1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * Functions for dealing with DT resolution
4  *
5  * Copyright (C) 2012 Pantelis Antoniou <panto@antoniou-consulting.com>
6  * Copyright (C) 2012 Texas Instruments Inc.
7  */
8 
9 #define pr_fmt(fmt)	"OF: resolver: " fmt
10 
11 #include <linux/kernel.h>
12 #include <linux/module.h>
13 #include <linux/of.h>
14 #include <linux/of_device.h>
15 #include <linux/string.h>
16 #include <linux/ctype.h>
17 #include <linux/errno.h>
18 #include <linux/slab.h>
19 
20 #include "of_private.h"
21 
live_tree_max_phandle(void)22 static phandle live_tree_max_phandle(void)
23 {
24 	struct device_node *node;
25 	phandle phandle;
26 	unsigned long flags;
27 
28 	raw_spin_lock_irqsave(&devtree_lock, flags);
29 	phandle = 0;
30 	for_each_of_allnodes(node) {
31 		if (node->phandle != OF_PHANDLE_ILLEGAL &&
32 				node->phandle > phandle)
33 			phandle = node->phandle;
34 	}
35 	raw_spin_unlock_irqrestore(&devtree_lock, flags);
36 
37 	return phandle;
38 }
39 
adjust_overlay_phandles(struct device_node * overlay,int phandle_delta)40 static void adjust_overlay_phandles(struct device_node *overlay,
41 		int phandle_delta)
42 {
43 	struct device_node *child;
44 	struct property *prop;
45 	phandle phandle;
46 
47 	/* adjust node's phandle in node */
48 	if (overlay->phandle != 0 && overlay->phandle != OF_PHANDLE_ILLEGAL)
49 		overlay->phandle += phandle_delta;
50 
51 	/* copy adjusted phandle into *phandle properties */
52 	for_each_property_of_node(overlay, prop) {
53 
54 		if (of_prop_cmp(prop->name, "phandle") &&
55 		    of_prop_cmp(prop->name, "linux,phandle"))
56 			continue;
57 
58 		if (prop->length < 4)
59 			continue;
60 
61 		phandle = be32_to_cpup(prop->value);
62 		if (phandle == OF_PHANDLE_ILLEGAL)
63 			continue;
64 
65 		*(__be32 *)prop->value = cpu_to_be32(overlay->phandle);
66 	}
67 
68 	for_each_child_of_node(overlay, child)
69 		adjust_overlay_phandles(child, phandle_delta);
70 }
71 
update_usages_of_a_phandle_reference(struct device_node * overlay,struct property * prop_fixup,phandle phandle)72 static int update_usages_of_a_phandle_reference(struct device_node *overlay,
73 		struct property *prop_fixup, phandle phandle)
74 {
75 	struct device_node *refnode;
76 	struct property *prop;
77 	char *value, *cur, *end, *node_path, *prop_name, *s;
78 	int offset, len;
79 	int err = 0;
80 
81 	value = kmemdup(prop_fixup->value, prop_fixup->length, GFP_KERNEL);
82 	if (!value)
83 		return -ENOMEM;
84 
85 	/* prop_fixup contains a list of tuples of path:property_name:offset */
86 	end = value + prop_fixup->length;
87 	for (cur = value; cur < end; cur += len + 1) {
88 		len = strlen(cur);
89 
90 		node_path = cur;
91 		s = strchr(cur, ':');
92 		if (!s) {
93 			err = -EINVAL;
94 			goto err_fail;
95 		}
96 		*s++ = '\0';
97 
98 		prop_name = s;
99 		s = strchr(s, ':');
100 		if (!s) {
101 			err = -EINVAL;
102 			goto err_fail;
103 		}
104 		*s++ = '\0';
105 
106 		err = kstrtoint(s, 10, &offset);
107 		if (err)
108 			goto err_fail;
109 
110 		refnode = __of_find_node_by_full_path(of_node_get(overlay), node_path);
111 		if (!refnode)
112 			continue;
113 
114 		for_each_property_of_node(refnode, prop) {
115 			if (!of_prop_cmp(prop->name, prop_name))
116 				break;
117 		}
118 		of_node_put(refnode);
119 
120 		if (!prop) {
121 			err = -ENOENT;
122 			goto err_fail;
123 		}
124 
125 		if (offset < 0 || offset + sizeof(__be32) > prop->length) {
126 			err = -EINVAL;
127 			goto err_fail;
128 		}
129 
130 		*(__be32 *)(prop->value + offset) = cpu_to_be32(phandle);
131 	}
132 
133 err_fail:
134 	kfree(value);
135 	return err;
136 }
137 
138 /* compare nodes taking into account that 'name' strips out the @ part */
node_name_cmp(const struct device_node * dn1,const struct device_node * dn2)139 static int node_name_cmp(const struct device_node *dn1,
140 		const struct device_node *dn2)
141 {
142 	const char *n1 = kbasename(dn1->full_name);
143 	const char *n2 = kbasename(dn2->full_name);
144 
145 	return of_node_cmp(n1, n2);
146 }
147 
148 /*
149  * Adjust the local phandle references by the given phandle delta.
150  *
151  * Subtree @local_fixups, which is overlay node __local_fixups__,
152  * mirrors the fragment node structure at the root of the overlay.
153  *
154  * For each property in the fragments that contains a phandle reference,
155  * @local_fixups has a property of the same name that contains a list
156  * of offsets of the phandle reference(s) within the respective property
157  * value(s).  The values at these offsets will be fixed up.
158  */
adjust_local_phandle_references(struct device_node * local_fixups,struct device_node * overlay,int phandle_delta)159 static int adjust_local_phandle_references(struct device_node *local_fixups,
160 		struct device_node *overlay, int phandle_delta)
161 {
162 	struct device_node *child, *overlay_child;
163 	struct property *prop_fix, *prop;
164 	int err, i, count;
165 	unsigned int off;
166 
167 	if (!local_fixups)
168 		return 0;
169 
170 	for_each_property_of_node(local_fixups, prop_fix) {
171 
172 		/* skip properties added automatically */
173 		if (!of_prop_cmp(prop_fix->name, "name") ||
174 		    !of_prop_cmp(prop_fix->name, "phandle") ||
175 		    !of_prop_cmp(prop_fix->name, "linux,phandle"))
176 			continue;
177 
178 		if ((prop_fix->length % 4) != 0 || prop_fix->length == 0)
179 			return -EINVAL;
180 		count = prop_fix->length / sizeof(__be32);
181 
182 		for_each_property_of_node(overlay, prop) {
183 			if (!of_prop_cmp(prop->name, prop_fix->name))
184 				break;
185 		}
186 
187 		if (!prop)
188 			return -EINVAL;
189 
190 		for (i = 0; i < count; i++) {
191 			off = be32_to_cpu(((__be32 *)prop_fix->value)[i]);
192 			if ((off + 4) > prop->length)
193 				return -EINVAL;
194 
195 			be32_add_cpu(prop->value + off, phandle_delta);
196 		}
197 	}
198 
199 	/*
200 	 * These nested loops recurse down two subtrees in parallel, where the
201 	 * node names in the two subtrees match.
202 	 *
203 	 * The roots of the subtrees are the overlay's __local_fixups__ node
204 	 * and the overlay's root node.
205 	 */
206 	for_each_child_of_node(local_fixups, child) {
207 
208 		for_each_child_of_node(overlay, overlay_child)
209 			if (!node_name_cmp(child, overlay_child)) {
210 				of_node_put(overlay_child);
211 				break;
212 			}
213 
214 		if (!overlay_child) {
215 			of_node_put(child);
216 			return -EINVAL;
217 		}
218 
219 		err = adjust_local_phandle_references(child, overlay_child,
220 				phandle_delta);
221 		if (err) {
222 			of_node_put(child);
223 			return err;
224 		}
225 	}
226 
227 	return 0;
228 }
229 
230 /**
231  * of_resolve_phandles - Relocate and resolve overlay against live tree
232  *
233  * @overlay:	Pointer to devicetree overlay to relocate and resolve
234  *
235  * Modify (relocate) values of local phandles in @overlay to a range that
236  * does not conflict with the live expanded devicetree.  Update references
237  * to the local phandles in @overlay.  Update (resolve) phandle references
238  * in @overlay that refer to the live expanded devicetree.
239  *
240  * Phandle values in the live tree are in the range of
241  * 1 .. live_tree_max_phandle().  The range of phandle values in the overlay
242  * also begin with at 1.  Adjust the phandle values in the overlay to begin
243  * at live_tree_max_phandle() + 1.  Update references to the phandles to
244  * the adjusted phandle values.
245  *
246  * The name of each property in the "__fixups__" node in the overlay matches
247  * the name of a symbol (a label) in the live tree.  The values of each
248  * property in the "__fixups__" node is a list of the property values in the
249  * overlay that need to be updated to contain the phandle reference
250  * corresponding to that symbol in the live tree.  Update the references in
251  * the overlay with the phandle values in the live tree.
252  *
253  * @overlay must be detached.
254  *
255  * Resolving and applying @overlay to the live expanded devicetree must be
256  * protected by a mechanism to ensure that multiple overlays are processed
257  * in a single threaded manner so that multiple overlays will not relocate
258  * phandles to overlapping ranges.  The mechanism to enforce this is not
259  * yet implemented.
260  *
261  * Return: %0 on success or a negative error value on error.
262  */
of_resolve_phandles(struct device_node * overlay)263 int of_resolve_phandles(struct device_node *overlay)
264 {
265 	struct device_node *child, *local_fixups, *refnode;
266 	struct device_node *tree_symbols, *overlay_fixups;
267 	struct property *prop;
268 	const char *refpath;
269 	phandle phandle, phandle_delta;
270 	int err;
271 
272 	tree_symbols = NULL;
273 
274 	if (!overlay) {
275 		pr_err("null overlay\n");
276 		err = -EINVAL;
277 		goto out;
278 	}
279 
280 	if (!of_node_check_flag(overlay, OF_DETACHED)) {
281 		pr_err("overlay not detached\n");
282 		err = -EINVAL;
283 		goto out;
284 	}
285 
286 	phandle_delta = live_tree_max_phandle() + 1;
287 	adjust_overlay_phandles(overlay, phandle_delta);
288 
289 	for_each_child_of_node(overlay, local_fixups)
290 		if (of_node_name_eq(local_fixups, "__local_fixups__"))
291 			break;
292 
293 	err = adjust_local_phandle_references(local_fixups, overlay, phandle_delta);
294 	if (err)
295 		goto out;
296 
297 	overlay_fixups = NULL;
298 
299 	for_each_child_of_node(overlay, child) {
300 		if (of_node_name_eq(child, "__fixups__"))
301 			overlay_fixups = child;
302 	}
303 
304 	if (!overlay_fixups) {
305 		err = 0;
306 		goto out;
307 	}
308 
309 	tree_symbols = of_find_node_by_path("/__symbols__");
310 	if (!tree_symbols) {
311 		pr_err("no symbols in root of device tree.\n");
312 		err = -EINVAL;
313 		goto out;
314 	}
315 
316 	for_each_property_of_node(overlay_fixups, prop) {
317 
318 		/* skip properties added automatically */
319 		if (!of_prop_cmp(prop->name, "name"))
320 			continue;
321 
322 		err = of_property_read_string(tree_symbols,
323 				prop->name, &refpath);
324 		if (err) {
325 			pr_err("node label '%s' not found in live devicetree symbols table\n",
326 			       prop->name);
327 			goto out;
328 		}
329 
330 		refnode = of_find_node_by_path(refpath);
331 		if (!refnode) {
332 			err = -ENOENT;
333 			goto out;
334 		}
335 
336 		phandle = refnode->phandle;
337 		of_node_put(refnode);
338 
339 		err = update_usages_of_a_phandle_reference(overlay, prop, phandle);
340 		if (err)
341 			break;
342 	}
343 
344 out:
345 	if (err)
346 		pr_err("overlay phandle fixup failed: %d\n", err);
347 	of_node_put(tree_symbols);
348 
349 	return err;
350 }
351 EXPORT_SYMBOL_GPL(of_resolve_phandles);
352