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-rw-r--r--Documentation/kernel-parameters.txt19
-rw-r--r--include/linux/mm.h17
-rw-r--r--include/linux/page-debug-flags.h4
-rw-r--r--mm/Kconfig.debug5
-rw-r--r--mm/page_alloc.c75
5 files changed, 113 insertions, 7 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.
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 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
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 3cba4b67203f..93baebcc06f3 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;
/*