Re: [PATCH 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Fix ASSERT for success.

["Dong, Eric" <eric.dong@intel.com>]

Hi Marvin,

Thanks for your contribution. I have reviewed them and pushed to trunk.
SHA numbers are: 
SHA-1: 4222e8e7e421e9c8d2c2f319a3860dd3332d6255
SHA-1: 37fba7c2762e114a280e3b361b53ded034aac7e3

One more question which just curious by me, how you find this issue? by tool or code review?

Thanks,
Eric

> -----Original Message-----
> From: Marvin Häuser [mailto:Marvin.Haeuser@outlook.com]
> Sent: Sunday, October 28, 2018 4:51 PM
> To: edk2-devel@lists.01.org
> Cc: Dong, Eric <eric.dong@intel.com>; lersek@redhat.com
> Subject: [PATCH 2/2] UefiCpuPkg/PiSmmCpuDxeSmm: Fix ASSERT for
> success.
> 
> Index is initialized to MAX_UINT16 as default failure value, which is what the
> ASSERT is supposed to test for.  The ASSERT condition however can never
> return FALSE for INT16 != int, as due to Integer Promotion[1], Index is
> converted to int, which can never result in -1.
> 
> Furthermore, Index is used as a for loop index variable inbetween its
> initialization and the ASSERT, so the value is unconditionally overwritten too.
> 
> Fix the ASSERT check to compare Index to its upper boundary, which it will be
> equal to if the loop was not broken out of on success.
> 
> [1] ISO/IEC 9899:2011, 6.5.9.4
> 
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Marvin Haeuser <Marvin.Haeuser@outlook.com>
> ---
>  UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c
> b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c
> index b7c3ad31e82c..89b3f2b7257f 100644
> --- a/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c
> +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/X64/SmmFuncsArch.c
> @@ -110,7 +110,6 @@ GetProtectedModeCS (
>    UINTN                    GdtEntryCount;
>    UINT16                   Index;
> 
> -  Index = (UINT16) -1;
>    AsmReadGdtr (&GdtrDesc);
>    GdtEntryCount = (GdtrDesc.Limit + 1) / sizeof
> (IA32_SEGMENT_DESCRIPTOR);
>    GdtEntry = (IA32_SEGMENT_DESCRIPTOR *) GdtrDesc.Base; @@ -122,7
> +121,7 @@ GetProtectedModeCS (
>      }
>      GdtEntry++;
>    }
> -  ASSERT (Index != -1);
> +  ASSERT (Index != GdtEntryCount);
>    return Index * 8;
>  }
> 
> --
> 2.19.1.windows.1