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Subject: Re: make PROT_WRITE imply PROT_READ
From: Arjan van de Ven <arjan@infradead.org>
To: Jason Baron <jbaron@redhat.com>
Cc: Robert Hancock <hancockr@shaw.ca>, akpm@osdl.org,
       linux-kernel@vger.kernel.org
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Date: Fri, 23 Jun 2006 16:06:21 +0200
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> 
> hi,
> 
> So if i create a PROT_WRITE only mapping and then read from first and then 
> writte to it a get a SEGV. However, if i write to it first and then read 
> from it, i don't get a SEGV...Why should the read/write ordering matter? 

it matters only on those cpus that don't have explicit/separate read
permissions (just like PROT_EXEC is implied on cpus that don't have a
special permission bit for that)...