linux-kernel - [PATCH] oprofile, x86: Fix overflow and warning (commit 1d12d35)

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Date:	Wed, 17 Aug 2011 00:11:08 +0200
From:	Robert Richter <robert.richter@....com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Maarten Lankhorst <m.b.lankhorst@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	"x86@...nel.org" <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] oprofile, x86: Fix overflow and warning (commit 1d12d35)

On 02.08.11 00:16:25, Robert Richter wrote:
> On 01.08.11 17:41:30, Andi Kleen wrote:
> > And what happens when the CPU reports more than 32 counters?
> > You have a silent buffer overflow then.
> 
> From the layout of IA32_PERF_GLOBAL_CTRL MSR it seems to be limited to
> 32. Anyway, if there might be cpus out soon with more than 32 counters
> we can either extend the array to 256 or limit the counters used to 32.

See my patch below.

-Robert


>From 298557db42eb2d6efca81669dc369425b46c5be6 Mon Sep 17 00:00:00 2001
From: Robert Richter <robert.richter@....com>
Date: Tue, 16 Aug 2011 23:39:53 +0200
Subject: [PATCH] oprofile, x86: Fix overflow and warning (commit 1d12d35)
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Following fixes for:

 1d12d35 oprofile, x86: Convert memory allocation to static array

Fix potential buffer overflow.

Fix the following warning:

 arch/x86/oprofile/op_model_ppro.c: In function ‘ppro_check_ctrs’:
 arch/x86/oprofile/op_model_ppro.c:143: warning: label ‘out’ defined but not used

Cc: Maarten Lankhorst <m.b.lankhorst@...il.com>
Cc: Andi Kleen <andi@...stfloor.org>
Signed-off-by: Robert Richter <robert.richter@....com>
---
 arch/x86/oprofile/op_model_ppro.c |    3 +--
 1 files changed, 1 insertions(+), 2 deletions(-)

diff --git a/arch/x86/oprofile/op_model_ppro.c b/arch/x86/oprofile/op_model_ppro.c
index 608874b..d90528e 100644
--- a/arch/x86/oprofile/op_model_ppro.c
+++ b/arch/x86/oprofile/op_model_ppro.c
@@ -140,7 +140,6 @@ static int ppro_check_ctrs(struct pt_regs * const regs,
 		wrmsrl(msrs->counters[i].addr, -reset_value[i]);
 	}
 
-out:
 	/* Only P6 based Pentium M need to re-unmask the apic vector but it
 	 * doesn't hurt other P6 variant */
 	apic_write(APIC_LVTPC, apic_read(APIC_LVTPC) & ~APIC_LVT_MASKED);
@@ -220,7 +219,7 @@ static void arch_perfmon_setup_counters(void)
 		eax.split.bit_width = 40;
 	}
 
-	num_counters = eax.split.num_counters;
+	num_counters = min((int)eax.split.num_counters, OP_MAX_COUNTER);
 
 	op_arch_perfmon_spec.num_counters = num_counters;
 	op_arch_perfmon_spec.num_controls = num_counters;
-- 
1.7.5.3



-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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