Allow dynamic enabling/disabling of KStackWatch through user input of proc.
With this patch, the entire system becomes functional.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 mm/kstackwatch/kernel.c | 55 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 54 insertions(+), 1 deletion(-)

diff --git a/mm/kstackwatch/kernel.c b/mm/kstackwatch/kernel.c
index 4a06ddadd9c7..11aa06908ff1 100644
--- a/mm/kstackwatch/kernel.c
+++ b/mm/kstackwatch/kernel.c
@@ -13,6 +13,43 @@
 static struct ksw_config *ksw_config;
 static atomic_t config_file_busy = ATOMIC_INIT(0);
 
+static bool watching_active;
+
+static int ksw_start_watching(void)
+{
+	int ret;
+
+	/*
+	 * Watch init will preallocate the HWBP,
+	 * so it must happen before stack init
+	 */
+	ret = ksw_watch_init();
+	if (ret) {
+		pr_err("ksw_watch_init ret: %d\n", ret);
+		return ret;
+	}
+
+	ret = ksw_stack_init();
+	if (ret) {
+		pr_err("ksw_stack_init ret: %d\n", ret);
+		ksw_watch_exit();
+		return ret;
+	}
+	watching_active = true;
+
+	pr_info("start watching: %s\n", ksw_config->user_input);
+	return 0;
+}
+
+static void ksw_stop_watching(void)
+{
+	ksw_stack_exit();
+	ksw_watch_exit();
+	watching_active = false;
+
+	pr_info("stop watching: %s\n", ksw_config->user_input);
+}
+
 struct param_map {
 	const char *name;       /* long name */
 	const char *short_name; /* short name (2 letters) */
@@ -126,6 +163,9 @@ static ssize_t kstackwatch_proc_write(struct file *file,
 	if (copy_from_user(input, buffer, count))
 		return -EFAULT;
 
+	if (watching_active)
+		ksw_stop_watching();
+
 	input[count] = '\0';
 	strim(input);
 
@@ -140,12 +180,22 @@ static ssize_t kstackwatch_proc_write(struct file *file,
 		return ret;
 	}
 
+	ret = ksw_start_watching();
+	if (ret) {
+		pr_err("Failed to start watching with %d\n", ret);
+		return ret;
+	}
+
 	return count;
 }
 
 static int kstackwatch_proc_show(struct seq_file *m, void *v)
 {
-	seq_printf(m, "%s\n", ksw_config->user_input);
+	if (watching_active)
+		seq_printf(m, "%s\n", ksw_config->user_input);
+	else
+		seq_puts(m, "not watching\n");
+
 	return 0;
 }
 
@@ -193,6 +243,9 @@ static int __init kstackwatch_init(void)
 
 static void __exit kstackwatch_exit(void)
 {
+	if (watching_active)
+		ksw_stop_watching();
+
 	remove_proc_entry("kstackwatch", NULL);
 	kfree(ksw_config->func_name);
 	kfree(ksw_config->user_input);
-- 
2.43.0