1/* 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 bool have_node; /* True if any node is included */ 81 struct fdt_region_ptrs ptrs; /* Pointers for what we are up to */ 82}; 83 84/** 85 * fdt_find_regions() - find regions in device tree 86 * 87 * Given a list of nodes to include and properties to exclude, find 88 * the regions of the device tree which describe those included parts. 89 * 90 * The intent is to get a list of regions which will be invariant provided 91 * those parts are invariant. For example, if you request a list of regions 92 * for all nodes but exclude the property "data", then you will get the 93 * same region contents regardless of any change to "data" properties. 94 * 95 * This function can be used to produce a byte-stream to send to a hashing 96 * function to verify that critical parts of the FDT have not changed. 97 * 98 * Nodes which are given in 'inc' are included in the region list, as 99 * are the names of the immediate subnodes nodes (but not the properties 100 * or subnodes of those subnodes). 101 * 102 * For eaxample "/" means to include the root node, all root properties 103 * and the FDT_BEGIN_NODE and FDT_END_NODE of all subnodes of /. The latter 104 * ensures that we capture the names of the subnodes. In a hashing situation 105 * it prevents the root node from changing at all Any change to non-excluded 106 * properties, names of subnodes or number of subnodes would be detected. 107 * 108 * When used with FITs this provides the ability to hash and sign parts of 109 * the FIT based on different configurations in the FIT. Then it is 110 * impossible to change anything about that configuration (include images 111 * attached to the configuration), but it may be possible to add new 112 * configurations, new images or new signatures within the existing 113 * framework. 114 * 115 * Adding new properties to a device tree may result in the string table 116 * being extended (if the new property names are different from those 117 * already added). This function can optionally include a region for 118 * the string table so that this can be part of the hash too. 119 * 120 * The device tree header is not included in the list. 121 * 122 * @fdt: Device tree to check 123 * @inc: List of node paths to included 124 * @inc_count: Number of node paths in list 125 * @exc_prop: List of properties names to exclude 126 * @exc_prop_count: Number of properties in exclude list 127 * @region: Returns list of regions 128 * @max_region: Maximum length of region list 129 * @path: Pointer to a temporary string for the function to use for 130 * building path names 131 * @path_len: Length of path, must be large enough to hold the longest 132 * path in the tree 133 * @add_string_tab: 1 to add a region for the string table 134 * Return: number of regions in list. If this is >max_regions then the 135 * region array was exhausted. You should increase max_regions and try 136 * the call again. 137 */ 138int fdt_find_regions(const void *fdt, char * const inc[], int inc_count, 139 char * const exc_prop[], int exc_prop_count, 140 struct fdt_region region[], int max_regions, 141 char *path, int path_len, int add_string_tab); 142 143/** 144 * fdt_first_region() - find regions in device tree 145 * 146 * Given a nodes and properties to include and properties to exclude, find 147 * the regions of the device tree which describe those included parts. 148 * 149 * The use for this function is twofold. Firstly it provides a convenient 150 * way of performing a structure-aware grep of the tree. For example it is 151 * possible to grep for a node and get all the properties associated with 152 * that node. Trees can be subsetted easily, by specifying the nodes that 153 * are required, and then writing out the regions returned by this function. 154 * This is useful for small resource-constrained systems, such as boot 155 * loaders, which want to use an FDT but do not need to know about all of 156 * it. 157 * 158 * Secondly it makes it easy to hash parts of the tree and detect changes. 159 * The intent is to get a list of regions which will be invariant provided 160 * those parts are invariant. For example, if you request a list of regions 161 * for all nodes but exclude the property "data", then you will get the 162 * same region contents regardless of any change to "data" properties. 163 * 164 * This function can be used to produce a byte-stream to send to a hashing 165 * function to verify that critical parts of the FDT have not changed. 166 * Note that semantically null changes in order could still cause false 167 * hash misses. Such reordering might happen if the tree is regenerated 168 * from source, and nodes are reordered (the bytes-stream will be emitted 169 * in a different order and many hash functions will detect this). However 170 * if an existing tree is modified using libfdt functions, such as 171 * fdt_add_subnode() and fdt_setprop(), then this problem is avoided. 172 * 173 * The nodes/properties to include/exclude are defined by a function 174 * provided by the caller. This function is called for each node and 175 * property, and must return: 176 * 177 * 0 - to exclude this part 178 * 1 - to include this part 179 * -1 - for FDT_IS_PROP only: no information is available, so include 180 * if its containing node is included 181 * 182 * The last case is only used to deal with properties. Often a property is 183 * included if its containing node is included - this is the case where 184 * -1 is returned.. However if the property is specifically required to be 185 * included/excluded, then 0 or 1 can be returned. Note that including a 186 * property when the FDT_REG_SUPERNODES flag is given will force its 187 * containing node to be included since it is not valid to have a property 188 * that is not in a node. 189 * 190 * Using the information provided, the inclusion of a node can be controlled 191 * either by a node name or its compatible string, or any other property 192 * that the function can determine. 193 * 194 * As an example, including node "/" means to include the root node and all 195 * root properties. A flag provides a way of also including supernodes (of 196 * which there is none for the root node), and another flag includes 197 * immediate subnodes, so in this case we would get the FDT_BEGIN_NODE and 198 * FDT_END_NODE of all subnodes of /. 199 * 200 * The subnode feature helps in a hashing situation since it prevents the 201 * root node from changing at all. Any change to non-excluded properties, 202 * names of subnodes or number of subnodes would be detected. 203 * 204 * When used with FITs this provides the ability to hash and sign parts of 205 * the FIT based on different configurations in the FIT. Then it is 206 * impossible to change anything about that configuration (include images 207 * attached to the configuration), but it may be possible to add new 208 * configurations, new images or new signatures within the existing 209 * framework. 210 * 211 * Adding new properties to a device tree may result in the string table 212 * being extended (if the new property names are different from those 213 * already added). This function can optionally include a region for 214 * the string table so that this can be part of the hash too. This is always 215 * the last region. 216 * 217 * The FDT also has a mem_rsvmap table which can also be included, and is 218 * always the first region if so. 219 * 220 * The device tree header is not included in the region list. Since the 221 * contents of the FDT are changing (shrinking, often), the caller will need 222 * to regenerate the header anyway. 223 * 224 * @fdt: Device tree to check 225 * @h_include: Function to call to determine whether to include a part or 226 * not: 227 * 228 * @priv: Private pointer as passed to fdt_find_regions() 229 * @fdt: Pointer to FDT blob 230 * @offset: Offset of this node / property 231 * @type: Type of this part, FDT_IS_... 232 * @data: Pointer to data (node name, property name, compatible 233 * string, value (not yet supported) 234 * @size: Size of data, or 0 if none 235 * Return: 0 to exclude, 1 to include, -1 if no information is 236 * available 237 * @priv: Private pointer passed to h_include 238 * @region: Returns list of regions, sorted by offset 239 * @max_regions: Maximum length of region list 240 * @path: Pointer to a temporary string for the function to use for 241 * building path names 242 * @path_len: Length of path, must be large enough to hold the longest 243 * path in the tree 244 * @flags: Various flags that control the region algortihm, see 245 * FDT_REG_... 246 * Return: number of regions in list. If this is >max_regions then the 247 * region array was exhausted. You should increase max_regions and try 248 * the call again. Only the first max_regions elements are available in the 249 * array. 250 * 251 * On error a -ve value is return, which can be: 252 * 253 * -FDT_ERR_BADSTRUCTURE (too deep or more END tags than BEGIN tags 254 * -FDT_ERR_BADLAYOUT 255 * -FDT_ERR_NOSPACE (path area is too small) 256 */ 257int fdt_first_region(const void *fdt, 258 int (*h_include)(void *priv, const void *fdt, int offset, 259 int type, const char *data, int size), 260 void *priv, struct fdt_region *region, 261 char *path, int path_len, int flags, 262 struct fdt_region_state *info); 263 264/** fdt_next_region() - find next region 265 * 266 * See fdt_first_region() for full description. This function finds the 267 * next region according to the provided parameters, which must be the same 268 * as passed to fdt_first_region(). 269 * 270 * This function can additionally return -FDT_ERR_NOTFOUND when there are no 271 * more regions 272 */ 273int fdt_next_region(const void *fdt, 274 int (*h_include)(void *priv, const void *fdt, int offset, 275 int type, const char *data, int size), 276 void *priv, struct fdt_region *region, 277 char *path, int path_len, int flags, 278 struct fdt_region_state *info); 279 280/** 281 * fdt_add_alias_regions() - find aliases that point to existing regions 282 * 283 * Once a device tree grep is complete some of the nodes will be present 284 * and some will have been dropped. This function checks all the alias nodes 285 * to figure out which points point to nodes which are still present. These 286 * aliases need to be kept, along with the nodes they reference. 287 * 288 * Given a list of regions function finds the aliases that still apply and 289 * adds more regions to the list for these. This function is called after 290 * fdt_next_region() has finished returning regions and requires the same 291 * state. 292 * 293 * @fdt: Device tree file to reference 294 * @region: List of regions that will be kept 295 * @count: Number of regions 296 * @max_regions: Number of entries that can fit in @region 297 * @info: Region state as returned from fdt_next_region() 298 * Return: new number of regions in @region (i.e. count + the number added) 299 * or -FDT_ERR_NOSPACE if there was not enough space. 300 */ 301int fdt_add_alias_regions(const void *fdt, struct fdt_region *region, int count, 302 int max_regions, struct fdt_region_state *info); 303#endif /* SWIG */ 304 305#endif /* _FDT_REGION_H */ 306