create/run: bindmount kernel source at /src/kernel

Add 9p bind mount for convenience, ensure uid matches for guest user so we
can just map it.

We let the foreign (i.e. cross-compiled) version bitrot for now as it's already
somewhat bitrotted, will return to that if I need to use it.

Author: lorenzo-stoakes

kerndev-create

@@ -67,7 +67,7 @@ echo Running chroot-ed rootfs image config script...
 cp $chroot_script_path /mnt/chroot.sh
 # Copy ssh keys + config.
 cp -R /home/$SUDO_USER/.ssh /mnt/
-arch-chroot /mnt /chroot.sh $SUDO_USER $ROOT_PASSWORD
+arch-chroot /mnt /chroot.sh $SUDO_USER $(id -u $SUDO_USER) $ROOT_PASSWORD
 rm /mnt/chroot.sh
 # arch-chroot mounts the system's /etc/resolv.conf, so do this outside the
 # chroot.
@@ -116,13 +116,15 @@ fi
 unmount
 trap - EXIT
 
-echo Building linux...
-# Install separately so we can update user on progress separately, also this
-# means we can run as the user and thus not write root owned files!
-NO_DONE=y DONT_INSTALL=y sudo -E -u $SUDO_USER kerndev-build
+if [[ -n "$KERNEL_BUILD_ON_CREATE" ]]; then
+	echo Building linux...
+	# Install separately so we can update user on progress separately, also this
+	# means we can run as the user and thus not write root owned files!
+	NO_DONE=y DONT_INSTALL=y sudo -E -u $SUDO_USER kerndev-build
 
-echo Installing modules into image...
-NO_DONE=y kerndev-install
+	echo Installing modules into image...
+	NO_DONE=y kerndev-install
+fi
 
 pop
 

kerndev-create.chroot.sh

@@ -8,7 +8,8 @@ CONSOLE_COLS=${CONSOLE_COLS:-80}
 
 # Passed by calling script.
 username=$1 # == $SUDO_USER
-password=$2 # Optional, if not provided script will prompt.
+uid=$2      # The user ID associated with $username so we can sync bindmount.
+password=$3 # Optional, if not provided script will prompt.
 
 # Functions.
 
@@ -44,6 +45,8 @@ echo "nohook resolv.conf" >> /etc/dhcpcd.conf
 # No delay for incorrect password reattempt. Pet peeve!
 sed -i 's/try_first_pass/try_first_pass nodelay/' /etc/pam.d/system-auth
 echo tux > /etc/hostname
+# Set up directory for kernel source bindmount.
+mkdir -p /src/kernel
 
 # Now get the packages we want.
 echo Installing packages...
@@ -62,7 +65,7 @@ else
 fi
 
 echo Setting up user $username with auto-login...
-useradd -m $username -G wheel >&/dev/null || true
+useradd -m $username -u $uid -G wheel >&/dev/null || true
 passwd -d $username >/dev/null
 echo "%wheel ALL=(ALL) ALL" >> /etc/sudoers
 mkdir -p /etc/systemd/system/serial-getty@ttyS0.service.d
@@ -89,6 +92,8 @@ EOF
 chmod +x /usr/bin/leave
 mv /.ssh /home/$username/
 chown -R $username:$username /home/$username/.ssh
+chown -R $username:$username /src
+echo "kernel /src/kernel 9p trans=virtio,version=9p2000.L 0 0" >> /etc/fstab
 
 echo Configuring zsh...
 
@@ -107,6 +112,11 @@ chsh -s /usr/bin/zsh $username >/dev/null
 cat >>$user_zshrc <<EOF
 stty icrnl
 stty rows $CONSOLE_ROWS cols $CONSOLE_COLS
+
+# The bindmounted kernel source chokes on fancy git plugin. Stub it out.
+git_custom_status() {
+}
+
 EOF
 chown $username:$username $user_zshrc
 

kerndev-run

@@ -104,6 +104,8 @@ esac
 
 # '-echr 0x02' moves escape key to C-b to avoid C-a getting nerfed.
 shared_opts="-nographic -s -echr 0x02"
+# We expose the kernel source as a 9p bindmount to /src/kernel in the guest.
+shared_opts+=" -virtfs local,path=$LINUX_DEV_PATH,mount_tag=kernel,security_model=mapped,id=kernel"
 # Can add the latter in case heavier log output is required -> console.
 shared_append="root=/dev/vda rw earlyprintk=ttyS0 nokaslr no_hash_pointers loglevel=2" #loglevel=7 systemd.journald.forward_to_console=1"