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Date: Fri, 13 Dec 1996 23:31:06 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199612131231.XAA32237@godzilla.zeta.org.au>
To: gena@NetVision.net.il, hackers@FreeBSD.ORG
Subject: Re: mmap() with offset
Sender: owner-hackers@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

>For some reason mmap(...) call with offset other then 0 fails with invalid
>argument error.
>
>The code looks like:
>  msg->msg_body = (char *)mmap(NULL, (size_t)mlen, PROT_READ, 0,mfd,
>            (off_t)mofft)) == (char *)-1);
>
>You can reproduce it by running cmp with skip arguments (cmp file1 file2 10 10).
>Any ideas?

mmap() currently requires the offset to be a multiple of PAGE_SIZE (4096).
This is a bug according to the man page.  Similar restrictions on other
mmap args were removed in February 1996.  The args get rounded up or down
to a multiple of PAGE_SIZE as appropriate.

Bruce