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[Bug libc/6816] Support for POWER7 VSX registers in *context routines


------- Additional Comments From drepper at redhat dot com  2008-10-16 14:56 -------
(In reply to comment #17)
> We want to allow user space applications continued API access to the context via
> the get/set/swap context interface to the new VSX aware swapcontext syscall.

The context shouldn't contain the new registers, that's the point.  The *context
functions are function calls.  Hence registers which are not preserved don't
have to be included in the context data structures.  This eliminates the
versioning problem and it is exactly the way this is handled on x86.



> The kernel will support the new context size none-the-less and, as you've
> pointed out, a user may copy the context on a signal and then attempt to use the
> setcontext API on that context.

That's fine, they can do this.  But only the registers which are callee-saved
have any guarantee.  There is no reason IMO to add the new registers.

This will all _significantly_ slow down code as well.  All those big registers
have to be stored and reloaded.

-- 


http://sourceware.org/bugzilla/show_bug.cgi?id=6816

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