Re: [edk2-devel] [PATCH v4 0/6] UefiCpuPkg, OvmfPkg: Simplify CpuExceptionHandlerLib

["Lendacky, Thomas" <thomas.lendacky@amd.com>]

On 4/3/23 09:29, Ard Biesheuvel via groups.io wrote:
> We have a special version of CpuExceptionHandlerLib for XCODE5, whose
> linker (LLD) does not permit absolute symbol references in read-only
> sections.
> 
> Instead of fixing this up at runtime for all toolchains (which is done
> by writing the fixed up values to the .text section, which we'd prefer
> to avoid), tweak the SEC/PEI version so it does not need this, and
> update the remaining versions to only incorporate this logic when using
> the XCODE toolchain.
> 
> Changes since v3:
> - Add another patch to move PeiCpuExceptionHandlerLib to SEC/PEI version
>    of the NASM source file
> - Improve commit logs
> 
> Changes since v2:
> -  As Marvin points out, using '-read_only_relocs suppress' with the X64
>     XCODE linker is a terrible idea, as it corrupts the resulting PE
>     binaries, so instead, let's do the following:
>     . tweak the SEC/PEI version of the library so the relocs are emitted
>       into .data when using XCODE;
>     . tweak the other versions so the runtime fixups are only done when
>       using XCODE
> - add acks from Jiewen and Ray
> 
> Changes since v1:
> - pass linker switches to permit absolute relocations in read-only
>    regions, and keep all code in .text
> 
> Cc: "Ni, Ray" <ray.ni@intel.com>
> Cc: Andrew Fish <afish@apple.com>
> Cc: "Kinney, Michael D" <michael.d.kinney@intel.com>
> Cc: "Liu, Zhiguang" <zhiguang.liu@intel.com>
> Cc: Rebecca Cran <rebecca@bsdio.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Cc: Marvin Häuser <mhaeuser@posteo.de>

Validated against SEV-ES (which was part of the original reason for the 
split out) and SEV-SNP guests. Both guest types boot successfully.

Tested-by: Tom Lendacky <thomas.lendacky@amd.com>

> 
> Ard Biesheuvel (6):
>    BaseTools/tools_def CLANGDWARF: Permit text relocations
>    UefiCpuPkg/CpuExceptionHandlerLib: Use single SEC/PEI version
>    UefiCpuPkg/PeiCpuExceptionHandlerLib: Use SEC/PEI specific asm
>      component
>    UefiCpuPkg/CpuExceptionHandlerLib: Make runtime fixups XCODE-only
>    OvmfPkg: Drop special Xcode5 version of exception handler library
>    UefiCpuPkg/CpuExceptionHandlerLib: Drop special XCODE5 version
> 
>   BaseTools/Conf/tools_def.template                                                                                |   2 +-
>   OvmfPkg/AmdSev/AmdSevX64.dsc                                                                                     |   4 -
>   OvmfPkg/CloudHv/CloudHvX64.dsc                                                                                   |   4 -
>   OvmfPkg/IntelTdx/IntelTdxX64.dsc                                                                                 |   4 -
>   OvmfPkg/Microvm/MicrovmX64.dsc                                                                                   |   4 -
>   OvmfPkg/OvmfPkgIa32.dsc                                                                                          |   4 -
>   OvmfPkg/OvmfPkgIa32X64.dsc                                                                                       |   4 -
>   OvmfPkg/OvmfPkgX64.dsc                                                                                           |   4 -
>   OvmfPkg/OvmfXen.dsc                                                                                              |   4 -
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeCpuExceptionHandlerLib.inf                                          |   5 +-
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf                                          |   4 +-
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib.inf                                       |   4 +-
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.inf                                          |   4 +-
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nasm                                           | 116 +++++++++++++++++---
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/{Xcode5ExceptionHandlerAsm.nasm => SecPeiExceptionHandlerAsm.nasm} | 108 +++---------------
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf                                 |  65 -----------
>   UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.uni                                 |  18 ---
>   UefiCpuPkg/UefiCpuPkg.dsc                                                                                        |   7 --
>   18 files changed, 133 insertions(+), 232 deletions(-)
>   rename UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/{Xcode5ExceptionHandlerAsm.nasm => SecPeiExceptionHandlerAsm.nasm} (70%)
>   delete mode 100644 UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.inf
>   delete mode 100644 UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHandlerLib.uni
>