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Date: Wed, 4 Nov 2015 19:06:56 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Stephen Smalley <sds@tycho.nsa.gov>
Cc: Sander Eikelenboom <linux@eikelenboom.it>,
        David Vrabel <david.vrabel@citrix.com>, xen-devel@lists.xen.org,
        linux-kernel@vger.kernel.org, "x86@kernel.org" <x86@kernel.org>
Subject: Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled:
 RIP: ptdump_walk_pgd_level_core
Message-ID: <20151104180655.GA9892@gmail.com>
References: <9184aedc84bf5274c290183fa60b48e9@eikelenboom.it>
 <563A29C4.7020400@tycho.nsa.gov>
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* Stephen Smalley <sds@tycho.nsa.gov> wrote:

> On 11/04/2015 06:55 AM, Sander Eikelenboom wrote:
> >Hi All,
> >
> >I just tried to boot with the current linus mergewindow tree under Xen.
> >It fails with a kernel panic at boot with the new "CONFIG_DEBUG_WX"
> >option enabled.
> >Disabling it makes the kernel boot fine.
> >
> >The splat:
> >[   18.424241] Freeing unused kernel memory: 1104K (ffffffff822fc000 -
> >ffffffff82410000)
> >[   18.430314] Write protecting the kernel read-only data: 18432k
> >[   18.441054] Freeing unused kernel memory: 1144K (ffff880001ae2000 -
> >ffff880001c00000)
> >[   18.447966] Freeing unused kernel memory: 1560K (ffff88000207a000 -
> >ffff880002200000)
> >[   18.453947] BUG: unable to handle kernel paging request at
> >ffff88055c883000
> >[   18.459943] IP: [<ffffffff8105af8e>]
> >ptdump_walk_pgd_level_core+0x20e/0x440
> >[   18.465847] PGD 2212067 PUD 0
> >[   18.471564] Oops: 0000 [#1] SMP
> >[   18.477248] Modules linked in:
> >[   18.482918] CPU: 2 PID: 1 Comm: swapper/0 Not tainted
> >4.3.0-mw-20151104-linus-doflr+ #1
> >[   18.488804] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS
> >V1.8B1 09/13/2010
> >[   18.494778] task: ffff880059b90000 ti: ffff880059b98000 task.ti:
> >ffff880059b98000
> >[   18.500852] RIP: e030:[<ffffffff8105af8e>]  [<ffffffff8105af8e>]
> >ptdump_walk_pgd_level_core+0x20e/0x440

It would be nice to see which line of code this corresponds to. Doing this:

  gdb vmlinux
  list *0xffffffff8105af8e

should normally do the trick.

Thanks,

	Ingo
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