[llvm] r209478 - [RuntimeDyld] Teach RuntimeDyldMachO how to handle scattered VANILLA relocs on

[David Blaikie]

On Thu, May 22, 2014 at 3:30 PM, Lang Hames <lhames at gmail.com> wrote:
> Author: lhames
> Date: Thu May 22 17:30:13 2014
> New Revision: 209478
>
> URL: http://llvm.org/viewvc/llvm-project?rev=209478&view=rev
> Log:
> [RuntimeDyld] Teach RuntimeDyldMachO how to handle scattered VANILLA relocs on
> i386.
>
> This fixes two more MCJIT regression tests on i386:

Do we have a public bot running these tests? (why weren't they XFAIL'd
until now?) Do you have one internally at least that's green (how is
it green if these tests aren't XFAIL'd on i386?) so you'll know (&
presumably tell the community) if these regress?

>
>   ExecutionEngine/MCJIT/2003-05-06-LivenessClobber.ll
>   ExecutionEngine/MCJIT/2013-04-04-RelocAddend.ll
>
> The implementation of processScatteredVANILLA is tasteless (*ba-dum-ching*),
> but I'm working on a substantial tidy-up of RuntimeDyldMachO that should
> improve things.
>
> This patch also fixes a type-o in RuntimeDyldMachO::processSECTDIFFRelocation,
> and teaches that method to skip over the PAIR reloc following the SECTDIFF.
>
> <rdar://problem/16961886>
>
>
> Modified:
>     llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
>     llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.h
>
> Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp?rev=209478&r1=209477&r2=209478&view=diff
> ==============================================================================
> --- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp (original)
> +++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.cpp Thu May 22 17:30:13 2014
> @@ -460,7 +460,7 @@ relocation_iterator RuntimeDyldMachO::pr
>
>    uint32_t AddrB = MachO->getScatteredRelocationValue(RE2);
>    section_iterator SBI = getSectionByAddress(*MachO, AddrB);
> -  assert(SBI != MachO->section_end() && "Can't find seciton for address B");
> +  assert(SBI != MachO->section_end() && "Can't find section for address B");
>    uint64_t SectionBBase;
>    SBI->getAddress(SectionBBase);
>    uint64_t SectionBOffset = AddrB - SectionBBase;
> @@ -483,7 +483,48 @@ relocation_iterator RuntimeDyldMachO::pr
>    addRelocationForSection(R, SectionAID);
>    addRelocationForSection(R, SectionBID);
>
> -  return RelI;
> +  return ++RelI;
> +}
> +
> +relocation_iterator RuntimeDyldMachO::processI386ScatteredVANILLA(
> +                                            unsigned SectionID,
> +                                            relocation_iterator RelI,
> +                                            ObjectImage &Obj,
> +                                            ObjSectionToIDMap &ObjSectionToID) {
> +  const MachOObjectFile *MachO =
> +    static_cast<const MachOObjectFile*>(Obj.getObjectFile());
> +  MachO::any_relocation_info RE =
> +    MachO->getRelocation(RelI->getRawDataRefImpl());
> +
> +  SectionEntry &Section = Sections[SectionID];
> +  uint32_t RelocType = MachO->getAnyRelocationType(RE);
> +  bool IsPCRel = MachO->getAnyRelocationPCRel(RE);
> +  unsigned Size = MachO->getAnyRelocationLength(RE);
> +  uint64_t Offset;
> +  RelI->getOffset(Offset);
> +  uint8_t *LocalAddress = Section.Address + Offset;
> +  unsigned NumBytes = 1 << Size;
> +  int64_t Addend = 0;
> +  memcpy(&Addend, LocalAddress, NumBytes);
> +
> +  unsigned SymbolBaseAddr = MachO->getScatteredRelocationValue(RE);
> +  section_iterator TargetSI = getSectionByAddress(*MachO, SymbolBaseAddr);
> +  assert(TargetSI != MachO->section_end() && "Can't find section for symbol");
> +  uint64_t SectionBaseAddr;
> +  TargetSI->getAddress(SectionBaseAddr);
> +  SectionRef TargetSection = *TargetSI;
> +  bool IsCode;
> +  TargetSection.isText(IsCode);
> +  uint32_t TargetSectionID = findOrEmitSection(Obj, TargetSection, IsCode,
> +                                               ObjSectionToID);
> +
> +  Addend -= SectionBaseAddr;
> +  RelocationEntry R(SectionID, Offset, RelocType, Addend,
> +                    IsPCRel, Size);
> +
> +  addRelocationForSection(R, TargetSectionID);
> +
> +  return ++RelI;
>  }
>
>  relocation_iterator RuntimeDyldMachO::processRelocationRef(
> @@ -498,17 +539,22 @@ relocation_iterator RuntimeDyldMachO::pr
>    uint32_t RelType = MachO->getAnyRelocationType(RE);
>
>    // FIXME: Properly handle scattered relocations.
> -  //        For now, optimistically skip these: they can often be ignored, as
> -  //        the static linker will already have applied the relocation, and it
> -  //        only needs to be reapplied if symbols move relative to one another.
> -  //        Note: This will fail horribly where the relocations *do* need to be
> -  //        applied, but that was already the case.
> +  //        Special case the couple of scattered relocations that we know how
> +  //        to handle: SECTDIFF relocations, and scattered VANILLA relocations
> +  //        on I386.
> +  //        For all other scattered relocations, just bail out and hope for the
> +  //        best, since the offsets computed by scattered relocations have often
> +  //        been optimisticaly filled in by the compiler. This will fail
> +  //        horribly where the relocations *do* need to be applied, but that was
> +  //        already the case.
>    if (MachO->isRelocationScattered(RE)) {
>      if (RelType == MachO::GENERIC_RELOC_SECTDIFF ||
>          RelType == MachO::GENERIC_RELOC_LOCAL_SECTDIFF)
>        return processSECTDIFFRelocation(SectionID, RelI, Obj, ObjSectionToID);
> -
> -    return ++RelI;
> +    else if (Arch == Triple::x86 && RelType == MachO::GENERIC_RELOC_VANILLA)
> +      return processI386ScatteredVANILLA(SectionID, RelI, Obj, ObjSectionToID);
> +    else
> +      return ++RelI;
>    }
>
>    RelocationValueRef Value;
>
> Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.h
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.h?rev=209478&r1=209477&r2=209478&view=diff
> ==============================================================================
> --- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.h (original)
> +++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldMachO.h Thu May 22 17:30:13 2014
> @@ -71,6 +71,12 @@ private:
>                                               ObjectImage &ObjImg,
>                                               ObjSectionToIDMap &ObjSectionToID);
>
> +  relocation_iterator processI386ScatteredVANILLA(
> +                                            unsigned SectionID,
> +                                            relocation_iterator RelI,
> +                                            ObjectImage &ObjImg,
> +                                            ObjSectionToIDMap &ObjSectionToID);
> +
>    struct EHFrameRelatedSections {
>      EHFrameRelatedSections()
>          : EHFrameSID(RTDYLD_INVALID_SECTION_ID),
>
>
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