[PATCH v7 16/23] mm/ksw: add self-debug helpers

[Jinchao Wang <wangjinchao600@gmail.com>]

Provide two debug helpers:

- ksw_watch_show(): print the current watch target address and length.
- ksw_watch_fire(): intentionally trigger the watchpoint immediately
  by writing to the watched address, useful for testing HWBP behavior.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 mm/kstackwatch/kstackwatch.h |  2 ++
 mm/kstackwatch/watch.c       | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
index 4045890e5652..528001534047 100644
--- a/mm/kstackwatch/kstackwatch.h
+++ b/mm/kstackwatch/kstackwatch.h
@@ -52,5 +52,7 @@ void ksw_watch_exit(void);
 int ksw_watch_get(struct ksw_watchpoint **out_wp);
 int ksw_watch_on(struct ksw_watchpoint *wp, ulong watch_addr, u16 watch_len);
 int ksw_watch_off(struct ksw_watchpoint *wp);
+void ksw_watch_show(void);
+void ksw_watch_fire(void);
 
 #endif /* _KSTACKWATCH_H */
diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c
index f32b1e46168c..9837d6873d92 100644
--- a/mm/kstackwatch/watch.c
+++ b/mm/kstackwatch/watch.c
@@ -269,3 +269,37 @@ void ksw_watch_exit(void)
 {
 	ksw_watch_free();
 }
+
+/* self debug function */
+void ksw_watch_show(void)
+{
+	struct ksw_watchpoint *wp = current->ksw_ctx.wp;
+
+	if (!wp) {
+		pr_info("nothing to show\n");
+		return;
+	}
+
+	pr_info("watch target bp_addr: 0x%llx len:%llu\n", wp->attr.bp_addr,
+		wp->attr.bp_len);
+}
+EXPORT_SYMBOL_GPL(ksw_watch_show);
+
+/* self debug function */
+void ksw_watch_fire(void)
+{
+	struct ksw_watchpoint *wp;
+	char *ptr;
+
+	wp = current->ksw_ctx.wp;
+
+	if (!wp) {
+		pr_info("nothing to fire\n");
+		return;
+	}
+
+	ptr = (char *)wp->attr.bp_addr;
+	pr_warn("watch triggered immediately\n");
+	*ptr = 0x42; // This should trigger immediately for any bp_len
+}
+EXPORT_SYMBOL_GPL(ksw_watch_fire);
-- 
2.43.0