From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by kanga.kvack.org (Postfix) with ESMTP id D4C028E0034 for ; Fri, 21 Sep 2018 11:14:05 -0400 (EDT) Received: by mail-wm1-f72.google.com with SMTP id y13-v6so1382421wmi.9 for ; Fri, 21 Sep 2018 08:14:05 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id b13-v6sor20863104wrp.25.2018.09.21.08.14.04 for (Google Transport Security); Fri, 21 Sep 2018 08:14:04 -0700 (PDT) From: Andrey Konovalov Subject: [PATCH v9 10/20] mm: move obj_to_index to include/linux/slab_def.h Date: Fri, 21 Sep 2018 17:13:32 +0200 Message-Id: <9d62f917393456653c1d38c7173dc876cef03c93.1537542735.git.andreyknvl@google.com> In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrey Ryabinin , Alexander Potapenko , Dmitry Vyukov , Catalin Marinas , Will Deacon , Christoph Lameter , Andrew Morton , Mark Rutland , Nick Desaulniers , Marc Zyngier , Dave Martin , Ard Biesheuvel , "Eric W . Biederman" , Ingo Molnar , Paul Lawrence , Geert Uytterhoeven , Arnd Bergmann , "Kirill A . Shutemov" , Greg Kroah-Hartman , Kate Stewart , Mike Rapoport , kasan-dev@googlegroups.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sparse@vger.kernel.org, linux-mm@kvack.org, linux-kbuild@vger.kernel.org Cc: Kostya Serebryany , Evgeniy Stepanov , Lee Smith , Ramana Radhakrishnan , Jacob Bramley , Ruben Ayrapetyan , Jann Horn , Mark Brand , Chintan Pandya , Vishwath Mohan , Andrey Konovalov While with SLUB we can actually preassign tags for caches with contructors and store them in pointers in the freelist, SLAB doesn't allow that since the freelist is stored as an array of indexes, so there are no pointers to store the tags. Instead we compute the tag twice, once when a slab is created before calling the constructor and then again each time when an object is allocated with kmalloc. Tag is computed simply by taking the lowest byte of the index that corresponds to the object. However in kasan_kmalloc we only have access to the objects pointer, so we need a way to find out which index this object corresponds to. This patch moves obj_to_index from slab.c to include/linux/slab_def.h to be reused by KASAN. Signed-off-by: Andrey Konovalov --- include/linux/slab_def.h | 13 +++++++++++++ mm/slab.c | 13 ------------- 2 files changed, 13 insertions(+), 13 deletions(-) diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h index 3485c58cfd1c..9a5eafb7145b 100644 --- a/include/linux/slab_def.h +++ b/include/linux/slab_def.h @@ -104,4 +104,17 @@ static inline void *nearest_obj(struct kmem_cache *cache, struct page *page, return object; } +/* + * We want to avoid an expensive divide : (offset / cache->size) + * Using the fact that size is a constant for a particular cache, + * we can replace (offset / cache->size) by + * reciprocal_divide(offset, cache->reciprocal_buffer_size) + */ +static inline unsigned int obj_to_index(const struct kmem_cache *cache, + const struct page *page, void *obj) +{ + u32 offset = (obj - page->s_mem); + return reciprocal_divide(offset, cache->reciprocal_buffer_size); +} + #endif /* _LINUX_SLAB_DEF_H */ diff --git a/mm/slab.c b/mm/slab.c index fe0ddf08aa2c..6d8de7630944 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -406,19 +406,6 @@ static inline void *index_to_obj(struct kmem_cache *cache, struct page *page, return page->s_mem + cache->size * idx; } -/* - * We want to avoid an expensive divide : (offset / cache->size) - * Using the fact that size is a constant for a particular cache, - * we can replace (offset / cache->size) by - * reciprocal_divide(offset, cache->reciprocal_buffer_size) - */ -static inline unsigned int obj_to_index(const struct kmem_cache *cache, - const struct page *page, void *obj) -{ - u32 offset = (obj - page->s_mem); - return reciprocal_divide(offset, cache->reciprocal_buffer_size); -} - #define BOOT_CPUCACHE_ENTRIES 1 /* internal cache of cache description objs */ static struct kmem_cache kmem_cache_boot = { -- 2.19.0.444.g18242da7ef-goog