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=-6.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 CBE5DC433E7 for ; Wed, 2 Sep 2020 09:36:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9EA1E206F0 for ; Wed, 2 Sep 2020 09:36:48 +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="m5yZH7JL" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726167AbgIBJgs (ORCPT ); Wed, 2 Sep 2020 05:36:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52106 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726124AbgIBJgr (ORCPT ); Wed, 2 Sep 2020 05:36:47 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C7FFC061244; Wed, 2 Sep 2020 02:36:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=CVKEqJ8VyRUxV18RMo+VlglQJ7cxy86dcBr7cGPxf7Y=; b=m5yZH7JL8dt+/qaFKkqSkHCry4 pWPuDkOH4lEEQIGy6PkdEl2zH4iSODB+w69Ktxi/JQdBqbiMOeY97fRfrKqosnwimzLCIQh4e8GkZ luum03hjmwT1uYHLsKB7T4qrNMsbSY3EvnStY4kIvdIwYOv4nOtIBCfNEZyhxwM9mpSsA+d+nIFlY jRHyOq0uUHQX4ZShGk2QAUUAh93kD7zrxmWd8ISYKR0oocjVwR9uJ9UycvNJEha9ODECfEQf9pxVV ChN36dgeYob5bsQ6gZDdVr1VYD06wr917Xro7usDZTiEwSuPd91dz0+Wvjkl8kS/9i0QhOomRDk3g VJZ6bMxw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1kDPBf-0006nb-Nh; Wed, 02 Sep 2020 09:36:15 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id B06F63003E5; Wed, 2 Sep 2020 11:36:13 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 66A1323D3D729; Wed, 2 Sep 2020 11:36:13 +0200 (CEST) Date: Wed, 2 Sep 2020 11:36:13 +0200 From: peterz@infradead.org To: Masami Hiramatsu Cc: Ingo Molnar , linux-kernel@vger.kernel.org, Eddy_Wu@trendmicro.com, x86@kernel.org, davem@davemloft.net, rostedt@goodmis.org, 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 00/21] kprobes: Unify kretprobe trampoline handlers and make kretprobe lockless Message-ID: <20200902093613.GY1362448@hirez.programming.kicks-ass.net> References: <159870598914.1229682.15230803449082078353.stgit@devnote2> <20200901190808.GK29142@worktop.programming.kicks-ass.net> <20200902093739.8bd13603380951eaddbcd8a5@kernel.org> <20200902070226.GG2674@hirez.programming.kicks-ass.net> <20200902171755.b126672093a3c5d1b3a62a4f@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200902171755.b126672093a3c5d1b3a62a4f@kernel.org> Sender: linux-arch-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org On Wed, Sep 02, 2020 at 05:17:55PM +0900, Masami Hiramatsu wrote: > > Ok, but then lockdep will yell at you if you have that enabled and run > > the unoptimized things. > > Oh, does it warn for all spinlock things in kprobes if it is unoptimized? > Hmm, it has to be noted in the documentation. Lockdep will warn about spinlocks used in NMI context that are also used outside NMI context. Now, for the kretprobe that kprobe_busy flag prevents the actual recursion self-deadlock, but lockdep isn't smart enough to see that. One way around this might be to use SINGLE_DEPTH_NESTING for locks when we use them from INT3 context. That way they'll have a different class and lockdep will not see the recursion. pre_handler_kretprobe() is always called from INT3, right? Something like the below might then work... --- diff --git a/kernel/kprobes.c b/kernel/kprobes.c index 287b263c9cb9..b78f4fe08e86 100644 --- a/kernel/kprobes.c +++ b/kernel/kprobes.c @@ -1255,11 +1255,11 @@ __acquires(hlist_lock) NOKPROBE_SYMBOL(kretprobe_hash_lock); static void kretprobe_table_lock(unsigned long hash, - unsigned long *flags) + unsigned long *flags, int nesting) __acquires(hlist_lock) { raw_spinlock_t *hlist_lock = kretprobe_table_lock_ptr(hash); - raw_spin_lock_irqsave(hlist_lock, *flags); + raw_spin_lock_irqsave_nested(hlist_lock, *flags, nesting); } NOKPROBE_SYMBOL(kretprobe_table_lock); @@ -1326,7 +1326,7 @@ void kprobe_flush_task(struct task_struct *tk) INIT_HLIST_HEAD(&empty_rp); hash = hash_ptr(tk, KPROBE_HASH_BITS); head = &kretprobe_inst_table[hash]; - kretprobe_table_lock(hash, &flags); + kretprobe_table_lock(hash, &flags, 0); hlist_for_each_entry_safe(ri, tmp, head, hlist) { if (ri->task == tk) recycle_rp_inst(ri, &empty_rp); @@ -1361,7 +1361,7 @@ static void cleanup_rp_inst(struct kretprobe *rp) /* No race here */ for (hash = 0; hash < KPROBE_TABLE_SIZE; hash++) { - kretprobe_table_lock(hash, &flags); + kretprobe_table_lock(hash, &flags, 0); head = &kretprobe_inst_table[hash]; hlist_for_each_entry_safe(ri, next, head, hlist) { if (ri->rp == rp) @@ -1950,7 +1950,7 @@ 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); + raw_spin_lock_irqsave_nested(&rp->lock, flags, SINGLE_DEPTH_NESTING); if (!hlist_empty(&rp->free_instances)) { ri = hlist_entry(rp->free_instances.first, struct kretprobe_instance, hlist); @@ -1961,7 +1961,7 @@ 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, SINGLE_DEPTH_NESTING); hlist_add_head(&ri->hlist, &rp->free_instances); raw_spin_unlock_irqrestore(&rp->lock, flags); return 0; @@ -1971,7 +1971,7 @@ static int pre_handler_kretprobe(struct kprobe *p, struct pt_regs *regs) /* XXX(hch): why is there no hlist_move_head? */ INIT_HLIST_NODE(&ri->hlist); - kretprobe_table_lock(hash, &flags); + kretprobe_table_lock(hash, &flags, SINGLE_DEPTH_NESTING); hlist_add_head(&ri->hlist, &kretprobe_inst_table[hash]); kretprobe_table_unlock(hash, &flags); } else {