Revert "kbuild: make all file references relative to source root"

This reverts commit cacd22ce69.

-ffile-prefix-map breaks the ability of debuggers to find the source
file corresponding to object files. As there is no simple or uniform
way to specify the source directory explicitly, this breaks developers
workflows.

Revert the unconditional usage of -ffile-prefix-map.

Reported-by: Matthieu Baerts <matttbe@kernel.org>
Closes: https://lore.kernel.org/lkml/edc50aa7-0740-4942-8c15-96f12f2acc7e@kernel.org/
Reported-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Closes: https://lore.kernel.org/lkml/aBEttQH4kimHFScx@intel.com/
Fixes: cacd22ce69 ("kbuild: make all file references relative to source root")
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Thomas Weißschuh 2025-05-11 08:02:27 +02:00 committed by Masahiro Yamada
parent f0e4b333cf
commit 020d7f1448
2 changed files with 18 additions and 1 deletions

View File

@ -46,6 +46,21 @@ The kernel embeds the building user and host names in
`KBUILD_BUILD_USER and KBUILD_BUILD_HOST`_ variables. If you are
building from a git commit, you could use its committer address.
Absolute filenames
------------------
When the kernel is built out-of-tree, debug information may include
absolute filenames for the source files. This must be overridden by
including the ``-fdebug-prefix-map`` option in the `KCFLAGS`_ variable.
Depending on the compiler used, the ``__FILE__`` macro may also expand
to an absolute filename in an out-of-tree build. Kbuild automatically
uses the ``-fmacro-prefix-map`` option to prevent this, if it is
supported.
The Reproducible Builds web site has more information about these
`prefix-map options`_.
Generated files in source packages
----------------------------------
@ -116,5 +131,7 @@ See ``scripts/setlocalversion`` for details.
.. _KBUILD_BUILD_TIMESTAMP: kbuild.html#kbuild-build-timestamp
.. _KBUILD_BUILD_USER and KBUILD_BUILD_HOST: kbuild.html#kbuild-build-user-kbuild-build-host
.. _KCFLAGS: kbuild.html#kcflags
.. _prefix-map options: https://reproducible-builds.org/docs/build-path/
.. _Reproducible Builds project: https://reproducible-builds.org/
.. _SOURCE_DATE_EPOCH: https://reproducible-builds.org/docs/source-date-epoch/

View File

@ -1068,7 +1068,7 @@ KBUILD_CFLAGS += -fno-builtin-wcslen
# change __FILE__ to the relative path to the source directory
ifdef building_out_of_srctree
KBUILD_CPPFLAGS += $(call cc-option,-ffile-prefix-map=$(srcroot)/=)
KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srcroot)/=)
KBUILD_RUSTFLAGS += --remap-path-prefix=$(srcroot)/=
endif