linux-kernel - Re: [tip:x86/mm] x86, mm: NX protection for kernel data

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Message-ID: <4B82BCB0.9060903@zytor.com>
Date:	Mon, 22 Feb 2010 09:19:44 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	mingo@...hat.com, sliakh.lkml@...il.com, jmorris@...ei.org,
	linux-kernel@...r.kernel.org, arjan@...ux.intel.com,
	tglx@...utronix.de, jiang@...ncsu.edu,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mm] x86, mm: NX protection for kernel data

On 02/22/2010 03:01 AM, Ingo Molnar wrote:
>>
>>> Commit-ID:  01ab31371da90a795b774d87edf2c21bb3a64dda
>>> Gitweb:     http://git.kernel.org/tip/01ab31371da90a795b774d87edf2c21bb3a64dda
>>> Author:     Siarhei Liakh <sliakh.lkml@...il.com>
>>> AuthorDate: Sun, 31 Jan 2010 18:27:55 -0500
>>> Committer:  H. Peter Anvin <hpa@...or.com>
>>> CommitDate: Wed, 17 Feb 2010 10:11:24 -0800
>>>
>>> x86, mm: NX protection for kernel data
>>>
>>> This patch expands functionality of CONFIG_DEBUG_RODATA to set main
>>> (static) kernel data area as NX.
>>
>> -tip testing is seeing boot hangs along the lines of:
>>
>> [   15.568108] EXT3-fs (sda1): recovery complete
>> [   15.573064] EXT3-fs (sda1): mounted filesystem with ordered data mode
>> [   15.580313] VFS: Mounted root (ext3 filesystem) readonly on device 8:1.
>> [   15.584021] async_waiting @ 1
>> [   15.588008] async_continuing @ 1 after 0 usec
>> [   15.592163] Freeing unused kernel memory: 540k freed
>> [   15.600126] NX-protecting the kernel data: c15ab000, 2919 pages
>>
>> which i suspect could be due to the commit above.
> 
> Yep, that's confirmed now, applying these 3 reverts makes it boot fine:
> 
> 833e0ca: Revert "x86, mm: NX protection for kernel data"
> ce4b6b4: Revert "x86: RO/NX protection for loadable kernel modules"
> e357312: Revert "module: fix () used as prototype in include/linux/module.h"
> 

Given that e357312 is a () -> (void) prototype fix, is hardly seems
likely to be at fault.  The RO/NX stuff, on the other hand, make a lot
of sense.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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