[PATCH] s390/kaslr: Fix casts in get_random

[Nathan Chancellor]

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 <natecha...@gmail.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

[Nick Desaulniers]

On Sat, Feb 8, 2020 at 3:11 PM Nathan Chancellor
<natecha...@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 <natecha...@gmail.com>

Thanks for the patch!
Reviewed-by: Nick Desaulniers <ndesau...@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
>

> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-li...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200208141052.48476-1-natechancellor%40gmail.com.



--
Thanks,
~Nick Desaulniers

[Joe Perches]

Why not change the function to take void *?

static inline int cpacf_kmc(unsigned long func, void *param,

u8 *dest, const u8 *src, long src_len)

vs:

static inline int cpacf_kmc(unsigned long func, void *param,
void *dest, const void *src, long src_len)

and remove the casts?

[Nathan Chancellor]

I can certainly do that if the maintainers prefer it.

Cheers,
Nathan

[Vasily Gorbik]

KBUILD_CFLAGS contains -Wno-pointer-sign but special arch/s390/boot code
has a separate set of build flags. Anyhow the change makes sense as it is.
Applied to fixes, thanks