Author: vedantk
Date: Thu Dec 7 17:51:47 2017
New Revision: 320128
URL: http://llvm.org/viewvc/llvm-project?rev=320128&view=rev
Log:
[ubsan] Use pass_object_size info in bounds checks
Teach UBSan's bounds check to opportunistically use pass_object_size
information to check array accesses.
rdar://33272922
Added:
cfe/trunk/test/CodeGen/ubsan-pass-object-size.c
Modified:
cfe/trunk/lib/CodeGen/CGExpr.cpp
cfe/trunk/lib/CodeGen/CodeGenFunction.h
Modified: cfe/trunk/lib/CodeGen/CGExpr.cpp
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExpr.cpp?rev=320128&r1=320127&r2=320128&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGExpr.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGExpr.cpp Thu Dec 7 17:51:47 2017
@@ -814,6 +814,53 @@ static bool isFlexibleArrayMemberExpr(co
return false;
}
+llvm::Value *CodeGenFunction::LoadPassedObjectSize(const Expr *E,
+ QualType EltTy) {
+ ASTContext &C = getContext();
+ uint64_t EltSize = C.getTypeSizeInChars(EltTy).getQuantity();
+ if (!EltSize)
+ return nullptr;
+
+ auto *ArrayDeclRef = dyn_cast<DeclRefExpr>(E->IgnoreParenImpCasts());
+ if (!ArrayDeclRef)
+ return nullptr;
+
+ auto *ParamDecl = dyn_cast<ParmVarDecl>(ArrayDeclRef->getDecl());
+ if (!ParamDecl)
+ return nullptr;
+
+ // Arrays don't have pass_object_size attributes, but if they have a constant
+ // size modifier it's the array size (C99 6.5.7.2p1).
+ if (auto *DecayedArrayTy = dyn_cast<DecayedType>(ParamDecl->getType()))
+ if (auto *ArrayTy =
+ dyn_cast<ConstantArrayType>(DecayedArrayTy->getOriginalType()))
+ return llvm::ConstantInt::get(SizeTy,
+ ArrayTy->getSize().getLimitedValue());
+
+ auto *POSAttr = ParamDecl->getAttr<PassObjectSizeAttr>();
+ if (!POSAttr)
+ return nullptr;
+
+ // Don't load the size if it's a lower bound.
+ int POSType = POSAttr->getType();
+ if (POSType != 0 && POSType != 1)
+ return nullptr;
+
+ // Find the implicit size parameter.
+ auto PassedSizeIt = SizeArguments.find(ParamDecl);
+ if (PassedSizeIt == SizeArguments.end())
+ return nullptr;
+
+ const ImplicitParamDecl *PassedSizeDecl = PassedSizeIt->second;
+ assert(LocalDeclMap.count(PassedSizeDecl) && "Passed size not loadable");
+ Address AddrOfSize = LocalDeclMap.find(PassedSizeDecl)->second;
+ llvm::Value *SizeInBytes = EmitLoadOfScalar(AddrOfSize, /*Volatile=*/false,
+ C.getSizeType(),
E->getExprLoc());
+ llvm::Value *SizeOfElement =
+ llvm::ConstantInt::get(SizeInBytes->getType(), EltSize);
+ return Builder.CreateUDiv(SizeInBytes, SizeOfElement);
+}
+
/// If Base is known to point to the start of an array, return the length of
/// that array. Return 0 if the length cannot be determined.
static llvm::Value *getArrayIndexingBound(
@@ -835,9 +882,16 @@ static llvm::Value *getArrayIndexingBoun
return CGF.Builder.getInt(CAT->getSize());
else if (const auto *VAT = dyn_cast<VariableArrayType>(AT))
return CGF.getVLASize(VAT).first;
+ // Ignore pass_object_size here. It's not applicable on decayed pointers.
}
}
+ QualType EltTy{Base->getType()->getPointeeOrArrayElementType(), 0};
+ if (llvm::Value *POS = CGF.LoadPassedObjectSize(Base, EltTy)) {
+ IndexedType = Base->getType();
+ return POS;
+ }
+
return nullptr;
}
Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=320128&r1=320127&r2=320128&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original)
+++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Thu Dec 7 17:51:47 2017
@@ -3927,6 +3927,11 @@ public:
LValueBaseInfo *BaseInfo = nullptr,
TBAAAccessInfo *TBAAInfo = nullptr);
+ /// If \p E references a parameter with pass_object_size info or a constant
+ /// array size modifier, emit the object size divided by the size of \p
EltTy.
+ /// Otherwise return null.
+ llvm::Value *LoadPassedObjectSize(const Expr *E, QualType EltTy);
+
void EmitSanitizerStatReport(llvm::SanitizerStatKind SSK);
private:
Added: cfe/trunk/test/CodeGen/ubsan-pass-object-size.c
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/ubsan-pass-object-size.c?rev=320128&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/ubsan-pass-object-size.c (added)
+++ cfe/trunk/test/CodeGen/ubsan-pass-object-size.c Thu Dec 7 17:51:47 2017
@@ -0,0 +1,69 @@
+// RUN: %clang_cc1 %s -emit-llvm -w -triple x86_64-apple-darwin10
-fsanitize=array-bounds -o - | FileCheck %s
+
+// CHECK-LABEL: define i32 @foo(
+int foo(int *const p __attribute__((pass_object_size(0))), int n) {
+ int x = (p)[n];
+
+ // CHECK: [[SIZE_ALLOCA:%.*]] = alloca i64, align 8
+ // CHECK: store i64 %{{.*}}, i64* [[SIZE_ALLOCA]], align 8
+ // CHECK: [[LOAD_SIZE:%.*]] = load i64, i64* [[SIZE_ALLOCA]], align 8,
!nosanitize
+ // CHECK-NEXT: [[SCALED_SIZE:%.*]] = udiv i64 [[LOAD_SIZE]], 4, !nosanitize
+ // CHECK-NEXT: [[SEXT_N:%.*]] = sext i32 %{{.*}} to i64, !nosanitize
+ // CHECK-NEXT: [[ICMP:%.*]] = icmp ult i64 [[SEXT_N]], [[SCALED_SIZE]],
!nosanitize
+ // CHECK-NEXT: br i1 [[ICMP]], {{.*}} !nosanitize
+ // CHECK: __ubsan_handle_out_of_bounds
+
+ {
+ int **p = &p; // Shadow the parameter. The pass_object_size info is lost.
+ // CHECK-NOT: __ubsan_handle_out_of_bounds
+ x = *p[n];
+ }
+
+ // CHECK: ret i32
+ return x;
+}
+
+typedef struct {} ZeroSizedType;
+
+// CHECK-LABEL: define void @bar(
+ZeroSizedType bar(ZeroSizedType *const p __attribute__((pass_object_size(0))),
int n) {
+ // CHECK-NOT: __ubsan_handle_out_of_bounds
+ // CHECK: ret void
+ return p[n];
+}
+
+// CHECK-LABEL: define i32 @baz(
+int baz(int *const p __attribute__((pass_object_size(1))), int n) {
+ // CHECK: __ubsan_handle_out_of_bounds
+ // CHECK: ret i32
+ return p[n];
+}
+
+// CHECK-LABEL: define i32 @mat(
+int mat(int *const p __attribute__((pass_object_size(2))), int n) {
+ // CHECK-NOT: __ubsan_handle_out_of_bounds
+ // CHECK: ret i32
+ return p[n];
+}
+
+// CHECK-LABEL: define i32 @pat(
+int pat(int *const p __attribute__((pass_object_size(3))), int n) {
+ // CHECK-NOT: __ubsan_handle_out_of_bounds
+ // CHECK: ret i32
+ return p[n];
+}
+
+// CHECK-LABEL: define i32 @cat(
+int cat(int p[static 10], int n) {
+ // CHECK: icmp ult i64 {{.*}}, 10, !nosanitize
+ // CHECK: __ubsan_handle_out_of_bounds
+ // CHECK: ret i32
+ return p[n];
+}
+
+// CHECK-LABEL: define i32 @bat(
+int bat(int n, int p[n]) {
+ // CHECK-NOT: __ubsan_handle_out_of_bounds
+ // CHECK: ret i32
+ return p[n];
+}
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