linux-kernel - Re: [PATCH v3] moduleparam: Save information about built-in modules in separate file

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Message-ID: <20190429142156.GA31567@linux-8ccs>
Date:   Mon, 29 Apr 2019 16:21:56 +0200
From:   Jessica Yu <jeyu@...nel.org>
To:     Alexey Gladkov <gladkov.alexey@...il.com>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        linux-api@...r.kernel.org, linux-modules@...r.kernel.org,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Gleb Fotengauer-Malinovskiy <glebfm@...linux.org>,
        "Dmitry V. Levin" <ldv@...linux.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rusty Russell <rusty@...tcorp.com.au>,
        Lucas De Marchi <lucas.de.marchi@...il.com>
Subject: Re: [PATCH v3] moduleparam: Save information about built-in modules
 in separate file

+++ Alexey Gladkov [29/04/19 11:08 +0200]:
>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.
>
>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.
>
>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.
>
>Proposal:
>
>The proposed patch does not remove .modinfo section with module
>information from the vmlinux at the build time and saves it into a
>separate file after kernel linking. So, the kernel does not increase in
>size and no additional information remains in it. Information is stored
>in the same format as in the separate modules (null-terminated string
>array). Because the .modinfo section is already exported with a separate
>modules, we are not creating a new API.
>
>It can be easily read in the userspace:
>
>$ tr '\0' '\n' < kernel.builtin

s/kernel.builtin/modules.builtin.modinfo/

Otherwise, for module.h and moduleparam.h:

Acked-by: Jessica Yu <jeyu@...nel.org>

And it would be great if Lucas can confirm if the file format and name
would be OK for kmod.

Thanks!

Jessica