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

[Stephen Neuendorffer]

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

Steve

> -----Original Message-----
> From: John Williams [mailto:john.williams@xxxxxxxxxxxxx]
> Sent: Monday, May 05, 2008 5:26 PM
> To: Stephen Neuendorffer
> Cc: monstr@xxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; arnd@xxxxxxxx;
linux-arch@xxxxxxxxxxxxxxx; John
> Linn; matthew@xxxxxx; will.newton@xxxxxxxxx; drepper@xxxxxxxxxx;
microblaze-uclinux@xxxxxxxxxxxxxx;
> grant.likely@xxxxxxxxxxxx; 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
> 
> 


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