Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to PE/COFF

[Ard Biesheuvel <ard.biesheuvel@linaro.org>]

On 10 August 2016 at 10:55, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> The CLANG38 toolchain creates a PIE binary at link time. This is
> necessary since the LTO code generation may otherwise result in
> code that cannot execute correctly when loaded above 2 GB.
>
> PIE executables contain a RELA section consisting of dynamic
> relocation entries that are intended for consumption by the loader
> at runtime. For this reason, it has the SHF_ALLOC attribute set by
> default, and will be identified by GenFw as a section that needs to
> be copied into the PE/COFF binary, resulting in waste of space since
> the PE/COFF loader does not use this data at all.
>
> So mark the RELA section as informational: this will prevent the
> linker from setting the SHF_ALLOC attribute, causing GenFw to
> ignore it.
>
> DxeCore.efi before:
>
>     Detected 'X64' type PE/COFF image consisting of 3 sections
>     Section alignment:      0x40
>     File alignment:         0x40
>     Section '.text' @ 0x00000240
>     File offset:            0x240
>     Virtual size:           0x21000
>     Raw size:               0x21000
>     Section '.data' @ 0x00021240
>     File offset:            0x21240
>     Virtual size:           0x3640
>     Raw size:               0x3640
>     Section '.reloc' @ 0x00024880
>     File offset:            0x24880
>     Virtual size:           0x280
>     Raw size:               0x280
>
> DxeCore.efi after:
>
>     Detected 'X64' type PE/COFF image consisting of 3 sections
>     Section alignment:      0x40
>     File alignment:         0x40
>     Section '.text' @ 0x00000240
>     File offset:            0x240
>     Virtual size:           0x1f440
>     Raw size:               0x1f440
>     Section '.data' @ 0x0001f680
>     File offset:            0x1f680
>     Virtual size:           0x3640
>     Raw size:               0x3640
>     Section '.reloc' @ 0x00022cc0
>     File offset:            0x22cc0
>     Virtual size:           0x280
>     Raw size:               0x280
>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Steven, Liming: any comments?

> ---
>  BaseTools/Scripts/GccBase.lds | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/BaseTools/Scripts/GccBase.lds b/BaseTools/Scripts/GccBase.lds
> index 281af8a9bd33..900848747144 100644
> --- a/BaseTools/Scripts/GccBase.lds
> +++ b/BaseTools/Scripts/GccBase.lds
> @@ -54,7 +54,7 @@ SECTIONS {
>      KEEP (*(.eh_frame))
>    }
>
> -  .rela ALIGN(CONSTANT(COMMONPAGESIZE)) : {
> +  .rela (INFO) : {
>      *(.rela .rela.*)
>    }
>
> --
> 2.7.4
>