1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * hugepage-mmap:
4*4882a593Smuzhiyun *
5*4882a593Smuzhiyun * Example of using huge page memory in a user application using the mmap
6*4882a593Smuzhiyun * system call. Before running this application, make sure that the
7*4882a593Smuzhiyun * administrator has mounted the hugetlbfs filesystem (on some directory
8*4882a593Smuzhiyun * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this
9*4882a593Smuzhiyun * example, the app is requesting memory of size 256MB that is backed by
10*4882a593Smuzhiyun * huge pages.
11*4882a593Smuzhiyun *
12*4882a593Smuzhiyun * For the ia64 architecture, the Linux kernel reserves Region number 4 for
13*4882a593Smuzhiyun * huge pages. That means that if one requires a fixed address, a huge page
14*4882a593Smuzhiyun * aligned address starting with 0x800000... will be required. If a fixed
15*4882a593Smuzhiyun * address is not required, the kernel will select an address in the proper
16*4882a593Smuzhiyun * range.
17*4882a593Smuzhiyun * Other architectures, such as ppc64, i386 or x86_64 are not so constrained.
18*4882a593Smuzhiyun */
19*4882a593Smuzhiyun
20*4882a593Smuzhiyun #include <stdlib.h>
21*4882a593Smuzhiyun #include <stdio.h>
22*4882a593Smuzhiyun #include <unistd.h>
23*4882a593Smuzhiyun #include <sys/mman.h>
24*4882a593Smuzhiyun #include <fcntl.h>
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun #define FILE_NAME "huge/hugepagefile"
27*4882a593Smuzhiyun #define LENGTH (256UL*1024*1024)
28*4882a593Smuzhiyun #define PROTECTION (PROT_READ | PROT_WRITE)
29*4882a593Smuzhiyun
30*4882a593Smuzhiyun /* Only ia64 requires this */
31*4882a593Smuzhiyun #ifdef __ia64__
32*4882a593Smuzhiyun #define ADDR (void *)(0x8000000000000000UL)
33*4882a593Smuzhiyun #define FLAGS (MAP_SHARED | MAP_FIXED)
34*4882a593Smuzhiyun #else
35*4882a593Smuzhiyun #define ADDR (void *)(0x0UL)
36*4882a593Smuzhiyun #define FLAGS (MAP_SHARED)
37*4882a593Smuzhiyun #endif
38*4882a593Smuzhiyun
check_bytes(char * addr)39*4882a593Smuzhiyun static void check_bytes(char *addr)
40*4882a593Smuzhiyun {
41*4882a593Smuzhiyun printf("First hex is %x\n", *((unsigned int *)addr));
42*4882a593Smuzhiyun }
43*4882a593Smuzhiyun
write_bytes(char * addr)44*4882a593Smuzhiyun static void write_bytes(char *addr)
45*4882a593Smuzhiyun {
46*4882a593Smuzhiyun unsigned long i;
47*4882a593Smuzhiyun
48*4882a593Smuzhiyun for (i = 0; i < LENGTH; i++)
49*4882a593Smuzhiyun *(addr + i) = (char)i;
50*4882a593Smuzhiyun }
51*4882a593Smuzhiyun
read_bytes(char * addr)52*4882a593Smuzhiyun static int read_bytes(char *addr)
53*4882a593Smuzhiyun {
54*4882a593Smuzhiyun unsigned long i;
55*4882a593Smuzhiyun
56*4882a593Smuzhiyun check_bytes(addr);
57*4882a593Smuzhiyun for (i = 0; i < LENGTH; i++)
58*4882a593Smuzhiyun if (*(addr + i) != (char)i) {
59*4882a593Smuzhiyun printf("Mismatch at %lu\n", i);
60*4882a593Smuzhiyun return 1;
61*4882a593Smuzhiyun }
62*4882a593Smuzhiyun return 0;
63*4882a593Smuzhiyun }
64*4882a593Smuzhiyun
main(void)65*4882a593Smuzhiyun int main(void)
66*4882a593Smuzhiyun {
67*4882a593Smuzhiyun void *addr;
68*4882a593Smuzhiyun int fd, ret;
69*4882a593Smuzhiyun
70*4882a593Smuzhiyun fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755);
71*4882a593Smuzhiyun if (fd < 0) {
72*4882a593Smuzhiyun perror("Open failed");
73*4882a593Smuzhiyun exit(1);
74*4882a593Smuzhiyun }
75*4882a593Smuzhiyun
76*4882a593Smuzhiyun addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0);
77*4882a593Smuzhiyun if (addr == MAP_FAILED) {
78*4882a593Smuzhiyun perror("mmap");
79*4882a593Smuzhiyun unlink(FILE_NAME);
80*4882a593Smuzhiyun exit(1);
81*4882a593Smuzhiyun }
82*4882a593Smuzhiyun
83*4882a593Smuzhiyun printf("Returned address is %p\n", addr);
84*4882a593Smuzhiyun check_bytes(addr);
85*4882a593Smuzhiyun write_bytes(addr);
86*4882a593Smuzhiyun ret = read_bytes(addr);
87*4882a593Smuzhiyun
88*4882a593Smuzhiyun munmap(addr, LENGTH);
89*4882a593Smuzhiyun close(fd);
90*4882a593Smuzhiyun unlink(FILE_NAME);
91*4882a593Smuzhiyun
92*4882a593Smuzhiyun return ret;
93*4882a593Smuzhiyun }
94