2009-06-11 13:25:51

by Pekka Enberg

Subject: [PATCH] init: setup traps before mem_init()

From: Pekka Enberg <[email protected]>

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 <[email protected]>
Cc: Linus Torvalds <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>
---
Ingo,

I don't see other architectures doing anything like this in mem_init() so
moving test_wp_bit() out of the function is probably a better long-term
fix. I have only tested this on x86-64 so please give it a try.

init/main.c | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/init/main.c b/init/main.c
index 859af21..6d38f96 100644
--- a/init/main.c
+++ b/init/main.c
@@ -588,6 +588,8 @@ asmlinkage void __init start_kernel(void)
*/
pidhash_init();
vfs_caches_init_early();
+ sort_main_extable();
+ trap_init();
/*
* Set up kernel memory allocators
*/
@@ -610,8 +612,6 @@ asmlinkage void __init start_kernel(void)
"enabled *very* early, fixing it\n");
local_irq_disable();
}
- sort_main_extable();
- trap_init();
rcu_init();
/* init some links before init_ISA_irqs() */
early_irq_init();
--
1.6.0.4

2009-06-11 16:29:08

by Pekka Enberg

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 <[email protected]>
>
> 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 <[email protected]>
> Cc: Linus Torvalds <[email protected]>
> Signed-off-by: Pekka Enberg <[email protected]>

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

Pekka