Sanity Check: Bogus(?) General Protection Fault
Eric van Gyzen
eric at vangyzen.net
Wed Aug 6 14:12:08 UTC 2014
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
stack pointer = 0x28:0xfffffe0463d45660
frame pointer = 0x28:0xfffffe0463d456d0
code segment = base 0x0, limit 0xfffff, type 0x1b
= DPL 0, pres 1, long 1, def32 0, gran 1
processor eflags = interrupt enabled, resume, IOPL = 0
db> bt
Tracing pid 1017 tid 100169 td 0xfffff801d4500000
vm_reserv_alloc_contig() at vm_reserv_alloc_contig+0x3b3/frame
0xfffffe0463d456d0
vm_page_alloc_contig() at vm_page_alloc_contig+0x13b/frame
0xfffffe0463d45760
kmem_alloc_contig() at kmem_alloc_contig+0x12f/frame 0xfffffe0463d45810
contigmalloc() at contigmalloc+0x33/frame 0xfffffe0463d45850
[snip]
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)
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