RE: [PATCH 07/56] microblaze_v2: Signal support

Stephen Neuendorffer
2008-05-06T00:34:28Z

You're right. (I think I've been staring at this too much today... :)

Steve

> -----Original Message-----
> From: John Williams [mailto:john.williams@petalogix.com]
> Sent: Monday, May 05, 2008 5:26 PM
> To: Stephen Neuendorffer
> Cc: monstr@seznam.cz; linux-kernel@vger.kernel.org; arnd@arndb.de;
linux-arch@vger.kernel.org; John
> Linn; matthew@wil.cx; will.newton@gmail.com; drepper@redhat.com;
microblaze-uclinux@itee.uq.edu.au;
> grant.likely@secretlab.ca; Michal Simek
> Subject: RE: [PATCH 07/56] microblaze_v2: Signal support
>
> On Mon, 2008-05-05 at 17:13 -0700, Stephen Neuendorffer wrote:
> > I'm somewhat ignorant about what this code is attempting to do, but
with
> > some quick poking around (m68knommu, blackfin) seems to suggest that
> > other architectures don't do this, while others (v850) have almost
> > exactly the same code (although they are somewhat smarter and are
> > careful not to flush the whole cache).
> >
> > At the very least, it seems like there is some work in this area
needed.
>
> flush_cache_sigtramp should just invalidate 8 bytes up from the base
> address of the trampoline. This is just the region on the process
stack
> where we insert a kind of call-back back. Writing the opcodes goes
via
> the dcache, and so there's a vanishingly small possibility that the
CPU
> will get a false hit on on an icache fetch when the code is executed.
>
> That was what Michal's patch had when I scanned it yesterday. It
> certainly won't/shouldn't be invalidating the entire cache.
>
> Cheers,
>
> John
>
>