EmulatorPkg and the state of DlLoadImage()


Marvin Häuser
 

Good day everyone,

I'm currently refining the port of EmulatorPkg to my new PE/COFF loader library instance.
In the process, I found the function DlOpenImage() [1], which loads UEFI Images via the OS loader to utilise its symbol loading capability. Theoretically, this should e.g. allow arbitrary debuggers using the OS APIs to symbolise the backtrace.

macOS: The function seems to be unused entirely. [2]

Linux: On my system running Fedora 34, the function neither works out-of-the-box, nor after significant time of trying to fix it. The first issue is that it only proceeds if the Image has a PDB path with ".pdb" extension [3], while the GCC5 toolchain generates Images with ".dll" files for PDB paths (see errors below). Once this is resolved, there is an error message indicating insufficient Image section alignment:

[...]/Build/EmulatorX64/DEBUG_GCC5/X64/MdeModulePkg/Universal/EbcDxe/EbcDxe/DEBUG/EbcDxe.dll: ELF load command alignment not page-aligned

Resolving this yields an error that executable files cannot be loaded dynamically:

[...]/Build/EmulatorX64/DEBUG_GCC5/X64/MdeModulePkg/Core/Pei/PeiMain/DEBUG/PeiCore.dll: cannot dynamically load executable

With my very limited knowledge about Linux and ELF I tried the naive approach of building the Images as shared (hoping it would be similar to DLLs, which are built on Windows), but this just silently crashes.

So my questions are:
1) Does this code currently work for anyone?
2) Does anyone use a debugging setup that is incompatible with Images loaded by EDK II rather than the OS?
3) Are the issues above known and planned to be fixed?

Thank you for your time!

Best regards,
Marvin


[1]
https://github.com/tianocore/edk2/blob/be282b14938846960cce30825a9fe762e14ca8c9/EmulatorPkg/Unix/Host/Host.c#L1065-L1113

[2]
https://github.com/tianocore/edk2/blob/be282b14938846960cce30825a9fe762e14ca8c9/EmulatorPkg/Unix/Host/Host.c#L1071-L1073

[3]
https://github.com/tianocore/edk2/blob/be282b14938846960cce30825a9fe762e14ca8c9/EmulatorPkg/Unix/Host/Host.c#L1084-L1086
https://github.com/tianocore/edk2/blob/be282b14938846960cce30825a9fe762e14ca8c9/EmulatorPkg/Unix/Host/Host.c#L1003-L1026

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