17.8.5. mmap
The mmap system call allows us to share memory between user and kernel space without copying:
./mmap.sh echo $?
Outcome: the test passes:
0
Sources:
In this example, we make a tiny 4 byte kernel buffer available to user-space, and we then modify it on userspace, and check that the kernel can see the modification.
mmap, like most more complex File operations, does not work with debugfs as of 4.9, so we use a procfs file for it.
Example adapted from: https://coherentmusings.wordpress.com/2014/06/10/implementing-mmap-for-transferring-data-from-user-space-to-kernel-space/
Bibliography: