From patchwork Fri Jan 22 11:09:09 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Qais Yousef X-Patchwork-Id: 12039001 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=-16.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT 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 275C2C433DB for ; Fri, 22 Jan 2021 11:11:24 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (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 C996A235DD for ; Fri, 22 Jan 2021 11:11:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C996A235DD Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:Message-Id:Date:Subject:To:From: Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender :Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=pNb6NAoUg+/Z7ZEaN8AQh3fFQjLJaRqoizQAbAH11aI=; b=HT6L9NnXRctc09xZAB25gpv94K +FKGVwU3HpHh1PJ4b5BwCqUD7gFjI8fotUHnQfaMShQ8/9qeQO/frS9D3bZcJbDS4Q54r58qtvonM QDvAYxueSuYQzvqFkU60g7ADNa1ZNYsBDBRlrjYN/pgFD+o4DNR4I1MsH1GhjRTaeWdAbVAriP8FS EfDFGPM0Oi1mKr8+/kweJsMsu0SZzOcGuWgGK4WTIno+4sV2mpQ9OcjGDGEFl/m1KLt3iB7ZMI1c1 WV8R3ubATW8J4zH7ihMFa2f0lw6iYLWmAlJsOq/v7GxjeZaEXxmrwzlPtTZI+QtvVa68yhTMj3rYY LpRH+9Hg==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2uKB-00046E-3r; Fri, 22 Jan 2021 11:09:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l2uK9-00045W-1G for linux-arm-kernel@lists.infradead.org; Fri, 22 Jan 2021 11:09:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 8853A11D4; Fri, 22 Jan 2021 03:09:50 -0800 (PST) Received: from e107158-lin.cambridge.arm.com (e107158-lin.cambridge.arm.com [10.1.194.78]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 87E733F719; Fri, 22 Jan 2021 03:09:49 -0800 (PST) From: Qais Yousef To: Catalin Marinas , Will Deacon Subject: [PATCH] arm64: kprobes: Fix Uexpected kernel BRK exception at EL1 Date: Fri, 22 Jan 2021 11:09:09 +0000 Message-Id: <20210122110909.3324607-1-qais.yousef@arm.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210122_060953_201260_1D4FE0F9 X-CRM114-Status: GOOD ( 16.72 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jean-Philippe Brucker , Qais Yousef , Masami Hiramatsu , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org I was hitting the below panic continuously when attaching kprobes to scheduler functions [ 159.045212] Unexpected kernel BRK exception at EL1 [ 159.053753] Internal error: BRK handler: f2000006 [#1] PREEMPT SMP [ 159.059954] Modules linked in: [ 159.063025] CPU: 2 PID: 0 Comm: swapper/2 Not tainted 5.11.0-rc4-00008-g1e2a199f6ccd #56 [rt-app] [1] Exiting.[ 159.071166] Hardware name: ARM Juno development board (r2) (DT) [ 159.079689] pstate: 600003c5 (nZCv DAIF -PAN -UAO -TCO BTYPE=--) [ 159.085723] pc : 0xffff80001624501c [ 159.089377] lr : attach_entity_load_avg+0x2ac/0x350 [ 159.094271] sp : ffff80001622b640 [rt-app] [0] Exiting.[ 159.097591] x29: ffff80001622b640 x28: 0000000000000001 [ 159.105515] x27: 0000000000000049 x26: ffff000800b79980 [ 159.110847] x25: ffff00097ef37840 x24: 0000000000000000 [ 159.116331] x23: 00000024eacec1ec x22: ffff00097ef12b90 [ 159.121663] x21: ffff00097ef37700 x20: ffff800010119170 [rt-app] [11] Exiting.[ 159.126995] x19: ffff00097ef37840 x18: 000000000000000e [ 159.135003] x17: 0000000000000001 x16: 0000000000000019 [ 159.140335] x15: 0000000000000000 x14: 0000000000000000 [ 159.145666] x13: 0000000000000002 x12: 0000000000000002 [ 159.150996] x11: ffff80001592f9f0 x10: 0000000000000060 [ 159.156327] x9 : ffff8000100f6f9c x8 : be618290de0999a1 [ 159.161659] x7 : ffff80096a4b1000 x6 : 0000000000000000 [ 159.166990] x5 : ffff00097ef37840 x4 : 0000000000000000 [ 159.172321] x3 : ffff000800328948 x2 : 0000000000000000 [ 159.177652] x1 : 0000002507d52fec x0 : ffff00097ef12b90 [ 159.182983] Call trace: [ 159.185433] 0xffff80001624501c [ 159.188581] update_load_avg+0x2d0/0x778 [ 159.192516] enqueue_task_fair+0x134/0xe20 [ 159.196625] enqueue_task+0x4c/0x2c8 [ 159.200211] ttwu_do_activate+0x70/0x138 [ 159.204147] sched_ttwu_pending+0xbc/0x160 [ 159.208253] flush_smp_call_function_queue+0x16c/0x320 [ 159.213408] generic_smp_call_function_single_interrupt+0x1c/0x28 [ 159.219521] ipi_handler+0x1e8/0x3c8 [ 159.223106] handle_percpu_devid_irq+0xd8/0x460 [ 159.227650] generic_handle_irq+0x38/0x50 [ 159.231672] __handle_domain_irq+0x6c/0xc8 [ 159.235781] gic_handle_irq+0xcc/0xf0 [ 159.239452] el1_irq+0xb4/0x180 [ 159.242600] rcu_is_watching+0x28/0x70 [ 159.246359] rcu_read_lock_held_common+0x44/0x88 [ 159.250991] rcu_read_lock_any_held+0x30/0xc0 [ 159.255360] kretprobe_dispatcher+0xc4/0xf0 [ 159.259555] __kretprobe_trampoline_handler+0xc0/0x150 [ 159.264710] trampoline_probe_handler+0x38/0x58 [ 159.269255] kretprobe_trampoline+0x70/0xc4 [ 159.273450] run_rebalance_domains+0x54/0x80 [ 159.277734] __do_softirq+0x164/0x684 [ 159.281406] irq_exit+0x198/0x1b8 [ 159.284731] __handle_domain_irq+0x70/0xc8 [ 159.288840] gic_handle_irq+0xb0/0xf0 [ 159.292510] el1_irq+0xb4/0x180 [ 159.295658] arch_cpu_idle+0x18/0x28 [ 159.299245] default_idle_call+0x9c/0x3e8 [ 159.303265] do_idle+0x25c/0x2a8 [ 159.306502] cpu_startup_entry+0x2c/0x78 [ 159.310436] secondary_start_kernel+0x160/0x198 [ 159.314984] Code: d42000c0 aa1e03e9 d42000c0 aa1e03e9 (d42000c0) After a bit of head scratching and debugging it turned out that it is due to kprobe handler being interrupted by a tick that causes us to go into (I think another) kprobe handler. The culprit was kprobe_breakpoint_ss_handler() returning DBG_HOOK_ERROR which leads to the Unexpected kernel BRK exception. Reverting commit ba090f9cafd5 ("arm64: kprobes: Remove redundant kprobe_step_ctx") seemed to fix the problem for me. Further analysis showed that kcb->kprobe_status is set to KPROBE_REENTER when the error occurs. By teaching kprobe_breakpoint_ss_handler() to handle this status I can no longer reproduce the problem. Fixes: ba090f9cafd5 ("arm64: kprobes: Remove redundant kprobe_step_ctx") Signed-off-by: Qais Yousef Acked-by: Masami Hiramatsu Acked-by: Will Deacon --- Another change in behavior I noticed is that before ba090f9cafd5 ("arm64: kprobes: Remove redundant kprobe_step_ctx") if 'cur' was NULL we wouldn't return DBG_HOOK_ERROR, but after the change we do. I didn't hit a problem because of that it's just something I noticed when I realized that this commit was causing my problem. arch/arm64/kernel/probes/kprobes.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm64/kernel/probes/kprobes.c b/arch/arm64/kernel/probes/kprobes.c index 89c64ada8732..66aac2881ba8 100644 --- a/arch/arm64/kernel/probes/kprobes.c +++ b/arch/arm64/kernel/probes/kprobes.c @@ -352,8 +352,8 @@ kprobe_breakpoint_ss_handler(struct pt_regs *regs, unsigned int esr) unsigned long addr = instruction_pointer(regs); struct kprobe *cur = kprobe_running(); - if (cur && (kcb->kprobe_status == KPROBE_HIT_SS) - && ((unsigned long)&cur->ainsn.api.insn[1] == addr)) { + if (cur && (kcb->kprobe_status & (KPROBE_HIT_SS | KPROBE_REENTER)) && + ((unsigned long)&cur->ainsn.api.insn[1] == addr)) { kprobes_restore_local_irqflag(kcb, regs); post_kprobe_handler(cur, kcb, regs);