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Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h5vx9-0007zK-Ea; Mon, 18 Mar 2019 17:21:35 +0000 Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h5vw6-00074g-K1 for linux-arm-kernel@lists.infradead.org; Mon, 18 Mar 2019 17:20:53 +0000 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 6443B3082AEE; Mon, 18 Mar 2019 17:20:29 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.34]) by smtp.corp.redhat.com (Postfix) with SMTP id 7D66860FAB; Mon, 18 Mar 2019 17:20:25 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 18 Mar 2019 18:20:29 +0100 (CET) Date: Mon, 18 Mar 2019 18:20:24 +0100 From: Oleg Nesterov To: Sudeep Holla Subject: Re: [PATCH v2 4/6] powerpc: use common ptrace_syscall_enter hook to handle _TIF_SYSCALL_EMU Message-ID: <20190318172024.GB23521@redhat.com> References: <20190318104925.16600-1-sudeep.holla@arm.com> <20190318104925.16600-5-sudeep.holla@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190318104925.16600-5-sudeep.holla@arm.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Mon, 18 Mar 2019 17:20:29 +0000 (UTC) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190318_102031_370766_5B0EB284 X-CRM114-Status: GOOD ( 20.08 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Haibo Xu , Steve Capper , Catalin Marinas , jdike@addtoit.com, x86@kernel.org, Will Deacon , linux-kernel@vger.kernel.org, Bin Lu , Richard Weinberger , Ingo Molnar , Paul Mackerras , Andy Lutomirski , Michael Ellerman , Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 03/18, Sudeep Holla wrote: > > --- a/arch/powerpc/kernel/ptrace.c > +++ b/arch/powerpc/kernel/ptrace.c > @@ -3278,35 +3278,29 @@ long do_syscall_trace_enter(struct pt_regs *regs) > > user_exit(); > > - flags = READ_ONCE(current_thread_info()->flags) & > - (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE); > - > - if (flags) { > - int rc = tracehook_report_syscall_entry(regs); > + if (unlikely(ptrace_syscall_enter(regs))) { > + /* > + * A nonzero return code from tracehook_report_syscall_entry() > + * tells us to prevent the syscall execution, but we are not > + * going to execute it anyway. > + * > + * Returning -1 will skip the syscall execution. We want to > + * avoid clobbering any registers, so we don't goto the skip > + * label below. > + */ > + return -1; > + } > > - if (unlikely(flags & _TIF_SYSCALL_EMU)) { > - /* > - * A nonzero return code from > - * tracehook_report_syscall_entry() tells us to prevent > - * the syscall execution, but we are not going to > - * execute it anyway. > - * > - * Returning -1 will skip the syscall execution. We want > - * to avoid clobbering any registers, so we don't goto > - * the skip label below. > - */ > - return -1; > - } > + flags = READ_ONCE(current_thread_info()->flags) & _TIF_SYSCALL_TRACE; Why do we need READ_ONCE() with this change? And now that we change a single bit "flags" doesn't look like a good name. Again, to me this patch just makes the code look worse. Honestly, I don't think that the new (badly named) ptrace_syscall_enter() hook makes any sense. Oleg. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel