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Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core



On 2015-11-04 19:06, Ingo Molnar wrote:
* Stephen Smalley <sds@xxxxxxxxxxxxx> 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

Hi Ingo,

(gdb) list *0xffffffff8105af8e
0xffffffff8105af8e is in ptdump_walk_pgd_level_core (arch/x86/mm/dump_pagetables.c:181).
warning: Source file is more recent than executable.
176      * On 64 bits, sign-extend the 48 bit address to 64 bit
177      */
178     static unsigned long normalize_addr(unsigned long u)
179     {
180     #ifdef CONFIG_X86_64
181             return (signed long)(u << 16) >> 16;
182     #else
183             return u;
184     #endif
185     }

--
Sander



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