[Qemu-devel] Re: How to debug Linux kernel on qemu with kgdb?

[Neo Jia]

On 4/25/07, Jan Kiszka <address@hidden> wrote:
> Neo Jia wrote:
> > On 4/25/07, Jan Kiszka <address@hidden> wrote:
> >> Neo Jia wrote:
> >> > hi,
> >> >
> >> > I am trying to use debug kgdb patched linux kernel on my qemu. Both
> >> > the native and target platform are IA32. I am wondering if there is
> >> > anyone can show me the procedure?
> >>
> >> Yep, see https://mail.gna.org/public/xenomai-core/2006-09/msg00202.html
> >>
> >> (BTW, I think that kgdb bug is still unfixed - I never got a feedback.)
> >
> > I can connect gdb through /dev/pts/XX. My qemu is lanuched by
> >
> > qemu -nographic -hda linux.img -kernel
> > ./2.6.15.5-kgdb/vmlinuz-2.6.15.5-kgdb -serial pty -append "kgdbwait
> > console=ttyS0 root=/dev/hda sb=0x220,5,1,5 ide2=noprobe ide3=noprobe
> > ide4=noprobe ide5=noprobe"
> >
> > Do you know where can I get the console output?
> >
>
> Use "... -serial stdio -serial pty ..." and attached kgdb to the second
> serial port (I think to recall that is default anyway). The first one is
> then used for the kernel console.
>
> > I would like to work out kgdb + qemu to debug linux kernel.
>
> ??? So you really want to debug the kernel when kgdb is applied, ie.
> actually debug kgdb? If you only intend to debug the kernel itself, qemu
> -s + gdb is enough.

Jan,

I just would like to debug kernel itself. I have tried qemu -s + gdb
but it keeps
getting "apic_timer_interrupt" when I am using "n" command.

The following is the output:

> gdb vmlinux
GNU gdb 6.5.50.20060621-cvs
Copyright (C) 2006 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you are
welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i686-pc-linux-gnu"...Using host
libthread_db library "/lib/tls/libthread_db.so.1".

(gdb) target remote localhost:1234
Remote debugging using localhost:1234
0x0000fff0 in ?? ()
warning: shared library handler failed to enable breakpoint
(gdb) c
Continuing.

Program received signal SIGINT, Interrupt.
default_idle () at include/asm/bitops.h:252
252             return ((1UL << (nr & 31)) & (addr[nr >> 5])) != 0;
(gdb) b sys_ex
sys_execve      sys_exit        sys_exit_group
(gdb) b sys_execve
Breakpoint 1 at 0xc0101ac1: file arch/i386/kernel/process.c, line 791.
(gdb) c
Continuing.

Breakpoint 1, sys_execve (regs=
     {ebx = 135197704, ecx = 135197864, edx = 135244936, esi =
135197704, edi = 135197704, ebp = -1079176984, eax = 11, xds = 123,
xes = 123, orig_eax = 11, eip = -1208835017, xcs = 115, eflags = 582,
esp = -1079177012, xss = 123})
   at arch/i386/kernel/process.c:791
791             filename = getname((char __user *) regs.ebx);
(gdb) n
0xc0103666 in apic_timer_interrupt () at include/asm/current.h:9
9       {
(gdb) quit

Thanks,
Neo

> Jan


--
I would remember that if researchers were not ambitious
probably today we haven't the technology we are using!