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;

libc/include/sys/syscall.h

@@ -45,6 +45,8 @@ __BEGIN_DECLS
 #define SYS_KILL 38
 #define SYS_SIGNAL 39
 #define SYS_SIGNAL_DONE 40
+#define SYS_TCSETPGRP 41
+#define SYS_GET_PID 42
 
 __END_DECLS
 

libc/unistd.cpp

@@ -286,6 +286,18 @@ long syscall(long syscall, ...)
 			ret = Kernel::syscall(SYS_SIGNAL, signal, (uintptr_t)handler);
 			break;
 		}
+		case SYS_TCSETPGRP:
+		{
+			int fd = va_arg(args, int);
+			pid_t pgrp = va_arg(args, pid_t);
+			ret = Kernel::syscall(SYS_TCSETPGRP, fd, pgrp);
+			break;
+		}
+		case SYS_GET_PID:
+		{
+			ret = Kernel::syscall(SYS_GET_PID);
+			break;
+		}
 		case SYS_SIGNAL_DONE:
 			// Should not be called by an user
 			// fall through
@@ -438,6 +450,11 @@ int chdir(const char* path)
 	return syscall(SYS_SET_PWD, path);
 }
 
+pid_t getpid(void)
+{
+	return syscall(SYS_GET_PID);
+}
+
 uid_t getuid(void)
 {
 	return syscall(SYS_GET_UID);
@@ -487,3 +504,8 @@ int setregid(gid_t rgid, gid_t egid)
 {
 	return syscall(SYS_SET_REGID, rgid, egid);
 }
+
+int tcsetpgrp(int fildes, pid_t pgid_id)
+{
+	return syscall(SYS_TCSETPGRP, fildes, pgid_id);
+}