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

[PATCH v3 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>


----
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

[PATCH v3 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..3a451db3c067
--- /dev/null
+++ b/scripts/make-version.sh
@@ -0,0 +1,13 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Print the GNU make 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 v3 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

Re: [PATCH v3 1/2] Kbuild: lto: add CONFIG_MAKE_VERSION

[Nathan Chancellor]

On Fri, Jul 02, 2021 at 11:29:42AM +0800, Lecopzer Chen wrote:
> 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>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  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..3a451db3c067
> --- /dev/null
> +++ b/scripts/make-version.sh
> @@ -0,0 +1,13 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Print the GNU make 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

Re: [PATCH v3 2/2] Kbuild: lto: add make version checking

[Nathan Chancellor]

On Fri, Jul 02, 2021 at 11:29:43AM +0800, Lecopzer Chen wrote:
> 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>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
>  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

Re: [PATCH v3 1/2] Kbuild: lto: add CONFIG_MAKE_VERSION

[Masahiro Yamada]

On Fri, Jul 2, 2021 at 12:29 PM Lecopzer Chen
<lecopzer.chen@mediatek.com> wrote:
>
> 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>
> ---


NACK.

"Let's add MAKE_VERSION >= 40200 restriction
just because I cannot write correct code that
works for older Make" is a horrible idea.

Also, Kconfig is supposed to check the compiler
(or toolchains) capability, not host tool versions.







>  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..3a451db3c067
> --- /dev/null
> +++ b/scripts/make-version.sh
> @@ -0,0 +1,13 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0
> +#
> +# Print the GNU make 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
>


--
Best Regards
Masahiro Yamada

Re: [PATCH v3 2/2] Kbuild: lto: add make version checking

[Masahiro Yamada]

On Fri, Jul 2, 2021 at 12:29 PM Lecopzer Chen
<lecopzer.chen@mediatek.com> wrote:
>
> 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>
> ---

NACK for the same reason as 1/2.

We need to write correct code.
If we cannot, we need to add 'depends on BROKEN'.




>  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
>


-- 
Best Regards
Masahiro Yamada

Re: [PATCH v3 1/2] Kbuild: lto: add CONFIG_MAKE_VERSION

[Sami Tolvanen]

On Sun, Jul 4, 2021 at 7:03 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Fri, Jul 2, 2021 at 12:29 PM Lecopzer Chen
> <lecopzer.chen@mediatek.com> wrote:
> >
> > 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>
> > ---
>
>
> NACK.
>
> "Let's add MAKE_VERSION >= 40200 restriction
> just because I cannot write correct code that
> works for older Make" is a horrible idea.
>
> Also, Kconfig is supposed to check the compiler
> (or toolchains) capability, not host tool versions.

I feel like requiring a Make that's half a decade old for a feature
that also requires a toolchain released last October ago isn't
entirely unreasonable.

That being said, if Masahiro prefers not to rely on the wildcard
function's behavior here, which is a reasonable request, we could
simply use the shell to test for the file's existence:

diff --git a/scripts/Makefile.build b/scripts/Makefile.build
index 34d257653fb4..c6bd62f518ff 100644
--- a/scripts/Makefile.build
+++ b/scripts/Makefile.build
@@ -388,7 +388,7 @@ ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
       cmd_update_lto_symversions =                                     \
        rm -f $@.symversions                                            \
        $(foreach n, $(filter-out FORCE,$^),                            \
-               $(if $(wildcard $(n).symversions),                      \
+               $(if $(shell test -s $(n).symversions && echo y),       \
                        ; cat $(n).symversions >> $@.symversions))
 else
       cmd_update_lto_symversions = echo >/dev/null

This is not quite as efficient as using wildcard, but should work with
older Make versions too. Thoughts?

Sami

Re: [PATCH v3 1/2] Kbuild: lto: add CONFIG_MAKE_VERSION

[Lecopzer Chen]

> On Sun, Jul 4, 2021 at 7:03 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > On Fri, Jul 2, 2021 at 12:29 PM Lecopzer Chen
> > <lecopzer.chen@mediatek.com> wrote:
> > >
> > > 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>
> > > ---
> >
> >
> > NACK.
> >
> > "Let's add MAKE_VERSION >= 40200 restriction
> > just because I cannot write correct code that
> > works for older Make" is a horrible idea.
> >
> > Also, Kconfig is supposed to check the compiler
> > (or toolchains) capability, not host tool versions.
> 
> I feel like requiring a Make that's half a decade old for a feature
> that also requires a toolchain released last October ago isn't
> entirely unreasonable.
> 
> That being said, if Masahiro prefers not to rely on the wildcard
> function's behavior here, which is a reasonable request, we could
> simply use the shell to test for the file's existence:
> 
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index 34d257653fb4..c6bd62f518ff 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -388,7 +388,7 @@ ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
>        cmd_update_lto_symversions =                                     \
>         rm -f $@.symversions                                            \
>         $(foreach n, $(filter-out FORCE,$^),                            \
> -               $(if $(wildcard $(n).symversions),                      \
> +               $(if $(shell test -s $(n).symversions && echo y),       \
>                         ; cat $(n).symversions >> $@.symversions))
>  else
>        cmd_update_lto_symversions = echo >/dev/null
> 
> This is not quite as efficient as using wildcard, but should work with
> older Make versions too. Thoughts?
> 


I've tested this in both make-4.3 and 3.81, and the CRC is correct.
But I'm not sure if anyone would have the "arg list too long" issue.

Tested-by: Lecopzer Chen <lecopzer.chen@mediatek.com>

Re: [PATCH v3 1/2] Kbuild: lto: add CONFIG_MAKE_VERSION

[Sami Tolvanen]

On Tue, Jul 6, 2021 at 2:06 AM Lecopzer Chen <lecopzer.chen@mediatek.com> wrote:
>
> > On Sun, Jul 4, 2021 at 7:03 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
> > >
> > > On Fri, Jul 2, 2021 at 12:29 PM Lecopzer Chen
> > > <lecopzer.chen@mediatek.com> wrote:
> > > >
> > > > 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>
> > > > ---
> > >
> > >
> > > NACK.
> > >
> > > "Let's add MAKE_VERSION >= 40200 restriction
> > > just because I cannot write correct code that
> > > works for older Make" is a horrible idea.
> > >
> > > Also, Kconfig is supposed to check the compiler
> > > (or toolchains) capability, not host tool versions.
> >
> > I feel like requiring a Make that's half a decade old for a feature
> > that also requires a toolchain released last October ago isn't
> > entirely unreasonable.
> >
> > That being said, if Masahiro prefers not to rely on the wildcard
> > function's behavior here, which is a reasonable request, we could
> > simply use the shell to test for the file's existence:
> >
> > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > index 34d257653fb4..c6bd62f518ff 100644
> > --- a/scripts/Makefile.build
> > +++ b/scripts/Makefile.build
> > @@ -388,7 +388,7 @@ ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
> >        cmd_update_lto_symversions =                                     \
> >         rm -f $@.symversions                                            \
> >         $(foreach n, $(filter-out FORCE,$^),                            \
> > -               $(if $(wildcard $(n).symversions),                      \
> > +               $(if $(shell test -s $(n).symversions && echo y),       \
> >                         ; cat $(n).symversions >> $@.symversions))
> >  else
> >        cmd_update_lto_symversions = echo >/dev/null
> >
> > This is not quite as efficient as using wildcard, but should work with
> > older Make versions too. Thoughts?
> >
>
>
> I've tested this in both make-4.3 and 3.81, and the CRC is correct.
> But I'm not sure if anyone would have the "arg list too long" issue.
>
> Tested-by: Lecopzer Chen <lecopzer.chen@mediatek.com>

Thank you for testing. This should produce a command identical to the
wildcard version (with newer Make versions), so that shouldn't be an
issue. If nobody objects to this approach, would you mind putting this
into a proper patch and sending it as v4?

Sami

Re: [PATCH v3 1/2] Kbuild: lto: add CONFIG_MAKE_VERSION

[Lecopzer Chen]

> On Tue, Jul 6, 2021 at 2:06 AM Lecopzer Chen <lecopzer.chen@mediatek.com> wrote:
> >
> > > On Sun, Jul 4, 2021 at 7:03 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
> > > >
> > > > On Fri, Jul 2, 2021 at 12:29 PM Lecopzer Chen
> > > > <lecopzer.chen@mediatek.com> wrote:
> > > > >
> > > > > 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>
> > > > > ---
> > > >
> > > >
> > > > NACK.
> > > >
> > > > "Let's add MAKE_VERSION >= 40200 restriction
> > > > just because I cannot write correct code that
> > > > works for older Make" is a horrible idea.
> > > >
> > > > Also, Kconfig is supposed to check the compiler
> > > > (or toolchains) capability, not host tool versions.
> > >
> > > I feel like requiring a Make that's half a decade old for a feature
> > > that also requires a toolchain released last October ago isn't
> > > entirely unreasonable.
> > >
> > > That being said, if Masahiro prefers not to rely on the wildcard
> > > function's behavior here, which is a reasonable request, we could
> > > simply use the shell to test for the file's existence:
> > >
> > > diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> > > index 34d257653fb4..c6bd62f518ff 100644
> > > --- a/scripts/Makefile.build
> > > +++ b/scripts/Makefile.build
> > > @@ -388,7 +388,7 @@ ifeq ($(CONFIG_LTO_CLANG) $(CONFIG_MODVERSIONS),y y)
> > >        cmd_update_lto_symversions =                                     \
> > >         rm -f $@.symversions                                            \
> > >         $(foreach n, $(filter-out FORCE,$^),                            \
> > > -               $(if $(wildcard $(n).symversions),                      \
> > > +               $(if $(shell test -s $(n).symversions && echo y),       \
> > >                         ; cat $(n).symversions >> $@.symversions))
> > >  else
> > >        cmd_update_lto_symversions = echo >/dev/null
> > >
> > > This is not quite as efficient as using wildcard, but should work with
> > > older Make versions too. Thoughts?
> > >
> >
> >
> > I've tested this in both make-4.3 and 3.81, and the CRC is correct.
> > But I'm not sure if anyone would have the "arg list too long" issue.
> >
> > Tested-by: Lecopzer Chen <lecopzer.chen@mediatek.com>
> 
> Thank you for testing. This should produce a command identical to the
> wildcard version (with newer Make versions), so that shouldn't be an
> issue. If nobody objects to this approach, would you mind putting this
> into a proper patch and sending it as v4?

Sure, I'll rebase the whole commit and send as v4 soon.