linux-kernel - [PATCH 20/37] perf jit: Make perf skip unknown records

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Message-Id: <1477326057-24080-21-git-send-email-acme@kernel.org>
Date:   Mon, 24 Oct 2016 13:20:40 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Stefano Sanfilippo <ssanfilippo@...omium.org>,
        Ross McIlroy <rmcilroy@...omium.org>,
        Anton Blanchard <anton@...abs.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 20/37] perf jit: Make perf skip unknown records

From: Stefano Sanfilippo <ssanfilippo@...omium.org>

The behavior before this commit was to skip the remaining portion of the
jitdump in case an unknown record was found, including those records
that perf could handle.

With this change, parsing a record with an unknown id will cause a
warning to be emitted, the record will be skipped and parsing will
resume from the next (valid) one.

The patch aims at making perf more future proof, by extracting as much
information as possible from jitdumps.

Signed-off-by: Stefano Sanfilippo <ssanfilippo@...omium.org>
Signed-off-by: Ross McIlroy <rmcilroy@...omium.org>
Reviewed-by: Stephane Eranian <eranian@...gle.com>
Cc: Anton Blanchard <anton@...abs.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Link: http://lkml.kernel.org/r/1476356383-30100-5-git-send-email-eranian@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/jitdump.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/jitdump.c b/tools/perf/util/jitdump.c
index f3ed3c963c71..75b66bbf8429 100644
--- a/tools/perf/util/jitdump.c
+++ b/tools/perf/util/jitdump.c
@@ -263,8 +263,7 @@ jit_get_next_entry(struct jit_buf_desc *jd)
 		return NULL;
 
 	if (id >= JIT_CODE_MAX) {
-		pr_warning("next_entry: unknown prefix %d, skipping\n", id);
-		return NULL;
+		pr_warning("next_entry: unknown record type %d, skipping\n", id);
 	}
 	if (bs > jd->bufsize) {
 		void *n;
@@ -322,7 +321,8 @@ jit_get_next_entry(struct jit_buf_desc *jd)
 		break;
 	case JIT_CODE_MAX:
 	default:
-		return NULL;
+		/* skip unknown record (we have read them) */
+		break;
 	}
 	return jr;
 }
-- 
2.7.4