How to trap unaligned memory access?

Question

I am working on a pet open-source project that implements some stream cipher algorithms and I am having trouble with a bug triggered only when I run it on an ARM processor.

Answer 1

Linux can do the fixup for you or warn about the access.

You can enable the behavior in /proc/cpu/alignment, see http://www.mjmwired.net/kernel/Documentation/arm/mem_alignment for an explanation of the different values.

0 - Do nothing (default behavior)
1 - Warning in kernel-log with PC and Memory-Address printed.
2 - Fixup error
3 - Warn and Fixup
4 - Send a SIGBUS to the process
5 - Send SIGBUS and output Warning