From b7dfc9ff7a470fec67846a036284167ac5f1c339 Mon Sep 17 00:00:00 2001 From: Dmitry Goldin Date: Fri, 4 Oct 2019 10:40:07 +0000 Subject: [PATCH] kheaders: make headers archive reproducible In commit eaae2b3dc54b ("Provide in-kernel headers to make extending kernel easier") a new mechanism was introduced, for kernels >=5.2, which embeds the kernel headers in the kernel image or a module and exposes them in procfs for use by userland tools. The archive containing the header files has nondeterminism caused by header files metadata. This patch normalizes the metadata and utilizes KBUILD_BUILD_TIMESTAMP if provided and otherwise falls back to the default behaviour. In commit e113b0ab8986 ("kheaders: Move from proc to sysfs") it was modified to use sysfs and the script for generation of the archive was renamed to what is being patched. Signed-off-by: Dmitry Goldin Reviewed-by: Greg Kroah-Hartman Reviewed-by: Joel Fernandes (Google) Signed-off-by: Masahiro Yamada --- Documentation/kbuild/reproducible-builds.rst | 13 +++++++++---- kernel/gen_kheaders.sh | 5 ++++- 2 files changed, 13 insertions(+), 5 deletions(-) diff --git a/Documentation/kbuild/reproducible-builds.rst b/Documentation/kbuild/reproducible-builds.rst index ab92e98c89c86..503393854e2e2 100644 --- a/Documentation/kbuild/reproducible-builds.rst +++ b/Documentation/kbuild/reproducible-builds.rst @@ -16,16 +16,21 @@ the kernel may be unreproducible, and how to avoid them. Timestamps ---------- -The kernel embeds a timestamp in two places: +The kernel embeds timestamps in three places: * The version string exposed by ``uname()`` and included in ``/proc/version`` * File timestamps in the embedded initramfs -By default the timestamp is the current time. This must be overridden -using the `KBUILD_BUILD_TIMESTAMP`_ variable. If you are building -from a git commit, you could use its commit date. +* If enabled via ``CONFIG_IKHEADERS``, file timestamps of kernel + headers embedded in the kernel or respective module, + exposed via ``/sys/kernel/kheaders.tar.xz`` + +By default the timestamp is the current time and in the case of +``kheaders`` the various files' modification times. This must +be overridden using the `KBUILD_BUILD_TIMESTAMP`_ variable. +If you are building from a git commit, you could use its commit date. The kernel does *not* use the ``__DATE__`` and ``__TIME__`` macros, and enables warnings if they are used. If you incorporate external diff --git a/kernel/gen_kheaders.sh b/kernel/gen_kheaders.sh index 9ff449888d9cd..aff79e461fc97 100755 --- a/kernel/gen_kheaders.sh +++ b/kernel/gen_kheaders.sh @@ -71,7 +71,10 @@ done | cpio --quiet -pd $cpio_dir >/dev/null 2>&1 find $cpio_dir -type f -print0 | xargs -0 -P8 -n1 perl -pi -e 'BEGIN {undef $/;}; s/\/\*((?!SPDX).)*?\*\///smg;' -tar -Jcf $tarfile -C $cpio_dir/ . > /dev/null +# Create archive and try to normalize metadata for reproducibility +tar "${KBUILD_BUILD_TIMESTAMP:+--mtime=$KBUILD_BUILD_TIMESTAMP}" \ + --owner=0 --group=0 --sort=name --numeric-owner \ + -Jcf $tarfile -C $cpio_dir/ . > /dev/null echo "$src_files_md5" > kernel/kheaders.md5 echo "$obj_files_md5" >> kernel/kheaders.md5 -- 2.39.5