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  • 2020-06-01
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    fdt_overlay.c NaN GiB
    #include "libfdt_env.h"
    
    #include <fdt.h>
    #include <libfdt.h>
    
    #include "libfdt_internal.h"
    
    /**
     * overlay_get_target_phandle - retrieves the target phandle of a fragment
     * @fdto: pointer to the device tree overlay blob
     * @fragment: node offset of the fragment in the overlay
     *
     * overlay_get_target_phandle() retrieves the target phandle of an
     * overlay fragment when that fragment uses a phandle (target
     * property) instead of a path (target-path property).
     *
     * returns:
     *      the phandle pointed by the target property
     *      0, if the phandle was not found
     *	-1, if the phandle was malformed
     */
    static uint32_t overlay_get_target_phandle(const void *fdto, int fragment)
    {
    	const fdt32_t *val;
    	int len;
    
    	val = fdt_getprop(fdto, fragment, "target", &len);
    	if (!val)
    		return 0;
    
    	if ((len != sizeof(*val)) || (fdt32_to_cpu(*val) == (uint32_t)-1))
    		return (uint32_t)-1;
    
    	return fdt32_to_cpu(*val);
    }
    
    /**
     * overlay_get_target - retrieves the offset of a fragment's target
     * @fdt: Base device tree blob
     * @fdto: Device tree overlay blob
     * @fragment: node offset of the fragment in the overlay
     * @pathp: pointer which receives the path of the target (or NULL)
     *
     * overlay_get_target() retrieves the target offset in the base
     * device tree of a fragment, no matter how the actual targetting is
     * done (through a phandle or a path)
     *
     * returns:
     *      the targetted node offset in the base device tree
     *      Negative error code on error
     */
    static int overlay_get_target(const void *fdt, const void *fdto,
    			      int fragment, char const **pathp)
    {
    	uint32_t phandle;
    	const char *path = NULL;
    	int path_len = 0, ret;
    
    	/* Try first to do a phandle based lookup */
    	phandle = overlay_get_target_phandle(fdto, fragment);
    	if (phandle == (uint32_t)-1)
    		return -FDT_ERR_BADPHANDLE;
    
    	/* no phandle, try path */
    	if (!phandle) {
    		/* And then a path based lookup */
    		path = fdt_getprop(fdto, fragment, "target-path", &path_len);
    		if (path)
    			ret = fdt_path_offset(fdt, path);
    		else
    			ret = path_len;
    	} else
    		ret = fdt_node_offset_by_phandle(fdt, phandle);
    
    	/*
    	* If we haven't found either a target or a
    	* target-path property in a node that contains a
    	* __overlay__ subnode (we wouldn't be called
    	* otherwise), consider it a improperly written
    	* overlay
    	*/
    	if (ret < 0 && path_len == -FDT_ERR_NOTFOUND)
    		ret = -FDT_ERR_BADOVERLAY;
    
    	/* return on error */
    	if (ret < 0)
    		return ret;
    
    	/* return pointer to path (if available) */
    	if (pathp)
    		*pathp = path ? path : NULL;
    
    	return ret;
    }
    
    /**
     * overlay_phandle_add_offset - Increases a phandle by an offset
     * @fdt: Base device tree blob
     * @node: Device tree overlay blob
     * @name: Name of the property to modify (phandle or linux,phandle)
     * @delta: offset to apply
     *
     * overlay_phandle_add_offset() increments a node phandle by a given
     * offset.
     *
     * returns:
     *      0 on success.
     *      Negative error code on error
     */
    static int overlay_phandle_add_offset(void *fdt, int node,
    				      const char *name, uint32_t delta)
    {
    	const fdt32_t *val;
    	uint32_t adj_val;
    	int len;
    
    	val = fdt_getprop(fdt, node, name, &len);
    	if (!val)
    		return len;
    
    	if (len != sizeof(*val))
    		return -FDT_ERR_BADPHANDLE;
    
    	adj_val = fdt32_to_cpu(*val);
    	if ((adj_val + delta) < adj_val)
    		return -FDT_ERR_NOPHANDLES;
    
    	adj_val += delta;
    	if (adj_val == (uint32_t)-1)
    		return -FDT_ERR_NOPHANDLES;
    
    	return fdt_setprop_inplace_u32(fdt, node, name, adj_val);
    }
    
    /**
     * overlay_adjust_node_phandles - Offsets the phandles of a node
     * @fdto: Device tree overlay blob
     * @node: Offset of the node we want to adjust
     * @delta: Offset to shift the phandles of
     *
     * overlay_adjust_node_phandles() adds a constant to all the phandles
     * of a given node. This is mainly use as part of the overlay
     * application process, when we want to update all the overlay
     * phandles to not conflict with the overlays of the base device tree.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_adjust_node_phandles(void *fdto, int node,
    					uint32_t delta)
    {
    	int child;
    	int ret;
    
    	ret = overlay_phandle_add_offset(fdto, node, "phandle", delta);
    	if (ret && ret != -FDT_ERR_NOTFOUND)
    		return ret;
    
    	ret = overlay_phandle_add_offset(fdto, node, "linux,phandle", delta);
    	if (ret && ret != -FDT_ERR_NOTFOUND)
    		return ret;
    
    	fdt_for_each_subnode(child, fdto, node) {
    		ret = overlay_adjust_node_phandles(fdto, child, delta);
    		if (ret)
    			return ret;
    	}
    
    	return 0;
    }
    
    /**
     * overlay_adjust_local_phandles - Adjust the phandles of a whole overlay
     * @fdto: Device tree overlay blob
     * @delta: Offset to shift the phandles of
     *
     * overlay_adjust_local_phandles() adds a constant to all the
     * phandles of an overlay. This is mainly use as part of the overlay
     * application process, when we want to update all the overlay
     * phandles to not conflict with the overlays of the base device tree.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_adjust_local_phandles(void *fdto, uint32_t delta)
    {
    	/*
    	 * Start adjusting the phandles from the overlay root
    	 */
    	return overlay_adjust_node_phandles(fdto, 0, delta);
    }
    
    /**
     * overlay_update_local_node_references - Adjust the overlay references
     * @fdto: Device tree overlay blob
     * @tree_node: Node offset of the node to operate on
     * @fixup_node: Node offset of the matching local fixups node
     * @delta: Offset to shift the phandles of
     *
     * overlay_update_local_nodes_references() update the phandles
     * pointing to a node within the device tree overlay by adding a
     * constant delta.
     *
     * This is mainly used as part of a device tree application process,
     * where you want the device tree overlays phandles to not conflict
     * with the ones from the base device tree before merging them.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_update_local_node_references(void *fdto,
    						int tree_node,
    						int fixup_node,
    						uint32_t delta)
    {
    	int fixup_prop;
    	int fixup_child;
    	int ret;
    
    	fdt_for_each_property_offset(fixup_prop, fdto, fixup_node) {
    		const fdt32_t *fixup_val;
    		const char *tree_val;
    		const char *name;
    		int fixup_len;
    		int tree_len;
    		int i;
    
    		fixup_val = fdt_getprop_by_offset(fdto, fixup_prop,
    						  &name, &fixup_len);
    		if (!fixup_val)
    			return fixup_len;
    
    		if (fixup_len % sizeof(uint32_t))
    			return -FDT_ERR_BADOVERLAY;
    
    		tree_val = fdt_getprop(fdto, tree_node, name, &tree_len);
    		if (!tree_val) {
    			if (tree_len == -FDT_ERR_NOTFOUND)
    				return -FDT_ERR_BADOVERLAY;
    
    			return tree_len;
    		}
    
    		for (i = 0; i < (fixup_len / sizeof(uint32_t)); i++) {
    			fdt32_t adj_val;
    			uint32_t poffset;
    
    			poffset = fdt32_to_cpu(fixup_val[i]);
    
    			/*
    			 * phandles to fixup can be unaligned.
    			 *
    			 * Use a memcpy for the architectures that do
    			 * not support unaligned accesses.
    			 */
    			memcpy(&adj_val, tree_val + poffset, sizeof(adj_val));
    
    			adj_val = cpu_to_fdt32(fdt32_to_cpu(adj_val) + delta);
    
    			ret = fdt_setprop_inplace_namelen_partial(fdto,
    								  tree_node,
    								  name,
    								  strlen(name),
    								  poffset,
    								  &adj_val,
    								  sizeof(adj_val));
    			if (ret == -FDT_ERR_NOSPACE)
    				return -FDT_ERR_BADOVERLAY;
    
    			if (ret)
    				return ret;
    		}
    	}
    
    	fdt_for_each_subnode(fixup_child, fdto, fixup_node) {
    		const char *fixup_child_name = fdt_get_name(fdto, fixup_child,
    							    NULL);
    		int tree_child;
    
    		tree_child = fdt_subnode_offset(fdto, tree_node,
    						fixup_child_name);
    		if (tree_child == -FDT_ERR_NOTFOUND)
    			return -FDT_ERR_BADOVERLAY;
    		if (tree_child < 0)
    			return tree_child;
    
    		ret = overlay_update_local_node_references(fdto,
    							   tree_child,
    							   fixup_child,
    							   delta);
    		if (ret)
    			return ret;
    	}
    
    	return 0;
    }
    
    /**
     * overlay_update_local_references - Adjust the overlay references
     * @fdto: Device tree overlay blob
     * @delta: Offset to shift the phandles of
     *
     * overlay_update_local_references() update all the phandles pointing
     * to a node within the device tree overlay by adding a constant
     * delta to not conflict with the base overlay.
     *
     * This is mainly used as part of a device tree application process,
     * where you want the device tree overlays phandles to not conflict
     * with the ones from the base device tree before merging them.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_update_local_references(void *fdto, uint32_t delta)
    {
    	int fixups;
    
    	fixups = fdt_path_offset(fdto, "/__local_fixups__");
    	if (fixups < 0) {
    		/* There's no local phandles to adjust, bail out */
    		if (fixups == -FDT_ERR_NOTFOUND)
    			return 0;
    
    		return fixups;
    	}
    
    	/*
    	 * Update our local references from the root of the tree
    	 */
    	return overlay_update_local_node_references(fdto, 0, fixups,
    						    delta);
    }
    
    /**
     * overlay_fixup_one_phandle - Set an overlay phandle to the base one
     * @fdt: Base Device Tree blob
     * @fdto: Device tree overlay blob
     * @symbols_off: Node offset of the symbols node in the base device tree
     * @path: Path to a node holding a phandle in the overlay
     * @path_len: number of path characters to consider
     * @name: Name of the property holding the phandle reference in the overlay
     * @name_len: number of name characters to consider
     * @poffset: Offset within the overlay property where the phandle is stored
     * @label: Label of the node referenced by the phandle
     *
     * overlay_fixup_one_phandle() resolves an overlay phandle pointing to
     * a node in the base device tree.
     *
     * This is part of the device tree overlay application process, when
     * you want all the phandles in the overlay to point to the actual
     * base dt nodes.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_fixup_one_phandle(void *fdt, void *fdto,
    				     int symbols_off,
    				     const char *path, uint32_t path_len,
    				     const char *name, uint32_t name_len,
    				     int poffset, const char *label)
    {
    	const char *symbol_path;
    	uint32_t phandle;
    	fdt32_t phandle_prop;
    	int symbol_off, fixup_off;
    	int prop_len;
    
    	if (symbols_off < 0)
    		return symbols_off;
    
    	symbol_path = fdt_getprop(fdt, symbols_off, label,
    				  &prop_len);
    	if (!symbol_path)
    		return prop_len;
    
    	symbol_off = fdt_path_offset(fdt, symbol_path);
    	if (symbol_off < 0)
    		return symbol_off;
    
    	phandle = fdt_get_phandle(fdt, symbol_off);
    	if (!phandle)
    		return -FDT_ERR_NOTFOUND;
    
    	fixup_off = fdt_path_offset_namelen(fdto, path, path_len);
    	if (fixup_off == -FDT_ERR_NOTFOUND)
    		return -FDT_ERR_BADOVERLAY;
    	if (fixup_off < 0)
    		return fixup_off;
    
    	phandle_prop = cpu_to_fdt32(phandle);
    	return fdt_setprop_inplace_namelen_partial(fdto, fixup_off,
    						   name, name_len, poffset,
    						   &phandle_prop,
    						   sizeof(phandle_prop));
    };
    
    /**
     * overlay_fixup_phandle - Set an overlay phandle to the base one
     * @fdt: Base Device Tree blob
     * @fdto: Device tree overlay blob
     * @symbols_off: Node offset of the symbols node in the base device tree
     * @property: Property offset in the overlay holding the list of fixups
     *
     * overlay_fixup_phandle() resolves all the overlay phandles pointed
     * to in a __fixups__ property, and updates them to match the phandles
     * in use in the base device tree.
     *
     * This is part of the device tree overlay application process, when
     * you want all the phandles in the overlay to point to the actual
     * base dt nodes.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_fixup_phandle(void *fdt, void *fdto, int symbols_off,
    				 int property)
    {
    	const char *value;
    	const char *label;
    	int len;
    
    	value = fdt_getprop_by_offset(fdto, property,
    				      &label, &len);
    	if (!value) {
    		if (len == -FDT_ERR_NOTFOUND)
    			return -FDT_ERR_INTERNAL;
    
    		return len;
    	}
    
    	do {
    		const char *path, *name, *fixup_end;
    		const char *fixup_str = value;
    		uint32_t path_len, name_len;
    		uint32_t fixup_len;
    		char *sep, *endptr;
    		int poffset, ret;
    
    		fixup_end = memchr(value, '\0', len);
    		if (!fixup_end)
    			return -FDT_ERR_BADOVERLAY;
    		fixup_len = fixup_end - fixup_str;
    
    		len -= fixup_len + 1;
    		value += fixup_len + 1;
    
    		path = fixup_str;
    		sep = memchr(fixup_str, ':', fixup_len);
    		if (!sep || *sep != ':')
    			return -FDT_ERR_BADOVERLAY;
    
    		path_len = sep - path;
    		if (path_len == (fixup_len - 1))
    			return -FDT_ERR_BADOVERLAY;
    
    		fixup_len -= path_len + 1;
    		name = sep + 1;
    		sep = memchr(name, ':', fixup_len);
    		if (!sep || *sep != ':')
    			return -FDT_ERR_BADOVERLAY;
    
    		name_len = sep - name;
    		if (!name_len)
    			return -FDT_ERR_BADOVERLAY;
    
    		poffset = strtoul(sep + 1, &endptr, 10);
    		if ((*endptr != '\0') || (endptr <= (sep + 1)))
    			return -FDT_ERR_BADOVERLAY;
    
    		ret = overlay_fixup_one_phandle(fdt, fdto, symbols_off,
    						path, path_len, name, name_len,
    						poffset, label);
    		if (ret)
    			return ret;
    	} while (len > 0);
    
    	return 0;
    }
    
    /**
     * overlay_fixup_phandles - Resolve the overlay phandles to the base
     *                          device tree
     * @fdt: Base Device Tree blob
     * @fdto: Device tree overlay blob
     *
     * overlay_fixup_phandles() resolves all the overlay phandles pointing
     * to nodes in the base device tree.
     *
     * This is one of the steps of the device tree overlay application
     * process, when you want all the phandles in the overlay to point to
     * the actual base dt nodes.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_fixup_phandles(void *fdt, void *fdto)
    {
    	int fixups_off, symbols_off;
    	int property;
    
    	/* We can have overlays without any fixups */
    	fixups_off = fdt_path_offset(fdto, "/__fixups__");
    	if (fixups_off == -FDT_ERR_NOTFOUND)
    		return 0; /* nothing to do */
    	if (fixups_off < 0)
    		return fixups_off;
    
    	/* And base DTs without symbols */
    	symbols_off = fdt_path_offset(fdt, "/__symbols__");
    	if ((symbols_off < 0 && (symbols_off != -FDT_ERR_NOTFOUND)))
    		return symbols_off;
    
    	fdt_for_each_property_offset(property, fdto, fixups_off) {
    		int ret;
    
    		ret = overlay_fixup_phandle(fdt, fdto, symbols_off, property);
    		if (ret)
    			return ret;
    	}
    
    	return 0;
    }
    
    /**
     * overlay_apply_node - Merges a node into the base device tree
     * @fdt: Base Device Tree blob
     * @target: Node offset in the base device tree to apply the fragment to
     * @fdto: Device tree overlay blob
     * @node: Node offset in the overlay holding the changes to merge
     *
     * overlay_apply_node() merges a node into a target base device tree
     * node pointed.
     *
     * This is part of the final step in the device tree overlay
     * application process, when all the phandles have been adjusted and
     * resolved and you just have to merge overlay into the base device
     * tree.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_apply_node(void *fdt, int target,
    			      void *fdto, int node)
    {
    	int property;
    	int subnode;
    
    	fdt_for_each_property_offset(property, fdto, node) {
    		const char *name;
    		const void *prop;
    		int prop_len;
    		int ret;
    
    		prop = fdt_getprop_by_offset(fdto, property, &name,
    					     &prop_len);
    		if (prop_len == -FDT_ERR_NOTFOUND)
    			return -FDT_ERR_INTERNAL;
    		if (prop_len < 0)
    			return prop_len;
    
    		ret = fdt_setprop(fdt, target, name, prop, prop_len);
    		if (ret)
    			return ret;
    	}
    
    	fdt_for_each_subnode(subnode, fdto, node) {
    		const char *name = fdt_get_name(fdto, subnode, NULL);
    		int nnode;
    		int ret;
    
    		nnode = fdt_add_subnode(fdt, target, name);
    		if (nnode == -FDT_ERR_EXISTS) {
    			nnode = fdt_subnode_offset(fdt, target, name);
    			if (nnode == -FDT_ERR_NOTFOUND)
    				return -FDT_ERR_INTERNAL;
    		}
    
    		if (nnode < 0)
    			return nnode;
    
    		ret = overlay_apply_node(fdt, nnode, fdto, subnode);
    		if (ret)
    			return ret;
    	}
    
    	return 0;
    }
    
    /**
     * overlay_merge - Merge an overlay into its base device tree
     * @fdt: Base Device Tree blob
     * @fdto: Device tree overlay blob
     *
     * overlay_merge() merges an overlay into its base device tree.
     *
     * This is the next to last step in the device tree overlay application
     * process, when all the phandles have been adjusted and resolved and
     * you just have to merge overlay into the base device tree.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_merge(void *fdt, void *fdto)
    {
    	int fragment;
    
    	fdt_for_each_subnode(fragment, fdto, 0) {
    		int overlay;
    		int target;
    		int ret;
    
    		/*
    		 * Each fragments will have an __overlay__ node. If
    		 * they don't, it's not supposed to be merged
    		 */
    		overlay = fdt_subnode_offset(fdto, fragment, "__overlay__");
    		if (overlay == -FDT_ERR_NOTFOUND)
    			continue;
    
    		if (overlay < 0)
    			return overlay;
    
    		target = overlay_get_target(fdt, fdto, fragment, NULL);
    		if (target < 0)
    			return target;
    
    		ret = overlay_apply_node(fdt, target, fdto, overlay);
    		if (ret)
    			return ret;
    	}
    
    	return 0;
    }
    
    static int get_path_len(const void *fdt, int nodeoffset)
    {
    	int len = 0, namelen;
    	const char *name;
    
    	FDT_CHECK_HEADER(fdt);
    
    	for (;;) {
    		name = fdt_get_name(fdt, nodeoffset, &namelen);
    		if (!name)
    			return namelen;
    
    		/* root? we're done */
    		if (namelen == 0)
    			break;
    
    		nodeoffset = fdt_parent_offset(fdt, nodeoffset);
    		if (nodeoffset < 0)
    			return nodeoffset;
    		len += namelen + 1;
    	}
    
    	/* in case of root pretend it's "/" */
    	if (len == 0)
    		len++;
    	return len;
    }
    
    /**
     * overlay_symbol_update - Update the symbols of base tree after a merge
     * @fdt: Base Device Tree blob
     * @fdto: Device tree overlay blob
     *
     * overlay_symbol_update() updates the symbols of the base tree with the
     * symbols of the applied overlay
     *
     * This is the last step in the device tree overlay application
     * process, allowing the reference of overlay symbols by subsequent
     * overlay operations.
     *
     * returns:
     *      0 on success
     *      Negative error code on failure
     */
    static int overlay_symbol_update(void *fdt, void *fdto)
    {
    	int root_sym, ov_sym, prop, path_len, fragment, target;
    	int len, frag_name_len, ret, rel_path_len;
    	const char *s, *e;
    	const char *path;
    	const char *name;
    	const char *frag_name;
    	const char *rel_path;
    	const char *target_path;
    	char *buf;
    	void *p;
    
    	ov_sym = fdt_subnode_offset(fdto, 0, "__symbols__");
    
    	/* if no overlay symbols exist no problem */
    	if (ov_sym < 0)
    		return 0;
    
    	root_sym = fdt_subnode_offset(fdt, 0, "__symbols__");
    
    	/* it no root symbols exist we should create them */
    	if (root_sym == -FDT_ERR_NOTFOUND)
    		root_sym = fdt_add_subnode(fdt, 0, "__symbols__");
    
    	/* any error is fatal now */
    	if (root_sym < 0)
    		return root_sym;
    
    	/* iterate over each overlay symbol */
    	fdt_for_each_property_offset(prop, fdto, ov_sym) {
    		path = fdt_getprop_by_offset(fdto, prop, &name, &path_len);
    		if (!path)
    			return path_len;
    
    		/* verify it's a string property (terminated by a single \0) */
    		if (path_len < 1 || memchr(path, '\0', path_len) != &path[path_len - 1])
    			return -FDT_ERR_BADVALUE;
    
    		/* keep end marker to avoid strlen() */
    		e = path + path_len;
    
    		/* format: /<fragment-name>/__overlay__/<relative-subnode-path> */
    
    		if (*path != '/')
    			return -FDT_ERR_BADVALUE;
    
    		/* get fragment name first */
    		s = strchr(path + 1, '/');
    		if (!s)
    			return -FDT_ERR_BADOVERLAY;
    
    		frag_name = path + 1;
    		frag_name_len = s - path - 1;
    
    		/* verify format; safe since "s" lies in \0 terminated prop */
    		len = sizeof("/__overlay__/") - 1;
    		if ((e - s) < len || memcmp(s, "/__overlay__/", len))
    			return -FDT_ERR_BADOVERLAY;
    
    		rel_path = s + len;
    		rel_path_len = e - rel_path;
    
    		/* find the fragment index in which the symbol lies */
    		ret = fdt_subnode_offset_namelen(fdto, 0, frag_name,
    					       frag_name_len);
    		/* not found? */
    		if (ret < 0)
    			return -FDT_ERR_BADOVERLAY;
    		fragment = ret;
    
    		/* an __overlay__ subnode must exist */
    		ret = fdt_subnode_offset(fdto, fragment, "__overlay__");
    		if (ret < 0)
    			return -FDT_ERR_BADOVERLAY;
    
    		/* get the target of the fragment */
    		ret = overlay_get_target(fdt, fdto, fragment, &target_path);
    		if (ret < 0)
    			return ret;
    		target = ret;
    
    		/* if we have a target path use */
    		if (!target_path) {
    			ret = get_path_len(fdt, target);
    			if (ret < 0)
    				return ret;
    			len = ret;
    		} else {
    			len = strlen(target_path);
    		}
    
    		ret = fdt_setprop_placeholder(fdt, root_sym, name,
    				len + (len > 1) + rel_path_len + 1, &p);
    		if (ret < 0)
    			return ret;
    
    		if (!target_path) {
    			/* again in case setprop_placeholder changed it */
    			ret = overlay_get_target(fdt, fdto, fragment, &target_path);
    			if (ret < 0)
    				return ret;
    			target = ret;
    		}
    
    		buf = p;
    		if (len > 1) { /* target is not root */
    			if (!target_path) {
    				ret = fdt_get_path(fdt, target, buf, len + 1);
    				if (ret < 0)
    					return ret;
    			} else
    				memcpy(buf, target_path, len + 1);
    
    		} else
    			len--;
    
    		buf[len] = '/';
    		memcpy(buf + len + 1, rel_path, rel_path_len);
    		buf[len + 1 + rel_path_len] = '\0';
    	}
    
    	return 0;
    }
    
    int fdt_overlay_apply(void *fdt, void *fdto)
    {
    	uint32_t delta = fdt_get_max_phandle(fdt);
    	int ret;
    
    	FDT_CHECK_HEADER(fdt);
    	FDT_CHECK_HEADER(fdto);
    
    	ret = overlay_adjust_local_phandles(fdto, delta);
    	if (ret)
    		goto err;
    
    	ret = overlay_update_local_references(fdto, delta);
    	if (ret)
    		goto err;
    
    	ret = overlay_fixup_phandles(fdt, fdto);
    	if (ret)
    		goto err;
    
    	ret = overlay_merge(fdt, fdto);
    	if (ret)
    		goto err;
    
    	ret = overlay_symbol_update(fdt, fdto);
    	if (ret)
    		goto err;
    
    	/*
    	 * The overlay has been damaged, erase its magic.
    	 */
    	fdt_set_magic(fdto, ~0);
    
    	return 0;
    
    err:
    	/*
    	 * The overlay might have been damaged, erase its magic.
    	 */
    	fdt_set_magic(fdto, ~0);
    
    	/*
    	 * The base device tree might have been damaged, erase its
    	 * magic.
    	 */
    	fdt_set_magic(fdt, ~0);
    
    	return ret;
    }