Add flashmap (fmap) support to Flashrom

fmap.c

+/* Copyright 2010, Google Inc.
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+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Alternatively, this software may be distributed under the terms of the
+ * GNU General Public License ("GPL") version 2 as published by the Free
+ * Software Foundation.
+ *
+ * This is ported from the flashmap utility: http://flashmap.googlecode.com
+ */
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "flash.h"      /* for ARRAY_SIZE macro */
+#include "fmap.h"
+
+long int fmap_find(const uint8_t *image, size_t image_len)

[Louis, 2011/03/04 00:40:59]

To find out where the fmap is in the fastest way, I'd like to suggest the
following algo:
1. check crossystem/fmap  (code may be not ready yet)
2. pass *flash into this function, rather than *image. So that we can jump every
64KB, 4KB... etc without reading whole flash content which takes about 5 secs.

[dhendrix, 2011/03/04 08:04:46]

I'm not sure how 1) works. I like the idea in 2). I'll implement that after we
submit this CL.

+{
+        long int offset = -1;
+        uint64_t sig;
+        unsigned int strides[] = { 64, 4 };

[Louis, 2011/03/04 00:40:59]

Smart!  How about adding 64KB and 4KB, which are the usually cases we align to. 

Please also consider remove 4 (or change to 16) to avoid long loop when fmap is
not existed.

[dhendrix, 2011/03/04 08:04:46]

Done.

+        int i;
+
+        memcpy(&sig, FMAP_SIGNATURE, strlen(FMAP_SIGNATURE));
+
+        /*
+         * Find FMAP signature within image. The alignment requirements
+         * increased over time due to speed concerns, so we'll try using more
+         * coarse alignments to start with and fall back to smaller ones only
+         * if necessary.
+         */

[Louis, 2011/03/04 00:40:59]

Shall we implement a bit array to indicate the address we have checked based on
the fact that the numbers in strides[] are usually multiples? sample code is
like:

visited = malloc(flash->size / min_strides / 8);

for each strides {
  for (offset = 0; ....) {
    if (!(visited[offset/min_strides/8] & (1<<((offset/min_strides)%8)))) {
         uint8_t buf[sizeof(sig)];
         flash->read(offset, sizeof(buf), buf);
         if (!memcmp(buf, &sig, sizeof(sig)) goto fmap_find_exit;
         visited[offset/min_strides/8] |= (1<<((offset/min_strides)%8));
     }
  }
}

[dhendrix, 2011/03/04 08:04:46]

done using the mod trick :-)

+        for (i = 0; i < ARRAY_SIZE(strides); i++) {
+                for (offset = 0;
+                     offset + sizeof(sig) <= image_len;
+                     offset += strides[i]) {
+                        if (!memcmp(&image[offset], &sig, sizeof(sig))) {
+                                goto fmap_find_exit;
+                        }
+                }
+        }
+
+fmap_find_exit:
+        msg_gdbg("%s: fmap_offset: 0x%lx\n", __func__, offset);
+        if (offset + sizeof(sig) <= image_len)
+                return offset;
+        else
+                return -1;
+}