linux-kernel - [PATCH 11/17] mm/ksw: add self-debug functions for kstackwatch watch

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Message-ID: <20250828073311.1116593-12-wangjinchao600@gmail.com>
Date: Thu, 28 Aug 2025 15:32:44 +0800
From: Jinchao Wang <wangjinchao600@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	"Naveen N . Rao" <naveen@...nel.org>,
	linux-mm@...ck.org,
	linux-trace-kernel@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Jinchao Wang <wangjinchao600@...il.com>
Subject: [PATCH 11/17] mm/ksw: add self-debug functions for kstackwatch watch

Introduce ksw_watch_show() and ksw_watch_fire() for runtime debugging of
kstackwatch's watch mechanism:

 - ksw_watch_show(): prints the currently armed watch address and length
 - ksw_watch_fire(): forcibly triggers the watch by writing to the watched
   address

These functions help validate the dynamic watch behavior and facilitate
testing without requiring real events.

Signed-off-by: Jinchao Wang <wangjinchao600@...il.com>
---
 mm/kstackwatch/kstackwatch.h |  2 ++
 mm/kstackwatch/watch.c       | 17 ++++++++++++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/mm/kstackwatch/kstackwatch.h b/mm/kstackwatch/kstackwatch.h
index bc8664af4fa6..d1bb5ae75aae 100644
--- a/mm/kstackwatch/kstackwatch.h
+++ b/mm/kstackwatch/kstackwatch.h
@@ -47,5 +47,7 @@ int ksw_watch_init(struct ksw_config *config);
 void ksw_watch_exit(void);
 int ksw_watch_on(u64 watch_addr, u64 watch_len);
 void ksw_watch_off(void);
+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 284facaac8fc..158843876958 100644
--- a/mm/kstackwatch/watch.c
+++ b/mm/kstackwatch/watch.c
@@ -118,7 +118,6 @@ int ksw_watch_on(u64 watch_addr, u64 watch_len)
 			ksw_watch_on_local_cpu(&watch_info);
 		} else {
 			call_single_data_t *csd = &per_cpu(watch_csd, cpu);
-
 			smp_call_function_single_async(cpu, csd);
 		}
 	}
@@ -160,3 +159,19 @@ void ksw_watch_exit(void)
 
 	pr_info("KSW: watch exited\n");
 }
+
+/* self debug function */
+void ksw_watch_show(void)
+{
+	pr_info("KSW: watch target bp_addr: 0x%llx len:%llu\n",
+		watch_info.addr, watch_info.len);
+}
+
+/* self debug function */
+void ksw_watch_fire(void)
+{
+	char *ptr = (char *)watch_info.addr;
+
+	pr_warn("KSW: watch triggered immediately\n");
+	*ptr = 0x42; // This should trigger immediately
+}
-- 
2.43.0