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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Sat, 8 Feb 2020 17:12:21 +0000
Message-ID: <CAKwvOdm8-nL=BnTaCort+tAm27bkBzygmipZ7L3eBD4zvmyb8g@mail.gmail.com>
Subject: Re: [PATCH] s390/kaslr: Fix casts in get_random
To:     Nathan Chancellor <natechancellor@gmail.com>
Cc:     Heiko Carstens <heiko.carstens@de.ibm.com>,
        Vasily Gorbik <gor@linux.ibm.com>,
        Christian Borntraeger <borntraeger@de.ibm.com>,
        linux-s390 <linux-s390@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>
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On Sat, Feb 8, 2020 at 3:11 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> Clang warns:
>
> ../arch/s390/boot/kaslr.c:78:25: warning: passing 'char *' to parameter
> of type 'const u8 *' (aka 'const unsigned char *') converts between
> pointers to integer
> types with different sign [-Wpointer-sign]
>                                   (char *) entropy, (char *) entropy,
>                                                     ^~~~~~~~~~~~~~~~
> ../arch/s390/include/asm/cpacf.h:280:28: note: passing argument to
> parameter 'src' here
>                             u8 *dest, const u8 *src, long src_len)
>                                                 ^
> 2 warnings generated.
>
> Fix the cast to match what else is done in this function.
>
> Fixes: b2d24b97b2a9 ("s390/kernel: add support for kernel address space layout randomization (KASLR)")
> Link: https://github.com/ClangBuiltLinux/linux/issues/862
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  arch/s390/boot/kaslr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/s390/boot/kaslr.c b/arch/s390/boot/kaslr.c
> index 5d12352545c5..5591243d673e 100644
> --- a/arch/s390/boot/kaslr.c
> +++ b/arch/s390/boot/kaslr.c
> @@ -75,7 +75,7 @@ static unsigned long get_random(unsigned long limit)
>                 *(unsigned long *) prng.parm_block ^= seed;
>                 for (i = 0; i < 16; i++) {
>                         cpacf_kmc(CPACF_KMC_PRNG, prng.parm_block,
> -                                 (char *) entropy, (char *) entropy,
> +                                 (u8 *) entropy, (u8 *) entropy,
>                                   sizeof(entropy));
>                         memcpy(prng.parm_block, entropy, sizeof(entropy));
>                 }
> --
> 2.25.0
>
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-- 
Thanks,
~Nick Desaulniers