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Date: Thu, 14 Jun 2018 02:43:56 +0900
From: Masahiro Yamada <yamada.masahiro@...ionext.com>
To: Nadav Amit <namit@...are.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
X86 ML <x86@...nel.org>,
Michal Marek <michal.lkml@...kovi.net>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>
Subject: Re: [PATCH v4 1/9] Makefile: Prepare for using macros for inline asm
Hi.
2018-06-12 20:50 GMT+09:00 Nadav Amit <namit@...are.com>:
> Using macros for inline assembly improves both readability and
> compilation decisions that are distorted by big assembly blocks that use
> alternative sections. Compile macros.S and use it to assemble all C
> files. Currently, only x86 will use it.
>
> Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
> Cc: Michal Marek <michal.lkml@...kovi.net>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: x86@...nel.org
> Cc: linux-kbuild@...r.kernel.org
>
> Signed-off-by: Nadav Amit <namit@...are.com>
I have not fully understood this series yet.
I do not have enough skill in x86 architecture,
but just some comments from the build system point of view.
I guess this will probably break the parallel building.
Kbuild can build 'prepare' and 'scripts' simultaneously.
I locally modified the following line:
diff --git a/Makefile b/Makefile
index 2dea909440..6ad484a 100644
--- a/Makefile
+++ b/Makefile
@@ -1030,7 +1030,7 @@ $(sort $(vmlinux-deps)): $(vmlinux-dirs) ;
# Error messages still appears in the original language
PHONY += $(vmlinux-dirs)
-$(vmlinux-dirs): prepare scripts
+$(vmlinux-dirs): scripts prepare
$(Q)$(MAKE) $(build)=$@ need-builtin=1
define filechk_kernel.release
masahiro@...ver:~/workspace/linux-kbuild$ make defconfig
HOSTCC scripts/basic/fixdep
HOSTCC scripts/kconfig/conf.o
YACC scripts/kconfig/zconf.tab.c
LEX scripts/kconfig/zconf.lex.c
HOSTCC scripts/kconfig/zconf.tab.o
HOSTLD scripts/kconfig/conf
*** Default configuration is based on 'x86_64_defconfig'
#
# configuration written to .config
#
masahiro@...ver:~/workspace/linux-kbuild$ make all
scripts/kconfig/conf --syncconfig Kconfig
WRAP arch/x86/include/generated/uapi/asm/bpf_perf_event.h
WRAP arch/x86/include/generated/uapi/asm/poll.h
WRAP arch/x86/include/generated/asm/dma-contiguous.h
WRAP arch/x86/include/generated/asm/early_ioremap.h
WRAP arch/x86/include/generated/asm/mcs_spinlock.h
WRAP arch/x86/include/generated/asm/mm-arch-hooks.h
CC scripts/mod/empty.o
Assembler messages:
Error: can't open arch/x86/kernel/macros.s for reading: No such file
or directory
make[2]: *** [scripts/Makefile.build:318: scripts/mod/empty.o] Error 1
make[1]: *** [scripts/Makefile.build:558: scripts/mod] Error 2
make: *** [Makefile:1050: scripts] Error 2
> ---
> Makefile | 9 +++++++--
> arch/x86/Makefile | 11 +++++++++--
> arch/x86/kernel/Makefile | 6 ++++++
> arch/x86/kernel/macros.S | 7 +++++++
> scripts/Kbuild.include | 4 +++-
> 5 files changed, 32 insertions(+), 5 deletions(-)
> create mode 100644 arch/x86/kernel/macros.S
>
> diff --git a/Makefile b/Makefile
> index 554dcaddbce4..026586db2f26 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1085,7 +1085,7 @@ scripts: scripts_basic include/config/auto.conf include/config/tristate.conf \
> # version.h and scripts_basic is processed / created.
>
> # Listed in dependency order
> -PHONY += prepare archprepare prepare0 prepare1 prepare2 prepare3
> +PHONY += prepare archprepare macroprepare prepare0 prepare1 prepare2 prepare3
>
> # prepare3 is used to check if we are building in a separate output directory,
> # and if so do:
> @@ -1109,7 +1109,9 @@ prepare1: prepare2 $(version_h) $(autoksyms_h) include/generated/utsrelease.h \
> include/config/auto.conf
> $(cmd_crmodverdir)
>
> -archprepare: archheaders archscripts prepare1 scripts_basic
> +macroprepare: prepare1 archmacros
> +
> +archprepare: archheaders archscripts macroprepare scripts_basic
Are you planning to support for all architectures, or x86-specific?
Currently, there are some hooks to do arch-specific things such as
'archprepare', 'archscripts'.
> prepare0: archprepare gcc-plugins
> $(Q)$(MAKE) $(build)=.
> @@ -1214,6 +1216,9 @@ archheaders:
> PHONY += archscripts
> archscripts:
>
> +PHONY += archmacros
> +archmacros:
> +
> PHONY += __headers
> __headers: $(version_h) scripts_basic uapi-asm-generic archheaders archscripts
> $(Q)$(MAKE) $(build)=scripts build_unifdef
> diff --git a/arch/x86/Makefile b/arch/x86/Makefile
> index 60135cbd905c..6b82314776fd 100644
> --- a/arch/x86/Makefile
> +++ b/arch/x86/Makefile
> @@ -235,8 +235,8 @@ ifdef CONFIG_X86_64
> LDFLAGS += $(call ld-option, -z max-page-size=0x200000)
> endif
>
> -# Speed up the build
> -KBUILD_CFLAGS += -pipe
> +# We cannot use -pipe flag since we give an additional .s file to the compiler
> +#KBUILD_CFLAGS += -pipe
> # Workaround for a gcc prelease that unfortunately was shipped in a suse release
> KBUILD_CFLAGS += -Wno-sign-compare
> #
> @@ -258,11 +258,18 @@ archscripts: scripts_basic
> archheaders:
> $(Q)$(MAKE) $(build)=arch/x86/entry/syscalls all
>
> +archmacros:
> + $(Q)$(MAKE) $(build)=arch/x86/kernel macros
> +
> archprepare:
> ifeq ($(CONFIG_KEXEC_FILE),y)
> $(Q)$(MAKE) $(build)=arch/x86/purgatory arch/x86/purgatory/kexec-purgatory.c
> endif
>
> +ASM_MACRO_FLAGS = -Wa,arch/x86/kernel/macros.s
> +export ASM_MACRO_FLAGS
> +KBUILD_CFLAGS += $(ASM_MACRO_FLAGS)
> +
> ###
> # Kernel objects
>
> diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
> index 02d6f5cf4e70..fdb6c5b2a922 100644
> --- a/arch/x86/kernel/Makefile
> +++ b/arch/x86/kernel/Makefile
> @@ -9,6 +9,12 @@ extra-y += ebda.o
> extra-y += platform-quirks.o
> extra-y += vmlinux.lds
>
> +$(obj)/macros.s: $(obj)/macros.S FORCE
> + $(call if_changed_dep,cpp_s_S)
This is unnecessary.
Kbuild will find the correct pattern rule
in scripts/Makefile.build
> +macros: $(obj)/macros.s
> + @:
If you add a phony target, it should be added to 'PHONY'.
Like this:
PHONY += macros
macros: $(obj)/macros.s
@:
> CPPFLAGS_vmlinux.lds += -U$(UTS_MACHINE)
>
> ifdef CONFIG_FUNCTION_TRACER
> diff --git a/arch/x86/kernel/macros.S b/arch/x86/kernel/macros.S
> new file mode 100644
> index 000000000000..cfc1c7d1a6eb
> --- /dev/null
> +++ b/arch/x86/kernel/macros.S
> @@ -0,0 +1,7 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +/*
> + * This file includes headers whose assembly part includes macros which are
> + * commonly used. The macros are precompiled into assmebly file which is later
> + * assembled together with each compiled file.
> + */
> diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
> index 50cee534fd64..ad2c02062aa4 100644
> --- a/scripts/Kbuild.include
> +++ b/scripts/Kbuild.include
> @@ -189,7 +189,9 @@ __cc-option = $(call try-run-cached,\
>
> # Do not attempt to build with gcc plugins during cc-option tests.
> # (And this uses delayed resolution so the flags will be up to date.)
> -CC_OPTION_CFLAGS = $(filter-out $(GCC_PLUGINS_CFLAGS),$(KBUILD_CFLAGS))
> +# In addition, do not include the asm macros which are built later.
> +CC_OPTION_FILTERED = $(GCC_PLUGINS_CFLAGS) $(ASM_MACRO_FLAGS)
> +CC_OPTION_CFLAGS = $(filter-out $(CC_OPTION_FILTERED),$(KBUILD_CFLAGS))
>
> # cc-option
> # Usage: cflags-y += $(call cc-option,-march=winchip-c6,-march=i586)
> --
> 2.17.0
>
--
Best Regards
Masahiro Yamada
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