Currently, 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:
<snip>
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
</snip>
Signed-off-by: Jeff Xie <jeff....@linux.dev>
---
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..273b8c7eeb2d 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 *tr)
tracing_reset_online_cpus(&tr->array_buffer);
}
+static 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;
+}
+
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
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 +256,7 @@ 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 +325,7 @@ 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 +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 = 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);
--
2.34.1
