tools/testing/selftests/vm/map_hugetlb.c

   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
  35 static void check_bytes(char *addr)
  36 {
  37         printf("First hex is %x\n", *((unsigned int *)addr));
  38 }
  39
  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
  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
  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 }