forked from DGNum/liminix
why we decided not to depend on kexec
This commit is contained in:
Daniel Barlow
parent
f9f4d97bb8
commit
f45326b9d3
1 changed files with 117 additions and 1 deletions
118
THOUGHTS.txt
118
THOUGHTS.txt
|
|
@ -2913,7 +2913,6 @@ ourselves somehow which seems silly when qemu already does it
|
|||
- we don't have any way to do a tftpboot ubifs
|
||||
- ext4 doesn't care
|
||||
|
||||
|
||||
3) the rootfstype needs thought.
|
||||
|
||||
- for all but squashfs it implies an initramfs
|
||||
|
|
@ -2955,3 +2954,120 @@ is that the turris output is a directory with a symlink to the
|
|||
tarball and an informative README containing the instructions.
|
||||
Although we also want the instructions in the manual where people
|
||||
can read them before building anything.
|
||||
|
||||
Fri Nov 10 21:27:50 GMT 2023
|
||||
|
||||
Realising now that outputs and installers aren't the same thing.
|
||||
|
||||
e.g. flashimage can be installed from u-boot or from kexecboot
|
||||
|
||||
perhaps we distinguish between the
|
||||
|
||||
"installation image":
|
||||
- firmware.bin
|
||||
- tarball
|
||||
- ubifs image
|
||||
- kernel + rootfs
|
||||
|
||||
and "installer"
|
||||
- kexecboot script
|
||||
- u-boot script to flash squashfs image
|
||||
|
||||
Sun Nov 12 17:17:30 GMT 2023
|
||||
|
||||
What TODO?
|
||||
|
||||
- "does the kernel live on the filesystem" depends on the bootloader
|
||||
not the filesystem
|
||||
- could we implement this with a module that adds to config.filesystem ?
|
||||
it would depend on whether the bootloader can follow symlinks to
|
||||
files not in /boot (probably fine unless crossing filesystems)
|
||||
- the other question is how much futzing around in u-boot can/do we do
|
||||
to tell u-boot how to boot? for grown-up u-boot it's not a
|
||||
problem as we can saveenv but are there broken u-boots that would
|
||||
prevent this?
|
||||
|
||||
- kexecboot is unloved and documented in the wrong place. do we have a
|
||||
test for it even?
|
||||
- it won't work on aarch64 because it needs memmap=
|
||||
- hardcodes memory size, which we should probably work out dynamically
|
||||
|
||||
- how to put device name into the device docs
|
||||
maybe devices
|
||||
|
||||
- make config.boot.commandLine a single string
|
||||
- finish omnia
|
||||
- for installation on turris omnia we need tarball not ext4 image
|
||||
(but keep the ext4 image anyway for tftpboot and possibly kexecboot)
|
||||
[done] - now we have lim.parseInt should we use it consistently?
|
||||
- usefulness tiers for devices ("stable", "experimental", "wip")
|
||||
- params for ubi(fs) are a mess
|
||||
- create an l2tp configuration
|
||||
- iperf and tuning
|
||||
- wlan country code
|
||||
|
||||
|
||||
Fri Nov 17 17:30:39 GMT 2023
|
||||
|
||||
kexec is fraught. I spent some time trying (unsuccesfully) to get a
|
||||
kexecboot test running, but it doesn't work in qemu for the reason
|
||||
that the kernel I built for qemu has SMP support but does not have
|
||||
kexec_nonboot_cpu_func() - which is the needed function to stop
|
||||
non-boot CPUs before jumping into the new kernel. That this code is
|
||||
all MIPS-specific (I have to assume that other architectures have
|
||||
entirely different ways to stop non-boot CPUs?) is a bit worrisome: how
|
||||
many other ways is kexec hardware-dependent?
|
||||
|
||||
We have two scenarios where we may want to use it:
|
||||
|
||||
1) the "installer": e.g. for UBI platforms, we want to plonk
|
||||
a new ubifs on the device without clobbering the erase counters, which
|
||||
means either doing it from U-Boot - needs serial connection -
|
||||
or doing it from a Linux of some kind that is not running on the
|
||||
filesystem we're toasting.
|
||||
|
||||
2) reinstalling after the initial install - this is a big deal for
|
||||
squashfs where there is no other way to change data, and an only slightly
|
||||
smaller deal for jffs2, where there isn't much room to change much
|
||||
data.
|
||||
|
||||
Maybe instead of kexec we could do this by stopping services and then
|
||||
pivot_root into a ramfs. We would, I assume, need to stop any processes
|
||||
that have open files on the root fs, but we would need to have network
|
||||
interfaces running. So we need a subset of services that run in recovery:
|
||||
can make this a bundle
|
||||
|
||||
* mount a ramfs
|
||||
* copy the closure of the bundle into the ramfs
|
||||
* stop all processes (including init?)
|
||||
|
||||
sending pid 1 a signal FOO will cause it to run .s6-svscan/SIGFOO
|
||||
|
||||
Fri Nov 17 23:53:43 GMT 2023
|
||||
|
||||
So we need to extend .s6-svscan/finish to
|
||||
|
||||
if test -e /maintenance/bin/init
|
||||
cd /maintenance
|
||||
mount --bind /maintenance/ /
|
||||
chroot .
|
||||
exec /bin/init -D maintenance
|
||||
fi
|
||||
|
||||
|
||||
foreground {
|
||||
if { test -e /maintenance/bin/init }
|
||||
cd /maintenance
|
||||
foreground { mount --move /maintenance/ / }
|
||||
foreground { chroot . }
|
||||
redirfd -r 0 /dev/console
|
||||
redirfd -w 1 /dev/console
|
||||
fdmove -c 2 1
|
||||
emptyenv /bin/init -D maintenance
|
||||
}
|
||||
${s6-linux-init}/bin/s6-linux-init-hpr -fr
|
||||
|
||||
|
||||
|
||||
|
||||
https://openwrt.org/docs/techref/sysupgrade
|
||||
|
|
|
|||
Loading…
Reference in a new issue