lib/libfdt/fdt_region.c

   1 /*
   2  * libfdt - Flat Device Tree manipulation
   3  * Copyright (C) 2013 Google, Inc
   4  * Written by Simon Glass <sjg@chromium.org>
   5  * SPDX-License-Identifier:     GPL-2.0+ BSD-2-Clause
   6  */
   7
   8 #include <libfdt_env.h>
   9
  10 #ifndef USE_HOSTCC
  11 #include <fdt.h>
  12 #include <libfdt.h>
  13 #else
  14 #include "fdt_host.h"
  15 #endif
  16
  17 #include "libfdt_internal.h"
  18
  19 /**
  20  * fdt_add_region() - Add a new region to our list
  21  * @info:       State information
  22  * @offset:     Start offset of region
  23  * @size:       Size of region
  24  *
  25  * The region is added if there is space, but in any case we increment the
  26  * count. If permitted, and the new region overlaps the last one, we merge
  27  * them.
  28  */
  29 static int fdt_add_region(struct fdt_region_state *info, int offset, int size)
  30 {
  31         struct fdt_region *reg;
  32
  33         reg = info->region ? &info->region[info->count - 1] : NULL;
  34         if (info->can_merge && info->count &&
  35             info->count <= info->max_regions &&
  36             reg && offset <= reg->offset + reg->size) {
  37                 reg->size = offset + size - reg->offset;
  38         } else if (info->count++ < info->max_regions) {
  39                 if (reg) {
  40                         reg++;
  41                         reg->offset = offset;
  42                         reg->size = size;
  43                 }
  44         } else {
  45                 return -1;
  46         }
  47
  48         return 0;
  49 }
  50
  51 static int region_list_contains_offset(struct fdt_region_state *info,
  52                                        const void *fdt, int target)
  53 {
  54         struct fdt_region *reg;
  55         int num;
  56
  57         target += fdt_off_dt_struct(fdt);
  58         for (reg = info->region, num = 0; num < info->count; reg++, num++) {
  59                 if (target >= reg->offset && target < reg->offset + reg->size)
  60                         return 1;
  61         }
  62
  63         return 0;
  64 }
  65
  66 /**
  67  * fdt_add_alias_regions() - Add regions covering the aliases that we want
  68  *
  69  * The /aliases node is not automatically included by fdtgrep unless the
  70  * command-line arguments cause to be included (or not excluded). However
  71  * aliases are special in that we generally want to include those which
  72  * reference a node that fdtgrep includes.
  73  *
  74  * In fact we want to include only aliases for those nodes still included in
  75  * the fdt, and drop the other aliases since they point to nodes that will not
  76  * be present.
  77  *
  78  * This function scans the aliases and adds regions for those which we want
  79  * to keep.
  80  *
  81  * @fdt: Device tree to scan
  82  * @region: List of regions
  83  * @count: Number of regions in the list so far (i.e. starting point for this
  84  *      function)
  85  * @max_regions: Maximum number of regions in @region list
  86  * @info: Place to put the region state
  87  * @return number of regions after processing, or -FDT_ERR_NOSPACE if we did
  88  * not have enough room in the regions table for the regions we wanted to add.
  89  */
  90 int fdt_add_alias_regions(const void *fdt, struct fdt_region *region, int count,
  91                           int max_regions, struct fdt_region_state *info)
  92 {
  93         int base = fdt_off_dt_struct(fdt);
  94         int node, node_end, offset;
  95         int did_alias_header;
  96
  97         node = fdt_subnode_offset(fdt, 0, "aliases");
  98         if (node < 0)
  99                 return -FDT_ERR_NOTFOUND;
 100
 101         /*
 102          * Find the next node so that we know where the /aliases node ends. We
 103          * need special handling if /aliases is the last node.
 104          */
 105         node_end = fdt_next_subnode(fdt, node);
 106         if (node_end == -FDT_ERR_NOTFOUND)
 107                 /* Move back to the FDT_END_NODE tag of '/' */
 108                 node_end = fdt_size_dt_struct(fdt) - sizeof(fdt32_t) * 2;
 109         else if (node_end < 0) /* other error */
 110                 return node_end;
 111         node_end -= sizeof(fdt32_t);  /* Move to FDT_END_NODE tag of /aliases */
 112
 113         did_alias_header = 0;
 114         info->region = region;
 115         info->count = count;
 116         info->can_merge = 0;
 117         info->max_regions = max_regions;
 118
 119         for (offset = fdt_first_property_offset(fdt, node);
 120              offset >= 0;
 121              offset = fdt_next_property_offset(fdt, offset)) {
 122                 const struct fdt_property *prop;
 123                 const char *name;
 124                 int target, next;
 125
 126                 prop = fdt_get_property_by_offset(fdt, offset, NULL);
 127                 name = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
 128                 target = fdt_path_offset(fdt, name);
 129                 if (!region_list_contains_offset(info, fdt, target))
 130                         continue;
 131                 next = fdt_next_property_offset(fdt, offset);
 132                 if (next < 0)
 133                         next = node_end;
 134
 135                 if (!did_alias_header) {
 136                         fdt_add_region(info, base + node, 12);
 137                         did_alias_header = 1;
 138                 }
 139                 fdt_add_region(info, base + offset, next - offset);
 140         }
 141
 142         /* Add the FDT_END_NODE tag */
 143         if (did_alias_header)
 144                 fdt_add_region(info, base + node_end, sizeof(fdt32_t));
 145
 146         return info->count < max_regions ? info->count : -FDT_ERR_NOSPACE;
 147 }
 148
 149 /**
 150  * fdt_include_supernodes() - Include supernodes required by this node
 151  * @info:       State information
 152  * @depth:      Current stack depth
 153  *
 154  * When we decided to include a node or property which is not at the top
 155  * level, this function forces the inclusion of higher level nodes. For
 156  * example, given this tree:
 157  *
 158  * / {
 159  *     testing {
 160  *     }
 161  * }
 162  *
 163  * If we decide to include testing then we need the root node to have a valid
 164  * tree. This function adds those regions.
 165  */
 166 static int fdt_include_supernodes(struct fdt_region_state *info, int depth)
 167 {
 168         int base = fdt_off_dt_struct(info->fdt);
 169         int start, stop_at;
 170         int i;
 171
 172         /*
 173          * Work down the stack looking for supernodes that we didn't include.
 174          * The algortihm here is actually pretty simple, since we know that
 175          * no previous subnode had to include these nodes, or if it did, we
 176          * marked them as included (on the stack) already.
 177          */
 178         for (i = 0; i <= depth; i++) {
 179                 if (!info->stack[i].included) {
 180                         start = info->stack[i].offset;
 181
 182                         /* Add the FDT_BEGIN_NODE tag of this supernode */
 183                         fdt_next_tag(info->fdt, start, &stop_at);
 184                         if (fdt_add_region(info, base + start, stop_at - start))
 185                                 return -1;
 186
 187                         /* Remember that this supernode is now included */
 188                         info->stack[i].included = 1;
 189                         info->can_merge = 1;
 190                 }
 191
 192                 /* Force (later) generation of the FDT_END_NODE tag */
 193                 if (!info->stack[i].want)
 194                         info->stack[i].want = WANT_NODES_ONLY;
 195         }
 196
 197         return 0;
 198 }
 199
 200 enum {
 201         FDT_DONE_NOTHING,
 202         FDT_DONE_MEM_RSVMAP,
 203         FDT_DONE_STRUCT,
 204         FDT_DONE_END,
 205         FDT_DONE_STRINGS,
 206         FDT_DONE_ALL,
 207 };
 208
 209 int fdt_first_region(const void *fdt,
 210                 int (*h_include)(void *priv, const void *fdt, int offset,
 211                                  int type, const char *data, int size),
 212                 void *priv, struct fdt_region *region,
 213                 char *path, int path_len, int flags,
 214                 struct fdt_region_state *info)
 215 {
 216         struct fdt_region_ptrs *p = &info->ptrs;
 217
 218         /* Set up our state */
 219         info->fdt = fdt;
 220         info->can_merge = 1;
 221         info->max_regions = 1;
 222         info->start = -1;
 223         p->want = WANT_NOTHING;
 224         p->end = path;
 225         *p->end = '\0';
 226         p->nextoffset = 0;
 227         p->depth = -1;
 228         p->done = FDT_DONE_NOTHING;
 229
 230         return fdt_next_region(fdt, h_include, priv, region,
 231                                path, path_len, flags, info);
 232 }
 233
 234 /***********************************************************************
 235  *
 236  *      Theory of operation
 237  *
 238  * Note: in this description 'included' means that a node (or other part
 239  * of the tree) should be included in the region list, i.e. it will have
 240  * a region which covers its part of the tree.
 241  *
 242  * This function maintains some state from the last time it is called.
 243  * It checks the next part of the tree that it is supposed to look at
 244  * (p.nextoffset) to see if that should be included or not. When it
 245  * finds something to include, it sets info->start to its offset. This
 246  * marks the start of the region we want to include.
 247  *
 248  * Once info->start is set to the start (i.e. not -1), we continue
 249  * scanning until we find something that we don't want included. This
 250  * will be the end of a region. At this point we can close off the
 251  * region and add it to the list. So we do so, and reset info->start
 252  * to -1.
 253  *
 254  * One complication here is that we want to merge regions. So when we
 255  * come to add another region later, we may in fact merge it with the
 256  * previous one if one ends where the other starts.
 257  *
 258  * The function fdt_add_region() will return -1 if it fails to add the
 259  * region, because we already have a region ready to be returned, and
 260  * the new one cannot be merged in with it. In this case, we must return
 261  * the region we found, and wait for another call to this function.
 262  * When it comes, we will repeat the processing of the tag and again
 263  * try to add a region. This time it will succeed.
 264  *
 265  * The current state of the pointers (stack, offset, etc.) is maintained
 266  * in a ptrs member. At the start of every loop iteration we make a copy
 267  * of it.  The copy is then updated as the tag is processed. Only if we
 268  * get to the end of the loop iteration (and successfully call
 269  * fdt_add_region() if we need to) can we commit the changes we have
 270  * made to these pointers. For example, if we see an FDT_END_NODE tag,
 271  * we will decrement the depth value. But if we need to add a region
 272  * for this tag (let's say because the previous tag is included and this
 273  * FDT_END_NODE tag is not included) then we will only commit the result
 274  * if we were able to add the region. That allows us to retry again next
 275  * time.
 276  *
 277  * We keep track of a variable called 'want' which tells us what we want
 278  * to include when there is no specific information provided by the
 279  * h_include function for a particular property. This basically handles
 280  * the inclusion of properties which are pulled in by virtue of the node
 281  * they are in. So if you include a node, its properties are also
 282  * included.  In this case 'want' will be WANT_NODES_AND_PROPS. The
 283  * FDT_REG_DIRECT_SUBNODES feature also makes use of 'want'. While we
 284  * are inside the subnode, 'want' will be set to WANT_NODES_ONLY, so
 285  * that only the subnode's FDT_BEGIN_NODE and FDT_END_NODE tags will be
 286  * included, and properties will be skipped. If WANT_NOTHING is
 287  * selected, then we will just rely on what the h_include() function
 288  * tells us.
 289  *
 290  * Using 'want' we work out 'include', which tells us whether this
 291  * current tag should be included or not. As you can imagine, if the
 292  * value of 'include' changes, that means we are on a boundary between
 293  * nodes to include and nodes to exclude. At this point we either close
 294  * off a previous region and add it to the list, or mark the start of a
 295  * new region.
 296  *
 297  * Apart from the nodes, we have mem_rsvmap, the FDT_END tag and the
 298  * string list. Each of these dealt with as a whole (i.e. we create a
 299  * region for each if it is to be included). For mem_rsvmap we don't
 300  * allow it to merge with the first struct region. For the stringlist,
 301  * we don't allow it to merge with the last struct region (which
 302  * contains at minimum the FDT_END tag).
 303  *
 304  *********************************************************************/
 305
 306 int fdt_next_region(const void *fdt,
 307                 int (*h_include)(void *priv, const void *fdt, int offset,
 308                                  int type, const char *data, int size),
 309                 void *priv, struct fdt_region *region,
 310                 char *path, int path_len, int flags,
 311                 struct fdt_region_state *info)
 312 {
 313         int base = fdt_off_dt_struct(fdt);
 314         int last_node = 0;
 315         const char *str;
 316
 317         info->region = region;
 318         info->count = 0;
 319         if (info->ptrs.done < FDT_DONE_MEM_RSVMAP &&
 320             (flags & FDT_REG_ADD_MEM_RSVMAP)) {
 321                 /* Add the memory reserve map into its own region */
 322                 if (fdt_add_region(info, fdt_off_mem_rsvmap(fdt),
 323                                    fdt_off_dt_struct(fdt) -
 324                                    fdt_off_mem_rsvmap(fdt)))
 325                         return 0;
 326                 info->can_merge = 0;    /* Don't allow merging with this */
 327                 info->ptrs.done = FDT_DONE_MEM_RSVMAP;
 328         }
 329
 330         /*
 331          * Work through the tags one by one, deciding whether each needs to
 332          * be included or not. We set the variable 'include' to indicate our
 333          * decision. 'want' is used to track what we want to include - it
 334          * allows us to pick up all the properties (and/or subnode tags) of
 335          * a node.
 336          */
 337         while (info->ptrs.done < FDT_DONE_STRUCT) {
 338                 const struct fdt_property *prop;
 339                 struct fdt_region_ptrs p;
 340                 const char *name;
 341                 int include = 0;
 342                 int stop_at = 0;
 343                 uint32_t tag;
 344                 int offset;
 345                 int val;
 346                 int len;
 347
 348                 /*
 349                  * Make a copy of our pointers. If we make it to the end of
 350                  * this block then we will commit them back to info->ptrs.
 351                  * Otherwise we can try again from the same starting state
 352                  * next time we are called.
 353                  */
 354                 p = info->ptrs;
 355
 356                 /*
 357                  * Find the tag, and the offset of the next one. If we need to
 358                  * stop including tags, then by default we stop *after*
 359                  * including the current tag
 360                  */
 361                 offset = p.nextoffset;
 362                 tag = fdt_next_tag(fdt, offset, &p.nextoffset);
 363                 stop_at = p.nextoffset;
 364
 365                 switch (tag) {
 366                 case FDT_PROP:
 367                         stop_at = offset;
 368                         prop = fdt_get_property_by_offset(fdt, offset, NULL);
 369                         str = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
 370                         val = h_include(priv, fdt, last_node, FDT_IS_PROP, str,
 371                                             strlen(str) + 1);
 372                         if (val == -1) {
 373                                 include = p.want >= WANT_NODES_AND_PROPS;
 374                         } else {
 375                                 include = val;
 376                                 /*
 377                                  * Make sure we include the } for this block.
 378                                  * It might be more correct to have this done
 379                                  * by the call to fdt_include_supernodes() in
 380                                  * the case where it adds the node we are
 381                                  * currently in, but this is equivalent.
 382                                  */
 383                                 if ((flags & FDT_REG_SUPERNODES) && val &&
 384                                     !p.want)
 385                                         p.want = WANT_NODES_ONLY;
 386                         }
 387
 388                         /* Value grepping is not yet supported */
 389                         break;
 390
 391                 case FDT_NOP:
 392                         include = p.want >= WANT_NODES_AND_PROPS;
 393                         stop_at = offset;
 394                         break;
 395
 396                 case FDT_BEGIN_NODE:
 397                         last_node = offset;
 398                         p.depth++;
 399                         if (p.depth == FDT_MAX_DEPTH)
 400                                 return -FDT_ERR_BADSTRUCTURE;
 401                         name = fdt_get_name(fdt, offset, &len);
 402                         if (p.end - path + 2 + len >= path_len)
 403                                 return -FDT_ERR_NOSPACE;
 404
 405                         /* Build the full path of this node */
 406                         if (p.end != path + 1)
 407                                 *p.end++ = '/';
 408                         strcpy(p.end, name);
 409                         p.end += len;
 410                         info->stack[p.depth].want = p.want;
 411                         info->stack[p.depth].offset = offset;
 412
 413                         /*
 414                          * If we are not intending to include this node unless
 415                          * it matches, make sure we stop *before* its tag.
 416                          */
 417                         if (p.want == WANT_NODES_ONLY ||
 418                             !(flags & (FDT_REG_DIRECT_SUBNODES |
 419                                        FDT_REG_ALL_SUBNODES))) {
 420                                 stop_at = offset;
 421                                 p.want = WANT_NOTHING;
 422                         }
 423                         val = h_include(priv, fdt, offset, FDT_IS_NODE, path,
 424                                         p.end - path + 1);
 425
 426                         /* Include this if requested */
 427                         if (val) {
 428                                 p.want = (flags & FDT_REG_ALL_SUBNODES) ?
 429                                         WANT_ALL_NODES_AND_PROPS :
 430                                         WANT_NODES_AND_PROPS;
 431                         }
 432
 433                         /* If not requested, decay our 'p.want' value */
 434                         else if (p.want) {
 435                                 if (p.want != WANT_ALL_NODES_AND_PROPS)
 436                                         p.want--;
 437
 438                         /* Not including this tag, so stop now */
 439                         } else {
 440                                 stop_at = offset;
 441                         }
 442
 443                         /*
 444                          * Decide whether to include this tag, and update our
 445                          * stack with the state for this node
 446                          */
 447                         include = p.want;
 448                         info->stack[p.depth].included = include;
 449                         break;
 450
 451                 case FDT_END_NODE:
 452                         include = p.want;
 453                         if (p.depth < 0)
 454                                 return -FDT_ERR_BADSTRUCTURE;
 455
 456                         /*
 457                          * If we don't want this node, stop right away, unless
 458                          * we are including subnodes
 459                          */
 460                         if (!p.want && !(flags & FDT_REG_DIRECT_SUBNODES))
 461                                 stop_at = offset;
 462                         p.want = info->stack[p.depth].want;
 463                         p.depth--;
 464                         while (p.end > path && *--p.end != '/')
 465                                 ;
 466                         *p.end = '\0';
 467                         break;
 468
 469                 case FDT_END:
 470                         /* We always include the end tag */
 471                         include = 1;
 472                         p.done = FDT_DONE_STRUCT;
 473                         break;
 474                 }
 475
 476                 /* If this tag is to be included, mark it as region start */
 477                 if (include && info->start == -1) {
 478                         /* Include any supernodes required by this one */
 479                         if (flags & FDT_REG_SUPERNODES) {
 480                                 if (fdt_include_supernodes(info, p.depth))
 481                                         return 0;
 482                         }
 483                         info->start = offset;
 484                 }
 485
 486                 /*
 487                  * If this tag is not to be included, finish up the current
 488                  * region.
 489                  */
 490                 if (!include && info->start != -1) {
 491                         if (fdt_add_region(info, base + info->start,
 492                                            stop_at - info->start))
 493                                 return 0;
 494                         info->start = -1;
 495                         info->can_merge = 1;
 496                 }
 497
 498                 /* If we have made it this far, we can commit our pointers */
 499                 info->ptrs = p;
 500         }
 501
 502         /* Add a region for the END tag and a separate one for string table */
 503         if (info->ptrs.done < FDT_DONE_END) {
 504                 if (info->ptrs.nextoffset != fdt_size_dt_struct(fdt))
 505                         return -FDT_ERR_BADSTRUCTURE;
 506
 507                 if (fdt_add_region(info, base + info->start,
 508                                    info->ptrs.nextoffset - info->start))
 509                         return 0;
 510                 info->ptrs.done++;
 511         }
 512         if (info->ptrs.done < FDT_DONE_STRINGS) {
 513                 if (flags & FDT_REG_ADD_STRING_TAB) {
 514                         info->can_merge = 0;
 515                         if (fdt_off_dt_strings(fdt) <
 516                             base + info->ptrs.nextoffset)
 517                                 return -FDT_ERR_BADLAYOUT;
 518                         if (fdt_add_region(info, fdt_off_dt_strings(fdt),
 519                                            fdt_size_dt_strings(fdt)))
 520                                 return 0;
 521                 }
 522                 info->ptrs.done++;
 523         }
 524
 525         return info->count > 0 ? 0 : -FDT_ERR_NOTFOUND;
 526 }