linux-kernel - [PATCH v4 1/5] perf cs-etm: Refactor instruction size handling

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Date:   Mon,  3 Feb 2020 10:07:12 +0800
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mike Leach <mike.leach@...aro.org>,
        Robert Walker <robert.walker@....com>,
        Coresight ML <coresight@...ts.linaro.org>
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v4 1/5] perf cs-etm: Refactor instruction size handling

cs-etm.c has several functions which need to know instruction size
based on address, e.g. cs_etm__instr_addr() and cs_etm__copy_insn()
two functions both calculate the instruction size separately with its
duplicated code.  Furthermore, adding new features later which might
require to calculate instruction size as well.

For this reason, this patch refactors the code to introduce a new
function cs_etm__instr_size(), this function is central place to
calculate the instruction size based on ISA type and instruction
address.

For a neat implementation, cs_etm__instr_addr() will always execute the
loop without checking ISA type, this allows cs_etm__instr_size() and
cs_etm__instr_addr() have no any duplicate code with each other and both
functions are independent and can be changed separately without breaking
anything.  As a side effect, cs_etm__instr_addr() will do a few more
iterations for A32/A64 instructions, this would be fine if consider perf
is a tool running in the user space.

Signed-off-by: Leo Yan <leo.yan@...aro.org>
---
 tools/perf/util/cs-etm.c | 48 +++++++++++++++++++++++-----------------
 1 file changed, 28 insertions(+), 20 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 720108bd8dba..cb6fcc2acca0 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -918,6 +918,26 @@ static inline int cs_etm__t32_instr_size(struct cs_etm_queue *etmq,
 	return ((instrBytes[1] & 0xF8) >= 0xE8) ? 4 : 2;
 }
 
+static inline int cs_etm__instr_size(struct cs_etm_queue *etmq,
+				     u8 trace_chan_id,
+				     enum cs_etm_isa isa,
+				     u64 addr)
+{
+	int insn_len;
+
+	/*
+	 * T32 instruction size might be 32-bit or 16-bit, decide by calling
+	 * cs_etm__t32_instr_size().
+	 */
+	if (isa == CS_ETM_ISA_T32)
+		insn_len = cs_etm__t32_instr_size(etmq, trace_chan_id, addr);
+	/* Otherwise, A64 and A32 instruction size are always 32-bit. */
+	else
+		insn_len = 4;
+
+	return insn_len;
+}
+
 static inline u64 cs_etm__first_executed_instr(struct cs_etm_packet *packet)
 {
 	/* Returns 0 for the CS_ETM_DISCONTINUITY packet */
@@ -942,19 +962,15 @@ static inline u64 cs_etm__instr_addr(struct cs_etm_queue *etmq,
 				     const struct cs_etm_packet *packet,
 				     u64 offset)
 {
-	if (packet->isa == CS_ETM_ISA_T32) {
-		u64 addr = packet->start_addr;
+	u64 addr = packet->start_addr;
 
-		while (offset) {
-			addr += cs_etm__t32_instr_size(etmq,
-						       trace_chan_id, addr);
-			offset--;
-		}
-		return addr;
+	while (offset) {
+		addr += cs_etm__instr_size(etmq, trace_chan_id,
+					   packet->isa, addr);
+		offset--;
 	}
 
-	/* Assume a 4 byte instruction size (A32/A64) */
-	return packet->start_addr + offset * 4;
+	return addr;
 }
 
 static void cs_etm__update_last_branch_rb(struct cs_etm_queue *etmq,
@@ -1094,16 +1110,8 @@ static void cs_etm__copy_insn(struct cs_etm_queue *etmq,
 		return;
 	}
 
-	/*
-	 * T32 instruction size might be 32-bit or 16-bit, decide by calling
-	 * cs_etm__t32_instr_size().
-	 */
-	if (packet->isa == CS_ETM_ISA_T32)
-		sample->insn_len = cs_etm__t32_instr_size(etmq, trace_chan_id,
-							  sample->ip);
-	/* Otherwise, A64 and A32 instruction size are always 32-bit. */
-	else
-		sample->insn_len = 4;
+	sample->insn_len = cs_etm__instr_size(etmq, trace_chan_id,
+					      packet->isa, sample->ip);
 
 	cs_etm__mem_access(etmq, trace_chan_id, sample->ip,
 			   sample->insn_len, (void *)sample->insn);
-- 
2.17.1