tracing: Use TRACE_FLAGS macro to keep enums and strings matched

Use a cute little macro trick to keep the names of the trace flags file
guaranteed to match the corresponding masks.

The macro TRACE_FLAGS is defined as a serious of enum names followed by
the string name of the file that matches it. For example:

 #define TRACE_FLAGS						\
		C(PRINT_PARENT,		"print-parent"),	\
		C(SYM_OFFSET,		"sym-offset"),		\
		C(SYM_ADDR,		"sym-addr"),		\
		C(VERBOSE,		"verbose"),

Now we can define the following:

 #undef C
 #define C(a, b) TRACE_ITER_##a##_BIT
 enum trace_iterator_bits { TRACE_FLAGS };

The above creates:

 enum trace_iterator_bits {
	TRACE_ITER_PRINT_PARENT_BIT,
	TRACE_ITER_SYM_OFFSET_BIT,
	TRACE_ITER_SYM_ADDR_BIT,
	TRACE_ITER_VERBOSE_BIT,
 };

Then we can redefine C as:

 #undef C
 #define C(a, b) TRACE_ITER_##a = (1 << TRACE_ITER_##a##_BIT)
 enum trace_iterator_flags { TRACE_FLAGS };

Which creates:

 enum trace_iterator_flags {
	TRACE_ITER_PRINT_PARENT	= (1 << TRACE_ITER_PRINT_PARENT_BIT),
	TRACE_ITER_SYM_OFFSET	= (1 << TRACE_ITER_SYM_OFFSET_BIT),
	TRACE_ITER_SYM_ADDR	= (1 << TRACE_ITER_SYM_ADDR_BIT),
	TRACE_ITER_VERBOSE	= (1 << TRACE_ITER_VERBOSE_BIT),
 };

Then finally we can create the list of file names:

 #undef C
 #define C(a, b) b
 static const char *trace_options[] = {
	TRACE_FLAGS
	NULL
 };

Which creates:
 static const char *trace_options[] = {
	"print-parent",
	"sym-offset",
	"sym-addr",
	"verbose",
	NULL
 };

The importance of this is that the strings match the bit index.

	trace_options[TRACE_ITER_SYM_ADDR_BIT] == "sym-addr"

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 10 insertions, 26 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index f2fbf610d20e..e80e380d0238 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -854,34 +854,18 @@ unsigned long nsecs_to_usecs(unsigned long nsecs)
 	return nsecs / 1000;
 }
 
+/*
+ * TRACE_FLAGS is defined as a tuple matching bit masks with strings.
+ * It uses C(a, b) where 'a' is the enum name and 'b' is the string that
+ * matches it. By defining "C(a, b) b", TRACE_FLAGS becomes a list
+ * of strings in the order that the enums were defined.
+ */
+#undef C
+#define C(a, b) b
+
 /* These must match the bit postions in trace_iterator_flags */
 static const char *trace_options[] = {
-	"print-parent",
-	"sym-offset",
-	"sym-addr",
-	"verbose",
-	"raw",
-	"hex",
-	"bin",
-	"block",
-	"stacktrace",
-	"trace_printk",
-	"branch",
-	"annotate",
-	"userstacktrace",
-	"sym-userobj",
-	"printk-msg-only",
-	"context-info",
-	"latency-format",
-	"sleep-time",
-	"graph-time",
-	"record-cmd",
-	"overwrite",
-	"disable_on_free",
-	"irq-info",
-	"markers",
-	"function-trace",
-	"display-graph",
+	TRACE_FLAGS
 	NULL
 };