Re: instruction pointers

["Leif Svalgaard" <leif@xxxxxxxx>]

 

Does the powerpc risc have the ability to branch to code in another pgm?

===> yes, but the MI architecture does not support it directly.

(also a security risk)

 

What specifically would not work?

 

===> the problem is the contents of the registers that must match from

one program to the next. The code assumes that no one else changes

any registers.

 

But, would the code be able to execute and then return to the branched from pgm and resume normal operations?

 

===> I have actually done this, but it is limited what you can do because of the

registers. Maybe with code to save/restore them one might make some headway,

but there are eariser wayst to do what you might want to do.

 

 

===> if you patch the program you can arrange to branch to

a parameter. This gives you the ability to execute RISC

instructions that are part of your data (and therefore are

under your control).

 

So you could execute risc code in a usrspc?

 

===> yes or in any other area of memory,

e.g. DCL DD CODE CHAR(256) BDRY(4);

 

 

 

thank you,

Steve Richter