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[203.11.71.1]) by mx.google.com with ESMTPS id x1si27510806pfx.152.2019.06.05.04.19.29 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 05 Jun 2019 04:19:29 -0700 (PDT) Received-SPF: neutral (google.com: 203.11.71.1 is neither permitted nor denied by best guess record for domain of mpe@ellerman.id.au) client-ip=203.11.71.1; Authentication-Results: mx.google.com; spf=neutral (google.com: 203.11.71.1 is neither permitted nor denied by best guess record for domain of mpe@ellerman.id.au) smtp.mailfrom=mpe@ellerman.id.au Received: from authenticated.ozlabs.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.ozlabs.org (Postfix) with ESMTPSA id 45JmXD0rHVz9sN6; Wed, 5 Jun 2019 21:19:23 +1000 (AEST) From: Michael Ellerman To: Anshuman Khandual , linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Anshuman Khandual , 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, Andrew Morton , Michal Hocko , Matthew Wilcox , Mark Rutland , Christophe Leroy , Stephen Rothwell , Andrey Konovalov , Paul Mackerras , Russell King , Catalin Marinas , Will Deacon , Tony Luck , Fenghua Yu , Martin Schwidefsky , Heiko Carstens , Yoshinori Sato , "David S. Miller" , Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Andy Lutomirski , Dave Hansen Subject: Re: [RFC V2] mm: Generalize notify_page_fault() In-Reply-To: <1559630046-12940-1-git-send-email-anshuman.khandual@arm.com> References: <1559630046-12940-1-git-send-email-anshuman.khandual@arm.com> Date: Wed, 05 Jun 2019 21:19:22 +1000 Message-ID: <87sgsomg91.fsf@concordia.ellerman.id.au> MIME-Version: 1.0 Content-Type: text/plain X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Anshuman Khandual writes: > Similar notify_page_fault() definitions are being used by architectures > duplicating much of the same code. This attempts to unify them into a > single implementation, generalize it and then move it to a common place. > kprobes_built_in() can detect CONFIG_KPROBES, hence notify_page_fault() > need not be wrapped again within CONFIG_KPROBES. Trap number argument can > now contain upto an 'unsigned int' accommodating all possible platforms. ... > diff --git a/arch/arm/mm/fault.c b/arch/arm/mm/fault.c > index 58f69fa..1bc3b18 100644 > --- a/arch/arm/mm/fault.c > +++ b/arch/arm/mm/fault.c > @@ -30,28 +30,6 @@ > > #ifdef CONFIG_MMU > > -#ifdef CONFIG_KPROBES > -static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr) > -{ > - int ret = 0; > - > - if (!user_mode(regs)) { > - /* kprobe_running() needs smp_processor_id() */ > - preempt_disable(); > - if (kprobe_running() && kprobe_fault_handler(regs, fsr)) > - ret = 1; > - preempt_enable(); > - } > - > - return ret; > -} > -#else You've changed several of the architectures from something like above, where it disables preemption around the call into the below: > +int __kprobes notify_page_fault(struct pt_regs *regs, unsigned int trap) > +{ > + int ret = 0; > + > + /* > + * To be potentially processing a kprobe fault and to be allowed > + * to call kprobe_running(), we have to be non-preemptible. > + */ > + if (kprobes_built_in() && !preemptible() && !user_mode(regs)) { > + if (kprobe_running() && kprobe_fault_handler(regs, trap)) > + ret = 1; > + } > + return ret; > +} Which skips everything if we're preemptible. Is that an equivalent change? If so can you please explain why in more detail. Also why not have it return bool? cheers