Date:   Sat, 16 Jan 2021 08:35:42 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     Paul Gortmaker <paul.gortmaker@...driver.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Miguel Ojeda <ojeda@...nel.org>,
        Sedat Dilek <sedat.dilek@...il.com>,
        Will Deacon <will@...nel.org>,
        clang-built-linux@...glegroups.com, linux-kernel@...r.kernel.org
Subject: [PATCH v6] kbuild: check the minimum compiler version in Kconfig

Paul Gortmaker reported a regression in the GCC version check. [1]
If you use GCC 4.8, the build breaks before showing the error message
"error Sorry, your version of GCC is too old - please use 4.9 or newer."

I do not want to apply his fix-up since it implies we would not be able
to remove any cc-option test. Anyway, I admit checking the GCC version
in <linux/compiler-gcc.h> is too late.

Almost at the same time, Linus also suggested to move the compiler
version error to Kconfig time. [2]

I unified the two similar scripts, gcc-version.sh and clang-version.sh
into cc-version.sh. The old scripts invoked the compiler multiple times
(3 times for gcc-version.sh, 4 times for clang-version.sh). I refactored
the code so the new one invokes the compiler just once, and also tried
my best to use shell-builtin commands where possible.

The new script runs faster.

  $ time ./scripts/clang-version.sh clang
  120000

  real    0m0.029s
  user    0m0.012s
  sys     0m0.021s

  $ time ./scripts/cc-version.sh clang
  Clang 120000

  real    0m0.009s
  user    0m0.006s
  sys     0m0.004s

cc-version.sh also shows the error if the compiler is too old:

  $ make defconfig CC=clang-9
  *** Default configuration is based on 'x86_64_defconfig'
  ***
  *** Compiler is too old.
  ***   Your Clang version:    9.0.1
  ***   Minimum Clang version: 10.0.1
  ***
  scripts/Kconfig.include:46: Sorry, this compiler is not supported.
  make[1]: *** [scripts/kconfig/Makefile:81: defconfig] Error 1
  make: *** [Makefile:602: defconfig] Error 2

The new script takes care of ICC because we have <linux/compiler-intel.h>
although I am not sure if building the kernel with ICC is well-supported.

[1]: https://lore.kernel.org/r/20210110190807.134996-1-paul.gortmaker@windriver.com
[2]: https://lore.kernel.org/r/CAHk-=wh-+TMHPTFo1qs-MYyK7tZh-OQovA=pP3=e06aCVp6_kA@mail.gmail.com

Fixes: 87de84c9140e ("kbuild: remove cc-option test of -Werror=date-time")
Reported-by: Paul Gortmaker <paul.gortmaker@...driver.com>
Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
Tested-by: Nick Desaulniers <ndesaulniers@...gle.com>
Reviewed-by: Nathan Chancellor <natechancellor@...il.com>
Tested-by: Nathan Chancellor <natechancellor@...il.com>
Reviewed-by: Miguel Ojeda <ojeda@...nel.org>
Tested-by: Miguel Ojeda <ojeda@...nel.org>
Tested-by: Sedat Dilek <sedat.dilek@...il.com>
Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
---

Changes in v6:
  - Now that https://lore.kernel.org/r/20210112224832.10980-1-will@kernel.org
    landed in Linus' tree, I cleaned up <linux/compiler-gcc.h> as well.

Changes in v5:
  - double-quote $(cc-name) in the CC_IS_GCC and CC_IS_CLANG

Changes in v4:
  - use lore version of the links

Changes in v3:
  - add $(srctree)/ to fix out-of-tree build
  - support ICC version

Changes in v2:
  - fix the function name

 include/linux/compiler-clang.h | 10 -----
 include/linux/compiler-gcc.h   | 11 -----
 init/Kconfig                   |  9 ++--
 scripts/Kconfig.include        |  6 +++
 scripts/cc-version.sh          | 82 ++++++++++++++++++++++++++++++++++
 scripts/clang-version.sh       | 19 --------
 scripts/gcc-version.sh         | 20 ---------
 7 files changed, 93 insertions(+), 64 deletions(-)
 create mode 100755 scripts/cc-version.sh
 delete mode 100755 scripts/clang-version.sh
 delete mode 100755 scripts/gcc-version.sh

diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
index 98cff1b4b088..04c0a5a717f7 100644
--- a/include/linux/compiler-clang.h
+++ b/include/linux/compiler-clang.h
@@ -3,16 +3,6 @@
 #error "Please don't include <linux/compiler-clang.h> directly, include <linux/compiler.h> instead."
 #endif
 
-#define CLANG_VERSION (__clang_major__ * 10000	\
-		     + __clang_minor__ * 100	\
-		     + __clang_patchlevel__)
-
-#if CLANG_VERSION < 100001
-#ifndef __BPF_TRACING__
-# error Sorry, your version of Clang is too old - please use 10.0.1 or newer.
-#endif
-#endif
-
 /* Compiler specific definitions for Clang compiler */
 
 /* same as gcc, this was present in clang-2.6 so we can assume it works
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 555ab0fddbef..48750243db4c 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -10,17 +10,6 @@
 		     + __GNUC_MINOR__ * 100	\
 		     + __GNUC_PATCHLEVEL__)
 
-/* https://gcc.gnu.org/bugzilla/show_bug.cgi?id=58145 */
-#if GCC_VERSION < 40900
-# error Sorry, your version of GCC is too old - please use 4.9 or newer.
-#elif defined(CONFIG_ARM64) && GCC_VERSION < 50100
-/*
- * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63293
- * https://lore.kernel.org/r/20210107111841.GN1551@shell.armlinux.org.uk
- */
-# error Sorry, your version of GCC is too old - please use 5.1 or newer.
-#endif
-
 /*
  * This macro obfuscates arithmetic on a variable address so that gcc
  * shouldn't recognize the original var, and make assumptions about it.
diff --git a/init/Kconfig b/init/Kconfig
index b77c60f8b963..8f04e5db2001 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -26,11 +26,11 @@ config CC_VERSION_TEXT
 	    and then every file will be rebuilt.
 
 config CC_IS_GCC
-	def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q gcc)
+	def_bool $(success,test "$(cc-name)" = GCC)
 
 config GCC_VERSION
 	int
-	default $(shell,$(srctree)/scripts/gcc-version.sh $(CC)) if CC_IS_GCC
+	default $(cc-version) if CC_IS_GCC
 	default 0
 
 config LD_VERSION
@@ -38,14 +38,15 @@ config LD_VERSION
 	default $(shell,$(LD) --version | $(srctree)/scripts/ld-version.sh)
 
 config CC_IS_CLANG
-	def_bool $(success,echo "$(CC_VERSION_TEXT)" | grep -q clang)
+	def_bool $(success,test "$(cc-name)" = Clang)
 
 config LD_IS_LLD
 	def_bool $(success,$(LD) -v | head -n 1 | grep -q LLD)
 
 config CLANG_VERSION
 	int
-	default $(shell,$(srctree)/scripts/clang-version.sh $(CC))
+	default $(cc-version) if CC_IS_CLANG
+	default 0
 
 config LLD_VERSION
 	int
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index a5fe72c504ff..0228cb9c74aa 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -39,6 +39,12 @@ as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler
 $(error-if,$(failure,command -v $(CC)),compiler '$(CC)' not found)
 $(error-if,$(failure,command -v $(LD)),linker '$(LD)' not found)
 
+# Get the compiler name, version, and error out if it is not supported.
+cc-info := $(shell,$(srctree)/scripts/cc-version.sh $(CC))
+$(error-if,$(success,test -z "$(cc-info)"),Sorry$(comma) this compiler is not supported.)
+cc-name := $(shell,set -- $(cc-info) && echo $1)
+cc-version := $(shell,set -- $(cc-info) && echo $2)
+
 # Fail if the linker is gold as it's not capable of linking the kernel proper
 $(error-if,$(success, $(LD) -v | grep -q gold), gold linker '$(LD)' not supported)
 
diff --git a/scripts/cc-version.sh b/scripts/cc-version.sh
new file mode 100755
index 000000000000..d1edbe4d140c
--- /dev/null
+++ b/scripts/cc-version.sh
@@ -0,0 +1,82 @@
+#!/bin/sh
+# SPDX-License-Identifier: GPL-2.0
+#
+# Print the compiler name and its version in a 5 or 6-digit form.
+# Also, perform the minimum version check.
+
+set -e
+
+# When you raise the 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 [ "$SRCARCH" = arm64 ]; then
+	gcc_min_version=5.1.0
+fi
+
+# print the compiler name and versions
+get_compiler_info()
+{
+	cat <<- EOF | "$@" -E -P -x c - 2>/dev/null
+	#if defined(__clang__)
+	Clang	__clang_major__  __clang_minor__  __clang_patchlevel__
+	#elif defined(__INTEL_COMPILER)
+	ICC	__INTEL_COMPILER  __INTEL_COMPILER_UPDATE
+	#elif defined(__GNUC__)
+	GCC	__GNUC__  __GNUC_MINOR__  __GNUC_PATCHLEVEL__
+	#else
+	unknown
+	#endif
+	EOF
+}
+
+# convert the version string x.y.z to a canonical 5 or 6-digit form
+get_canonical_version()
+{
+	IFS=.
+	set -- $1
+	echo $((10000 * $1 + 100 * $2 + $3))
+}
+
+# $@ instead of $1 because multiple words might be given e.g. CC="ccache gcc"
+orig_args="$@"
+set -- $(get_compiler_info "$@")
+
+name=$1
+
+case "$name" in
+GCC)
+	version=$2.$3.$4
+	min_version=$gcc_min_version
+	;;
+Clang)
+	version=$2.$3.$4
+	min_version=$clang_min_version
+	;;
+ICC)
+	version=$(($2 / 100)).$(($2 % 100)).$3
+	min_version=$icc_min_version
+	;;
+*)
+	echo "$orig_args: unknown compiler" >&2
+	exit 1
+	;;
+esac
+
+cversion=$(get_canonical_version $version)
+min_cversion=$(get_canonical_version $min_version)
+
+if [ "$cversion" -lt "$min_cversion" ]; then
+	echo >&2 "***"
+	echo >&2 "*** Compiler is too old."
+	echo >&2 "***   Your $name version:    $version"
+	echo >&2 "***   Minimum $name version: $min_version"
+	echo >&2 "***"
+	exit 1
+fi
+
+echo $name $cversion
diff --git a/scripts/clang-version.sh b/scripts/clang-version.sh
deleted file mode 100755
index 6fabf0695761..000000000000
--- a/scripts/clang-version.sh
+++ /dev/null
@@ -1,19 +0,0 @@
-#!/bin/sh
-# SPDX-License-Identifier: GPL-2.0
-#
-# clang-version clang-command
-#
-# Print the compiler version of `clang-command' in a 5 or 6-digit form
-# such as `50001' for clang-5.0.1 etc.
-
-compiler="$*"
-
-if ! ( $compiler --version | grep -q clang) ; then
-	echo 0
-	exit 1
-fi
-
-MAJOR=$(echo __clang_major__ | $compiler -E -x c - | tail -n 1)
-MINOR=$(echo __clang_minor__ | $compiler -E -x c - | tail -n 1)
-PATCHLEVEL=$(echo __clang_patchlevel__ | $compiler -E -x c - | tail -n 1)
-printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL
diff --git a/scripts/gcc-version.sh b/scripts/gcc-version.sh
deleted file mode 100755
index ae353432539b..000000000000
--- a/scripts/gcc-version.sh
+++ /dev/null
@@ -1,20 +0,0 @@
-#!/bin/sh
-# SPDX-License-Identifier: GPL-2.0
-#
-# gcc-version gcc-command
-#
-# Print the gcc version of `gcc-command' in a 5 or 6-digit form
-# such as `29503' for gcc-2.95.3, `30301' for gcc-3.3.1, etc.
-
-compiler="$*"
-
-if [ ${#compiler} -eq 0 ]; then
-	echo "Error: No compiler specified." >&2
-	printf "Usage:\n\t$0 <gcc-command>\n" >&2
-	exit 1
-fi
-
-MAJOR=$(echo __GNUC__ | $compiler -E -x c - | tail -n 1)
-MINOR=$(echo __GNUC_MINOR__ | $compiler -E -x c - | tail -n 1)
-PATCHLEVEL=$(echo __GNUC_PATCHLEVEL__ | $compiler -E -x c - | tail -n 1)
-printf "%d%02d%02d\\n" $MAJOR $MINOR $PATCHLEVEL
-- 
2.27.0

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