Re: [rfa] Attach vsyscall support for GNU/Linux

[Andrew Cagney <cagney at gnu dot org>]

Mark Kettenis wrote:
>    Date: Mon, 25 Oct 2004 18:44:37 -0400
>    From: Andrew Cagney <cagney@gnu.org>
>
> Thos funny little diagrams are UML isn't it?
>
>    It needs to be changed so more like:
>
> 		       SYMBOL
> 			/|\
> 			 |
>        FRAME <>----- FUNCTION <>------ UNWINDER
>
>    and have the FUNCTION provide:
>
>       - signal trampoline?

In english:

frame has-a function
function has-a unwinder
function is-a symbol

> I think this is wrong.  It's probably true that functions that are
> used as signal trampolines in traditional UNIX systems are only usable
> as such, this is not true for interrupt handlers.  On i386 systems you
> can write interrupt handlers that are also usable as trap handlers.
> Where interrupt handlers are sigtramp-like, trap handlers are musch
> more normal.  This kind of attributes depend more on the context and
> thereforeit is more logical to put them in the frame.  I think the
> same is true for the unwinder.
>
> That said, it is perfectly reasonable to let the frame inherit some of
> these attributes from the function.
>
> Mark