Populate entry point into ELF executable.

llvm-svn: 168461

7 files changed, 72 insertions, 24 deletions

diff --git a/lld/include/lld/ReaderWriter/WriterELF.h b/lld/include/lld/ReaderWriter/WriterELF.h
index ebd559147a2..87f64e43bfa 100644
--- a/lld/include/lld/ReaderWriter/WriterELF.h
+++ b/lld/include/lld/ReaderWriter/WriterELF.h
@@ -35,7 +35,7 @@ public:
     , _machine(llvm::ELF::EM_386)
     , _baseAddress(0x400000)
     , _pageSize(0x1000)
-  {}
+    , _entryPoint("start") {}
 
   /// \brief Create a specific instance of an architecture.
   ///
@@ -56,7 +56,8 @@ public:
   , _pointerWidth(pointerWidth)
   , _machine(Machine)
   , _baseAddress(baseAddress)
-  , _pageSize(pageSize) {}
+  , _pageSize(pageSize)
+  , _entryPoint("start") {}
 
   bool is64Bit() const { return _is64Bit; }
   llvm::support::endianness endianness() const { return _endianness; }
@@ -65,6 +66,7 @@ public:
   uint16_t pointerWidth() const { return _pointerWidth; }
   uint64_t baseAddress() const { return _baseAddress; }
   uint64_t pageSize() const { return _pageSize; }
+  void setEntryPoint(StringRef name) { _entryPoint = name; }
 
   /// \brief Get the entry point if type() is ET_EXEC. Empty otherwise.
   StringRef entryPoint() const;
@@ -77,6 +79,7 @@ protected:
   uint16_t                  _machine;
   uint64_t                  _baseAddress;
   uint64_t                  _pageSize;
+  StringRef                 _entryPoint;
 };
 
 /// \brief Create a WriterELF using the given options.
diff --git a/lld/lib/ReaderWriter/ELF/ReaderELF.cpp b/lld/lib/ReaderWriter/ELF/ReaderELF.cpp
index ad0227fa6cd..35a4d81a07c 100644
--- a/lld/lib/ReaderWriter/ELF/ReaderELF.cpp
+++ b/lld/lib/ReaderWriter/ELF/ReaderELF.cpp
@@ -294,11 +294,14 @@ public:
 
     ContentType ret = typeUnknown;
 
-
     switch (_section->sh_type) {
     case llvm::ELF::SHT_PROGBITS:
     case llvm::ELF::SHT_DYNAMIC:
       switch (_section->sh_flags) {
+      case (llvm::ELF::SHF_ALLOC | llvm::ELF::SHF_EXECINSTR
+            | llvm::ELF::SHF_WRITE):
+        ret = typeCode;
+        break;
       case (llvm::ELF::SHF_ALLOC | llvm::ELF::SHF_EXECINSTR):
         ret = typeCode;
         break;
diff --git a/lld/lib/ReaderWriter/ELF/WriterELF.cpp b/lld/lib/ReaderWriter/ELF/WriterELF.cpp
index 2c4d384cd5d..4282732e0f4 100644
--- a/lld/lib/ReaderWriter/ELF/WriterELF.cpp
+++ b/lld/lib/ReaderWriter/ELF/WriterELF.cpp
@@ -88,6 +88,9 @@ enum {
 template<support::endianness target_endianness, bool is64Bits>
 class ELFWriter;
 
+template<support::endianness target_endianness, bool is64Bits>
+class StockSectionChunk;
+
 /// \brief A Chunk is a contiguous range of space.
 template<support::endianness target_endianness, bool is64Bits>
 class Chunk {
@@ -188,7 +191,7 @@ public:
                uint64_t flags , uint64_t link,  uint64_t info ,
                uint64_t type, uint64_t entsz, const WriterOptionsELF &op, 
                ELFWriter<target_endianness, is64Bits> &writer);
-
+  
   static inline bool classof(const Chunk<target_endianness, is64Bits> *c) {
     return c->getChunkKind() == Chunk<target_endianness, is64Bits>::Kind
                                                                   ::Section;
@@ -215,6 +218,24 @@ bool IsBss(const  Chunk<target_endianness, is64Bits> *A) {
   return false;
 }
 
+/// \brief Return  pointer to a defined atom whose name is specified as parameter 
+///        if present in the specified section.
+///        When all the atoms are resolved, get addresses and offsets, we 
+///        have atoms with unique names. Only then this routine is guaranteed 
+///        to return the atom of interest. This routine is useful in finding atoms 
+///        which are special such as entry point to a file 
+template<support::endianness target_endianness, bool is64Bits>
+static const DefinedAtom* findDefinedAtomByName(StringRef name,
+                                          StockSectionChunk<target_endianness, 
+                                                            is64Bits> *sec) {
+  ArrayRef<AtomInfo> atoms = sec->atoms();
+  for (auto ai = atoms.begin(); ai != atoms.end(); ai++) {
+    if ((std::get<0>(*ai))->name() == name )
+      return std::get<0>(*ai);
+  }
+  return nullptr;
+}
+
 /// \brief A StockSectionChunk is a section created by linker with all 
 ///        attributes concluded from the defined atom contained within.
 template<support::endianness target_endianness, bool is64Bits>
@@ -266,7 +287,6 @@ public:
     return c->getChunkKind() ==  Chunk<target_endianness, is64Bits>::Kind
                                                                    ::Header;
   }
-
 private:
   Elf_Ehdr             _eh;
 };
@@ -740,9 +760,6 @@ void ELFSymbolTableChunk<target_endianness, is64Bits>
         symbol->st_shndx = ELF::SHN_COMMON;
       }
       break;
-    case DefinedAtom::typeFirstInSection:
-      t = ELF::STT_SECTION;
-      break;
    // TODO:: How to find STT_FILE symbols?
     default:
       t = ELF::STT_NOTYPE;
@@ -847,7 +864,7 @@ ELFHeaderChunk<target_endianness, is64Bits>
   e_phoff(0);
   e_shoff(0ULL);
   
-  e_flags(0);
+  e_flags(2);
   e_ehsize(this->_size);
   e_phentsize(0);
   e_phnum(0);
@@ -1190,6 +1207,12 @@ void ELFWriter<target_endianness, is64Bits>::build(const lld::File &file){
   ehc->e_phnum(_phdr->computeNumber());
   ehc->e_phoff(_phdr->fileOffset());
   ehc->e_phentsize(sizeof(Elf_Phdr));
+  for (auto i : _stockSectionChunks) {
+    if(const DefinedAtom* da = findDefinedAtomByName(_options.entryPoint(), i)) {
+      ehc->e_entry(this->addressOfAtom(da));
+      return;
+    }
+  }
 }
 
 template<support::endianness target_endianness, bool is64Bits>
@@ -1237,7 +1260,11 @@ void ELFWriter<target_endianness, is64Bits>
 
 //TODO: implement .hash section
 
+  DEBUG_WITH_TYPE("WriterELF-layout", dbgs() 
+                    << "Atoms in file" << file.path()<<":\n");
   for (const DefinedAtom *a : file.defined() ) {
+    DEBUG_WITH_TYPE("WriterELF-layout", dbgs() 
+                    << a->name() << " type: " << a->contentType() <<"\n");
     StringRef sectionName = a->customSectionName();
     if (a->sectionChoice() == 
         DefinedAtom::SectionChoice::sectionBasedOnContent) {
@@ -1302,19 +1329,17 @@ void ELFWriter<target_endianness, is64Bits>
      return A->ordinal() < B->ordinal();}));
 
   // Populate symbol table  with correct st_shndx member.
-  if (_options.type() == ELF::ET_REL) {
-    for (auto chnk : _sectionChunks ) {
-       Elf_Sym *sym  = new (_chunkAllocate.Allocate<Elf_Sym>()) Elf_Sym;
-       sym->st_name  = 0;
-       sym->st_value = 0;
-       sym->st_size  = 0;
-       sym->st_other = ELF::STV_DEFAULT;
-      // first two chunks are not sections hence we subtract 2 but there is a 
-      // NULL section in section table so add 1
-       sym->st_shndx = chnk->ordinal() - 1 ;
-       sym->setBindingAndType(ELF::STB_LOCAL, ELF::STT_SECTION);
-       _symtable->addSymbol(sym);
-    }
+  for (auto chnk : _sectionChunks ) {
+     Elf_Sym *sym  = new (_chunkAllocate.Allocate<Elf_Sym>()) Elf_Sym;
+     sym->st_name  = 0;
+     sym->st_value = 0;
+     sym->st_size  = 0;
+     sym->st_other = ELF::STV_DEFAULT;
+    // first two chunks are not sections hence we subtract 2 but there is a 
+    // NULL section in section table so add 1
+     sym->st_shndx = chnk->ordinal() - 1 ;
+     sym->setBindingAndType(ELF::STB_LOCAL, ELF::STT_SECTION);
+     _symtable->addSymbol(sym);
   }
  for (const auto ssc : _stockSectionChunks){
    for (const auto da : ssc->atoms()) {
diff --git a/lld/lib/ReaderWriter/ELF/WriterOptionsELF.cpp b/lld/lib/ReaderWriter/ELF/WriterOptionsELF.cpp
index 1a7d84484e0..4d832aed05e 100644
--- a/lld/lib/ReaderWriter/ELF/WriterOptionsELF.cpp
+++ b/lld/lib/ReaderWriter/ELF/WriterOptionsELF.cpp
@@ -21,7 +21,7 @@ namespace lld {
 
 StringRef WriterOptionsELF::entryPoint() const {
   if (_type == llvm::ELF::ET_EXEC)
-    return "start";
+    return _entryPoint;
   return StringRef();
 }
 
diff --git a/lld/test/elf/Inputs/phdr.i386 b/lld/test/elf/Inputs/phdr.i386
new file mode 100644
index 00000000000..7c83dd31489
--- /dev/null
+++ b/lld/test/elf/Inputs/phdr.i386
diff --git a/lld/test/elf/phdr.objtxt b/lld/test/elf/phdr.objtxt
new file mode 100644
index 00000000000..d1633017f99
--- /dev/null
+++ b/lld/test/elf/phdr.objtxt
@@ -0,0 +1,17 @@
+RUN: lld-core -reader ELF -writer ELF -o %t1 %p/Inputs/phdr.i386 | elf-dump %t1 |  FileCheck -check-prefix=ED %s 
+
+ED: # Program Header 0
+ED: 'p_flags', 0x00000005
+ED: 'p_filesz', 0x0000002a
+ED: # Program Header 1
+ED: 'p_flags', 0x00000004
+ED: 'p_vaddr', 0x004010e0
+ED: 'p_memsz', 0x00000078
+ED: # Program Header 2
+ED: 'p_flags', 0x00000006
+ED: 'p_vaddr', 0x00402158
+ED: 'p_memsz', 0x000000ac
+ED: # Program Header 3
+ED: 'p_flags', 0x00000006
+ED: 'p_vaddr', 0x00404000
+ED: 'p_memsz', 0x00000005
diff --git a/lld/test/elf/sections.objtxt b/lld/test/elf/sections.objtxt
index 6b499e1be4b..3909cf9a2c0 100644
--- a/lld/test/elf/sections.objtxt
+++ b/lld/test/elf/sections.objtxt
@@ -10,7 +10,7 @@ OBJDUMP:  4 .anotherspecial 000000004 00000000000401088 DATA
 OBJDUMP:  5 .bss          000000001 0000000000040108c BSS
 OBJDUMP:  6 .shstrtab     000000045 0000000000040108d
 OBJDUMP:  7 .strtab       00000003b 000000000004010d2
-OBJDUMP:  8 .symtab       0000000c0 00000000000401110
+OBJDUMP:  8 .symtab       000000140 00000000000401110
 
 READOBJ: File Format : ELF32-i386
 READOBJ: Arch        : i386