linux-kernel - [PATCH 13/13] kmemcheck: enable in the x86 Kconfig

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Date:	Wed, 16 Jul 2008 02:25:00 +0200
From:	Vegard Nossum <vegard.nossum@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: [PATCH 13/13] kmemcheck: enable in the x86 Kconfig

>From 443d8b28cb141b3fe8bbe6dd1daa0ef41bc21d80 Mon Sep 17 00:00:00 2001
From: Vegard Nossum <vegard.nossum@...il.com>
Date: Fri, 4 Apr 2008 00:51:41 +0200
Subject: [PATCH 13/13] kmemcheck: enable in the x86 Kconfig

let it rip!

Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>
Signed-off-by: Vegard Nossum <vegardno@....uio.no>
---
 arch/x86/Kconfig.debug |  109 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 109 insertions(+), 0 deletions(-)

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 1836337..552cf57 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -246,6 +246,115 @@ config DEFAULT_IO_DELAY_TYPE
 	default IO_DELAY_TYPE_NONE
 endif
 
+menuconfig KMEMCHECK
+	bool "kmemcheck: trap use of uninitialized memory"
+	depends on X86
+	depends on !X86_USE_3DNOW
+	depends on SLUB || (SLAB && !DEBUG_SLAB)
+	depends on !CC_OPTIMIZE_FOR_SIZE
+	depends on !DEBUG_PAGEALLOC
+	select FRAME_POINTER
+	select STACKTRACE
+	default n
+	help
+	  This option enables tracing of dynamically allocated kernel memory
+	  to see if memory is used before it has been given an initial value.
+	  Be aware that this requires half of your memory for bookkeeping and
+	  will insert extra code at *every* read and write to tracked memory
+	  thus slow down the kernel code (but user code is unaffected).
+
+	  The kernel may be started with kmemcheck=0 or kmemcheck=1 to disable
+	  or enable kmemcheck at boot-time. If the kernel is started with
+	  kmemcheck=0, the large memory and CPU overhead is not incurred.
+
+choice
+	prompt "kmemcheck: default mode at boot"
+	depends on KMEMCHECK
+	default KMEMCHECK_ONESHOT_BY_DEFAULT
+	help
+	  This option controls the default behaviour of kmemcheck when the
+	  kernel boots and no kmemcheck= parameter is given.
+
+config KMEMCHECK_DISABLED_BY_DEFAULT
+	bool "disabled"
+	depends on KMEMCHECK
+
+config KMEMCHECK_ENABLED_BY_DEFAULT
+	bool "enabled"
+	depends on KMEMCHECK
+
+config KMEMCHECK_ONESHOT_BY_DEFAULT
+	bool "one-shot"
+	depends on KMEMCHECK
+	help
+	  In one-shot mode, only the first error detected is reported before
+	  kmemcheck is disabled.
+
+endchoice
+
+config KMEMCHECK_USE_SMP
+	bool "kmemcheck: use multiple CPUs"
+	depends on KMEMCHECK
+	depends on SMP
+	depends on BROKEN
+	default n
+	help
+	  This option will prevent kmemcheck from disabling all but one CPU
+	  on boot. This means that whenever a page fault is taken, all the
+	  other CPUs in the system are halted. This is potentially extremely
+	  expensive, depending on the number of CPUs in the system (the more
+	  the worse).
+
+	  The upside is that kmemcheck can be compiled into the kernel with
+	  very little overhead by default if kmemcheck is disabled at run-
+	  time.
+
+	  If you want to compile a kernel specifically for the purpose of
+	  playing with kmemcheck, you should say N here. If you want a normal
+	  kernel with the possibility of enabling kmemcheck without
+	  recompiling, you should say Y here.
+
+config KMEMCHECK_QUEUE_SIZE
+	int "kmemcheck: error queue size"
+	depends on KMEMCHECK
+	default 64
+	help
+	  Select the maximum number of errors to store in the queue. This
+	  queue will be emptied once every second, so this is effectively a
+	  limit on how many reports to print in one go. Note however, that
+	  if the number of errors occuring between two bursts is larger than
+	  this number, the extra error reports will get lost.
+
+config KMEMCHECK_SHADOW_COPY_SHIFT
+	int "kmemcheck: shadow copy size (5 => 32 bytes, 6 => 64 bytes)"
+	depends on KMEMCHECK
+	range 2 8
+	default 6
+	help
+	  Select the number of shadow bytes to save along with each entry of
+	  the queue. These bytes indicate what parts of an allocation are
+	  initialized, uninitialized, etc. and will be displayed when an
+	  error is detected to help the debugging of a particular problem.
+
+config KMEMCHECK_PARTIAL_OK
+	bool "kmemcheck: allow partially uninitialized memory"
+	depends on KMEMCHECK
+	default y
+	help
+	  This option works around certain GCC optimizations that produce
+	  32-bit reads from 16-bit variables where the upper 16 bits are
+	  thrown away afterwards. This may of course also hide some real
+	  bugs.
+
+config KMEMCHECK_BITOPS_OK
+	bool "kmemcheck: allow bit-field manipulation"
+	depends on KMEMCHECK
+	default n
+	help
+	  This option silences warnings that would be generated for bit-field
+	  accesses where not all the bits are initialized at the same time.
+	  This may also hide some real bugs.
+
 config DEBUG_BOOT_PARAMS
 	bool "Debug boot parameters"
 	depends on DEBUG_KERNEL
-- 
1.5.5.1

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