Re: [PATCH 09/10] perf intel pt: Add new JMPABS instruction to the Intel PT instruction decoder

[Adrian Hunter <adrian.hunter@intel.com>]

On 2/05/24 13:58, Adrian Hunter wrote:
> JMPABS is 64-bit absolute direct jump instruction, encoded with a mandatory
> REX2 prefix. JMPABS is designed to be used in the procedure linkage table
> (PLT) to replace indirect jumps, because it has better performance. In that
> case the jump target will be amended at run time. To enable Intel PT to
> follow the code, a TIP packet is always emitted when JMPABS is traced under
> Intel PT.
> 
> Refer to the Intel Advanced Performance Extensions (Intel APX) Architecture
> Specification for details.
> 
> Decode JMPABS as an indirect jump, because it has an associated TIP packet
> the same as an indirect jump and the control flow should follow the TIP
> packet payload, and not assume it is the same as the on-file object code
> JMPABS target address.
> 
> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>

Patches 1-8 are in perf-tools-next now, so this and patch 10
could be applied.

> ---
>  tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c
> index c5d57027ec23..4407130d91f8 100644
> --- a/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c
> +++ b/tools/perf/util/intel-pt-decoder/intel-pt-insn-decoder.c
> @@ -92,6 +92,15 @@ static void intel_pt_insn_decoder(struct insn *insn,
>  		op = INTEL_PT_OP_JCC;
>  		branch = INTEL_PT_BR_CONDITIONAL;
>  		break;
> +	case 0xa1:
> +		if (insn_is_rex2(insn)) { /* jmpabs */
> +			intel_pt_insn->op = INTEL_PT_OP_JMP;
> +			/* jmpabs causes a TIP packet like an indirect branch */
> +			intel_pt_insn->branch = INTEL_PT_BR_INDIRECT;
> +			intel_pt_insn->length = insn->length;
> +			return;
> +		}
> +		break;
>  	case 0xc2: /* near ret */
>  	case 0xc3: /* near ret */
>  	case 0xca: /* far ret */