Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758825Ab1ELV4k (ORCPT ); Thu, 12 May 2011 17:56:40 -0400 Received: from smtp-out.google.com ([216.239.44.51]:6843 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758797Ab1ELV4i (ORCPT ); Thu, 12 May 2011 17:56:38 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; b=kw0tUWTaW1jSi+aQmAZAXq2CrAzFOGtcIxjbE5ZP57xhy8Vwc9Twavlk5Z4L76XnAN 0OPmZVk5H98oSWgddHyg== MIME-Version: 1.0 In-Reply-To: <20110512215023.GA20939@elte.hu> References: <20110512213542.GB17596@elte.hu> <20110512215023.GA20939@elte.hu> Date: Thu, 12 May 2011 23:56:35 +0200 Message-ID: Subject: Re: [BUG] perf: bogus correlation of kernel symbols From: Stephane Eranian To: Ingo Molnar Cc: Linus Torvalds , Arnaldo Carvalho de Melo , LKML Content-Type: text/plain; charset=UTF-8 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1619 Lines: 37 On Thu, May 12, 2011 at 11:50 PM, Ingo Molnar wrote: > > * Stephane Eranian wrote: > >> On Thu, May 12, 2011 at 11:35 PM, Ingo Molnar wrote: >> > >> > * Stephane Eranian wrote: >> > >> >> The other contradiction, I see, is that you have perf_event paranoia level >> >> and this new kptr masquerading feature which conflict with each >> >> other. >> >> >> >> You can be allowed to monitor at the kernel level (paranoid=1, default) >> >> but you cannot correlate symbols: >> >> >> >> $ perf record -e cycles:k foo >> >> >> >> I suspect if you have this kptr thing turned on, then you need to disallow >> >> monitoring at the kernel level too. >> > >> > The better (and consistent) solution would be to turn the kptr_restrict thing >> > off - see the patch i sent. >> >> I saw that. But I think that when someone turns it back on, then you need to >> increase the perf_events paranoia level to disallow kernel monitoring to >> regular users such that you maintain consistency across the board. > > Dunno, i would not couple them necessarily - certain users might still have > access to kernel symbols via some other channel - for example the System.map. > Ok, that's true, but then you'd need to have perf print a message or refuse to use /proc/kallsyms and suggest that the user provides a System.map. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/