From: Masami Hiramatsu (Google) <[email protected]> With the introduction of container_of-style BTF typecasting and per-CPU variable access support in trace probes, we need a way to verify their functionality and prevent regressions.
Add a new ftrace kselftest and update the trace event sample module to test and validate these features. Specifically, update the trace-events-sample module to set up a periodic timer whose callback accesses a per-CPU counter. Introduce a new sample trace event, foo_timer_fn, to trace this callback and log the current counter value. Then, add a new test case, btf_probe_event.tc, which defines a dynamic probe on the timer callback. The probe uses BTF typecasting to recover the parent structure from the timer argument and this_cpu_read() to fetch the per-CPU counter. The test verifies the integrity of the implementation by ensuring the values recorded by the dynamic probe match those from the static tracepoint. Assisted-by: Antigravity:gemini-3.5-flash Signed-off-by: Masami Hiramatsu (Google) <[email protected]> --- Changes in v2: - Use timer_shutdown_sync() instead of timer_delete_sync() for teardown. --- samples/trace_events/trace-events-sample.c | 40 +++++++++++++++- samples/trace_events/trace-events-sample.h | 34 ++++++++++++- .../ftrace/test.d/dynevent/btf_probe_event.tc | 51 ++++++++++++++++++++ 3 files changed, 120 insertions(+), 5 deletions(-) create mode 100644 tools/testing/selftests/ftrace/test.d/dynevent/btf_probe_event.tc diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c index b61766864b54..2a1f73533a38 100644 --- a/samples/trace_events/trace-events-sample.c +++ b/samples/trace_events/trace-events-sample.c @@ -93,6 +93,20 @@ static int simple_thread_fn(void *arg) static DEFINE_MUTEX(thread_mutex); +static struct foo_timer_data *foo_timer_data; + +static void sample_timer_cb(struct timer_list *t) +{ + struct foo_timer_data *data = container_of(t, struct foo_timer_data, timer); + + get_cpu(); + trace_foo_timer_fn(data); + (*this_cpu_ptr(data->counter))++; + put_cpu(); + + mod_timer(t, jiffies + HZ); +} + int foo_bar_reg(void) { mutex_lock(&thread_mutex); @@ -124,9 +138,27 @@ void foo_bar_unreg(void) static int __init trace_event_init(void) { + foo_timer_data = kzalloc_obj(*foo_timer_data, GFP_KERNEL); + if (!foo_timer_data) + return -ENOMEM; + + foo_timer_data->name = "sample_timer_counter"; + foo_timer_data->counter = alloc_percpu(int); + if (!foo_timer_data->counter) { + kfree(foo_timer_data); + return -ENOMEM; + } + + timer_setup(&foo_timer_data->timer, sample_timer_cb, 0); + mod_timer(&foo_timer_data->timer, jiffies + HZ); + simple_tsk = kthread_run(simple_thread, NULL, "event-sample"); - if (IS_ERR(simple_tsk)) - return -1; + if (IS_ERR(simple_tsk)) { + timer_shutdown_sync(&foo_timer_data->timer); + free_percpu(foo_timer_data->counter); + kfree(foo_timer_data); + return PTR_ERR(simple_tsk); + } return 0; } @@ -139,6 +171,10 @@ static void __exit trace_event_exit(void) kthread_stop(simple_tsk_fn); simple_tsk_fn = NULL; mutex_unlock(&thread_mutex); + + timer_shutdown_sync(&foo_timer_data->timer); + free_percpu(foo_timer_data->counter); + kfree(foo_timer_data); } module_init(trace_event_init); diff --git a/samples/trace_events/trace-events-sample.h b/samples/trace_events/trace-events-sample.h index 1a05fc153353..816848a456a2 100644 --- a/samples/trace_events/trace-events-sample.h +++ b/samples/trace_events/trace-events-sample.h @@ -247,12 +247,14 @@ */ /* - * It is OK to have helper functions in the file, but they need to be protected - * from being defined more than once. Remember, this file gets included more - * than once. + * It is OK to have helper functions and data structures in the file, but they + * need to be protected from being defined more than once. Remember, this file + * gets included more than once. */ #ifndef __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS #define __TRACE_EVENT_SAMPLE_HELPER_FUNCTIONS +#include <linux/timer.h> + static inline int __length_of(const int *list) { int i; @@ -270,6 +272,13 @@ enum { TRACE_SAMPLE_BAR = 4, TRACE_SAMPLE_ZOO = 8, }; + +struct foo_timer_data { + const char *name; + struct timer_list timer; + int __percpu *counter; +}; + #endif /* @@ -595,6 +604,25 @@ TRACE_EVENT(foo_rel_loc, __get_rel_bitmask(bitmask), __get_rel_cpumask(cpumask)) ); + +TRACE_EVENT(foo_timer_fn, + + TP_PROTO(struct foo_timer_data *data), + + TP_ARGS(data), + + TP_STRUCT__entry( + __string( name, data->name ) + __field( int, count ) + ), + + TP_fast_assign( + __assign_str(name); + __entry->count = *this_cpu_ptr(data->counter); + ), + + TP_printk("name=%s count=%d", __get_str(name), __entry->count) +); #endif /***** NOTICE! The #if protection ends here. *****/ diff --git a/tools/testing/selftests/ftrace/test.d/dynevent/btf_probe_event.tc b/tools/testing/selftests/ftrace/test.d/dynevent/btf_probe_event.tc new file mode 100644 index 000000000000..96791e120b7d --- /dev/null +++ b/tools/testing/selftests/ftrace/test.d/dynevent/btf_probe_event.tc @@ -0,0 +1,51 @@ +#!/bin/sh +# SPDX-License-Identifier: GPL-2.0 +# description: BTF event with typecast and percpu access +# requires: dynamic_events "this_cpu_read(<fetcharg>)":README "[(structname[,field])]<argname>[->field[->field|.field...]]":README + +# Check if the sample module is loaded +if ! lsmod | grep -q trace_events_sample; then + modprobe trace-events-sample || exit_unsupported +fi + +echo 0 > events/enable +echo > dynamic_events + +# The sample_timer_cb(struct timer_list *t) is called. +# We want to check (STRUCT,FIELD)VAR typecast and this_cpu_read() access. +# (foo_timer_data,timer)t converts t to struct foo_timer_data * using container_of. +# data->counter is a per-cpu pointer to int. +# this_cpu_read(data->counter) should give the value of the counter. + +echo 'f:mysample/myevent sample_timer_cb name=(foo_timer_data,timer)t->name:string count=this_cpu_read((foo_timer_data,timer)t->counter)' >> dynamic_events + +echo 1 > events/mysample/myevent/enable +echo 1 > events/sample-trace/foo_timer_fn/enable + +sleep 2 + +echo 0 > events/mysample/myevent/enable +echo 0 > events/sample-trace/foo_timer_fn/enable + +# Compare the values. +MATCH=0 +while read line; do + if echo $line | grep -q "foo_timer_fn:"; then + NAME=`echo $line | sed 's/.*name=\([^ ]*\) .*/\1/'` + COUNT=`echo $line | sed 's/.*count=\([^ ]*\).*/\1/'` + if grep -q "myevent:.*name=\"${NAME}\" count=$COUNT" trace; then + MATCH=$((MATCH+1)) + fi + fi +done < trace + +if [ $MATCH -eq 0 ]; then + echo "No matching events found" + exit_fail +fi + +# Clean up +echo 0 > events/mysample/myevent/enable +echo 0 > events/sample-trace/foo_timer_fn/enable +echo > dynamic_events +clear_trace
