From: Roland Dreier <rdreier@cisco.com>
To: wharms@bfs.de
Cc: Julia Lawall <julia@diku.dk>, Roland Dreier <rolandd@cisco.com>,
Sean Hefty <sean.hefty@intel.com>,
Hal Rosenstock <hal.rosenstock@gmail.com>,
linux-rdma@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-janitors@vger.kernel.org
Subject: Re: [PATCH 10/27] drivers/infiniband/core: Use memdup_user
Date: Sat, 22 May 2010 08:15:50 -0700 [thread overview]
Message-ID: <adaaars0xy1.fsf@roland-alpha.cisco.com> (raw)
In-Reply-To: <4BF7A65D.1070501@bfs.de> (walter harms's message of "Sat, 22 May 2010 11:39:41 +0200")
> > + data = memdup_user((void __user *)(unsigned long)src, len);
> > + if (IS_ERR(data))
> > + return PTR_ERR(data);
> This cast look strange, can it happen that (unsigned long)<(u64) ?
> (is there a 32bit infiniband) ?
There is 32-bit infiniband. Linux kernel assumes that unsigned long is
equivalent to uintptr_t -- in other words all pointers are the same size
as longs. So when casting from integer to pointer we add a cast to
unsigned long to avoid a warning precisely in the 32-bit case -- we
would get a warning about cast to pointer from integer of different size
when casting from 64-bit integer to 32-bit pointer.
--
Roland Dreier <rolandd@cisco.com> || For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/index.html
next prev parent reply other threads:[~2010-05-22 15:15 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-22 8:21 [PATCH 10/27] drivers/infiniband/core: Use memdup_user Julia Lawall
2010-05-22 9:39 ` walter harms
2010-05-22 15:15 ` Roland Dreier [this message]
2010-05-26 4:11 ` Roland Dreier
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