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System Table contains pointers to the active concole devices, a pointer to the Boot Services Table,
a pointer to the Runtime Services Table, and a pointer to the list of system configuration tables such as
ACPI, SMBIOS and the SAL System Table.
Entry point is the same for UEFI applications and UEDI drivers.
PROTOTYPE
typedef
EFI_STATUS
(EFIAPI *EFI_IMAGE_ENTRY_POINT) (
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTabel
);
PARAMETERS
ImageHandle The firmware allocated handle for the UEFI image
SystemTable A pointer to the EFI System Table. Contains standard output and input handles,
plus pointers to the EFI_BOOT_SERVICES and EFI RUNTIME_SERVICES tables.
The service tables contain the entry points in the firmware for accessing the core EFI system
functionality. The handles in the system table are used to obtain basci access to the console.
In addition, the System Table contains pointers to other standard tables that a loaded image
may use if the associated pointers are initialized to nonzero values.
Example of such tables: ACPI, SMBIOS, SAL System Table, ...
If the UEFI image is a UEFI application that is not a UEFI OS loader, then the application executes and
either returns or calls the EFI Boot Services EFI_BOOT_SERVICES.Exit(). A UEFI application is always
unloaded from memory when it exits, and its return status is returned to the component that started the
UEFI application.
EFI_TABLE_HEADER
Datastructure that precedes all of the standard EFI table types
typedef struct {
UINT64 Signature;
UINT32 Revision;
UINT32 HeaderSize;
UINT32 CRC32;
UINT32 Reserved;
} EFI_TABLE_HEADER;
EFI_SYSTEM_TABLE
Except for the table header, all elements in the service tables are pointers to functions as defined
in Section7 (Services - Boot Services) and Section8 (Services - Runtime Services).
Prior to a call to EFI_BOOT_SERVICES.ExitBootServices(), all of the fields of the EFI System Table are valid.
After an operating system has taken control of the platform with a call to ExitBootServices(), pmöy
Hdr, FirmwareVendor, FirmwareRevision, RuntimeServices, NumberOfTableEntries, ConfigurationTable fields
are valid.
typedef struct {
EFI_TABLE_HEADER Hdr;
CHAR16 *FirmwareVendor;
UINT32 FirmwareRevision;
EFI_HANDLE ConsoleInHandle;
EFI_SIMPLE_TEXT_INPUT_PROTOCOL *ConIn;
EFI_HANDLE ConsoleOutHandle;
EFI_SYSTEM_TEXT_OUTPUT_PROTOCOL *ConOut;
EFI_HANDLE StandardErrorHandle;
EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL *stdErr;
EFI_RUNTIME_SERVICES *RuntimeServices:
EFI_BOOT_SERVICES *BootServices;
UINTN NumberOfTableEntries;
EFI_CONFIGURATION_TABLE *Configuration_Table;
} EFI_SYSTEM_TABLE;
PARAMETERS
ConcoleHandle The handle for the active console input device. This handle must support
EFI_SIMPLE_TEXT_INPUT_PROTOCOL and EFI_SIMPLE_TECT_INPUT_EX_PROTOCOL.
ConIn A pointer to the EFI_SIMPLE_TEXT_INPUT_PROTOCOL interface that is
associated with ConsoleInHandle.
ConsoleOutHandle The handle for the active console output device. This handle must
EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.
ConOut A pointer to the EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL interface that is
associated with ConsoleOutHandle.
StandardErrorHandle The handle for the active standard error console device. Must support
EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL.
StdErr A pointer to the EFI_SIMPLE_TEXT_OUTPUT_PROTOCOL inte4rface that is
assiciated with StandardErrorHandle
RuntimeServices A pointer to the EFI Runtime Services Table (Section 4.5)
BootServices Section 4.4
NumberOfTableEntries Number of system configuration tables in the buffer ConfigurationTable
ConfigurationTable A pointer to the system configuration tables. Number of entries in the table is
NumberOfTableEntries.
References
[1] UEFI Specification 2.8 Errata A, February 2020 - 4.1 UEFI Image Entry Point - pp 89
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