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-rw-r--r--Documentation/kbuild/reproducible-builds.rst17
1 files changed, 17 insertions, 0 deletions
diff --git a/Documentation/kbuild/reproducible-builds.rst b/Documentation/kbuild/reproducible-builds.rst
index a7762486c93f..f2dcc39044e6 100644
--- a/Documentation/kbuild/reproducible-builds.rst
+++ b/Documentation/kbuild/reproducible-builds.rst
@@ -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/