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| author | Masahiro Yamada <yamada.masahiro@socionext.com> | 2018-03-30 07:15:26 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2019-11-10 13:23:30 +0300 |
| commit | 2e1dff7b0df33327dacfb94f82f6d82e8f2ffa01 (patch) | |
| tree | b3b77aa63b847406223ebc453f5665f5fd8dcc5c /Makefile | |
| parent | a250cab009b578679496f53fe3532ef79821fe8f (diff) | |
| download | linux-2e1dff7b0df33327dacfb94f82f6d82e8f2ffa01.tar.xz | |
kbuild: use -fmacro-prefix-map to make __FILE__ a relative path
[ Upstream commit a73619a845d5625079cc1b3b820f44c899618388 ]
The __FILE__ macro is used everywhere in the kernel to locate the file
printing the log message, such as WARN_ON(), etc. If the kernel is
built out of tree, this can be a long absolute path, like this:
WARNING: CPU: 1 PID: 1 at /path/to/build/directory/arch/arm64/kernel/foo.c:...
This is because Kbuild runs in the objtree instead of the srctree,
then __FILE__ is expanded to a file path prefixed with $(srctree)/.
Commit 9da0763bdd82 ("kbuild: Use relative path when building in a
subdir of the source tree") improved this to some extent; $(srctree)
becomes ".." if the objtree is a child of the srctree.
For other cases of out-of-tree build, __FILE__ is still the absolute
path. It also means the kernel image depends on where it was built.
A brand-new option from GCC, -fmacro-prefix-map, solves this problem.
If your compiler supports it, __FILE__ is the relative path from the
srctree regardless of O= option. This provides more readable log and
more reproducible builds.
Please note __FILE__ is always an absolute path for external modules.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'Makefile')
| -rw-r--r-- | Makefile | 3 |
1 files changed, 3 insertions, 0 deletions
@@ -837,6 +837,9 @@ KBUILD_CFLAGS += $(call cc-option,-Werror=incompatible-pointer-types) # Require designated initializers for all marked structures KBUILD_CFLAGS += $(call cc-option,-Werror=designated-init) +# change __FILE__ to the relative path from the srctree +KBUILD_CFLAGS += $(call cc-option,-fmacro-prefix-map=$(srctree)/=) + # use the deterministic mode of AR if available KBUILD_ARFLAGS := $(call ar-option,D) |