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

["Marvin Häuser" <mhaeuser@posteo.de>]

Hi Ray,

> On 31. Mar 2023, at 12:09, Ni, Ray <ray.ni@intel.com> wrote:
> 
> Ard,
> What does "-read_only_relocs suppress" control?

It controls whether relocs that target read-only segments yield a build error or not. I think lld uses “-z notext”.

> Linker doesn't produce relocation entries that modifies .text section silently
> so the final .text just cannot run at all?

Could you please rephrase? I’m not sure I understand, but I think it’s important everyone understands the issues at play to make a good judgment call.

Best regards,
Marvin

> 
> 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
>> 
>> 
>> 
>> 
>> 
>> -=-=-=-=-=-=
>> Groups.io Links: You receive all messages sent to this group.
>> View/Reply Online (#102255):
>> https://edk2.groups.io/g/devel/message/102255
>> Mute This Topic: https://groups.io/mt/97969646/1712937
>> Group Owner: devel+owner@edk2.groups.io
>> Unsubscribe: https://edk2.groups.io/g/devel/unsub [ray.ni@intel.com]
>> -=-=-=-=-=-=
>> 
>