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]
We can suppress it with -Wno-builtin-macro-redefined. However,
this option is not recognized by old compilers. So, __FILE__
is re-defined only when the option is supported.
I am adding stringify helper because '"..."' wrapping is the same
pattern as in KBUILD_BASENAME, KBUILD_MODNAME.
Please note __FILE__ is always an absolute path for external
modules. We can strip KBUILD_EXTMOD from the path if we want,
but I am not doing that. It would make it difficult to figure out
the module in question in case of WARN_ON().
Signed-off-by: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
---
This is another possible approach.
Please see these as well:
https://patchwork.kernel.org/patch/9693559/
https://patchwork.kernel.org/patch/9693563/
Pro:
this is only touching 3 makefiles.
Con:
this does not work for old compilers.
Makefile | 3 +++
scripts/Kbuild.include | 4 ++++
scripts/Makefile.lib | 6 ++++--
3 files changed, 11 insertions(+), 2 deletions(-)
diff --git a/Makefile b/Makefile
index 8804aae..293ef6d 100644
--- a/Makefile
+++ b/Makefile
@@ -798,6 +798,9 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=strict-prototypes)
# Prohibit date/time macros, which would make the build non-deterministic
KBUILD_CFLAGS += $(call cc-option,-Werror=date-time)
+# Is is possible to redefine __FILE__?
+KBUILD_CFLAGS += $(call cc-disable-warning, builtin-macro-redefined)
+
# enforce correct pointer usage
KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types)
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 61f87a9..7fc3841 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -31,6 +31,10 @@ 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 9e70196..1d789df 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -96,10 +96,12 @@ 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)))
+filepath_flags = $(if $(filter -Wno-builtin-macro-redefined, $(KBUILD_CFLAGS)), \
+ -D__FILE__=$(call stringify,$(src)/$(notdir $<)))
orig_c_flags = $(KBUILD_CPPFLAGS) $(KBUILD_CFLAGS) $(KBUILD_SUBDIR_CCFLAGS) \
$(ccflags-y) $(CFLAGS_$(basetarget).o)
@@ -163,7 +165,7 @@ endif
c_flags = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) \
$(__c_flags) $(modkern_cflags) \
- $(basename_flags) $(modname_flags)
+ $(basename_flags) $(modname_flags) $(filepath_flags)
a_flags = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(LINUXINCLUDE) \
$(__a_flags) $(modkern_aflags)
--
2.7.4
--
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