Question about trap

I'm a new poster here, but this question would seem to be on-topic.

I have a program which is generating integer overflow and trapping it
with the INTO instruction.
After a lot of experimentation I find that Linux (both the 2.4 and 2.6
kernels) is generating a SIGSEGV signal with error_code=128. This
doesn't seem to make a lot of sense to me. I've tried looking at the
kernel source to find out what it's actually doing, but these bits of
code are even more obscure than most. I'm hoping someone here knows
why this is happening and whether the 128 is a specific code or a
stand-in for a generic error.

Thanks.
.