linux-kernel - Re: [PATCH] powerpc/powermac: Fix low_sleep

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Date:   Fri, 11 Sep 2020 09:56:10 +1000
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Christophe Leroy <christophe.leroy@...roup.eu>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>
Cc:     linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH] powerpc/powermac: Fix low_sleep_handler with KUAP and KUEP

Christophe Leroy <christophe.leroy@...roup.eu> writes:
> low_sleep_handler() has an hardcoded restore of segment registers
> that doesn't take KUAP and KUEP into account.
>
> Use head_32's load_segment_registers() routine instead.
>
> Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
> Fixes: a68c31fc01ef ("powerpc/32s: Implement Kernel Userspace Access Protection")
> Fixes: 31ed2b13c48d ("powerpc/32s: Implement Kernel Userspace Execution Prevention.")
> Cc: stable@...r.kernel.org
> ---
>  arch/powerpc/platforms/powermac/sleep.S | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)

Doesn't build? pmac32_defconfig, gcc 9.3.0:

ld: arch/powerpc/platforms/powermac/sleep.o: in function `core99_wake_up':
(.text+0x25c): undefined reference to `load_segment_registers'

Missing _GLOBAL() presumably?

cheers

> diff --git a/arch/powerpc/platforms/powermac/sleep.S b/arch/powerpc/platforms/powermac/sleep.S
> index f9a680fdd9c4..51bfdfe85058 100644
> --- a/arch/powerpc/platforms/powermac/sleep.S
> +++ b/arch/powerpc/platforms/powermac/sleep.S
> @@ -294,14 +294,7 @@ grackle_wake_up:
>  	 * we do any r1 memory access as we are not sure they
>  	 * are in a sane state above the first 256Mb region
>  	 */
> -	li	r0,16		/* load up segment register values */
> -	mtctr	r0		/* for context 0 */
> -	lis	r3,0x2000	/* Ku = 1, VSID = 0 */
> -	li	r4,0
> -3:	mtsrin	r3,r4
> -	addi	r3,r3,0x111	/* increment VSID */
> -	addis	r4,r4,0x1000	/* address of next segment */
> -	bdnz	3b
> +	bl	load_segment_registers
>  	sync
>  	isync
>  
> -- 
> 2.25.0