[Mips] In case of executable file linking MIPS ABI requires to add even

undefined symbols to '.dynsym' if these symbols have corresponding entries
in a global part of GOT.

llvm-svn: 200716

lld/lib/ReaderWriter/ELF/Mips/MipsELFWriters.h

@@ -64,6 +64,10 @@ protected:
     }
   }
 
+  bool hasGlobalGOTEntry(const Atom *a) const {
+    return _mipsTargetLayout.getGOTSection().hasGlobalGOTEntry(a);
+  }
+
 private:
   MipsLinkingContext &_mipsLinkingContext LLVM_ATTRIBUTE_UNUSED;
   MipsTargetLayout<ELFT> &_mipsTargetLayout;

lld/lib/ReaderWriter/ELF/Mips/MipsExecutableWriter.h

@@ -27,6 +27,8 @@ public:
                        MipsTargetLayout<ELFT> &layout);
 
 protected:
+  virtual void buildDynamicSymbolTable(const File &file);
+
   // Add any runtime files and their atoms to the output
   virtual bool createImplicitFiles(std::vector<std::unique_ptr<File>> &);
 
@@ -64,6 +66,20 @@ MipsExecutableWriter<ELFT>::MipsExecutableWriter(MipsLinkingContext &context,
       _mipsRuntimeFile(new MipsRuntimeFile<ELFT>(context)),
       _mipsContext(context), _mipsTargetLayout(layout) {}
 
+template <class ELFT>
+void MipsExecutableWriter<ELFT>::buildDynamicSymbolTable(const File &file) {
+  // MIPS ABI requires to add to dynsym even undefined symbols
+  // if they have a corresponding entries in a global part of GOT.
+  for (const UndefinedAtom *a : file.undefined())
+    // FIXME (simon): Consider to move this check to the
+    // MipsELFUndefinedAtom class method. That allows to
+    // handle more complex coditions in the future.
+    if (this->hasGlobalGOTEntry(a))
+      this->_dynamicSymbolTable->addSymbol(a, ELF::SHN_UNDEF);
+
+  ExecutableWriter<ELFT>::buildDynamicSymbolTable(file);
+}
+
 template <class ELFT>
 bool MipsExecutableWriter<ELFT>::createImplicitFiles(
     std::vector<std::unique_ptr<File>> &result) {

lld/lib/ReaderWriter/ELF/Mips/MipsSectionChunks.h

@@ -35,6 +35,9 @@ public:
   /// \brief Number of global GOT entries.
   std::size_t getGlobalCount() const { return _globalCount; }
 
+  /// \brief Does the atom have a global GOT entry?
+  bool hasGlobalGOTEntry(const Atom *a) const { return _posMap.count(a); }
+
   /// \brief Compare two atoms accordingly theirs positions in the GOT.
   bool compare(const Atom *a, const Atom *b) const {
     auto ia = _posMap.find(a);

lld/test/elf/Mips/exe-dynsym.test

@@ -0,0 +1,69 @@
+# Check that symbol referenced by an entry in the global part of GOT
+# has a corresponded entry in the .dynsym section.
+
+# Build executable
+# RUN: llvm-mc -triple=mipsel -filetype=obj -o=%t-main %s
+# RUN: lld -flavor gnu -target mipsel -e glob -o %t-exe %t-main
+# RUN: llvm-readobj -dyn-symbols %t-exe | FileCheck -check-prefix=CHECK-DYN %s
+
+# Build executabl (yaml format)e
+# RUN: lld -flavor gnu -target mipsel -e glob \
+# RUN:     --output-filetype=yaml -o %t-yaml %t-main
+# RUN: FileCheck -check-prefix=CHECK-GOT %s < %t-yaml
+
+# CHECK-DYN: Format: ELF32-mips
+# CHECK-DYN: Arch: mipsel
+# CHECK-DYN: AddressSize: 32bit
+# CHECK-DYN: LoadName:
+# CHECK-DYN: DynamicSymbols [
+# CHECK-DYN:   Symbol {
+# CHECK-DYN:     Name: @ (0)
+# CHECK-DYN:     Value: 0x0
+# CHECK-DYN:     Size: 0
+# CHECK-DYN:     Binding: Local (0x0)
+# CHECK-DYN:     Type: None (0x0)
+# CHECK-DYN:     Other: 0
+# CHECK-DYN:     Section:  (0x0)
+# CHECK-DYN:   }
+# CHECK-DYN:   Symbol {
+# CHECK-DYN:     Name: weakf@ (1)
+# CHECK-DYN:     Value: 0x0
+# CHECK-DYN:     Size: 0
+# CHECK-DYN:     Binding: Weak (0x2)
+# CHECK-DYN:     Type: None (0x0)
+# CHECK-DYN:     Other: 0
+# CHECK-DYN:     Section:  (0x0)
+# CHECK-DYN:   }
+# CHECK-DYN: ]
+
+# CHECK-GOT: - type:            got
+# CHECK-GOT:   content:         [ 00, 00, 00, 00 ]
+# CHECK-GOT:   alignment:       2^2
+# CHECK-GOT:   section-choice:  custom-required
+# CHECK-GOT:   section-name:    .got
+# CHECK-GOT:   permissions:     rw-
+# CHECK-GOT: - type:            got
+# CHECK-GOT:   content:         [ 00, 00, 00, 80 ]
+# CHECK-GOT:   alignment:       2^2
+# CHECK-GOT:   section-choice:  custom-required
+# CHECK-GOT:   section-name:    .got
+# CHECK-GOT:   permissions:     rw-
+# CHECK-GOT: - ref-name:        L000
+# CHECK-GOT:   type:            got
+# CHECK-GOT:   content:         [ 00, 00, 00, 00 ]
+# CHECK-GOT:   alignment:       2^2
+# CHECK-GOT:   section-choice:  custom-required
+# CHECK-GOT:   section-name:    .got
+# CHECK-GOT:   permissions:     rw-
+# CHECK-GOT:   references:
+# CHECK-GOT:     - kind:            LLD_R_MIPS_GLOBAL_GOT
+# CHECK-GOT:       offset:          0
+# CHECK-GOT:       target:          weakf
+
+    .abicalls
+    .global glob
+    .ent    glob
+glob:
+    lw      $4,%got(weakf)($28)
+    .end    glob
+    .weak   weakf