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// Copyright 2020 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 zos && s390x
// This test is based on mmap_unix_test, but tweaked for z/OS, which does not support memadvise
// or anonymous mmapping.
package unix_test
import (
"fmt"
"os"
"path/filepath"
"testing"
"golang.org/x/sys/unix"
)
func TestMmap(t *testing.T) {
tmpdir := filepath.Join(t.TempDir(), "testdata")
if err := os.Mkdir(tmpdir, 0700); err != nil {
t.Fatal(err)
}
filename := filepath.Join(tmpdir, "memmapped_file")
destination, err := os.Create(filename)
if err != nil {
t.Fatal("os.Create:", err)
return
}
fmt.Fprintf(destination, "%s\n", "0 <- Flipped between 0 and 1 when test runs successfully")
fmt.Fprintf(destination, "%s\n", "//Do not change contents - mmap test relies on this")
destination.Close()
fd, err := unix.Open(filename, unix.O_RDWR, 0777)
if err != nil {
t.Fatalf("Open: %v", err)
}
b, err := unix.Mmap(fd, 0, 8, unix.PROT_READ, unix.MAP_SHARED)
if err != nil {
t.Fatalf("Mmap: %v", err)
}
if err := unix.Mprotect(b, unix.PROT_READ|unix.PROT_WRITE); err != nil {
t.Fatalf("Mprotect: %v", err)
}
// Flip flag in test file via mapped memory
flagWasZero := true
if b[0] == '0' {
b[0] = '1'
} else if b[0] == '1' {
b[0] = '0'
flagWasZero = false
}
if err := unix.Msync(b, unix.MS_SYNC); err != nil {
t.Fatalf("Msync: %v", err)
}
// Read file from FS to ensure flag flipped after msync
buf, err := os.ReadFile(filename)
if err != nil {
t.Fatalf("Could not read mmapped file from disc for test: %v", err)
}
if flagWasZero && buf[0] != '1' || !flagWasZero && buf[0] != '0' {
t.Error("Flag flip in MAP_SHARED mmapped file not visible")
}
if err := unix.Munmap(b); err != nil {
t.Fatalf("Munmap: %v", err)
}
}
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