[LinkerScript] Handle symbols defined in linker scripts in case of shared lib

[atanasyan]

Summary

This patch is a follow-up to the rL232409 and allows define symbols in a linker script in case of linking shared library.

[rafaelauler]

Hi Simon,

LGTM, thanks!

[rafaelauler]

Sure!

[atanasyan]

Thanks for review.

Closed by commit rL234163.

lib/ReaderWriter/ELF/DynamicLibraryWriter.h

void DynamicLibraryWriter<ELFT>::buildDynamicSymbolTable(const File &file) {
 
   for (const UndefinedAtom *a : file.undefined())
     this->_dynamicSymbolTable->addSymbol(a, ELF::SHN_UNDEF);
 
   OutputELFWriter<ELFT>::buildDynamicSymbolTable(file);
 }
 
 template <class ELFT> void DynamicLibraryWriter<ELFT>::addDefaultAtoms() {
+  OutputELFWriter<ELFT>::addDefaultAtoms();
   _runtimeFile->addAbsoluteAtom("_end");
 }
 
 /// \brief Hook in lld to add CRuntime file
 template <class ELFT>
 bool DynamicLibraryWriter<ELFT>::createImplicitFiles(
     std::vector<std::unique_ptr<File> > &result) {
   // Add the default atoms as defined by executables
   DynamicLibraryWriter<ELFT>::addDefaultAtoms();
   OutputELFWriter<ELFT>::createImplicitFiles(result);
   result.push_back(std::move(_runtimeFile));
   return true;
 }
 
 template <class ELFT>
 void DynamicLibraryWriter<ELFT>::finalizeDefaultAtomValues() {
+  OutputELFWriter<ELFT>::finalizeDefaultAtomValues();
   lld::AtomLayout *underScoreEndAtom = this->_layout.findAbsoluteAtom("_end");
   assert(underScoreEndAtom);
 
   if (auto bssSection = this->_layout.findOutputSection(".bss")) {
     underScoreEndAtom->_virtualAddr =
         bssSection->virtualAddr() + bssSection->memSize();
   } else if (auto dataSection = this->_layout.findOutputSection(".data")) {
     underScoreEndAtom->_virtualAddr =
         dataSection->virtualAddr() + dataSection->memSize();
   }
 }
 
 } // namespace elf
 } // namespace lld
 
 #endif // LLD_READER_WRITER_ELF_DYNAMIC_LIBRARY_WRITER_H

test/elf/linkerscript/Inputs/simple-pic.o.yaml

+FileHeader:
+  Class:           ELFCLASS64
+  Data:            ELFDATA2LSB
+  Type:            ET_REL
+  Machine:         EM_X86_64
+
+Sections:
+  - Name:          .text
+    Type:          SHT_PROGBITS
+    Flags:         [ SHF_ALLOC, SHF_EXECINSTR ]
+    AddressAlign:  4
+    Size:          16
+
+  - Name:          .data
+    Type:          SHT_PROGBITS
+    Flags:         [ SHF_WRITE, SHF_ALLOC ]
+    AddressAlign:  4
+    Size:          16
+
+Symbols:
+  Local:
+    - Name:        .data
+      Type:        STT_SECTION
+      Section:     .data
+    - Name:        .text
+      Type:        STT_SECTION
+      Section:     .text
+  Global:
+    - Name:        foo
+      Type:        STT_FUNC
+      Section:     .text
+      Size:        16

test/elf/linkerscript/symbol-definition-so.test

+/*
+We test whether we can define symbols in a linker script and have them exported
+to the output file symbol table. This test is the same as symbol-definition.test
+but make checking in case of shared library linking.
+
+We use the following linker script for this test:
+*/
+
+SECTIONS
+{
+  .text : { *(.text) }
+  MYSTRING = .;
+  .data : { *(.data) }
+}
+
+/*
+RUN: yaml2obj -format=elf %p/Inputs/simple-pic.o.yaml -o=%t.o
+
+RUN: lld -flavor gnu -target x86_64 -shared -T %s %t.o -o %t.so
+RUN: llvm-readobj -s -symbols %t.so | FileCheck -check-prefix CHECKSYMS %s
+
+CHECKSYMS:      Name: .data
+CHECKSYMS-NEXT: Type: SHT_PROGBITS
+CHECKSYMS-NEXT: Flags [
+CHECKSYMS-NEXT:   SHF_ALLOC
+CHECKSYMS-NEXT:   SHF_WRITE
+CHECKSYMS-NEXT: ]
+CHECKSYMS-NEXT: Address: 0x401060
+
+CHECKSYMS:      Name: MYSTRING
+CHECKSYMS-NEXT: Value: 0x401060
+*/