From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 9756 invoked by alias); 20 Nov 2013 18:11:36 -0000 Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org Received: (qmail 9726 invoked by uid 89); 20 Nov 2013 18:11:35 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.4 required=5.0 tests=AWL,BAYES_50,RDNS_NONE,SPF_HELO_PASS,SPF_PASS autolearn=no version=3.3.2 X-HELO: mx1.redhat.com Received: from Unknown (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 20 Nov 2013 18:10:12 +0000 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id rAKI9ovt018380 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Wed, 20 Nov 2013 13:09:50 -0500 Received: from [10.3.113.82] (ovpn-113-82.phx2.redhat.com [10.3.113.82]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id rAKI9nDT011091; Wed, 20 Nov 2013 13:09:49 -0500 Message-ID: <528CFAED.1000703@redhat.com> Date: Wed, 20 Nov 2013 18:11:00 -0000 From: Josh Stone User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.1.0 MIME-Version: 1.0 To: Steven Rostedt , "Frank Ch. Eigler" CC: Ingo Molnar , Masami Hiramatsu , linux-arch@vger.kernel.org, Ananth N Mavinakayanahalli , Sandeepa Prabhu , x86@kernel.org, lkml , virtualization@lists.linux-foundation.org, systemtap@sourceware.org, "David S. Miller" Subject: Re: [PATCH -tip v3 00/23] kprobes: introduce NOKPROBE_SYMBOL() and general cleaning of kprobe blacklist References: <20131120042148.15296.88360.stgit@kbuild-fedora.novalocal> <20131120153801.GA9743@gmail.com> <20131120173600.GK8993@redhat.com> <20131120125649.40ca99c3@gandalf.local.home> In-Reply-To: <20131120125649.40ca99c3@gandalf.local.home> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2013-q4/txt/msg00254.txt.bz2 On 11/20/2013 09:56 AM, Steven Rostedt wrote: > On Wed, 20 Nov 2013 12:36:00 -0500 > "Frank Ch. Eigler" wrote: > >> Hi - >> >>>> Does this new blacklist cover enough that the kernel now survives a >>>> broadly wildcarded perf-probe, e.g. over e.g. all of its kallsyms? >>> >>> That's generally the purpose of the annotations - if it doesn't then >>> that's a bug. >> >> AFAIK, no kernel since kprobes was introduced has ever stood up to >> that test. perf probe lacks the wildcarding powers of systemtap, so >> one needs to resort to something like: >> >> # cat /proc/kallsyms | grep ' [tT] ' | while read addr type symbol; do >> perf probe $symbol >> done > > I'm curious to why one would do that. IIUC, perf now has function > tracing support. Then consider something like probing all inline "call" sites, which will be sprinkled in the middle where ftrace doesn't apply. The point is not whether there's an alternative - kprobes really ought to be wholly safe regardless. Slow, if you did such broad probing, sure, but still safe. And a real use-case probably wouldn't probe *all* functions/inlines, but it illustrates that there are at least a few in the full set that don't behave well.