kernel: Add initial VFS implementation

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

1 files changed, 193 insertions, 0 deletions

diff --git a/sys/kern/vfs_subr.c b/sys/kern/vfs_subr.c
new file mode 100644
index 0000000..04b644e
--- /dev/null
+++ b/sys/kern/vfs_subr.c
@@ -0,0 +1,193 @@
+/*
+ * Copyright (c) 2023-2024 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.
+ */
+
+#include <sys/types.h>
+#include <sys/vfs.h>
+#include <sys/errno.h>
+#include <sys/mount.h>
+#include <vm/dynalloc.h>
+#include <string.h>
+
+/* FNV-1a defines */
+#define FNV_OFFSET 14695981039346656037ULL
+#define FNV_PRIME 1099511628211ULL
+
+/*
+ * 32-bit FNV-1a hash function
+ * https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function
+ */
+static size_t
+vfs_hash(const char *data)
+{
+    size_t hash = FNV_OFFSET;
+    const char *p = data;
+
+    while (*p) {
+        hash ^= (size_t)(uint8_t)(*p);
+        hash *= FNV_PRIME;
+        ++p;
+    }
+
+    return hash;
+}
+
+/*
+ * Hashes a path
+ *
+ * @path: Path to hash.
+ *
+ * Returns 0 on failure, non-zero return values
+ * are valid.
+ */
+size_t
+vfs_hash_path(const char *path)
+{
+    char *name = NULL;
+    size_t i = 0, hash = 0;
+
+    if (strcmp(path, "/") == 0 || !vfs_is_valid_path(path)) {
+        return 0;
+    } else if (*path != '/') {
+        return 0;
+    }
+
+    do {
+        name = vfs_get_fname_at(path, i++);
+        if (name != NULL)
+            hash += vfs_hash(name);
+    } while (name != NULL);
+
+    return hash;
+}
+
+
+/*
+ * This function checks if a path is valid.
+ *
+ * @path: Path to check.
+ *
+ * Returns true if valid, otherwise false.
+ */
+bool
+vfs_is_valid_path(const char *path)
+{
+    const char *ptr = path;
+    char c;
+
+    while (*ptr != '\0') {
+        c = *(ptr++);
+        switch (c) {
+        case '/':
+        case '-':
+        case '_':
+            /* Valid char, can continue */
+            continue;
+        default:
+            /*
+             * This could be an alphabetical or "numeric" char which
+             * is valid. We want to handle this too. To make things
+             * easier we'll OR the char by 0x20 to convert it to
+             * lowercase if it is alphabetical.
+             */
+            c |= 0x20;
+            if (c >= 'a' && c <= 'z')
+                continue;
+            else if (c >= '0' && c <= '9')
+                continue;
+
+            /* We got an invalid char */
+            return false;
+        }
+    }
+
+    return true;
+}
+
+/*
+ * Allocates a vnode
+ *
+ * @vnode: Pointer to vnode pointer where newly allocated
+ *         vnode will be stored.
+ *
+ * @mp: Mountpoint this vnode is associated with.
+ * @type: Vnode type.
+ *
+ * This function will return 0 upon success and < 0 on failure.
+ */
+int
+vfs_alloc_vnode(struct vnode **vnode, struct mount *mp, int type)
+{
+    struct vnode *new_vnode = dynalloc(sizeof(struct vnode));
+
+    if (new_vnode == NULL) {
+        return -ENOMEM;
+    }
+
+    memset(new_vnode, 0, sizeof(struct vnode));
+    new_vnode->type = type;
+    new_vnode->mp = mp;
+
+    *vnode = new_vnode;
+    return 0;
+}
+
+/*
+ * This function mounts a `mount' structure
+ * at a specific path.
+ *
+ * @mp_out: Where to store copy of new mountpoint (NULL if none)
+ * @path: Path to mount on.
+ * @mnt_flags: Mount flags (MNT_* from sys/mount.h)
+ *
+ * Returns 0 upon success, otherwise a < 0 value.
+ *
+ * XXX: This function assumes the mountpoint has its mount
+ *      routine set in its vfsops.
+ */
+int
+vfs_mount(struct mount **mp_out, const char *path, int mnt_flags)
+{
+    struct mount *mp;
+    int cache_status;
+
+    mp = dynalloc(sizeof(struct mount));
+    if (mp == NULL) {
+        return -ENOMEM;
+    }
+
+    mp->flags = mnt_flags;
+    cache_status = vfs_cache_mp(mp, path);
+
+    if (cache_status != 0) {
+        return cache_status;
+    }
+
+    *mp_out = mp;
+    return 0;
+}