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Date: Sat, 02 Oct 1999 12:20:51 -0700 (PDT)
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From: John Polstra <jdp@polstra.com>
To: "David O'Brien" <obrien@freebsd.org>
Subject: Re: Now that sigcontext is gone ...
Cc: current@freebsd.org, Alan Cox <alc@cs.rice.edu>
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David O'Brien wrote:
>> > P.S.  This also reminds me that FreeBSD is non-standard relative
>> > to Linux and all of the major vender commercial Unices in that a disallowed
>> > access, such as a write to a read-only region of memory, generates
>> > a SIGBUS rather than a SIGSEGV.
>> 
>> Yes, this even violates the 1996 POSIX spec.
> 
> So lets make the change for 4.0. :-)

Hang on, hang on.  This has been discussed in the mailing list
before.  Bruce pointed out that it's useful for distinguishing between
protection violations and unmapped pages.  He requested that we
first implement the SA_SIGINFO support to the point where it could
accomplish that before changing SIGBUS to SIGSEGV.  I think that makes
sense.

> Just how much code will break?

Boehm-gc, maybe.  Modula-3, maybe.  I can't remember whether it
catches both signals or just SIGBUS.

John


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