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=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_2 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 DE31DC2D0A3 for ; Tue, 3 Nov 2020 16:09:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A586B2236F for ; Tue, 3 Nov 2020 16:09:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727754AbgKCQJc convert rfc822-to-8bit (ORCPT ); Tue, 3 Nov 2020 11:09:32 -0500 Received: from mail.kernel.org ([198.145.29.99]:45522 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727743AbgKCQJc (ORCPT ); Tue, 3 Nov 2020 11:09:32 -0500 Received: from rorschach.local.home (unknown [172.58.235.9]) (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 2B33E22264; Tue, 3 Nov 2020 16:09:26 +0000 (UTC) Date: Tue, 3 Nov 2020 11:09:13 -0500 From: Steven Rostedt To: Masami Hiramatsu Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Peter Zijlstra , Eddy_Wu@trendmicro.com, x86@kernel.org, davem@davemloft.net, naveen.n.rao@linux.ibm.com, anil.s.keshavamurthy@intel.com, linux-arch@vger.kernel.org, cameron@moodycamel.com, oleg@redhat.com, will@kernel.org, paulmck@kernel.org Subject: Re: [PATCH v5 14/21] kprobes: Remove NMI context check Message-ID: <20201103110913.2d7b4cea@rorschach.local.home> In-Reply-To: <20201103143938.704c7974e93c854511580c38@kernel.org> References: <159870598914.1229682.15230803449082078353.stgit@devnote2> <159870615628.1229682.6087311596892125907.stgit@devnote2> <20201030213831.04e81962@oasis.local.home> <20201102141138.1fa825113742f3bea23bc383@kernel.org> <20201102145334.23d4ba691c13e0b6ca87f36d@kernel.org> <20201102160234.fa0ae70915ad9e2b21c08b85@kernel.org> <20201102092726.57cb643f@gandalf.local.home> <20201103143938.704c7974e93c854511580c38@kernel.org> X-Mailer: Claws Mail 3.17.4git76 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Tue, 3 Nov 2020 14:39:38 +0900 Masami Hiramatsu wrote: > Ah, OK. This looks good to me. > > BTW, in_nmi() in pre_handler_kretprobe() always be true because > now int3 is treated as an NMI. So you can always pass 1 there. What about the below patch then? > > Acked-by: Masami Hiramatsu Thanks! >From 29ac1a5c9068df06f3196173d4325c8076759551 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Mon, 2 Nov 2020 09:17:49 -0500 Subject: [PATCH] kprobes: Tell lockdep about kprobe nesting Since the kprobe handlers have protection that prohibits other handlers from executing in other contexts (like if an NMI comes in while processing a kprobe, and executes the same kprobe, it will get fail with a "busy" return). Lockdep is unaware of this protection. Use lockdep's nesting api to differentiate between locks taken in INT3 context and other context to suppress the false warnings. Link: https://lore.kernel.org/r/20201102160234.fa0ae70915ad9e2b21c08b85@kernel.org Cc: Peter Zijlstra Signed-off-by: Steven Rostedt (VMware) --- kernel/kprobes.c | 23 +++++++++++++++++++---- 1 file changed, 19 insertions(+), 4 deletions(-) diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 8a12a25fa40d..30889ea5514f 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1249,7 +1249,12 @@ __acquires(hlist_lock) *head = &kretprobe_inst_table[hash]; hlist_lock = kretprobe_table_lock_ptr(hash); - raw_spin_lock_irqsave(hlist_lock, *flags); + /* + * Nested is a workaround that will soon not be needed. + * There's other protections that make sure the same lock + * is not taken on the same CPU that lockdep is unaware of. + */ + raw_spin_lock_irqsave_nested(hlist_lock, *flags, 1); } NOKPROBE_SYMBOL(kretprobe_hash_lock); @@ -1258,7 +1263,12 @@ static void kretprobe_table_lock(unsigned long hash, __acquires(hlist_lock) { raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash); - raw_spin_lock_irqsave(hlist_lock, *flags); + /* + * Nested is a workaround that will soon not be needed. + * There's other protections that make sure the same lock + * is not taken on the same CPU that lockdep is unaware of. + */ + raw_spin_lock_irqsave_nested(hlist_lock, *flags, 1); } NOKPROBE_SYMBOL(kretprobe_table_lock); @@ -2028,7 +2038,12 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) /* TODO: consider to only swap the RA after the last pre_handler fired */ hash = hash_ptr(current, KPROBE_HASH_BITS); - raw_spin_lock_irqsave(&rp->lock, flags); + /* + * Nested is a workaround that will soon not be needed. + * There's other protections that make sure the same lock + * is not taken on the same CPU that lockdep is unaware of. + */ + raw_spin_lock_irqsave_nested(&rp->lock, flags, 1); if (!hlist_empty(&rp->free_instances)) { ri = hlist_entry(rp->free_instances.first, struct kretprobe_instance, hlist); @@ -2039,7 +2054,7 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) ri->task = current; if (rp->entry_handler && rp->entry_handler(ri, regs)) { - raw_spin_lock_irqsave(&rp->lock, flags); + raw_spin_lock_irqsave_nested(&rp->lock, flags, 1); hlist_add_head(&ri->hlist, &rp->free_instances); raw_spin_unlock_irqrestore(&rp->lock, flags); return 0; -- 2.25.4