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 
43 static void check_bytes(char *addr)
44 {
45 	printf("First hex is %x\n", *((unsigned int *)addr));
46 }
47 
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 
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 
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