Messages in this thread | | | Date | Thu, 25 Sep 2008 01:53:26 -0700 | From | "H. Peter Anvin" <> | Subject | Re: v2.6.27-rc7: x86: #GP on panic? |
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Ingo Molnar wrote: > * Vegard Nossum <vegard.nossum@gmail.com> wrote: > >> Hi, >> >> With 2.6.27-rc7 on qemu-x86_64, it seems that panic will trigger a >> General Protection Fault. I haven't seen it before. > >> [ 4.523641] Code: eb fd 55 48 89 e5 53 51 83 3d 25 e8 78 00 00 75 >> 1a 31 d2 31 f6 48 c7 c7 e1 9c 01 81 e8 f7 a4 03 00 9c 5b fa e8 94 09 >> 00 00 53 9d <5a> 5b c9 c3 55 31 c0 48 89 e5 89 04 25 b0 c0 5f ff 65 83 >> 04 25 > > hm, 0x5a is a simple pop %rdx. A #GP there means the stack segment is > bust? >
No, that would be #SS (and segments don't really exist in 64-bit mode anyway.) In 32-bit mode it could mean a code segment overrun.
*However*...
[ 4.523477] general protection fault: fff2 [1] SMP
There is an error code attached to the #GP, which is supposed to mean that somehow a segment selector was involved. This doesn't look like a very valid segment selector at all.
> hm: > >> ffffffff8101a6b9 <disable_local_APIC> >> ffffffff81019d25: 53 push %rbx >> ffffffff81019d26: 9d popfq >> ffffffff81019d27: 5a pop %rdx > > so it's preceded by a popfq and on the next instruction we #GP. > > but the stack and flags state looks good: > > [ 4.523641] RSP: 0018:ffff880007867d70 EFLAGS: 00000286 >
My guess is that the popfq enables interrupts, and we try to take an interrupt through an IDT entry which isn't set up correctly.
-hpa
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