Modify the reboot() syscall handler in kernel/reboot.c to call
liveupdate_reboot() when processing the LINUX_REBOOT_CMD_KEXEC
command.

This ensures that the Live Update Orchestrator is notified just
before the kernel executes the kexec jump. The liveupdate_reboot()
function triggers the final LIVEUPDATE_FREEZE event, allowing
participating subsystems to perform last-minute state saving within
the blackout window, and transitions the LUO state machine to FROZEN.

The call is placed immediately before kernel_kexec() to ensure LUO
finalization happens at the latest possible moment before the kernel
transition.

If liveupdate_reboot() returns an error (indicating a failure during
LUO finalization), the kexec operation is aborted to prevent proceeding
with an inconsistent state.

Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
---
 kernel/reboot.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/reboot.c b/kernel/reboot.c
index ec087827c85c..bdeb04a773db 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -13,6 +13,7 @@
 #include <linux/kexec.h>
 #include <linux/kmod.h>
 #include <linux/kmsg_dump.h>
+#include <linux/liveupdate.h>
 #include <linux/reboot.h>
 #include <linux/suspend.h>
 #include <linux/syscalls.h>
@@ -797,6 +798,9 @@ SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
 
 #ifdef CONFIG_KEXEC_CORE
 	case LINUX_REBOOT_CMD_KEXEC:
+		ret = liveupdate_reboot();
+		if (ret)
+			break;
 		ret = kernel_kexec();
 		break;
 #endif
-- 
2.50.1.565.gc32cd1483b-goog