[PATCH v2 0/2] Kbuild: lto: add make version checking for MODVERSIONS

[PATCH v2 0/2] Kbuild: lto: add make version checking for MODVERSIONS

[Lecopzer Chen]

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 >> $@.symversions))

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@mediatek.com>


----
v2:
- 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

[PATCH v2 1/2] [PATCH 1/2] Kbuild: lto: add CONFIG_MAKE_VERSION

[Lecopzer Chen]

To check the GNU make version. Used by the LTO Kconfig.

LTO with MODVERSIONS will fail in generating correct CRC because
the makefile rule doesn't work for make with version 3.8X.[1]

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@mediatek.com>
---
 Makefile                |  2 +-
 init/Kconfig            |  4 ++++
 scripts/make-version.sh | 13 +++++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)
 create mode 100755 scripts/make-version.sh

diff --git a/Makefile b/Makefile
index 88888fff4c62..2402745b2ba9 100644
--- a/Makefile
+++ b/Makefile
@@ -516,7 +516,7 @@ CLANG_FLAGS :=
 
 export ARCH SRCARCH CONFIG_SHELL BASH HOSTCC KBUILD_HOSTCFLAGS CROSS_COMPILE LD CC
 export CPP AR NM STRIP OBJCOPY OBJDUMP READELF PAHOLE RESOLVE_BTFIDS LEX YACC AWK INSTALLKERNEL
-export PERL PYTHON3 CHECK CHECKFLAGS MAKE UTS_MACHINE HOSTCXX
+export PERL PYTHON3 CHECK CHECKFLAGS MAKE MAKE_VERSION UTS_MACHINE HOSTCXX
 export KGZIP KBZIP2 KLZOP LZMA LZ4 XZ ZSTD
 export KBUILD_HOSTCXXFLAGS KBUILD_HOSTLDFLAGS KBUILD_HOSTLDLIBS LDFLAGS_MODULE
 
diff --git a/init/Kconfig b/init/Kconfig
index 55f9f7738ebb..ecc110504f87 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -86,6 +86,10 @@ config CC_HAS_ASM_INLINE
 config CC_HAS_NO_PROFILE_FN_ATTR
 	def_bool $(success,echo '__attribute__((no_profile_instrument_function)) int x();' | $(CC) -x c - -c -o /dev/null -Werror)
 
+config MAKE_VERSION
+	int
+	default $(shell,$(srctree)/scripts/make-version.sh $(MAKE_VERSION))
+
 config CONSTRUCTORS
 	bool
 
diff --git a/scripts/make-version.sh b/scripts/make-version.sh
new file mode 100755
index 000000000000..ce5af96696cc
--- /dev/null
+++ b/scripts/make-version.sh
@@ -0,0 +1,13 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Print the linker name and its version in a 5 or 6-digit form.
+
+set -e
+
+# Convert the version string x.y.z to a canonical 5 or 6-digit form.
+IFS=.
+set -- $1
+
+# If the 2nd or 3rd field is missing, fill it with a zero.
+echo $((10000 * $1 + 100 * ${2:-0} + ${3:-0}))
-- 
2.18.0

[PATCH v2 2/2] Kbuild: lto: add make version checking

[Lecopzer Chen]

LTO with MODVERSIONS will fail in generating correct CRC because
the makefile rule doesn't work for make with version 3.8X.[1]

Thus we need to check make version during selecting on LTO Kconfig.
and the suitable version should be 4.2(40200) which released in 2016[2].

[1] https://lore.kernel.org/lkml/20210616080252.32046-1-lecopzer.chen@mediatek.com/
[2] https://ftp.gnu.org/gnu/make/
Signed-off-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
---
 arch/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/Kconfig b/arch/Kconfig
index 129df498a8e1..beee68149da8 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -639,6 +639,7 @@ config HAS_LTO_CLANG
 	def_bool y
 	# Clang >= 11: https://github.com/ClangBuiltLinux/linux/issues/510
 	depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
+	depends on !MODVERSIONS || MAKE_VERSION >= 40200
 	depends on $(success,$(NM) --help | head -n 1 | grep -qi llvm)
 	depends on $(success,$(AR) --help | head -n 1 | grep -qi llvm)
 	depends on ARCH_SUPPORTS_LTO_CLANG
-- 
2.18.0