Add arch_reinstall_hw_breakpoint() to restore a hardware breakpoint
in an atomic context. Unlike the full uninstall and reallocation
path, this lightweight function re-establishes an existing breakpoint
efficiently and safely.

This aligns ARM64 with x86 support for atomic breakpoint reinstalls.
---
 arch/arm64/Kconfig                     | 1 +
 arch/arm64/include/asm/hw_breakpoint.h | 1 +
 arch/arm64/kernel/hw_breakpoint.c      | 5 +++++
 3 files changed, 7 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 6663ffd23f25..fa35dfa2f5cc 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -232,6 +232,7 @@ config ARM64
 	select HAVE_HARDLOCKUP_DETECTOR_PERF if PERF_EVENTS && \
 		HW_PERF_EVENTS && HAVE_PERF_EVENTS_NMI
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS
+	select HAVE_REINSTALL_HW_BREAKPOINT if PERF_EVENTS
 	select HAVE_IOREMAP_PROT
 	select HAVE_IRQ_TIME_ACCOUNTING
 	select HAVE_LIVEPATCH
diff --git a/arch/arm64/include/asm/hw_breakpoint.h b/arch/arm64/include/asm/hw_breakpoint.h
index bd81cf17744a..6c98bbbc6aa6 100644
--- a/arch/arm64/include/asm/hw_breakpoint.h
+++ b/arch/arm64/include/asm/hw_breakpoint.h
@@ -119,6 +119,7 @@ extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
 					   unsigned long val, void *data);
 
 extern int arch_install_hw_breakpoint(struct perf_event *bp);
+extern int arch_reinstall_hw_breakpoint(struct perf_event *bp);
 extern void arch_uninstall_hw_breakpoint(struct perf_event *bp);
 extern void hw_breakpoint_pmu_read(struct perf_event *bp);
 extern int hw_breakpoint_slots(int type);
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index ab76b36dce82..bd7d23d7893d 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -292,6 +292,11 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
 	return hw_breakpoint_control(bp, HW_BREAKPOINT_INSTALL);
 }
 
+int arch_reinstall_hw_breakpoint(struct perf_event *bp)
+{
+	return hw_breakpoint_control(bp, HW_BREAKPOINT_RESTORE);
+}
+
 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 {
 	hw_breakpoint_control(bp, HW_BREAKPOINT_UNINSTALL);
-- 
2.43.0