Re: [PATCH] MdePkg/BasePeCoffLib: skip runtime relocation if relocation info is invalid.

["Hsueh, Hong-chihX" <hong-chihx.hsueh@intel.com>]

Hi Laszlo,
Thank you for your comment.
I've sent an updated patch for review.
https://lists.01.org/pipermail/edk2-devel/2019-January/035806.html

Regards,
Neo

> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com]
> Sent: Friday, January 25, 2019 1:07 AM
> To: Hsueh, Hong-chihX <hong-chihx.hsueh@intel.com>; edk2-devel@lists.01.org
> Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Bi, Dandan
> <dandan.bi@intel.com>; Gao, Liming <liming.gao@intel.com>
> Subject: Re: [edk2] [PATCH] MdePkg/BasePeCoffLib: skip runtime relocation if
> relocation info is invalid.
> 
> On 01/25/19 00:18, Neo Hsueh wrote:
> > 1.Skip runtime relocation for PE images that provide invalid relocation
> >   infomation (ex: RelocDir->Size = 0) to fix a hang observed while booting
> >   Windows.
> > 2.Add a magic number check for PE32+ image.
> >
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Neo Hsueh <hong-chihx.hsueh@intel.com>
> > Cc: Michael D Kinney <michael.d.kinney@intel.com>
> > Cc: Liming Gao <liming.gao@intel.com>
> > Cc: Dandan Bi <dandan.bi@intel.com>
> > ---
> >  MdePkg/Library/BasePeCoffLib/BasePeCoff.c | 19 ++++++++++++++++---
> >  1 file changed, 16 insertions(+), 3 deletions(-)
> 
> I can't comment on the technical details of the patch, but I have some
> comments on the organization of the patch.
> 
> First, the two changes that it implements should be separate patches.
> 
> > diff --git a/MdePkg/Library/BasePeCoffLib/BasePeCoff.c
> > b/MdePkg/Library/BasePeCoffLib/BasePeCoff.c
> > index 1bd079ad6a..6477ef0759 100644
> > --- a/MdePkg/Library/BasePeCoffLib/BasePeCoff.c
> > +++ b/MdePkg/Library/BasePeCoffLib/BasePeCoff.c
> > @@ -1725,11 +1725,18 @@ PeCoffLoaderRelocateImageForRuntime (
> >      NumberOfRvaAndSizes = Hdr.Pe32-
> >OptionalHeader.NumberOfRvaAndSizes;
> >      DataDirectory = (EFI_IMAGE_DATA_DIRECTORY *)&(Hdr.Pe32-
> >OptionalHeader.DataDirectory[0]);
> >    } else {
> > +    if (Hdr.Pe32Plus->OptionalHeader.Magic ==
> EFI_IMAGE_NT_OPTIONAL_HDR64_MAGIC) {
> > +      //
> > +      // Use PE32+ offset
> > +      //
> > +      NumberOfRvaAndSizes = Hdr.Pe32Plus-
> >OptionalHeader.NumberOfRvaAndSizes;
> > +      DataDirectory = (EFI_IMAGE_DATA_DIRECTORY *)&(Hdr.Pe32Plus-
> >OptionalHeader.DataDirectory[0]);
> > +    } else {
> >      //
> > -    // Use PE32+ offset
> > +    // Not a valid PE image so Exit
> >      //
> > -    NumberOfRvaAndSizes = Hdr.Pe32Plus-
> >OptionalHeader.NumberOfRvaAndSizes;
> > -    DataDirectory = (EFI_IMAGE_DATA_DIRECTORY *)&(Hdr.Pe32Plus-
> >OptionalHeader.DataDirectory[0]);
> > +    return;
> > +    }
> >    }
> >
> >    //
> 
> Second, my understanding is that in edk2, we don't do
> 
>   if (Condition1) {
>   } else {
>     if (Condition2) {
>     } else {
>     }
>   }
> 
> Instead, we prefer
> 
>   if (Condition1) {
>   } else if (Condition2) {
>   } else {
>   }
> 
> As far as I know, this is the only construct where we don't require braces after
> an "else". See:
> 
> https://edk2-docs.gitbooks.io/edk-ii-c-coding-standards-
> specification/content/5_source_files/57_c_programming.html#57342-when-
> an-else-is-used-it-may-start-on-the-same-line-as-the-close-brace-of-the-if-or-
> be-on-the-following-line-and-aligned-with-the-closing-brace
> 
> 
> Third, the return statement and the comment are not properly indented in the
> last branch.
> 
> Thanks
> Laszlo
> 
> > @@ -1746,6 +1753,12 @@ PeCoffLoaderRelocateImageForRuntime (
> >                                                                              RelocDir->VirtualAddress +
> RelocDir->Size - 1,
> >                                                                              0
> >
> > );
> > +    if (RelocBase == NULL || RelocBaseEnd == NULL || RelocBaseEnd <
> RelocBase) {
> > +      //
> > +      // relocation block is not valid, just return
> > +      //
> > +      return;
> > +    }
> >    } else {
> >      //
> >      // Cannot find relocations, cannot continue to relocate the image, ASSERT
> for this invalid image.
> >