From patchwork Wed May 3 01:32:33 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Steven Rostedt X-Patchwork-Id: 13229437 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 BCE57C7EE21 for ; Wed, 3 May 2023 01:32:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229449AbjECBc4 (ORCPT ); Tue, 2 May 2023 21:32:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32962 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229606AbjECBcy (ORCPT ); Tue, 2 May 2023 21:32:54 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C5E4E2700; Tue, 2 May 2023 18:32:52 -0700 (PDT) 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 447BF629D9; Wed, 3 May 2023 01:32:37 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D17A2C433EF; Wed, 3 May 2023 01:32:35 +0000 (UTC) Date: Tue, 2 May 2023 21:32:33 -0400 From: Steven Rostedt To: LKML , Linux Trace Kernel Cc: Masami Hiramatsu , Mark Rutland Subject: [PATCH] ftrace: Add MODIFIED flag to show if IPMODIFY or direct was attached Message-ID: <20230502213233.004e3ae4@gandalf.local.home> X-Mailer: Claws Mail 3.17.8 (GTK+ 2.24.33; x86_64-pc-linux-gnu) MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org From: "Steven Rostedt (Google)" If a function had ever had IPMODIFY or DIRECT attached to it, where this is how live kernel patching and BPF overrides work, mark them and display an "M" in the enabled_functions and touched_functions files. This can be used for debugging. If a function had been modified and later there's a bug in the code related to that function, this can be used to know if the cause is possibly from a live kernel patch or a BPF program that changed the behavior of the code. Also update the documentation on the enabled_functions and touched_functions output, as it was missing direct callers and CALL_OPS. And include this new modify attribute. Signed-off-by: Steven Rostedt (Google) Acked-by: Masami Hiramatsu (Google) --- Documentation/trace/ftrace.rst | 25 +++++++++++++++++++++++++ include/linux/ftrace.h | 4 +++- kernel/trace/ftrace.c | 12 +++++++++--- 3 files changed, 37 insertions(+), 4 deletions(-) diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst index aaebb821912e..d5766229c71a 100644 --- a/Documentation/trace/ftrace.rst +++ b/Documentation/trace/ftrace.rst @@ -350,6 +350,19 @@ of ftrace. Here is a list of some of the key files: an 'I' will be displayed on the same line as the function that can be overridden. + If a non ftrace trampoline is attached (BPF) a 'D' will be displayed. + Note, normal ftrace trampolines can also be attached, but only one + "direct" trampoline can be attached to a given function at a time. + + Some architectures can not call direct trampolines, but instead have + the ftrace ops function located above the function entry point. In + such cases an 'O' will be displayed. + + If a function had either the "ip modify" or a "direct" call attached to + it in the past, a 'M' will be shown. This flag is never cleared. It is + used to know if a function was every modified by the ftrace infrastructure, + and can be used for debugging. + If the architecture supports it, it will also show what callback is being directly called by the function. If the count is greater than 1 it most likely will be ftrace_ops_list_func(). @@ -359,6 +372,18 @@ of ftrace. Here is a list of some of the key files: its address will be printed as well as the function that the trampoline calls. + touched_functions: + + This file contains all the functions that ever had a function callback + to it via the ftrace infrastructure. It has the same format as + enabled_functions but shows all functions that have every been + traced. + + To see any function that has every been modified by "ip modify" or a + direct trampoline, one can perform the following command: + + grep ' M ' /sys/kernel/tracing/touched_functions + function_profile_enabled: When set it will enable all functions with either the function diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 327046f1278d..7dffd740e784 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -549,6 +549,7 @@ bool is_ftrace_trampoline(unsigned long addr); * CALL_OPS - the record can use callsite-specific ops * CALL_OPS_EN - the function is set up to use callsite-specific ops * TOUCHED - A callback was added since boot up + * MODIFIED - The function had IPMODIFY or DIRECT attached to it * * When a new ftrace_ops is registered and wants a function to save * pt_regs, the rec->flags REGS is set. When the function has been @@ -569,9 +570,10 @@ enum { FTRACE_FL_CALL_OPS = (1UL << 22), FTRACE_FL_CALL_OPS_EN = (1UL << 21), FTRACE_FL_TOUCHED = (1UL << 20), + FTRACE_FL_MODIFIED = (1UL << 19), }; -#define FTRACE_REF_MAX_SHIFT 20 +#define FTRACE_REF_MAX_SHIFT 19 #define FTRACE_REF_MAX ((1UL << FTRACE_REF_MAX_SHIFT) - 1) #define ftrace_rec_count(rec) ((rec)->flags & FTRACE_REF_MAX) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index db8532a4d5c8..885845fc851d 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -46,7 +46,8 @@ #include "trace_stat.h" /* Flags that do not get reset */ -#define FTRACE_NOCLEAR_FLAGS (FTRACE_FL_DISABLED | FTRACE_FL_TOUCHED) +#define FTRACE_NOCLEAR_FLAGS (FTRACE_FL_DISABLED | FTRACE_FL_TOUCHED | \ + FTRACE_FL_MODIFIED) #define FTRACE_INVALID_FUNCTION "__ftrace_invalid_address__" @@ -2273,6 +2274,10 @@ static int ftrace_check_record(struct dyn_ftrace *rec, bool enable, bool update) rec->flags &= ~FTRACE_FL_TRAMP_EN; } + /* Keep track of anything that modifies the function */ + if (rec->flags & (FTRACE_FL_DIRECT | FTRACE_FL_IPMODIFY)) + rec->flags |= FTRACE_FL_MODIFIED; + if (flag & FTRACE_FL_DIRECT) { /* * If there's only one user (direct_ops helper) @@ -3866,12 +3871,13 @@ static int t_show(struct seq_file *m, void *v) if (iter->flags & (FTRACE_ITER_ENABLED | FTRACE_ITER_TOUCHED)) { struct ftrace_ops *ops; - seq_printf(m, " (%ld)%s%s%s%s", + seq_printf(m, " (%ld)%s%s%s%s%s", ftrace_rec_count(rec), rec->flags & FTRACE_FL_REGS ? " R" : " ", rec->flags & FTRACE_FL_IPMODIFY ? " I" : " ", rec->flags & FTRACE_FL_DIRECT ? " D" : " ", - rec->flags & FTRACE_FL_CALL_OPS ? " O" : " "); + rec->flags & FTRACE_FL_CALL_OPS ? " O" : " ", + rec->flags & FTRACE_FL_MODIFIED ? " M " : " "); if (rec->flags & FTRACE_FL_TRAMP_EN) { ops = ftrace_find_tramp_ops_any(rec); if (ops) {