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=-1.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_PASS,T_DKIMWL_WL_HIGH autolearn=ham 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 60FA2C433F5 for ; Wed, 29 Aug 2018 00:08:39 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 05E4020880 for ; Wed, 29 Aug 2018 00:08:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="qEcf8rhF" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 05E4020880 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727042AbeH2ECl (ORCPT ); Wed, 29 Aug 2018 00:02:41 -0400 Received: from mail.kernel.org ([198.145.29.99]:39268 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725747AbeH2ECl (ORCPT ); Wed, 29 Aug 2018 00:02:41 -0400 Received: from devbox (NE2965lan1.rev.em-net.ne.jp [210.141.244.193]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 089212087F; Wed, 29 Aug 2018 00:08:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1535501316; bh=pM2kxnMIXwI2qObLyygiDEhDeSMfeo6CVtV5f86HIf0=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qEcf8rhFCa77MFdY5IShKj2xRdcKSH3UI0o1YQqD59hZ4LpC9vr8MVKxEUSr1eoSm 5nwijxDcCSXutD2aTDNX44Z6VI7s/tCB1ov5k4FwY/dLPsoxAsFao87z1nAyRKPhg5 myQ5/vvPifJ7EsKSBbdtj8OwGzB7CvF4yjRXyPZk= Date: Wed, 29 Aug 2018 09:08:32 +0900 From: Masami Hiramatsu To: Jann Horn Cc: Kees Cook , Thomas Gleixner , Ingo Molnar , x86@kernel.org, Andy Lutomirski , kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org, dvyukov@google.com, Masami Hiramatsu , "Naveen N. Rao" , Anil S Keshavamurthy , "David S. Miller" , Alexander Viro , linux-fsdevel@vger.kernel.org, Borislav Petkov Subject: Re: [PATCH v3 2/7] x86: inline kprobe_exceptions_notify() into do_general_protection() Message-Id: <20180829090832.337553da18089643a107cf56@kernel.org> In-Reply-To: <20180828201421.157735-3-jannh@google.com> References: <20180828201421.157735-1-jannh@google.com> <20180828201421.157735-3-jannh@google.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 28 Aug 2018 22:14:16 +0200 Jann Horn wrote: > The opaque plumbing of #GP from do_general_protection() through > notify_die() into kprobe_exceptions_notify() makes it hard to understand > what's going on. OK, this seems reasonable optimization, since kprobe_exceptions_notify only handles DIE_GPF now. Acked-by: Masami Hiramatsu Hmm, I think I should introduce ARCH_KPROBE_HANDLE_EXCEPTION and if it is enabled, kernel/kprobes.c stops using exception notifier. It is no more needed on x86. Thank you! > > Suggested-by: Andy Lutomirski > Signed-off-by: Jann Horn > --- > arch/x86/kernel/kprobes/core.c | 31 +------------------------------ > arch/x86/kernel/traps.c | 10 ++++++++++ > 2 files changed, 11 insertions(+), 30 deletions(-) > > diff --git a/arch/x86/kernel/kprobes/core.c b/arch/x86/kernel/kprobes/core.c > index b0d1e81c96bb..467ac22691b0 100644 > --- a/arch/x86/kernel/kprobes/core.c > +++ b/arch/x86/kernel/kprobes/core.c > @@ -1028,42 +1028,13 @@ int kprobe_fault_handler(struct pt_regs *regs, int trapnr) > if (fixup_exception(regs, trapnr)) > return 1; > > - /* > - * fixup routine could not handle it, > - * Let do_page_fault() fix it. > - */ > + /* fixup routine could not handle it. */ > } > > return 0; > } > NOKPROBE_SYMBOL(kprobe_fault_handler); > > -/* > - * Wrapper routine for handling exceptions. > - */ > -int kprobe_exceptions_notify(struct notifier_block *self, unsigned long val, > - void *data) > -{ > - struct die_args *args = data; > - int ret = NOTIFY_DONE; > - > - if (args->regs && user_mode(args->regs)) > - return ret; > - > - if (val == DIE_GPF) { > - /* > - * To be potentially processing a kprobe fault and to > - * trust the result from kprobe_running(), we have > - * be non-preemptible. > - */ > - if (!preemptible() && kprobe_running() && > - kprobe_fault_handler(args->regs, args->trapnr)) > - ret = NOTIFY_STOP; > - } > - return ret; > -} > -NOKPROBE_SYMBOL(kprobe_exceptions_notify); > - > bool arch_within_kprobe_blacklist(unsigned long addr) > { > bool is_in_entry_trampoline_section = false; > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c > index e6db475164ed..bf9ab1aaa175 100644 > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -556,6 +556,16 @@ do_general_protection(struct pt_regs *regs, long error_code) > > tsk->thread.error_code = error_code; > tsk->thread.trap_nr = X86_TRAP_GP; > + > + /* > + * To be potentially processing a kprobe fault and to > + * trust the result from kprobe_running(), we have to > + * be non-preemptible. > + */ > + if (!preemptible() && kprobe_running() && > + kprobe_fault_handler(regs, X86_TRAP_GP)) > + return; > + > if (notify_die(DIE_GPF, "general protection fault", regs, error_code, > X86_TRAP_GP, SIGSEGV) != NOTIFY_STOP) > die("general protection fault", regs, error_code); > -- > 2.19.0.rc0.228.g281dcd1b4d0-goog > -- Masami Hiramatsu