[uml-devel] Cannot see stack after add-symbol-file

[uml-devel] Cannot see stack after add-symbol-file

[Etay Meiri]

Hi,

I have a strange problem when debugging my module under uml.
When the module crashes, I go into the debugger and display
the stack trace. There are several frame and there is one named
"????". I assume this is my module so I add the symbol file according
to the howto. The symbols load ok but the next time I do 'bt' I get
only the frame of the panic.
Here's a sample (I annotated it a bit):

<<< uml starting >>>

Breakpoint 3, start_kernel () at init/main.c:361
361             printk(linux_banner);
(gdb) c
Continuing.

<<< crashed caused here.... >>>

Breakpoint 1, panic (
     fmt=0xa01ef540 "Kernel mode fault at addr 0x%lx, ip 0x%lx") at 
panic.c:52
52              bust_spinlocks(1);
(gdb) bt
#0  panic (fmt=0xa01ef540 "Kernel mode fault at addr 0x%lx, ip 0x%lx")
     at panic.c:52
#1  0xa00f0f36 in segv (address=7286388, ip=2743086726, is_write=0, 
is_user=0,
     sc=0xa20d8274) at trap_kern.c:149
#2  0xa00f135e in segv_handler (sig=11, regs=0xa20d8274) at trap_user.c:69
#3  0xa00f49a6 in sig_handler_common_tt (sig=11, sc_ptr=0x58) at 
trap_user.c:37
#4  0xa00f143b in sig_handler (sig=0, sc=
       {gs = 0, __gsh = 0, fs = 0, __fsh = 0, es = 123, __esh = 0, ds = 
123, __ds
h = 0, edi = 0, esi = 4294967280, ebp = 2718809004, esp = 2718808924, 
ebx = 2687
597856, edx = 0, ecx = 2718808656, eax = 7286388, trapno = 14, err = 4, 
eip = 27
43086726, cs = 115, __csh = 0, eflags = 66118, esp_at_signal = 
2718808924, ss =
123, __ssh = 0, fpstate = 0x0, oldmask = 134283264, cr2 = 7286388})
     at trap_user.c:104
#5  <signal handler called>
#6  0xa3802e86 in ?? ()
#7  0xa0012df4 in sys_delete_module (name_user=0xa0317d20 "??\r?$}1?$}1?")
     at module.c:636

<<< adding the symbols >>>

(gdb) p module_list
$1 = (struct module *) 0xa3802000
(gdb) add-symbol-file /home/cl/hacking/kernel/plkp/knet/modknet.o 0xa3802060
add symbol table from file "/home/cl/hacking/kernel/plkp/knet/modknet.o" at
         .text_addr = 0xa3802060
(y or n) y
Reading symbols from /home/cl/hacking/kernel/plkp/knet/modknet.o...
done.

<<< another backtraced >>>

(gdb) bt
#0  panic (fmt=0xa01ef540 "Kernel mode fault at addr 0x%lx, ip 0x%lx")
     at panic.c:52
(gdb)


The host is RH9 running kernel 2.6.0-test4. The uml is 2.4.22. This also
happened when I loaded the symbols before the module crashed.

Any idea?


-- 
--------------------------------
Etay Meiri
etay-m@bezeqint.net
--------------------------------



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Re: [uml-devel] Cannot see stack after add-symbol-file

[BlaisorBlade]

Alle 20:58, venerdì 12 settembre 2003, Etay Meiri wrote:
> Hi,
>
> I have a strange problem when debugging my module under uml.
> When the module crashes, I go into the debugger and display
> the stack trace. There are several frame and there is one named
> "????". I assume this is my module so I add the symbol file according
> to the howto. The symbols load ok but the next time I do 'bt' I get
> only the frame of the panic.

>
> <<< another backtraced >>>
>
> (gdb) bt
> #0  panic (fmt=0xa01ef540 "Kernel mode fault at addr 0x%lx, ip 0x%lx")
>      at panic.c:52
> (gdb)
>
>
> The host is RH9 running kernel 2.6.0-test4. The uml is 2.4.22. This also
> happened when I loaded the symbols before the module crashed.
>
> Any idea?
What version of GDB are you running? Some time ago, there were various threads 
in both lists(devel/user) about GDB showing only the last frame in all 
backtraces. The bug was tracked down... and it came from binutils, IIRC(the 
proposed fix was a workaround in GDB). Maybe it is appearing here in a 
different form.
-- 
cat <<EOSIGN
Paolo Giarrusso, aka Blaisorblade
Linux Kernel 2.4.21/2.6.0-test on an i686; Linux registered user n. 292729
EOSIGN



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