linux-kernel - Re: [PATCH] crypto: jitterentropy: build without sanitizer

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Message-ID: <20190802045523.GF18077@gondor.apana.org.au>
Date:   Fri, 2 Aug 2019 14:55:23 +1000
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     "David S. Miller" <davem@...emloft.net>,
        kasan-dev@...glegroups.com,
        Stephan Müller <smueller@...onox.de>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Eric Biggers <ebiggers@...gle.com>,
        Vitaly Chikunov <vt@...linux.org>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] crypto: jitterentropy: build without sanitizer

On Wed, Jul 24, 2019 at 08:51:55PM +0200, Arnd Bergmann wrote:
> Recent clang-9 snapshots double the kernel stack usage when building
> this file with -O0 -fsanitize=kernel-hwaddress, compared to clang-8
> and older snapshots, this changed between commits svn364966 and
> svn366056:
> 
> crypto/jitterentropy.c:516:5: error: stack frame size of 2640 bytes in function 'jent_entropy_init' [-Werror,-Wframe-larger-than=]
> int jent_entropy_init(void)
>     ^
> crypto/jitterentropy.c:185:14: error: stack frame size of 2224 bytes in function 'jent_lfsr_time' [-Werror,-Wframe-larger-than=]
> static __u64 jent_lfsr_time(struct rand_data *ec, __u64 time, __u64 loop_cnt)
>              ^
> 
> I prepared a reduced test case in case any clang developers want to
> take a closer look, but from looking at the earlier output it seems
> that even with clang-8, something was very wrong here.
> 
> Turn off any KASAN and UBSAN sanitizing for this file, as that likely
> clashes with -O0 anyway.  Turning off just KASAN avoids the warning
> already, but I suspect both of these have undesired side-effects
> for jitterentropy.
> 
> Link: https://godbolt.org/z/fDcwZ5
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  crypto/Makefile | 2 ++
>  1 file changed, 2 insertions(+)

Patch applied.  Thanks.
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt