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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 PREEMPTION 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 PREEMPTION 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 PREEMPTION 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 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 DYNAMIC_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, uprobe, and tracepoint 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