From: Stanislaw Gruszka Date: Thu, 8 Dec 2011 04:41:46 +0000 (+1100) Subject: mm: more intensive memory corruption debugging X-Git-Tag: next-20111213~1^2~153 X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=f670ad4961f26fc163f0e40094dcf88c6f0b0ec9;p=karo-tx-linux.git 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. 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 --- diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 0b53aad7fed8..9906afe52b65 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -623,6 +623,24 @@ bytes respectively. Such letter suffixes can also be entirely omitted. no_debug_objects [KNL] Disable object debugging + debug_guardpage_minorder= + [KNL] When CONFIG_DEBUG_PAGEALLOC is set, this + parameter allows control order of pages that will be + intentionally kept free (and hence protected) by buddy + allocator. Bigger value increase probability of + catching random memory corruption, but reduce amount + of memory for normal system use. 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/drivers + code when CPU write to (or read from) random memory + location. Note that there exist 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 CPU MMU is bypassed), which + are not detectable by CONFIG_DEBUG_PAGEALLOC, hence this + option would not help tracking down these problems too. + debugpat [X86] Enable PAT debugging decnet.addr= [HW,NET] diff --git a/include/linux/mm.h b/include/linux/mm.h index 02e39b0042b1..91b72c9b3c0e 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1608,5 +1608,22 @@ 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 diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug index 8b1a477162dc..4b2443254de2 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -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 diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 76db4e2ad517..8b13233f851f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -57,6 +57,7 @@ #include #include #include +#include #include #include @@ -401,6 +402,37 @@ static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags) clear_highpage(page + i); } +#ifdef CONFIG_DEBUG_PAGEALLOC +unsigned int _debug_guardpage_minorder; + +static int __init debug_guardpage_minorder_setup(char *buf) +{ + unsigned long res; + + if (kstrtoul(buf, 10, &res) < 0 || res > MAX_ORDER / 2) { + printk(KERN_ERR "Bad debug_guardpage_minorder value\n"); + return 0; + } + _debug_guardpage_minorder = res; + printk(KERN_INFO "Setting debug_guardpage_minorder to %lu\n", res); + return 0; +} +__setup("debug_guardpage_minorder=", debug_guardpage_minorder_setup); + +static inline void set_page_guard_flg(struct page *page) +{ + __set_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); +} + +static inline void clear_page_guard_flg(struct page *page) +{ + __clear_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); +} +#else +static inline void set_page_guard_flg(struct page *page) { } +static inline void clear_page_guard_flg(struct page *page) { } +#endif + static inline void set_page_order(struct page *page, int order) { set_page_private(page, order); @@ -458,6 +490,11 @@ static inline int page_is_buddy(struct page *page, struct page *buddy, if (page_zone_id(page) != page_zone_id(buddy)) return 0; + if (page_is_guard(buddy) && page_order(buddy) == order) { + VM_BUG_ON(page_count(buddy) != 0); + return 1; + } + if (PageBuddy(buddy) && page_order(buddy) == order) { VM_BUG_ON(page_count(buddy) != 0); return 1; @@ -514,11 +551,19 @@ static inline void __free_one_page(struct page *page, buddy = page + (buddy_idx - page_idx); if (!page_is_buddy(page, buddy, order)) break; - - /* Our buddy is free, merge with it and move up one order. */ - list_del(&buddy->lru); - zone->free_area[order].nr_free--; - rmv_page_order(buddy); + /* + * Our buddy is free or it is CONFIG_DEBUG_PAGEALLOC guard page, + * merge with it and move up one order. + */ + if (page_is_guard(buddy)) { + clear_page_guard_flg(buddy); + set_page_private(page, 0); + __mod_zone_page_state(zone, NR_FREE_PAGES, 1 << order); + } else { + list_del(&buddy->lru); + zone->free_area[order].nr_free--; + rmv_page_order(buddy); + } combined_idx = buddy_idx & page_idx; page = page + (combined_idx - page_idx); page_idx = combined_idx; @@ -744,6 +789,23 @@ static inline void expand(struct zone *zone, struct page *page, high--; size >>= 1; VM_BUG_ON(bad_range(zone, &page[size])); + +#ifdef CONFIG_DEBUG_PAGEALLOC + if (high < debug_guardpage_minorder()) { + /* + * Mark as guard pages (or page), that will allow to + * merge back to allocator when buddy will be freed. + * Corresponding page table entries will not be touched, + * pages will stay not present in virtual address space + */ + INIT_LIST_HEAD(&page[size].lru); + set_page_guard_flg(&page[size]); + set_page_private(&page[size], high); + /* Guard pages are not available for any usage */ + __mod_zone_page_state(zone, NR_FREE_PAGES, -(1 << high)); + continue; + } +#endif list_add(&page[size].lru, &area->free_list[migratetype]); area->nr_free++; set_page_order(&page[size], high); @@ -1767,7 +1829,8 @@ void warn_alloc_failed(gfp_t gfp_mask, int order, const char *fmt, ...) { unsigned int filter = SHOW_MEM_FILTER_NODES; - if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs)) + if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) || + debug_guardpage_minorder() > 0) return; /*