dtrace ustack kernel panic

[Andriy Gapon]

on 30/07/2011 21:19 maestro something said the following:
> 
> 
> On Sat, Jul 30, 2011 at 12:50 AM, Andriy Gapon <avg at freebsd.org
> <mailto:avg at freebsd.org>> wrote:
> 
>     on 30/07/2011 00:27 maestro something said the following:
>     > Hi,
>     >
>     > trying to do so I don't really find my way around. This is what I get when
>     I run
>     > kgdb
>     >
>     > On startup the assert frame is #7 and the probe frame is #8.
>     >
>     [snip]
>     > kernel trap 12 with interrupts disabled
>     >
> 
>     I am not quite sure.  Apparently there is some issue with either what
>     information we store in a crash dump and how, or with how kgdb interprets that
>     information, or with a combination of both...
>     Perhaps this is a result of -O2 optimization and -O1 would improve the situation
> 
> 
> I guess I have to recompile the kernel without -O then ... does that work for
> freebsd (I remember linux has issues i.e., does not compile without any -O)

Not sure about -O0; -O1/-O should work fine.

> How would I do that the in the most straight forward way?

See man make.conf: CFLAGS, etc.

>     Meanwhile, there is something simple that you can do without much hassle:
>     (kgdb) list *dtrace_probe+0x135c
> 
> 
> True there was not a lot hassle involved. However the result is not really
> satisfactory either :-)
> 
> (kgdb) list *dtrace_probe+0x135c
> No source file for address 0xc10fb28c.
> 
> The address is in accordance with the stack-trace (i.e., frame #8)
>  
> 
>     where the address is taken from the backtrace printed by panic(9).

Have you started kgdb with the correct kernel and core file?
If yes, then I am out of ideas.

> 
>     > On Tue, Jul 26, 2011 at 4:05 AM, Andriy Gapon <avg at freebsd.org
>     <mailto:avg at freebsd.org>
>     > <mailto:avg at freebsd.org <mailto:avg at freebsd.org>>> wrote:
>     >
>     >     on 26/07/2011 04:20 maestro something said the following:
>     >     > Hi,
>     >     >
>     >     > when using the ustack action on the latest FreeBSD8.2 i386 the kernel
>     >     > panics.
>     >     >
>     >     > Here is the information I could gather:
>     >     >
>     >     > let me know if I can provide more information. (i.e., i have the
>     full crash
>     >     > information 80+mbs handy)
>     >
>     >     Use kgdb on the crash dump, go to the dtrace_probe frame and see which
>     exactly
>     >     assert fails and why.
>     >
>     >     > Here is the backtrace:
>     >     >
>     >     > Fatal trap 12: page fault while in kernel mode
>     >     > cpuid = 0; apic id = 00
>     >     > fault virtual address   = 0x108
>     >     > fault code              = supervisor write, page not present
>     >     > instruction pointer     = 0x20:0xc11012d7
>     >     > stack pointer           = 0x28:0xcd3ed9f4
>     >     > frame pointer           = 0x28:0xcd3eda0c
>     >     > code segment            = base 0x0, limit 0xfffff, type 0x1b
>     >     >                         = DPL 0, pres 1, def32 1, gran 1
>     >     > processor eflags        = resume, IOPL = 0
>     >     > current process         = 1132 (nc)
>     >     > trap number             = 12
>     >     > panic: page fault
>     >     > cpuid = 0
>     >     > KDB: stack backtrace:
>     >     > #0 0xc09036a7 at kdb_backtrace+0x47
>     >     > #1 0xc08d1a07 at panic+0x117
>     >     > #2 0xc0c158c3 at trap_fatal+0x323
>     >     > #3 0xc0c15bc0 at trap_pfault+0x2f0
>     >     > #4 0xc0c1612a at trap+0x48a
>     >     > #5 0xc0bfc97c at calltrap+0x6
>     >     > #6 0xc10e992b at dtrace_panic+0x1b
>     >     > #7 0xc10e995d at dtrace_assfail+0x2d
>     >     > #8 0xc10fb28c at dtrace_probe+0x135c
>     >     > #9 0xc1237f72 at systrace_probe+0x62
>     >     > #10 0xc090f63f at syscallenter+0x47f
>     >     > #11 0xc0c15c14 at syscall+0x34
>     >     > #12 0xc0bfca11 at Xint0x80_syscall+0x21
>     >     > Uptime: 3m0s
>     >     > Physical memory: 239 MB
>     >     > Dumping 79 MB: 64 48 32 16
>     >     >
>     >     >
>     >     > Steps To reproduce:
>     >     >
>     >     > the dtrace program (i.e., test.d) was:
>     >     >
>     >     > #!/usr/sbin/dtrace -s
>     >     >
>     >     > syscall::accept:return
>     >     > / execname == "nc" /
>     >     > {
>     >     >     printf("%s accept:return\n", execname);
>     >     >     ustack();
>     >     > }
>     >     >
>     >     > % dtrace -s test.d
>     >     >
>     >     > then running
>     >     > % nc -vl 8080
>     >     > on one shell and
>     >     > % nc localhost 8080
>     >     > on another would make the kernel panic
> 
> 
>     --
>     Andriy Gapon
> 
> 


-- 
Andriy Gapon