From patchwork Wed Jan 10 00:13:06 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Masami Hiramatsu (Google)" X-Patchwork-Id: 13515544 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A7410A59; Wed, 10 Jan 2024 00:13:11 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Bqi4B/uk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 86FEAC433C7; Wed, 10 Jan 2024 00:13:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1704845591; bh=Gv4c6KiHO29Wy6P60cNBnzMOUtlrYYrwMdYxxWKGGFY=; h=From:To:Cc:Subject:Date:From; b=Bqi4B/uk/VltCFfhEXjIjNk7QvDsCS+7JyqKYmONimHrhav1/UluI5Nj7jT6Lq2Mn ZjeclY/aL5T1PCOQ9r97Zqh8QTFuRJzLX9GKFEKzgqXIrLh/G9Mn2IEhg9H82xM5BY MtEIot4/yqrFGesVhf70KaGIjvY94GeRS9jpjAskeudO24Awc36Kei+WjyQouYjMow oJ4Qw5RB8JL4BoE42UFOjtd4UeEp0vsowgqhRTyBbsjaXNjIp7fp5EqK3HMrG3lPYA YR4xeaIyW1bIaiPwW6kEqAx3MudklNnZG5QxCo18Ub5g/GV7QN50w2p0+AjbNl8ZO2 77p9tjUs4nF3w== From: "Masami Hiramatsu (Google)" To: Steven Rostedt , Jiri Olsa Cc: linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, Florent Revest , Mark Rutland Subject: [PATCH] ftrace: Fix DIRECT_CALLS to use SAVE_REGS by default Date: Wed, 10 Jan 2024 09:13:06 +0900 Message-Id: <170484558617.178953.1590516949390270842.stgit@devnote2> X-Mailer: git-send-email 2.34.1 User-Agent: StGit/0.19 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Masami Hiramatsu (Google) The commit 60c8971899f3 ("ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS") changed DIRECT_CALLS to use SAVE_ARGS when there are multiple ftrace_ops at the same function, but since the x86 only support to jump to direct_call from ftrace_regs_caller, when we set the function tracer on the same target function on x86, ftrace-direct does not work as below (this actually works on arm64.) At first, insmod ftrace-direct.ko to put a direct_call on 'wake_up_process()'. # insmod kernel/samples/ftrace/ftrace-direct.ko # less trace ... -0 [006] ..s1. 564.686958: my_direct_func: waking up rcu_preempt-17 -0 [007] ..s1. 564.687836: my_direct_func: waking up kcompactd0-63 -0 [006] ..s1. 564.690926: my_direct_func: waking up rcu_preempt-17 -0 [006] ..s1. 564.696872: my_direct_func: waking up rcu_preempt-17 -0 [007] ..s1. 565.191982: my_direct_func: waking up kcompactd0-63 Setup a function filter to the 'wake_up_process' too, and enable it. # cd /sys/kernel/tracing/ # echo wake_up_process > set_ftrace_filter # echo function > current_tracer # less trace ... -0 [006] ..s3. 686.180972: wake_up_process <-call_timer_fn -0 [006] ..s3. 686.186919: wake_up_process <-call_timer_fn -0 [002] ..s3. 686.264049: wake_up_process <-call_timer_fn -0 [002] d.h6. 686.515216: wake_up_process <-kick_pool -0 [002] d.h6. 686.691386: wake_up_process <-kick_pool Then, only function tracer is shown on x86. But if you enable 'kprobe on ftrace' event (which uses SAVE_REGS flag) on the same function, it is shown again. # echo 'p wake_up_process' >> dynamic_events # echo 1 > events/kprobes/p_wake_up_process_0/enable # echo > trace # less trace ... -0 [006] ..s2. 2710.345919: p_wake_up_process_0: (wake_up_process+0x4/0x20) -0 [006] ..s3. 2710.345923: wake_up_process <-call_timer_fn -0 [006] ..s1. 2710.345928: my_direct_func: waking up rcu_preempt-17 -0 [006] ..s2. 2710.349931: p_wake_up_process_0: (wake_up_process+0x4/0x20) -0 [006] ..s3. 2710.349934: wake_up_process <-call_timer_fn -0 [006] ..s1. 2710.349937: my_direct_func: waking up rcu_preempt-17 To fix this issue, use SAVE_REGS flag for multiple ftrace_ops flag of direct_call by default. Fixes: 60c8971899f3 ("ftrace: Make DIRECT_CALLS work WITH_ARGS and !WITH_REGS") Cc: stable@vger.kernel.org Signed-off-by: Masami Hiramatsu (Google) Reviewed-by: Mark Rutland Tested-by: Mark Rutland [arm64] Acked-by: Jiri Olsa --- kernel/trace/ftrace.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index b01ae7d36021..c060d5b47910 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5325,7 +5325,17 @@ static LIST_HEAD(ftrace_direct_funcs); static int register_ftrace_function_nolock(struct ftrace_ops *ops); +/* + * If there are multiple ftrace_ops, use SAVE_REGS by default, so that direct + * call will be jumped from ftrace_regs_caller. Only if the architecture does + * not support ftrace_regs_caller but direct_call, use SAVE_ARGS so that it + * jumps from ftrace_caller for multiple ftrace_ops. + */ +#ifndef HAVE_DYNAMIC_FTRACE_WITH_REGS #define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_ARGS) +#else +#define MULTI_FLAGS (FTRACE_OPS_FL_DIRECT | FTRACE_OPS_FL_SAVE_REGS) +#endif static int check_direct_multi(struct ftrace_ops *ops) {