Hi Ard, I don't see you add below code for case R_X86_64_PLT32. Is it right?
*(UINT32 *)Targ = (UINT32) (*(UINT32 *)Targ + (mCoffSectionsOffset[Sym->st_shndx] - SymShdr->sh_addr) - (SecOffset - SecShdr->sh_addr)); Steven Shi Intel\SSG\STO\UEFI Firmware Tel: +86 021-61166522 iNet: 821-6522 > -----Original Message----- > From: Ard Biesheuvel [mailto:ard.biesheu...@linaro.org] > Sent: Thursday, August 04, 2016 4:46 PM > To: Shi, Steven <steven....@intel.com>; Zhu, Yonghong > <yonghong....@intel.com>; Gao, Liming <liming....@intel.com>; Justen, > Jordan L <jordan.l.jus...@intel.com>; edk2-devel@lists.01.org > Cc: misch...@offblast.org; Ard Biesheuvel <ard.biesheu...@linaro.org> > Subject: [PATCH] BaseTools X64: fold PLT relocations into simple relative > references > > For X64/GCC, we use position independent code with hidden visibility > to inform the compiler that symbols references are never resolved at > runtime, which removes the need for PLTs and GOTs. However, in some > cases GCC has been reported to still emit PLT based relocations, which > we need to handle in the ELF to PE/COFF perform by GenFw. > > Unlike GOT based relocations, which are non-trivial to handle since the > indirections in the code can not be fixed up easily (although relocation > types exist for X64 that annotate relocation targets as suitable for > relaxation), PLT relocations simply point to jump targets, and we can > relax such relocations by resolving them using the symbol directly rather > than via a PLT entry that does nothing more than tail call the function > we already know it is going to call (since all symbol references are > resolved in the same module). > > So handle R_X86_64_PLT32 as a R_X86_64_PC32 relocation. > > Suggested-by: Steven Shi <steven....@intel.com> > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org> > --- > BaseTools/Source/C/GenFw/Elf64Convert.c | 11 +++++++++++ > 1 file changed, 11 insertions(+) > > diff --git a/BaseTools/Source/C/GenFw/Elf64Convert.c > b/BaseTools/Source/C/GenFw/Elf64Convert.c > index 944c94b8f8b4..7cbff0df0996 100644 > --- a/BaseTools/Source/C/GenFw/Elf64Convert.c > +++ b/BaseTools/Source/C/GenFw/Elf64Convert.c > @@ -785,6 +785,17 @@ WriteSections64 ( > *(INT32 *)Targ = (INT32)((INT64)(*(INT32 *)Targ) - > SymShdr->sh_addr > + mCoffSectionsOffset[Sym->st_shndx]); > VerboseMsg ("Relocation: 0x%08X", *(UINT32*)Targ); > break; > + > + case R_X86_64_PLT32: > + // > + // Treat R_X86_64_PLT32 relocations as R_X86_64_PC32: this is > + // possible since we know all code symbol references resolve to > + // definitions in the same module (UEFI has no shared libraries), > + // and so there is never a reason to jump via a PLT entry, > + // allowing us to resolve the reference using the symbol > directly. > + // > + VerboseMsg ("Treating R_X86_64_PLT32 as R_X86_64_PC32 ..."); > + /* fall through */ > case R_X86_64_PC32: > // > // Relative relocation: Symbol - Ip + Addend > -- > 2.7.4 _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel