linux-kernel - Re: kunit stack usage, was: pmwg-ci report v5.5-rc4-147-gc62d43442481

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Message-ID: <202001151727.C07DA17@keescook>
Date:   Wed, 15 Jan 2020 17:29:32 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     PMWG CI <pmwg-ci@...aro.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Private Kernel Alias <private-kwg@...aro.org>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: Re: kunit stack usage, was: pmwg-ci report v5.5-rc4-147-gc62d43442481

On Tue, Jan 07, 2020 at 01:37:07PM +0100, Arnd Bergmann wrote:
> On Mon, Dec 30, 2019 at 6:16 PM PMWG CI <pmwg-ci@...aro.org> wrote:
> >
> >
> > The error/warning: 1 drivers/base/test/property-entry-test.c:214:1: warning: the frame size of 3128 bytes is larger than 2048 bytes [-Wframe-larger-than=]
> > ... was introduced by commit:
> >
> > commit c032ace71c29d513bf9df64ace1885fe5ff24981
> > Author: Dmitry Torokhov <dmitry.torokhov@...il.com>
> > Date:   Wed Dec 4 10:53:15 2019 -0800
> >
> >     software node: add basic tests for property entries
> 
> This problem is a result of the KUNIT_ASSERTION() definition that puts
> a local struct on the stack interacting badly with the structleak_plugin
> when CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL is set in
> allmodconfig:

Geh, BYREF_ALL strikes again. I'm at LCA currently, but I'd like to try
to revisit actually fixing the basic-block splitting in the plugin. This
was looked at before, but I need to dig up the thread.

If a fast fix is needed, I'm fine with disabling BYREF_ALL with KUNIT.
It's not optimal, but I feel it's on the BYREF_ALL code to solve this. :)

-- 
Kees Cook