On 05/20/2016 07:34 AM, Rafael J. Wysocki wrote: > On Fri, May 20, 2016 at 9:15 AM, Ingo Molnar <mi...@kernel.org> wrote: >> >> * Logan Gunthorpe <log...@deltatee.com> wrote: >> >>> Hi, >>> >>> I have been working on a bug that causes my laptop to freeze during >>> resume from hibernation. I did a bisect to find the offending commit: >>> >>> [ab76f7b4ab] x86/mm: Set NX on gap between __ex_table and rodata >>> >>> There is more information in the bugzilla report [1] that >>> I've been working on but I will summarize things below. >>> >>> I've experienced intermittent but reproducible freezes when resuming >>> from hibernation since about kernel version 3.19. The freeze was >>> significantly more reproducible when a few applications were loaded >>> before hibernation and would largely not happen if hibernated >>> immediately after booting to a desktop. I did some tracing work to find >>> that the kernel gets as far as the resume_image call in >>> swsusp_arch_resume and I could not find any response from the image >>> kernel when I hit the bug. I also did testing that seemed to rule out >>> this being caused by a problematic driver. >>> >>> I did a successful bisect between 3.18 and 3.19 which found a bug in >>> commit f5b2831d6 that was then later fixed by commit 55696b1f66 in 4.4. >>> Then, I did a second bisect with a ported version of the fix to the >>> first bug and found commit ab76f7b4ab in 4.3 to also break hibernation >>> with what appears to be the exact same symptoms. Reverting that commit >>> in recent kernels up to and including 4.6 fixes the issue and restores >>> reliable hibernation. However, it's not at all clear to me why that >>> commit would cause this issue or how to fix the issue without reverting. >> >> I've attached that commit below and also Cc:-ed a few more people who might >> have >> an idea about why this regressed. Worst-case we'll have to revert it. > > Without looking deep into mm, my theory would be that after this patch > the final jump from the boot kernel to the image kernel's trampoline > code during resume may crash the kernel if the trampoline page turns > out to be NX in the boot kernel (it has to be executable in both the > boot and the image kernels).
So, pardon my ignorance, but where is this trampoline page placed in kernel memory?