Re: [PATCH 2/2] SourceLevelDebugPkg/DebugAgent: Delete the CRC16 implementation

["Pedro Falcato" <pedro.falcato@gmail.com>]

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Hi,

Hao, you are 100% correct. It seems that not only is SourceLevelDebugPkg
using a different CRC-16 algorithm, my CalculateCrc16()'s lookup table is
incorrect.

I'll re-submit a v2 that fixes these issues.
Sorry for the trouble.

Thanks,
Pedro

On Mon, Mar 28, 2022 at 1:14 AM Wu, Hao A <hao.a.wu@intel.com> wrote:

> Hello,
>
> My local test shows that the results between the old (SourceLevelDebugPkg)
> & new (MdePkg) CRC16 implementation are different:
>
> UINT8  Array[16] = {1,2,3,4,5,6,7,8,8,7,6,5,4,3,2,1};
> UINT16 a, b;
> a = CalculateCrc16New(Array, sizeof(Array), 0xFFFF);
> b = CalculateCrc16Old(Array, sizeof(Array), 0xFFFF);
>
> Result:
> a = 0x0af5
> b = 0x2778
>
> My take is that for the SourceLevelDebugPkg case, the CRC16 result should
> be the same (at BIOS host side). Otherwise, the target side will have issue
> for the CRC check.
>
> Best Regards,
> Hao Wu
>
> > -----Original Message-----
> > From: Pedro Falcato <pedro.falcato@gmail.com>
> > Sent: Sunday, March 27, 2022 8:58 AM
> > To: devel@edk2.groups.io
> > Cc: Wu, Hao A <hao.a.wu@intel.com>
> > Subject: [PATCH 2/2] SourceLevelDebugPkg/DebugAgent: Delete the CRC16
> > implementation
> >
> > BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3871
> >
> > Deletes the CRC16 implementation as CalculateCrc16() is being merged into
> > BaseLib.
> >
> > Cc: Hao A Wu <hao.a.wu@intel.com>
> > Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
> > ---
> >  .../DebugAgent/DebugAgentCommon/DebugAgent.c  | 35 -------------------
> >  1 file changed, 35 deletions(-)
> >
> > diff --git
> > a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgen
> > t.c
> > b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgen
> > t.c
> > index a1e61a6ef90e..62c6a235d425 100644
> > ---
> > a/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgen
> > t.c
> > +++
> > b/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugAgen
> > t
> > +++ .c
> > @@ -126,41 +126,6 @@ GLOBAL_REMOVE_IF_UNREFERENCED
> > EFI_VECTOR_HANDOFF_INFO  mVectorHandoffInfoDebugAg
> >
> >  GLOBAL_REMOVE_IF_UNREFERENCED UINTN  mVectorHandoffInfoCount =
> > sizeof (mVectorHandoffInfoDebugAgent) / sizeof
> > (EFI_VECTOR_HANDOFF_INFO);
> >
> > -/**
> > -  Calculate CRC16 for target data.
> > -
> > -  @param[in]  Data              The target data.
> > -  @param[in]  DataSize          The target data size.
> > -  @param[in]  Crc               Initial CRC.
> > -
> > -  @return UINT16     The CRC16 value.
> > -
> > -**/
> > -UINT16
> > -CalculateCrc16 (
> > -  IN UINT8   *Data,
> > -  IN UINTN   DataSize,
> > -  IN UINT16  Crc
> > -  )
> > -{
> > -  UINTN  Index;
> > -  UINTN  BitIndex;
> > -
> > -  for (Index = 0; Index < DataSize; Index++) {
> > -    Crc ^= (UINT16)Data[Index];
> > -    for (BitIndex = 0; BitIndex < 8; BitIndex++) {
> > -      if ((Crc & 0x8000) != 0) {
> > -        Crc <<= 1;
> > -        Crc  ^= 0x1021;
> > -      } else {
> > -        Crc <<= 1;
> > -      }
> > -    }
> > -  }
> > -
> > -  return Crc;
> > -}
> > -
> >  /**
> >    Read IDT entry to check if IDT entries are setup by Debug Agent.
> >
> > --
> > 2.35.1
>
>

-- 
Pedro Falcato

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