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