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Subject: Re: make PROT_WRITE imply PROT_READ
From: Arjan van de Ven <arjan@infradead.org>
To: Ulrich Drepper <drepper@gmail.com>
Cc: Pavel Machek <pavel@ucw.cz>, Jason Baron <jbaron@redhat.com>,
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Date: Fri, 30 Jun 2006 10:35:45 +0200
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On Thu, 2006-06-29 at 20:48 -0700, Ulrich Drepper wrote:
> On 6/29/06, Arjan van de Ven <arjan@infradead.org> wrote:
> > the thing is.. you can say EXACTLY the same about PROT_EXEC.. not all
> > processors support enforcing that.. so should we just always imply
> > PROT_EXEC as well?
> 
> There is a fundamental difference: not setting PROT_EXEC has no
> negative side effects.  You might be able to execute code and it just
> works.
> 
> With PROT_READ this is not the case, there _are_ side effects which are visible.

there are side effects which are visible with PROT_EXEC too, and even
the same kind...

with PROT_READ you may read even if you didn't specify it
with PROT_EXEC you may execute even if you didn't specifiy it

apps like JVM's forgot PROT_EXEC and break when the hardware enforces it
apps that forget PROT_READ break when the kernel/hardware enforce it

not too much difference....