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 * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
9 * That means the addresses starting with 0x800000... will need to be
10 * specified.  Specifying a fixed address is not required on ppc64, i386
11 * or x86_64.
12 */
13#include <stdlib.h>
14#include <stdio.h>
15#include <unistd.h>
16#include <sys/mman.h>
17#include <fcntl.h>
18
19#define LENGTH (256UL*1024*1024)
20#define PROTECTION (PROT_READ | PROT_WRITE)
21
22#ifndef MAP_HUGETLB
23#define MAP_HUGETLB 0x40000 /* arch specific */
24#endif
25
26#ifndef MAP_HUGE_SHIFT
27#define MAP_HUGE_SHIFT 26
28#endif
29
30#ifndef MAP_HUGE_MASK
31#define MAP_HUGE_MASK 0x3f
32#endif
33
34/* Only ia64 requires this */
35#ifdef __ia64__
36#define ADDR (void *)(0x8000000000000000UL)
37#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
38#else
39#define ADDR (void *)(0x0UL)
40#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
41#endif
42
43static void check_bytes(char *addr)
44{
45	printf("First hex is %x\n", *((unsigned int *)addr));
46}
47
48static void write_bytes(char *addr, size_t length)
49{
50	unsigned long i;
51
52	for (i = 0; i < length; i++)
53		*(addr + i) = (char)i;
54}
55
56static int read_bytes(char *addr, size_t length)
57{
58	unsigned long i;
59
60	check_bytes(addr);
61	for (i = 0; i < length; i++)
62		if (*(addr + i) != (char)i) {
63			printf("Mismatch at %lu\n", i);
64			return 1;
65		}
66	return 0;
67}
68
69int main(int argc, char **argv)
70{
71	void *addr;
72	int ret;
73	size_t length = LENGTH;
74	int flags = FLAGS;
75	int shift = 0;
76
77	if (argc > 1)
78		length = atol(argv[1]) << 20;
79	if (argc > 2) {
80		shift = atoi(argv[2]);
81		if (shift)
82			flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
83	}
84
85	if (shift)
86		printf("%u kB hugepages\n", 1 << (shift - 10));
87	else
88		printf("Default size hugepages\n");
89	printf("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
90
91	addr = mmap(ADDR, length, PROTECTION, flags, -1, 0);
92	if (addr == MAP_FAILED) {
93		perror("mmap");
94		exit(1);
95	}
96
97	printf("Returned address is %p\n", addr);
98	check_bytes(addr);
99	write_bytes(addr, length);
100	ret = read_bytes(addr, length);
101
102	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
103	if (munmap(addr, length)) {
104		perror("munmap");
105		exit(1);
106	}
107
108	return ret;
109}
110