resolver.c

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