LXR linux/tools/testing/selftests/vm/map

   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
  35static void check_bytes(char *addr)
  36{
  37        printf("First hex is %x\n", *((unsigned int *)addr));
  38}
  39
  40static 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
  48static 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
  61int 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