[PATCH v4 1/9] Makefile: Prepare for using macros for inline asm

[PATCH v4 1/9] Makefile: Prepare for using macros for inline asm

[Nadav Amit]

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@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-kbuild@vger.kernel.org

Signed-off-by: Nadav Amit <namit@vmware.com>
---
 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
 
 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)
+
+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

Re: [PATCH v4 1/9] Makefile: Prepare for using macros for inline asm

[Masahiro Yamada]

Hi.


2018-06-12 20:50 GMT+09:00 Nadav Amit <namit@vmware.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@socionext.com>
> Cc: Michal Marek <michal.lkml@markovi.net>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: x86@kernel.org
> Cc: linux-kbuild@vger.kernel.org
>
> Signed-off-by: Nadav Amit <namit@vmware.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@grover:~/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@grover:~/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

Re: [PATCH v4 1/9] Makefile: Prepare for using macros for inline asm

[Sam Ravnborg]

> 
> > +macros: $(obj)/macros.s
> > +       @:
> 
> If you add a phony target, it should be added to 'PHONY'.

Or this part:
> +archmacros:
> +       $(Q)$(MAKE) $(build)=arch/x86/kernel macros

could be modified to specify the exact filename so this indirection is not needed.

PS. Only one file posted to kbuild, so impossible to review as context is missing.

	Sam

Re: [PATCH v4 1/9] Makefile: Prepare for using macros for inline asm

[Nadav Amit]

Thanks for your comment! I am certainly Makefile-challenged, so your help is
highly appreciated.

Please see my responses/questions inline.

at 10:43 AM, Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> 2018-06-12 20:50 GMT+09:00 Nadav Amit <namit@vmware.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@socionext.com>
>> Cc: Michal Marek <michal.lkml@markovi.net>
>> Cc: Thomas Gleixner <tglx@linutronix.de>
>> Cc: Ingo Molnar <mingo@redhat.com>
>> Cc: "H. Peter Anvin" <hpa@zytor.com>
>> Cc: x86@kernel.org
>> Cc: linux-kbuild@vger.kernel.org
>> 
>> Signed-off-by: Nadav Amit <namit@vmware.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@grover:~/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@grover:~/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

You are right. I tried to filter out the use of the switch (exported as
ASM_MACRO_FLAGS) for empty.o. Any suggestions on how to do it properly?

> Are you planning to support for all architectures, or x86-specific?

Not right now. But I think that other architectures will also prefer to
separate the inline assembly chunks in a similar manner, for better
compilation, easier readability, and better code maintainability.

Thanks again,
Nadav

Re: [PATCH v4 1/9] Makefile: Prepare for using macros for inline asm

[Masahiro Yamada]

Hi.

2018-06-14 7:19 GMT+09:00 Nadav Amit <namit@vmware.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@grover:~/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@grover:~/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
>
> You are right. I tried to filter out the use of the switch (exported as
> ASM_MACRO_FLAGS) for empty.o. Any suggestions on how to do it properly?


You can do like this:


diff --git a/scripts/mod/Makefile b/scripts/mod/Makefile
index 42c5d50..a5b4af4 100644
--- a/scripts/mod/Makefile
+++ b/scripts/mod/Makefile
@@ -4,6 +4,8 @@ OBJECT_FILES_NON_STANDARD := y
 hostprogs-y    := modpost mk_elfconfig
 always         := $(hostprogs-y) empty.o

+CFLAGS_REMOVE_empty.o := $(ASM_MACRO_FLAGS)
+
 modpost-objs   := modpost.o file2alias.o sumversion.o

 devicetable-offsets-file := devicetable-offsets.h





modpost is an exceptional hostprogam - it depends on
target compiler, which makes the build order complicated.

I want to compile under scripts/ only with $(HOSTCC).

I am planning to change modpost
target-independent by detecting
32/64 bit, little/big-endianness run-time.
Then, empty.c will go away.


In the meanwhile, CFLAGS_REMOVE_ will do
as a workaround.


-- 
Best Regards
Masahiro Yamada

Re: [PATCH v4 1/9] Makefile: Prepare for using macros for inline asm

[Masahiro Yamada]

2018-06-14 5:36 GMT+09:00 Sam Ravnborg <sam@ravnborg.org>:
>>
>> > +macros: $(obj)/macros.s
>> > +       @:
>>
>> If you add a phony target, it should be added to 'PHONY'.
>
> Or this part:
>> +archmacros:
>> +       $(Q)$(MAKE) $(build)=arch/x86/kernel macros
>
> could be modified to specify the exact filename so this indirection is not needed.

Yes, it could work.

Actually, two styles co-exist in arch/x86/Makefile.
(archprepare vs archscripts)




-- 
Best Regards
Masahiro Yamada

Re: [PATCH v4 1/9] Makefile: Prepare for using macros for inline asm

[Nadav Amit]

at 5:40 PM, Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> In the meanwhile, CFLAGS_REMOVE_ will do
> as a workaround.

Thanks! I appreciate your help.

I will submit tomorrow an updated version.

Regards,
Nadav