Re: [PATCH 087/100] powerpc: Restore registers on error exit from csum_partial_copy_generic()

[Luis Henriques <luis.henriques@canonical.com>]

Luis Henriques <luis.henriques@canonical.com> writes:

> 3.5.7.23 -stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>
> commit 8f21bd0090052e740944f9397e2be5ac7957ded7 upstream.

I'm dropping this patch as it is causing some build failures on
powerpc configs.

Cheers,
-- 
Luis


>
> The csum_partial_copy_generic() function saves the PowerPC
>non-volatile
> r14, r15, and r16 registers for the main checksum-and-copy loop.
> Unfortunately, it fails to restore them upon error exit from this loop,
> which results in silent corruption of these registers in the presumably
> rare event of an access exception within that loop.
>
> This commit therefore restores these register on error exit from the loop.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Signed-off-by: Anton Blanchard <anton@samba.org>
> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
> ---
>  arch/powerpc/lib/checksum_64.S | 54 +++++++++++++++++++++++++++++++-----------
>  1 file changed, 40 insertions(+), 14 deletions(-)
>
> diff --git a/arch/powerpc/lib/checksum_64.S b/arch/powerpc/lib/checksum_64.S
> index afa2eba..d0e8390 100644
> --- a/arch/powerpc/lib/checksum_64.S
> +++ b/arch/powerpc/lib/checksum_64.S
> @@ -229,19 +229,35 @@ _GLOBAL(csum_partial)
>  	blr
>  
>  
> -	.macro source
> +	.macro srcnr
>  100:
>  	.section __ex_table,"a"
>  	.align 3
> -	.llong 100b,.Lsrc_error
> +	.llong 100b,.Lsrc_error_nr
>  	.previous
>  	.endm
>  
> -	.macro dest
> +	.macro source
> +150:
> +	.section __ex_table,"a"
> +	.align 3
> +	.llong 150b,.Lsrc_error
> +	.previous
> +	.endm
> +
> +	.macro dstnr
>  200:
>  	.section __ex_table,"a"
>  	.align 3
> -	.llong 200b,.Ldest_error
> +	.llong 200b,.Ldest_error_nr
> +	.previous
> +	.endm
> +
> +	.macro dest
> +250:
> +	.section __ex_table,"a"
> +	.align 3
> +	.llong 250b,.Ldest_error
>  	.previous
>  	.endm
>  
> @@ -277,11 +293,11 @@ _GLOBAL(csum_partial_copy_generic)
>  	mtctr	r6
>  
>  1:
> -source;	lhz	r6,0(r3)		/* align to doubleword */
> +srcnr;	lhz	r6,0(r3)		/* align to doubleword */
>  	subi	r5,r5,2
>  	addi	r3,r3,2
>  	adde	r0,r0,r6
> -dest;	sth	r6,0(r4)
> +dstnr;	sth	r6,0(r4)
>  	addi	r4,r4,2
>  	bdnz	1b
>  
> @@ -395,10 +411,10 @@ dest;	std	r16,56(r4)
>  
>  	mtctr	r6
>  3:
> -source;	ld	r6,0(r3)
> +srcnr;	ld	r6,0(r3)
>  	addi	r3,r3,8
>  	adde	r0,r0,r6
> -dest;	std	r6,0(r4)
> +dstnr;	std	r6,0(r4)
>  	addi	r4,r4,8
>  	bdnz	3b
>  
> @@ -408,10 +424,10 @@ dest;	std	r6,0(r4)
>  	srdi.	r6,r5,2
>  	beq	.Lcopy_tail_halfword
>  
> -source;	lwz	r6,0(r3)
> +srcnr;	lwz	r6,0(r3)
>  	addi	r3,r3,4
>  	adde	r0,r0,r6
> -dest;	stw	r6,0(r4)
> +dstnr;	stw	r6,0(r4)
>  	addi	r4,r4,4
>  	subi	r5,r5,4
>  
> @@ -419,10 +435,10 @@ dest;	stw	r6,0(r4)
>  	srdi.	r6,r5,1
>  	beq	.Lcopy_tail_byte
>  
> -source;	lhz	r6,0(r3)
> +srcnr;	lhz	r6,0(r3)
>  	addi	r3,r3,2
>  	adde	r0,r0,r6
> -dest;	sth	r6,0(r4)
> +dstnr;	sth	r6,0(r4)
>  	addi	r4,r4,2
>  	subi	r5,r5,2
>  
> @@ -430,10 +446,10 @@ dest;	sth	r6,0(r4)
>  	andi.	r6,r5,1
>  	beq	.Lcopy_finish
>  
> -source;	lbz	r6,0(r3)
> +srcnr;	lbz	r6,0(r3)
>  	sldi	r9,r6,8			/* Pad the byte out to 16 bits */
>  	adde	r0,r0,r9
> -dest;	stb	r6,0(r4)
> +dstnr;	stb	r6,0(r4)
>  
>  .Lcopy_finish:
>  	addze	r0,r0			/* add in final carry */
> @@ -443,6 +459,11 @@ dest;	stb	r6,0(r4)
>  	blr
>  
>  .Lsrc_error:
> +	ld	r14,STK_REG(R14)(r1)
> +	ld	r15,STK_REG(R15)(r1)
> +	ld	r16,STK_REG(R16)(r1)
> +	addi	r1,r1,STACKFRAMESIZE
> +.Lsrc_error_nr:
>  	cmpdi	0,r7,0
>  	beqlr
>  	li	r6,-EFAULT
> @@ -450,6 +471,11 @@ dest;	stb	r6,0(r4)
>  	blr
>  
>  .Ldest_error:
> +	ld	r14,STK_REG(R14)(r1)
> +	ld	r15,STK_REG(R15)(r1)
> +	ld	r16,STK_REG(R16)(r1)
> +	addi	r1,r1,STACKFRAMESIZE
> +.Ldest_error_nr:
>  	cmpdi	0,r8,0
>  	beqlr
>  	li	r6,-EFAULT