[LTP] [PATCH v2 1/2] syscalls/pidfd_open01.c: Add check for close-on-exec flag

[Petr Vorel <pvorel@suse.cz>]

Hi Yang,

one more note:

> > As my pervious mail said, It is just a possible situation? for example:
> > Upstream kernel introduces btrfs filesystem long long ago but the
> > kernel of RHEL8 drops btrfs filesystem because of some reasons.
> I guess filesystem changes are the most frequent. But as I said, I wouldn't mind
> this implementation:
> void fsopen_supported_by_kernel(void)
> {
> 	TEST(tst_syscall(__NR_fsopen, NULL, 0));
> 	if (TST_RET != -1)
> 		SAFE_CLOSE(TST_RET);
> }
BTW the same approach is used in include/lapi/openat2.h

void openat2_supported_by_kernel(void)
{
	if ((tst_kvercmp(5, 6, 0)) < 0) {
		/* Check if the syscall is backported on an older kernel */
		TEST(syscall(__NR_openat2, -1, NULL, NULL, 0));
		if (TST_RET == -1 && TST_ERR == ENOSYS)
			tst_brk(TCONF, "Test not supported on kernel version < v5.6");
	}
}

and clone3_supported_by_kernel(). Both merged by Cyril.

To be honest I like this approach, because 1) it defines when new syscall was
backported 2) if there is really problem that some functionality was removed, we
can always handle it. But IMHO that's going to be rare (btrfs removed in RHEL 8
is IMHO because RHEL does not want to support it, but that would not happen for
syscalls).

I'd also like to be consistent how we handle these new syscalls.

Kind regards,
Petr