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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 6:46 
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Dump of blocks 2048/2049/2050/2051 (begin part of the blocks)


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dump1.png
dump1.png [ 2.49 MiB | Viewed 15275 times ]
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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 6:48 
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End part of the block :

Attachment:
dump2.png
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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 6:53 
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We can see block separation, and there are at the beginning of pages :

- 1 bit always 0
- 12 bits always 0

And 48 bytes of 0xFF at the end.

I though the always zero bits can be bad columns, but that's very curious because these potential bad columns are same in the 2 planes of the first chip (CE0), but also the same in the 2 planes of second chip (CE1) !!

Seems everything is Xored (data+spare areas) !?


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 8:53 
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I spied communication between controller and nand during mmc initialization, it reads some pages but only the first 32 bytes, and after a small pause it reads next data of the page.
Thus it make sense with my dump, the blank column is the 32th byte, it's the spare area. and because there are 48 byte 0xFF a the end, the page mapping is :

32 byte SA + 8 x (1024 data byte + 70 byte ecc) + 48 data byte 0xFF = 8832 bytes

In 15 min the full dump will be finished :)


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 9:15 
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The SA seems scrambled or XORed but I think it's not the case because one bit is always 0.
Maybe the 256 pages inside a block are not in the right order, or maybe they are interleaved with others blocks/planes/crystals :idea:


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 10:44 
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This is kinda ridiculously cool! What's the size of the dump?

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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:03 
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2 chips select * 2 planes * 1046 blocks * 256 pages * 8832 bytes = 8.81GiB :D


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:33 
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Based on my expirience when I look on bitmap, it shows me information that dumps was read with terrible quality. Generally it was read wrong.

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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:35 
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I have some bad bits in the dump :

Attachment:
bit_flip.png
bit_flip.png [ 65.09 KiB | Viewed 15188 times ]


But I think the dump quality is good, because the white column is 12 bits wide, and on a dump sample of 8192 pages, thus 98304 bits, I counted only 89 bad bits (0.00091%)
If I'm not mistaken, the 70 bytes ECC for 1024 data byte (total 8752 bits) can correct up to 40 bit errors, thus up to 40/8752 = 0.004%


Last edited by nlc on May 31st, 2020, 11:40, edited 1 time in total.

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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:37 
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arvika wrote:
Based on my expirience when I look on bitmap, it shows me information that dumps was read with terrible quality. Generally it was read wrong.


Thank you, you confirmed my intuition :)

Now I need to try to find the XOR key....


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:41 
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As I write, dump was read wrong.

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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:48 
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arvika wrote:
As I write, dump was read wrong.


:lol: This is encouraging ..

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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:53 
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arvika wrote:
As I write, dump was read wrong.


Oups sorry I don't understood that :)

What is wrong on the dump ? I think it's just page order which are not good, but look the blank column, only 91 bads bit per 98304 bits !?


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:53 
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Arch Stanton wrote:
:lol: This is encouraging ..


Yes :lol:


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 11:54 
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nlc, first work on dump quality. Finding XOR when dump is wrong is completly waste of time.
Noise on bitmap looks not good, it should look other. At this case bit errors on white column lead you in wrong direction.

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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 12:13 
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Which noice ?

Looked on other blocks for example, here 4 block :
Attachment:
noice.png
noice.png [ 1.13 MiB | Viewed 15154 times ]


Maybe SA is not good and has no sense because page are mixed, but I see no difference with some tutorials which explain data recovery ?


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 12:42 
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Look much better. You can send me few blocks, I will check ECC.

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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 12:49 
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arvika wrote:
Look much better. You can send me few blocks, I will check ECC.


Maybe even upload the dump somewhere ... ?

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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 13:12 
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I attached a 2 blocks dump sample (512 pages) :)

Attachment:
block.data.zip [4.22 MiB]
Downloaded 525 times


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 Post subject: Re: Which NAND flash reader ?
PostPosted: May 31st, 2020, 13:18 
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But to test ECC, XOR should be applied first, no ?


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