linux-kernel - Re: [ARCH question] Do syscall_get_nr and syscall_get

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Message-ID: <CALCETrXXnSdyc5VpT8f6uu6kbO1cq4QwdKqr9z8AOhY_wsoBLA@mail.gmail.com>
Date:	Fri, 7 Feb 2014 08:40:45 -0800
From:	Andy Lutomirski <luto@...capital.net>
To:	Jonas Bonn <jonas.bonn@...il.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	linux-arch <linux-arch@...r.kernel.org>, linux-audit@...hat.com,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>,
	Steve Grubb <sgrubb@...hat.com>, Eric Paris <eparis@...hat.com>
Subject: Re: [ARCH question] Do syscall_get_nr and syscall_get_arguments
 always work?

On Fri, Feb 7, 2014 at 4:58 AM, Jonas Bonn <jonas.bonn@...il.com> wrote:
> Hi Andy,
>
> On 5 February 2014 00:50, Andy Lutomirski <luto@...capital.net> wrote:
>>
>> I can't even find the system call entry point on mips.
>>
>>
>> Is there a semi-official answer here?
>
> I don't have an official answer for you, but when I wanted to do
> something with these entry points a couple of years back I discovered
> that they aren't very thoroughly implemented across the various
> architectures.  I started cleaning this up and can probably dig up
> some of this for you if you need it.

The syscall_get_xyz functions are certainly implemented and functional
in all relevant architectures -- the audit code is already using them.
 The thing I'm uncertain about is whether they are usable with no
syscall slow path bits set.

I guess that, if the syscall restart logic needs to read the argument
registers, then they're probably reliably saved...

--Andy
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