Re: [PATCH] MIPS: BCM47XX: Cast memcmp() of function to (void *)

[Gustavo A. R. Silva]

On Wed, Sep 07, 2022 at 04:05:56PM -0700, Kees Cook wrote:
> Clang is especially sensitive about argument type matching when using
> __overloaded functions (like memcmp(), etc). Help it see that function
> pointers are just "void *". Avoids this error:
> 
> arch/mips/bcm47xx/prom.c:89:8: error: no matching function for call to 'memcmp'
>                    if (!memcmp(prom_init, prom_init + mem, 32))
>                         ^~~~~~
> include/linux/string.h:156:12: note: candidate function not viable: no known conversion from 'void (void)' to 'const void *' for 1st argument extern int memcmp(const void *,const void *,__kernel_size_t);
> 

Don't we have the same problem at line 162?

(next-20220908)arch/mips/bcm47xx/prom.c:
161         for (extmem = 128 << 20; extmem < 512 << 20; extmem <<= 1) {
162                 if (!memcmp(prom_init, (void *)(off + extmem), 16))
163                         break;
164         }

--
Gustavo

> Cc: Hauke Mehrtens <hauke@xxxxxxxxxx>
> Cc: "Rafał Miłecki" <zajec5@xxxxxxxxx>
> Cc: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
> Cc: linux-mips@xxxxxxxxxxxxxxx
> Cc: Nathan Chancellor <nathan@xxxxxxxxxx>
> Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> Cc: llvm@xxxxxxxxxxxxxxx
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Link: https://lore.kernel.org/lkml/202209080652.sz2d68e5-lkp@xxxxxxxxx
> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
> ---
>  arch/mips/bcm47xx/prom.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/mips/bcm47xx/prom.c b/arch/mips/bcm47xx/prom.c
> index ab203e66ba0d..eb5c04a24531 100644
> --- a/arch/mips/bcm47xx/prom.c
> +++ b/arch/mips/bcm47xx/prom.c
> @@ -86,7 +86,7 @@ static __init void prom_init_mem(void)
>  			pr_debug("Assume 128MB RAM\n");
>  			break;
>  		}
> -		if (!memcmp(prom_init, prom_init + mem, 32))
> +		if (!memcmp((void *)prom_init, (void *)prom_init + mem, 32))
>  			break;
>  	}
>  	lowmem = mem;
> -- 
> 2.34.1
>