linux-kernel - [PATCH v4 14/21] mm/ksw: add self-debug helpers

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Message-ID: <20250912101145.465708-15-wangjinchao600@gmail.com>
Date: Fri, 12 Sep 2025 18:11:24 +0800
From: Jinchao Wang <wangjinchao600@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
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Cc: Jinchao Wang <wangjinchao600@...il.com>
Subject: [PATCH v4 14/21] mm/ksw: add self-debug helpers

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@...il.com>
---
 mm/kstackwatch/kstackwatch.h |  2 ++
 mm/kstackwatch/watch.c       | 18 ++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
index 5ea2db76cdfb..9a4900df8ff8 100644
--- a/mm/kstackwatch/kstackwatch.h
+++ b/mm/kstackwatch/kstackwatch.h
@@ -47,5 +47,7 @@ int ksw_watch_init(void);
 void ksw_watch_exit(void);
 int ksw_watch_on(ulong watch_addr, u16 watch_len);
 int ksw_watch_off(ulong watch_addr, u16 watch_len);
+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 795e779792da..2e9294595bf3 100644
--- a/mm/kstackwatch/watch.c
+++ b/mm/kstackwatch/watch.c
@@ -161,3 +161,21 @@ void ksw_watch_exit(void)
 	unregister_wide_hw_breakpoint(watch_events);
 	watch_events = NULL;
 }
+
+/* self debug function */
+void ksw_watch_show(void)
+{
+	pr_info("watch target bp_addr: 0x%llx len:%llu\n", watch_attr.bp_addr,
+		watch_attr.bp_len);
+}
+EXPORT_SYMBOL_GPL(ksw_watch_show);
+
+/* self debug function */
+void ksw_watch_fire(void)
+{
+	char *ptr = (char *)watch_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