linux-kernel - Re: [PATCH v3 2/6] modules: Add macros to specify modinfo prefix

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Message-ID: <aEarYndP4uo-a0eL@example.org>
Date: Mon, 9 Jun 2025 11:37:38 +0200
From: Alexey Gladkov <legion@...nel.org>
To: Masahiro Yamada <masahiroy@...nel.org>
Cc: Petr Pavlu <petr.pavlu@...e.com>, Luis Chamberlain <mcgrof@...nel.org>,
	Sami Tolvanen <samitolvanen@...gle.com>,
	Daniel Gomez <da.gomez@...sung.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	linux-kernel@...r.kernel.org, linux-modules@...r.kernel.org,
	linux-kbuild@...r.kernel.org
Subject: Re: [PATCH v3 2/6] modules: Add macros to specify modinfo prefix

On Mon, Jun 02, 2025 at 04:49:24PM +0900, Masahiro Yamada wrote:
> On Tue, May 27, 2025 at 6:08 PM Alexey Gladkov <legion@...nel.org> wrote:
> >
> > The __MODULE_INFO macros always use __MODULE_INFO_PREFIX. The only way
> > to use a different prefix is to override __MODULE_INFO_PREFIX, which is
> > not very useful.
> 
> Not necessarily.
> This would be a very special case only used in modpost,
> and modpost can use MODULE_INFO() instead.
> 
> 
>         list_for_each_entry_safe(alias, next, &mod->aliases, node) {
> -               buf_printf(&buf, "MODULE_ALIAS_MODNAME(\"%s\", \"%s\");\n",
> +               buf_printf(&buf, "MODULE_INFO(\"%s\".alias, \"%s\");\n",
>                            alias->builtin_modname, alias->str);
>                 list_del(&alias->node);
>                 free(alias->builtin_modname);

You can't do that because a character can't contain quotation marks
and periods.

.vmlinux.export.c:16163:17: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘.’ token
16163 | MODULE_INFO(ahci.alias, "pci:v*d*sv*sd*bc01sc06i01*");
      |                 ^
././include/linux/compiler_types.h:83:23: note: in definition of macro ‘___PASTE’
   83 | #define ___PASTE(a,b) a##b
      |                       ^

The same thing for variant with quotes:

.vmlinux.export.c:16163:13: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before string constant
16163 | MODULE_INFO("ahci".alias, "pci:v*d*sv*sd*bc01sc06i01*");
      |             ^~~~~~

But I can do something like this to make it work:

	buf_printf(&buf,
		   "#undef __MODULE_INFO_PREFIX\n"
		   "#define __MODULE_INFO_PREFIX\n");

	list_for_each_entry_safe(alias, next, &mod->aliases, node) {
		buf_printf(&buf, "__MODULE_INFO(%s.alias, unused, \"%s\");\n",
			   alias->builtin_modname, alias->str);

> 
> > The new macro will be used in file2alias.c to generate modalias for
> > builtin modules.
> >
> > Signed-off-by: Alexey Gladkov <legion@...nel.org>
> > Reviewed-by: Petr Pavlu <petr.pavlu@...e.com>
> > ---
> >  include/linux/module.h      | 3 +++
> >  include/linux/moduleparam.h | 7 +++++--
> >  2 files changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/linux/module.h b/include/linux/module.h
> > index 8050f77c3b64..88048561360f 100644
> > --- a/include/linux/module.h
> > +++ b/include/linux/module.h
> > @@ -170,6 +170,9 @@ struct module_kobject *lookup_or_create_module_kobject(const char *name);
> >  /* For userspace: you can also call me... */
> >  #define MODULE_ALIAS(_alias) MODULE_INFO(alias, _alias)
> >
> > +#define MODULE_ALIAS_MODNAME(_modname, _alias) \
> > +       __MODULE_INFO_WITH_PREFIX(_modname ".", alias, alias, _alias)
> > +
> >  /* Soft module dependencies. See man modprobe.d for details.
> >   * Example: MODULE_SOFTDEP("pre: module-foo module-bar post: module-baz")
> >   */
> > diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
> > index bfb85fd13e1f..3f819fc67c43 100644
> > --- a/include/linux/moduleparam.h
> > +++ b/include/linux/moduleparam.h
> > @@ -20,10 +20,13 @@
> >  /* Chosen so that structs with an unsigned long line up. */
> >  #define MAX_PARAM_PREFIX_LEN (64 - sizeof(unsigned long))
> >
> > -#define __MODULE_INFO(tag, name, info)                                   \
> > +#define __MODULE_INFO_WITH_PREFIX(prefix, tag, name, info)               \
> >         static const char __UNIQUE_ID(name)[]                             \
> >                 __used __section(".modinfo") __aligned(1)                 \
> > -               = __MODULE_INFO_PREFIX __stringify(tag) "=" info
> > +               = prefix __stringify(tag) "=" info
> > +
> > +#define __MODULE_INFO(tag, name, info)                                   \
> > +       __MODULE_INFO_WITH_PREFIX(__MODULE_INFO_PREFIX, tag, name, info)
> >
> >  #define __MODULE_PARM_TYPE(name, _type)                                          \
> >         __MODULE_INFO(parmtype, name##type, #name ":" _type)
> > --
> > 2.49.0
> >
> 
> 
> -- 
> Best Regards
> Masahiro Yamada
> 

-- 
Rgrds, legion