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

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Date: Thu,  2 May 2024 13:58:52 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: linux-kernel@...r.kernel.org
Cc: "Chang S. Bae" <chang.seok.bae@...el.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Nikolay Borisov <nik.borisov@...e.com>,
	Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	x86@...nel.org,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	linux-perf-users@...r.kernel.org
Subject: [PATCH 09/10] perf intel pt: Add new JMPABS instruction to the Intel PT instruction decoder

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@...el.com>
---
 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 */
-- 
2.34.1