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[UBSan] Diagnose assumption violation #104741

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Sep 25, 2024
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21 changes: 18 additions & 3 deletions clang/lib/CodeGen/CGBuiltin.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1997,8 +1997,8 @@ struct CallObjCArcUse final : EHScopeStack::Cleanup {

Value *CodeGenFunction::EmitCheckedArgForBuiltin(const Expr *E,
BuiltinCheckKind Kind) {
assert((Kind == BCK_CLZPassedZero || Kind == BCK_CTZPassedZero)
&& "Unsupported builtin check kind");
assert((Kind == BCK_CLZPassedZero || Kind == BCK_CTZPassedZero) &&
"Unsupported builtin check kind");

Value *ArgValue = EmitScalarExpr(E);
if (!SanOpts.has(SanitizerKind::Builtin))
Expand All @@ -2015,6 +2015,21 @@ Value *CodeGenFunction::EmitCheckedArgForBuiltin(const Expr *E,
return ArgValue;
}

Value *CodeGenFunction::EmitCheckedArgForAssume(const Expr *E) {
Value *ArgValue = EvaluateExprAsBool(E);
if (!SanOpts.has(SanitizerKind::Builtin))
return ArgValue;

SanitizerScope SanScope(this);
EmitCheck(
std::make_pair(ArgValue, SanitizerKind::Builtin),
SanitizerHandler::InvalidBuiltin,
{EmitCheckSourceLocation(E->getExprLoc()),
llvm::ConstantInt::get(Builder.getInt8Ty(), BCK_AssumePassedFalse)},
std::nullopt);
return ArgValue;
}

static Value *EmitAbs(CodeGenFunction &CGF, Value *ArgValue, bool HasNSW) {
return CGF.Builder.CreateBinaryIntrinsic(
Intrinsic::abs, ArgValue,
Expand Down Expand Up @@ -3428,7 +3443,7 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
if (E->getArg(0)->HasSideEffects(getContext()))
return RValue::get(nullptr);

Value *ArgValue = EmitScalarExpr(E->getArg(0));
Value *ArgValue = EmitCheckedArgForAssume(E->getArg(0));
Function *FnAssume = CGM.getIntrinsic(Intrinsic::assume);
Builder.CreateCall(FnAssume, ArgValue);
return RValue::get(nullptr);
Expand Down
2 changes: 1 addition & 1 deletion clang/lib/CodeGen/CGStmt.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -754,7 +754,7 @@ void CodeGenFunction::EmitAttributedStmt(const AttributedStmt &S) {
const Expr *Assumption = cast<CXXAssumeAttr>(A)->getAssumption();
if (getLangOpts().CXXAssumptions && Builder.GetInsertBlock() &&
!Assumption->HasSideEffects(getContext())) {
llvm::Value *AssumptionVal = EvaluateExprAsBool(Assumption);
llvm::Value *AssumptionVal = EmitCheckedArgForAssume(Assumption);
Builder.CreateAssumption(AssumptionVal);
}
} break;
Expand Down
5 changes: 5 additions & 0 deletions clang/lib/CodeGen/CodeGenFunction.h
Original file line number Diff line number Diff line change
Expand Up @@ -5084,12 +5084,17 @@ class CodeGenFunction : public CodeGenTypeCache {
enum BuiltinCheckKind {
BCK_CTZPassedZero,
BCK_CLZPassedZero,
BCK_AssumePassedFalse,
};

/// Emits an argument for a call to a builtin. If the builtin sanitizer is
/// enabled, a runtime check specified by \p Kind is also emitted.
llvm::Value *EmitCheckedArgForBuiltin(const Expr *E, BuiltinCheckKind Kind);

/// Emits an argument for a call to a `__builtin_assume`. If the builtin
/// sanitizer is enabled, a runtime check is also emitted.
llvm::Value *EmitCheckedArgForAssume(const Expr *E);

/// Emit a description of a type in a format suitable for passing to
/// a runtime sanitizer handler.
llvm::Constant *EmitCheckTypeDescriptor(QualType T);
Expand Down
17 changes: 17 additions & 0 deletions clang/test/CodeGen/ubsan-builtin-checks.c
Original file line number Diff line number Diff line change
Expand Up @@ -51,3 +51,20 @@ void check_clz(int n) {
// CHECK: call void @__ubsan_handle_invalid_builtin
__builtin_clzg((unsigned int)n);
}

// CHECK: define{{.*}} void @check_assume
void check_assume(int n) {
// CHECK: [[TOBOOL:%.*]] = icmp ne i32 [[N:%.*]], 0
// CHECK-NEXT: br i1 [[TOBOOL]]
//
// Handler block:
// CHECK: call void @__ubsan_handle_invalid_builtin
// CHECK-NEXT: unreachable
//
// Continuation block:
// CHECK: call void @llvm.assume(i1 [[TOBOOL]])
__builtin_assume(n);

// CHECK: call void @__ubsan_handle_invalid_builtin
__attribute__((assume(n)));
}
9 changes: 6 additions & 3 deletions compiler-rt/lib/ubsan/ubsan_handlers.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -633,9 +633,12 @@ static void handleInvalidBuiltin(InvalidBuiltinData *Data, ReportOptions Opts) {

ScopedReport R(Opts, Loc, ET);

Diag(Loc, DL_Error, ET,
"passing zero to __builtin_%0(), which is not a valid argument")
<< ((Data->Kind == BCK_CTZPassedZero) ? "ctz" : "clz");
if (Data->Kind == BCK_AssumePassedFalse)
Diag(Loc, DL_Error, ET, "assumption is violated during execution");
else
Diag(Loc, DL_Error, ET,
"passing zero to __builtin_%0(), which is not a valid argument")
<< ((Data->Kind == BCK_CTZPassedZero) ? "ctz" : "clz");
}

void __ubsan::__ubsan_handle_invalid_builtin(InvalidBuiltinData *Data) {
Expand Down
1 change: 1 addition & 0 deletions compiler-rt/lib/ubsan/ubsan_handlers.h
Original file line number Diff line number Diff line change
Expand Up @@ -159,6 +159,7 @@ RECOVERABLE(implicit_conversion, ImplicitConversionData *Data, ValueHandle Src,
enum BuiltinCheckKind : unsigned char {
BCK_CTZPassedZero,
BCK_CLZPassedZero,
BCK_AssumePassedFalse,
};

struct InvalidBuiltinData {
Expand Down
16 changes: 14 additions & 2 deletions compiler-rt/test/ubsan/TestCases/Misc/builtins.cpp
Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
// REQUIRES: target={{x86_64.*}}
//
// RUN: %clangxx -fsanitize=builtin -w %s -O3 -o %t
// RUN: %clangxx -fsanitize=builtin -fno-inline -w %s -O3 -o %t
// RUN: %run %t 2>&1 | FileCheck %s --check-prefix=RECOVER
// RUN: %clangxx -fsanitize=builtin -fno-sanitize-recover=builtin -w %s -O3 -o %t.abort
// RUN: %clangxx -fsanitize=builtin -fno-inline -fno-sanitize-recover=builtin -w %s -O3 -o %t.abort
// RUN: not %run %t.abort 2>&1 | FileCheck %s --check-prefix=ABORT

void check_ctz(int n) {
Expand All @@ -28,8 +28,20 @@ void check_clz(int n) {
__builtin_clzll(n);
}

void check_assume(int n) {
// RECOVER: builtins.cpp:[[@LINE+1]]:20: runtime error: assumption is violated during execution
__builtin_assume(n);
}

void check_assume_attr(int n) {
// RECOVER: builtins.cpp:[[@LINE+1]]:25: runtime error: assumption is violated during execution
__attribute__((assume(n)));
}

int main() {
check_ctz(0);
check_clz(0);
check_assume(0);
check_assume_attr(0);
return 0;
}
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