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ftrace: Allow tracing of some of the tracing code 

There is times when tracing the tracing infrastructure can be useful for
debugging the tracing code. Currently all files in the tracing directory
are set to "notrace" the functions.

Add a new config option FUNCTION_SELF_TRACING that will allow some of the
files in the tracing infrastructure to be traced. It requires a config to
enable because it will add noise to the function tracer if events and
other tracing features are enabled. Tracing functions and events together
is quite common, so not tracing the event code should be the default.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Link: https://patch.msgid.link/20251120181514.736f2d5f@gandalf.local.home
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
This commit is contained in:
Steven Rostedt 2025-11-20 18:15:14 -05:00 committed by Steven Rostedt (Google)
parent 400ddf1dbe
commit f93a7d0cac
2 changed files with 31 additions and 0 deletions
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14
kernel/trace/Kconfig
View File

@ -330,6 +330,20 @@ config DYNAMIC_FTRACE_WITH_ARGS
depends on DYNAMIC_FTRACE
depends on HAVE_DYNAMIC_FTRACE_WITH_ARGS
config FUNCTION_SELF_TRACING
bool "Function trace tracing code"
depends on FUNCTION_TRACER
help
Normally all the tracing code is set to notrace, where the function
tracer will ignore all the tracing functions. Sometimes it is useful
for debugging to trace some of the tracing infratructure itself.
Enable this to allow some of the tracing infrastructure to be traced
by the function tracer. Note, this will likely add noise to function
tracing if events and other tracing features are enabled along with
function tracing.
If unsure, say N.
config FPROBE
bool "Kernel Function Probe (fprobe)"
depends on HAVE_FUNCTION_GRAPH_FREGS && HAVE_FTRACE_GRAPH_FUNC

17
kernel/trace/Makefile
View File

@ -16,6 +16,23 @@ obj-y += trace_selftest_dynamic.o
endif
endif
# Allow some files to be function traced
ifdef CONFIG_FUNCTION_SELF_TRACING
CFLAGS_trace_output.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_seq.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_stat.o = $(CC_FLAGS_FTRACE)
CFLAGS_tracing_map.o = $(CC_FLAGS_FTRACE)
CFLAGS_synth_event_gen_test.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_events.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_syscalls.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_events_filter.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_events_trigger.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_events_synth.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_events_hist.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_events_user.o = $(CC_FLAGS_FTRACE)
CFLAGS_trace_dynevent.o = $(CC_FLAGS_FTRACE)
endif
ifdef CONFIG_FTRACE_STARTUP_TEST
CFLAGS_trace_kprobe_selftest.o = $(CC_FLAGS_FTRACE)
obj-$(CONFIG_KPROBE_EVENTS) += trace_kprobe_selftest.o