On 10 August 2016 at 10:55, Ard Biesheuvel <[email protected]> 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 <[email protected]>
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
>
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