[PATCH] print reason for failure in kcmp_test

[Dave Jones <davej@redhat.com>]

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>

diff --git a/tools/testing/selftests/kcmp/kcmp_test.c b/tools/testing/selftests/kcmp/kcmp_test.c
index 358cc6b..fa4f1b3 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");