Use the hardware watchdog timer. When the machine resets, the bootloader can check a hardware register to determine the reset cause, and then boot into a differ

Use the hardware watchdog timer. When the machine resets, the bootloader can check a hardware register to determine the reset cause, and then boot into a different OS partition. (note: not every SoC has a register indicating reset cause, I’ve worked with Allwinner chips that don’t, so alternate methods may be required) Enable the watchdog timer at the start of the bootloader. (I work with arm systems so this would be in uboot). If no bootable OS is found, or the system crashes before the kernel fully boots, the watchdog times out. In Linux, enable the watchdog timer at boot in your kconfig. Then have a userspace service that periodically pings /dev/watchdog to keep the system alive. Have your panic handler just hang, and the watchdog will reset the machine. Another helpful trick to save panic logs is to use pstore/ramoops to keep a portion of the kernel logs across resets, and then save the pstore buffer out to disk after booting into the recovery system.