LXR linux/tools/testing/selftests/vm/hugepage-mmap.c

   1/*
   2 * hugepage-mmap:
   3 *
   4 * Example of using huge page memory in a user application using the mmap
   5 * system call.  Before running this application, make sure that the
   6 * administrator has mounted the hugetlbfs filesystem (on some directory
   7 * like /mnt) using the command mount -t hugetlbfs nodev /mnt. In this
   8 * example, the app is requesting memory of size 256MB that is backed by
   9 * huge pages.
  10 *
  11 * For the ia64 architecture, the Linux kernel reserves Region number 4 for
  12 * huge pages.  That means that if one requires a fixed address, a huge page
  13 * aligned address starting with 0x800000... will be required.  If a fixed
  14 * address is not required, the kernel will select an address in the proper
  15 * range.
  16 * Other architectures, such as ppc64, i386 or x86_64 are not so constrained.
  17 */
  18
  19#include <stdlib.h>
  20#include <stdio.h>
  21#include <unistd.h>
  22#include <sys/mman.h>
  23#include <fcntl.h>
  24
  25#define FILE_NAME "huge/hugepagefile"
  26#define LENGTH (256UL*1024*1024)
  27#define PROTECTION (PROT_READ | PROT_WRITE)
  28
  29/* Only ia64 requires this */
  30#ifdef __ia64__
  31#define ADDR (void *)(0x8000000000000000UL)
  32#define FLAGS (MAP_SHARED | MAP_FIXED)
  33#else
  34#define ADDR (void *)(0x0UL)
  35#define FLAGS (MAP_SHARED)
  36#endif
  37
  38static void check_bytes(char *addr)
  39{
  40        printf("First hex is %x\n", *((unsigned int *)addr));
  41}
  42
  43static void write_bytes(char *addr)
  44{
  45        unsigned long i;
  46
  47        for (i = 0; i < LENGTH; i++)
  48                *(addr + i) = (char)i;
  49}
  50
  51static int read_bytes(char *addr)
  52{
  53        unsigned long i;
  54
  55        check_bytes(addr);
  56        for (i = 0; i < LENGTH; i++)
  57                if (*(addr + i) != (char)i) {
  58                        printf("Mismatch at %lu\n", i);
  59                        return 1;
  60                }
  61        return 0;
  62}
  63
  64int main(void)
  65{
  66        void *addr;
  67        int fd, ret;
  68
  69        fd = open(FILE_NAME, O_CREAT | O_RDWR, 0755);
  70        if (fd < 0) {
  71                perror("Open failed");
  72                exit(1);
  73        }
  74
  75        addr = mmap(ADDR, LENGTH, PROTECTION, FLAGS, fd, 0);
  76        if (addr == MAP_FAILED) {
  77                perror("mmap");
  78                unlink(FILE_NAME);
  79                exit(1);
  80        }
  81
  82        printf("Returned address is %p\n", addr);
  83        check_bytes(addr);
  84        write_bytes(addr);
  85        ret = read_bytes(addr);
  86
  87        munmap(addr, LENGTH);
  88        close(fd);
  89        unlink(FILE_NAME);
  90
  91        return ret;
  92}
  93