tracing: Move pid_list write processing into its own function

The addition of PIDs into a pid_list via the write operation of
set_event_pid is a bit complex. The same operation will be needed for
function tracing pids. Move the code into its own generic function in
trace.c, so that we can avoid duplication of this code.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace.c

@@ -25,7 +25,7 @@
 #include <linux/hardirq.h>
 #include <linux/linkage.h>
 #include <linux/uaccess.h>
-#include <linux/kprobes.h>
+#include <linux/vmalloc.h>
 #include <linux/ftrace.h>
 #include <linux/module.h>
 #include <linux/percpu.h>
@@ -319,6 +319,12 @@ int call_filter_check_discard(struct trace_event_call *call, void *rec,
 	return 0;
 }
 
+void trace_free_pid_list(struct trace_pid_list *pid_list)
+{
+	vfree(pid_list->pids);
+	kfree(pid_list);
+}
+
 /**
  * trace_find_filtered_pid - check if a pid exists in a filtered_pid list
  * @filtered_pids: The list of pids to check
@@ -468,6 +474,107 @@ int trace_pid_show(struct seq_file *m, void *v)
 	return 0;
 }
 
+/* 128 should be much more than enough */
+#define PID_BUF_SIZE		127
+
+int trace_pid_write(struct trace_pid_list *filtered_pids,
+		    struct trace_pid_list **new_pid_list,
+		    const char __user *ubuf, size_t cnt)
+{
+	struct trace_pid_list *pid_list;
+	struct trace_parser parser;
+	unsigned long val;
+	int nr_pids = 0;
+	ssize_t read = 0;
+	ssize_t ret = 0;
+	loff_t pos;
+	pid_t pid;
+
+	if (trace_parser_get_init(&parser, PID_BUF_SIZE + 1))
+		return -ENOMEM;
+
+	/*
+	 * Always recreate a new array. The write is an all or nothing
+	 * operation. Always create a new array when adding new pids by
+	 * the user. If the operation fails, then the current list is
+	 * not modified.
+	 */
+	pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL);
+	if (!pid_list)
+		return -ENOMEM;
+
+	pid_list->pid_max = READ_ONCE(pid_max);
+
+	/* Only truncating will shrink pid_max */
+	if (filtered_pids && filtered_pids->pid_max > pid_list->pid_max)
+		pid_list->pid_max = filtered_pids->pid_max;
+
+	pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
+	if (!pid_list->pids) {
+		kfree(pid_list);
+		return -ENOMEM;
+	}
+
+	if (filtered_pids) {
+		/* copy the current bits to the new max */
+		pid = find_first_bit(filtered_pids->pids,
+				     filtered_pids->pid_max);
+		while (pid < filtered_pids->pid_max) {
+			set_bit(pid, pid_list->pids);
+			pid = find_next_bit(filtered_pids->pids,
+					    filtered_pids->pid_max,
+					    pid + 1);
+			nr_pids++;
+		}
+	}
+
+	while (cnt > 0) {
+
+		pos = 0;
+
+		ret = trace_get_user(&parser, ubuf, cnt, &pos);
+		if (ret < 0 || !trace_parser_loaded(&parser))
+			break;
+
+		read += ret;
+		ubuf += ret;
+		cnt -= ret;
+
+		parser.buffer[parser.idx] = 0;
+
+		ret = -EINVAL;
+		if (kstrtoul(parser.buffer, 0, &val))
+			break;
+		if (val >= pid_list->pid_max)
+			break;
+
+		pid = (pid_t)val;
+
+		set_bit(pid, pid_list->pids);
+		nr_pids++;
+
+		trace_parser_clear(&parser);
+		ret = 0;
+	}
+	trace_parser_put(&parser);
+
+	if (ret < 0) {
+		trace_free_pid_list(pid_list);
+		return ret;
+	}
+
+	if (!nr_pids) {
+		/* Cleared the list of pids */
+		trace_free_pid_list(pid_list);
+		read = ret;
+		pid_list = NULL;
+	}
+
+	*new_pid_list = pid_list;
+
+	return read;
+}
+
 static cycle_t buffer_ftrace_now(struct trace_buffer *buf, int cpu)
 {
 	u64 ts;

kernel/trace/trace.h

@@ -629,6 +629,9 @@ extern unsigned long nsecs_to_usecs(unsigned long nsecs);
 extern unsigned long tracing_thresh;
 
 /* PID filtering */
+
+extern int pid_max;
+
 bool trace_find_filtered_pid(struct trace_pid_list *filtered_pids,
 			     pid_t search_pid);
 bool trace_ignore_this_task(struct trace_pid_list *filtered_pids,
@@ -639,6 +642,10 @@ void trace_filter_add_remove_task(struct trace_pid_list *pid_list,
 void *trace_pid_next(struct trace_pid_list *pid_list, void *v, loff_t *pos);
 void *trace_pid_start(struct trace_pid_list *pid_list, loff_t *pos);
 int trace_pid_show(struct seq_file *m, void *v);
+void trace_free_pid_list(struct trace_pid_list *pid_list);
+int trace_pid_write(struct trace_pid_list *filtered_pids,
+		    struct trace_pid_list **new_pid_list,
+		    const char __user *ubuf, size_t cnt);
 
 #ifdef CONFIG_TRACER_MAX_TRACE
 void update_max_tr(struct trace_array *tr, struct task_struct *tsk, int cpu);

kernel/trace/trace_events.c

@@ -15,7 +15,6 @@
 #include <linux/kthread.h>
 #include <linux/tracefs.h>
 #include <linux/uaccess.h>
-#include <linux/vmalloc.h>
 #include <linux/module.h>
 #include <linux/ctype.h>
 #include <linux/sort.h>
@@ -499,9 +498,6 @@ static void ftrace_clear_events(struct trace_array *tr)
 	mutex_unlock(&event_mutex);
 }
 
-/* Shouldn't this be in a header? */
-extern int pid_max;
-
 static void
 event_filter_pid_sched_process_exit(void *data, struct task_struct *task)
 {
@@ -634,8 +630,7 @@ static void __ftrace_clear_event_pids(struct trace_array *tr)
 	/* Wait till all users are no longer using pid filtering */
 	synchronize_sched();
 
-	vfree(pid_list->pids);
-	kfree(pid_list);
+	trace_free_pid_list(pid_list);
 }
 
 static void ftrace_clear_event_pids(struct trace_array *tr)
@@ -1587,13 +1582,7 @@ ftrace_event_pid_write(struct file *filp, const char __user *ubuf,
 	struct trace_pid_list *filtered_pids = NULL;
 	struct trace_pid_list *pid_list;
 	struct trace_event_file *file;
-	struct trace_parser parser;
-	unsigned long val;
-	loff_t this_pos;
-	ssize_t read = 0;
-	ssize_t ret = 0;
-	pid_t pid;
-	int nr_pids = 0;
+	ssize_t ret;
 
 	if (!cnt)
 		return 0;
@@ -1602,93 +1591,15 @@ ftrace_event_pid_write(struct file *filp, const char __user *ubuf,
 	if (ret < 0)
 		return ret;
 
-	if (trace_parser_get_init(&parser, EVENT_BUF_SIZE + 1))
-		return -ENOMEM;
-
 	mutex_lock(&event_mutex);
+
 	filtered_pids = rcu_dereference_protected(tr->filtered_pids,
 					     lockdep_is_held(&event_mutex));
 
-	/*
-	 * Always recreate a new array. The write is an all or nothing
-	 * operation. Always create a new array when adding new pids by
-	 * the user. If the operation fails, then the current list is
-	 * not modified.
-	 */
-	pid_list = kmalloc(sizeof(*pid_list), GFP_KERNEL);
-	if (!pid_list) {
-		read = -ENOMEM;
-		goto out;
-	}
-	pid_list->pid_max = READ_ONCE(pid_max);
-	/* Only truncating will shrink pid_max */
-	if (filtered_pids && filtered_pids->pid_max > pid_list->pid_max)
-		pid_list->pid_max = filtered_pids->pid_max;
-	pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
-	if (!pid_list->pids) {
-		kfree(pid_list);
-		read = -ENOMEM;
-		goto out;
-	}
-	if (filtered_pids) {
-		/* copy the current bits to the new max */
-		pid = find_first_bit(filtered_pids->pids,
-				     filtered_pids->pid_max);
-		while (pid < filtered_pids->pid_max) {
-			set_bit(pid, pid_list->pids);
-			pid = find_next_bit(filtered_pids->pids,
-					    filtered_pids->pid_max,
-					    pid + 1);
-			nr_pids++;
-		}
-	}
-
-	while (cnt > 0) {
-
-		this_pos = 0;
-
-		ret = trace_get_user(&parser, ubuf, cnt, &this_pos);
-		if (ret < 0 || !trace_parser_loaded(&parser))
-			break;
-
-		read += ret;
-		ubuf += ret;
-		cnt -= ret;
-
-		parser.buffer[parser.idx] = 0;
-
-		ret = -EINVAL;
-		if (kstrtoul(parser.buffer, 0, &val))
-			break;
-		if (val >= pid_list->pid_max)
-			break;
-
-		pid = (pid_t)val;
-
-		set_bit(pid, pid_list->pids);
-		nr_pids++;
-
-		trace_parser_clear(&parser);
-		ret = 0;
-	}
-	trace_parser_put(&parser);
-
-	if (ret < 0) {
-		vfree(pid_list->pids);
-		kfree(pid_list);
-		read = ret;
+	ret = trace_pid_write(filtered_pids, &pid_list, ubuf, cnt);
+	if (ret < 0)
 		goto out;
-	}
 
-	if (!nr_pids) {
-		/* Cleared the list of pids */
-		vfree(pid_list->pids);
-		kfree(pid_list);
-		read = ret;
-		if (!filtered_pids)
-			goto out;
-		pid_list = NULL;
-	}
 	rcu_assign_pointer(tr->filtered_pids, pid_list);
 
 	list_for_each_entry(file, &tr->events, list) {
@@ -1697,10 +1608,8 @@ ftrace_event_pid_write(struct file *filp, const char __user *ubuf,
 
 	if (filtered_pids) {
 		synchronize_sched();
-
-		vfree(filtered_pids->pids);
-		kfree(filtered_pids);
-	} else {
+		trace_free_pid_list(filtered_pids);
+	} else if (pid_list) {
 		/*
 		 * Register a probe that is called before all other probes
 		 * to set ignore_pid if next or prev do not match.
@@ -1738,9 +1647,8 @@ ftrace_event_pid_write(struct file *filp, const char __user *ubuf,
  out:
 	mutex_unlock(&event_mutex);
 
-	ret = read;
-	if (read > 0)
-		*ppos += read;
+	if (ret > 0)
+		*ppos += ret;
 
 	return ret;
 }