linux-kernel - [PATCH 3/3] perf: Fix unaligned accesses while fetching trace values

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Date:	Thu, 20 May 2010 11:44:19 +0200
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Tom Zanussi <tzanussi@...il.com>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	David Miller <davem@...emloft.net>
Subject: [PATCH 3/3] perf: Fix unaligned accesses while fetching trace values

Accessing trace values of an 8 size may end up in a segfault
on archs that can't deal with misaligned access, which is the
case for sparc 64. This is because PERF_SAMPLE_RAW are aligned
to 4 and not to 8.

Fix this on the macros that get the values of 8 size.

This fixes segfaults on perf tools in sparc 64.

Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
Cc: Ingo Molnar <mingo@...e.hu>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Tom Zanussi <tzanussi@...il.com>
Cc: Masami Hiramatsu <mhiramat@...hat.com>
Cc: David Miller <davem@...emloft.net>
---
 tools/perf/util/trace-event.h |    7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diff --git a/tools/perf/util/trace-event.h b/tools/perf/util/trace-event.h
index 406d452..b3e86b1 100644
--- a/tools/perf/util/trace-event.h
+++ b/tools/perf/util/trace-event.h
@@ -233,7 +233,12 @@ static inline unsigned long long __data2host8(unsigned long long data)
 
 #define data2host2(ptr)		__data2host2(*(unsigned short *)ptr)
 #define data2host4(ptr)		__data2host4(*(unsigned int *)ptr)
-#define data2host8(ptr)		__data2host8(*(unsigned long long *)ptr)
+#define data2host8(ptr)		({				\
+	unsigned long long __val;				\
+								\
+	memcpy(&__val, (ptr), sizeof(unsigned long long));	\
+	__data2host8(__val);					\
+})
 
 extern int header_page_ts_offset;
 extern int header_page_ts_size;
-- 
1.6.2.3

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