Kernel: Remove SYS_OPEN

This can be done with SYS_OPENAT with fd set to AT_FDCWD

userspace/libraries/LibC/fcntl.cpp

@@ -15,7 +15,7 @@ int open(const char* path, int oflag, ...)
 	mode_t mode = va_arg(args, mode_t);
 	va_end(args);
 
-	return syscall(SYS_OPEN, path, oflag, __UMASKED_MODE(mode));
+	return openat(AT_FDCWD, path, oflag, mode);
 }
 
 int openat(int fd, const char* path, int oflag, ...)

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

@@ -11,7 +11,6 @@ __BEGIN_DECLS
 	O(SYS_WRITE,			write)			\
 	O(SYS_TERMID,			termid)			\
 	O(SYS_CLOSE,			close)			\
-	O(SYS_OPEN,				open)			\
 	O(SYS_OPENAT,			openat)			\
 	O(SYS_SEEK,				seek)			\
 	O(SYS_TELL,				tell)			\

userspace/programs/DynamicLoader/main.cpp

@@ -557,7 +557,7 @@ static void handle_dynamic(LoadedElf& elf)
 		if (auto ret = syscall(SYS_REALPATH, path_buffer, realpath); ret < 0)
 			print_error_and_exit("realpath", ret);
 
-		int library_fd = syscall(SYS_OPEN, realpath, O_RDONLY);
+		int library_fd = syscall(SYS_OPENAT, AT_FDCWD, realpath, O_RDONLY);
 		if (library_fd < 0)
 			print_error_and_exit("could not open library", library_fd);
 
@@ -882,7 +882,7 @@ int _entry(int argc, char** argv, char** envp, int fd)
 		argc--;
 		argv++;
 
-		fd = syscall(SYS_OPEN, argv[0], O_RDONLY);
+		fd = syscall(SYS_OPENAT, AT_FDCWD, argv[0], O_RDONLY);
 		if (fd < 0)
 			print_error_and_exit("could not open program", fd);
 	}

userspace/programs/DynamicLoader/utils.cpp

@@ -68,7 +68,7 @@ static int s_random_fd;
 
 void init_random()
 {
-	s_random_fd = syscall(SYS_OPEN, "/dev/random", O_RDONLY);
+	s_random_fd = syscall(SYS_OPENAT, AT_FDCWD, "/dev/random", O_RDONLY);
 	if (s_random_fd < 0)
 		print_error_and_exit("could not open /dev/random", s_random_fd);
 }