Saving data structure at Pre EFI Initialization phase in memory to use it at DXE phase by some UEFI application?

Saving data structure at Pre EFI Initialization phase in memory to use it at DXE phase by some UEFI application?

[sergestus]

[-- Attachment #1: Type: text/plain, Size: 144 bytes --]

Is it possible to save SYSHOST data structure at PEI phase in memory at some default location to use it at DXE phase by some UEFI application?

[-- Attachment #2: Type: text/html, Size: 188 bytes --]

Re: [edk2-devel] Saving data structure at Pre EFI Initialization phase in memory to use it at DXE phase by some UEFI application?

[Marvin Häuser]

Hey,

Are HOBs ("Hand-Off Blocks") what you are looking for? They are passed 
from PEI to DXE (see PI 1.6, 9.3 "Passing the Hand-Off Block (HOB) List").

Regards,
Marvin

Am 30.01.2020 um 10:51 schrieb sergestus@yandex.ru:
> Is it possible to save SYSHOST data structure at PEI phase in memory at 
> some default location to use it at DXE phase by some UEFI application?
> 

Re: [edk2-devel] Saving data structure at Pre EFI Initialization phase in memory to use it at DXE phase by some UEFI application?

[sergestus]

[-- Attachment #1: Type: text/plain, Size: 254 bytes --]

I need to use some code from PEIM driver in DXE phase. This code is using the SYSHOST structure and I think it not easy to restore it from HOBs becuase there are a lot of information. So I thought it easy to save the structure completely in the memory.

[-- Attachment #2: Type: text/html, Size: 254 bytes --]

Re: [edk2-devel] Saving data structure at Pre EFI Initialization phase in memory to use it at DXE phase by some UEFI application?

[Laszlo Ersek]

On 01/30/20 12:03, sergestus@yandex.ru wrote:
> I need to use some code from PEIM driver in DXE phase. This code is
> using the SYSHOST structure and I think it not easy to restore it
> from HOBs becuase there are a lot of information. So I thought it
> easy to save the structure completely in the memory.

In the PEIM, assuming your code runs after permanent RAM has been
discovered, you can allocate memory for the SYSHOST structure with the
AllocatePages() PEI service. Stash the allocation address in a vendor
GUID HOB. In the DXE phase, look up the HOB by GUID.

Thanks
Laszlo

Re: [edk2-devel] Saving data structure at Pre EFI Initialization phase in memory to use it at DXE phase by some UEFI application?

[sergestus]

[-- Attachment #1: Type: text/plain, Size: 243 bytes --]

Thank you, may I just create a new GUID (sysHostGuid), then call BuildGuidDataHob passing in it the sysHostGuid and SYSHOST structure? Will I be able to find the structure in the DXE phase looking up by the sysHostGuid?

Thank you,
Sergey

[-- Attachment #2: Type: text/html, Size: 255 bytes --]

Re: [edk2-devel] Saving data structure at Pre EFI Initialization phase in memory to use it at DXE phase by some UEFI application?

[Laszlo Ersek]

On 01/30/20 13:57, sergestus@yandex.ru wrote:
> Thank you, may I just create a new GUID (sysHostGuid),

Right, just get your own GUID with "uuidgen".

> then call BuildGuidDataHob passing in it the sysHostGuid

Yes.

> and SYSHOST structure?

Well, not exactly. It depends.

If your SYSHOST structure is a few KB tops (up to 64-ish KB), then sure,
you can embed the SYSHOST structure right into the HOB.

Otherwise, you should
- make your PEI code dependent on gEfiPeiMemoryDiscoveredPpiGuid,
- call the AllocatePages() PEI service,
- populate the allocated area with the SYSHOST structure,
- take the 64-bit EFI_PHYSICAL_ADDRESS, output by AllocatePages(), as a
UINT64,
- call BuildGuidDataHob() on the *UINT64*. In other words, embed the
address of the structure, not the structure.

> Will I be able to find the structure in the DXE phase looking up by the sysHostGuid?

Yes, with GetFirstGuidHob().

If you embedded the structure in the HOB, then you can consume it right
from the HOB (at the address returned by GetFirstGuidHob()).

Otherwise, you should read the address (the UINT64 object) out of the
HOB. Then dereference it as a pointer, and that's where your struct will be.

The point is that memory allocated in the PEI phase with the
AllocatePages() PEI service, *after* permanent RAM has been installed
(i.e. after gEfiPeiMemoryDiscoveredPpiGuid is placed in the PPI
database), is stable. You can pass the address from PEI to DXE using a
GUID HOB.

Thanks
Laszlo

Re: [edk2-devel] Saving data structure at Pre EFI Initialization phase in memory to use it at DXE phase by some UEFI application?

[sergestus]

[-- Attachment #1: Type: text/plain, Size: 40 bytes --]

I've understood, thanks a lot!
Sergey

[-- Attachment #2: Type: text/html, Size: 44 bytes --]