commit 8edb55379f3d7b4648dc6d2c6ed91e4d283cc7a3
author Jiyong Park <jiyong@google.com> Thu Jul 07 15:51:41 2022 +0900
committer Jiyong Park <jiyong@google.com> Fri Jul 08 11:46:49 2022 +0900
tree 0f8cd296ed3a4b14d7099466199196260060e4d0
parent 9117f013f5b389b5002c90f476bdb102150b5077

Add crashdump kernel

microdroid_crashdump_kernel is a very small kernel that is executed when
a kernel panic occurs. Since it's only use case is to run the crashdump
binary, the kernel is very minimal. In addition, it has to be as small
as possible because the kernel has to be loaded (using kexec) in the VM
RAM before a panic occurs.

To support these needs, it is built with most configuration options
turned off, except for the followings needed for dumping the RAM:

* CONFIG_CRASH_DUMP
* CONFIG_PROC_VMCORE
* CONFIG_RELOCATABLE

This is basically following the guideline at [1].

In addition, the following device drivers are enabled.

* CONFIG_SERIAL_8250 // for use as the earlycon
* CONFIG_VIRTIO_CONSOLE // for use as the dump target

[1] https://www.kernel.org/doc/html/latest/admin-guide/kdump/kdump.html#dump-capture-kernel-config-options-arch-independent

These kernel prebuilts are for now locally built. It will soon be
replaced with the prebuilts from the build bot when the kernel config is
uploaded to the Android common kernel repo.

Bug: 237380607
Test: N/A (follow-up CLs needed)

Change-Id: I238e1dbb74c0fc47fd4bb926b7d09caef4b90e78