[PATCH 1/6] powerpc test_emulate_step: update nip with patched instruction address

[Jordan Niethe]

On Mon, Jun 22, 2020 at 5:10 PM Balamuruhan S <bala24 at linux.ibm.com> wrote:
>
> pt_regs are initialized to zero in the test infrastructure, R bit
> in prefixed instruction form is used to specify whether the effective
> address of the storage operand is computed relative to the address
> of the instruction.
>
> If R = 1 and RA = R0|0, the sum of the address of the instruction
> and the value SI is placed into register RT. So to assert the emulated
> instruction with executed instruction, update nip of emulated pt_regs.
>
> Signed-off-by: Balamuruhan S <bala24 at linux.ibm.com>
> ---
>  arch/powerpc/lib/test_emulate_step.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/lib/test_emulate_step.c b/arch/powerpc/lib/test_emulate_step.c
> index 33a72b7d2764..d5902b7b4e5c 100644
> --- a/arch/powerpc/lib/test_emulate_step.c
> +++ b/arch/powerpc/lib/test_emulate_step.c
> @@ -1204,13 +1204,24 @@ static struct compute_test compute_tests[] = {
>  static int __init emulate_compute_instr(struct pt_regs *regs,
>                                         struct ppc_inst instr)
>  {
> +       int prefix_r, ra;
>         extern s32 patch__exec_instr;
>         struct instruction_op op;
>
>         if (!regs || !ppc_inst_val(instr))
>                 return -EINVAL;
>
> -       regs->nip = patch_site_addr(&patch__exec_instr);
Is there any harm in just always setting the NIP like this instead of
only setting it for relative prefixed instructions?
> +       /*
> +        * If R=1 and RA=0 in Prefixed instruction form, calculate the address
> +        * of the instruction and update nip to assert with executed
> +        * instruction
> +        */
> +       if (ppc_inst_prefixed(instr)) {
> +               prefix_r = ppc_inst_val(instr) & (1UL << 20);
> +               ra = (ppc_inst_suffix(instr) >> 16) & 0x1f;
> +               if (prefix_r && !ra)
> +                       regs->nip = patch_site_addr(&patch__exec_instr);
> +       }
>
>         if (analyse_instr(&op, regs, instr) != 1 ||
>             GETTYPE(op.type) != COMPUTE) {
> --
> 2.24.1
>