Re: Compat 32-bit syscall entry from 64-bit task!?

[H. Peter Anvin]

On 01/18/2012 01:51 PM, Roland McGrath wrote:
> 
> There are all the concerns about obscure ABI compatibility with
> expectations of existing debuggers and so forth, which Linus has mentioned.
> For that I can accept his point that things today so mishandle the
> int80-from-64 case that something like a new meaning for high bits of
> orig_ax or whatnot in just that case would not be actually problematic.
> When you and I were discussing a more general feature of distinguishing
> int80 from sysenter from syscall from traps from asynchronous interrupts,
> that was of more concern.
> 
> I do feel strongly that any new means of exposing bona fide user state
> ought to be done via the user_regset mechanism.  (i.e., either overloading
> some existing user_regs_struct bits if that truly is harmless to
> compatibility, or adding a new regset flavor.)  That way it is
> automatically recorded in core files, accessible with PTRACE_GETREGSET,
> etc.  (But I'm not really working on this stuff any more, so I'm out of the
> business of arguing strenuously about such opinions.)
> 

I think we can obviously agree that regsets is the only way to go for
any kind of new state.

	-hpa

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