lib: Add mlibc

Signed-off-by: Ian Moffett <ian@osmora.org>

1 files changed, 342 insertions, 0 deletions

diff --git a/lib/mlibc/options/internal/generic/threads.cpp b/lib/mlibc/options/internal/generic/threads.cpp
new file mode 100644
index 0000000..5f1168c
--- /dev/null
+++ b/lib/mlibc/options/internal/generic/threads.cpp
@@ -0,0 +1,342 @@
+#include <abi-bits/errno.h>
+#include <bits/threads.h>
+#include <bits/ensure.h>
+#include <mlibc/all-sysdeps.hpp>
+#include <mlibc/debug.hpp>
+#include <mlibc/lock.hpp>
+#include <mlibc/threads.hpp>
+#include <mlibc/tcb.hpp>
+
+extern "C" Tcb *__rtdl_allocateTcb();
+
+namespace mlibc {
+
+int thread_create(struct __mlibc_thread_data **__restrict thread, const struct __mlibc_threadattr *__restrict attrp, void *entry, void *__restrict user_arg, bool returns_int) {
+	auto new_tcb = __rtdl_allocateTcb();
+	pid_t tid;
+	struct __mlibc_threadattr attr = {};
+	if (!attrp)
+		thread_attr_init(&attr);
+	else
+		attr = *attrp;
+
+	if (attr.__mlibc_cpuset)
+		mlibc::infoLogger() << "pthread_create(): cpuset is ignored!" << frg::endlog;
+	if (attr.__mlibc_sigmaskset)
+		mlibc::infoLogger() << "pthread_create(): sigmask is ignored!" << frg::endlog;
+
+	// TODO: due to alignment guarantees, the stackaddr and stacksize might change
+	// when the stack is allocated. Currently this isn't propagated to the TCB,
+	// but it should be.
+	void *stack = attr.__mlibc_stackaddr;
+	if (!mlibc::sys_prepare_stack) {
+		MLIBC_MISSING_SYSDEP();
+		return ENOSYS;
+	}
+	int ret = mlibc::sys_prepare_stack(&stack, entry,
+			user_arg, new_tcb, &attr.__mlibc_stacksize, &attr.__mlibc_guardsize, &new_tcb->stackAddr);
+	if (ret)
+		return ret;
+
+	if (!mlibc::sys_clone) {
+		MLIBC_MISSING_SYSDEP();
+		return ENOSYS;
+	}
+	new_tcb->stackSize = attr.__mlibc_stacksize;
+	new_tcb->guardSize = attr.__mlibc_guardsize;
+	new_tcb->returnValueType = (returns_int) ? TcbThreadReturnValue::Integer : TcbThreadReturnValue::Pointer;
+	mlibc::sys_clone(new_tcb, &tid, stack);
+	*thread = reinterpret_cast<struct __mlibc_thread_data *>(new_tcb);
+
+	__atomic_store_n(&new_tcb->tid, tid, __ATOMIC_RELAXED);
+	mlibc::sys_futex_wake(&new_tcb->tid);
+
+	return 0;
+}
+
+int thread_join(struct __mlibc_thread_data *thread, void *ret) {
+	auto tcb = reinterpret_cast<Tcb *>(thread);
+
+	if (!__atomic_load_n(&tcb->isJoinable, __ATOMIC_ACQUIRE))
+		return EINVAL;
+
+	while (!__atomic_load_n(&tcb->didExit, __ATOMIC_ACQUIRE)) {
+		mlibc::sys_futex_wait(&tcb->didExit, 0, nullptr);
+	}
+
+	if(ret && tcb->returnValueType == TcbThreadReturnValue::Pointer)
+		*reinterpret_cast<void **>(ret) = tcb->returnValue.voidPtr;
+	else if(ret && tcb->returnValueType == TcbThreadReturnValue::Integer)
+		*reinterpret_cast<int *>(ret) = tcb->returnValue.intVal;
+
+	// FIXME: destroy tcb here, currently we leak it
+
+	return 0;
+}
+
+static constexpr size_t default_stacksize = 0x200000;
+static constexpr size_t default_guardsize = 4096;
+
+int thread_attr_init(struct __mlibc_threadattr *attr) {
+	*attr = __mlibc_threadattr{};
+	attr->__mlibc_stacksize = default_stacksize;
+	attr->__mlibc_guardsize = default_guardsize;
+	attr->__mlibc_detachstate = __MLIBC_THREAD_CREATE_JOINABLE;
+	return 0;
+}
+
+static constexpr unsigned int mutexRecursive = 1;
+static constexpr unsigned int mutexErrorCheck = 2;
+
+// TODO: either use uint32_t or determine the bit based on sizeof(int).
+static constexpr unsigned int mutex_owner_mask = (static_cast<uint32_t>(1) << 30) - 1;
+static constexpr unsigned int mutex_waiters_bit = static_cast<uint32_t>(1) << 31;
+
+// Only valid for the internal __mlibc_m mutex of wrlocks.
+static constexpr unsigned int mutex_excl_bit = static_cast<uint32_t>(1) << 30;
+
+int thread_mutex_init(struct __mlibc_mutex *__restrict mutex,
+		const struct __mlibc_mutexattr *__restrict attr) {
+	auto type = attr ? attr->__mlibc_type : __MLIBC_THREAD_MUTEX_DEFAULT;
+	auto robust = attr ? attr->__mlibc_robust : __MLIBC_THREAD_MUTEX_STALLED;
+	auto protocol = attr ? attr->__mlibc_protocol : __MLIBC_THREAD_PRIO_NONE;
+	auto pshared = attr ? attr->__mlibc_pshared : __MLIBC_THREAD_PROCESS_PRIVATE;
+
+	mutex->__mlibc_state = 0;
+	mutex->__mlibc_recursion = 0;
+	mutex->__mlibc_flags = 0;
+	mutex->__mlibc_prioceiling = 0; // TODO: We don't implement this.
+
+	if(type == __MLIBC_THREAD_MUTEX_RECURSIVE) {
+		mutex->__mlibc_flags |= mutexRecursive;
+	}else if(type == __MLIBC_THREAD_MUTEX_ERRORCHECK) {
+		mutex->__mlibc_flags |= mutexErrorCheck;
+	}else{
+		__ensure(type == __MLIBC_THREAD_MUTEX_NORMAL);
+	}
+
+	// TODO: Other values aren't supported yet.
+	__ensure(robust == __MLIBC_THREAD_MUTEX_STALLED);
+	__ensure(protocol == __MLIBC_THREAD_PRIO_NONE);
+	__ensure(pshared == __MLIBC_THREAD_PROCESS_PRIVATE);
+
+	return 0;
+}
+
+int thread_mutex_destroy(struct __mlibc_mutex *mutex) {
+	__ensure(!mutex->__mlibc_state);
+	return 0;
+}
+
+int thread_mutex_lock(struct __mlibc_mutex *mutex) {
+	unsigned int this_tid = mlibc::this_tid();
+	unsigned int expected = 0;
+	while(true) {
+		if(!expected) {
+			// Try to take the mutex here.
+			if(__atomic_compare_exchange_n(&mutex->__mlibc_state,
+					&expected, this_tid, false, __ATOMIC_ACQUIRE, __ATOMIC_ACQUIRE)) {
+				__ensure(!mutex->__mlibc_recursion);
+				mutex->__mlibc_recursion = 1;
+				return 0;
+			}
+		}else{
+			// If this (recursive) mutex is already owned by us, increment the recursion level.
+			if((expected & mutex_owner_mask) == this_tid) {
+				if(!(mutex->__mlibc_flags & mutexRecursive)) {
+					if (mutex->__mlibc_flags & mutexErrorCheck)
+						return EDEADLK;
+					else
+						mlibc::panicLogger() << "mlibc: pthread_mutex deadlock detected!"
+							<< frg::endlog;
+				}
+				++mutex->__mlibc_recursion;
+				return 0;
+			}
+
+			// Wait on the futex if the waiters flag is set.
+			if(expected & mutex_waiters_bit) {
+				int e = mlibc::sys_futex_wait((int *)&mutex->__mlibc_state, expected, nullptr);
+
+				// If the wait returns EAGAIN, that means that the mutex_waiters_bit was just unset by
+				// some other thread. In this case, we should loop back around.
+				if (e && e != EAGAIN)
+					mlibc::panicLogger() << "sys_futex_wait() failed with error code " << e << frg::endlog;
+
+				// Opportunistically try to take the lock after we wake up.
+				expected = 0;
+			}else{
+				// Otherwise we have to set the waiters flag first.
+				unsigned int desired = expected | mutex_waiters_bit;
+				if(__atomic_compare_exchange_n((int *)&mutex->__mlibc_state,
+						reinterpret_cast<int*>(&expected), desired, false, __ATOMIC_RELAXED, __ATOMIC_RELAXED))
+					expected = desired;
+			}
+		}
+	}
+}
+
+int thread_mutex_unlock(struct __mlibc_mutex *mutex) {
+	// Decrement the recursion level and unlock if we hit zero.
+	__ensure(mutex->__mlibc_recursion);
+	if(--mutex->__mlibc_recursion)
+		return 0;
+
+	auto flags = mutex->__mlibc_flags;
+
+	// Reset the mutex to the unlocked state.
+	auto state = __atomic_exchange_n(&mutex->__mlibc_state, 0, __ATOMIC_RELEASE);
+
+	// After this point the mutex is unlocked, and therefore we cannot access its contents as it
+	// may have been destroyed by another thread.
+
+	unsigned int this_tid = mlibc::this_tid();
+	if ((flags & mutexErrorCheck) && (state & mutex_owner_mask) != this_tid)
+		return EPERM;
+
+	if ((flags & mutexErrorCheck) && !(state & mutex_owner_mask))
+		return EINVAL;
+
+	__ensure((state & mutex_owner_mask) == this_tid);
+
+	if(state & mutex_waiters_bit) {
+		// Wake the futex if there were waiters. Since the mutex might not exist at this location
+		// anymore, we must conservatively ignore EACCES and EINVAL which may occur as a result.
+		int e = mlibc::sys_futex_wake((int *)&mutex->__mlibc_state);
+		__ensure(e >= 0 || e == EACCES || e == EINVAL);
+	}
+
+	return 0;
+}
+
+int thread_mutexattr_init(struct __mlibc_mutexattr *attr) {
+	attr->__mlibc_type = __MLIBC_THREAD_MUTEX_DEFAULT;
+	attr->__mlibc_robust = __MLIBC_THREAD_MUTEX_STALLED;
+	attr->__mlibc_pshared = __MLIBC_THREAD_PROCESS_PRIVATE;
+	attr->__mlibc_protocol = __MLIBC_THREAD_PRIO_NONE;
+	return 0;
+}
+
+int thread_mutexattr_destroy(struct __mlibc_mutexattr *attr) {
+	memset(attr, 0, sizeof(*attr));
+	return 0;
+}
+
+int thread_mutexattr_gettype(const struct __mlibc_mutexattr *__restrict attr, int *__restrict type) {
+	*type = attr->__mlibc_type;
+	return 0;
+}
+
+int thread_mutexattr_settype(struct __mlibc_mutexattr *attr, int type) {
+	if (type != __MLIBC_THREAD_MUTEX_NORMAL && type != __MLIBC_THREAD_MUTEX_ERRORCHECK
+			&& type != __MLIBC_THREAD_MUTEX_RECURSIVE)
+		return EINVAL;
+
+	attr->__mlibc_type = type;
+	return 0;
+}
+
+int thread_cond_init(struct __mlibc_cond *__restrict cond, const struct __mlibc_condattr *__restrict attr) {
+	auto clock = attr ? attr->__mlibc_clock : CLOCK_REALTIME;
+	auto pshared = attr ? attr->__mlibc_pshared : __MLIBC_THREAD_PROCESS_PRIVATE;
+
+	cond->__mlibc_clock = clock;
+	cond->__mlibc_flags = pshared;
+
+	__atomic_store_n(&cond->__mlibc_seq, 1, __ATOMIC_RELAXED);
+
+	return 0;
+}
+
+int thread_cond_destroy(struct __mlibc_cond *) {
+	return 0;
+}
+
+int thread_cond_broadcast(struct __mlibc_cond *cond) {
+	__atomic_fetch_add(&cond->__mlibc_seq, 1, __ATOMIC_RELEASE);
+	if(int e = mlibc::sys_futex_wake((int *)&cond->__mlibc_seq); e)
+		__ensure(!"sys_futex_wake() failed");
+
+	return 0;
+}
+
+int thread_cond_timedwait(struct __mlibc_cond *__restrict cond, __mlibc_mutex *__restrict mutex,
+		const struct timespec *__restrict abstime) {
+	// TODO: pshared isn't supported yet.
+	__ensure(cond->__mlibc_flags == 0);
+
+	constexpr long nanos_per_second = 1'000'000'000;
+	if (abstime && (abstime->tv_nsec < 0 || abstime->tv_nsec >= nanos_per_second))
+		return EINVAL;
+
+	auto seq = __atomic_load_n(&cond->__mlibc_seq, __ATOMIC_ACQUIRE);
+
+	// TODO: handle locking errors and cancellation properly.
+	while (true) {
+		if (thread_mutex_unlock(mutex))
+			__ensure(!"Failed to unlock the mutex");
+
+		int e;
+		if (abstime) {
+			// Adjust for the fact that sys_futex_wait accepts a *timeout*, but
+			// pthread_cond_timedwait accepts an *absolute time*.
+			// Note: mlibc::sys_clock_get is available unconditionally.
+			struct timespec now;
+			if (mlibc::sys_clock_get(cond->__mlibc_clock, &now.tv_sec, &now.tv_nsec))
+				__ensure(!"sys_clock_get() failed");
+
+			struct timespec timeout;
+			timeout.tv_sec = abstime->tv_sec - now.tv_sec;
+			timeout.tv_nsec = abstime->tv_nsec - now.tv_nsec;
+
+			// Check if abstime has already passed.
+			if (timeout.tv_sec < 0 || (timeout.tv_sec == 0 && timeout.tv_nsec < 0)) {
+				if (thread_mutex_lock(mutex))
+					__ensure(!"Failed to lock the mutex");
+				return ETIMEDOUT;
+			} else if (timeout.tv_nsec >= nanos_per_second) {
+				timeout.tv_nsec -= nanos_per_second;
+				timeout.tv_sec++;
+				__ensure(timeout.tv_nsec < nanos_per_second);
+			} else if (timeout.tv_nsec < 0) {
+				timeout.tv_nsec += nanos_per_second;
+				timeout.tv_sec--;
+				__ensure(timeout.tv_nsec >= 0);
+			}
+
+			e = mlibc::sys_futex_wait((int *)&cond->__mlibc_seq, seq, &timeout);
+		} else {
+			e = mlibc::sys_futex_wait((int *)&cond->__mlibc_seq, seq, nullptr);
+		}
+
+		if (thread_mutex_lock(mutex))
+			__ensure(!"Failed to lock the mutex");
+
+		// There are four cases to handle:
+		//   1. e == 0: this indicates a (potentially spurious) wakeup. The value of
+		//      seq *must* be checked to distinguish these two cases.
+		//   2. e == EAGAIN: this indicates that the value of seq changed before we
+		//      went to sleep. We don't need to check seq in this case.
+		//   3. e == EINTR: a signal was delivered. The man page allows us to choose
+		//      whether to go to sleep again or to return 0, but we do the former
+		//      to match other libcs.
+		//   4. e == ETIMEDOUT: this should only happen if abstime is set.
+		if (e == 0) {
+			auto cur_seq = __atomic_load_n(&cond->__mlibc_seq, __ATOMIC_ACQUIRE);
+			if (cur_seq > seq)
+				return 0;
+		} else if (e == EAGAIN) {
+			__ensure(__atomic_load_n(&cond->__mlibc_seq, __ATOMIC_ACQUIRE) > seq);
+			return 0;
+		} else if (e == EINTR) {
+			continue;
+		} else if (e == ETIMEDOUT) {
+			__ensure(abstime);
+			return ETIMEDOUT;
+		} else {
+			mlibc::panicLogger() << "sys_futex_wait() failed with error " << e << frg::endlog;
+		}
+	}
+}
+
+} // namespace mlibc