From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Maxin John <maxin.john@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: regarding mprotect() implementation in 2.6.26 kernel
Date: Thu, 31 Jul 2008 08:09:02 -0700 [thread overview]
Message-ID: <4891D58E.1070308@goop.org> (raw)
In-Reply-To: <9debc4410807310324m4a76aaf5s253242e5cc2bb130@mail.gmail.com>
Maxin John wrote:
> Dear Christoph Hellwig,
>
> ( I guess you are the right person to ask this question ?)
>
> The POSIX.2 specification of mprotect() says:
>
> errorno should be set as ENOMEM if the addresses in the range [addr,
> (addr + len)] are invalid for the address space of a process, or
> specify one or more pages which are not mapped.
>
> However, in the mprotect implementation (asmlinkage long
> sys_mprotect(unsigned long start, size_t len, unsigned long prot)) in
> linux/mm/mprotect.c file, if we call mprotect() with start as NULL and
> len as 0, mprotect() returns 0 and it is not setting the errono.The
> following code confirms this behaviour.
>
Address 0 is a valid process address. And you've set the length to
zero, so you technically haven't referred to any memory at all, so it
doesn't matter what the address is.
J
next prev parent reply other threads:[~2008-07-31 15:09 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <9debc4410807310315n4da5beafh853a71f532420e9a@mail.gmail.com>
2008-07-31 10:24 ` regarding mprotect() implementation in 2.6.26 kernel Maxin John
2008-07-31 15:09 ` Jeremy Fitzhardinge [this message]
2008-08-04 10:19 ` Maxin John
2008-08-04 10:34 ` Michael Kerrisk
2008-08-04 10:41 ` Michael Kerrisk
2008-08-04 11:18 ` Maxin John
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