From nobody Sat Feb 7 21:15:20 2026 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) (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 D045826ACB for ; Wed, 21 Aug 2024 23:30:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.182 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724283057; cv=none; b=qn/NwBoDJxdvJYbSkGdRF3OffEnR0q1iAlwK1cz+++iIZO8EoQi+BV13fsrOTl3NpljAMus91ezN1zRGsndgwuflbUC0kpdZEVR8m9P947UavyJD0GTYZCw/W8s+zR6o5Q1Q0R1jQ9msRxv13/ioYFjSaBxSpZ4LVew/rULL6RU= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724283057; c=relaxed/simple; bh=hSPFWkbleapwLpN1BRkiPikR+p6dqOEqdJ+vNeKRGhk=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=la8L3C5RpoNkztGozEiOx8coO1RA7EykssLcr09MrBsOjViEvJgLS5o4BZhISyCGT/P1DEYzR0jUjFX+o7mVTFbc6T9aoB2KFzQZWapoIR8tVRyxeN26quwTE9kJ8wnvbw/4VwNAp/eQopCm5axyJXjSQNd6WGGZzUuzg8lCyr0= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=KYnhPRYb; arc=none smtp.client-ip=95.215.58.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="KYnhPRYb" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1724283052; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=8fGX8MYAy6DkBNWKTzTkMmR/It722mAyKkHXHLYbIFQ=; b=KYnhPRYbKL5yTSAtVWVY+42Xj65hD1o2wfUQmN3FBuIdyGwSllSOWM75SJYXLcPp8g95U5 avdnqLLNWMi+MXT3OrIGqOcUa7SwajNjq9jHA9YMRtVG96Q84FXq33AN/+warPM7qetf5n GOQPqovtG6/pUJ1jypn0HOmi06jN62Y= From: Jeff Xie To: rostedt@goodmis.org, mhiramat@kernel.org Cc: mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org, xiehuan09@gmail.com, Jeff Xie Subject: [PATCH v2] ftrace: Get the true parent ip for function tracer Date: Thu, 22 Aug 2024 07:30:21 +0800 Message-Id: <20240821233021.2785584-1-jeff.xie@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Migadu-Flow: FLOW_OUT Content-Type: text/plain; charset="utf-8" Currently, when using both function tracer and function graph simultaneousl= y, 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+0x4/0= x60 <-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+0x4/0x3= 0 <-return_to_handler+0x0/0x40 [...] The following is my simple trace script: jeff-labs:~/bin # cat ./trace-net.sh TRACE_PATH=3D"/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 > ${TRACE_PATH}/current_tracer INSTANCE_FOO=3D${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 Signed-off-by: Jeff Xie --- v2: - Adding __always_inline to function_get_true_parent_ip suggested by Steve kernel/trace/trace_functions.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/kernel/trace/trace_functions.c b/kernel/trace/trace_functions.c index 3b0cea37e029..d989e927c898 100644 --- a/kernel/trace/trace_functions.c +++ b/kernel/trace/trace_functions.c @@ -176,6 +176,19 @@ static void function_trace_start(struct trace_array *t= r) tracing_reset_online_cpus(&tr->array_buffer); } =20 +static __always_inline unsigned long +function_get_true_parent_ip(unsigned long parent_ip, struct ftrace_regs *f= regs) +{ + unsigned long true_parent_ip; + int idx =3D 0; + + true_parent_ip =3D parent_ip; + if (unlikely(parent_ip =3D=3D (unsigned long)&return_to_handler)) + true_parent_ip =3D ftrace_graph_ret_addr(current, &idx, parent_ip, + (unsigned long *)fregs->regs.sp); + return true_parent_ip; +} + static void function_trace_call(unsigned long ip, unsigned long parent_ip, struct ftrace_ops *op, struct ftrace_regs *fregs) @@ -193,6 +206,8 @@ function_trace_call(unsigned long ip, unsigned long par= ent_ip, if (bit < 0) return; =20 + parent_ip =3D function_get_true_parent_ip(parent_ip, fregs); + trace_ctx =3D tracing_gen_ctx(); =20 cpu =3D smp_processor_id(); @@ -241,6 +256,7 @@ function_stack_trace_call(unsigned long ip, unsigned lo= ng parent_ip, * recursive protection is performed. */ local_irq_save(flags); + parent_ip =3D function_get_true_parent_ip(parent_ip, fregs); cpu =3D raw_smp_processor_id(); data =3D per_cpu_ptr(tr->array_buffer.data, cpu); disabled =3D atomic_inc_return(&data->disabled); @@ -309,6 +325,7 @@ function_no_repeats_trace_call(unsigned long ip, unsign= ed long parent_ip, if (bit < 0) return; =20 + parent_ip =3D function_get_true_parent_ip(parent_ip, fregs); cpu =3D smp_processor_id(); data =3D per_cpu_ptr(tr->array_buffer.data, cpu); if (atomic_read(&data->disabled)) @@ -356,6 +373,7 @@ function_stack_no_repeats_trace_call(unsigned long ip, = unsigned long parent_ip, * recursive protection is performed. */ local_irq_save(flags); + parent_ip =3D function_get_true_parent_ip(parent_ip, fregs); cpu =3D raw_smp_processor_id(); data =3D per_cpu_ptr(tr->array_buffer.data, cpu); disabled =3D atomic_inc_return(&data->disabled); --=20 2.34.1