linux-kernel - Re: [PATCH -tip] x86: headers - fix export private data to userspace

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Date:	Tue, 13 Jan 2009 22:00:07 +0300
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Harvey Harrison <harvey.harrison@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sam Ravnborg <sam@...nborg.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jaswinder Singh Rajput <jaswinderlinux@...il.com>
Subject: Re: [PATCH -tip] x86: headers - fix export private data to
	userspace

[H. Peter Anvin - Tue, Jan 13, 2009 at 10:55:30AM -0800]
| Cyrill Gorcunov wrote:
| > | > 
| > | >> 4) setup.h - COMMAND_LINE_SIZE saved for userspace, bootloaders
| > | >>    could use it.
| > | > 
| > | > Doesn't this need to be (at least) _COMMAND_LINE_SIZE to avoid
| > | > polluting the namespace, not sure it can be changed though as the
| > | > horse is already out of the barn.
| > | 
| > | No, this is not one of those cases, but it's worth explaining why.
| > | 
| > | You can introduce symbols into the general namespace if *and only if*
| > | they are in a header file that is invoked directly by the user.  In
| > | other words, such a header file is unusable by libc, but setup.h doesn't
| > | contain anything needed by libc in the first place.
| > | 
| > | 	-hpa
| > | 
| > 
| > So we could just fence it by __KERNEL__?
| > 
| 
| We might, as userspace shouldn't need COMMAND_LINE_SIZE anyway (see
| other post), but I'm rather confused as how you got that from what I
| wrote above.
| 
| 	-hpa
| 
| -- 
| H. Peter Anvin, Intel Open Source Technology Center
| I work for Intel.  I don't speak on their behalf.
| 

The thing is that kernel headers are not only touched by libc.
Someone could write a program and include setup.h there.
Or I translated you wrong :)

		- Cyrill -
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