Subject: Re: Data Abort Exceptions
To: None <>
From: Jay Monkman <>
List: port-arm
Date: 07/22/2002 13:38:41
On Mon, Jul 22, 2002 at 05:48:56PM +0100, Richard Earnshaw wrote:
> Current releases of NetBSD are configured not to abort the above, but to 
> use a load-and-rotate type of operation, so in the above func2 would print 
> the value contained by loading (*p & ~3) rotated by 8 bits.

How do you make the compiler generate code to do that? I've looked
through GCC's documentation, and haven't found it, nor have I found
the where it's set up in NetBSD.

> On ELF builds we've outlawed this, and on processors that support faulting 
> unaligned accesses we will probably make the CPU abort the access (though 
> I don't believe we do so yet).

On ELF, will you have an exception handler that looks at the aborted
instrcution, basically interprets it? I believe that's how Linux does
it, although I didn't look closely. Or will you just kill the process
that does it?

Thanks for the help.

Jay Monkman	    The truth knocks on the door and you say "Go away, I'm 
                    looking for the truth," and so it goes away. Puzzling.
		     - from _Zen_and_the_Art_of_Motorcycle_Maintenance_