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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, 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 E57FEC433DF for ; Mon, 15 Jun 2020 20:22:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C27F4207D3 for ; Mon, 15 Jun 2020 20:22:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731507AbgFOUWs (ORCPT ); Mon, 15 Jun 2020 16:22:48 -0400 Received: from mail.kernel.org ([198.145.29.99]:59750 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731172AbgFOUWs (ORCPT ); Mon, 15 Jun 2020 16:22:48 -0400 Received: from oasis.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (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 6E22A2074D; Mon, 15 Jun 2020 20:22:47 +0000 (UTC) Date: Mon, 15 Jun 2020 16:22:45 -0400 From: Steven Rostedt To: Oscar Carter Cc: Kees Cook , Ingo Molnar , kernel-hardening@lists.openwall.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH] kernel/trace: Remove function callback casts Message-ID: <20200615162245.13d3feff@oasis.local.home> In-Reply-To: <20200615161738.18d07ce6@oasis.local.home> References: <20200614070154.6039-1-oscar.carter@gmx.com> <20200615161738.18d07ce6@oasis.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 15 Jun 2020 16:17:38 -0400 Steven Rostedt wrote: > On Sun, 14 Jun 2020 09:01:54 +0200 > Oscar Carter wrote: > > > In an effort to enable -Wcast-function-type in the top-level Makefile to > > support Control Flow Integrity builds, remove all the function callback > > casts. > > > > To do this, use the ftrace_ops_list_func function as a wrapper when the > > arch not supports ftrace ops instead of the use of a function cast. > > > > We need more tricker than this. > > > Signed-off-by: Oscar Carter > > --- > > kernel/trace/ftrace.c | 11 ++++++++--- > > 1 file changed, 8 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > > index c163c3531faf..ed1efc0e3a25 100644 > > --- a/kernel/trace/ftrace.c > > +++ b/kernel/trace/ftrace.c > > @@ -119,13 +119,12 @@ struct ftrace_ops __rcu *ftrace_ops_list __read_mostly = &ftrace_list_end; > > ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub; > > struct ftrace_ops global_ops; > > > > -#if ARCH_SUPPORTS_FTRACE_OPS > > static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, > > struct ftrace_ops *op, struct pt_regs *regs); > > -#else > > + > > +#if !ARCH_SUPPORTS_FTRACE_OPS > > /* See comment below, where ftrace_ops_list_func is defined */ > > static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip); > > -#define ftrace_ops_list_func ((ftrace_func_t)ftrace_ops_no_ops) > > The reason for the typecast is because this gets called from asm with only two parameters. [ Some how hit a short cut key that sent this before I was finished! :-p ] As I was saying. This typecast is being paranoid, as archs will call the ftrace_ops_list_func directly, and only pass in two parameters. Now one way around this is to instead of having the typecast, I could use linker magic to create another function that I can define without the typecast to get the same effect. Similar to what I did in commit: 46f9469247c6f ("ftrace: Rename ftrace_graph_stub to ftrace_stub_graph") -- Steve > > > #endif > > > > static inline void ftrace_ops_init(struct ftrace_ops *ops) > > @@ -6860,6 +6859,12 @@ static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, > > } > > NOKPROBE_SYMBOL(ftrace_ops_list_func); > > #else > > +static void ftrace_ops_list_func(unsigned long ip, unsigned long parent_ip, > > + struct ftrace_ops *op, struct pt_regs *regs) > > +{ > > + ftrace_ops_no_ops(ip, parent_ip); > > +} > > + > > static void ftrace_ops_no_ops(unsigned long ip, unsigned long parent_ip) > > { > > __ftrace_ops_list_func(ip, parent_ip, NULL, NULL); > > -- > > 2.20.1 >