Add support for identifying KStackWatch watchpoints in the ARM64
hardware breakpoint handler. When a watchpoint belongs to KStackWatch,
the handler bypasses single-step re-arming to allow proper recovery.

Introduce is_ksw_watch_handler() to detect KStackWatch-managed
breakpoints and use it in watchpoint_report() under
CONFIG_KSTACKWATCH.

Signed-off-by: Jinchao Wang <wangjinchao600@gmail.com>
---
 arch/arm64/kernel/hw_breakpoint.c | 7 +++++++
 include/linux/kstackwatch.h       | 2 ++
 mm/kstackwatch/watch.c            | 8 ++++++++
 3 files changed, 17 insertions(+)

diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index bd7d23d7893d..7abcd988c5c2 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -14,6 +14,9 @@
 #include <linux/errno.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/kprobes.h>
+#ifdef CONFIG_KSTACKWATCH
+#include <linux/kstackwatch.h>
+#endif
 #include <linux/perf_event.h>
 #include <linux/ptrace.h>
 #include <linux/smp.h>
@@ -738,6 +741,10 @@ static int watchpoint_report(struct perf_event *wp, unsigned long addr,
 			     struct pt_regs *regs)
 {
 	int step = is_default_overflow_handler(wp);
+#ifdef CONFIG_KSTACKWATCH
+	if (is_ksw_watch_handler(wp))
+		step = 1;
+#endif
 	struct arch_hw_breakpoint *info = counter_arch_bp(wp);
 
 	info->trigger = addr;
diff --git a/include/linux/kstackwatch.h b/include/linux/kstackwatch.h
index afedd9823de9..ce3882acc5dc 100644
--- a/include/linux/kstackwatch.h
+++ b/include/linux/kstackwatch.h
@@ -53,6 +53,8 @@ struct ksw_watchpoint {
 	struct llist_node node; // for atomic watch_on and off
 	struct list_head list; // for cpu online and offline
 };
+
+bool is_ksw_watch_handler(struct perf_event *event);
 int ksw_watch_init(void);
 void ksw_watch_exit(void);
 int ksw_watch_get(struct ksw_watchpoint **out_wp);
diff --git a/mm/kstackwatch/watch.c b/mm/kstackwatch/watch.c
index 99184f63d7e3..c2aa912bf4c4 100644
--- a/mm/kstackwatch/watch.c
+++ b/mm/kstackwatch/watch.c
@@ -64,6 +64,14 @@ static void ksw_watch_handler(struct perf_event *bp,
 		panic("Stack corruption detected");
 }
 
+bool is_ksw_watch_handler(struct perf_event *event)
+{
+	perf_overflow_handler_t overflow_handler = event->overflow_handler;
+
+	if (unlikely(overflow_handler == ksw_watch_handler))
+		return true;
+	return false;
+}
 static void ksw_watch_on_local_cpu(void *info)
 {
 	struct ksw_watchpoint *wp = info;
-- 
2.43.0