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 #include "vm_util.h"
19
20 #define LENGTH (256UL*1024*1024)
21 #define PROTECTION (PROT_READ | PROT_WRITE)
22
23 #ifndef MAP_HUGETLB
24 #define MAP_HUGETLB 0x40000 /* arch specific */
25 #endif
26
27 #ifndef MAP_HUGE_SHIFT
28 #define MAP_HUGE_SHIFT 26
29 #endif
30
31 #ifndef MAP_HUGE_MASK
32 #define MAP_HUGE_MASK 0x3f
33 #endif
34
35 /* Only ia64 requires this */
36 #ifdef __ia64__
37 #define ADDR (void *)(0x8000000000000000UL)
38 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
39 #else
40 #define ADDR (void *)(0x0UL)
41 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
42 #endif
43
check_bytes(char * addr)44 static void check_bytes(char *addr)
45 {
46 printf("First hex is %x\n", *((unsigned int *)addr));
47 }
48
write_bytes(char * addr,size_t length)49 static void write_bytes(char *addr, size_t length)
50 {
51 unsigned long i;
52
53 for (i = 0; i < length; i++)
54 *(addr + i) = (char)i;
55 }
56
read_bytes(char * addr,size_t length)57 static int read_bytes(char *addr, size_t length)
58 {
59 unsigned long i;
60
61 check_bytes(addr);
62 for (i = 0; i < length; i++)
63 if (*(addr + i) != (char)i) {
64 printf("Mismatch at %lu\n", i);
65 return 1;
66 }
67 return 0;
68 }
69
main(int argc,char ** argv)70 int main(int argc, char **argv)
71 {
72 void *addr;
73 int ret;
74 size_t hugepage_size;
75 size_t length = LENGTH;
76 int flags = FLAGS;
77 int shift = 0;
78
79 hugepage_size = default_huge_page_size();
80 /* munmap with fail if the length is not page aligned */
81 if (hugepage_size > length)
82 length = hugepage_size;
83
84 if (argc > 1)
85 length = atol(argv[1]) << 20;
86 if (argc > 2) {
87 shift = atoi(argv[2]);
88 if (shift)
89 flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
90 }
91
92 if (shift)
93 printf("%u kB hugepages\n", 1 << (shift - 10));
94 else
95 printf("Default size hugepages\n");
96 printf("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
97
98 addr = mmap(ADDR, length, PROTECTION, flags, -1, 0);
99 if (addr == MAP_FAILED) {
100 perror("mmap");
101 exit(1);
102 }
103
104 printf("Returned address is %p\n", addr);
105 check_bytes(addr);
106 write_bytes(addr, length);
107 ret = read_bytes(addr, length);
108
109 /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
110 if (munmap(addr, length)) {
111 perror("munmap");
112 exit(1);
113 }
114
115 return ret;
116 }
117