From owner-freebsd-hackers Sat Mar 3 14:59: 8 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from homer.softweyr.com (bsdconspiracy.net [208.187.122.220]) by hub.freebsd.org (Postfix) with ESMTP id 8EB2037B719 for ; Sat, 3 Mar 2001 14:59:03 -0800 (PST) (envelope-from wes@softweyr.com) Received: from [127.0.0.1] (helo=softweyr.com ident=Fools trust ident!) by homer.softweyr.com with esmtp (Exim 3.16 #1) id 14ZLAL-0005Yc-00; Sat, 03 Mar 2001 16:10:21 -0700 Message-ID: <3AA179DC.131B8112@softweyr.com> Date: Sat, 03 Mar 2001 16:10:20 -0700 From: Wes Peters Organization: Softweyr LLC X-Mailer: Mozilla 4.75 [en] (X11; U; Linux 2.2.12 i386) X-Accept-Language: en MIME-Version: 1.0 To: James Howard Cc: Alfred Perlstein , Dan Phoenix , freebsd-hackers@FreeBSD.ORG Subject: Re: easy way to crash freebsd References: Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG James Howard wrote: > > On Sat, 3 Mar 2001, Wes Peters wrote: > > > You don't even have to overwrite it some times. Accessing word-size-only > > registers in memory a byte at a time can cause a bus error and panic... > > I have never worked with FreeBSD at this low a level. How does one do > this and why? :) Some memory locations are memory-mapped I/O registers, rather than "just RAM", and have to be read at the correct width for the register. Reading a 32-bit register with an 8-bit read can cause a bus error; since you're poking around in kernel memory (/dev/*k*mem) a panic ensues. This was a sure-fire way to crash RISC Ultrix, and I think SunOS M68K too. I don't know that this will work on x86, with it's separate I/O address space, and it doesn't work on SPARC because you can't get to the right Address Space Identifier (ASI) for anything other than RAM (and maybe some ROM). -- "Where am I, and what am I doing in this handbasket?" Wes Peters Softweyr LLC wes@softweyr.com http://softweyr.com/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message