From 8db26a3d47354ce7271a8cab03cd65b9d3d610b9 Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Mon, 14 Dec 2020 19:13:34 -0800 Subject: [PATCH] mm, page_poison: use static key more efficiently Commit 11c9c7edae06 ("mm/page_poison.c: replace bool variable with static key") changed page_poisoning_enabled() to a static key check. However, the function is not inlined, so each check still involves a function call with overhead not eliminated when page poisoning is disabled. Analogically to how debug_pagealloc is handled, this patch converts page_poisoning_enabled() back to boolean check, and introduces page_poisoning_enabled_static() for fast paths. Both functions are inlined. The function kernel_poison_pages() is also called unconditionally and does the static key check inside. Remove it from there and put it to callers. Also split it to two functions kernel_poison_pages() and kernel_unpoison_pages() instead of the confusing bool parameter. Also optimize the check that enables page poisoning instead of debug_pagealloc for architectures without proper debug_pagealloc support. Move the check to init_mem_debugging_and_hardening() to enable a single static key instead of having two static branches in page_poisoning_enabled_static(). Link: https://lkml.kernel.org/r/20201113104033.22907-3-vbabka@suse.cz Signed-off-by: Vlastimil Babka Reviewed-by: David Hildenbrand Cc: Mike Rapoport Cc: Rafael J. Wysocki Cc: Alexander Potapenko Cc: Kees Cook Cc: Laura Abbott Cc: Mateusz Nosek Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/virtio/virtio_balloon.c | 2 +- include/linux/mm.h | 33 +++++++++++++++++--- mm/page_alloc.c | 18 +++++++++-- mm/page_poison.c | 53 +++++---------------------------- 4 files changed, 52 insertions(+), 54 deletions(-) diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c index 481611c09dae..e53faed6ba93 100644 --- a/drivers/virtio/virtio_balloon.c +++ b/drivers/virtio/virtio_balloon.c @@ -1116,7 +1116,7 @@ static int virtballoon_validate(struct virtio_device *vdev) */ if (!want_init_on_free() && (IS_ENABLED(CONFIG_PAGE_POISONING_NO_SANITY) || - !page_poisoning_enabled())) + !page_poisoning_enabled_static())) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_PAGE_POISON); else if (!virtio_has_feature(vdev, VIRTIO_BALLOON_F_PAGE_POISON)) __virtio_clear_bit(vdev, VIRTIO_BALLOON_F_REPORTING); diff --git a/include/linux/mm.h b/include/linux/mm.h index 591c784277ea..026707a58159 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -2874,12 +2874,37 @@ extern int apply_to_existing_page_range(struct mm_struct *mm, extern void init_mem_debugging_and_hardening(void); #ifdef CONFIG_PAGE_POISONING -extern bool page_poisoning_enabled(void); -extern void kernel_poison_pages(struct page *page, int numpages, int enable); +extern void __kernel_poison_pages(struct page *page, int numpages); +extern void __kernel_unpoison_pages(struct page *page, int numpages); +extern bool _page_poisoning_enabled_early; +DECLARE_STATIC_KEY_FALSE(_page_poisoning_enabled); +static inline bool page_poisoning_enabled(void) +{ + return _page_poisoning_enabled_early; +} +/* + * For use in fast paths after init_mem_debugging() has run, or when a + * false negative result is not harmful when called too early. + */ +static inline bool page_poisoning_enabled_static(void) +{ + return static_branch_unlikely(&_page_poisoning_enabled); +} +static inline void kernel_poison_pages(struct page *page, int numpages) +{ + if (page_poisoning_enabled_static()) + __kernel_poison_pages(page, numpages); +} +static inline void kernel_unpoison_pages(struct page *page, int numpages) +{ + if (page_poisoning_enabled_static()) + __kernel_unpoison_pages(page, numpages); +} #else static inline bool page_poisoning_enabled(void) { return false; } -static inline void kernel_poison_pages(struct page *page, int numpages, - int enable) { } +static inline bool page_poisoning_enabled_static(void) { return false; } +static inline void kernel_poison_pages(struct page *page, int numpages) { } +static inline void kernel_unpoison_pages(struct page *page, int numpages) { } #endif DECLARE_STATIC_KEY_FALSE(init_on_alloc); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3fd0c8d5745f..efcd1baa35e4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -777,6 +777,17 @@ void init_mem_debugging_and_hardening(void) static_branch_enable(&init_on_free); } +#ifdef CONFIG_PAGE_POISONING + /* + * Page poisoning is debug page alloc for some arches. If + * either of those options are enabled, enable poisoning. + */ + if (page_poisoning_enabled() || + (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && + debug_pagealloc_enabled())) + static_branch_enable(&_page_poisoning_enabled); +#endif + #ifdef CONFIG_DEBUG_PAGEALLOC if (!debug_pagealloc_enabled()) return; @@ -1262,7 +1273,8 @@ static __always_inline bool free_pages_prepare(struct page *page, if (want_init_on_free()) kernel_init_free_pages(page, 1 << order); - kernel_poison_pages(page, 1 << order, 0); + kernel_poison_pages(page, 1 << order); + /* * arch_free_page() can make the page's contents inaccessible. s390 * does this. So nothing which can access the page's contents should @@ -2219,7 +2231,7 @@ static inline int check_new_page(struct page *page) static inline bool free_pages_prezeroed(void) { return (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) && - page_poisoning_enabled()) || want_init_on_free(); + page_poisoning_enabled_static()) || want_init_on_free(); } #ifdef CONFIG_DEBUG_VM @@ -2281,7 +2293,7 @@ inline void post_alloc_hook(struct page *page, unsigned int order, arch_alloc_page(page, order); debug_pagealloc_map_pages(page, 1 << order); kasan_alloc_pages(page, order); - kernel_poison_pages(page, 1 << order, 1); + kernel_unpoison_pages(page, 1 << order); set_page_owner(page, order, gfp_flags); if (!free_pages_prezeroed() && want_init_on_alloc(gfp_flags)) diff --git a/mm/page_poison.c b/mm/page_poison.c index ae0482cded87..4d75fc9ccc7a 100644 --- a/mm/page_poison.c +++ b/mm/page_poison.c @@ -8,45 +8,17 @@ #include #include -static DEFINE_STATIC_KEY_FALSE_RO(want_page_poisoning); +bool _page_poisoning_enabled_early; +EXPORT_SYMBOL(_page_poisoning_enabled_early); +DEFINE_STATIC_KEY_FALSE(_page_poisoning_enabled); +EXPORT_SYMBOL(_page_poisoning_enabled); static int __init early_page_poison_param(char *buf) { - int ret; - bool tmp; - - ret = strtobool(buf, &tmp); - if (ret) - return ret; - - if (tmp) - static_branch_enable(&want_page_poisoning); - else - static_branch_disable(&want_page_poisoning); - - return 0; + return kstrtobool(buf, &_page_poisoning_enabled_early); } early_param("page_poison", early_page_poison_param); -/** - * page_poisoning_enabled - check if page poisoning is enabled - * - * Return true if page poisoning is enabled, or false if not. - */ -bool page_poisoning_enabled(void) -{ - /* - * Assumes that debug_pagealloc_enabled is set before - * memblock_free_all. - * Page poisoning is debug page alloc for some arches. If - * either of those options are enabled, enable poisoning. - */ - return (static_branch_unlikely(&want_page_poisoning) || - (!IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC) && - debug_pagealloc_enabled())); -} -EXPORT_SYMBOL_GPL(page_poisoning_enabled); - static void poison_page(struct page *page) { void *addr = kmap_atomic(page); @@ -58,7 +30,7 @@ static void poison_page(struct page *page) kunmap_atomic(addr); } -static void poison_pages(struct page *page, int n) +void __kernel_poison_pages(struct page *page, int n) { int i; @@ -117,7 +89,7 @@ static void unpoison_page(struct page *page) kunmap_atomic(addr); } -static void unpoison_pages(struct page *page, int n) +void __kernel_unpoison_pages(struct page *page, int n) { int i; @@ -125,17 +97,6 @@ static void unpoison_pages(struct page *page, int n) unpoison_page(page + i); } -void kernel_poison_pages(struct page *page, int numpages, int enable) -{ - if (!page_poisoning_enabled()) - return; - - if (enable) - unpoison_pages(page, numpages); - else - poison_pages(page, numpages); -} - #ifndef CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC void __kernel_map_pages(struct page *page, int numpages, int enable) {