Kernel/LibC: Implement SYS_ISATTY and isatty()

kernel/include/kernel/Process.h

@@ -162,6 +162,8 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_smo_delete(SharedMemoryObjectManager::Key);
 		BAN::ErrorOr<long> sys_smo_map(SharedMemoryObjectManager::Key);
 
+		BAN::ErrorOr<long> sys_isatty(int fildes);
+
 		BAN::ErrorOr<long> sys_tty_ctrl(int fildes, int command, int flags);
 
 		BAN::ErrorOr<long> sys_signal(int, void (*)(int));

kernel/kernel/Process.cpp

@@ -1433,6 +1433,15 @@ namespace Kernel
 		return m_mapped_regions.back()->vaddr();
 	}
 
+	BAN::ErrorOr<long> Process::sys_isatty(int fildes)
+	{
+		LockGuard _(m_process_lock);
+		auto inode = TRY(m_open_file_descriptors.inode_of(fildes));
+		if (!inode->is_tty())
+			return BAN::Error::from_errno(ENOTTY);
+		return 0;
+	}
+
 	BAN::ErrorOr<long> Process::sys_tty_ctrl(int fildes, int command, int flags)
 	{
 		LockGuard _(m_process_lock);

libc/include/sys/syscall.h

@@ -77,6 +77,7 @@ __BEGIN_DECLS
 	O(SYS_SMO_CREATE,		smo_create)		\
 	O(SYS_SMO_DELETE,		smo_delete)		\
 	O(SYS_SMO_MAP,			smo_map)		\
+	O(SYS_ISATTY,			isatty)			\
 
 enum Syscall
 {

libc/unistd.cpp

@@ -114,6 +114,11 @@ int dup2(int fildes, int fildes2)
 	return syscall(SYS_DUP2, fildes, fildes2);
 }
 
+int isatty(int fildes)
+{
+	return syscall(SYS_ISATTY, fildes) >= 0;
+}
+
 int execl(const char* pathname, const char* arg0, ...)
 {
 	if (arg0 == nullptr)