[ASan] Use metadata to pass source-level information from Clang to ASan.

Instead of creating global variables for source locations and global names,
just create metadata nodes and strings. They will be transformed into actual
globals in the instrumentation pass (if necessary). This approach is more
flexible:
1) we don't have to ensure that our custom globals survive all the optimizations
2) if globals are discarded for some reason, we will simply ignore metadata for them
   and won't have to erase corresponding globals
3) metadata for source locations can be reused for other purposes: e.g. we may
   attach source location metadata to alloca instructions and provide better descriptions
   for stack variables in ASan error reports.

No functionality change.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@214604 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index ad3abed2a37179199f72f419c5f69cb36a3bee05..02d68d4e7ee6825fc3e86cae9e954a0b496031ad 100644 (file)
--- a/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -212,15 +212,34 @@ STATISTIC(NumOptimizedAccessesToGlobalVar,
           "Number of optimized accesses to global vars");
 
 namespace {
+/// Frontend-provided metadata for source location.
+struct LocationMetadata {
+  StringRef Filename;
+  int LineNo;
+  int ColumnNo;
+
+  LocationMetadata() : Filename(), LineNo(0), ColumnNo(0) {}
+
+  bool empty() const { return Filename.empty(); }
+
+  void parse(MDNode *MDN) {
+    assert(MDN->getNumOperands() == 3);
+    MDString *MDFilename = cast<MDString>(MDN->getOperand(0));
+    Filename = MDFilename->getString();
+    LineNo = cast<ConstantInt>(MDN->getOperand(1))->getLimitedValue();
+    ColumnNo = cast<ConstantInt>(MDN->getOperand(2))->getLimitedValue();
+  }
+};
+
 /// Frontend-provided metadata for global variables.
 class GlobalsMetadata {
  public:
   struct Entry {
     Entry()
-        : SourceLoc(nullptr), Name(nullptr), IsDynInit(false),
+        : SourceLoc(), Name(), IsDynInit(false),
           IsBlacklisted(false) {}
-    GlobalVariable *SourceLoc;
-    GlobalVariable *Name;
+    LocationMetadata SourceLoc;
+    StringRef Name;
     bool IsDynInit;
     bool IsBlacklisted;
   };
@@ -244,15 +263,11 @@ class GlobalsMetadata {
       // We can already have an entry for GV if it was merged with another
       // global.
       Entry &E = Entries[GV];
-      if (Value *Loc = MDN->getOperand(1)) {
-        GlobalVariable *GVLoc = cast<GlobalVariable>(Loc);
-        E.SourceLoc = GVLoc;
-        addSourceLocationGlobal(GVLoc);
-      }
+      if (Value *Loc = MDN->getOperand(1))
+        E.SourceLoc.parse(cast<MDNode>(Loc));
       if (Value *Name = MDN->getOperand(2)) {
-        GlobalVariable *GVName = cast<GlobalVariable>(Name);
-        E.Name = GVName;
-        InstrumentationGlobals.insert(GVName);
+        MDString *MDName = cast<MDString>(Name);
+        E.Name = MDName->getString();
       }
       ConstantInt *IsDynInit = cast<ConstantInt>(MDN->getOperand(3));
       E.IsDynInit |= IsDynInit->isOne();
@@ -267,31 +282,9 @@ class GlobalsMetadata {
     return (Pos != Entries.end()) ? Pos->second : Entry();
   }
 
-  /// Check if the global was generated by the instrumentation
-  /// (we don't want to instrument it again in this case).
-  bool isInstrumentationGlobal(GlobalVariable *G) const {
-    return InstrumentationGlobals.count(G);
-  }
-
  private:
   bool inited_;
   DenseMap<GlobalVariable*, Entry> Entries;
-  // Globals generated by the frontend instrumentation.
-  DenseSet<GlobalVariable*> InstrumentationGlobals;
-
-  void addSourceLocationGlobal(GlobalVariable *SourceLocGV) {
-    // Source location global is a struct with layout:
-    // {
-    //    filename,
-    //    i32 line_number,
-    //    i32 column_number,
-    // }
-    InstrumentationGlobals.insert(SourceLocGV);
-    ConstantStruct *Contents =
-        cast<ConstantStruct>(SourceLocGV->getInitializer());
-    GlobalVariable *FilenameGV = cast<GlobalVariable>(Contents->getOperand(0));
-    InstrumentationGlobals.insert(FilenameGV);
-  }
 };
 
 /// This struct defines the shadow mapping using the rule:
@@ -616,6 +609,22 @@ static GlobalVariable *createPrivateGlobalForString(
   return GV;
 }
 
+/// \brief Create a global describing a source location.
+static GlobalVariable *createPrivateGlobalForSourceLoc(Module &M,
+                                                       LocationMetadata MD) {
+  Constant *LocData[] = {
+      createPrivateGlobalForString(M, MD.Filename, true),
+      ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.LineNo),
+      ConstantInt::get(Type::getInt32Ty(M.getContext()), MD.ColumnNo),
+  };
+  auto LocStruct = ConstantStruct::getAnon(LocData);
+  auto GV = new GlobalVariable(M, LocStruct->getType(), true,
+                               GlobalValue::PrivateLinkage, LocStruct,
+                               kAsanGenPrefix);
+  GV->setUnnamedAddr(true);
+  return GV;
+}
+
 static bool GlobalWasGeneratedByAsan(GlobalVariable *G) {
   return G->getName().find(kAsanGenPrefix) == 0;
 }
@@ -920,7 +929,6 @@ bool AddressSanitizerModule::ShouldInstrumentGlobal(GlobalVariable *G) {
   DEBUG(dbgs() << "GLOBAL: " << *G << "\n");
 
   if (GlobalsMD.get(G).IsBlacklisted) return false;
-  if (GlobalsMD.isInstrumentationGlobal(G)) return false;
   if (!Ty->isSized()) return false;
   if (!G->hasInitializer()) return false;
   if (GlobalWasGeneratedByAsan(G)) return false;  // Our own global.
@@ -1062,11 +1070,11 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
     GlobalVariable *G = GlobalsToChange[i];
 
     auto MD = GlobalsMD.get(G);
-    // Create string holding the global name unless it was provided by
-    // the metadata.
-    GlobalVariable *Name =
-        MD.Name ? MD.Name : createPrivateGlobalForString(M, G->getName(),
-                                                         /*AllowMerging*/ true);
+    // Create string holding the global name (use global name from metadata
+    // if it's available, otherwise just write the name of global variable).
+    GlobalVariable *Name = createPrivateGlobalForString(
+        M, MD.Name.empty() ? G->getName() : MD.Name,
+        /*AllowMerging*/ true);
 
     PointerType *PtrTy = cast<PointerType>(G->getType());
     Type *Ty = PtrTy->getElementType();
@@ -1108,16 +1116,21 @@ bool AddressSanitizerModule::InstrumentGlobals(IRBuilder<> &IRB, Module &M) {
     NewGlobal->takeName(G);
     G->eraseFromParent();
 
+    Constant *SourceLoc;
+    if (!MD.SourceLoc.empty()) {
+      auto SourceLocGlobal = createPrivateGlobalForSourceLoc(M, MD.SourceLoc);
+      SourceLoc = ConstantExpr::getPointerCast(SourceLocGlobal, IntptrTy);
+    } else {
+      SourceLoc = ConstantInt::get(IntptrTy, 0);
+    }
+
     Initializers[i] = ConstantStruct::get(
         GlobalStructTy, ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
         ConstantInt::get(IntptrTy, SizeInBytes),
         ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
         ConstantExpr::getPointerCast(Name, IntptrTy),
         ConstantExpr::getPointerCast(ModuleName, IntptrTy),
-        ConstantInt::get(IntptrTy, MD.IsDynInit),
-        MD.SourceLoc ? ConstantExpr::getPointerCast(MD.SourceLoc, IntptrTy)
-                     : ConstantInt::get(IntptrTy, 0),
-        NULL);
+        ConstantInt::get(IntptrTy, MD.IsDynInit), SourceLoc, NULL);
 
     if (ClInitializers && MD.IsDynInit)
       HasDynamicallyInitializedGlobals = true;

diff --git a/test/Instrumentation/AddressSanitizer/global_metadata.ll b/test/Instrumentation/AddressSanitizer/global_metadata.ll
index 4dcd53b3ad839adc9e4c22f8e863f2ec8f6d31b8..fd5a8c6fefd354ebe675d7a060bfc45a75a98fbb 100644 (file)
--- a/test/Instrumentation/AddressSanitizer/global_metadata.ll
+++ b/test/Instrumentation/AddressSanitizer/global_metadata.ll
@@ -11,28 +11,18 @@ target triple = "x86_64-unknown-linux-gnu"
 @.str = private unnamed_addr constant [14 x i8] c"Hello, world!\00", align 1
 @llvm.global_ctors = appending global [1 x { i32, void ()*, i8* }] [{ i32, void ()*, i8* } { i32 65535, void ()* @_GLOBAL__sub_I_asan_globals.cpp, i8* null }]
 
-; Sanitizer location descriptors:
-@.str1 = private unnamed_addr constant [22 x i8] c"/tmp/asan-globals.cpp\00", align 1
-@.asan_loc_descr = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* @.str1, i32 5, i32 5 }
-@.asan_loc_descr1 = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* @.str1, i32 7, i32 5 }
-@.asan_loc_descr2 = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* @.str1, i32 12, i32 14 }
-@.asan_loc_descr4 = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* @.str1, i32 14, i32 25 }
-
-; Global names:
-@.str2 = private unnamed_addr constant [7 x i8] c"global\00", align 1
-@.str3 = private unnamed_addr constant [16 x i8] c"dyn_init_global\00", align 1
-@.str4 = private unnamed_addr constant [11 x i8] c"static_var\00", align 1
-@.str5 = private unnamed_addr constant [17 x i8] c"<string literal>\00", align 1
-
-; Check that globals were instrumented, but sanitizer location descriptors weren't:
+; Check that globals were instrumented:
 ; CHECK: @global = global { i32, [60 x i8] } zeroinitializer, align 32
 ; CHECK: @.str = internal unnamed_addr constant { [14 x i8], [50 x i8] } { [14 x i8] c"Hello, world!\00", [50 x i8] zeroinitializer }, align 32
-; CHECK: @.asan_loc_descr = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* @.str1, i32 5, i32 5 }
-; CHECK: @.str2 = private unnamed_addr constant [7 x i8] c"global\00", align 1
+
+; Check emitted location descriptions:
+; CHECK: [[VARNAME:@__asan_gen_[0-9]+]] = private unnamed_addr constant [7 x i8] c"global\00", align 1
+; CHECK: [[FILENAME:@__asan_gen_[0-9]+]] = private unnamed_addr constant [22 x i8] c"/tmp/asan-globals.cpp\00", align 1
+; CHECK: [[LOCDESCR:@__asan_gen_[0-9]+]] = private unnamed_addr constant { [22 x i8]*, i32, i32 } { [22 x i8]* [[FILENAME]], i32 5, i32 5 }
 
 ; Check that location decriptors and global names were passed into __asan_register_globals:
-; CHECK: i64 ptrtoint ([7 x i8]* @.str2 to i64)
-; CHECK: i64 ptrtoint ({ [22 x i8]*, i32, i32 }* @.asan_loc_descr to i64)
+; CHECK: i64 ptrtoint ([7 x i8]* [[VARNAME]] to i64)
+; CHECK: i64 ptrtoint ({ [22 x i8]*, i32, i32 }* [[LOCDESCR]] to i64)
 
 ; Function Attrs: nounwind sanitize_address
 define internal void @__cxx_global_var_init() #0 section ".text.startup" {
@@ -63,9 +53,15 @@ attributes #1 = { nounwind sanitize_address "less-precise-fpmad"="false" "no-fra
 !llvm.asan.globals = !{!0, !1, !2, !3, !4}
 !llvm.ident = !{!5}
 
-!0 = metadata !{i32* @global, { [22 x i8]*, i32, i32 }* @.asan_loc_descr, [7 x i8]* @.str2, i1 false, i1 false}
-!1 = metadata !{i32* @dyn_init_global, { [22 x i8]*, i32, i32 }* @.asan_loc_descr1, [16 x i8]* @.str3, i1 true, i1 false}
+!0 = metadata !{i32* @global, metadata !6, metadata !"global", i1 false, i1 false}
+!1 = metadata !{i32* @dyn_init_global, metadata !7, metadata !"dyn_init_global", i1 true, i1 false}
 !2 = metadata !{i32* @blacklisted_global, null, null, i1 false, i1 true}
-!3 = metadata !{i32* @_ZZ4funcvE10static_var, { [22 x i8]*, i32, i32 }* @.asan_loc_descr2, [11 x i8]* @.str4, i1 false, i1 false}
-!4 = metadata !{[14 x i8]* @.str, { [22 x i8]*, i32, i32 }* @.asan_loc_descr4, [17 x i8]* @.str5, i1 false, i1 false}
+!3 = metadata !{i32* @_ZZ4funcvE10static_var, metadata !8, metadata !"static_var", i1 false, i1 false}
+!4 = metadata !{[14 x i8]* @.str, metadata !9, metadata !"<string literal>", i1 false, i1 false}
+
 !5 = metadata !{metadata !"clang version 3.5.0 (211282)"}
+
+!6 = metadata !{metadata !"/tmp/asan-globals.cpp", i32 5, i32 5}
+!7 = metadata !{metadata !"/tmp/asan-globals.cpp", i32 7, i32 5}
+!8 = metadata !{metadata !"/tmp/asan-globals.cpp", i32 12, i32 14}
+!9 = metadata !{metadata !"/tmp/asan-globals.cpp", i32 14, i32 25}