[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/cfe/trunk@214604 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/SanitizerMetadata.cpp b/lib/CodeGen/SanitizerMetadata.cpp
index 46191523c8b2885fccf9867fbed3637cf4b4371f..dd8c133621595db664d9020d4e4ea16d042e6a60 100644 (file)
--- a/lib/CodeGen/SanitizerMetadata.cpp
+++ b/lib/CodeGen/SanitizerMetadata.cpp
@@ -28,35 +28,15 @@ void SanitizerMetadata::reportGlobalToASan(llvm::GlobalVariable *GV,
   IsDynInit &= !CGM.getSanitizerBlacklist().isIn(*GV, "init");
   IsBlacklisted |= CGM.getSanitizerBlacklist().isIn(*GV);
 
-  llvm::GlobalVariable *LocDescr = nullptr;
-  llvm::GlobalVariable *GlobalName = nullptr;
+  llvm::Value *LocDescr = nullptr;
+  llvm::Value *GlobalName = nullptr;
   llvm::LLVMContext &VMContext = CGM.getLLVMContext();
   if (!IsBlacklisted) {
     // Don't generate source location and global name if it is blacklisted -
     // it won't be instrumented anyway.
-    PresumedLoc PLoc = CGM.getContext().getSourceManager().getPresumedLoc(Loc);
-    if (PLoc.isValid()) {
-      llvm::Constant *LocData[] = {
-          CGM.GetAddrOfConstantCString(PLoc.getFilename()),
-          llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
-                                 PLoc.getLine()),
-          llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
-                                 PLoc.getColumn()),
-      };
-      auto LocStruct = llvm::ConstantStruct::getAnon(LocData);
-      LocDescr = new llvm::GlobalVariable(
-          CGM.getModule(), LocStruct->getType(), true,
-          llvm::GlobalValue::PrivateLinkage, LocStruct, ".asan_loc_descr");
-      LocDescr->setUnnamedAddr(true);
-      // Add LocDescr to llvm.compiler.used, so that it won't be removed by
-      // the optimizer before the ASan instrumentation pass.
-      CGM.addCompilerUsedGlobal(LocDescr);
-    }
-    if (!Name.empty()) {
-      GlobalName = CGM.GetAddrOfConstantCString(Name);
-      // GlobalName shouldn't be removed by the optimizer.
-      CGM.addCompilerUsedGlobal(GlobalName);
-    }
+    LocDescr = getLocationMetadata(Loc);
+    if (!Name.empty())
+      GlobalName = llvm::MDString::get(VMContext, Name);
   }
 
   llvm::Value *GlobalMetadata[] = {
@@ -86,3 +66,17 @@ void SanitizerMetadata::disableSanitizerForGlobal(llvm::GlobalVariable *GV) {
   if (CGM.getLangOpts().Sanitize.Address)
     reportGlobalToASan(GV, SourceLocation(), "", false, true);
 }
+
+llvm::MDNode *SanitizerMetadata::getLocationMetadata(SourceLocation Loc) {
+  PresumedLoc PLoc = CGM.getContext().getSourceManager().getPresumedLoc(Loc);
+  if (!PLoc.isValid())
+    return nullptr;
+  llvm::LLVMContext &VMContext = CGM.getLLVMContext();
+  llvm::Value *LocMetadata[] = {
+      llvm::MDString::get(VMContext, PLoc.getFilename()),
+      llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), PLoc.getLine()),
+      llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
+                             PLoc.getColumn()),
+  };
+  return llvm::MDNode::get(VMContext, LocMetadata);
+}

diff --git a/lib/CodeGen/SanitizerMetadata.h b/lib/CodeGen/SanitizerMetadata.h
index 3062b4a62ed86f683fcf0e4582953b4ea7393699..6d66cbe917f8698aefbfba7485c4fe6f5b50212a 100644 (file)
--- a/lib/CodeGen/SanitizerMetadata.h
+++ b/lib/CodeGen/SanitizerMetadata.h
@@ -18,6 +18,7 @@
 
 namespace llvm {
 class GlobalVariable;
+class MDNode;
 }
 
 namespace clang {
@@ -40,6 +41,8 @@ public:
                           StringRef Name, bool IsDynInit = false,
                           bool IsBlacklisted = false);
   void disableSanitizerForGlobal(llvm::GlobalVariable *GV);
+private:
+  llvm::MDNode *getLocationMetadata(SourceLocation Loc);
 };
 }  // end namespace CodeGen
 }  // end namespace clang

diff --git a/test/CodeGen/asan-globals.cpp b/test/CodeGen/asan-globals.cpp
index d9ecc64615421189cf1700a0933b1c3afd65c30e..a9b9b5fe1fd330a3d791548eeb1c8098250bdba5 100644 (file)
--- a/test/CodeGen/asan-globals.cpp
+++ b/test/CodeGen/asan-globals.cpp
@@ -5,28 +5,24 @@
 // REQUIRES: shell
 
 int global;
-// CHECK: [[GLOBAL_LOC:@.asan_loc_descr[0-9]*]] = private unnamed_addr constant {{.*}} i32 [[@LINE-1]], i32 5
-// CHECK: [[GLOBAL_NAME:@.str[0-9]+]] = private unnamed_addr constant {{.*}} c"global\00"
 int dyn_init_global = global;
-// CHECK: [[DYN_INIT_LOC:@.asan_loc_descr[0-9]*]] = {{.*}} i32 [[@LINE-1]], i32 5
-// CHECK: [[DYN_INIT_NAME:@.str[0-9]+]] = private unnamed_addr constant {{.*}} c"dyn_init_global\00"
 int blacklisted_global;
 
 void func() {
   static int static_var = 0;
-  // CHECK: [[STATIC_LOC:@.asan_loc_descr[0-9]*]] = {{.*}} i32 [[@LINE-1]], i32 14
-  // CHECK: [[STATIC_NAME:@.str[0-9]+]] = private unnamed_addr constant {{.*}} c"static_var\00"
   const char *literal = "Hello, world!";
-  // CHECK: [[LITERAL_LOC:@.asan_loc_descr[0-9]*]] = {{.*}} i32 [[@LINE-1]], i32 25
-  // CHECK: [[LITERAL_NAME:@.str[0-9]+]] = private unnamed_addr constant {{.*}} c"<string literal>\00"
 }
 
 // CHECK: !llvm.asan.globals = !{![[GLOBAL:[0-9]+]], ![[DYN_INIT_GLOBAL:[0-9]+]], ![[BLACKLISTED_GLOBAL:[0-9]+]], ![[STATIC_VAR:[0-9]+]], ![[LITERAL:[0-9]+]]}
-// CHECK: ![[GLOBAL]] = metadata !{{{.*}} [[GLOBAL_LOC]], {{.*}} [[GLOBAL_NAME]], i1 false, i1 false}
-// CHECK: ![[DYN_INIT_GLOBAL]] = metadata !{{{.*}} [[DYN_INIT_LOC]], {{.*}} [[DYN_INIT_NAME]], i1 true, i1 false}
+// CHECK: ![[GLOBAL]] = metadata !{{{.*}} metadata ![[GLOBAL_LOC:[0-9]+]], metadata !"global", i1 false, i1 false}
+// CHECK: ![[GLOBAL_LOC]] = metadata !{metadata !"{{.*}}asan-globals.cpp", i32 7, i32 5}
+// CHECK: ![[DYN_INIT_GLOBAL]] = metadata !{{{.*}} metadata ![[DYN_INIT_LOC:[0-9]+]], metadata !"dyn_init_global", i1 true, i1 false}
+// CHECK: ![[DYN_INIT_LOC]] = metadata !{metadata !"{{.*}}asan-globals.cpp", i32 8, i32 5}
 // CHECK: ![[BLACKLISTED_GLOBAL]] = metadata !{{{.*}}, null, null, i1 false, i1 true}
-// CHECK: ![[STATIC_VAR]] = metadata !{{{.*}} [[STATIC_LOC]], {{.*}} [[STATIC_NAME]], i1 false, i1 false}
-// CHECK: ![[LITERAL]] = metadata !{{{.*}} [[LITERAL_LOC]], {{.*}} [[LITERAL_NAME]], i1 false, i1 false}
+// CHECK: ![[STATIC_VAR]] = metadata !{{{.*}} metadata ![[STATIC_LOC:[0-9]+]], metadata !"static_var", i1 false, i1 false}
+// CHECK: ![[STATIC_LOC]] = metadata !{metadata !"{{.*}}asan-globals.cpp", i32 12, i32 14}
+// CHECK: ![[LITERAL]] = metadata !{{{.*}} metadata ![[LITERAL_LOC:[0-9]+]], metadata !"<string literal>", i1 false, i1 false}
+// CHECK: ![[LITERAL_LOC]] = metadata !{metadata !"{{.*}}asan-globals.cpp", i32 13, i32 25}
 
 // BLACKLIST-SRC: !llvm.asan.globals = !{![[GLOBAL:[0-9]+]], ![[DYN_INIT_GLOBAL:[0-9]+]], ![[BLACKLISTED_GLOBAL:[0-9]+]], ![[STATIC_VAR:[0-9]+]], ![[LITERAL:[0-9]+]]}
 // BLACKLIST-SRC: ![[GLOBAL]] = metadata !{{{.*}} null, null, i1 false, i1 true}