[Object][ELF] Add a maximum alignment. This is used by createELFObjectFile to create a properly aligned reader.

llvm-svn: 171520

llvm/lib/ExecutionEngine/RuntimeDyld/RuntimeDyldELF.cpp

@@ -28,6 +28,8 @@
 using namespace llvm;
 using namespace llvm::object;
 
+using support::endianness;
+
 namespace {
 
 static inline
@@ -38,19 +40,22 @@ error_code check(error_code Err) {
   return Err;
 }
 
-template<support::endianness target_endianness, bool is64Bits>
-class DyldELFObject : public ELFObjectFile<target_endianness, is64Bits> {
-  LLVM_ELF_IMPORT_TYPES(target_endianness, is64Bits)
+template<endianness target_endianness, std::size_t max_alignment, bool is64Bits>
+class DyldELFObject
+  : public ELFObjectFile<target_endianness, max_alignment, is64Bits> {
+  LLVM_ELF_IMPORT_TYPES(target_endianness, max_alignment, is64Bits)
 
-  typedef Elf_Shdr_Impl<target_endianness, is64Bits> Elf_Shdr;
-  typedef Elf_Sym_Impl<target_endianness, is64Bits> Elf_Sym;
-  typedef Elf_Rel_Impl<target_endianness, is64Bits, false> Elf_Rel;
-  typedef Elf_Rel_Impl<target_endianness, is64Bits, true> Elf_Rela;
+  typedef Elf_Shdr_Impl<target_endianness, max_alignment, is64Bits> Elf_Shdr;
+  typedef Elf_Sym_Impl<target_endianness, max_alignment, is64Bits> Elf_Sym;
+  typedef
+    Elf_Rel_Impl<target_endianness, max_alignment, is64Bits, false> Elf_Rel;
+  typedef
+    Elf_Rel_Impl<target_endianness, max_alignment, is64Bits, true> Elf_Rela;
 
-  typedef Elf_Ehdr_Impl<target_endianness, is64Bits> Elf_Ehdr;
+  typedef Elf_Ehdr_Impl<target_endianness, max_alignment, is64Bits> Elf_Ehdr;
 
   typedef typename ELFDataTypeTypedefHelper<
-          target_endianness, is64Bits>::value_type addr_type;
+          target_endianness, max_alignment, is64Bits>::value_type addr_type;
 
 public:
   DyldELFObject(MemoryBuffer *Wrapper, error_code &ec);
@@ -60,24 +65,25 @@ public:
 
   // Methods for type inquiry through isa, cast and dyn_cast
   static inline bool classof(const Binary *v) {
-    return (isa<ELFObjectFile<target_endianness, is64Bits> >(v)
-            && classof(cast<ELFObjectFile<target_endianness, is64Bits> >(v)));
+    return (isa<ELFObjectFile<target_endianness, max_alignment, is64Bits> >(v)
+            && classof(cast<ELFObjectFile
+                <target_endianness, max_alignment, is64Bits> >(v)));
   }
   static inline bool classof(
-      const ELFObjectFile<target_endianness, is64Bits> *v) {
+      const ELFObjectFile<target_endianness, max_alignment, is64Bits> *v) {
     return v->isDyldType();
   }
 };
 
-template<support::endianness target_endianness, bool is64Bits>
+template<endianness target_endianness, std::size_t max_alignment, bool is64Bits>
 class ELFObjectImage : public ObjectImageCommon {
   protected:
-    DyldELFObject<target_endianness, is64Bits> *DyldObj;
+    DyldELFObject<target_endianness, max_alignment, is64Bits> *DyldObj;
     bool Registered;
 
   public:
     ELFObjectImage(ObjectBuffer *Input,
-                   DyldELFObject<target_endianness, is64Bits> *Obj)
+                 DyldELFObject<target_endianness, max_alignment, is64Bits> *Obj)
     : ObjectImageCommon(Input, Obj),
       DyldObj(Obj),
       Registered(false) {}
@@ -113,17 +119,16 @@ class ELFObjectImage : public ObjectImageCommon {
 // The MemoryBuffer passed into this constructor is just a wrapper around the
 // actual memory.  Ultimately, the Binary parent class will take ownership of
 // this MemoryBuffer object but not the underlying memory.
-template<support::endianness target_endianness, bool is64Bits>
-DyldELFObject<target_endianness, is64Bits>::DyldELFObject(MemoryBuffer *Wrapper,
-                                                          error_code &ec)
-  : ELFObjectFile<target_endianness, is64Bits>(Wrapper, ec) {
+template<endianness target_endianness, std::size_t max_alignment, bool is64Bits>
+DyldELFObject<target_endianness, max_alignment, is64Bits>
+             ::DyldELFObject(MemoryBuffer *Wrapper, error_code &ec)
+  : ELFObjectFile<target_endianness, max_alignment, is64Bits>(Wrapper, ec) {
   this->isDyldELFObject = true;
 }
 
-template<support::endianness target_endianness, bool is64Bits>
-void DyldELFObject<target_endianness, is64Bits>::updateSectionAddress(
-                                                       const SectionRef &Sec,
-                                                       uint64_t Addr) {
+template<endianness target_endianness, std::size_t max_alignment, bool is64Bits>
+void DyldELFObject<target_endianness, max_alignment, is64Bits>
+                  ::updateSectionAddress(const SectionRef &Sec, uint64_t Addr) {
   DataRefImpl ShdrRef = Sec.getRawDataRefImpl();
   Elf_Shdr *shdr = const_cast<Elf_Shdr*>(
                           reinterpret_cast<const Elf_Shdr *>(ShdrRef.p));
@@ -133,14 +138,13 @@ void DyldELFObject<target_endianness, is64Bits>::updateSectionAddress(
   shdr->sh_addr = static_cast<addr_type>(Addr);
 }
 
-template<support::endianness target_endianness, bool is64Bits>
-void DyldELFObject<target_endianness, is64Bits>::updateSymbolAddress(
-                                                       const SymbolRef &SymRef,
-                                                       uint64_t Addr) {
+template<endianness target_endianness, std::size_t max_align, bool is64Bits>
+void DyldELFObject<target_endianness, max_align, is64Bits>
+                  ::updateSymbolAddress(const SymbolRef &SymRef, uint64_t Addr){
 
   Elf_Sym *sym = const_cast<Elf_Sym*>(
-                                 ELFObjectFile<target_endianness, is64Bits>::
-                                   getSymbol(SymRef.getRawDataRefImpl()));
+    ELFObjectFile<target_endianness, max_align, is64Bits>
+                 ::getSymbol(SymRef.getRawDataRefImpl()));
 
   // This assumes the address passed in matches the target address bitness
   // The template-based type cast handles everything else.
@@ -149,7 +153,6 @@ void DyldELFObject<target_endianness, is64Bits>::updateSymbolAddress(
 
 } // namespace
 
-
 namespace llvm {
 
 ObjectImage *RuntimeDyldELF::createObjectImage(ObjectBuffer *Buffer) {
@@ -161,24 +164,24 @@ ObjectImage *RuntimeDyldELF::createObjectImage(ObjectBuffer *Buffer) {
   error_code ec;
 
   if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB) {
-    DyldELFObject<support::little, false> *Obj =
-           new DyldELFObject<support::little, false>(Buffer->getMemBuffer(), ec);
-    return new ELFObjectImage<support::little, false>(Buffer, Obj);
+    DyldELFObject<support::little, 4, false> *Obj =
+      new DyldELFObject<support::little, 4, false>(Buffer->getMemBuffer(), ec);
+    return new ELFObjectImage<support::little, 4, false>(Buffer, Obj);
   }
   else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB) {
-    DyldELFObject<support::big, false> *Obj =
-           new DyldELFObject<support::big, false>(Buffer->getMemBuffer(), ec);
-    return new ELFObjectImage<support::big, false>(Buffer, Obj);
+    DyldELFObject<support::big, 4, false> *Obj =
+      new DyldELFObject<support::big, 4, false>(Buffer->getMemBuffer(), ec);
+    return new ELFObjectImage<support::big, 4, false>(Buffer, Obj);
   }
   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB) {
-    DyldELFObject<support::big, true> *Obj =
-           new DyldELFObject<support::big, true>(Buffer->getMemBuffer(), ec);
-    return new ELFObjectImage<support::big, true>(Buffer, Obj);
+    DyldELFObject<support::big, 8, true> *Obj =
+      new DyldELFObject<support::big, 8, true>(Buffer->getMemBuffer(), ec);
+    return new ELFObjectImage<support::big, 8, true>(Buffer, Obj);
   }
   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
-    DyldELFObject<support::little, true> *Obj =
-           new DyldELFObject<support::little, true>(Buffer->getMemBuffer(), ec);
-    return new ELFObjectImage<support::little, true>(Buffer, Obj);
+    DyldELFObject<support::little, 8, true> *Obj =
+      new DyldELFObject<support::little, 8, true>(Buffer->getMemBuffer(), ec);
+    return new ELFObjectImage<support::little, 8, true>(Buffer, Obj);
   }
   else
     llvm_unreachable("Unexpected ELF format");
@@ -207,7 +210,7 @@ void RuntimeDyldELF::resolveX86_64Relocation(const SectionEntry &Section,
   case ELF::R_X86_64_32S: {
     Value += Addend;
     assert((Type == ELF::R_X86_64_32 && (Value <= UINT32_MAX)) ||
-           (Type == ELF::R_X86_64_32S && 
+           (Type == ELF::R_X86_64_32S &&
              ((int64_t)Value <= INT32_MAX && (int64_t)Value >= INT32_MIN)));
     uint32_t TruncatedAddr = (Value & 0xFFFFFFFF);
     uint32_t *Target = reinterpret_cast<uint32_t*>(Section.Address + Offset);
@@ -288,7 +291,7 @@ void RuntimeDyldELF::resolveARMRelocation(const SectionEntry &Section,
   default:
     llvm_unreachable("Not implemented relocation type!");
 
-  // Write a 32bit value to relocation address, taking into account the 
+  // Write a 32bit value to relocation address, taking into account the
   // implicit addend encoded in the target.
   case ELF::R_ARM_TARGET1 :
   case ELF::R_ARM_ABS32 :
@@ -299,7 +302,7 @@ void RuntimeDyldELF::resolveARMRelocation(const SectionEntry &Section,
   // Last 4 bit should be shifted.
   case ELF::R_ARM_MOVW_ABS_NC :
     // We are not expecting any other addend in the relocation address.
-    // Using 0x000F0FFF because MOVW has its 16 bit immediate split into 2 
+    // Using 0x000F0FFF because MOVW has its 16 bit immediate split into 2
     // non-contiguous fields.
     assert((*TargetPtr & 0x000F0FFF) == 0);
     Value = Value & 0xFFFF;
@@ -550,7 +553,6 @@ void RuntimeDyldELF::resolvePPC64Relocation(const SectionEntry &Section,
   }
 }
 
-
 void RuntimeDyldELF::resolveRelocation(const SectionEntry &Section,
                                        uint64_t Offset,
                                        uint64_t Value,
@@ -630,9 +632,9 @@ void RuntimeDyldELF::processRelocationRef(const ObjRelocationInfo &Rel,
           // Default to 'true' in case isText fails (though it never does).
           bool isCode = true;
           si->isText(isCode);
-          Value.SectionID = findOrEmitSection(Obj, 
-                                              (*si), 
-                                              isCode, 
+          Value.SectionID = findOrEmitSection(Obj,
+                                              (*si),
+                                              isCode,
                                               ObjSectionToID);
           Value.Addend = Addend;
           break;

llvm/lib/Object/ELFObjectFile.cpp

@@ -12,6 +12,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Object/ELF.h"
+#include "llvm/Support/MathExtras.h"
 
 namespace llvm {
 
@@ -22,16 +23,37 @@ ObjectFile *ObjectFile::createELFObjectFile(MemoryBuffer *Object) {
   std::pair<unsigned char, unsigned char> Ident = getElfArchType(Object);
   error_code ec;
 
+  std::size_t MaxAlignment =
+    1ULL << CountTrailingZeros_64(uintptr_t(Object->getBufferStart()));
+
   if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2LSB)
-    return new ELFObjectFile<support::little, false>(Object, ec);
+    if (MaxAlignment >= 4)
+      return new ELFObjectFile<support::little, 4, false>(Object, ec);
+    else if (MaxAlignment >= 2)
+      return new ELFObjectFile<support::little, 2, false>(Object, ec);
+    else
+      llvm_unreachable("Invalid alignment for ELF file!");
   else if (Ident.first == ELF::ELFCLASS32 && Ident.second == ELF::ELFDATA2MSB)
-    return new ELFObjectFile<support::big, false>(Object, ec);
+    if (MaxAlignment >= 4)
+      return new ELFObjectFile<support::big, 4, false>(Object, ec);
+    else if (MaxAlignment >= 2)
+      return new ELFObjectFile<support::big, 2, false>(Object, ec);
+    else
+      llvm_unreachable("Invalid alignment for ELF file!");
   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2MSB)
-    return new ELFObjectFile<support::big, true>(Object, ec);
+    if (MaxAlignment >= 8)
+      return new ELFObjectFile<support::big, 8, true>(Object, ec);
+    else if (MaxAlignment >= 2)
+      return new ELFObjectFile<support::big, 2, true>(Object, ec);
+    else
+      llvm_unreachable("Invalid alignment for ELF file!");
   else if (Ident.first == ELF::ELFCLASS64 && Ident.second == ELF::ELFDATA2LSB) {
-    ELFObjectFile<support::little, true> *result =
-          new ELFObjectFile<support::little, true>(Object, ec);
-    return result;
+    if (MaxAlignment >= 8)
+      return new ELFObjectFile<support::little, 8, true>(Object, ec);
+    else if (MaxAlignment >= 2)
+      return new ELFObjectFile<support::little, 2, true>(Object, ec);
+    else
+      llvm_unreachable("Invalid alignment for ELF file!");
   }
 
   report_fatal_error("Buffer is not an ELF object file!");