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Message-ID: <CALCETrX1RpjZxdo1aauQa8hGQPO1Dzn5gU6NoT1CvSKo8ea1uQ@mail.gmail.com>
Date: Wed, 8 Mar 2017 14:20:24 -0800
From: Andy Lutomirski <luto@...capital.net>
To: Russell King - ARM Linux <linux@...linux.org.uk>
Cc: Thomas Garnier <thgarnie@...gle.com>, Arnd Bergmann <arnd@...db.de>,
David Howells <dhowells@...hat.com>, Al Viro <viro@...iv.linux.org.uk>,
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Subject: Re: [PATCH v1 1/4] syscalls: Restore address limit after a syscall
On Wed, Mar 8, 2017 at 1:58 PM, Russell King - ARM Linux
<linux@...linux.org.uk> wrote:
> On Wed, Mar 08, 2017 at 01:38:41PM -0800, Thomas Garnier wrote:
>> This patch prevents a syscall to modify the address limit of the
>> caller. The address limit is kept by the syscall wrapper and restored
>> just after the syscall ends.
>
> I would much rather architectures were given the opportunity to code up
> checks like this efficiently (iow, inline in the exit path assembly),
> rather than having to unconditionally call an additional function on
> every syscall, with its register saving overheads.
>
Me too. I think the two config choices should be:
(a) BUG_ON(!segment_eq(...));
(b) No generic check at all -- arch code will handle it
--Andy
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