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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2017 Intel Corporation. */
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
#define MiB(a) ((a)*1024*1024)
void err_exit(char *op)
{
fprintf(stderr, "%s: %s\n", op, strerror(errno));
exit(1);
}
int main(int argc, char *argv[])
{
volatile int a __attribute__((__unused__));
char *buffer = "HELLO WORLD!";
char *data;
int fd, err, ret = 0;
if (argc < 2) {
printf("Usage: %s <pmem file>\n", basename(argv[0]));
exit(0);
}
fd = open(argv[1], O_RDWR|O_CREAT, S_IRUSR|S_IWUSR);
if (fd < 0)
err_exit("fd");
/*
* This allows us to map a huge zero page, and we do it at a non-zero
* offset for a little additional testing.
*/
ftruncate(fd, 0);
ftruncate(fd, MiB(4));
data = mmap(NULL, MiB(2), PROT_READ, MAP_SHARED, fd, MiB(2));
if (data == MAP_FAILED)
err_exit("mmap");
/*
* This faults in a 2MiB zero page to satisfy the read.
* 'a' is volatile so this read doesn't get optimized out.
*/
a = data[0];
pwrite(fd, buffer, strlen(buffer), MiB(2));
/*
* Try and use the mmap to read back the data we just wrote with
* pwrite(). If the kernel bug is present the mapping from the 2MiB
* zero page will still be intact, and we'll read back zeros instead.
*/
if (strncmp(buffer, data, strlen(buffer))) {
fprintf(stderr, "strncmp mismatch: '%s' vs '%s'\n", buffer,
data);
ret = 1;
}
err = munmap(data, MiB(2));
if (err < 0)
err_exit("munmap");
err = close(fd);
if (err < 0)
err_exit("close");
return ret;
}
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