How to send a "signal" from kernel module to user-space application?

Question

I have a Linux kernel module which contains the interrupt handler, and would like to somehow notify the user-space application after the interrupt was handled. Please tell me, how to do it?

Can we assume that you're talking about Linux? Either way, please add the relevant tag to your question. — Oliver Charlesworth, Jun 02 '13 at 20:51
@OliCharlesworth Yes, we are talking about Linux, but I ran out of tags — Jake Badlands, Jun 02 '13 at 20:53
You could, e.g., remove “hardware” in favour of “linux”. Hardware knowledge is not really important to answer this question. — chirlu, Jun 02 '13 at 20:56
@chirlu Okay I have done it. Please lets return to the question — Jake Badlands, Jun 02 '13 at 21:13
The tags are important to get the right people to look at your question. See? Answers are coming. :-) — chirlu, Jun 02 '13 at 21:32

score 4 · Accepted Answer · edited May 23 '17 at 12:28

4

You can always use normal sockets, like UDP or UNIX.
You can export this information via /proc or /sys (see this question).
You can use Netlink (see this question).

edited May 23 '17 at 12:28

Community

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answered Jun 02 '13 at 21:29

kirelagin

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message queue, or shared memory? – eduardosufan Aug 14 '13 at 22:59
You can use signals too to userspace :).. Only thing your kernel module should know is PID of the process which needs to trigger. I have used IOCTL to the kernel module to pass PID :). – duslabo Mar 18 '14 at 10:02

score 3 · Answer 2 · answered Jun 02 '13 at 21:26

Use the netlink.

Netlink socket is a special IPC used for transferring information between kernel and user-space processes. It provides a full-duplex communication link between the two by way of standard socket APIs for user-space processes and a special kernel API for kernel modules. Netlink socket uses the address family AF_NETLINK, as compared to AF_INET used by TCP/IP socket. Each netlink socket feature defines its own protocol type in the kernel header file include/linux/netlink.h.

score 0 · Answer 3 · answered Mar 08 '14 at 04:22

I'm directly answering this question as it's the top result in Google for "kernel send signal to user space".

I typically use signal to kill the userspace process to examine it's stack as it calls ioctls. Typically the following works for me:

force_sig(SIGSEGV, current);

How to send a "signal" from kernel module to user-space application?

3 Answers3