[PATCH 1/2] powerpc: Fix emulation of mcrf in emulate_step()

[Naveen N. Rao]

On 2017/06/15 09:46AM, Anton Blanchard wrote:
> From: Anton Blanchard <anton at samba.org>
> 
> The mcrf emulation code was looking at the CR fields in the reverse
> order. It also relied on reserved fields being zero which is somewhat
> fragile, so fix that too.

Yikes! Amazing catch!
Acked-by: Naveen N. Rao <naveen.n.rao at linux.vnet.ibm.com>

Thanks,
Naveen

> 
> Cc: stable at vger.kernel.org
> Signed-off-by: Anton Blanchard <anton at samba.org>
> ---
>  arch/powerpc/lib/sstep.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index 33117f8a0882..fb84f51b1f0b 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -683,8 +683,10 @@ int analyse_instr(struct instruction_op *op, struct pt_regs *regs,
>  	case 19:
>  		switch ((instr >> 1) & 0x3ff) {
>  		case 0:		/* mcrf */
> -			rd = (instr >> 21) & 0x1c;
> -			ra = (instr >> 16) & 0x1c;
> +			rd = 7 - ((instr >> 23) & 0x7);
> +			ra = 7 - ((instr >> 18) & 0x7);
> +			rd *= 4;
> +			ra *= 4;
>  			val = (regs->ccr >> ra) & 0xf;
>  			regs->ccr = (regs->ccr & ~(0xfUL << rd)) | (val << rd);
>  			goto instr_done;
> -- 
> 2.11.0
>