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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9A2C3C4332F for ; Sun, 11 Dec 2022 03:29:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229821AbiLKD1o (ORCPT ); Sat, 10 Dec 2022 22:27:44 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51830 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229538AbiLKD1k (ORCPT ); Sat, 10 Dec 2022 22:27:40 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3237CC3 for ; Sat, 10 Dec 2022 19:27:36 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id BE53260D27 for ; Sun, 11 Dec 2022 03:27:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86343C433EF; Sun, 11 Dec 2022 03:27:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1670729255; bh=SLRW9XaslzwlpQy6leJBYpMTuYIaNwDRf33UV6+Ao14=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=idDjc3uCqWJjnZF16XCZDJO66hS7lkkDiIcGq6/UKMwWocZcnfuiSaKLZkDMKJYlI 4g/U0GeRdgDdQ32dXwkTOZ1ZC34UeGWlAQGu9maCWgA9eK/nzySbCVrLWM8a76pWVf wyrfKKFWmgDC2mvbP0rAylq8FsZGYZGXShJN9ljuP7e7tFoFSaWaFm/GGN1KDpl9OW C2IcsmI2F+8zk7v8v3KQPtp4rgAIREN3H64ano+Fep86knUPDQipY5X9iJrUpTrwbX fRFKDdOQUGPnCMq7CyN3rgsTHbaVS5xmnKOtKr492jtj2j0sMVbnITkTfKFJrd5euu 0FF+YLliePkhA== Date: Sun, 11 Dec 2022 12:27:31 +0900 From: Masami Hiramatsu (Google) To: Ard Biesheuvel Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com, will@kernel.org, rostedt@goodmis.org, samitolvanen@google.com, keescook@chromium.org, mhiramat@kernel.org Subject: Re: [PATCH] ftrace: Allow WITH_ARGS flavour of graph tracer with shadow call stack Message-Id: <20221211122731.f909ac15e227675229f03ecf@kernel.org> In-Reply-To: <20221209143402.3332369-1-ardb@kernel.org> References: <20221209143402.3332369-1-ardb@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 9 Dec 2022 15:34:02 +0100 Ard Biesheuvel wrote: > The recent switch on arm64 from DYNAMIC_FTRACE_WITH_REGS to > DYNAMIC_FTRACE_WITH_ARGS failed to take into account that we currently > require the former in order to allow the function graph tracer to be > enabled in combination with shadow call stacks. This means that this is > no longer permitted at all, in spite of the fact that either flavour of > ftrace works perfectly fine in this combination. > > Given that arm64 is the only arch that implements shadow call stacks in > the first place, let's update the condition to just reflect the arm64 > change. When other architectures adopt shadow call stack support, this > can be revisited if needed. This brings a question. Is the SCS safe if kretprobe(rethook) is enabled? it also changes the stack entry after a calling function. Thank you, > > Signed-off-by: Ard Biesheuvel > --- > arch/Kconfig | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/Kconfig b/arch/Kconfig > index 072a1b39e3afd0d1..683f365b5e31c856 100644 > --- a/arch/Kconfig > +++ b/arch/Kconfig > @@ -635,7 +635,7 @@ config ARCH_SUPPORTS_SHADOW_CALL_STACK > config SHADOW_CALL_STACK > bool "Shadow Call Stack" > depends on ARCH_SUPPORTS_SHADOW_CALL_STACK > - depends on DYNAMIC_FTRACE_WITH_REGS || !FUNCTION_GRAPH_TRACER > + depends on DYNAMIC_FTRACE_WITH_ARGS || !FUNCTION_GRAPH_TRACER > help > This option enables the compiler's Shadow Call Stack, which > uses a shadow stack to protect function return addresses from > -- > 2.35.1 > -- Masami Hiramatsu (Google)