I did a very similar thing, but without secure boot, and only for PXE booting Linux kernels that are EFI stubs.
If you are lucky and have PXE BC available, then you can actually "re-use" the IP address assigned to your machine if you PXE boot into your application. From there, you can issue two TFTP commands, set up a configuration table with LINUX_EFI_INITRD_MEDIA_GUID pointing to the start of initrd in memory (the memory has to have type LOADER_DATA), load the kernel, use LoadedImage::set_load_options to provide kernel parameters (init, loglevel, etc.), and finally call start_image.
Also went down a rabbit hole yesterday and ended up implementing a very basic DHCP client on top of bare SNP. For reference, SNP is essentially writing raw ethernet frames to the transmit buffer of a NIC. I didn't pursue TFTP or PXE protocols because those would be too much to implement myself. In any case, I successfully got an IP address assigned on real hardware.
The coolest part about Rust is that my DHCP implementation was taken from another of my Rust projects where I implemented a basic PXE server. All I had to do was copy-paste one file and rename a std::net import to core::net. That is where Rust truly feels like "cheating" when targetting no_std environments.
If you are lucky and have PXE BC available, then you can actually "re-use" the IP address assigned to your machine if you PXE boot into your application. From there, you can issue two TFTP commands, set up a configuration table with LINUX_EFI_INITRD_MEDIA_GUID pointing to the start of initrd in memory (the memory has to have type LOADER_DATA), load the kernel, use LoadedImage::set_load_options to provide kernel parameters (init, loglevel, etc.), and finally call start_image.
Also went down a rabbit hole yesterday and ended up implementing a very basic DHCP client on top of bare SNP. For reference, SNP is essentially writing raw ethernet frames to the transmit buffer of a NIC. I didn't pursue TFTP or PXE protocols because those would be too much to implement myself. In any case, I successfully got an IP address assigned on real hardware.
The coolest part about Rust is that my DHCP implementation was taken from another of my Rust projects where I implemented a basic PXE server. All I had to do was copy-paste one file and rename a std::net import to core::net. That is where Rust truly feels like "cheating" when targetting no_std environments.