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.z...@intel.com>; edk2-devel@lists.01.org Cc: Gao, Liming <liming....@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...@intel.com>; edk2-devel@lists.01.org > Cc: Gao, Liming <liming....@intel.com>; Zeng, Star > <star.z...@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.z...@intel.com>; edk2-devel@lists.01.org > Cc: Gao, Liming <liming....@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...@intel.com>; edk2-devel@lists.01.org > >Cc: Gao, Liming <liming....@intel.com>; Zeng, Star > ><star.z...@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.z...@intel.com>; edk2-devel@lists.01.org > >Cc: Gao, Liming <liming....@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.z...@intel.com>; Gao, Liming > >> <liming....@intel.com>; Ni, Ruiyu <ruiyu...@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....@intel.com> > >> Cc: Ruiyu Ni <ruiyu...@intel.com> > >> Contributed-under: TianoCore Contribution Agreement 1.0 > >> Signed-off-by: Star Zeng <star.z...@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 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel