Andrew:
When TempRamSupportPpi is not provided, PeiCore will take role to migrate
data from temp memory to physical memory. So, PeiCore also need to reinitialize
the IDT in the permanent memory per PI 5.4.1.1 and PI5.4.2.1 section.
Because SetPeiServicesTablePointer() is only called by PeiCore, I add IDT
reinitialization in this library instance. PI spec says PEI service pointer at
the IDT - sizeof(UINTN). So, I just copy it. I think this implementation
follows PI spec.
If you use more IDT resource, you could provide your instance to handle it.
Thanks
Liming
From: Andrew Fish [mailto:[email protected]]
Sent: Thursday, January 09, 2014 2:38 PM
To: [email protected]
Subject: [edk2] Adding TempRam support to PeiServicesTablePointerLibIdt caused
my platform to crash.
I was wondering what the history was behind svn r14846?
When I synced with this version my platform crashed. It seems to be making an
implementation assumptions that go beyond what is in the PI spec, and that
would imply this library should be in the MdeModulePkg. Not mention the
assumptions should be document.
This code seems to assume it is safe to move the PEI Services Table Retrieval
location plus the IDT. This is not the case on our system, and we had the
debugger doing the relocation. So doing the migration here, and updating the
IDTR break us. I don't see how we are doing anything wrong from a PI 1.3 point
of view?
Just to be clear it is not illegal for us to store info at the ITD - 0x10 per
the PI spec, but this code would break that scheme.
https://svn.code.sf.net/p/edk2/code/trunk/edk2/MdePkg/Library/PeiServicesTablePointerLibIdt/PeiServicesTablePointer.c
VOID
EFIAPI
SetPeiServicesTablePointer (
IN CONST EFI_PEI_SERVICES ** PeiServicesTablePointer
)
{
IA32_DESCRIPTOR Idtr;
EFI_PHYSICAL_ADDRESS IdtBase;
EFI_STATUS Status;
EFI_PEI_TEMPORARY_RAM_SUPPORT_PPI *TemporaryRamSupportPpi;
ASSERT (PeiServicesTablePointer != NULL);
AsmReadIdtr (&Idtr);
if ((*(UINTN*)(Idtr.Base - sizeof (UINTN))) !=
(UINTN)PeiServicesTablePointer) {
(*(UINTN*)(Idtr.Base - sizeof (UINTN))) = (UINTN)PeiServicesTablePointer;
Status = (*PeiServicesTablePointer)->LocatePpi (
PeiServicesTablePointer,
&gEfiTemporaryRamSupportPpiGuid,
0,
NULL,
(VOID**)&TemporaryRamSupportPpi
);
if (EFI_ERROR (Status)) {
//
// If TemporaryRamSupportPpi is not found, Idt table needs to be migrated
into memory.
//
Status = (*PeiServicesTablePointer)->AllocatePages (
PeiServicesTablePointer,
EfiBootServicesCode,
EFI_SIZE_TO_PAGES(Idtr.Limit + 1 +
sizeof (UINTN)),
&IdtBase
);
if (!EFI_ERROR (Status)) {
//
// Migrate Idt table
//
CopyMem ((VOID *) (UINTN) IdtBase, (VOID *) (Idtr.Base - sizeof
(UINTN)), Idtr.Limit + 1 + sizeof (UINTN));
Idtr.Base = (UINTN) IdtBase + sizeof (UINTN);
AsmWriteIdtr (&Idtr);
}
}
}
}
Thanks,
Andrew Fish
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