, err = cmd.CombinedOutput()
108	if err != nil {
109		t.Fatalf("Program built with external linking failed to run with err %v, output: %s", err, out)
110	}
111}
112