[lld] r252131 - [elf2] Fix R_X86_64_TPOFF32 handling.

[Rui Ueyama via llvm-commits]

On Wed, Nov 4, 2015 at 6:00 PM, Michael J. Spencer via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: mspencer
> Date: Wed Nov  4 20:00:35 2015
> New Revision: 252131
>
> URL: http://llvm.org/viewvc/llvm-project?rev=252131&view=rev
> Log:
> [elf2] Fix R_X86_64_TPOFF32 handling.
>
> For x86-64 the initial executable TLS block is placed directly before the
> thread specific data register so compilers can directly access it via
> R_X86_64_TPOFF32. Generate the correct (negative) offset for this case.
>
> Modified:
>     lld/trunk/ELF/OutputSections.h
>     lld/trunk/ELF/Target.cpp
>     lld/trunk/ELF/Writer.cpp
>     lld/trunk/test/elf2/tls.s
>
> Modified: lld/trunk/ELF/OutputSections.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.h?rev=252131&r1=252130&r2=252131&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.h (original)
> +++ lld/trunk/ELF/OutputSections.h Wed Nov  4 20:00:35 2015
> @@ -372,6 +372,7 @@ template <class ELFT> struct Out {
>    static SymbolTableSection<ELFT> *DynSymTab;
>    static SymbolTableSection<ELFT> *SymTab;
>    static uintX_t TlsInitImageVA;
> +  static size_t TlsInitImageAlignedSize;
>  };
>
>  template <class ELFT> DynamicSection<ELFT> *Out<ELFT>::Dynamic;
> @@ -392,6 +393,7 @@ template <class ELFT> StringTableSection
>  template <class ELFT> SymbolTableSection<ELFT> *Out<ELFT>::DynSymTab;
>  template <class ELFT> SymbolTableSection<ELFT> *Out<ELFT>::SymTab;
>  template <class ELFT> typename Out<ELFT>::uintX_t
> Out<ELFT>::TlsInitImageVA;
> +template <class ELFT> size_t Out<ELFT>::TlsInitImageAlignedSize;
>
>  } // namespace elf2
>  } // namespace lld
>
> Modified: lld/trunk/ELF/Target.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Target.cpp?rev=252131&r1=252130&r2=252131&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Target.cpp (original)
> +++ lld/trunk/ELF/Target.cpp Wed Nov  4 20:00:35 2015
> @@ -340,7 +340,7 @@ void X86_64TargetInfo::relocateOne(uint8
>      write32le(Loc, SA);
>      break;
>    case R_X86_64_TPOFF32:
> -    write32le(Loc, SA);
> +    write32le(Loc, SA -
> Out<llvm::object::ELF64LE>::TlsInitImageAlignedSize);
>      break;
>    default:
>      error("unrecognized reloc " + Twine(Type));
>
> Modified: lld/trunk/ELF/Writer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=252131&r1=252130&r2=252131&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/Writer.cpp (original)
> +++ lld/trunk/ELF/Writer.cpp Wed Nov  4 20:00:35 2015
> @@ -740,8 +740,11 @@ template <class ELFT> void Writer<ELFT>:
>      }
>    }
>
> -  if (TlsPhdr.p_vaddr)
> +  if (TlsPhdr.p_vaddr) {
>      Phdrs[++PhdrIdx] = TlsPhdr;
> +    Out<ELFT>::TlsInitImageAlignedSize =
> +        RoundUpToAlignment(TlsPhdr.p_memsz, TlsPhdr.p_align);
> +  }
>

Can you give me the pointer to the spec that says "TLS block end" is an
aligned value this way?


>
>    // Add an entry for .dynamic.
>    if (isOutputDynamic()) {
>
> Modified: lld/trunk/test/elf2/tls.s
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/tls.s?rev=252131&r1=252130&r2=252131&view=diff
>
> ==============================================================================
> --- lld/trunk/test/elf2/tls.s (original)
> +++ lld/trunk/test/elf2/tls.s Wed Nov  4 20:00:35 2015
> @@ -164,7 +164,7 @@ d:
>
>  // DIS:      Disassembly of section .text:
>  // DIS-NEXT: _start:
> -// DIS-NEXT:    11000: {{.+}} movl    %fs:8, %eax
> -// DIS-NEXT:    11008: {{.+}} movl    %fs:0, %eax
> -// DIS-NEXT:    11010: {{.+}} movl    %fs:12, %eax
> -// DIS-NEXT:    11018: {{.+}} movl    %fs:4, %eax
> +// DIS-NEXT:    11000: {{.+}} movl    %fs:-8, %eax
> +// DIS-NEXT:    11008: {{.+}} movl    %fs:-16, %eax
> +// DIS-NEXT:    11010: {{.+}} movl    %fs:-4, %eax
> +// DIS-NEXT:    11018: {{.+}} movl    %fs:-12, %eax
>
>
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