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"      /* for ARRAY_SIZE macro */
+#include "fmap.h"
+
+long int fmap_find(const uint8_t *image, size_t image_len)
+{
+        long int offset = -1;
+        uint64_t sig;
+        int i;
+        /* 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 };
+
+        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;
+                     offset + sizeof(sig) <= image_len;
+                     offset += strides[i]) {
+                        if (i > 0) {
+                                if (offset % strides[i-1] == 0)

[Louis, 2011/03/04 11:01:13]

Awesome! Much better than my stupid bitarray approach.

+                                        continue;
+                        }
+
+                        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;
+}