Kernel/LibC: Implement sigwait

kernel/include/kernel/Process.h

@@ -194,6 +194,7 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_sigpending(sigset_t* set);
 		BAN::ErrorOr<long> sys_sigprocmask(int how, const sigset_t* set, sigset_t* oset);
 		BAN::ErrorOr<long> sys_sigsuspend(const sigset_t* set);
+		BAN::ErrorOr<long> sys_sigwait(const sigset_t* set, int* sig);
 
 		BAN::ErrorOr<long> sys_futex(int op, const uint32_t* addr, uint32_t val, const timespec* abstime);
 		BAN::ErrorOr<long> sys_yield();

kernel/kernel/Process.cpp

@@ -2665,6 +2665,42 @@ namespace Kernel
 		return BAN::Error::from_errno(EINTR);
 	}
 
+	BAN::ErrorOr<long> Process::sys_sigwait(const sigset_t* set, int* sig)
+	{
+		LockGuard _(m_process_lock);
+
+		auto& thread = Thread::current();
+		for (;;)
+		{
+			TRY(validate_pointer_access(set, sizeof(sigset_t), false));
+			TRY(validate_pointer_access(sig, sizeof(int), true));
+
+			{
+				SpinLockGuard _1(thread.m_signal_lock);
+				SpinLockGuard _2(m_signal_lock);
+
+				const uint64_t pending = thread.m_signal_pending_mask | this->m_signal_pending_mask;
+				if (const auto wait_mask = pending & *set)
+				{
+					for (size_t i = _SIGMIN; i <= _SIGMAX; i++)
+					{
+						const auto mask = 1ull << i;
+						if (!(wait_mask & mask))
+							continue;
+						thread.m_signal_pending_mask &= ~mask;
+						this->m_signal_pending_mask &= ~mask;
+						*sig = i;
+						return 0;
+					}
+
+					ASSERT_NOT_REACHED();
+				}
+			}
+
+			Processor::scheduler().block_current_thread(nullptr, -1, &m_process_lock);
+		}
+	}
+
 	BAN::ErrorOr<long> Process::sys_futex(int op, const uint32_t* addr, uint32_t val, const timespec* abstime)
 	{
 		const vaddr_t vaddr = reinterpret_cast<vaddr_t>(addr);

userspace/libraries/LibC/include/sys/syscall.h

@@ -91,6 +91,7 @@ __BEGIN_DECLS
 	O(SYS_SIGPENDING,		sigpending)		\
 	O(SYS_SIGPROCMASK,		sigprocmask)	\
 	O(SYS_SIGSUSPEND,		sigsuspend)		\
+	O(SYS_SIGWAIT,			sigwait)		\
 	O(SYS_SETITIMER,		setitimer)		\
 	O(SYS_POSIX_OPENPT,		posix_openpt)	\
 	O(SYS_PTSNAME,			ptsname)		\

userspace/libraries/LibC/signal.cpp

@@ -169,3 +169,10 @@ int sigsuspend(const sigset_t* sigmask)
 {
 	return syscall(SYS_SIGSUSPEND, sigmask);
 }
+
+int sigwait(const sigset_t* __restrict set, int* __restrict sig)
+{
+	if (syscall(SYS_SIGWAIT, set, sig) == -1)
+		return errno;
+	return 0;
+}