1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * Example of using hugepage memory in a user application using the mmap
4*4882a593Smuzhiyun * system call with MAP_HUGETLB flag. Before running this program make
5*4882a593Smuzhiyun * sure the administrator has allocated enough default sized huge pages
6*4882a593Smuzhiyun * to cover the 256 MB allocation.
7*4882a593Smuzhiyun *
8*4882a593Smuzhiyun * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
9*4882a593Smuzhiyun * That means the addresses starting with 0x800000... will need to be
10*4882a593Smuzhiyun * specified. Specifying a fixed address is not required on ppc64, i386
11*4882a593Smuzhiyun * or x86_64.
12*4882a593Smuzhiyun */
13*4882a593Smuzhiyun #include <stdlib.h>
14*4882a593Smuzhiyun #include <stdio.h>
15*4882a593Smuzhiyun #include <unistd.h>
16*4882a593Smuzhiyun #include <sys/mman.h>
17*4882a593Smuzhiyun #include <fcntl.h>
18*4882a593Smuzhiyun
19*4882a593Smuzhiyun #define LENGTH (256UL*1024*1024)
20*4882a593Smuzhiyun #define PROTECTION (PROT_READ | PROT_WRITE)
21*4882a593Smuzhiyun
22*4882a593Smuzhiyun #ifndef MAP_HUGETLB
23*4882a593Smuzhiyun #define MAP_HUGETLB 0x40000 /* arch specific */
24*4882a593Smuzhiyun #endif
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun #ifndef MAP_HUGE_SHIFT
27*4882a593Smuzhiyun #define MAP_HUGE_SHIFT 26
28*4882a593Smuzhiyun #endif
29*4882a593Smuzhiyun
30*4882a593Smuzhiyun #ifndef MAP_HUGE_MASK
31*4882a593Smuzhiyun #define MAP_HUGE_MASK 0x3f
32*4882a593Smuzhiyun #endif
33*4882a593Smuzhiyun
34*4882a593Smuzhiyun /* Only ia64 requires this */
35*4882a593Smuzhiyun #ifdef __ia64__
36*4882a593Smuzhiyun #define ADDR (void *)(0x8000000000000000UL)
37*4882a593Smuzhiyun #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
38*4882a593Smuzhiyun #else
39*4882a593Smuzhiyun #define ADDR (void *)(0x0UL)
40*4882a593Smuzhiyun #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
41*4882a593Smuzhiyun #endif
42*4882a593Smuzhiyun
check_bytes(char * addr)43*4882a593Smuzhiyun static void check_bytes(char *addr)
44*4882a593Smuzhiyun {
45*4882a593Smuzhiyun printf("First hex is %x\n", *((unsigned int *)addr));
46*4882a593Smuzhiyun }
47*4882a593Smuzhiyun
write_bytes(char * addr,size_t length)48*4882a593Smuzhiyun static void write_bytes(char *addr, size_t length)
49*4882a593Smuzhiyun {
50*4882a593Smuzhiyun unsigned long i;
51*4882a593Smuzhiyun
52*4882a593Smuzhiyun for (i = 0; i < length; i++)
53*4882a593Smuzhiyun *(addr + i) = (char)i;
54*4882a593Smuzhiyun }
55*4882a593Smuzhiyun
read_bytes(char * addr,size_t length)56*4882a593Smuzhiyun static int read_bytes(char *addr, size_t length)
57*4882a593Smuzhiyun {
58*4882a593Smuzhiyun unsigned long i;
59*4882a593Smuzhiyun
60*4882a593Smuzhiyun check_bytes(addr);
61*4882a593Smuzhiyun for (i = 0; i < length; i++)
62*4882a593Smuzhiyun if (*(addr + i) != (char)i) {
63*4882a593Smuzhiyun printf("Mismatch at %lu\n", i);
64*4882a593Smuzhiyun return 1;
65*4882a593Smuzhiyun }
66*4882a593Smuzhiyun return 0;
67*4882a593Smuzhiyun }
68*4882a593Smuzhiyun
main(int argc,char ** argv)69*4882a593Smuzhiyun int main(int argc, char **argv)
70*4882a593Smuzhiyun {
71*4882a593Smuzhiyun void *addr;
72*4882a593Smuzhiyun int ret;
73*4882a593Smuzhiyun size_t length = LENGTH;
74*4882a593Smuzhiyun int flags = FLAGS;
75*4882a593Smuzhiyun int shift = 0;
76*4882a593Smuzhiyun
77*4882a593Smuzhiyun if (argc > 1)
78*4882a593Smuzhiyun length = atol(argv[1]) << 20;
79*4882a593Smuzhiyun if (argc > 2) {
80*4882a593Smuzhiyun shift = atoi(argv[2]);
81*4882a593Smuzhiyun if (shift)
82*4882a593Smuzhiyun flags |= (shift & MAP_HUGE_MASK) << MAP_HUGE_SHIFT;
83*4882a593Smuzhiyun }
84*4882a593Smuzhiyun
85*4882a593Smuzhiyun if (shift)
86*4882a593Smuzhiyun printf("%u kB hugepages\n", 1 << (shift - 10));
87*4882a593Smuzhiyun else
88*4882a593Smuzhiyun printf("Default size hugepages\n");
89*4882a593Smuzhiyun printf("Mapping %lu Mbytes\n", (unsigned long)length >> 20);
90*4882a593Smuzhiyun
91*4882a593Smuzhiyun addr = mmap(ADDR, length, PROTECTION, flags, -1, 0);
92*4882a593Smuzhiyun if (addr == MAP_FAILED) {
93*4882a593Smuzhiyun perror("mmap");
94*4882a593Smuzhiyun exit(1);
95*4882a593Smuzhiyun }
96*4882a593Smuzhiyun
97*4882a593Smuzhiyun printf("Returned address is %p\n", addr);
98*4882a593Smuzhiyun check_bytes(addr);
99*4882a593Smuzhiyun write_bytes(addr, length);
100*4882a593Smuzhiyun ret = read_bytes(addr, length);
101*4882a593Smuzhiyun
102*4882a593Smuzhiyun /* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
103*4882a593Smuzhiyun if (munmap(addr, length)) {
104*4882a593Smuzhiyun perror("munmap");
105*4882a593Smuzhiyun exit(1);
106*4882a593Smuzhiyun }
107*4882a593Smuzhiyun
108*4882a593Smuzhiyun return ret;
109*4882a593Smuzhiyun }
110