tracing/ftrace: implement a set_flag callback for tracers

index 396fda0..8c4eb80 100644
@@ -2432,6 +2432,9 @@ tracing_trace_options_read(struct file *filp, char __user *ubuf,
 	int r = 0;
 	int len = 0;
 	int i;
+	u32 tracer_flags = 0;
+	struct tracer_opt *trace_opts = NULL;
+
 
 	/* calulate max size */
 	for (i = 0; trace_options[i]; i++) {

@@ -2439,6 +2442,22 @@ tracing_trace_options_read(struct file *filp, char __user *ubuf,
 		len += 3; /* "no" and space */
 	}
 
+	if (current_trace->flags) {
+		trace_opts = current_trace->flags->opts;
+		tracer_flags = current_trace->flags->val;
+	}
+
+	/*
+	 * Increase the size with names of options specific
+	 * of the current tracer.
+	 */
+	if (trace_opts) {
+		for (i = 0; trace_opts[i].name; i++) {
+			len += strlen(trace_opts[i].name);
+			len += 3;
+		}
+	}
+
 	/* +2 for \n and \0 */
 	buf = kmalloc(len + 2, GFP_KERNEL);
 	if (!buf)

@@ -2451,6 +2470,16 @@ tracing_trace_options_read(struct file *filp, char __user *ubuf,
 			r += sprintf(buf + r, "no%s ", trace_options[i]);
 	}
 
+	if (trace_opts) {
+		for (i = 0; trace_opts[i].name; i++) {
+			if (tracer_flags & trace_opts[i].bit)
+				r += sprintf(buf + r, "%s ",
+					trace_opts[i].name);
+			else
+				r += sprintf(buf + r, "no%s ",
+					trace_opts[i].name);
+		}
+	}
 	r += sprintf(buf + r, "\n");
 	WARN_ON(r >= len + 2);
 

@@ -2461,6 +2490,44 @@ tracing_trace_options_read(struct file *filp, char __user *ubuf,
 	return r;
 }
 
+/* Try to assign a tracer specific option */
+static int set_tracer_option(struct tracer *trace, char *cmp, int neg)
+{
+	struct tracer_flags *trace_flags = trace->flags;
+	struct tracer_opt *opts = NULL;
+	int ret = 0, i = 0;
+	int len;
+
+	if (!trace_flags || !trace_flags->opts)
+		return -EINVAL;
+
+	for (i = 0; trace_flags->opts[i].name; i++) {
+		opts = &trace_flags->opts[i];
+		len = strlen(opts->name);
+
+		if (strncmp(cmp, opts->name, len) == 0) {
+			if (trace->set_flag)
+					ret = trace->set_flag(trace_flags->val,
+							opts->bit, !neg);
+			break;
+		}
+	}
+	/* Not found */
+	if (!trace_flags->opts[i].name)
+		return -EINVAL;
+
+	/* Refused to handle */
+	if (ret)
+		return ret;
+
+	if (neg)
+		trace_flags->val &= ~opts->bit;
+	else
+		trace_flags->val |= opts->bit;
+
+	return 0;
+}
+
 static ssize_t
 tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 			size_t cnt, loff_t *ppos)

@@ -2469,6 +2536,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 	char *cmp = buf;
 	int neg = 0;
 	int i;
+	int ret;
 
 	if (cnt >= sizeof(buf))
 		return -EINVAL;

@@ -2494,11 +2562,13 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 			break;
 		}
 	}
-	/*
-	 * If no option could be set, return an error:
-	 */
-	if (!trace_options[i])
-		return -EINVAL;
+
+	/* If no option could be set, test the specific tracer options */
+	if (!trace_options[i]) {
+		ret = set_tracer_option(current_trace, cmp, neg);
+		if (ret)
+			return ret;
+	}
 
 	filp->f_pos += cnt;
 

index cdbd5cc..fc06485 100644
@@ -259,6 +259,29 @@ enum print_line_t {
 	TRACE_TYPE_UNHANDLED	= 2	/* Relay to other output functions */
 };
 
+
+/*
+ * An option specific to a tracer. This is a boolean value.
+ * The bit is the bit index that sets its value on the
+ * flags value in struct tracer_flags.
+ */
+struct tracer_opt {
+	const char *name; /* Will appear on the trace_options file */
+	u32 bit; /* The mask assigned in val field in tracer_flags */
+};
+
+/*
+ * The set of specific options for a tracer. Your tracer
+ * have to set the initial value of the flags val.
+ */
+struct tracer_flags {
+	u32	val;
+	struct tracer_opt *opts;
+};
+
+/* Makes more easy to define a tracer opt */
+#define TRACER_OPT(s, b) .name = #s, .bit = b
+
 /*
  * A specific tracer, represented by methods that operate on a trace array:
  */

@@ -280,8 +303,12 @@ struct tracer {
 					    struct trace_array *tr);
 #endif
 	enum print_line_t	(*print_line)(struct trace_iterator *iter);
+	/* If you handled the flag setting, return 0 */
+	int			(*set_flag)(u32 old_flags, u32 bit,
+							int set);
 	struct tracer		*next;
 	int			print_max;
+	struct tracer_flags *flags;
 };
 
 struct trace_seq {

@@ -484,6 +511,7 @@ enum trace_iterator_flags {
 #define TRACE_ITER_SYM_MASK \
 	(TRACE_ITER_PRINT_PARENT|TRACE_ITER_SYM_OFFSET|TRACE_ITER_SYM_ADDR)
 
+
 extern struct tracer nop_trace;
 
 /**

index 4a90462..cd123e2 100644
@@ -43,6 +43,20 @@
 unsigned long __read_mostly	tracing_max_latency = (cycle_t)ULONG_MAX;
 unsigned long __read_mostly	tracing_thresh;
 
+/* For tracers that don't implement custom flags */
+static struct tracer_opt dummy_tracer_opt[] = {
+	{ }
+};
+
+static struct tracer_flags dummy_tracer_flags = {
+	.val = 0,
+	.opts = dummy_tracer_opt
+};
+
+static int dummy_set_flag(u32 old_flags, u32 bit, int set)
+{
+	return 0;
+}
 
 /*
  * Kill all tracing for good (never come back).

@@ -531,6 +545,14 @@ int register_tracer(struct tracer *type)
 		}
 	}
 
+	if (!type->set_flag)
+		type->set_flag = &dummy_set_flag;
+	if (!type->flags)
+		type->flags = &dummy_tracer_flags;
+	else
+		if (!type->flags->opts)
+			type->flags->opts = dummy_tracer_opt;
+
 #ifdef CONFIG_FTRACE_STARTUP_TEST
 	if (type->selftest) {
 		struct tracer *saved_tracer = current_trace;

@@ -2428,10 +2450,13 @@ static ssize_t
 tracing_trace_options_read(struct file *filp, char __user *ubuf,
 		       size_t cnt, loff_t *ppos)
 {
+	int i;
 	char *buf;
 	int r = 0;
 	int len = 0;
-	int i;
+	u32 tracer_flags = current_trace->flags->val;
+	struct tracer_opt *trace_opts = current_trace->flags->opts;
+
 
 	/* calulate max size */
 	for (i = 0; trace_options[i]; i++) {

@@ -2439,6 +2464,15 @@ tracing_trace_options_read(struct file *filp, char __user *ubuf,
 		len += 3; /* "no" and space */
 	}
 
+	/*
+	 * Increase the size with names of options specific
+	 * of the current tracer.
+	 */
+	for (i = 0; trace_opts[i].name; i++) {
+		len += strlen(trace_opts[i].name);
+		len += 3; /* "no" and space */
+	}
+
 	/* +2 for \n and \0 */
 	buf = kmalloc(len + 2, GFP_KERNEL);
 	if (!buf)

@@ -2451,6 +2485,15 @@ tracing_trace_options_read(struct file *filp, char __user *ubuf,
 			r += sprintf(buf + r, "no%s ", trace_options[i]);
 	}
 
+	for (i = 0; trace_opts[i].name; i++) {
+		if (tracer_flags & trace_opts[i].bit)
+			r += sprintf(buf + r, "%s ",
+				trace_opts[i].name);
+		else
+			r += sprintf(buf + r, "no%s ",
+				trace_opts[i].name);
+	}
+
 	r += sprintf(buf + r, "\n");
 	WARN_ON(r >= len + 2);
 

@@ -2461,6 +2504,40 @@ tracing_trace_options_read(struct file *filp, char __user *ubuf,
 	return r;
 }
 
+/* Try to assign a tracer specific option */
+static int set_tracer_option(struct tracer *trace, char *cmp, int neg)
+{
+	struct tracer_flags *trace_flags = trace->flags;
+	struct tracer_opt *opts = NULL;
+	int ret = 0, i = 0;
+	int len;
+
+	for (i = 0; trace_flags->opts[i].name; i++) {
+		opts = &trace_flags->opts[i];
+		len = strlen(opts->name);
+
+		if (strncmp(cmp, opts->name, len) == 0) {
+			ret = trace->set_flag(trace_flags->val,
+				opts->bit, !neg);
+			break;
+		}
+	}
+	/* Not found */
+	if (!trace_flags->opts[i].name)
+		return -EINVAL;
+
+	/* Refused to handle */
+	if (ret)
+		return ret;
+
+	if (neg)
+		trace_flags->val &= ~opts->bit;
+	else
+		trace_flags->val |= opts->bit;
+
+	return 0;
+}
+
 static ssize_t
 tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 			size_t cnt, loff_t *ppos)

@@ -2468,6 +2545,7 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 	char buf[64];
 	char *cmp = buf;
 	int neg = 0;
+	int ret;
 	int i;
 
 	if (cnt >= sizeof(buf))

@@ -2494,11 +2572,13 @@ tracing_trace_options_write(struct file *filp, const char __user *ubuf,
 			break;
 		}
 	}
-	/*
-	 * If no option could be set, return an error:
-	 */
-	if (!trace_options[i])
-		return -EINVAL;
+
+	/* If no option could be set, test the specific tracer options */
+	if (!trace_options[i]) {
+		ret = set_tracer_option(current_trace, cmp, neg);
+		if (ret)
+			return ret;
+	}
 
 	filp->f_pos += cnt;
 

index 790ea8c..23c8b67 100644
@@ -259,6 +259,29 @@ enum print_line_t {
 	TRACE_TYPE_UNHANDLED	= 2	/* Relay to other output functions */
 };
 
+
+/*
+ * An option specific to a tracer. This is a boolean value.
+ * The bit is the bit index that sets its value on the
+ * flags value in struct tracer_flags.
+ */
+struct tracer_opt {
+	const char 	*name; /* Will appear on the trace_options file */
+	u32 		bit; /* Mask assigned in val field in tracer_flags */
+};
+
+/*
+ * The set of specific options for a tracer. Your tracer
+ * have to set the initial value of the flags val.
+ */
+struct tracer_flags {
+	u32			val;
+	struct tracer_opt 	*opts;
+};
+
+/* Makes more easy to define a tracer opt */
+#define TRACER_OPT(s, b)	.name = #s, .bit = b
+
 /*
  * A specific tracer, represented by methods that operate on a trace array:
  */

@@ -279,8 +302,11 @@ struct tracer {
 					    struct trace_array *tr);
 #endif
 	enum print_line_t	(*print_line)(struct trace_iterator *iter);
+	/* If you handled the flag setting, return 0 */
+	int			(*set_flag)(u32 old_flags, u32 bit, int set);
 	struct tracer		*next;
 	int			print_max;
+	struct tracer_flags 	*flags;
 };
 
 struct trace_seq {