none/tests/linux/mremap3.c

   1 #define _GNU_SOURCE 1
   2 #include <sys/mman.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <string.h>
   6 #include <unistd.h>
   7
   8 int main(void)
   9 {
  10    /* first  find free segment of 40K, then unmap it */
  11    void *initial_area = mmap((void *)0x10000000, 40960, PROT_READ|PROT_WRITE,
  12                              MAP_ANONYMOUS|MAP_PRIVATE,0,0);
  13
  14    if (initial_area == MAP_FAILED)
  15       perror ("initial area");
  16    printf("initial_area= %p\n", initial_area);
  17    if (munmap(initial_area, 40960) != 0)
  18       perror ("munmap initial_area");
  19
  20    /* remap the same segment, but with 4K size */
  21    void *area = mmap(initial_area, 4096, PROT_READ|PROT_WRITE,
  22                      MAP_ANONYMOUS|MAP_PRIVATE,0,0);
  23    if (area == MAP_FAILED)
  24       perror ("area");
  25    if (area != initial_area)
  26       printf("FAILED : was expecting to get back the initial_area\n");
  27    printf("area= %p\n", area);
  28    strcpy(area, "Hello World");
  29
  30    /* extend it to 40K */
  31    void *a2 = mremap(area, 4096, 40960, 0);
  32    if (a2 == MAP_FAILED) {
  33       perror("mremap");
  34    }
  35    if (a2 != initial_area)
  36       printf("FAILED : was expecting to get back the same area increased\n");
  37    printf("increased area= %p\n", a2);
  38    printf("%s\n", (char *)a2);
  39    return 0;
  40 }