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1#
2# Architectures that offer an FUNCTION_TRACER implementation should
3# select HAVE_FUNCTION_TRACER:
4#
5
6config USER_STACKTRACE_SUPPORT
7 bool
8
9config NOP_TRACER
10 bool
11
12config HAVE_FTRACE_NMI_ENTER
13 bool
14 help
15 See Documentation/trace/ftrace-design.txt
16
17config HAVE_FUNCTION_TRACER
18 bool
19 help
20 See Documentation/trace/ftrace-design.txt
21
22config HAVE_FUNCTION_GRAPH_TRACER
23 bool
24 help
25 See Documentation/trace/ftrace-design.txt
26
27config HAVE_FUNCTION_GRAPH_FP_TEST
28 bool
29 help
30 See Documentation/trace/ftrace-design.txt
31
32config HAVE_DYNAMIC_FTRACE
33 bool
34 help
35 See Documentation/trace/ftrace-design.txt
36
37config HAVE_DYNAMIC_FTRACE_WITH_REGS
38 bool
39
40config HAVE_FTRACE_MCOUNT_RECORD
41 bool
42 help
43 See Documentation/trace/ftrace-design.txt
44
45config HAVE_SYSCALL_TRACEPOINTS
46 bool
47 help
48 See Documentation/trace/ftrace-design.txt
49
50config HAVE_FENTRY
51 bool
52 help
53 Arch supports the gcc options -pg with -mfentry
54
55config HAVE_C_RECORDMCOUNT
56 bool
57 help
58 C version of recordmcount available?
59
60config TRACER_MAX_TRACE
61 bool
62
63config TRACE_CLOCK
64 bool
65
66config RING_BUFFER
67 bool
68 select TRACE_CLOCK
69 select IRQ_WORK
70
71config FTRACE_NMI_ENTER
72 bool
73 depends on HAVE_FTRACE_NMI_ENTER
74 default y
75
76config EVENT_TRACING
77 select CONTEXT_SWITCH_TRACER
78 bool
79
80config CONTEXT_SWITCH_TRACER
81 bool
82
83config RING_BUFFER_ALLOW_SWAP
84 bool
85 help
86 Allow the use of ring_buffer_swap_cpu.
87 Adds a very slight overhead to tracing when enabled.
88
89# All tracer options should select GENERIC_TRACER. For those options that are
90# enabled by all tracers (context switch and event tracer) they select TRACING.
91# This allows those options to appear when no other tracer is selected. But the
92# options do not appear when something else selects it. We need the two options
93# GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
94# hiding of the automatic options.
95
96config TRACING
97 bool
98 select DEBUG_FS
99 select RING_BUFFER
100 select STACKTRACE if STACKTRACE_SUPPORT
101 select TRACEPOINTS
102 select NOP_TRACER
103 select BINARY_PRINTF
104 select EVENT_TRACING
105 select TRACE_CLOCK
106
107config GENERIC_TRACER
108 bool
109 select TRACING
110
111#
112# Minimum requirements an architecture has to meet for us to
113# be able to offer generic tracing facilities:
114#
115config TRACING_SUPPORT
116 bool
117 # PPC32 has no irqflags tracing support, but it can use most of the
118 # tracers anyway, they were tested to build and work. Note that new
119 # exceptions to this list aren't welcomed, better implement the
120 # irqflags tracing for your architecture.
121 depends on TRACE_IRQFLAGS_SUPPORT || PPC32
122 depends on STACKTRACE_SUPPORT
123 default y
124
125if TRACING_SUPPORT
126
127menuconfig FTRACE
128 bool "Tracers"
129 default y if DEBUG_KERNEL
130 help
131 Enable the kernel tracing infrastructure.
132
133if FTRACE
134
135config FUNCTION_TRACER
136 bool "Kernel Function Tracer"
137 depends on HAVE_FUNCTION_TRACER
138 select KALLSYMS
139 select GENERIC_TRACER
140 select CONTEXT_SWITCH_TRACER
141 help
142 Enable the kernel to trace every kernel function. This is done
143 by using a compiler feature to insert a small, 5-byte No-Operation
144 instruction at the beginning of every kernel function, which NOP
145 sequence is then dynamically patched into a tracer call when
146 tracing is enabled by the administrator. If it's runtime disabled
147 (the bootup default), then the overhead of the instructions is very
148 small and not measurable even in micro-benchmarks.
149
150config FUNCTION_GRAPH_TRACER
151 bool "Kernel Function Graph Tracer"
152 depends on HAVE_FUNCTION_GRAPH_TRACER
153 depends on FUNCTION_TRACER
154 depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
155 default y
156 help
157 Enable the kernel to trace a function at both its return
158 and its entry.
159 Its first purpose is to trace the duration of functions and
160 draw a call graph for each thread with some information like
161 the return value. This is done by setting the current return
162 address on the current task structure into a stack of calls.
163
164
165config IRQSOFF_TRACER
166 bool "Interrupts-off Latency Tracer"
167 default n
168 depends on TRACE_IRQFLAGS_SUPPORT
169 depends on !ARCH_USES_GETTIMEOFFSET
170 select TRACE_IRQFLAGS
171 select GENERIC_TRACER
172 select TRACER_MAX_TRACE
173 select RING_BUFFER_ALLOW_SWAP
174 select TRACER_SNAPSHOT
175 select TRACER_SNAPSHOT_PER_CPU_SWAP
176 help
177 This option measures the time spent in irqs-off critical
178 sections, with microsecond accuracy.
179
180 The default measurement method is a maximum search, which is
181 disabled by default and can be runtime (re-)started
182 via:
183
184 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
185
186 (Note that kernel size and overhead increase with this option
187 enabled. This option and the preempt-off timing option can be
188 used together or separately.)
189
190config PREEMPT_TRACER
191 bool "Preemption-off Latency Tracer"
192 default n
193 depends on !ARCH_USES_GETTIMEOFFSET
194 depends on PREEMPT
195 select GENERIC_TRACER
196 select TRACER_MAX_TRACE
197 select RING_BUFFER_ALLOW_SWAP
198 select TRACER_SNAPSHOT
199 select TRACER_SNAPSHOT_PER_CPU_SWAP
200 help
201 This option measures the time spent in preemption-off critical
202 sections, with microsecond accuracy.
203
204 The default measurement method is a maximum search, which is
205 disabled by default and can be runtime (re-)started
206 via:
207
208 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
209
210 (Note that kernel size and overhead increase with this option
211 enabled. This option and the irqs-off timing option can be
212 used together or separately.)
213
214config SCHED_TRACER
215 bool "Scheduling Latency Tracer"
216 select GENERIC_TRACER
217 select CONTEXT_SWITCH_TRACER
218 select TRACER_MAX_TRACE
219 select TRACER_SNAPSHOT
220 help
221 This tracer tracks the latency of the highest priority task
222 to be scheduled in, starting from the point it has woken up.
223
224config ENABLE_DEFAULT_TRACERS
225 bool "Trace process context switches and events"
226 depends on !GENERIC_TRACER
227 select TRACING
228 help
229 This tracer hooks to various trace points in the kernel,
230 allowing the user to pick and choose which trace point they
231 want to trace. It also includes the sched_switch tracer plugin.
232
233config FTRACE_SYSCALLS
234 bool "Trace syscalls"
235 depends on HAVE_SYSCALL_TRACEPOINTS
236 select GENERIC_TRACER
237 select KALLSYMS
238 help
239 Basic tracer to catch the syscall entry and exit events.
240
241config TRACER_SNAPSHOT
242 bool "Create a snapshot trace buffer"
243 select TRACER_MAX_TRACE
244 help
245 Allow tracing users to take snapshot of the current buffer using the
246 ftrace interface, e.g.:
247
248 echo 1 > /sys/kernel/debug/tracing/snapshot
249 cat snapshot
250
251config TRACER_SNAPSHOT_PER_CPU_SWAP
252 bool "Allow snapshot to swap per CPU"
253 depends on TRACER_SNAPSHOT
254 select RING_BUFFER_ALLOW_SWAP
255 help
256 Allow doing a snapshot of a single CPU buffer instead of a
257 full swap (all buffers). If this is set, then the following is
258 allowed:
259
260 echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
261
262 After which, only the tracing buffer for CPU 2 was swapped with
263 the main tracing buffer, and the other CPU buffers remain the same.
264
265 When this is enabled, this adds a little more overhead to the
266 trace recording, as it needs to add some checks to synchronize
267 recording with swaps. But this does not affect the performance
268 of the overall system. This is enabled by default when the preempt
269 or irq latency tracers are enabled, as those need to swap as well
270 and already adds the overhead (plus a lot more).
271
272config TRACE_BRANCH_PROFILING
273 bool
274 select GENERIC_TRACER
275
276choice
277 prompt "Branch Profiling"
278 default BRANCH_PROFILE_NONE
279 help
280 The branch profiling is a software profiler. It will add hooks
281 into the C conditionals to test which path a branch takes.
282
283 The likely/unlikely profiler only looks at the conditions that
284 are annotated with a likely or unlikely macro.
285
286 The "all branch" profiler will profile every if-statement in the
287 kernel. This profiler will also enable the likely/unlikely
288 profiler.
289
290 Either of the above profilers adds a bit of overhead to the system.
291 If unsure, choose "No branch profiling".
292
293config BRANCH_PROFILE_NONE
294 bool "No branch profiling"
295 help
296 No branch profiling. Branch profiling adds a bit of overhead.
297 Only enable it if you want to analyse the branching behavior.
298 Otherwise keep it disabled.
299
300config PROFILE_ANNOTATED_BRANCHES
301 bool "Trace likely/unlikely profiler"
302 select TRACE_BRANCH_PROFILING
303 help
304 This tracer profiles all likely and unlikely macros
305 in the kernel. It will display the results in:
306
307 /sys/kernel/debug/tracing/trace_stat/branch_annotated
308
309 Note: this will add a significant overhead; only turn this
310 on if you need to profile the system's use of these macros.
311
312config PROFILE_ALL_BRANCHES
313 bool "Profile all if conditionals"
314 select TRACE_BRANCH_PROFILING
315 help
316 This tracer profiles all branch conditions. Every if ()
317 taken in the kernel is recorded whether it hit or miss.
318 The results will be displayed in:
319
320 /sys/kernel/debug/tracing/trace_stat/branch_all
321
322 This option also enables the likely/unlikely profiler.
323
324 This configuration, when enabled, will impose a great overhead
325 on the system. This should only be enabled when the system
326 is to be analyzed in much detail.
327endchoice
328
329config TRACING_BRANCHES
330 bool
331 help
332 Selected by tracers that will trace the likely and unlikely
333 conditions. This prevents the tracers themselves from being
334 profiled. Profiling the tracing infrastructure can only happen
335 when the likelys and unlikelys are not being traced.
336
337config BRANCH_TRACER
338 bool "Trace likely/unlikely instances"
339 depends on TRACE_BRANCH_PROFILING
340 select TRACING_BRANCHES
341 help
342 This traces the events of likely and unlikely condition
343 calls in the kernel. The difference between this and the
344 "Trace likely/unlikely profiler" is that this is not a
345 histogram of the callers, but actually places the calling
346 events into a running trace buffer to see when and where the
347 events happened, as well as their results.
348
349 Say N if unsure.
350
351config STACK_TRACER
352 bool "Trace max stack"
353 depends on HAVE_FUNCTION_TRACER
354 select FUNCTION_TRACER
355 select STACKTRACE
356 select KALLSYMS
357 help
358 This special tracer records the maximum stack footprint of the
359 kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
360
361 This tracer works by hooking into every function call that the
362 kernel executes, and keeping a maximum stack depth value and
363 stack-trace saved. If this is configured with DYNAMIC_FTRACE
364 then it will not have any overhead while the stack tracer
365 is disabled.
366
367 To enable the stack tracer on bootup, pass in 'stacktrace'
368 on the kernel command line.
369
370 The stack tracer can also be enabled or disabled via the
371 sysctl kernel.stack_tracer_enabled
372
373 Say N if unsure.
374
375config BLK_DEV_IO_TRACE
376 bool "Support for tracing block IO actions"
377 depends on SYSFS
378 depends on BLOCK
379 select RELAY
380 select DEBUG_FS
381 select TRACEPOINTS
382 select GENERIC_TRACER
383 select STACKTRACE
384 help
385 Say Y here if you want to be able to trace the block layer actions
386 on a given queue. Tracing allows you to see any traffic happening
387 on a block device queue. For more information (and the userspace
388 support tools needed), fetch the blktrace tools from:
389
390 git://git.kernel.dk/blktrace.git
391
392 Tracing also is possible using the ftrace interface, e.g.:
393
394 echo 1 > /sys/block/sda/sda1/trace/enable
395 echo blk > /sys/kernel/debug/tracing/current_tracer
396 cat /sys/kernel/debug/tracing/trace_pipe
397
398 If unsure, say N.
399
400config KPROBE_EVENT
401 depends on KPROBES
402 depends on HAVE_REGS_AND_STACK_ACCESS_API
403 bool "Enable kprobes-based dynamic events"
404 select TRACING
405 select PROBE_EVENTS
406 default y
407 help
408 This allows the user to add tracing events (similar to tracepoints)
409 on the fly via the ftrace interface. See
410 Documentation/trace/kprobetrace.txt for more details.
411
412 Those events can be inserted wherever kprobes can probe, and record
413 various register and memory values.
414
415 This option is also required by perf-probe subcommand of perf tools.
416 If you want to use perf tools, this option is strongly recommended.
417
418config UPROBE_EVENT
419 bool "Enable uprobes-based dynamic events"
420 depends on ARCH_SUPPORTS_UPROBES
421 depends on MMU
422 depends on PERF_EVENTS
423 select UPROBES
424 select PROBE_EVENTS
425 select TRACING
426 default n
427 help
428 This allows the user to add tracing events on top of userspace
429 dynamic events (similar to tracepoints) on the fly via the trace
430 events interface. Those events can be inserted wherever uprobes
431 can probe, and record various registers.
432 This option is required if you plan to use perf-probe subcommand
433 of perf tools on user space applications.
434
435config BPF_EVENTS
436 depends on BPF_SYSCALL
437 depends on (KPROBE_EVENT || UPROBE_EVENT) && PERF_EVENTS
438 bool
439 default y
440 help
441 This allows the user to attach BPF programs to kprobe events.
442
443config PROBE_EVENTS
444 def_bool n
445
446config DYNAMIC_FTRACE
447 bool "enable/disable function tracing dynamically"
448 depends on FUNCTION_TRACER
449 depends on HAVE_DYNAMIC_FTRACE
450 default y
451 help
452 This option will modify all the calls to function tracing
453 dynamically (will patch them out of the binary image and
454 replace them with a No-Op instruction) on boot up. During
455 compile time, a table is made of all the locations that ftrace
456 can function trace, and this table is linked into the kernel
457 image. When this is enabled, functions can be individually
458 enabled, and the functions not enabled will not affect
459 performance of the system.
460
461 See the files in /sys/kernel/debug/tracing:
462 available_filter_functions
463 set_ftrace_filter
464 set_ftrace_notrace
465
466 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
467 otherwise has native performance as long as no tracing is active.
468
469config DYNAMIC_FTRACE_WITH_REGS
470 def_bool y
471 depends on DYNAMIC_FTRACE
472 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
473
474config FUNCTION_PROFILER
475 bool "Kernel function profiler"
476 depends on FUNCTION_TRACER
477 default n
478 help
479 This option enables the kernel function profiler. A file is created
480 in debugfs called function_profile_enabled which defaults to zero.
481 When a 1 is echoed into this file profiling begins, and when a
482 zero is entered, profiling stops. A "functions" file is created in
483 the trace_stats directory; this file shows the list of functions that
484 have been hit and their counters.
485
486 If in doubt, say N.
487
488config FTRACE_MCOUNT_RECORD
489 def_bool y
490 depends on DYNAMIC_FTRACE
491 depends on HAVE_FTRACE_MCOUNT_RECORD
492
493config FTRACE_SELFTEST
494 bool
495
496config FTRACE_STARTUP_TEST
497 bool "Perform a startup test on ftrace"
498 depends on GENERIC_TRACER
499 select FTRACE_SELFTEST
500 help
501 This option performs a series of startup tests on ftrace. On bootup
502 a series of tests are made to verify that the tracer is
503 functioning properly. It will do tests on all the configured
504 tracers of ftrace.
505
506config EVENT_TRACE_TEST_SYSCALLS
507 bool "Run selftest on syscall events"
508 depends on FTRACE_STARTUP_TEST
509 help
510 This option will also enable testing every syscall event.
511 It only enables the event and disables it and runs various loads
512 with the event enabled. This adds a bit more time for kernel boot
513 up since it runs this on every system call defined.
514
515 TBD - enable a way to actually call the syscalls as we test their
516 events
517
518config MMIOTRACE
519 bool "Memory mapped IO tracing"
520 depends on HAVE_MMIOTRACE_SUPPORT && PCI
521 select GENERIC_TRACER
522 help
523 Mmiotrace traces Memory Mapped I/O access and is meant for
524 debugging and reverse engineering. It is called from the ioremap
525 implementation and works via page faults. Tracing is disabled by
526 default and can be enabled at run-time.
527
528 See Documentation/trace/mmiotrace.txt.
529 If you are not helping to develop drivers, say N.
530
531config MMIOTRACE_TEST
532 tristate "Test module for mmiotrace"
533 depends on MMIOTRACE && m
534 help
535 This is a dumb module for testing mmiotrace. It is very dangerous
536 as it will write garbage to IO memory starting at a given address.
537 However, it should be safe to use on e.g. unused portion of VRAM.
538
539 Say N, unless you absolutely know what you are doing.
540
541config TRACEPOINT_BENCHMARK
542 bool "Add tracepoint that benchmarks tracepoints"
543 help
544 This option creates the tracepoint "benchmark:benchmark_event".
545 When the tracepoint is enabled, it kicks off a kernel thread that
546 goes into an infinite loop (calling cond_sched() to let other tasks
547 run), and calls the tracepoint. Each iteration will record the time
548 it took to write to the tracepoint and the next iteration that
549 data will be passed to the tracepoint itself. That is, the tracepoint
550 will report the time it took to do the previous tracepoint.
551 The string written to the tracepoint is a static string of 128 bytes
552 to keep the time the same. The initial string is simply a write of
553 "START". The second string records the cold cache time of the first
554 write which is not added to the rest of the calculations.
555
556 As it is a tight loop, it benchmarks as hot cache. That's fine because
557 we care most about hot paths that are probably in cache already.
558
559 An example of the output:
560
561 START
562 first=3672 [COLD CACHED]
563 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
564 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
565 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
566 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
567 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
568 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
569
570
571config RING_BUFFER_BENCHMARK
572 tristate "Ring buffer benchmark stress tester"
573 depends on RING_BUFFER
574 help
575 This option creates a test to stress the ring buffer and benchmark it.
576 It creates its own ring buffer such that it will not interfere with
577 any other users of the ring buffer (such as ftrace). It then creates
578 a producer and consumer that will run for 10 seconds and sleep for
579 10 seconds. Each interval it will print out the number of events
580 it recorded and give a rough estimate of how long each iteration took.
581
582 It does not disable interrupts or raise its priority, so it may be
583 affected by processes that are running.
584
585 If unsure, say N.
586
587config RING_BUFFER_STARTUP_TEST
588 bool "Ring buffer startup self test"
589 depends on RING_BUFFER
590 help
591 Run a simple self test on the ring buffer on boot up. Late in the
592 kernel boot sequence, the test will start that kicks off
593 a thread per cpu. Each thread will write various size events
594 into the ring buffer. Another thread is created to send IPIs
595 to each of the threads, where the IPI handler will also write
596 to the ring buffer, to test/stress the nesting ability.
597 If any anomalies are discovered, a warning will be displayed
598 and all ring buffers will be disabled.
599
600 The test runs for 10 seconds. This will slow your boot time
601 by at least 10 more seconds.
602
603 At the end of the test, statics and more checks are done.
604 It will output the stats of each per cpu buffer. What
605 was written, the sizes, what was read, what was lost, and
606 other similar details.
607
608 If unsure, say N
609
610config TRACE_ENUM_MAP_FILE
611 bool "Show enum mappings for trace events"
612 depends on TRACING
613 help
614 The "print fmt" of the trace events will show the enum names instead
615 of their values. This can cause problems for user space tools that
616 use this string to parse the raw data as user space does not know
617 how to convert the string to its value.
618
619 To fix this, there's a special macro in the kernel that can be used
620 to convert the enum into its value. If this macro is used, then the
621 print fmt strings will have the enums converted to their values.
622
623 If something does not get converted properly, this option can be
624 used to show what enums the kernel tried to convert.
625
626 This option is for debugging the enum conversions. A file is created
627 in the tracing directory called "enum_map" that will show the enum
628 names matched with their values and what trace event system they
629 belong too.
630
631 Normally, the mapping of the strings to values will be freed after
632 boot up or module load. With this option, they will not be freed, as
633 they are needed for the "enum_map" file. Enabling this option will
634 increase the memory footprint of the running kernel.
635
636 If unsure, say N
637
638config TRACING_EVENTS_GPIO
639 bool "Trace gpio events"
640 depends on GPIOLIB
641 default y
642 help
643 Enable tracing events for gpio subsystem
644
645endif # FTRACE
646
647endif # TRACING_SUPPORT
648
1# SPDX-License-Identifier: GPL-2.0-only
2#
3# Architectures that offer an FUNCTION_TRACER implementation should
4# select HAVE_FUNCTION_TRACER:
5#
6
7config USER_STACKTRACE_SUPPORT
8 bool
9
10config NOP_TRACER
11 bool
12
13config HAVE_FTRACE_NMI_ENTER
14 bool
15 help
16 See Documentation/trace/ftrace-design.rst
17
18config HAVE_FUNCTION_TRACER
19 bool
20 help
21 See Documentation/trace/ftrace-design.rst
22
23config HAVE_FUNCTION_GRAPH_TRACER
24 bool
25 help
26 See Documentation/trace/ftrace-design.rst
27
28config HAVE_DYNAMIC_FTRACE
29 bool
30 help
31 See Documentation/trace/ftrace-design.rst
32
33config HAVE_DYNAMIC_FTRACE_WITH_REGS
34 bool
35
36config HAVE_FTRACE_MCOUNT_RECORD
37 bool
38 help
39 See Documentation/trace/ftrace-design.rst
40
41config HAVE_SYSCALL_TRACEPOINTS
42 bool
43 help
44 See Documentation/trace/ftrace-design.rst
45
46config HAVE_FENTRY
47 bool
48 help
49 Arch supports the gcc options -pg with -mfentry
50
51config HAVE_NOP_MCOUNT
52 bool
53 help
54 Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
55
56config HAVE_C_RECORDMCOUNT
57 bool
58 help
59 C version of recordmcount available?
60
61config TRACER_MAX_TRACE
62 bool
63
64config TRACE_CLOCK
65 bool
66
67config RING_BUFFER
68 bool
69 select TRACE_CLOCK
70 select IRQ_WORK
71
72config FTRACE_NMI_ENTER
73 bool
74 depends on HAVE_FTRACE_NMI_ENTER
75 default y
76
77config EVENT_TRACING
78 select CONTEXT_SWITCH_TRACER
79 select GLOB
80 bool
81
82config CONTEXT_SWITCH_TRACER
83 bool
84
85config RING_BUFFER_ALLOW_SWAP
86 bool
87 help
88 Allow the use of ring_buffer_swap_cpu.
89 Adds a very slight overhead to tracing when enabled.
90
91config PREEMPTIRQ_TRACEPOINTS
92 bool
93 depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
94 select TRACING
95 default y
96 help
97 Create preempt/irq toggle tracepoints if needed, so that other parts
98 of the kernel can use them to generate or add hooks to them.
99
100# All tracer options should select GENERIC_TRACER. For those options that are
101# enabled by all tracers (context switch and event tracer) they select TRACING.
102# This allows those options to appear when no other tracer is selected. But the
103# options do not appear when something else selects it. We need the two options
104# GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
105# hiding of the automatic options.
106
107config TRACING
108 bool
109 select DEBUG_FS
110 select RING_BUFFER
111 select STACKTRACE if STACKTRACE_SUPPORT
112 select TRACEPOINTS
113 select NOP_TRACER
114 select BINARY_PRINTF
115 select EVENT_TRACING
116 select TRACE_CLOCK
117
118config GENERIC_TRACER
119 bool
120 select TRACING
121
122#
123# Minimum requirements an architecture has to meet for us to
124# be able to offer generic tracing facilities:
125#
126config TRACING_SUPPORT
127 bool
128 depends on TRACE_IRQFLAGS_SUPPORT
129 depends on STACKTRACE_SUPPORT
130 default y
131
132if TRACING_SUPPORT
133
134menuconfig FTRACE
135 bool "Tracers"
136 default y if DEBUG_KERNEL
137 help
138 Enable the kernel tracing infrastructure.
139
140if FTRACE
141
142config FUNCTION_TRACER
143 bool "Kernel Function Tracer"
144 depends on HAVE_FUNCTION_TRACER
145 select KALLSYMS
146 select GENERIC_TRACER
147 select CONTEXT_SWITCH_TRACER
148 select GLOB
149 select TASKS_RCU if PREEMPTION
150 help
151 Enable the kernel to trace every kernel function. This is done
152 by using a compiler feature to insert a small, 5-byte No-Operation
153 instruction at the beginning of every kernel function, which NOP
154 sequence is then dynamically patched into a tracer call when
155 tracing is enabled by the administrator. If it's runtime disabled
156 (the bootup default), then the overhead of the instructions is very
157 small and not measurable even in micro-benchmarks.
158
159config FUNCTION_GRAPH_TRACER
160 bool "Kernel Function Graph Tracer"
161 depends on HAVE_FUNCTION_GRAPH_TRACER
162 depends on FUNCTION_TRACER
163 depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
164 default y
165 help
166 Enable the kernel to trace a function at both its return
167 and its entry.
168 Its first purpose is to trace the duration of functions and
169 draw a call graph for each thread with some information like
170 the return value. This is done by setting the current return
171 address on the current task structure into a stack of calls.
172
173config TRACE_PREEMPT_TOGGLE
174 bool
175 help
176 Enables hooks which will be called when preemption is first disabled,
177 and last enabled.
178
179config PREEMPTIRQ_EVENTS
180 bool "Enable trace events for preempt and irq disable/enable"
181 select TRACE_IRQFLAGS
182 select TRACE_PREEMPT_TOGGLE if PREEMPTION
183 select GENERIC_TRACER
184 default n
185 help
186 Enable tracing of disable and enable events for preemption and irqs.
187
188config IRQSOFF_TRACER
189 bool "Interrupts-off Latency Tracer"
190 default n
191 depends on TRACE_IRQFLAGS_SUPPORT
192 depends on !ARCH_USES_GETTIMEOFFSET
193 select TRACE_IRQFLAGS
194 select GENERIC_TRACER
195 select TRACER_MAX_TRACE
196 select RING_BUFFER_ALLOW_SWAP
197 select TRACER_SNAPSHOT
198 select TRACER_SNAPSHOT_PER_CPU_SWAP
199 help
200 This option measures the time spent in irqs-off critical
201 sections, with microsecond accuracy.
202
203 The default measurement method is a maximum search, which is
204 disabled by default and can be runtime (re-)started
205 via:
206
207 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
208
209 (Note that kernel size and overhead increase with this option
210 enabled. This option and the preempt-off timing option can be
211 used together or separately.)
212
213config PREEMPT_TRACER
214 bool "Preemption-off Latency Tracer"
215 default n
216 depends on !ARCH_USES_GETTIMEOFFSET
217 depends on PREEMPTION
218 select GENERIC_TRACER
219 select TRACER_MAX_TRACE
220 select RING_BUFFER_ALLOW_SWAP
221 select TRACER_SNAPSHOT
222 select TRACER_SNAPSHOT_PER_CPU_SWAP
223 select TRACE_PREEMPT_TOGGLE
224 help
225 This option measures the time spent in preemption-off critical
226 sections, with microsecond accuracy.
227
228 The default measurement method is a maximum search, which is
229 disabled by default and can be runtime (re-)started
230 via:
231
232 echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
233
234 (Note that kernel size and overhead increase with this option
235 enabled. This option and the irqs-off timing option can be
236 used together or separately.)
237
238config SCHED_TRACER
239 bool "Scheduling Latency Tracer"
240 select GENERIC_TRACER
241 select CONTEXT_SWITCH_TRACER
242 select TRACER_MAX_TRACE
243 select TRACER_SNAPSHOT
244 help
245 This tracer tracks the latency of the highest priority task
246 to be scheduled in, starting from the point it has woken up.
247
248config HWLAT_TRACER
249 bool "Tracer to detect hardware latencies (like SMIs)"
250 select GENERIC_TRACER
251 help
252 This tracer, when enabled will create one or more kernel threads,
253 depending on what the cpumask file is set to, which each thread
254 spinning in a loop looking for interruptions caused by
255 something other than the kernel. For example, if a
256 System Management Interrupt (SMI) takes a noticeable amount of
257 time, this tracer will detect it. This is useful for testing
258 if a system is reliable for Real Time tasks.
259
260 Some files are created in the tracing directory when this
261 is enabled:
262
263 hwlat_detector/width - time in usecs for how long to spin for
264 hwlat_detector/window - time in usecs between the start of each
265 iteration
266
267 A kernel thread is created that will spin with interrupts disabled
268 for "width" microseconds in every "window" cycle. It will not spin
269 for "window - width" microseconds, where the system can
270 continue to operate.
271
272 The output will appear in the trace and trace_pipe files.
273
274 When the tracer is not running, it has no affect on the system,
275 but when it is running, it can cause the system to be
276 periodically non responsive. Do not run this tracer on a
277 production system.
278
279 To enable this tracer, echo in "hwlat" into the current_tracer
280 file. Every time a latency is greater than tracing_thresh, it will
281 be recorded into the ring buffer.
282
283config ENABLE_DEFAULT_TRACERS
284 bool "Trace process context switches and events"
285 depends on !GENERIC_TRACER
286 select TRACING
287 help
288 This tracer hooks to various trace points in the kernel,
289 allowing the user to pick and choose which trace point they
290 want to trace. It also includes the sched_switch tracer plugin.
291
292config FTRACE_SYSCALLS
293 bool "Trace syscalls"
294 depends on HAVE_SYSCALL_TRACEPOINTS
295 select GENERIC_TRACER
296 select KALLSYMS
297 help
298 Basic tracer to catch the syscall entry and exit events.
299
300config TRACER_SNAPSHOT
301 bool "Create a snapshot trace buffer"
302 select TRACER_MAX_TRACE
303 help
304 Allow tracing users to take snapshot of the current buffer using the
305 ftrace interface, e.g.:
306
307 echo 1 > /sys/kernel/debug/tracing/snapshot
308 cat snapshot
309
310config TRACER_SNAPSHOT_PER_CPU_SWAP
311 bool "Allow snapshot to swap per CPU"
312 depends on TRACER_SNAPSHOT
313 select RING_BUFFER_ALLOW_SWAP
314 help
315 Allow doing a snapshot of a single CPU buffer instead of a
316 full swap (all buffers). If this is set, then the following is
317 allowed:
318
319 echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
320
321 After which, only the tracing buffer for CPU 2 was swapped with
322 the main tracing buffer, and the other CPU buffers remain the same.
323
324 When this is enabled, this adds a little more overhead to the
325 trace recording, as it needs to add some checks to synchronize
326 recording with swaps. But this does not affect the performance
327 of the overall system. This is enabled by default when the preempt
328 or irq latency tracers are enabled, as those need to swap as well
329 and already adds the overhead (plus a lot more).
330
331config TRACE_BRANCH_PROFILING
332 bool
333 select GENERIC_TRACER
334
335choice
336 prompt "Branch Profiling"
337 default BRANCH_PROFILE_NONE
338 help
339 The branch profiling is a software profiler. It will add hooks
340 into the C conditionals to test which path a branch takes.
341
342 The likely/unlikely profiler only looks at the conditions that
343 are annotated with a likely or unlikely macro.
344
345 The "all branch" profiler will profile every if-statement in the
346 kernel. This profiler will also enable the likely/unlikely
347 profiler.
348
349 Either of the above profilers adds a bit of overhead to the system.
350 If unsure, choose "No branch profiling".
351
352config BRANCH_PROFILE_NONE
353 bool "No branch profiling"
354 help
355 No branch profiling. Branch profiling adds a bit of overhead.
356 Only enable it if you want to analyse the branching behavior.
357 Otherwise keep it disabled.
358
359config PROFILE_ANNOTATED_BRANCHES
360 bool "Trace likely/unlikely profiler"
361 select TRACE_BRANCH_PROFILING
362 help
363 This tracer profiles all likely and unlikely macros
364 in the kernel. It will display the results in:
365
366 /sys/kernel/debug/tracing/trace_stat/branch_annotated
367
368 Note: this will add a significant overhead; only turn this
369 on if you need to profile the system's use of these macros.
370
371config PROFILE_ALL_BRANCHES
372 bool "Profile all if conditionals" if !FORTIFY_SOURCE
373 select TRACE_BRANCH_PROFILING
374 imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
375 help
376 This tracer profiles all branch conditions. Every if ()
377 taken in the kernel is recorded whether it hit or miss.
378 The results will be displayed in:
379
380 /sys/kernel/debug/tracing/trace_stat/branch_all
381
382 This option also enables the likely/unlikely profiler.
383
384 This configuration, when enabled, will impose a great overhead
385 on the system. This should only be enabled when the system
386 is to be analyzed in much detail.
387endchoice
388
389config TRACING_BRANCHES
390 bool
391 help
392 Selected by tracers that will trace the likely and unlikely
393 conditions. This prevents the tracers themselves from being
394 profiled. Profiling the tracing infrastructure can only happen
395 when the likelys and unlikelys are not being traced.
396
397config BRANCH_TRACER
398 bool "Trace likely/unlikely instances"
399 depends on TRACE_BRANCH_PROFILING
400 select TRACING_BRANCHES
401 help
402 This traces the events of likely and unlikely condition
403 calls in the kernel. The difference between this and the
404 "Trace likely/unlikely profiler" is that this is not a
405 histogram of the callers, but actually places the calling
406 events into a running trace buffer to see when and where the
407 events happened, as well as their results.
408
409 Say N if unsure.
410
411config STACK_TRACER
412 bool "Trace max stack"
413 depends on HAVE_FUNCTION_TRACER
414 select FUNCTION_TRACER
415 select STACKTRACE
416 select KALLSYMS
417 help
418 This special tracer records the maximum stack footprint of the
419 kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
420
421 This tracer works by hooking into every function call that the
422 kernel executes, and keeping a maximum stack depth value and
423 stack-trace saved. If this is configured with DYNAMIC_FTRACE
424 then it will not have any overhead while the stack tracer
425 is disabled.
426
427 To enable the stack tracer on bootup, pass in 'stacktrace'
428 on the kernel command line.
429
430 The stack tracer can also be enabled or disabled via the
431 sysctl kernel.stack_tracer_enabled
432
433 Say N if unsure.
434
435config BLK_DEV_IO_TRACE
436 bool "Support for tracing block IO actions"
437 depends on SYSFS
438 depends on BLOCK
439 select RELAY
440 select DEBUG_FS
441 select TRACEPOINTS
442 select GENERIC_TRACER
443 select STACKTRACE
444 help
445 Say Y here if you want to be able to trace the block layer actions
446 on a given queue. Tracing allows you to see any traffic happening
447 on a block device queue. For more information (and the userspace
448 support tools needed), fetch the blktrace tools from:
449
450 git://git.kernel.dk/blktrace.git
451
452 Tracing also is possible using the ftrace interface, e.g.:
453
454 echo 1 > /sys/block/sda/sda1/trace/enable
455 echo blk > /sys/kernel/debug/tracing/current_tracer
456 cat /sys/kernel/debug/tracing/trace_pipe
457
458 If unsure, say N.
459
460config KPROBE_EVENTS
461 depends on KPROBES
462 depends on HAVE_REGS_AND_STACK_ACCESS_API
463 bool "Enable kprobes-based dynamic events"
464 select TRACING
465 select PROBE_EVENTS
466 select DYNAMIC_EVENTS
467 default y
468 help
469 This allows the user to add tracing events (similar to tracepoints)
470 on the fly via the ftrace interface. See
471 Documentation/trace/kprobetrace.rst for more details.
472
473 Those events can be inserted wherever kprobes can probe, and record
474 various register and memory values.
475
476 This option is also required by perf-probe subcommand of perf tools.
477 If you want to use perf tools, this option is strongly recommended.
478
479config KPROBE_EVENTS_ON_NOTRACE
480 bool "Do NOT protect notrace function from kprobe events"
481 depends on KPROBE_EVENTS
482 depends on KPROBES_ON_FTRACE
483 default n
484 help
485 This is only for the developers who want to debug ftrace itself
486 using kprobe events.
487
488 If kprobes can use ftrace instead of breakpoint, ftrace related
489 functions are protected from kprobe-events to prevent an infinit
490 recursion or any unexpected execution path which leads to a kernel
491 crash.
492
493 This option disables such protection and allows you to put kprobe
494 events on ftrace functions for debugging ftrace by itself.
495 Note that this might let you shoot yourself in the foot.
496
497 If unsure, say N.
498
499config UPROBE_EVENTS
500 bool "Enable uprobes-based dynamic events"
501 depends on ARCH_SUPPORTS_UPROBES
502 depends on MMU
503 depends on PERF_EVENTS
504 select UPROBES
505 select PROBE_EVENTS
506 select DYNAMIC_EVENTS
507 select TRACING
508 default y
509 help
510 This allows the user to add tracing events on top of userspace
511 dynamic events (similar to tracepoints) on the fly via the trace
512 events interface. Those events can be inserted wherever uprobes
513 can probe, and record various registers.
514 This option is required if you plan to use perf-probe subcommand
515 of perf tools on user space applications.
516
517config BPF_EVENTS
518 depends on BPF_SYSCALL
519 depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
520 bool
521 default y
522 help
523 This allows the user to attach BPF programs to kprobe, uprobe, and
524 tracepoint events.
525
526config DYNAMIC_EVENTS
527 def_bool n
528
529config PROBE_EVENTS
530 def_bool n
531
532config DYNAMIC_FTRACE
533 bool "enable/disable function tracing dynamically"
534 depends on FUNCTION_TRACER
535 depends on HAVE_DYNAMIC_FTRACE
536 default y
537 help
538 This option will modify all the calls to function tracing
539 dynamically (will patch them out of the binary image and
540 replace them with a No-Op instruction) on boot up. During
541 compile time, a table is made of all the locations that ftrace
542 can function trace, and this table is linked into the kernel
543 image. When this is enabled, functions can be individually
544 enabled, and the functions not enabled will not affect
545 performance of the system.
546
547 See the files in /sys/kernel/debug/tracing:
548 available_filter_functions
549 set_ftrace_filter
550 set_ftrace_notrace
551
552 This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
553 otherwise has native performance as long as no tracing is active.
554
555config DYNAMIC_FTRACE_WITH_REGS
556 def_bool y
557 depends on DYNAMIC_FTRACE
558 depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
559
560config FUNCTION_PROFILER
561 bool "Kernel function profiler"
562 depends on FUNCTION_TRACER
563 default n
564 help
565 This option enables the kernel function profiler. A file is created
566 in debugfs called function_profile_enabled which defaults to zero.
567 When a 1 is echoed into this file profiling begins, and when a
568 zero is entered, profiling stops. A "functions" file is created in
569 the trace_stat directory; this file shows the list of functions that
570 have been hit and their counters.
571
572 If in doubt, say N.
573
574config BPF_KPROBE_OVERRIDE
575 bool "Enable BPF programs to override a kprobed function"
576 depends on BPF_EVENTS
577 depends on FUNCTION_ERROR_INJECTION
578 default n
579 help
580 Allows BPF to override the execution of a probed function and
581 set a different return value. This is used for error injection.
582
583config FTRACE_MCOUNT_RECORD
584 def_bool y
585 depends on DYNAMIC_FTRACE
586 depends on HAVE_FTRACE_MCOUNT_RECORD
587
588config FTRACE_SELFTEST
589 bool
590
591config FTRACE_STARTUP_TEST
592 bool "Perform a startup test on ftrace"
593 depends on GENERIC_TRACER
594 select FTRACE_SELFTEST
595 help
596 This option performs a series of startup tests on ftrace. On bootup
597 a series of tests are made to verify that the tracer is
598 functioning properly. It will do tests on all the configured
599 tracers of ftrace.
600
601config EVENT_TRACE_STARTUP_TEST
602 bool "Run selftest on trace events"
603 depends on FTRACE_STARTUP_TEST
604 default y
605 help
606 This option performs a test on all trace events in the system.
607 It basically just enables each event and runs some code that
608 will trigger events (not necessarily the event it enables)
609 This may take some time run as there are a lot of events.
610
611config EVENT_TRACE_TEST_SYSCALLS
612 bool "Run selftest on syscall events"
613 depends on EVENT_TRACE_STARTUP_TEST
614 help
615 This option will also enable testing every syscall event.
616 It only enables the event and disables it and runs various loads
617 with the event enabled. This adds a bit more time for kernel boot
618 up since it runs this on every system call defined.
619
620 TBD - enable a way to actually call the syscalls as we test their
621 events
622
623config MMIOTRACE
624 bool "Memory mapped IO tracing"
625 depends on HAVE_MMIOTRACE_SUPPORT && PCI
626 select GENERIC_TRACER
627 help
628 Mmiotrace traces Memory Mapped I/O access and is meant for
629 debugging and reverse engineering. It is called from the ioremap
630 implementation and works via page faults. Tracing is disabled by
631 default and can be enabled at run-time.
632
633 See Documentation/trace/mmiotrace.rst.
634 If you are not helping to develop drivers, say N.
635
636config TRACING_MAP
637 bool
638 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
639 help
640 tracing_map is a special-purpose lock-free map for tracing,
641 separated out as a stand-alone facility in order to allow it
642 to be shared between multiple tracers. It isn't meant to be
643 generally used outside of that context, and is normally
644 selected by tracers that use it.
645
646config HIST_TRIGGERS
647 bool "Histogram triggers"
648 depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
649 select TRACING_MAP
650 select TRACING
651 select DYNAMIC_EVENTS
652 default n
653 help
654 Hist triggers allow one or more arbitrary trace event fields
655 to be aggregated into hash tables and dumped to stdout by
656 reading a debugfs/tracefs file. They're useful for
657 gathering quick and dirty (though precise) summaries of
658 event activity as an initial guide for further investigation
659 using more advanced tools.
660
661 Inter-event tracing of quantities such as latencies is also
662 supported using hist triggers under this option.
663
664 See Documentation/trace/histogram.rst.
665 If in doubt, say N.
666
667config MMIOTRACE_TEST
668 tristate "Test module for mmiotrace"
669 depends on MMIOTRACE && m
670 help
671 This is a dumb module for testing mmiotrace. It is very dangerous
672 as it will write garbage to IO memory starting at a given address.
673 However, it should be safe to use on e.g. unused portion of VRAM.
674
675 Say N, unless you absolutely know what you are doing.
676
677config TRACEPOINT_BENCHMARK
678 bool "Add tracepoint that benchmarks tracepoints"
679 help
680 This option creates the tracepoint "benchmark:benchmark_event".
681 When the tracepoint is enabled, it kicks off a kernel thread that
682 goes into an infinite loop (calling cond_sched() to let other tasks
683 run), and calls the tracepoint. Each iteration will record the time
684 it took to write to the tracepoint and the next iteration that
685 data will be passed to the tracepoint itself. That is, the tracepoint
686 will report the time it took to do the previous tracepoint.
687 The string written to the tracepoint is a static string of 128 bytes
688 to keep the time the same. The initial string is simply a write of
689 "START". The second string records the cold cache time of the first
690 write which is not added to the rest of the calculations.
691
692 As it is a tight loop, it benchmarks as hot cache. That's fine because
693 we care most about hot paths that are probably in cache already.
694
695 An example of the output:
696
697 START
698 first=3672 [COLD CACHED]
699 last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
700 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
701 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
702 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
703 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
704 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
705
706
707config RING_BUFFER_BENCHMARK
708 tristate "Ring buffer benchmark stress tester"
709 depends on RING_BUFFER
710 help
711 This option creates a test to stress the ring buffer and benchmark it.
712 It creates its own ring buffer such that it will not interfere with
713 any other users of the ring buffer (such as ftrace). It then creates
714 a producer and consumer that will run for 10 seconds and sleep for
715 10 seconds. Each interval it will print out the number of events
716 it recorded and give a rough estimate of how long each iteration took.
717
718 It does not disable interrupts or raise its priority, so it may be
719 affected by processes that are running.
720
721 If unsure, say N.
722
723config RING_BUFFER_STARTUP_TEST
724 bool "Ring buffer startup self test"
725 depends on RING_BUFFER
726 help
727 Run a simple self test on the ring buffer on boot up. Late in the
728 kernel boot sequence, the test will start that kicks off
729 a thread per cpu. Each thread will write various size events
730 into the ring buffer. Another thread is created to send IPIs
731 to each of the threads, where the IPI handler will also write
732 to the ring buffer, to test/stress the nesting ability.
733 If any anomalies are discovered, a warning will be displayed
734 and all ring buffers will be disabled.
735
736 The test runs for 10 seconds. This will slow your boot time
737 by at least 10 more seconds.
738
739 At the end of the test, statics and more checks are done.
740 It will output the stats of each per cpu buffer. What
741 was written, the sizes, what was read, what was lost, and
742 other similar details.
743
744 If unsure, say N
745
746config PREEMPTIRQ_DELAY_TEST
747 tristate "Preempt / IRQ disable delay thread to test latency tracers"
748 depends on m
749 help
750 Select this option to build a test module that can help test latency
751 tracers by executing a preempt or irq disable section with a user
752 configurable delay. The module busy waits for the duration of the
753 critical section.
754
755 For example, the following invocation forces a one-time irq-disabled
756 critical section for 500us:
757 modprobe preemptirq_delay_test test_mode=irq delay=500000
758
759 If unsure, say N
760
761config TRACE_EVAL_MAP_FILE
762 bool "Show eval mappings for trace events"
763 depends on TRACING
764 help
765 The "print fmt" of the trace events will show the enum/sizeof names
766 instead of their values. This can cause problems for user space tools
767 that use this string to parse the raw data as user space does not know
768 how to convert the string to its value.
769
770 To fix this, there's a special macro in the kernel that can be used
771 to convert an enum/sizeof into its value. If this macro is used, then
772 the print fmt strings will be converted to their values.
773
774 If something does not get converted properly, this option can be
775 used to show what enums/sizeof the kernel tried to convert.
776
777 This option is for debugging the conversions. A file is created
778 in the tracing directory called "eval_map" that will show the
779 names matched with their values and what trace event system they
780 belong too.
781
782 Normally, the mapping of the strings to values will be freed after
783 boot up or module load. With this option, they will not be freed, as
784 they are needed for the "eval_map" file. Enabling this option will
785 increase the memory footprint of the running kernel.
786
787 If unsure, say N
788
789config GCOV_PROFILE_FTRACE
790 bool "Enable GCOV profiling on ftrace subsystem"
791 depends on GCOV_KERNEL
792 help
793 Enable GCOV profiling on ftrace subsystem for checking
794 which functions/lines are tested.
795
796 If unsure, say N.
797
798 Note that on a kernel compiled with this config, ftrace will
799 run significantly slower.
800
801endif # FTRACE
802
803endif # TRACING_SUPPORT
804