From mboxrd@z Thu Jan 1 00:00:00 1970 From: matthieu.castet@parrot.com (Matthieu CASTET) Date: Mon, 21 Jan 2013 10:56:31 +0100 Subject: [PATCH] slab : allow SLAB_RED_ZONE and SLAB_STORE_USER to work on arm Message-ID: <1358762191-13839-1-git-send-email-matthieu.castet@parrot.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org The current slab code only allow to put redzone( and user store) info if "buffer alignment(ralign) <= __alignof__(unsigned long long)". This was done because we want to keep the buffer aligned for user even after adding redzone@the beginning of the buffer (the user store is stored after user buffer) [1] But instead of disabling this feature when "ralign > __alignof__(unsigned long long)", we can force the alignment by allocating ralign before user buffer. This is done by setting ralign in obj_offset when "ralign > __alignof__(unsigned long long)" and keeping the old behavior when "ralign <= __alignof__(unsigned long long)" (we set sizeof(unsigned long long)). The 5c5e3b33b7cb959a401f823707bee006caadd76e commit wasn't handling "ralign <= __alignof__(unsigned long long)", that's why it broked some configuration. This was tested on omap3 (ralign is 64 and __alignof__(unsigned long long) is 8) [1] /* * memory layout of objects: * 0 : objp * 0 .. cachep->obj_offset - BYTES_PER_WORD - 1: padding. This ensures that * the end of an object is aligned with the end of the real * allocation. Catches writes behind the end of the allocation. * cachep->obj_offset - BYTES_PER_WORD .. cachep->obj_offset - 1: * redzone word. * cachep->obj_offset: The real object. * cachep->buffer_size - 2* BYTES_PER_WORD: redzone word [BYTES_PER_WORD long] * cachep->buffer_size - 1* BYTES_PER_WORD: last caller address * [BYTES_PER_WORD long] */ Signed-off-by: Matthieu Castet CC: Russell King CC: Pekka Enberg --- mm/slab.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/mm/slab.c b/mm/slab.c index e7667a3..d2380d9 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -2392,9 +2392,6 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags) if (ralign < cachep->align) { ralign = cachep->align; } - /* disable debug if necessary */ - if (ralign > __alignof__(unsigned long long)) - flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); /* * 4) Store it. */ @@ -2414,8 +2411,9 @@ __kmem_cache_create (struct kmem_cache *cachep, unsigned long flags) */ if (flags & SLAB_RED_ZONE) { /* add space for red zone words */ - cachep->obj_offset += sizeof(unsigned long long); - size += 2 * sizeof(unsigned long long); + int offset = max(ralign, sizeof(unsigned long long)); + cachep->obj_offset += offset; + size += offset + sizeof(unsigned long long); } if (flags & SLAB_STORE_USER) { /* user store requires one word storage behind the end of -- 1.7.10.4