implement open() for FD_SPECIAL_TTY (`/tty`)

4 files changed, 42 insertions, 2 deletions

diff --git a/src/init/main.c b/src/init/main.c
index c08cf21..0e74e93 100644
--- a/src/init/main.c
+++ b/src/init/main.c
@@ -30,6 +30,7 @@ int main(void) {
 	fd = _syscall_fs_open(
 			multipageify("/tty"),
 			      sizeof("/tty") - 1);
+	// TODO don't dispatch /ttywhatever to the tty driver
 
 	if (fd < 0) {
 		_syscall_exit("couldn't open tty",
diff --git a/src/kernel/fd.c b/src/kernel/fd.c
index 810cdb7..e875061 100644
--- a/src/kernel/fd.c
+++ b/src/kernel/fd.c
@@ -24,6 +24,16 @@ static int fdop_special_tty(struct fdop_args *args) {
 		case FDOP_MOUNT:
 			return 0; // no special action needed
 
+		case FDOP_OPEN:
+			/* don't allow anything after the mount point
+			 * this is a file, not a directory
+			 * for example: open("/tty") is allowed. open("/tty/smth") isn't */
+			if (args->open.len == 0) {
+				args->open.target->type = FD_SPECIAL_TTY;
+				return 0;
+			}
+			return -1;
+
 		case FDOP_READ:
 			return -1; // input not implemented yet
 
diff --git a/src/kernel/fd.h b/src/kernel/fd.h
index bcc9902..c7c5182 100644
--- a/src/kernel/fd.h
+++ b/src/kernel/fd.h
@@ -18,6 +18,8 @@ struct fd {
 
 enum fdop { // describes the operations which can be done on file descriptors
 	FDOP_MOUNT, // also closes the original fd
+	FDOP_OPEN,  // when the file descriptor is mounted, open a file relative to it
+
 	FDOP_READ,
 	FDOP_WRITE,
 	FDOP_CLOSE,
@@ -30,6 +32,11 @@ struct fdop_args {
 		struct { // FDOP_MOUNT
 			struct mount *target;
 		} mnt;
+		struct { // FDOP_OPEN
+			struct fd *target;
+			const char *path; // relative to the mount point
+			size_t len;
+		} open;
 		struct { // FDOP_READ, FDOP_WRITE
 			user_ptr ptr;
 			size_t len;
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 737484d..1c0a687 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -70,9 +70,17 @@ fd_t _syscall_fs_open(const user_ptr path, int len) {
 	struct virt_iter iter;
 	struct vfs_mount *mount = process_current->mount;
 	static char buffer[PATH_MAX]; // holds the path
+	int fd, res;
 
 	if (len > PATH_MAX) return -1;
 
+	// find the first free fd
+	for (fd = 0; fd < FD_MAX; fd++) {
+		if (process_current->fds[fd].type == FD_EMPTY)
+			break;
+	}
+	if (fd == FD_MAX) return -1;
+
 	// copy the path to the kernel
 	virt_iter_new(&iter, path, len, process_current->pages, true, false);
 	while (virt_iter_next(&iter))
@@ -90,14 +98,28 @@ fd_t _syscall_fs_open(const user_ptr path, int len) {
 			break;
 	}
 
-	tty_write(buffer, len);
+	tty_write(buffer + mount->prefix_len, len - mount->prefix_len);
 	tty_const(" from mount ");
 	if (mount)
 		tty_write(mount->prefix, mount->prefix_len);
 	else
 		tty_const("[none]");
 
-	return -1;
+	if (!mount) return -1;
+
+	res = fdop_dispatch((struct fdop_args){
+			.type = FDOP_OPEN,
+			.fd = &mount->fd,
+			.open = {
+				.target = &process_current->fds[fd],
+				.path   = &buffer[mount->prefix_len],
+				.len    = len - mount->prefix_len,
+			}
+		});
+	if (res < 0)
+		return res;
+	else
+		return fd;
 }
 
 int _syscall_fd_mount(fd_t fd, const user_ptr path, int len) {