[PATCH] [PATCH] powerpc/sstep: Check ISA 3.0 instruction validity before emulation

[Naveen N. Rao]

On 2021/01/20 03:16PM, Ananth N Mavinakayanahalli wrote:
> We currently unconditionally try to newer emulate instructions on older
				      ^^^^^ never?
				      Or: "emulate newer"?

> Power versions that could cause issues. Gate it.
> 
> Signed-off-by: Ananth N Mavinakayanahalli <ananth at linux.ibm.com>
> ---
>  arch/powerpc/lib/sstep.c |   40 ++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 40 insertions(+)

Thanks!

> 
> diff --git a/arch/powerpc/lib/sstep.c b/arch/powerpc/lib/sstep.c
> index bf7a7d62ae8b..ed119858e5e9 100644
> --- a/arch/powerpc/lib/sstep.c
> +++ b/arch/powerpc/lib/sstep.c
> @@ -1528,6 +1528,8 @@ int analyse_instr(struct instruction_op *op, const struct pt_regs *regs,
>  		goto compute_done;
>  
>  	case 19:
> +		if (!cpu_has_feature(CPU_FTR_ARCH_300))
> +			return -1;
>  		if (((word >> 1) & 0x1f) == 2) {
>  			/* addpcis */
>  			imm = (short) (word & 0xffc1);	/* d0 + d2 fields */

The cpu feature check should be within the if condition above since 
there are other instructions under opcode 19. This is not an issue right 
now as we don't emulate any of the others after this point, but it would 
be good to restrict the change to specific instructions.

Rest of the changes below look good to me. The only other v3.0 
instruction we need to gate is the 'scv' instruction. It would be good 
to handle that too.

- Naveen