b194cf1e40
This introduces the attribute discussed in https://discourse.llvm.org/t/rfc-function-type-attribute-to-prevent-cfi-instrumentation/85458. The proposed name has been changed from `no_cfi` to `cfi_unchecked_callee` to help differentiate from `no_sanitize("cfi")` more easily. The proposed attribute has the following semantics: 1. Indirect calls to a function type with this attribute will not be instrumented with CFI. That is, the indirect call will not be checked. Note that this only changes the behavior for indirect calls on pointers to function types having this attribute. It does not prevent all indirect function calls for a given type from being checked. 2. All direct references to a function whose type has this attribute will always reference the true function definition rather than an entry in the CFI jump table. 3. When a pointer to a function with this attribute is implicitly cast to a pointer to a function without this attribute, the compiler will give a warning saying this attribute is discarded. This warning can be silenced with an explicit C-style cast or C++ static_cast.
236 lines
12 KiB
C++
236 lines
12 KiB
C++
// RUN: %clang_cc1 -Wall -Wno-unused -Wno-uninitialized -std=c++2b -verify %s
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#define CFI_UNCHECKED_CALLEE __attribute__((cfi_unchecked_callee))
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void unchecked(void) CFI_UNCHECKED_CALLEE {}
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void checked(void) {}
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void (*checked_ptr)(void) = unchecked; // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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void (CFI_UNCHECKED_CALLEE *unchecked_ptr)(void) = unchecked;
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void (CFI_UNCHECKED_CALLEE *from_normal)(void) = checked;
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void (CFI_UNCHECKED_CALLEE *c_no_function_decay)(void) = &unchecked;
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void (CFI_UNCHECKED_CALLEE *arr[10])(void);
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void (*cfi_elem)(void) = arr[1]; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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void (CFI_UNCHECKED_CALLEE *cfi_unchecked_elem)(void) = arr[1];
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void (CFI_UNCHECKED_CALLEE &ref)(void) = unchecked;
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void (CFI_UNCHECKED_CALLEE &ref2)(void) = *unchecked;
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void (&ref_cfi_checked)(void) = unchecked; // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void ()' discards 'cfi_unchecked_callee' attribute}}
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void (&ref_cfi_checked2)(void) = *unchecked; // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void ()' discards 'cfi_unchecked_callee' attribute}}
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void (CFI_UNCHECKED_CALLEE *unchecked_from_deref)(void) = &*unchecked;
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void (*checked_from_deref)(void) = &*unchecked; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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typedef void (CFI_UNCHECKED_CALLEE unchecked_func_t)(void);
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typedef void (checked_func_t)(void);
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typedef void (CFI_UNCHECKED_CALLEE *unchecked_func_ptr_t)(void);
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typedef void (*checked_func_ptr_t)(void);
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checked_func_t *checked_func = unchecked; // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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unchecked_func_t *unchecked_func = unchecked;
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void CFI_UNCHECKED_CALLEE before_func(void);
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CFI_UNCHECKED_CALLEE void before_return_type(void);
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void (* CFI_UNCHECKED_CALLEE after_name)(void);
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void UsageOnImproperTypes() {
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int CFI_UNCHECKED_CALLEE i; // expected-warning{{'cfi_unchecked_callee' only applies to function types; type here is 'int'}}
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}
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/// Explicit casts suppress the warning.
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void CheckCasts() {
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void (*should_warn)(void) = unchecked; // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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void (*no_warn_c_style_cast)(void) = (void (*)(void))unchecked;
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void (*no_warn_static_cast)(void) = static_cast<void (*)(void)>(unchecked);
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void (*no_warn_reinterpret_cast)(void) = reinterpret_cast<void (*)(void)>(unchecked);
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unsigned long long ull = (unsigned long long)unchecked;
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struct A {};
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void (CFI_UNCHECKED_CALLEE A::*cfi_unchecked_member_ptr)(void);
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void (A::*member_ptr)(void) = cfi_unchecked_member_ptr; // expected-warning{{implicit conversion from 'void (A::*)() __attribute__((cfi_unchecked_callee))' to 'void (A::*)()' discards 'cfi_unchecked_callee' attribute}}
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struct B {} CFI_UNCHECKED_CALLEE b; // expected-warning{{'cfi_unchecked_callee' attribute only applies to functions and methods}}
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struct CFI_UNCHECKED_CALLEE C {} c; // expected-warning{{'cfi_unchecked_callee' attribute only applies to functions and methods}}
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CFI_UNCHECKED_CALLEE struct D {} d; // expected-warning{{'cfi_unchecked_callee' only applies to function types; type here is 'struct D'}}
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void *ptr2 = (void *)unchecked;
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}
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void CheckDifferentConstructions() {
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checked_func_t *checked_func(unchecked_func); // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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new (checked_func_t *)(unchecked_func); // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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struct S {
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checked_func_t *checked_func;
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S(unchecked_func_t *unchecked_func) : checked_func(unchecked_func) {} // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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};
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checked_func_t *checked_func2{unchecked_func}; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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checked_ptr = checked_func_ptr_t(unchecked);
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auto checked_auto = checked;
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auto unchecked_auto = unchecked;
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unchecked_ptr = checked_auto;
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unchecked_ptr = unchecked_auto;
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checked_ptr = checked_auto;
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checked_ptr = unchecked_auto; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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}
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checked_func_t *returning_checked_func() {
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return unchecked; // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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}
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int checked_arg_func(checked_func_t *checked_func);
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int invoke = checked_arg_func(unchecked); // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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template <typename T>
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struct S {
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S(T *ptr) {}
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};
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S<unchecked_func_t> s(checked);
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S<unchecked_func_t> s2(unchecked);
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S<checked_func_t> s3(checked);
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S<checked_func_t> s4(unchecked); // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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S s5(checked);
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S s6(unchecked);
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template <typename T, typename U>
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struct is_same {
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static constexpr bool value = false;
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};
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template <typename T>
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struct is_same<T,T> {
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static constexpr bool value = true;
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};
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template <typename T>
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struct ExpectingCFIUncheckedCallee {
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static_assert(is_same<T, unchecked_func_t>::value);
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ExpectingCFIUncheckedCallee(T *) {}
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ExpectingCFIUncheckedCallee() = default;
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};
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ExpectingCFIUncheckedCallee<unchecked_func_t> expecting;
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ExpectingCFIUncheckedCallee expecting2(unchecked);
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void no_args() __attribute__((cfi_unchecked_callee(10))); // expected-error{{'cfi_unchecked_callee' attribute takes no arguments}}
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void bracket_cfi_unchecked(void) [[clang::cfi_unchecked_callee]] {}
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void BracketNotation() {
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checked_ptr = bracket_cfi_unchecked; // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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}
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void Comparisons() {
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/// Let's be able to compare checked and unchecked pointers without warnings.
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unchecked == checked_ptr;
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checked_ptr == unchecked;
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unchecked == unchecked_ptr;
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unchecked != checked_ptr;
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checked_ptr != unchecked;
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unchecked != unchecked_ptr;
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(void (*)(void))unchecked == checked_ptr;
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checked_ptr == (void (*)(void))unchecked;
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struct S {
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typedef void CB() CFI_UNCHECKED_CALLEE;
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constexpr bool operator==(const S &other) const {
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return cb == other.cb;
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}
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CB *cb;
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};
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}
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/// Type aliasing
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typedef void (BaseType)(void);
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using WithoutAttr = BaseType;
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using WithAttr = __attribute__((cfi_unchecked_callee)) BaseType;
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WithoutAttr *checked_func_alias = unchecked; // expected-warning{{implicit conversion from 'void () __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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WithAttr *unchecked_func_allias = unchecked;
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WithoutAttr *checked_func_alias2 = checked;
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WithAttr *unchecked_func_alias2 = checked;
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using MyType = WithAttr; // expected-note{{previous definition is here}}
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using MyType = WithoutAttr; // expected-error{{type alias redefinition with different types ('WithoutAttr' (aka 'void ()') vs 'WithAttr' (aka 'void () __attribute__((cfi_unchecked_callee))'))}}
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void MemberFunctionPointer() {
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struct A {
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void unchecked() CFI_UNCHECKED_CALLEE {}
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virtual void unchecked_virtual() CFI_UNCHECKED_CALLEE {}
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static void unchecked_static() CFI_UNCHECKED_CALLEE {}
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void unchecked_explicit_this(this A&) CFI_UNCHECKED_CALLEE {}
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int operator+=(int i) CFI_UNCHECKED_CALLEE { return i; }
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void checked() {}
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virtual void checked_virtual() {}
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static void checked_static() {}
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void checked_explicit_this(this A&) {}
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int operator-=(int i) { return i; }
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};
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void (CFI_UNCHECKED_CALLEE A::*unchecked)() = &A::unchecked;
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unchecked = &A::unchecked_virtual;
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void (CFI_UNCHECKED_CALLEE *unchecked_explicit_this)(A&) = &A::unchecked_explicit_this;
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void (CFI_UNCHECKED_CALLEE *unchecked_static)() = &A::unchecked_static;
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int (CFI_UNCHECKED_CALLEE A::*unchecked_overloaded)(int) = &A::operator+=;
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void (A::*checked)() = &A::unchecked; // expected-warning{{implicit conversion from 'void (A::*)() __attribute__((cfi_unchecked_callee))' to 'void (A::*)()' discards 'cfi_unchecked_callee' attribute}}
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checked = &A::unchecked_virtual; // expected-warning{{implicit conversion from 'void (A::*)() __attribute__((cfi_unchecked_callee))' to 'void (A::*)()' discards 'cfi_unchecked_callee' attribute}}
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void (*checked_explicit_this)(A&) = &A::unchecked_explicit_this; // expected-warning{{implicit conversion from 'void (*)(A &) __attribute__((cfi_unchecked_callee))' to 'void (*)(A &)' discards 'cfi_unchecked_callee' attribute}}
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void (*checked_static)() = &A::unchecked_static; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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int (A::*checked_overloaded)(int) = &A::operator+=; // expected-warning{{implicit conversion from 'int (A::*)(int) __attribute__((cfi_unchecked_callee))' to 'int (A::*)(int)' discards 'cfi_unchecked_callee' attribute}}
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unchecked = &A::checked;
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unchecked = &A::checked_virtual;
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unchecked_explicit_this = &A::checked_explicit_this;
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unchecked_static = &A::checked_static;
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unchecked_overloaded = &A::operator-=;
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checked = &A::checked;
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checked = &A::checked_virtual;
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checked_explicit_this = &A::checked_explicit_this;
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checked_static = &A::checked_static;
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checked_overloaded = &A::operator-=;
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typedef void (CFI_UNCHECKED_CALLEE A::*WithAttr)();
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typedef void (CFI_UNCHECKED_CALLEE A::*WithoutAttr)();
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using WithoutAttr = decltype(unchecked);
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}
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void lambdas() {
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auto unchecked_lambda = [](void) CFI_UNCHECKED_CALLEE -> void {};
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auto checked_lambda = [](void) -> void {};
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void (CFI_UNCHECKED_CALLEE *unchecked_func)(void) = unchecked_lambda;
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unchecked_func = checked_lambda;
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void (*checked_func)(void) = unchecked_lambda; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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checked_func = checked_lambda;
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auto capture_by_value = [unchecked_lambda, checked_lambda]() {
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void (CFI_UNCHECKED_CALLEE *unchecked_func)(void) = unchecked_lambda;
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unchecked_func = checked_lambda;
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void (*checked_func)(void) = unchecked_lambda; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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checked_func = checked_lambda;
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};
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auto capture_by_ref = [&unchecked_lambda, &checked_lambda]() {
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void (CFI_UNCHECKED_CALLEE *unchecked_func)(void) = unchecked_lambda;
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unchecked_func = checked_lambda;
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void (*checked_func)(void) = unchecked_lambda; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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checked_func = checked_lambda;
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};
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auto capture_all_by_value = [=]() {
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void (CFI_UNCHECKED_CALLEE *unchecked_func)(void) = unchecked_lambda;
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unchecked_func = checked_lambda;
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void (*checked_func)(void) = unchecked_lambda; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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checked_func = checked_lambda;
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};
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auto capture_all_by_ref = [&]() {
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void (CFI_UNCHECKED_CALLEE *unchecked_func)(void) = unchecked_lambda;
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unchecked_func = checked_lambda;
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void (*checked_func)(void) = unchecked_lambda; // expected-warning{{implicit conversion from 'void (*)() __attribute__((cfi_unchecked_callee))' to 'void (*)()' discards 'cfi_unchecked_callee' attribute}}
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checked_func = checked_lambda;
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};
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}
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