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Date: Tue, 6 Oct 2015 14:26:47 +0100
From: Brian Norris <computersforpeace@gmail.com>
To: ispamyou <ispamyou@gmail.com>
Cc: linux-mtd@lists.infradead.org
Subject: Re: Kernel segfault when using nandsim on Debian kernel 4.1
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On Thu, Oct 01, 2015 at 08:25:04AM +0800, ispamyou wrote:
> Hi,
> 
> when I try and use nandsim to emulate "SDTNRGAMA 64G 3.3V 8-bit" using
> the following command I get a segmentation fault:
> 
> modprobe nandsim id_bytes=0x45,0xde,0x94,0x93,0x76,0x50 cache_file=./test.img
> 
> [  142.734637] [nandsim] warning: read_byte: unexpected data output
> cycle, state is STATE_READY return 0x0
> [  142.734637] [nandsim] warning: read_byte: unexpected data output
> cycle, state is STATE_READY return 0x0
> [  142.734640] nand: device found, Manufacturer ID: 0x45, Chip ID: 0xde
> [  142.734641] nand: SanDisk SDTNRGAMA 64G 3.3V 8-bit
> [  142.734644] nand: 8192 MiB, MLC, erase size: 4096 KiB, page size:
> 16384, OOB size: 1280
> [  142.734650] nand: No oob scheme defined for oobsize 1280

^^ this is the key

> [  142.734672] ------------[ cut here ]------------
> [  142.734674] kernel BUG at
> /build/linux-PoJsUp/linux-4.1.6/drivers/mtd/nand/nand_base.c:3952!

^^ and this too. You could look up your source code to find the exact
code context that triggers this BUG().

[...]

> I have also witnessed this segmentation fault on Ubuntu 14.04 LTS with
> an older kernel (3.19).
> 
> Is there any more information I can provide to try and help fix this issue?

The problem is that nand_base doesn't provide a default ECC layout for
odd/large OOB sizes on soft (Hamming) ECC (the default for nandsim). If
you want to use odd OOB sizes, I think you'll have better luck with soft
BCH, which generates ECC layouts dynamically. You can get this by using
the 'bch' module parameter to nandsim. See 'modinfo nandsim'.

Brian