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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 /* Only ia64 requires this */
27 #ifdef __ia64__
28 #define ADDR (void *)(0x8000000000000000UL)
29 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
30 #else
31 #define ADDR (void *)(0x0UL)
32 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
33 #endif
34 
check_bytes(char * addr)35 static void check_bytes(char *addr)
36 {
37 	printf("First hex is %x\n", *((unsigned int *)addr));
38 }
39 
write_bytes(char * addr)40 static void write_bytes(char *addr)
41 {
42 	unsigned long i;
43 
44 	for (i = 0; i < LENGTH; i++)
45 		*(addr + i) = (char)i;
46 }
47 
read_bytes(char * addr)48 static int read_bytes(char *addr)
49 {
50 	unsigned long i;
51 
52 	check_bytes(addr);
53 	for (i = 0; i < LENGTH; i++)
54 		if (*(addr + i) != (char)i) {
55 			printf("Mismatch at %lu\n", i);
56 			return 1;
57 		}
58 	return 0;
59 }
60 
main(void)61 int main(void)
62 {
63 	void *addr;
64 	int ret;
65 
66 	addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, -1, 0);
67 	if (addr == MAP_FAILED) {
68 		perror("mmap");
69 		exit(1);
70 	}
71 
72 	printf("Returned address is %p\n", addr);
73 	check_bytes(addr);
74 	write_bytes(addr);
75 	ret = read_bytes(addr);
76 
77 	/* munmap() length of MAP_HUGETLB memory must be hugepage aligned */
78 	if (munmap(addr, LENGTH)) {
79 		perror("munmap");
80 		exit(1);
81 	}
82 
83 	return ret;
84 }
85