diff options
| -rw-r--r-- | Documentation/kernel-parameters.txt | 19 | ||||
| -rw-r--r-- | include/linux/mm.h | 17 | ||||
| -rw-r--r-- | include/linux/page-debug-flags.h | 4 | ||||
| -rw-r--r-- | mm/Kconfig.debug | 5 | ||||
| -rw-r--r-- | mm/page_alloc.c | 75 |
5 files changed, 113 insertions, 7 deletions
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 7b2e5c5eefa..7ed7030e772 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. no_debug_objects [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] diff --git a/include/linux/mm.h b/include/linux/mm.h index 5d9b4c9813b..5568553a41f 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 b0638fd91e9..22691f61404 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 8b1a477162d..4b2443254de 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 3cba4b67203..93baebcc06f 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -57,6 +57,7 @@ #include <linux/ftrace_event.h> #include <linux/memcontrol.h> #include <linux/prefetch.h> +#include <linux/page-debug-flags.h> #include <asm/tlbflush.h> #include <asm/div64.h> @@ -388,6 +389,37 @@ 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_flag(struct page *page) +{ + __set_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); +} + +static inline void clear_page_guard_flag(struct page *page) +{ + __clear_bit(PAGE_DEBUG_FLAG_GUARD, &page->debug_flags); +} +#else +static inline void set_page_guard_flag(struct page *page) { } +static inline void clear_page_guard_flag(struct page *page) { } +#endif + static inline void set_page_order(struct page *page, int order) { set_page_private(page, order); @@ -445,6 +477,11 @@ 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; @@ -501,11 +538,19 @@ 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_flag(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; @@ -731,6 +776,23 @@ 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_flag(&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); @@ -1754,7 +1816,8 @@ 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; /* |