Re: Stack issue after warm UEFI reset and MMU enabling on an Armv8 platform

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 19 September 2018 at 16:58, Vladimir Olovyannikov <
vladimir.olovyannikov@broadcom.com> wrote:

> >From: Ard Biesheuvel [mailto:ard.biesheuvel@linaro.org]
> >Sent: Wednesday, September 19, 2018 4:38 PM
> >To: Vladimir Olovyannikov
> >Cc: edk2-devel@lists.01.org
> >Subject: Re: Stack issue after warm UEFI reset and MMU enabling on an
> Armv8
> >platform
>
>
> >On 19 September 2018 at 15:55, Vladimir Olovyannikov
> ><vladimir.olovyannikov@broadcom.com> wrote:
> >>Hi All,
>
> >>I need UEFI experts help on the problem with Armv8 board on warm UEFI
> >>reset.
> >>Cold reset works fine.
>
> >>Here is how I set up a warm reset:
>
> >>STATIC
> >>EFI_STATUS
> >>ShutdownUefiBootServices (
> >>  VOID
> >>  )
> >>{
> >>  EFI_STATUS              Status;
> >>  UINTN                   MemoryMapSize;
> >>  EFI_MEMORY_DESCRIPTOR   *MemoryMap;
> >>  UINTN                   MapKey;
> >>  UINTN                   DescriptorSize;
> >>  UINT32                  DescriptorVersion;
> >>  UINTN                   Pages;
>
> >>  MemoryMap = NULL;
> >>  MemoryMapSize = 0;
> >>  Pages = 0;
> >>
> >>  do {
> >>    Status = gBS->GetMemoryMap (
> >>                    &MemoryMapSize,
> >>                    MemoryMap,
> >>                    &MapKey,
> >>                    &DescriptorSize,
> >>                    &DescriptorVersion
> >>                    );
> >>    if (Status == EFI_BUFFER_TOO_SMALL) {
> >>
> >>      Pages = EFI_SIZE_TO_PAGES (MemoryMapSize) + 1;
> >>      MemoryMap = AllocatePages (Pages);
> >>
> >>      //
> >>      // Get System MemoryMap
> >>      //
> >>      Status = gBS->GetMemoryMap (
> >>                      &MemoryMapSize,
> >>                      MemoryMap,
> >>                      &MapKey,
> >>                      &DescriptorSize,
> >>                      &DescriptorVersion
> >>                      );
> >>    }
> >>
> >>    // Don't do anything between the GetMemoryMap() and
> ExitBootServices()
> >>    if (!EFI_ERROR(Status)) {
> >>      Status = gBS->ExitBootServices (gImageHandle, MapKey);
> >>      if (EFI_ERROR(Status)) {
> >>        FreePages (MemoryMap, Pages);
> >>        MemoryMap = NULL;
> >>        MemoryMapSize = 0;
> >>      }
> >>    }
> >>  } while (EFI_ERROR(Status));
> >>
> >>  return Status;
> >>}
> >>
> >>Then perform
> >>ArmCleanDataCache ();
> >>ArmInvalidateDataCache ();
> >>ArmDisableInstructionCache ();
> >>ArmInvalidateInstructionCache ();
>
> >These don't do anything useful on ARM. You can only reliably perform cache
> >maintenance by virtual address.
> So, should I just remove them altogether?
>
> >>ArmDisableMmu ();
>
> >... so after this call returns, all bets are off with regards to whether
> >what is popped from the stack is actually what we pushed when we entered
> >the function.
> OK, thank you for explanation.
> But this call returns back into ResetLib implementation as it should, and
> then there is a direct jump to the start of FV.
> Am I doing anything wrong here?
> Then, up to the point of enabling of MMU the stack is OK. But right after
> enabling MMU it points at _ModuleEntryPoint end of function in
> DxeCoreEntryPoint.c
> Am I missing anything? Maybe some stack cleanup before jumping to the start
> of FV?
>
>
I guess you should be disabling interrupts as well. And quiesce all DMA
capable devices like network controllers that may corrupt your memory.