I have a kernel module and a userspace program. Each need to be able to
send messages to the other. I've looked into get_user and put_user but
they require an address argument from userland. If the address is from
userland, wouldn't the address be virtual in the process address space?
How would the kernel know from which process the pointer came and thus be
able to translate it to an absolute address? Also, any code that I've seen
seems to assume that the user code is calling the kernel code and can hence
pass a pointer. Well what if the kernel wants to initiate communication
with the user process? How can they set up a meeting place?
My other thought was to use /proc and attempt to send messages by creating
a /proc/videomessage file. Two way communication would require the
userland portion to run as root, but that doesn't bother me. Finding
documentation on how to write proc files from a module has been more
difficult than I thought.
Once again, any code, links to code, or advice is welcome.
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