Kernel/LibC: Implement tcgetpgrp

kernel/include/kernel/Process.h

@@ -179,6 +179,7 @@ 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_tcgetpgrp(int fd);
 		BAN::ErrorOr<long> sys_tcsetpgrp(int fd, pid_t pgid);
 
 		BAN::ErrorOr<long> sys_termid(char*);

kernel/kernel/Process.cpp

@@ -2012,6 +2012,24 @@ namespace Kernel
 		return 0;
 	}
 
+	BAN::ErrorOr<long> Process::sys_tcgetpgrp(int fd)
+	{
+		LockGuard _(m_process_lock);
+
+		if (!m_controlling_terminal)
+			return BAN::Error::from_errno(ENOTTY);
+
+		auto inode = TRY(m_open_file_descriptors.inode_of(fd));
+		if (!inode->is_tty())
+			return BAN::Error::from_errno(ENOTTY);
+
+		auto* tty = static_cast<TTY*>(inode.ptr());
+		if (tty != m_controlling_terminal.ptr())
+			return BAN::Error::from_errno(ENOTTY);
+
+		return tty->foreground_pgrp();
+	}
+
 	BAN::ErrorOr<long> Process::sys_tcsetpgrp(int fd, pid_t pgrp)
 	{
 		LockGuard _(m_process_lock);

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

@@ -39,6 +39,7 @@ __BEGIN_DECLS
 	O(SYS_DUP,				dup)			\
 	O(SYS_DUP2,				dup2)			\
 	O(SYS_KILL,				kill)			\
+	O(SYS_TCGETPGRP,		tcgetpgrp)		\
 	O(SYS_TCSETPGRP,		tcsetpgrp)		\
 	O(SYS_GET_PID,			getpid)			\
 	O(SYS_GET_PGID,			getpgid)		\

userspace/libraries/LibC/unistd.cpp

@@ -483,6 +483,11 @@ pid_t getpgid(pid_t pid)
 	return syscall(SYS_GET_PGID, pid);
 }
 
+int tcgetpgrp(int fildes)
+{
+	return syscall(SYS_TCGETPGRP, fildes);
+}
+
 int seteuid(uid_t uid)
 {
 	return syscall(SYS_SET_EUID, uid);