Ard: Thanks for the detail information. Your patch makes sense. Reviewed-by: Liming Gao <[email protected]>
> -----Original Message----- > From: edk2-devel [mailto:[email protected]] On Behalf Of > Ard Biesheuvel > Sent: Monday, August 22, 2016 3:26 PM > To: Gao, Liming <[email protected]> > Cc: edk2-devel-01 <[email protected]> > Subject: Re: [edk2] [PATCH] BaseTools/GccBase.lds: don't copy RELA section > to PE/COFF > > On 22 August 2016 at 09:22, Gao, Liming <[email protected]> wrote: > > Ard: > > Sorry. I miss this patch. GccBase.lds is used by GCC44~GCC5. > GCC44~GCC49 doesn't enable LTO, GCC5 enables LTO. That means RELA > section is not used with LTO or without LTO. Right? > > The allocatable RELA section is only emitted when linking a PIE binary > (i.e., the -pie linker switch, not the -fpie compiler switch). It > contains ELF relocations that the PE/COFF loader does not understand. > CLANG38LTO is the first toolchain to use the -pie linker switch, GCC5 > does use PIE objects but does not create a PIE binary at link time. > > In some cases, (i.e., when we add support for GOT based relocations), > the contents of this RELA section must be taken into account by GenFw, > but currently, it can only contain relocations that are duplicates of > the relocations we encounter in the non-allocatable RELA sections > (.rela.text, .rela.data etc etc) > > So it never makes sense to copy it into the PE/COFF binary, regardless > of whether we inspect its contents or not. > > -- > Ard. > > > > > Thanks > > Liming > >> -----Original Message----- > >> From: Ard Biesheuvel [mailto:[email protected]] > >> Sent: Monday, August 22, 2016 3:11 PM > >> To: Shi, Steven <[email protected]>; Zhu, Yonghong > >> <[email protected]>; Gao, Liming <[email protected]>; edk2- > >> devel-01 <[email protected]> > >> Cc: Ard Biesheuvel <[email protected]> > >> Subject: Re: [PATCH] BaseTools/GccBase.lds: don't copy RELA section to > >> PE/COFF > >> > >> 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 > >> > > _______________________________________________ > edk2-devel mailing list > [email protected] > https://lists.01.org/mailman/listinfo/edk2-devel _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
