[PATCH v2 1/3] kbuild: collect minimum tool versions into scripts/min-tool-version.sh

[PATCH v2 1/3] kbuild: collect minimum tool versions into scripts/min-tool-version.sh

[Masahiro Yamada]

The kernel build uses various tools, many of which are provided by the
same software suite, for example, LLVM and Binutils.

When you raise the minimum version of Clang/LLVM, you need to update
clang_min_version in scripts/cc-version.sh and also lld_min_version in
scripts/ld-version.sh.

Kbuild can handle CC=clang and LD=ld.lld independently, but it does not
make much sense to maintain their versions separately.

Let's create a central place of minimum tool versions so you do not need
to touch multiple files. scripts/min-tool-version.sh prints the minimum
version of the given tool.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
Acked-by: Miguel Ojeda <ojeda@kernel.org>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
---

Changes in v2:
  - Use case ... esac

 scripts/cc-version.sh       | 20 +++++--------------
 scripts/ld-version.sh       | 11 ++++-------
 scripts/min-tool-version.sh | 39 +++++++++++++++++++++++++++++++++++++
 3 files changed, 48 insertions(+), 22 deletions(-)
 create mode 100755 scripts/min-tool-version.sh

diff --git a/scripts/cc-version.sh b/scripts/cc-version.sh
index 3f2ee885b116..f1952c522466 100755
--- a/scripts/cc-version.sh
+++ b/scripts/cc-version.sh
@@ -6,18 +6,6 @@
 
 set -e
 
-# When you raise the minimum compiler version, please update
-# Documentation/process/changes.rst as well.
-gcc_min_version=4.9.0
-clang_min_version=10.0.1
-icc_min_version=16.0.3 # temporary
-
-# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63293
-# https://lore.kernel.org/r/20210107111841.GN1551@shell.armlinux.org.uk
-if [ "$SRCARCH" = arm64 ]; then
-	gcc_min_version=5.1.0
-fi
-
 # Print the compiler name and some version components.
 get_compiler_info()
 {
@@ -48,18 +36,20 @@ set -- $(get_compiler_info "$@")
 
 name=$1
 
+min_tool_version=$(dirname $0)/min-tool-version.sh
+
 case "$name" in
 GCC)
 	version=$2.$3.$4
-	min_version=$gcc_min_version
+	min_version=$($min_tool_version gcc)
 	;;
 Clang)
 	version=$2.$3.$4
-	min_version=$clang_min_version
+	min_version=$($min_tool_version llvm)
 	;;
 ICC)
 	version=$(($2 / 100)).$(($2 % 100)).$3
-	min_version=$icc_min_version
+	min_version=$($min_tool_version icc)
 	;;
 *)
 	echo "$orig_args: unknown compiler" >&2
diff --git a/scripts/ld-version.sh b/scripts/ld-version.sh
index 1bf3aadde9de..a78b804b680c 100755
--- a/scripts/ld-version.sh
+++ b/scripts/ld-version.sh
@@ -6,11 +6,6 @@
 
 set -e
 
-# When you raise the minimum linker version, please update
-# Documentation/process/changes.rst as well.
-bfd_min_version=2.23.0
-lld_min_version=10.0.1
-
 # Convert the version string x.y.z to a canonical 5 or 6-digit form.
 get_canonical_version()
 {
@@ -35,10 +30,12 @@ set -- $(LC_ALL=C "$@" --version)
 IFS=' '
 set -- $1
 
+min_tool_version=$(dirname $0)/min-tool-version.sh
+
 if [ "$1" = GNU -a "$2" = ld ]; then
 	shift $(($# - 1))
 	version=$1
-	min_version=$bfd_min_version
+	min_version=$($min_tool_version binutils)
 	name=BFD
 	disp_name="GNU ld"
 elif [ "$1" = GNU -a "$2" = gold ]; then
@@ -51,7 +48,7 @@ else
 
 	if [ "$1" = LLD ]; then
 		version=$2
-		min_version=$lld_min_version
+		min_version=$($min_tool_version llvm)
 		name=LLD
 		disp_name=LLD
 	else
diff --git a/scripts/min-tool-version.sh b/scripts/min-tool-version.sh
new file mode 100755
index 000000000000..d22cf91212b0
--- /dev/null
+++ b/scripts/min-tool-version.sh
@@ -0,0 +1,39 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Print the minimum supported version of the given tool.
+# When you raise the minimum version, please update
+# Documentation/process/changes.rst as well.
+
+set -e
+
+if [ $# != 1 ]; then
+	echo "Usage: $0 toolname" >&2
+	exit 1
+fi
+
+case "$1" in
+binutils)
+	echo 2.23.0
+	;;
+gcc)
+	# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63293
+	# https://lore.kernel.org/r/20210107111841.GN1551@shell.armlinux.org.uk
+	if [ "$SRCARCH" = arm64 ]; then
+		echo 5.1.0
+	else
+		echo 4.9.0
+	fi
+	;;
+icc)
+	# temporary
+	echo 16.0.3
+	;;
+llvm)
+	echo 10.0.1
+	;;
+*)
+	echo "$1: unknown tool" >&2
+	exit 1
+	;;
+esac
-- 
2.27.0

[PATCH v2 2/3] kbuild: check the minimum assembler version in Kconfig

[Masahiro Yamada]

Documentation/process/changes.rst defines the minimum assembler version
(binutils version), but we have never checked it in the build time.

Kbuild never invokes 'as' directly because all assembly files in the
kernel tree are *.S, hence must be preprocessed. I do not expect
raw assembly source files (*.s) would be added to the kernel tree.

Therefore, we always use $(CC) as the assembler driver, and commit
aa824e0c962b ("kbuild: remove AS variable") removed 'AS'. However,
we are still interested in the version of the assembler acting behind.

As usual, the --version option prints the version string.

  $ as --version | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

But, we do not have $(AS). So, we can add the -Wa prefix so that
$(CC) passes --version down to the backing assembler.

  $ gcc -Wa,--version | head -n 1
  gcc: fatal error: no input files
  compilation terminated.

OK, we need to input something to satisfy gcc.

  $ gcc -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

The combination of Clang and GNU assembler works in the same way:

  $ clang -no-integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  GNU assembler (GNU Binutils for Ubuntu) 2.35.1

Clang with the integrated assembler fails like this:

  $ clang -integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
  clang: error: unsupported argument '--version' to option 'Wa,'

For the last case, checking the error message is fragile. If the
proposal for -Wa,--version support [1] is accepted, this may not be
even an error in the future.

One easy way is to check if -integrated-as is present in the passed
arguments. We did not pass -integrated-as to CLANG_FLAGS before, but
we can make it explicit.

Nathan pointed out -integrated-as is the default for all of the
architectures/targets that the kernel cares about, but it goes
along with "explicit is better than implicit" policy. [2]

With all this in my mind, I implemented scripts/as-version.sh to
check the assembler version in Kconfig time.

  $ scripts/as-version.sh gcc
  GNU 23501
  $ scripts/as-version.sh clang -no-integrated-as
  GNU 23501
  $ scripts/as-version.sh clang -integrated-as
  LLVM 0

[1]: https://github.com/ClangBuiltLinux/linux/issues/1320
[2]: https://lore.kernel.org/linux-kbuild/20210307044253.v3h47ucq6ng25iay@archlinux-ax161/

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

Changes in v2:
  - Check -integrated-as option instead of error message.
  - Add LC_ALL=C just in case.

  The Italian locale did not tweak the message from 'as --version'
  but we never know what would happen on locale.

  $ LC_MESSAGES=it_IT.UTF-8 ld --version | head -n 1
  ld di GNU (GNU Binutils for Debian) 2.35.2
  $ LC_MESSAGES=it_IT.UTF-8 as --version | head -n 1
  GNU assembler (GNU Binutils for Debian) 2.35.2

 Makefile                |  4 +-
 arch/Kconfig            |  3 +-
 init/Kconfig            | 12 ++++++
 scripts/Kconfig.include |  6 +++
 scripts/as-version.sh   | 82 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 104 insertions(+), 3 deletions(-)
 create mode 100755 scripts/as-version.sh

diff --git a/Makefile b/Makefile
index cc5b7e39fde4..2b161f5a5a66 100644
--- a/Makefile
+++ b/Makefile
@@ -580,7 +580,9 @@ ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
 ifneq ($(CROSS_COMPILE),)
 CLANG_FLAGS	+= --target=$(notdir $(CROSS_COMPILE:%-=%))
 endif
-ifneq ($(LLVM_IAS),1)
+ifeq ($(LLVM_IAS),1)
+CLANG_FLAGS	+= -integrated-as
+else
 CLANG_FLAGS	+= -no-integrated-as
 GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
 CLANG_FLAGS	+= --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
diff --git a/arch/Kconfig b/arch/Kconfig
index ecfd3520b676..555b4f09a9b2 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -631,8 +631,7 @@ config ARCH_SUPPORTS_LTO_CLANG_THIN
 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
-	depends on $(success,test $(LLVM_IAS) -eq 1)
+	depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
 	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
diff --git a/init/Kconfig b/init/Kconfig
index 5f5c776ef192..019c1874e609 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -41,6 +41,18 @@ config CLANG_VERSION
 	default $(cc-version) if CC_IS_CLANG
 	default 0
 
+config AS_IS_GNU
+	def_bool $(success,test "$(as-name)" = GNU)
+
+config AS_IS_LLVM
+	def_bool $(success,test "$(as-name)" = LLVM)
+
+config AS_VERSION
+	int
+	# Use clang version if this is the integrated assembler
+	default CLANG_VERSION if AS_IS_LLVM
+	default $(as-version)
+
 config LD_IS_BFD
 	def_bool $(success,test "$(ld-name)" = BFD)
 
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index 58fdb5308725..0496efd6e117 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -45,6 +45,12 @@ $(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this compiler is not su
 cc-name := $(shell,set -- $(cc-info) && echo $1)
 cc-version := $(shell,set -- $(cc-info) && echo $2)
 
+# Get the assembler name, version, and error out if it is not supported.
+as-info := $(shell,$(srctree)/scripts/as-version.sh $(CC) $(CLANG_FLAGS))
+$(error-if,$(success,test -z "$(as-info)"),Sorry$(comma) this assembler is not supported.)
+as-name := $(shell,set -- $(as-info) && echo $1)
+as-version := $(shell,set -- $(as-info) && echo $2)
+
 # Get the linker name, version, and error out if it is not supported.
 ld-info := $(shell,$(srctree)/scripts/ld-version.sh $(LD))
 $(error-if,$(success,test -z "$(ld-info)"),Sorry$(comma) this linker is not supported.)
diff --git a/scripts/as-version.sh b/scripts/as-version.sh
new file mode 100755
index 000000000000..953ff000bcbc
--- /dev/null
+++ b/scripts/as-version.sh
@@ -0,0 +1,82 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0-only
+#
+# Print the assembler name and its version in a 5 or 6-digit form.
+# Also, perform the minimum version check.
+# (If it is the integrated assembler, return 0 as the version, and
+# skip the version check.)
+
+set -e
+
+# Convert the version string x.y.z to a canonical 5 or 6-digit form.
+get_canonical_version()
+{
+	IFS=.
+	set -- $1
+
+	# If the 2nd or 3rd field is missing, fill it with a zero.
+	#
+	# The 4th field, if present, is ignored.
+	# This occurs in development snapshots as in 2.35.1.20201116
+	echo $((10000 * $1 + 100 * ${2:-0} + ${3:-0}))
+}
+
+# Clang failes to handle -Wa,--version fails unless -no-integrated-as is given.
+# We check -(f)integrated-as, expecting it is explicitly passed in for the
+# integrated assembler case.
+check_integrated_as()
+{
+	while [ $# -gt 0 ]; do
+		if [ "$1" = -integrated-as -o "$1" = -fintegrated-as ]; then
+			# For the intergrated assembler, we do not check the
+			# version here. It is the same as the clang version, and
+			# it has been already checked by scripts/cc-version.sh.
+			echo LLVM 0
+			exit 0
+		fi
+		shift
+	done
+}
+
+check_integrated_as "$@"
+
+orig_args="$@"
+
+# Get the first line of the --version output.
+IFS='
+'
+set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
+
+# Split the line on spaces.
+IFS=' '
+set -- $1
+
+min_tool_version=$(dirname $0)/min-tool-version.sh
+
+if [ "$1" = GNU -a "$2" = assembler ]; then
+	shift $(($# - 1))
+	version=$1
+	min_version=$($min_tool_version binutils)
+	name=GNU
+else
+	echo "$orig_args: unknown assembler invoked" >&2
+	exit 1
+fi
+
+# Some distributions append a package release number, as in 2.34-4.fc32
+# Trim the hyphen and any characters that follow.
+version=${version%-*}
+
+cversion=$(get_canonical_version $version)
+min_cversion=$(get_canonical_version $min_version)
+
+if [ "$cversion" -lt "$min_cversion" ]; then
+	echo >&2 "***"
+	echo >&2 "*** Assembler is too old."
+	echo >&2 "***   Your $name assembler version:    $version"
+	echo >&2 "***   Minimum $name assembler version: $min_version"
+	echo >&2 "***"
+	exit 1
+fi
+
+echo $name $cversion
-- 
2.27.0

[PATCH v2 3/3] kbuild: dwarf: use AS_VERSION instead of test_dwarf5_support.sh

[Masahiro Yamada]

The test code in scripts/test_dwarf5_support.sh is somewhat difficult
to understand, but after all, we want to check binutils >= 2.35.2

From the former discussion, the requirement for generating DWARF v5 from
C code is as follows:

 - gcc + gnu as          -> requires gcc 5.0+ (but 7.0+ for full support)
 - clang + gnu as        -> requires binutils 2.35.2+
 - clang + integrated as -> OK

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
---

Changes in v2:
  - fix typos
  - simplify the dependency expression

 lib/Kconfig.debug              | 3 +--
 scripts/test_dwarf5_support.sh | 8 --------
 2 files changed, 1 insertion(+), 10 deletions(-)
 delete mode 100755 scripts/test_dwarf5_support.sh

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index b479ae609a31..c85d5f7a1aeb 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -284,8 +284,7 @@ config DEBUG_INFO_DWARF4
 
 config DEBUG_INFO_DWARF5
 	bool "Generate DWARF Version 5 debuginfo"
-	depends on GCC_VERSION >= 50000 || CC_IS_CLANG
-	depends on CC_IS_GCC || $(success,$(srctree)/scripts/test_dwarf5_support.sh $(CC) $(CLANG_FLAGS))
+	depends on GCC_VERSION >= 50000 || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
 	depends on !DEBUG_INFO_BTF
 	help
 	  Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
diff --git a/scripts/test_dwarf5_support.sh b/scripts/test_dwarf5_support.sh
deleted file mode 100755
index c46e2456b47a..000000000000
--- a/scripts/test_dwarf5_support.sh
+++ /dev/null
@@ -1,8 +0,0 @@
-#!/bin/sh
-# SPDX-License-Identifier: GPL-2.0
-
-# Test that the assembler doesn't need -Wa,-gdwarf-5 when presented with DWARF
-# v5 input, such as `.file 0` and `md5 0x00`. Should be fixed in GNU binutils
-# 2.35.2. https://sourceware.org/bugzilla/show_bug.cgi?id=25611
-echo '.file 0 "filename" md5 0x7a0b65214090b6693bd1dc24dd248245' | \
-  $* -gdwarf-5 -Wno-unused-command-line-argument -c -x assembler -o /dev/null -
-- 
2.27.0

Re: [PATCH v2 3/3] kbuild: dwarf: use AS_VERSION instead of test_dwarf5_support.sh

[Nick Desaulniers]

On Mon, Mar 15, 2021 at 9:13 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> The test code in scripts/test_dwarf5_support.sh is somewhat difficult
> to understand, but after all, we want to check binutils >= 2.35.2
>
> From the former discussion, the requirement for generating DWARF v5 from
> C code is as follows:
>
>  - gcc + gnu as          -> requires gcc 5.0+ (but 7.0+ for full support)
>  - clang + gnu as        -> requires binutils 2.35.2+
>  - clang + integrated as -> OK
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>
> Changes in v2:
>   - fix typos
>   - simplify the dependency expression
>
>  lib/Kconfig.debug              | 3 +--
>  scripts/test_dwarf5_support.sh | 8 --------
>  2 files changed, 1 insertion(+), 10 deletions(-)
>  delete mode 100755 scripts/test_dwarf5_support.sh
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index b479ae609a31..c85d5f7a1aeb 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -284,8 +284,7 @@ config DEBUG_INFO_DWARF4
>
>  config DEBUG_INFO_DWARF5
>         bool "Generate DWARF Version 5 debuginfo"
> -       depends on GCC_VERSION >= 50000 || CC_IS_CLANG
> -       depends on CC_IS_GCC || $(success,$(srctree)/scripts/test_dwarf5_support.sh $(CC) $(CLANG_FLAGS))
> +       depends on GCC_VERSION >= 50000 || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
>         depends on !DEBUG_INFO_BTF
>         help
>           Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
> diff --git a/scripts/test_dwarf5_support.sh b/scripts/test_dwarf5_support.sh
> deleted file mode 100755
> index c46e2456b47a..000000000000
> --- a/scripts/test_dwarf5_support.sh
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -#!/bin/sh
> -# SPDX-License-Identifier: GPL-2.0
> -
> -# Test that the assembler doesn't need -Wa,-gdwarf-5 when presented with DWARF
> -# v5 input, such as `.file 0` and `md5 0x00`. Should be fixed in GNU binutils
> -# 2.35.2. https://sourceware.org/bugzilla/show_bug.cgi?id=25611
> -echo '.file 0 "filename" md5 0x7a0b65214090b6693bd1dc24dd248245' | \
> -  $* -gdwarf-5 -Wno-unused-command-line-argument -c -x assembler -o /dev/null -
> --
> 2.27.0
>


-- 
Thanks,
~Nick Desaulniers

On Mon, Mar 15, 2021 at 9:13 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> The test code in scripts/test_dwarf5_support.sh is somewhat difficult
> to understand, but after all, we want to check binutils >= 2.35.2
>
> From the former discussion, the requirement for generating DWARF v5 from
> C code is as follows:
>
>  - gcc + gnu as          -> requires gcc 5.0+ (but 7.0+ for full support)
>  - clang + gnu as        -> requires binutils 2.35.2+
>  - clang + integrated as -> OK
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> ---
>
> Changes in v2:
>   - fix typos
>   - simplify the dependency expression
>
>  lib/Kconfig.debug              | 3 +--
>  scripts/test_dwarf5_support.sh | 8 --------
>  2 files changed, 1 insertion(+), 10 deletions(-)
>  delete mode 100755 scripts/test_dwarf5_support.sh
>
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index b479ae609a31..c85d5f7a1aeb 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -284,8 +284,7 @@ config DEBUG_INFO_DWARF4
>
>  config DEBUG_INFO_DWARF5
>         bool "Generate DWARF Version 5 debuginfo"
> -       depends on GCC_VERSION >= 50000 || CC_IS_CLANG
> -       depends on CC_IS_GCC || $(success,$(srctree)/scripts/test_dwarf5_support.sh $(CC) $(CLANG_FLAGS))
> +       depends on GCC_VERSION >= 50000 || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
>         depends on !DEBUG_INFO_BTF
>         help
>           Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
> diff --git a/scripts/test_dwarf5_support.sh b/scripts/test_dwarf5_support.sh
> deleted file mode 100755
> index c46e2456b47a..000000000000
> --- a/scripts/test_dwarf5_support.sh
> +++ /dev/null
> @@ -1,8 +0,0 @@
> -#!/bin/sh
> -# SPDX-License-Identifier: GPL-2.0
> -
> -# Test that the assembler doesn't need -Wa,-gdwarf-5 when presented with DWARF
> -# v5 input, such as `.file 0` and `md5 0x00`. Should be fixed in GNU binutils
> -# 2.35.2. https://sourceware.org/bugzilla/show_bug.cgi?id=25611
> -echo '.file 0 "filename" md5 0x7a0b65214090b6693bd1dc24dd248245' | \
> -  $* -gdwarf-5 -Wno-unused-command-line-argument -c -x assembler -o /dev/null -
> --
> 2.27.0
>


-- 
Thanks,
~Nick Desaulniers

Re: [PATCH v2 2/3] kbuild: check the minimum assembler version in Kconfig

[Nathan Chancellor]

On Tue, Mar 16, 2021 at 01:12:56AM +0900, Masahiro Yamada wrote:
> Documentation/process/changes.rst defines the minimum assembler version
> (binutils version), but we have never checked it in the build time.
> 
> Kbuild never invokes 'as' directly because all assembly files in the
> kernel tree are *.S, hence must be preprocessed. I do not expect
> raw assembly source files (*.s) would be added to the kernel tree.
> 
> Therefore, we always use $(CC) as the assembler driver, and commit
> aa824e0c962b ("kbuild: remove AS variable") removed 'AS'. However,
> we are still interested in the version of the assembler acting behind.
> 
> As usual, the --version option prints the version string.
> 
>   $ as --version | head -n 1
>   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
> 
> But, we do not have $(AS). So, we can add the -Wa prefix so that
> $(CC) passes --version down to the backing assembler.
> 
>   $ gcc -Wa,--version | head -n 1
>   gcc: fatal error: no input files
>   compilation terminated.
> 
> OK, we need to input something to satisfy gcc.
> 
>   $ gcc -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
>   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
> 
> The combination of Clang and GNU assembler works in the same way:
> 
>   $ clang -no-integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
>   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
> 
> Clang with the integrated assembler fails like this:
> 
>   $ clang -integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
>   clang: error: unsupported argument '--version' to option 'Wa,'
> 
> For the last case, checking the error message is fragile. If the
> proposal for -Wa,--version support [1] is accepted, this may not be
> even an error in the future.
> 
> One easy way is to check if -integrated-as is present in the passed
> arguments. We did not pass -integrated-as to CLANG_FLAGS before, but
> we can make it explicit.
> 
> Nathan pointed out -integrated-as is the default for all of the
> architectures/targets that the kernel cares about, but it goes
> along with "explicit is better than implicit" policy. [2]
> 
> With all this in my mind, I implemented scripts/as-version.sh to
> check the assembler version in Kconfig time.
> 
>   $ scripts/as-version.sh gcc
>   GNU 23501
>   $ scripts/as-version.sh clang -no-integrated-as
>   GNU 23501
>   $ scripts/as-version.sh clang -integrated-as
>   LLVM 0
> 
> [1]: https://github.com/ClangBuiltLinux/linux/issues/1320
> [2]: https://lore.kernel.org/linux-kbuild/20210307044253.v3h47ucq6ng25iay@archlinux-ax161/
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

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

> ---
> 
> Changes in v2:
>   - Check -integrated-as option instead of error message.
>   - Add LC_ALL=C just in case.
> 
>   The Italian locale did not tweak the message from 'as --version'
>   but we never know what would happen on locale.
> 
>   $ LC_MESSAGES=it_IT.UTF-8 ld --version | head -n 1
>   ld di GNU (GNU Binutils for Debian) 2.35.2
>   $ LC_MESSAGES=it_IT.UTF-8 as --version | head -n 1
>   GNU assembler (GNU Binutils for Debian) 2.35.2
> 
>  Makefile                |  4 +-
>  arch/Kconfig            |  3 +-
>  init/Kconfig            | 12 ++++++
>  scripts/Kconfig.include |  6 +++
>  scripts/as-version.sh   | 82 +++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 104 insertions(+), 3 deletions(-)
>  create mode 100755 scripts/as-version.sh
> 
> diff --git a/Makefile b/Makefile
> index cc5b7e39fde4..2b161f5a5a66 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -580,7 +580,9 @@ ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
>  ifneq ($(CROSS_COMPILE),)
>  CLANG_FLAGS	+= --target=$(notdir $(CROSS_COMPILE:%-=%))
>  endif
> -ifneq ($(LLVM_IAS),1)
> +ifeq ($(LLVM_IAS),1)
> +CLANG_FLAGS	+= -integrated-as
> +else
>  CLANG_FLAGS	+= -no-integrated-as
>  GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
>  CLANG_FLAGS	+= --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
> diff --git a/arch/Kconfig b/arch/Kconfig
> index ecfd3520b676..555b4f09a9b2 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -631,8 +631,7 @@ config ARCH_SUPPORTS_LTO_CLANG_THIN
>  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
> -	depends on $(success,test $(LLVM_IAS) -eq 1)
> +	depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
>  	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
> diff --git a/init/Kconfig b/init/Kconfig
> index 5f5c776ef192..019c1874e609 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -41,6 +41,18 @@ config CLANG_VERSION
>  	default $(cc-version) if CC_IS_CLANG
>  	default 0
>  
> +config AS_IS_GNU
> +	def_bool $(success,test "$(as-name)" = GNU)
> +
> +config AS_IS_LLVM
> +	def_bool $(success,test "$(as-name)" = LLVM)
> +
> +config AS_VERSION
> +	int
> +	# Use clang version if this is the integrated assembler
> +	default CLANG_VERSION if AS_IS_LLVM
> +	default $(as-version)
> +
>  config LD_IS_BFD
>  	def_bool $(success,test "$(ld-name)" = BFD)
>  
> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> index 58fdb5308725..0496efd6e117 100644
> --- a/scripts/Kconfig.include
> +++ b/scripts/Kconfig.include
> @@ -45,6 +45,12 @@ $(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this compiler is not su
>  cc-name := $(shell,set -- $(cc-info) && echo $1)
>  cc-version := $(shell,set -- $(cc-info) && echo $2)
>  
> +# Get the assembler name, version, and error out if it is not supported.
> +as-info := $(shell,$(srctree)/scripts/as-version.sh $(CC) $(CLANG_FLAGS))
> +$(error-if,$(success,test -z "$(as-info)"),Sorry$(comma) this assembler is not supported.)
> +as-name := $(shell,set -- $(as-info) && echo $1)
> +as-version := $(shell,set -- $(as-info) && echo $2)
> +
>  # Get the linker name, version, and error out if it is not supported.
>  ld-info := $(shell,$(srctree)/scripts/ld-version.sh $(LD))
>  $(error-if,$(success,test -z "$(ld-info)"),Sorry$(comma) this linker is not supported.)
> diff --git a/scripts/as-version.sh b/scripts/as-version.sh
> new file mode 100755
> index 000000000000..953ff000bcbc
> --- /dev/null
> +++ b/scripts/as-version.sh
> @@ -0,0 +1,82 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# Print the assembler name and its version in a 5 or 6-digit form.
> +# Also, perform the minimum version check.
> +# (If it is the integrated assembler, return 0 as the version, and
> +# skip the version check.)
> +
> +set -e
> +
> +# Convert the version string x.y.z to a canonical 5 or 6-digit form.
> +get_canonical_version()
> +{
> +	IFS=.
> +	set -- $1
> +
> +	# If the 2nd or 3rd field is missing, fill it with a zero.
> +	#
> +	# The 4th field, if present, is ignored.
> +	# This occurs in development snapshots as in 2.35.1.20201116
> +	echo $((10000 * $1 + 100 * ${2:-0} + ${3:-0}))
> +}
> +
> +# Clang failes to handle -Wa,--version fails unless -no-integrated-as is given.
> +# We check -(f)integrated-as, expecting it is explicitly passed in for the
> +# integrated assembler case.
> +check_integrated_as()
> +{
> +	while [ $# -gt 0 ]; do
> +		if [ "$1" = -integrated-as -o "$1" = -fintegrated-as ]; then
> +			# For the intergrated assembler, we do not check the
> +			# version here. It is the same as the clang version, and
> +			# it has been already checked by scripts/cc-version.sh.
> +			echo LLVM 0
> +			exit 0
> +		fi
> +		shift
> +	done
> +}
> +
> +check_integrated_as "$@"
> +
> +orig_args="$@"
> +
> +# Get the first line of the --version output.
> +IFS='
> +'
> +set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
> +
> +# Split the line on spaces.
> +IFS=' '
> +set -- $1
> +
> +min_tool_version=$(dirname $0)/min-tool-version.sh
> +
> +if [ "$1" = GNU -a "$2" = assembler ]; then
> +	shift $(($# - 1))
> +	version=$1
> +	min_version=$($min_tool_version binutils)
> +	name=GNU
> +else
> +	echo "$orig_args: unknown assembler invoked" >&2
> +	exit 1
> +fi
> +
> +# Some distributions append a package release number, as in 2.34-4.fc32
> +# Trim the hyphen and any characters that follow.
> +version=${version%-*}
> +
> +cversion=$(get_canonical_version $version)
> +min_cversion=$(get_canonical_version $min_version)
> +
> +if [ "$cversion" -lt "$min_cversion" ]; then
> +	echo >&2 "***"
> +	echo >&2 "*** Assembler is too old."
> +	echo >&2 "***   Your $name assembler version:    $version"
> +	echo >&2 "***   Minimum $name assembler version: $min_version"
> +	echo >&2 "***"
> +	exit 1
> +fi
> +
> +echo $name $cversion
> -- 
> 2.27.0
> 

Re: [PATCH v2 2/3] kbuild: check the minimum assembler version in Kconfig

[Masahiro Yamada]

On Tue, Mar 16, 2021 at 1:14 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> Documentation/process/changes.rst defines the minimum assembler version
> (binutils version), but we have never checked it in the build time.
>
> Kbuild never invokes 'as' directly because all assembly files in the
> kernel tree are *.S, hence must be preprocessed. I do not expect
> raw assembly source files (*.s) would be added to the kernel tree.
>
> Therefore, we always use $(CC) as the assembler driver, and commit
> aa824e0c962b ("kbuild: remove AS variable") removed 'AS'. However,
> we are still interested in the version of the assembler acting behind.
>
> As usual, the --version option prints the version string.
>
>   $ as --version | head -n 1
>   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
>
> But, we do not have $(AS). So, we can add the -Wa prefix so that
> $(CC) passes --version down to the backing assembler.
>
>   $ gcc -Wa,--version | head -n 1
>   gcc: fatal error: no input files
>   compilation terminated.
>
> OK, we need to input something to satisfy gcc.
>
>   $ gcc -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
>   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
>
> The combination of Clang and GNU assembler works in the same way:
>
>   $ clang -no-integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
>   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
>
> Clang with the integrated assembler fails like this:
>
>   $ clang -integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
>   clang: error: unsupported argument '--version' to option 'Wa,'
>
> For the last case, checking the error message is fragile. If the
> proposal for -Wa,--version support [1] is accepted, this may not be
> even an error in the future.
>
> One easy way is to check if -integrated-as is present in the passed
> arguments. We did not pass -integrated-as to CLANG_FLAGS before, but
> we can make it explicit.
>
> Nathan pointed out -integrated-as is the default for all of the
> architectures/targets that the kernel cares about, but it goes
> along with "explicit is better than implicit" policy. [2]
>
> With all this in my mind, I implemented scripts/as-version.sh to
> check the assembler version in Kconfig time.
>
>   $ scripts/as-version.sh gcc
>   GNU 23501
>   $ scripts/as-version.sh clang -no-integrated-as
>   GNU 23501
>   $ scripts/as-version.sh clang -integrated-as
>   LLVM 0
>
> [1]: https://github.com/ClangBuiltLinux/linux/issues/1320
> [2]: https://lore.kernel.org/linux-kbuild/20210307044253.v3h47ucq6ng25iay@archlinux-ax161/
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
> Changes in v2:
>   - Check -integrated-as option instead of error message.
>   - Add LC_ALL=C just in case.
>
>   The Italian locale did not tweak the message from 'as --version'
>   but we never know what would happen on locale.
>
>   $ LC_MESSAGES=it_IT.UTF-8 ld --version | head -n 1
>   ld di GNU (GNU Binutils for Debian) 2.35.2
>   $ LC_MESSAGES=it_IT.UTF-8 as --version | head -n 1
>   GNU assembler (GNU Binutils for Debian) 2.35.2
>
>  Makefile                |  4 +-
>  arch/Kconfig            |  3 +-
>  init/Kconfig            | 12 ++++++
>  scripts/Kconfig.include |  6 +++
>  scripts/as-version.sh   | 82 +++++++++++++++++++++++++++++++++++++++++
>  5 files changed, 104 insertions(+), 3 deletions(-)
>  create mode 100755 scripts/as-version.sh
>
> diff --git a/Makefile b/Makefile
> index cc5b7e39fde4..2b161f5a5a66 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -580,7 +580,9 @@ ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
>  ifneq ($(CROSS_COMPILE),)
>  CLANG_FLAGS    += --target=$(notdir $(CROSS_COMPILE:%-=%))
>  endif
> -ifneq ($(LLVM_IAS),1)
> +ifeq ($(LLVM_IAS),1)
> +CLANG_FLAGS    += -integrated-as
> +else
>  CLANG_FLAGS    += -no-integrated-as
>  GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
>  CLANG_FLAGS    += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
> diff --git a/arch/Kconfig b/arch/Kconfig
> index ecfd3520b676..555b4f09a9b2 100644
> --- a/arch/Kconfig
> +++ b/arch/Kconfig
> @@ -631,8 +631,7 @@ config ARCH_SUPPORTS_LTO_CLANG_THIN
>  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
> -       depends on $(success,test $(LLVM_IAS) -eq 1)
> +       depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
>         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
> diff --git a/init/Kconfig b/init/Kconfig
> index 5f5c776ef192..019c1874e609 100644
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -41,6 +41,18 @@ config CLANG_VERSION
>         default $(cc-version) if CC_IS_CLANG
>         default 0
>
> +config AS_IS_GNU
> +       def_bool $(success,test "$(as-name)" = GNU)
> +
> +config AS_IS_LLVM
> +       def_bool $(success,test "$(as-name)" = LLVM)
> +
> +config AS_VERSION
> +       int
> +       # Use clang version if this is the integrated assembler
> +       default CLANG_VERSION if AS_IS_LLVM
> +       default $(as-version)
> +
>  config LD_IS_BFD
>         def_bool $(success,test "$(ld-name)" = BFD)
>
> diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> index 58fdb5308725..0496efd6e117 100644
> --- a/scripts/Kconfig.include
> +++ b/scripts/Kconfig.include
> @@ -45,6 +45,12 @@ $(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this compiler is not su
>  cc-name := $(shell,set -- $(cc-info) && echo $1)
>  cc-version := $(shell,set -- $(cc-info) && echo $2)
>
> +# Get the assembler name, version, and error out if it is not supported.
> +as-info := $(shell,$(srctree)/scripts/as-version.sh $(CC) $(CLANG_FLAGS))
> +$(error-if,$(success,test -z "$(as-info)"),Sorry$(comma) this assembler is not supported.)
> +as-name := $(shell,set -- $(as-info) && echo $1)
> +as-version := $(shell,set -- $(as-info) && echo $2)
> +
>  # Get the linker name, version, and error out if it is not supported.
>  ld-info := $(shell,$(srctree)/scripts/ld-version.sh $(LD))
>  $(error-if,$(success,test -z "$(ld-info)"),Sorry$(comma) this linker is not supported.)
> diff --git a/scripts/as-version.sh b/scripts/as-version.sh
> new file mode 100755
> index 000000000000..953ff000bcbc
> --- /dev/null
> +++ b/scripts/as-version.sh
> @@ -0,0 +1,82 @@
> +#!/bin/sh
> +# SPDX-License-Identifier: GPL-2.0-only
> +#
> +# Print the assembler name and its version in a 5 or 6-digit form.
> +# Also, perform the minimum version check.
> +# (If it is the integrated assembler, return 0 as the version, and
> +# skip the version check.)
> +
> +set -e
> +
> +# Convert the version string x.y.z to a canonical 5 or 6-digit form.
> +get_canonical_version()
> +{
> +       IFS=.
> +       set -- $1
> +
> +       # If the 2nd or 3rd field is missing, fill it with a zero.
> +       #
> +       # The 4th field, if present, is ignored.
> +       # This occurs in development snapshots as in 2.35.1.20201116
> +       echo $((10000 * $1 + 100 * ${2:-0} + ${3:-0}))
> +}
> +
> +# Clang failes to handle -Wa,--version fails unless -no-integrated-as is given.

This line got strange after some editing.

I will rephrase it to:

  Clang fails to handle -Wa,--version unless -no-integrated-as is given.





> +# We check -(f)integrated-as, expecting it is explicitly passed in for the
> +# integrated assembler case.
> +check_integrated_as()
> +{
> +       while [ $# -gt 0 ]; do
> +               if [ "$1" = -integrated-as -o "$1" = -fintegrated-as ]; then
> +                       # For the intergrated assembler, we do not check the
> +                       # version here. It is the same as the clang version, and
> +                       # it has been already checked by scripts/cc-version.sh.
> +                       echo LLVM 0
> +                       exit 0
> +               fi
> +               shift
> +       done
> +}
> +
> +check_integrated_as "$@"
> +
> +orig_args="$@"
> +
> +# Get the first line of the --version output.
> +IFS='
> +'
> +set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
> +
> +# Split the line on spaces.
> +IFS=' '
> +set -- $1
> +
> +min_tool_version=$(dirname $0)/min-tool-version.sh
> +
> +if [ "$1" = GNU -a "$2" = assembler ]; then
> +       shift $(($# - 1))
> +       version=$1
> +       min_version=$($min_tool_version binutils)
> +       name=GNU
> +else
> +       echo "$orig_args: unknown assembler invoked" >&2
> +       exit 1
> +fi
> +
> +# Some distributions append a package release number, as in 2.34-4.fc32
> +# Trim the hyphen and any characters that follow.
> +version=${version%-*}
> +
> +cversion=$(get_canonical_version $version)
> +min_cversion=$(get_canonical_version $min_version)
> +
> +if [ "$cversion" -lt "$min_cversion" ]; then
> +       echo >&2 "***"
> +       echo >&2 "*** Assembler is too old."
> +       echo >&2 "***   Your $name assembler version:    $version"
> +       echo >&2 "***   Minimum $name assembler version: $min_version"
> +       echo >&2 "***"
> +       exit 1
> +fi
> +
> +echo $name $cversion
> --
> 2.27.0
>
> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20210315161257.788477-2-masahiroy%40kernel.org.



-- 
Best Regards
Masahiro Yamada

Re: [PATCH v2 2/3] kbuild: check the minimum assembler version in Kconfig

[Nick Desaulniers]

On Tue, Mar 16, 2021 at 12:14 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> On Tue, Mar 16, 2021 at 1:14 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > Documentation/process/changes.rst defines the minimum assembler version
> > (binutils version), but we have never checked it in the build time.
> >
> > Kbuild never invokes 'as' directly because all assembly files in the
> > kernel tree are *.S, hence must be preprocessed. I do not expect
> > raw assembly source files (*.s) would be added to the kernel tree.
> >
> > Therefore, we always use $(CC) as the assembler driver, and commit
> > aa824e0c962b ("kbuild: remove AS variable") removed 'AS'. However,
> > we are still interested in the version of the assembler acting behind.
> >
> > As usual, the --version option prints the version string.
> >
> >   $ as --version | head -n 1
> >   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
> >
> > But, we do not have $(AS). So, we can add the -Wa prefix so that
> > $(CC) passes --version down to the backing assembler.
> >
> >   $ gcc -Wa,--version | head -n 1
> >   gcc: fatal error: no input files
> >   compilation terminated.
> >
> > OK, we need to input something to satisfy gcc.
> >
> >   $ gcc -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
> >   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
> >
> > The combination of Clang and GNU assembler works in the same way:
> >
> >   $ clang -no-integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
> >   GNU assembler (GNU Binutils for Ubuntu) 2.35.1
> >
> > Clang with the integrated assembler fails like this:
> >
> >   $ clang -integrated-as -Wa,--version -c -x assembler /dev/null -o /dev/null | head -n 1
> >   clang: error: unsupported argument '--version' to option 'Wa,'

Jian just landed support for this, it will ship in clang-13:
https://reviews.llvm.org/rG3cc3c0f8352ec33ca2f2636f94cb1d85fc57ac16
https://github.com/ClangBuiltLinux/linux/issues/1320
Thanks Jian!

> >
> > For the last case, checking the error message is fragile. If the
> > proposal for -Wa,--version support [1] is accepted, this may not be
> > even an error in the future.
> >
> > One easy way is to check if -integrated-as is present in the passed
> > arguments. We did not pass -integrated-as to CLANG_FLAGS before, but
> > we can make it explicit.
> >
> > Nathan pointed out -integrated-as is the default for all of the
> > architectures/targets that the kernel cares about, but it goes
> > along with "explicit is better than implicit" policy. [2]
> >
> > With all this in my mind, I implemented scripts/as-version.sh to
> > check the assembler version in Kconfig time.
> >
> >   $ scripts/as-version.sh gcc
> >   GNU 23501
> >   $ scripts/as-version.sh clang -no-integrated-as
> >   GNU 23501
> >   $ scripts/as-version.sh clang -integrated-as
> >   LLVM 0
> >
> > [1]: https://github.com/ClangBuiltLinux/linux/issues/1320
> > [2]: https://lore.kernel.org/linux-kbuild/20210307044253.v3h47ucq6ng25iay@archlinux-ax161/
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > ---
> >
> > Changes in v2:
> >   - Check -integrated-as option instead of error message.
> >   - Add LC_ALL=C just in case.
> >
> >   The Italian locale did not tweak the message from 'as --version'
> >   but we never know what would happen on locale.
> >
> >   $ LC_MESSAGES=it_IT.UTF-8 ld --version | head -n 1
> >   ld di GNU (GNU Binutils for Debian) 2.35.2
> >   $ LC_MESSAGES=it_IT.UTF-8 as --version | head -n 1
> >   GNU assembler (GNU Binutils for Debian) 2.35.2
> >
> >  Makefile                |  4 +-
> >  arch/Kconfig            |  3 +-
> >  init/Kconfig            | 12 ++++++
> >  scripts/Kconfig.include |  6 +++
> >  scripts/as-version.sh   | 82 +++++++++++++++++++++++++++++++++++++++++
> >  5 files changed, 104 insertions(+), 3 deletions(-)
> >  create mode 100755 scripts/as-version.sh
> >
> > diff --git a/Makefile b/Makefile
> > index cc5b7e39fde4..2b161f5a5a66 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -580,7 +580,9 @@ ifneq ($(findstring clang,$(CC_VERSION_TEXT)),)
> >  ifneq ($(CROSS_COMPILE),)
> >  CLANG_FLAGS    += --target=$(notdir $(CROSS_COMPILE:%-=%))
> >  endif
> > -ifneq ($(LLVM_IAS),1)
> > +ifeq ($(LLVM_IAS),1)
> > +CLANG_FLAGS    += -integrated-as
> > +else
> >  CLANG_FLAGS    += -no-integrated-as
> >  GCC_TOOLCHAIN_DIR := $(dir $(shell which $(CROSS_COMPILE)elfedit))
> >  CLANG_FLAGS    += --prefix=$(GCC_TOOLCHAIN_DIR)$(notdir $(CROSS_COMPILE))
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index ecfd3520b676..555b4f09a9b2 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -631,8 +631,7 @@ config ARCH_SUPPORTS_LTO_CLANG_THIN
> >  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
> > -       depends on $(success,test $(LLVM_IAS) -eq 1)
> > +       depends on CC_IS_CLANG && CLANG_VERSION >= 110000 && LD_IS_LLD && AS_IS_LLVM
> >         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
> > diff --git a/init/Kconfig b/init/Kconfig
> > index 5f5c776ef192..019c1874e609 100644
> > --- a/init/Kconfig
> > +++ b/init/Kconfig
> > @@ -41,6 +41,18 @@ config CLANG_VERSION
> >         default $(cc-version) if CC_IS_CLANG
> >         default 0
> >
> > +config AS_IS_GNU
> > +       def_bool $(success,test "$(as-name)" = GNU)
> > +
> > +config AS_IS_LLVM
> > +       def_bool $(success,test "$(as-name)" = LLVM)
> > +
> > +config AS_VERSION
> > +       int
> > +       # Use clang version if this is the integrated assembler
> > +       default CLANG_VERSION if AS_IS_LLVM
> > +       default $(as-version)
> > +
> >  config LD_IS_BFD
> >         def_bool $(success,test "$(ld-name)" = BFD)
> >
> > diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> > index 58fdb5308725..0496efd6e117 100644
> > --- a/scripts/Kconfig.include
> > +++ b/scripts/Kconfig.include
> > @@ -45,6 +45,12 @@ $(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this compiler is not su
> >  cc-name := $(shell,set -- $(cc-info) && echo $1)
> >  cc-version := $(shell,set -- $(cc-info) && echo $2)
> >
> > +# Get the assembler name, version, and error out if it is not supported.
> > +as-info := $(shell,$(srctree)/scripts/as-version.sh $(CC) $(CLANG_FLAGS))
> > +$(error-if,$(success,test -z "$(as-info)"),Sorry$(comma) this assembler is not supported.)
> > +as-name := $(shell,set -- $(as-info) && echo $1)
> > +as-version := $(shell,set -- $(as-info) && echo $2)
> > +
> >  # Get the linker name, version, and error out if it is not supported.
> >  ld-info := $(shell,$(srctree)/scripts/ld-version.sh $(LD))
> >  $(error-if,$(success,test -z "$(ld-info)"),Sorry$(comma) this linker is not supported.)
> > diff --git a/scripts/as-version.sh b/scripts/as-version.sh
> > new file mode 100755
> > index 000000000000..953ff000bcbc
> > --- /dev/null
> > +++ b/scripts/as-version.sh
> > @@ -0,0 +1,82 @@
> > +#!/bin/sh
> > +# SPDX-License-Identifier: GPL-2.0-only
> > +#
> > +# Print the assembler name and its version in a 5 or 6-digit form.
> > +# Also, perform the minimum version check.
> > +# (If it is the integrated assembler, return 0 as the version, and
> > +# skip the version check.)
> > +
> > +set -e
> > +
> > +# Convert the version string x.y.z to a canonical 5 or 6-digit form.
> > +get_canonical_version()
> > +{
> > +       IFS=.
> > +       set -- $1
> > +
> > +       # If the 2nd or 3rd field is missing, fill it with a zero.
> > +       #
> > +       # The 4th field, if present, is ignored.
> > +       # This occurs in development snapshots as in 2.35.1.20201116
> > +       echo $((10000 * $1 + 100 * ${2:-0} + ${3:-0}))
> > +}
> > +
> > +# Clang failes to handle -Wa,--version fails unless -no-integrated-as is given.
>
> This line got strange after some editing.
>
> I will rephrase it to:
>
>   Clang fails to handle -Wa,--version unless -no-integrated-as is given.
>
>
>
>
>
> > +# We check -(f)integrated-as, expecting it is explicitly passed in for the
> > +# integrated assembler case.
> > +check_integrated_as()
> > +{
> > +       while [ $# -gt 0 ]; do
> > +               if [ "$1" = -integrated-as -o "$1" = -fintegrated-as ]; then
> > +                       # For the intergrated assembler, we do not check the
> > +                       # version here. It is the same as the clang version, and
> > +                       # it has been already checked by scripts/cc-version.sh.
> > +                       echo LLVM 0
> > +                       exit 0
> > +               fi
> > +               shift
> > +       done
> > +}
> > +
> > +check_integrated_as "$@"
> > +
> > +orig_args="$@"
> > +
> > +# Get the first line of the --version output.
> > +IFS='
> > +'
> > +set -- $(LC_ALL=C "$@" -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
> > +
> > +# Split the line on spaces.
> > +IFS=' '
> > +set -- $1
> > +
> > +min_tool_version=$(dirname $0)/min-tool-version.sh
> > +
> > +if [ "$1" = GNU -a "$2" = assembler ]; then
> > +       shift $(($# - 1))
> > +       version=$1
> > +       min_version=$($min_tool_version binutils)
> > +       name=GNU
> > +else
> > +       echo "$orig_args: unknown assembler invoked" >&2
> > +       exit 1
> > +fi
> > +
> > +# Some distributions append a package release number, as in 2.34-4.fc32
> > +# Trim the hyphen and any characters that follow.
> > +version=${version%-*}
> > +
> > +cversion=$(get_canonical_version $version)
> > +min_cversion=$(get_canonical_version $min_version)
> > +
> > +if [ "$cversion" -lt "$min_cversion" ]; then
> > +       echo >&2 "***"
> > +       echo >&2 "*** Assembler is too old."
> > +       echo >&2 "***   Your $name assembler version:    $version"
> > +       echo >&2 "***   Minimum $name assembler version: $min_version"
> > +       echo >&2 "***"
> > +       exit 1
> > +fi
> > +
> > +echo $name $cversion
> > --
> > 2.27.0
> >
> > --

-- 
Thanks,
~Nick Desaulniers