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Dumping the firmware:
This technique consists on reconstructing a firmware image dumping
pieces at certain offsets of the device internal memory.
Technical details:
* The internal flash memory is exposed to the system as MTD devices.
* Is possible to dump the individual sections of a flashed firmware.
*
* READ src/local.c for detailed information.
mtd0 - contains xloader and secondary pieces of the bootloaders
0x00000 - xloader.bin (size is 0x03600)
0x04000 - secondary.bin (size is 0x15400)
0x1FFFF - eof
mtd1 - looks like there's a pool ConF structures
mtd2 - starts with NOLO img\x5c\x13 and \x00 padding
0x00800 - zImage
> NOLO is a four byte marker, next four bytes
> can vary since it is kernel image size
mtd3 - initfs.jffs2 (2M) aka 0x200000 vs 0x3900000
mtd4 - rootfs.jffs2 (a fucking copy of the above rootfs?)
For dumping mtd partition is used tool nanddump. Here is example how to dump
kernel image without padding to file zImage:
$ nanddump -i -o -b -s 0x00000800 -l 0x001FF800 -f zImage /dev/mtd2
Params means:
-i - "Ignore errors"
-o - "Omit oob data"
-b - "Omit bad blocks"
-s - "Start address"
-l - "Length"
-f - "Output file"
Please note that some new versions of nanddump have some options removed and
some are enabled by default. Before using check params of your nanddump version.
// Extra notes //
[MTD] NAND Consolidate oobinfo handling
The info structure for out of band data was copied into
the mtd structure. Make it a pointer and remove the ability
to set it from userspace. The position of ecc bytes is
defined by the hardware and should not be changed by software.
// The oob stuff
In mtd3 the OOB data is 64 bytes aka 0x40, and this oob stuff
appears every 2KB aka 0x800 bytes.
/*
* Obsolete legacy interface. Keep it in order not to break userspace
* interfaces
*/
struct nand_oobinfo {
uint32_t useecc;
uint32_t eccbytes;
uint32_t oobfree[8][2];
uint32_t eccpos[32];
};
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