r352829 - [Sanitizers] UBSan unreachable incompatible with ASan in the presence of `noreturn` calls
Julian Lettner via cfe-commits
cfe-commits at lists.llvm.org
Thu Jan 31 18:51:00 PST 2019
Author: yln
Date: Thu Jan 31 18:51:00 2019
New Revision: 352829
URL: http://llvm.org/viewvc/llvm-project?rev=352829&view=rev
Log:
[Sanitizers] UBSan unreachable incompatible with ASan in the presence of `noreturn` calls
Summary:
UBSan wants to detect when unreachable code is actually reached, so it
adds instrumentation before every unreachable instruction. However, the
optimizer will remove code after calls to functions marked with
noreturn. To avoid this UBSan removes noreturn from both the call
instruction as well as from the function itself. Unfortunately, ASan
relies on this annotation to unpoison the stack by inserting calls to
_asan_handle_no_return before noreturn functions. This is important for
functions that do not return but access the the stack memory, e.g.,
unwinder functions *like* longjmp (longjmp itself is actually
"double-proofed" via its interceptor). The result is that when ASan and
UBSan are combined, the noreturn attributes are missing and ASan cannot
unpoison the stack, so it has false positives when stack unwinding is
used.
Changes:
Clang-CodeGen now directly insert calls to `__asan_handle_no_return`
when a call to a noreturn function is encountered and both
UBsan-unreachable and ASan are enabled. This allows UBSan to continue
removing the noreturn attribute from functions without any changes to
the ASan pass.
Previously generated code:
```
call void @longjmp
call void @__asan_handle_no_return
call void @__ubsan_handle_builtin_unreachable
```
Generated code (for now):
```
call void @__asan_handle_no_return
call void @longjmp
call void @__asan_handle_no_return
call void @__ubsan_handle_builtin_unreachable
```
rdar://problem/40723397
Reviewers: delcypher, eugenis, vsk
Differential Revision: https://reviews.llvm.org/D57278
llvm-svn: 352690
Added:
cfe/trunk/test/CodeGen/ubsan-asan-noreturn.c
Modified:
cfe/trunk/lib/CodeGen/CGCall.cpp
cfe/trunk/lib/CodeGen/CodeGenFunction.h
cfe/trunk/test/CodeGenCXX/ubsan-unreachable.cpp
Modified: cfe/trunk/lib/CodeGen/CGCall.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGCall.cpp?rev=352829&r1=352828&r2=352829&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGCall.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGCall.cpp Thu Jan 31 18:51:00 2019
@@ -4398,10 +4398,23 @@ RValue CodeGenFunction::EmitCall(const C
// Strip away the noreturn attribute to better diagnose unreachable UB.
if (SanOpts.has(SanitizerKind::Unreachable)) {
+ // Also remove from function since CI->hasFnAttr(..) also checks attributes
+ // of the called function.
if (auto *F = CI->getCalledFunction())
F->removeFnAttr(llvm::Attribute::NoReturn);
CI->removeAttribute(llvm::AttributeList::FunctionIndex,
llvm::Attribute::NoReturn);
+
+ // Avoid incompatibility with ASan which relies on the `noreturn`
+ // attribute to insert handler calls.
+ if (SanOpts.has(SanitizerKind::Address)) {
+ SanitizerScope SanScope(this);
+ llvm::IRBuilder<>::InsertPointGuard IPGuard(Builder);
+ Builder.SetInsertPoint(CI);
+ auto *FnType = llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
+ auto *Fn = CGM.CreateRuntimeFunction(FnType, "__asan_handle_no_return");
+ EmitNounwindRuntimeCall(Fn);
+ }
}
EmitUnreachable(Loc);
Modified: cfe/trunk/lib/CodeGen/CodeGenFunction.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CodeGenFunction.h?rev=352829&r1=352828&r2=352829&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CodeGenFunction.h (original)
+++ cfe/trunk/lib/CodeGen/CodeGenFunction.h Thu Jan 31 18:51:00 2019
@@ -4084,8 +4084,8 @@ public:
/// passing to a runtime sanitizer handler.
llvm::Constant *EmitCheckSourceLocation(SourceLocation Loc);
- /// Create a basic block that will call a handler function in a
- /// sanitizer runtime with the provided arguments, and create a conditional
+ /// Create a basic block that will either trap or call a handler function in
+ /// the UBSan runtime with the provided arguments, and create a conditional
/// branch to it.
void EmitCheck(ArrayRef<std::pair<llvm::Value *, SanitizerMask>> Checked,
SanitizerHandler Check, ArrayRef<llvm::Constant *> StaticArgs,
Added: cfe/trunk/test/CodeGen/ubsan-asan-noreturn.c
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/ubsan-asan-noreturn.c?rev=352829&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/ubsan-asan-noreturn.c (added)
+++ cfe/trunk/test/CodeGen/ubsan-asan-noreturn.c Thu Jan 31 18:51:00 2019
@@ -0,0 +1,21 @@
+// Ensure compatiblity of UBSan unreachable with ASan in the presence of
+// noreturn functions.
+// RUN: %clang_cc1 -fsanitize=unreachable,address -triple x86_64-linux -emit-llvm -o - %s | FileCheck %s
+
+void my_longjmp(void) __attribute__((noreturn));
+
+// CHECK-LABEL: define void @calls_noreturn()
+void calls_noreturn() {
+ my_longjmp();
+ // CHECK: @__asan_handle_no_return{{.*}} !nosanitize
+ // CHECK-NEXT: @my_longjmp(){{[^#]*}}
+ // CHECK: @__asan_handle_no_return()
+ // CHECK-NEXT: @__ubsan_handle_builtin_unreachable{{.*}} !nosanitize
+ // CHECK-NEXT: unreachable
+}
+
+// CHECK: declare void @my_longjmp() [[FN_ATTR:#[0-9]+]]
+// CHECK: declare void @__asan_handle_no_return()
+
+// CHECK-LABEL: attributes
+// CHECK-NOT: [[FN_ATTR]] = { {{.*noreturn.*}} }
Modified: cfe/trunk/test/CodeGenCXX/ubsan-unreachable.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/ubsan-unreachable.cpp?rev=352829&r1=352828&r2=352829&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/ubsan-unreachable.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/ubsan-unreachable.cpp Thu Jan 31 18:51:00 2019
@@ -1,39 +1,37 @@
// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -o - %s -fsanitize=unreachable | FileCheck %s
-extern void __attribute__((noreturn)) abort();
+void abort() __attribute__((noreturn));
-// CHECK-LABEL: define void @_Z14calls_noreturnv
+// CHECK-LABEL: define void @_Z14calls_noreturnv()
void calls_noreturn() {
+ // Check absence ([^#]*) of call site attributes (including noreturn)
+ // CHECK: call void @_Z5abortv(){{[^#]*}}
abort();
- // Check that there are no attributes on the call site.
- // CHECK-NOT: call void @_Z5abortv{{.*}}#
-
// CHECK: __ubsan_handle_builtin_unreachable
// CHECK: unreachable
}
struct A {
- // CHECK: declare void @_Z5abortv{{.*}} [[ABORT_ATTR:#[0-9]+]]
+ // CHECK: declare void @_Z5abortv() [[EXTERN_FN_ATTR:#[0-9]+]]
// CHECK-LABEL: define linkonce_odr void @_ZN1A5call1Ev
void call1() {
- // CHECK-NOT: call void @_ZN1A16does_not_return2Ev{{.*}}#
+ // CHECK: call void @_ZN1A16does_not_return2Ev({{.*}}){{[^#]*}}
does_not_return2();
// CHECK: __ubsan_handle_builtin_unreachable
// CHECK: unreachable
}
- // Test static members.
- static void __attribute__((noreturn)) does_not_return1() {
- // CHECK-NOT: call void @_Z5abortv{{.*}}#
+ // Test static members. Checks are below after `struct A` scope ends.
+ static void does_not_return1() __attribute__((noreturn)) {
abort();
}
// CHECK-LABEL: define linkonce_odr void @_ZN1A5call2Ev
void call2() {
- // CHECK-NOT: call void @_ZN1A16does_not_return1Ev{{.*}}#
+ // CHECK: call void @_ZN1A16does_not_return1Ev(){{[^#]*}}
does_not_return1();
// CHECK: __ubsan_handle_builtin_unreachable
@@ -41,23 +39,23 @@ struct A {
}
// Test calls through pointers to non-static member functions.
- typedef void __attribute__((noreturn)) (A::*MemFn)();
+ typedef void (A::*MemFn)() __attribute__((noreturn));
// CHECK-LABEL: define linkonce_odr void @_ZN1A5call3Ev
void call3() {
MemFn MF = &A::does_not_return2;
+ // CHECK: call void %{{[0-9]+\(.*}}){{[^#]*}}
(this->*MF)();
- // CHECK-NOT: call void %{{.*}}#
// CHECK: __ubsan_handle_builtin_unreachable
// CHECK: unreachable
}
// Test regular members.
// CHECK-LABEL: define linkonce_odr void @_ZN1A16does_not_return2Ev({{.*}})
- // CHECK-SAME: [[DOES_NOT_RETURN_ATTR:#[0-9]+]]
- void __attribute__((noreturn)) does_not_return2() {
- // CHECK-NOT: call void @_Z5abortv(){{.*}}#
+ // CHECK-SAME: [[USER_FN_ATTR:#[0-9]+]]
+ void does_not_return2() __attribute__((noreturn)) {
+ // CHECK: call void @_Z5abortv(){{[^#]*}}
abort();
// CHECK: call void @__ubsan_handle_builtin_unreachable
@@ -68,7 +66,9 @@ struct A {
}
};
-// CHECK: define linkonce_odr void @_ZN1A16does_not_return1Ev() [[DOES_NOT_RETURN_ATTR]]
+// CHECK-LABEL: define linkonce_odr void @_ZN1A16does_not_return1Ev()
+// CHECK-SAME: [[USER_FN_ATTR]]
+// CHECK: call void @_Z5abortv(){{[^#]*}}
void force_irgen() {
A a;
@@ -77,5 +77,7 @@ void force_irgen() {
a.call3();
}
-// CHECK-NOT: [[ABORT_ATTR]] = {{[^}]+}}noreturn
-// CHECK-NOT: [[DOES_NOT_RETURN_ATTR]] = {{[^}]+}}noreturn
+// `noreturn` should be removed from functions and call sites
+// CHECK-LABEL: attributes
+// CHECK-NOT: [[USER_FN_ATTR]] = { {{.*noreturn.*}} }
+// CHECK-NOT: [[EXTERN_FN_ATTR]] = { {{.*noreturn.*}} }
More information about the cfe-commits
mailing list