Date: Fri, 15 May 2015 13:57:03 -0400 From: Ryan Stone <rysto32@gmail.com> To: Sean Bruno <sbruno@freebsd.org> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: How to get anything useful out of kgdb? Message-ID: <CAFMmRNyM6Tc7P8rLJmMSVXOFkK4Tc0OCOtc=E9dLEtzKrEtjLg@mail.gmail.com> In-Reply-To: <555627EC.2020007@ignoranthack.me> References: <554E41EE.2010202@ignoranthack.me> <2063489.pgabuk9nPJ@ralph.baldwin.cx> <55561803.9050102@ignoranthack.me> <19618854.y3EeXVtCGX@ralph.baldwin.cx> <55561D9A.30309@ignoranthack.me> <CAFMmRNydJdVm%2BDpptQY_LnRvMfUMmoLkLXZFd1zP3OxaMFHgxw@mail.gmail.com> <555627EC.2020007@ignoranthack.me>
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On Fri, May 15, 2015 at 1:07 PM, Sean Bruno <sbruno@ignoranthack.me> wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
>
> Hrm, when I look at them directly in the crashdump, I don't see
> anything useful.
>
> (kgdb) tid 100058
> [Switching to thread 54 (Thread 100058)]#0 cpustop_handler () at
> /home/sbruno/bsd/em_mq/sys/x86/x86/mp_x86.c:987
> 987 CPU_SET_ATOMIC(cpu, &stopped_cpus);
> Current language: auto; currently minimal
> (kgdb) whe
> #0 cpustop_handler () at /home/sbruno/bsd/em_mq/sys/x86/x86/mp_x86.c:98
> 7
> #1 0xffffffff80f76f7a in ipi_nmi_handler () at
> /home/sbruno/bsd/em_mq/sys/x86/x86/mp_x86.c:969
> #2 0xffffffff80e3657a in trap (frame=0xffffffff817eb910) at
> /home/sbruno/bsd/em_mq/sys/amd64/amd64/trap.c:188
> #3 0xffffffff80e1b273 in nmi_calltrap () at
> /home/sbruno/bsd/em_mq/sys/amd64/amd64/exception.S:509
> #4 0x0000000800841841 in ?? ()
> Previous frame inner to this frame (corrupt stack?)
>
*Sigh*, kgdb isn't unwinding the trap frame properly. You can try this to
figure out where it was running:
frame 2
info line *frame->tf_rip
That gives you the top of the callstack at the time that the core was
taken. To get the rest of it, try:
define trace_stack
set $frame_ptr=$arg0
set $iters=0
while $frame_ptr != 0 && $iters < $arg1
set $ret_addr=((char*)$frame_ptr) + sizeof(void*)
printf "frameptr=%p, ret_addr=%p\n", (void*)$frame_ptr,
*(void**)$ret_addr
printf " "
info line **(void***)$ret_addr
set $frame_ptr=*(void**)$frame_ptr
set $iters=$iters+1
end
end
trace_stack frame->tf_rbp 20
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