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Groups > linux.kernel > #1262241 > unrolled thread

Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

Started bySander Eikelenboom <linux@eikelenboom.it>
First post2015-11-04 13:10 +0100
Last post2015-11-04 21:20 +0100
Articles 11 — 4 participants

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  Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-04 13:10 +0100
    Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled:  RIP: ptdump_walk_pgd_level_core Stephen Smalley <sds@tycho.nsa.gov> - 2015-11-04 17:00 +0100
      Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled:  RIP: ptdump_walk_pgd_level_core Ingo Molnar <mingo@kernel.org> - 2015-11-04 19:10 +0100
        Re: Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-04 19:20 +0100
      Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled:  RIP: ptdump_walk_pgd_level_core Stephen Smalley <sds@tycho.nsa.gov> - 2015-11-04 19:50 +0100
        Re: Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-04 21:10 +0100
          Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-05 00:20 +0100
            Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-05 10:20 +0100
              Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-05 15:00 +0100
                Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Sander Eikelenboom <linux@eikelenboom.it> - 2015-11-05 15:10 +0100
        Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with  CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2015-11-04 21:20 +0100

#1262241 — Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromSander Eikelenboom <linux@eikelenboom.it>
Date2015-11-04 13:10 +0100
SubjectLinux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qr535-eP-31@gated-at.bofh.it>
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
[   18.507102] RSP: e02b:ffff880059b9be48  EFLAGS: 00010296
[   18.513351] RAX: ffff88055c883000 RBX: ffffffff81ae2000 RCX: 
ffff880000000000
[   18.519733] RDX: 0000000000000067 RSI: ffff880059b9be98 RDI: 
ffff880000001000
[   18.526129] RBP: ffff880059b9bf00 R08: 0000000000000000 R09: 
0000000000000000
[   18.532522] R10: ffff88005fd0e790 R11: 0000000000000001 R12: 
ffff880080000000
[   18.538891] R13: ffffc00000000fff R14: ffff880059b9be98 R15: 
0000000000000000
[   18.545247] FS:  0000000000000000(0000) GS:ffff88005f680000(0000) 
knlGS:0000000000000000
[   18.551708] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
[   18.558153] CR2: ffff88055c883000 CR3: 0000000002211000 CR4: 
0000000000000660
[   18.564686] Stack:
[   18.571106]  0000000159b9be50 ffffffff82211000 ffff88055c884000 
0000000000000800
[   18.577704]  0000800000000000 ffff88055c883000 0000000000000007 
ffff88005fd0e790
[   18.584291]  ffff880059b9bed8 ffffffff81156ace 0000000000000001 
0000000000000000
[   18.590916] Call Trace:
[   18.597458]  [<ffffffff81156ace>] ? free_reserved_area+0x11e/0x120
[   18.604180]  [<ffffffff8105b1e2>] 
ptdump_walk_pgd_level_checkwx+0x12/0x20
[   18.611014]  [<ffffffff810515b9>] mark_rodata_ro+0xe9/0xf0
[   18.617819]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
[   18.624512]  [<ffffffff81ad3398>] kernel_init+0x18/0xe0
[   18.631095]  [<ffffffff81adadcf>] ret_from_fork+0x3f/0x70
[   18.637650]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
[   18.644178] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe ff ff 
48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 70 ff 
ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 4c 89
[   18.658246] RIP  [<ffffffff8105af8e>] 
ptdump_walk_pgd_level_core+0x20e/0x440
[   18.665211]  RSP <ffff880059b9be48>
[   18.672073] CR2: ffff88055c883000
[   18.678852] ---[ end trace d84e34461c40637a ]---
[   18.685641] Kernel panic - not syncing: Attempted to kill init! 
exitcode=0x00000009
[   18.685641]
[   18.699520] Kernel Offset: disable

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#1262393 — Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromStephen Smalley <sds@tycho.nsa.gov>
Date2015-11-04 17:00 +0100
SubjectRe: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qr8DD-2nj-1@gated-at.bofh.it>
In reply to#1262241
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
> [   18.507102] RSP: e02b:ffff880059b9be48  EFLAGS: 00010296
> [   18.513351] RAX: ffff88055c883000 RBX: ffffffff81ae2000 RCX:
> ffff880000000000
> [   18.519733] RDX: 0000000000000067 RSI: ffff880059b9be98 RDI:
> ffff880000001000
> [   18.526129] RBP: ffff880059b9bf00 R08: 0000000000000000 R09:
> 0000000000000000
> [   18.532522] R10: ffff88005fd0e790 R11: 0000000000000001 R12:
> ffff880080000000
> [   18.538891] R13: ffffc00000000fff R14: ffff880059b9be98 R15:
> 0000000000000000
> [   18.545247] FS:  0000000000000000(0000) GS:ffff88005f680000(0000)
> knlGS:0000000000000000
> [   18.551708] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
> [   18.558153] CR2: ffff88055c883000 CR3: 0000000002211000 CR4:
> 0000000000000660
> [   18.564686] Stack:
> [   18.571106]  0000000159b9be50 ffffffff82211000 ffff88055c884000
> 0000000000000800
> [   18.577704]  0000800000000000 ffff88055c883000 0000000000000007
> ffff88005fd0e790
> [   18.584291]  ffff880059b9bed8 ffffffff81156ace 0000000000000001
> 0000000000000000
> [   18.590916] Call Trace:
> [   18.597458]  [<ffffffff81156ace>] ? free_reserved_area+0x11e/0x120
> [   18.604180]  [<ffffffff8105b1e2>]
> ptdump_walk_pgd_level_checkwx+0x12/0x20
> [   18.611014]  [<ffffffff810515b9>] mark_rodata_ro+0xe9/0xf0
> [   18.617819]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
> [   18.624512]  [<ffffffff81ad3398>] kernel_init+0x18/0xe0
> [   18.631095]  [<ffffffff81adadcf>] ret_from_fork+0x3f/0x70
> [   18.637650]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
> [   18.644178] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe ff ff
> 48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 70 ff
> ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 4c 89
> [   18.658246] RIP  [<ffffffff8105af8e>]
> ptdump_walk_pgd_level_core+0x20e/0x440
> [   18.665211]  RSP <ffff880059b9be48>
> [   18.672073] CR2: ffff88055c883000
> [   18.678852] ---[ end trace d84e34461c40637a ]---
> [   18.685641] Kernel panic - not syncing: Attempted to kill init!
> exitcode=0x00000009
> [   18.685641]
> [   18.699520] Kernel Offset: disable
>

What's your .config?  Does cat /sys/kernel/debug/kernel_page_tables 
produce a similar fault even with CONFIG_DEBUG_WX=n?
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#1262478 — Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromIngo Molnar <mingo@kernel.org>
Date2015-11-04 19:10 +0100
SubjectRe: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qraFs-3T7-33@gated-at.bofh.it>
In reply to#1262393
* 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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#1262482 — Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromSander Eikelenboom <linux@eikelenboom.it>
Date2015-11-04 19:20 +0100
SubjectRe: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qraP7-3Xl-13@gated-at.bofh.it>
In reply to#1262478
On 2015-11-04 19:06, Ingo Molnar wrote:
> * 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

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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#1262505 — Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromStephen Smalley <sds@tycho.nsa.gov>
Date2015-11-04 19:50 +0100
SubjectRe: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qrbi9-47z-13@gated-at.bofh.it>
In reply to#1262393
On 11/04/2015 01:28 PM, Sander Eikelenboom wrote:
> On 2015-11-04 16:52, Stephen Smalley 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
>>> [   18.507102] RSP: e02b:ffff880059b9be48  EFLAGS: 00010296
>>> [   18.513351] RAX: ffff88055c883000 RBX: ffffffff81ae2000 RCX:
>>> ffff880000000000
>>> [   18.519733] RDX: 0000000000000067 RSI: ffff880059b9be98 RDI:
>>> ffff880000001000
>>> [   18.526129] RBP: ffff880059b9bf00 R08: 0000000000000000 R09:
>>> 0000000000000000
>>> [   18.532522] R10: ffff88005fd0e790 R11: 0000000000000001 R12:
>>> ffff880080000000
>>> [   18.538891] R13: ffffc00000000fff R14: ffff880059b9be98 R15:
>>> 0000000000000000
>>> [   18.545247] FS:  0000000000000000(0000) GS:ffff88005f680000(0000)
>>> knlGS:0000000000000000
>>> [   18.551708] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
>>> [   18.558153] CR2: ffff88055c883000 CR3: 0000000002211000 CR4:
>>> 0000000000000660
>>> [   18.564686] Stack:
>>> [   18.571106]  0000000159b9be50 ffffffff82211000 ffff88055c884000
>>> 0000000000000800
>>> [   18.577704]  0000800000000000 ffff88055c883000 0000000000000007
>>> ffff88005fd0e790
>>> [   18.584291]  ffff880059b9bed8 ffffffff81156ace 0000000000000001
>>> 0000000000000000
>>> [   18.590916] Call Trace:
>>> [   18.597458]  [<ffffffff81156ace>] ? free_reserved_area+0x11e/0x120
>>> [   18.604180]  [<ffffffff8105b1e2>]
>>> ptdump_walk_pgd_level_checkwx+0x12/0x20
>>> [   18.611014]  [<ffffffff810515b9>] mark_rodata_ro+0xe9/0xf0
>>> [   18.617819]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>> [   18.624512]  [<ffffffff81ad3398>] kernel_init+0x18/0xe0
>>> [   18.631095]  [<ffffffff81adadcf>] ret_from_fork+0x3f/0x70
>>> [   18.637650]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>> [   18.644178] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe ff ff
>>> 48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 70 ff
>>> ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 4c 89
>>> [   18.658246] RIP  [<ffffffff8105af8e>]
>>> ptdump_walk_pgd_level_core+0x20e/0x440
>>> [   18.665211]  RSP <ffff880059b9be48>
>>> [   18.672073] CR2: ffff88055c883000
>>> [   18.678852] ---[ end trace d84e34461c40637a ]---
>>> [   18.685641] Kernel panic - not syncing: Attempted to kill init!
>>> exitcode=0x00000009
>>> [   18.685641]
>>> [   18.699520] Kernel Offset: disable
>>>
>>
>> What's your .config?  Does cat /sys/kernel/debug/kernel_page_tables
>> produce a similar fault even with CONFIG_DEBUG_WX=n?
>
> .config is attached
>
> Hmm that sysfs file doesn't seem to exist then:
> # cat /sys/kernel/debug/kernel_page_tables
> cat: /sys/kernel/debug/kernel_page_tables: No such file or directory

Needs CONFIG_X86_PTDUMP=y.
Also assumes you have debugfs mounted there.


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#1262559 — Re: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromSander Eikelenboom <linux@eikelenboom.it>
Date2015-11-04 21:10 +0100
SubjectRe: Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qrcxA-59d-9@gated-at.bofh.it>
In reply to#1262505
On 2015-11-04 19:47, Stephen Smalley wrote:
> On 11/04/2015 01:28 PM, Sander Eikelenboom wrote:
>> On 2015-11-04 16:52, Stephen Smalley 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
>>>> [   18.507102] RSP: e02b:ffff880059b9be48  EFLAGS: 00010296
>>>> [   18.513351] RAX: ffff88055c883000 RBX: ffffffff81ae2000 RCX:
>>>> ffff880000000000
>>>> [   18.519733] RDX: 0000000000000067 RSI: ffff880059b9be98 RDI:
>>>> ffff880000001000
>>>> [   18.526129] RBP: ffff880059b9bf00 R08: 0000000000000000 R09:
>>>> 0000000000000000
>>>> [   18.532522] R10: ffff88005fd0e790 R11: 0000000000000001 R12:
>>>> ffff880080000000
>>>> [   18.538891] R13: ffffc00000000fff R14: ffff880059b9be98 R15:
>>>> 0000000000000000
>>>> [   18.545247] FS:  0000000000000000(0000) GS:ffff88005f680000(0000)
>>>> knlGS:0000000000000000
>>>> [   18.551708] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
>>>> [   18.558153] CR2: ffff88055c883000 CR3: 0000000002211000 CR4:
>>>> 0000000000000660
>>>> [   18.564686] Stack:
>>>> [   18.571106]  0000000159b9be50 ffffffff82211000 ffff88055c884000
>>>> 0000000000000800
>>>> [   18.577704]  0000800000000000 ffff88055c883000 0000000000000007
>>>> ffff88005fd0e790
>>>> [   18.584291]  ffff880059b9bed8 ffffffff81156ace 0000000000000001
>>>> 0000000000000000
>>>> [   18.590916] Call Trace:
>>>> [   18.597458]  [<ffffffff81156ace>] ? 
>>>> free_reserved_area+0x11e/0x120
>>>> [   18.604180]  [<ffffffff8105b1e2>]
>>>> ptdump_walk_pgd_level_checkwx+0x12/0x20
>>>> [   18.611014]  [<ffffffff810515b9>] mark_rodata_ro+0xe9/0xf0
>>>> [   18.617819]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>>> [   18.624512]  [<ffffffff81ad3398>] kernel_init+0x18/0xe0
>>>> [   18.631095]  [<ffffffff81adadcf>] ret_from_fork+0x3f/0x70
>>>> [   18.637650]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>>> [   18.644178] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe ff 
>>>> ff
>>>> 48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 70 
>>>> ff
>>>> ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 4c 
>>>> 89
>>>> [   18.658246] RIP  [<ffffffff8105af8e>]
>>>> ptdump_walk_pgd_level_core+0x20e/0x440
>>>> [   18.665211]  RSP <ffff880059b9be48>
>>>> [   18.672073] CR2: ffff88055c883000
>>>> [   18.678852] ---[ end trace d84e34461c40637a ]---
>>>> [   18.685641] Kernel panic - not syncing: Attempted to kill init!
>>>> exitcode=0x00000009
>>>> [   18.685641]
>>>> [   18.699520] Kernel Offset: disable
>>>> 
>>> 
>>> What's your .config?  Does cat /sys/kernel/debug/kernel_page_tables
>>> produce a similar fault even with CONFIG_DEBUG_WX=n?
>> 
>> .config is attached
>> 
>> Hmm that sysfs file doesn't seem to exist then:
>> # cat /sys/kernel/debug/kernel_page_tables
>> cat: /sys/kernel/debug/kernel_page_tables: No such file or directory
> 
> Needs CONFIG_X86_PTDUMP=y.
> Also assumes you have debugfs mounted there.

Recompiled, and the result is that it also blows up:
[  902.389247] BUG: unable to handle kernel paging request at 
ffff88055c883000
[  902.402749] IP: [<ffffffff8105af7e>] 
ptdump_walk_pgd_level_core+0x20e/0x440
[  902.416261] PGD 2212067 PUD 0
[  902.427768] Oops: 0000 [#1] SMP
[  902.438137] Modules linked in:
[  902.448299] CPU: 2 PID: 21951 Comm: cat Not tainted 
4.3.0-mw-20151104-linus-doflr-nodebugwx-withptdump+ #1
[  902.458581] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS 
V1.8B1 09/13/2010
[  902.468850] task: ffff88004b49e300 ti: ffff88005928c000 task.ti: 
ffff88005928c000
[  902.479133] RIP: e030:[<ffffffff8105af7e>]  [<ffffffff8105af7e>] 
ptdump_walk_pgd_level_core+0x20e/0x440
[  902.489536] RSP: e02b:ffff88005928fd20  EFLAGS: 00010296
[  902.499692] RAX: ffff88055c883000 RBX: 0000000000000000 RCX: 
ffff880000000000
[  902.509755] RDX: 0000000000000067 RSI: ffff88005928fd70 RDI: 
ffff880000001000
[  902.519680] RBP: ffff88005928fdd8 R08: 0000000000001000 R09: 
000000000000ffff
[  902.529555] R10: 0000000000000000 R11: 0000000000000246 R12: 
ffff88005928ff20
[  902.539349] R13: ffffc00000000fff R14: ffff88005928fd70 R15: 
ffff880033c773c0
[  902.549081] FS:  00007f56b07d4700(0000) GS:ffff88005f680000(0000) 
knlGS:0000000000000000
[  902.558690] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
[  902.568111] CR2: ffff88055c883000 CR3: 000000004563f000 CR4: 
0000000000000660
[  902.577508] Stack:
[  902.586741]  00000000810ffd21 ffffffff82211000 ffff88055c884000 
0000000000000800
[  902.596090]  0000800000000000 ffff88055c883000 00007f56b0629000 
0000000000000001
[  902.605395]  ffff88005928ff20 ffffffff81ad88ba 0000000000000001 
0000000000000000
[  902.614452] Call Trace:
[  902.623254]  [<ffffffff81ad88ba>] ? __mutex_lock_slowpath+0x27a/0x3a0
[  902.632067]  [<ffffffff8105b1bd>] ptdump_show+0xd/0x20
[  902.640767]  [<ffffffff811c857b>] seq_read+0xcb/0x380
[  902.649379]  [<ffffffff811a8273>] __vfs_read+0x23/0xd0
[  902.657909]  [<ffffffff81167cb5>] ? vm_mmap_pgoff+0x75/0xa0
[  902.666195]  [<ffffffff811a8a01>] vfs_read+0x81/0x130
[  902.674248]  [<ffffffff811a96f4>] SyS_read+0x44/0xb0
[  902.682220]  [<ffffffff81ada6ae>] entry_SYSCALL_64_fastpath+0x12/0x71
[  902.690182] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe ff ff 
48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 70 ff 
ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 4c 89
[  902.706831] RIP  [<ffffffff8105af7e>] 
ptdump_walk_pgd_level_core+0x20e/0x440
[  902.715008]  RSP <ffff88005928fd20>
[  902.722955] CR2: ffff88055c883000
[  902.730630] ---[ end trace 5d94ee3d1b42814b ]---

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#1262729 — Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromBoris Ostrovsky <boris.ostrovsky@oracle.com>
Date2015-11-05 00:20 +0100
SubjectRe: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qrfvr-72q-1@gated-at.bofh.it>
In reply to#1262559
On 11/04/2015 03:02 PM, Sander Eikelenboom wrote:
> On 2015-11-04 19:47, Stephen Smalley wrote:
>> On 11/04/2015 01:28 PM, Sander Eikelenboom wrote:
>>> On 2015-11-04 16:52, Stephen Smalley 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
>>>>> [   18.507102] RSP: e02b:ffff880059b9be48  EFLAGS: 00010296
>>>>> [   18.513351] RAX: ffff88055c883000 RBX: ffffffff81ae2000 RCX:
>>>>> ffff880000000000
>>>>> [   18.519733] RDX: 0000000000000067 RSI: ffff880059b9be98 RDI:
>>>>> ffff880000001000
>>>>> [   18.526129] RBP: ffff880059b9bf00 R08: 0000000000000000 R09:
>>>>> 0000000000000000
>>>>> [   18.532522] R10: ffff88005fd0e790 R11: 0000000000000001 R12:
>>>>> ffff880080000000
>>>>> [   18.538891] R13: ffffc00000000fff R14: ffff880059b9be98 R15:
>>>>> 0000000000000000
>>>>> [   18.545247] FS:  0000000000000000(0000) GS:ffff88005f680000(0000)
>>>>> knlGS:0000000000000000
>>>>> [   18.551708] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
>>>>> [   18.558153] CR2: ffff88055c883000 CR3: 0000000002211000 CR4:
>>>>> 0000000000000660
>>>>> [   18.564686] Stack:
>>>>> [   18.571106]  0000000159b9be50 ffffffff82211000 ffff88055c884000
>>>>> 0000000000000800
>>>>> [   18.577704]  0000800000000000 ffff88055c883000 0000000000000007
>>>>> ffff88005fd0e790
>>>>> [   18.584291]  ffff880059b9bed8 ffffffff81156ace 0000000000000001
>>>>> 0000000000000000
>>>>> [   18.590916] Call Trace:
>>>>> [   18.597458]  [<ffffffff81156ace>] ? free_reserved_area+0x11e/0x120
>>>>> [   18.604180]  [<ffffffff8105b1e2>]
>>>>> ptdump_walk_pgd_level_checkwx+0x12/0x20
>>>>> [   18.611014]  [<ffffffff810515b9>] mark_rodata_ro+0xe9/0xf0
>>>>> [   18.617819]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>>>> [   18.624512]  [<ffffffff81ad3398>] kernel_init+0x18/0xe0
>>>>> [   18.631095]  [<ffffffff81adadcf>] ret_from_fork+0x3f/0x70
>>>>> [   18.637650]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>>>> [   18.644178] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe 
>>>>> ff ff
>>>>> 48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 
>>>>> 70 ff
>>>>> ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 
>>>>> 4c 89
>>>>> [   18.658246] RIP  [<ffffffff8105af8e>]
>>>>> ptdump_walk_pgd_level_core+0x20e/0x440
>>>>> [   18.665211]  RSP <ffff880059b9be48>
>>>>> [   18.672073] CR2: ffff88055c883000
>>>>> [   18.678852] ---[ end trace d84e34461c40637a ]---
>>>>> [   18.685641] Kernel panic - not syncing: Attempted to kill init!
>>>>> exitcode=0x00000009
>>>>> [   18.685641]
>>>>> [   18.699520] Kernel Offset: disable
>>>>>
>>>>
>>>> What's your .config?  Does cat /sys/kernel/debug/kernel_page_tables
>>>> produce a similar fault even with CONFIG_DEBUG_WX=n?
>>>
>>> .config is attached
>>>
>>> Hmm that sysfs file doesn't seem to exist then:
>>> # cat /sys/kernel/debug/kernel_page_tables
>>> cat: /sys/kernel/debug/kernel_page_tables: No such file or directory
>>
>> Needs CONFIG_X86_PTDUMP=y.
>> Also assumes you have debugfs mounted there.
>
> Recompiled, and the result is that it also blows up:
>

Can you try this:


diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c
index 1bf417e..b534216 100644
--- a/arch/x86/mm/dump_pagetables.c
+++ b/arch/x86/mm/dump_pagetables.c
@@ -362,8 +362,13 @@ static void ptdump_walk_pgd_level_core(struct 
seq_file *m, pgd_t *pgd,
                         bool checkwx)
  {
  #ifdef CONFIG_X86_64
+/* ffff800000000000 - ffff87ffffffffff is reserved for hypervisor */
+#define is_hypervisor_range(idx)  (paravirt_enabled() && \
+                  ((idx >= pgd_index(__PAGE_OFFSET) - 16) && \
+                   (idx < pgd_index(__PAGE_OFFSET))))
      pgd_t *start = (pgd_t *) &init_level4_pgt;
  #else
+#define is_hypervisor_range(idx)   0
      pgd_t *start = swapper_pg_dir;
  #endif
      pgprotval_t prot;
@@ -381,7 +386,7 @@ static void ptdump_walk_pgd_level_core(struct 
seq_file *m, pgd_t *pgd,

      for (i = 0; i < PTRS_PER_PGD; i++) {
          st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
-        if (!pgd_none(*start)) {
+        if (!pgd_none(*start) && !is_hypervisor_range(i)) {
              if (pgd_large(*start) || !pgd_present(*start)) {
                  prot = pgd_flags(*start);
                  note_page(m, &st, __pgprot(prot), 1);


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#1263032 — Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromSander Eikelenboom <linux@eikelenboom.it>
Date2015-11-05 10:20 +0100
SubjectRe: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qroS5-4FF-3@gated-at.bofh.it>
In reply to#1262729
On 2015-11-05 00:13, Boris Ostrovsky wrote:
> On 11/04/2015 03:02 PM, Sander Eikelenboom wrote:
>> On 2015-11-04 19:47, Stephen Smalley wrote:
>>> On 11/04/2015 01:28 PM, Sander Eikelenboom wrote:
>>>> On 2015-11-04 16:52, Stephen Smalley 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
>>>>>> [   18.507102] RSP: e02b:ffff880059b9be48  EFLAGS: 00010296
>>>>>> [   18.513351] RAX: ffff88055c883000 RBX: ffffffff81ae2000 RCX:
>>>>>> ffff880000000000
>>>>>> [   18.519733] RDX: 0000000000000067 RSI: ffff880059b9be98 RDI:
>>>>>> ffff880000001000
>>>>>> [   18.526129] RBP: ffff880059b9bf00 R08: 0000000000000000 R09:
>>>>>> 0000000000000000
>>>>>> [   18.532522] R10: ffff88005fd0e790 R11: 0000000000000001 R12:
>>>>>> ffff880080000000
>>>>>> [   18.538891] R13: ffffc00000000fff R14: ffff880059b9be98 R15:
>>>>>> 0000000000000000
>>>>>> [   18.545247] FS:  0000000000000000(0000) 
>>>>>> GS:ffff88005f680000(0000)
>>>>>> knlGS:0000000000000000
>>>>>> [   18.551708] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
>>>>>> [   18.558153] CR2: ffff88055c883000 CR3: 0000000002211000 CR4:
>>>>>> 0000000000000660
>>>>>> [   18.564686] Stack:
>>>>>> [   18.571106]  0000000159b9be50 ffffffff82211000 ffff88055c884000
>>>>>> 0000000000000800
>>>>>> [   18.577704]  0000800000000000 ffff88055c883000 0000000000000007
>>>>>> ffff88005fd0e790
>>>>>> [   18.584291]  ffff880059b9bed8 ffffffff81156ace 0000000000000001
>>>>>> 0000000000000000
>>>>>> [   18.590916] Call Trace:
>>>>>> [   18.597458]  [<ffffffff81156ace>] ? 
>>>>>> free_reserved_area+0x11e/0x120
>>>>>> [   18.604180]  [<ffffffff8105b1e2>]
>>>>>> ptdump_walk_pgd_level_checkwx+0x12/0x20
>>>>>> [   18.611014]  [<ffffffff810515b9>] mark_rodata_ro+0xe9/0xf0
>>>>>> [   18.617819]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>>>>> [   18.624512]  [<ffffffff81ad3398>] kernel_init+0x18/0xe0
>>>>>> [   18.631095]  [<ffffffff81adadcf>] ret_from_fork+0x3f/0x70
>>>>>> [   18.637650]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>>>>> [   18.644178] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe 
>>>>>> ff ff
>>>>>> 48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 
>>>>>> 70 ff
>>>>>> ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 
>>>>>> 4c 89
>>>>>> [   18.658246] RIP  [<ffffffff8105af8e>]
>>>>>> ptdump_walk_pgd_level_core+0x20e/0x440
>>>>>> [   18.665211]  RSP <ffff880059b9be48>
>>>>>> [   18.672073] CR2: ffff88055c883000
>>>>>> [   18.678852] ---[ end trace d84e34461c40637a ]---
>>>>>> [   18.685641] Kernel panic - not syncing: Attempted to kill init!
>>>>>> exitcode=0x00000009
>>>>>> [   18.685641]
>>>>>> [   18.699520] Kernel Offset: disable
>>>>>> 
>>>>> 
>>>>> What's your .config?  Does cat /sys/kernel/debug/kernel_page_tables
>>>>> produce a similar fault even with CONFIG_DEBUG_WX=n?
>>>> 
>>>> .config is attached
>>>> 
>>>> Hmm that sysfs file doesn't seem to exist then:
>>>> # cat /sys/kernel/debug/kernel_page_tables
>>>> cat: /sys/kernel/debug/kernel_page_tables: No such file or directory
>>> 
>>> Needs CONFIG_X86_PTDUMP=y.
>>> Also assumes you have debugfs mounted there.
>> 
>> Recompiled, and the result is that it also blows up:
>> 
> 
> Can you try this:
> 
> 
> diff --git a/arch/x86/mm/dump_pagetables.c 
> b/arch/x86/mm/dump_pagetables.c
> index 1bf417e..b534216 100644
> --- a/arch/x86/mm/dump_pagetables.c
> +++ b/arch/x86/mm/dump_pagetables.c
> @@ -362,8 +362,13 @@ static void ptdump_walk_pgd_level_core(struct
> seq_file *m, pgd_t *pgd,
>                         bool checkwx)
>  {
>  #ifdef CONFIG_X86_64
> +/* ffff800000000000 - ffff87ffffffffff is reserved for hypervisor */
> +#define is_hypervisor_range(idx)  (paravirt_enabled() && \
> +                  ((idx >= pgd_index(__PAGE_OFFSET) - 16) && \
> +                   (idx < pgd_index(__PAGE_OFFSET))))
>      pgd_t *start = (pgd_t *) &init_level4_pgt;
>  #else
> +#define is_hypervisor_range(idx)   0
>      pgd_t *start = swapper_pg_dir;
>  #endif
>      pgprotval_t prot;
> @@ -381,7 +386,7 @@ static void ptdump_walk_pgd_level_core(struct
> seq_file *m, pgd_t *pgd,
> 
>      for (i = 0; i < PTRS_PER_PGD; i++) {
>          st.current_address = normalize_addr(i * PGD_LEVEL_MULT);
> -        if (!pgd_none(*start)) {
> +        if (!pgd_none(*start) && !is_hypervisor_range(i)) {
>              if (pgd_large(*start) || !pgd_present(*start)) {
>                  prot = pgd_flags(*start);
>                  note_page(m, &st, __pgprot(prot), 1);

Hi Boris,

Thank for your patch !
It makes "cat /sys/kernel/debug/kernel_page_tables" work and
prevents a kernel with CONFIG_DEBUG_WX=y from crashing at boot.

It now does give a warning about an insecure W+X mapping, so 
CONFIG_DEBUG_WX=y
seems to be working. No idea how to interpret it though (and if it's a 
legit
warning).

--
Sander

[   19.034706] Freeing unused kernel memory: 1104K (ffffffff822fc000 - 
ffffffff82410000)
[   19.041339] Write protecting the kernel read-only data: 18432k
[   19.052596] Freeing unused kernel memory: 1144K (ffff880001ae2000 - 
ffff880001c00000)
[   19.060285] Freeing unused kernel memory: 1560K (ffff88000207a000 - 
ffff880002200000)
[   19.067079] ------------[ cut here ]------------
[   19.073931] WARNING: CPU: 5 PID: 1 at 
arch/x86/mm/dump_pagetables.c:225 note_page+0x619/0x7e0()
[   19.081039] x86/mm: Found insecure W+X mapping at address 
ffff880000000000/0xffff880000000000
[   19.088293] Modules linked in:
[   19.095477] CPU: 5 PID: 1 Comm: swapper/0 Not tainted 
4.3.0-mw-20151104-linus-doflr-withdebugwx-noptdump-ptdumppatch+ #1
[   19.102971] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS 
V1.8B1 09/13/2010
[   19.110594]  ffffffff81f381d3 ffff880059b9bd60 ffffffff81428992 
ffff880059b9bda8
[   19.118239]  ffff880059b9bd98 ffffffff810ca7ec ffff8800025d8010 
0000000000000004
[   19.125870]  0010000000000067 ffff880059b9be98 0000000000000000 
ffff880059b9bdf8
[   19.133526] Call Trace:
[   19.141212]  [<ffffffff81428992>] dump_stack+0x44/0x62
[   19.148983]  [<ffffffff810ca7ec>] warn_slowpath_common+0x7c/0xb0
[   19.156877]  [<ffffffff810ca867>] warn_slowpath_fmt+0x47/0x50
[   19.164813]  [<ffffffff8105abb9>] note_page+0x619/0x7e0
[   19.172656]  [<ffffffff8105b135>] 
ptdump_walk_pgd_level_core+0x3b5/0x450
[   19.180583]  [<ffffffff8105b1f2>] 
ptdump_walk_pgd_level_checkwx+0x12/0x20
[   19.188427]  [<ffffffff810515b9>] mark_rodata_ro+0xe9/0xf0
[   19.196221]  [<ffffffff81ad2f70>] ? rest_init+0x80/0x80
[   19.204012]  [<ffffffff81ad2f88>] kernel_init+0x18/0xe0
[   19.211732]  [<ffffffff81ada98f>] ret_from_fork+0x3f/0x70
[   19.219467]  [<ffffffff81ad2f70>] ? rest_init+0x80/0x80
[   19.227145] ---[ end trace 5fc0f4297b911570 ]---
[   19.244382] x86/mm: Checked W+X mappings: FAILED, 4602 W+X pages 
found.

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#1263220 — Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromBoris Ostrovsky <boris.ostrovsky@oracle.com>
Date2015-11-05 15:00 +0100
SubjectRe: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qrtf4-7pc-3@gated-at.bofh.it>
In reply to#1263032
On 11/05/2015 04:13 AM, Sander Eikelenboom wrote:
>
> It makes "cat /sys/kernel/debug/kernel_page_tables" work and
> prevents a kernel with CONFIG_DEBUG_WX=y from crashing at boot.

Great. Our nightly runs also failed spectacularly due to this bug.

>
> It now does give a warning about an insecure W+X mapping, so 
> CONFIG_DEBUG_WX=y
> seems to be working. No idea how to interpret it though (and if it's a 
> legit
> warning).
>
> -- 
> Sander
>
> [   19.034706] Freeing unused kernel memory: 1104K (ffffffff822fc000 - 
> ffffffff82410000)
> [   19.041339] Write protecting the kernel read-only data: 18432k
> [   19.052596] Freeing unused kernel memory: 1144K (ffff880001ae2000 - 
> ffff880001c00000)
> [   19.060285] Freeing unused kernel memory: 1560K (ffff88000207a000 - 
> ffff880002200000)
> [   19.067079] ------------[ cut here ]------------
> [   19.073931] WARNING: CPU: 5 PID: 1 at 
> arch/x86/mm/dump_pagetables.c:225 note_page+0x619/0x7e0()

Yes, this apparently is a known issue: https://lkml.org/lkml/2015/11/4/476

-boris


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#1263230 — Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromSander Eikelenboom <linux@eikelenboom.it>
Date2015-11-05 15:10 +0100
SubjectRe: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qrtoJ-7I5-7@gated-at.bofh.it>
In reply to#1263220
Thursday, November 5, 2015, 2:53:40 PM, you wrote:

> On 11/05/2015 04:13 AM, Sander Eikelenboom wrote:
>>
>> It makes "cat /sys/kernel/debug/kernel_page_tables" work and
>> prevents a kernel with CONFIG_DEBUG_WX=y from crashing at boot.

> Great. Our nightly runs also failed spectacularly due to this bug.

>>
>> It now does give a warning about an insecure W+X mapping, so 
>> CONFIG_DEBUG_WX=y
>> seems to be working. No idea how to interpret it though (and if it's a 
>> legit
>> warning).
>>
>> -- 
>> Sander
>>
>> [   19.034706] Freeing unused kernel memory: 1104K (ffffffff822fc000 - 
>> ffffffff82410000)
>> [   19.041339] Write protecting the kernel read-only data: 18432k
>> [   19.052596] Freeing unused kernel memory: 1144K (ffff880001ae2000 - 
>> ffff880001c00000)
>> [   19.060285] Freeing unused kernel memory: 1560K (ffff88000207a000 - 
>> ffff880002200000)
>> [   19.067079] ------------[ cut here ]------------
>> [   19.073931] WARNING: CPU: 5 PID: 1 at 
>> arch/x86/mm/dump_pagetables.c:225 note_page+0x619/0x7e0()

> Yes, this apparently is a known issue: https://lkml.org/lkml/2015/11/4/476

> -boris

Ah thx for the pointer :)

--
Sander




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#1262565 — Re: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core

FromBoris Ostrovsky <boris.ostrovsky@oracle.com>
Date2015-11-04 21:20 +0100
SubjectRe: [Xen-devel] Linux 4.4 MW: Boot under Xen fails with CONFIG_DEBUG_WX enabled: RIP: ptdump_walk_pgd_level_core
Message-ID<qrcHg-5df-21@gated-at.bofh.it>
In reply to#1262505
On 11/04/2015 01:47 PM, Stephen Smalley wrote:
> On 11/04/2015 01:28 PM, Sander Eikelenboom wrote:
>> On 2015-11-04 16:52, Stephen Smalley 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
>>>> [   18.507102] RSP: e02b:ffff880059b9be48  EFLAGS: 00010296
>>>> [   18.513351] RAX: ffff88055c883000 RBX: ffffffff81ae2000 RCX:
>>>> ffff880000000000
>>>> [   18.519733] RDX: 0000000000000067 RSI: ffff880059b9be98 RDI:
>>>> ffff880000001000
>>>> [   18.526129] RBP: ffff880059b9bf00 R08: 0000000000000000 R09:
>>>> 0000000000000000
>>>> [   18.532522] R10: ffff88005fd0e790 R11: 0000000000000001 R12:
>>>> ffff880080000000
>>>> [   18.538891] R13: ffffc00000000fff R14: ffff880059b9be98 R15:
>>>> 0000000000000000
>>>> [   18.545247] FS:  0000000000000000(0000) GS:ffff88005f680000(0000)
>>>> knlGS:0000000000000000
>>>> [   18.551708] CS:  e033 DS: 0000 ES: 0000 CR0: 000000008005003b
>>>> [   18.558153] CR2: ffff88055c883000 CR3: 0000000002211000 CR4:
>>>> 0000000000000660
>>>> [   18.564686] Stack:
>>>> [   18.571106]  0000000159b9be50 ffffffff82211000 ffff88055c884000
>>>> 0000000000000800
>>>> [   18.577704]  0000800000000000 ffff88055c883000 0000000000000007
>>>> ffff88005fd0e790
>>>> [   18.584291]  ffff880059b9bed8 ffffffff81156ace 0000000000000001
>>>> 0000000000000000
>>>> [   18.590916] Call Trace:
>>>> [   18.597458]  [<ffffffff81156ace>] ? free_reserved_area+0x11e/0x120
>>>> [   18.604180]  [<ffffffff8105b1e2>]
>>>> ptdump_walk_pgd_level_checkwx+0x12/0x20
>>>> [   18.611014]  [<ffffffff810515b9>] mark_rodata_ro+0xe9/0xf0
>>>> [   18.617819]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>>> [   18.624512]  [<ffffffff81ad3398>] kernel_init+0x18/0xe0
>>>> [   18.631095]  [<ffffffff81adadcf>] ret_from_fork+0x3f/0x70
>>>> [   18.637650]  [<ffffffff81ad3380>] ? rest_init+0x80/0x80
>>>> [   18.644178] Code: 70 ff ff ff 48 3b 85 58 ff ff ff 0f 84 c0 fe 
>>>> ff ff
>>>> 48 8b 85 68 ff ff ff 48 c1 e0 10 48 c1 f8 10 48 89 45 b0 48 8b 85 
>>>> 70 ff
>>>> ff ff <48> 8b 38 48 85 ff 0f 85 4e ff ff ff b9 02 00 00 00 31 d2 4c 89
>>>> [   18.658246] RIP  [<ffffffff8105af8e>]
>>>> ptdump_walk_pgd_level_core+0x20e/0x440
>>>> [   18.665211]  RSP <ffff880059b9be48>
>>>> [   18.672073] CR2: ffff88055c883000
>>>> [   18.678852] ---[ end trace d84e34461c40637a ]---
>>>> [   18.685641] Kernel panic - not syncing: Attempted to kill init!
>>>> exitcode=0x00000009
>>>> [   18.685641]
>>>> [   18.699520] Kernel Offset: disable
>>>>
>>>
>>> What's your .config?  Does cat /sys/kernel/debug/kernel_page_tables
>>> produce a similar fault even with CONFIG_DEBUG_WX=n?
>>
>> .config is attached
>>
>> Hmm that sysfs file doesn't seem to exist then:
>> # cat /sys/kernel/debug/kernel_page_tables
>> cat: /sys/kernel/debug/kernel_page_tables: No such file or directory
>
> Needs CONFIG_X86_PTDUMP=y.
> Also assumes you have debugfs mounted there.


I don't think this code (including original page tables dump) can work 
on Xen PV guests: we are walking full PGD, including the hypervisor hole 
(entries 256-272).

-boris

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