Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/kernel/reboot.c b/kernel/reboot.c
index 8fb44de..c4d472b 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/kernel/reboot.c
  *
@@ -31,6 +32,7 @@
 #define DEFAULT_REBOOT_MODE
 #endif
 enum reboot_mode reboot_mode DEFAULT_REBOOT_MODE;
+enum reboot_mode panic_reboot_mode = REBOOT_UNDEFINED;
 
 /*
  * This variable is used privately to keep track of whether or not
@@ -49,6 +51,7 @@
  */
 
 void (*pm_power_off_prepare)(void);
+EXPORT_SYMBOL_GPL(pm_power_off_prepare);
 
 /**
  *	emergency_restart - reboot the system
@@ -518,6 +521,8 @@
 static int __init reboot_setup(char *str)
 {
 	for (;;) {
+		enum reboot_mode *mode;
+
 		/*
 		 * Having anything passed on the command line via
 		 * reboot= will cause us to disable DMI checking
@@ -525,17 +530,24 @@
 		 */
 		reboot_default = 0;
 
+		if (!strncmp(str, "panic_", 6)) {
+			mode = &panic_reboot_mode;
+			str += 6;
+		} else {
+			mode = &reboot_mode;
+		}
+
 		switch (*str) {
 		case 'w':
-			reboot_mode = REBOOT_WARM;
+			*mode = REBOOT_WARM;
 			break;
 
 		case 'c':
-			reboot_mode = REBOOT_COLD;
+			*mode = REBOOT_COLD;
 			break;
 
 		case 'h':
-			reboot_mode = REBOOT_HARD;
+			*mode = REBOOT_HARD;
 			break;
 
 		case 's':
@@ -552,11 +564,11 @@
 				if (rc)
 					return rc;
 			} else
-				reboot_mode = REBOOT_SOFT;
+				*mode = REBOOT_SOFT;
 			break;
 		}
 		case 'g':
-			reboot_mode = REBOOT_GPIO;
+			*mode = REBOOT_GPIO;
 			break;
 
 		case 'b':