Intel Extensible Firmware Interface, Specification

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Extensible Firmware Interface Specification
246 12/12/00 Version 1.02
Description
The basic mechanisms and flow for remote booting in EFI are identical to the remote boot
functionality described in detail in the
PXE Specification . However, the actual execution
environment, linkage, and calling conventions are replaced and enhanced for the EFI environment.
The DHCP Option for the Client System Architecture is used to inform the DHCP server if the
client is an IA-32 or Itanium-based EFI environment. The server may use this information to
provide default images if it does not have a specific boot profile for the client.
A handle that supports
EFI_PXE_BASE_CODE
protocol is required to support the
LOAD_FILE
protocol. The
LOAD_FILE
protocol function
LoadFile()
is used by the firmware to load files
from devices that do not support file system type accesses. Specifically, the firmware’s boot
manager invokes
LoadFile()
with
BootPolicy
being
TRUE
when attempting to boot from
the device. The firmware then loads and transfers control to the downloaded PXE boot image.
Once the remote image is successfully loaded, it may utilize the
EFI_PXE_BASE_CODE
interfaces, or even the
EFI_SIMPLE_NETWORK
interfaces, to continue the remote process.