[DWARF] Don't attempt to parse line tables at invalid offsets

[jhenderson]

Summary

Whilst working on improvements to the error handling of the debug line parsing code, I noticed that if an invalid offset were to be specified in a call to getOrParseLineTable(), an entry in the LineTableMap would still be created, even if the offset was not within the section range. The immediate parsing attempt afterwards would fail (it would end up getting a version of 0), and thereafter, any subsequent calls to getOrParseLineTable or getLineTable would return the default-constructed, invalid line table. In reality, we shouldn't even attempt to parse this table, and we should always return a nullptr from these two functions for this situation.

I have tested this via a unit test, which required some new framework for unit testing debug line. My plan is to add quite a few more unit tests for the new error reporting mechanism that will follow shortly, hence the reason why the supporting code for the tests are written the way they are - I intend to extend the DwarfGenerator class to support generating debug line.

[JDevlieghere]

Thanks! I was thinking a positive test would be nice but you already tackled that in the summary. LGTM!

llvm/trunk/lib/DebugInfo/DWARF/DWARFDebugLine.cpp

if (Pos != LineTableMap.end())
     return &Pos->second;
   return nullptr;
 }
 
 const DWARFDebugLine::LineTable *
 DWARFDebugLine::getOrParseLineTable(DWARFDataExtractor &DebugLineData,
                                     uint32_t Offset, const DWARFContext &Ctx,
                                     const DWARFUnit *U) {
+  if (!DebugLineData.isValidOffset(Offset))
+    return nullptr;
+
   std::pair<LineTableIter, bool> Pos =
       LineTableMap.insert(LineTableMapTy::value_type(Offset, LineTable()));
   LineTable *LT = &Pos.first->second;
   if (Pos.second) {
     if (!LT->parse(DebugLineData, &Offset, Ctx, U))
       return nullptr;
   }
   return LT;

llvm/trunk/unittests/DebugInfo/DWARF/CMakeLists.txt

 set(LLVM_LINK_COMPONENTS
   ${LLVM_TARGETS_TO_BUILD}
   AsmPrinter
   DebugInfoDWARF
   MC
   Object
   ObjectYAML
   Support
   )
 
 set(DebugInfoSources
   DwarfGenerator.cpp
+  DwarfUtils.cpp
   DWARFDebugInfoTest.cpp
+  DWARFDebugLineTest.cpp
   DWARFFormValueTest.cpp
   )
 
 add_llvm_unittest(DebugInfoDWARFTests
   ${DebugInfoSources}
   )
 
 target_link_libraries(DebugInfoDWARFTests PRIVATE LLVMTestingSupport)

llvm/trunk/unittests/DebugInfo/DWARF/DWARFDebugInfoTest.cpp

-//===- llvm/unittest/DebugInfo/DWARFFormValueTest.cpp ---------------------===//
+//===- llvm/unittest/DebugInfo/DWARFDebugInfoTest.cpp ---------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "DwarfGenerator.h"
+#include "DwarfUtils.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/BinaryFormat/Dwarf.h"
 #include "llvm/CodeGen/AsmPrinter.h"
 #include "llvm/Config/llvm-config.h"

 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Testing/Support/Error.h"
 #include "gtest/gtest.h"
 #include <string>
 
 using namespace llvm;
 using namespace dwarf;
+using namespace utils;
 
 namespace {
 
-void initLLVMIfNeeded() {
-  static bool gInitialized = false;
-  if (!gInitialized) {
-    gInitialized = true;
-    InitializeAllTargets();
-    InitializeAllTargetMCs();
-    InitializeAllAsmPrinters();
-    InitializeAllAsmParsers();
-  }
-}
-
-Triple getHostTripleForAddrSize(uint8_t AddrSize) {
-  Triple PT(Triple::normalize(LLVM_HOST_TRIPLE));
-
-  if (AddrSize == 8 && PT.isArch32Bit())
-    return PT.get64BitArchVariant();
-  if (AddrSize == 4 && PT.isArch64Bit())
-    return PT.get32BitArchVariant();
-  return PT;
-}
-
-static bool isConfigurationSupported(Triple &T) {
-  initLLVMIfNeeded();
-  std::string Err;
-  return TargetRegistry::lookupTarget(T.getTriple(), Err);
-}
-
 template <uint16_t Version, class AddrType, class RefAddrType>
 void TestAllForms() {
   Triple Triple = getHostTripleForAddrSize(sizeof(AddrType));
   if (!isConfigurationSupported(Triple))
     return;
 
   // Test that we can decode all DW_FORM values correctly.
   const AddrType AddrValue = (AddrType)0x0123456789abcdefULL;

llvm/trunk/unittests/DebugInfo/DWARF/DWARFDebugLineTest.cpp

+//===- DWARFDebugLineTest.cpp ---------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DwarfGenerator.h"
+#include "DwarfUtils.h"
+#include "llvm/DebugInfo/DWARF/DWARFContext.h"
+#include "llvm/DebugInfo/DWARF/DWARFDebugLine.h"
+#include "llvm/Object/ObjectFile.h"
+#include "llvm/Testing/Support/Error.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace dwarf;
+using namespace object;
+using namespace utils;
+
+namespace {
+
+struct DebugLineGenerator {
+  bool init() {
+    Triple T = getHostTripleForAddrSize(8);
+    if (!isConfigurationSupported(T))
+      return false;
+    auto ExpectedGenerator = dwarfgen::Generator::create(T, 4);
+    if (ExpectedGenerator)
+      Generator.reset(ExpectedGenerator->release());
+    return true;
+  }
+
+  std::unique_ptr<DWARFContext> createContext() {
+    if (!Generator)
+      return nullptr;
+    StringRef FileBytes = Generator->generate();
+    MemoryBufferRef FileBuffer(FileBytes, "dwarf");
+    auto Obj = object::ObjectFile::createObjectFile(FileBuffer);
+    if (Obj)
+      return DWARFContext::create(**Obj);
+    return nullptr;
+  }
+
+  std::unique_ptr<dwarfgen::Generator> Generator;
+};
+
+TEST(DWARFDebugLine, GetLineTableAtInvalidOffset) {
+  DebugLineGenerator LineGen;
+  if (!LineGen.init())
+    return;
+
+  DWARFDebugLine Line;
+  std::unique_ptr<DWARFContext> Context = LineGen.createContext();
+  ASSERT_TRUE(Context != nullptr);
+  const DWARFObject &Obj = Context->getDWARFObj();
+  DWARFDataExtractor LineData(Obj, Obj.getLineSection(), true, 8);
+
+  EXPECT_EQ(Line.getOrParseLineTable(LineData, 0, *Context, nullptr), nullptr);
+}
+
+} // end anonymous namespace

llvm/trunk/unittests/DebugInfo/DWARF/DwarfUtils.h

+//===--- unittests/DebugInfo/DWARF/DwarfUtils.h -----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_UNITTESTS_DEBUG_INFO_DWARF_DWARFUTILS_H
+#define LLVM_UNITTESTS_DEBUG_INFO_DWARF_DWARFUTILS_H
+
+#include <cstdint>
+
+namespace llvm {
+
+class Triple;
+
+namespace dwarf {
+namespace utils {
+
+Triple getHostTripleForAddrSize(uint8_t AddrSize);
+bool isConfigurationSupported(Triple &T);
+
+} // end namespace utils
+} // end namespace dwarf
+} // end namespace llvm
+
+#endif // LLVM_UNITTESTS_DEBUG_INFO_DWARF_DWARFUTILS_H

llvm/trunk/unittests/DebugInfo/DWARF/DwarfUtils.cpp

+//===--- unittests/DebugInfo/DWARF/DwarfUtils.cpp ---------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "DwarfUtils.h"
+#include "llvm/ADT/Triple.h"
+#include "llvm/Support/TargetRegistry.h"
+#include "llvm/Support/TargetSelect.h"
+
+using namespace llvm;
+
+static void initLLVMIfNeeded() {
+  static bool gInitialized = false;
+  if (!gInitialized) {
+    gInitialized = true;
+    InitializeAllTargets();
+    InitializeAllTargetMCs();
+    InitializeAllAsmPrinters();
+    InitializeAllAsmParsers();
+  }
+}
+
+Triple llvm::dwarf::utils::getHostTripleForAddrSize(uint8_t AddrSize) {
+  Triple T(Triple::normalize(LLVM_HOST_TRIPLE));
+
+  if (AddrSize == 8 && T.isArch32Bit())
+    return T.get64BitArchVariant();
+  if (AddrSize == 4 && T.isArch64Bit())
+    return T.get32BitArchVariant();
+  return T;
+}
+
+bool llvm::dwarf::utils::isConfigurationSupported(Triple &T) {
+  initLLVMIfNeeded();
+  std::string Err;
+  return TargetRegistry::lookupTarget(T.getTriple(), Err);
+}