DM issue on PI v1 model B

[bla42]

Unlike with other updates, my v1 B model (256M ram) boots "beyond the rainbow", but it does not find device mapper and thus cannot mount the encrypted root partition [1],[2]. A v2 B of a friend which i setup myself seems to work fine with the same setup. Any idea what fux up dm in my case (reports it can't find /dev/mapper/control)?

I'm still stuck to this version: Linux raspberrypi 3.18.11+ #776 PREEMPT Mon Apr 6 13:13:58 BST 2015 armv6l GNU/Linux (though not even every commit of 3.18.11 boots with my pi AFAIR).

[code]modprobe: chdir(4.1.5+): No such file or directory
Unlocking the disk /dev/mmcblk0p2 (xxx)
Enter passphrase: /dev/mapper/control: open failed: No such device
Failure to communicate with kernel device-mapper driver.
Check that device-mapper is available in the kernel.
Cannot initialize device-mapper. Is dm_mod kernel module loaded?[/code]

w/ the working kernel mention above, the output is as follows (connection to dropbear is supposed to be closed upon successful decryption, see pages cited above).

[code]Unlocking the disk /dev/mmcblk0p2 (xxx)
Enter passphrase:
cryptsetup: xxx set up successfully
Connection to xxx closed.[/code]

I have retried it again, definitely building the initrd just before boot. The problem is still the same. Also have tried remaking initrd for 3.8.11 now: works fine. Any hint on how to debug this problem is appreciated! I am willing to take almost every effort including compiling kernels on my pi. Just let me know anything I can do. Cheers!

The problem is indeed the encryption [b]and[/b] the latest version of the kernel so I am afraid neither the authors of the guides mentioned above nor an example not using encryption might help. Thanks for the time your have spend on understanding my prob!

[1] http://paxswill.com/blog/2013/11/04/encrypted-raspberry-pi/
[2] https://www.ofthedeed.org/posts/Encrypted_Raspberry_Pi/

P.S.: see also https://www.raspberrypi.org/forums/viewtopic.php?p=803146#p803146