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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>
utp
Simon Glass 2013-06-13 15:10:08 -07:00 committed by Tom Rini
parent 399c744b22
commit 3e06cd1f97
2 changed files with 193 additions and 0 deletions
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64
include/libfdt.h
View File

@ -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 */

129
lib/libfdt/fdt_wip.c
View File

@ -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;
}