Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753461AbaGKNYd (ORCPT ); Fri, 11 Jul 2014 09:24:33 -0400 Received: from cantor2.suse.de ([195.135.220.15]:55493 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751695AbaGKNYc (ORCPT ); Fri, 11 Jul 2014 09:24:32 -0400 Date: Fri, 11 Jul 2014 15:24:28 +0200 (CEST) From: Jiri Kosina To: Masami Hiramatsu cc: Josh Poimboeuf , Steven Rostedt , linux-kernel@vger.kernel.org, Ingo Molnar , Andrew Morton , Thomas Gleixner , "Paul E. McKenney" , Namhyung Kim , "H. Peter Anvin" , Oleg Nesterov , Seth Jennings , Jiri Slaby Subject: Re: [RFC][PATCH 0/3] ftrace: Add dynamically allocated trampolines In-Reply-To: <53BF4B5A.3000302@hitachi.com> Message-ID: References: <20140703200750.648550267@goodmis.org> <20140710213620.GA19858@treble.redhat.com> <53BF4B5A.3000302@hitachi.com> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 11 Jul 2014, Masami Hiramatsu wrote: > >> I did some testing with kpatch and I found one minor issue. The dynamically > >> allocated trampoline seems to confuse dump_stack() somewhat. > >> > >> I added a dump_stack() call in my ftrace_ops callback function > >> (kpatch_ftrace_handler) which had a filter on meminfo_proc_show(). > > > > Interesting. Are you using dwarf2 unwinder for stack dumping by any > > chance? It seems to get things right here. Will look into it more > > tomorrow. > > Hmm, can dwarf2 unwinder work on the trampoline method? Since the > trampoline just a copy of instructions which will not have CFI(which is > stored in dwarf section), I guess it may not work... Frame pointer (push > bp and save sp to bp on the entry) can work anyway. That was exactly my idea and that's why I asked, thanks for confirming. I am afraid we'll have to declare dynamic trampolines incompatible with drawf2 stack dumping. -- Jiri Kosina SUSE Labs -- 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/