[U-Boot] [RFC PATCH 41/44] libfdt: Add fdt_find_regions()

Simon Glass
2013-01-05T01:52:10Z

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;
+}
--
1.7.7.3