[RaspberryPi] Kernel Fault when using "cat /dev/rfm12b.0.1" and hitting CTRL-C

[richbayliss]

Firstly, thanks for this amazing effort at getting the tricky RFM12B module working on the Pi. I tried in vain to get it working using SPIDEV and Python but alas it was too slow to cope with the tiny buffer on the RFM12.

I have compiled your module using the Yocto project system and I can load the module into the kernel. When I open the device using "cat /dev/rfm12b.0.1" I can see the nIRQ line go high but when hitting CTRL-C I get a kernel fault:

[ 94.090169] Unable to handle kernel NULL pointer dereference at virtual address 0000001c

I don't know if this is expected, but I was wondering if you could either explain it?

Thanks again.

[gkaindl]

hmm, no, that is not expected, of course.

I can't seem to reproduce this problem with my setup, though (I tried with a script that waits a random amount of time before sending the SIGINT to cat) – Could you please send me the full stack dump from your logs, please?

Other than that, maybe it has to do with the build system? I haven't used Yocto yet...

[Frankenslag]

I got a similar thing to this also. But I didn't have any RFM12b hardware connected. When I actually built the hardware then the issue went away

[droloff]

same problem here. Let me know if you need any more info's. I really would like to use this driver. The userland library is working fine, but i don't like the polling of the IRQ GPIO.
I am using a rpi3 with Kernel 4.4.38-v7+

after:

insmod ./rfm12b.ko
cat /dev/rfm12b.0.1
CTRL-C

i will get a kernel oops ...
[370249.160787] rfm12b: added RFM12(B) transceiver rfm12b.0.1
[370249.160930] rfm12b : driver loaded.
[370260.417152] rfm12b: transceiver <0x7f05b748> (RFM12(B)) settings now: group 211, band 1, bit rate 0x06 (49261 bps), jee id: 15,
jee autoack: 1.
[370278.919110] Unable to handle kernel NULL pointer dereference at virtual address 0000001c
[370278.919128] pgd = 80004000
[370278.919134] [0000001c] *pgd=00000000
[370278.919145] Internal error: Oops: 5 [#1] SMP ARM
[370278.919152] Modules linked in: rfm12b(O) bnep hci_uart btbcm bluetooth brcmfmac brcmutil cfg80211 rfkill snd_bcm2835 snd_pcm sn
d_timer snd spi_bcm2835 bcm2835_gpiomem bcm2835_wdt w1_gpio uio_pdrv_genirq uio w1_therm wire cn i2c_dev fuse ipv6
[370278.919212] CPU: 1 PID: 206 Comm: spi0 Tainted: G O 4.4.38-v7+ #938
[370278.919217] Hardware name: BCM2709
[370278.919223] task: b90ae780 ti: b85ca000 task.ti: b85ca000
[370278.919238] PC is at rfmXX_handle_interrupt+0x18/0x1fc [rfm12b]
[370278.919247] LR is at platform_irq_handled+0x80/0x84 [rfm12b]
[370278.919254] pc : [<7f0599b8>] lr : [<7f059c1c>] psr: 60000013
sp : b85cbe20 ip : b85cbe40 fp : b85cbe3c
[370278.919261] r10: b85ca000 r9 : b99fc810 r8 : 20000013
[370278.919267] r7 : aa96580c r6 : 00000000 r5 : 00000000 r4 : 7f05b748
[370278.919272] r3 : 808a5718 r2 : b9ac690c r1 : 00000019 r0 : 00000000
[370278.919280] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
[370278.919286] Control: 10c5383d Table: 2aac806a DAC: 00000055
[370278.919292] Process spi0 (pid: 206, stack limit = 0xb85ca210)
[370278.919298] Stack: (0xb85cbe20 to 0xb85cc000)
[370278.919308] be20: 8034f2bc 8034dc1c 808a5718 7f05b748 b85cbe54 b85cbe40 7f059c1c 7f0599ac
[370278.919318] be40: aa96587c aa965800 b85cbe7c b85cbe58 7f059cb4 7f059ba8 7f059c20 b99b2000
[370278.919327] be60: 60000013 b99b21ec aa96587c b99fc810 b85cbea4 b85cbe80 803ffcf4 7f059c2c
[370278.919337] be80: 00000000 aa96587c b99b2000 b3a9bdb0 b99b2240 805c0e5c b85cbee4 b85cbea8
[370278.919347] bea0: 80400100 803ffbbc 00000000 b3a9bc00 b3a9bdb0 00000001 b85ca000 aa965848
[370278.919355] bec0: aa96587c b99fc810 b99fc810 00000001 00000002 b99b2000 b85cbf24 b85cbee8
[370278.919364] bee0: 804005bc 803ffde4 b99b21c4 808f6b0c b85ca000 b99b21c4 b99b21c4 b99b21dc
[370278.919372] bf00: b99b21c4 808f6b0c b85ca000 808f6b0c b85ca038 00000000 b85cbf34 b85cbf28
[370278.919381] bf20: 80400890 80400224 b85cbf5c b85cbf38 800428dc 8040087c 00000000 b86971c0
[370278.919391] bf40: b99b21c4 80042878 00000000 00000000 b85cbfac b85cbf60 80042860 80042884
[370278.919400] bf60: 39712000 00000000 00000000 b99b21c4 00000000 00000000 b85cbf78 b85cbf78
[370278.919409] bf80: 00000000 00000000 b85cbf88 b85cbf88 b86971c0 80042774 00000000 00000000
[370278.919417] bfa0: 00000000 b85cbfb0 8000fbc8 80042780 00000000 00000000 00000000 00000000
[370278.919425] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
[370278.919433] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 3a7fa861 3a7fac61
[370278.919464] [<7f0599b8>] (rfmXX_handle_interrupt [rfm12b]) from [<7f059c1c>] (platform_irq_handled+0x80/0x84 [rfm12b])
[370278.919479] [<7f059c1c>] (platform_irq_handled [rfm12b]) from [<7f059cb4>] (rfm12_recv_spi_completion_handler+0x94/0x140 [rfm12b])
[370278.919495] [<7f059cb4>] (rfm12_recv_spi_completion_handler [rfm12b]) from [<803ffcf4>] (spi_finalize_current_message+0x144/0x228)
[370278.919506] [<803ffcf4>] (spi_finalize_current_message) from [<80400100>] (spi_transfer_one_message+0x328/0x440)
[370278.919515] [<80400100>] (spi_transfer_one_message) from [<804005bc>] (__spi_pump_messages+0x3a4/0x658)
[370278.919524] [<804005bc>] (__spi_pump_messages) from [<80400890>] (spi_pump_messages+0x20/0x24)
[370278.919536] [<80400890>] (spi_pump_messages) from [<800428dc>] (kthread_worker_fn+0x64/0x198)
[370278.919546] [<800428dc>] (kthread_worker_fn) from [<80042860>] (kthread+0xec/0x104)
[370278.919556] [<80042860>] (kthread) from [<8000fbc8>] (ret_from_fork+0x14/0x2c)
[370278.919566] Code: e24cb004 e24dd00c e52de004 e8bd4000 (e590301c)
[370278.919573] ---[ end trace c014630e859bd441 ]---