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[3/4] kbuild: check the minimum assembler version in Kconfig

Message ID 20210303183333.46543-3-masahiroy@kernel.org (mailing list archive)
State New
Headers show
Series [1/4] kbuild: remove LLVM=1 test from HAS_LTO_CLANG | expand

Commit Message

Masahiro Yamada March 3, 2021, 6:33 p.m. UTC
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 sitting 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,'

With all this in my mind, I implemented scripts/as-version.sh.

  $ 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

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

 arch/Kconfig            |  3 +-
 init/Kconfig            | 12 +++++++
 scripts/Kconfig.include |  6 ++++
 scripts/as-version.sh   | 77 +++++++++++++++++++++++++++++++++++++++++
 4 files changed, 96 insertions(+), 2 deletions(-)
 create mode 100755 scripts/as-version.sh

Comments

Nathan Chancellor March 4, 2021, 12:28 a.m. UTC | #1
On Thu, Mar 04, 2021 at 03:33:32AM +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 sitting 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,'
> 
> With all this in my mind, I implemented scripts/as-version.sh.
> 
>   $ 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
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
>  arch/Kconfig            |  3 +-
>  init/Kconfig            | 12 +++++++
>  scripts/Kconfig.include |  6 ++++
>  scripts/as-version.sh   | 77 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 96 insertions(+), 2 deletions(-)
>  create mode 100755 scripts/as-version.sh
> 
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 2af10ebe5ed0..d7214f4ae1f7 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 22946fe5ded9..f76e5a44e4fe 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
> +	# If it is integrated assembler, the version is the same as Clang's one.
> +	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..205d8b9fc4d4
> --- /dev/null
> +++ b/scripts/as-version.sh
> @@ -0,0 +1,77 @@
> +#!/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
> +# the version check is skipped.)
> +
> +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} + ${3:-0}))
> +}
> +
> +orig_args="$@"
> +
> +# Get the first line of the --version output.
> +IFS='
> +'
> +# Add 2>&1 to check both stdout and stderr.
> +# If the backing assembler is binutils, we get the version string in stdout.
> +# If it is clang's integrated assembler, we get the following error in stderr:
> +#   clang: error: unsupported argument '--version' to option 'Wa,'
> +# To avoid the error message affected by locale, set LC_MESSAGES=C just in case.
> +set -- $(LC_MESSAGES=C "$@" -Wno-unused-command-line-argument -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
> +line="$1"
> +
> +if [ "$line" = "clang: error: unsupported argument '--version' to option 'Wa,'" ]; then

It looks like Debian and Ubuntu do something interesting with their
clang packaging. Normally, "clang" is a symlink to "clang-#" in the same
folder. In my folder from just running "ninja install"

$ ls -l clang clang-13
lrwxrwxrwx   8 nathan  2 Mar 20:58 clang -> clang-13
.rwxr-xr-x 93M nathan  2 Mar 20:58 clang-13

The same thing is true for Arch Linux:

$ ls -l /usr/bin/{clang,clang-11}
lrwxrwxrwx    8 root 17 Feb  8:54 /usr/bin/clang -> clang-11
.rwxr-xr-x 145k root 17 Feb  8:54 /usr/bin/clang-11

As a result, this does not quite work.

$ LC_MESSAGES=C /usr/bin/clang -Wno-unused-command-line-argument -Wa,--version -c -x assembler /dev/null -o /dev/null
clang-11: error: unsupported argument '--version' to option 'Wa,'

I am not sure what the cleanest fix would be. The rest of the patch looks okay to me.

Cheers,
Nathan

> +	# 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
> +
> +# Split the line on spaces.
> +IFS=' '
> +set -- $line
> +
> +tool_version=$(dirname $0)/tool-version.sh
> +
> +if [ "$1" = GNU -a "$2" = assembler ]; then
> +	shift $(($# - 1))
> +	version=$1
> +	min_version=$($tool_version binutils)
> +	name=GNU
> +else
> +	echo "$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
>
Nick Desaulniers March 5, 2021, 1:25 a.m. UTC | #2
On Wed, Mar 3, 2021 at 10:34 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 sitting 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,'

Was this a feature request to "please implement -Wa,--version for clang?" :-P
https://github.com/ClangBuiltLinux/linux/issues/1320

>
> With all this in my mind, I implemented scripts/as-version.sh.
>
>   $ 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
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
>  arch/Kconfig            |  3 +-
>  init/Kconfig            | 12 +++++++
>  scripts/Kconfig.include |  6 ++++
>  scripts/as-version.sh   | 77 +++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 96 insertions(+), 2 deletions(-)
>  create mode 100755 scripts/as-version.sh
>
> diff --git a/arch/Kconfig b/arch/Kconfig
> index 2af10ebe5ed0..d7214f4ae1f7 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 22946fe5ded9..f76e5a44e4fe 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
> +       # If it is integrated assembler, the version is the same as Clang's one.
> +       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..205d8b9fc4d4
> --- /dev/null
> +++ b/scripts/as-version.sh
> @@ -0,0 +1,77 @@
> +#!/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
> +# the version check is skipped.)
> +
> +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} + ${3:-0}))
> +}
> +
> +orig_args="$@"
> +
> +# Get the first line of the --version output.
> +IFS='
> +'
> +# Add 2>&1 to check both stdout and stderr.
> +# If the backing assembler is binutils, we get the version string in stdout.
> +# If it is clang's integrated assembler, we get the following error in stderr:
> +#   clang: error: unsupported argument '--version' to option 'Wa,'
> +# To avoid the error message affected by locale, set LC_MESSAGES=C just in case.
> +set -- $(LC_MESSAGES=C "$@" -Wno-unused-command-line-argument -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
> +line="$1"
> +
> +if [ "$line" = "clang: error: unsupported argument '--version' to option 'Wa,'" ]; then

Checking the precise error message is too brittle; what if it changes?
Why not check the return code a la cc-option and friends?  Is checking
the return code of a subshell an issue here?

> +       # For the intergrated assembler, we do not check the version here.

s/intergrated/integrated/

> +       # 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
> +
> +# Split the line on spaces.
> +IFS=' '
> +set -- $line
> +
> +tool_version=$(dirname $0)/tool-version.sh
> +
> +if [ "$1" = GNU -a "$2" = assembler ]; then
> +       shift $(($# - 1))
> +       version=$1
> +       min_version=$($tool_version binutils)
> +       name=GNU
> +else
> +       echo "$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
>
Masahiro Yamada March 5, 2021, 5:48 p.m. UTC | #3
On Fri, Mar 5, 2021 at 10:26 AM Nick Desaulniers
<ndesaulniers@google.com> wrote:
>
> On Wed, Mar 3, 2021 at 10:34 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 sitting 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,'
>
> Was this a feature request to "please implement -Wa,--version for clang?" :-P
> https://github.com/ClangBuiltLinux/linux/issues/1320
>
> >
> > With all this in my mind, I implemented scripts/as-version.sh.
> >
> >   $ 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
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > ---
> >
> >  arch/Kconfig            |  3 +-
> >  init/Kconfig            | 12 +++++++
> >  scripts/Kconfig.include |  6 ++++
> >  scripts/as-version.sh   | 77 +++++++++++++++++++++++++++++++++++++++++
> >  4 files changed, 96 insertions(+), 2 deletions(-)
> >  create mode 100755 scripts/as-version.sh
> >
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 2af10ebe5ed0..d7214f4ae1f7 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 22946fe5ded9..f76e5a44e4fe 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
> > +       # If it is integrated assembler, the version is the same as Clang's one.
> > +       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..205d8b9fc4d4
> > --- /dev/null
> > +++ b/scripts/as-version.sh
> > @@ -0,0 +1,77 @@
> > +#!/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
> > +# the version check is skipped.)
> > +
> > +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} + ${3:-0}))
> > +}
> > +
> > +orig_args="$@"
> > +
> > +# Get the first line of the --version output.
> > +IFS='
> > +'
> > +# Add 2>&1 to check both stdout and stderr.
> > +# If the backing assembler is binutils, we get the version string in stdout.
> > +# If it is clang's integrated assembler, we get the following error in stderr:
> > +#   clang: error: unsupported argument '--version' to option 'Wa,'
> > +# To avoid the error message affected by locale, set LC_MESSAGES=C just in case.
> > +set -- $(LC_MESSAGES=C "$@" -Wno-unused-command-line-argument -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
> > +line="$1"
> > +
> > +if [ "$line" = "clang: error: unsupported argument '--version' to option 'Wa,'" ]; then
>
> Checking the precise error message is too brittle; what if it changes?
> Why not check the return code a la cc-option and friends?  Is checking
> the return code of a subshell an issue here?

As Nathan pointed out, this is fragile.

I just tried my best to make this script work stand-alone.

With the only exit code chec,

 scripts/as-version.sh false

would return LLVM, which is false-positive.
Probably this is not a big deal
since completely wrong input was blocked by
scripts/cc-version.sh


If we give up making this script stand-alone,
another idea is to check LLVM_IAS=1, which
is passed from the top Makefile.

Yet another idea is to explicitly pass
-integrated-as as CLANG_FLAGS.
Then, this script can parse the presence
of -integrated-as.


BTW, is there any guarantee that the integrated assembler
is always enabled by default? Or, is it dependent on
the configuration?

The top Makefile adds -no-integrated-as if LLVM_IAS != 1,
but adds nothing if LLVM_IAS == 1.
So, -integrated-as must be always default.







>
> > +       # For the intergrated assembler, we do not check the version here.
>
> s/intergrated/integrated/
>
> > +       # 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
> > +
> > +# Split the line on spaces.
> > +IFS=' '
> > +set -- $line
> > +
> > +tool_version=$(dirname $0)/tool-version.sh
> > +
> > +if [ "$1" = GNU -a "$2" = assembler ]; then
> > +       shift $(($# - 1))
> > +       version=$1
> > +       min_version=$($tool_version binutils)
> > +       name=GNU
> > +else
> > +       echo "$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
Nathan Chancellor March 7, 2021, 4:42 a.m. UTC | #4
On Sat, Mar 06, 2021 at 02:48:38AM +0900, Masahiro Yamada wrote:
> On Fri, Mar 5, 2021 at 10:26 AM Nick Desaulniers
> <ndesaulniers@google.com> wrote:
> >
> > On Wed, Mar 3, 2021 at 10:34 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 sitting 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,'
> >
> > Was this a feature request to "please implement -Wa,--version for clang?" :-P
> > https://github.com/ClangBuiltLinux/linux/issues/1320
> >
> > >
> > > With all this in my mind, I implemented scripts/as-version.sh.
> > >
> > >   $ 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
> > >
> > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > > ---
> > >
> > >  arch/Kconfig            |  3 +-
> > >  init/Kconfig            | 12 +++++++
> > >  scripts/Kconfig.include |  6 ++++
> > >  scripts/as-version.sh   | 77 +++++++++++++++++++++++++++++++++++++++++
> > >  4 files changed, 96 insertions(+), 2 deletions(-)
> > >  create mode 100755 scripts/as-version.sh
> > >
> > > diff --git a/arch/Kconfig b/arch/Kconfig
> > > index 2af10ebe5ed0..d7214f4ae1f7 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 22946fe5ded9..f76e5a44e4fe 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
> > > +       # If it is integrated assembler, the version is the same as Clang's one.
> > > +       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..205d8b9fc4d4
> > > --- /dev/null
> > > +++ b/scripts/as-version.sh
> > > @@ -0,0 +1,77 @@
> > > +#!/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
> > > +# the version check is skipped.)
> > > +
> > > +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} + ${3:-0}))
> > > +}
> > > +
> > > +orig_args="$@"
> > > +
> > > +# Get the first line of the --version output.
> > > +IFS='
> > > +'
> > > +# Add 2>&1 to check both stdout and stderr.
> > > +# If the backing assembler is binutils, we get the version string in stdout.
> > > +# If it is clang's integrated assembler, we get the following error in stderr:
> > > +#   clang: error: unsupported argument '--version' to option 'Wa,'
> > > +# To avoid the error message affected by locale, set LC_MESSAGES=C just in case.
> > > +set -- $(LC_MESSAGES=C "$@" -Wno-unused-command-line-argument -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
> > > +line="$1"
> > > +
> > > +if [ "$line" = "clang: error: unsupported argument '--version' to option 'Wa,'" ]; then
> >
> > Checking the precise error message is too brittle; what if it changes?
> > Why not check the return code a la cc-option and friends?  Is checking
> > the return code of a subshell an issue here?
> 
> As Nathan pointed out, this is fragile.
> 
> I just tried my best to make this script work stand-alone.
> 
> With the only exit code chec,
> 
>  scripts/as-version.sh false
> 
> would return LLVM, which is false-positive.
> Probably this is not a big deal
> since completely wrong input was blocked by
> scripts/cc-version.sh
> 
> 
> If we give up making this script stand-alone,
> another idea is to check LLVM_IAS=1, which
> is passed from the top Makefile.
> 
> Yet another idea is to explicitly pass
> -integrated-as as CLANG_FLAGS.
> Then, this script can parse the presence
> of -integrated-as.

This is probably the easiest thing to do for all versions of LLVM
(adding -Wa,--version support to the integrated assembler as Nick
suggests only fixes future versions of LLVM) and goes along with the
"explicit is better than implicit" policy, which I tend to align with.
It makes easy to quickly see what assembler was used when looking at a
clang invocation as well.

> BTW, is there any guarantee that the integrated assembler
> is always enabled by default? Or, is it dependent on
> the configuration?

There is a virtual method called IsIntegratedAssemblerDefault(), which
defaults to false but is overridden to true by various targets. For all
of the architectures/targets that the kernel cares about, this appears
to be true.

https://github.com/llvm/llvm-project/blob/45f949ee469f3e59d30a88c97aa7c1139069b261/clang/lib/Driver/ToolChains/Gnu.cpp#L2738-L2774

Cheers,
Nathan

> The top Makefile adds -no-integrated-as if LLVM_IAS != 1,
> but adds nothing if LLVM_IAS == 1.
> So, -integrated-as must be always default.
> 
> 
> 
> 
> 
> 
> 
> >
> > > +       # For the intergrated assembler, we do not check the version here.
> >
> > s/intergrated/integrated/
> >
> > > +       # 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
> > > +
> > > +# Split the line on spaces.
> > > +IFS=' '
> > > +set -- $line
> > > +
> > > +tool_version=$(dirname $0)/tool-version.sh
> > > +
> > > +if [ "$1" = GNU -a "$2" = assembler ]; then
> > > +       shift $(($# - 1))
> > > +       version=$1
> > > +       min_version=$($tool_version binutils)
> > > +       name=GNU
> > > +else
> > > +       echo "$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
> 
> 
> 
> -- 
> Best Regards
> Masahiro Yamada
diff mbox series

Patch

diff --git a/arch/Kconfig b/arch/Kconfig
index 2af10ebe5ed0..d7214f4ae1f7 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 22946fe5ded9..f76e5a44e4fe 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
+	# If it is integrated assembler, the version is the same as Clang's one.
+	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..205d8b9fc4d4
--- /dev/null
+++ b/scripts/as-version.sh
@@ -0,0 +1,77 @@ 
+#!/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
+# the version check is skipped.)
+
+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} + ${3:-0}))
+}
+
+orig_args="$@"
+
+# Get the first line of the --version output.
+IFS='
+'
+# Add 2>&1 to check both stdout and stderr.
+# If the backing assembler is binutils, we get the version string in stdout.
+# If it is clang's integrated assembler, we get the following error in stderr:
+#   clang: error: unsupported argument '--version' to option 'Wa,'
+# To avoid the error message affected by locale, set LC_MESSAGES=C just in case.
+set -- $(LC_MESSAGES=C "$@" -Wno-unused-command-line-argument -Wa,--version -c -x assembler /dev/null -o /dev/null 2>&1)
+line="$1"
+
+if [ "$line" = "clang: error: unsupported argument '--version' to option 'Wa,'" ]; 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
+
+# Split the line on spaces.
+IFS=' '
+set -- $line
+
+tool_version=$(dirname $0)/tool-version.sh
+
+if [ "$1" = GNU -a "$2" = assembler ]; then
+	shift $(($# - 1))
+	version=$1
+	min_version=$($tool_version binutils)
+	name=GNU
+else
+	echo "$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