Re: [RFC] x86: xsave/xrstor support, ucontext_t extensions

[H. Peter Anvin]

Suresh Siddha wrote:
> > > The kernel needs to accept one(*) of the formats it can produce, which
> > > is not necessarily what it last produced. It's not inconceivable that
> > > user-space will construct sigframes on the fly (to emulate setcontext),
> > > or that it will mangle sigframes (e.g. to map non-rt to rt before 
> > > sigreturn).
> > >
> > > (*) The format is determined by which version of sys_sigreturn the
> > > user invokes.
> > No.  You CANNOT restore from a frame that doesn't have the full state - 
> > you don't have enough information to do so!
>
> What I was doing in the RFC is: restore the state what ever that was present and
> init the state that was not present in the stack frame.

Either way, I find it somewhat surprising that the user would invoke a 
different sys_sigreturn especially if using a restorer function (which 
gcc always does.)

I really think I need to understand your application better, 
*especially* in the light of the fact you wouldn't at the moment know 
how even get the size of the frame.

	-hpa
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/