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* fmd.c, parser frontend and utility functions for flashmap descriptor language
* Copyright (C) 2015 Google, Inc.
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; version 2 of the License.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc.
#include "fmd.h"
#include "common.h"
#include "fmd_parser.h"
#include "fmd_scanner.h"
#include "option.h"
#include <assert.h>
#include <search.h>
#include <string.h>
* Validate the given flashmap descriptor node's properties. In particular:
* - Ensure its name is globally unique.
* - Ensure its offset, if known, isn't located before the end of the previous
* section, if this can be determined.
* - Ensure its offset, if known, isn't located after the beginning of the next
* section or off the end of its parent section, if this can be determined.
* - Ensure its size is nonzero.
* - Ensure that the combination of its size and offset, if they are both
* known, doesn't place its end after the beginning of the next section or
* off the end of its parent section, if this can be determined.
* In the case of a validation error, the particular problem is reported to
* standard error and this function returns false. It should be noted that this
* function makes no claim that the members of the node's child list are valid:
* under no circumstances is any recursive validation performed.
* @param node The flashmap descriptor node to be validated
* @param start Optional minimum permissible base of the section to be
* validated, to be provided if known
* @param end Optional maximum permissible offset to the end of the section to
* be validated, to be provided if known
* @return Whether the node is valid
static bool validate_descriptor_node(const struct flashmap_descriptor *node,
struct unsigned_option start, struct unsigned_option end) {
ENTRY search_key = {node->name, NULL};
if (hsearch(search_key, FIND)) {
ERROR("Multiple sections with name '%s'\n", node->name);
return false;
if (!hsearch(search_key, ENTER))
if (node->offset_known) {
if (start.val_known && node->offset < start.val) {
ERROR("Section '%s' starts too low\n", node->name);
return false;
} else if (end.val_known && node->offset > end.val) {
ERROR("Section '%s' starts too high\n", node->name);
return false;
if (node->size_known) {
if (node->size == 0) {
ERROR("Section '%s' given no space\n", node->name);
return false;
} else if (node->offset_known) {
unsigned node_end = node->offset + node->size;
if (end.val_known && node_end > end.val) {
ERROR("Section '%s' too big\n", node->name);
return false;
return true;
* Performs reverse lateral processing of sibling nodes, as described by the
* documentation of its caller, validate_and_complete_info(). If it encounters
* a node that is invalid in a way that couldn't have been discovered earlier,
* it explains the problem to standard output and returns false.
* @param first_incomplete_it First node whose offset or size couldn't be
* determined during forward processing
* @param cur_incomplete_it Last node whose offset or size is unknown
* @param end_watermark Offset to the end of the unresolved region
* @return Whether all completed nodes were still valid
static bool complete_missing_info_backward(
flashmap_descriptor_iterator_t first_incomplete_it,
flashmap_descriptor_iterator_t cur_incomplete_it,
unsigned end_watermark)
assert(cur_incomplete_it >= first_incomplete_it);
do {
struct flashmap_descriptor *cur = *cur_incomplete_it;
assert(cur->offset_known || cur->size_known);
if (!cur->offset_known) {
if (cur->size > end_watermark) {
ERROR("Section '%s' too big\n", cur->name);
return false;
cur->offset_known = true;
cur->offset = end_watermark -= cur->size;
} else if (!cur->size_known) {
if (cur->offset > end_watermark) {
ERROR("Section '%s' starts too high\n",
return false;
cur->size_known = true;
cur->size = end_watermark - cur->offset;
end_watermark = cur->offset;
} while (--cur_incomplete_it >= first_incomplete_it);
return true;
* Recursively examine each descendant of the provided flashmap descriptor node
* to ensure its position and size are known, attempt to infer them otherwise,
* and validate their values once they've been populated.
* This processes nodes according to the following algorithm:
* - At each level of the tree, it moves laterally between siblings, keeping
* a watermark of its current offset relative to the previous section, which
* it uses to fill in any unknown offsets it encounters along the way.
* - The first time it encounters a sibling with unknown size, it loses track
* of the watermark, and is therefore unable to complete further offsets;
* instead, if the watermark was known before, it marks the current node as
* the first that couldn't be completed in the initial pass.
* - If the current watermark is unknown (i.e. a node has been marked as the
* first incomplete one) and one with a fixed offset is encountered, a
* reverse lateral traversal is dispatched that uses that provided offset as
* a reverse watermark to complete all unknown fields until it finishes with
* the node marked as the first incomplete one: at this point, that flag is
* cleared, the watermark is updated, and forward processing resumes from
* where it left off.
* - If the watermark is unknown (i.e. node(s) are incomplete) after traversing
* all children of a particular parent node, reverse processing is employed
* as described above, except that the reverse watermark is initialized to
* the parent node's size instead of the (nonexistent) next node's offset.
* - Once all of a node's children have been processed, the algorithm applies
* itself recursively to each of the child nodes; thus, lower levels of the
* tree are processed only after their containing levels are finished.
* This approach can fail in two possible ways (in which case the problem is
* reported to standard output and this function returns false):
* - Processing reveals that some node's provided value is invalid in some way.
* - Processing determines that one or more provided values require an omitted
* field to take a nonsensical value.
* - Processing determines that it is impossible to determine a group of
* omitted values. This state is detected when a node whose offset *and*
* value are omitted is encountered during forward processing and while the
* current watermark is unknown: in such a case, neither can be known without
* being provided with either the other or more context.
* The function notably performs neither validation nor completion on the parent
* node it is passed; thus, it is important to ensure that that node is valid.
* (At the very least, it must have a valid size field in order for the
* algorithm to work on its children.)
* @param cur_level Parent node, which must minimally already have a valid size
* @return Whether completing and validating the children succeeded
static bool validate_and_complete_info(struct flashmap_descriptor *cur_level)
// Our watermark is only known when first_incomplete_it is NULL.
flashmap_descriptor_iterator_t first_incomplete_it = NULL;
unsigned watermark = 0;
fmd_foreach_child_iterator(cur_it, cur_level) {
struct flashmap_descriptor *cur_section = *cur_it;
if (first_incomplete_it) {
if (cur_section->offset_known) {
if (complete_missing_info_backward(
first_incomplete_it, cur_it - 1,
cur_section->offset)) {
first_incomplete_it = NULL;
watermark = cur_section->offset;
} else {
return false;
// Otherwise, we can't go back until a provided offset.
} else if (!cur_section->offset_known) {
cur_section->offset_known = true;
cur_section->offset = watermark;
struct unsigned_option max_endpoint = {true, cur_level->size};
if (cur_it != cur_level->list + cur_level->list_len - 1) {
struct flashmap_descriptor *next_section = cur_it[1];
max_endpoint.val_known = next_section->offset_known;
max_endpoint.val = next_section->offset;
if (!validate_descriptor_node(cur_section,
(struct unsigned_option)
{!first_incomplete_it, watermark},
return false;
if (!cur_section->size_known) {
if (!cur_section->offset_known) {
ERROR("Cannot determine either offset or size of section '%s'\n",
return false;
} else if (!first_incomplete_it) {
first_incomplete_it = cur_it;
} else {
// We shouldn't find an unknown size within an
// incomplete region because the backward
// traversal at the beginning of this node's
// processing should have concluded said region.
} else if (!first_incomplete_it) {
watermark = cur_section->offset + cur_section->size;
if (first_incomplete_it &&
cur_level->list + cur_level->list_len - 1,
return false;
fmd_foreach_child(cur_section, cur_level) {
if (!validate_and_complete_info(cur_section))
return false;
return true;
static void print_with_prefix(const struct flashmap_descriptor *tree,
const char *pre)
printf("%ssection '%s' has ", pre, tree->name);
if (tree->offset_known)
printf("offset %uB, ", tree->offset);
fputs("unknown offset, ", stdout);
if (tree->size_known)
printf("size %uB, ", tree->size);
fputs("unknown size, ", stdout);
printf("and %zu subsections", tree->list_len);
if (tree->list_len) {
char child_prefix[strlen(pre) + 1];
strcpy(child_prefix, pre);
strcat(child_prefix, "\t");
fmd_foreach_child(each, tree)
print_with_prefix(each, child_prefix);
} else {
struct flashmap_descriptor *fmd_create(FILE *stream)
yyin = stream;
struct flashmap_descriptor *ret = NULL;
if (yyparse() == 0)
ret = res;
yyin = NULL;
res = NULL;
if (ret) {
// This hash table is used to store the declared name of each
// section and ensure that each is globally unique.
if (!hcreate(fmd_count_nodes(ret))) {
perror("E: While initializing hashtable");
return NULL;
// Even though we haven't checked that the root node (ret) has
// a size field as required by this function, the parser
// warrants that it does because the grammar requires it.
if (!validate_and_complete_info(ret)) {
return NULL;
return ret;
void fmd_cleanup(struct flashmap_descriptor *victim)
if (!victim)
for (unsigned idx = 0; idx < victim->list_len; ++idx)
size_t fmd_count_nodes(const struct flashmap_descriptor *tree)
if (!tree->list_len)
return 1;
unsigned count = 1;
fmd_foreach_child(lower, tree)
count += fmd_count_nodes(lower);
return count;
const struct flashmap_descriptor *fmd_find_node(
const struct flashmap_descriptor *root, const char *name)
if (strcmp(root->name, name) == 0)
return root;
fmd_foreach_child(descendant, root) {
const struct flashmap_descriptor *match =
fmd_find_node(descendant, name);
if (match)
return match;
return NULL;
unsigned fmd_calc_absolute_offset(const struct flashmap_descriptor *root,
const char *name)
if (strcmp(root->name, name) == 0)
return 0;
fmd_foreach_child(descendant, root) {
unsigned subtotal = fmd_calc_absolute_offset(descendant, name);
if (subtotal != FMD_NOTFOUND)
return descendant->offset + subtotal;
void fmd_print(const struct flashmap_descriptor *tree)
print_with_prefix(tree, "");