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 /* Only ia64 requires this */
27 #ifdef __ia64__
28 #define ADDR (void *)(0x8000000000000000UL)
29 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
30 #else
31 #define ADDR (void *)(0x0UL)
32 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
33 #endif
34
check_bytes(char * addr)35 static void check_bytes(char *addr)
36 {
37 printf("First hex is %x\n", *((unsigned int *)addr));
38 }
39
write_bytes(char * addr)40 static void write_bytes(char *addr)
41 {
42 unsigned long i;
43
44 for (i = 0; i < LENGTH; i++)
45 *(addr + i) = (char)i;
46 }
47
read_bytes(char * addr)48 static int read_bytes(char *addr)
49 {
50 unsigned long i;
51
52 check_bytes(addr);
53 for (i = 0; i < LENGTH; i++)
54 if (*(addr + i) != (char)i) {
55 printf("Mismatch at %lu\n", i);
56 return 1;
57 }
58 return 0;
59 }
60
main(void)61 int main(void)
62 {
63 void *addr;
64 int ret;
65
66 addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, -1, 0);
67 if (addr == MAP_FAILED) {
68 perror("mmap");
69 exit(1);
70 }
71
72 printf("Returned address is %p\n", addr);
73 check_bytes(addr);
74 write_bytes(addr);
75 ret = read_bytes(addr);
76
77 /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
78 if (munmap(addr, LENGTH)) {
79 perror("munmap");
80 exit(1);
81 }
82
83 return ret;
84 }
85