Skip site navigation (1)Skip section navigation (2)
Date:      Mon, 22 Apr 2002 10:06:55 -0400 (EDT)
From:      Andrew Gallatin <gallatin@cs.duke.edu>
To:        Kenneth Culver <culverk@yumyumyum.org>
Cc:        freebsd-hackers@freebsd.org, freebsd-emulation@freebsd.org
Subject:   Re: implementing linux mmap2 syscall
Message-ID:  <15556.6399.62081.426193@grasshopper.cs.duke.edu>
In-Reply-To: <200204211525.08827.culverk@yumyumyum.org>
References:  <200204211525.08827.culverk@yumyumyum.org>

next in thread | previous in thread | raw e-mail | index | archive | help

Kenneth Culver writes:
 > static inline unsigned long do_mmap(struct file *file, unsigned long addr,

<..>
 > 		ret = do_mmap_pgoff(file, addr, len, prot, flag, offset >> PAGE_SHIFT);
 > out:
 > 	return ret;
 > }
 > 
 > This is what mmap2 does:
 > 
 > andstatic inline long do_mmap2(
 > 	unsigned long addr, unsigned long len,
 > 	unsigned long prot, unsigned long flags,
 > 	unsigned long fd, unsigned long pgoff)
<...>
 > 	error = do_mmap_pgoff(file, addr, len, prot, flags, pgoff);

 > 
 > So what it looks like to me is that mmap2 expects an offset that's already 
 > page-aligned (I'm not sure if this is the right way to say it), where mmap 
 > doesn't. the FreeBSD code in the linuxulator basically just takes the offset 

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

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-hackers" in the body of the message




Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?15556.6399.62081.426193>