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=-3.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 87A7DC4363A for ; Thu, 29 Oct 2020 00:23:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3F356207DE for ; Thu, 29 Oct 2020 00:23:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388710AbgJ2AWz (ORCPT ); Wed, 28 Oct 2020 20:22:55 -0400 Received: from mail.kernel.org ([198.145.29.99]:48322 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727567AbgJ2AWz (ORCPT ); Wed, 28 Oct 2020 20:22:55 -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 635E62054F; Thu, 29 Oct 2020 00:22:54 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94) (envelope-from ) id 1kXviO-005fg9-PQ; Wed, 28 Oct 2020 20:22:52 -0400 Message-ID: <20201029000816.272878754@goodmis.org> User-Agent: quilt/0.66 Date: Wed, 28 Oct 2020 20:08:16 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Masami Hiramatsu , Andrew Morton , Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Alexei Starovoitov , Jiri Olsa , Josh Poimboeuf , Jiri Kosina Subject: [RFC][PATCH 0/3 v3] 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. This could be extended to move the REGS portion to kprobes itself, and remove the SAVE_REGS flag completely, but for now, kprobes still uses the full SAVE_REGS support. The last patch extends the WITH_ARGS to allow default function tracing to modify the instruction pointer, where livepatching for x86 no longer needs to save all registers. The idea of this approach is to give enough information to a callback that it could retrieve all arguments, which includes the stack pointer and instruction pointer. This can also be extended to modify the function graph tracer to use the function tracer instead of having a separate trampoline. Changes since v2: - Change all callback args to use struct ftrace_regs, and if something requires the full regs, it must use the ftrace_get_regs() helper macro, which will return NULL if the regs isn't full (FL_SAVE_REGS set). This addresses a concern by both Peter Zijlsta and Thomas Gleixner that a partially filled pt_regs may be used inappropriately. - No test patch in this version. - Use case using livepatching is added. This passes the test_livepatch.sh selftest. Steven Rostedt (VMware) (3): ftrace: Have the callbacks receive a struct ftrace_regs instead of pt_regs ftrace/x86: Allow for arguments to be passed in to ftrace_regs by default livepatching: Use the default ftrace_ops instead of REGS when ARGS is available ---- arch/powerpc/include/asm/livepatch.h | 4 +++- arch/s390/include/asm/livepatch.h | 5 ++++- arch/x86/Kconfig | 1 + arch/x86/include/asm/ftrace.h | 18 ++++++++++++++++++ arch/x86/include/asm/livepatch.h | 4 ++-- arch/x86/kernel/ftrace_64.S | 15 +++++++++++++-- arch/x86/kernel/kprobes/ftrace.c | 3 ++- include/linux/ftrace.h | 28 ++++++++++++++++++++++++++-- include/linux/kprobes.h | 2 +- kernel/livepatch/patch.c | 10 ++++++---- kernel/trace/Kconfig | 9 +++++++++ kernel/trace/ftrace.c | 27 +++++++++++++++------------ kernel/trace/trace_event_perf.c | 2 +- kernel/trace/trace_functions.c | 9 ++++----- kernel/trace/trace_irqsoff.c | 2 +- kernel/trace/trace_sched_wakeup.c | 2 +- kernel/trace/trace_selftest.c | 20 +++++++++++--------- kernel/trace/trace_stack.c | 2 +- 18 files changed, 119 insertions(+), 44 deletions(-)