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Leif:

On Thu, 27 September 2001, "Leif Svalgaard" wrote:

> Well, the RISC code to check if a pointer is valid is:
> LQ R6, addr  ;  load pointer into R6, R7. set bit in exception reg if no tag
> TXER nn ; trap if no tag
>
> to me that is software. The trap can be disabled by replacing the TXER
> instruction by a NOOP.
>
> The overhead is the TXER instruction and is not unacceptable.


I would expect a software function that tells me whether a pointer is valid. 
The alternative might be having to use the pointer to see if an exception is 
raised and then having to properly handle that exception. I'd find a software 
test very convenient.

However, I'm not sure I see that this is really anything more than,... uh... 
well, a convenient way for a program to tell whether a pointer is valid.

Tom Liotta
(p.s. to anyone who's curious: Yes, I bought the book but haven't learned at 
all yet.)

--
Tom Liotta
The PowerTech Group, Inc.
19426 68th Avenue South
Kent, WA 98032
Phone  253-872-7788
Fax  253-872-7904
http://www.400Security.com


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