[PATCH] s390/kaslr: Fix casts in get_random

[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 <natechancellor@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

Re: [PATCH] s390/kaslr: Fix casts in get_random

[Nick Desaulniers]

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

Re: [PATCH] s390/kaslr: Fix casts in get_random

[Joe Perches]

On Sat, 2020-02-08 at 07:10 -0700, Nathan Chancellor 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>
> ---
>  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,

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?

Re: [PATCH] s390/kaslr: Fix casts in get_random

[Nathan Chancellor]

On Sat, Feb 08, 2020 at 12:17:20PM -0800, Joe Perches wrote:
> On Sat, 2020-02-08 at 07:10 -0700, Nathan Chancellor 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>
> > ---
> >  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,
> 
> 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?

I can certainly do that if the maintainers prefer it.

Cheers,
Nathan

Re: [PATCH] s390/kaslr: Fix casts in get_random

[Vasily Gorbik]

On Thu, Feb 13, 2020 at 11:46:28PM -0700, Nathan Chancellor wrote:
> On Sat, Feb 08, 2020 at 12:17:20PM -0800, Joe Perches wrote:
> > On Sat, 2020-02-08 at 07:10 -0700, Nathan Chancellor 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>
> > > ---
> > >  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,
> > 
> > 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?
> 
> I can certainly do that if the maintainers prefer it.
> 
> Cheers,
> Nathan
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