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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,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 79E17C04AB5 for ; Mon, 3 Jun 2019 11:49:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4F1DA2816A for ; Mon, 3 Jun 2019 11:49:16 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="WpH/SjXc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726964AbfFCLtP (ORCPT ); Mon, 3 Jun 2019 07:49:15 -0400 Received: from merlin.infradead.org ([205.233.59.134]:51932 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726269AbfFCLtP (ORCPT ); Mon, 3 Jun 2019 07:49:15 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=WiO2mn3woi/r7lP5k1BKjBs2USXIXc3rzXUfTZbHKBE=; b=WpH/SjXc35CVQSZxNCwzfw1j2 usNiiOSoEngwndhXrsRAkow6BZ4Yi11XiGpDWSVeHpLpZs5O/O8G+lSoJfm8y//npuJYLya+8gfaW gkOYRCBe51zwzkPJ+DO7Q+Tg5w1XYZYN9wOauaS4KrE8DbjFQeGTFDuTzvNXXn/7TaB7STTYlvm+y JHFzO26h8k9HDZrTyltLtVBUh0H+MJ9RPN5yoOkVSE9Td67tcKy3KvGSXavjeFKWvLhEBcMxShYoI nJwztkUMqaMybvhDWgzSZ1aN1CQlyjQC4N2M+g93m1b6HIgnZmAPF1edU7sqrFv5M/dwN0bgylBhw siss48hZw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hXlS2-0002aR-Nk; Mon, 03 Jun 2019 11:48:30 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4964A201EB76F; Mon, 3 Jun 2019 13:48:29 +0200 (CEST) Date: Mon, 3 Jun 2019 13:48:29 +0200 From: Peter Zijlstra To: Will Deacon Cc: Ravi Bangoria , Young Xiao <92siuyang@gmail.com>, linux@armlinux.org.uk, mark.rutland@arm.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, x86@kernel.org, kan.liang@linux.intel.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, ravi.bangoria@linux.vnet.ibm.com, mpe@ellerman.id.au, acme@redhat.com, eranian@google.com, fweisbec@gmail.com, jolsa@redhat.com Subject: Re: [PATCH] perf: Fix oops when kthread execs user process Message-ID: <20190603114829.GI3436@hirez.programming.kicks-ass.net> References: <20190528140103.GT2623@hirez.programming.kicks-ass.net> <20190528153224.GE20758@fuggles.cambridge.arm.com> <20190528173228.GW2623@hirez.programming.kicks-ass.net> <20190529091733.GA4485@fuggles.cambridge.arm.com> <20190529101042.GN2623@hirez.programming.kicks-ass.net> <20190529102022.GC4485@fuggles.cambridge.arm.com> <20190529125557.GU2623@hirez.programming.kicks-ass.net> <8b55f79a-c324-0701-e85f-c7797a60a708@linux.ibm.com> <20190531153703.GA21288@fuggles.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190531153703.GA21288@fuggles.cambridge.arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, May 31, 2019 at 04:37:03PM +0100, Will Deacon wrote: > On Thu, May 30, 2019 at 03:57:36PM +0530, Ravi Bangoria wrote: > > On 5/30/19 2:08 PM, Ravi Bangoria wrote: > > >> --- a/kernel/events/core.c > > >> +++ b/kernel/events/core.c > > >> @@ -5923,7 +5923,7 @@ static void perf_sample_regs_user(struct > > >> if (user_mode(regs)) { > > >> regs_user->abi = perf_reg_abi(current); > > >> regs_user->regs = regs; > > >> - } else if (current->mm) { > > >> + } else if (!(current->flags & PF_KTHREAD)) { > > > > With this patch applied and my patch reverted, I still see it crashing > > because current->flags does not have PF_KTHREAD set. Sample trace with > > v5.0 kernel: > > > > > > BUG: Kernel NULL pointer dereference at 0x00000000 > > Faulting instruction address: 0xc0000000000f1a6c > > Oops: Kernel access of bad area, sig: 11 [#1] > > LE SMP NR_CPUS=2048 NUMA pSeries > > CPU: 17 PID: 3241 Comm: systemd-cgroups Kdump: loaded Not tainted 5.0.0+ #7 > > NIP: c0000000000f1a6c LR: c0000000002acc7c CTR: c0000000002a8f90 > > REGS: c0000001e80469a0 TRAP: 0300 Not tainted (5.0.0+) > > MSR: 8000000000001033 CR: 48022448 XER: 20000000 > > CFAR: c00000000000deb4 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 1 > > GPR00: c0000000002acc7c c0000001e8046c30 c000000001607500 0000000000000000 > > GPR04: 0000000000000000 0000000000000000 0000000000000000 c000000000128618 > > GPR08: 000007ffffffffff 0000000000000000 ffffffffffffffff c00000000001cd40 > > GPR12: c000000000446fd8 c00000003ffdf080 00000000ffff0000 0000000000000007 > > GPR16: c0000001edd74988 c0000001edd60400 00007fff89801130 000000000005e1b0 > > GPR20: c0000001edb77a08 c0000001e8047208 c0000001f03d9800 c0000001e8046e00 > > GPR24: 000000000000b1af c000000001126938 c0000001f03d9b28 0000000000010000 > > GPR28: c0000001e8046d30 0000000000000000 0000000000000000 0000000000000000 > > NIP [c0000000000f1a6c] perf_reg_value+0x5c/0xc0 > > LR [c0000000002acc7c] perf_output_sample_regs+0x6c/0xd0 > > Call Trace: > > [c0000001e8046c30] [c0000000002acc7c] perf_output_sample_regs+0x6c/0xd0 (unreliable) > > [c0000001e8046c80] [c0000000002b9cd0] perf_output_sample+0x620/0x8c0 > > [c0000001e8046d10] [c0000000002ba6b4] perf_event_output_forward+0x64/0x90 > > [c0000001e8046d80] [c0000000002b2908] __perf_event_overflow+0x88/0x1e0 > > [c0000001e8046dd0] [c0000000000f3d18] record_and_restart+0x288/0x670 > > [c0000001e8047180] [c0000000000f4c18] perf_event_interrupt+0x2b8/0x4b0 > > [c0000001e8047280] [c00000000002b380] performance_monitor_exception+0x50/0x70 > > [c0000001e80472a0] [c000000000009ca0] performance_monitor_common+0x110/0x120 > > --- interrupt: f01 at slice_scan_available+0x20/0xc0 > > LR = slice_find_area+0x174/0x210 > > [c0000001e8047630] [c000000000083ea0] slice_get_unmapped_area+0x3d0/0x7f0 > > [c0000001e8047ae0] [c00000000032d5b0] get_unmapped_area+0xa0/0x170 > > [c0000001e8047b10] [c00000000001cd40] arch_setup_additional_pages+0xc0/0x1c0 > > [c0000001e8047b60] [c000000000446fd8] load_elf_binary+0xb48/0x1580 > > [c0000001e8047c80] [c0000000003c3938] search_binary_handler+0xe8/0x2a0 > > [c0000001e8047d10] [c0000000003c42f4] __do_execve_file.isra.13+0x694/0x980 > > [c0000001e8047de0] [c000000000128618] call_usermodehelper_exec_async+0x248/0x290 > > [c0000001e8047e20] [c00000000000b65c] ret_from_kernel_thread+0x5c/0x80 > > Instruction dump: > > 7c9e2378 7c7f1b78 f8010010 f821ffd1 419e0044 3d22ff6b 7bc41764 3929ae10 > > 7d29202e 2b890150 419d003c 38210030 <7c7f482a> e8010010 ebc1fff0 ebe1fff8 > > ---[ end trace 54f3492ad1d403d8 ]--- > > Oh, nice! I think this happens because Power doesn't actually initialise > the regs after a kthread execs() until late in start_thread(). But the plot > thickens somewhat, since current_pt_regs() is different to > task_pt_regs(current) on Power (the former cannot return NULL). So one possibility would be to have activate_mm() initialize the user regs set. Doing it there ensure that the moment PF_KTHREAD gets cleared, task_pt_regs() is valid. 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Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hXlS2-0002aR-Nk; Mon, 03 Jun 2019 11:48:30 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 4964A201EB76F; Mon, 3 Jun 2019 13:48:29 +0200 (CEST) Date: Mon, 3 Jun 2019 13:48:29 +0200 From: Peter Zijlstra To: Will Deacon Subject: Re: [PATCH] perf: Fix oops when kthread execs user process Message-ID: <20190603114829.GI3436@hirez.programming.kicks-ass.net> References: <20190528140103.GT2623@hirez.programming.kicks-ass.net> <20190528153224.GE20758@fuggles.cambridge.arm.com> <20190528173228.GW2623@hirez.programming.kicks-ass.net> <20190529091733.GA4485@fuggles.cambridge.arm.com> <20190529101042.GN2623@hirez.programming.kicks-ass.net> <20190529102022.GC4485@fuggles.cambridge.arm.com> <20190529125557.GU2623@hirez.programming.kicks-ass.net> <8b55f79a-c324-0701-e85f-c7797a60a708@linux.ibm.com> <20190531153703.GA21288@fuggles.cambridge.arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190531153703.GA21288@fuggles.cambridge.arm.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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: mark.rutland@arm.com, Ravi Bangoria , Young Xiao <92siuyang@gmail.com>, mpe@ellerman.id.au, jolsa@redhat.com, x86@kernel.org, linux@armlinux.org.uk, eranian@google.com, linux-kernel@vger.kernel.org, acme@redhat.com, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, ravi.bangoria@linux.vnet.ibm.com, fweisbec@gmail.com, linux-arm-kernel@lists.infradead.org, kan.liang@linux.intel.com 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 Fri, May 31, 2019 at 04:37:03PM +0100, Will Deacon wrote: > On Thu, May 30, 2019 at 03:57:36PM +0530, Ravi Bangoria wrote: > > On 5/30/19 2:08 PM, Ravi Bangoria wrote: > > >> --- a/kernel/events/core.c > > >> +++ b/kernel/events/core.c > > >> @@ -5923,7 +5923,7 @@ static void perf_sample_regs_user(struct > > >> if (user_mode(regs)) { > > >> regs_user->abi = perf_reg_abi(current); > > >> regs_user->regs = regs; > > >> - } else if (current->mm) { > > >> + } else if (!(current->flags & PF_KTHREAD)) { > > > > With this patch applied and my patch reverted, I still see it crashing > > because current->flags does not have PF_KTHREAD set. Sample trace with > > v5.0 kernel: > > > > > > BUG: Kernel NULL pointer dereference at 0x00000000 > > Faulting instruction address: 0xc0000000000f1a6c > > Oops: Kernel access of bad area, sig: 11 [#1] > > LE SMP NR_CPUS=2048 NUMA pSeries > > CPU: 17 PID: 3241 Comm: systemd-cgroups Kdump: loaded Not tainted 5.0.0+ #7 > > NIP: c0000000000f1a6c LR: c0000000002acc7c CTR: c0000000002a8f90 > > REGS: c0000001e80469a0 TRAP: 0300 Not tainted (5.0.0+) > > MSR: 8000000000001033 CR: 48022448 XER: 20000000 > > CFAR: c00000000000deb4 DAR: 0000000000000000 DSISR: 40000000 IRQMASK: 1 > > GPR00: c0000000002acc7c c0000001e8046c30 c000000001607500 0000000000000000 > > GPR04: 0000000000000000 0000000000000000 0000000000000000 c000000000128618 > > GPR08: 000007ffffffffff 0000000000000000 ffffffffffffffff c00000000001cd40 > > GPR12: c000000000446fd8 c00000003ffdf080 00000000ffff0000 0000000000000007 > > GPR16: c0000001edd74988 c0000001edd60400 00007fff89801130 000000000005e1b0 > > GPR20: c0000001edb77a08 c0000001e8047208 c0000001f03d9800 c0000001e8046e00 > > GPR24: 000000000000b1af c000000001126938 c0000001f03d9b28 0000000000010000 > > GPR28: c0000001e8046d30 0000000000000000 0000000000000000 0000000000000000 > > NIP [c0000000000f1a6c] perf_reg_value+0x5c/0xc0 > > LR [c0000000002acc7c] perf_output_sample_regs+0x6c/0xd0 > > Call Trace: > > [c0000001e8046c30] [c0000000002acc7c] perf_output_sample_regs+0x6c/0xd0 (unreliable) > > [c0000001e8046c80] [c0000000002b9cd0] perf_output_sample+0x620/0x8c0 > > [c0000001e8046d10] [c0000000002ba6b4] perf_event_output_forward+0x64/0x90 > > [c0000001e8046d80] [c0000000002b2908] __perf_event_overflow+0x88/0x1e0 > > [c0000001e8046dd0] [c0000000000f3d18] record_and_restart+0x288/0x670 > > [c0000001e8047180] [c0000000000f4c18] perf_event_interrupt+0x2b8/0x4b0 > > [c0000001e8047280] [c00000000002b380] performance_monitor_exception+0x50/0x70 > > [c0000001e80472a0] [c000000000009ca0] performance_monitor_common+0x110/0x120 > > --- interrupt: f01 at slice_scan_available+0x20/0xc0 > > LR = slice_find_area+0x174/0x210 > > [c0000001e8047630] [c000000000083ea0] slice_get_unmapped_area+0x3d0/0x7f0 > > [c0000001e8047ae0] [c00000000032d5b0] get_unmapped_area+0xa0/0x170 > > [c0000001e8047b10] [c00000000001cd40] arch_setup_additional_pages+0xc0/0x1c0 > > [c0000001e8047b60] [c000000000446fd8] load_elf_binary+0xb48/0x1580 > > [c0000001e8047c80] [c0000000003c3938] search_binary_handler+0xe8/0x2a0 > > [c0000001e8047d10] [c0000000003c42f4] __do_execve_file.isra.13+0x694/0x980 > > [c0000001e8047de0] [c000000000128618] call_usermodehelper_exec_async+0x248/0x290 > > [c0000001e8047e20] [c00000000000b65c] ret_from_kernel_thread+0x5c/0x80 > > Instruction dump: > > 7c9e2378 7c7f1b78 f8010010 f821ffd1 419e0044 3d22ff6b 7bc41764 3929ae10 > > 7d29202e 2b890150 419d003c 38210030 <7c7f482a> e8010010 ebc1fff0 ebe1fff8 > > ---[ end trace 54f3492ad1d403d8 ]--- > > Oh, nice! I think this happens because Power doesn't actually initialise > the regs after a kthread execs() until late in start_thread(). But the plot > thickens somewhat, since current_pt_regs() is different to > task_pt_regs(current) on Power (the former cannot return NULL). So one possibility would be to have activate_mm() initialize the user regs set. Doing it there ensure that the moment PF_KTHREAD gets cleared, task_pt_regs() is valid. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel