Kernel Debugging using Qemu

[Saket Sinha]

Hi Aruna,

Please find the steps below -


The kernel needs to be compiled with debugging support, for the same
add -g option in KBUILD_CFLAGS and KBUILD_CXXFLAGS.
CONFIG_DEBUG_INFO=y

make ARCH=i386 menuconfig
make ARCH=i386 bzImage -j 5
Now we have compiled the 32 bit binaries


Starting the qemu with the kernel image
qemu -s -S  -kernel arch/x86/boot/bzImage -append "console=ttyS0"
-serial mon:stdio -nographic
OR
qemu -s -S -smp 1,cores=1  -hda /dev/zero -kernel arch/x86/boot/bzImage


Debugging using plane gdb
$gdb vmlinux
(gdb) target remote localhost:1234
(gdb) b start_kernel
(gdb) c



Regards,
Saket Sinha


On Sat, Aug 15, 2015 at 7:47 AM, Aruna Hewapathirane
<aruna.hewapathirane at gmail.com> wrote:
> Hi,
>
> If anyone uses Qemu can someone please show me how to get started ?
>
> I tried :
>
> sudo qemu-system-x86_64 -s -S -kernel arch/x86/boot/bzImage -initrd
> /boot/initrd.img-4.1.2-vtaqemu+ /dev/zero
>
> And it does allow me to access through gdb using target remote
> localhost:1234 but when I set a breakpoint in kernel_start and
> continue it hangs and tells me /bin/sh: can't access tty; job control
> turned off ?
>
> I am runing a Debian 4.1.2 custom kernel. I have enabled Intel
> virtulization in the bios. And menuconfig have setup virtualization.
>
> After many tries have finally managed to get this far but now I can
> use all the help I can get.
>
> And and all suggestions, guidance, *pointers are most welcome.
>
> Thanks - Aruna
>
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