[Qemu-devel] Problem in setting breakpoints at kernel code using "qemu and gdb"

[Qemu-devel] Problem in setting breakpoints at kernel code using "qemu and gdb"

[Amirali Shambayati]

Dear all,
I want to use combination of qemu and gdb to debug my modified linux
kernel code. First I tried this
link:http://issaris.blogspot.com/2007/12/download-linux-kernel-sourcecode-from.html
to configure eclipse CDT and qemu to achieve my goal.

According to the tutorial, I tried following command to run qemu:
sudo qemu -s -S -hda linux-0.2.img -append "root=/dev/sda" -kernel
/mnt/build/linux-2.6/arch/x86/boot/bzImage

As I used my modified kernel code, I encountered with kernel oops; So
I tried to find the related code line which causes problem, using
breakpoints.
Now my problem is, when I set breakpoints before start debugging in
eclipse, it seems that it ignores breakpoints and kernel goes to oops
condition again.

Also I tried combination of gdb and qemu using following commands:
#gdb
(gdb) symbol-file vmlinux.o
(gdb) target remote localhost:1234
(gdb) break scsi_lib.c 1420
(gdb) c

I tried above commands to check if stops at breakpoint or not. I put a
printk after breakpoint line. It printed it and it means that it has
ignored breakpoint.
Would you guide me what is wrong with what I have done?

It's related to my thesis project, and I need to pass this step as
soon as possible.

Thanks in advance,
--
Amirali Shambayati
Bachelor Student
Computer Engineering Department
Sharif University of Technology
Tehran, Iran

Re: [Qemu-devel] Problem in setting breakpoints at kernel code using "qemu and gdb"

[Craig Brozefsky]

On Thu, Apr 14, 2011 at 10:16 AM, Amirali Shambayati
<amirali.shambayati@gmail.com> wrote:

>
> Also I tried combination of gdb and qemu using following commands:
> #gdb
> (gdb) symbol-file vmlinux.o
> (gdb) target remote localhost:1234
> (gdb) break scsi_lib.c 1420
> (gdb) c
>
> I tried above commands to check if stops at breakpoint or not. I put a
> printk after breakpoint line. It printed it and it means that it has
> ignored breakpoint.

Try using a hbreak, hardware breakpoint, instead of the software breakpoint.

Re: [Qemu-devel] Problem in setting breakpoints at kernel code using "qemu and gdb"

[Amirali Shambayati]

That works well. Thanks so much Craig.

On Fri, Apr 15, 2011 at 10:08 AM, Craig Brozefsky <craig@red-bean.com> wrote:
> On Thu, Apr 14, 2011 at 10:16 AM, Amirali Shambayati
> <amirali.shambayati@gmail.com> wrote:
>
>>
>> Also I tried combination of gdb and qemu using following commands:
>> #gdb
>> (gdb) symbol-file vmlinux.o
>> (gdb) target remote localhost:1234
>> (gdb) break scsi_lib.c 1420
>> (gdb) c
>>
>> I tried above commands to check if stops at breakpoint or not. I put a
>> printk after breakpoint line. It printed it and it means that it has
>> ignored breakpoint.
>
> Try using a hbreak, hardware breakpoint, instead of the software breakpoint.
>



-- 
Amirali Shambayati
Bachelor Student
Computer Engineering Department
Sharif University of Technology
Tehran, Iran