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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 <pthread.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)
#define NUM_THREADS 2
void err_exit(char *op)
{
fprintf(stderr, "%s: %s\n", op, strerror(errno));
exit(1);
}
void worker_fn(void *ptr)
{
char *data = (char *)ptr;
volatile int a;
int i, err;
for (i = 0; i < 10; i++) {
a = data[0];
data[0] = a;
err = madvise(data, MiB(2), MADV_DONTNEED);
if (err < 0)
err_exit("madvise");
/* Mix up the thread timings to encourage the race. */
err = usleep(rand() % 100);
if (err < 0)
err_exit("usleep");
}
}
int main(int argc, char *argv[])
{
pthread_t thread[NUM_THREADS];
int i, j, fd, err;
char *data;
if (argc < 2) {
printf("Usage: %s <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 page. */
ftruncate(fd, 0);
ftruncate(fd, MiB(2));
/*
* First we set up a shared mapping. Our write will (hopefully) get
* the filesystem to give us a 2MiB huge page DAX mapping. We will
* then use this 2MiB page for our private mapping race.
*/
data = mmap(NULL, MiB(2), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
if (data == MAP_FAILED)
err_exit("shared mmap");
data[0] = 1;
err = munmap(data, MiB(2));
if (err < 0)
err_exit("shared munmap");
for (i = 0; i < 500; i++) {
data = mmap(NULL, MiB(2), PROT_READ|PROT_WRITE, MAP_PRIVATE,
fd, 0);
if (data == MAP_FAILED)
err_exit("private mmap");
for (j = 0; j < NUM_THREADS; j++) {
err = pthread_create(&thread[j], NULL,
(void*)&worker_fn, data);
if (err)
err_exit("pthread_create");
}
for (j = 0; j < NUM_THREADS; j++) {
err = pthread_join(thread[j], NULL);
if (err)
err_exit("pthread_join");
}
err = munmap(data, MiB(2));
if (err < 0)
err_exit("private munmap");
}
err = close(fd);
if (err < 0)
err_exit("close");
return 0;
}
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