Windbg Setup for QEMU

For general instructions see postbuild/os/README.md

Enabling Windbg

If Windows doesn't boot properly on QEMU you are basically stuck wondering what is happening with no output after bootmgr starts there will be no further update in the serial port. To debug windows we need to connect windbg to the QEMU to see what is happening as drivers boot.

As long as you pull the published windows image it has Windbg enabled by default. If you don't attach the debugger it will continue to boot after 30 seconds.

    Write-Host "Enabling debug"
    bcdedit /store ${efiLetter}:\EFI\Microsoft\Boot\BCD /set "{default}" debug on

If you want to debug early boot process because it is not making it into NTOS you can enable bootdebug as well

bcdedit /store BCD /set {globalsettings} bootdebug yes

Windbg can be connected on windbg -k com:ipport=56789,port=127.0.0.1 -v

Debugging QEMU with GDB

When debugging in UEFI, secure world, or when system isn't responding you will often find yourself needing a GDB connection to the device. QEMU has built in support for GDB interface and makes it very easy to debug with GDB.

Ffter your system starts or is in the state you want to connect you can use

gdb-multiarch
(gdb) set debug aarch64
(gdb) target extended-remote localhost:5555

For more details debugging with GDB or using Windbg with GDB you can read the following documents. Patina Debugging