Kernel: Implement SYS_GET_PID and SYS_TCSETPGID

we don't have consept of process groups yet

kernel/include/kernel/Process.h

@@ -104,6 +104,8 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_raise(int signal);
 		static BAN::ErrorOr<long> sys_kill(pid_t pid, int signal);
 
+		BAN::ErrorOr<long> sys_tcsetpgrp(int fd, pid_t pgid);
+
 		BAN::ErrorOr<long> sys_termid(char*) const;
 
 		BAN::ErrorOr<long> sys_clock_gettime(clockid_t, timespec*) const;

kernel/kernel/Process.cpp

@@ -848,10 +848,31 @@ namespace Kernel
 		return 0;
 	}
 
-	pid_t Process::foreground_pid()
+	BAN::ErrorOr<long> Process::sys_tcsetpgrp(int fd, pid_t pgid)
 	{
-		ASSERT(s_foreground_pid);
-		return s_foreground_pid;
+		LockGuard _(m_lock);
+
+		// FIXME: validate the inode
+		auto inode = TRY(m_open_file_descriptors.inode_of(fd));
+		if (!inode->is_tty())
+			return BAN::Error::from_errno(ENOTTY);
+
+		// FIXME: use process groups instead of process ids
+		// FIXME: return values
+
+		LockGuard process_guard(s_process_lock);
+		for (auto* process : s_processes)
+		{
+			if (process->pid() == pgid)
+			{
+				if (!process->is_userspace())
+					return BAN::Error::from_errno(EINVAL);
+				((TTY*)inode.ptr())->set_foreground_process(pgid);
+				return 0;
+			}
+		}
+
+		return BAN::Error::from_errno(EPERM);
 	}
 
 	BAN::ErrorOr<long> Process::sys_setuid(uid_t uid)

kernel/kernel/Syscall.cpp

@@ -160,6 +160,12 @@ namespace Kernel
 		case SYS_SIGNAL_DONE:
 			// Handled above
 			ASSERT_NOT_REACHED();
+		case SYS_TCSETPGRP:
+			ret = Process::current().sys_tcsetpgrp((int)arg1, (pid_t)arg2);
+			break;
+		case SYS_GET_PID:
+			ret = Process::current().pid();
+			break;
 		default:
 			dwarnln("Unknown syscall {}", syscall);
 			break;