4 files changed, 24 insertions, 1 deletions
diff --git a/src/kernel/fd.c b/src/kernel/fd.c
index 77fea05..810cdb7 100644
--- a/src/kernel/fd.c
+++ b/src/kernel/fd.c
@@ -7,8 +7,11 @@ static int fdop_special_tty(struct fdop_args *args);
 
 int fdop_dispatch(struct fdop_args args) {
 	switch(args.fd->type) {
-		case FD_EMPTY:
+		case FD_EMPTY: {
+			if (args.type == FDOP_MOUNT) // mounting an empty fd is allowed
+				return 0;
 			return -1;
+		}
 		case FD_SPECIAL_TTY:
 			return fdop_special_tty(&args);
 		default:
@@ -18,6 +21,9 @@ int fdop_dispatch(struct fdop_args args) {
 
 static int fdop_special_tty(struct fdop_args *args) {
 	switch(args->type) {
+		case FDOP_MOUNT:
+			return 0; // no special action needed
+
 		case FDOP_READ:
 			return -1; // input not implemented yet
 
diff --git a/src/kernel/fd.h b/src/kernel/fd.h
index b35c979..bcc9902 100644
--- a/src/kernel/fd.h
+++ b/src/kernel/fd.h
@@ -17,6 +17,7 @@ struct fd {
 
 
 enum fdop { // describes the operations which can be done on file descriptors
+	FDOP_MOUNT, // also closes the original fd
 	FDOP_READ,
 	FDOP_WRITE,
 	FDOP_CLOSE,
@@ -26,6 +27,9 @@ struct fdop_args {
 	enum fdop type;
 	struct fd *fd;
 	union {
+		struct { // FDOP_MOUNT
+			struct mount *target;
+		} mnt;
 		struct { // FDOP_READ, FDOP_WRITE
 			user_ptr ptr;
 			size_t len;
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index bf17fd3..737484d 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -104,8 +104,10 @@ int _syscall_fd_mount(fd_t fd, const user_ptr path, int len) {
 	struct virt_iter iter;
 	struct vfs_mount *mount;
 	char *path_buf;
+	int res;
 
 	if (len > PATH_MAX) return -1;
+	if (fd < 0 || fd >= FD_MAX) return -1;
 
 	// copy the path to the kernel
 	path_buf = kmalloc(len);
@@ -124,10 +126,19 @@ int _syscall_fd_mount(fd_t fd, const user_ptr path, int len) {
 	mount->prev = process_current->mount;
 	mount->prefix = path_buf;
 	mount->prefix_len = len;
+	memcpy(&mount->fd, &process_current->fds[fd], sizeof(struct fd));
+
+	res = fdop_dispatch((struct fdop_args){
+			.type = FDOP_MOUNT,
+			.fd = &process_current->fds[fd],
+			.mnt = {mount},
+		});
+	if (res < 0) goto fail;
 	process_current->mount = mount;
 	return 0;
 fail:
 	kfree(path_buf);
+	kfree(mount);
 	return -1;
 }
 
diff --git a/src/kernel/vfs/mount.h b/src/kernel/vfs/mount.h
index b99f97e..3e9d8ae 100644
--- a/src/kernel/vfs/mount.h
+++ b/src/kernel/vfs/mount.h
@@ -1,7 +1,9 @@
 #pragma once
+#include <kernel/fd.h>
 
 struct vfs_mount {
 	struct vfs_mount *prev;
 	char *prefix;
 	size_t prefix_len;
+	struct fd fd;
 };