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mm: more intensive memory corruption debugging

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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.

[[email protected]: tweak documentation, s/flg/flag/]
Signed-off-by: Stanislaw Gruszka <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Pekka Enberg <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Stanislaw Gruszka 2012-01-10 15:07:28 -08:00 • committed by Linus Torvalds
commit c0a32fc5a2
5 changed files with 113 additions and 7 deletions
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5
mm/Kconfig.debug
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@ -4,6 +4,7 @@ config DEBUG_PAGEALLOC
depends on !HIBERNATION || ARCH_SUPPORTS_DEBUG_PAGEALLOC && !PPC && !SPARC
depends on !KMEMCHECK
select PAGE_POISONING if !ARCH_SUPPORTS_DEBUG_PAGEALLOC
select PAGE_GUARD if ARCH_SUPPORTS_DEBUG_PAGEALLOC
---help---
Unmap pages from the kernel linear mapping after free_pages().
This results in a large slowdown, but helps to find certain types
@ -22,3 +23,7 @@ config WANT_PAGE_DEBUG_FLAGS
config PAGE_POISONING
bool
select WANT_PAGE_DEBUG_FLAGS
config PAGE_GUARD
bool
select WANT_PAGE_DEBUG_FLAGS