path: root/include/linux/tracepoint.h
diff options
authorSteven Rostedt (Red Hat) <rostedt@goodmis.org>2015-03-24 17:58:09 -0400
committerSteven Rostedt <rostedt@goodmis.org>2015-04-08 09:39:56 -0400
commit0c564a538aa934ad15b2145aaf8b64f3feb0be63 (patch)
tree136ee858e4d9b1c4e2d9d39d4614eb8af175afb0 /include/linux/tracepoint.h
parent889204278ccf98c5c097b1d1ae69babc6a3222fd (diff)
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 <cox@computer.org> Cc: Tony Luck <tony.luck@gmail.com> Cc: Xie XiuQi <xiexiuqi@huawei.com> Acked-by: Namhyung Kim <namhyung@kernel.org> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/tracepoint.h')
1 files changed, 8 insertions, 0 deletions
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index c72851328ca9..a5f7f3ecafa3 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -36,6 +36,12 @@ struct tracepoint {
struct tracepoint_func __rcu *funcs;
+struct trace_enum_map {
+ const char *system;
+ const char *enum_string;
+ unsigned long enum_value;
extern int
tracepoint_probe_register(struct tracepoint *tp, void *probe, void *data);
extern int
@@ -87,6 +93,8 @@ extern void syscall_unregfunc(void);
#define PARAMS(args...) args
#endif /* _LINUX_TRACEPOINT_H */