2018-03-30 13:15 GMT+09:00 Masahiro Yamada <[email protected]>: > 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 <[email protected]> > --- > > I tested this on GCC 8. > (not released yet, but you can get the source code from the trunk.)
Applied to linux-kbuild. -- Best Regards Masahiro Yamada
