[warm/fast-reboot] Fix kexec portion to support platforms based on Device Tree (#1966)

The warm-reboot and fast-reboot commands currently expect a platform that uses
GRUB.  Information about the current kernel boot arguments is extracted from
the GRUB config file. This commit adds support for platforms that do not use
GRUB but rather use Device Tree to define the current kernel boot arguments.
Example platform architectures using Device Tree include armhf and arm64.

This commit also includes a minor improvement to a similar change made to the
soft-reboot command in PR# 1963

Author: dflynn-Nokia

scripts/fast-reboot

@@ -27,6 +27,7 @@ SSD_FW_UPDATE="ssd-fw-upgrade"
 TAG_LATEST=yes
 DETACH=no
 LOG_PATH="/var/log/${REBOOT_TYPE}.txt"
+UIMAGE_HDR_SIZE=64
 
 # Require 100M available on the hard drive for warm reboot temp files,
 # Size is in 1K blocks:
@@ -327,15 +328,33 @@ function setup_reboot_variables()
             KERNEL_IMAGE="$(ls $IMAGE_PATH/boot/vmlinuz-*)"
             BOOT_OPTIONS="$(cat "$IMAGE_PATH/kernel-cmdline" | tr '\n' ' ') SONIC_BOOT_TYPE=${BOOT_TYPE_ARG}"
         fi
+        INITRD=$(echo $KERNEL_IMAGE | sed 's/vmlinuz/initrd.img/g')
     elif grep -q onie_platform= /host/machine.conf; then
-        KERNEL_OPTIONS=$(cat /host/grub/grub.cfg | sed "/$NEXT_SONIC_IMAGE'/,/}/"'!'"g" | grep linux)
-        KERNEL_IMAGE="/host$(echo $KERNEL_OPTIONS | cut -d ' ' -f 2)"
-        BOOT_OPTIONS="$(echo $KERNEL_OPTIONS | sed -e 's/\s*linux\s*/BOOT_IMAGE=/') SONIC_BOOT_TYPE=${BOOT_TYPE_ARG}"
+        if [ -r /host/grub/grub.cfg ]; then
+            KERNEL_OPTIONS=$(cat /host/grub/grub.cfg | sed "/$NEXT_SONIC_IMAGE'/,/}/"'!'"g" | grep linux)
+            KERNEL_IMAGE="/host$(echo $KERNEL_OPTIONS | cut -d ' ' -f 2)"
+            BOOT_OPTIONS="$(echo $KERNEL_OPTIONS | sed -e 's/\s*linux\s*/BOOT_IMAGE=/') SONIC_BOOT_TYPE=${BOOT_TYPE_ARG}"
+            INITRD=$(echo $KERNEL_IMAGE | sed 's/vmlinuz/initrd.img/g')
+        # Handle architectures supporting Device Tree
+        elif [ -f /sys/firmware/devicetree/base/chosen/bootargs ]; then
+            KERNEL_IMAGE="$(ls $IMAGE_PATH/boot/vmlinuz-*)"
+            BOOT_OPTIONS="$(cat /sys/firmware/devicetree/base/chosen/bootargs | sed 's/.$//') SONIC_BOOT_TYPE=${BOOT_TYPE_ARG}"
+            INITRD=$(echo $KERNEL_IMAGE | sed 's/vmlinuz/initrd.img/g')
+
+            # If initrd is a U-Boot uImage, remove the uImage header
+            if file ${INITRD} | grep -q uImage; then
+                INITRD_RAW=$(echo $KERNEL_IMAGE | sed 's/vmlinuz/initrd-raw.img/g')
+                tail -c+$((${UIMAGE_HDR_SIZE}+1)) < ${INITRD} > ${INITRD_RAW}
+                INITRD=${INITRD_RAW}
+            fi
+        else
+            error "Unknown ONIE platform bootloader. ${REBOOT_TYPE} is not supported."
+            exit "${EXIT_NOT_SUPPORTED}"
+        fi
     else
         error "Unknown bootloader. ${REBOOT_TYPE} is not supported."
         exit "${EXIT_NOT_SUPPORTED}"
     fi
-    INITRD=$(echo $KERNEL_IMAGE | sed 's/vmlinuz/initrd.img/g')
 }
 
 function check_docker_exec()
@@ -393,7 +412,7 @@ function reboot_pre_check()
         error "Failed to verify next image. Exit code: $INSTALLER_VERIFY_RC"
         exit ${EXIT_SONIC_INSTALLER_VERIFY_REBOOT}
     fi
-    
+
     # Make sure ASIC configuration has not changed between images
     ASIC_CONFIG_CHECK_SCRIPT="/usr/local/bin/asic_config_check"
     ASIC_CONFIG_CHECK_SUCCESS=0

scripts/soft-reboot

@@ -5,6 +5,7 @@ REBOOT_TIME=$(date)
 REBOOT_METHOD="/sbin/kexec -e"
 LOG_SSD_HEALTH="/usr/local/bin/log_ssd_health"
 WATCHDOG_UTIL="/usr/local/bin/watchdogutil"
+UIMAGE_HDR_SIZE=64
 
 EXIT_SUCCESS=0
 EXIT_FAILURE=1
@@ -133,7 +134,7 @@ function setup_reboot_variables()
             # If initrd is a U-Boot uImage, remove the uImage header
             if file ${INITRD} | grep -q uImage; then
                 INITRD_RAW=$(echo $KERNEL_IMAGE | sed 's/vmlinuz/initrd-raw.img/g')
-                tail -c+65 < ${INITRD} > ${INITRD_RAW}
+                tail -c+$((${UIMAGE_HDR_SIZE}+1)) < ${INITRD} > ${INITRD_RAW}
                 INITRD=${INITRD_RAW}
             fi
         else