openwrt ag71xx as module

This commit is contained in:
Daniel Barlow 2022-10-15 16:28:19 +01:00
parent 7d1c85f680
commit fa31d00d6a

View file

@ -346,3 +346,58 @@ For Liminix we're not going to do that.
Sat Oct 8 11:23:08 BST 2022
"halt" and "reboot" don't work on gl-ar750
Sat Oct 8 13:10:00 BST 2022
Where do we go with this ar750?
- wired networking
- wifi
Sun Oct 9 09:57:35 BST 2022
We want to be able to package kernel modules as regular derivations, so that
they get added to the filesystem
This means they need access to kernel.modulesupport
This means kernel.modulesupport needs to be in pkgs too?
This is fine, probably, but we'd like to avoid closing over vmlinux because
there's no need for it to be in the filesystem
Mon Oct 10 22:57:23 BST 2022
The problem is that kernel kconfig options are manipulated in the
liminix modules, which means that data must be (transitively) available
to modules, so they can't be regular packages as they're tied so tightly
to the exact config. Unless we define a second overlay that references
the configuration object, but my head hurts when I start to think about that
so maybe not.
Tue Oct 11 00:00:13 BST 2022
Building ag71xx (ethernet driver) as a module doesn't work because
it references a symbol ath79_pll_base in the kernel that hasn't been
marked with EXPORT_SYMBOL.
We could forge an object file that "declares" it with a gross and disgusting hack like this
$ echo > empty # not actually "empty", objcopy complains about that
$ grep ath79_pll_base /nix/store/jcc114cd13xa8aa4mil35rlnmxnlmv09-vmlinux-mips-unknown-linux-musl-modulesupport/System.map
ffffffff807b2094 B ath79_pll_base
$ mips-unknown-linux-musl-objcopy -I binary -O elf32-big --add-section .bss=empty --add-symbol ath79_pll_base=.bss:0x807b2094 empty f.o
I don't claim this is a good idea, just an idea. Thought was that we would not
have to declare its type this way. Also it might not work with kaslr
https://stackoverflow.com/a/68903503
Backstory: why are we trying to build this as a module? because the
openwrt fork of it seems to be a bit more advanced than the mainline,
and I *suspect* that the mainline version doesn't work with our
openwrt-based device tree which ahs the mdio as a nested node inside
the ag71xx node - in mainline the driver seems to have all the mdio
stuff inline. So, could we build the openwrt driver without patching
the crap out of our kernel