options/internal: remove and poison __cxa_guard_{acquire,release}

Author: avdgrinten

options/internal/gcc/guard-abi.cpp

@@ -6,89 +6,15 @@
 #include <mlibc/debug.hpp>
 #include <mlibc/tid.hpp>
 
-namespace {
-
-// Itanium ABI static initialization guard.
-struct Guard {
-	static constexpr uint32_t waitersBit = 0x80000000;
-	static constexpr uint32_t ownerMask = 0x3FFFFFFF;
-
-	void lock() {
-		uint32_t tid = mlibc::this_tid();
-		uint32_t expected = 0;
-
-		while (true) {
-			if (!expected) {
-				if (__atomic_compare_exchange_n(
-				        &mutex, &expected, tid, false, __ATOMIC_ACQUIRE, __ATOMIC_ACQUIRE
-				    ))
-					return;
-			} else {
-				if ((expected & ownerMask) == tid)
-					mlibc::panicLogger()
-					    << "mlibc: __cxa_guard_acquire deadlock detected!" << frg::endlog;
-
-				if (expected & waitersBit) {
-					int e = mlibc::sysdep<FutexWait>((int *)&mutex, expected, nullptr);
-					if (e && e != EAGAIN && e != EINTR)
-						mlibc::panicLogger()
-						    << "sys_futex_wait() failed with error code " << e << frg::endlog;
-					expected = 0;
-				} else {
-					uint32_t desired = expected | waitersBit;
-					if (__atomic_compare_exchange_n(
-					        &mutex, &expected, desired, false, __ATOMIC_RELAXED, __ATOMIC_RELAXED
-					    ))
-						expected = desired;
-				}
-			}
-		}
-	}
-
-	void unlock() {
-		uint32_t state = __atomic_exchange_n(&mutex, 0, __ATOMIC_RELEASE);
-		__ensure((state & ownerMask) == mlibc::this_tid());
-		if(state & waitersBit)
-			mlibc::sysdep<FutexWake>((int *)&mutex, true);
-	}
-
-	// the first byte's meaning is fixed by the ABI.
-	// it indicates whether initialization has already been completed.
-	uint8_t complete;
-	// padding to ensure correct alignment on certain platforms.
-	uint8_t padding[3];
-
-	// we use some of the remaining bytes to implement a mutex.
-	uint32_t mutex;
-};
-
-static_assert(sizeof(Guard) == sizeof(int64_t));
-
-} // namespace
-
 extern "C" [[ gnu::visibility("hidden") ]] void __cxa_pure_virtual() {
 	mlibc::panicLogger() << "mlibc: Pure virtual function called from IP "
 			<< (void *)__builtin_return_address(0) << frg::endlog;
 }
 
-extern "C" [[ gnu::visibility("hidden") ]] int __cxa_guard_acquire(int64_t *ptr) {
-	auto guard = reinterpret_cast<Guard *>(ptr);
-	guard->lock();
-	// relaxed ordering is sufficient because
-	// Guard::complete is only modified while the mutex is held.
-	if(__atomic_load_n(&guard->complete, __ATOMIC_RELAXED)) {
-		guard->unlock();
-		return 0;
-	}else{
-		return 1;
-	}
-}
-
-extern "C" [[ gnu::visibility("hidden") ]] void __cxa_guard_release(int64_t *ptr) {
-	auto guard = reinterpret_cast<Guard *>(ptr);
-	// do a store-release so that compiler generated code can skip calling
-	// __cxa_guard_acquire by doing a load-acquire on Guard::complete.
-	__atomic_store_n(&guard->complete, 1, __ATOMIC_RELEASE);
-	guard->unlock();
-}
+static const char __poison_cxa_guard_acquire[]
+    __attribute__((used, section(".gnu.warning.__cxa_guard_acquire"))) =
+        "mlibc cannot use static singletons, use lazy_eternal instead";
 
+static const char __poison_cxa_guard_release[]
+    __attribute__((used, section(".gnu.warning.__cxa_guard_release"))) =
+        "mlibc cannot use static singletons, use lazy_eternal instead";