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 /* Only ia64 requires this */
23 #ifdef __ia64__
24 #define ADDR (void *)(0x8000000000000000UL)
25 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
26 #else
27 #define ADDR (void *)(0x0UL)
28 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
29 #endif
30
check_bytes(char * addr)31 static void check_bytes(char *addr)
32 {
33 printf("First hex is %x\n", *((unsigned int *)addr));
34 }
35
write_bytes(char * addr,size_t length)36 static void write_bytes(char *addr, size_t length)
37 {
38 unsigned long i;
39
40 for (i = 0; i < length; i++)
41 *(addr + i) = (char)i;
42 }
43
read_bytes(char * addr,size_t length)44 static int read_bytes(char *addr, size_t length)
45 {
46 unsigned long i;
47
48 check_bytes(addr);
49 for (i = 0; i < length; i++)
50 if (*(addr + i) != (char)i) {
51 printf("Mismatch at %lu\n", i);
52 return 1;
53 }
54 return 0;
55 }
56
main(int argc,char ** argv)57 int main(int argc, char **argv)
58 {
59 void *addr;
60 int ret;
61 size_t length = LENGTH;
62 int flags = FLAGS;
63 int shift = 0;
64
65 if (argc > 1)
66 length = atol(argv[1]) << 20;
67 if (argc > 2) {
68 shift = atoi(argv[2]);
69 if (shift)
70 flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
71 }
72
73 if (shift)
74 printf("%u kB hugepages\n", 1 << (shift - 10));
75 else
76 printf("Default size hugepages\n");
77 printf("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
78
79 addr = mmap(ADDR, length, PROTECTION, flags, -1, 0);
80 if (addr == MAP_FAILED) {
81 perror("mmap");
82 exit(1);
83 }
84
85 printf("Returned address is %p\n", addr);
86 check_bytes(addr);
87 write_bytes(addr, length);
88 ret = read_bytes(addr, length);
89
90 /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
91 if (munmap(addr, length)) {
92 perror("munmap");
93 exit(1);
94 }
95
96 return ret;
97 }
98
