kernel: Add initial support for tmpfs

Introduce the initial support for tmpfs, a readable and writable in-memory
filesystem.

Signed-off-by: Ian Moffett <ian@osmora.org>

2 files changed, 75 insertions, 0 deletions

diff --git a/sys/include/fs/tmpfs.h b/sys/include/fs/tmpfs.h
new file mode 100644
index 0000000..b2a5bbe
--- /dev/null
+++ b/sys/include/fs/tmpfs.h
@@ -0,0 +1,73 @@
+/*
+ * Copyright (c) 2023-2025 Ian Marco Moffett and the Osmora Team.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright notice,
+ *    this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. Neither the name of Hyra nor the names of its
+ *    contributors may be used to endorse or promote products derived from
+ *    this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _FS_TMPFS_H_
+#define _FS_TMPFS_H_
+
+#include <sys/types.h>
+#include <sys/limits.h>
+#include <sys/vnode.h>
+#include <sys/queue.h>
+#include <sys/spinlock.h>
+#include <vm/vm_obj.h>
+
+extern const struct vops g_tmpfs_vops;
+
+/* Tmpfs node types */
+#define TMPFS_NONE  (VNON)        /* No type */
+#define TMPFS_REG   (VREG)        /* Regular file [f] */
+#define TMPFS_DIR   (VDIR)        /* Directory    [d] */
+
+struct tmpfs_node;
+
+/*
+ * A tmpfs node represents an object within the
+ * tmpfs namespace such as a file, directory, etc.
+ *
+ * @rpath: /tmp/ relative path (for lookups)
+ * @type: The tmpfs node type [one-to-one to vtype]
+ * @len: Length of buffer
+ * @data: The backing file data
+ * @dirvp: Vnode of the parent node
+ * @vp: Vnode of the current node
+ * @lock: Lock protecting this node
+ */
+struct tmpfs_node {
+    char rpath[PATH_MAX];
+    uint8_t type;
+    size_t len;
+    void *data;
+    struct vnode *dirvp;
+    struct vnode *vp;
+    struct spinlock lock;
+    TAILQ_HEAD(, tmpfs_node) dirents;
+    TAILQ_ENTRY(tmpfs_node) link;
+};
+
+#endif  /* !_FS_TMPFS_H_ */
diff --git a/sys/include/sys/mount.h b/sys/include/sys/mount.h
index 1fcdbfa..636c7bf 100644
--- a/sys/include/sys/mount.h
+++ b/sys/include/sys/mount.h
@@ -47,6 +47,7 @@
 #define MOUNT_RAMFS "initramfs"
 #define MOUNT_DEVFS "devfs"
 #define MOUNT_CTLFS "ctlfs"
+#define MOUNT_TMPFS "tmpfs"
 
 struct vfsops;
 struct mount;
@@ -59,6 +60,7 @@ extern mountlist_t g_mountlist;
 extern const struct vfsops g_initramfs_vfsops;
 extern const struct vfsops g_devfs_vfsops;
 extern const struct vfsops g_ctlfs_vfsops;
+extern const struct vfsops g_tmpfs_vfsops;
 
 struct mount {
     char *name;