commit e558ab1c451b01193c6c7a9dfaa2d639b0212584
author Jiyong Park <jiyong@google.com> Thu Jul 07 20:18:55 2022 +0900
committer Jiyong Park <jiyong@google.com> Fri Jul 08 14:48:46 2022 +0900
tree 99953931c385460ddda96a1efb2c953b6d073fc1
parent 9e5ae63ae9d8c2fac84486feb1c1b9fe227610a0

VirtualizationService notifies to its client when ramdump is available

When a kernel panic occurs in a pVM and the ramdump is enabled there, a
ramdump file is generated.

This file should eventually be consumed by the client (the owner of the
VM) for further analysis. VirtualizationService let its client know that
a ramdump has been created and provide access to it.

Specifically, the end-to-end flow is as follows:

1) When starting a VM, an empty file is created under the VM-specific
   directory (`/data/misc/virtualizationservice/<cid>/ramdump`).

2) The file becomes a backing store for a virtio-console device
   (/dev/hvc3).

3) When a kernel panic occurs, the `crashdump` binary is executed and
   the `/proc/vmcore` is written to `/dev/hvc3`. After the dump is done,
   the VM triggers a reboot which is kills crosvm.

4) Virtualizationservice is notified with the exit of crosvm. It then
   checks the size of the ramdump file. If that is not empty, it can
   assume that a ramdump was occurred in the pVM.

5) Then virtualizationservice notifies the event via
   `IVirtualMachineCallback.onRamdump(ParcelFileDescriptor)`, where the
   parcel file descriptor is the handle to the ramdump file.

6) Client reads the ramdump file.

This change also adds `--ramdump` option to the `vm` tool to designate
the path where ramdump is saved to.

Bug: 238278104
Test: follow the steps. Automated tests will be added in a followup CL
1) Run a pVM:
adb shell /apex/com.android.virt/bin/vm run-app --debug full --mem 300 \
--ramdump /data/local/tmp/virt/myramdump \
/data/local/tmp/virt/MicrodroidDemoApp.apk \
/data/local/tmp/virt/apk.idsig /data/local/tmp/virt/instance.img \
assets/vm_config.json

2) Adb shell into the VM
adb forward tcp:8000 vsock:10:5555
adb connect localhost:8000
adb -s localhost:8000 root
adb -s localhost:8000 shell

3) Load the crashdump kernel
/system/bin/kexec \
/system/etc/microdroid_crashdump_kernel \
/system/etc/microdroid_crashdump_initrd.img \
"1 rdinit=/bin/crashdump nr_cpus=1 reset_devices console=hvc0 earlycon=uart8250,mmio,0x3f8"

4) Trigger a crash
echo c > /proc/sysrq-trigger

5) Check the ramdump at /data/local/tmp/virt/myramdump

Change-Id: I1f90537961632708ca5a889cdd53390030518bb8