From 0c564a538aa934ad15b2145aaf8b64f3feb0be63 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Red Hat)" Date: Tue, 24 Mar 2015 17:58:09 -0400 Subject: tracing: Add TRACE_DEFINE_ENUM() macro to map enums to their values Several tracepoints use the helper functions __print_symbolic() or __print_flags() and pass in enums that do the mapping between the binary data stored and the value to print. This works well for reading the ASCII trace files, but when the data is read via userspace tools such as perf and trace-cmd, the conversion of the binary value to a human string format is lost if an enum is used, as userspace does not have access to what the ENUM is. For example, the tracepoint trace_tlb_flush() has: __print_symbolic(REC->reason, { TLB_FLUSH_ON_TASK_SWITCH, "flush on task switch" }, { TLB_REMOTE_SHOOTDOWN, "remote shootdown" }, { TLB_LOCAL_SHOOTDOWN, "local shootdown" }, { TLB_LOCAL_MM_SHOOTDOWN, "local mm shootdown" }) Which maps the enum values to the strings they represent. But perf and trace-cmd do no know what value TLB_LOCAL_MM_SHOOTDOWN is, and would not be able to map it. With TRACE_DEFINE_ENUM(), developers can place these in the event header files and ftrace will convert the enums to their values: By adding: TRACE_DEFINE_ENUM(TLB_FLUSH_ON_TASK_SWITCH); TRACE_DEFINE_ENUM(TLB_REMOTE_SHOOTDOWN); TRACE_DEFINE_ENUM(TLB_LOCAL_SHOOTDOWN); TRACE_DEFINE_ENUM(TLB_LOCAL_MM_SHOOTDOWN); $ cat /sys/kernel/debug/tracing/events/tlb/tlb_flush/format [...] __print_symbolic(REC->reason, { 0, "flush on task switch" }, { 1, "remote shootdown" }, { 2, "local shootdown" }, { 3, "local mm shootdown" }) The above is what userspace expects to see, and tools do not need to be modified to parse them. Link: http://lkml.kernel.org/r/20150403013802.220157513@goodmis.org Cc: Guilherme Cox Cc: Tony Luck Cc: Xie XiuQi Acked-by: Namhyung Kim Reviewed-by: Masami Hiramatsu Tested-by: Masami Hiramatsu Signed-off-by: Steven Rostedt --- include/trace/ftrace.h | 22 +++++++++++++++++++--- 1 file changed, 19 insertions(+), 3 deletions(-) (limited to 'include/trace') diff --git a/include/trace/ftrace.h b/include/trace/ftrace.h index 2f9b95b6d3fb..37d4b10b111d 100644 --- a/include/trace/ftrace.h +++ b/include/trace/ftrace.h @@ -33,6 +33,19 @@ TRACE_MAKE_SYSTEM_STR(); +#undef TRACE_DEFINE_ENUM +#define TRACE_DEFINE_ENUM(a) \ + static struct trace_enum_map __used __initdata \ + __##TRACE_SYSTEM##_##a = \ + { \ + .system = TRACE_SYSTEM_STRING, \ + .enum_string = #a, \ + .enum_value = a \ + }; \ + static struct trace_enum_map __used \ + __attribute__((section("_ftrace_enum_map"))) \ + *TRACE_SYSTEM##_##a = &__##TRACE_SYSTEM##_##a + /* * DECLARE_EVENT_CLASS can be used to add a generic function * handlers for events. That is, if all events have the same @@ -136,6 +149,9 @@ TRACE_MAKE_SYSTEM_STR(); * The size of an array is also encoded, in the higher 16 bits of . */ +#undef TRACE_DEFINE_ENUM +#define TRACE_DEFINE_ENUM(a) + #undef __field #define __field(type, item) @@ -553,7 +569,7 @@ static inline notrace int ftrace_get_offsets_##call( \ * .trace = ftrace_raw_output_, <-- stage 2 * }; * - * static const char print_fmt_[] = ; + * static char print_fmt_[] = ; * * static struct ftrace_event_class __used event_class_