Linux Kernel  3.7.1
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map_hugetlb.c
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1 /*
2  * Example of using hugepage memory in a user application using the mmap
3  * system call with MAP_HUGETLB flag. Before running this program make
4  * sure the administrator has allocated enough default sized huge pages
5  * to cover the 256 MB allocation.
6  *
7  * For ia64 architecture, Linux kernel reserves Region number 4 for hugepages.
8  * That means the addresses starting with 0x800000... will need to be
9  * specified. Specifying a fixed address is not required on ppc64, i386
10  * or x86_64.
11  */
12 #include <stdlib.h>
13 #include <stdio.h>
14 #include <unistd.h>
15 #include <sys/mman.h>
16 #include <fcntl.h>
17 
18 #define LENGTH (256UL*1024*1024)
19 #define PROTECTION (PROT_READ | PROT_WRITE)
20 
21 #ifndef MAP_HUGETLB
22 #define MAP_HUGETLB 0x40000 /* arch specific */
23 #endif
24 
25 /* Only ia64 requires this */
26 #ifdef __ia64__
27 #define ADDR (void *)(0x8000000000000000UL)
28 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_FIXED)
29 #else
30 #define ADDR (void *)(0x0UL)
31 #define FLAGS (MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB)
32 #endif
33 
34 static void check_bytes(char *addr)
35 {
36  printf("First hex is %x\n", *((unsigned int *)addr));
37 }
38 
39 static void write_bytes(char *addr)
40 {
41  unsigned long i;
42 
43  for (i = 0; i < LENGTH; i++)
44  *(addr + i) = (char)i;
45 }
46 
47 static int read_bytes(char *addr)
48 {
49  unsigned long i;
50 
51  check_bytes(addr);
52  for (i = 0; i < LENGTH; i++)
53  if (*(addr + i) != (char)i) {
54  printf("Mismatch at %lu\n", i);
55  return 1;
56  }
57  return 0;
58 }
59 
60 int main(void)
61 {
62  void *addr;
63  int ret;
64 
65  addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, 0, 0);
66  if (addr == MAP_FAILED) {
67  perror("mmap");
68  exit(1);
69  }
70 
71  printf("Returned address is %p\n", addr);
72  check_bytes(addr);
73  write_bytes(addr);
74  ret = read_bytes(addr);
75 
76  munmap(addr, LENGTH);
77 
78  return ret;
79 }