On Tue, May 25, 2021 at 3:00 PM Andrey Konovalov <andreyknvl@xxxxxxxxx> wrote: > > On Wed, May 12, 2021 at 11:09 PM Peter Collingbourne <pcc@xxxxxxxxxx> wrote: > > > > Currently with integrated init page_alloc.c needs to know whether > > kasan_alloc_pages() will zero initialize memory, but this will start > > becoming more complicated once we start adding tag initialization > > support for user pages. To avoid page_alloc.c needing to know more > > details of what integrated init will do, move the unpoisoning logic > > for integrated init into the HW tags implementation. Currently the > > logic is identical but it will diverge in subsequent patches. > > > > For symmetry do the same for poisoning although this logic will > > be unaffected by subsequent patches. > > > > Signed-off-by: Peter Collingbourne <pcc@xxxxxxxxxx> > > Link: https://linux-review.googlesource.com/id/I2c550234c6c4a893c48c18ff0c6ce658c7c67056 > > --- > > v3: > > - use BUILD_BUG() > > > > v2: > > - fix build with KASAN disabled > > > > include/linux/kasan.h | 66 +++++++++++++++++++++++++++---------------- > > mm/kasan/common.c | 4 +-- > > mm/kasan/hw_tags.c | 14 +++++++++ > > mm/mempool.c | 6 ++-- > > mm/page_alloc.c | 56 +++++++++++++++++++----------------- > > 5 files changed, 91 insertions(+), 55 deletions(-) > > > > diff --git a/include/linux/kasan.h b/include/linux/kasan.h > > index b1678a61e6a7..38061673e6ac 100644 > > --- a/include/linux/kasan.h > > +++ b/include/linux/kasan.h > > @@ -2,6 +2,7 @@ > > #ifndef _LINUX_KASAN_H > > #define _LINUX_KASAN_H > > > > +#include <linux/bug.h> > > #include <linux/static_key.h> > > #include <linux/types.h> > > > > @@ -79,14 +80,6 @@ static inline void kasan_disable_current(void) {} > > > > #endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */ > > > > -#ifdef CONFIG_KASAN > > - > > -struct kasan_cache { > > - int alloc_meta_offset; > > - int free_meta_offset; > > - bool is_kmalloc; > > -}; > > - > > #ifdef CONFIG_KASAN_HW_TAGS > > > > DECLARE_STATIC_KEY_FALSE(kasan_flag_enabled); > > @@ -101,11 +94,18 @@ static inline bool kasan_has_integrated_init(void) > > return kasan_enabled(); > > } > > > > +void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags); > > +void kasan_free_pages(struct page *page, unsigned int order); > > + > > #else /* CONFIG_KASAN_HW_TAGS */ > > > > static inline bool kasan_enabled(void) > > { > > +#ifdef CONFIG_KASAN > > return true; > > +#else > > + return false; > > +#endif > > } > > > > static inline bool kasan_has_integrated_init(void) > > @@ -113,8 +113,30 @@ static inline bool kasan_has_integrated_init(void) > > return false; > > } > > > > +static __always_inline void kasan_alloc_pages(struct page *page, > > + unsigned int order, gfp_t flags) > > +{ > > + /* Only available for integrated init. */ > > + BUILD_BUG(); > > +} > > + > > +static __always_inline void kasan_free_pages(struct page *page, > > + unsigned int order) > > +{ > > + /* Only available for integrated init. */ > > + BUILD_BUG(); > > +} > > + > > #endif /* CONFIG_KASAN_HW_TAGS */ > > > > +#ifdef CONFIG_KASAN > > + > > +struct kasan_cache { > > + int alloc_meta_offset; > > + int free_meta_offset; > > + bool is_kmalloc; > > +}; > > + > > slab_flags_t __kasan_never_merge(void); > > static __always_inline slab_flags_t kasan_never_merge(void) > > { > > @@ -130,20 +152,20 @@ static __always_inline void kasan_unpoison_range(const void *addr, size_t size) > > __kasan_unpoison_range(addr, size); > > } > > > > -void __kasan_alloc_pages(struct page *page, unsigned int order, bool init); > > -static __always_inline void kasan_alloc_pages(struct page *page, > > +void __kasan_poison_pages(struct page *page, unsigned int order, bool init); > > +static __always_inline void kasan_poison_pages(struct page *page, > > unsigned int order, bool init) > > { > > if (kasan_enabled()) > > - __kasan_alloc_pages(page, order, init); > > + __kasan_poison_pages(page, order, init); > > } > > > > -void __kasan_free_pages(struct page *page, unsigned int order, bool init); > > -static __always_inline void kasan_free_pages(struct page *page, > > - unsigned int order, bool init) > > +void __kasan_unpoison_pages(struct page *page, unsigned int order, bool init); > > +static __always_inline void kasan_unpoison_pages(struct page *page, > > + unsigned int order, bool init) > > { > > if (kasan_enabled()) > > - __kasan_free_pages(page, order, init); > > + __kasan_unpoison_pages(page, order, init); > > } > > > > void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size, > > @@ -285,21 +307,15 @@ void kasan_restore_multi_shot(bool enabled); > > > > #else /* CONFIG_KASAN */ > > > > -static inline bool kasan_enabled(void) > > -{ > > - return false; > > -} > > -static inline bool kasan_has_integrated_init(void) > > -{ > > - return false; > > -} > > static inline slab_flags_t kasan_never_merge(void) > > { > > return 0; > > } > > static inline void kasan_unpoison_range(const void *address, size_t size) {} > > -static inline void kasan_alloc_pages(struct page *page, unsigned int order, bool init) {} > > -static inline void kasan_free_pages(struct page *page, unsigned int order, bool init) {} > > +static inline void kasan_poison_pages(struct page *page, unsigned int order, > > + bool init) {} > > +static inline void kasan_unpoison_pages(struct page *page, unsigned int order, > > + bool init) {} > > static inline void kasan_cache_create(struct kmem_cache *cache, > > unsigned int *size, > > slab_flags_t *flags) {} > > diff --git a/mm/kasan/common.c b/mm/kasan/common.c > > index 6bb87f2acd4e..0ecd293af344 100644 > > --- a/mm/kasan/common.c > > +++ b/mm/kasan/common.c > > @@ -97,7 +97,7 @@ slab_flags_t __kasan_never_merge(void) > > return 0; > > } > > > > -void __kasan_alloc_pages(struct page *page, unsigned int order, bool init) > > +void __kasan_unpoison_pages(struct page *page, unsigned int order, bool init) > > { > > u8 tag; > > unsigned long i; > > @@ -111,7 +111,7 @@ void __kasan_alloc_pages(struct page *page, unsigned int order, bool init) > > kasan_unpoison(page_address(page), PAGE_SIZE << order, init); > > } > > > > -void __kasan_free_pages(struct page *page, unsigned int order, bool init) > > +void __kasan_poison_pages(struct page *page, unsigned int order, bool init) > > { > > if (likely(!PageHighMem(page))) > > kasan_poison(page_address(page), PAGE_SIZE << order, > > diff --git a/mm/kasan/hw_tags.c b/mm/kasan/hw_tags.c > > index 4004388b4e4b..45e552cb9172 100644 > > --- a/mm/kasan/hw_tags.c > > +++ b/mm/kasan/hw_tags.c > > @@ -238,6 +238,20 @@ struct kasan_track *kasan_get_free_track(struct kmem_cache *cache, > > return &alloc_meta->free_track[0]; > > } > > > > +void kasan_alloc_pages(struct page *page, unsigned int order, gfp_t flags) > > +{ > > + bool init = !want_init_on_free() && want_init_on_alloc(flags); > > This check is now duplicated. One check here, the same one in > page_alloc.c. Please either add a helper that gets used in both > places, or at least a comment that the checks must be kept in sync. Added a comment in v4. > > + > > + kasan_unpoison_pages(page, order, init); > > +} > > + > > +void kasan_free_pages(struct page *page, unsigned int order) > > +{ > > + bool init = want_init_on_free(); > > Same here. Likewise. > > + > > + kasan_poison_pages(page, order, init); > > +} > > + > > #if IS_ENABLED(CONFIG_KASAN_KUNIT_TEST) > > > > void kasan_set_tagging_report_once(bool state) > > diff --git a/mm/mempool.c b/mm/mempool.c > > index a258cf4de575..0b8afbec3e35 100644 > > --- a/mm/mempool.c > > +++ b/mm/mempool.c > > @@ -106,7 +106,8 @@ static __always_inline void kasan_poison_element(mempool_t *pool, void *element) > > if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc) > > kasan_slab_free_mempool(element); > > else if (pool->alloc == mempool_alloc_pages) > > - kasan_free_pages(element, (unsigned long)pool->pool_data, false); > > + kasan_poison_pages(element, (unsigned long)pool->pool_data, > > + false); > > } > > > > static void kasan_unpoison_element(mempool_t *pool, void *element) > > @@ -114,7 +115,8 @@ static void kasan_unpoison_element(mempool_t *pool, void *element) > > if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc) > > kasan_unpoison_range(element, __ksize(element)); > > else if (pool->alloc == mempool_alloc_pages) > > - kasan_alloc_pages(element, (unsigned long)pool->pool_data, false); > > + kasan_unpoison_pages(element, (unsigned long)pool->pool_data, > > + false); > > } > > > > static __always_inline void add_element(mempool_t *pool, void *element) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > index aaa1655cf682..6e82a7f6fd6f 100644 > > --- a/mm/page_alloc.c > > +++ b/mm/page_alloc.c > > @@ -382,7 +382,7 @@ int page_group_by_mobility_disabled __read_mostly; > > static DEFINE_STATIC_KEY_TRUE(deferred_pages); > > > > /* > > - * Calling kasan_free_pages() only after deferred memory initialization > > + * Calling kasan_poison_pages() only after deferred memory initialization > > * has completed. Poisoning pages during deferred memory init will greatly > > * lengthen the process and cause problem in large memory systems as the > > * deferred pages initialization is done with interrupt disabled. > > @@ -394,15 +394,11 @@ static DEFINE_STATIC_KEY_TRUE(deferred_pages); > > * on-demand allocation and then freed again before the deferred pages > > * initialization is done, but this is not likely to happen. > > */ > > -static inline void kasan_free_nondeferred_pages(struct page *page, int order, > > - bool init, fpi_t fpi_flags) > > +static inline bool should_skip_kasan_poison(fpi_t fpi_flags) > > { > > - if (static_branch_unlikely(&deferred_pages)) > > - return; > > - if (!IS_ENABLED(CONFIG_KASAN_GENERIC) && > > - (fpi_flags & FPI_SKIP_KASAN_POISON)) > > - return; > > - kasan_free_pages(page, order, init); > > + return static_branch_unlikely(&deferred_pages) || > > + (!IS_ENABLED(CONFIG_KASAN_GENERIC) && > > + (fpi_flags & FPI_SKIP_KASAN_POISON)); > > } > > > > /* Returns true if the struct page for the pfn is uninitialised */ > > @@ -453,13 +449,10 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn) > > return false; > > } > > #else > > -static inline void kasan_free_nondeferred_pages(struct page *page, int order, > > - bool init, fpi_t fpi_flags) > > +static inline bool should_skip_kasan_poison(fpi_t fpi_flags) > > { > > - if (!IS_ENABLED(CONFIG_KASAN_GENERIC) && > > - (fpi_flags & FPI_SKIP_KASAN_POISON)) > > - return; > > - kasan_free_pages(page, order, init); > > + return (!IS_ENABLED(CONFIG_KASAN_GENERIC) && > > + (fpi_flags & FPI_SKIP_KASAN_POISON)); > > } > > > > static inline bool early_page_uninitialised(unsigned long pfn) > > @@ -1245,7 +1238,7 @@ static __always_inline bool free_pages_prepare(struct page *page, > > unsigned int order, bool check_free, fpi_t fpi_flags) > > { > > int bad = 0; > > - bool init; > > + bool skip_kasan_poison = should_skip_kasan_poison(fpi_flags); > > > > VM_BUG_ON_PAGE(PageTail(page), page); > > > > @@ -1314,10 +1307,17 @@ static __always_inline bool free_pages_prepare(struct page *page, > > * With hardware tag-based KASAN, memory tags must be set before the > > * page becomes unavailable via debug_pagealloc or arch_free_page. > > */ > > - init = want_init_on_free(); > > - if (init && !kasan_has_integrated_init()) > > - kernel_init_free_pages(page, 1 << order); > > - kasan_free_nondeferred_pages(page, order, init, fpi_flags); > > + if (kasan_has_integrated_init()) { > > Is it guaranteed that this branch will be eliminated when > kasan_has_integrated_init() is static inline returning false? I know > this works with macros, but I don't remember seeing cases with static > inline functions. I guess it's the same, but mentioning just in case > because BUILD_BUG() stood out. Here's one example of where we rely on optimization after inlining to eliminate a BUILD_BUG(): https://github.com/torvalds/linux/blob/3224374f7eb08fbb36d3963895da20ff274b8e6a/arch/arm64/include/asm/arm_dsu_pmu.h#L123 Peter
