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Masahiro Yamada64045a62020-04-16 18:30:18 +09001/* SPDX-License-Identifier: GPL-2.0 */
2
3#ifndef _FDT_REGION_H
4#define _FDT_REGION_H
5
6#ifndef SWIG /* Not available in Python */
7struct fdt_region {
8 int offset;
9 int size;
10};
11
12/*
13 * Flags for fdt_find_regions()
14 *
15 * Add a region for the string table (always the last region)
16 */
17#define FDT_REG_ADD_STRING_TAB (1 << 0)
18
19/*
20 * Add all supernodes of a matching node/property, useful for creating a
21 * valid subset tree
22 */
23#define FDT_REG_SUPERNODES (1 << 1)
24
25/* Add the FDT_BEGIN_NODE tags of subnodes, including their names */
26#define FDT_REG_DIRECT_SUBNODES (1 << 2)
27
28/* Add all subnodes of a matching node */
29#define FDT_REG_ALL_SUBNODES (1 << 3)
30
31/* Add a region for the mem_rsvmap table (always the first region) */
32#define FDT_REG_ADD_MEM_RSVMAP (1 << 4)
33
34/* Indicates what an fdt part is (node, property, value) */
35#define FDT_IS_NODE (1 << 0)
36#define FDT_IS_PROP (1 << 1)
37#define FDT_IS_VALUE (1 << 2) /* not supported */
38#define FDT_IS_COMPAT (1 << 3) /* used internally */
39#define FDT_NODE_HAS_PROP (1 << 4) /* node contains prop */
40
41#define FDT_ANY_GLOBAL (FDT_IS_NODE | FDT_IS_PROP | FDT_IS_VALUE | \
42 FDT_IS_COMPAT)
43#define FDT_IS_ANY 0x1f /* all the above */
44
45/* We set a reasonable limit on the number of nested nodes */
46#define FDT_MAX_DEPTH 32
47
48/* Decribes what we want to include from the current tag */
49enum want_t {
50 WANT_NOTHING,
51 WANT_NODES_ONLY, /* No properties */
52 WANT_NODES_AND_PROPS, /* Everything for one level */
53 WANT_ALL_NODES_AND_PROPS /* Everything for all levels */
54};
55
56/* Keeps track of the state at parent nodes */
57struct fdt_subnode_stack {
58 int offset; /* Offset of node */
59 enum want_t want; /* The 'want' value here */
60 int included; /* 1 if we included this node, 0 if not */
61};
62
63struct fdt_region_ptrs {
64 int depth; /* Current tree depth */
65 int done; /* What we have completed scanning */
66 enum want_t want; /* What we are currently including */
67 char *end; /* Pointer to end of full node path */
68 int nextoffset; /* Next node offset to check */
69};
70
71/* The state of our finding algortihm */
72struct fdt_region_state {
73 struct fdt_subnode_stack stack[FDT_MAX_DEPTH]; /* node stack */
74 struct fdt_region *region; /* Contains list of regions found */
75 int count; /* Numnber of regions found */
76 const void *fdt; /* FDT blob */
77 int max_regions; /* Maximum regions to find */
78 int can_merge; /* 1 if we can merge with previous region */
79 int start; /* Start position of current region */
80 struct fdt_region_ptrs ptrs; /* Pointers for what we are up to */
81};
82
83/**
84 * fdt_find_regions() - find regions in device tree
85 *
86 * Given a list of nodes to include and properties to exclude, find
87 * the regions of the device tree which describe those included parts.
88 *
89 * The intent is to get a list of regions which will be invariant provided
90 * those parts are invariant. For example, if you request a list of regions
91 * for all nodes but exclude the property "data", then you will get the
92 * same region contents regardless of any change to "data" properties.
93 *
94 * This function can be used to produce a byte-stream to send to a hashing
95 * function to verify that critical parts of the FDT have not changed.
96 *
97 * Nodes which are given in 'inc' are included in the region list, as
98 * are the names of the immediate subnodes nodes (but not the properties
99 * or subnodes of those subnodes).
100 *
101 * For eaxample "/" means to include the root node, all root properties
102 * and the FDT_BEGIN_NODE and FDT_END_NODE of all subnodes of /. The latter
103 * ensures that we capture the names of the subnodes. In a hashing situation
104 * it prevents the root node from changing at all Any change to non-excluded
105 * properties, names of subnodes or number of subnodes would be detected.
106 *
107 * When used with FITs this provides the ability to hash and sign parts of
108 * the FIT based on different configurations in the FIT. Then it is
109 * impossible to change anything about that configuration (include images
110 * attached to the configuration), but it may be possible to add new
111 * configurations, new images or new signatures within the existing
112 * framework.
113 *
114 * Adding new properties to a device tree may result in the string table
115 * being extended (if the new property names are different from those
116 * already added). This function can optionally include a region for
117 * the string table so that this can be part of the hash too.
118 *
119 * The device tree header is not included in the list.
120 *
121 * @fdt: Device tree to check
122 * @inc: List of node paths to included
123 * @inc_count: Number of node paths in list
124 * @exc_prop: List of properties names to exclude
125 * @exc_prop_count: Number of properties in exclude list
126 * @region: Returns list of regions
127 * @max_region: Maximum length of region list
128 * @path: Pointer to a temporary string for the function to use for
129 * building path names
130 * @path_len: Length of path, must be large enough to hold the longest
131 * path in the tree
132 * @add_string_tab: 1 to add a region for the string table
133 * @return number of regions in list. If this is >max_regions then the
134 * region array was exhausted. You should increase max_regions and try
135 * the call again.
136 */
137int fdt_find_regions(const void *fdt, char * const inc[], int inc_count,
138 char * const exc_prop[], int exc_prop_count,
139 struct fdt_region region[], int max_regions,
140 char *path, int path_len, int add_string_tab);
141
142/**
143 * fdt_first_region() - find regions in device tree
144 *
145 * Given a nodes and properties to include and properties to exclude, find
146 * the regions of the device tree which describe those included parts.
147 *
148 * The use for this function is twofold. Firstly it provides a convenient
149 * way of performing a structure-aware grep of the tree. For example it is
150 * possible to grep for a node and get all the properties associated with
151 * that node. Trees can be subsetted easily, by specifying the nodes that
152 * are required, and then writing out the regions returned by this function.
153 * This is useful for small resource-constrained systems, such as boot
154 * loaders, which want to use an FDT but do not need to know about all of
155 * it.
156 *
157 * Secondly it makes it easy to hash parts of the tree and detect changes.
158 * The intent is to get a list of regions which will be invariant provided
159 * those parts are invariant. For example, if you request a list of regions
160 * for all nodes but exclude the property "data", then you will get the
161 * same region contents regardless of any change to "data" properties.
162 *
163 * This function can be used to produce a byte-stream to send to a hashing
164 * function to verify that critical parts of the FDT have not changed.
165 * Note that semantically null changes in order could still cause false
166 * hash misses. Such reordering might happen if the tree is regenerated
167 * from source, and nodes are reordered (the bytes-stream will be emitted
168 * in a different order and many hash functions will detect this). However
169 * if an existing tree is modified using libfdt functions, such as
170 * fdt_add_subnode() and fdt_setprop(), then this problem is avoided.
171 *
172 * The nodes/properties to include/exclude are defined by a function
173 * provided by the caller. This function is called for each node and
174 * property, and must return:
175 *
176 * 0 - to exclude this part
177 * 1 - to include this part
178 * -1 - for FDT_IS_PROP only: no information is available, so include
179 * if its containing node is included
180 *
181 * The last case is only used to deal with properties. Often a property is
182 * included if its containing node is included - this is the case where
183 * -1 is returned.. However if the property is specifically required to be
184 * included/excluded, then 0 or 1 can be returned. Note that including a
185 * property when the FDT_REG_SUPERNODES flag is given will force its
186 * containing node to be included since it is not valid to have a property
187 * that is not in a node.
188 *
189 * Using the information provided, the inclusion of a node can be controlled
190 * either by a node name or its compatible string, or any other property
191 * that the function can determine.
192 *
193 * As an example, including node "/" means to include the root node and all
194 * root properties. A flag provides a way of also including supernodes (of
195 * which there is none for the root node), and another flag includes
196 * immediate subnodes, so in this case we would get the FDT_BEGIN_NODE and
197 * FDT_END_NODE of all subnodes of /.
198 *
199 * The subnode feature helps in a hashing situation since it prevents the
200 * root node from changing at all. Any change to non-excluded properties,
201 * names of subnodes or number of subnodes would be detected.
202 *
203 * When used with FITs this provides the ability to hash and sign parts of
204 * the FIT based on different configurations in the FIT. Then it is
205 * impossible to change anything about that configuration (include images
206 * attached to the configuration), but it may be possible to add new
207 * configurations, new images or new signatures within the existing
208 * framework.
209 *
210 * Adding new properties to a device tree may result in the string table
211 * being extended (if the new property names are different from those
212 * already added). This function can optionally include a region for
213 * the string table so that this can be part of the hash too. This is always
214 * the last region.
215 *
216 * The FDT also has a mem_rsvmap table which can also be included, and is
217 * always the first region if so.
218 *
219 * The device tree header is not included in the region list. Since the
220 * contents of the FDT are changing (shrinking, often), the caller will need
221 * to regenerate the header anyway.
222 *
223 * @fdt: Device tree to check
224 * @h_include: Function to call to determine whether to include a part or
225 * not:
226 *
227 * @priv: Private pointer as passed to fdt_find_regions()
228 * @fdt: Pointer to FDT blob
229 * @offset: Offset of this node / property
230 * @type: Type of this part, FDT_IS_...
231 * @data: Pointer to data (node name, property name, compatible
232 * string, value (not yet supported)
233 * @size: Size of data, or 0 if none
234 * @return 0 to exclude, 1 to include, -1 if no information is
235 * available
236 * @priv: Private pointer passed to h_include
237 * @region: Returns list of regions, sorted by offset
238 * @max_regions: Maximum length of region list
239 * @path: Pointer to a temporary string for the function to use for
240 * building path names
241 * @path_len: Length of path, must be large enough to hold the longest
242 * path in the tree
243 * @flags: Various flags that control the region algortihm, see
244 * FDT_REG_...
245 * @return number of regions in list. If this is >max_regions then the
246 * region array was exhausted. You should increase max_regions and try
247 * the call again. Only the first max_regions elements are available in the
248 * array.
249 *
250 * On error a -ve value is return, which can be:
251 *
252 * -FDT_ERR_BADSTRUCTURE (too deep or more END tags than BEGIN tags
253 * -FDT_ERR_BADLAYOUT
254 * -FDT_ERR_NOSPACE (path area is too small)
255 */
256int fdt_first_region(const void *fdt,
257 int (*h_include)(void *priv, const void *fdt, int offset,
258 int type, const char *data, int size),
259 void *priv, struct fdt_region *region,
260 char *path, int path_len, int flags,
261 struct fdt_region_state *info);
262
263/** fdt_next_region() - find next region
264 *
265 * See fdt_first_region() for full description. This function finds the
266 * next region according to the provided parameters, which must be the same
267 * as passed to fdt_first_region().
268 *
269 * This function can additionally return -FDT_ERR_NOTFOUND when there are no
270 * more regions
271 */
272int fdt_next_region(const void *fdt,
273 int (*h_include)(void *priv, const void *fdt, int offset,
274 int type, const char *data, int size),
275 void *priv, struct fdt_region *region,
276 char *path, int path_len, int flags,
277 struct fdt_region_state *info);
278
279/**
280 * fdt_add_alias_regions() - find aliases that point to existing regions
281 *
282 * Once a device tree grep is complete some of the nodes will be present
283 * and some will have been dropped. This function checks all the alias nodes
284 * to figure out which points point to nodes which are still present. These
285 * aliases need to be kept, along with the nodes they reference.
286 *
287 * Given a list of regions function finds the aliases that still apply and
288 * adds more regions to the list for these. This function is called after
289 * fdt_next_region() has finished returning regions and requires the same
290 * state.
291 *
292 * @fdt: Device tree file to reference
293 * @region: List of regions that will be kept
294 * @count: Number of regions
295 * @max_regions: Number of entries that can fit in @region
296 * @info: Region state as returned from fdt_next_region()
297 * @return new number of regions in @region (i.e. count + the number added)
298 * or -FDT_ERR_NOSPACE if there was not enough space.
299 */
300int fdt_add_alias_regions(const void *fdt, struct fdt_region *region, int count,
301 int max_regions, struct fdt_region_state *info);
302#endif /* SWIG */
303
304#endif /* _FDT_REGION_H */