[Galaxy Note GT-N7000 General] v.cecchetto:
Hi again...

After MBR, GPT, PIT... we have the CHECKSUM HEADER SECTOR (LBA 42, LBA 43)

I have called it this way cause on this page:

http://xdaforums.com/showthread.php?t=1313588

Adam Outler pointed out to his experiment on UART sniffing and i found this in one of his logs:

http://pastebin.ubuntu.com/715182/

if you look at line 130:

CHECKSUM_HEADER_SECTOR :42

offset:42, size:1024

the phone model is different but I am pretty sure it is the same on Note

# hd -n1024 -s42b /dev/block/mmcblk0

0005400: 00 00 00 00 0c 00 00 00 4d 42 52 00 00 00 00 00 ........MBR.....
0005410: 46 31 46 35 45 38 44 33 32 43 44 38 44 36 34 31 F1F5E8D32CD8D641
0005420: 46 31 37 44 34 44 46 45 42 39 44 42 42 45 37 43 F17D4DFEB9DBBE7C
0005430: 00 02 00 00 47 50 54 00 00 00 00 00 33 44 37 32 ....GPT.....3D72
0005440: 42 44 30 44 34 38 38 30 33 36 43 45 39 37 43 42 BD0D488036CE97CB
0005450: 46 39 36 44 46 34 37 33 45 39 30 42 00 00 00 00 F96DF473E90B....
0005460: 50 49 54 00 00 00 00 00 39 33 46 46 36 45 31 38 PIT.....93FF6E18
0005470: 33 44 31 42 31 41 31 45 44 45 46 45 32 43 45 43 3D1B1A1EDEFE2CEC
0005480: 38 37 32 43 31 41 39 46 00 08 00 00 43 45 58 54 872C1A9F....CEXT
0005490: 34 00 00 00 35 39 32 39 42 44 43 35 44 42 42 43 4...5929BDC5DBBC
00054a0: 36 42 38 32 46 43 46 41 35 31 44 37 42 36 35 30 6B82FCFA51D7B650
00054b0: 35 44 41 37 88 00 00 00 4e 4f 4e 45 00 00 00 00 5DA7....NONE....
00054c0: 33 31 35 31 45 36 34 46 36 32 36 38 45 35 36 36 3151E64F6268E566
00054d0: 41 39 38 43 41 32 42 38 37 41 33 32 31 44 46 46 A98CA2B87A321DFF
00054e0: 00 00 14 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
00054f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0005500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0005510: 4e 4f 4e 45 00 00 00 00 36 37 43 36 32 35 44 34 NONE....67C625D4
0005520: 34 45 33 43 30 31 37 32 33 36 46 45 42 41 36 41 4E3C017236FEBA6A
0005530: 30 34 34 35 31 46 34 43 00 c8 11 00 4e 4f 4e 45 04451F4C....NONE
0005540: 00 00 00 00 32 31 31 44 36 36 37 41 38 39 35 33 ....211D667A8953
0005550: 32 39 34 46 31 41 31 37 33 42 42 46 38 46 30 39 294F1A173BBF8F09
0005560: 44 32 32 44 00 fe 7f 00 00 00 00 00 00 00 00 00 D22D............
0005570: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0005580: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
0005590: 00 00 00 00 43 45 58 54 34 00 00 00 44 46 35 38 ....CEXT4...DF58
00055a0: 42 38 36 38 36 43 30 33 30 37 42 37 37 33 45 30 B8686C0307B773E0
00055b0: 44 38 39 31 33 34 32 44 34 44 38 37 ac 00 00 00 D891342D4D87....
00055c0: 4e 4f 4e 45 00 00 00 00 39 42 36 44 37 37 37 36 NONE....9B6D7776
00055d0: 33 34 41 32 33 37 42 46 34 41 45 30 30 45 46 34 34A237BF4AE00EF4
00055e0: 44 31 44 36 41 38 35 32 00 02 c0 00 43 45 58 54 D1D6A852....CEXT
00055f0: 34 00 00 00 45 31 46 30 43 45 31 39 46 37 32 33 4...E1F0CE19F723
0005600: 41 33 46 43 43 39 41 41 44 30 31 34 44 32 32 33 A3FCC9AAD014D223
0005610: 34 46 44 41 c4 45 00 00 43 45 58 54 34 00 00 00 4FDA.E..CEXT4...
0005620: 44 46 45 41 46 35 31 44 34 37 32 34 32 39 37 44 DFEAF51D4724297D
0005630: 38 37 45 36 37 38 46 32 33 32 42 46 41 43 32 37 87E678F232BFAC27
0005640: c8 02 00 00 52 46 53 00 00 00 00 00 36 31 46 44 ....RFS.....61FD
0005650: 38 34 41 38 36 42 30 31 34 43 35 39 33 41 41 41 84A86B014C593AAA
0005660: 44 45 41 43 46 31 31 41 39 37 46 33 00 62 bb 16 DEACF11A97F3.b..
0005670: 43 45 58 54 34 00 00 00 36 30 37 42 36 46 37 33 CEXT4...607B6F73
0005680: 45 36 45 43 44 43 46 30 41 34 39 39 34 45 42 37 E6ECDCF0A4994EB7
0005690: 33 44 45 38 43 31 33 44 cc 01 00 00 00 00 00 00 3DE8C13D........
00056a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
*
0005740: 00 00 00 00 00 00 00 00 00 00 00 00 42 43 44 39 ............BCD9
0005750: xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xxxxxxxxxxxxxxxx
0005760: xx xx xx xx xx xx xx xx xx xx xx xx 00 00 00 00 xxxxxxxxxxxx....
0005770: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................

Checksum... md5!

# dd if=/dev/block/mmcblk0 of=MBR.bin bs=512 count=1

# md5sum MBR.bin

f1f5e8d32cd8d641f17d4dfeb9dbbe7c MBR.bin

I tried to reorganize the bytes in this way, skipping the first 8 bytes (I think it is some kind of header)

4d42 5200 0000 0000 - 4631 4635 4538 4433 3243 4438 4436 3431 4631 3744 3444 4645 4239 4442 4245 3743 - 00 02 00 00
4750 5400 0000 0000 - 3344 3732 4244 3044 3438 3830 3336 4345 3937 4342 4639 3644 4634 3733 4539 3042 - 00 00 00 00
5049 5400 0000 0000 - 3933 4646 3645 3138 3344 3142 3141 3145 4445 4645 3243 4543 3837 3243 3141 3946 - 00 08 00 00
4345 5854 3400 0000 - 3539 3239 4244 4335 4442 4243 3642 3832 4643 4641 3531 4437 4236 3530 3544 4137 - 88 00 00 00
4e4f 4e45 0000 0000 - 3331 3531 4536 3446 3632 3638 4535 3636 4139 3843 4132 4238 3741 3332 3144 4646 - 00 00 14 00
0000 0000 0000 0000 - 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 - 00 00 00 00
4e4f 4e45 0000 0000 - 3637 4336 3235 4434 3445 3343 3031 3732 3336 4645 4241 3641 3034 3435 3146 3443 - 00 c8 11 00
4e4f 4e45 0000 0000 - 3231 3144 3636 3741 3839 3533 3239 3446 3141 3137 3342 4246 3846 3039 4432 3244 - 00 fe 7f 00
0000 0000 0000 0000 - 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 - 00 00 00 00
4345 5854 3400 0000 - 4446 3538 4238 3638 3643 3033 3037 4237 3733 4530 4438 3931 3334 3244 3444 3837 - ac 00 00 00
4e4f 4e45 0000 0000 - 3942 3644 3737 3736 3334 4132 3337 4246 3441 4530 3045 4634 4431 4436 4138 3532 - 00 02 c0 00
4345 5854 3400 0000 - 4531 4630 4345 3139 4637 3233 4133 4643 4339 4141 4430 3134 4432 3233 3446 4441 - c4 45 00 00
4345 5854 3400 0000 - 4446 4541 4635 3144 3437 3234 3239 3744 3837 4536 3738 4632 3332 4246 4143 3237 - c8 02 00 00
5246 5300 0000 0000 - 3631 4644 3834 4138 3642 3031 3443 3539 3341 4141 4445 4143 4631 3141 3937 4633 - 00 62 bb 16
4345 5854 3400 0000 - 3630 3742 3646 3733 4536 4543 4443 4630 4134 3939 3445 4237 3344 4538 4331 3344 - cc 01 00 00

MBR..... - F1F5E8D32CD8D641F17D4DFEB9DBBE7C - ....
GPT..... - 3D72BD0D488036CE97CBF96DF473E90B - ....
PIT..... - 93FF6E183D1B1A1EDEFE2CEC872C1A9F - ....
CEXT4... - 5929BDC5DBBC6B82FCFA51D7B6505DA7 - ....
NONE.... - 3151E64F6268E566A98CA2B87A321DFF - ....
....... - ................................. - ....
NONE.... - 67C625D44E3C017236FEBA6A04451F4C - ....
NONE.... - 211D667A8953294F1A173BBF8F09D22D - ....
........ - ................................ - ....
CEXT4... - DF58B8686C0307B773E0D891342D4D87 - ....
NONE.... - 9B6D777634A237BF4AE00EF4D1D6A852 - ....
CEXT4... - E1F0CE19F723A3FCC9AAD014D2234FDA - .E..
CEXT4... - DFEAF51D4724297D87E678F232BFAC27 - ....
RFS..... - 61FD84A86B014C593AAADEACF11A97F3 - .b..
CEXT4... - 607B6F73E6ECDCF0A4994EB73DE8C13D - ....

You can recognize easily the 12 partition, each one has indicated the file system used (CEXT4 for ext4, RFS for fat32) and an md5sum, plus other 4 bytes I cannot understand yet.

I was able only to obtain another md5

# dd if=/dev/block/mmcblk0 of=PIT.bin bs=512 count=4 skip=34
# md5sum PIT.bin
93ff6e183d1b1a1edefe2cec872c1a9f PIT.bin

I tried to calculate md5 of other partitions, md5 of GPT, only GPT HEADER, only GPT entry table... nothing to do md5 are not the same...

Open questions:

- are these md5 the ones used during the boot? I mean in particular when you got checksum error

- what is the meaning of the very first 8 bytes?

- md5 are not calculated on real partition in my Note, neither on official images contained in stock rom (cache.img, factoryfs.img, hidden.img, modem.bin, Sbl.bin, zImage). Those numbers refer to which file image/partitions?

- for every partition information we have NAME-MD5-4BYTES What is the meaning of the last 4 bytes?

- there are some last bytes at the end i cannot decode (for this reason I obfuscated them)

0005740: 00 00 00 00 00 00 00 00 00 00 00 00 42 43 44 39 ............BCD9
0005750: xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xxxxxxxxxxxxxxxx
0005760: xx xx xx xx xx xx xx xx xx xx xx xx 00 00 00 00 xxxxxxxxxxxx....

what they are for?

Last notes.

In following sectors from LBA 44 to LBA 81 I found some kind of file system...???

0005800: 3a ff 26 ed 01 00 00 00 1c 00 0c 00 00 10 00 00 :.&.............

I call it filesystem cause I have found the same pattern of bytes at the beginning of cache.img, factoryfs.img, hidden.img... I am trying to give all this a sense! :o

From LBA 82 to LBA 8191 only zeroes... than TADA! :D

At LBA 8192 starts the first partition but here you are in the solid standard of the ext4 filesystem (http://en.wikipedia.org/wiki/Ext4).

I hope you have found my examination usefull and that someone will try to investigate further to clarify what we got in that sea of information contained in those few bytes "hidden" before the first partition. ;)