On Wed, Feb 24, 2021 at 10:37 PM Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Feb 24, 2021 at 1:30 PM Linus Torvalds
> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> >
> > Hmm. I haven't bisected things yet, but I suspect it's something with
> > the KASAN patches. With this all applied, I get:
> >
> > lib/crypto/curve25519-hacl64.c: In function ‘ladder_cmult.constprop’:
> > lib/crypto/curve25519-hacl64.c:601:1: warning: the frame size of
> > 2288 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> >
> > and
> >
> > lib/bitfield_kunit.c: In function ‘test_bitfields_constants’:
> > lib/bitfield_kunit.c:93:1: warning: the frame size of 11200 bytes is
> > larger than 2048 bytes [-Wframe-larger-than=]
> >
> > which is obviously not really acceptable. A 11kB stack frame _will_
> > cause issues.
>
> A quick bisect shoes that this was introduced by "[patch 101/173]
> kasan: remove redundant config option".
>
> I didn't check what part of that patch screws up, but it's definitely
> doing something bad.
I'm not sure why that patch surfaced the bug, but it's worth pointing
out that the underlying problem is asan-stack in combination
with the structleak plugin. This will happen for every user of kunit.
I sent a series[1] out earlier this year to turn off the structleak
plugin as an alternative workaround, but need to follow up on
the remaining patches. Someone suggested adding a more
generic way to turn off the plugin for a file instead of open-coding
the CLFAGS_REMOVE_*.o Makefile bit, which would help.
I am also still hoping that someone can come up with a way
to make kunit work better with the structleak plugin, as there
shouldn't be a fundamental reason why it can't work, just that
it the code pattern triggers a particularly bad case in the compiler.
Arnd
[1] https://lore.kernel.org/lkml/20210125124533.101339-1-arnd@xxxxxxxxxx/
