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

From: Boris Ostrovsky
Date: Thu Nov 05 2015 - 08:54:03 EST

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


[ 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:


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