Re: [MdeModulePkg/PeiCore] How is Data being NULL on entry ensured?

[Andrew Fish <afish@apple.com>]

> On Aug 12, 2016, at 7:01 PM, Marvin H?user <Marvin.Haeuser@outlook.com> wrote:
> 
> Dear list subscribers,
> 
> I have just been looking around the PeiCore code and wondered, how it is ensured, that the third ("Data") argument of the entry point is NULL on the first run.
> EFI_PEI_CORE_ENTRY_POINT only has two arguments and hence most SEC implementations, including MdeModulePkg/SecCore, are going to pass only the first two arguments to the entry point.
> I'm aware that the code works and I have never seen an occasion of it failing or seeming to fail because of this design, though I wondered, how is it assured, that the third argument, which is not part of the first call, is being NULL on entry and not some leftover on the temporary stack/in the argument 3 register?
> 

Marvin,

The code you are looking for is in the entry point library. 

https://github.com/tianocore/edk2/blob/master/MdePkg/Library/PeiCoreEntryPoint/PeiCoreEntryPoint.c#L59

**/
VOID
EFIAPI 
_ModuleEntryPoint(
  IN CONST  EFI_SEC_PEI_HAND_OFF    *SecCoreData,
  IN CONST  EFI_PEI_PPI_DESCRIPTOR  *PpiList
)
{
  ProcessModuleEntryPointList (SecCoreData, PpiList, NULL);
  
  //
  // Should never return
  //
  ASSERT(FALSE);
  CpuDeadLoop ();  
}


ProcessModuleEntryPointList() call is auto-generated and it will cal the entry point listed in the PEI Core INF file. So that is why it is hard to grep for. 

Thanks,

Andrew Fish

> Thank you for your time!
> 
> Regards,
> Marvin.
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel