Re: [edk2-devel] [PATCH] UefiCpuPkg: Fix CPU stack guard support by aligning GDT buffer

["Leif Lindholm" <leif@nuviainc.com>]

UefiCpuPkg maintainers - please respond.

Meanwhile, Vitaly, could you please provide a commit message?
The BZ link is needed, but it's not a substitute.

/
    Leif

On Mon, Sep 20, 2021 at 17:13:47 +0300, Vitaly Cheptsov wrote:
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3639
> 
> 
> 
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> 
> Cc: Eric Dong <eric.dong@intel.com>
> 
> Cc: Michael Kinney <michael.d.kinney@intel.com>
> 
> Cc: Jian J Wang <jian.j.wang@intel.com>
> 
> Cc: Jeff Fan <vanjeff_919@hotmail.com>
> 
> Cc: Mikhail Krichanov <krichanov@ispras.ru>
> 
> Cc: Marvin Häuser <mhaeuser@posteo.de>
> 
> Signed-off-by: Vitaly Cheptsov <cheptsov@ispras.ru>
> 
> ---
> 
>  .../Library/CpuExceptionHandlerLib/DxeException.c    | 12 +++++++-----
> 
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> 
> 
> diff --git a/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeException.c b/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeException.c
> 
> index fd59f09ecd..12874811e1 100644
> 
> --- a/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeException.c
> 
> +++ b/UefiCpuPkg/Library/CpuExceptionHandlerLib/DxeException.c
> 
> @@ -22,7 +22,7 @@ EXCEPTION_HANDLER_DATA      mExceptionHandlerData;
> 
>  
> 
>  UINT8                       mNewStack[CPU_STACK_SWITCH_EXCEPTION_NUMBER *
> 
>                                        CPU_KNOWN_GOOD_STACK_SIZE];
> 
> -UINT8                       mNewGdt[CPU_TSS_GDT_SIZE];
> 
> +UINT8                       mNewGdt[CPU_TSS_GDT_SIZE + IA32_GDT_ALIGNMENT];
> 
>  
> 
>  /**
> 
>    Common exception handler.
> 
> @@ -238,6 +238,7 @@ InitializeCpuExceptionHandlersEx (
> 
>    CPU_EXCEPTION_INIT_DATA           EssData;
> 
>    IA32_DESCRIPTOR                   Idtr;
> 
>    IA32_DESCRIPTOR                   Gdtr;
> 
> +  UINT8                             *Gdt;
> 
>  
> 
>    //
> 
>    // To avoid repeat initialization of default handlers, the caller should pass
> 
> @@ -259,6 +260,7 @@ InitializeCpuExceptionHandlersEx (
> 
>      if (PcdGetBool (PcdCpuStackGuard)) {
> 
>        if (InitData == NULL) {
> 
>          SetMem (mNewGdt, sizeof (mNewGdt), 0);
> 
> +        Gdt = ALIGN_POINTER (mNewGdt, IA32_GDT_ALIGNMENT);
> 
>  
> 
>          AsmReadIdtr (&Idtr);
> 
>          AsmReadGdtr (&Gdtr);
> 
> @@ -270,11 +272,11 @@ InitializeCpuExceptionHandlersEx (
> 
>          EssData.X64.StackSwitchExceptionNumber = CPU_STACK_SWITCH_EXCEPTION_NUMBER;
> 
>          EssData.X64.IdtTable = (VOID *)Idtr.Base;
> 
>          EssData.X64.IdtTableSize = Idtr.Limit + 1;
> 
> -        EssData.X64.GdtTable = mNewGdt;
> 
> -        EssData.X64.GdtTableSize = sizeof (mNewGdt);
> 
> -        EssData.X64.ExceptionTssDesc = mNewGdt + Gdtr.Limit + 1;
> 
> +        EssData.X64.GdtTable = Gdt;
> 
> +        EssData.X64.GdtTableSize = CPU_TSS_GDT_SIZE;
> 
> +        EssData.X64.ExceptionTssDesc = Gdt + Gdtr.Limit + 1;
> 
>          EssData.X64.ExceptionTssDescSize = CPU_TSS_DESC_SIZE;
> 
> -        EssData.X64.ExceptionTss = mNewGdt + Gdtr.Limit + 1 + CPU_TSS_DESC_SIZE;
> 
> +        EssData.X64.ExceptionTss = Gdt + Gdtr.Limit + 1 + CPU_TSS_DESC_SIZE;
> 
>          EssData.X64.ExceptionTssSize = CPU_TSS_SIZE;
> 
>  
> 
>          InitData = &EssData;
> 
> -- 
> 
> 2.30.1 (Apple Git-130)
> 
> 
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>