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Groups > linux.kernel > #1606006
| From | Linus Torvalds <torvalds@linux-foundation.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage |
| Date | 2017-03-21 22:20 +0100 |
| Message-ID | <tnzma-yy-25@gated-at.bofh.it> (permalink) |
| References | <tnk3L-6MU-1@gated-at.bofh.it> <tnwHE-73c-9@gated-at.bofh.it> <tnxDI-7Ii-19@gated-at.bofh.it> <tnxDI-7Ii-17@gated-at.bofh.it> <tnyzM-8nv-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Tue, Mar 21, 2017 at 1:25 PM, Thomas Garnier <thgarnie@google.com> wrote:
> The issue seems to be related to exceptions happening in close pages
> to the fixmap GDT remapping.
>
> The original page fault happen in do_test_wp_bit which set a fixmap
> entry to test WP flag. If I grow the number of processors supported
> increasing the distance between the remapped GDT page and the WP test
> page, the error does not reproduce.
>
> I am still looking at the exact distance between repro and no-repro as
> well as the exact root cause.
Hmm. Have we set the GDT limit incorrectly, somehow? The GDT *can*
cover 8k entries, which at 8 bytes each would be 64kB.
So somebody trying to load an invalid segment (say, 0xffff) might end
up causing an access to the GDT base + 64k - 8.
It is also possible that the CPU might do a page table writability
check *before* it does the limit check. That would sound odd, though.
Might be a CPU errata.
Linus
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Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Thomas Garnier <thgarnie@google.com> - 2017-03-21 19:30 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Thomas Garnier <thgarnie@google.com> - 2017-03-21 20:30 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Thomas Garnier <thgarnie@google.com> - 2017-03-21 21:30 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-21 22:20 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Andy Lutomirski <luto@amacapital.net> - 2017-03-21 23:40 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Andy Lutomirski <luto@kernel.org> - 2017-03-22 01:10 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Thomas Garnier <thgarnie@google.com> - 2017-03-22 01:50 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Andy Lutomirski <luto@kernel.org> - 2017-03-22 05:50 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Thomas Garnier <thgarnie@google.com> - 2017-03-22 06:20 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Ingo Molnar <mingo@kernel.org> - 2017-03-22 08:40 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Andy Lutomirski <luto@amacapital.net> - 2017-03-22 17:40 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Thomas Garnier <thgarnie@google.com> - 2017-03-22 17:50 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Andy Lutomirski <luto@kernel.org> - 2017-03-22 18:10 +0100
Re: [lkp-robot] [x86] 69218e4799: BUG:kernel_hang_in_boot_stage Linus Torvalds <torvalds@linux-foundation.org> - 2017-03-21 20:30 +0100
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