[edk2-devel] How to add a DXE driver to an OVMF image?

[Andrew Fish via groups.io]

> On Nov 4, 2022, at 6:20 AM, d.meneses via groups.io <d.meneses=softi9.pt at groups.io> wrote:
> 
> Using DebugLib instead to print a message, I was able to confirm that my driver is now running properly:
> cat debug.log | grep Hello
> This works both when adding it in the OVMF build and also when inserted by UEFITool.
> 
> The drivers is not being listed by the EFI Shell drivers command.
> This is expected to me as Dxe Drivers are unloaded after they return.
> Nonetheless, the same is happening when I package it as a DXE_RUNTIME_DRIVER.
> What is it that I'm missing?
> 

The UEFI Shell drivers command is managing UEFI Driver Model Drivers [1]. A UEFI Driver Model Driver has no depex and publishes an EFI Driver Binding protocol [2]. The idea is the BDS (platform) can now have the policy of what driver gets connected to what device. This is all managed by gBS->ConnectController()/gBS->DisconnectController(). 

A DXE Driver just publishes an arbitrary protocol. 

[1] https://uefi.org/specs/UEFI/2.10/11_Protocols_UEFI_Driver_Model.html
[2] https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Protocol/DriverBinding.h


PS I seem to remember a question about launching an App….

It is possible to customize a generic UEFIs system boot policy via NVRAM variable. You can read up on that here [3]. 

If you want to change the platform policy in a secure way to do something you likely need to modify the BDS (Boot Device Selection). The design idea around BDS is you could make a system an ATM or a PC just by changing the policy in the BDS, thus the BDS is a place to centralize the platform policy. The easiest way to customize the edk2 BDS is via a custom PlatformBootManagerLib. You can look at the OVMF instance here [4]. You can use this library to add extra policy on top of the NVRAM variables in the UEFI Spec [3]. If you look at the OVMF example this is how the OVMF platform makes the UEFI Shell a default boot option [5].

[3] https://uefi.org/specs/UEFI/2.10/03_Boot_Manager.html#globally-defined-variables
[4] https://github.com/tianocore/edk2/tree/master/OvmfPkg/Library/PlatformBootManagerLib
[5] https://github.com/tianocore/edk2/blob/master/OvmfPkg/Library/PlatformBootManagerLib/BdsPlatform.c#L1717

Sorry if I’m mixing up threads. So much email, and so little time….

> Thank you for your attention,
> Diogo
> 



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