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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 76EE4C4360C for ; Wed, 16 Oct 2019 09:54:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 550D12168B for ; Wed, 16 Oct 2019 09:54:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404364AbfJPJyN (ORCPT ); Wed, 16 Oct 2019 05:54:13 -0400 Received: from foss.arm.com ([217.140.110.172]:34420 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404266AbfJPJyM (ORCPT ); Wed, 16 Oct 2019 05:54:12 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id A6076142F; Wed, 16 Oct 2019 02:54:11 -0700 (PDT) Received: from [10.163.1.216] (unknown [10.163.1.216]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DD8023F6C4; Wed, 16 Oct 2019 02:53:56 -0700 (PDT) Subject: Re: [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers To: Qian Cai , linux-mm@kvack.org Cc: Andrew Morton , Vlastimil Babka , Greg Kroah-Hartman , Thomas Gleixner , Mike Rapoport , Jason Gunthorpe , Dan Williams , Peter Zijlstra , Michal Hocko , Mark Rutland , Mark Brown , Steven Price , Ard Biesheuvel , Masahiro Yamada , Kees Cook , Tetsuo Handa , Matthew Wilcox , Sri Krishna chowdary , Dave Hansen , Russell King - ARM Linux , Michael Ellerman , Paul Mackerras , Martin Schwidefsky , Heiko Carstens , "David S. Miller" , Vineet Gupta , James Hogan , Paul Burton , Ralf Baechle , "Kirill A . Shutemov" , Gerald Schaefer , Christophe Leroy , linux-snps-arc@lists.infradead.org, linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org References: <1571131302-32290-1-git-send-email-anshuman.khandual@arm.com> <1571131302-32290-3-git-send-email-anshuman.khandual@arm.com> <1571162982.5937.42.camel@lca.pw> From: Anshuman Khandual Message-ID: <7cd03155-6713-3116-1e88-f81f84dd794f@arm.com> Date: Wed, 16 Oct 2019 15:24:23 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1571162982.5937.42.camel@lca.pw> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/15/2019 11:39 PM, Qian Cai wrote: > On Tue, 2019-10-15 at 14:51 +0530, Anshuman Khandual wrote: >> +static unsigned long __init get_random_vaddr(void) >> +{ >> + unsigned long random_vaddr, random_pages, total_user_pages; >> + >> + total_user_pages = (TASK_SIZE - FIRST_USER_ADDRESS) / PAGE_SIZE; >> + >> + random_pages = get_random_long() % total_user_pages; >> + random_vaddr = FIRST_USER_ADDRESS + random_pages * PAGE_SIZE; >> + >> + WARN_ON(random_vaddr > TASK_SIZE); >> + WARN_ON(random_vaddr < FIRST_USER_ADDRESS); > > It would be nice if this patch does not introduce a new W=1 GCC warning here on > x86 because FIRST_USER_ADDRESS is 0, and GCC think the code is dumb because > "random_vaddr" is unsigned, > > In file included from ./arch/x86/include/asm/bug.h:83, >                  from ./include/linux/bug.h:5, >                  from ./include/linux/mmdebug.h:5, >                  from ./include/linux/gfp.h:5, >                  from mm/debug_vm_pgtable.c:13: > mm/debug_vm_pgtable.c: In function ‘get_random_vaddr’: > mm/debug_vm_pgtable.c:359:23: warning: comparison of unsigned expression < 0 is > always false [-Wtype-limits] >   WARN_ON(random_vaddr < FIRST_USER_ADDRESS); >                        ^ > ./include/asm-generic/bug.h:113:25: note: in definition of macro ‘WARN_ON’ >   int __ret_warn_on = !!(condition);    \ >                          ^~~~~~~~~ The test checks against an erroneous unsigned long overflow when FIRST_USER_ADDRESS is not 0 but a positive number. Wondering if the compiler will still complain if we merge both the WARN_ON() checks as || on a single statement.