1/*
2 * Example of using hugepage memory in a user application using the mmap
3 * system call with MAP_HUGETLB flag.  Before running this program make
4 * sure the administrator has allocated enough default sized huge pages
5 * to cover the 256 MB allocation.
6 *
7 * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
8 * That means the addresses starting with 0x800000... will need to be
9 * specified.  Specifying a fixed address is not required on ppc64, i386
10 * or x86_64.
11 */
12#include <stdlib.h>
13#include <stdio.h>
14#include <unistd.h>
15#include <sys/mman.h>
16#include <fcntl.h>
17
18#define LENGTH (256UL*1024*1024)
19#define PROTECTION (PROT_READ | PROT_WRITE)
20
21#ifndef MAP_HUGETLB
22#define MAP_HUGETLB 0x40000 /* arch specific */
23#endif
24
25/* Only ia64 requires this */
26#ifdef __ia64__
27#define ADDR (void *)(0x8000000000000000UL)
28#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
29#else
30#define ADDR (void *)(0x0UL)
31#define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
32#endif
33
34static void check_bytes(char *addr)
35{
36	printf("First hex is %x\n", *((unsigned int *)addr));
37}
38
39static void write_bytes(char *addr)
40{
41	unsigned long i;
42
43	for (i = 0; i < LENGTH; i++)
44		*(addr + i) = (char)i;
45}
46
47static int read_bytes(char *addr)
48{
49	unsigned long i;
50
51	check_bytes(addr);
52	for (i = 0; i < LENGTH; i++)
53		if (*(addr + i) != (char)i) {
54			printf("Mismatch at %lu\n", i);
55			return 1;
56		}
57	return 0;
58}
59
60int main(void)
61{
62	void *addr;
63	int ret;
64
65	addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, 0, 0);
66	if (addr == MAP_FAILED) {
67		perror("mmap");
68		exit(1);
69	}
70
71	printf("Returned address is %p\n", addr);
72	check_bytes(addr);
73	write_bytes(addr);
74	ret = read_bytes(addr);
75
76	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
77	if (munmap(addr, LENGTH)) {
78		perror("munmap");
79		exit(1);
80	}
81
82	return ret;
83}
84