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Message-ID: <CABYd82bVo4+M18dZ1d2x6e6-_o8YMs50v-VV_Z_DUr2vdRb-Bg@mail.gmail.com>
Date: Thu, 7 Jan 2021 16:30:25 -0800
From: Will McVicker <willmcvicker@...gle.com>
To: Jessica Yu <jeyu@...nel.org>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Christoph Hellwig <hch@...radead.org>,
Saravana Kannan <saravanak@...gle.com>,
linux-kernel@...r.kernel.org, linux-kbuild@...r.kernel.org,
kernel-team@...roid.com
Subject: Re: [PATCH v4] modules: introduce the MODULE_SCMVERSION config
Hi Jessica,
I looked into the LOCALVERSION= part more and finally figured out how
that part of the script works. I wasn't familiar with how the
parameter substitution worked -- ${parameter:+alt_value}. I verified
that we will only get an SCM version returned when LOCALVERSION_AUTO=y
and updated the Documentation in v5.
Thanks,
Will
On Thu, Jan 7, 2021 at 6:31 AM Jessica Yu <jeyu@...nel.org> wrote:
>
> +++ Will McVicker [06/01/21 10:44 -0800]:
> >Thanks for the vacation notice Jessica! I'm just letting you know I'm
> >back as well and am happy to respond to any concerns regarding v4 when
> >you get all caught up.
> >
> >I hope you had a relaxing holiday :)
>
> Hi Will - thanks, same to you!
>
> >On Fri, Dec 18, 2020 at 4:01 AM Jessica Yu <jeyu@...nel.org> wrote:
> >>
> >> +++ Will McVicker [16/12/20 22:08 +0000]:
> >> >Config MODULE_SCMVERSION introduces a new module attribute --
> >> >`scmversion` -- which can be used to identify a given module's SCM
> >> >version. This is very useful for developers that update their kernel
> >> >independently from their kernel modules or vice-versa since the SCM
> >> >version provided by UTS_RELEASE (`uname -r`) will now differ from the
> >> >module's vermagic attribute.
> >> >
> >> >For example, we have a CI setup that tests new kernel changes on the
> >> >hikey960 and db845c devices without updating their kernel modules. When
> >> >these tests fail, we need to be able to identify the exact device
> >> >configuration the test was using. By including MODULE_SCMVERSION, we can
> >> >identify the exact kernel and modules' SCM versions for debugging the
> >> >failures.
> >> >
> >> >Additionally, by exposing the SCM version via the sysfs node
> >> >/sys/module/MODULENAME/scmversion, one can also verify the SCM versions
> >> >of the modules loaded from the initramfs. Currently, modinfo can only
> >> >retrieve module attributes from the module's ko on disk and not from the
> >> >actual module that is loaded in RAM.
> >> >
> >> >You can retrieve the SCM version in two ways,
> >> >
> >> >1) By using modinfo:
> >> > > modinfo -F scmversion MODULENAME
> >> >2) By module sysfs node:
> >> > > cat /sys/module/MODULENAME/scmversion
> >> >
> >> >Signed-off-by: Will McVicker <willmcvicker@...gle.com>
> >> >---
> [ added back diff ]
> >> >Changelog since v3:
> >> >- Dropped [PATCH v2 1/2] scripts/setlocalversion: allow running in a subdir
> >> >
> >> > Documentation/ABI/stable/sysfs-module | 18 ++++++++++++++++++
> >> > include/linux/module.h | 1 +
> >> > init/Kconfig | 12 ++++++++++++
> >> > kernel/module.c | 2 ++
> >> > scripts/Makefile.modpost | 22 ++++++++++++++++++++++
> >> > scripts/mod/modpost.c | 24 +++++++++++++++++++++++-
> >> > 6 files changed, 78 insertions(+), 1 deletion(-)
> >> >
> >> >diff --git a/Documentation/ABI/stable/sysfs-module b/Documentation/ABI/stable/sysfs-module
> >> >index 6272ae5fb366..2ba731767737 100644
> >> >--- a/Documentation/ABI/stable/sysfs-module
> >> >+++ b/Documentation/ABI/stable/sysfs-module
> >> >@@ -32,3 +32,21 @@ Description:
> >> > Note: If the module is built into the kernel, or if the
> >> > CONFIG_MODULE_UNLOAD kernel configuration value is not enabled,
> >> > this file will not be present.
> >> >+
> >> >+What: /sys/module/MODULENAME/scmversion
> >> >+Date: November 2020
> >> >+KernelVersion: 5.11
>
> I guess we'll have to bump KernelVersion now (sorry about the timing!)
>
> >> >+Contact: Will McVicker <willmcvicker@...gle.com>
> >> >+Description: This read-only file will appear if modpost was supplied with an
> >> >+ SCM version for the module. It can be enabled with the config
> >> >+ MODULE_SCMVERSION. The SCM version is retrieved by
> >> >+ scripts/setlocalversion, which means that the presence of this
> >> >+ file depends on CONFIG_LOCALVERSION_AUTO=y or LOCALVERSION=.
>
> I think the "or LOCALVERSION=" part is inaccurate, right? We need
> just LOCALVERSION_AUTO for the full scm string for this to work.
>
> >> >+ When read, the SCM version that the module was compiled with is
> >> >+ returned. The SCM version is returned in the following format::
> >> >+
> >> >+ ===
> >> >+ Git: g[a-f0-9]\+(-dirty)\?
> >> >+ Mercurial: hg[a-f0-9]\+(-dirty)\?
> >> >+ Subversion: svn[0-9]\+
> >> >+ ===
> >> >diff --git a/include/linux/module.h b/include/linux/module.h
> >> >index c4e7a887f469..6bd710308863 100644
> >> >--- a/include/linux/module.h
> >> >+++ b/include/linux/module.h
> >> >@@ -372,6 +372,7 @@ struct module {
> >> > struct module_attribute *modinfo_attrs;
> >> > const char *version;
> >> > const char *srcversion;
> >> >+ const char *scmversion;
> >> > struct kobject *holders_dir;
> >> >
> >> > /* Exported symbols */
> >> >diff --git a/init/Kconfig b/init/Kconfig
> >> >index b77c60f8b963..d9ae12f16ba2 100644
> >> >--- a/init/Kconfig
> >> >+++ b/init/Kconfig
> >> >@@ -2131,6 +2131,18 @@ config MODULE_SRCVERSION_ALL
> >> > the version). With this option, such a "srcversion" field
> >> > will be created for all modules. If unsure, say N.
> >> >
> >> >+config MODULE_SCMVERSION
> >> >+ bool "SCM version for modules"
> >> >+ depends on LOCALVERSION_AUTO
> >> >+ help
> >> >+ This enables the module attribute "scmversion" which can be used
> >> >+ by developers to identify the SCM version of a given module, e.g.
> >> >+ git sha1 or hg sha1. The SCM version can be queried by modinfo or
> >> >+ via the sysfs node: /sys/modules/MODULENAME/scmversion. This is
> >> >+ useful when the kernel or kernel modules are updated separately
> >> >+ since that causes the vermagic of the kernel and the module to
> >> >+ differ.
>
> Since I consider this a debug/developer option, let's add a "If
> unsure, say N." at the end of this, similar to the other
> module options.
>
> Thanks!
>
> Jessica
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