linux-kernel - [PATCH] perf symbols: Synthesize anonymous mmap events

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Date:	Tue, 30 Aug 2011 09:15:06 +1000
From:	Anton Blanchard <anton@...ba.org>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>, Ingo Molnar <mingo@...e.hu>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	emunson@...bm.net, penberg@...helsinki.fi
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] perf symbols: Synthesize anonymous mmap events


perf_event__synthesize_mmap_events does not create anonymous mmap
events even though the kernel does. As a result an already running
application with dynamically created code will not get profiled -
all samples end up in the unknown bucket.

This patch skips any entries with '[' in the name to avoid adding
events for special regions (eg the vsyscall page). All other
executable mmaps are assumed to be anonymous and an event is
synthesized.

Signed-off-by: Anton Blanchard <anton@...ba.org>
---

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 3c1b8a6..437f8ca 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -169,12 +169,17 @@ static int perf_event__synthesize_mmap_events(union perf_event *event,
 			continue;
 		pbf += n + 3;
 		if (*pbf == 'x') { /* vm_exec */
+			char anonstr[] = "//anon\n";
 			char *execname = strchr(bf, '/');
 
 			/* Catch VDSO */
 			if (execname == NULL)
 				execname = strstr(bf, "[vdso]");
 
+			/* Catch anonymous mmaps */
+			if ((execname == NULL) && !strstr(bf, "["))
+				execname = anonstr;
+
 			if (execname == NULL)
 				continue;
 
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