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=-12.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 84579C4363A for ; Tue, 27 Oct 2020 10:13:53 +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 10E0022263 for ; Tue, 27 Oct 2020 10:13:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="z6dhJyMK"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="iSBk7tVi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10E0022263 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-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:References:In-Reply-To:Message-Id: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=gHgqjRPWBQBQwMHDR/cSCkzGKJ4zlIpznOd0r3o8sxE=; b=z6dhJyMKxAnDybPpm1j23VuGW giQ20s51LVNCreaPkIJxirpL67ahRpOND95e2lMRgb7kXKdXEdTgyN9/x5ce60Fs7ltCbEkf9pLGE LmPo1XYRKv1a7dlkYZwdz9ThVZPcR883UR81YxarWfsRH5txaToTYv8oHiQWYrXlXdQbzqSsGXP7d GnO07jTVAtHdfl63M4Y9eV4m3ktPxmIfPXmQ28I+xEWedKbjgxF2F7GuXwnKn5Kx5BQh/GyVSCI7B zBG4kX2mcia+a1C1K6D7pQuQ5ILvv0ua/HMudbZQWuFI8I2do5cu8+psLN1iALXyEjUgjpF7/qRML 6hBdCUjbw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1kXLyn-0002fN-4q; Tue, 27 Oct 2020 10:13:25 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1kXLyk-0002eY-IK for linux-arm-kernel@lists.infradead.org; Tue, 27 Oct 2020 10:13:23 +0000 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 A2EF122281; Tue, 27 Oct 2020 10:13:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1603793601; bh=3KsZ/CqBr0TPR0nqfqR8AaEtRTYyaLNva2fG8yB+60I=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=iSBk7tViDk2MWqvofKOPk1FWqusW+iGUHyj7ixvhqIzZy06Nm4P0TCXYLnGHV6v/0 FffXWES00Us/FNphXz6vxmr6dpw9dgtjTSxKgioVdrBBmkKCnRagSDQE93R1vDu93r U/poZJpfBwCklboymEZ8McnlFIs32LLrG+mO7UrI= Date: Tue, 27 Oct 2020 19:13:18 +0900 From: Masami Hiramatsu To: Jean-Philippe Brucker Subject: Re: [PATCH] arm64: Fix early single-stepping Message-Id: <20201027191318.aba935f7ccf00af9acd89388@kernel.org> In-Reply-To: <20201026172907.1468294-1-jean-philippe@linaro.org> References: <20201026172907.1468294-1-jean-philippe@linaro.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201027_061322_780825_75DDC4D8 X-CRM114-Status: GOOD ( 24.80 ) 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: catalin.marinas@arm.com, will@kernel.org, dianders@chromium.org, linux-arm-kernel@lists.infradead.org, mhiramat@kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, 26 Oct 2020 18:29:09 +0100 Jean-Philippe Brucker wrote: > To use debug features such as single-step, the OS lock must be unlocked > in the debug registers. Currently this is done in postcore_initcall > which is now too late. > > Commit 36dadef23fcc ("kprobes: Init kprobes in early_initcall") enabled > using kprobes from early_initcall, when OS lock is still locked. So when > kprobe attempts to single-step a patched instruction, instead of > trapping, execution continues until it throws an undef exception: > > [ 0.064233] Kprobe smoke test: started > [ 0.151133] ------------[ cut here ]------------ > [ 0.151458] kernel BUG at arch/arm64/kernel/traps.c:406! > [ 0.151812] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > ... > [ 0.162689] Call trace: > [ 0.163014] do_undefinstr+0x1d4/0x1f4 > [ 0.163336] el1_sync_handler+0xbc/0x140 > [ 0.163839] el1_sync+0x80/0x100 > [ 0.164154] 0xffffffc01001d004 > [ 0.164527] init_kprobes+0x13c/0x154 > [ 0.164968] do_one_initcall+0x54/0x2e0 > [ 0.165322] kernel_init_freeable+0xf4/0x258 > [ 0.165783] kernel_init+0x20/0x12c > [ 0.166117] ret_from_fork+0x10/0x30 > [ 0.166595] Code: 97ffff53 a9425bf5 17ffff9b f9001bf7 (d4210000) > [ 0.167084] ---[ end trace 36778fdf576e9a79 ]--- > > To fix this, unlock the OS lock as early as possible. Do it in > traps_init() for CPU0, since KGDB wants to use single-step from that > point on according to commit b322c65f8ca3 ("arm64: Call > debug_traps_init() from trap_init() to help early kgdb"). > For secondary CPUs, setup the CPU hotplug handler at early_initcall. > > Fixes: 36dadef23fcc ("kprobes: Init kprobes in early_initcall") > Signed-off-by: Jean-Philippe Brucker Hi Jean, How have you confirmed this fixes the issue? On my environment, this doesn't fix the issue. We need to call debug_monitors_init() before calling init_kprobe(). But since both are early_initcall, it doesn't guarantee that the debug_monitors_init() is called before init_kprobes(). I think there are 2 ways to fix this (in addition to this patch), - split kprobe selftest from init_kprobe() and call the selftest in core_initcall() - call clear_os_lock(0) from arch_init_kprobes() Thank you, > --- > arch/arm64/kernel/debug-monitors.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c > index 75a423c3336a..80f082021234 100644 > --- a/arch/arm64/kernel/debug-monitors.c > +++ b/arch/arm64/kernel/debug-monitors.c > @@ -135,7 +135,7 @@ static int __init debug_monitors_init(void) > "arm64/debug_monitors:starting", > clear_os_lock, NULL); > } > -postcore_initcall(debug_monitors_init); > +early_initcall(debug_monitors_init); > > /* > * Single step API and exception handling. > @@ -380,6 +380,7 @@ NOKPROBE_SYMBOL(aarch32_break_handler); > > void __init debug_traps_init(void) > { > + clear_os_lock(0); > hook_debug_fault_code(DBG_ESR_EVT_HWSS, single_step_handler, SIGTRAP, > TRAP_TRACE, "single-step handler"); > hook_debug_fault_code(DBG_ESR_EVT_BRK, brk_handler, SIGTRAP, > -- > 2.29.1 > -- Masami Hiramatsu _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel