On Wed, Mar 27, 2019 at 04:40:25PM +0100, Jessica Yu wrote: > +++ Alexey Gladkov [26/03/19 18:24 +0100]: > >On Fri, Mar 22, 2019 at 02:34:12PM +0900, Masahiro Yamada wrote: > >> Hi. > >> > >> (added some people to CC) > > (Thanks Masahiro for the CC!) > > >> > >> On Fri, Mar 15, 2019 at 7:10 PM Alexey Gladkov <gladkov.alexey@xxxxxxxxx> wrote: > >> > > >> > Problem: > >> > > >> > When a kernel module is compiled as a separate module, some important > >> > information about the kernel module is available via .modinfo section of > >> > the module. In contrast, when the kernel module is compiled into the > >> > kernel, that information is not available. > >> > >> > >> I might be missing something, but > >> vmlinux provides info of builtin modules > >> in /sys/module/. > > > >No. There are definitely not all modules. I have a builtin sha256_generic, > >but I can't find him in the /sys/module. > > Yeah, you'll only find builtin modules under /sys/module/ if it has any module > parameters, otherwise you won't find it there. As Masahiro already mentioned, > if a builtin module has any parameters, they would be accessible under /sys/module/. > > >> (Looks like currently only module_param and MODULE_VERSION) > >> > >> This patch is not exactly the same, but I see a kind of overwrap. > >> I'd like to be sure if we want this new scheme. > > > >The /sys/module is only for running kernel. One of my use cases is > >to create an initrd for a new kernel. > > > >> > >> > Information about built-in modules is necessary in the following cases: > >> > > >> > 1. When it is necessary to find out what additional parameters can be > >> > passed to the kernel at boot time. > >> > >> > >> Actually, /sys/module/<module>/parameters/ > >> exposes this information. > >> > >> Doesn't it work for your purpose? > > > >No, since creating an initrd needs to know all the modalias before > >I get the sysfs for new kernel. Also there are no modalias at all. > > > >> > 2. When you need to know which module names and their aliases are in > >> > the kernel. This is very useful for creating an initrd image. > >> > > > Hm, I do see one possible additional use-case for preserving module alias > information for built-in modules - modprobe will currently error (I think, > correct me if I'm wrong) if we try invoking modprobe with an alias of a > built-in module, simply because this information is not in modules.builtin or > modules.alias. Yes. Patch for modprobe in my todo list. The reason I didn’t do it was because I wasn’t sure that the file format was final. > Since kbuild already outputs modules.builtin, I would suggest outputting > something like a modules.builtin.alias file (and I guess maybe a modules.builtin.param > file too if that's deemed useful), in a format that is consumable by kmod/modprobe, > so that modprobing an alias of a built-in module doesn't produce an error. I > think this should be easy to do if we keep and parse the resulting .modinfo for > builtin modules. This is just an idea, opinions welcome. I've added Lucas to CC > in case he has any thoughts. You don't like kernel.builtin.modinfo ? It is much easier to create and it has almost the same format as the modules. So I think it will be easier to parse in kmod. -- Rgrds, legion
