include/fdt_region.h

   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 */