Re: [edk2-devel] [RFT PATCH v3 0/5] UefiCpuPkg, OvmfPkg: Simplify CpuExceptionHandlerLib

["Ni, Ray" <ray.ni@intel.com>]

Ard,
What does "-read_only_relocs suppress" control?
Linker doesn't produce relocation entries that modifies .text section silently
so the final .text just cannot run at all?

Thanks,
Ray

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Ard
> Biesheuvel
> Sent: Friday, March 31, 2023 5:15 PM
> To: devel@edk2.groups.io
> Cc: Ard Biesheuvel <ardb@kernel.org>; Ni, Ray <ray.ni@intel.com>; Andrew
> Fish <afish@apple.com>; Kinney, Michael D <michael.d.kinney@intel.com>;
> Liu, Zhiguang <zhiguang.liu@intel.com>; Rebecca Cran
> <rebecca@bsdio.com>; Tom Lendacky <thomas.lendacky@amd.com>;
> Marvin Häuser <mhaeuser@posteo.de>
> Subject: [edk2-devel] [RFT PATCH v3 0/5] UefiCpuPkg, OvmfPkg: Simplify
> CpuExceptionHandlerLib
> 
> 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:
> 
> -  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 v2:
> 
> - 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>
> 
> 
> 
> Ard Biesheuvel (5):
> 
>   BaseTools/tools_def CLANGDWARF: Permit text relocations
> 
>   UefiCpuPkg/CpuExceptionHandlerLib: Use single SEC/PEI version
> 
>   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.in
> f                                          |   5 +-
> 
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/PeiCpuExceptionHandlerLib.inf
> |   4 +-
> 
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib
> .inf                                       |   4 +-
> 
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/SmmCpuExceptionHandlerLib.i
> nf                                          |   4 +-
> 
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nas
> m                                           | 116 +++++++++++++++++---
> 
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/{Xcode5ExceptionHandler
> Asm.nasm => SecPeiExceptionHandlerAsm.nasm} | 108 +++---------------
> 
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHa
> ndlerLib.inf                                 |  65 -----------
> 
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHa
> ndlerLib.uni                                 |  18 ---
> 
>  UefiCpuPkg/UefiCpuPkg.dsc                                                                                        |   7
> --
> 
>  18 files changed, 133 insertions(+), 232 deletions(-)
> 
>  rename
> UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/{Xcode5ExceptionHandler
> Asm.nasm => SecPeiExceptionHandlerAsm.nasm} (70%)
> 
>  delete mode 100644
> UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHa
> ndlerLib.inf
> 
>  delete mode 100644
> UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHa
> ndlerLib.uni
> 
> 
> 
> --
> 
> 2.39.2
> 
> 
> 
> 
> 
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