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Re: Broken autoconf mmap test
- From: Christopher Faylor <cgf-use-the-mailinglist-please at cygwin dot com>
- To: Eric Blake <eblake at redhat dot com>, cygwin-developers at cygwin dot com
- Date: Thu, 24 Mar 2011 12:44:48 -0400
- Subject: Re: Broken autoconf mmap test
- References: <20110323132622.GM31220@calimero.vinschen.de> <4D89FEC7.firstname.lastname@example.org> <20110323154421.GN31220@calimero.vinschen.de> <4D8A308F.email@example.com> <4D8A3206.firstname.lastname@example.org> <4D8A3329.email@example.com> <20110323181507.GV31220@calimero.vinschen.de> <20110324095945.GD31220@calimero.vinschen.de> <20110324162125.GA4754@ednor.casa.cgf.cx> <4D8B701D.firstname.lastname@example.org>
- Reply-to: cygwin-developers at cygwin dot com
On Thu, Mar 24, 2011 at 10:23:57AM -0600, Eric Blake wrote:
>On 03/24/2011 10:21 AM, Christopher Faylor wrote:
>>> - In all three possible solutions above: What if the original file
>>> handle used in the mmap call has been closed and the file permissions
>>> have been changed in the meantime so that the process does not have
>>> write permissions anymore?
>> - Isn't it going to be really slow? I guess if it only happens once
>> per page it won't be that bad but still: ouch.
>And if I'm understanding correctly, it only needs to happen for the one
>page at the end of the file; all earlier 64k chunks of the file can be
>mapped normally, if you can guarantee that the normal mappings are
>adjacent with the one special mapping.
Ah. So that would make it like a stack guard page then.