1 files changed, 307 insertions, 296 deletions

diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index 8c804e24f96f..b10c0d90a6ff 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -60,6 +60,13 @@ static int last_ftrace_enabled;
 /* Quick disabling of function tracer. */
 int function_trace_stop;
 
+/* List for set_ftrace_pid's pids. */
+LIST_HEAD(ftrace_pids);
+struct ftrace_pid {
+	struct list_head list;
+	struct pid *pid;
+};
+
 /*
  * ftrace_disabled is set when an anomaly is discovered.
  * ftrace_disabled is much stronger than ftrace_enabled.
@@ -78,6 +85,10 @@ ftrace_func_t ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t __ftrace_trace_function __read_mostly = ftrace_stub;
 ftrace_func_t ftrace_pid_function __read_mostly = ftrace_stub;
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static int ftrace_set_func(unsigned long *array, int *idx, char *buffer);
+#endif
+
 static void ftrace_list_func(unsigned long ip, unsigned long parent_ip)
 {
 	struct ftrace_ops *op = ftrace_list;
@@ -155,7 +166,7 @@ static int __register_ftrace_function(struct ftrace_ops *ops)
 		else
 			func = ftrace_list_func;
 
-		if (ftrace_pid_trace) {
+		if (!list_empty(&ftrace_pids)) {
 			set_ftrace_pid_function(func);
 			func = ftrace_pid_func;
 		}
@@ -203,7 +214,7 @@ static int __unregister_ftrace_function(struct ftrace_ops *ops)
 		if (ftrace_list->next == &ftrace_list_end) {
 			ftrace_func_t func = ftrace_list->func;
 
-			if (ftrace_pid_trace) {
+			if (!list_empty(&ftrace_pids)) {
 				set_ftrace_pid_function(func);
 				func = ftrace_pid_func;
 			}
@@ -225,9 +236,13 @@ static void ftrace_update_pid_func(void)
 	if (ftrace_trace_function == ftrace_stub)
 		return;
 
+#ifdef CONFIG_HAVE_FUNCTION_TRACE_MCOUNT_TEST
 	func = ftrace_trace_function;
+#else
+	func = __ftrace_trace_function;
+#endif
 
-	if (ftrace_pid_trace) {
+	if (!list_empty(&ftrace_pids)) {
 		set_ftrace_pid_function(func);
 		func = ftrace_pid_func;
 	} else {
@@ -817,8 +832,6 @@ static __init void ftrace_profile_debugfs(struct dentry *d_tracer)
 }
 #endif /* CONFIG_FUNCTION_PROFILER */
 
-/* set when tracing only a pid */
-struct pid *ftrace_pid_trace;
 static struct pid * const ftrace_swapper_pid = &init_struct_pid;
 
 #ifdef CONFIG_DYNAMIC_FTRACE
@@ -1074,14 +1087,9 @@ static void ftrace_replace_code(int enable)
 		failed = __ftrace_replace_code(rec, enable);
 		if (failed) {
 			rec->flags |= FTRACE_FL_FAILED;
-			if ((system_state == SYSTEM_BOOTING) ||
-			    !core_kernel_text(rec->ip)) {
-				ftrace_free_rec(rec);
-				} else {
-				ftrace_bug(failed, rec->ip);
-					/* Stop processing */
-					return;
-				}
+			ftrace_bug(failed, rec->ip);
+			/* Stop processing */
+			return;
 		}
 	} while_for_each_ftrace_rec();
 }
@@ -1262,12 +1270,34 @@ static int ftrace_update_code(struct module *mod)
 		ftrace_new_addrs = p->newlist;
 		p->flags = 0L;
 
-		/* convert record (i.e, patch mcount-call with NOP) */
-		if (ftrace_code_disable(mod, p)) {
-			p->flags |= FTRACE_FL_CONVERTED;
-			ftrace_update_cnt++;
-		} else
+		/*
+		 * Do the initial record convertion from mcount jump
+		 * to the NOP instructions.
+		 */
+		if (!ftrace_code_disable(mod, p)) {
 			ftrace_free_rec(p);
+			continue;
+		}
+
+		p->flags |= FTRACE_FL_CONVERTED;
+		ftrace_update_cnt++;
+
+		/*
+		 * If the tracing is enabled, go ahead and enable the record.
+		 *
+		 * The reason not to enable the record immediatelly is the
+		 * inherent check of ftrace_make_nop/ftrace_make_call for
+		 * correct previous instructions.  Making first the NOP
+		 * conversion puts the module to the correct state, thus
+		 * passing the ftrace_make_call check.
+		 */
+		if (ftrace_start_up) {
+			int failed = __ftrace_replace_code(p, 1);
+			if (failed) {
+				ftrace_bug(failed, p->ip);
+				ftrace_free_rec(p);
+			}
+		}
 	}
 
 	stop = ftrace_now(raw_smp_processor_id());
@@ -1323,11 +1353,10 @@ static int __init ftrace_dyn_table_alloc(unsigned long num_to_init)
 
 enum {
 	FTRACE_ITER_FILTER	= (1 << 0),
-	FTRACE_ITER_CONT	= (1 << 1),
-	FTRACE_ITER_NOTRACE	= (1 << 2),
-	FTRACE_ITER_FAILURES	= (1 << 3),
-	FTRACE_ITER_PRINTALL	= (1 << 4),
-	FTRACE_ITER_HASH	= (1 << 5),
+	FTRACE_ITER_NOTRACE	= (1 << 1),
+	FTRACE_ITER_FAILURES	= (1 << 2),
+	FTRACE_ITER_PRINTALL	= (1 << 3),
+	FTRACE_ITER_HASH	= (1 << 4),
 };
 
 #define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */
@@ -1337,8 +1366,7 @@ struct ftrace_iterator {
 	int			hidx;
 	int			idx;
 	unsigned		flags;
-	unsigned char		buffer[FTRACE_BUFF_MAX+1];
-	unsigned		buffer_idx;
+	struct trace_parser	parser;
 };
 
 static void *
@@ -1407,7 +1435,7 @@ static int t_hash_show(struct seq_file *m, void *v)
 	if (rec->ops->print)
 		return rec->ops->print(m, rec->ip, rec->ops, rec->data);
 
-	seq_printf(m, "%pf:%pf", (void *)rec->ip, (void *)rec->ops->func);
+	seq_printf(m, "%ps:%ps", (void *)rec->ip, (void *)rec->ops->func);
 
 	if (rec->data)
 		seq_printf(m, ":%p", rec->data);
@@ -1517,12 +1545,12 @@ static int t_show(struct seq_file *m, void *v)
 	if (!rec)
 		return 0;
 
-	seq_printf(m, "%pf\n", (void *)rec->ip);
+	seq_printf(m, "%ps\n", (void *)rec->ip);
 
 	return 0;
 }
 
-static struct seq_operations show_ftrace_seq_ops = {
+static const struct seq_operations show_ftrace_seq_ops = {
 	.start = t_start,
 	.next = t_next,
 	.stop = t_stop,
@@ -1604,6 +1632,11 @@ ftrace_regex_open(struct inode *inode, struct file *file, int enable)
 	if (!iter)
 		return -ENOMEM;
 
+	if (trace_parser_get_init(&iter->parser, FTRACE_BUFF_MAX)) {
+		kfree(iter);
+		return -ENOMEM;
+	}
+
 	mutex_lock(&ftrace_regex_lock);
 	if ((file->f_mode & FMODE_WRITE) &&
 	    (file->f_flags & O_TRUNC))
@@ -1618,8 +1651,10 @@ ftrace_regex_open(struct inode *inode, struct file *file, int enable)
 		if (!ret) {
 			struct seq_file *m = file->private_data;
 			m->private = iter;
-		} else
+		} else {
+			trace_parser_put(&iter->parser);
 			kfree(iter);
+		}
 	} else
 		file->private_data = iter;
 	mutex_unlock(&ftrace_regex_lock);
@@ -1652,60 +1687,6 @@ ftrace_regex_lseek(struct file *file, loff_t offset, int origin)
 	return ret;
 }
 
-enum {
-	MATCH_FULL,
-	MATCH_FRONT_ONLY,
-	MATCH_MIDDLE_ONLY,
-	MATCH_END_ONLY,
-};
-
-/*
- * (static function - no need for kernel doc)
- *
- * Pass in a buffer containing a glob and this function will
- * set search to point to the search part of the buffer and
- * return the type of search it is (see enum above).
- * This does modify buff.
- *
- * Returns enum type.
- *  search returns the pointer to use for comparison.
- *  not returns 1 if buff started with a '!'
- *     0 otherwise.
- */
-static int
-ftrace_setup_glob(char *buff, int len, char **search, int *not)
-{
-	int type = MATCH_FULL;
-	int i;
-
-	if (buff[0] == '!') {
-		*not = 1;
-		buff++;
-		len--;
-	} else
-		*not = 0;
-
-	*search = buff;
-
-	for (i = 0; i < len; i++) {
-		if (buff[i] == '*') {
-			if (!i) {
-				*search = buff + 1;
-				type = MATCH_END_ONLY;
-			} else {
-				if (type == MATCH_END_ONLY)
-					type = MATCH_MIDDLE_ONLY;
-				else
-					type = MATCH_FRONT_ONLY;
-				buff[i] = 0;
-				break;
-			}
-		}
-	}
-
-	return type;
-}
-
 static int ftrace_match(char *str, char *regex, int len, int type)
 {
 	int matched = 0;
@@ -1754,7 +1735,7 @@ static void ftrace_match_records(char *buff, int len, int enable)
 	int not;
 
 	flag = enable ? FTRACE_FL_FILTER : FTRACE_FL_NOTRACE;
-	type = ftrace_setup_glob(buff, len, &search, &not);
+	type = filter_parse_regex(buff, len, &search, &not);
 
 	search_len = strlen(search);
 
@@ -1822,7 +1803,7 @@ static void ftrace_match_module_records(char *buff, char *mod, int enable)
 	}
 
 	if (strlen(buff)) {
-		type = ftrace_setup_glob(buff, strlen(buff), &search, &not);
+		type = filter_parse_regex(buff, strlen(buff), &search, &not);
 		search_len = strlen(search);
 	}
 
@@ -1987,7 +1968,7 @@ register_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 	int count = 0;
 	char *search;
 
-	type = ftrace_setup_glob(glob, strlen(glob), &search, &not);
+	type = filter_parse_regex(glob, strlen(glob), &search, &not);
 	len = strlen(search);
 
 	/* we do not support '!' for function probes */
@@ -2059,12 +2040,12 @@ __unregister_ftrace_function_probe(char *glob, struct ftrace_probe_ops *ops,
 	int i, len = 0;
 	char *search;
 
-	if (glob && (strcmp(glob, "*") || !strlen(glob)))
+	if (glob && (strcmp(glob, "*") == 0 || !strlen(glob)))
 		glob = NULL;
-	else {
+	else if (glob) {
 		int not;
 
-		type = ftrace_setup_glob(glob, strlen(glob), &search, &not);
+		type = filter_parse_regex(glob, strlen(glob), &search, &not);
 		len = strlen(search);
 
 		/* we do not support '!' for function probes */
@@ -2196,11 +2177,10 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
 		   size_t cnt, loff_t *ppos, int enable)
 {
 	struct ftrace_iterator *iter;
-	char ch;
-	size_t read = 0;
-	ssize_t ret;
+	struct trace_parser *parser;
+	ssize_t ret, read;
 
-	if (!cnt || cnt < 0)
+	if (!cnt)
 		return 0;
 
 	mutex_lock(&ftrace_regex_lock);
@@ -2211,72 +2191,23 @@ ftrace_regex_write(struct file *file, const char __user *ubuf,
 	} else
 		iter = file->private_data;
 
-	if (!*ppos) {
-		iter->flags &= ~FTRACE_ITER_CONT;
-		iter->buffer_idx = 0;
-	}
-
-	ret = get_user(ch, ubuf++);
-	if (ret)
-		goto out;
-	read++;
-	cnt--;
+	parser = &iter->parser;
+	read = trace_get_user(parser, ubuf, cnt, ppos);
 
-	/*
-	 * If the parser haven't finished with the last write,
-	 * continue reading the user input without skipping spaces.
-	 */
-	if (!(iter->flags & FTRACE_ITER_CONT)) {
-		/* skip white space */
-		while (cnt && isspace(ch)) {
-			ret = get_user(ch, ubuf++);
-			if (ret)
-				goto out;
-			read++;
-			cnt--;
-		}
-
-		/* only spaces were written */
-		if (isspace(ch)) {
-			*ppos += read;
-			ret = read;
-			goto out;
-		}
-
-		iter->buffer_idx = 0;
-	}
-
-	while (cnt && !isspace(ch)) {
-		if (iter->buffer_idx < FTRACE_BUFF_MAX)
-			iter->buffer[iter->buffer_idx++] = ch;
-		else {
-			ret = -EINVAL;
-			goto out;
-		}
-		ret = get_user(ch, ubuf++);
+	if (read >= 0 && trace_parser_loaded(parser) &&
+	    !trace_parser_cont(parser)) {
+		ret = ftrace_process_regex(parser->buffer,
+					   parser->idx, enable);
 		if (ret)
 			goto out;
-		read++;
-		cnt--;
-	}
 
-	if (isspace(ch)) {
-		iter->buffer[iter->buffer_idx] = 0;
-		ret = ftrace_process_regex(iter->buffer,
-					   iter->buffer_idx, enable);
-		if (ret)
-			goto out;
-		iter->buffer_idx = 0;
-	} else {
-		iter->flags |= FTRACE_ITER_CONT;
-		iter->buffer[iter->buffer_idx++] = ch;
+		trace_parser_clear(parser);
 	}
 
-	*ppos += read;
 	ret = read;
- out:
-	mutex_unlock(&ftrace_regex_lock);
 
+	mutex_unlock(&ftrace_regex_lock);
+out:
 	return ret;
 }
 
@@ -2343,6 +2274,7 @@ void ftrace_set_notrace(unsigned char *buf, int len, int reset)
 #define FTRACE_FILTER_SIZE		COMMAND_LINE_SIZE
 static char ftrace_notrace_buf[FTRACE_FILTER_SIZE] __initdata;
 static char ftrace_filter_buf[FTRACE_FILTER_SIZE] __initdata;
+static char ftrace_graph_buf[FTRACE_FILTER_SIZE] __initdata;
 
 static int __init set_ftrace_notrace(char *str)
 {
@@ -2358,6 +2290,31 @@ static int __init set_ftrace_filter(char *str)
 }
 __setup("ftrace_filter=", set_ftrace_filter);
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+static int __init set_graph_function(char *str)
+{
+	strlcpy(ftrace_graph_buf, str, FTRACE_FILTER_SIZE);
+	return 1;
+}
+__setup("ftrace_graph_filter=", set_graph_function);
+
+static void __init set_ftrace_early_graph(char *buf)
+{
+	int ret;
+	char *func;
+
+	while (buf) {
+		func = strsep(&buf, ",");
+		/* we allow only one expression at a time */
+		ret = ftrace_set_func(ftrace_graph_funcs, &ftrace_graph_count,
+				      func);
+		if (ret)
+			printk(KERN_DEBUG "ftrace: function %s not "
+					  "traceable\n", func);
+	}
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
+
 static void __init set_ftrace_early_filter(char *buf, int enable)
 {
 	char *func;
@@ -2374,6 +2331,10 @@ static void __init set_ftrace_early_filters(void)
 		set_ftrace_early_filter(ftrace_filter_buf, 1);
 	if (ftrace_notrace_buf[0])
 		set_ftrace_early_filter(ftrace_notrace_buf, 0);
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	if (ftrace_graph_buf[0])
+		set_ftrace_early_graph(ftrace_graph_buf);
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 }
 
 static int
@@ -2381,6 +2342,7 @@ ftrace_regex_release(struct inode *inode, struct file *file, int enable)
 {
 	struct seq_file *m = (struct seq_file *)file->private_data;
 	struct ftrace_iterator *iter;
+	struct trace_parser *parser;
 
 	mutex_lock(&ftrace_regex_lock);
 	if (file->f_mode & FMODE_READ) {
@@ -2390,9 +2352,10 @@ ftrace_regex_release(struct inode *inode, struct file *file, int enable)
 	} else
 		iter = file->private_data;
 
-	if (iter->buffer_idx) {
-		iter->buffer[iter->buffer_idx] = 0;
-		ftrace_match_records(iter->buffer, iter->buffer_idx, enable);
+	parser = &iter->parser;
+	if (trace_parser_loaded(parser)) {
+		parser->buffer[parser->idx] = 0;
+		ftrace_match_records(parser->buffer, parser->idx, enable);
 	}
 
 	mutex_lock(&ftrace_lock);
@@ -2400,7 +2363,9 @@ ftrace_regex_release(struct inode *inode, struct file *file, int enable)
 		ftrace_run_update_code(FTRACE_ENABLE_CALLS);
 	mutex_unlock(&ftrace_lock);
 
+	trace_parser_put(parser);
 	kfree(iter);
+
 	mutex_unlock(&ftrace_regex_lock);
 	return 0;
 }
@@ -2457,11 +2422,9 @@ unsigned long ftrace_graph_funcs[FTRACE_GRAPH_MAX_FUNCS] __read_mostly;
 static void *
 __g_next(struct seq_file *m, loff_t *pos)
 {
-	unsigned long *array = m->private;
-
 	if (*pos >= ftrace_graph_count)
 		return NULL;
-	return &array[*pos];
+	return &ftrace_graph_funcs[*pos];
 }
 
 static void *
@@ -2499,12 +2462,12 @@ static int g_show(struct seq_file *m, void *v)
 		return 0;
 	}
 
-	seq_printf(m, "%pf\n", v);
+	seq_printf(m, "%ps\n", (void *)*ptr);
 
 	return 0;
 }
 
-static struct seq_operations ftrace_graph_seq_ops = {
+static const struct seq_operations ftrace_graph_seq_ops = {
 	.start = g_start,
 	.next = g_next,
 	.stop = g_stop,
@@ -2525,16 +2488,10 @@ ftrace_graph_open(struct inode *inode, struct file *file)
 		ftrace_graph_count = 0;
 		memset(ftrace_graph_funcs, 0, sizeof(ftrace_graph_funcs));
 	}
+	mutex_unlock(&graph_lock);
 
-	if (file->f_mode & FMODE_READ) {
+	if (file->f_mode & FMODE_READ)
 		ret = seq_open(file, &ftrace_graph_seq_ops);
-		if (!ret) {
-			struct seq_file *m = file->private_data;
-			m->private = ftrace_graph_funcs;
-		}
-	} else
-		file->private_data = ftrace_graph_funcs;
-	mutex_unlock(&graph_lock);
 
 	return ret;
 }
@@ -2563,7 +2520,7 @@ ftrace_set_func(unsigned long *array, int *idx, char *buffer)
 		return -ENODEV;
 
 	/* decode regex */
-	type = ftrace_setup_glob(buffer, strlen(buffer), &search, &not);
+	type = filter_parse_regex(buffer, strlen(buffer), &search, &not);
 	if (not)
 		return -EINVAL;
 
@@ -2602,12 +2559,8 @@ static ssize_t
 ftrace_graph_write(struct file *file, const char __user *ubuf,
 		   size_t cnt, loff_t *ppos)
 {
-	unsigned char buffer[FTRACE_BUFF_MAX+1];
-	unsigned long *array;
-	size_t read = 0;
-	ssize_t ret;
-	int index = 0;
-	char ch;
+	struct trace_parser parser;
+	ssize_t read, ret;
 
 	if (!cnt || cnt < 0)
 		return 0;
@@ -2616,60 +2569,31 @@ ftrace_graph_write(struct file *file, const char __user *ubuf,
 
 	if (ftrace_graph_count >= FTRACE_GRAPH_MAX_FUNCS) {
 		ret = -EBUSY;
-		goto out;
+		goto out_unlock;
 	}
 
-	if (file->f_mode & FMODE_READ) {
-		struct seq_file *m = file->private_data;
-		array = m->private;
-	} else
-		array = file->private_data;
-
-	ret = get_user(ch, ubuf++);
-	if (ret)
-		goto out;
-	read++;
-	cnt--;
-
-	/* skip white space */
-	while (cnt && isspace(ch)) {
-		ret = get_user(ch, ubuf++);
-		if (ret)
-			goto out;
-		read++;
-		cnt--;
+	if (trace_parser_get_init(&parser, FTRACE_BUFF_MAX)) {
+		ret = -ENOMEM;
+		goto out_unlock;
 	}
 
-	if (isspace(ch)) {
-		*ppos += read;
-		ret = read;
-		goto out;
-	}
+	read = trace_get_user(&parser, ubuf, cnt, ppos);
 
-	while (cnt && !isspace(ch)) {
-		if (index < FTRACE_BUFF_MAX)
-			buffer[index++] = ch;
-		else {
-			ret = -EINVAL;
-			goto out;
-		}
-		ret = get_user(ch, ubuf++);
+	if (read >= 0 && trace_parser_loaded((&parser))) {
+		parser.buffer[parser.idx] = 0;
+
+		/* we allow only one expression at a time */
+		ret = ftrace_set_func(ftrace_graph_funcs, &ftrace_graph_count,
+					parser.buffer);
 		if (ret)
-			goto out;
-		read++;
-		cnt--;
+			goto out_free;
 	}
-	buffer[index] = 0;
-
-	/* we allow only one expression at a time */
-	ret = ftrace_set_func(array, &ftrace_graph_count, buffer);
-	if (ret)
-		goto out;
-
-	file->f_pos += read;
 
 	ret = read;
- out:
+
+out_free:
+	trace_parser_put(&parser);
+out_unlock:
 	mutex_unlock(&graph_lock);
 
 	return ret;
@@ -2707,7 +2631,7 @@ static __init int ftrace_init_dyn_debugfs(struct dentry *d_tracer)
 	return 0;
 }
 
-static int ftrace_convert_nops(struct module *mod,
+static int ftrace_process_locs(struct module *mod,
 			       unsigned long *start,
 			       unsigned long *end)
 {
@@ -2740,19 +2664,17 @@ static int ftrace_convert_nops(struct module *mod,
 }
 
 #ifdef CONFIG_MODULES
-void ftrace_release(void *start, void *end)
+void ftrace_release_mod(struct module *mod)
 {
 	struct dyn_ftrace *rec;
 	struct ftrace_page *pg;
-	unsigned long s = (unsigned long)start;
-	unsigned long e = (unsigned long)end;
 
-	if (ftrace_disabled || !start || start == end)
+	if (ftrace_disabled)
 		return;
 
 	mutex_lock(&ftrace_lock);
 	do_for_each_ftrace_rec(pg, rec) {
-		if ((rec->ip >= s) && (rec->ip < e)) {
+		if (within_module_core(rec->ip, mod)) {
 			/*
 			 * rec->ip is changed in ftrace_free_rec()
 			 * It should not between s and e if record was freed.
@@ -2769,7 +2691,7 @@ static void ftrace_init_module(struct module *mod,
 {
 	if (ftrace_disabled || start == end)
 		return;
-	ftrace_convert_nops(mod, start, end);
+	ftrace_process_locs(mod, start, end);
 }
 
 static int ftrace_module_notify(struct notifier_block *self,
@@ -2784,9 +2706,7 @@ static int ftrace_module_notify(struct notifier_block *self,
 				   mod->num_ftrace_callsites);
 		break;
 	case MODULE_STATE_GOING:
-		ftrace_release(mod->ftrace_callsites,
-			       mod->ftrace_callsites +
-			       mod->num_ftrace_callsites);
+		ftrace_release_mod(mod);
 		break;
 	}
 
@@ -2832,7 +2752,7 @@ void __init ftrace_init(void)
 
 	last_ftrace_enabled = ftrace_enabled = 1;
 
-	ret = ftrace_convert_nops(NULL,
+	ret = ftrace_process_locs(NULL,
 				  __start_mcount_loc,
 				  __stop_mcount_loc);
 
@@ -2865,23 +2785,6 @@ static inline void ftrace_startup_enable(int command) { }
 # define ftrace_shutdown_sysctl()	do { } while (0)
 #endif /* CONFIG_DYNAMIC_FTRACE */
 
-static ssize_t
-ftrace_pid_read(struct file *file, char __user *ubuf,
-		       size_t cnt, loff_t *ppos)
-{
-	char buf[64];
-	int r;
-
-	if (ftrace_pid_trace == ftrace_swapper_pid)
-		r = sprintf(buf, "swapper tasks\n");
-	else if (ftrace_pid_trace)
-		r = sprintf(buf, "%u\n", pid_vnr(ftrace_pid_trace));
-	else
-		r = sprintf(buf, "no pid\n");
-
-	return simple_read_from_buffer(ubuf, cnt, ppos, buf, r);
-}
-
 static void clear_ftrace_swapper(void)
 {
 	struct task_struct *p;
@@ -2932,14 +2835,12 @@ static void set_ftrace_pid(struct pid *pid)
 	rcu_read_unlock();
 }
 
-static void clear_ftrace_pid_task(struct pid **pid)
+static void clear_ftrace_pid_task(struct pid *pid)
 {
-	if (*pid == ftrace_swapper_pid)
+	if (pid == ftrace_swapper_pid)
 		clear_ftrace_swapper();
 	else
-		clear_ftrace_pid(*pid);
-
-	*pid = NULL;
+		clear_ftrace_pid(pid);
 }
 
 static void set_ftrace_pid_task(struct pid *pid)
@@ -2950,11 +2851,140 @@ static void set_ftrace_pid_task(struct pid *pid)
 		set_ftrace_pid(pid);
 }
 
+static int ftrace_pid_add(int p)
+{
+	struct pid *pid;
+	struct ftrace_pid *fpid;
+	int ret = -EINVAL;
+
+	mutex_lock(&ftrace_lock);
+
+	if (!p)
+		pid = ftrace_swapper_pid;
+	else
+		pid = find_get_pid(p);
+
+	if (!pid)
+		goto out;
+
+	ret = 0;
+
+	list_for_each_entry(fpid, &ftrace_pids, list)
+		if (fpid->pid == pid)
+			goto out_put;
+
+	ret = -ENOMEM;
+
+	fpid = kmalloc(sizeof(*fpid), GFP_KERNEL);
+	if (!fpid)
+		goto out_put;
+
+	list_add(&fpid->list, &ftrace_pids);
+	fpid->pid = pid;
+
+	set_ftrace_pid_task(pid);
+
+	ftrace_update_pid_func();
+	ftrace_startup_enable(0);
+
+	mutex_unlock(&ftrace_lock);
+	return 0;
+
+out_put:
+	if (pid != ftrace_swapper_pid)
+		put_pid(pid);
+
+out:
+	mutex_unlock(&ftrace_lock);
+	return ret;
+}
+
+static void ftrace_pid_reset(void)
+{
+	struct ftrace_pid *fpid, *safe;
+
+	mutex_lock(&ftrace_lock);
+	list_for_each_entry_safe(fpid, safe, &ftrace_pids, list) {
+		struct pid *pid = fpid->pid;
+
+		clear_ftrace_pid_task(pid);
+
+		list_del(&fpid->list);
+		kfree(fpid);
+	}
+
+	ftrace_update_pid_func();
+	ftrace_startup_enable(0);
+
+	mutex_unlock(&ftrace_lock);
+}
+
+static void *fpid_start(struct seq_file *m, loff_t *pos)
+{
+	mutex_lock(&ftrace_lock);
+
+	if (list_empty(&ftrace_pids) && (!*pos))
+		return (void *) 1;
+
+	return seq_list_start(&ftrace_pids, *pos);
+}
+
+static void *fpid_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	if (v == (void *)1)
+		return NULL;
+
+	return seq_list_next(v, &ftrace_pids, pos);
+}
+
+static void fpid_stop(struct seq_file *m, void *p)
+{
+	mutex_unlock(&ftrace_lock);
+}
+
+static int fpid_show(struct seq_file *m, void *v)
+{
+	const struct ftrace_pid *fpid = list_entry(v, struct ftrace_pid, list);
+
+	if (v == (void *)1) {
+		seq_printf(m, "no pid\n");
+		return 0;
+	}
+
+	if (fpid->pid == ftrace_swapper_pid)
+		seq_printf(m, "swapper tasks\n");
+	else
+		seq_printf(m, "%u\n", pid_vnr(fpid->pid));
+
+	return 0;
+}
+
+static const struct seq_operations ftrace_pid_sops = {
+	.start = fpid_start,
+	.next = fpid_next,
+	.stop = fpid_stop,
+	.show = fpid_show,
+};
+
+static int
+ftrace_pid_open(struct inode *inode, struct file *file)
+{
+	int ret = 0;
+
+	if ((file->f_mode & FMODE_WRITE) &&
+	    (file->f_flags & O_TRUNC))
+		ftrace_pid_reset();
+
+	if (file->f_mode & FMODE_READ)
+		ret = seq_open(file, &ftrace_pid_sops);
+
+	return ret;
+}
+
 static ssize_t
 ftrace_pid_write(struct file *filp, const char __user *ubuf,
 		   size_t cnt, loff_t *ppos)
 {
-	struct pid *pid;
 	char buf[64];
 	long val;
 	int ret;
@@ -2967,57 +2997,38 @@ ftrace_pid_write(struct file *filp, const char __user *ubuf,
 
 	buf[cnt] = 0;
 
+	/*
+	 * Allow "echo > set_ftrace_pid" or "echo -n '' > set_ftrace_pid"
+	 * to clean the filter quietly.
+	 */
+	strstrip(buf);
+	if (strlen(buf) == 0)
+		return 1;
+
 	ret = strict_strtol(buf, 10, &val);
 	if (ret < 0)
 		return ret;
 
-	mutex_lock(&ftrace_lock);
-	if (val < 0) {
-		/* disable pid tracing */
-		if (!ftrace_pid_trace)
-			goto out;
-
-		clear_ftrace_pid_task(&ftrace_pid_trace);
-
-	} else {
-		/* swapper task is special */
-		if (!val) {
-			pid = ftrace_swapper_pid;
-			if (pid == ftrace_pid_trace)
-				goto out;
-		} else {
-			pid = find_get_pid(val);
-
-			if (pid == ftrace_pid_trace) {
-				put_pid(pid);
-				goto out;
-			}
-		}
-
-		if (ftrace_pid_trace)
-			clear_ftrace_pid_task(&ftrace_pid_trace);
-
-		if (!pid)
-			goto out;
+	ret = ftrace_pid_add(val);
 
-		ftrace_pid_trace = pid;
-
-		set_ftrace_pid_task(ftrace_pid_trace);
-	}
-
-	/* update the function call */
-	ftrace_update_pid_func();
-	ftrace_startup_enable(0);
+	return ret ? ret : cnt;
+}
 
- out:
-	mutex_unlock(&ftrace_lock);
+static int
+ftrace_pid_release(struct inode *inode, struct file *file)
+{
+	if (file->f_mode & FMODE_READ)
+		seq_release(inode, file);
 
-	return cnt;
+	return 0;
 }
 
 static const struct file_operations ftrace_pid_fops = {
-	.read = ftrace_pid_read,
-	.write = ftrace_pid_write,
+	.open		= ftrace_pid_open,
+	.write		= ftrace_pid_write,
+	.read		= seq_read,
+	.llseek		= seq_lseek,
+	.release	= ftrace_pid_release,
 };
 
 static __init int ftrace_init_debugfs(void)
@@ -3100,7 +3111,7 @@ int unregister_ftrace_function(struct ftrace_ops *ops)
 
 int
 ftrace_enable_sysctl(struct ctl_table *table, int write,
-		     struct file *file, void __user *buffer, size_t *lenp,
+		     void __user *buffer, size_t *lenp,
 		     loff_t *ppos)
 {
 	int ret;
@@ -3110,7 +3121,7 @@ ftrace_enable_sysctl(struct ctl_table *table, int write,
 
 	mutex_lock(&ftrace_lock);
 
-	ret  = proc_dointvec(table, write, file, buffer, lenp, ppos);
+	ret  = proc_dointvec(table, write, buffer, lenp, ppos);
 
 	if (ret || !write || (last_ftrace_enabled == !!ftrace_enabled))
 		goto out;