tools/testing/selftests/powerpc/mm/hugetlb_vs_thp_test.c

   1 #include <stdio.h>
   2 #include <sys/mman.h>
   3 #include <unistd.h>
   4
   5 #include "utils.h"
   6
   7 /* This must match the huge page & THP size */
   8 #define SIZE    (16 * 1024 * 1024)
   9
  10 static int test_body(void)
  11 {
  12         void *addr;
  13         char *p;
  14
  15         addr = (void *)0xa0000000;
  16
  17         p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,
  18                  MAP_HUGETLB | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
  19         if (p != MAP_FAILED) {
  20                 /*
  21                  * Typically the mmap will fail because no huge pages are
  22                  * allocated on the system. But if there are huge pages
  23                  * allocated the mmap will succeed. That's fine too, we just
  24                  * munmap here before continuing.
  25                  */
  26                 munmap(addr, SIZE);
  27         }
  28
  29         p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,
  30                  MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
  31         if (p == MAP_FAILED) {
  32                 printf("Mapping failed @ %p\n", addr);
  33                 perror("mmap");
  34                 return 1;
  35         }
  36
  37         /*
  38          * Either a user or kernel access is sufficient to trigger the bug.
  39          * A kernel access is easier to spot & debug, as it will trigger the
  40          * softlockup or RCU stall detectors, and when the system is kicked
  41          * into xmon we get a backtrace in the kernel.
  42          *
  43          * A good option is:
  44          *  getcwd(p, SIZE);
  45          *
  46          * For the purposes of this testcase it's preferable to spin in
  47          * userspace, so the harness can kill us if we get stuck. That way we
  48          * see a test failure rather than a dead system.
  49          */
  50         *p = 0xf;
  51
  52         munmap(addr, SIZE);
  53
  54         return 0;
  55 }
  56
  57 static int test_main(void)
  58 {
  59         int i;
  60
  61         /* 10,000 because it's a "bunch", and completes reasonably quickly */
  62         for (i = 0; i < 10000; i++)
  63                 if (test_body())
  64                         return 1;
  65
  66         return 0;
  67 }
  68
  69 int main(void)
  70 {
  71         return test_harness(test_main, "hugetlb_vs_thp");
  72 }