Re: [edk2] About PXE Discover

[Andrew Fish]

On Jul 4, 2014, at 9:50 PM, Gurinder Singh  wrote:

> Hi guys,
> 
> I need a little help with PXE Discover.
> 
> Here's the background:
> 
> We have a PXE boot server that we have written. We are trying to boot UEFI 
> machines with it. We wish to have these machines booted using bootmgfw.efi, 
> which is Microsoft's bootloader. However, we'd like to display some of our 
> own branding before bootmgfw.efi starts.
> 
> For this purpose, we're writing a thin shim loader. The idea is, this shim is 
> the first loader our PXE server serves. It runs on the client and displays 
> our branding. Then it downloads bootmgfw.efi and runs it.
> 
> The way I'm implementing this is that:
> 1. The shim, when it runs on the client, will trigger a PXE Discover.
> 2. In the Pxe REQUEST message it'll somehow add a special DHCP option.
> 3. My server will recognize this option and advertise bootmgf.efi in the PXE 
> ACK.
> 4. The client will then (I'm hoping) automatically download bootmgf.efi and 
> run it.
> 

Not sure why you would want to change the DHCP handshakes? Why not just have 
the shim do a TFTP read to get the extra info. 

Thanks,

Andrew Fish

> 
> My first question is will this work as I'm expecting it to?
> 
> Secondly, I've written the following code in the shim to achieve this:
> 
> 
> EFI_PXE_BASE_CODE_CALLBACK_STATUS 
> PxeCallback(EFI_PXE_BASE_CODE_CALLBACK_PROTOCOL *This, 
> EFI_PXE_BASE_CODE_FUNCTION Function, BOOLEAN Received, UINT32 PacketLen, 
> EFI_PXE_BASE_CODE_PACKET *Packet)
> {
> Print(L"Callback invoked. Doing %d. Received %d, Packet len %d\n", 
> Function, Received, PacketLen);
> return EFI_PXE_BASE_CODE_CALLBACK_STATUS_CONTINUE;
> }
> 
> 
> /* Shim Entry Point */
> 
> EFI_STATUS
> EFIAPI
> UefiMain(
> IN EFI_HANDLEImageHandle,
> IN EFI_SYSTEM_TABLE  *SystemTable
> )
> {
> 
> // 
> 
> gBS->OpenProtocol(ImageHandle, &gEfiPxeBaseCodeProtocolGuid, 
> &pxeProtocol, ImageHandle, NULL, EFI_OPEN_PROTOCOL_GET_PROTOCOL);
> gBS->OpenProtocol(ImageHandle, &gEfiPxeBaseCodeCallbackProtocolGuid, 
> &pxeCallbackProtocol, ImageHandle, NULL, EFI_OPEN_PROTOCOL_GET_PROTOCOL);
> pxeCallbackProtocol->Callback = PxeCallback;
> pxeProtocol->Start(pxeProtocol, FALSE);
>
> bootLayer = EFI_PXE_BASE_CODE_BOOT_LAYER_INITIAL;
> pxeProtocol->Discover(pxeProtocol, 
> EFI_PXE_BASE_CODE_BOOT_TYPE_MS_WINNT_RIS, &bootLayer, FALSE, NULL);
> 
> return EFI_SUCCESS;
> }
> 
> It does seem to seem to cause a full DORA sequence as well as PXE discover. 
> However, how do I set my special DHCP option in the PXE REQUEST packet before 
> starting the Discover? Will PxeCallback be of any help in that?
> 
> Thanks for your help in advance.
> 
> Cheers,
> Gurinder
> --
> Open source business process management suite built on Java and Eclipse
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--
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Turn processes into business applications with Bonita BPM Community Edition
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[edk2] Vfr.vfr Question with Regard to "text"

[Tim Lewis]

In DriverSampleDxe's vfr.vfr, there is the following text statement:

text
  help   = STRING_TOKEN(0x0053),
  text   = STRING_TOKEN(0x0053),
text   = STRING_TOKEN(0x0053),
  flags  = INTERACTIVE,
  key= 0x1237;

Notice that (a) this has the INTERACTIVE flag set (making it an ACTION opcode) 
but (b) it also has a 2nd "text" statement.

As far as I can tell, this should be illegal. Here is the corresponding 
statement in VfrSyntax.g:

CIfrAction AObj;

mCVfrQuestionDB.RegisterQuestion (NULL, NULL, QId);
AObj.SetLineNo 
(F->getLine());
AObj.SetQuestionId 
(QId);
AObj.SetPrompt 
(_STOSID(S2->getText()));
AObj.SetHelp 
(_STOSID(S1->getText()));

_PCATCH(AObj.SetFlags (Flags), F->getLine());
AssignQuestionKey 
(AObj, KN);
CRT_END_OP (KN);

You can see the basic question header being created but there is no reference 
to the 2nd text. Here, on the other hand, is the code for the EFI_IFR_TEXT, 
which does use the 2nd text item.

CIfrText TObj;
TObj.SetLineNo 
(T->getLine());
TObj.SetHelp 
(_STOSID(S1->getText()));
TObj.SetPrompt 
(_STOSID(S2->getText()));
TObj.SetTextTwo 
(TxtTwo);

In my opinion, the 2nd text item should generate an error with VfrCompile, 
because it will not and cannot ever be used for a "text" statement that has the 
INTERACTIVE flag set.

Tim

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