user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/options/internal/gcc/guard-abi.cpp

@@ -0,0 +1,70 @@
+
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <mlibc/debug.hpp>
+#include <mlibc/internal-sysdeps.hpp>
+
+namespace {
+
+// Itanium ABI static initialization guard.
+struct Guard {
+	// bit of the mutex member variable.
+	// indicates that the mutex is locked.
+	static constexpr int32_t locked = 1;
+
+	void lock() {
+		uint32_t v = 0;
+		if(__atomic_compare_exchange_n(&mutex, &v, Guard::locked, false,
+				__ATOMIC_ACQUIRE, __ATOMIC_RELAXED))
+			return;
+
+		mlibc::sys_libc_log("__cxa_guard_acquire contention");
+		__builtin_trap();
+	}
+
+	void unlock() {
+		__atomic_store_n(&mutex, 0, __ATOMIC_RELEASE);
+	}
+
+	// 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();
+}
+

user/include/mlibc/options/internal/gcc/stack_protector.cpp

@@ -0,0 +1,31 @@
+#include <stdint.h>
+#include <string.h>
+#include <mlibc/debug.hpp>
+#include <mlibc/stack_protector.hpp>
+
+uintptr_t __stack_chk_guard = 0;
+
+namespace mlibc {
+
+void initStackGuard(void *entropy) {
+	if(entropy != nullptr) {
+		memcpy(&__stack_chk_guard, entropy, sizeof(__stack_chk_guard));
+	} else {
+		// If no entropy is available, set it to the terminator canary
+		__stack_chk_guard = 0;
+		__stack_chk_guard |= ('\n' << 16);
+		__stack_chk_guard |= (255 << 24);
+	}
+}
+
+} // namespace mlibc
+
+extern "C" [[noreturn]] void __stack_chk_fail() {
+	mlibc::panicLogger() << "Stack smashing detected!" << frg::endlog;
+	__builtin_unreachable();
+}
+
+extern "C" [[noreturn, gnu::visibility("hidden")]] void __stack_chk_fail_local() {
+	__stack_chk_fail();
+};
+