kern: vfs: Add initial vfsops, and mount code

This commit introduces the groundwork for mountpoints, filesystems and
the VFS as a whole. OMAR is now initialized as its own filesystem by the
VFS

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

6 files changed, 404 insertions, 8 deletions

diff --git a/src/sys/include/os/vfs.h b/src/sys/include/os/vfs.h
new file mode 100644
index 0000000..ec7eb77
--- /dev/null
+++ b/src/sys/include/os/vfs.h
@@ -0,0 +1,57 @@
+/*
+ * 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.
+ */
+
+#ifndef _OS_VFS_H_
+#define _OS_VFS_H_ 1
+
+#include <sys/types.h>
+#include <sys/mount.h>
+
+/*
+ * Initialize the virtual filesystem
+ * layer
+ *
+ * Returns zero on success, otherwise a less
+ * than zero value on failure.
+ */
+int vfs_init(void);
+
+/*
+ * Get a VFS file table entry by index.
+ *
+ * @index: Index to desired entry
+ * @resp: Result pointer is written here
+ *
+ * Returns zero on success and the entry being
+ * found, otherwise a less than zero failure if
+ * the entry has not been found.
+ */
+int vfs_by_index(uint16_t index, struct fs_info **resp);
+
+#endif  /* !_OS_VFS_H_ */
diff --git a/src/sys/include/sys/mount.h b/src/sys/include/sys/mount.h
new file mode 100644
index 0000000..c2beb8d
--- /dev/null
+++ b/src/sys/include/sys/mount.h
@@ -0,0 +1,137 @@
+/*
+ * 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.
+ */
+
+#ifndef _SYS_MOUNT_H_
+#define _SYS_MOUNT_H_
+
+#include <sys/queue.h>
+#include <sys/types.h>
+#include <os/vnode.h>
+
+#if defined(_KERNEL)
+
+/*
+ * Number of bytes allowed in a filesystem
+ * name including the null termination
+ */
+#define FSNAME_MAX 16
+
+/*
+ * Mount filesystem string names
+ */
+#define MOUNT_INITRD "initrd"   /* Initial ramdisk */
+
+/* Forward declarations */
+struct vfsops;
+struct mount;
+
+/* Filesystem vfsops */
+extern struct vfsops g_omar_vfsops;
+
+/*
+ * Represents a mountpoint
+ */
+struct mount {
+    struct vnode *vp;
+    const char *name;
+    TAILQ_ENTRY(mount) link;
+    TAILQ_HEAD(, mount) buckets;
+};
+
+/*
+ * Represents a list of mountpoints
+ *
+ * @i: Initialized (set if initialized)
+ */
+struct mountlist {
+    uint8_t i : 1;
+    TAILQ_HEAD(, mount) list;
+};
+/*
+ * Arguments for mount()
+ *
+ * @source: Specifies the source filesystem to mount
+ * @target: Specifies the location to mount source
+ * @fstype: File system type
+ * @data: Filesystem specific data
+ */
+struct mount_args {
+    const char *source;
+    const char *target;
+    const char *fstype;
+    const void *data;
+};
+
+/*
+ * Represents information about a filesystem
+ *
+ * @name: Filesystem type name
+ * @vfsops: VFS operations vector
+ * @refcount: Mount count of this type
+ */
+struct fs_info {
+    char name[FSNAME_MAX];
+    const struct vfsops *vfsops;
+    int refcount;
+};
+
+/*
+ * VFS operations vector
+ *
+ * @init: Initialize the filesystem
+ * @mount: Mount a filesystem
+ */
+struct vfsops {
+    int(*init)(struct fs_info *fip);
+    int(*mount)(struct fs_info *fip, struct mount_args *margs);
+};
+
+/*
+ * Mount a specific filesystem
+ *
+ * @margs: Mount arguments
+ * @flags: Mount flags
+ *
+ * Returns zero on success, otherwise a less than zero
+ * failure upon failure.
+ */
+int mount(struct mount_args *margs, uint32_t flags);
+
+/*
+ * Initialize a mountpoint to a known state
+ *
+ * @mp: Pointer to mountlist [if NULL, use root]
+ *
+ * Returns zero on success, otherwise a less than
+ * zero value on failure.
+ */
+int mountlist_init(struct mountlist *mlp);
+
+#endif  /* !_KERNEL */
+#endif  /* !_SYS_MOUNT_H_ */
diff --git a/src/sys/os/os_init.c b/src/sys/os/os_init.c
index 8480a3f..7628574 100644
--- a/src/sys/os/os_init.c
+++ b/src/sys/os/os_init.c
@@ -32,9 +32,11 @@
 #include <sys/sysvar.h>
 #include <sys/syslog.h>
 #include <sys/proc.h>
+#include <sys/mount.h>
 #include <sys/cpuvar.h>
 #include <os/sched.h>
 #include <os/elfload.h>
+#include <os/vfs.h>
 #include <acpi/acpi.h>
 #include <io/cons/cons.h>
 #include <vm/vm.h>
@@ -73,6 +75,10 @@ main(void)
     cpu_init(&g_bsp);
     bsp_ap_startup();
 
+    /* Mount root */
+    vfs_init();
+    mountlist_init(NULL);
+
     sched_init();
     core = this_core();
     proc_init(&g_rootproc, 0);
diff --git a/src/sys/os/os_omar.c b/src/sys/os/os_omar.c
index 63493b0..186ca57 100644
--- a/src/sys/os/os_omar.c
+++ b/src/sys/os/os_omar.c
@@ -32,6 +32,7 @@
 #include <sys/errno.h>
 #include <sys/bootvars.h>
 #include <sys/cdefs.h>
+#include <sys/mount.h>
 #include <sys/panic.h>
 #include <sys/syslog.h>
 #include <os/omar.h>
@@ -143,7 +144,7 @@ initrd_get_file(const char *path, struct initrd_node *res)
  * Initialize the initrd
  */
 static int
-initrd_init(void)
+initrd_init(struct fs_info *fip)
 {
     struct bootvars bootvars;
     struct bootvar_io *bvio = NULL;
@@ -187,13 +188,6 @@ initrd_open(const char *path, char **res)
         return -ENOENT;
     }
 
-    if (__initrd_root == NULL) {
-        error = initrd_init();
-        if (error < 0) {
-            panic("initrd: failed to setup initrd\n");
-        }
-    }
-
     error = initrd_get_file(path, &node);
     if (error < 0) {
         printf("initrd: failed to open '%s'\n", path);
@@ -203,3 +197,7 @@ initrd_open(const char *path, char **res)
     *res = node.data;
     return node.size;
 }
+
+struct vfsops g_omar_vfsops = {
+    .init = initrd_init
+};
diff --git a/src/sys/os/vfs_init.c b/src/sys/os/vfs_init.c
new file mode 100644
index 0000000..b40b74d
--- /dev/null
+++ b/src/sys/os/vfs_init.c
@@ -0,0 +1,79 @@
+/*
+ * 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/errno.h>
+#include <sys/param.h>
+#include <sys/mount.h>
+#include <os/vfs.h>
+
+/*
+ * The filesystem table
+ */
+static struct fs_info fstab[] = {
+    { MOUNT_INITRD, &g_omar_vfsops, 0 }
+};
+
+/*
+ * Get entry by index
+ */
+int
+vfs_by_index(uint16_t index, struct fs_info **resp)
+{
+    if (resp == NULL) {
+        return -EINVAL;
+    }
+
+    if (index >= NELEM(fstab)) {
+        return -ENOENT;
+    }
+
+    *resp = &fstab[index];
+    return 0;
+}
+
+int
+vfs_init(void)
+{
+    const struct vfsops *vfsops;
+    struct fs_info *fip;
+    size_t nelem = NELEM(fstab);
+
+    /*
+     * Initialize each filesystem
+     */
+    for (size_t i = 0; i < nelem; ++i) {
+        fip = &fstab[i];
+        vfsops = fip->vfsops;
+        if (vfsops->init != NULL) {
+            vfsops->init(fip);
+        }
+    }
+    return 0;
+}
diff --git a/src/sys/os/vfs_mount.c b/src/sys/os/vfs_mount.c
new file mode 100644
index 0000000..f1d7ffd
--- /dev/null
+++ b/src/sys/os/vfs_mount.c
@@ -0,0 +1,119 @@
+/*
+ * 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/syslog.h>
+#include <sys/errno.h>
+#include <sys/cdefs.h>
+#include <sys/mount.h>
+#include <os/vfs.h>
+#include <string.h>
+
+/*
+ * Represents the root mountlist, every other
+ * mountpoint is put here.
+ */
+static struct mountlist root;
+
+/*
+ * Mount a filesystem
+ */
+int
+mount(struct mount_args *margs, uint32_t flags)
+{
+    const struct vfsops *vfsops;
+    struct fs_info *fip = NULL;
+    int error;
+
+    if (margs == NULL) {
+        return -EINVAL;
+    }
+
+    /* XXX: Unused as of now */
+    (void)margs->source;
+    (void)margs->target;
+    (void)margs->data;
+
+    /* XXX: Requires fstype for now */
+    if (margs->fstype == NULL) {
+        return -ENOENT;
+    }
+
+    /*
+     * Now we go through each entry of the filesystem
+     * table and if it matches the filesystem type,
+     * we're good.
+     */
+    for (uint8_t i = 0;; ++i) {
+        error = vfs_by_index(i, &fip);
+        if (error != 0) {
+            return -ENOENT;
+        }
+
+        if (strcmp(fip->name, margs->fstype) == 0) {
+            break;
+        }
+    }
+
+
+    /* Sanity check */
+    if (__unlikely(fip == NULL)) {
+        printf("mount: got NULL filesystem info\n");
+        return -ENOENT;
+    }
+
+    vfsops = fip->vfsops;
+    if (__unlikely(vfsops->mount == NULL)) {
+        printf("mount: fs does not implement mount!\n");
+        return -EIO;
+    }
+
+    vfsops->mount(fip, margs);
+    return 0;
+}
+
+/*
+ * Initialize the mountlist
+ */
+int
+mountlist_init(struct mountlist *mlp)
+{
+    if (mlp == NULL) {
+        mlp = &root;
+    }
+
+    /* Don't initialize twice */
+    if (mlp->i) {
+        return -EPERM;
+    }
+
+    TAILQ_INIT(&mlp->list);
+    mlp->i = 1;
+    return 0;
+}