[PATCH] COFF: Minor fix to Section size calculation

[Keno Fischer]

Bump. I'm not really sure who could best review this.


On Tue, Jun 10, 2014 at 1:49 PM, Keno Fischer <kfischer at college.harvard.edu>
wrote:

> I noticed llvm-dwarfdump was crashing on COFF dlls with embedded DWARF
> debug info. The reason was that SizeOfRawData actually indicates the size
> on disc which is not the size of the actual section data in a PE file
> (*.dll, *.exe), because of alignment rules. Instead the size of given by
> min(SizeOfRawData,VirtualSize).
>
> I'm not sure what to do with respect to testing, since compiling a file
> from source would require a COFF capable linker. Is it acceptable to commit
> an entire PE exectuable to the repository? If so, I'll try to come up with
> a minimal example where this happens.
>
> http://reviews.llvm.org/D4087
>
> Files:
>   lib/Object/COFFObjectFile.cpp
>
> Index: lib/Object/COFFObjectFile.cpp
> ===================================================================
> --- lib/Object/COFFObjectFile.cpp
> +++ lib/Object/COFFObjectFile.cpp
> @@ -829,11 +829,21 @@
>    // within the file bounds. We don't need to make sure it doesn't cover
> other
>    // data, as there's nothing that says that is not allowed.
>    uintptr_t ConStart = uintptr_t(base()) + Sec->PointerToRawData;
> -  uintptr_t ConEnd = ConStart + Sec->SizeOfRawData;
> +  // COFF requires sections to follow certain alignment rules in PE
> +  // files. Thus (in a PE file) a section's actual data may be smaller
> +  // than SizeOfRawData.
> +  // Since for debug sections later on the actual data matters, we take
> +  // the min of SizeOfRawData and VirtualSize which is the acutal size
> +  // of the data.
> +  uintptr_t Size = Sec->SizeOfRawData;
> +  // COFF Object files always have VirtualSize set to 0
> +  if (Sec->VirtualSize != 0)
> +    Size = std::min(Size,(uintptr_t)Sec->VirtualSize);
> +  uintptr_t ConEnd = ConStart + Size;
>    if (ConEnd > uintptr_t(Data->getBufferEnd()))
>      return object_error::parse_failed;
>    Res = ArrayRef<uint8_t>(reinterpret_cast<const unsigned
> char*>(ConStart),
> -                          Sec->SizeOfRawData);
> +                          Size);
>    return object_error::success;
>  }
>
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