In this lesson we would explore some internals behind the HII database.
First of all let's look at the main structure of the HII database:
typedef struct _HII_DATABASE_PRIVATE_DATA {
UINTN Signature;
LIST_ENTRY DatabaseList;
LIST_ENTRY DatabaseNotifyList;
EFI_HII_FONT_PROTOCOL HiiFont;
EFI_HII_IMAGE_PROTOCOL HiiImage;
EFI_HII_IMAGE_EX_PROTOCOL HiiImageEx;
EFI_HII_STRING_PROTOCOL HiiString;
EFI_HII_DATABASE_PROTOCOL HiiDatabase;
EFI_HII_CONFIG_ROUTING_PROTOCOL ConfigRouting;
EFI_CONFIG_KEYWORD_HANDLER_PROTOCOL ConfigKeywordHandler;
LIST_ENTRY HiiHandleList;
INTN HiiHandleCount;
LIST_ENTRY FontInfoList;
UINTN Attribute;
EFI_GUID CurrentLayoutGuid;
EFI_HII_KEYBOARD_LAYOUT *CurrentLayout;
} HII_DATABASE_PRIVATE_DATA;
This structure contains pointers to the main HII protocols. Each of these protocols is responsible for interactons with different parts of HII. For example one is responsible for interaction with fonts in the HII database (EFI_HII_FONT_PROTOCOL), another one for interaction with images (EFI_HII_IMAGE_PROTOCOL/EFI_HII_IMAGE_EX_PROTOCOL) and another one for interaction with strings (EFI_HII_STRING_PROTOCOL).
We've already glimpsed at the EFI_HII_DATABASE_PROTOCOL that is responsible for adding/removing HII packages to/from the databse.
We will investigate possibilities of this protocols more as we would go through different HII elements.
Besides the protocols this structure maintains a set of double linked list to different elements. https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Base.h:
///
/// LIST_ENTRY structure definition.
///
typedef struct _LIST_ENTRY LIST_ENTRY;
///
/// _LIST_ENTRY structure definition.
///
struct _LIST_ENTRY {
LIST_ENTRY *ForwardLink;
LIST_ENTRY *BackLink;
};
Among these lists there is a double linked list to database records LIST_ENTRY DatabaseList.
You can look at the definition of a database record at the https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/HiiDatabaseDxe/HiiDatabase.h:
#define HII_DATABASE_RECORD_SIGNATURE SIGNATURE_32 ('h','i','d','r')
typedef struct _HII_DATABASE_RECORD {
UINTN Signature;
HII_DATABASE_PACKAGE_LIST_INSTANCE *PackageList;
EFI_HANDLE DriverHandle;
EFI_HII_HANDLE Handle;
LIST_ENTRY DatabaseEntry;
} HII_DATABASE_RECORD;
LIST_ENTRY DatabaseList points to the DatabaseEntry field in the first HII_DATABASE_RECORD. DatabaseEntry in this structure in turn points to the DatabaseEntry field in the next HII_DATABASE_RECORD and so on.
Each database record have a HII_DATABASE_PACKAGE_LIST_INSTANCE *PackageList field, let's look at this definition (https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/HiiDatabaseDxe/HiiDatabase.h):
typedef struct _HII_DATABASE_PACKAGE_LIST_INSTANCE {
EFI_HII_PACKAGE_LIST_HEADER PackageListHdr;
LIST_ENTRY GuidPkgHdr;
LIST_ENTRY FormPkgHdr;
LIST_ENTRY KeyboardLayoutHdr;
LIST_ENTRY StringPkgHdr;
LIST_ENTRY FontPkgHdr;
HII_IMAGE_PACKAGE_INSTANCE *ImagePkg;
LIST_ENTRY SimpleFontPkgHdr;
UINT8 *DevicePathPkg;
} HII_DATABASE_PACKAGE_LIST_INSTANCE;
Each of these double linked list contains pointers to packages of corresponding type present in this package list.
In the previous lesson we've recieved all the package lists and its packages as a continious data array, but this was only a handy feature of the ExportPackageLists function from the EFI_HII_DATABASE_PROTOCOL. As you can see now in a reality HII data is represented in a double linked lists that could be sparsed all over the platform memory.
Another important field that is present in the HII_DATABASE_RECORD is a EFI_HII_HANDLE Handle. Each HII_DATABASE_RECORD defines a package list and is identified by this EFI_HII_HANDLE. According to the https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Uefi/UefiInternalFormRepresentation.h it is:
typedef VOID* EFI_HII_HANDLE;
But if you look to the implementation of the GenerateHiiDatabaseRecord function in the https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/HiiDatabaseDxe/Database.c you could see the actual implementation of the HII handle:
EFI_STATUS
GenerateHiiDatabaseRecord (
IN HII_DATABASE_PRIVATE_DATA *Private,
OUT HII_DATABASE_RECORD **DatabaseNode
)
{
...
HII_HANDLE *HiiHandle;
HII_DATABASE_RECORD *DatabaseRecord;
...
DatabaseRecord->Handle = (EFI_HII_HANDLE) HiiHandle;
...
}
The type HII_HANDLE is defined in the https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/HiiDatabaseDxe/HiiDatabase.h:
#define HII_HANDLE_SIGNATURE SIGNATURE_32 ('h','i','h','l')
typedef struct {
UINTN Signature;
LIST_ENTRY Handle;
UINTN Key;
} HII_HANDLE;
The Key field here corresponds to the current value of the HiiHandleCount field in the main HII_DATABASE_PRIVATE_DATA.
And the LIST_ENTRY Handle helps to connect all the HII_HANDLEs in the system together. The important point to note that the LIST_ENTRY HiiHandleList field in the main HII_DATABASE_PRIVATE_DATA is the same handle list.
Here is a picture of the HII database structure that we've just covered:
This HII database structure has static initializiation in the HiiDatabaseDxe (https://github.com/tianocore/edk2/blob/master/MdeModulePkg/Universal/HiiDatabaseDxe/HiiDatabaseEntry.c):
HII_DATABASE_PRIVATE_DATA mPrivate = {
HII_DATABASE_PRIVATE_DATA_SIGNATURE,
{
(LIST_ENTRY *) NULL,
(LIST_ENTRY *) NULL
},
{
(LIST_ENTRY *) NULL,
(LIST_ENTRY *) NULL
},
{
HiiStringToImage,
HiiStringIdToImage,
HiiGetGlyph,
HiiGetFontInfo
},
{
HiiNewImage,
HiiGetImage,
HiiSetImage,
HiiDrawImage,
HiiDrawImageId
},
{
HiiNewImageEx,
HiiGetImageEx,
HiiSetImageEx,
HiiDrawImageEx,
HiiDrawImageIdEx,
HiiGetImageInfo
},
{
HiiNewString,
HiiGetString,
HiiSetString,
HiiGetLanguages,
HiiGetSecondaryLanguages
},
{
HiiNewPackageList,
HiiRemovePackageList,
HiiUpdatePackageList,
HiiListPackageLists,
HiiExportPackageLists,
HiiRegisterPackageNotify,
HiiUnregisterPackageNotify,
HiiFindKeyboardLayouts,
HiiGetKeyboardLayout,
HiiSetKeyboardLayout,
HiiGetPackageListHandle
},
{
HiiConfigRoutingExtractConfig,
HiiConfigRoutingExportConfig,
HiiConfigRoutingRouteConfig,
HiiBlockToConfig,
HiiConfigToBlock,
HiiGetAltCfg
},
{
EfiConfigKeywordHandlerSetData,
EfiConfigKeywordHandlerGetData
},
{
(LIST_ENTRY *) NULL,
(LIST_ENTRY *) NULL
},
0,
{
(LIST_ENTRY *) NULL,
(LIST_ENTRY *) NULL
},
EFI_TEXT_ATTR (EFI_LIGHTGRAY, EFI_BLACK),
{
0x00000000,
0x0000,
0x0000,
{0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00}
},
NULL
};
In the HiiDatabaseDxe driver entry point it initializes linked lists (LIST_ENTRY) and installs all the protocols from the HII database to the system:
EFI_STATUS
EFIAPI
InitializeHiiDatabase (
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTable
)
{
EFI_STATUS Status;
EFI_HANDLE Handle;
...
InitializeListHead (&mPrivate.DatabaseList);
InitializeListHead (&mPrivate.DatabaseNotifyList);
InitializeListHead (&mPrivate.HiiHandleList);
InitializeListHead (&mPrivate.FontInfoList);
...
Handle = NULL;
Status = gBS->InstallMultipleProtocolInterfaces (
&Handle,
&gEfiHiiFontProtocolGuid,
&mPrivate.HiiFont,
&gEfiHiiStringProtocolGuid,
&mPrivate.HiiString,
&gEfiHiiDatabaseProtocolGuid,
&mPrivate.HiiDatabase,
&gEfiHiiConfigRoutingProtocolGuid,
&mPrivate.ConfigRouting,
&gEfiConfigKeywordHandlerProtocolGuid,
&mPrivate.ConfigKeywordHandler,
NULL
);
...
if (FeaturePcdGet (PcdSupportHiiImageProtocol)) {
Status = gBS->InstallMultipleProtocolInterfaces (
&Handle,
&gEfiHiiImageProtocolGuid, &mPrivate.HiiImage,
&gEfiHiiImageExProtocolGuid, &mPrivate.HiiImageEx,
NULL
);
}
...
}
Just in case here is some preprocessor magic that helps to get pointer to a structure by a pointer to its field.
It is easy to get pointer to HII_DATABASE_RECORD by the pointer to its field DatabaseEntry with a help of CR macro:
LIST_ENTRY* Link;
HII_DATABASE_RECORD* DatabaseRecord = CR (Link, HII_DATABASE_RECORD, DatabaseEntry, HII_DATABASE_RECORD_SIGNATURE);
In case you wonder definition for the CR macro can be found https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Library/DebugLib.h
@param Record The pointer to the field specified by Field within a data
structure of type TYPE.
@param TYPE The name of the data structure type to return This
data structure must contain the field specified by Field.
@param Field The name of the field in the data structure specified
by TYPE to which Record points.
@param TestSignature The 32-bit signature value to match.
**/
#if !defined(MDEPKG_NDEBUG)
#define CR(Record, TYPE, Field, TestSignature) \
(DebugAssertEnabled () && (BASE_CR (Record, TYPE, Field)->Signature != TestSignature)) ? \
(TYPE *) (_ASSERT (CR has Bad Signature), Record) : \
BASE_CR (Record, TYPE, Field)
#else
#define CR(Record, TYPE, Field, TestSignature) \
BASE_CR (Record, TYPE, Field)
#endif
And the definition for BASE_CR is placed under https://github.com/tianocore/edk2/blob/master/MdePkg/Include/Base.h:
/**
Macro that returns a pointer to the data structure that contains a specified field of
that data structure. This is a lightweight method to hide information by placing a
public data structure inside a larger private data structure and using a pointer to
the public data structure to retrieve a pointer to the private data structure.
This function computes the offset, in bytes, of field specified by Field from the beginning
of the data structure specified by TYPE. This offset is subtracted from Record, and is
used to return a pointer to a data structure of the type specified by TYPE. If the data type
specified by TYPE does not contain the field specified by Field, then the module will not compile.
@param Record Pointer to the field specified by Field within a data structure of type TYPE.
@param TYPE The name of the data structure type to return. This data structure must
contain the field specified by Field.
@param Field The name of the field in the data structure specified by TYPE to which Record points.
@return A pointer to the structure from one of it's elements.
**/
#define BASE_CR(Record, TYPE, Field) ((TYPE *) ((CHAR8 *) (Record) - OFFSET_OF (TYPE, Field)))
/**
The macro that returns the byte offset of a field in a data structure.
This function returns the offset, in bytes, of field specified by Field from the
beginning of the data structure specified by TYPE. If TYPE does not contain Field,
the module will not compile.
@param TYPE The name of the data structure that contains the field specified by Field.
@param Field The name of the field in the data structure.
@return Offset, in bytes, of field.
**/
#if (defined(__GNUC__) && __GNUC__ >= 4) || defined(__clang__)
#define OFFSET_OF(TYPE, Field) ((UINTN) __builtin_offsetof(TYPE, Field))
#endif
#ifndef OFFSET_OF
#define OFFSET_OF(TYPE, Field) ((UINTN) &(((TYPE *)0)->Field))
#endif