[PATCH] kbuild: use $(abspath ...) instead of $(shell cd ... && /bin/pwd)

[PATCH] kbuild: use $(abspath ...) instead of $(shell cd ... && /bin/pwd)

[Masahiro Yamada]

Kbuild conventionally uses $(shell cd ... && /bin/pwd) idiom to get
the absolute path of the directory because GNU Make 3.80, the minimal
supported version at that time, did not support $(abspath ...) or
$(realpath ...).

Commit 37d69ee30808 ("docs: bump minimal GNU Make version to 3.81")
dropped the GNU Make 3.80 support, so we are now allowed to use those
make-builtin helpers.

This conversion will provide better portability without relying on
the pwd command or its location /bin/pwd.

I am intentionally using $(realpath ...) instead $(abspath ...) in
some places.  The difference between the two is $(realpath ...)
returns an empty string if the given path does not exist.  It is
convenient in places where we need to error-out if the makefile fails
to create an output directory.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 Makefile                       | 12 ++++++------
 scripts/gdb/linux/Makefile     |  2 +-
 tools/power/cpupower/Makefile  |  2 +-
 tools/scripts/Makefile.include |  6 +++---
 4 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/Makefile b/Makefile
index 90da7bdc3f45..dfb6c88ea859 100644
--- a/Makefile
+++ b/Makefile
@@ -130,8 +130,8 @@ endif
 ifneq ($(KBUILD_OUTPUT),)
 # check that the output directory actually exists
 saved-output := $(KBUILD_OUTPUT)
-KBUILD_OUTPUT := $(shell mkdir -p $(KBUILD_OUTPUT) && cd $(KBUILD_OUTPUT) \
-								&& /bin/pwd)
+$(shell [ -d $(KBUILD_OUTPUT) ] || mkdir -p $(KBUILD_OUTPUT))
+KBUILD_OUTPUT := $(realpath $(KBUILD_OUTPUT))
 $(if $(KBUILD_OUTPUT),, \
      $(error failed to create output directory "$(saved-output)"))
 
@@ -978,7 +978,7 @@ ifdef CONFIG_HEADERS_CHECK
 	$(Q)$(MAKE) -f $(srctree)/Makefile headers_check
 endif
 ifdef CONFIG_GDB_SCRIPTS
-	$(Q)ln -fsn `cd $(srctree) && /bin/pwd`/scripts/gdb/vmlinux-gdb.py
+	$(Q)ln -fsn $(abspath $(srctree)/scripts/gdb/vmlinux-gdb.py)
 endif
 ifdef CONFIG_TRIM_UNUSED_KSYMS
 	$(Q)$(CONFIG_SHELL) $(srctree)/scripts/adjust_autoksyms.sh \
@@ -1237,7 +1237,7 @@ _modinst_:
 	@rm -rf $(MODLIB)/kernel
 	@rm -f $(MODLIB)/source
 	@mkdir -p $(MODLIB)/kernel
-	@ln -s `cd $(srctree) && /bin/pwd` $(MODLIB)/source
+	@ln -s $(abspath $(srctree)) $(MODLIB)/source
 	@if [ ! $(objtree) -ef  $(MODLIB)/build ]; then \
 		rm -f $(MODLIB)/build ; \
 		ln -s $(CURDIR) $(MODLIB)/build ; \
@@ -1629,11 +1629,11 @@ image_name:
 # Clear a bunch of variables before executing the submake
 tools/: FORCE
 	$(Q)mkdir -p $(objtree)/tools
-	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(shell cd $(objtree) && /bin/pwd) subdir=tools -C $(src)/tools/
+	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(src)/tools/
 
 tools/%: FORCE
 	$(Q)mkdir -p $(objtree)/tools
-	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(shell cd $(objtree) && /bin/pwd) subdir=tools -C $(src)/tools/ $*
+	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(src)/tools/ $*
 
 # Single targets
 # ---------------------------------------------------------------------------
diff --git a/scripts/gdb/linux/Makefile b/scripts/gdb/linux/Makefile
index 8b00031f5349..ab3cfe727a4e 100644
--- a/scripts/gdb/linux/Makefile
+++ b/scripts/gdb/linux/Makefile
@@ -1,6 +1,6 @@
 always := gdb-scripts
 
-SRCTREE := $(shell cd $(srctree) && /bin/pwd)
+SRCTREE := $(abspath $(srctree))
 
 $(obj)/gdb-scripts:
 ifneq ($(KBUILD_SRC),)
diff --git a/tools/power/cpupower/Makefile b/tools/power/cpupower/Makefile
index d6e1c02ddcfe..4c5a481a850c 100644
--- a/tools/power/cpupower/Makefile
+++ b/tools/power/cpupower/Makefile
@@ -26,7 +26,7 @@ endif
 
 ifneq ($(OUTPUT),)
 # check that the output directory actually exists
-OUTDIR := $(shell cd $(OUTPUT) && /bin/pwd)
+OUTDIR := $(realpath $(OUTPUT))
 $(if $(OUTDIR),, $(error output directory "$(OUTPUT)" does not exist))
 endif
 
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index ccad8ce925e4..57a850978cef 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -1,7 +1,7 @@
 ifneq ($(O),)
 ifeq ($(origin O), command line)
-	dummy := $(if $(shell test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
-	ABSOLUTE_O := $(shell cd $(O) ; pwd)
+	ABSOLUTE_O := $(realpath $(O))
+	dummy := $(if $(ABSOLUTE_O),,$(error O=$(O) does not exist))
 	OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
 	COMMAND_O := O=$(ABSOLUTE_O)
 ifeq ($(objtree),)
@@ -12,7 +12,7 @@ endif
 
 # check that the output directory actually exists
 ifneq ($(OUTPUT),)
-OUTDIR := $(shell cd $(OUTPUT) && /bin/pwd)
+OUTDIR := $(realpath $(OUTPUT))
 $(if $(OUTDIR),, $(error output directory "$(OUTPUT)" does not exist))
 endif
 
-- 
2.7.4

Re: [PATCH] kbuild: use $(abspath ...) instead of $(shell cd ... && /bin/pwd)

[Thierry Reding]

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On Sun, Aug 20, 2017 at 03:04:11PM +0900, Masahiro Yamada wrote:
> Kbuild conventionally uses $(shell cd ... && /bin/pwd) idiom to get
> the absolute path of the directory because GNU Make 3.80, the minimal
> supported version at that time, did not support $(abspath ...) or
> $(realpath ...).
> 
> Commit 37d69ee30808 ("docs: bump minimal GNU Make version to 3.81")
> dropped the GNU Make 3.80 support, so we are now allowed to use those
> make-builtin helpers.
> 
> This conversion will provide better portability without relying on
> the pwd command or its location /bin/pwd.
> 
> I am intentionally using $(realpath ...) instead $(abspath ...) in
> some places.  The difference between the two is $(realpath ...)
> returns an empty string if the given path does not exist.  It is
> convenient in places where we need to error-out if the makefile fails
> to create an output directory.
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> ---
> 
>  Makefile                       | 12 ++++++------
>  scripts/gdb/linux/Makefile     |  2 +-
>  tools/power/cpupower/Makefile  |  2 +-
>  tools/scripts/Makefile.include |  6 +++---
>  4 files changed, 11 insertions(+), 11 deletions(-)

This looks very similar to a patch I had written a long time ago:

Acked-by: Thierry Reding <treding@nvidia.com>

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Re: [PATCH] kbuild: use $(abspath ...) instead of $(shell cd ... && /bin/pwd)

[Masahiro Yamada]

2017-08-21 17:49 GMT+09:00 Thierry Reding <treding@nvidia.com>:
> On Sun, Aug 20, 2017 at 03:04:11PM +0900, Masahiro Yamada wrote:
>> Kbuild conventionally uses $(shell cd ... && /bin/pwd) idiom to get
>> the absolute path of the directory because GNU Make 3.80, the minimal
>> supported version at that time, did not support $(abspath ...) or
>> $(realpath ...).
>>
>> Commit 37d69ee30808 ("docs: bump minimal GNU Make version to 3.81")
>> dropped the GNU Make 3.80 support, so we are now allowed to use those
>> make-builtin helpers.
>>
>> This conversion will provide better portability without relying on
>> the pwd command or its location /bin/pwd.
>>
>> I am intentionally using $(realpath ...) instead $(abspath ...) in
>> some places.  The difference between the two is $(realpath ...)
>> returns an empty string if the given path does not exist.  It is
>> convenient in places where we need to error-out if the makefile fails
>> to create an output directory.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>> ---
>>
>>  Makefile                       | 12 ++++++------
>>  scripts/gdb/linux/Makefile     |  2 +-
>>  tools/power/cpupower/Makefile  |  2 +-
>>  tools/scripts/Makefile.include |  6 +++---
>>  4 files changed, 11 insertions(+), 11 deletions(-)
>
> This looks very similar to a patch I had written a long time ago:
>
> Acked-by: Thierry Reding <treding@nvidia.com>


Yup.

Three month ago, I sent a reminder to you,
but I did not get a response.

https://lkml.org/lkml/2017/5/18/1370




This time, Bjorn sent a patch to replace /bin/pwd with pwd.

I asked him to use $(abspath ...) / $(realpath ...),
but he did not like to do it.

https://patchwork.kernel.org/patch/9859591/


So, I am doing it by myself.



-- 
Best Regards
Masahiro Yamada

Re: [PATCH] kbuild: use $(abspath ...) instead of $(shell cd ... && /bin/pwd)

[Masahiro Yamada]

2017-08-21 18:04 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
> 2017-08-21 17:49 GMT+09:00 Thierry Reding <treding@nvidia.com>:
>> On Sun, Aug 20, 2017 at 03:04:11PM +0900, Masahiro Yamada wrote:
>>> Kbuild conventionally uses $(shell cd ... && /bin/pwd) idiom to get
>>> the absolute path of the directory because GNU Make 3.80, the minimal
>>> supported version at that time, did not support $(abspath ...) or
>>> $(realpath ...).
>>>
>>> Commit 37d69ee30808 ("docs: bump minimal GNU Make version to 3.81")
>>> dropped the GNU Make 3.80 support, so we are now allowed to use those
>>> make-builtin helpers.
>>>
>>> This conversion will provide better portability without relying on
>>> the pwd command or its location /bin/pwd.
>>>
>>> I am intentionally using $(realpath ...) instead $(abspath ...) in
>>> some places.  The difference between the two is $(realpath ...)
>>> returns an empty string if the given path does not exist.  It is
>>> convenient in places where we need to error-out if the makefile fails
>>> to create an output directory.
>>>
>>> Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
>

Applied to linux-kbuild.