Messages in this thread | | | Date | Thu, 8 May 2014 05:12:56 +0530 | From | Afzal Mohammed <> | Subject | Re: [PATCH] arm: memset: zero out upper bytes in r1 |
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Hi Andrey,
On Mon, May 05, 2014 at 11:11:13AM +0400, Andrey Ryabinin wrote:
> memset doesn't work right for following example: > > signed char c = 0xF0; > memset(addr, c, size); > > Variable c is signed, so after typcasting to int the value will be 0xFFFFFFF0. > This value will be passed through r1 regitster to memset function. > memset doesn't zero out upper bytes in r1, so memory will be filled > with 0xFFFFFFF0 instead of expected 0xF0F0F0F0.
> --- a/arch/arm/lib/memset.S > +++ b/arch/arm/lib/memset.S > @@ -22,7 +22,8 @@ ENTRY(memset) > /* > * we know that the pointer in ip is aligned to a word boundary. > */ > -1: orr r1, r1, r1, lsl #8 > +1: and r1, r1, #0xff > + orr r1, r1, r1, lsl #8
int is to be converted to unsigned char in memset, would having above change immediately upon entry to memset rather than at a place where it won't always execute make intention clearer ? (although it doesn't make difference)
ubfx r1, r1, #0, #8 would have given the needed typecasting, but seems it is available only on ARMv6T2 & above.
Regards Afzal
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