[PATCH 0/2] kbuild: use relative path from $(srctree) instead of __FILE__

[PATCH 0/2] kbuild: use relative path from $(srctree) instead of __FILE__

[Masahiro Yamada]

Kbuild works in objtree, not in srctree.  So, __FILE__ is prefixed
with $(srctree)/ for out-of-tree build.

For example, WARN_ON() will look as follows if you built your kernel
out of source tree:

WARNING: CPU: 1 PID: 1 at /path/to/build/directory/arch/arm64/kernel/foo.c:...

With this series, it will always look like follows regardless of O= option.

WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/foo.c:...

If GCC does not support -Wno-builtin-macro-redefined (i.e. gcc version < 4.4),
the output is prefixed with absolute path.



Masahiro Yamada (2):
  kbuild: add stringify helper to quote a string passed to C files
  kbuild: redefine __FILE__ as relative path from $(srctree) if possible

 Makefile               | 9 +++++++++
 scripts/Kbuild.include | 4 ++++
 scripts/Makefile.lib   | 2 +-
 3 files changed, 14 insertions(+), 1 deletion(-)

-- 
2.7.4

[PATCH 1/2] kbuild: add stringify helper to quote a string passed to C files

[Masahiro Yamada]

I want to reuse $(squote)$(quote)...$(quote)$(squote) in the next
commit.  Move it to a helper.

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

 scripts/Kbuild.include | 4 ++++
 scripts/Makefile.lib   | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index db81df3..0b97354 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -33,6 +33,10 @@ baseprereq = $(basename $(notdir $<))
 escsq = $(subst $(squote),'\$(squote)',$1)
 
 ###
+# Quote a string to pass it to C files. foo => '"foo"'
+stringify = $(squote)$(quote)$1$(quote)$(squote)
+
+###
 # Easy method for doing a status message
        kecho := :
  quiet_kecho := echo
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 580e605..9bbb019 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -89,7 +89,7 @@ obj-dirs	:= $(addprefix $(obj)/,$(obj-dirs))
 # Note: Files that end up in two or more modules are compiled without the
 #       KBUILD_MODNAME definition. The reason is that any made-up name would
 #       differ in different configs.
-name-fix = $(squote)$(quote)$(subst $(comma),_,$(subst -,_,$1))$(quote)$(squote)
+name-fix = $(call stringify,$(subst $(comma),_,$(subst -,_,$1)))
 basename_flags = -DKBUILD_BASENAME=$(call name-fix,$(basetarget))
 modname_flags  = $(if $(filter 1,$(words $(modname))),\
                  -DKBUILD_MODNAME=$(call name-fix,$(modname)))
-- 
2.7.4

[PATCH 2/2] kbuild: redefine __FILE__ as relative path from $(srctree) if possible

[Masahiro Yamada]

Since Kbuild runs in the objtree, __FILE__ can be a very long path
depending of $(srctree).

Commit 9da0763bdd82 ("kbuild: Use relative path when building in a
subdir of the source tree") made the situation better for cases where
objtree is a child of srctree.  ($(srctree) is "..")

For other cases of out-of-tree build, filenames in WARN_ON() etc. are
still an absolute path.  It also means the kernel image depends on
where it was built.

Here, the idea is to redefine __FILE__ as the relative path from
$(srctree), but doing so causes a compiler warning:
  warning: "__FILE__" redefined [-Wbuiltin-macro-redefined]

The option -Wno-builtin-macro-redefined can suppress it, but it is
only recognized by GCC 4.4 or newer.  Re-define __FILE__ only when
possible.

Please note __FILE__ is always an absolute path for external modules.

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

 Makefile | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Makefile b/Makefile
index 2c4a238..a3e8931 100644
--- a/Makefile
+++ b/Makefile
@@ -1091,6 +1091,15 @@ ifdef stackp-check
 endif
 	@:
 
+# If possible, redefne __FILE__ as relative path from $(srctree).
+# $$ is needed to expand the following in submake
+ifeq ($(call cc-option-yn,-Wno-builtin-macro-redefined),y)
+KBUILD_CFLAGS   += -Wno-builtin-macro-redefined \
+		   -D__FILE__=$$(call stringify,$$(src)/$$(notdir $$<))
+endif
+# CAUTION: Do not add any reference to KBUILD_CFLAGS below this line.
+# Any call of cc-option, etc. will fail.
+
 # Generate some files
 # ---------------------------------------------------------------------------
 
-- 
2.7.4

Re: [PATCH 0/2] kbuild: use relative path from $(srctree) instead of __FILE__

[Masahiro Yamada]

2017-10-12 18:56 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
>
> Kbuild works in objtree, not in srctree.  So, __FILE__ is prefixed
> with $(srctree)/ for out-of-tree build.
>
> For example, WARN_ON() will look as follows if you built your kernel
> out of source tree:
>
> WARNING: CPU: 1 PID: 1 at /path/to/build/directory/arch/arm64/kernel/foo.c:...
>
> With this series, it will always look like follows regardless of O= option.
>
> WARNING: CPU: 1 PID: 1 at arch/arm64/kernel/foo.c:...
>
> If GCC does not support -Wno-builtin-macro-redefined (i.e. gcc version < 4.4),
> the output is prefixed with absolute path.
>

I expect to replace __FILE__ with its relative path,
but actually it replaces __FILE__ with relative path of __BASE_FILE__.
This will change the behavior in several places.

I take back this series.


-- 
Best Regards
Masahiro Yamada

Re: [PATCH 2/2] kbuild: redefine __FILE__ as relative path from $(srctree) if possible

[kbuild test robot]

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Hi Masahiro,

[auto build test WARNING on mmarek/for-next]
[also build test WARNING on next-20171013]
[if your patch is applied to the wrong git tree, please drop us a note to help improve the system]

url:    https://github.com/0day-ci/linux/commits/Masahiro-Yamada/kbuild-use-relative-path-from-srctree-instead-of-__FILE__/20171015-012234
base:   git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild for-next
config: sparc64-allmodconfig (attached as .config)
compiler: sparc64-linux-gnu-gcc (Debian 6.1.1-9) 6.1.1 20160705
reproduce:
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # save the attached .config to linux build tree
        make.cross ARCH=sparc64 

All warnings (new ones prefixed by >>):

   lib/dynamic_debug.c: In function 'trim_prefix':
>> lib/dynamic_debug.c:71:13: warning: overflow in implicit constant conversion [-Woverflow]
     int skip = strlen(__FILE__) - strlen("lib/dynamic_debug.c");
                ^~~~~~

vim +71 lib/dynamic_debug.c

e9d376f0 Jason Baron 2009-02-05  67  
2b678319 Jim Cromie  2011-12-19  68  /* Return the path relative to source root */
2b678319 Jim Cromie  2011-12-19  69  static inline const char *trim_prefix(const char *path)
2b678319 Jim Cromie  2011-12-19  70  {
2b678319 Jim Cromie  2011-12-19 @71  	int skip = strlen(__FILE__) - strlen("lib/dynamic_debug.c");
2b678319 Jim Cromie  2011-12-19  72  
2b678319 Jim Cromie  2011-12-19  73  	if (strncmp(path, __FILE__, skip))
2b678319 Jim Cromie  2011-12-19  74  		skip = 0; /* prefix mismatch, don't skip */
2b678319 Jim Cromie  2011-12-19  75  
2b678319 Jim Cromie  2011-12-19  76  	return path + skip;
2b678319 Jim Cromie  2011-12-19  77  }
2b678319 Jim Cromie  2011-12-19  78  

:::::: The code at line 71 was first introduced by commit
:::::: 2b6783191da7211c88f98eb1a2bd2027bff36e30 dynamic_debug: add trim_prefix() to provide source-root relative paths

:::::: TO: Jim Cromie <jim.cromie@gmail.com>
:::::: CC: Greg Kroah-Hartman <gregkh@suse.de>

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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