[Sony Ericsson XPERIA X10 Mini] sonty:
I tried building a couple of modules myself. one of them is tun.ko and for the other I moved a bunch of code to try to force compile netfilter as a module.

for tun.ko the result I get is the same with yours: kernel oops and reboot. I'm trying with openvpn started from command line. what are you trying with?

for netfilter I'm sort of stuck at the point where with x_tables.ko loaded the device reboots on wlan0 state change.

here's the dump:

/data/crashsms/crashes # cat 1295440566.txt

crashtime:1295440566

crashtype:1

cpuid:0

processname:openvpn

crashstring:Kernel Panic

logname:

crashlog:[ 1331.875506] Kernel panic - not syncing: Fatal exception

[ 1331.869108] Code: e5830004 e3520000 e59a136c 0a000002 (e5910000)

[ 1331.863470] r7:00000036 r6:000d806c r5:000f3e48 r4:bea9b39c

[ 1331.855135] [<c00ec7f0>] (sys_ioctl+0x0/0x64) from [<c002be80>] (ret_fast_syscall+0x0/0x2c)

[ 1331.852532] r4:c5dcc9a0

[ 1331.846022] r9:c81ce000 r8:c002c004 r7:00000004 r6:400454ca r5:bea9b39c

[ 1331.837860] [<c00ec274>] (do_vfs_ioctl+0x0/0x57c) from [<c00ec830>] (sys_ioctl+0x40/0x64)

[ 1331.832220] r7:00000004 r6:400454ca r5:c5dcc9a0 r4:bea9b39c

[ 1331.823972] [<c00ec0e8>] (vfs_ioctl+0x0/0x94) from [<c00ec77c>] (do_vfs_ioctl+0x508/0x57c)

[ 1331.815205] [<bf0f8660>] (tun_chr_ioctl+0x0/0x928 [tun]) from [<c00ec160>] (vfs_ioctl+0x78/0x94)

[ 1331.812772] Backtrace:

[ 1331.804525] ffe0: 000d8088 bea9b338 afe1f5c9 afe0ca8c 80000010 00000004 656c7564 6c626154

[ 1331.796278] ffc0: bea9b39c 000f3e48 000d806c 00000036 00000000 00000000 00000000 00000000

[ 1331.788033] ffa0: c002be80 c00ec7fc bea9b39c 000f3e48 00000004 400454ca bea9b39c bea9b354

[ 1331.779787] ff80: 00000005 00000000 bea9b39c 000f3e48 000d806c 00000036 00000000 c81cffa8

[ 1331.771540] ff60: 400454ca 00000004 c002c004 c81ce000 c81cffa4 c81cff80 c00ec830 c00ec280

[ 1331.763293] ff40: 00000004 c5ba0000 c5dcc9a0 c3615870 00000020 c81ce000 c5dcc9a0 bea9b39c

[ 1331.755047] ff20: 00000000 c5dcc9a0 c81cff64 c81cff38 00000000 00000000 00000000 00000004

[ 1331.746800] ff00: 400454ca 00000004 c81cff7c c81cff18 c00ec77c c00ec0f4 00000000 00020003

[ 1331.738553] fee0: c81ce000 00000000 c81cff14 c81cfef8 c00ec160 bf0f866c bea9b39c c5dcc9a0

[ 1331.730307] fec0: 00000000 c00b7500 cc5a9358 c5dcc9a0 00000000 bea9b39c 400454ca c002c004

[ 1331.722060] fea0: c00eae18 00000000 00000000 00000000 00000000 00003001 00000000 00000000

[ 1331.713815] fe80: c81cff64 c81cfea8

[ 1331.709482] Stack: (0xc81cfe98 to 0xc81d0000)

[ 1331.703405] Process openvpn (pid: 2130, stack limit = 0xc81ce260)

[ 1331.695237] 69ac 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

[ 1331.687077] 698c 00000000 00000000 c3691e60 00000000 00000000 00000000 00000000 00000000

[ 1331.678918] 696c c9a30da0 c5853520 cbeba4e0 00000000 c5dcc620 c5ac4c40 c3923c40 c5107120

[ 1331.670758] 694c 00027bff c3691e60 c3691e60 c3691e60 c5dccca0 c5dcc9a0 c9a30420 cc13bc60

[ 1331.662598] 692c ccb06950 ccb06948 ccb0694c 00000000 00000000 00000000 00000005 00000008

[ 1331.654438] 690c 00000000 c947d8e0 c947d860 c947d7e0 c947d760 00000001 ccb06928 00000020

[ 1331.646278] 68ec 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

[ 1331.638120] 68cc 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000

[ 1331.633792] R10: 0xccb068cc:

[ 1331.633782]

[ 1331.625618] ca00 00000000 00000000 00000000 c5dcca0c c5dcca0c c3615908 00000000 00000000

[ 1331.617458] c9e0 00000000 00000000 00000000 00000000 00000000 00000000 ffffffff ffffffff

[ 1331.609300] c9c0 00000000 00000000 00000000 00000000 00000000 00000000 00000000 ccb05ec0

[ 1331.601140] c9a0 c38acec0 ccb1a28c cca0a2a0 cc475338 bf0f98f0 00000001 00020002 0000001f

[ 1331.592980] c980 00000000 00000000 00000000 c5dcc98c c5dcc98c cc7d79b8 00000000 00000000

[ 1331.584820] c960 00000000 00000000 00000000 00000020 00000000 00000000 00000d69 00000000

[ 1331.576662] c940 00000d69 00000000 00000000 00000000 00000000 00000000 00000000 ccb05ec0

[ 1331.568502] c920 c3819c60 c00dfe1c 00000000 00000000 c03891bc 00000000 00020000 0000001d

[ 1331.564262] R9: 0xc5dcc920:

[ 1331.564250]

[ 1331.556088] c064 c00ac218 c009d1b8 c008fe58 c009d1b8 c009d1b8 c009192c c009d1b8 c009d1b8

[ 1331.547928] c044 c00ac5b4 c009d1b8 c009d1b8 c00de688 c0090f9c c00f8978 c009d1b8 c00ac4e8

[ 1331.539768] c024 c00dcea0 c00eaa58 c00ea348 c002c5ec c00dd928 c009d1b8 c00ea78c c00dd808

[ 1331.531608] c004 c00918dc c008a2f4 c002c5dc c00df758 c00df524 c00dce78 c00dcbd0 c009d1b8

[ 1331.523450] bfe4 e1a02007 e1a0100d e3a00001 eb0004a1 eaffffb6 e320f000 e320f000 c04cfc98

[ 1331.515290] bfc4 e28fe014 e1a0

I'll try to analyze it too in the next few days.