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 */ 7 struct 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 */ 49 enum 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 */ 57 struct 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 63 struct 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 */ 72 struct 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 */ 137 int 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 */ 256 int 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 */ 272 int 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 */ 300 int 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 */ 305