linux-kernel - Re: [PATCH] init: setup traps before mem

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Message-Id: <1244737737.6281.8.camel@penberg-laptop>
Date:	Thu, 11 Jun 2009 19:28:57 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	mingo@...e.hu
Cc:	linux-kernel@...r.kernel.org, torvalds@...ux-foundation.org
Subject: Re: [PATCH] init: setup traps before mem_init()

On Thu, 2009-06-11 at 16:25 +0300, Pekka J Enberg wrote:
> From: Pekka Enberg <penberg@...helsinki.fi>
> 
> 32-bit x86 does WP protect test in mem_init() so we must setup traps before we
> call mem_init() during boot. This patch should fix the following bug 
> reported by Ingo Molnar:
> 
>   We have a hard crash in the WP-protect code:
> 
>   [    0.000000] Checking if this processor honours the WP bit even in supervisor mode...BUG: Int 14: CR2 ffcff000
>   [    0.000000]      EDI 00000188  ESI 00000ac7  EBP c17eaf9c  ESP c17eaf8c
>   [    0.000000]      EBX 000014e0  EDX 0000000e  ECX 01856067  EAX 00000001
>   [    0.000000]      err 00000003  EIP c10135b1   CS 00000060  flg 00010002
>   [    0.000000] Stack: c17eafa8 c17fd410 c16747bc c17eafc4 c17fd7e5 000011fd f8616000 c18237cc
>   [    0.000000]        00099800 c17bb000 c17eafec c17f1668 000001c5 c17f1322 c166e039 c1822bf0
>   [    0.000000]        c166e033 c153a014 c18237cc 00020800 c17eaff8 c17f106a 00020800 01ba5003
>   [    0.000000] Pid: 0, comm: swapper Not tainted 2.6.30-tip-02161-g7a74539-dirty #52203
>   [    0.000000] Call Trace:
>   [    0.000000]  [<c15357c2>] ? printk+0x14/0x16
>   [    0.000000]  [<c10135b1>] ? do_test_wp_bit+0x19/0x23
>   [    0.000000]  [<c17fd410>] ? test_wp_bit+0x26/0x64
>   [    0.000000]  [<c17fd7e5>] ? mem_init+0x1ba/0x1d8
>   [    0.000000]  [<c17f1668>] ? start_kernel+0x164/0x2f7
>   [    0.000000]  [<c17f1322>] ? unknown_bootoption+0x0/0x19c
>   [    0.000000]  [<c17f106a>] ? __init_begin+0x6a/0x6f
> 
> Reported-by: Ingo Molnar <mingo@...e.hu>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Pekka Enberg <penberg@...helsinki.fi>

OK, I tested this on 32-bit and it works just fine.

			Pekka

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