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

John Williams
2008-05-06T00:26:39Z

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