LibC/Kernel: Implement ttyname

kernel/include/kernel/Process.h

@@ -168,6 +168,7 @@ namespace Kernel
 		BAN::ErrorOr<long> sys_smo_delete(SharedMemoryObjectManager::Key);
 		BAN::ErrorOr<long> sys_smo_map(SharedMemoryObjectManager::Key);
 
+		BAN::ErrorOr<long> sys_ttyname(int fildes, char* storage);
 		BAN::ErrorOr<long> sys_isatty(int fildes);
 
 		BAN::ErrorOr<long> sys_tty_ctrl(int fildes, int command, int flags);

kernel/kernel/Process.cpp

@@ -1497,6 +1497,20 @@ namespace Kernel
 		return m_mapped_regions.back()->vaddr();
 	}
 
+	BAN::ErrorOr<long> Process::sys_ttyname(int fildes, char* storage)
+	{
+		LockGuard _(m_process_lock);
+		TRY(validate_pointer_access(storage, TTY_NAME_MAX));
+		auto inode = TRY(m_open_file_descriptors.inode_of(fildes));
+		if (!inode->is_tty())
+			return BAN::Error::from_errno(ENOTTY);
+		auto path = TRY(m_open_file_descriptors.path_of(fildes));
+		ASSERT(path.size() < TTY_NAME_MAX);
+		strncpy(storage, path.data(), path.size());
+		storage[path.size()] = '\0';
+		return 0;
+	}
+
 	BAN::ErrorOr<long> Process::sys_isatty(int fildes)
 	{
 		LockGuard _(m_process_lock);

userspace/libraries/LibC/include/limits.h

@@ -62,6 +62,7 @@ __BEGIN_DECLS
 #define PATH_MAX 256
 #define LOGIN_NAME_MAX 256
 #define HOST_NAME_MAX 255
+#define TTY_NAME_MAX PATH_MAX
 
 __END_DECLS
 

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

@@ -82,6 +82,7 @@ __BEGIN_DECLS
 	O(SYS_GETSOCKOPT,		getsockopt)		\
 	O(SYS_SETSOCKOPT,		setsockopt)		\
 	O(SYS_REALPATH,			realpath)		\
+	O(SYS_TTYNAME,			ttyname)		\
 
 enum Syscall
 {

userspace/libraries/LibC/unistd.cpp

@@ -488,3 +488,11 @@ char* getlogin(void)
 	endpwent();
 	return buffer;
 }
+
+char* ttyname(int fildes)
+{
+	static char storage[_POSIX_TTY_NAME_MAX];
+	if (syscall(SYS_TTYNAME, fildes, storage) == -1)
+		return nullptr;
+	return storage;
+}