[fs][v9fs] Add VirtIO 9p filesystem structure

Add the fundamental filesystem structure to attach a VirtualIO 9p
device. With the implementation of VirtIO 9p devices (lk/dev/virtio/9p),
we can use those APIs to connect to a shared folder as a LK filesystem.

Signed-off-by: Cody Wong <codycswong@google.com>

5 files changed, 184 insertions, 0 deletions

diff --git a/lib/fs/9p/include/lib/fs/9p.h b/lib/fs/9p/include/lib/fs/9p.h
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/lib/fs/9p/include/lib/fs/9p.h
diff --git a/lib/fs/9p/rules.mk b/lib/fs/9p/rules.mk
new file mode 100644
index 00000000..94a3891d
--- /dev/null
+++ b/lib/fs/9p/rules.mk
@@ -0,0 +1,13 @@
+LOCAL_DIR := $(GET_LOCAL_DIR)
+
+MODULE := $(LOCAL_DIR)
+
+MODULE_DEPS += \
+	lib/bio \
+	lib/fs \
+	dev/virtio/9p
+
+MODULE_SRCS += \
+	$(LOCAL_DIR)/v9fs.c
+
+include make/module.mk
diff --git a/lib/fs/9p/v9fs.c b/lib/fs/9p/v9fs.c
new file mode 100644
index 00000000..1d67258f
--- /dev/null
+++ b/lib/fs/9p/v9fs.c
@@ -0,0 +1,128 @@
+/*
+ * Copyright (c) 2024, Google Inc. All rights reserved.
+ * Author: codycswong@google.com (Cody Wong)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include <dev/virtio/9p.h>
+
+#include <stdlib.h>
+#include <string.h>
+#include <lk/trace.h>
+#include <lk/init.h>
+#include <lk/list.h>
+#include <lk/err.h>
+#include <lib/fs.h>
+#include <kernel/mutex.h>
+
+#include "v9fs_priv.h"
+
+#define LOCAL_TRACE 0
+
+status_t v9fs_mount(bdev_t *dev, fscookie **cookie)
+{
+    status_t ret;
+
+    LTRACEF("bdev (%p) cookie (%p)\n", dev, cookie);
+
+    v9fs_t *v9fs = calloc(1, sizeof(v9fs_t));
+
+    if (!v9fs)
+        return ERR_NO_MEMORY;
+
+    // initialize v9fs structure
+    v9fs->dev = virtio_9p_bdev_to_virtio_device(dev);
+    v9fs->bdev = dev;
+    v9fs->unused_fid = 0;
+    list_initialize(&v9fs->files);
+    list_initialize(&v9fs->dirs);
+    mutex_init(&v9fs->lock);
+    v9fs->root.fid = get_unused_fid(v9fs);
+
+    LTRACEF("v9fs->root.fid: %u\n", v9fs->root.fid);
+    // attach to the host
+    virtio_9p_msg_t tatt = {
+        .msg_type = P9_TATTACH,
+        .tag = P9_TAG_DEFAULT,
+        .msg.tattach = {
+            .fid = v9fs->root.fid,
+            .afid = P9_FID_NOFID,
+            .uname = "root",
+            .aname = V9P_MOUNT_ANAME,
+            .n_uname = P9_UNAME_NONUNAME,
+        }
+    };
+    virtio_9p_msg_t ratt = {};
+
+    if ((ret = virtio_9p_rpc(v9fs->dev, &tatt, &ratt)) != NO_ERROR)
+        goto err;
+
+    v9fs->root.qid = ratt.msg.rattach.qid;
+
+    virtio_9p_msg_destroy(&ratt);
+
+    *cookie = (fscookie *)v9fs;
+
+    return NO_ERROR;
+
+err:
+    LTRACEF("mount 9p dev (%s) failed: %d\n", dev->name, ret);
+
+    free(v9fs);
+    v9fs = NULL;
+    return ret;
+}
+
+status_t v9fs_unmount(fscookie *cookie)
+{
+    v9fs_t *v9fs = (v9fs_t *)cookie;
+
+    LTRACEF("v9fs (%p)\n", v9fs);
+
+    if (v9fs)
+        free(v9fs);
+
+    return 0;
+}
+
+static const struct fs_api v9fs_api = {
+    .format = NULL,
+    .fs_stat = NULL,
+
+    .mount = v9fs_mount,
+    .unmount = v9fs_unmount,
+    .open = NULL,
+    .create = NULL,
+    .remove = NULL,
+    .truncate = NULL,
+    .stat = NULL,
+    .read = NULL,
+    .write = NULL,
+    .close = NULL,
+
+    .mkdir = NULL,
+    .opendir = NULL,
+    .readdir = NULL,
+    .closedir = NULL,
+
+    .file_ioctl = NULL,
+};
+
+STATIC_FS_IMPL(9p, &v9fs_api);
diff --git a/lib/fs/9p/v9fs_priv.h b/lib/fs/9p/v9fs_priv.h
new file mode 100644
index 00000000..9120c605
--- /dev/null
+++ b/lib/fs/9p/v9fs_priv.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2024, Google Inc. All rights reserved.
+ * Author: codycswong@google.com (Cody Wong)
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include <dev/virtio/9p.h>
+#include <lib/fs.h>
+#include <lk/list.h>
+#include <kernel/mutex.h>
+
+typedef struct v9fs {
+    struct virtio_device *dev;
+    bdev_t *bdev;
+
+    uint32_t unused_fid;
+    v9fs_fid_t root;
+    mutex_t lock;
+
+    struct list_node files;
+    struct list_node dirs;
+} v9fs_t;
+
+status_t v9fs_mount(bdev_t *dev, fscookie **cookie);
+status_t v9fs_unmount(fscookie *cookie);
diff --git a/platform/qemu-virt-arm/rules.mk b/platform/qemu-virt-arm/rules.mk
index eb00bda1..34019338 100644
--- a/platform/qemu-virt-arm/rules.mk
+++ b/platform/qemu-virt-arm/rules.mk
@@ -36,6 +36,7 @@ MODULE_DEPS += \
     dev/virtio/9p \
     lib/cbuf \
     lib/fdtwalk \
+    lib/fs/9p \
 
 GLOBAL_DEFINES += \
     MEMBASE=$(MEMBASE) \