[PATCH 1/2] efi_loader: efi_setup: Add efi_start_obj_list() to efi_setup.c

[Simon Glass]

Hi Heinrich,

On Fri, 3 Jan 2025 at 12:55, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>
> On 06.12.24 18:30, Adriano Cordova wrote:
> > The command bootefi calls efi_init_obj_list to do the efi set up
> > before launching an .efi payload, but efi_init_obj_list is called
> > only once. There are some initializations which depend on the
> > environment and should be done each time a payload gets launched and
> > not only once and can now be done in efi_start_obj_list(). A motivation
> > for this change is the following order of events:
> >
> > 1. Launch an EFI application (e.g. bootefi hello)
> > 2. Change the ip address
> > 3. Launch another application which uses the pxe protocol
>
> Hello Adriano,
>
> Thanks for addressing this issue.
>
> There are a number of events that can lead to updating the IP address:
>
> * EFI_PXE_BASE_CODE_PROTOCOL.Dhcp()
> * EFI_PXE_BASE_CODE_PROTOCOL.SetStationIp()
> * EFI_HTTP_PROTOCOL.Configure()
> * command set env ethaddr#
> * command dhcp
>
> All of these events require:
>
> * Updating the relevant ethaddr* variable.
> * Updating any other references to the IP address.
>
> When not only considering EFI applications but also EFI drivers
> installed via the bootefi command all of these events can occur during
> the runtime of EFI binaries.
>
> Function efi_init_obj_list() is used for setups that are needed only
> once before accessing the UEFI sub-system. It is not able to handle events.
>
> If we need to update any internal UEFI data structures, we should do
> this instantaneously when the event occurs and not when executing a UEFI
> related shell command.
>
> U-Boot already has callbacks invoked when variables are changed. These
> are set up with U_BOOT_ENV_CALLBACK(). There is even a command 'env
> callbacks' to list these callbacks.
>
> You could define a new function to handle changes of the IP address and
> invoke it via U_BOOT_ENV_CALLBACK(ipaddr, <function name>) or
> U_BOOT_ENV_CALLBACK(netmask, <function name>).
>
> With lwIP we can have multiple network interfaces. Each has a different
> variable ipaddr# assigned to it. We will have to extend the concept of
> U_BOOT_ENV_CALLBACK() to allow for wildcard matches by adjusting
> find_env_callback(). With CONFIG_REGEX=y regular expressions could be
> used for this purpose (cf. include/slre.h) but we should better avoid
> the code size increase.
>

I have been saying for some time that EFI_LOADER should make use of
U-Boot's existing tables, rather than creating its own duplicate ones
with extra info.

This seems to have been understood as 'hang the EFI tables onto
existing data structures', e.g. efi_disk_create_part(). But this leads
to duplication.

Perhaps the EFI_LOADER init should be quite small, and be done each
time an app starts, to deal with the 'current' state of U-Boot?

Regards,
Simon