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
check_bytes(char * addr)43 static void check_bytes(char *addr)
44 {
45 printf("First hex is %x\n", *((unsigned int *)addr));
46 }
47
write_bytes(char * addr,size_t length)48 static 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
read_bytes(char * addr,size_t length)56 static 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
main(int argc,char ** argv)69 int 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