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>

2 files changed, 55 insertions, 83 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
 };
 
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 31d8395c8dc5..d164845edddd 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -884,65 +884,53 @@ extern int trace_get_user(struct trace_parser *parser, const char __user *ubuf,
  * positions into trace_flags that controls the output.
  *
  * NOTE: These bits must match the trace_options array in
- *       trace.c.
+ *       trace.c (this macro guarantees it).
  */
-enum trace_iterator_bits {
-        TRACE_ITER_PRINT_PARENT_BIT     = 0,
-        TRACE_ITER_SYM_OFFSET_BIT,
-        TRACE_ITER_SYM_ADDR_BIT,
-        TRACE_ITER_VERBOSE_BIT,
-        TRACE_ITER_RAW_BIT,
-        TRACE_ITER_HEX_BIT,
-        TRACE_ITER_BIN_BIT,
-        TRACE_ITER_BLOCK_BIT,
-        TRACE_ITER_STACKTRACE_BIT,
-        TRACE_ITER_PRINTK_BIT,
-        TRACE_ITER_BRANCH_BIT,
-        TRACE_ITER_ANNOTATE_BIT,
-        TRACE_ITER_USERSTACKTRACE_BIT,
-        TRACE_ITER_SYM_USEROBJ_BIT,
-        TRACE_ITER_PRINTK_MSGONLY_BIT,
-        TRACE_ITER_CONTEXT_INFO_BIT,    /* Print pid/cpu/time */
-        TRACE_ITER_LATENCY_FMT_BIT,
-        TRACE_ITER_SLEEP_TIME_BIT,
-        TRACE_ITER_GRAPH_TIME_BIT,
-        TRACE_ITER_RECORD_CMD_BIT,
-        TRACE_ITER_OVERWRITE_BIT,
-        TRACE_ITER_STOP_ON_FREE_BIT,
-        TRACE_ITER_IRQ_INFO_BIT,
-        TRACE_ITER_MARKERS_BIT,
-        TRACE_ITER_FUNCTION_BIT,
-        TRACE_ITER_DISPLAY_GRAPH_BIT,
-};
+#define TRACE_FLAGS                                             \
+                C(PRINT_PARENT,         "print-parent"),        \
+                C(SYM_OFFSET,           "sym-offset"),          \
+                C(SYM_ADDR,             "sym-addr"),            \
+                C(VERBOSE,              "verbose"),             \
+                C(RAW,                  "raw"),                 \
+                C(HEX,                  "hex"),                 \
+                C(BIN,                  "bin"),                 \
+                C(BLOCK,                "block"),               \
+                C(STACKTRACE,           "stacktrace"),          \
+                C(PRINTK,               "trace_printk"),        \
+                C(BRANCH,               "branch"),              \
+                C(ANNOTATE,             "annotate"),            \
+                C(USERSTACKTRACE,       "userstacktrace"),      \
+                C(SYM_USEROBJ,          "sym-userobj"),         \
+                C(PRINTK_MSGONLY,       "printk-msg-only"),     \
+                C(CONTEXT_INFO,         "context-info"),   /* Print pid/cpu/time */ \
+                C(LATENCY_FMT,          "latency-format"),      \
+                C(SLEEP_TIME,           "sleep-time"),          \
+                C(GRAPH_TIME,           "graph-time"),          \
+                C(RECORD_CMD,           "record-cmd"),          \
+                C(OVERWRITE,            "overwrite"),           \
+                C(STOP_ON_FREE,         "disable_on_free"),     \
+                C(IRQ_INFO,             "irq-info"),            \
+                C(MARKERS,              "markers"),             \
+                C(FUNCTION,             "function-trace"),      \
+                C(DISPLAY_GRAPH,        "display-graph"),
 
-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),
-        TRACE_ITER_RAW                  = (1 << TRACE_ITER_RAW_BIT),
-        TRACE_ITER_HEX                  = (1 << TRACE_ITER_HEX_BIT),
-        TRACE_ITER_BIN                  = (1 << TRACE_ITER_BIN_BIT),
-        TRACE_ITER_BLOCK                = (1 << TRACE_ITER_BLOCK_BIT),
-        TRACE_ITER_STACKTRACE           = (1 << TRACE_ITER_STACKTRACE_BIT),
-        TRACE_ITER_PRINTK               = (1 << TRACE_ITER_PRINTK_BIT),
-        TRACE_ITER_BRANCH               = (1 << TRACE_ITER_BRANCH_BIT),
-        TRACE_ITER_ANNOTATE             = (1 << TRACE_ITER_ANNOTATE_BIT),
-        TRACE_ITER_USERSTACKTRACE       = (1 << TRACE_ITER_USERSTACKTRACE_BIT),
-        TRACE_ITER_SYM_USEROBJ          = (1 << TRACE_ITER_SYM_USEROBJ_BIT),
-        TRACE_ITER_PRINTK_MSGONLY       = (1 << TRACE_ITER_PRINTK_MSGONLY_BIT),
-        TRACE_ITER_CONTEXT_INFO         = (1 << TRACE_ITER_CONTEXT_INFO_BIT),
-        TRACE_ITER_LATENCY_FMT          = (1 << TRACE_ITER_LATENCY_FMT_BIT),
-        TRACE_ITER_SLEEP_TIME           = (1 << TRACE_ITER_SLEEP_TIME_BIT),
-        TRACE_ITER_GRAPH_TIME           = (1 << TRACE_ITER_GRAPH_TIME_BIT),
-        TRACE_ITER_RECORD_CMD           = (1 << TRACE_ITER_RECORD_CMD_BIT),
-        TRACE_ITER_OVERWRITE            = (1 << TRACE_ITER_OVERWRITE_BIT),
-        TRACE_ITER_STOP_ON_FREE         = (1 << TRACE_ITER_STOP_ON_FREE_BIT),
-        TRACE_ITER_IRQ_INFO             = (1 << TRACE_ITER_IRQ_INFO_BIT),
-        TRACE_ITER_MARKERS              = (1 << TRACE_ITER_MARKERS_BIT),
-        TRACE_ITER_FUNCTION             = (1 << TRACE_ITER_FUNCTION_BIT),
-        TRACE_ITER_DISPLAY_GRAPH        = (1 << TRACE_ITER_DISPLAY_GRAPH_BIT),
-};
+/*
+ * By defining C, we can make TRACE_FLAGS a list of bit names
+ * that will define the bits for the flag masks.
+ */
+#undef C
+#define C(a, b) TRACE_ITER_##a##_BIT
+
+enum trace_iterator_bits { TRACE_FLAGS };
+
+/*
+ * By redefining C, we can make TRACE_FLAGS a list of masks that
+ * use the bits as defined above.
+ */
+#undef C
+#define C(a, b) TRACE_ITER_##a = (1 << TRACE_ITER_##a##_BIT)
+
+enum trace_iterator_flags { TRACE_FLAGS };
 
 /*
  * TRACE_ITER_SYM_MASK masks the options in trace_flags that