Intel Extensible Firmware Interface, Specification

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Services
Version 1.02 12/12/00 73
3.4.4 EFI_IMAGE_ENTRY_POINT
Summary
This is the declaration of an EFI image entry point. This can be the entry point to an EFI
application, an EFI boot service driver, or an EFI runtime driver.
Prototype
typedef
EFI_STATUS
(EFIAPI *EFI_IMAGE_ENTRY_POINT) (
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTable
);
Parameters
ImageHandle
Handle that identifies the loaded image. Type
EFI_HANDLE
is defined
in Section 3.3.1.
SystemTable
System Table for this image. Type
EFI_SYSTEM_TABLE
is defined in
Chapter 4.
Description
An image’s entry point is of type
EFI_IMAGE_ENTRY_POINT
. After firmware loads an image
into memory, control is passed to the image’s entry point. The entry point is responsible for
initializing the image. The image’s
ImageHandle
is passed to the image. The
ImageHandle
provides the image with all the binding and data information it needs. This information is available
through protocol interfaces. However, to access the protocol interfaces on
ImageHandle
requires access to boot services functions. Therefore,
LoadImage()
passes to the
EFI_IMAGE_ENTRY_POINT
a
SystemTable
that is inherited from the current scope of
LoadImage()
.
All image handles support the
LOADED_IMAGE
protocol. This protocol can be used to obtain
information about the loaded image’s state — for example, the device from which the image was
loaded and the image’s load options. In addition, the
ImageHandle
may support other protocols
provided by the parent image.
If the image supports dynamic unloading, it must supply an unload function in the
LOADED_IMAGE
structure before returning control from its entry point.
In general, an image returns control from its initialization entry point by calling
Exit()
or by
returning control from its entry point. If the image returns control from its entry point, the
firmware passes control to
Exit()
using the return code as the
ExitStatus
parameter to
Exit()
.
See
Exit()
for entry point exit conditions (Section 3.4.5).