kern: fs: Add initial tmpfs implementation

Supported VOPs as of now:

- lookup()
- create()
- reclaim()

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

3 files changed, 253 insertions, 1 deletions

diff --git a/src/sys/fs/tmpfs.c b/src/sys/fs/tmpfs.c
new file mode 100644
index 0000000..4a5c607
--- /dev/null
+++ b/src/sys/fs/tmpfs.c
@@ -0,0 +1,250 @@
+/*
+ * Copyright (c) 2025 Ian Marco Moffett and L5 engineers
+ * 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 the project 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.
+ */
+
+#include <sys/types.h>
+#include <sys/mount.h>
+#include <sys/syslog.h>
+#include <sys/errno.h>
+#include <sys/queue.h>
+#include <sys/param.h>
+#include <os/vnode.h>
+#include <os/kalloc.h>
+#include <string.h>
+
+#define TMPFS_NAMEMAX 128
+#define TMPFS_INIT_SIZE 8
+
+/*
+ * Represents a single tmpfs node
+ */
+struct tmpfs_node {
+    char name[TMPFS_NAMEMAX];
+    char *data;
+    size_t len;
+    int ref;
+    TAILQ_ENTRY(tmpfs_node) link;
+};
+
+#define tmpfs_ref(TMP_NODEP) \
+    atomic_inc_int(&(TMP_NODEP)->ref)
+
+static TAILQ_HEAD(, tmpfs_node) tmpfs;
+static struct vop tmpfs_vops;
+
+/*
+ * Create a new tmpfs node
+ *
+ * @name: Name of node to create
+ * @np_res: Result pointer is written here
+ *
+ * Returns zero on success, otherwise a less than
+ * zero value on failure
+ */
+static int
+tmpfs_new(const char *name, struct tmpfs_node **np_res)
+{
+    struct tmpfs_node *np;
+    size_t name_len;
+
+    if (name == NULL) {
+        return -EINVAL;
+    }
+
+    name_len = strlen(name);
+    if (name_len > sizeof(np->name) - 1) {
+        return -ENAMETOOLONG;
+    }
+
+    np = kalloc(sizeof(*np));
+    if (np == NULL) {
+        return -ENOMEM;
+    }
+
+    memset(np, 0, sizeof(*np));
+    np->data = kalloc(TMPFS_INIT_SIZE);
+    if (np->data == NULL) {
+        kfree(np);
+        return -ENOMEM;
+    }
+
+    np->len = TMPFS_INIT_SIZE;
+    np->ref = 1;
+    memset(np->data, 0, TMPFS_INIT_SIZE);
+    memcpy(np->name, name, name_len);
+
+    if (np_res != NULL) {
+        *np_res = np;
+    }
+
+    TAILQ_INSERT_TAIL(&tmpfs, np, link);
+    return 0;
+}
+
+/*
+ * Lookup a tmpfs node by name
+ *
+ * @name: Name to lookup
+ * @np_res: Result is written here
+ */
+static int
+tmpfs_byname(const char *name, struct tmpfs_node **np_res)
+{
+    struct tmpfs_node *npcur;
+    int retval = -ENOENT;
+
+    if (name == NULL || np_res == NULL) {
+        return -EINVAL;
+    }
+
+    TAILQ_FOREACH(npcur, &tmpfs, link) {
+        if (npcur == NULL) {
+            continue;
+        }
+
+        if (strcmp(npcur->name, name) == 0) {
+            retval = 0;
+            *np_res = npcur;
+            break;
+        }
+    }
+
+    return retval;
+}
+
+/*
+ * VFS tmpfs lookup callback
+ */
+static int
+tmpfs_lookup(struct vop_lookup_args *args)
+{
+    struct tmpfs_node *np;
+    struct vnode *vp;
+    int error;
+
+    /* Sanity checks */
+    if (args == NULL)
+        return -EINVAL;
+    if (args->name == NULL)
+        return -EINVAL;
+    if (args->vpp == NULL)
+        return -EINVAL;
+
+    error = tmpfs_byname(args->name, &np);
+    if (error < 0) {
+        return error;
+    }
+
+    error = vfs_valloc(&vp, VTYPE_FILE, 0);
+    if (error < 0) {
+        return error;
+    }
+
+    /* Ref that node and give it */
+    tmpfs_ref(np);
+    vp->data = np;
+    vp->vops = &tmpfs_vops;
+    *args->vpp = vp;
+    return 0;
+}
+
+/*
+ * Create a tmpfs node
+ */
+static int
+tmpfs_create(struct vop_create_args *args)
+{
+    struct nameidata *ndp;
+    struct tmpfs_node *np = NULL;
+
+    if (args == NULL) {
+        return -EINVAL;
+    }
+
+    if ((ndp = args->ndp) == NULL) {
+        return -EINVAL;
+    }
+
+    /* Does it already exist? */
+    if (tmpfs_byname(ndp->path, &np) == 0) {
+        return -EEXIST;
+    }
+
+    return tmpfs_new(ndp->path, NULL);
+}
+
+/*
+ * Initialize the temporary filesystem
+ */
+static int
+tmpfs_init(struct fs_info *fip)
+{
+    TAILQ_INIT(&tmpfs);
+    return 0;
+}
+
+/*
+ * Mount the filesystem
+ */
+static int
+tmpfs_mount(struct fs_info *fip, struct mount_args *margs)
+{
+    int error;
+    struct vnode *vp;
+
+    if (fip == NULL || margs == NULL) {
+        return -1;
+    }
+
+    /* Allocate a vnode for this mountpoint */
+    error = vfs_valloc(&margs->vp_res, VTYPE_DIR, 0);
+    if (error < 0) {
+        return error;
+    }
+
+    vp = margs->vp_res;
+    vp->vops = &tmpfs_vops;
+    return 0;
+}
+
+static int
+tmpfs_reclaim(struct vnode *vp, int flags)
+{
+    return 0;
+}
+
+static struct vop tmpfs_vops = {
+    .lookup = tmpfs_lookup,
+    .create = tmpfs_create,
+    .reclaim = tmpfs_reclaim
+};
+
+struct vfsops g_tmpfs_vfsops = {
+    .init = tmpfs_init,
+    .mount = tmpfs_mount,
+};
diff --git a/src/sys/include/sys/mount.h b/src/sys/include/sys/mount.h
index 4a190a4..5f6fa6b 100644
--- a/src/sys/include/sys/mount.h
+++ b/src/sys/include/sys/mount.h
@@ -42,6 +42,7 @@
  */
 #define MOUNT_INITRD "initrd"   /* Initial ramdisk */
 #define MOUNT_DEVFS  "devfs"    /* Device filesystem */
+#define MOUNT_TMPFS  "tmpfs"    /* Temporary filesystem */
 
 /*
  * The mount system call
@@ -66,6 +67,7 @@ struct mount;
 /* Filesystem vfsops */
 extern struct vfsops g_omar_vfsops;
 extern struct vfsops g_devfs_vfsops;
+extern struct vfsops g_tmpfs_vfsops;
 
 /*
  * Represents a mountpoint
@@ -133,7 +135,6 @@ struct fs_info {
  */
 #define FS_ATTR_IMAGE BIT(0)    /* Is an image kind e.g., OSMORA OMAR */
 
-
 /*
  * VFS operations vector
  *
diff --git a/src/sys/os/vfs_init.c b/src/sys/os/vfs_init.c
index 90747d6..1b6f815 100644
--- a/src/sys/os/vfs_init.c
+++ b/src/sys/os/vfs_init.c
@@ -40,6 +40,7 @@
 static struct fs_info fstab[] = {
     { MOUNT_INITRD, &g_omar_vfsops, 0 },
     { MOUNT_DEVFS, &g_devfs_vfsops, 0 },
+    { MOUNT_TMPFS, &g_tmpfs_vfsops, 0 }
 };
 
 /*