Pre-allocate per-CPU hardware breakpoints at init with a place holder
address, which will be retargeted dynamically in kprobe handler.
This avoids allocation in atomic context.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 mm/kstackwatch/kstackwatch.h |  4 +++
 mm/kstackwatch/watch.c       | 55 ++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+)

diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
index 277b192f80fa..3ea191370970 100644
--- a/mm/kstackwatch/kstackwatch.h
+++ b/mm/kstackwatch/kstackwatch.h
@@ -38,4 +38,8 @@ struct ksw_config {
 // singleton, only modified in kernel.c
 const struct ksw_config *ksw_get_config(void);
 
+/* watch management */
+int ksw_watch_init(void);
+void ksw_watch_exit(void);
+
 #endif /* _KSTACKWATCH_H */
diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c
index cec594032515..d3399ac840b2 100644
--- a/mm/kstackwatch/watch.c
+++ b/mm/kstackwatch/watch.c
@@ -1 +1,56 @@
 // SPDX-License-Identifier: GPL-2.0
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/hw_breakpoint.h>
+#include <linux/perf_event.h>
+#include <linux/printk.h>
+
+#include "kstackwatch.h"
+
+static struct perf_event *__percpu *watch_events;
+
+static unsigned long watch_holder;
+
+static struct perf_event_attr watch_attr;
+
+bool panic_on_catch;
+module_param(panic_on_catch, bool, 0644);
+MODULE_PARM_DESC(panic_on_catch, "panic immediately on corruption catch");
+static void ksw_watch_handler(struct perf_event *bp,
+			      struct perf_sample_data *data,
+			      struct pt_regs *regs)
+{
+	pr_err("========== KStackWatch: Caught stack corruption =======\n");
+	pr_err("config %s\n", ksw_get_config()->config_str);
+	dump_stack();
+	pr_err("=================== KStackWatch End ===================\n");
+
+	if (panic_on_catch)
+		panic("Stack corruption detected");
+}
+
+int ksw_watch_init(void)
+{
+	int ret;
+
+	hw_breakpoint_init(&watch_attr);
+	watch_attr.bp_addr = (unsigned long)&watch_holder;
+	watch_attr.bp_len = sizeof(watch_holder);
+	watch_attr.bp_type = HW_BREAKPOINT_W;
+	watch_events = register_wide_hw_breakpoint(&watch_attr,
+						   ksw_watch_handler,
+						   NULL);
+	if (IS_ERR(watch_events)) {
+		ret = PTR_ERR(watch_events);
+		pr_err("failed to register wide hw breakpoint: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
+void ksw_watch_exit(void)
+{
+	unregister_wide_hw_breakpoint(watch_events);
+	watch_events = NULL;
+}
-- 
2.43.0