Re: [PATCH V2 3/3] DuetPkg FsVariable: Update GetNextVariableName to follow UEFI 2.7

["Ni, Ruiyu" <ruiyu.ni@intel.com>]

Can you add more comments here to describe the purpose is to change the return status
from Not Found to Invalid Parameter, and the reason of choosing Invalid Parameter?

Thanks/Ray

> -----Original Message-----
> From: Zeng, Star
> Sent: Monday, June 26, 2017 1:41 PM
> To: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org
> Cc: Gao, Liming <liming.gao@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: RE: [PATCH V2 3/3] DuetPkg FsVariable: Update
> GetNextVariableName to follow UEFI 2.7
> 
> It is to return EFI_INVALID_PARAMETER when the input VariableName and
> VendorGuid are not a valid variable to search next variable.
> It is added from UEFI 2.7 spec.
> Before the spec change, the code is to return EFI_NOT_FOUND at that case.
> After the spec change, EFI_NOT_FOUND seemingly is reserved to indicate
> the ending of searching.
> 
> 
> Thanks,
> Star
> -----Original Message-----
> From: Ni, Ruiyu
> Sent: Monday, June 26, 2017 1:37 PM
> To: Zeng, Star <star.zeng@intel.com>; edk2-devel@lists.01.org
> Cc: Gao, Liming <liming.gao@intel.com>
> Subject: RE: [PATCH V2 3/3] DuetPkg FsVariable: Update
> GetNextVariableName to follow UEFI 2.7
> 
> I understand your point.
> But I do think it hurts readability.
> 
> BTW, what does the below change does?
>    if (Variable.CurrPtr == NULL || EFI_ERROR (Status)) {
> +    if (VariableName[0] != 0) {
> +      //
> +      // The input values of VariableName and VendorGuid are not a name
> and GUID of an existing variable.
> +      //
> +      Status = EFI_INVALID_PARAMETER;
> +    }
>      return Status;
>    }
> 
> 
> Thanks/Ray
> 
> > -----Original Message-----
> > From: Zeng, Star
> > Sent: Monday, June 26, 2017 11:05 AM
> > To: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org
> > Cc: Gao, Liming <liming.gao@intel.com>; Zeng, Star
> > <star.zeng@intel.com>
> > Subject: RE: [PATCH V2 3/3] DuetPkg FsVariable: Update
> > GetNextVariableName to follow UEFI 2.7
> >
> > Ray,
> >
> > The code is like low hanging fruit from my practice for me, and I
> > don't think it hurts readability although it may not bring performance
> > improvement, it depends on how many variables in variable region, how
> > many times of calling GetNextVariableName, and how fast of
> GetNextVariableName.
> >
> > The code practice I did is on NT32 and my real platforms. Is there
> > anyone can make sure he/she tested all the systems in the world for their
> code?
> >
> >
> > Anyway, I can update the patch if you insist.
> >
> >
> > Thanks,
> > Star
> > -----Original Message-----
> > From: Ni, Ruiyu
> > Sent: Saturday, June 24, 2017 10:08 AM
> > To: Zeng, Star <star.zeng@intel.com>; edk2-devel@lists.01.org
> > Cc: Gao, Liming <liming.gao@intel.com>
> > Subject: RE: [PATCH V2 3/3] DuetPkg FsVariable: Update
> > GetNextVariableName to follow UEFI 2.7
> >
> > Star,
> > I don't recommend to add the additional check for performance
> > consideration.
> > Because we have no idea what the input VariableName buffer is like.
> > If the VariableName is like ['\0', '?', '?', '?'] with MaxLen equals
> > to 4, "VariableName[MaxLen-1] != 0" check is redundant.
> > The NT32 case you met cannot represent the all possible cases.
> > You could use the possibility theory to decide what the most efficient way
> is.
> >
> > Additionally I think code readability is more important than efficiency.
> > In this case, we need the data about the performance improvement to
> > decide whether this check is necessary.
> >
> >
> > Regards,
> > Ray
> >
> > >-----Original Message-----
> > >From: Zeng, Star
> > >Sent: Friday, June 23, 2017 5:33 PM
> > >To: Ni, Ruiyu <ruiyu.ni@intel.com>; edk2-devel@lists.01.org
> > >Cc: Gao, Liming <liming.gao@intel.com>; Zeng, Star
> > ><star.zeng@intel.com>
> > >Subject: RE: [PATCH V2 3/3] DuetPkg FsVariable: Update
> > >GetNextVariableName to follow UEFI 2.7
> > >
> > >Ray,
> > >
> > >It is to pass the check quickly and avoid scanning all the chars in
> > >VariableName by StrnLenS for normal boot without invalid cases.
> > >I did experiments in the code of GetNextVariableName with below debug
> > >code for normal boot on NT32 and my real platforms, all the cases
> > >will go
> > into the branch "xxx 2".
> > >  if (((VariableName[MaxLen - 1] != 0))) {
> > >    DEBUG ((DEBUG_INFO, "xxx 1\n"));
> > >  } else {
> > >    DEBUG ((DEBUG_INFO, "xxx 2\n"));
> > >  }
> > >
> > >
> > >Thanks,
> > >Star
> > >-----Original Message-----
> > >From: Ni, Ruiyu
> > >Sent: Friday, June 23, 2017 4:20 PM
> > >To: Zeng, Star <star.zeng@intel.com>; edk2-devel@lists.01.org
> > >Cc: Gao, Liming <liming.gao@intel.com>
> > >Subject: RE: [PATCH V2 3/3] DuetPkg FsVariable: Update
> > >GetNextVariableName to follow UEFI 2.7
> > >
> > >Star,
> > >What's the benefit of this check "VariableName[MaxLen - 1] != 0"?
> > >I think this check "StrnLenS (VariableName, MaxLen) == MaxLen" should
> > >be
> > enough.
> > >
> > >Thanks/Ray
> > >
> > >> -----Original Message-----
> > >> From: Zeng, Star
> > >> Sent: Friday, June 23, 2017 4:08 PM
> > >> To: edk2-devel@lists.01.org
> > >> Cc: Zeng, Star <star.zeng@intel.com>; Gao, Liming
> > >> <liming.gao@intel.com>; Ni, Ruiyu <ruiyu.ni@intel.com>
> > >> Subject: [PATCH V2 3/3] DuetPkg FsVariable: Update
> > >> GetNextVariableName to follow UEFI 2.7
> > >>
> > >> "The size must be large enough to fit input string supplied in
> > >> VariableName buffer" is added in the description for VariableNameSize.
> > >> And two cases of EFI_INVALID_PARAMETER are added.
> > >> 1. The input values of VariableName and VendorGuid are not a name
> and
> > >>    GUID of an existing variable.
> > >> 2. Null-terminator is not found in the first VariableNameSize bytes of
> > >>    the input VariableName buffer.
> > >>
> > >> This patch is to update code to follow them.
> > >>
> > >> Cc: Liming Gao <liming.gao@intel.com>
> > >> Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> > >> Contributed-under: TianoCore Contribution Agreement 1.0
> > >> Signed-off-by: Star Zeng <star.zeng@intel.com>
> > >> ---
> > >>  DuetPkg/FSVariable/FSVariable.c | 21 ++++++++++++++++++++-
> > >>  1 file changed, 20 insertions(+), 1 deletion(-)
> > >>
> > >> diff --git a/DuetPkg/FSVariable/FSVariable.c
> > >> b/DuetPkg/FSVariable/FSVariable.c index 34b79305c871..6069cfa8fb98
> > >> 100644
> > >> --- a/DuetPkg/FSVariable/FSVariable.c
> > >> +++ b/DuetPkg/FSVariable/FSVariable.c
> > >> @@ -6,7 +6,7 @@ disk. They can be changed by user. BIOS is not able
> > >> to protoect those.
> > >>  Duet trusts all meta data from disk. If variable code, variable
> > >> metadata and variable  data is modified in inproper way, the
> > >> behavior is undefined.
> > >>
> > >> -Copyright (c) 2006 - 2016, Intel Corporation. All rights
> > >> reserved.<BR>
> > >> +Copyright (c) 2006 - 2017, Intel Corporation. All rights
> > >> +reserved.<BR>
> > >>  This program and the accompanying materials  are licensed and made
> > >> available under the terms and conditions of the BSD License  which
> > >> accompanies this distribution.  The full text of the license may be
> > >> found at @@ -1400,14 +1400,33 @@ Returns:
> > >>    VARIABLE_POINTER_TRACK  Variable;
> > >>    UINTN                   VarNameSize;
> > >>    EFI_STATUS              Status;
> > >> +  UINTN                   MaxLen;
> > >>
> > >>    if (VariableNameSize == NULL || VariableName == NULL ||
> > >> VendorGuid ==
> > >> NULL) {
> > >>      return EFI_INVALID_PARAMETER;
> > >>    }
> > >>
> > >> +  //
> > >> +  // Calculate the possible maximum length of name string,
> > >> + including the Null
> > >> terminator.
> > >> +  //
> > >> +  MaxLen = *VariableNameSize / sizeof (CHAR16);  if ((MaxLen == 0)
> > >> + ||
> > >> +      ((VariableName[MaxLen - 1] != 0) && (StrnLenS (VariableName,
> > >> + MaxLen)
> > >> == MaxLen))) {
> > >> +    //
> > >> +    // Null-terminator is not found in the first VariableNameSize
> > >> + bytes of the
> > >> input VariableName buffer.
> > >> +    //
> > >> +    return EFI_INVALID_PARAMETER;
> > >> +  }
> > >> +
> > >>    Status = FindVariable (VariableName, VendorGuid, &Variable);
> > >>
> > >>    if (Variable.CurrPtr == NULL || EFI_ERROR (Status)) {
> > >> +    if (VariableName[0] != 0) {
> > >> +      //
> > >> +      // The input values of VariableName and VendorGuid are not a
> > >> + name
> > >> and GUID of an existing variable.
> > >> +      //
> > >> +      Status = EFI_INVALID_PARAMETER;
> > >> +    }
> > >>      return Status;
> > >>    }
> > >>
> > >> --
> > >> 2.7.0.windows.1