Re: [PATCH v4 2/6] UefiCpuPkg/CpuExceptionHandlerLib: Use single SEC/PEI version

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

Reviewed-by: Ray Ni <ray.ni@intel.com>

> -----Original Message-----
> From: Ard Biesheuvel <ardb@kernel.org>
> Sent: Monday, April 3, 2023 10:29 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: [PATCH v4 2/6] UefiCpuPkg/CpuExceptionHandlerLib: Use single
> SEC/PEI version
> 
> Currently, we use the non-Xcode5 version of ExceptionHandlerAsm.nasm
> only for the SEC and PEI phases, and this version was not compatible
> with the XCODE or LLD linkers, which do not permit absolute relocations
> in read-only sections.
> 
> Given that SEC and PEI code typically executes in place from flash and
> does not use page alignment for sections, we can simply emit the code
> carrying the absolute symbol references into the .data segment instead.
> This works around the linker's objections, and the resulting image will
> be mapped executable in its entirety anyway. Since this is only needed
> for XCODE, let's make this change conditionally using a preprocessor
> macro.
> 
> Let's rename the .nasm file to reflect the fact that is used for the
> SecPei flavor of this library only, and while at it, remove some
> unnecessary absolute references.
> 
> Also update the Xcode specific version of this library, and use this
> source file instead. This is necesessary, as the Xcode specific version
> modifies its own code at runtime, which is not permitted in SEC or PEI.
> Note that this also removes CET support from the Xcode5 specific build
> of the SEC/PEI version of this library, but this is not needed this
> early in any case, and this aligns it with other toolchains, which use
> this version of the library, which does not have CET support either.
> 
> 1. Change for non-XCODE SecPeiCpuExceptionHandlerLib:
> . Use SecPeiExceptionHandlerAsm.nasm (renamed from
>   ExceptionHandlerAsm.nasm)
> . Removed some unnecessary absolute references
>   (32 IDT stubs are still in .text.)
> 
> 2. Change for XCODE SecPeiCpuExceptionHandlerLib:
> . Use SecPeiExceptionHandlerAsm.nasm instead of
>   Xcode5ExceptionHandlerAsm.nasm
> . CET logic is not in SecPeiExceptionHandlerAsm.nasm (but aligns to
>   non-XCODE lib instance)
> . Fixed a bug that does runtime fixup in TEXT section in SPI flash.
> . Emitted the code carrying the absolute symbol references into the
>   .data which XCODE or LLD linkers allow.
> . Then fixup can be done by other build tools such as GenFv if the code
>   runs in SPI flash, or by PE coff loader if the code is loaded to
>   memory.
> 
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandlerLib
> .inf                                 |  4 +++-
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/{ExceptionHandlerAsm.na
> sm => SecPeiExceptionHandlerAsm.nasm} | 12 ++++++++----
> 
> UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuExceptionHa
> ndlerLib.inf                           |  4 +++-
>  3 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandler
> Lib.inf
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandler
> Lib.inf
> index df44371fe018e06d..e7b1144f694183b7 100644
> ---
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandler
> Lib.inf
> +++
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/SecPeiCpuExceptionHandler
> Lib.inf
> @@ -28,7 +28,7 @@ [Sources.Ia32]
>    Ia32/ArchInterruptDefs.h
> 
> 
> 
>  [Sources.X64]
> 
> -  X64/ExceptionHandlerAsm.nasm
> 
> +  X64/SecPeiExceptionHandlerAsm.nasm
> 
>    X64/ArchExceptionHandler.c
> 
>    X64/ArchInterruptDefs.h
> 
> 
> 
> @@ -58,3 +58,5 @@ [Pcd]
>  [FeaturePcd]
> 
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard                    ##
> CONSUMES
> 
> 
> 
> +[BuildOptions]
> 
> +  XCODE:*_*_X64_NASM_FLAGS = -D NO_ABSOLUTE_RELOCS_IN_TEXT
> 
> diff --git
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.n
> asm
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/SecPeiExceptionHandler
> Asm.nasm
> similarity index 94%
> rename from
> UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.nas
> m
> rename to
> UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/SecPeiExceptionHandlerA
> sm.nasm
> index aaf8d622e6f3b8f1..5c7a59c99d3210f1 100644
> ---
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/ExceptionHandlerAsm.n
> asm
> +++
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/X64/SecPeiExceptionHandler
> Asm.nasm
> @@ -27,7 +27,9 @@ extern ASM_PFX(CommonExceptionHandler)
>  SECTION .data
> 
> 
> 
>  DEFAULT REL
> 
> +%ifndef NO_ABSOLUTE_RELOCS_IN_TEXT
> 
>  SECTION .text
> 
> +%endif
> 
> 
> 
>  ALIGN   8
> 
> 
> 
> @@ -51,6 +53,9 @@ HookAfterStubHeaderBegin:
>      push    rax
> 
>      mov     rax, HookAfterStubHeaderEnd
> 
>      jmp     rax
> 
> +
> 
> +SECTION .text
> 
> +
> 
>  HookAfterStubHeaderEnd:
> 
>      mov     rax, rsp
> 
>      and     sp,  0xfff0        ; make sure 16-byte aligned for exception context
> 
> @@ -276,8 +281,7 @@ DrFinish:
>      ; and make sure RSP is 16-byte aligned
> 
>      ;
> 
>      sub     rsp, 4 * 8 + 8
> 
> -    mov     rax, ASM_PFX(CommonExceptionHandler)
> 
> -    call    rax
> 
> +    call    ASM_PFX(CommonExceptionHandler)
> 
>      add     rsp, 4 * 8 + 8
> 
> 
> 
>      cli
> 
> @@ -384,10 +388,10 @@ DoIret:
>  ; comments here for definition of address map
> 
>  global ASM_PFX(AsmGetTemplateAddressMap)
> 
>  ASM_PFX(AsmGetTemplateAddressMap):
> 
> -    mov     rax, AsmIdtVectorBegin
> 
> +    lea     rax, [AsmIdtVectorBegin]
> 
>      mov     qword [rcx], rax
> 
>      mov     qword [rcx + 0x8],  (AsmIdtVectorEnd - AsmIdtVectorBegin) / 32
> 
> -    mov     rax, HookAfterStubHeaderBegin
> 
> +    lea     rax, [HookAfterStubHeaderBegin]
> 
>      mov     qword [rcx + 0x10], rax
> 
>      ret
> 
> 
> 
> diff --git
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuException
> HandlerLib.inf
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuException
> HandlerLib.inf
> index 619b39d7f1de9ae3..accc081a95f53453 100644
> ---
> a/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuException
> HandlerLib.inf
> +++
> b/UefiCpuPkg/Library/CpuExceptionHandlerLib/Xcode5SecPeiCpuException
> HandlerLib.inf
> @@ -33,7 +33,7 @@ [Sources.Ia32]
>    Ia32/ArchInterruptDefs.h
> 
> 
> 
>  [Sources.X64]
> 
> -  X64/Xcode5ExceptionHandlerAsm.nasm
> 
> +  X64/SecPeiExceptionHandlerAsm.nasm
> 
>    X64/ArchExceptionHandler.c
> 
>    X64/ArchInterruptDefs.h
> 
> 
> 
> @@ -63,3 +63,5 @@ [Pcd]
>  [FeaturePcd]
> 
>    gUefiCpuPkgTokenSpaceGuid.PcdCpuSmmStackGuard                    ##
> CONSUMES
> 
> 
> 
> +[BuildOptions]
> 
> +  XCODE:*_*_X64_NASM_FLAGS = -D NO_ABSOLUTE_RELOCS_IN_TEXT
> 
> --
> 2.39.2