Wireshark · Wireshark-dev: Re: [Wireshark-dev] Use of MAP_ANON in epan/emem.c

[Guy Harris <guy@xxxxxxxxxxxx>]

On Jun 16, 2006, at 3:25 PM, Albert Chin wrote:

> On Fri, Jun 16, 2006 at 11:32:32PM +0200, Jaap Keuter wrote:
> > Checked in.
>
> Thanks. What do we do for IRIX which has neither MAP_ANONYMOUS or
> MAP_ANON? #define MAP_ANONYMOUS to 0 in this case?

The goal here is to get anonymous pages.

One of the earliest implementations of mmap() that could map a region  
of the address space to a vendor of anonymous pages was SunOS 4.0;  
the way you did it in 4.0 was to open "/dev/zero" and mmap that.   
(You can also read from "/dev/zero" if you want an infinite stream of  
zeroes....)

The IRIX 6.5 man page for /dev/zero indicates you can mmap it to get  
anonymous pages.  Are there any UN*Xes we support that *don't* allow  
you to mmap /dev/zero to get anonymous pages?  If not, we might just  
want to open /dev/zero and hold it open, and use that for anonymous  
pages; if so, we might want to use MAP_ANONYMOUS on systems that  
define it, otherwise use MAP_ANON on systems that define it (OS X  
10.4 defines MAP_ANON but *NOT* MAP_ANONYMOUS, and that seems to be a  
general BSD characteristic - I don't find any definitions of  
MAP_ANONYMOUS in the sys/sys source directory of fairly recent  
{Free,Net,Open}BSD), otherwise use "/dev/zero".