path: root/Documentation
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authorStanislaw Gruszka <sgruszka@redhat.com>2012-01-10 15:07:28 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-10 16:30:42 -0800
commitc0a32fc5a2e470d0b02597b23ad79a317735253e (patch)
tree2d164edae0062918ca2088772c00b0615781353b /Documentation
parent1399ff86f2a2bbacbbe68fa00c5f8c752b344723 (diff)
mm: more intensive memory corruption debugging
With CONFIG_DEBUG_PAGEALLOC configured, the CPU will generate an exception on access (read,write) to an unallocated page, which permits us to catch code which corrupts memory. However the kernel is trying to maximise memory usage, hence there are usually few free pages in the system and buggy code usually corrupts some crucial data. This patch changes the buddy allocator to keep more free/protected pages and to interlace free/protected and allocated pages to increase the probability of catching corruption. When the kernel is compiled with CONFIG_DEBUG_PAGEALLOC, debug_guardpage_minorder defines the minimum order used by the page allocator to grant a request. The requested size will be returned with the remaining pages used as guard pages. The default value of debug_guardpage_minorder is zero: no change from current behaviour. [akpm@linux-foundation.org: tweak documentation, s/flg/flag/] Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Rafael J. Wysocki" <rjw@sisk.pl> Cc: Christoph Lameter <cl@linux-foundation.org> Cc: Pekka Enberg <penberg@cs.helsinki.fi> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
1 files changed, 19 insertions, 0 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7b2e5c5eefa6..7ed7030e7722 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -623,6 +623,25 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
[KNL] Disable object debugging
+ debug_guardpage_minorder=
+ [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this
+ parameter allows control of the order of pages that will
+ be intentionally kept free (and hence protected) by the
+ buddy allocator. Bigger value increase the probability
+ of catching random memory corruption, but reduce the
+ amount of memory for normal system use. The maximum
+ possible value is MAX_ORDER/2. Setting this parameter
+ to 1 or 2 should be enough to identify most random
+ memory corruption problems caused by bugs in kernel or
+ driver code when a CPU writes to (or reads from) a
+ random memory location. Note that there exists a class
+ of memory corruptions problems caused by buggy H/W or
+ F/W or by drivers badly programing DMA (basically when
+ memory is written at bus level and the CPU MMU is
+ bypassed) which are not detectable by
+ CONFIG_DEBUG_PAGEALLOC, hence this option will not help
+ tracking down these problems.
debugpat [X86] Enable PAT debugging
decnet.addr= [HW,NET]