linux-kernel - [PATCH 1/3] perf events: Fix mmap offset determination

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Date:	Wed,  4 Aug 2010 18:26:02 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Dave Martin <dave.martin@...aro.org>,
	Anton Blanchard <anton@...ba.org>,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Will Deacon <Will.Deacon@....com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 1/3] perf events: Fix mmap offset determination

From: Dave Martin <dave.martin@...aro.org>

Fix buggy-looking code which unnecessarily adjusts the file offset
fields read from /proc/*/maps.

This may have gone unnoticed since the offset is usually 0 (and the
logic in util/symbol.c may work incorrectly for other offset values).

Commiter note:

This fixes a bug introduced in 4af8b35, there is no need to shift pgoff
twice, the show_map_vma routine in fs/proc/task_mmu.c already converts
it from the number of pages to the size in bytes, and that is what
appears in /proc/PID/map.

Cc: Anton Blanchard <anton@...ba.org>
Cc: Nicolas Pitre <nicolas.pitre@...aro.org>
Cc: Will Deacon <Will.Deacon@....com>
LKML-Reference: <1280836116-6654-2-git-send-email-dave.martin@...aro.org>
Signed-off-by: Dave Martin <dave.martin@...aro.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
---
 tools/perf/util/event.c |    8 +-------
 1 files changed, 1 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index 6b0db55..db8a1d4 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -151,7 +151,6 @@ static int event__synthesize_mmap_events(pid_t pid, pid_t tgid,
 			continue;
 		pbf += n + 3;
 		if (*pbf == 'x') { /* vm_exec */
-			u64 vm_pgoff;
 			char *execname = strchr(bf, '/');
 
 			/* Catch VDSO */
@@ -162,12 +161,7 @@ static int event__synthesize_mmap_events(pid_t pid, pid_t tgid,
 				continue;
 
 			pbf += 3;
-			n = hex2u64(pbf, &vm_pgoff);
-			/* pgoff is in bytes, not pages */
-			if (n >= 0)
-				ev.mmap.pgoff = vm_pgoff << getpagesize();
-			else
-				ev.mmap.pgoff = 0;
+			n = hex2u64(pbf, &ev.mmap.pgoff);
 
 			size = strlen(execname);
 			execname[size - 1] = '\0'; /* Remove \n */
-- 
1.6.2.5

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