linux-kernel - Re: [PATCH 16/18] arm64: ptrace: handle ptrace_request differently for aarch32 and ilp32

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Message-ID: <20161207165913.GD31779@e104818-lin.cambridge.arm.com>
Date:   Wed, 7 Dec 2016 16:59:13 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Yury Norov <ynorov@...iumnetworks.com>
Cc:     linux-doc@...r.kernel.org, szabolcs.nagy@....com,
        heiko.carstens@...ibm.com, cmetcalf@...hip.com,
        philipp.tomsich@...obroma-systems.com, joseph@...esourcery.com,
        linux-arch@...r.kernel.org, zhouchengming1@...wei.com,
        Prasun.Kapoor@...iumnetworks.com, agraf@...e.de,
        geert@...ux-m68k.org, kilobyte@...band.pl,
        manuel.montezelo@...il.com, arnd@...db.de, pinskia@...il.com,
        linyongting@...wei.com, klimov.linux@...il.com, broonie@...nel.org,
        bamvor.zhangjian@...wei.com,
        Bamvor Zhang Jian <bamvor.zhangjian@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, maxim.kuvyrkov@...aro.org,
        Nathan_Lynch@...tor.com, linux-kernel@...r.kernel.org,
        schwidefsky@...ibm.com, davem@...emloft.net,
        christoph.muellner@...obroma-systems.com
Subject: Re: [PATCH 16/18] arm64: ptrace: handle ptrace_request differently
 for aarch32 and ilp32

On Tue, Dec 06, 2016 at 11:55:08AM +0530, Yury Norov wrote:
> On Mon, Dec 05, 2016 at 04:34:23PM +0000, Catalin Marinas wrote:
> > On Fri, Oct 21, 2016 at 11:33:15PM +0300, Yury Norov wrote:
> > > New aarch32 ptrace syscall handler is introduced to avoid run-time
> > > detection of the task type.
> > 
> > What's wrong with the run-time detection? If it's just to avoid a
> > negligible overhead, I would rather keep the code simpler by avoiding
> > duplicating the generic compat_sys_ptrace().
> 
> Nothing wrong. This is how Arnd asked me to do. You already asked this
> question: http://lkml.iu.edu/hypermail/linux/kernel/1604.3/00930.html

Hmm, I completely forgot about this ;). There is still an advantage to
doing run-time checking if we avoid touching core code (less acks to
gather and less code duplication).

Let's see what Arnd says but the initial patch looked simpler.

-- 
Catalin