From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Christoph Hellwig <hch@lst.de>
Cc: linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
linux-kernel@vger.kernel.org
Subject: Re: [RFC][POWERPC] Provide a way to protect 4k subpages when using 64k pages
Date: Wed, 12 Dec 2007 10:38:08 +1100 [thread overview]
Message-ID: <1197416288.8385.21.camel@pasglop> (raw)
In-Reply-To: <20071211155305.GA28055@lst.de>
On Tue, 2007-12-11 at 16:53 +0100, Christoph Hellwig wrote:
> All these process would use plain mmap/
> mprotect to deal with the subpage protections.
That seems very hard to do ... all of the generic code here only knows
about the base page size, so except if we're going to fully re-implement
the mmap/mprotect logic from scratch, it's going to hurt, or am I
missing something ?
I suppose we could add wrappers to those syscalls that always set the
protection map to "no access" over the target area (from within
get_unmapped_area for mmap as we don't know the area yet), and then,
update it after the successful call.
But mprotect seems a clumsy way to control the per-sub-page permission
in that case as we don't want to change the underlying real 64k page
permission.
Ben.
prev parent reply other threads:[~2007-12-11 23:38 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-07 6:09 [RFC][POWERPC] Provide a way to protect 4k subpages when using 64k pages Paul Mackerras
2007-12-07 12:03 ` Arnd Bergmann
2007-12-11 15:53 ` Christoph Hellwig
2007-12-11 21:21 ` Arnd Bergmann
2007-12-11 21:37 ` Paul Mackerras
2007-12-11 23:38 ` Benjamin Herrenschmidt [this message]
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