From: benh@kernel.crashing.org (Benjamin Herrenschmidt)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH 0/4] Fix PROT_NONE page permissions when !CPU_USE_DOMAINS
Date: Fri, 21 Sep 2012 08:23:53 +1000 [thread overview]
Message-ID: <1348179833.1132.36.camel@pasglop> (raw)
In-Reply-To: <20120920221215.GA1837@n2100.arm.linux.org.uk>
On Thu, 2012-09-20 at 23:12 +0100, Russell King - ARM Linux wrote:
.../...
> That'll make the set_pte assembly more horrid, but I guess that's the
> price you pay for removing useful features which architecture folk don't
> like from CPUs... and it gets more horrid because you can't encode some
> of those bit patterns with the standard 8-bit and shift opcode
> representation.
>
> Really fun bug, but it needs more thought about how to solve it.
Yeah, fun isn't it ? :-)
The x86 way to solve it is simple, though ugly ... They use a SW bit
called "PROTNONE". A PROT_NONE page gets that instead of the HW valid
bit and pte_present() test if any of them is set.
Cheers,
Ben.
next prev parent reply other threads:[~2012-09-20 22:23 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-20 15:56 [PATCH 0/4] Fix PROT_NONE page permissions when !CPU_USE_DOMAINS Will Deacon
2012-09-20 15:56 ` [PATCH 1/4] ARM: mm: use pteval_t to represent page protection values Will Deacon
2012-09-20 18:28 ` Nicolas Pitre
2012-09-20 21:07 ` Will Deacon
2012-09-21 8:48 ` Catalin Marinas
2012-09-20 15:56 ` [PATCH 2/4] ARM: mm: don't use the access flag permissions mechanism for classic MMU Will Deacon
2012-09-21 8:40 ` Catalin Marinas
2012-09-20 15:56 ` [PATCH 3/4] ARM: mm: introduce L_PTE_VALID for page table entries Will Deacon
2012-09-20 22:21 ` Russell King - ARM Linux
2012-09-21 9:22 ` Will Deacon
2012-09-20 15:56 ` [PATCH 4/4] ARM: mm: introduce present, faulting entries for PAGE_NONE Will Deacon
2012-09-20 22:12 ` [PATCH 0/4] Fix PROT_NONE page permissions when !CPU_USE_DOMAINS Russell King - ARM Linux
2012-09-20 22:23 ` Benjamin Herrenschmidt [this message]
2012-09-21 9:32 ` Will Deacon
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