Demi Marie Obenour <demiobenour@gmail.com> writes:

> This is the same as 14483e1a690c (img/app: add /dev/fd and /dev/std*),
> but for the host and for vm/sys/net.  While only Spectrum-provided code
> should run in these VMs, third-party dependencies of Spectrum might
> assume these links exist, and them being missing could cause severe
> bugs.  For instance, code writing to /dev/stdout could create a file in
> /dev rather than actually writing to stdout.
>
> In the host, the links are added in the initramfs.  Since /dev is
> created by the kernel and moved (via mount --move) from the initramfs to
> the main system, adding the links in the main system is not necessary
> and in fact would fail.
>
> Also reorder the moving of /sys, /proc, and /dev from the initramfs to
> the root filesystem to minimize the time that /dev and /proc are not
> mounted.  /proc is considered more important than /dev.
>
> Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>

This is really two independent patches in one as well.

> ---
>  host/initramfs/etc/init                      | 7 ++++++-
>  vm/sys/net/etc/s6-linux-init/scripts/rc.init | 5 +++++
>  2 files changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/host/initramfs/etc/init b/host/initramfs/etc/init
> index 719488741b6d31564c2c17c0e41f15d16b1c0a08..b72108ab96630e2a846063551772b0b29ca27bdf 100755
> --- a/host/initramfs/etc/init
> +++ b/host/initramfs/etc/init
> @@ -6,6 +6,11 @@ export PATH /bin
>  
>  if { mount -a }
>  
> +if { ln -s /proc/self/fd /dev }
> +if { ln -s /proc/self/fd/0 /dev/stdin }
> +if { ln -s /proc/self/fd/1 /dev/stdout }
> +if { ln -s /proc/self/fd/2 /dev/stderr }
> +

Would prefer to do this in host/rootfs, in the interest of not creating
more implicit requirements on initramfs in that system.  initramfs is
deterministic enough that it's vanishingly unlikely we'll find that it
requires these only sometimes.

>  piperw 3 4
>  if { fdmove 1 4 /etc/getuuids }
>  fdclose 4
> @@ -45,9 +50,9 @@ background { rm /dev/rootfs /dev/verity }
>  if { mount /dev/mapper/root-verity /mnt/root }
>  wait { $mdevd_pid }
>  
> -if { mount --move /proc /mnt/root/proc }
>  if { mount --move /sys /mnt/root/sys }
>  if { mount --move /dev /mnt/root/dev }
> +if { mount --move /proc /mnt/root/proc }

I don't understand this.  There are no other processes running, so how
could the order possibly matter?  There's nothing to race against.

>  
>  switch_root /mnt/root
>  /etc/init
> diff --git a/vm/sys/net/etc/s6-linux-init/scripts/rc.init b/vm/sys/net/etc/s6-linux-init/scripts/rc.init
> index 1016d0c62bc6103bc9e865a389f5d482ef6c2b76..eaf037ec123afcaeafced93096c4f35c2388f385 100755
> --- a/vm/sys/net/etc/s6-linux-init/scripts/rc.init
> +++ b/vm/sys/net/etc/s6-linux-init/scripts/rc.init
> @@ -2,6 +2,11 @@
>  # SPDX-License-Identifier: EUPL-1.2+
>  # SPDX-FileCopyrightText: 2020-2022 Alyssa Ross <hi@alyssa.is>
>  
> +if { ln -s /proc/self/fd /dev }
> +if { ln -s /proc/self/fd/0 /dev/stdin }
> +if { ln -s /proc/self/fd/1 /dev/stdout }
> +if { ln -s /proc/self/fd/2 /dev/stderr }
> +
>  if { s6-rc-init -c /etc/s6-rc /run/service }
>  
>  if { mkdir -p /dev/pts /dev/shm }
>
> -- 
> 2.51.0