From mboxrd@z Thu Jan 1 00:00:00 1970 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 940FD1D318A; Mon, 7 Oct 2024 12:24:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728303863; cv=none; b=nrVe6faq/iqId+8P2uio87wCz3ZXr/h/k+SnyZZaAyMEy44hs+fCG+7IEzLTyh2yLXWSOPIdjnLFRWNrSQLfWubfTXyxjsCiOemPU826I4NyhWHXFCu/Qc6y5caMgpdo6I25C9/G5aoau3yhZ+xgtfcvdz9QmnF1qYKDQT1Ji+A= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728303863; c=relaxed/simple; bh=UU6wLBGnm1CbrpwWS2xyw4JVMQssEeBg4IEK1MEqFBA=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=ShYMbX8TrfaddRAd1qc73Jw943EWfs4WHO7X/YVDTAQVeUrPQDhSwHNn7ZTHkTobBIgHkgQ8MUkSBkK6ALbEmRgVZ4gj0pVUaGxpa6DBqlcxU1okrBU1htSsH/8cvdliN5LZ3num8wvM/CVGig5x1Cj5RzbRlQ/kJw/ujs+wcng= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=lAHNuIDZ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="lAHNuIDZ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DA9FDC4CECF; Mon, 7 Oct 2024 12:24:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728303863; bh=UU6wLBGnm1CbrpwWS2xyw4JVMQssEeBg4IEK1MEqFBA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=lAHNuIDZTPFabM7bIaxGgjuStXbKn94uubuHpRWi7tne8m4DFsSFCAB5EkrnPDS97 w5Hz26GSrPObEO3o+1+bkxR8u/Fij4ZGlbQMOc1n8huc03ICARzrD2FmrvFSKlUix1 fiiS1hc7qJLnlm/WeY735GKTVHoqiC12VecsPS/rfyFUDKwM/M9J4AnSZle7mOrgdp IOLcj8DbNy0EwNj3o4O+eKnnyIoH5X1SCZ9P8hZaLO9Ki+txIbQkX7k3AcdbpZxTg0 qsAz17u7sdI07cSAobUqm3WTKS5eXb6nAg3nkfJL87KJ3LdgM9RPJk7GUe97LhKZtg F7dDHVH7oHm/w== Date: Mon, 7 Oct 2024 21:24:17 +0900 From: Masami Hiramatsu (Google) To: Jeff Xie Cc: rostedt@goodmis.org, mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, xiehuan09@gmail.com, dolinux.peng@gmail.com, chensong_2000@189.cn Subject: Re: [PATCH v4] ftrace: Get the true parent ip for function tracer Message-Id: <20241007212417.64a199fbe0c80fc4e2cd4b7b@kernel.org> In-Reply-To: <20241007113537.19686-1-jeff.xie@linux.dev> References: <20241007113537.19686-1-jeff.xie@linux.dev> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 7 Oct 2024 19:35:37 +0800 Jeff Xie wrote: > When using both function tracer and function graph simultaneously, > it is found that function tracer sometimes captures a fake parent ip > (return_to_handler) instead of the true parent ip. > > This issue is easy to reproduce. Below are my reproduction steps: > > jeff-labs:~/bin # ./trace-net.sh > > jeff-labs:~/bin # cat /sys/kernel/debug/tracing/instances/foo/trace | grep return_to_handler > trace-net.sh-405 [001] ...2. 31.859501: avc_has_perm+0x4/0x190 <-return_to_handler+0x0/0x40 > trace-net.sh-405 [001] ...2. 31.859503: simple_setattr+0x4/0x70 <-return_to_handler+0x0/0x40 > trace-net.sh-405 [001] ...2. 31.859503: truncate_pagecache+0x4/0x60 <-return_to_handler+0x0/0x40 > trace-net.sh-405 [001] ...2. 31.859505: unmap_mapping_range+0x4/0x140 <-return_to_handler+0x0/0x40 > trace-net.sh-405 [001] ...3. 31.859508: _raw_spin_unlock+0x4/0x30 <-return_to_handler+0x0/0x40 > [...] > > The following is my simple trace script: > > > jeff-labs:~/bin # cat ./trace-net.sh > TRACE_PATH="/sys/kernel/debug/tracing" > > set_events() { > echo 1 > $1/events/net/enable > echo 1 > $1/events/tcp/enable > echo 1 > $1/events/sock/enable > echo 1 > $1/events/napi/enable > echo 1 > $1/events/fib/enable > echo 1 > $1/events/neigh/enable > } > > set_events ${TRACE_PATH} > echo 1 > ${TRACE_PATH}/options/sym-offset > echo 1 > ${TRACE_PATH}/options/funcgraph-tail > echo 1 > ${TRACE_PATH}/options/funcgraph-proc > echo 1 > ${TRACE_PATH}/options/funcgraph-abstime > > echo 'tcp_orphan*' > ${TRACE_PATH}/set_ftrace_notrace > echo function_graph > ${TRACE_PATH}/current_tracer > > INSTANCE_FOO=${TRACE_PATH}/instances/foo > if [ ! -e $INSTANCE_FOO ]; then > mkdir ${INSTANCE_FOO} > fi > set_events ${INSTANCE_FOO} > echo 1 > ${INSTANCE_FOO}/options/sym-offset > echo 'tcp_orphan*' > ${INSTANCE_FOO}/set_ftrace_notrace > echo function > ${INSTANCE_FOO}/current_tracer > > echo 1 > ${TRACE_PATH}/tracing_on > echo 1 > ${INSTANCE_FOO}/tracing_on > > echo > ${TRACE_PATH}/trace > echo > ${INSTANCE_FOO}/trace > > Looks good to me. Acked-by: Masami Hiramatsu (Google) Thank you, > Signed-off-by: Jeff Xie > --- > v4: > https://lore.kernel.org/linux-trace-kernel/20241005101320.766c1100@rorschach.local.home/ > - fixed the crash when accessing the "current" if the arch has not implemented noinstr > thanks steve for the testing and the detailed explanation > > v3: > https://lore.kernel.org/linux-trace-kernel/20240910001326.87f27e6b312f1d956cf352a2@kernel.org/ > - fixed build error when CONFIG_FUNCTION_GRAPH_TRACER=n suggested by Masami > > v2: > https://lore.kernel.org/linux-trace-kernel/20240821095910.1888d7fa@gandalf.local.home/ > - Adding __always_inline to function_get_true_parent_ip suggested by Steve > > kernel/trace/trace_functions.c | 26 ++++++++++++++++++++++++++ > 1 file changed, 26 insertions(+) > > diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c > index 3b0cea37e029..46b663d22c37 100644 > --- a/kernel/trace/trace_functions.c > +++ b/kernel/trace/trace_functions.c > @@ -176,6 +176,27 @@ static void function_trace_start(struct trace_array *tr) > tracing_reset_online_cpus(&tr->array_buffer); > } > > +#if defined(CONFIG_FUNCTION_GRAPH_TRACER) && defined(CONFIG_ARCH_WANTS_NO_INSTR) > +static __always_inline unsigned long > +function_get_true_parent_ip(unsigned long parent_ip, struct ftrace_regs *fregs) > +{ > + unsigned long true_parent_ip; > + int idx = 0; > + > + true_parent_ip = parent_ip; > + if (unlikely(parent_ip == (unsigned long)&return_to_handler)) > + true_parent_ip = ftrace_graph_ret_addr(current, &idx, parent_ip, > + (unsigned long *)fregs->regs.sp); > + return true_parent_ip; > +} > +#else > +static __always_inline unsigned long > +function_get_true_parent_ip(unsigned long parent_ip, struct ftrace_regs *fregs) > +{ > + return parent_ip; > +} > +#endif > + > static void > function_trace_call(unsigned long ip, unsigned long parent_ip, > struct ftrace_ops *op, struct ftrace_regs *fregs) > @@ -193,6 +214,8 @@ function_trace_call(unsigned long ip, unsigned long parent_ip, > if (bit < 0) > return; > > + parent_ip = function_get_true_parent_ip(parent_ip, fregs); > + > trace_ctx = tracing_gen_ctx(); > > cpu = smp_processor_id(); > @@ -241,6 +264,7 @@ function_stack_trace_call(unsigned long ip, unsigned long parent_ip, > * recursive protection is performed. > */ > local_irq_save(flags); > + parent_ip = function_get_true_parent_ip(parent_ip, fregs); > cpu = raw_smp_processor_id(); > data = per_cpu_ptr(tr->array_buffer.data, cpu); > disabled = atomic_inc_return(&data->disabled); > @@ -309,6 +333,7 @@ function_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip, > if (bit < 0) > return; > > + parent_ip = function_get_true_parent_ip(parent_ip, fregs); > cpu = smp_processor_id(); > data = per_cpu_ptr(tr->array_buffer.data, cpu); > if (atomic_read(&data->disabled)) > @@ -356,6 +381,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, unsigned long parent_ip, > * recursive protection is performed. > */ > local_irq_save(flags); > + parent_ip = function_get_true_parent_ip(parent_ip, fregs); > cpu = raw_smp_processor_id(); > data = per_cpu_ptr(tr->array_buffer.data, cpu); > disabled = atomic_inc_return(&data->disabled); > -- > 2.43.0 > -- Masami Hiramatsu (Google)