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=-4.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED autolearn=no 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 654D6C432C0 for ; Wed, 27 Nov 2019 06:56:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 37E0C206F0 for ; Wed, 27 Nov 2019 06:56:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574837794; bh=kyXfm7AOEZ8Syg1jiA3cZuR2h8U5E3zuVBPHsT7+B1s=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=sox7Sm3J0BEW/OxtjpctXCgpI8txL9c548b3JVlf/ZcLHm3lJCtJf16w7aIJsEDZJ bHmRiTIgE3kxsM8AZEYuY+2/E30i+PQIfbLslhgupN2XpW6id1i/wUqLR7pTfXZOEK LQtMyW9Snv0KfogK6eGYOeEnx6Xy+AayjQVOb4Ok= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726470AbfK0G4d (ORCPT ); Wed, 27 Nov 2019 01:56:33 -0500 Received: from mail.kernel.org ([198.145.29.99]:47168 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726026AbfK0G4c (ORCPT ); Wed, 27 Nov 2019 01:56:32 -0500 Received: from devnote2 (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 109E120665; Wed, 27 Nov 2019 06:56:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1574837791; bh=kyXfm7AOEZ8Syg1jiA3cZuR2h8U5E3zuVBPHsT7+B1s=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Lfnfzy4NPW0+4d6PcBHZS+myWitxFIrLLcDf67hUfyCKxlOrRdxZR28q2AOk41INa oObBqgvBH4swW6AijumXLgcGMCqdZ6lG1ubPEnglbXMNldJdFpiUjHRqlNKXNDapUe 66V3dPiL6PFbqbeJXOUpQNbAT8gfQp7zVOy6h8+U= Date: Wed, 27 Nov 2019 15:56:26 +0900 From: Masami Hiramatsu To: Alexei Starovoitov Cc: Ingo Molnar , Steven Rostedt , Peter Zijlstra , x86@kernel.org, linux-kernel@vger.kernel.org, bristot@redhat.com, jbaron@akamai.com, torvalds@linux-foundation.org, tglx@linutronix.de, namit@vmware.com, hpa@zytor.com, luto@kernel.org, ard.biesheuvel@linaro.org, jpoimboe@redhat.com, jeyu@kernel.org Subject: Re: [PATCH -tip 2/2] kprobes: Set unoptimized flag after unoptimizing code Message-Id: <20191127155626.5386bc3a25195cfd0fa82a08@kernel.org> In-Reply-To: <20191127061910.nbfmzds4k5wxorwz@ast-mbp.dhcp.thefacebook.com> References: <157483420094.25881.9190014521050510942.stgit@devnote2> <157483422375.25881.13508326028469515760.stgit@devnote2> <20191127061910.nbfmzds4k5wxorwz@ast-mbp.dhcp.thefacebook.com> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-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, 26 Nov 2019 22:19:11 -0800 Alexei Starovoitov wrote: > On Wed, Nov 27, 2019 at 02:57:04PM +0900, Masami Hiramatsu wrote: > > Fix to set unoptimized flag after confirming the code is completely > > unoptimized. Without this fix, when a kprobe hits the intermediate > > modified instruction (the first byte is replaced by int3, but > > latter bytes still be a jump address operand) while unoptimizing, > > it can return to the middle byte of the modified code. And it causes > > an invalid instruction exception in the kernel. > > > > Usually, this is a rare case, but if we put a probe on the function > > called while text patching, it always causes a kernel panic as below. > > (text_poke() is used for patching the code in optprobe) > > > > # echo p text_poke+5 > kprobe_events > > # echo 1 > events/kprobes/enable > > # echo 0 > events/kprobes/enable > > invalid opcode: 0000 [#1] PREEMPT SMP PTI > > CPU: 7 PID: 137 Comm: kworker/7:1 Not tainted 5.4.0-rc8+ #29 > > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 > > Workqueue: events kprobe_optimizer > > RIP: 0010:text_poke+0x9/0x50 > > Code: 01 00 00 5b 5d 41 5c 41 5d c3 89 c0 0f b7 4c 02 fe 66 89 4c 05 fe e9 31 ff ff ff e8 71 ac 03 00 90 55 48 89 f5 53 cc 30 cb fd <1e> ec 08 8b 05 72 98 31 01 85 c0 75 11 48 83 c4 08 48 89 ee 48 89 > > RSP: 0018:ffffc90000343df0 EFLAGS: 00010686 > > RAX: 0000000000000000 RBX: ffffffff81025796 RCX: 0000000000000000 > > RDX: 0000000000000004 RSI: ffff88807c983148 RDI: ffffffff81025796 > > RBP: ffff88807c983148 R08: 0000000000000001 R09: 0000000000000000 > > R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff82284fe0 > > R13: ffff88807c983138 R14: ffffffff82284ff0 R15: 0ffff88807d9eee0 > > FS: 0000000000000000(0000) GS:ffff88807d9c0000(0000) knlGS:0000000000000000 > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > CR2: 000000000058158b CR3: 000000007b372000 CR4: 00000000000006a0 > > Call Trace: > > arch_unoptimize_kprobe+0x22/0x28 > > arch_unoptimize_kprobes+0x39/0x87 > > kprobe_optimizer+0x6e/0x290 > > process_one_work+0x2a0/0x610 > > worker_thread+0x28/0x3d0 > > ? process_one_work+0x610/0x610 > > kthread+0x10d/0x130 > > ? kthread_park+0x80/0x80 > > ret_from_fork+0x3a/0x50 > > Modules linked in: > > ---[ end trace 83b34b22a228711b ]--- > > > > This can happen even if we blacklist text_poke() and other functions, > > because there is a small time window which showing the intermediate > > code to other CPUs. > > > > Fixes: 6274de4984a6 ("kprobes: Support delayed unoptimizing") > > Signed-off-by: Masami Hiramatsu > > Awesome. It fixes the crash for me. > Tested-by: Alexei Starovoitov That's a good news :) Thank you for testing! -- Masami Hiramatsu