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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0
 /*
  * Functions for working with device tree overlays
  *
  * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com>
  * Copyright (C) 2012 Texas Instruments Inc.
  */
 
 #define pr_fmt(fmt) "OF: overlay: " fmt
 
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
 #include <linux/of_fdt.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
 #include <linux/errno.h>
 #include <linux/slab.h>
 #include <linux/libfdt.h>
 #include <linux/err.h>
 #include <linux/idr.h>
 
 #include "of_private.h"
 
 /**
  * struct target - info about current target node as recursing through overlay
  * @np:         node where current level of overlay will be applied
  * @in_livetree:    @np is a node in the live devicetree
  *
  * Used in the algorithm to create the portion of a changeset that describes
  * an overlay fragment, which is a devicetree subtree.  Initially @np is a node
  * in the live devicetree where the overlay subtree is targeted to be grafted
  * into.  When recursing to the next level of the overlay subtree, the target
  * also recurses to the next level of the live devicetree, as long as overlay
  * subtree node also exists in the live devicetree.  When a node in the overlay
  * subtree does not exist at the same level in the live devicetree, target->np
  * points to a newly allocated node, and all subsequent targets in the subtree
  * will be newly allocated nodes.
  */
 struct target {
     struct device_node *np;
     bool in_livetree;
 };
 
 /**
  * struct fragment - info about fragment nodes in overlay expanded device tree
  * @target: target of the overlay operation
  * @overlay:    pointer to the __overlay__ node
  */
 struct fragment {
     struct device_node *overlay;
     struct device_node *target;
 };
 
 /**
  * struct overlay_changeset
  * @id:         changeset identifier
  * @ovcs_list:      list on which we are located
  * @new_fdt:        Memory allocated to hold unflattened aligned FDT
  * @overlay_mem:    the memory chunk that contains @overlay_root
  * @overlay_root:   expanded device tree that contains the fragment nodes
  * @notify_state:   most recent notify action used on overlay
  * @count:      count of fragment structures
  * @fragments:      fragment nodes in the overlay expanded device tree
  * @symbols_fragment:   last element of @fragments[] is the  __symbols__ node
  * @cset:       changeset to apply fragments to live device tree
  */
 struct overlay_changeset {
     int id;
     struct list_head ovcs_list;
     const void *new_fdt;
     const void *overlay_mem;
     struct device_node *overlay_root;
     enum of_overlay_notify_action notify_state;
     int count;
     struct fragment *fragments;
     bool symbols_fragment;
     struct of_changeset cset;
 };
 
 /* flags are sticky - once set, do not reset */
 static int devicetree_state_flags;
 #define DTSF_APPLY_FAIL     0x01
 #define DTSF_REVERT_FAIL    0x02
 
 /*
  * If a changeset apply or revert encounters an error, an attempt will
  * be made to undo partial changes, but may fail.  If the undo fails
  * we do not know the state of the devicetree.
  */
 static int devicetree_corrupt(void)
 {
     return devicetree_state_flags &
         (DTSF_APPLY_FAIL | DTSF_REVERT_FAIL);
 }
 
 static int build_changeset_next_level(struct overlay_changeset *ovcs,
         struct target *target, const struct device_node *overlay_node);
 
 /*
  * of_resolve_phandles() finds the largest phandle in the live tree.
  * of_overlay_apply() may add a larger phandle to the live tree.
  * Do not allow race between two overlays being applied simultaneously:
  *    mutex_lock(&of_overlay_phandle_mutex)
  *    of_resolve_phandles()
  *    of_overlay_apply()
  *    mutex_unlock(&of_overlay_phandle_mutex)
  */
 static DEFINE_MUTEX(of_overlay_phandle_mutex);
 
 void of_overlay_mutex_lock(void)
 {
     mutex_lock(&of_overlay_phandle_mutex);
 }
 
 void of_overlay_mutex_unlock(void)
 {
     mutex_unlock(&of_overlay_phandle_mutex);
 }
 
 static LIST_HEAD(ovcs_list);
 static DEFINE_IDR(ovcs_idr);
 
 static BLOCKING_NOTIFIER_HEAD(overlay_notify_chain);
 
 /**
  * of_overlay_notifier_register() - Register notifier for overlay operations
  * @nb:     Notifier block to register
  *
  * Register for notification on overlay operations on device tree nodes. The
  * reported actions definied by @of_reconfig_change. The notifier callback
  * furthermore receives a pointer to the affected device tree node.
  *
  * Note that a notifier callback is not supposed to store pointers to a device
  * tree node or its content beyond @OF_OVERLAY_POST_REMOVE corresponding to the
  * respective node it received.
  */
 int of_overlay_notifier_register(struct notifier_block *nb)
 {
     return blocking_notifier_chain_register(&overlay_notify_chain, nb);
 }
 EXPORT_SYMBOL_GPL(of_overlay_notifier_register);
 
 /**
  * of_overlay_notifier_unregister() - Unregister notifier for overlay operations
  * @nb:     Notifier block to unregister
  */
 int of_overlay_notifier_unregister(struct notifier_block *nb)
 {
     return blocking_notifier_chain_unregister(&overlay_notify_chain, nb);
 }
 EXPORT_SYMBOL_GPL(of_overlay_notifier_unregister);
 
 static int overlay_notify(struct overlay_changeset *ovcs,
         enum of_overlay_notify_action action)
 {
     struct of_overlay_notify_data nd;
     int i, ret;
 
     ovcs->notify_state = action;
 
     for (i = 0; i < ovcs->count; i++) {
         struct fragment *fragment = &ovcs->fragments[i];
 
         nd.target = fragment->target;
         nd.overlay = fragment->overlay;
 
         ret = blocking_notifier_call_chain(&overlay_notify_chain,
                            action, &nd);
         if (notifier_to_errno(ret)) {
             ret = notifier_to_errno(ret);
             pr_err("overlay changeset %s notifier error %d, target: %pOF\n",
                    of_overlay_action_name(action), ret, nd.target);
             return ret;
         }
     }
 
     return 0;
 }
 
 /*
  * The values of properties in the "/__symbols__" node are paths in
  * the ovcs->overlay_root.  When duplicating the properties, the paths
  * need to be adjusted to be the correct path for the live device tree.
  *
  * The paths refer to a node in the subtree of a fragment node's "__overlay__"
  * node, for example "/fragment@0/__overlay__/symbol_path_tail",
  * where symbol_path_tail can be a single node or it may be a multi-node path.
  *
  * The duplicated property value will be modified by replacing the
  * "/fragment_name/__overlay/" portion of the value  with the target
  * path from the fragment node.
  */
 static struct property *dup_and_fixup_symbol_prop(
         struct overlay_changeset *ovcs, const struct property *prop)
 {
     struct fragment *fragment;
     struct property *new_prop;
     struct device_node *fragment_node;
     struct device_node *overlay_node;
     const char *path;
     const char *path_tail;
     const char *target_path;
     int k;
     int overlay_name_len;
     int path_len;
     int path_tail_len;
     int target_path_len;
 
     if (!prop->value)
         return NULL;
     if (strnlen(prop->value, prop->length) >= prop->length)
         return NULL;
     path = prop->value;
     path_len = strlen(path);
 
     if (path_len < 1)
         return NULL;
     fragment_node = __of_find_node_by_path(ovcs->overlay_root, path + 1);
     overlay_node = __of_find_node_by_path(fragment_node, "__overlay__/");
     of_node_put(fragment_node);
     of_node_put(overlay_node);
 
     for (k = 0; k < ovcs->count; k++) {
         fragment = &ovcs->fragments[k];
         if (fragment->overlay == overlay_node)
             break;
     }
     if (k >= ovcs->count)
         return NULL;
 
     overlay_name_len = snprintf(NULL, 0, "%pOF", fragment->overlay);
 
     if (overlay_name_len > path_len)
         return NULL;
     path_tail = path + overlay_name_len;
     path_tail_len = strlen(path_tail);
 
     target_path = kasprintf(GFP_KERNEL, "%pOF", fragment->target);
     if (!target_path)
         return NULL;
     target_path_len = strlen(target_path);
 
     new_prop = kzalloc(sizeof(*new_prop), GFP_KERNEL);
     if (!new_prop)
         goto err_free_target_path;
 
     new_prop->name = kstrdup(prop->name, GFP_KERNEL);
     new_prop->length = target_path_len + path_tail_len + 1;
     new_prop->value = kzalloc(new_prop->length, GFP_KERNEL);
     if (!new_prop->name || !new_prop->value)
         goto err_free_new_prop;
 
     strcpy(new_prop->value, target_path);
     strcpy(new_prop->value + target_path_len, path_tail);
 
     of_property_set_flag(new_prop, OF_DYNAMIC);
 
     kfree(target_path);
 
     return new_prop;
 
 err_free_new_prop:
     kfree(new_prop->name);
     kfree(new_prop->value);
     kfree(new_prop);
 err_free_target_path:
     kfree(target_path);
 
     return NULL;
 }
 
 /**
  * add_changeset_property() - add @overlay_prop to overlay changeset
  * @ovcs:       overlay changeset
  * @target:     where @overlay_prop will be placed
  * @overlay_prop:   property to add or update, from overlay tree
  * @is_symbols_prop:    1 if @overlay_prop is from node "/__symbols__"
  *
  * If @overlay_prop does not already exist in live devicetree, add changeset
  * entry to add @overlay_prop in @target, else add changeset entry to update
  * value of @overlay_prop.
  *
  * @target may be either in the live devicetree or in a new subtree that
  * is contained in the changeset.
  *
  * Some special properties are not added or updated (no error returned):
  * "name", "phandle", "linux,phandle".
  *
  * Properties "#address-cells" and "#size-cells" are not updated if they
  * are already in the live tree, but if present in the live tree, the values
  * in the overlay must match the values in the live tree.
  *
  * Update of property in symbols node is not allowed.
  *
  * Return: 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
  * invalid @overlay.
  */
 static int add_changeset_property(struct overlay_changeset *ovcs,
         struct target *target, struct property *overlay_prop,
         bool is_symbols_prop)
 {
     struct property *new_prop = NULL, *prop;
     int ret = 0;
 
     if (target->in_livetree)
         if (!of_prop_cmp(overlay_prop->name, "name") ||
             !of_prop_cmp(overlay_prop->name, "phandle") ||
             !of_prop_cmp(overlay_prop->name, "linux,phandle"))
             return 0;
 
     if (target->in_livetree)
         prop = of_find_property(target->np, overlay_prop->name, NULL);
     else
         prop = NULL;
 
     if (prop) {
         if (!of_prop_cmp(prop->name, "#address-cells")) {
             if (!of_prop_val_eq(prop, overlay_prop)) {
                 pr_err("ERROR: changing value of #address-cells is not allowed in %pOF\n",
                        target->np);
                 ret = -EINVAL;
             }
             return ret;
 
         } else if (!of_prop_cmp(prop->name, "#size-cells")) {
             if (!of_prop_val_eq(prop, overlay_prop)) {
                 pr_err("ERROR: changing value of #size-cells is not allowed in %pOF\n",
                        target->np);
                 ret = -EINVAL;
             }
             return ret;
         }
     }
 
     if (is_symbols_prop) {
         if (prop)
             return -EINVAL;
         new_prop = dup_and_fixup_symbol_prop(ovcs, overlay_prop);
     } else {
         new_prop = __of_prop_dup(overlay_prop, GFP_KERNEL);
     }
 
     if (!new_prop)
         return -ENOMEM;
 
     if (!prop) {
         if (!target->in_livetree) {
             new_prop->next = target->np->deadprops;
             target->np->deadprops = new_prop;
         }
         ret = of_changeset_add_property(&ovcs->cset, target->np,
                         new_prop);
     } else {
         ret = of_changeset_update_property(&ovcs->cset, target->np,
                            new_prop);
     }
 
     if (!of_node_check_flag(target->np, OF_OVERLAY))
         pr_err("WARNING: memory leak will occur if overlay removed, property: %pOF/%s\n",
                target->np, new_prop->name);
 
     if (ret) {
         kfree(new_prop->name);
         kfree(new_prop->value);
         kfree(new_prop);
     }
     return ret;
 }
 
 /**
  * add_changeset_node() - add @node (and children) to overlay changeset
  * @ovcs:   overlay changeset
  * @target: where @node will be placed in live tree or changeset
  * @node:   node from within overlay device tree fragment
  *
  * If @node does not already exist in @target, add changeset entry
  * to add @node in @target.
  *
  * If @node already exists in @target, and the existing node has
  * a phandle, the overlay node is not allowed to have a phandle.
  *
  * If @node has child nodes, add the children recursively via
  * build_changeset_next_level().
  *
  * NOTE_1: A live devicetree created from a flattened device tree (FDT) will
  *       not contain the full path in node->full_name.  Thus an overlay
  *       created from an FDT also will not contain the full path in
  *       node->full_name.  However, a live devicetree created from Open
  *       Firmware may have the full path in node->full_name.
  *
  *       add_changeset_node() follows the FDT convention and does not include
  *       the full path in node->full_name.  Even though it expects the overlay
  *       to not contain the full path, it uses kbasename() to remove the
  *       full path should it exist.  It also uses kbasename() in comparisons
  *       to nodes in the live devicetree so that it can apply an overlay to
  *       a live devicetree created from Open Firmware.
  *
  * NOTE_2: Multiple mods of created nodes not supported.
  *
  * Return: 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
  * invalid @overlay.
  */
 static int add_changeset_node(struct overlay_changeset *ovcs,
         struct target *target, struct device_node *node)
 {
     const char *node_kbasename;
     const __be32 *phandle;
     struct device_node *tchild;
     struct target target_child;
     int ret = 0, size;
 
     node_kbasename = kbasename(node->full_name);
 
     for_each_child_of_node(target->np, tchild)
         if (!of_node_cmp(node_kbasename, kbasename(tchild->full_name)))
             break;
 
     if (!tchild) {
         tchild = __of_node_dup(NULL, node_kbasename);
         if (!tchild)
             return -ENOMEM;
 
         tchild->parent = target->np;
         tchild->name = __of_get_property(node, "name", NULL);
 
         if (!tchild->name)
             tchild->name = "<NULL>";
 
         /* ignore obsolete "linux,phandle" */
         phandle = __of_get_property(node, "phandle", &size);
         if (phandle && (size == 4))
             tchild->phandle = be32_to_cpup(phandle);
 
         of_node_set_flag(tchild, OF_OVERLAY);
 
         ret = of_changeset_attach_node(&ovcs->cset, tchild);
         if (ret)
             return ret;
 
         target_child.np = tchild;
         target_child.in_livetree = false;
 
         ret = build_changeset_next_level(ovcs, &target_child, node);
         of_node_put(tchild);
         return ret;
     }
 
     if (node->phandle && tchild->phandle) {
         ret = -EINVAL;
     } else {
         target_child.np = tchild;
         target_child.in_livetree = target->in_livetree;
         ret = build_changeset_next_level(ovcs, &target_child, node);
     }
     of_node_put(tchild);
 
     return ret;
 }
 
 /**
  * build_changeset_next_level() - add level of overlay changeset
  * @ovcs:       overlay changeset
  * @target:     where to place @overlay_node in live tree
  * @overlay_node:   node from within an overlay device tree fragment
  *
  * Add the properties (if any) and nodes (if any) from @overlay_node to the
  * @ovcs->cset changeset.  If an added node has child nodes, they will
  * be added recursively.
  *
  * Do not allow symbols node to have any children.
  *
  * Return: 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
  * invalid @overlay_node.
  */
 static int build_changeset_next_level(struct overlay_changeset *ovcs,
         struct target *target, const struct device_node *overlay_node)
 {
     struct device_node *child;
     struct property *prop;
     int ret;
 
     for_each_property_of_node(overlay_node, prop) {
         ret = add_changeset_property(ovcs, target, prop, 0);
         if (ret) {
             pr_debug("Failed to apply prop @%pOF/%s, err=%d\n",
                  target->np, prop->name, ret);
             return ret;
         }
     }
 
     for_each_child_of_node(overlay_node, child) {
         ret = add_changeset_node(ovcs, target, child);
         if (ret) {
             pr_debug("Failed to apply node @%pOF/%pOFn, err=%d\n",
                  target->np, child, ret);
             of_node_put(child);
             return ret;
         }
     }
 
     return 0;
 }
 
 /*
  * Add the properties from __overlay__ node to the @ovcs->cset changeset.
  */
 static int build_changeset_symbols_node(struct overlay_changeset *ovcs,
         struct target *target,
         const struct device_node *overlay_symbols_node)
 {
     struct property *prop;
     int ret;
 
     for_each_property_of_node(overlay_symbols_node, prop) {
         ret = add_changeset_property(ovcs, target, prop, 1);
         if (ret) {
             pr_debug("Failed to apply symbols prop @%pOF/%s, err=%d\n",
                  target->np, prop->name, ret);
             return ret;
         }
     }
 
     return 0;
 }
 
 static int find_dup_cset_node_entry(struct overlay_changeset *ovcs,
         struct of_changeset_entry *ce_1)
 {
     struct of_changeset_entry *ce_2;
     char *fn_1, *fn_2;
     int node_path_match;
 
     if (ce_1->action != OF_RECONFIG_ATTACH_NODE &&
         ce_1->action != OF_RECONFIG_DETACH_NODE)
         return 0;
 
     ce_2 = ce_1;
     list_for_each_entry_continue(ce_2, &ovcs->cset.entries, node) {
         if ((ce_2->action != OF_RECONFIG_ATTACH_NODE &&
              ce_2->action != OF_RECONFIG_DETACH_NODE) ||
             of_node_cmp(ce_1->np->full_name, ce_2->np->full_name))
             continue;
 
         fn_1 = kasprintf(GFP_KERNEL, "%pOF", ce_1->np);
         fn_2 = kasprintf(GFP_KERNEL, "%pOF", ce_2->np);
         node_path_match = !strcmp(fn_1, fn_2);
         kfree(fn_1);
         kfree(fn_2);
         if (node_path_match) {
             pr_err("ERROR: multiple fragments add and/or delete node %pOF\n",
                    ce_1->np);
             return -EINVAL;
         }
     }
 
     return 0;
 }
 
 static int find_dup_cset_prop(struct overlay_changeset *ovcs,
         struct of_changeset_entry *ce_1)
 {
     struct of_changeset_entry *ce_2;
     char *fn_1, *fn_2;
     int node_path_match;
 
     if (ce_1->action != OF_RECONFIG_ADD_PROPERTY &&
         ce_1->action != OF_RECONFIG_REMOVE_PROPERTY &&
         ce_1->action != OF_RECONFIG_UPDATE_PROPERTY)
         return 0;
 
     ce_2 = ce_1;
     list_for_each_entry_continue(ce_2, &ovcs->cset.entries, node) {
         if ((ce_2->action != OF_RECONFIG_ADD_PROPERTY &&
              ce_2->action != OF_RECONFIG_REMOVE_PROPERTY &&
              ce_2->action != OF_RECONFIG_UPDATE_PROPERTY) ||
             of_node_cmp(ce_1->np->full_name, ce_2->np->full_name))
             continue;
 
         fn_1 = kasprintf(GFP_KERNEL, "%pOF", ce_1->np);
         fn_2 = kasprintf(GFP_KERNEL, "%pOF", ce_2->np);
         node_path_match = !strcmp(fn_1, fn_2);
         kfree(fn_1);
         kfree(fn_2);
         if (node_path_match &&
             !of_prop_cmp(ce_1->prop->name, ce_2->prop->name)) {
             pr_err("ERROR: multiple fragments add, update, and/or delete property %pOF/%s\n",
                    ce_1->np, ce_1->prop->name);
             return -EINVAL;
         }
     }
 
     return 0;
 }
 
 /**
  * changeset_dup_entry_check() - check for duplicate entries
  * @ovcs:   Overlay changeset
  *
  * Check changeset @ovcs->cset for multiple {add or delete} node entries for
  * the same node or duplicate {add, delete, or update} properties entries
  * for the same property.
  *
  * Return: 0 on success, or -EINVAL if duplicate changeset entry found.
  */
 static int changeset_dup_entry_check(struct overlay_changeset *ovcs)
 {
     struct of_changeset_entry *ce_1;
     int dup_entry = 0;
 
     list_for_each_entry(ce_1, &ovcs->cset.entries, node) {
         dup_entry |= find_dup_cset_node_entry(ovcs, ce_1);
         dup_entry |= find_dup_cset_prop(ovcs, ce_1);
     }
 
     return dup_entry ? -EINVAL : 0;
 }
 
 /**
  * build_changeset() - populate overlay changeset in @ovcs from @ovcs->fragments
  * @ovcs:   Overlay changeset
  *
  * Create changeset @ovcs->cset to contain the nodes and properties of the
  * overlay device tree fragments in @ovcs->fragments[].  If an error occurs,
  * any portions of the changeset that were successfully created will remain
  * in @ovcs->cset.
  *
  * Return: 0 on success, -ENOMEM if memory allocation failure, or -EINVAL if
  * invalid overlay in @ovcs->fragments[].
  */
 static int build_changeset(struct overlay_changeset *ovcs)
 {
     struct fragment *fragment;
     struct target target;
     int fragments_count, i, ret;
 
     /*
      * if there is a symbols fragment in ovcs->fragments[i] it is
      * the final element in the array
      */
     if (ovcs->symbols_fragment)
         fragments_count = ovcs->count - 1;
     else
         fragments_count = ovcs->count;
 
     for (i = 0; i < fragments_count; i++) {
         fragment = &ovcs->fragments[i];
 
         target.np = fragment->target;
         target.in_livetree = true;
         ret = build_changeset_next_level(ovcs, &target,
                          fragment->overlay);
         if (ret) {
             pr_debug("fragment apply failed '%pOF'\n",
                  fragment->target);
             return ret;
         }
     }
 
     if (ovcs->symbols_fragment) {
         fragment = &ovcs->fragments[ovcs->count - 1];
 
         target.np = fragment->target;
         target.in_livetree = true;
         ret = build_changeset_symbols_node(ovcs, &target,
                            fragment->overlay);
         if (ret) {
             pr_debug("symbols fragment apply failed '%pOF'\n",
                  fragment->target);
             return ret;
         }
     }
 
     return changeset_dup_entry_check(ovcs);
 }
 
 /*
  * Find the target node using a number of different strategies
  * in order of preference:
  *
  * 1) "target" property containing the phandle of the target
  * 2) "target-path" property containing the path of the target
  */
 static struct device_node *find_target(struct device_node *info_node)
 {
     struct device_node *node;
     const char *path;
     u32 val;
     int ret;
 
     ret = of_property_read_u32(info_node, "target", &val);
     if (!ret) {
         node = of_find_node_by_phandle(val);
         if (!node)
             pr_err("find target, node: %pOF, phandle 0x%x not found\n",
                    info_node, val);
         return node;
     }
 
     ret = of_property_read_string(info_node, "target-path", &path);
     if (!ret) {
         node =  of_find_node_by_path(path);
         if (!node)
             pr_err("find target, node: %pOF, path '%s' not found\n",
                    info_node, path);
         return node;
     }
 
     pr_err("find target, node: %pOF, no target property\n", info_node);
 
     return NULL;
 }
 
 /**
  * init_overlay_changeset() - initialize overlay changeset from overlay tree
  * @ovcs:       Overlay changeset to build
  *
  * Initialize @ovcs.  Populate @ovcs->fragments with node information from
  * the top level of @overlay_root.  The relevant top level nodes are the
  * fragment nodes and the __symbols__ node.  Any other top level node will
  * be ignored.  Populate other @ovcs fields.
  *
  * Return: 0 on success, -ENOMEM if memory allocation failure, -EINVAL if error
  * detected in @overlay_root.  On error return, the caller of
  * init_overlay_changeset() must call free_overlay_changeset().
  */
 static int init_overlay_changeset(struct overlay_changeset *ovcs)
 {
     struct device_node *node, *overlay_node;
     struct fragment *fragment;
     struct fragment *fragments;
     int cnt, ret;
 
     /*
      * None of the resources allocated by this function will be freed in
      * the error paths.  Instead the caller of this function is required
      * to call free_overlay_changeset() (which will free the resources)
      * if error return.
      */
 
     /*
      * Warn for some issues.  Can not return -EINVAL for these until
      * of_unittest_apply_overlay() is fixed to pass these checks.
      */
     if (!of_node_check_flag(ovcs->overlay_root, OF_DYNAMIC))
         pr_debug("%s() ovcs->overlay_root is not dynamic\n", __func__);
 
     if (!of_node_check_flag(ovcs->overlay_root, OF_DETACHED))
         pr_debug("%s() ovcs->overlay_root is not detached\n", __func__);
 
     if (!of_node_is_root(ovcs->overlay_root))
         pr_debug("%s() ovcs->overlay_root is not root\n", __func__);
 
     of_changeset_init(&ovcs->cset);
 
     cnt = 0;
 
     /* fragment nodes */
     for_each_child_of_node(ovcs->overlay_root, node) {
         overlay_node = of_get_child_by_name(node, "__overlay__");
         if (overlay_node) {
             cnt++;
             of_node_put(overlay_node);
         }
     }
 
     node = of_get_child_by_name(ovcs->overlay_root, "__symbols__");
     if (node) {
         cnt++;
         of_node_put(node);
     }
 
     fragments = kcalloc(cnt, sizeof(*fragments), GFP_KERNEL);
     if (!fragments) {
         ret = -ENOMEM;
         goto err_out;
     }
     ovcs->fragments = fragments;
 
     cnt = 0;
     for_each_child_of_node(ovcs->overlay_root, node) {
         overlay_node = of_get_child_by_name(node, "__overlay__");
         if (!overlay_node)
             continue;
 
         fragment = &fragments[cnt];
         fragment->overlay = overlay_node;
         fragment->target = find_target(node);
         if (!fragment->target) {
             of_node_put(fragment->overlay);
             ret = -EINVAL;
             of_node_put(node);
             goto err_out;
         }
 
         cnt++;
     }
 
     /*
      * if there is a symbols fragment in ovcs->fragments[i] it is
      * the final element in the array
      */
     node = of_get_child_by_name(ovcs->overlay_root, "__symbols__");
     if (node) {
         ovcs->symbols_fragment = 1;
         fragment = &fragments[cnt];
         fragment->overlay = node;
         fragment->target = of_find_node_by_path("/__symbols__");
 
         if (!fragment->target) {
             pr_err("symbols in overlay, but not in live tree\n");
             ret = -EINVAL;
             goto err_out;
         }
 
         cnt++;
     }
 
     if (!cnt) {
         pr_err("no fragments or symbols in overlay\n");
         ret = -EINVAL;
         goto err_out;
     }
 
     ovcs->count = cnt;
 
     return 0;
 
 err_out:
     pr_err("%s() failed, ret = %d\n", __func__, ret);
 
     return ret;
 }
 
 static void free_overlay_changeset(struct overlay_changeset *ovcs)
 {
     int i;
 
     if (ovcs->cset.entries.next)
         of_changeset_destroy(&ovcs->cset);
 
     if (ovcs->id) {
         idr_remove(&ovcs_idr, ovcs->id);
         list_del(&ovcs->ovcs_list);
         ovcs->id = 0;
     }
 
 
     for (i = 0; i < ovcs->count; i++) {
         of_node_put(ovcs->fragments[i].target);
         of_node_put(ovcs->fragments[i].overlay);
     }
     kfree(ovcs->fragments);
 
     /*
      * There should be no live pointers into ovcs->overlay_mem and
      * ovcs->new_fdt due to the policy that overlay notifiers are not
      * allowed to retain pointers into the overlay devicetree other
      * than during the window from OF_OVERLAY_PRE_APPLY overlay
      * notifiers until the OF_OVERLAY_POST_REMOVE overlay notifiers.
      *
      * A memory leak will occur here if within the window.
      */
 
     if (ovcs->notify_state == OF_OVERLAY_INIT ||
         ovcs->notify_state == OF_OVERLAY_POST_REMOVE) {
         kfree(ovcs->overlay_mem);
         kfree(ovcs->new_fdt);
     }
     kfree(ovcs);
 }
 
 /*
  * internal documentation
  *
  * of_overlay_apply() - Create and apply an overlay changeset
  * @ovcs:   overlay changeset
  *
  * Creates and applies an overlay changeset.
  *
  * If an error is returned by an overlay changeset pre-apply notifier
  * then no further overlay changeset pre-apply notifier will be called.
  *
  * If an error is returned by an overlay changeset post-apply notifier
  * then no further overlay changeset post-apply notifier will be called.
  *
  * If more than one notifier returns an error, then the last notifier
  * error to occur is returned.
  *
  * If an error occurred while applying the overlay changeset, then an
  * attempt is made to revert any changes that were made to the
  * device tree.  If there were any errors during the revert attempt
  * then the state of the device tree can not be determined, and any
  * following attempt to apply or remove an overlay changeset will be
  * refused.
  *
  * Returns 0 on success, or a negative error number.  On error return,
  * the caller of of_overlay_apply() must call free_overlay_changeset().
  */
 
 static int of_overlay_apply(struct overlay_changeset *ovcs)
 {
     int ret = 0, ret_revert, ret_tmp;
 
     ret = of_resolve_phandles(ovcs->overlay_root);
     if (ret)
         goto out;
 
     ret = init_overlay_changeset(ovcs);
     if (ret)
         goto out;
 
     ret = overlay_notify(ovcs, OF_OVERLAY_PRE_APPLY);
     if (ret)
         goto out;
 
     ret = build_changeset(ovcs);
     if (ret)
         goto out;
 
     ret_revert = 0;
     ret = __of_changeset_apply_entries(&ovcs->cset, &ret_revert);
     if (ret) {
         if (ret_revert) {
             pr_debug("overlay changeset revert error %d\n",
                  ret_revert);
             devicetree_state_flags |= DTSF_APPLY_FAIL;
         }
         goto out;
     }
 
     ret = __of_changeset_apply_notify(&ovcs->cset);
     if (ret)
         pr_err("overlay apply changeset entry notify error %d\n", ret);
     /* notify failure is not fatal, continue */
 
     ret_tmp = overlay_notify(ovcs, OF_OVERLAY_POST_APPLY);
     if (ret_tmp)
         if (!ret)
             ret = ret_tmp;
 
 out:
     pr_debug("%s() err=%d\n", __func__, ret);
 
     return ret;
 }
 
 /*
  * of_overlay_fdt_apply() - Create and apply an overlay changeset
  * @overlay_fdt:    pointer to overlay FDT
  * @overlay_fdt_size:   number of bytes in @overlay_fdt
  * @ret_ovcs_id:    pointer for returning created changeset id
  *
  * Creates and applies an overlay changeset.
  *
  * See of_overlay_apply() for important behavior information.
  *
  * Return: 0 on success, or a negative error number.  *@ret_ovcs_id is set to
  * the value of overlay changeset id, which can be passed to of_overlay_remove()
  * to remove the overlay.
  *
  * On error return, the changeset may be partially applied.  This is especially
  * likely if an OF_OVERLAY_POST_APPLY notifier returns an error.  In this case
  * the caller should call of_overlay_remove() with the value in *@ret_ovcs_id.
  */
 
 int of_overlay_fdt_apply(const void *overlay_fdt, u32 overlay_fdt_size,
              int *ret_ovcs_id)
 {
     void *new_fdt;
     void *new_fdt_align;
     void *overlay_mem;
     int ret;
     u32 size;
     struct overlay_changeset *ovcs;
 
     *ret_ovcs_id = 0;
 
     if (devicetree_corrupt()) {
         pr_err("devicetree state suspect, refuse to apply overlay\n");
         return -EBUSY;
     }
 
     if (overlay_fdt_size < sizeof(struct fdt_header) ||
         fdt_check_header(overlay_fdt)) {
         pr_err("Invalid overlay_fdt header\n");
         return -EINVAL;
     }
 
     size = fdt_totalsize(overlay_fdt);
     if (overlay_fdt_size < size)
         return -EINVAL;
 
     ovcs = kzalloc(sizeof(*ovcs), GFP_KERNEL);
     if (!ovcs)
         return -ENOMEM;
 
     of_overlay_mutex_lock();
     mutex_lock(&of_mutex);
 
     /*
      * ovcs->notify_state must be set to OF_OVERLAY_INIT before allocating
      * ovcs resources, implicitly set by kzalloc() of ovcs
      */
 
     ovcs->id = idr_alloc(&ovcs_idr, ovcs, 1, 0, GFP_KERNEL);
     if (ovcs->id <= 0) {
         ret = ovcs->id;
         goto err_free_ovcs;
     }
 
     INIT_LIST_HEAD(&ovcs->ovcs_list);
     list_add_tail(&ovcs->ovcs_list, &ovcs_list);
 
     /*
      * Must create permanent copy of FDT because of_fdt_unflatten_tree()
      * will create pointers to the passed in FDT in the unflattened tree.
      */
     new_fdt = kmalloc(size + FDT_ALIGN_SIZE, GFP_KERNEL);
     if (!new_fdt) {
         ret = -ENOMEM;
         goto err_free_ovcs;
     }
     ovcs->new_fdt = new_fdt;
 
     new_fdt_align = PTR_ALIGN(new_fdt, FDT_ALIGN_SIZE);
     memcpy(new_fdt_align, overlay_fdt, size);
 
     overlay_mem = of_fdt_unflatten_tree(new_fdt_align, NULL,
                         &ovcs->overlay_root);
     if (!overlay_mem) {
         pr_err("unable to unflatten overlay_fdt\n");
         ret = -EINVAL;
         goto err_free_ovcs;
     }
     ovcs->overlay_mem = overlay_mem;
 
     ret = of_overlay_apply(ovcs);
     /*
      * If of_overlay_apply() error, calling free_overlay_changeset() may
      * result in a memory leak if the apply partly succeeded, so do NOT
      * goto err_free_ovcs.  Instead, the caller of of_overlay_fdt_apply()
      * can call of_overlay_remove();
      */
     *ret_ovcs_id = ovcs->id;
     goto out_unlock;
 
 err_free_ovcs:
     free_overlay_changeset(ovcs);
 
 out_unlock:
     mutex_unlock(&of_mutex);
     of_overlay_mutex_unlock();
     return ret;
 }
 EXPORT_SYMBOL_GPL(of_overlay_fdt_apply);
 
 /*
  * Find @np in @tree.
  *
  * Returns 1 if @np is @tree or is contained in @tree, else 0
  */
 static int find_node(struct device_node *tree, struct device_node *np)
 {
     struct device_node *child;
 
     if (tree == np)
         return 1;
 
     for_each_child_of_node(tree, child) {
         if (find_node(child, np)) {
             of_node_put(child);
             return 1;
         }
     }
 
     return 0;
 }
 
 /*
  * Is @remove_ce_node a child of, a parent of, or the same as any
  * node in an overlay changeset more topmost than @remove_ovcs?
  *
  * Returns 1 if found, else 0
  */
 static int node_overlaps_later_cs(struct overlay_changeset *remove_ovcs,
         struct device_node *remove_ce_node)
 {
     struct overlay_changeset *ovcs;
     struct of_changeset_entry *ce;
 
     list_for_each_entry_reverse(ovcs, &ovcs_list, ovcs_list) {
         if (ovcs == remove_ovcs)
             break;
 
         list_for_each_entry(ce, &ovcs->cset.entries, node) {
             if (find_node(ce->np, remove_ce_node)) {
                 pr_err("%s: #%d overlaps with #%d @%pOF\n",
                     __func__, remove_ovcs->id, ovcs->id,
                     remove_ce_node);
                 return 1;
             }
             if (find_node(remove_ce_node, ce->np)) {
                 pr_err("%s: #%d overlaps with #%d @%pOF\n",
                     __func__, remove_ovcs->id, ovcs->id,
                     remove_ce_node);
                 return 1;
             }
         }
     }
 
     return 0;
 }
 
 /*
  * We can safely remove the overlay only if it's the top-most one.
  * Newly applied overlays are inserted at the tail of the overlay list,
  * so a top most overlay is the one that is closest to the tail.
  *
  * The topmost check is done by exploiting this property. For each
  * affected device node in the log list we check if this overlay is
  * the one closest to the tail. If another overlay has affected this
  * device node and is closest to the tail, then removal is not permited.
  */
 static int overlay_removal_is_ok(struct overlay_changeset *remove_ovcs)
 {
     struct of_changeset_entry *remove_ce;
 
     list_for_each_entry(remove_ce, &remove_ovcs->cset.entries, node) {
         if (node_overlaps_later_cs(remove_ovcs, remove_ce->np)) {
             pr_err("overlay #%d is not topmost\n", remove_ovcs->id);
             return 0;
         }
     }
 
     return 1;
 }
 
 /**
  * of_overlay_remove() - Revert and free an overlay changeset
  * @ovcs_id:    Pointer to overlay changeset id
  *
  * Removes an overlay if it is permissible.  @ovcs_id was previously returned
  * by of_overlay_fdt_apply().
  *
  * If an error occurred while attempting to revert the overlay changeset,
  * then an attempt is made to re-apply any changeset entry that was
  * reverted.  If an error occurs on re-apply then the state of the device
  * tree can not be determined, and any following attempt to apply or remove
  * an overlay changeset will be refused.
  *
  * A non-zero return value will not revert the changeset if error is from:
  *   - parameter checks
  *   - overlay changeset pre-remove notifier
  *   - overlay changeset entry revert
  *
  * If an error is returned by an overlay changeset pre-remove notifier
  * then no further overlay changeset pre-remove notifier will be called.
  *
  * If more than one notifier returns an error, then the last notifier
  * error to occur is returned.
  *
  * A non-zero return value will revert the changeset if error is from:
  *   - overlay changeset entry notifier
  *   - overlay changeset post-remove notifier
  *
  * If an error is returned by an overlay changeset post-remove notifier
  * then no further overlay changeset post-remove notifier will be called.
  *
  * Return: 0 on success, or a negative error number.  *@ovcs_id is set to
  * zero after reverting the changeset, even if a subsequent error occurs.
  */
 int of_overlay_remove(int *ovcs_id)
 {
     struct overlay_changeset *ovcs;
     int ret, ret_apply, ret_tmp;
 
     if (devicetree_corrupt()) {
         pr_err("suspect devicetree state, refuse to remove overlay\n");
         ret = -EBUSY;
         goto out;
     }
 
     mutex_lock(&of_mutex);
 
     ovcs = idr_find(&ovcs_idr, *ovcs_id);
     if (!ovcs) {
         ret = -ENODEV;
         pr_err("remove: Could not find overlay #%d\n", *ovcs_id);
         goto err_unlock;
     }
 
     if (!overlay_removal_is_ok(ovcs)) {
         ret = -EBUSY;
         goto err_unlock;
     }
 
     ret = overlay_notify(ovcs, OF_OVERLAY_PRE_REMOVE);
     if (ret)
         goto err_unlock;
 
     ret_apply = 0;
     ret = __of_changeset_revert_entries(&ovcs->cset, &ret_apply);
     if (ret) {
         if (ret_apply)
             devicetree_state_flags |= DTSF_REVERT_FAIL;
         goto err_unlock;
     }
 
     ret = __of_changeset_revert_notify(&ovcs->cset);
     if (ret)
         pr_err("overlay remove changeset entry notify error %d\n", ret);
     /* notify failure is not fatal, continue */
 
     *ovcs_id = 0;
 
     /*
      * Note that the overlay memory will be kfree()ed by
      * free_overlay_changeset() even if the notifier for
      * OF_OVERLAY_POST_REMOVE returns an error.
      */
     ret_tmp = overlay_notify(ovcs, OF_OVERLAY_POST_REMOVE);
     if (ret_tmp)
         if (!ret)
             ret = ret_tmp;
 
     free_overlay_changeset(ovcs);
 
 err_unlock:
     /*
      * If jumped over free_overlay_changeset(), then did not kfree()
      * overlay related memory.  This is a memory leak unless a subsequent
      * of_overlay_remove() of this overlay is successful.
      */
     mutex_unlock(&of_mutex);
 
 out:
     pr_debug("%s() err=%d\n", __func__, ret);
 
     return ret;
 }
 EXPORT_SYMBOL_GPL(of_overlay_remove);
 
 /**
  * of_overlay_remove_all() - Reverts and frees all overlay changesets
  *
  * Removes all overlays from the system in the correct order.
  *
  * Return: 0 on success, or a negative error number
  */
 int of_overlay_remove_all(void)
 {
     struct overlay_changeset *ovcs, *ovcs_n;
     int ret;
 
     /* the tail of list is guaranteed to be safe to remove */
     list_for_each_entry_safe_reverse(ovcs, ovcs_n, &ovcs_list, ovcs_list) {
         ret = of_overlay_remove(&ovcs->id);
         if (ret)
             return ret;
     }
 
     return 0;
 }
 EXPORT_SYMBOL_GPL(of_overlay_remove_all);

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