Re: %gs:0x14

[Thomas Schwinge]

Hello!

On Tue, Nov 14, 2006 at 04:26:26PM +0100, Samuel Thibault wrote:
> Thomas Schwinge, le Tue 14 Nov 2006 16:15:08 +0100, a ?crit :
> > Using `-fstack-protector' with GCC 4.1 made it include assembler code
> > using ``%gs:0x14'' even with `-ffreestanding'.  However, this isn't the
> > correct thing to do in kernel
> > space (with `-ffreestanding').  I think I've now tracked where this is
> > coming from.  This is not an issue anymore with GCC 4.2 or a GCC 4.1 that
> > is recent enough,
> 
> You mean that gcc now correctly switches to using __stack_chk_guard in
> freestanding mode?

It always does that on x86 on GNU/Linux with such a fixed version of GCC,
i.e. even in hosted mode.  Hm.


> > But then, if this was `*-*-*gnu*' instead of `*-*-linux*' in the above
> > configure check, I guess that the smashing stack protector wouldn't work
> > (and would instead make all compiled programs crash) in user space on
> > GNU/Hurd then, as then not `[GCC]/gcc/libgcc/''s generic code would be
> > used, but instead the Linux-tls-specific macros.
> 
> Well, we'll have to fix GNU/Hurd's TLS someday anyway.

We should, yes.  But even then, it's not decided that ``%gs:0x14'' would
be the correct thing to use on GNU/Hurd, isn't it?


Regards,
 Thomas

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