vfs: Add devtmpfs + memfiles

fs/devtmpfs.c

@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: ISC
+
+#include <zinnia/assert.h>
+#include <zinnia/chardev.h>
+#include <zinnia/ident.h>
+#include <zinnia/vfs.h>
+
+static struct vfs_mount* dev_mount;
+
+struct vfs_path devtmpfs_root() {
+    return vfs_path_clone((struct vfs_path){.mount = dev_mount, .entry = dev_mount->root});
+}
+
+static errno_t devtmpfs_mount(
+    const struct vfs_filesystem* fs,
+    enum mount_flags flags,
+    void* arg,
+    struct vfs_mount** out
+) {
+    return vfs_mount_new(flags, dev_mount->root, out);
+}
+
+static const struct vfs_filesystem devtmpfs = {
+    .name = "devtmpfs",
+    .mount = devtmpfs_mount,
+};
+
+static void devtmpfs_stage_init(struct boot_info* info) {
+    errno_t status = vfs_mount("tmpfs", 0, nullptr, &dev_mount);
+    assert(status == 0, "Unable to create the devtmpfs (%i)", status);
+
+    status = vfs_register_filesystem(&devtmpfs);
+    assert(status == 0, "Unable to register the devtmpfs (%i)", status);
+}
+
+INIT_TASK(devtmpfs_stage, "fs.devtmpfs", devtmpfs_stage_init);
+INIT_DEPENDS(devtmpfs_stage, vfs_stage);
+
+static void devtmpfs_mount_stage_init(struct boot_info* info) {
+    // Create /dev.
+    struct vfs_path root = vfs_get_root();
+    errno_t status = vfs_mkdir(root, root, "/dev", 0755, ident_kernel());
+    assert(status == 0 || status == EEXIST, "Unable to create /dev (%i)", status);
+
+    // Get /dev.
+    struct vfs_path target;
+    status = vfs_path_lookup(root, root, "/dev", ident_kernel(), VFS_LOOKUP_MUST_EXIST, &target);
+    vfs_path_drop(root);
+    assert(status == 0, "Unable to look up /dev (%i)", status);
+
+    // Prepare a devtmpfs for mounting.
+    struct vfs_mount* mount;
+    status = vfs_mount("devtmpfs", 0, nullptr, &mount);
+    assert(status == 0, "Unable to mount the devtmpfs (%i)", status);
+
+    // Mount it on /dev.
+    status = vfs_path_mount(target, mount);
+    assert(status == 0, "Unable to mount the devtmpfs on /dev (%i)", status);
+    vfs_mount_unref(mount);
+    vfs_path_drop(target);
+}
+
+INIT_TASK(devtmpfs_mount_stage, "fs.devtmpfs.mount", devtmpfs_mount_stage_init);
+INIT_DEPENDS(devtmpfs_mount_stage, devtmpfs_stage);

fs/meson.build

@@ -1,6 +1,7 @@
 kernel_sources += files(
     'anon.c',
     'cache.c',
+    'devtmpfs.c',
     'file.c',
     'ident.c',
     'init.c',