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
[EMAIL PROTECTED] http://softweyr.com/
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