Re: [PATCH v2 3/5] kasan, mm: integrate page_alloc init with HW_TAGS

From: Marco Elver
Date: Mon Mar 08 2021 - 11:09:03 EST

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On Mon, Mar 08, 2021 at 04:55PM +0100, Andrey Konovalov wrote:
> This change uses the previously added memory initialization feature
> of HW_TAGS KASAN routines for page_alloc memory when init_on_alloc/free
> is enabled.
>
> With this change, kernel_init_free_pages() is no longer called when
> both HW_TAGS KASAN and init_on_alloc/free are enabled. Instead, memory
> is initialized in KASAN runtime.
>
> To avoid discrepancies with which memory gets initialized that can be
> caused by future changes, both KASAN and kernel_init_free_pages() hooks
> are put together and a warning comment is added.
>
> This patch changes the order in which memory initialization and page
> poisoning hooks are called. This doesn't lead to any side-effects, as
> whenever page poisoning is enabled, memory initialization gets disabled.
>
> Combining setting allocation tags with memory initialization improves
> HW_TAGS KASAN performance when init_on_alloc/free is enabled.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Reviewed-by: Marco Elver <elver@xxxxxxxxxx>

> ---
> include/linux/kasan.h | 30 ++++++++++++++++++++++--------
> mm/kasan/common.c | 8 ++++----
> mm/mempool.c | 4 ++--
> mm/page_alloc.c | 37 ++++++++++++++++++++++++++-----------
> 4 files changed, 54 insertions(+), 25 deletions(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index 1d89b8175027..c89613caa8cf 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -96,6 +96,11 @@ static __always_inline bool kasan_enabled(void)
> return static_branch_likely(&kasan_flag_enabled);
> }
>
> +static inline bool kasan_has_integrated_init(void)
> +{
> + return kasan_enabled();

Good catch that we need enabled, too.

> +}
> +
> #else /* CONFIG_KASAN_HW_TAGS */
>
> static inline bool kasan_enabled(void)
> @@ -103,6 +108,11 @@ static inline bool kasan_enabled(void)
> return true;
> }
>
> +static inline bool kasan_has_integrated_init(void)
> +{
> + return false;
> +}
> +
> #endif /* CONFIG_KASAN_HW_TAGS */
>
> slab_flags_t __kasan_never_merge(void);
> @@ -120,20 +130,20 @@ 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);
> +void __kasan_alloc_pages(struct page *page, unsigned int order, bool init);
> static __always_inline void kasan_alloc_pages(struct page *page,
> - unsigned int order)
> + unsigned int order, bool init)
> {
> if (kasan_enabled())
> - __kasan_alloc_pages(page, order);
> + __kasan_alloc_pages(page, order, init);
> }
>
> -void __kasan_free_pages(struct page *page, unsigned int order);
> +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)
> + unsigned int order, bool init)
> {
> if (kasan_enabled())
> - __kasan_free_pages(page, order);
> + __kasan_free_pages(page, order, init);
> }
>
> void __kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
> @@ -277,13 +287,17 @@ 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) {}
> -static inline void kasan_free_pages(struct page *page, unsigned int order) {}
> +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_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 316f7f8cd8e6..6107c795611f 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)
> +void __kasan_alloc_pages(struct page *page, unsigned int order, bool init)
> {
> u8 tag;
> unsigned long i;
> @@ -108,14 +108,14 @@ void __kasan_alloc_pages(struct page *page, unsigned int order)
> tag = kasan_random_tag();
> for (i = 0; i < (1 << order); i++)
> page_kasan_tag_set(page + i, tag);
> - kasan_unpoison(page_address(page), PAGE_SIZE << order, false);
> + kasan_unpoison(page_address(page), PAGE_SIZE << order, init);
> }
>
> -void __kasan_free_pages(struct page *page, unsigned int order)
> +void __kasan_free_pages(struct page *page, unsigned int order, bool init)
> {
> if (likely(!PageHighMem(page)))
> kasan_poison(page_address(page), PAGE_SIZE << order,
> - KASAN_FREE_PAGE, false);
> + KASAN_FREE_PAGE, init);
> }
>
> /*
> diff --git a/mm/mempool.c b/mm/mempool.c
> index 79959fac27d7..fe19d290a301 100644
> --- a/mm/mempool.c
> +++ b/mm/mempool.c
> @@ -106,7 +106,7 @@ 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);
> + kasan_free_pages(element, (unsigned long)pool->pool_data, false);
> }
>
> static void kasan_unpoison_element(mempool_t *pool, void *element)
> @@ -114,7 +114,7 @@ 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);
> + kasan_alloc_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 0efb07b5907c..aba9cd673eac 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -396,14 +396,14 @@ static DEFINE_STATIC_KEY_TRUE(deferred_pages);
> * initialization is done, but this is not likely to happen.
> */
> static inline void kasan_free_nondeferred_pages(struct page *page, int order,
> - fpi_t fpi_flags)
> + bool init, 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);
> + kasan_free_pages(page, order, init);
> }
>
> /* Returns true if the struct page for the pfn is uninitialised */
> @@ -455,12 +455,12 @@ defer_init(int nid, unsigned long pfn, unsigned long end_pfn)
> }
> #else
> static inline void kasan_free_nondeferred_pages(struct page *page, int order,
> - fpi_t fpi_flags)
> + bool init, fpi_t fpi_flags)
> {
> if (!IS_ENABLED(CONFIG_KASAN_GENERIC) &&
> (fpi_flags & FPI_SKIP_KASAN_POISON))
> return;
> - kasan_free_pages(page, order);
> + kasan_free_pages(page, order, init);
> }
>
> static inline bool early_page_uninitialised(unsigned long pfn)
> @@ -1242,6 +1242,7 @@ 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;
>
> VM_BUG_ON_PAGE(PageTail(page), page);
>
> @@ -1299,16 +1300,21 @@ static __always_inline bool free_pages_prepare(struct page *page,
> debug_check_no_obj_freed(page_address(page),
> PAGE_SIZE << order);
> }
> - if (want_init_on_free())
> - kernel_init_free_pages(page, 1 << order);
>
> kernel_poison_pages(page, 1 << order);
>
> /*
> + * As memory initialization might be integrated into KASAN,
> + * kasan_free_pages and kernel_init_free_pages must be
> + * kept together to avoid discrepancies in behavior.
> + *
> * With hardware tag-based KASAN, memory tags must be set before the
> * page becomes unavailable via debug_pagealloc or arch_free_page.
> */
> - kasan_free_nondeferred_pages(page, order, fpi_flags);
> + 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);
>
> /*
> * arch_free_page() can make the page's contents inaccessible. s390
> @@ -2315,17 +2321,26 @@ static bool check_new_pages(struct page *page, unsigned int order)
> inline void post_alloc_hook(struct page *page, unsigned int order,
> gfp_t gfp_flags)
> {
> + bool init;
> +
> set_page_private(page, 0);
> set_page_refcounted(page);
>
> arch_alloc_page(page, order);
> debug_pagealloc_map_pages(page, 1 << order);
> - kasan_alloc_pages(page, order);
> - kernel_unpoison_pages(page, 1 << order);
> - set_page_owner(page, order, gfp_flags);
>
> - if (!want_init_on_free() && want_init_on_alloc(gfp_flags))
> + /*
> + * As memory initialization might be integrated into KASAN,
> + * kasan_alloc_pages and kernel_init_free_pages must be
> + * kept together to avoid discrepancies in behavior.
> + */
> + init = !want_init_on_free() && want_init_on_alloc(gfp_flags);
> + kasan_alloc_pages(page, order, init);
> + if (init && !kasan_has_integrated_init())
> kernel_init_free_pages(page, 1 << order);
> +
> + kernel_unpoison_pages(page, 1 << order);
> + set_page_owner(page, order, gfp_flags);
> }
>
> static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
> --
> 2.30.1.766.gb4fecdf3b7-goog
>

Next message: Mark Brown: "Re: (subset) [PATCH v2 00/15] Report jack and button detection + Capture Support"
Previous message: Arnd Bergmann: "Re: [PATCH] power: supply: max8997_charger: make EXTCON dependency unconditional"
In reply to: Andrey Konovalov: "[PATCH v2 3/5] kasan, mm: integrate page_alloc init with HW_TAGS"
Next in thread: Andrey Konovalov: "[PATCH v2 5/5] kasan, mm: integrate slab init_on_free with HW_TAGS"
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