kmemcheck: enable in the x86 Kconfig

let it rip!

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

[rebased for mainline inclusion]
Signed-off-by: Vegard Nossum <vegardno@ifi.uio.no>

arch/x86/Kconfig.debug

@@ -260,6 +260,94 @@ config DEFAULT_IO_DELAY_TYPE
 	default IO_DELAY_TYPE_NONE
 endif
 
+menuconfig KMEMCHECK
+	bool "kmemcheck: trap use of uninitialized memory"
+	depends on DEBUG_KERNEL
+	depends on !X86_USE_3DNOW
+	depends on SLUB || SLAB
+	depends on !CC_OPTIMIZE_FOR_SIZE
+	depends on !FUNCTION_TRACER
+	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_QUEUE_SIZE
+	int "kmemcheck: error queue size"
+	depends on KMEMCHECK
+	default 64
+	help
+	  Select the maximum number of errors to store in the queue. Since
+	  errors can occur virtually anywhere and in any context, we need a
+	  temporary storage area which is guarantueed not to generate any
+	  other faults. The queue will be emptied as soon as a tasklet may
+	  be scheduled. If the queue is full, new error reports will be
+	  lost.
+
+config KMEMCHECK_SHADOW_COPY_SHIFT
+	int "kmemcheck: shadow copy size (5 => 32 bytes, 6 => 64 bytes)"
+	depends on KMEMCHECK
+	range 2 8
+	default 5
+	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

lib/Kconfig.debug

@@ -300,7 +300,7 @@ config DEBUG_OBJECTS_ENABLE_DEFAULT
 
 config DEBUG_SLAB
 	bool "Debug slab memory allocations"
-	depends on DEBUG_KERNEL && SLAB
+	depends on DEBUG_KERNEL && SLAB && !KMEMCHECK
 	help
 	  Say Y here to have the kernel do limited verification on memory
 	  allocation as well as poisoning memory on free to catch use of freed
@@ -312,7 +312,7 @@ config DEBUG_SLAB_LEAK
 
 config SLUB_DEBUG_ON
 	bool "SLUB debugging on by default"
-	depends on SLUB && SLUB_DEBUG
+	depends on SLUB && SLUB_DEBUG && !KMEMCHECK
 	default n
 	help
 	  Boot with debugging on by default. SLUB boots by default with

mm/Kconfig.debug

@@ -2,6 +2,7 @@ config DEBUG_PAGEALLOC
 	bool "Debug page memory allocations"
 	depends on DEBUG_KERNEL && ARCH_SUPPORTS_DEBUG_PAGEALLOC
 	depends on !HIBERNATION || !PPC && !SPARC
+	depends on !KMEMCHECK
 	---help---
 	  Unmap pages from the kernel linear mapping after free_pages().
 	  This results in a large slowdown, but helps to find certain types