From owner-freebsd-hackers  Tue Mar 12 22: 5:56 2002
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Date: Tue, 12 Mar 2002 22:05:53 -0800
From: Alfred Perlstein <bright@mu.org>
To: Farooq Mela <fmela0@sm.socccd.cc.ca.us>
Cc: freebsd-hackers@freebsd.org
Subject: Re: Recv() to a mmap'ed file?
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* Farooq Mela <fmela0@sm.socccd.cc.ca.us> [020312 21:56] wrote:
> Alfred Perlstein wrote:
> > 
> > * Farooq Mela <fmela0@sm.socccd.cc.ca.us> [020312 13:01] wrote:
> > >
> > > Rather than the usual recv() to a fixed size buffer, write() to the
> > > file descriptor, loop, etc.  However when I try to do this recv gives
> > > me back an EFAULT (bad address).  Is there a limitation of the
> > > architecture which does not allows us to recv() to an mmap'ed area of
> > > a file, or is it just something which hasn't been implemented?
> > 
> > You may not extend a file using mmap(2), you must use ftuncate(2)
> > or write(2).
> > 
> > -Alfred
> 
> I am aware of this, this is why I stated:
> 
> > /* file_fd points to a regular file which is filled with SIZE nul
> > bytes */
> 
> The file is already the required size.

Gah... oops :)

Have you tried the mapping with PROT_READ as well?  I don't think
most arches allow for access without PROT_READ along with PROT_WRITE.

-Alfred

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