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From: Roland Dreier <rdreier@cisco.com>
To: wharms-fPG8STNUNVg@public.gmane.org
Cc: Julia Lawall <julia-dAYI7NvHqcQ@public.gmane.org>,
	Roland Dreier <rolandd-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>,
	Sean Hefty <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Hal Rosenstock
	<hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	kernel-janitors-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 10/27] drivers/infiniband/core: Use memdup_user
Date: Sat, 22 May 2010 15:15:50 +0000	[thread overview]
Message-ID: <adaaars0xy1.fsf@roland-alpha.cisco.com> (raw)
In-Reply-To: <4BF7A65D.1070501-fPG8STNUNVg@public.gmane.org> (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

WARNING: multiple messages have this Message-ID (diff)
From: Roland Dreier <rdreier-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>
To: wharms-fPG8STNUNVg@public.gmane.org
Cc: Julia Lawall <julia-dAYI7NvHqcQ@public.gmane.org>,
	Roland Dreier <rolandd-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org>,
	Sean Hefty <sean.hefty-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>,
	Hal Rosenstock
	<hal.rosenstock-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	kernel-janitors-u79uwXL29TY76Z2rM5mHXA@public.gmane.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-fPG8STNUNVg@public.gmane.org> (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-FYB4Gu1CFyUAvxtiuMwx3w@public.gmane.org> || For corporate legal information go to:
http://www.cisco.com/web/about/doing_business/legal/cri/index.html
--
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WARNING: multiple messages have this Message-ID (diff)
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

  parent reply	other threads:[~2010-05-22 15:15 UTC|newest]

Thread overview: 11+ 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  8:21 ` Julia Lawall
2010-05-22  8:21 ` Julia Lawall
     [not found] ` <Pine.LNX.4.64.1005221021030.13021-QfmoRoYWmW9knbxzx/v8hQ@public.gmane.org>
2010-05-22  9:39   ` walter harms
2010-05-22  9:39     ` walter harms
2010-05-22  9:39     ` walter harms
     [not found]     ` <4BF7A65D.1070501-fPG8STNUNVg@public.gmane.org>
2010-05-22 15:15       ` Roland Dreier [this message]
2010-05-22 15:15         ` Roland Dreier
2010-05-22 15:15         ` Roland Dreier
2010-05-26  4:11 ` Roland Dreier
2010-05-26  4:11   ` Roland Dreier

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