From: Arnd Bergmann <arnd@kernel.org>
To: Eric Biggers <ebiggers@kernel.org>
Cc: kernel test robot <lkp@intel.com>,
kbuild-all@lists.01.org,
clang-built-linux <clang-built-linux@googlegroups.com>,
Linux Memory Management List <linux-mm@kvack.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
"open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
<linux-crypto@vger.kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Kees Cook <keescook@chromium.org>,
Marco Elver <elver@google.com>,
George Popescu <georgepope@android.com>
Subject: Re: [linux-next:master 952/3956] crypto/blake2b_generic.c:73:13: warning: stack frame size of 9776 bytes in function 'blake2b_compress_one_generic'
Date: Sat, 16 Jan 2021 16:36:44 +0100 [thread overview]
Message-ID: <CAK8P3a1FTzwK=xK2eC5hiBSC+Xjq1eNO_cv3=CRB4csNiMpsUA@mail.gmail.com> (raw)
In-Reply-To: <YAJIhjzmvszXAXUb@gmail.com>
On Sat, Jan 16, 2021 at 2:59 AM Eric Biggers <ebiggers@kernel.org> wrote:
> On Sat, Jan 16, 2021 at 08:59:50AM +0800, kernel test robot wrote
>
> Looks like the clang bug that causes large stack usage in this function
> (https://bugs.llvm.org/show_bug.cgi?id=45803 which is still unfixed) got
> triggered again. Note that the function only has 264 bytes of local variables,
> so there's no reason why it should use anywhere near 9776 bytes of stack space.
>
> I'm not sure what we can do about this. Last time the solution was commit
> 0c0408e86dbe which randomly added a 'pragma nounroll' to the loop at the end.
>
> Anyone have any better idea than randomly trying adding optimization pragmas and
> seeing what makes the report go away?
>
> Also this was reported with clang 12.0.0 which is a prerelease version, so I'm
> not sure how much I'm supposed to care about this report.
I sent a workaround to disable UBSAN_UNSIGNED_OVERFLOW an
x86-32, after showing that this did not affect arm32, arm64 or x86-64:
27c287b41659 ("ubsan: disable unsigned-overflow check for i386")
As the report is for ppc64, it appears that this is not just specific to x86-32
after all. I have had no success in isolating the problem in clang, but I
did not try too hard either. I see this .config also enables
CONFIG_UBSAN_UNSIGNED_OVERFLOW=y, so it would be a
reasonable assumption that this is the same problem as on x86-32.
There is also another thread on CONFIG_UBSAN_UNSIGNED_OVERFLOW
causing BUILD_BUG_ON() failures.
Arnd
prev parent reply other threads:[~2021-01-16 15:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-16 0:59 kernel test robot
2021-01-16 1:59 ` Eric Biggers
2021-01-16 15:36 ` Arnd Bergmann [this message]
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