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Date:      Mon, 22 Apr 2002 16:04:18 -0400 (EDT)
From:      Kenneth Culver <culverk@alpha.yumyumyum.org>
To:        Andrew Gallatin <gallatin@cs.duke.edu>
Cc:        freebsd-hackers@freebsd.org, <freebsd-emulation@freebsd.org>
Subject:   Re: implementing linux mmap2 syscall
Message-ID:  <20020422155927.E22719-100000@alpha.yumyumyum.org>
In-Reply-To: <15556.6399.62081.426193@grasshopper.cs.duke.edu>

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> To me, it looks like mmap2 takes an offset that's a page index, rather
> than a byte position.   Since linux passes the offset with a 32-bit
> long, rather than a 64-bit off_t like we do, they need to do this in
> order to be able to map offsets larger than 4GB into a file.
>
> For linux_mmap2, I'd think we want to do roughly the same things as
> linux_mmap, but with bsd_args.pos = ctob((off_t)linux_args.pos)
>
> Drew
>
>
AHH, ok I was wondering where PAGE_SHIFT was for FreeBSD. I guess ctob
does what I need it to. I think that's probably why it still wasn't
working yet... I think it also has to be page aligned before you pass it
in though, I have to look at linux's do_mmap_pgoff() (I think that's the
right function name) to see if it's expecting an already page-aligned arg,
or if it's aligning it before it uses it.

Thanks

Ken


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