Often times, fdts get embedded in other larger files. Rather than force
people to `dd` the blob out themselves, make the fdtdump file smarter.
It can now scan the blob looking for the fdt magic. Once locate, it does
a little validation on the main struct to make sure we didn't hit random
binary data.
Signed-off-by: Mike Frysinger <vap...@gentoo.org>
---
fdtdump.c | 46 ++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 44 insertions(+), 2 deletions(-)
diff --git a/fdtdump.c b/fdtdump.c
index b685ed1..7b967aa 100644
--- a/fdtdump.c
+++ b/fdtdump.c
@@ -2,12 +2,14 @@
* fdtdump.c - Contributed by Pantelis Antoniou <pantelis.antoniou AT
gmail.com>
*/
+#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
+#include <libfdt.h>
#include <libfdt_env.h>
#include <fdt.h>
@@ -119,11 +121,13 @@ static void dump_blob(void *blob)
/* Usage related data. */
static const char usage_synopsis[] = "fdtdump [options] <file>";
-static const char usage_short_opts[] = USAGE_COMMON_SHORT_OPTS;
+static const char usage_short_opts[] = "s" USAGE_COMMON_SHORT_OPTS;
static struct option const usage_long_opts[] = {
+ {"scan", no_argument, NULL, 's'},
USAGE_COMMON_LONG_OPTS
};
static const char * const usage_opts_help[] = {
+ "Scan for an embedded fdt in file",
USAGE_COMMON_OPTS_HELP
};
@@ -132,20 +136,58 @@ int main(int argc, char *argv[])
int opt;
const char *file;
char *buf;
+ bool scan = false;
+ off_t len;
while ((opt = util_getopt_long()) != EOF) {
switch (opt) {
case_USAGE_COMMON_FLAGS
+
+ case 's':
+ scan = true;
+ break;
}
}
if (optind != argc - 1)
long_usage("missing input filename");
file = argv[optind];
- buf = utilfdt_read(file, NULL);
+ buf = utilfdt_read(file, &len);
if (!buf)
die("could not read: %s\n", file);
+ /* try and locate an embedded fdt in a bigger blob */
+ if (scan) {
+ unsigned char smagic[4];
+ char *p = buf;
+ char *endp = buf + len;
+
+ fdt_set_magic(smagic, FDT_MAGIC);
+
+ /* poor man's memmem */
+ while (true) {
+ p = memchr(p, smagic[0], endp - p - 4);
+ if (!p)
+ break;
+ if (fdt_magic(p) == FDT_MAGIC) {
+ /* try and validate the main struct */
+ off_t this_len = endp - p;
+ fdt32_t max_version = 17;
+ if (fdt_version(p) <= max_version &&
+ fdt_last_comp_version(p) < max_version &&
+ fdt_totalsize(p) < this_len &&
+ fdt_off_dt_struct(p) < this_len &&
+ fdt_off_dt_strings(p) < this_len)
+ break;
+ }
+ ++p;
+ }
+ if (!p)
+ die("%s: could not locate fdt magic\n", file);
+ printf("%s: found fdt at offset %#zx\n", file, p - buf);
+ buf = p;
+ }
+
dump_blob(buf);
return 0;
--
1.8.1.2
_______________________________________________
devicetree-discuss mailing list
devicetree-discuss@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/devicetree-discuss
