--- /dev/null
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * This file is part of libmount from util-linux project.
+ *
+ * Copyright (C) 2022 Karel Zak <kzak@redhat.com>
+ *
+ * libmount is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ *
+ * This is fsconfig/fsopen based mount.
+ *
+ * Please, see the comment in libmount/src/hooks.c to understand how hooks work.
+ *
+ * Operations: functions and STAGE, all is prepared in hook_prepare():
+ *
+ * mount:
+ * - fsopen PRE
+ * - fsmount MOUNT
+ * - mount_setattr MOUNT (VFS flags)
+ * - mount_move POST
+ * - mount_setattr POST (propagation)
+ *
+ * remount:
+ * - open_tree PRE
+ * - reconfigure MOUNT
+ * - mount_setattr MOUNT (VFS flags)
+ * - mount_setattr POST (propagation)
+ *
+ * propagation-only:
+ * - open_tree PRE
+ * - mount_setattr POST (propagation)
+ *
+ * move:
+ * - open_tree PRE
+ * - mount_move POST
+ *
+ * bind:
+ * - open_tree PRE (clone)
+ * - mount_setattr MOUNT (VFS flags)
+ * - mount_move POST
+ */
+
+#include "mountP.h"
+
+#include <inttypes.h>
+
+/*
+ * This hookset uses 'struct libmnt_sysapi' (mountP.h) as hookset data.
+ */
+static void free_hookset_data( struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs)
+{
+ struct libmnt_sysapi *api = mnt_context_get_hookset_data(cxt, hs);
+
+ if (!api)
+ return;
+ if (api->fd_fs >= 0)
+ close(api->fd_fs);
+ if (api->fd_tree >= 0)
+ close(api->fd_tree);
+
+ free(api);
+ mnt_context_set_hookset_data(cxt, hs, NULL);
+}
+
+/* global data, used by all callbacks */
+static struct libmnt_sysapi *new_hookset_data(
+ struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs)
+{
+ struct libmnt_sysapi *api = calloc(1, sizeof(struct libmnt_sysapi));
+
+ if (!api)
+ return NULL;
+ api->fd_fs = api->fd_tree = -1;
+
+ if (mnt_context_set_hookset_data(cxt, hs, api) != 0) {
+ /* probably ENOMEM problem */
+ free(api);
+ api = NULL;
+ }
+ return api;
+}
+
+/* de-initiallize this module */
+static int hookset_deinit(struct libmnt_context *cxt, const struct libmnt_hookset *hs)
+{
+ DBG(HOOK, ul_debugobj(hs, "deinit '%s'", hs->name));
+
+ /* remove all our hooks */
+ while (mnt_context_remove_hook(cxt, hs, 0, NULL) == 0);
+
+ /* free and remove global hookset data */
+ free_hookset_data(cxt, hs);
+
+ return 0;
+}
+
+static inline struct libmnt_sysapi *get_sysapi(struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs)
+{
+ return mnt_context_get_hookset_data(cxt, hs);
+}
+
+static int set_vfs_flags(int fd, struct libmnt_context *cxt, int recursive)
+{
+ struct libmnt_optlist *ol;
+ struct mount_attr attr = { .attr_clr = 0 };
+ unsigned int callflags = AT_EMPTY_PATH;
+ uint64_t mask = 0;
+ int rc;
+
+ ol= mnt_context_get_optlist(cxt);
+ if (!ol)
+ return -ENOMEM;
+
+ mnt_optlist_get_attrs(ol, &mask);
+ attr.attr_set = mask;
+ if (recursive)
+ callflags |= AT_RECURSIVE;
+
+ DBG(HOOK, ul_debug(" mount_setattr(set=0x%" PRIx64")", mask));
+ rc = mount_setattr(fd, "", callflags, &attr, sizeof(attr));
+ if (rc)
+ return -errno;
+
+ return 0;
+}
+
+static int is_recursive_bind(struct libmnt_context *cxt)
+{
+ struct libmnt_optlist *ol = mnt_context_get_optlist(cxt);
+
+ if (!ol)
+ return 0;
+
+ return mnt_optlist_is_rbind(ol);
+}
+
+static int hook_bind_attach(struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs,
+ void *data __attribute__((__unused__)))
+{
+ struct libmnt_sysapi *api;
+ const char *target;
+
+ DBG(HOOK, ul_debugobj(hs, "bind: attach"));
+
+ target = mnt_fs_get_target(cxt->fs);
+ if (!target)
+ return -EINVAL;
+
+ api = get_sysapi(cxt, hs);
+ if (!api || api->fd_tree <= 0)
+ return -EINVAL;
+
+ DBG(HOOK, ul_debugobj(hs, " move_mount(to=%s)", target));
+ if (move_mount(api->fd_tree, "", AT_FDCWD, target, MOVE_MOUNT_F_EMPTY_PATH))
+ return -errno;
+
+ return 0;
+}
+
+static int hook_bind_setflags(struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs,
+ void *data __attribute__((__unused__)))
+{
+ struct libmnt_sysapi *api;
+ int rc;
+
+ DBG(HOOK, ul_debugobj(hs, "bind: setting VFS"));
+
+ api = get_sysapi(cxt, hs);
+ if (!api || api->fd_tree <= 0)
+ return -EINVAL;
+
+ rc = set_vfs_flags(api->fd_tree, cxt, is_recursive_bind(cxt));
+ if (rc)
+ return rc;
+
+ return mnt_context_append_hook(cxt, hs,
+ MNT_STAGE_MOUNT_POST, NULL, hook_bind_attach);
+}
+
+/*
+static int hook_remount(struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs, void *data)
+{
+ return 0;
+}
+
+
+static int hook_move(struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs, void *data)
+{
+ return 0;
+}
+
+static int hook_propagation(struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs, void *data)
+{
+ return 0;
+}
+
+static int hook_newmount(struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs, void *data)
+{
+ return 0;
+}
+*/
+
+/*
+ * analyze library context and register hook to call mount-like syscalls
+ */
+static int hook_prepare(struct libmnt_context *cxt,
+ const struct libmnt_hookset *hs,
+ void *data __attribute__((__unused__)))
+{
+ int rc = 0, next_stage = 0;
+ int (*next_hook)(struct libmnt_context *, const struct libmnt_hookset *, void *) = NULL;
+ unsigned long flags = 0, open_flags = 0;
+ const char *tree_path = NULL, *src = NULL, *target = NULL;
+ struct libmnt_sysapi *api;
+
+ assert(cxt);
+ assert(hs == &hookset_mount);
+
+ DBG(HOOK, ul_debugobj(hs, "prepare new API mount"));
+
+ target = mnt_fs_get_target(cxt->fs);
+ if (!target)
+ return -EINVAL;
+
+ src = mnt_fs_get_srcpath(cxt->fs);
+
+ rc = mnt_context_get_mflags(cxt, &flags);
+ if (rc)
+ return rc;
+
+ api = new_hookset_data(cxt, hs);
+ if (!api)
+ return -ENOMEM;
+
+ open_flags = OPEN_TREE_CLOEXEC;
+
+ if (flags & MS_REMOUNT) {
+ DBG(HOOK, ul_debugobj(hs, " prepare remount"));
+ tree_path = target;
+ next_stage = MNT_STAGE_MOUNT;
+ /*next_hook = hook_remount;*/
+
+ } else if (flags & MS_BIND) {
+ DBG(HOOK, ul_debugobj(hs, " prepare bind"));
+ tree_path = src;
+ next_stage = MNT_STAGE_MOUNT;
+ next_hook = (flags & MNT_BIND_SETTABLE) ? hook_bind_setflags :
+ hook_bind_attach;
+ open_flags |= OPEN_TREE_CLONE;
+ if (is_recursive_bind(cxt))
+ open_flags |= AT_RECURSIVE;
+
+ } else if (flags & MS_MOVE) {
+ DBG(HOOK, ul_debugobj(hs, " prepare move"));
+ tree_path = src;
+ next_stage = MNT_STAGE_MOUNT_POST;
+ /*next_hook = hook_move;*/
+
+ } else if (mnt_context_propagation_only(cxt)) {
+ DBG(HOOK, ul_debugobj(hs, " prepare propagation change"));
+ tree_path = target;
+ next_stage = MNT_STAGE_MOUNT_POST;
+ /*next_hook = hook_propagation;*/
+
+ } else {
+ const char *type;
+
+ DBG(HOOK, ul_debugobj(hs, " prepare mount"));
+ next_stage = MNT_STAGE_MOUNT;
+ /*next_hook = hook_newmount;*/
+
+ type = mnt_fs_get_fstype(cxt->fs);
+ if (!type)
+ return -EINVAL;
+
+ DBG(HOOK, ul_debugobj(hs, "fsopen(%s)", type));
+ api->fd_fs = fsopen(type, FSOPEN_CLOEXEC);
+ if (api->fd_fs < 0)
+ goto nothing;
+ }
+
+ if (api->fd_fs == -1) {
+ if (!tree_path) {
+ DBG(HOOK, ul_debugobj(hs, "tree path undefined"));
+ return -EINVAL;
+ }
+ DBG(HOOK, ul_debugobj(hs, "open_tree(path=%s, flags=0x%lx)",
+ tree_path, open_flags));
+ api->fd_tree = open_tree(AT_FDCWD, tree_path, open_flags);
+ if (api->fd_tree <= 0)
+ goto nothing;
+ }
+
+ return mnt_context_append_hook(cxt, hs, next_stage, NULL, next_hook);
+nothing:
+ /* let's assume that fsopen/open_tree() is not supported */
+ DBG(HOOK, ul_debugobj(hs, " open fs/tree failed [errno=%d %m]", errno));
+ free_hookset_data(cxt, hs);
+ return 0;
+}
+
+const struct libmnt_hookset hookset_mount =
+{
+ .name = "__mount",
+
+ .firststage = MNT_STAGE_PREP,
+ .firstcall = hook_prepare,
+
+ .deinit = hookset_deinit
+};
projects / thirdparty / util-linux.git / commitdiff
