linux-kernel - [PATCH v3 0/2] Kbuild: lto: add make version checking for MODVERSIONS

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Message-ID: <20210702032943.7865-1-lecopzer.chen@mediatek.com>
Date:   Fri, 2 Jul 2021 11:29:41 +0800
From:   Lecopzer Chen <lecopzer.chen@...iatek.com>
To:     <ndesaulniers@...gle.com>, <keescook@...omium.org>,
        <samitolvanen@...gle.com>, <linux-kbuild@...r.kernel.org>,
        <nathan@...nel.org>
CC:     <clang-built-linux@...glegroups.com>,
        <linux-kernel@...r.kernel.org>, <yj.chiang@...iatek.com>,
        <masahiroy@...nel.org>, <michal.lkml@...kovi.net>,
        Lecopzer Chen <lecopzer.chen@...iatek.com>
Subject: [PATCH v3 0/2] Kbuild: lto: add make version checking for MODVERSIONS

LTO with MODVERSIONS will fail in generating correct CRC because
the makefile rule doesn't work for make with version 3.8X.

Refer to [1]:
> When building modules(CONFIG_...=m), I found some of module versions
> are incorrect and set to 0.
> This can be found in build log for first clean build which shows

> WARNING: EXPORT symbol "XXXX" [drivers/XXX/XXX.ko] version generation failed,
> symbol will not be versioned.

> But in second build(incremental build), the WARNING disappeared and the
> module version becomes valid CRC and make someone who want to change
> modules without updating kernel image can't insert their modules.

> The problematic code is
> + $(foreach n, $(filter-out FORCE,$^),        \
> +   $(if $(wildcard $(n).symversions),      \
> +     ; cat $(n).symversions >> $@...mversions))

The issue is fixed when make version upgrading to 4.2.

Thus we need to check make version during selecting on LTO Kconfig.
Add CONFIG_MAKE_VERSION which means MAKE_VERSION in canonical digits
for arithmetic comparisons.

[1] https://lore.kernel.org/lkml/20210616080252.32046-1-lecopzer.chen@mediatek.com/
Signed-off-by: Lecopzer Chen <lecopzer.chen@...iatek.com>


----
v3:
- fix comment in make-version.sh

v2:
https://lore.kernel.org/lkml/20210701092841.1419-1-lecopzer.chen@mediatek.com/
- change MAKE_VERSION_INT to MAKE_VERSION
- remove $(make-version)
- tweak commit message

v1:
https://lore.kernel.org/lkml/20210630121436.19581-1-lecopzer.chen@mediatek.com/
----


Lecopzer Chen (2):
  Kbuild: lto: add CONFIG_MAKE_VERSION
  Kbuild: lto: add make version checking

 Makefile                |  2 +-
 arch/Kconfig            |  1 +
 init/Kconfig            |  4 ++++
 scripts/make-version.sh | 13 +++++++++++++
 4 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100755 scripts/make-version.sh

-- 
2.18.0