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.  munmap() length of
  25                  * MAP_HUGETLB memory must be hugepage aligned.
  26                  */
  27                 if (munmap(addr, SIZE)) {
  28                         perror("munmap");
  29                         return 1;
  30                 }
  31         }
  32
  33         p = mmap(addr, SIZE, PROT_READ | PROT_WRITE,
  34                  MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
  35         if (p == MAP_FAILED) {
  36                 printf("Mapping failed @ %p\n", addr);
  37                 perror("mmap");
  38                 return 1;
  39         }
  40
  41         /*
  42          * Either a user or kernel access is sufficient to trigger the bug.
  43          * A kernel access is easier to spot & debug, as it will trigger the
  44          * softlockup or RCU stall detectors, and when the system is kicked
  45          * into xmon we get a backtrace in the kernel.
  46          *
  47          * A good option is:
  48          *  getcwd(p, SIZE);
  49          *
  50          * For the purposes of this testcase it's preferable to spin in
  51          * userspace, so the harness can kill us if we get stuck. That way we
  52          * see a test failure rather than a dead system.
  53          */
  54         *p = 0xf;
  55
  56         munmap(addr, SIZE);
  57
  58         return 0;
  59 }
  60
  61 static int test_main(void)
  62 {
  63         int i;
  64
  65         /* 10,000 because it's a "bunch", and completes reasonably quickly */
  66         for (i = 0; i < 10000; i++)
  67                 if (test_body())
  68                         return 1;
  69
  70         return 0;
  71 }
  72
  73 int main(void)
  74 {
  75         return test_harness(test_main, "hugetlb_vs_thp");
  76 }