1 // SPDX-License-Identifier: GPL-2.0
3 * ring buffer based function tracer
5 * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
6 * Copyright (C) 2008 Ingo Molnar <mingo@redhat.com>
8 * Based on code from the latency_tracer, that is:
10 * Copyright (C) 2004-2006 Ingo Molnar
11 * Copyright (C) 2004 Nadia Yvette Chambers
13 #include <linux/ring_buffer.h>
14 #include <linux/debugfs.h>
15 #include <linux/uaccess.h>
16 #include <linux/ftrace.h>
17 #include <linux/slab.h>
22 static void tracing_start_function_trace(struct trace_array *tr);
23 static void tracing_stop_function_trace(struct trace_array *tr);
25 function_trace_call(unsigned long ip, unsigned long parent_ip,
26 struct ftrace_ops *op, struct pt_regs *pt_regs);
28 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
29 struct ftrace_ops *op, struct pt_regs *pt_regs);
30 static struct tracer_flags func_flags;
34 TRACE_FUNC_OPT_STACK = 0x1,
37 static int allocate_ftrace_ops(struct trace_array *tr)
39 struct ftrace_ops *ops;
41 ops = kzalloc(sizeof(*ops), GFP_KERNEL);
45 /* Currently only the non stack verision is supported */
46 ops->func = function_trace_call;
47 ops->flags = FTRACE_OPS_FL_RECURSION_SAFE | FTRACE_OPS_FL_PID;
55 int ftrace_create_function_files(struct trace_array *tr,
56 struct dentry *parent)
61 * The top level array uses the "global_ops", and the files are
64 if (tr->flags & TRACE_ARRAY_FL_GLOBAL)
67 ret = allocate_ftrace_ops(tr);
71 ftrace_create_filter_files(tr->ops, parent);
76 void ftrace_destroy_function_files(struct trace_array *tr)
78 ftrace_destroy_filter_files(tr->ops);
83 static int function_trace_init(struct trace_array *tr)
88 * Instance trace_arrays get their ops allocated
89 * at instance creation. Unless it failed
95 /* Currently only the global instance can do stack tracing */
96 if (tr->flags & TRACE_ARRAY_FL_GLOBAL &&
97 func_flags.val & TRACE_FUNC_OPT_STACK)
98 func = function_stack_trace_call;
100 func = function_trace_call;
102 ftrace_init_array_ops(tr, func);
104 tr->trace_buffer.cpu = get_cpu();
107 tracing_start_cmdline_record();
108 tracing_start_function_trace(tr);
112 static void function_trace_reset(struct trace_array *tr)
114 tracing_stop_function_trace(tr);
115 tracing_stop_cmdline_record();
116 ftrace_reset_array_ops(tr);
119 static void function_trace_start(struct trace_array *tr)
121 tracing_reset_online_cpus(&tr->trace_buffer);
125 function_trace_call(unsigned long ip, unsigned long parent_ip,
126 struct ftrace_ops *op, struct pt_regs *pt_regs)
128 struct trace_array *tr = op->private;
129 struct trace_array_cpu *data;
135 if (unlikely(!tr->function_enabled))
138 pc = preempt_count();
139 preempt_disable_notrace();
141 bit = trace_test_and_set_recursion(TRACE_FTRACE_START, TRACE_FTRACE_MAX);
145 cpu = smp_processor_id();
146 data = per_cpu_ptr(tr->trace_buffer.data, cpu);
147 if (!atomic_read(&data->disabled)) {
148 local_save_flags(flags);
149 trace_function(tr, ip, parent_ip, flags, pc);
151 trace_clear_recursion(bit);
154 preempt_enable_notrace();
158 function_stack_trace_call(unsigned long ip, unsigned long parent_ip,
159 struct ftrace_ops *op, struct pt_regs *pt_regs)
161 struct trace_array *tr = op->private;
162 struct trace_array_cpu *data;
168 if (unlikely(!tr->function_enabled))
172 * Need to use raw, since this must be called before the
173 * recursive protection is performed.
175 local_irq_save(flags);
176 cpu = raw_smp_processor_id();
177 data = per_cpu_ptr(tr->trace_buffer.data, cpu);
178 disabled = atomic_inc_return(&data->disabled);
180 if (likely(disabled == 1)) {
181 pc = preempt_count();
182 trace_function(tr, ip, parent_ip, flags, pc);
185 * __ftrace_trace_stack,
187 * function_stack_trace_call
191 __trace_stack(tr, flags, 5, pc);
194 atomic_dec(&data->disabled);
195 local_irq_restore(flags);
198 static struct tracer_opt func_opts[] = {
199 #ifdef CONFIG_STACKTRACE
200 { TRACER_OPT(func_stack_trace, TRACE_FUNC_OPT_STACK) },
202 { } /* Always set a last empty entry */
205 static struct tracer_flags func_flags = {
206 .val = 0, /* By default: all flags disabled */
210 static void tracing_start_function_trace(struct trace_array *tr)
212 tr->function_enabled = 0;
213 register_ftrace_function(tr->ops);
214 tr->function_enabled = 1;
217 static void tracing_stop_function_trace(struct trace_array *tr)
219 tr->function_enabled = 0;
220 unregister_ftrace_function(tr->ops);
223 static struct tracer function_trace;
226 func_set_flag(struct trace_array *tr, u32 old_flags, u32 bit, int set)
229 case TRACE_FUNC_OPT_STACK:
230 /* do nothing if already set */
231 if (!!set == !!(func_flags.val & TRACE_FUNC_OPT_STACK))
234 /* We can change this flag when not running. */
235 if (tr->current_trace != &function_trace)
238 unregister_ftrace_function(tr->ops);
241 tr->ops->func = function_stack_trace_call;
242 register_ftrace_function(tr->ops);
244 tr->ops->func = function_trace_call;
245 register_ftrace_function(tr->ops);
256 static struct tracer function_trace __tracer_data =
259 .init = function_trace_init,
260 .reset = function_trace_reset,
261 .start = function_trace_start,
262 .flags = &func_flags,
263 .set_flag = func_set_flag,
264 .allow_instances = true,
265 #ifdef CONFIG_FTRACE_SELFTEST
266 .selftest = trace_selftest_startup_function,
270 #ifdef CONFIG_DYNAMIC_FTRACE
271 static void update_traceon_count(struct ftrace_probe_ops *ops,
273 struct trace_array *tr, bool on,
276 struct ftrace_func_mapper *mapper = data;
281 * Tracing gets disabled (or enabled) once per count.
282 * This function can be called at the same time on multiple CPUs.
283 * It is fine if both disable (or enable) tracing, as disabling
284 * (or enabling) the second time doesn't do anything as the
285 * state of the tracer is already disabled (or enabled).
286 * What needs to be synchronized in this case is that the count
287 * only gets decremented once, even if the tracer is disabled
288 * (or enabled) twice, as the second one is really a nop.
290 * The memory barriers guarantee that we only decrement the
291 * counter once. First the count is read to a local variable
292 * and a read barrier is used to make sure that it is loaded
293 * before checking if the tracer is in the state we want.
294 * If the tracer is not in the state we want, then the count
295 * is guaranteed to be the old count.
297 * Next the tracer is set to the state we want (disabled or enabled)
298 * then a write memory barrier is used to make sure that
299 * the new state is visible before changing the counter by
300 * one minus the old counter. This guarantees that another CPU
301 * executing this code will see the new state before seeing
302 * the new counter value, and would not do anything if the new
305 * Note, there is no synchronization between this and a user
306 * setting the tracing_on file. But we currently don't care
309 count = (long *)ftrace_func_mapper_find_ip(mapper, ip);
315 /* Make sure we see count before checking tracing state */
318 if (on == !!tracer_tracing_is_on(tr))
322 tracer_tracing_on(tr);
324 tracer_tracing_off(tr);
326 /* Make sure tracing state is visible before updating count */
329 *count = old_count - 1;
333 ftrace_traceon_count(unsigned long ip, unsigned long parent_ip,
334 struct trace_array *tr, struct ftrace_probe_ops *ops,
337 update_traceon_count(ops, ip, tr, 1, data);
341 ftrace_traceoff_count(unsigned long ip, unsigned long parent_ip,
342 struct trace_array *tr, struct ftrace_probe_ops *ops,
345 update_traceon_count(ops, ip, tr, 0, data);
349 ftrace_traceon(unsigned long ip, unsigned long parent_ip,
350 struct trace_array *tr, struct ftrace_probe_ops *ops,
353 if (tracer_tracing_is_on(tr))
356 tracer_tracing_on(tr);
360 ftrace_traceoff(unsigned long ip, unsigned long parent_ip,
361 struct trace_array *tr, struct ftrace_probe_ops *ops,
364 if (!tracer_tracing_is_on(tr))
367 tracer_tracing_off(tr);
372 * ftrace_stacktrace()
373 * function_trace_probe_call()
374 * ftrace_ops_list_func()
379 static __always_inline void trace_stack(struct trace_array *tr)
384 local_save_flags(flags);
385 pc = preempt_count();
387 __trace_stack(tr, flags, STACK_SKIP, pc);
391 ftrace_stacktrace(unsigned long ip, unsigned long parent_ip,
392 struct trace_array *tr, struct ftrace_probe_ops *ops,
399 ftrace_stacktrace_count(unsigned long ip, unsigned long parent_ip,
400 struct trace_array *tr, struct ftrace_probe_ops *ops,
403 struct ftrace_func_mapper *mapper = data;
408 if (!tracing_is_on())
417 count = (long *)ftrace_func_mapper_find_ip(mapper, ip);
420 * Stack traces should only execute the number of times the
421 * user specified in the counter.
429 new_count = old_count - 1;
430 new_count = cmpxchg(count, old_count, new_count);
431 if (new_count == old_count)
434 if (!tracing_is_on())
437 } while (new_count != old_count);
440 static int update_count(struct ftrace_probe_ops *ops, unsigned long ip,
443 struct ftrace_func_mapper *mapper = data;
447 count = (long *)ftrace_func_mapper_find_ip(mapper, ip);
459 ftrace_dump_probe(unsigned long ip, unsigned long parent_ip,
460 struct trace_array *tr, struct ftrace_probe_ops *ops,
463 if (update_count(ops, ip, data))
464 ftrace_dump(DUMP_ALL);
467 /* Only dump the current CPU buffer. */
469 ftrace_cpudump_probe(unsigned long ip, unsigned long parent_ip,
470 struct trace_array *tr, struct ftrace_probe_ops *ops,
473 if (update_count(ops, ip, data))
474 ftrace_dump(DUMP_ORIG);
478 ftrace_probe_print(const char *name, struct seq_file *m,
479 unsigned long ip, struct ftrace_probe_ops *ops,
482 struct ftrace_func_mapper *mapper = data;
485 seq_printf(m, "%ps:%s", (void *)ip, name);
488 count = (long *)ftrace_func_mapper_find_ip(mapper, ip);
491 seq_printf(m, ":count=%ld\n", *count);
493 seq_puts(m, ":unlimited\n");
499 ftrace_traceon_print(struct seq_file *m, unsigned long ip,
500 struct ftrace_probe_ops *ops,
503 return ftrace_probe_print("traceon", m, ip, ops, data);
507 ftrace_traceoff_print(struct seq_file *m, unsigned long ip,
508 struct ftrace_probe_ops *ops, void *data)
510 return ftrace_probe_print("traceoff", m, ip, ops, data);
514 ftrace_stacktrace_print(struct seq_file *m, unsigned long ip,
515 struct ftrace_probe_ops *ops, void *data)
517 return ftrace_probe_print("stacktrace", m, ip, ops, data);
521 ftrace_dump_print(struct seq_file *m, unsigned long ip,
522 struct ftrace_probe_ops *ops, void *data)
524 return ftrace_probe_print("dump", m, ip, ops, data);
528 ftrace_cpudump_print(struct seq_file *m, unsigned long ip,
529 struct ftrace_probe_ops *ops, void *data)
531 return ftrace_probe_print("cpudump", m, ip, ops, data);
536 ftrace_count_init(struct ftrace_probe_ops *ops, struct trace_array *tr,
537 unsigned long ip, void *init_data, void **data)
539 struct ftrace_func_mapper *mapper = *data;
542 mapper = allocate_ftrace_func_mapper();
548 return ftrace_func_mapper_add_ip(mapper, ip, init_data);
552 ftrace_count_free(struct ftrace_probe_ops *ops, struct trace_array *tr,
553 unsigned long ip, void *data)
555 struct ftrace_func_mapper *mapper = data;
558 free_ftrace_func_mapper(mapper, NULL);
562 ftrace_func_mapper_remove_ip(mapper, ip);
565 static struct ftrace_probe_ops traceon_count_probe_ops = {
566 .func = ftrace_traceon_count,
567 .print = ftrace_traceon_print,
568 .init = ftrace_count_init,
569 .free = ftrace_count_free,
572 static struct ftrace_probe_ops traceoff_count_probe_ops = {
573 .func = ftrace_traceoff_count,
574 .print = ftrace_traceoff_print,
575 .init = ftrace_count_init,
576 .free = ftrace_count_free,
579 static struct ftrace_probe_ops stacktrace_count_probe_ops = {
580 .func = ftrace_stacktrace_count,
581 .print = ftrace_stacktrace_print,
582 .init = ftrace_count_init,
583 .free = ftrace_count_free,
586 static struct ftrace_probe_ops dump_probe_ops = {
587 .func = ftrace_dump_probe,
588 .print = ftrace_dump_print,
589 .init = ftrace_count_init,
590 .free = ftrace_count_free,
593 static struct ftrace_probe_ops cpudump_probe_ops = {
594 .func = ftrace_cpudump_probe,
595 .print = ftrace_cpudump_print,
598 static struct ftrace_probe_ops traceon_probe_ops = {
599 .func = ftrace_traceon,
600 .print = ftrace_traceon_print,
603 static struct ftrace_probe_ops traceoff_probe_ops = {
604 .func = ftrace_traceoff,
605 .print = ftrace_traceoff_print,
608 static struct ftrace_probe_ops stacktrace_probe_ops = {
609 .func = ftrace_stacktrace,
610 .print = ftrace_stacktrace_print,
614 ftrace_trace_probe_callback(struct trace_array *tr,
615 struct ftrace_probe_ops *ops,
616 struct ftrace_hash *hash, char *glob,
617 char *cmd, char *param, int enable)
619 void *count = (void *)-1;
623 /* hash funcs only work with set_ftrace_filter */
628 return unregister_ftrace_function_probe_func(glob+1, tr, ops);
633 number = strsep(¶m, ":");
639 * We use the callback data field (which is a pointer)
642 ret = kstrtoul(number, 0, (unsigned long *)&count);
647 ret = register_ftrace_function_probe(glob, tr, ops, count);
649 return ret < 0 ? ret : 0;
653 ftrace_trace_onoff_callback(struct trace_array *tr, struct ftrace_hash *hash,
654 char *glob, char *cmd, char *param, int enable)
656 struct ftrace_probe_ops *ops;
661 /* we register both traceon and traceoff to this callback */
662 if (strcmp(cmd, "traceon") == 0)
663 ops = param ? &traceon_count_probe_ops : &traceon_probe_ops;
665 ops = param ? &traceoff_count_probe_ops : &traceoff_probe_ops;
667 return ftrace_trace_probe_callback(tr, ops, hash, glob, cmd,
672 ftrace_stacktrace_callback(struct trace_array *tr, struct ftrace_hash *hash,
673 char *glob, char *cmd, char *param, int enable)
675 struct ftrace_probe_ops *ops;
680 ops = param ? &stacktrace_count_probe_ops : &stacktrace_probe_ops;
682 return ftrace_trace_probe_callback(tr, ops, hash, glob, cmd,
687 ftrace_dump_callback(struct trace_array *tr, struct ftrace_hash *hash,
688 char *glob, char *cmd, char *param, int enable)
690 struct ftrace_probe_ops *ops;
695 ops = &dump_probe_ops;
697 /* Only dump once. */
698 return ftrace_trace_probe_callback(tr, ops, hash, glob, cmd,
703 ftrace_cpudump_callback(struct trace_array *tr, struct ftrace_hash *hash,
704 char *glob, char *cmd, char *param, int enable)
706 struct ftrace_probe_ops *ops;
711 ops = &cpudump_probe_ops;
713 /* Only dump once. */
714 return ftrace_trace_probe_callback(tr, ops, hash, glob, cmd,
718 static struct ftrace_func_command ftrace_traceon_cmd = {
720 .func = ftrace_trace_onoff_callback,
723 static struct ftrace_func_command ftrace_traceoff_cmd = {
725 .func = ftrace_trace_onoff_callback,
728 static struct ftrace_func_command ftrace_stacktrace_cmd = {
729 .name = "stacktrace",
730 .func = ftrace_stacktrace_callback,
733 static struct ftrace_func_command ftrace_dump_cmd = {
735 .func = ftrace_dump_callback,
738 static struct ftrace_func_command ftrace_cpudump_cmd = {
740 .func = ftrace_cpudump_callback,
743 static int __init init_func_cmd_traceon(void)
747 ret = register_ftrace_command(&ftrace_traceoff_cmd);
751 ret = register_ftrace_command(&ftrace_traceon_cmd);
753 goto out_free_traceoff;
755 ret = register_ftrace_command(&ftrace_stacktrace_cmd);
757 goto out_free_traceon;
759 ret = register_ftrace_command(&ftrace_dump_cmd);
761 goto out_free_stacktrace;
763 ret = register_ftrace_command(&ftrace_cpudump_cmd);
770 unregister_ftrace_command(&ftrace_dump_cmd);
772 unregister_ftrace_command(&ftrace_stacktrace_cmd);
774 unregister_ftrace_command(&ftrace_traceon_cmd);
776 unregister_ftrace_command(&ftrace_traceoff_cmd);
781 static inline int init_func_cmd_traceon(void)
785 #endif /* CONFIG_DYNAMIC_FTRACE */
787 __init int init_function_trace(void)
789 init_func_cmd_traceon();
790 return register_tracer(&function_trace);