| Message ID | 20240821233021.2785584-1-jeff.xie@linux.dev (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] ftrace: Get the true parent ip for function tracer | expand |
August 22, 2024 at 7:30 AM, "Jeff Xie" <jeff.xie@linux.dev> wrote: Kindly ping, any comments here? Thanks. > > 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.xie@linux.dev> > > --- > > 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 *tr) > > tracing_reset_online_cpus(&tr->array_buffer); > > } > > > > +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; > > +} > > + > > 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 >
On Thu, 22 Aug 2024 07:30:21 +0800 Jeff Xie <jeff.xie@linux.dev> wrote: > 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 > [...] > Can you also add > 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.xie@linux.dev> > --- > 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 *tr) > tracing_reset_online_cpus(&tr->array_buffer); > } > > +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; > +} Can this work without CONFIG_FUNCTION_GRAPH_TRACER? Maybe it cause a build error because return_to_handler is not defined. Could you check it? Thank you, > + > 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 >
September 9, 2024 at 11:13 PM, "Masami Hiramatsu" <mhiramat@kernel.org> wrote: Hi Masami, > > On Thu, 22 Aug 2024 07:30:21 +0800 > > Jeff Xie <jeff.xie@linux.dev> wrote: > > > > > 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 > > > > [...] > > > > Can you also add Was there more you intended to say after this? > > > > > 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.xie@linux.dev> > > > > --- > > > > 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 *tr) > > > > tracing_reset_online_cpus(&tr->array_buffer); > > > > } > > > > > > > > +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; > > > > +} > > > > Can this work without CONFIG_FUNCTION_GRAPH_TRACER? Maybe it cause a build error > > because return_to_handler is not defined. > > Could you check it? I believed I had checked it before, but I actually found a build error. I will fix it. ;-) > > Thank you, > > > > > + > > > > 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 > > > > -- > > Masami Hiramatsu (Google) <mhiramat@kernel.org> >
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 *tr) tracing_reset_online_cpus(&tr->array_buffer); } +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; +} + 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);
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.xie@linux.dev> --- v2: - Adding __always_inline to function_get_true_parent_ip suggested by Steve kernel/trace/trace_functions.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)