[PATCH v1 2/2] selftests/mm: hugetlb_fault_after_madv: improve test output

[David Hildenbrand]

Let's improve the test output. For example, print the proper test
result. Install a SIGBUS handler to catch any SIGBUS instead of
crashing the test on failure.

With unsuitable hugetlb page count:
  $ ./hugetlb_fault_after_madv
  TAP version 13
  1..1
  # [INFO] detected default hugetlb page size: 2048 KiB
  ok 2 # SKIP This test needs one and only one page to execute. Got 0
  # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:1 error:0

On a failure:
  $ ./hugetlb_fault_after_madv
  TAP version 13
  1..1
  not ok 1 SIGBUS behavior
  Bail out! 1 out of 1 tests failed

On success:
  $ ./hugetlb_fault_after_madv
  TAP version 13
  1..1
  # [INFO] detected default hugetlb page size: 2048 KiB
  ok 1 SIGBUS behavior
  # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:0 error:0

Signed-off-by: David Hildenbrand <da...@redhat.com>
---
 .../selftests/mm/hugetlb_fault_after_madv.c   | 34 ++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c 
b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c
index ff3ba675278d..e2640529dbb2 100644
--- a/tools/testing/selftests/mm/hugetlb_fault_after_madv.c
+++ b/tools/testing/selftests/mm/hugetlb_fault_after_madv.c
@@ -5,6 +5,8 @@
 #include <sys/mman.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <setjmp.h>
+#include <signal.h>
 
 #include "vm_util.h"
 #include "../kselftest.h"
@@ -14,11 +16,25 @@
 static char *huge_ptr;
 static size_t huge_page_size;
 
+static sigjmp_buf sigbuf;
+static bool sigbus_triggered;
+
+static void signal_handler(int signal)
+{
+       if (signal == SIGBUS) {
+               sigbus_triggered = true;
+               siglongjmp(sigbuf, 1);
+       }
+}
+
 /* Touch the memory while it is being madvised() */
 void *touch(void *unused)
 {
        char *ptr = (char *)huge_ptr;
 
+       if (sigsetjmp(sigbuf, 1))
+               return NULL;
+
        for (int i = 0; i < INLOOP_ITER; i++)
                ptr[0] = '.';
 
@@ -44,13 +60,23 @@ int main(void)
         * interactions
         */
        int max = 10000;
+       int err;
+
+       ksft_print_header();
+       ksft_set_plan(1);
 
        srand(getpid());
 
+       if (signal(SIGBUS, signal_handler) == SIG_ERR)
+               ksft_exit_skip("Could not register signal handler.");
+
        huge_page_size = default_huge_page_size();
        if (!huge_page_size)
                ksft_exit_skip("Could not detect default hugetlb page size.");
 
+       ksft_print_msg("[INFO] detected default hugetlb page size: %zu KiB\n",
+                      huge_page_size / 1024);
+
        free_hugepages = get_free_hugepages();
        if (free_hugepages != 1) {
                ksft_exit_skip("This test needs one and only one page to 
execute. Got %lu\n",
@@ -73,5 +99,11 @@ int main(void)
                munmap(huge_ptr, huge_page_size);
        }
 
-       return KSFT_PASS;
+       ksft_test_result(!sigbus_triggered, "SIGBUS behavior\n");
+
+       err = ksft_get_fail_cnt();
+       if (err)
+               ksft_exit_fail_msg("%d out of %d tests failed\n",
+                                  err, ksft_test_num());
+       ksft_exit_pass();
 }
-- 
2.46.1