/**
Main entry for PCD PEIM driver.
This routine initialize the PCD database for PEI phase and install PCD_PPI/EFI_PEI_PCD_PPI.
@param FileHandle Handle of the file being invoked.
@param PeiServices Describes the list of possible PEI Services.
@return Status of install PCD_PPI
**/
EFI_STATUS
EFIAPI
PcdPeimInit (
IN EFI_PEI_FILE_HANDLE FileHandle,
IN CONST EFI_PEI_SERVICES **PeiServices
)
从代码上看，QEMU 模拟了 SPI ROM，使可以看到，这个 PEI Module 主要作用是注册了多个和PCD 相关的 Ppi Service 以便后续使用。
MdeModulePkg\Core\Pei\Dispatcher\Dispatcher.c
/**
Conduct PEIM dispatch.
@param SecCoreData Points to a data structure containing information about the PEI core's operating
environment, such as the size and location of temporary RAM, the stack location and
the BFV location.
@param Private Pointer to the private data passed in from caller
**/
VOID
PeiDispatcher (
IN CONST EFI_SEC_PEI_HAND_OFF *SecCoreData,
IN PEI_CORE_INSTANCE *Private
)
进去这个函数之后，因为刚开始内存并没有准备好，所以 (Private->PeiMemoryInstalled) 这个条件不会满足，会进入下面的do … while 循环。
//
// This is the main dispatch loop. It will search known FVs for PEIMs and
// attempt to dispatch them. If any PEIM gets dispatched through a single
// pass of the dispatcher, it will start over from the BFV again to see
// if any new PEIMs dependencies got satisfied. With a well ordered
// FV where PEIMs are found in the order their dependencies are also
// satisfied, this dispatcher should run only once.
//
跳转到DiscoverPeimsAndOrderWithApriori() 函数中
if (Private->CurrentPeimCount == 0) {
//
// When going through each FV, at first, search Apriori file to
// reorder all PEIMs to ensure the PEIMs in Apriori file to get
// dispatch at first.
//
DiscoverPeimsAndOrderWithApriori (Private, CoreFvHandle);
}
这个函数的作用是找到所有的 PEIM以及Apriori 文件。
/**
Discover all PEIMs and optional Apriori file in one FV. There is at most one
Apriori file in one FV.
@param Private Pointer to the private data passed in from caller
@param CoreFileHandle The instance of PEI_CORE_FV_HANDLE.
**/
VOID
DiscoverPeimsAndOrderWithApriori (
IN PEI_CORE_INSTANCE *Private,
IN PEI_CORE_FV_HANDLE *CoreFileHandle
)
函数中有一个 DEBUG 输出如下：
DEBUG ((
DEBUG_INFO,
"%a(): Found 0x%x PEI FFS files in the %dth FV\n",
__FUNCTION__,
PeimCount,
Private->CurrentPeimFvCount
));
对应的串口 Log 中有如下字样，就是说在找到了7个 PEIM
DiscoverPeimsAndOrderWithApriori(): Found 0x7 PEI FFS files in the 0th FV
为了更好的观测，加入代码，输出它找到的 PEIM 的 GUID:
for (Index = 0; Index < PeimCount; Index++) {
//
// Make an array of file name GUIDs that matches the FileHandle array so we can convert
// quickly from file name to file handle
//
Status = FvPpi->GetFileInfo (FvPpi, TempFileHandles[Index], &FileInfo);
ASSERT_EFI_ERROR (Status);
CopyMem (&TempFileGuid[Index], &FileInfo.FileName, sizeof(EFI_GUID));
DEBUG ((DEBUG_INFO , "%g\n", FileInfo.FileName));
}
//
// For PEIM driver, Load its entry point
//
Status = PeiLoadImage (
PeiServices,
PeimFileHandle,
PEIM_STATE_NOT_DISPATCHED,
&EntryPoint,
&AuthenticationState
);
/**
Routine to load image file for subsequent execution by LoadFile Ppi.
If any LoadFile Ppi is not found, the build-in support function for the PE32+/TE
XIP image format is used.
@param PeiServices - An indirect pointer to the EFI_PEI_SERVICES table published by the PEI Foundation
@param FileHandle - Pointer to the FFS file header of the image.
@param PeimState - The dispatch state of the input PEIM handle.
@param EntryPoint - Pointer to entry point of specified image file for output.
@param AuthenticationState - Pointer to attestation authentication state of image.
@retval EFI_SUCCESS - Image is successfully loaded.
@retval EFI_NOT_FOUND - Fail to locate necessary PPI
@retval Others - Fail to load file.
**/
EFI_STATUS
PeiLoadImage (
IN CONST EFI_PEI_SERVICES **PeiServices,
IN EFI_PEI_FILE_HANDLE FileHandle,
IN UINT8 PeimState,
OUT EFI_PHYSICAL_ADDRESS *EntryPoint,
OUT UINT32 *AuthenticationState
)
/**
Loads a PEIM into memory for subsequent execution. If there are compressed
images or images that need to be relocated into memory for performance reasons,
this service performs that transformation.
@param PeiServices An indirect pointer to the EFI_PEI_SERVICES table published by the PEI Foundation
@param FileHandle Pointer to the FFS file header of the image.
@param ImageAddressArg Pointer to PE/TE image.
@param ImageSizeArg Size of PE/TE image.
@param EntryPoint Pointer to entry point of specified image file for output.
@param AuthenticationState - Pointer to attestation authentication state of image.
@retval EFI_SUCCESS Image is successfully loaded.
@retval EFI_NOT_FOUND Fail to locate necessary PPI.
@retval EFI_UNSUPPORTED Image Machine Type is not supported.
@retval EFI_WARN_BUFFER_TOO_SMALL
There is not enough heap to allocate the requested size.
This will not prevent the XIP image from being invoked.
**/
EFI_STATUS
PeiLoadImageLoadImage (
IN CONST EFI_PEI_SERVICES **PeiServices,
IN EFI_PEI_FILE_HANDLE FileHandle,
OUT EFI_PHYSICAL_ADDRESS *ImageAddressArg, OPTIONAL
OUT UINT64 *ImageSizeArg, OPTIONAL
OUT EFI_PHYSICAL_ADDRESS *EntryPoint,
OUT UINT32 *AuthenticationState
)
CSME 算是 Intel X86 PC 上最神秘的部分了，本文根据 us-19-Hasarfaty-Behind-The-Scenes-Of-Intel-Security-And-Manageability-Engine 一文写成。讲述内容无法证伪，各位随便听听即可，了解这些能够帮助BIOS 工程师更好的理解一些操作的实现。文章基于 Intel 第八代第九代CPU（Coffee Lake 和 Whiskey Lake）进行描述。
