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

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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
This commit is contained in:
Alexey Samsonov
2014-08-02 00:35:50 +00:00
parent d61e28d3ec
commit cbd84586ef
2 changed files with 74 additions and 65 deletions
Download Patch File Download Diff File Expand all files Collapse all files

99
lib/Transforms/Instrumentation/AddressSanitizer.cpp
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@ -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;