From c0a32fc5a2e470d0b02597b23ad79a317735253e Mon Sep 17 00:00:00 2001 From: Stanislaw Gruszka Date: Tue, 10 Jan 2012 15:07:28 -0800 Subject: 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 Cc: Mel Gorman Cc: Andrea Arcangeli Cc: "Rafael J. Wysocki" Cc: Christoph Lameter Cc: Pekka Enberg Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm.h | 17 +++++++++++++++++ include/linux/page-debug-flags.h | 4 +++- 2 files changed, 20 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/mm.h b/include/linux/mm.h index 5d9b4c9813bd..5568553a41fd 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1618,5 +1618,22 @@ extern void copy_user_huge_page(struct page *dst, struct page *src, unsigned int pages_per_huge_page); #endif /* CONFIG_TRANSPARENT_HUGEPAGE || CONFIG_HUGETLBFS */ +#ifdef CONFIG_DEBUG_PAGEALLOC +extern unsigned int _debug_guardpage_minorder; + +static inline unsigned int debug_guardpage_minorder(void) +{ + return _debug_guardpage_minorder; +} + +static inline bool page_is_guard(struct page *page) +{ + return test_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); +} +#else +static inline unsigned int debug_guardpage_minorder(void) { return 0; } +static inline bool page_is_guard(struct page *page) { return false; } +#endif /* CONFIG_DEBUG_PAGEALLOC */ + #endif /* __KERNEL__ */ #endif /* _LINUX_MM_H */ diff --git a/include/linux/page-debug-flags.h b/include/linux/page-debug-flags.h index b0638fd91e92..22691f614043 100644 --- a/include/linux/page-debug-flags.h +++ b/include/linux/page-debug-flags.h @@ -13,6 +13,7 @@ enum page_debug_flags { PAGE_DEBUG_FLAG_POISON, /* Page is poisoned */ + PAGE_DEBUG_FLAG_GUARD, }; /* @@ -21,7 +22,8 @@ enum page_debug_flags { */ #ifdef CONFIG_WANT_PAGE_DEBUG_FLAGS -#if !defined(CONFIG_PAGE_POISONING) \ +#if !defined(CONFIG_PAGE_POISONING) && \ + !defined(CONFIG_PAGE_GUARD) \ /* && !defined(CONFIG_PAGE_DEBUG_SOMETHING_ELSE) && ... */ #error WANT_PAGE_DEBUG_FLAGS is turned on with no debug features! #endif -- cgit v1.2.3