Re: [PATCH] powerpc: Fix check for copy/paste instructions in alignment handler

[Nicholas Piggin <npiggin@au1.ibm.com>]

On Wed, 25 Oct 2017 18:16:53 +1100
Paul Mackerras <paulus@ozlabs.org> wrote:

> Commit 07d2a628bc00 ("powerpc/64s: Avoid cpabort in context switch
> when possible", 2017-06-09) changed the definition of PPC_INST_COPY
> and in so doing inadvertently broke the check for copy/paste
> instructions in the alignment fault handler.  The check currently
> matches no instructions.
> 
> This fixes it by ANDing both sides of the comparison with the mask.

Thanks for fixing it. Any reason not to change the mask to 0xfc2006fe
to include the 'last' bit that is now mandatory?

Thanks,
Nick

> 
> Fixes: 07d2a628bc00 ("powerpc/64s: Avoid cpabort in context switch
> when possible")
> Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
> Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
> ---
> Should go to 4.13 stable as well, and will probably apply there
> with fuzz.
> 
>  arch/powerpc/kernel/align.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/powerpc/kernel/align.c b/arch/powerpc/kernel/align.c
> index 43ef251..3e6c074 100644
> --- a/arch/powerpc/kernel/align.c
> +++ b/arch/powerpc/kernel/align.c
> @@ -332,7 +332,7 @@ int fix_alignment(struct pt_regs *regs)
>  	 * when pasting to a co-processor. Furthermore, paste_last is the
>  	 * synchronisation point for preceding copy/paste sequences.
>  	 */
> -	if ((instr & 0xfc0006fe) == PPC_INST_COPY)
> +	if ((instr & 0xfc0006fe) == (PPC_INST_COPY & 0xfc0006fe))
>  		return -EIO;
>  
>  	r = analyse_instr(&op, regs, instr);