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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 71B41C388F7 for ; Thu, 29 Oct 2020 00:57:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2626220724 for ; Thu, 29 Oct 2020 00:57:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403803AbgJ2A5X (ORCPT ); Wed, 28 Oct 2020 20:57:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:60546 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731610AbgJ1WRf (ORCPT ); Wed, 28 Oct 2020 18:17:35 -0400 Received: from gandalf.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 7060224742; Wed, 28 Oct 2020 13:19:11 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94) (envelope-from ) id 1kXlM5-005a6P-Mv; Wed, 28 Oct 2020 09:19:09 -0400 Message-ID: <20201028131542.963014814@goodmis.org> User-Agent: quilt/0.66 Date: Wed, 28 Oct 2020 09:15:42 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Andrew Morton , Jiri Olsa , Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Alexei Starovoitov Subject: [RFC][PATCH 0/2] ftrace: Add access to function arguments for all callbacks Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is something I wanted to implement a long time ago, but held off until there was a good reason to do so. Now it appears that having access to the arguments of the function by default is very useful. As a bonus, because arguments must be saved regardless before calling a callback, because they need to be restored before returning back to the start of the traced function, there's not much work to do to have them always be there for normal function callbacks. The basic idea is that if CONFIG_HAVE_DYNAMIC_FTRACE_WITH_ARGS is set, then all callbacks registered to ftrace can use the regs parameter for the stack and arguments (kernel_stack_pointer(regs), regs_get_kernel_argument(regs, n)), without the need to set REGS that causes overhead by saving all registers as REGS simulates a breakpoint. Only the first patch is to be applied. The second patch is just to show how this could work. Steven Rostedt (VMware) (2): ftrace/x86: Allow for arguments to be passed in to REGS by default ftrace: Test arguments by adding trace_printk in function tracer ---- arch/x86/Kconfig | 1 + arch/x86/kernel/ftrace_64.S | 12 +++++++----- kernel/trace/Kconfig | 9 +++++++++ kernel/trace/trace_functions.c | 13 ++++++++++++- 4 files changed, 29 insertions(+), 6 deletions(-)