[uml-devel] Kernel Panic

[uml-devel] Kernel Panic

[Torsten Boob]

Hi,
i have a problem that i cant solve.

I'm coding a Module using UML. That module calls

tcp_alloc_pskb()

inside the kernel. That function allocates memory for a socket buffer inside the network sending path used inside the kernel. 
But iam calling it inside my module.

But calling it in my module gives me a:

Kernel panic: Kernel mode fault at addr 0x28, ip 0xa003d050

And then the whole UML goes down. No chance to make a backtrace, because gdb is killed too.


While playing with breakpoints i got that message, but only one time:

0xa0109d14 in sig_handler (sig=-1610608640, sc= {gs = 1024, __gsh = 0, fs = 64304, __fsh = 40959, es = 53718, __esh = 16406, ds = 28232, __dsh = 16417, edi = 1075922592, esi = 1075922592, ebp = 1073912488, esp = 1, ebx = 0, edx = 1073911876, ecx = 8, eax = 2, trapno = 2684353328, err = 1075922600, eip = 1412, cs = 18080, __csh = 16417, eflags = 0, esp_at_signal = 2684353276, ss = 9185, __ssh = 16405, fpstate = 0x9ffffb30, oldmask = 12, cr2 = 1075908832}) at trap_user.c:105 105 } (gdb)

That gave me the hint, that it could possibly a uml specific problem.

Can anybody please help me to solve my problem ?

Is there any chance to make a backtrace even if gdb was completly killed ?

What does that error message mean ? Where can i start searching for the error ?

Or any other ideas ?

Many Thanks
  Torsten Boob



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Re: [uml-devel] Kernel Panic

[Jeff Dike]

ddflatrate@web.de said:
> Kernel panic: Kernel mode fault at addr 0x28, ip 0xa003d050 

Well, 'i sym *0xa003d050' will tell you where the segfault happened, at
least.

> And then the whole UML goes down. No chance to make a backtrace,
> because gdb is killed too. 

Hummm, that seems bad.  Any more info on that?

One thing I do when gdb isn't useful, and I know where I want to stop, is
put a 'printk("something\n"); while(1) ;' there, and just run UML with no 
debugger.

When it stops:
	if you're using skas mode, just attach gdb to it
	if you're using tt mode, do the following

		kill -STOP the 'R' UML process
		kill -9 the tracing thread
		attach gdb to the -STOPped process

Either way, you've got your stack trace.

				Jeff



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