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>

3 files changed, 91 insertions, 2 deletions

diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index d105f29bb6bb..3951ebb5f843 100644
--- a/arch/x86/Kconfig.debug
+++ b/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
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 116a35051be6..399ba811ba18 100644
--- a/lib/Kconfig.debug
+++ b/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
diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug
index bb01e298f260..aa99fd1f7109 100644
--- a/mm/Kconfig.debug
+++ b/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