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| 1 /* Copyright 2010, Google Inc. |
| 2 * All rights reserved. |
| 3 * |
| 4 * Redistribution and use in source and binary forms, with or without |
| 5 * modification, are permitted provided that the following conditions are |
| 6 * met: |
| 7 * |
| 8 * * Redistributions of source code must retain the above copyright |
| 9 * notice, this list of conditions and the following disclaimer. |
| 10 * * Redistributions in binary form must reproduce the above |
| 11 * copyright notice, this list of conditions and the following disclaimer |
| 12 * in the documentation and/or other materials provided with the |
| 13 * distribution. |
| 14 * * Neither the name of Google Inc. nor the names of its |
| 15 * contributors may be used to endorse or promote products derived from |
| 16 * this software without specific prior written permission. |
| 17 * |
| 18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| 19 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| 20 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
| 21 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT |
| 22 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 23 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT |
| 24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
| 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
| 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
| 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
| 28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 29 * |
| 30 * Alternatively, this software may be distributed under the terms of the |
| 31 * GNU General Public License ("GPL") version 2 as published by the Free |
| 32 * Software Foundation. |
| 33 * |
| 34 * This is ported from the flashmap utility: http://flashmap.googlecode.com |
| 35 */ |
| 36 |
| 37 #include <stdlib.h> |
| 38 #include <string.h> |
| 39 |
| 40 #include "flash.h" /* for ARRAY_SIZE macro */ |
| 41 #include "fmap.h" |
| 42 |
| 43 long int fmap_find(const uint8_t *image, size_t image_len) |
| 44 { |
| 45 long int offset = -1; |
| 46 uint64_t sig; |
| 47 int i; |
| 48 /* Note: keep the strides sorted in largest to smallest order for |
| 49 efficient operation below. Strides should all be powers of 2. */ |
| 50 unsigned int strides[] = { 64 * 1024, 4 * 1024, 64 }; |
| 51 |
| 52 memcpy(&sig, FMAP_SIGNATURE, strlen(FMAP_SIGNATURE)); |
| 53 |
| 54 /* |
| 55 * Find FMAP signature within image. The alignment requirements |
| 56 * increased over time due to speed concerns, so we'll use an array to |
| 57 * represent the strides we wish to attempt to use. |
| 58 * |
| 59 * For efficient operation, we start with the largest stride possible |
| 60 * and then decrease the stride on each iteration. We will check for a |
| 61 * remainder when modding the offset with the previous stride. This |
| 62 * makes it so that each offset is only checked once. |
| 63 */ |
| 64 for (i = 0; i < ARRAY_SIZE(strides); i++) { |
| 65 for (offset = 0; |
| 66 offset + sizeof(sig) <= image_len; |
| 67 offset += strides[i]) { |
| 68 if (i > 0) { |
| 69 if (offset % strides[i-1] == 0) |
| 70 continue; |
| 71 } |
| 72 |
| 73 if (!memcmp(&image[offset], &sig, sizeof(sig))) { |
| 74 goto fmap_find_exit; |
| 75 } |
| 76 } |
| 77 } |
| 78 |
| 79 fmap_find_exit: |
| 80 msg_gdbg("%s: fmap_offset: 0x%lx\n", __func__, offset); |
| 81 if (offset + sizeof(sig) <= image_len) |
| 82 return offset; |
| 83 else |
| 84 return -1; |
| 85 } |
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