| Message ID | 20241007113537.19686-1-jeff.xie@linux.dev (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v4] ftrace: Get the true parent ip for function tracer | expand |
On Mon, 7 Oct 2024 19:35:37 +0800 Jeff Xie <jeff.xie@linux.dev> 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: > > <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> > Looks good to me. Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thank you, > Signed-off-by: Jeff Xie <jeff.xie@linux.dev> > --- > 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 >
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);
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> --- 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(+)