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SubjectRe: [PATCH] modules: add modalias file to sysfs for modules.
When i get the modinfo for usbhid, there are no aliases listed:
```
localhost ~ # modinfo usbhid
name: usbhid
filename: (builtin)
author: Andreas Gal
author: Vojtech Pavlik
author: Jiri Kosina
description: USB HID core driver
file: drivers/hid/usbhid/usbhid
license: GPL
parm: quirks:Add/modify USB HID quirks by specifying
quirks=vendorID:productID:quirks where vendorID, productID, and quirks
are all in 0x-prefixed hex (array of charp)
parm: ignoreled:Autosuspend with active leds (uint)
parm: kbpoll:Polling interval of keyboards (uint)
parm: jspoll:Polling interval of joysticks (uint)
parm: mousepoll:Polling interval of mice (uint)
```

bluetooth however has an alias listed:
```
localhost ~ # modinfo bluetooth
filename:
/lib/modules/5.10.154-20424-gea7532c123d8/kernel/net/bluetooth/bluetooth.ko.gz
author: Marcel Holtmann <marcel@holtmann.org>
description: Bluetooth Core ver 2.22
version: 2.22
license: GPL
alias: net-pf-31
vermagic: 5.10.154-20424-gea7532c123d8 SMP preempt mod_unload
name: bluetooth
intree: Y
retpoline: Y
depends: ecdh_generic
srcversion: F8E46CD048C50B0AA1CD471
parm: disable_esco:Disable eSCO connection creation (bool)
parm: enable_ecred:Enable enhanced credit flow control mode (bool)
parm: disable_ertm:Disable enhanced retransmission mode (bool)
```

I believe the reason for this is many modules use `#define
MODULE_DEVICE_TABLE(type, name)` which is a noop for buildin modules.
I have a local patch that resolves that issue here:
See: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/3840672/1/include/linux/module.h#b246

However, I probably ought to rework that patch to create the
MODULE_ALIAS defines instead of the buildin.alias file.

On Tue, Nov 15, 2022 at 11:35 AM Luis Chamberlain <mcgrof@kernel.org> wrote:
>
> On Tue, Nov 15, 2022 at 10:05:35AM -0600, Allen Webb wrote:
> > On Mon, Nov 14, 2022 at 11:22 AM Lucas De Marchi
> > <lucas.demarchi@intel.com> wrote:
> > >
> > > On Mon, Nov 14, 2022 at 10:42:50AM -0600, Allen Webb wrote:
> > > >On Fri, Nov 11, 2022 at 12:29 PM Luis Chamberlain <mcgrof@kernel.org> wrote:
> > > >>
> > > >> On Fri, Nov 11, 2022 at 09:28:52AM -0600, Allen Webb wrote:
> > > >> > USB devices support the authorized attribute which can be used by
> > > >> > user-space to implement trust-based systems for enabling USB devices. It
> > > >> > would be helpful when building these systems to be able to know in
> > > >> > advance which kernel drivers (or modules) are reachable from a
> > > >> > particular USB device.
> > > >> >
> > > >> > This information is readily available for external modules in
> > > >> > modules.alias. However, builtin kernel modules are not covered. This
> > > >> > patch adds a sys-fs attribute to both builtin and loaded modules
> > > >> > exposing the matching rules in the modalias format for integration
> > > >> > with tools like USBGuard.
> > > >> >
> > > >> > Signed-off-by: Allen Webb <allenwebb@google.com>
> > > >>
> > > >> Thanks for the patch Allen!
> > > >>
> > > >> I'd rather have something generic though, and it would seem kmod [0] already
> > > >> does this, have you seen the kmod support for builtin.alias.bin
> > > >>
> > > >> Can't that be used?
> > > >
> > > >Probably, but I don't see the builtin.alias.bin in my build. Is it experimental?
> > >
> > > no. That is generated by depmod since v27 using modules.builtin.modinfo
> > > generated by the kernel build system. Highly recommend v30 though
> > > as there were fixes in v28 and v29 and some changes to speed up its
> > > generation/use in v30: See entries mentioning
> > > builtin.alias and bultin.modinfo in
> > > https://git.kernel.org/pub/scm/utils/kernel/kmod/kmod.git/tree/NEWS
> > >
> > > libkmod/modprobe/modinfo also have the corresponding changes to lookup that
> > > index when resolving aliases.
> >
> > I see the file but it is largely missing the aliases I am interested
> > in, so it looks like I might need to modify my patch that creates
> > buildin.alias to add the missing alias defines in the header along
> > with the other module metadata for builtin modules. Does this sound
> > right to you?
>
> Can you clarify what is missing and why? And an RFC is welcomed if it
> helps demonstrates what you mean.
>
> Luis

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