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# SPDX-License-Identifier: GPL-2.0-only
#
# Architectures that offer an FUNCTION_TRACER implementation should
# select HAVE_FUNCTION_TRACER:
#
config USER_STACKTRACE_SUPPORT
bool
config NOP_TRACER
bool
config HAVE_FTRACE_NMI_ENTER
bool
help
See Documentation/trace/ftrace-design.rst
config HAVE_FUNCTION_TRACER
bool
help
See Documentation/trace/ftrace-design.rst
config HAVE_FUNCTION_GRAPH_TRACER
bool
help
See Documentation/trace/ftrace-design.rst
config HAVE_DYNAMIC_FTRACE
bool
help
See Documentation/trace/ftrace-design.rst
config HAVE_DYNAMIC_FTRACE_WITH_REGS
bool
config HAVE_FTRACE_MCOUNT_RECORD
bool
help
See Documentation/trace/ftrace-design.rst
config HAVE_SYSCALL_TRACEPOINTS
bool
help
See Documentation/trace/ftrace-design.rst
config HAVE_FENTRY
bool
help
Arch supports the gcc options -pg with -mfentry
config HAVE_NOP_MCOUNT
bool
help
Arch supports the gcc options -pg with -mrecord-mcount and -nop-mcount
config HAVE_C_RECORDMCOUNT
bool
help
C version of recordmcount available?
config TRACER_MAX_TRACE
bool
config TRACE_CLOCK
bool
config RING_BUFFER
bool
select TRACE_CLOCK
select IRQ_WORK
config FTRACE_NMI_ENTER
bool
depends on HAVE_FTRACE_NMI_ENTER
default y
config EVENT_TRACING
select CONTEXT_SWITCH_TRACER
select GLOB
bool
config CONTEXT_SWITCH_TRACER
bool
config RING_BUFFER_ALLOW_SWAP
bool
help
Allow the use of ring_buffer_swap_cpu.
Adds a very slight overhead to tracing when enabled.
config PREEMPTIRQ_TRACEPOINTS
bool
depends on TRACE_PREEMPT_TOGGLE || TRACE_IRQFLAGS
select TRACING
default y
help
Create preempt/irq toggle tracepoints if needed, so that other parts
of the kernel can use them to generate or add hooks to them.
# All tracer options should select GENERIC_TRACER. For those options that are
# enabled by all tracers (context switch and event tracer) they select TRACING.
# This allows those options to appear when no other tracer is selected. But the
# options do not appear when something else selects it. We need the two options
# GENERIC_TRACER and TRACING to avoid circular dependencies to accomplish the
# hiding of the automatic options.
config TRACING
bool
select DEBUG_FS
select RING_BUFFER
select STACKTRACE if STACKTRACE_SUPPORT
select TRACEPOINTS
select NOP_TRACER
select BINARY_PRINTF
select EVENT_TRACING
select TRACE_CLOCK
config GENERIC_TRACER
bool
select TRACING
#
# Minimum requirements an architecture has to meet for us to
# be able to offer generic tracing facilities:
#
config TRACING_SUPPORT
bool
depends on TRACE_IRQFLAGS_SUPPORT
depends on STACKTRACE_SUPPORT
default y
if TRACING_SUPPORT
menuconfig FTRACE
bool "Tracers"
default y if DEBUG_KERNEL
help
Enable the kernel tracing infrastructure.
if FTRACE
config FUNCTION_TRACER
bool "Kernel Function Tracer"
depends on HAVE_FUNCTION_TRACER
select KALLSYMS
select GENERIC_TRACER
select CONTEXT_SWITCH_TRACER
select GLOB
select TASKS_RCU if PREEMPT
help
Enable the kernel to trace every kernel function. This is done
by using a compiler feature to insert a small, 5-byte No-Operation
instruction at the beginning of every kernel function, which NOP
sequence is then dynamically patched into a tracer call when
tracing is enabled by the administrator. If it's runtime disabled
(the bootup default), then the overhead of the instructions is very
small and not measurable even in micro-benchmarks.
config FUNCTION_GRAPH_TRACER
bool "Kernel Function Graph Tracer"
depends on HAVE_FUNCTION_GRAPH_TRACER
depends on FUNCTION_TRACER
depends on !X86_32 || !CC_OPTIMIZE_FOR_SIZE
default y
help
Enable the kernel to trace a function at both its return
and its entry.
Its first purpose is to trace the duration of functions and
draw a call graph for each thread with some information like
the return value. This is done by setting the current return
address on the current task structure into a stack of calls.
config TRACE_PREEMPT_TOGGLE
bool
help
Enables hooks which will be called when preemption is first disabled,
and last enabled.
config PREEMPTIRQ_EVENTS
bool "Enable trace events for preempt and irq disable/enable"
select TRACE_IRQFLAGS
select TRACE_PREEMPT_TOGGLE if PREEMPT
select GENERIC_TRACER
default n
help
Enable tracing of disable and enable events for preemption and irqs.
config IRQSOFF_TRACER
bool "Interrupts-off Latency Tracer"
default n
depends on TRACE_IRQFLAGS_SUPPORT
depends on !ARCH_USES_GETTIMEOFFSET
select TRACE_IRQFLAGS
select GENERIC_TRACER
select TRACER_MAX_TRACE
select RING_BUFFER_ALLOW_SWAP
select TRACER_SNAPSHOT
select TRACER_SNAPSHOT_PER_CPU_SWAP
help
This option measures the time spent in irqs-off critical
sections, with microsecond accuracy.
The default measurement method is a maximum search, which is
disabled by default and can be runtime (re-)started
via:
echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
(Note that kernel size and overhead increase with this option
enabled. This option and the preempt-off timing option can be
used together or separately.)
config PREEMPT_TRACER
bool "Preemption-off Latency Tracer"
default n
depends on !ARCH_USES_GETTIMEOFFSET
depends on PREEMPT
select GENERIC_TRACER
select TRACER_MAX_TRACE
select RING_BUFFER_ALLOW_SWAP
select TRACER_SNAPSHOT
select TRACER_SNAPSHOT_PER_CPU_SWAP
select TRACE_PREEMPT_TOGGLE
help
This option measures the time spent in preemption-off critical
sections, with microsecond accuracy.
The default measurement method is a maximum search, which is
disabled by default and can be runtime (re-)started
via:
echo 0 > /sys/kernel/debug/tracing/tracing_max_latency
(Note that kernel size and overhead increase with this option
enabled. This option and the irqs-off timing option can be
used together or separately.)
config SCHED_TRACER
bool "Scheduling Latency Tracer"
select GENERIC_TRACER
select CONTEXT_SWITCH_TRACER
select TRACER_MAX_TRACE
select TRACER_SNAPSHOT
help
This tracer tracks the latency of the highest priority task
to be scheduled in, starting from the point it has woken up.
config HWLAT_TRACER
bool "Tracer to detect hardware latencies (like SMIs)"
select GENERIC_TRACER
help
This tracer, when enabled will create one or more kernel threads,
depending on what the cpumask file is set to, which each thread
spinning in a loop looking for interruptions caused by
something other than the kernel. For example, if a
System Management Interrupt (SMI) takes a noticeable amount of
time, this tracer will detect it. This is useful for testing
if a system is reliable for Real Time tasks.
Some files are created in the tracing directory when this
is enabled:
hwlat_detector/width - time in usecs for how long to spin for
hwlat_detector/window - time in usecs between the start of each
iteration
A kernel thread is created that will spin with interrupts disabled
for "width" microseconds in every "window" cycle. It will not spin
for "window - width" microseconds, where the system can
continue to operate.
The output will appear in the trace and trace_pipe files.
When the tracer is not running, it has no affect on the system,
but when it is running, it can cause the system to be
periodically non responsive. Do not run this tracer on a
production system.
To enable this tracer, echo in "hwlat" into the current_tracer
file. Every time a latency is greater than tracing_thresh, it will
be recorded into the ring buffer.
config ENABLE_DEFAULT_TRACERS
bool "Trace process context switches and events"
depends on !GENERIC_TRACER
select TRACING
help
This tracer hooks to various trace points in the kernel,
allowing the user to pick and choose which trace point they
want to trace. It also includes the sched_switch tracer plugin.
config FTRACE_SYSCALLS
bool "Trace syscalls"
depends on HAVE_SYSCALL_TRACEPOINTS
select GENERIC_TRACER
select KALLSYMS
help
Basic tracer to catch the syscall entry and exit events.
config TRACER_SNAPSHOT
bool "Create a snapshot trace buffer"
select TRACER_MAX_TRACE
help
Allow tracing users to take snapshot of the current buffer using the
ftrace interface, e.g.:
echo 1 > /sys/kernel/debug/tracing/snapshot
cat snapshot
config TRACER_SNAPSHOT_PER_CPU_SWAP
bool "Allow snapshot to swap per CPU"
depends on TRACER_SNAPSHOT
select RING_BUFFER_ALLOW_SWAP
help
Allow doing a snapshot of a single CPU buffer instead of a
full swap (all buffers). If this is set, then the following is
allowed:
echo 1 > /sys/kernel/debug/tracing/per_cpu/cpu2/snapshot
After which, only the tracing buffer for CPU 2 was swapped with
the main tracing buffer, and the other CPU buffers remain the same.
When this is enabled, this adds a little more overhead to the
trace recording, as it needs to add some checks to synchronize
recording with swaps. But this does not affect the performance
of the overall system. This is enabled by default when the preempt
or irq latency tracers are enabled, as those need to swap as well
and already adds the overhead (plus a lot more).
config TRACE_BRANCH_PROFILING
bool
select GENERIC_TRACER
choice
prompt "Branch Profiling"
default BRANCH_PROFILE_NONE
help
The branch profiling is a software profiler. It will add hooks
into the C conditionals to test which path a branch takes.
The likely/unlikely profiler only looks at the conditions that
are annotated with a likely or unlikely macro.
The "all branch" profiler will profile every if-statement in the
kernel. This profiler will also enable the likely/unlikely
profiler.
Either of the above profilers adds a bit of overhead to the system.
If unsure, choose "No branch profiling".
config BRANCH_PROFILE_NONE
bool "No branch profiling"
help
No branch profiling. Branch profiling adds a bit of overhead.
Only enable it if you want to analyse the branching behavior.
Otherwise keep it disabled.
config PROFILE_ANNOTATED_BRANCHES
bool "Trace likely/unlikely profiler"
select TRACE_BRANCH_PROFILING
help
This tracer profiles all likely and unlikely macros
in the kernel. It will display the results in:
/sys/kernel/debug/tracing/trace_stat/branch_annotated
Note: this will add a significant overhead; only turn this
on if you need to profile the system's use of these macros.
config PROFILE_ALL_BRANCHES
bool "Profile all if conditionals" if !FORTIFY_SOURCE
select TRACE_BRANCH_PROFILING
imply CC_DISABLE_WARN_MAYBE_UNINITIALIZED # avoid false positives
help
This tracer profiles all branch conditions. Every if ()
taken in the kernel is recorded whether it hit or miss.
The results will be displayed in:
/sys/kernel/debug/tracing/trace_stat/branch_all
This option also enables the likely/unlikely profiler.
This configuration, when enabled, will impose a great overhead
on the system. This should only be enabled when the system
is to be analyzed in much detail.
endchoice
config TRACING_BRANCHES
bool
help
Selected by tracers that will trace the likely and unlikely
conditions. This prevents the tracers themselves from being
profiled. Profiling the tracing infrastructure can only happen
when the likelys and unlikelys are not being traced.
config BRANCH_TRACER
bool "Trace likely/unlikely instances"
depends on TRACE_BRANCH_PROFILING
select TRACING_BRANCHES
help
This traces the events of likely and unlikely condition
calls in the kernel. The difference between this and the
"Trace likely/unlikely profiler" is that this is not a
histogram of the callers, but actually places the calling
events into a running trace buffer to see when and where the
events happened, as well as their results.
Say N if unsure.
config STACK_TRACER
bool "Trace max stack"
depends on HAVE_FUNCTION_TRACER
select FUNCTION_TRACER
select STACKTRACE
select KALLSYMS
help
This special tracer records the maximum stack footprint of the
kernel and displays it in /sys/kernel/debug/tracing/stack_trace.
This tracer works by hooking into every function call that the
kernel executes, and keeping a maximum stack depth value and
stack-trace saved. If this is configured with DYNAMIC_FTRACE
then it will not have any overhead while the stack tracer
is disabled.
To enable the stack tracer on bootup, pass in 'stacktrace'
on the kernel command line.
The stack tracer can also be enabled or disabled via the
sysctl kernel.stack_tracer_enabled
Say N if unsure.
config BLK_DEV_IO_TRACE
bool "Support for tracing block IO actions"
depends on SYSFS
depends on BLOCK
select RELAY
select DEBUG_FS
select TRACEPOINTS
select GENERIC_TRACER
select STACKTRACE
help
Say Y here if you want to be able to trace the block layer actions
on a given queue. Tracing allows you to see any traffic happening
on a block device queue. For more information (and the userspace
support tools needed), fetch the blktrace tools from:
git://git.kernel.dk/blktrace.git
Tracing also is possible using the ftrace interface, e.g.:
echo 1 > /sys/block/sda/sda1/trace/enable
echo blk > /sys/kernel/debug/tracing/current_tracer
cat /sys/kernel/debug/tracing/trace_pipe
If unsure, say N.
config KPROBE_EVENTS
depends on KPROBES
depends on HAVE_REGS_AND_STACK_ACCESS_API
bool "Enable kprobes-based dynamic events"
select TRACING
select PROBE_EVENTS
select DYNAMIC_EVENTS
default y
help
This allows the user to add tracing events (similar to tracepoints)
on the fly via the ftrace interface. See
Documentation/trace/kprobetrace.rst for more details.
Those events can be inserted wherever kprobes can probe, and record
various register and memory values.
This option is also required by perf-probe subcommand of perf tools.
If you want to use perf tools, this option is strongly recommended.
config KPROBE_EVENTS_ON_NOTRACE
bool "Do NOT protect notrace function from kprobe events"
depends on KPROBE_EVENTS
depends on KPROBES_ON_FTRACE
default n
help
This is only for the developers who want to debug ftrace itself
using kprobe events.
If kprobes can use ftrace instead of breakpoint, ftrace related
functions are protected from kprobe-events to prevent an infinit
recursion or any unexpected execution path which leads to a kernel
crash.
This option disables such protection and allows you to put kprobe
events on ftrace functions for debugging ftrace by itself.
Note that this might let you shoot yourself in the foot.
If unsure, say N.
config UPROBE_EVENTS
bool "Enable uprobes-based dynamic events"
depends on ARCH_SUPPORTS_UPROBES
depends on MMU
depends on PERF_EVENTS
select UPROBES
select PROBE_EVENTS
select DYNAMIC_EVENTS
select TRACING
default y
help
This allows the user to add tracing events on top of userspace
dynamic events (similar to tracepoints) on the fly via the trace
events interface. Those events can be inserted wherever uprobes
can probe, and record various registers.
This option is required if you plan to use perf-probe subcommand
of perf tools on user space applications.
config BPF_EVENTS
depends on BPF_SYSCALL
depends on (KPROBE_EVENTS || UPROBE_EVENTS) && PERF_EVENTS
bool
default y
help
This allows the user to attach BPF programs to kprobe events.
config DYNAMIC_EVENTS
def_bool n
config PROBE_EVENTS
def_bool n
config DYNAMIC_FTRACE
bool "enable/disable function tracing dynamically"
depends on FUNCTION_TRACER
depends on HAVE_DYNAMIC_FTRACE
default y
help
This option will modify all the calls to function tracing
dynamically (will patch them out of the binary image and
replace them with a No-Op instruction) on boot up. During
compile time, a table is made of all the locations that ftrace
can function trace, and this table is linked into the kernel
image. When this is enabled, functions can be individually
enabled, and the functions not enabled will not affect
performance of the system.
See the files in /sys/kernel/debug/tracing:
available_filter_functions
set_ftrace_filter
set_ftrace_notrace
This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
otherwise has native performance as long as no tracing is active.
config DYNAMIC_FTRACE_WITH_REGS
def_bool y
depends on DYNAMIC_FTRACE
depends on HAVE_DYNAMIC_FTRACE_WITH_REGS
config FUNCTION_PROFILER
bool "Kernel function profiler"
depends on FUNCTION_TRACER
default n
help
This option enables the kernel function profiler. A file is created
in debugfs called function_profile_enabled which defaults to zero.
When a 1 is echoed into this file profiling begins, and when a
zero is entered, profiling stops. A "functions" file is created in
the trace_stat directory; this file shows the list of functions that
have been hit and their counters.
If in doubt, say N.
config BPF_KPROBE_OVERRIDE
bool "Enable BPF programs to override a kprobed function"
depends on BPF_EVENTS
depends on FUNCTION_ERROR_INJECTION
default n
help
Allows BPF to override the execution of a probed function and
set a different return value. This is used for error injection.
config FTRACE_MCOUNT_RECORD
def_bool y
depends on DYNAMIC_FTRACE
depends on HAVE_FTRACE_MCOUNT_RECORD
config FTRACE_SELFTEST
bool
config FTRACE_STARTUP_TEST
bool "Perform a startup test on ftrace"
depends on GENERIC_TRACER
select FTRACE_SELFTEST
help
This option performs a series of startup tests on ftrace. On bootup
a series of tests are made to verify that the tracer is
functioning properly. It will do tests on all the configured
tracers of ftrace.
config EVENT_TRACE_STARTUP_TEST
bool "Run selftest on trace events"
depends on FTRACE_STARTUP_TEST
default y
help
This option performs a test on all trace events in the system.
It basically just enables each event and runs some code that
will trigger events (not necessarily the event it enables)
This may take some time run as there are a lot of events.
config EVENT_TRACE_TEST_SYSCALLS
bool "Run selftest on syscall events"
depends on EVENT_TRACE_STARTUP_TEST
help
This option will also enable testing every syscall event.
It only enables the event and disables it and runs various loads
with the event enabled. This adds a bit more time for kernel boot
up since it runs this on every system call defined.
TBD - enable a way to actually call the syscalls as we test their
events
config MMIOTRACE
bool "Memory mapped IO tracing"
depends on HAVE_MMIOTRACE_SUPPORT && PCI
select GENERIC_TRACER
help
Mmiotrace traces Memory Mapped I/O access and is meant for
debugging and reverse engineering. It is called from the ioremap
implementation and works via page faults. Tracing is disabled by
default and can be enabled at run-time.
See Documentation/trace/mmiotrace.rst.
If you are not helping to develop drivers, say N.
config TRACING_MAP
bool
depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
help
tracing_map is a special-purpose lock-free map for tracing,
separated out as a stand-alone facility in order to allow it
to be shared between multiple tracers. It isn't meant to be
generally used outside of that context, and is normally
selected by tracers that use it.
config HIST_TRIGGERS
bool "Histogram triggers"
depends on ARCH_HAVE_NMI_SAFE_CMPXCHG
select TRACING_MAP
select TRACING
select DYNAMIC_EVENTS
default n
help
Hist triggers allow one or more arbitrary trace event fields
to be aggregated into hash tables and dumped to stdout by
reading a debugfs/tracefs file. They're useful for
gathering quick and dirty (though precise) summaries of
event activity as an initial guide for further investigation
using more advanced tools.
Inter-event tracing of quantities such as latencies is also
supported using hist triggers under this option.
See Documentation/trace/histogram.rst.
If in doubt, say N.
config MMIOTRACE_TEST
tristate "Test module for mmiotrace"
depends on MMIOTRACE && m
help
This is a dumb module for testing mmiotrace. It is very dangerous
as it will write garbage to IO memory starting at a given address.
However, it should be safe to use on e.g. unused portion of VRAM.
Say N, unless you absolutely know what you are doing.
config TRACEPOINT_BENCHMARK
bool "Add tracepoint that benchmarks tracepoints"
help
This option creates the tracepoint "benchmark:benchmark_event".
When the tracepoint is enabled, it kicks off a kernel thread that
goes into an infinite loop (calling cond_sched() to let other tasks
run), and calls the tracepoint. Each iteration will record the time
it took to write to the tracepoint and the next iteration that
data will be passed to the tracepoint itself. That is, the tracepoint
will report the time it took to do the previous tracepoint.
The string written to the tracepoint is a static string of 128 bytes
to keep the time the same. The initial string is simply a write of
"START". The second string records the cold cache time of the first
write which is not added to the rest of the calculations.
As it is a tight loop, it benchmarks as hot cache. That's fine because
we care most about hot paths that are probably in cache already.
An example of the output:
START
first=3672 [COLD CACHED]
last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712
last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337
last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064
last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411
last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389
last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666
config RING_BUFFER_BENCHMARK
tristate "Ring buffer benchmark stress tester"
depends on RING_BUFFER
help
This option creates a test to stress the ring buffer and benchmark it.
It creates its own ring buffer such that it will not interfere with
any other users of the ring buffer (such as ftrace). It then creates
a producer and consumer that will run for 10 seconds and sleep for
10 seconds. Each interval it will print out the number of events
it recorded and give a rough estimate of how long each iteration took.
It does not disable interrupts or raise its priority, so it may be
affected by processes that are running.
If unsure, say N.
config RING_BUFFER_STARTUP_TEST
bool "Ring buffer startup self test"
depends on RING_BUFFER
help
Run a simple self test on the ring buffer on boot up. Late in the
kernel boot sequence, the test will start that kicks off
a thread per cpu. Each thread will write various size events
into the ring buffer. Another thread is created to send IPIs
to each of the threads, where the IPI handler will also write
to the ring buffer, to test/stress the nesting ability.
If any anomalies are discovered, a warning will be displayed
and all ring buffers will be disabled.
The test runs for 10 seconds. This will slow your boot time
by at least 10 more seconds.
At the end of the test, statics and more checks are done.
It will output the stats of each per cpu buffer. What
was written, the sizes, what was read, what was lost, and
other similar details.
If unsure, say N
config PREEMPTIRQ_DELAY_TEST
tristate "Preempt / IRQ disable delay thread to test latency tracers"
depends on m
help
Select this option to build a test module that can help test latency
tracers by executing a preempt or irq disable section with a user
configurable delay. The module busy waits for the duration of the
critical section.
For example, the following invocation forces a one-time irq-disabled
critical section for 500us:
modprobe preemptirq_delay_test test_mode=irq delay=500000
If unsure, say N
config TRACE_EVAL_MAP_FILE
bool "Show eval mappings for trace events"
depends on TRACING
help
The "print fmt" of the trace events will show the enum/sizeof names
instead of their values. This can cause problems for user space tools
that use this string to parse the raw data as user space does not know
how to convert the string to its value.
To fix this, there's a special macro in the kernel that can be used
to convert an enum/sizeof into its value. If this macro is used, then
the print fmt strings will be converted to their values.
If something does not get converted properly, this option can be
used to show what enums/sizeof the kernel tried to convert.
This option is for debugging the conversions. A file is created
in the tracing directory called "eval_map" that will show the
names matched with their values and what trace event system they
belong too.
Normally, the mapping of the strings to values will be freed after
boot up or module load. With this option, they will not be freed, as
they are needed for the "eval_map" file. Enabling this option will
increase the memory footprint of the running kernel.
If unsure, say N
config GCOV_PROFILE_FTRACE
bool "Enable GCOV profiling on ftrace subsystem"
depends on GCOV_KERNEL
help
Enable GCOV profiling on ftrace subsystem for checking
which functions/lines are tested.
If unsure, say N.
Note that on a kernel compiled with this config, ftrace will
run significantly slower.
endif # FTRACE
endif # TRACING_SUPPORT
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