[PATCH V4 1/1] ARM : missing corrupted reg in __div64_32

[Dave Martin]

On Fri, Apr 01, 2016 at 06:28:49PM +0800, chengang wrote:
> __xl(R0 in little endian system, or R1 in big endian system) is corrupted
> by the call to  __do_div64i(). The  compiler is not aware of this, so if

Should that be "__do_div64", not "__do_div64i"?

> n is used afterwards __xl won't be reloaded and n will contain incorrect value.
> 
> Mark 64bits variable __n as inputi/output to inform compiler both r0 and r1

Typo: "inputi"

> are changed by the funciton call.
> 
> Signed-off-by: Chen Gang <gangchen at rdamicro.com>
> Signed-off-by: Chen Gang <changeang.beijing at outlook.com>
> ---
>  arch/arm/include/asm/div64.h | 22 ++++++++--------------
>  1 file changed, 8 insertions(+), 14 deletions(-)
> 
> diff --git a/arch/arm/include/asm/div64.h b/arch/arm/include/asm/div64.h
> index e1f0776..1153e6d 100644
> --- a/arch/arm/include/asm/div64.h
> +++ b/arch/arm/include/asm/div64.h
> @@ -21,30 +21,24 @@
>   * for arguments and results (beware).
>   */
>  
> -#ifdef __ARMEB__
> -#define __xh "r0"
> -#define __xl "r1"
> -#else
> -#define __xl "r0"
> -#define __xh "r1"
> -#endif
>  
>  static inline uint32_t __div64_32(uint64_t *n, uint32_t base)
>  {
>  	register unsigned int __base      asm("r4") = base;
>  	register unsigned long long __n   asm("r0") = *n;
>  	register unsigned long long __res asm("r2");
> -	register unsigned int __rem       asm(__xh);
> -	asm(	__asmeq("%0", __xh)
> +	asm(	__asmeq("%0", "r0")
>  		__asmeq("%1", "r2")
> -		__asmeq("%2", "r0")
> -		__asmeq("%3", "r4")
> +		__asmeq("%2", "r4")
>  		"bl	__do_div64"
> -		: "=r" (__rem), "=r" (__res)
> -		: "r" (__n), "r" (__base)
> +		: "+r" (__n), "=r" (__res)
> +		: "r" (__base)
>  		: "ip", "lr", "cc");
>  	*n = __res;
> -	return __rem;
> +	/*
> +	 * __do_div64 returns the remainder in the upper word of __n
> +	 */

Minor nit: ^ this is short enough to be a one-line comment

> +	return __n >> 32;
>  }
>  #define __div64_32 __div64_32

With those changes,

Reviewed-by: Dave Martin <Dave.Martin at arm.com>

Cheers
---Dave