Add a function to find regions in device tree given a list of nodes to include and properties to exclude.
See the header file for full documentation.
Signed-off-by: Simon Glass sjg@chromium.org --- include/libfdt.h | 64 +++++++++++++++++++++++++ lib/libfdt/fdt_wip.c | 129 ++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 193 insertions(+), 0 deletions(-)
diff --git a/include/libfdt.h b/include/libfdt.h index 0dfb8a0..c765abe 100644 --- a/include/libfdt.h +++ b/include/libfdt.h @@ -1492,4 +1492,68 @@ int fdt_del_node(void *fdt, int nodeoffset);
const char *fdt_strerror(int errval);
+struct fdt_region { + int offset; + int size; +}; + +/** + * fdt_find_regions() - find regions in device tree + * + * Given a list of nodes to include and properties to exclude, find + * the regions of the device tree which describe those included parts. + * + * The intent is to get a list of regions which will be invariant provided + * those parts are invariant. For example, if you request a list of regions + * for all nodes but exclude the property "data", then you will get the + * same region contents regardless of any change to "data" properties. + * + * This function can be used to produce a byte-stream to send to a hashing + * function to verify that critical parts of the FDT have not changed. + * + * Nodes which are given in 'inc' are included in the region list, as + * are the names of the immediate subnodes nodes (but not the properties + * or subnodes of those subnodes). + * + * For eaxample "/" means to include the root node, all root properties + * and the FDT_BEGIN_NODE and FDT_END_NODE of all subnodes of /. The latter + * ensures that we capture the names of the subnodes. In a hashing situation + * it prevents the root node from changing at all Any change to non-excluded + * properties, names of subnodes or number of subnodes would be detected. + * + * When used with FITs this provides the ability to hash and sign parts of + * the FIT based on different configurations in the FIT. Then it is + * impossible to change anything about that configuration (include images + * attached to the configuration), but it may be possible to add new + * configurations, new images or new signatures within the existing + * framework. + * + * Adding new properties to a device tree may result in the string table + * being extended (if the new property names are different from those + * already added). This function can optionally include a region for + * the string table so that this can be part of the hash too. + * + * The device tree header is not included in the list. + * + * @fdt: Device tree to check + * @inc: List of node paths to included + * @inc_count: Number of node paths in list + * @exc_prop: List of properties names to exclude + * @exc_prop_count: Number of properties in exclude list + * @region: Returns list of regions + * @max_region: Maximum length of region list + * @path: Pointer to a temporary string for the function to use for + * building path names + * @path_len: Length of path, must be large enough to hold the longest + * path in the tree + * @add_string_tab: 1 to add a region for the string table + * @return number of regions in list. If this is >max_regions then the + * region array was exhausted. You should increase max_regions and try + * the call again. + */ +int fdt_find_regions(const void *fdt, char * const inc[], int inc_count, + char * const exc_prop[], int exc_prop_count, + struct fdt_region region[], int max_regions, + char *path, int path_len, int add_string_tab); + #endif /* _LIBFDT_H */ diff --git a/lib/libfdt/fdt_wip.c b/lib/libfdt/fdt_wip.c index e373677..7fcc2a3 100644 --- a/lib/libfdt/fdt_wip.c +++ b/lib/libfdt/fdt_wip.c @@ -120,3 +120,132 @@ int fdt_nop_node(void *fdt, int nodeoffset) endoffset - nodeoffset); return 0; } + +#define FDT_MAX_DEPTH 32 + +static int str_in_list(const char *str, char * const list[], int count) +{ + int i; + + for (i = 0; i < count; i++) + if (!strcmp(list[i], str)) + return 1; + + return 0; +} + +int fdt_find_regions(const void *fdt, char * const inc[], int inc_count, + char * const exc_prop[], int exc_prop_count, + struct fdt_region region[], int max_regions, + char *path, int path_len, int add_string_tab) +{ + int stack[FDT_MAX_DEPTH]; + char *end; + int nextoffset = 0; + uint32_t tag; + int count = 0; + int start = -1; + int depth = -1; + int want = 0; + int base = fdt_off_dt_struct(fdt); + + end = path; + *end = '\0'; + do { + const struct fdt_property *prop; + const char *name; + int include = 0; + int stop_at = 0; + int offset; + int len; + + offset = nextoffset; + tag = fdt_next_tag(fdt, offset, &nextoffset); + stop_at = nextoffset; + + switch (tag) { + case FDT_PROP: + include = want >= 2; + stop_at = offset; + prop = fdt_get_property_by_offset(fdt, offset, NULL); + if (str_in_list(fdt_string(fdt, + fdt32_to_cpu(prop->nameoff)), exc_prop, + exc_prop_count)) + include = 0; + break; + + case FDT_NOP: + include = want >= 2; + stop_at = offset; + break; + + case FDT_BEGIN_NODE: + depth++; + if (depth == FDT_MAX_DEPTH) + return -FDT_ERR_BADSTRUCTURE; + name = fdt_get_name(fdt, offset, &len); + if (end - path + 2 + len >= path_len) + return -FDT_ERR_NOSPACE; + if (end != path + 1) + *end++ = '/'; + strcpy(end, name); + end += len; + stack[depth] = want; + if (want == 1) + stop_at = offset; + if (str_in_list(path, inc, inc_count)) + want = 2; + else if (want) + want--; + else + stop_at = offset; + include = want; + break; + + case FDT_END_NODE: + include = want; + want = stack[depth--]; + while (end > path && *--end != '/') + ; + *end = '\0'; + break; + + case FDT_END: + include = 1; + break; + } + + if (include && start == -1) { + /* Should we merge with previous? */ + if (count && count <= max_regions && + offset == region[count - 1].offset + + region[count - 1].size - base) + start = region[--count].offset - base; + else + start = offset; + } + + if (!include && start != -1) { + if (count < max_regions) { + region[count].offset = base + start; + region[count].size = stop_at - start; + } + count++; + start = -1; + } + } while (tag != FDT_END); + + if (nextoffset != fdt_size_dt_struct(fdt)) + return -FDT_ERR_BADLAYOUT; + + /* Add a region for the END tag and the string table */ + if (count < max_regions) { + region[count].offset = base + start; + region[count].size = nextoffset - start; + if (add_string_tab) + region[count].size += fdt_size_dt_strings(fdt); + } + count++; + + return count; +}