hugepage-mmap.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * hugepage-mmap:
 4 *
 5 * Example of using huge page memory in a user application using the mmap
 6 * system call.  Before running this application, make sure that the
 7 * administrator has mounted the hugetlbfs filesystem (on some directory
 8 * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this
 9 * example, the app is requesting memory of size 256MB that is backed by
10 * huge pages.
11 */
12#define _GNU_SOURCE
13#include <stdlib.h>
14#include <stdio.h>
15#include <unistd.h>
16#include <sys/mman.h>
17#include <fcntl.h>
18#include "kselftest.h"
19
20#define LENGTH (256UL*1024*1024)
21#define PROTECTION (PROT_READ | PROT_WRITE)
22
23static void check_bytes(char *addr)
24{
25	ksft_print_msg("First hex is %x\n", *((unsigned int *)addr));
26}
27
28static void write_bytes(char *addr)
29{
30	unsigned long i;
31
32	for (i = 0; i < LENGTH; i++)
33		*(addr + i) = (char)i;
34}
35
36static int read_bytes(char *addr)
37{
38	unsigned long i;
39
40	check_bytes(addr);
41	for (i = 0; i < LENGTH; i++)
42		if (*(addr + i) != (char)i) {
43			ksft_print_msg("Error: Mismatch at %lu\n", i);
44			return 1;
45		}
46	return 0;
47}
48
49int main(void)
50{
51	void *addr;
52	int fd, ret;
53
54	ksft_print_header();
55	ksft_set_plan(1);
56
57	fd = memfd_create("hugepage-mmap", MFD_HUGETLB);
58	if (fd < 0)
59		ksft_exit_fail_msg("memfd_create() failed: %s\n", strerror(errno));
60
61	addr = mmap(NULL, LENGTH, PROTECTION, MAP_SHARED, fd, 0);
62	if (addr == MAP_FAILED) {
63		close(fd);
64		ksft_exit_fail_msg("mmap(): %s\n", strerror(errno));
65	}
66
67	ksft_print_msg("Returned address is %p\n", addr);
68	check_bytes(addr);
69	write_bytes(addr);
70	ret = read_bytes(addr);
71
72	munmap(addr, LENGTH);
73	close(fd);
74
75	ksft_test_result(!ret, "Read same data\n");
76
77	ksft_exit(!ret);
78}