linux-brain/kernel/gen_kheaders.sh
Dmitry Goldin 86cdd2fdc4 kheaders: make headers archive reproducible
In commit 43d8ce9d65 ("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 f7b101d330 ("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 <dgoldin+lkml@protonmail.ch>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
2019-10-05 15:29:49 +09:00

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#!/bin/bash
# SPDX-License-Identifier: GPL-2.0
# This script generates an archive consisting of kernel headers
# for CONFIG_IKHEADERS.
set -e
sfile="$(readlink -f "$0")"
outdir="$(pwd)"
tarfile=$1
cpio_dir=$outdir/$tarfile.tmp
dir_list="
include/
arch/$SRCARCH/include/
"
# Support incremental builds by skipping archive generation
# if timestamps of files being archived are not changed.
# This block is useful for debugging the incremental builds.
# Uncomment it for debugging.
# if [ ! -f /tmp/iter ]; then iter=1; echo 1 > /tmp/iter;
# else iter=$(($(cat /tmp/iter) + 1)); echo $iter > /tmp/iter; fi
# find $src_file_list -name "*.h" | xargs ls -l > /tmp/src-ls-$iter
# find $obj_file_list -name "*.h" | xargs ls -l > /tmp/obj-ls-$iter
# include/generated/compile.h is ignored because it is touched even when none
# of the source files changed. This causes pointless regeneration, so let us
# ignore them for md5 calculation.
pushd $srctree > /dev/null
src_files_md5="$(find $dir_list -name "*.h" |
grep -v "include/generated/compile.h" |
grep -v "include/generated/autoconf.h" |
xargs ls -l | md5sum | cut -d ' ' -f1)"
popd > /dev/null
obj_files_md5="$(find $dir_list -name "*.h" |
grep -v "include/generated/compile.h" |
grep -v "include/generated/autoconf.h" |
xargs ls -l | md5sum | cut -d ' ' -f1)"
# Any changes to this script will also cause a rebuild of the archive.
this_file_md5="$(ls -l $sfile | md5sum | cut -d ' ' -f1)"
if [ -f $tarfile ]; then tarfile_md5="$(md5sum $tarfile | cut -d ' ' -f1)"; fi
if [ -f kernel/kheaders.md5 ] &&
[ "$(cat kernel/kheaders.md5|head -1)" == "$src_files_md5" ] &&
[ "$(cat kernel/kheaders.md5|head -2|tail -1)" == "$obj_files_md5" ] &&
[ "$(cat kernel/kheaders.md5|head -3|tail -1)" == "$this_file_md5" ] &&
[ "$(cat kernel/kheaders.md5|tail -1)" == "$tarfile_md5" ]; then
exit
fi
if [ "${quiet}" != "silent_" ]; then
echo " GEN $tarfile"
fi
rm -rf $cpio_dir
mkdir $cpio_dir
pushd $srctree > /dev/null
for f in $dir_list;
do find "$f" -name "*.h";
done | cpio --quiet -pd $cpio_dir
popd > /dev/null
# The second CPIO can complain if files already exist which can
# happen with out of tree builds. Just silence CPIO for now.
for f in $dir_list;
do find "$f" -name "*.h";
done | cpio --quiet -pd $cpio_dir >/dev/null 2>&1
# Remove comments except SDPX lines
find $cpio_dir -type f -print0 |
xargs -0 -P8 -n1 perl -pi -e 'BEGIN {undef $/;}; s/\/\*((?!SPDX).)*?\*\///smg;'
# Create archive and try to normalize metadata for reproducibility
tar "${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 "$obj_files_md5" >> kernel/kheaders.md5
echo "$this_file_md5" >> kernel/kheaders.md5
echo "$(md5sum $tarfile | cut -d ' ' -f1)" >> kernel/kheaders.md5
rm -rf $cpio_dir