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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id k54sm15559033qtf.28.2019.10.15.11.09.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 15 Oct 2019 11:09:45 -0700 (PDT) Message-ID: <1571162982.5937.42.camel@lca.pw> Subject: Re: [PATCH V6 2/2] mm/debug: Add tests validating architecture page table helpers From: Qian Cai To: Anshuman Khandual , 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 Date: Tue, 15 Oct 2019 14:09:42 -0400 In-Reply-To: <1571131302-32290-3-git-send-email-anshuman.khandual@arm.com> References: <1571131302-32290-1-git-send-email-anshuman.khandual@arm.com> <1571131302-32290-3-git-send-email-anshuman.khandual@arm.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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);    \                          ^~~~~~~~~