[LTP] [PATCH 2/2] syscalls/pidfd_open*.c: Drop .min_kver flag

Cyril Hrubis chrubis@suse.cz
Fri Jun 12 16:30:04 CEST 2020

> > First, I want to explain my check point:
> > 
> > Passing invalid argument can check the support of pidfd_open(2) by ENOSYS
> > errno and we don't need to close the pidfd.
> > 
> > Second, I don't like the implementation of fsopen_supported_by_kernel() and
> > give some suggestions:
> > 
> > a) syscall()/tst_syscall() is enough to check the support of pidfd_open(2)
> > and 'tst_kvercmp(5, 2, 0)) < 0' will skip the check

Hmm, man pidf_open says that it's implemented starting 5.3 or do I miss

> > ??? if a kernel on distribution is newer than v5.2 but drop the support of
> > pidfd_open(2) on purpose.
> I don't think kernel can drop support of syscalls just like that, we
> can't break user space. And if that is done, we need to fix userspace
> again separately for that.

For most cases we cannot, there are a few that are guarded by CONFIG_
macros though e.g. SysV IPC.

> We came to the implementation of fsopen_supported_by_kernel() after a
> lot of reviews and decided on that and so I asked you for the sake of
> keeping similar code throughout LTP (of course there will be old
> usages which are different) to have a similar implementation.
> Anyway, I will leave it to Cyril to decide on that :)

Agree here, doing the check only if kernel version is not sufficient
seems to be the most reasoanble strategy here.

Cyril Hrubis

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