linux-kernel - Re: ipv4/tcp.c:4234:1: error: the frame size of 1152 bytes is larger than 1024 bytes [-Werror=frame-larger-than=]

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Message-ID: <CAHk-=wiQoxwGkMF34k3twte0N2phNCjbxtsgoW9YNybVPXZtsA@mail.gmail.com>
Date:   Wed, 8 Sep 2021 15:27:52 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Brendan Higgins <brendanhiggins@...gle.com>
Cc:     Shuah Khan <skhan@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        Mathias Nyman <mathias.nyman@...el.com>,
        Johannes Berg <johannes@...solutions.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Ariel Elior <aelior@...vell.com>,
        GR-everest-linux-l2@...vell.com, Wei Liu <wei.liu@...nel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        open list <linux-kernel@...r.kernel.org>,
        Netdev <netdev@...r.kernel.org>, lkft-triage@...ts.linaro.org,
        "David S. Miller" <davem@...emloft.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        KUnit Development <kunit-dev@...glegroups.com>
Subject: Re: ipv4/tcp.c:4234:1: error: the frame size of 1152 bytes is larger
 than 1024 bytes [-Werror=frame-larger-than=]

On Wed, Sep 8, 2021 at 2:25 PM Brendan Higgins
<brendanhiggins@...gle.com> wrote:
>
> I definitely agree that in the cases where KUnit is not actually
> contributing to blowing the stack - struct leak just thinks it is,
> this is fine; however, it sounds like Linus' concerns with KUnit's
> macros go deeper than this.

I don't mind Kunit tests when they don't cause problems, but one very
natural way to use the Kunit test infrastructure does seem to be to
just put a lot of them into one function.

And then the individually fairly small structures just add up.
Probably mainly in some special configurations (ie together with
CONFIG_KASAN_STACK as pointed out by Arnd, but there might be other
cases that cause that issue too) where the compiler then doesn't merge
stack slots.

I wonder if those 'kunit_assert' structures could be split into two:
one part that could be 'static const', and at least shrink the dynamic
stack use that way. Because at a minimun, things like
type/file/line/format-msg seem to be things that really are just
static and const.

Hmm?

          Linus