Re: Feedback on my development setup

[ngn <ngn@ngn.tf>]

On Tue, Apr 16, 2024 at 08:38:54AM -0400, Josh Marshall wrote:
> Hello all,
> 
> I am trying to work on and improve some aspects of the "fanotify"
> parts of the VFS subsystem with Amir Goldstein being the person I
> brought these to.  Amir has me doing some work to see what is going on
> since I have observed some unexpected behaviors.  In doing so, I have
> cobbled together the following iteration pattern which I would like
> feedback on.  It doesn't feel like it is as concise as it should be in
> practice and I am hoping someone can offer pointers on how to improve
> it.  By the end of this, I would like to have a fully documented and
> replicable script to share for certain kinds of non-hardware kernel
> development like I am doing here.  As a word of warning, I haven't
> gotten to fully test this either.  It feels like I'm trying to cut
> down a hydra with everything new I need to account for.
> 
> ```
> Source:
> https://github.com/archlinux/arch-boxes
> 
> Term 1:
> guestmount -w -a ~/Downloads/Arch-Linux-x86_64-basic.qcow2 -m
> /dev/sda3 ~/mnt/arch/
> <copy sources, files, perform compilation steps, etc as needed to
> inside the VM image as needed each development iteration>
> cp ~/mnt/ arch/home/arch/linux/boot/x86/vmlinux .
> umount ~/mnt/arch
> 
> Term 2:
> kvm -s -cpu host -display gtk -vga qxl -accel kvm -drive
> format=qcow2,file=$HOME/Downloads/Arch-Linux-x86_64-basic.qcow2 -m 1G
> -smp 2 -S
> 
> Term 3:
> gdb vmlinux
> : target remote:1234
> <set break points>
> : continue
> 
> Qemu:
> <time sensitive, boot into the right kernel if available>
> <perform development tasks>
> ```
> 

Hello,

You don't have to mount and copy over the vmlinux file, QEMU/KVM has the -kernel option, 
which you can use to specify the kernel image:

kvm -s cpu host                                   \
    -display gtk                                  \
    -vga qxl                                      \
    -accel kvm                                    \
    -m 1G                                         \
    -kernel arch/home/arch/linux/boot/x86/vmlinux \
    -drive format=qcow2,file=$HOME/Downloads/Arch-Linux-x86_64-basic.qcow2

However you will need mount and copy any modules you build to the /lib/modules
directory or you won't be able to load them.