mmap_zos_test.go

Documentation: golang.org/x/sys/unix

     1  // Copyright 2020 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  //go:build zos && s390x
     6  
     7  // This test is based on mmap_unix_test, but tweaked for z/OS, which does not support memadvise
     8  // or anonymous mmapping.
     9  
    10  package unix_test
    11  
    12  import (
    13  	"fmt"
    14  	"os"
    15  	"path/filepath"
    16  	"testing"
    17  
    18  	"golang.org/x/sys/unix"
    19  )
    20  
    21  func TestMmap(t *testing.T) {
    22  	tmpdir := filepath.Join(t.TempDir(), "testdata")
    23  	if err := os.Mkdir(tmpdir, 0700); err != nil {
    24  		t.Fatal(err)
    25  	}
    26  	filename := filepath.Join(tmpdir, "memmapped_file")
    27  	destination, err := os.Create(filename)
    28  	if err != nil {
    29  		t.Fatal("os.Create:", err)
    30  		return
    31  	}
    32  
    33  	fmt.Fprintf(destination, "%s\n", "0 <- Flipped between 0 and 1 when test runs successfully")
    34  	fmt.Fprintf(destination, "%s\n", "//Do not change contents - mmap test relies on this")
    35  	destination.Close()
    36  	fd, err := unix.Open(filename, unix.O_RDWR, 0777)
    37  	if err != nil {
    38  		t.Fatalf("Open: %v", err)
    39  	}
    40  
    41  	b, err := unix.Mmap(fd, 0, 8, unix.PROT_READ, unix.MAP_SHARED)
    42  	if err != nil {
    43  		t.Fatalf("Mmap: %v", err)
    44  	}
    45  
    46  	if err := unix.Mprotect(b, unix.PROT_READ|unix.PROT_WRITE); err != nil {
    47  		t.Fatalf("Mprotect: %v", err)
    48  	}
    49  
    50  	// Flip flag in test file via mapped memory
    51  	flagWasZero := true
    52  	if b[0] == '0' {
    53  		b[0] = '1'
    54  	} else if b[0] == '1' {
    55  		b[0] = '0'
    56  		flagWasZero = false
    57  	}
    58  
    59  	if err := unix.Msync(b, unix.MS_SYNC); err != nil {
    60  		t.Fatalf("Msync: %v", err)
    61  	}
    62  
    63  	// Read file from FS to ensure flag flipped after msync
    64  	buf, err := os.ReadFile(filename)
    65  	if err != nil {
    66  		t.Fatalf("Could not read mmapped file from disc for test: %v", err)
    67  	}
    68  	if flagWasZero && buf[0] != '1' || !flagWasZero && buf[0] != '0' {
    69  		t.Error("Flag flip in MAP_SHARED mmapped file not visible")
    70  	}
    71  
    72  	if err := unix.Munmap(b); err != nil {
    73  		t.Fatalf("Munmap: %v", err)
    74  	}
    75  }
    76
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