b6c06dc28f
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 llvm-svn: 352829
84 lines
2.3 KiB
C++
84 lines
2.3 KiB
C++
// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -o - %s -fsanitize=unreachable | FileCheck %s
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void abort() __attribute__((noreturn));
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// CHECK-LABEL: define void @_Z14calls_noreturnv()
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void calls_noreturn() {
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// Check absence ([^#]*) of call site attributes (including noreturn)
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// CHECK: call void @_Z5abortv(){{[^#]*}}
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abort();
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// CHECK: __ubsan_handle_builtin_unreachable
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// CHECK: unreachable
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}
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struct A {
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// CHECK: declare void @_Z5abortv() [[EXTERN_FN_ATTR:#[0-9]+]]
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// CHECK-LABEL: define linkonce_odr void @_ZN1A5call1Ev
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void call1() {
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// CHECK: call void @_ZN1A16does_not_return2Ev({{.*}}){{[^#]*}}
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does_not_return2();
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// CHECK: __ubsan_handle_builtin_unreachable
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// CHECK: unreachable
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}
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// Test static members. Checks are below after `struct A` scope ends.
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static void does_not_return1() __attribute__((noreturn)) {
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abort();
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}
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// CHECK-LABEL: define linkonce_odr void @_ZN1A5call2Ev
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void call2() {
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// CHECK: call void @_ZN1A16does_not_return1Ev(){{[^#]*}}
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does_not_return1();
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// CHECK: __ubsan_handle_builtin_unreachable
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// CHECK: unreachable
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}
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// Test calls through pointers to non-static member functions.
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typedef void (A::*MemFn)() __attribute__((noreturn));
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// CHECK-LABEL: define linkonce_odr void @_ZN1A5call3Ev
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void call3() {
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MemFn MF = &A::does_not_return2;
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// CHECK: call void %{{[0-9]+\(.*}}){{[^#]*}}
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(this->*MF)();
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// CHECK: __ubsan_handle_builtin_unreachable
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// CHECK: unreachable
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}
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// Test regular members.
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// CHECK-LABEL: define linkonce_odr void @_ZN1A16does_not_return2Ev({{.*}})
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// CHECK-SAME: [[USER_FN_ATTR:#[0-9]+]]
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void does_not_return2() __attribute__((noreturn)) {
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// CHECK: call void @_Z5abortv(){{[^#]*}}
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abort();
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// CHECK: call void @__ubsan_handle_builtin_unreachable
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// CHECK: unreachable
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// CHECK: call void @__ubsan_handle_builtin_unreachable
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// CHECK: unreachable
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}
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};
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// CHECK-LABEL: define linkonce_odr void @_ZN1A16does_not_return1Ev()
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// CHECK-SAME: [[USER_FN_ATTR]]
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// CHECK: call void @_Z5abortv(){{[^#]*}}
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void force_irgen() {
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A a;
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a.call1();
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a.call2();
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a.call3();
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}
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// `noreturn` should be removed from functions and call sites
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// CHECK-LABEL: attributes
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// CHECK-NOT: [[USER_FN_ATTR]] = { {{.*noreturn.*}} }
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// CHECK-NOT: [[EXTERN_FN_ATTR]] = { {{.*noreturn.*}} }
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