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	<1264170977.31321.382.camel@gandalf.stny.rr.com> <20100122163700.GD6412@osiris.boeblingen.de.ibm.com>
From: Mike Frysinger <vapier.adi@gmail.com>
Date: Fri, 22 Jan 2010 14:32:56 -0500
Message-ID: <8bd0f97a1001221132h331224ccif94f169750c1714b@mail.gmail.com>
Subject: Re: [PATCH] ftrace: unify arch_syscall_addr() implementations
To: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>, linux-kernel@vger.kernel.org,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Ingo Molnar <mingo@redhat.com>,
       Hendrik Brueckner <brueckner@linux.vnet.ibm.com>,
       "David S. Miller" <davem@davemloft.net>,
       Paul Mundt <lethal@linux-sh.org>
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On Fri, Jan 22, 2010 at 11:37, Heiko Carstens wrote:
> On Fri, Jan 22, 2010 at 09:36:17AM -0500, Steven Rostedt wrote:
>> On Fri, 2010-01-22 at 08:43 -0500, Mike Frysinger wrote:
>> > Every arch_syscall_addr() implementation thus far is the same, so unify
>> > them as a default weak in common code so more arches don't have to waste
>> > time copying & pasting this simple function.  The Blackfin version is
>> > going to be exactly the same.
>> >
>> > Signed-off-by: Mike Frysinger <vapier@gentoo.org>
>> > ---
>> > note: only thing that needs double checking is s390 and sparc where they
>> > declared the sys_call_table as an array of ints.  considering this table
>> > is supposed to be an array of function pointers, this seems like more of
>> > a typo to me ...
>>
>> I would not be too sure. s390 is very strange, and I would definitely
>> want to get an Ack from the arch maintainers first.
>
> It's not a typo. The syscall table on s390 contains always 32 bit pointers
> since we know that the address of the function to be called is (way) below
> 4GB. So this saves us a few bytes.
> In addition this makes syscall patching done by some security modules a
> bit more difficult, since they would need to store a 64 bit pointer.
> That's because we make sure that module addresses are always above 4GB.

i'll update the s390 code to add an explanatory comment then and post
a new version
-mike
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