linux-kernel - Re: [PATCH] powerpc/32: fix csum_partial_copy

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Message-ID: <20160801131505.GA1742@gate.crashing.org>
Date:	Mon, 1 Aug 2016 08:15:06 -0500
From:	Segher Boessenkool <segher@...nel.crashing.org>
To:	Christophe Leroy <christophe.leroy@....fr>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Scott Wood <oss@...error.net>, antoine.blangy@....fr,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Subject: Re: [PATCH] powerpc/32: fix csum_partial_copy_generic()

On Mon, Aug 01, 2016 at 02:56:05PM +0200, Christophe Leroy wrote:
> --- a/arch/powerpc/lib/checksum_32.S
> +++ b/arch/powerpc/lib/checksum_32.S
> @@ -127,7 +127,8 @@ _GLOBAL(csum_partial_copy_generic)
>  	stw	r7,12(r1)
>  	stw	r8,8(r1)
>  
> -	andi.	r0,r4,1			/* is destination address even ? */
> +	rlwinm	r0,r4,3,0x8		/* is destination address even ? */
> +	rlwnm	r6,r6,r0,0,31		/* swap bytes for odd destination */
>  	cmplwi	cr7,r0,0
>  	addic	r12,r6,0
>  	addi	r6,r4,-4

That does not "swap bytes"; it shifts the word up by 8 bits, instead.
That may or may not do what is intended.


Segher