Re: [RFC] Provide in-kernel headers for making it easy to extend the kernel

From: hpa
Date: Mon Jan 21 2019 - 03:02:55 EST

On January 20, 2019 8:10:03 AM PST, Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote:
>On Sat, Jan 19, 2019 at 11:01:13PM -0800, hpa@xxxxxxxxx wrote:
>> On January 19, 2019 2:36:06 AM PST, Greg KH
><gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>> >On Sat, Jan 19, 2019 at 02:28:00AM -0800, Christoph Hellwig wrote:
>> >> This seems like a pretty horrible idea and waste of kernel memory.
>> >
>> >It's only a waste if you want it to be a waste, i.e. if you load the
>> >kernel module.
>> >
>> >This really isn't any different from how /proc/config.gz works.
>> >
>> >> Just add support to kbuild to store a compressed archive in
>> >> and unpack it in the right place.
>> >
>> >I think the issue is that some devices do not use initramfs, or
>> >away from it after init happens or something like that. Joel has
>> >of
>> >the looney details that he can provide.
>> >
>> >thanks,
>> >
>> >greg k-h
>> Yeah, well... but it is kind of a losing game... the more in-kernel
>stuff there is the less smiley are things to actually be supported.
>It is better than nothing, and if this makes things a bit easier and
>real-world issues people have been having, and is optional, then I
>don't see
>why not.
>> Modularizing is it in some ways even crazier in the sense that at
>that point you are relying on the filesystem containing the module,
>which has to be loaded into the kernel by a root user. One could even
>wonder if a better way to do this would be to have "make
>modules_install" park an archive file â or even a directory as opposed
>to a symlink â with this stuff in /lib/modules. We could even provide a
>tmpfs shim which autoloads such an archive via the firmware loader;
>this might even be generically useful, who knows.
>All this seems to assume where the modules are located. In Android, we
>have /lib/modules. This patch generically fits into the grand scheme
>and I think is just better made a part of the kernel since it is not
>huge once compressed, as Dan also pointed. The more complex, and the
>assumptions we make, the less likely people writing tools will get it
>and be able to easily use it.
>> Note also that initramfs contents can be built into the kernel.
>Extracting such content into a single-instance tmpfs would again be a
>Such an approach would bloat the kernel image size though, which may
>not work
>for everyone. The module based approach, on the other hand, gives an
>to the user to enable the feature, but not have it loaded into memory
>or used
>until it is really needed.
> - Joel

Well, where are the modules? They must exist in the filesystem.
Sent from my Android device with K-9 Mail. Please excuse my brevity.