RFC: UEFI/PXE and emulating grub-legacy-uefi-hacked behaviour

[Richard Chan]

I am interested in getting UEFI/PXE working using the EFI IP/TFTP
stack as hacked versions of grub-legacy (e,g., Fedora 17). Is there
any wisdom that the list would like to shed?

1. ON EFI platforms grub-legacy directly uses the  EFI TFTP stack and
not its own i386-pc/TFTP stack.
Network tftp-able files are referred to using the device (nd)

It has a (nd) "network device" and pulls, for it's configuration file,
(nd)/<UUID>
(nd)/<mac address)
(nd)/<IP address> reducing by the LS-Byte each time until finally
(nd)/efidefault

Subsequently, network tftp-able files, e.g. kernel, initrd are
referred to using the (nd) device.

2. GRUB refers to TFTP-able files using the (pxe:<server>) device;
these use the TFTP protocol which is implemented to the i386-pc TFTP
stack.

3. Some questions: would it be better to have a totally new device
name and protocol e.g. "(nd)" and "efitftp" so as not to clash with
the i386-pc infrastructure?

4. File system behaviour:  grub-legacy (with #ifdef for EFI) creates a
separate filesystem structure for EFI.
* mounting the device always succeeds if the PXE stack is started
* dir_open the files check using TFTP for the file size
* read, for the first read (offset 0), the whole file is downloaded
into to memory buffer
subsequent reads read from memory
Would these file  system semantics work for GRUB?

5. I have looked at the existing GRUB net+efinet stack. During my
simple testing I have to be unaable to trigger the code path where
grub populates the grub_net_structure from the UEFI PXE code. This
occurs in grub_efi_net_config_real()  in
grub-core/net/drivers/efi/efinet.c.

When I do
grub> insmod efinet
grub> net_ls_cards
grub> net_ls_addr
I cannot see any information from the PXE boot (i.e. I have booted
grub using UEFI PXE and I expected the efinet structures - at least
one of the cards - to be populated from PXE).

Nevertheless, since the UEFI/PXE stack works independently of Grub,
would it be ok to bypass the whole grub/net/drivers infrastructure and
use UEFI directly, as what grub-legacy currently does?

Thanks in advance for any comments and advice.

Richard