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SubjectRe: [PATCH] livepatch: core: Return ENOTSUPP instead of ENOSYS
On Mon, Jan 28, 2019 at 02:49:43PM -0500, Joe Lawrence wrote:
> On Sun, Jan 27, 2019 at 04:26:30AM +0900, Alice Ferrazzi wrote:
> > This patch fixes a checkpatch warning:
> > WARNING: ENOSYS means 'invalid syscall nr' and nothing else
> >
> > Signed-off-by: Alice Ferrazzi <alice.ferrazzi@miraclelinux.com>
> > ---
> > kernel/livepatch/core.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
> > index 5b77a7314e01..eea6b94fef89 100644
> > --- a/kernel/livepatch/core.c
> > +++ b/kernel/livepatch/core.c
> > @@ -897,7 +897,7 @@ int klp_register_patch(struct klp_patch *patch)
> >
> > if (!klp_have_reliable_stack()) {
> > pr_err("This architecture doesn't have support for the livepatch consistency model.\n");
> > - return -ENOSYS;
> > + return -ENOTSUPP;
> > }
> >
> > return klp_init_patch(patch);
> > --
> > 2.19.2
> >
>
> Hi Alice,
>
> Patches should be based off the upstream livepatching tree, found here:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/livepatching/livepatching.git
>
> and in this case, the for-next branch, which holds patches that have
> already been queued up for the next release. This one:
>
> 958ef1e39d24 ("livepatch: Simplify API by removing registration step")
>
> has moved the code in question from klp_register_patch() to
> klp_enable_patch().
>
>
> As far as the change itself, I don't have strong opinion about it
> either way.
>
> On the one hand, there is the checkpatch warning and -ENOTSUPP reads
> more intuitively than -ENOSYS.
>
> However, the current pattern seems to be more prevelent in the kernel.
> I wonder if the checkpatch warning would be better specified for return
> values that are actually passed back to userspace.
>
> Also, klp_register_patch(), now klp_enable_patch(), is exported for
> module use, though I don't believe anyone (samples / tests / kpatch /
> kgraft?) is inspecting which error value is returned.
>
> I would defer to whichever convention the maintainers prefer here.

Based on the commit description from 91c9afaf97ee ("checkpatch.pl: new
instances of ENOSYS are errors"), it sounds like there was a decision at
Kernel Summit to limit ENOSYS to mean "bad syscall" and nothing else.

So I'm ok with this change, though the patch description should have a
little more background on why it's being done -- checkpatch.pl alone
isn't a good justification because some checkpatch warnings are best
taken with a grain of salt.

--
Josh

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