You dont need any kernel support for this. You can redirect signal handlers
to your own routines which fake the desired result and any lcall or trap
isntructions will generate a SIGILL which you can trap in user space
and emulate
> sure. entry.S has entries for both lcall7 and syscall. There's only
> one lcall7 function defined in the kernel, and that sends SEGV.
The ibcs personality has its own lcall7 handler if you have the ibcs
module loaded.