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

["Zeng, Star" <star.zeng@intel.com>]

I meant
the behavior by the spec was unpredictable.

"Passing in a VariableName parameter that is neither a Null-terminated 
string nor a value that was returned on the previous call to
GetNextVariableName() may also produce *unpredictable* results."

The behavior by the code was to return EFI_NOT_FOUND, it was our code's implementation choice.


Do you mean which piece of comments to be put in code? :)



Thanks,
Star
-----Original Message-----
From: Ni, Ruiyu 
Sent: Monday, June 26, 2017 2:18 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

Thanks! Could you please put the comments in code?

But why do you say it's unpredictable? The behavior is to return EFI_NOT_FOUND.

Thanks/Ray

> -----Original Message-----
> From: Zeng, Star
> Sent: Monday, June 26, 2017 1:52 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
> 
> Before UEFI 2.6a and 2.7, the behavior is unpredictable, our *CODE* 
> chose to return EFI_NOT_FOUND.
> 
> "Passing in a VariableName parameter that is neither a Null-terminated 
> string nor a value that was returned on the previous call to
> GetNextVariableName() may also produce unpredictable results."
> 
> 
> 
> Thanks,
> Star
> -----Original Message-----
> From: Ni, Ruiyu
> Sent: Monday, June 26, 2017 1:47 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
> 
> 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