From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 810BEC56202 for ; Fri, 13 Nov 2020 10:40:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2CCB82224C for ; Fri, 13 Nov 2020 10:40:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726438AbgKMKkz (ORCPT ); Fri, 13 Nov 2020 05:40:55 -0500 Received: from mx2.suse.de ([195.135.220.15]:39836 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726267AbgKMKkv (ORCPT ); Fri, 13 Nov 2020 05:40:51 -0500 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 777D9AF0B; Fri, 13 Nov 2020 10:40:48 +0000 (UTC) From: Vlastimil Babka To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Alexander Potapenko , Kees Cook , Michal Hocko , David Hildenbrand , Mateusz Nosek , Laura Abbott , Vlastimil Babka Subject: [PATCH v3 5/5] mm, page_poison: remove CONFIG_PAGE_POISONING_ZERO Date: Fri, 13 Nov 2020 11:40:33 +0100 Message-Id: <20201113104033.22907-6-vbabka@suse.cz> X-Mailer: git-send-email 2.29.2 In-Reply-To: <20201113104033.22907-1-vbabka@suse.cz> References: <20201113104033.22907-1-vbabka@suse.cz> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org CONFIG_PAGE_POISONING_ZERO uses the zero pattern instead of 0xAA. It was introduced by commit 1414c7f4f7d7 ("mm/page_poisoning.c: allow for zero poisoning"), noting that using zeroes retains the benefit of sanitizing content of freed pages, with the benefit of not having to zero them again on alloc, and the downside of making some forms of corruption (stray writes of NULLs) harder to detect than with the 0xAA pattern. Together with CONFIG_PAGE_POISONING_NO_SANITY it made possible to sanitize the contents on free without checking it back on alloc. These days we have the init_on_free() option to achieve sanitization with zeroes and to save clearing on alloc (and without checking on alloc). Arguably if someone does choose to check the poison for corruption on alloc, the savings of not clearing the page are secondary, and it makes sense to always use the 0xAA poison pattern. Thus, remove the CONFIG_PAGE_POISONING_ZERO option for being redundant. Signed-off-by: Vlastimil Babka Acked-by: David Hildenbrand --- include/linux/poison.h | 4 ---- mm/Kconfig.debug | 12 ------------ mm/page_alloc.c | 8 +------- tools/include/linux/poison.h | 6 +----- 4 files changed, 2 insertions(+), 28 deletions(-) diff --git a/include/linux/poison.h b/include/linux/poison.h index dc8ae5d8db03..aff1c9250c82 100644 --- a/include/linux/poison.h +++ b/include/linux/poison.h @@ -27,11 +27,7 @@ #define TIMER_ENTRY_STATIC ((void *) 0x300 + POISON_POINTER_DELTA) /********** mm/page_poison.c **********/ -#ifdef CONFIG_PAGE_POISONING_ZERO -#define PAGE_POISON 0x00 -#else #define PAGE_POISON 0xaa -#endif /********** mm/page_alloc.c ************/ diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug index 14e29fe5bfa6..1e73717802f8 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -80,18 +80,6 @@ config PAGE_POISONING If unsure, say N -config PAGE_POISONING_ZERO - bool "Use zero for poisoning instead of debugging value" - depends on PAGE_POISONING - help - Instead of using the existing poison value, fill the pages with - zeros. This makes it harder to detect when errors are occurring - due to sanitization but the zeroing at free means that it is - no longer necessary to write zeros when GFP_ZERO is used on - allocation. - - If unsure, say N - config DEBUG_PAGE_REF bool "Enable tracepoint to track down page reference manipulation" depends on DEBUG_KERNEL diff --git a/mm/page_alloc.c b/mm/page_alloc.c index cd966829bed3..e80d5ce1b292 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2226,12 +2226,6 @@ static inline int check_new_page(struct page *page) return 1; } -static inline bool free_pages_prezeroed(void) -{ - return (IS_ENABLED(CONFIG_PAGE_POISONING_ZERO) && - page_poisoning_enabled_static()) || want_init_on_free(); -} - #ifdef CONFIG_DEBUG_VM /* * With DEBUG_VM enabled, order-0 pages are checked for expected state when @@ -2300,7 +2294,7 @@ static void prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags { post_alloc_hook(page, order, gfp_flags); - if (!free_pages_prezeroed() && want_init_on_alloc(gfp_flags)) + if (!want_init_on_free() && want_init_on_alloc(gfp_flags)) kernel_init_free_pages(page, 1 << order); if (order && (gfp_flags & __GFP_COMP)) diff --git a/tools/include/linux/poison.h b/tools/include/linux/poison.h index d29725769107..2e6338ac5eed 100644 --- a/tools/include/linux/poison.h +++ b/tools/include/linux/poison.h @@ -35,12 +35,8 @@ */ #define TIMER_ENTRY_STATIC ((void *) 0x300 + POISON_POINTER_DELTA) -/********** mm/debug-pagealloc.c **********/ -#ifdef CONFIG_PAGE_POISONING_ZERO -#define PAGE_POISON 0x00 -#else +/********** mm/page_poison.c **********/ #define PAGE_POISON 0xaa -#endif /********** mm/page_alloc.c ************/ -- 2.29.2