[lld] r249025 - Copy DT_SONAME to DT_NEEDED.

[Rui Ueyama via llvm-commits]

Thanks!

With this patch, a dynamically-linked "hello world" C program worked fine
on my system. That's awesome!

On Thu, Oct 1, 2015 at 8:47 AM, Rafael Espindola via llvm-commits <
llvm-commits at lists.llvm.org> wrote:

> Author: rafael
> Date: Thu Oct  1 10:47:50 2015
> New Revision: 249025
>
> URL: http://llvm.org/viewvc/llvm-project?rev=249025&view=rev
> Log:
> Copy DT_SONAME to DT_NEEDED.
>
> If a shared library has a DT_SONAME entry, that is what should be included
> in the DT_NEEDED of a program using it.
>
> We don't implement -soname yet, so check in a .so for now.
>
> Added:
>     lld/trunk/test/elf2/Inputs/soname.so   (with props)
>     lld/trunk/test/elf2/soname.s
> Modified:
>     lld/trunk/ELF/InputFiles.cpp
>     lld/trunk/ELF/InputFiles.h
>     lld/trunk/ELF/OutputSections.cpp
>
> Modified: lld/trunk/ELF/InputFiles.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.cpp?rev=249025&r1=249024&r2=249025&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/InputFiles.cpp (original)
> +++ lld/trunk/ELF/InputFiles.cpp Thu Oct  1 10:47:50 2015
> @@ -216,14 +216,39 @@ SharedFile<ELFT>::SharedFile(MemoryBuffe
>      : SharedFileBase(getStaticELFKind<ELFT>(), M), ELFData<ELFT>(M) {}
>
>  template <class ELFT> void SharedFile<ELFT>::parse() {
> -  for (const Elf_Shdr &Sec : this->ELFObj.sections()) {
> -    if (Sec.sh_type == SHT_DYNSYM) {
> +  typedef typename ELFFile<ELFT>::Elf_Dyn Elf_Dyn;
> +  typedef typename ELFFile<ELFT>::uintX_t uintX_t;
> +  const Elf_Shdr *DynamicSec = nullptr;
> +
> +  const ELFFile<ELFT> Obj = this->ELFObj;
> +  for (const Elf_Shdr &Sec : Obj.sections()) {
> +    uint32_t Type = Sec.sh_type;
> +    if (Type == SHT_DYNSYM)
>        this->Symtab = &Sec;
> -      break;
> -    }
> +    else if (Type == SHT_DYNAMIC)
> +      DynamicSec = &Sec;
>    }
>
> +  // Also sets StringTable
>    Elf_Sym_Range Syms = this->getNonLocalSymbols();
> +  SoName = getName();
> +
> +  if (DynamicSec) {
> +    auto *Begin =
> +        reinterpret_cast<const Elf_Dyn *>(Obj.base() +
> DynamicSec->sh_offset);
> +    const Elf_Dyn *End = Begin + DynamicSec->sh_size / sizeof(Elf_Dyn);
> +
> +    for (const Elf_Dyn &Dyn : make_range(Begin, End)) {
> +      if (Dyn.d_tag == DT_SONAME) {
> +        uintX_t Val = Dyn.getVal();
> +        if (Val >= this->StringTable.size())
> +          error("Invalid DT_SONAME entry");
> +        SoName = StringRef(this->StringTable.data() + Val);
> +        break;
> +      }
> +    }
> +  }
> +
>    uint32_t NumSymbols = std::distance(Syms.begin(), Syms.end());
>    SymbolBodies.reserve(NumSymbols);
>    for (const Elf_Sym &Sym : Syms) {
>
> Modified: lld/trunk/ELF/InputFiles.h
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/InputFiles.h?rev=249025&r1=249024&r2=249025&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/InputFiles.h (original)
> +++ lld/trunk/ELF/InputFiles.h Thu Oct  1 10:47:50 2015
> @@ -185,10 +185,14 @@ private:
>
>  // .so file.
>  class SharedFileBase : public ELFFileBase {
> +protected:
> +  StringRef SoName;
> +
>  public:
>    SharedFileBase(ELFKind EKind, MemoryBufferRef M)
>        : ELFFileBase(SharedKind, EKind, M) {}
>    static bool classof(const InputFile *F) { return F->kind() ==
> SharedKind; }
> +  StringRef getSoName() const { return SoName; }
>  };
>
>  template <class ELFT>
>
> Modified: lld/trunk/ELF/OutputSections.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/OutputSections.cpp?rev=249025&r1=249024&r2=249025&view=diff
>
> ==============================================================================
> --- lld/trunk/ELF/OutputSections.cpp (original)
> +++ lld/trunk/ELF/OutputSections.cpp Thu Oct  1 10:47:50 2015
> @@ -207,7 +207,7 @@ template <class ELFT> void DynamicSectio
>    const std::vector<std::unique_ptr<SharedFileBase>> &SharedFiles =
>        SymTab.getSharedFiles();
>    for (const std::unique_ptr<SharedFileBase> &File : SharedFiles)
> -    DynStrSec.add(File->getName());
> +    DynStrSec.add(File->getSoName());
>    NumEntries += SharedFiles.size();
>
>    ++NumEntries; // DT_NULL
> @@ -266,7 +266,7 @@ template <class ELFT> void DynamicSectio
>        SymTab.getSharedFiles();
>    for (const std::unique_ptr<SharedFileBase> &File : SharedFiles) {
>      P->d_tag = DT_NEEDED;
> -    P->d_un.d_val = DynStrSec.getFileOff(File->getName());
> +    P->d_un.d_val = DynStrSec.getFileOff(File->getSoName());
>      ++P;
>    }
>
>
> Added: lld/trunk/test/elf2/Inputs/soname.so
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/Inputs/soname.so?rev=249025&view=auto
>
> ==============================================================================
> Binary files lld/trunk/test/elf2/Inputs/soname.so (added) and
> lld/trunk/test/elf2/Inputs/soname.so Thu Oct  1 10:47:50 2015 differ
>
> Propchange: lld/trunk/test/elf2/Inputs/soname.so
>
> ------------------------------------------------------------------------------
>     svn:executable = *
>
> Added: lld/trunk/test/elf2/soname.s
> URL:
> http://llvm.org/viewvc/llvm-project/lld/trunk/test/elf2/soname.s?rev=249025&view=auto
>
> ==============================================================================
> --- lld/trunk/test/elf2/soname.s (added)
> +++ lld/trunk/test/elf2/soname.s Thu Oct  1 10:47:50 2015
> @@ -0,0 +1,8 @@
> +// RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
> +// RUN: lld -flavor gnu2 %t.o %p/Inputs/soname.so -o %t
> +// RUN: llvm-readobj --dynamic-table %t | FileCheck %s
> +
> +// CHECK:  0x0000000000000001 NEEDED               SharedLibrary (bar)
> +
> +.global _start
> +_start:
>
>
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