From: Masahiro Yamada <masahiroy@kernel.org>
To: linux-kbuild@vger.kernel.org
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Arvind Sankar <nivedita@alum.mit.edu>,
Masahiro Yamada <masahiroy@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Brendan Higgins <brendanhiggins@google.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Changbin Du <changbin.du@intel.com>,
Krzysztof Kozlowski <krzk@kernel.org>,
Mauro Carvalho Chehab <mchehab+huawei@kernel.org>,
Randy Dunlap <rdunlap@infradead.org>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 2/2] kconfig: unify cc-option and as-option
Date: Sun, 14 Jun 2020 23:43:41 +0900 [thread overview]
Message-ID: <20200614144341.1077495-2-masahiroy@kernel.org> (raw)
In-Reply-To: <20200614144341.1077495-1-masahiroy@kernel.org>
cc-option and as-option are almost the same; both pass the flag to
$(CC). The main difference is the cc-option stops before the assemble
stage (-S option) whereas as-option stops after it (-c option).
I chose -S because it is slightly faster, but $(cc-option,-gz=zlib)
returns a wrong result (https://lkml.org/lkml/2020/6/9/1529).
It has been fixed by a separate patch, but using -c is more robust.
However, you cannot simply replace -S with -c because the following
code would break:
depends on $(cc-option,-gsplit-dwarf)
The combination of -c and -gsplit-dwarf does not accept /dev/null as
output.
$ cat /dev/null | gcc -gsplit-dwarf -S -x c - -o /dev/null
$ echo $?
0
$ cat /dev/null | gcc -gsplit-dwarf -c -x c - -o /dev/null
objcopy: Warning: '/dev/null' is not an ordinary file
$ echo $?
1
$ cat /dev/null | gcc -gsplit-dwarf -c -x c - -o tmp.o
$ echo $?
0
There is another flag that creates an separate file based on the
object file path:
$ cat /dev/null | gcc -ftest-coverage -c -x c - -o /dev/null
<stdin>:1: error: cannot open /dev/null.gcno
So, we cannot use /dev/null to sink the output.
Align the cc-option implementation with scripts/Kbuild.include.
With -c option used in cc-option, as-option is unneeded.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---
arch/arm64/Kconfig | 2 +-
lib/Kconfig.debug | 1 -
scripts/Kconfig.include | 8 +-------
3 files changed, 2 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 31380da53689..6eb18f45258e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1564,7 +1564,7 @@ config CC_HAS_SIGN_RETURN_ADDRESS
def_bool $(cc-option,-msign-return-address=all)
config AS_HAS_PAC
- def_bool $(as-option,-Wa$(comma)-march=armv8.3-a)
+ def_bool $(cc-option,-Wa$(comma)-march=armv8.3-a)
config AS_HAS_CFI_NEGATE_RA_STATE
def_bool $(as-instr,.cfi_startproc\n.cfi_negate_ra_state\n.cfi_endproc\n)
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 96999d4d2dda..9ad9210d70a1 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -229,7 +229,6 @@ config DEBUG_INFO_COMPRESSED
bool "Compressed debugging information"
depends on DEBUG_INFO
depends on $(cc-option,-gz=zlib)
- depends on $(as-option,-gz=zlib)
depends on $(ld-option,--compress-debug-sections=zlib)
help
Compress the debug information using zlib. Requires GCC 5.0+ or Clang
diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
index c264da2b9b30..a5fe72c504ff 100644
--- a/scripts/Kconfig.include
+++ b/scripts/Kconfig.include
@@ -25,18 +25,12 @@ failure = $(if-success,$(1),n,y)
# $(cc-option,<flag>)
# Return y if the compiler supports <flag>, n otherwise
-cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -S -x c /dev/null -o /dev/null)
+cc-option = $(success,mkdir .tmp_$$$$; trap "rm -rf .tmp_$$$$" EXIT; $(CC) -Werror $(CLANG_FLAGS) $(1) -c -x c /dev/null -o .tmp_$$$$/tmp.o)
# $(ld-option,<flag>)
# Return y if the linker supports <flag>, n otherwise
ld-option = $(success,$(LD) -v $(1))
-# $(as-option,<flag>)
-# /dev/zero is used as output instead of /dev/null as some assembler cribs when
-# both input and output are same. Also both of them have same write behaviour so
-# can be easily substituted.
-as-option = $(success, $(CC) $(CLANG_FLAGS) $(1) -c -x assembler /dev/null -o /dev/zero)
-
# $(as-instr,<instr>)
# Return y if the assembler supports <instr>, n otherwise
as-instr = $(success,printf "%b\n" "$(1)" | $(CC) $(CLANG_FLAGS) -c -x assembler -o /dev/null -)
--
2.25.1
next prev parent reply other threads:[~2020-06-14 14:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-14 14:43 [PATCH 1/2] kbuild: improve cc-option to clean up all temporary files Masahiro Yamada
2020-06-14 14:43 ` Masahiro Yamada [this message]
2020-06-15 10:00 ` [PATCH 2/2] kconfig: unify cc-option and as-option Will Deacon
2021-05-04 20:17 ` Johannes Berg
2021-05-04 20:46 ` Masahiro Yamada
2021-05-04 20:52 ` Johannes Berg
2021-05-04 21:05 ` Masahiro Yamada
2021-05-04 21:08 ` Johannes Berg
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