Commit cacd22ce authored by Thomas Weißschuh's avatar Thomas Weißschuh Committed by Masahiro Yamada
Browse files

kbuild: make all file references relative to source root 



-fmacro-prefix-map only affects __FILE__ and __BASE_FILE__.
Other references, for example in debug information, are not affected.
This makes handling of file references in the compiler outputs harder to
use and creates problems for reproducible builds.

Switch to -ffile-prefix map which affects all references.

Also drop the documentation section advising manual specification of
-fdebug-prefix-map for reproducible builds, as it is not necessary
anymore.

Suggested-by: default avatarBen Hutchings <ben@decadent.org.uk>
Link: https://lore.kernel.org/lkml/c49cc967294f9a3a4a34f69b6a8727a6d3959ed8.camel@decadent.org.uk/


Signed-off-by: default avatarThomas Weißschuh <linux@weissschuh.net>
Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
parent 97282e6d

Documentation/kbuild/reproducible-builds.rst

+0 −17
Original line number Diff line number Diff line
@@ -46,21 +46,6 @@ 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

----------------------------------
@@ -131,7 +116,5 @@ 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/

Makefile

+1 −1
Original line number Diff line number Diff line
@@ -1067,7 +1067,7 @@ endif 


# change __FILE__ to the relative path to the source directory

ifdef building_out_of_srctree

KBUILD_CPPFLAGS += $(call cc-option,-fmacro-prefix-map=$(srcroot)/=)

KBUILD_CPPFLAGS += $(call cc-option,-ffile-prefix-map=$(srcroot)/=)

KBUILD_RUSTFLAGS += --remap-path-prefix=$(srcroot)/=

endif