Add flashmap (fmap) support to Flashrom

fmap.c

Index: fmap.c
diff --git a/fmap.c b/fmap.c
new file mode 100644
index 0000000000000000000000000000000000000000..faa13ad30ee4995dd679917908f63faf3215a03b
--- /dev/null
+++ b/fmap.c
@@ -0,0 +1,74 @@
+/* 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)

[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;
+}