[v1] Add generated modalias to modules.builtin.modinfo

[PATCH v1 0/7] Add generated modalias to modules.builtin.modinfo

Posted by Alexey Gladkov 9 months, 2 weeks ago

The modules.builtin.modinfo file is used by userspace (kmod to be specific) to
get information about builtin modules. Among other information about the module,
information about module aliases is stored. This is very important to determine
that a particular modalias will be handled by a module that is inside the
kernel.

There are several mechanisms for creating modalias for modules:

The first is to explicitly specify the MODULE_ALIAS of the macro. In this case,
the aliases go into the '.modinfo' section of the module if it is compiled
separately or into vmlinux.o if it is builtin into the kernel.

The second is the use of MODULE_DEVICE_TABLE followed by the use of the
modpost utility. In this case, vmlinux.o no longer has this information and
does not get it into modules.builtin.modinfo.

For example:

$ modinfo pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30
modinfo: ERROR: Module pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30 not found.

$ modinfo xhci_pci
name:           xhci_pci
filename:       (builtin)
license:        GPL
file:           drivers/usb/host/xhci-pci
description:    xHCI PCI Host Controller Driver

The builtin module is missing alias "pci:v*d*sv*sd*bc0Csc03i30*" which will be
generated by modpost if the module is built separately.

To fix this it is necessary to add the generated by modpost modalias to
modules.builtin.modinfo.

Fortunately modpost already generates .vmlinux.export.c for exported symbols. It
is possible to use this file to create a '.modinfo' section for builtin modules.
The modules.builtin.modinfo file becomes a composite file. One part is extracted
from vmlinux.o, the other part from .vmlinux.export.o.


Alexey Gladkov (7):
  mfd: stmpe-spi: Correct the name used in MODULE_DEVICE_TABLE
  scsi: Define MODULE_DEVICE_TABLE only if necessary
  modules: Add macros to specify modinfo prefix
  modpost: Make mod_device_table aliases more unique
  modpost: Create modalias for builtin modules
  kbuild: Move modules.builtin.modinfo to another makefile
  kbuild: Create modules.builtin.modinfo for modpost results

 drivers/mfd/stmpe-spi.c     |  2 +-
 drivers/scsi/BusLogic.c     |  2 +-
 include/linux/module.h      | 21 +++++++++++-----
 include/linux/moduleparam.h |  7 ++++--
 scripts/Makefile.vmlinux    | 50 +++++++++++++++++++++++++++++++++++++
 scripts/Makefile.vmlinux_o  | 26 +------------------
 scripts/mod/file2alias.c    | 31 +++++++++++++++++++----
 scripts/mod/modpost.c       | 21 +++++++++++++---
 scripts/mod/modpost.h       |  7 +++++-
 9 files changed, 123 insertions(+), 44 deletions(-)

-- 
2.49.0

[PATCH v2 0/6] Add generated modalias to modules.builtin.modinfo

Posted by Alexey Gladkov 9 months, 1 week ago

The modules.builtin.modinfo file is used by userspace (kmod to be specific) to
get information about builtin modules. Among other information about the module,
information about module aliases is stored. This is very important to determine
that a particular modalias will be handled by a module that is inside the
kernel.

There are several mechanisms for creating modalias for modules:

The first is to explicitly specify the MODULE_ALIAS of the macro. In this case,
the aliases go into the '.modinfo' section of the module if it is compiled
separately or into vmlinux.o if it is builtin into the kernel.

The second is the use of MODULE_DEVICE_TABLE followed by the use of the
modpost utility. In this case, vmlinux.o no longer has this information and
does not get it into modules.builtin.modinfo.

For example:

$ modinfo pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30
modinfo: ERROR: Module pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30 not found.

$ modinfo xhci_pci
name:           xhci_pci
filename:       (builtin)
license:        GPL
file:           drivers/usb/host/xhci-pci
description:    xHCI PCI Host Controller Driver

The builtin module is missing alias "pci:v*d*sv*sd*bc0Csc03i30*" which will be
generated by modpost if the module is built separately.

To fix this it is necessary to add the generated by modpost modalias to
modules.builtin.modinfo.

Fortunately modpost already generates .vmlinux.export.c for exported symbols. It
is possible to use this file to create a '.modinfo' section for builtin modules.
The modules.builtin.modinfo file becomes a composite file. One part is extracted
from vmlinux.o, the other part from .vmlinux.export.o.

Notes:
- v2:
  * Drop patch for mfd because it was already applied and is in linux-next.
  * The generation of aliases for builtin modules has been redone as
    suggested by Masahiro Yamada.
  * Rebase to v6.15-rc5-136-g9c69f8884904
  * v1: https://lore.kernel.org/all/cover.1745591072.git.legion@kernel.org/

Alexey Gladkov (6):
  scsi: Define MODULE_DEVICE_TABLE only if necessary
  modules: Add macros to specify modinfo prefix
  modpost: Make mod_device_table aliases more unique
  modpost: Create modalias for builtin modules
  kbuild: Move modules.builtin.modinfo to another makefile
  kbuild: Create modules.builtin.modinfo for modpost results

 drivers/scsi/BusLogic.c     |  2 +-
 include/linux/module.h      | 21 +++++++++++-----
 include/linux/moduleparam.h |  7 ++++--
 scripts/Makefile.vmlinux    | 50 +++++++++++++++++++++++++++++++++++++
 scripts/Makefile.vmlinux_o  | 26 +------------------
 scripts/mod/file2alias.c    | 34 ++++++++++++++++++++++---
 scripts/mod/modpost.c       | 13 +++++++++-
 scripts/mod/modpost.h       |  2 ++
 8 files changed, 116 insertions(+), 39 deletions(-)

-- 
2.49.0

Re: [PATCH v1 0/7] Add generated modalias to modules.builtin.modinfo

Posted by Petr Pavlu 9 months, 2 weeks ago

On 4/26/25 18:16, Alexey Gladkov wrote:
> The modules.builtin.modinfo file is used by userspace (kmod to be specific) to
> get information about builtin modules. Among other information about the module,
> information about module aliases is stored. This is very important to determine
> that a particular modalias will be handled by a module that is inside the
> kernel.
> 
> There are several mechanisms for creating modalias for modules:
> 
> The first is to explicitly specify the MODULE_ALIAS of the macro. In this case,
> the aliases go into the '.modinfo' section of the module if it is compiled
> separately or into vmlinux.o if it is builtin into the kernel.
> 
> The second is the use of MODULE_DEVICE_TABLE followed by the use of the
> modpost utility. In this case, vmlinux.o no longer has this information and
> does not get it into modules.builtin.modinfo.
> 
> For example:
> 
> $ modinfo pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30
> modinfo: ERROR: Module pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30 not found.
> 
> $ modinfo xhci_pci
> name:           xhci_pci
> filename:       (builtin)
> license:        GPL
> file:           drivers/usb/host/xhci-pci
> description:    xHCI PCI Host Controller Driver
> 
> The builtin module is missing alias "pci:v*d*sv*sd*bc0Csc03i30*" which will be
> generated by modpost if the module is built separately.

Could you explain what is currently broken because the device-table
alias information isn't available? I think adding this information is
reasonable, both for consistency and so kmod can display accurate
information, but is there more that I'm missing?

-- 
Thanks,
Petr

Re: [PATCH v1 0/7] Add generated modalias to modules.builtin.modinfo

Posted by Alexey Gladkov 9 months, 2 weeks ago

On Mon, Apr 28, 2025 at 03:47:06PM +0200, Petr Pavlu wrote:
> On 4/26/25 18:16, Alexey Gladkov wrote:
> > The modules.builtin.modinfo file is used by userspace (kmod to be specific) to
> > get information about builtin modules. Among other information about the module,
> > information about module aliases is stored. This is very important to determine
> > that a particular modalias will be handled by a module that is inside the
> > kernel.
> > 
> > There are several mechanisms for creating modalias for modules:
> > 
> > The first is to explicitly specify the MODULE_ALIAS of the macro. In this case,
> > the aliases go into the '.modinfo' section of the module if it is compiled
> > separately or into vmlinux.o if it is builtin into the kernel.
> > 
> > The second is the use of MODULE_DEVICE_TABLE followed by the use of the
> > modpost utility. In this case, vmlinux.o no longer has this information and
> > does not get it into modules.builtin.modinfo.
> > 
> > For example:
> > 
> > $ modinfo pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30
> > modinfo: ERROR: Module pci:v00008086d0000A36Dsv00001043sd00008694bc0Csc03i30 not found.
> > 
> > $ modinfo xhci_pci
> > name:           xhci_pci
> > filename:       (builtin)
> > license:        GPL
> > file:           drivers/usb/host/xhci-pci
> > description:    xHCI PCI Host Controller Driver
> > 
> > The builtin module is missing alias "pci:v*d*sv*sd*bc0Csc03i30*" which will be
> > generated by modpost if the module is built separately.
> 
> Could you explain what is currently broken because the device-table
> alias information isn't available? I think adding this information is
> reasonable, both for consistency and so kmod can display accurate
> information, but is there more that I'm missing?

Yes. Right now, aliases that are generated by modpost are not available
for kmod because it's not in the modules.builtin.modinfo.

-- 
Rgrds, legion