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=-2.4 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=unavailable 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 25478C5CFFE for ; Mon, 10 Dec 2018 13:30:39 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id DEF222084E for ; Mon, 10 Dec 2018 13:30:37 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DEF222084E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 43D3qH0t3XzDqrN for ; Tue, 11 Dec 2018 00:30:35 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: lists.ozlabs.org; spf=pass (mailfrom) smtp.mailfrom=redhat.com (client-ip=209.132.183.28; helo=mx1.redhat.com; envelope-from=oleg@redhat.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=redhat.com Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 43D3mZ6mQJzDqpy for ; Tue, 11 Dec 2018 00:28:14 +1100 (AEDT) Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E8F35811A9; Mon, 10 Dec 2018 13:28:12 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.131]) by smtp.corp.redhat.com (Postfix) with SMTP id E94F01A7D4; Mon, 10 Dec 2018 13:28:07 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 10 Dec 2018 14:28:12 +0100 (CET) Date: Mon, 10 Dec 2018 14:28:07 +0100 From: Oleg Nesterov To: "Dmitry V. Levin" Subject: Re: [PATCH v6] powerpc/ptrace: replace ptrace_report_syscall() with a tracehook call Message-ID: <20181210132806.GA4177@redhat.com> References: <20181116121701.14359da0@akathisia> <87ftw12nyn.fsf@concordia.ellerman.id.au> <20181119210139.GA8360@altlinux.org> <87efbe166y.fsf@concordia.ellerman.id.au> <20181203031823.GE11573@altlinux.org> <20181207011946.GA18558@altlinux.org> <87y391k2tq.fsf@concordia.ellerman.id.au> <20181207154255.GA28964@altlinux.org> <20181207155605.GB28964@altlinux.org> <20181207185226.GB31278@altlinux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181207185226.GB31278@altlinux.org> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 10 Dec 2018 13:28:13 +0000 (UTC) X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Eugene Syromyatnikov , linux-kernel@vger.kernel.org, Elvira Khabirova , Paul Mackerras , Andy Lutomirski , Breno Leitao , linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 12/07, Dmitry V. Levin wrote: > > Please make either v5 or v6 edition of this fix, or any similar fix, > into v4.20. IIUC, v5 above means [PATCH v5 23/25] powerpc/ptrace: replace ptrace_report_syscall() with a tracehook call you sent in another series... > long do_syscall_trace_enter(struct pt_regs *regs) > { > + struct thread_info *ti; > + u32 cached_flags; > + > user_exit(); > > - if (test_thread_flag(TIF_SYSCALL_EMU)) { > - ptrace_report_syscall(regs); > - /* > - * Returning -1 will skip the syscall execution. We want to > - * avoid clobbering any register also, thus, not 'gotoing' > - * skip label. > - */ > - return -1; > - } > + ti = current_thread_info(); > + cached_flags = READ_ONCE(ti->flags) & > + (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE | > + _TIF_SYSCALL_TRACEPOINT); > > - /* > - * The tracer may decide to abort the syscall, if so tracehook > - * will return !0. Note that the tracer may also just change > - * regs->gpr[0] to an invalid syscall number, that is handled > - * below on the exit path. > - */ > - if (test_thread_flag(TIF_SYSCALL_TRACE) && > - tracehook_report_syscall_entry(regs)) > - goto skip; > + if (cached_flags & (_TIF_SYSCALL_EMU | _TIF_SYSCALL_TRACE)) { > + int rc = tracehook_report_syscall_entry(regs); > + > + if (unlikely(cached_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 register also, > + * thus, not 'gotoing' skip label. > + */ > + return -1; > + } > + > + if (rc) { > + /* > + * The tracer decided to abort the syscall. > + * Note that the tracer may also just change > + * regs->gpr[0] to an invalid syscall number, > + * that is handled below on the exit path. > + */ > + goto skip; > + } > + } > > /* Run seccomp after ptrace; allow it to set gpr[3]. */ > if (do_seccomp(regs)) > @@ -3293,7 +3309,7 @@ long do_syscall_trace_enter(struct pt_regs *regs) > if (regs->gpr[0] >= NR_syscalls) > goto skip; > > - if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT))) > + if (unlikely(cached_flags & _TIF_SYSCALL_TRACEPOINT)) I will leave this to maintainers, but to me this change looks good and imo it also cleanups the code. However I am not sure cached_flags should include _TIF_SYSCALL_TRACEPOINT. If nothing else, the caller can sleep in ptrace_stop() unpredictably long and TIF_SYSCALL_TRACEPOINT can be set/cleared meanwhile. Oleg.