[LTP] [PATCH] syscalls/prctl04: Fix false positive report when SECCOMP_MODE_FILTER is not supported

[Cyril Hrubis]

Hi!
I did reply to the github issue already with:

Looking at the patch, maybe it would be cleaner if we did a test if
SECCOMP_MODE_FILTER is supported in the test setup and set up a global
variable based on that, something as:

diff --git a/testcases/kernel/syscalls/prctl/prctl04.c b/testcases/kernel/syscalls/prctl/prctl04.c
index b9f4c2a10..d4e44cb1b 100644
--- a/testcases/kernel/syscalls/prctl/prctl04.c
+++ b/testcases/kernel/syscalls/prctl/prctl04.c
@@ -61,6 +61,8 @@ static const struct sock_fprog  strict = {
        .filter = (struct sock_filter *)strict_filter
 };

+static int mode_filter_supported;
+
 static void check_strict_mode(int);
 static void check_filter_mode(int);

@@ -219,6 +221,16 @@ static void setup(void)
        TEST(prctl(PR_GET_SECCOMP));
        if (TST_RET == 0) {
                tst_res(TINFO, "kernel support PR_GET/SET_SECCOMP");
+
+               TEST(prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, NULL));
+
+               if (TST_ERR == EFAULT) {
+                       mode_filter_supported = 1;
+                       tst_res(TINFO, "kernel support SECCOMP_MODE_FILTER");
+                       return;
+               }
+
+               tst_res(TINFO, "kernel doesn't support SECCOMP_MODE_FILTER");
                return;
        }

Then we can simply use the mode_filter_supported either not to print the
failure or even to skip the test to begin with.

-- 
Cyril Hrubis
chrubis@suse.cz