From mboxrd@z Thu Jan  1 00:00:00 1970
From: will.deacon@arm.com (Will Deacon)
Date: Wed, 12 Nov 2014 11:00:47 +0000
Subject: [RFC] ptrace: add generic SET_SYSCALL request
In-Reply-To: <54633A69.6090202@linaro.org>
References: <1415346443-28915-1-git-send-email-takahiro.akashi@linaro.org>
 <20141107140405.GA30156@redhat.com> <54633A69.6090202@linaro.org>
Message-ID: <20141112110047.GB26437@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wed, Nov 12, 2014 at 10:46:01AM +0000, AKASHI Takahiro wrote:
> On 11/07/2014 11:04 PM, Oleg Nesterov wrote:
> > To me the fact that PTRACE_SET_SYSCALL can be undefined and syscall_set_nr()
> > is very much arch-dependant (but most probably trivial) means that this  code
> > should live in arch_ptrace().
> 
> Thinking of Oleg's comment above, it doesn't make sense neither to define generic
> NT_SYSTEM_CALL (user_regset) in uapi/linux/elf.h and implement it in ptrace_regset()
> in kernel/ptrace.c with arch-defined syscall_(g)set_nr().
> 
> Since we should have the same interface on arm and arm64, we'd better implement
> ptrace(PTRACE_SET_SYSCALL) locally on arm64 for now (as I originally submitted).

I think the regset approach is cleaner. We already do something similar for
TLS. That would be implemented under arch/arm64/ with it's own NT type.

Will