From fa31d00d6ac40eeeef1ec7565bfc3e27a6b4a443 Mon Sep 17 00:00:00 2001 From: Daniel Barlow Date: Sat, 15 Oct 2022 16:28:19 +0100 Subject: [PATCH] openwrt ag71xx as module --- THOUGHTS.txt | 55 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) diff --git a/THOUGHTS.txt b/THOUGHTS.txt index e324561a..6eaf3e71 100644 --- a/THOUGHTS.txt +++ b/THOUGHTS.txt @@ -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