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Masahiro Yamada ba64beb174 kbuild: check the minimum assembler version in Kconfig 
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
aa824e0c96 ("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>
2021-04-25 05:14:41 +09:00
..
atomic locking/atomics: Regenerate the atomics-check SHA1's 2020-11-07 13:20:41 +01:00
basic kbuild: introduce hostprogs-always-y and userprogs-always-y 2020-08-10 01:32:59 +09:00
clang-tools gen_compile_commands: prune some directories 2021-02-16 22:23:56 +09:00
coccinelle of: Remove of_dev_{get,put}() 2021-02-12 19:23:39 -06:00
dtc Devicetree fixes for v5.12-rc: 2021-03-05 12:12:28 -08:00
dummy-tools kbuild: check the minimum assembler version in Kconfig 2021-04-25 05:14:41 +09:00
gcc-plugins kbuild: rebuild GCC plugins when the compiler is upgraded 2021-03-11 14:40:50 +09:00
gdb scripts/gdb: fix list_for_each 2021-02-26 09:41:05 -08:00
genksyms genksyms: remove useless case DOTS 2021-02-16 12:01:45 +09:00
kconfig kconfig: unify rule of config, menuconfig, nconfig, gconfig, xconfig 2021-02-24 15:12:06 +09:00
ksymoops
mod Char/Misc driver patches for 5.12-rc1 2021-02-24 10:25:37 -08:00
package builddeb: Fix rootless build in setuid/setgid directory 2020-11-02 11:31:00 +09:00
selinux scripts/selinux,selinux: update mdp to enable policy capabilities 2020-08-17 20:42:00 -04:00
tracing tweewide: Fix most Shebang lines 2020-12-08 23:30:04 +09:00
.gitignore kbuild: preprocess module linker script 2020-09-25 00:36:41 +09:00
adjust_autoksyms.sh kbuild: do not include include/config/auto.conf from adjust_autoksyms.sh 2021-02-28 15:22:02 +09:00
as-version.sh kbuild: check the minimum assembler version in Kconfig 2021-04-25 05:14:41 +09:00
asn1_compiler.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 36 2019-05-24 17:27:11 +02:00
bin2c.c
bloat-o-meter scripts: switch explicitly to Python 3 2021-01-22 06:34:44 +09:00
bootgraph.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 391 2019-06-05 17:37:11 +02:00
bpf_helpers_doc.py bpf: Add a bpf_sock_from_file helper 2020-12-04 22:32:40 +01:00
cc-can-link.sh
cc-version.sh kbuild: collect minimum tool versions into scripts/min-tool-version.sh 2021-04-25 05:14:26 +09:00
check-sysctl-docs docs: add a script to check sysctl docs 2020-02-25 03:35:16 -07:00
check_extable.sh
checkincludes.pl
checkkconfigsymbols.py kconfig: remove '---help---' support 2020-08-14 13:30:03 +09:00
checkpatch.pl checkpatch: do not apply "initialise globals to 0" check to BPF progs 2021-02-26 09:41:04 -08:00
checkstack.pl scripts/checkstack.pl: fix arm sp regex 2020-05-26 00:03:16 +09:00
checksyscalls.sh
checkversion.pl
cleanfile
cleanpatch
coccicheck scripts: coccicheck: Correct usage of make coccicheck 2020-12-24 12:59:43 +01:00
config kconfig: config script: add a little user help 2021-01-04 10:38:11 +09:00
const_structs.checkpatch const_structs.checkpatch: add pinctrl_ops and pinmux_ops 2020-10-16 11:11:21 -07:00
decode_stacktrace.sh scripts/decode_stacktrace.sh: guess path to vmlinux by release name 2020-08-07 11:33:21 -07:00
decodecode scripts/decodecode: add the capability to supply the program counter 2020-10-13 18:38:26 -07:00
depmod.sh depmod: handle the case of /sbin/depmod without /sbin in PATH 2021-01-01 12:26:39 -08:00
dev-needs.sh scripts/dev-needs: Add script to list device dependencies 2020-09-04 18:19:37 +02:00
diffconfig scripts: switch explicitly to Python 3 2021-01-22 06:34:44 +09:00
documentation-file-ref-check scripts: documentation-file-ref-check: Add line break before exit 2020-04-15 15:13:13 -06:00
export_report.pl modpost: move the namespace field in Module.symvers last 2020-03-17 08:59:03 +09:00
extract-cert.c extract-cert: add static to local data 2020-08-18 20:16:46 +09:00
extract-ikconfig
extract-module-sig.pl
extract-sys-certs.pl
extract-vmlinux treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 378 2019-06-05 17:37:10 +02:00
extract_xc3028.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 339 2019-06-05 17:37:07 +02:00
faddr2line
file-size.sh
find-unused-docs.sh scripts/find-unused-docs: Fix massive false positives 2020-01-27 14:25:06 -07:00
gcc-goto.sh
gcc-ld
gcc-x86_32-has-stack-protector.sh
gcc-x86_64-has-stack-protector.sh
gen_autoksyms.sh kbuild: fix UNUSED_KSYMS_WHITELIST for Clang LTO 2021-02-28 15:19:21 +09:00
gen_ksymdeps.sh
generate_initcall_order.pl init: lto: ensure initcall ordering 2021-01-14 08:21:09 -08:00
get_abi.pl tweewide: Fix most Shebang lines 2020-12-08 23:30:04 +09:00
get_dvb_firmware treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 61 2019-05-24 17:36:45 +02:00
get_feat.pl scripts: get_feat.pl: reduce table width for all features output 2020-12-04 14:34:27 -07:00
get_maintainer.pl get_maintainer: exclude MAINTAINERS file(s) from --git-fallback 2020-10-16 11:11:19 -07:00
gfp-translate treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 166 2019-05-30 11:26:39 -07:00
headerdep.pl
headers_check.pl
headers_install.sh Merge branch 'work.fdpic' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-08-07 13:29:39 -07:00
insert-sys-cert.c
jobserver-exec kbuild: remove PYTHON variable 2021-02-01 10:37:19 +09:00
kallsyms.c kallsyms: fix nonconverging kallsyms table with lld 2021-02-05 17:53:28 +09:00
Kbuild.include kbuild: split cc-option and friends to scripts/Makefile.compiler 2021-04-25 05:09:32 +09:00
Kconfig.include kbuild: check the minimum assembler version in Kconfig 2021-04-25 05:14:41 +09:00
kernel-doc scripts: kernel-doc: fix array element capture in pointer-to-func parsing 2021-02-22 14:20:36 -07:00
ld-version.sh kbuild: collect minimum tool versions into scripts/min-tool-version.sh 2021-04-25 05:14:26 +09:00
leaking_addresses.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 166 2019-05-30 11:26:39 -07:00
Lindent
link-vmlinux.sh kbuild: apply fixdep logic to link-vmlinux.sh 2021-04-25 05:12:32 +09:00
Makefile scripts: set proper OpenSSL include dir also for sign-file 2021-02-15 01:54:11 +09:00
Makefile.asm-generic kbuild: prefix $(srctree)/ to some included Makefiles 2021-03-15 19:20:48 +09:00
Makefile.build kbuild: rename multi-used-* to multi-obj-* 2021-04-25 05:12:34 +09:00
Makefile.clean kbuild: prefix $(srctree)/ to some included Makefiles 2021-03-15 19:20:48 +09:00
Makefile.compiler kbuild: split cc-option and friends to scripts/Makefile.compiler 2021-04-25 05:09:32 +09:00
Makefile.dtbinst kbuild: prefix $(srctree)/ to some included Makefiles 2021-03-15 19:20:48 +09:00
Makefile.extrawarn Makefile.extrawarn: remove -Wnested-externs warning 2020-12-08 23:30:05 +09:00
Makefile.gcc-plugins gcc-plugins/stackleak: Use asm instrumentation to avoid useless register saving 2020-06-24 07:48:28 -07:00
Makefile.headersinst kbuild: prefix $(srctree)/ to some included Makefiles 2021-03-15 19:20:48 +09:00
Makefile.host kbuild: sort hostprogs before passing it to ifneq 2020-08-10 01:32:59 +09:00
Makefile.kasan kbuild: move CFLAGS_{KASAN,UBSAN,KCSAN} exports to relevant Makefiles 2020-09-25 00:36:50 +09:00
Makefile.kcov kbuild: include scripts/Makefile.* only when relevant CONFIG is enabled 2020-08-10 01:32:59 +09:00
Makefile.kcsan Kbuild updates for v5.10 2020-10-22 13:13:57 -07:00
Makefile.lib kbuild: move $(strip ) to suffix-search definition 2021-04-25 05:12:42 +09:00
Makefile.modfinal kbuild: lto: postpone objtool 2021-02-23 12:46:57 -08:00
Makefile.modinst kbuild: prefix $(srctree)/ to some included Makefiles 2021-03-15 19:20:48 +09:00
Makefile.modpost kbuild: prefix $(srctree)/ to some included Makefiles 2021-03-15 19:20:48 +09:00
Makefile.modsign kbuild: prefix $(srctree)/ to some included Makefiles 2021-03-15 19:20:48 +09:00
Makefile.package kbuild: fix broken builds because of GZIP,BZIP2,LZOP variables 2020-06-11 20:14:41 +09:00
Makefile.ubsan ubsan: remove overflow checks 2021-02-26 09:41:05 -08:00
Makefile.userprogs kbuild: add infrastructure to build userspace programs 2020-05-17 18:52:01 +09:00
makelst
markup_oops.pl treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 373 2019-06-05 17:37:10 +02:00
min-tool-version.sh kbuild: collect minimum tool versions into scripts/min-tool-version.sh 2021-04-25 05:14:26 +09:00
mkcompile_h kbuild: Use uname for LINUX_COMPILE_HOST detection 2020-10-21 00:46:04 +09:00
mkmakefile kbuild: get rid of $(realpath ...) from scripts/mkmakefile 2019-08-29 23:54:29 +09:00
mksysmap mksysmap: Fix the mismatch of '.L' symbols in System.map 2020-06-06 23:39:20 +09:00
mkuboot.sh
module.lds.S Modules updates for v5.12 2021-02-23 10:15:33 -08:00
modules-check.sh kbuild: make module name conflict fatal error 2020-05-26 00:03:16 +09:00
nsdeps kbuild: do not use scripts/ld-version.sh for checking spatch version 2020-12-12 18:31:29 +01:00
objdiff treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 199 2019-05-30 11:29:23 -07:00
parse-maintainers.pl parse-maintainers: Do not sort section content by default 2020-03-26 15:08:27 -07:00
patch-kernel
profile2linkerlist.pl
prune-kernel
recordmcount.c ftrace: Have recordmcount use w8 to read relp->r_info in arm64_is_fake_mcount 2021-03-02 17:27:18 -05:00
recordmcount.h recordmcount: support >64k sections 2020-06-16 21:21:00 -04:00
recordmcount.pl scripts/recordmcount.pl: support big endian for ARCH sh 2021-02-13 11:42:40 -08:00
setlocalversion scripts/setlocalversion: make git describe output more reliable 2020-09-25 02:28:12 +09:00
show_delta tweewide: Fix most Shebang lines 2020-12-08 23:30:04 +09:00
sign-file.c
sorttable.c s390/kernel: expand exception table logic to allow new handling options 2020-07-20 10:55:50 +02:00
sorttable.h scripts/sorttable: Implement build-time ORC unwind table sorting 2019-12-13 10:47:58 +01:00
spdxcheck-test.sh
spdxcheck.py spdxcheck.py: Use Python 3 2021-01-27 14:50:12 +01:00
spelling.txt scripts/spelling.txt: add more spellings to spelling.txt 2021-02-24 13:38:26 -08:00
sphinx-pre-install Docs: drop Python 2 support 2021-02-01 17:17:14 -07:00
split-man.pl tweewide: Fix most Shebang lines 2020-12-08 23:30:04 +09:00
stackdelta
stackusage
subarch.include
syscallhdr.sh scripts: add generic syscallhdr.sh 2021-02-22 08:22:04 +09:00
syscalltbl.sh scripts: add generic syscalltbl.sh 2021-02-22 08:22:03 +09:00
tags.sh Merge branch 'locking/urgent' into locking/core, to pick up fixes 2020-10-09 08:55:17 +02:00
test_dwarf5_support.sh Kconfig: allow explicit opt in to DWARF v5 2021-02-16 12:01:45 +09:00
tools-support-relr.sh scripts/tools-support-relr.sh: un-quote variables 2019-11-13 10:52:05 +00:00
unifdef.c
ver_linux ver_linux: Eliminate duplicate code in ldconfig processing logic 2021-01-27 14:54:42 +01:00
xen-hypercalls.sh
xz_wrap.sh kbuild: add variables for compression tools 2020-06-06 23:42:01 +09:00