libfdt: Add fdt_find_regions()

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>

diff --git a/include/libfdt.h b/include/libfdt.h
index c5ec2acfd82927f070923e118766aad22986b3a9..765d84f5e4574eaab187be553cdbd449bf22b819 100644 (file)
--- a/include/libfdt.h
+++ b/include/libfdt.h
@@ -1511,4 +1511,68 @@ 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 63e67b78c882b5621d30c6a2214034ba7c40356a..b9e3c4a742119fcea67cc4e60572d4da0b5b9957 100644 (file)
--- 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;
+               const char *str;
+               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);
+                       str = fdt_string(fdt, fdt32_to_cpu(prop->nameoff));
+                       if (str_in_list(str, 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;
+}