vsk updated this revision to Diff 125069.
vsk retitled this revision from "[ubsan] Diagnose reached-unreachable after
noreturn calls" to "[ubsan] Diagnose noreturn functions which return".
vsk edited the summary of this revision.
vsk added a comment.
- Emit the check in the noreturn function, so that the UB does not result in
the optimizer throwing away the diagnostic instrumentation.
https://reviews.llvm.org/D40698
Files:
docs/UndefinedBehaviorSanitizer.rst
lib/CodeGen/CGBuiltin.cpp
lib/CodeGen/CGCall.cpp
lib/CodeGen/CGExpr.cpp
lib/CodeGen/CodeGenFunction.h
test/CodeGen/ubsan-noreturn.c
Index: test/CodeGen/ubsan-noreturn.c
===================================================================
--- /dev/null
+++ test/CodeGen/ubsan-noreturn.c
@@ -0,0 +1,7 @@
+// RUN: %clang_cc1 %s -emit-llvm -fsanitize=unreachable -o - | FileCheck %s
+
+// CHECK-LABEL: @f(
+void __attribute__((noreturn)) f() {
+ // CHECK: __ubsan_handle_builtin_unreachable
+ // CHECK: unreachable
+}
Index: lib/CodeGen/CodeGenFunction.h
===================================================================
--- lib/CodeGen/CodeGenFunction.h
+++ lib/CodeGen/CodeGenFunction.h
@@ -3736,6 +3736,10 @@
llvm::ConstantInt *TypeId, llvm::Value *Ptr,
ArrayRef<llvm::Constant *> StaticArgs);
+ /// Emit a reached-unreachable diagnostic if \p Loc is valid and runtime
+ /// checking is enabled. Otherwise, just emit an unreachable instruction.
+ void EmitUnreachable(SourceLocation Loc);
+
/// \brief Create a basic block that will call the trap intrinsic, and emit a
/// conditional branch to it, for the -ftrapv checks.
void EmitTrapCheck(llvm::Value *Checked);
Index: lib/CodeGen/CGExpr.cpp
===================================================================
--- lib/CodeGen/CGExpr.cpp
+++ lib/CodeGen/CGExpr.cpp
@@ -3030,6 +3030,17 @@
CGM.addUsedGlobal(F);
}
+void CodeGenFunction::EmitUnreachable(SourceLocation Loc) {
+ if (SanOpts.has(SanitizerKind::Unreachable)) {
+ SanitizerScope SanScope(this);
+ EmitCheck(std::make_pair(static_cast<llvm::Value *>(Builder.getFalse()),
+ SanitizerKind::Unreachable),
+ SanitizerHandler::BuiltinUnreachable,
+ EmitCheckSourceLocation(Loc), None);
+ }
+ Builder.CreateUnreachable();
+}
+
void CodeGenFunction::EmitTrapCheck(llvm::Value *Checked) {
llvm::BasicBlock *Cont = createBasicBlock("cont");
Index: lib/CodeGen/CGCall.cpp
===================================================================
--- lib/CodeGen/CGCall.cpp
+++ lib/CodeGen/CGCall.cpp
@@ -2753,9 +2753,15 @@
void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI,
bool EmitRetDbgLoc,
SourceLocation EndLoc) {
+ if (FI.isNoReturn()) {
+ // Noreturn functions don't return.
+ EmitUnreachable(EndLoc);
+ return;
+ }
+
if (CurCodeDecl && CurCodeDecl->hasAttr<NakedAttr>()) {
// Naked functions don't have epilogues.
- Builder.CreateUnreachable();
+ EmitUnreachable(EndLoc);
return;
}
Index: lib/CodeGen/CGBuiltin.cpp
===================================================================
--- lib/CodeGen/CGBuiltin.cpp
+++ lib/CodeGen/CGBuiltin.cpp
@@ -1218,14 +1218,7 @@
case Builtin::BI__debugbreak:
return RValue::get(EmitTrapCall(Intrinsic::debugtrap));
case Builtin::BI__builtin_unreachable: {
- if (SanOpts.has(SanitizerKind::Unreachable)) {
- SanitizerScope SanScope(this);
- EmitCheck(std::make_pair(static_cast<llvm::Value *>(Builder.getFalse()),
- SanitizerKind::Unreachable),
- SanitizerHandler::BuiltinUnreachable,
- EmitCheckSourceLocation(E->getExprLoc()), None);
- } else
- Builder.CreateUnreachable();
+ EmitUnreachable(E->getExprLoc());
// We do need to preserve an insertion point.
EmitBlock(createBasicBlock("unreachable.cont"));
Index: docs/UndefinedBehaviorSanitizer.rst
===================================================================
--- docs/UndefinedBehaviorSanitizer.rst
+++ docs/UndefinedBehaviorSanitizer.rst
@@ -124,8 +124,8 @@
- ``-fsanitize=signed-integer-overflow``: Signed integer overflow,
including all the checks added by ``-ftrapv``, and checking for
overflow in signed division (``INT_MIN / -1``).
- - ``-fsanitize=unreachable``: If control flow reaches
- ``__builtin_unreachable``.
+ - ``-fsanitize=unreachable``: If control flow reaches an unreachable
+ program point.
- ``-fsanitize=unsigned-integer-overflow``: Unsigned integer
overflows. Note that unlike signed integer overflow, unsigned integer
is not undefined behavior. However, while it has well-defined semantics,
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