tools/testing/selftests/kcmp/kcmp_test.c: print reason for failure in kcmp_test

I was curious why sys_kcmp wasn't working, which led me to the testcase.
It turned out I hadn't enabled CHECKPOINT_RESTORE in the kernel I was
testing.  Add a decoding of errno to the testcase to make that obvious.

Signed-off-by: Dave Jones <davej@redhat.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/tools/testing/selftests/kcmp/kcmp_test.c b/tools/testing/selftests/kcmp/kcmp_test.c
index 358cc6bfa35d..fa4f1b37e045 100644
--- a/tools/testing/selftests/kcmp/kcmp_test.c
+++ b/tools/testing/selftests/kcmp/kcmp_test.c
@@ -72,7 +72,8 @@ int main(int argc, char **argv)
                 /* This one should return same fd */
                 ret = sys_kcmp(pid1, pid2, KCMP_FILE, fd1, fd1);
                 if (ret) {
-                        printf("FAIL: 0 expected but %d returned\n", ret);
+                        printf("FAIL: 0 expected but %d returned (%s)\n",
+                                ret, strerror(errno));
                         ret = -1;
                 } else
                         printf("PASS: 0 returned as expected\n");
@@ -80,7 +81,8 @@ int main(int argc, char **argv)
                 /* Compare with self */
                 ret = sys_kcmp(pid1, pid1, KCMP_VM, 0, 0);
                 if (ret) {
-                        printf("FAIL: 0 expected but %li returned\n", ret);
+                        printf("FAIL: 0 expected but %li returned (%s)\n",
+                                ret, strerror(errno));
                         ret = -1;
                 } else
                         printf("PASS: 0 returned as expected\n");