Re: [PATCH 09/27] irqchip: remove MODULE_LICENSE in non-modules

On Mon, Feb 27, 2023 at 01:24:31PM +0000, Nick Alcock wrote:

On 24 Feb 2023, Luis Chamberlain spake thusly:

quoted

Modules that are compiled in should succeed with a modprobe call as its
already loaded. The construct we're looking for is a way to detect
things which are built-in but *could* be modules. The annotation today
is done at build time for something built-in using a file path using
modinfo.

All of the module macros which peg .modinfo section information for
built-in code can be extracted from vmlinux using objcopy -j .modinfo, and
that's exactly how modules.builtin.modinfo is built:

objcopy -j .modinfo -O binary vmlinux.o modules.builtin.modinfo

From this we grep out the "file:" and sed it with a ^kernel prefix.
You can look at the commit 8b41fc4454e ("kbuild: create modules.builtin
without Makefile.modbuiltin or tristate.conf") which did that.

If a module is built-in then MODULE_FILE() is used we and we add a
MODULE_INFO(file, KBUILD_MODFILE), and so the modinfo exists for the
"file:" tag for it. At build time we sed for all those with a kernel prefix
to build the modules.builtin file. That file is used by modprobe to tell
us "yes your module is loaded as its built-in".

So the thing we wish to not have present is when built-in code is being
compiled but *cannot possibly* be module, and we have no way to verify that.

So one way to go about this is to simply *not* use the MODULE_LICENSE()
which cannot possibly be modules so to simplfy the build process.

I do wonder if I should drop this excellent description (up to the place
where you start musing on alternatives) into the cover letters for the
remaining two tranches in this series, to forestall further confusion.
Any objection? (I doubt it, but it seems right to ask.)

Cover letters die, commit logs don't. So use it either as part of the
commit log or refer to this thread on the commit log. You can also try
to condense / paraphrase my description somehow too.

  Luis