linux-kernel - [RFC][PATCH 0/5] Fixes for abs() usage on 64bit values

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Message-Id: <1442279124-7309-1-git-send-email-john.stultz@linaro.org>
Date:	Mon, 14 Sep 2015 18:05:19 -0700
From:	John Stultz <john.stultz@...aro.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Richard Cochran <richardcochran@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Theodore Ts'o" <tytso@....edu>,
	Andreas Dilger <adilger.kernel@...ger.ca>,
	Dave Chinner <dchinner@...hat.com>, Tejun Heo <tj@...nel.org>,
	Joe Perches <joe@...ches.com>
Subject: [RFC][PATCH 0/5] Fixes for abs() usage on 64bit values

As noted in include/linux/kernel.h:
 "abs() should not be used for 64-bit types (s64, u64, long long)
 - use abs64() for those."

Unfortunately, there are quite a number of places where abs()
was used w/ 64bit values in the kernel, and the results are
then silently capped to 32-bit values on 32-bit systems.

This series tries to address the problematic sites I found,
and then introduces a patch which modifies abs() so that the
build will fail if a 64-bit type is passed to it on a 32-bit
machine.

I'm sure there are additional sites that will need fixing,
but hopefully this will make them easy to find.

Comments and feedback would be greatly appreciated!

Thanks
-john

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Michal Nazarewicz <mina86@...a86.com>
Cc: Prarit Bhargava <prarit@...hat.com>
Cc: Richard Cochran <richardcochran@...il.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: "Theodore Ts'o" <tytso@....edu>
Cc: Andreas Dilger <adilger.kernel@...ger.ca>
Cc: Dave Chinner <dchinner@...hat.com>
Cc: Tejun Heo <tj@...nel.org>
Cc: Joe Perches <joe@...ches.com>


John Stultz (5):
  clocksource: Fix abs() usage w/ 64bit values
  time: Fix abs() usage with 64-bit values.
  ext4: Fix abs() usage in  ext4_mb_check_group_pa
  percpu: Fix abs() usage in percpu_counter_compare()
  abs(): Provide build error on passing 64bit value to abs()

 fs/ext4/mballoc.c         | 4 ++--
 include/linux/kernel.h    | 3 +++
 kernel/time/clocksource.c | 2 +-
 kernel/time/timekeeping.c | 2 +-
 lib/percpu_counter.c      | 2 +-
 5 files changed, 8 insertions(+), 5 deletions(-)

-- 
1.9.1

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