Sanity Check: Bogus(?) General Protection Fault

[Oliver Pinter]

Try to remove CPUTYPE?=foo from make.conf.

On 8/6/14, Eric van Gyzen <eric at vangyzen.net> wrote:
> On 08/06/2014 10:48, Matt Fleming wrote:
>> On Wed, 06 Aug, at 10:12:06AM, Eric van Gyzen wrote:
>>> Can someone give me a quick sanity check?  I'm debugging a General
>>> Protection Fault on an amd64 system.  The faulting instruction appears
>>> to be an immediate mov into %r11...right?  I ask because I can't imagine
>>> how that instruction could cause a GPF.  Any ideas?
>>>
>>> Thanks,
>>>
>>> Eric
>>>
>>> ====
>>>
>>> Fatal trap 9: general protection fault while in kernel mode
>>> cpuid = 0; apic id = 00
>>> instruction pointer     = 0x20:0xffffffff805d6e23
>> [...]
>>
>>> 0xffffffff805d6e23 <vm_reserv_alloc_contig+947>:    mov
>>> %rcx,0x10(%r11,%r9,1)
>> This is your faulting instruction.
>
> Thanks, Matt.  That has always been my understanding (and I just found
> the docs to confirm).  I doubted myself because the problem is now even
> more bizarre.  The mov before the faulting instruction apparently didn't
> complete.  %r11 is still an old value, not 0x....f7a8.
>
> Any ideas, anyone?
>
> Eric
>
> ====
>
> 0xffffffff805d6e0f <vm_reserv_alloc_contig+927>:    mov    0x30(%rax),%r9
> 0xffffffff805d6e13 <vm_reserv_alloc_contig+931>:    shr    $0x15,%r9
> 0xffffffff805d6e17 <vm_reserv_alloc_contig+935>:    shl    $0x6,%r9
> 0xffffffff805d6e1b <vm_reserv_alloc_contig+939>:    mov
>  0xffffffff809bf7a8,%r11
> 0xffffffff805d6e23 <vm_reserv_alloc_contig+947>:    mov
>  %rcx,0x10(%r11,%r9,1)
>
> db> show reg
> cs                0x20
> ds                0x3b
> es            0x3b003b
> fs            0x1b0013
> gs                0x1b
> ss                0x28
> rax         0xfffff8043efd6980
> rcx         0xfffff80423501000
> rdx         0xfffff80423501000
> rbx         0xffffffffffdce222
> rsp         0xfffffe0463d45660
> rbp         0xfffffe0463d456d0
> rsi         0xffffffff80a0f898  kernel_object_store+0xb0
> rdi         0xffffffff80a0f7e8  kernel_object_store
> r8                   0
> r9          0x1fffff0087dc0
> r10                  0
> r11         0xfffff80423501000
> r12         0xfffff80430b86980
> r13           0x707e00
> r14                  0
> r15                  0
> rip         0xffffffff805d6e23  vm_reserv_alloc_contig+0x3b3
> rflags         0x10206
> vm_reserv_alloc_contig+0x3b3:   movq    %rcx,0x10(%r11,%r9,1)
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