map_hugetlb.c

 1// SPDX-License-Identifier: GPL-2.0
 2/*
 3 * Example of using hugepage memory in a user application using the mmap
 4 * system call with MAP_HUGETLB flag.  Before running this program make
 5 * sure the administrator has allocated enough default sized huge pages
 6 * to cover the 256 MB allocation.
 7 */
 8#include <stdlib.h>
 9#include <stdio.h>
10#include <unistd.h>
11#include <sys/mman.h>
12#include <fcntl.h>
13#include "vm_util.h"
14#include "kselftest.h"
15
16#define LENGTH (256UL*1024*1024)
17#define PROTECTION (PROT_READ | PROT_WRITE)
18
19static void check_bytes(char *addr)
20{
21	ksft_print_msg("First hex is %x\n", *((unsigned int *)addr));
22}
23
24static void write_bytes(char *addr, size_t length)
25{
26	unsigned long i;
27
28	for (i = 0; i < length; i++)
29		*(addr + i) = (char)i;
30}
31
32static void read_bytes(char *addr, size_t length)
33{
34	unsigned long i;
35
36	check_bytes(addr);
37	for (i = 0; i < length; i++)
38		if (*(addr + i) != (char)i)
39			ksft_exit_fail_msg("Mismatch at %lu\n", i);
40
41	ksft_test_result_pass("Read correct data\n");
42}
43
44int main(int argc, char **argv)
45{
46	void *addr;
47	size_t hugepage_size;
48	size_t length = LENGTH;
49	int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB;
50	int shift = 0;
51
52	hugepage_size = default_huge_page_size();
53	/* munmap with fail if the length is not page aligned */
54	if (hugepage_size > length)
55		length = hugepage_size;
56
57	ksft_print_header();
58	ksft_set_plan(1);
59
60	if (argc > 1)
61		length = atol(argv[1]) << 20;
62	if (argc > 2) {
63		shift = atoi(argv[2]);
64		if (shift)
65			flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
66	}
67
68	if (shift)
69		ksft_print_msg("%u kB hugepages\n", 1 << (shift - 10));
70	else
71		ksft_print_msg("Default size hugepages\n");
72	ksft_print_msg("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
73
74	addr = mmap(NULL, length, PROTECTION, flags, -1, 0);
75	if (addr == MAP_FAILED)
76		ksft_exit_fail_msg("mmap: %s\n", strerror(errno));
77
78	ksft_print_msg("Returned address is %p\n", addr);
79	check_bytes(addr);
80	write_bytes(addr, length);
81	read_bytes(addr, length);
82
83	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
84	if (munmap(addr, length))
85		ksft_exit_fail_msg("munmap: %s\n", strerror(errno));
86
87	ksft_finished();
88}