Messages in this thread | | | Date | Fri, 12 Jul 2013 10:48:21 -0500 | From | Steve Wise <> | Subject | Oops mystery |
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Hello kernel experts,
I was wondering if someone has any ideas on this Oops. My analysis must be incorrect. From what I can tell, this shouldn't have caused a bad page fault, but it did :).
Here is what I see in the crash dump:
dmesg log shows this:
[ 1053.156266] BUG: unable to handle kernel paging request at 0000000000040fc0 [ 1053.216620] IP: [<ffffffffa02b202e>] c4iw_ev_handler+0x2e/0x84 [iw_cxgb4] [ 1053.216638] PGD 8b9877067 PUD 86cd37067 PMD 0 [ 1053.216642] Oops: 0002 [#1] SMP
c4iw_ev_handler+0x2e is:
crash> dis -r c4iw_ev_handler+0x2e 0xffffffffa02b2000 <c4iw_ev_handler>: push %rbp 0xffffffffa02b2001 <c4iw_ev_handler+1>: push %rbx 0xffffffffa02b2002 <c4iw_ev_handler+2>: sub $0x8,%rsp 0xffffffffa02b2006 <c4iw_ev_handler+6>: mov %rdi,%rbp 0xffffffffa02b2009 <c4iw_ev_handler+9>: mov %esi,%ebx 0xffffffffa02b200b <c4iw_ev_handler+11>: lea 0x8a0(%rdi),%rdi 0xffffffffa02b2012 <c4iw_ev_handler+18>: callq 0xffffffff811e1020 <idr_find> 0xffffffffa02b2017 <c4iw_ev_handler+23>: mov %rax,%rcx 0xffffffffa02b201a <c4iw_ev_handler+26>: test %rax,%rax 0xffffffffa02b201d <c4iw_ev_handler+29>: je 0xffffffffa02b203d <c4iw_ev_handler+61> 0xffffffffa02b201f <c4iw_ev_handler+31>: movzwl 0x88(%rax),%eax 0xffffffffa02b2026 <c4iw_ev_handler+38>: mov 0x38(%rcx),%rdx 0xffffffffa02b202a <c4iw_ev_handler+42>: shl $0x6,%rax 0xffffffffa02b202e <c4iw_ev_handler+46>: movb $0x0,0xe(%rax,%rdx,1)
Crash shows these regs:
crash> bt PID: 12915 TASK: ffff8808d50da200 CPU: 4 COMMAND: "DSI_SvrReceiveR" #0 [ffff880751c039b0] machine_kexec at ffffffff81020a62 #1 [ffff880751c03a00] crash_kexec at ffffffff81088780 #2 [ffff880751c03ad0] oops_end at ffffffff8139efe0 #3 [ffff880751c03af0] __bad_area_nosemaphore at ffffffff8102ed15 #4 [ffff880751c03bb0] page_fault at ffffffff8139e25f [exception RIP: c4iw_ev_handler+46] RIP: ffffffffa02b202e RSP: ffff880751c03c60 RFLAGS: 00010206 RAX: 0000000000040fc0 RBX: 0000000000000404 RCX: ffff880c35da9080 RDX: ffff8808b5500000 RSI: 0000000000000404 RDI: ffff8808d5fabd50 RBP: ffff880c2e5a4000 R8: 0000000000000000 R9: ffff8808d5fabb30 R10: 0000000000000110 R11: ffffffff8101f9b0 R12: 0000000000000000 R13: ffff880c20598230 R14: ffff880c2e5a4000 R15: ffff880c3dbf1480 ORIG_RAX: ffffffffffffffff CS: 0010 SS: 0018 <snip>
So 'movb $0x0,0xe(%rax,%rdx,1)' should be storing 0 into the byte location:
%rax + 0xe + (%rdx * 1) == 0x40fc+ 0xe + 0xffff8808b5500000 == 0xffff8808b5540fce.
That address is readable in the crash dump:
crash> x/8b 0x0000000000040fc0+0xe+0xffff8808b5500000 0xffff8808b5540fce: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
And why does the page fault show 0x40fc0 as the faulting address? It should be 0xffff8808b5540fce and it shouldn't have caused a page fault.
What am I missing?
Thanks in advance,
Steve.
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