Add flashmap (fmap) support to Flashrom

fmap.c

+/* Copyright 2010, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *    * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *    * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *    * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * 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"
+#include "fmap.h"
+
+extern int fmap_find(struct flashchip *flash, uint8_t **buf)
+{
+        unsigned long int offset = 0;
+        uint64_t sig;
+        int i, fmap_found = 0;
+        /* Note: keep the strides sorted in largest to smallest order for
+           efficient operation below. Strides should all be powers of 2. */
+        unsigned int strides[] = { 64 * 1024, 4 * 1024, 64 };

[Louis, 2011/03/05 01:05:01]

Feel free to add more granularities here since we have your awesome mod trick.
:-)

Actually the most optimized strides sequence would look like this:
  { flash_size / 2, ..., 1M, 512K, 256K, ..., sizeof(siganature)}
See below for sample code.

[dhendrix, 2011/03/05 02:34:14]

That's a good idea, though I don't think it will help much for the current ROM
images since the FMAP is in a (multiple of 64, but not 128, 1024, etc...).

+        struct fmap fmap;
+        int fmap_size;
+
+        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 use an array to
+         * represent the strides we wish to attempt to use.
+         *
+         * For efficient operation, we start with the largest stride possible
+         * and then decrease the stride on each iteration. We will check for a
+         * remainder when modding the offset with the previous stride. This
+         * makes it so that each offset is only checked once.
+         */
+        for (i = 0; i < ARRAY_SIZE(strides); i++) {
+                for (offset = 0;

[Louis, 2011/03/05 01:05:01]

hehehe... why not try the following way based on the assumption that RO VPD
usually rely on top of BIOS image.

for (stride = flash->total_size * 1024 / 2;
     stride >= sizeof(sig);
     stride >>= 1) {

    for (offset = flash->total_size * 1024 - strides[i];
         offset >= 0;
         offset -= stride) {

         // mod trick here

    }
}

[dhendrix, 2011/03/05 02:34:14]

Good thinking. I only incorporated the suggestion to start from top-of-ROM so
far, though. This dramatically sped up my test for reading the RO_VPD region:
1. Old approach which read whole ROM first: 4.998s
2. New approach which uses flash->read() in this function: 4.437s
3. Your approach which starts seeking at top-of-ROM: 1.751s.

+                     offset + sizeof(fmap) <= flash->total_size * 1024;
+                     offset += strides[i]) {
+                        if (i > 0) {
+                                if (offset % strides[i-1] == 0)
+                                        continue;
+                        }
+
+                        if (flash->read(flash, (uint8_t *)&fmap,
+                                        offset, sizeof(fmap))) {
+                                msg_gdbg("failed to read flash at "
+                                         "offset 0x%lx\n", offset);
+                                return -1;
+                        }
+
+                        if (!memcmp(&fmap.signature, &sig, sizeof(sig))) {
+                                fmap_found = 1;
+                                break;
+                        }
+                }
+                if (fmap_found)
+                        break;
+        }
+
+        if (!fmap_found)
+                return 0;
+
+        fmap_size = sizeof(fmap) + (fmap.nareas * sizeof(struct fmap_area));
+        *buf = malloc(fmap_size);
+
+        if (flash->read(flash, *buf, offset, fmap_size)) {
+                msg_gdbg("failed to read %d bytes at offset 0x%lx\n",
+                         fmap_size, offset);
+                return -1;
+        }
+        return fmap_size;
+}