linux-kernel - [PATCH v1] perf intel-pt: pkt-decoder: Fix alignment issues

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Date:   Mon,  2 Oct 2023 15:19:09 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Ian Rogers <irogers@...gle.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Liam Howlett <liam.howlett@...cle.com>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v1] perf intel-pt: pkt-decoder: Fix alignment issues

The byte aligned buffer is cast to large types and dereferenced
causing misaligned pointer warnings from undefined behavior sanitizer.
Fix the alignment issues with memcpy which may require the
introduction of temporaries.

Signed-off-by: Ian Rogers <irogers@...gle.com>
---
 .../intel-pt-decoder/intel-pt-pkt-decoder.c   | 21 ++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/intel-pt-decoder/intel-pt-pkt-decoder.c b/tools/perf/util/intel-pt-decoder/intel-pt-pkt-decoder.c
index af9710622a1f..28659874d84e 100644
--- a/tools/perf/util/intel-pt-decoder/intel-pt-pkt-decoder.c
+++ b/tools/perf/util/intel-pt-decoder/intel-pt-pkt-decoder.c
@@ -83,7 +83,7 @@ static int intel_pt_get_long_tnt(const unsigned char *buf, size_t len,
 	if (len < 8)
 		return INTEL_PT_NEED_MORE_BYTES;
 
-	payload = le64_to_cpu(*(uint64_t *)buf);
+	memcpy_le64(&payload, buf, sizeof(payload));
 
 	for (count = 47; count; count--) {
 		if (payload & BIT63)
@@ -220,6 +220,8 @@ static int intel_pt_get_3byte(const unsigned char *buf, size_t len,
 static int intel_pt_get_ptwrite(const unsigned char *buf, size_t len,
 				struct intel_pt_pkt *packet)
 {
+	uint32_t tmp;
+
 	packet->count = (buf[1] >> 5) & 0x3;
 	packet->type = buf[1] & BIT(7) ? INTEL_PT_PTWRITE_IP :
 					 INTEL_PT_PTWRITE;
@@ -228,12 +230,13 @@ static int intel_pt_get_ptwrite(const unsigned char *buf, size_t len,
 	case 0:
 		if (len < 6)
 			return INTEL_PT_NEED_MORE_BYTES;
-		packet->payload = le32_to_cpu(*(uint32_t *)(buf + 2));
+		memcpy(&tmp, buf + 2, sizeof(tmp));
+		packet->payload = le32_to_cpu(tmp);
 		return 6;
 	case 1:
 		if (len < 10)
 			return INTEL_PT_NEED_MORE_BYTES;
-		packet->payload = le64_to_cpu(*(uint64_t *)(buf + 2));
+		memcpy_le64(&packet->payload, buf + 2, sizeof(packet->payload));
 		return 10;
 	default:
 		return INTEL_PT_BAD_PACKET;
@@ -258,7 +261,7 @@ static int intel_pt_get_mwait(const unsigned char *buf, size_t len,
 	if (len < 10)
 		return INTEL_PT_NEED_MORE_BYTES;
 	packet->type = INTEL_PT_MWAIT;
-	packet->payload = le64_to_cpu(*(uint64_t *)(buf + 2));
+	memcpy_le64(&packet->payload, buf + 2, sizeof(packet->payload));
 	return 10;
 }
 
@@ -454,6 +457,8 @@ static int intel_pt_get_ip(enum intel_pt_pkt_type type, unsigned int byte,
 			   struct intel_pt_pkt *packet)
 {
 	int ip_len;
+	uint16_t tmp16;
+	uint32_t tmp32;
 
 	packet->count = byte >> 5;
 
@@ -465,13 +470,15 @@ static int intel_pt_get_ip(enum intel_pt_pkt_type type, unsigned int byte,
 		if (len < 3)
 			return INTEL_PT_NEED_MORE_BYTES;
 		ip_len = 2;
-		packet->payload = le16_to_cpu(*(uint16_t *)(buf + 1));
+		memcpy(&tmp16, buf + 1, sizeof(tmp16));
+		packet->payload = le16_to_cpu(tmp16);
 		break;
 	case 2:
 		if (len < 5)
 			return INTEL_PT_NEED_MORE_BYTES;
 		ip_len = 4;
-		packet->payload = le32_to_cpu(*(uint32_t *)(buf + 1));
+		memcpy(&tmp32, buf + 1, sizeof(tmp32));
+		packet->payload = le32_to_cpu(tmp32);
 		break;
 	case 3:
 	case 4:
@@ -484,7 +491,7 @@ static int intel_pt_get_ip(enum intel_pt_pkt_type type, unsigned int byte,
 		if (len < 9)
 			return INTEL_PT_NEED_MORE_BYTES;
 		ip_len = 8;
-		packet->payload = le64_to_cpu(*(uint64_t *)(buf + 1));
+		memcpy_le64(&packet->payload, buf + 1, sizeof(packet->payload));
 		break;
 	default:
 		return INTEL_PT_BAD_PACKET;
-- 
2.42.0.582.g8ccd20d70d-goog