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 
32 static void check_bytes(char *addr)
33 {
34 	printf("First hex is %x\n", *((unsigned int *)addr));
35 }
36 
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 
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 
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