Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
kheaders: rebuild kheaders_data.tar.xz when a file is modified within a minute
When a header file is changed, kernel/gen_kheaders.sh may fail to update
kernel/kheaders_data.tar.xz.
[steps to reproduce]
[1] Build kernel/kheaders_data.tar.xz
$ make -j$(nproc) kernel/kheaders.o
DESCEND objtool
INSTALL libsubcmd_headers
CALL scripts/checksyscalls.sh
CHK kernel/kheaders_data.tar.xz
GEN kernel/kheaders_data.tar.xz
CC kernel/kheaders.o
[2] Modify a header without changing the file size
$ sed -i s/0xdeadbeef/0xfeedbeef/ include/linux/elfnote.h
[3] Rebuild kernel/kheaders_data.tar.xz
$ make -j$(nproc) kernel/kheaders.o
DESCEND objtool
INSTALL libsubcmd_headers
CALL scripts/checksyscalls.sh
CHK kernel/kheaders_data.tar.xz
kernel/kheaders_data.tar.xz is not updated if steps [1] - [3] are run
within the same minute.
The headers_md5 variable stores the MD5 hash of the 'ls -l' output
for all header files. This hash value is used to determine whether
kheaders_data.tar.xz needs to be rebuilt. However, 'ls -l' prints the
modification times with minute-level granularity. If a file is modified
within the same minute and its size remains the same, the MD5 hash does
not change.
To reliably detect file modifications, this commit rewrites
kernel/gen_kheaders.sh to output header dependencies to
kernel/.kheaders_data.tar.xz.cmd. Then, Make compares the timestamps
and reruns kernel/gen_kheaders.sh when necessary. This is the standard
mechanism used by Make and Kbuild.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
+63
-74
+2
kernel/.gitignore
+2
kernel/.gitignore
+42
-5
kernel/Makefile
+42
-5
kernel/Makefile
···
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$(obj)/config_data: $(KCONFIG_CONFIG) FORCE
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$(call filechk,cat)
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# kheaders_data.tar.xz
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$(obj)/kheaders.o: $(obj)/kheaders_data.tar.xz
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quiet_cmd_genikh = CHK $(obj)/kheaders_data.tar.xz
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cmd_genikh = $(CONFIG_SHELL) $(srctree)/kernel/gen_kheaders.sh $@
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$(obj)/kheaders_data.tar.xz: FORCE
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$(call cmd,genikh)
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quiet_cmd_kheaders_data = GEN $@
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cmd_kheaders_data = "$<" "$@" "$(obj)/kheaders-srclist" "$(obj)/kheaders-objlist"
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cmd_kheaders_data_dep = cat $(depfile) >> $(dot-target).cmd; rm -f $(depfile)
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clean-files := kheaders_data.tar.xz kheaders.md5
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define rule_kheaders_data
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$(call cmd_and_savecmd,kheaders_data)
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$(call cmd,kheaders_data_dep)
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endef
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+
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targets += kheaders_data.tar.xz
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$(obj)/kheaders_data.tar.xz: $(src)/gen_kheaders.sh $(obj)/kheaders-srclist $(obj)/kheaders-objlist $(obj)/kheaders.md5 FORCE
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$(call if_changed_rule,kheaders_data)
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+
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# generated headers in objtree
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#
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# include/generated/utsversion.h is ignored because it is generated
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# after gen_kheaders.sh is executed. (utsversion.h is unneeded for kheaders)
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filechk_kheaders_objlist = \
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for d in include "arch/$(SRCARCH)/include"; do \
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find "$${d}/generated" ! -path "include/generated/utsversion.h" -a -name "*.h" -print; \
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done
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+
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$(obj)/kheaders-objlist: FORCE
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$(call filechk,kheaders_objlist)
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+
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# non-generated headers in srctree
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filechk_kheaders_srclist = \
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for d in include "arch/$(SRCARCH)/include"; do \
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find "$(srctree)/$${d}" -path "$(srctree)/$${d}/generated" -prune -o -name "*.h" -print; \
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done
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+
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$(obj)/kheaders-srclist: FORCE
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$(call filechk,kheaders_srclist)
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# Some files are symlinks. If symlinks are changed, kheaders_data.tar.xz should
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# be rebuilt.
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filechk_kheaders_md5sum = xargs -r -a $< stat -c %N | md5sum
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$(obj)/kheaders.md5: $(obj)/kheaders-srclist FORCE
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$(call filechk,kheaders_md5sum)
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clean-files := kheaders.md5 kheaders-srclist kheaders-objlist
+19
-69
kernel/gen_kheaders.sh
+19
-69
kernel/gen_kheaders.sh
···
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# This script generates an archive consisting of kernel headers
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# for CONFIG_IKHEADERS.
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set -e
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sfile="$(readlink -f "$0")"
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outdir="$(pwd)"
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tarfile=$1
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tmpdir=$outdir/${tarfile%/*}/.tmp_dir
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srclist=$2
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objlist=$3
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dir_list="
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include/
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arch/$SRCARCH/include/
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"
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dir=$(dirname "${tarfile}")
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tmpdir=${dir}/.tmp_dir
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depfile=${dir}/.$(basename "${tarfile}").d
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# Support incremental builds by skipping archive generation
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# if timestamps of files being archived are not changed.
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# generate dependency list.
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{
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echo
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echo "deps_${tarfile} := \\"
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sed 's:\(.*\): \1 \\:' "${srclist}"
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sed -n '/^include\/generated\/autoconf\.h$/!s:\(.*\): \1 \\:p' "${objlist}"
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echo
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echo "${tarfile}: \$(deps_${tarfile})"
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echo
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echo "\$(deps_${tarfile}):"
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# This block is useful for debugging the incremental builds.
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# Uncomment it for debugging.
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# if [ ! -f /tmp/iter ]; then iter=1; echo 1 > /tmp/iter;
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# else iter=$(($(cat /tmp/iter) + 1)); echo $iter > /tmp/iter; fi
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# find $all_dirs -name "*.h" | xargs ls -l > /tmp/ls-$iter
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-
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all_dirs=
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if [ "$building_out_of_srctree" ]; then
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for d in $dir_list; do
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all_dirs="$all_dirs $srctree/$d"
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done
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fi
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all_dirs="$all_dirs $dir_list"
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# include/generated/utsversion.h is ignored because it is generated after this
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# script is executed. (utsversion.h is unneeded for kheaders)
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#
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# When Kconfig regenerates include/generated/autoconf.h, its timestamp is
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# updated, but the contents might be still the same. When any CONFIG option is
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# changed, Kconfig touches the corresponding timestamp file include/config/*.
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# Hence, the md5sum detects the configuration change anyway. We do not need to
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# check include/generated/autoconf.h explicitly.
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#
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# Ignore them for md5 calculation to avoid pointless regeneration.
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headers_md5="$(find $all_dirs -name "*.h" -a \
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! -path include/generated/utsversion.h -a \
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! -path include/generated/autoconf.h |
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xargs ls -l | md5sum | cut -d ' ' -f1)"
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# Any changes to this script will also cause a rebuild of the archive.
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this_file_md5="$(ls -l $sfile | md5sum | cut -d ' ' -f1)"
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if [ -f $tarfile ]; then tarfile_md5="$(md5sum $tarfile | cut -d ' ' -f1)"; fi
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if [ -f kernel/kheaders.md5 ] &&
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[ "$(head -n 1 kernel/kheaders.md5)" = "$headers_md5" ] &&
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[ "$(head -n 2 kernel/kheaders.md5 | tail -n 1)" = "$this_file_md5" ] &&
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[ "$(tail -n 1 kernel/kheaders.md5)" = "$tarfile_md5" ]; then
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exit
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fi
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echo " GEN $tarfile"
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} > "${depfile}"
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rm -rf "${tmpdir}"
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mkdir "${tmpdir}"
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if [ "$building_out_of_srctree" ]; then
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(
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cd $srctree
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for f in $dir_list
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do find "$f" -name "*.h";
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done | tar -c -f - -T - | tar -xf - -C "${tmpdir}"
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)
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fi
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for f in $dir_list;
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do find "$f" -name "*.h";
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done | tar -c -f - -T - | tar -xf - -C "${tmpdir}"
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# Always exclude include/generated/utsversion.h
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# Otherwise, the contents of the tarball may vary depending on the build steps.
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rm -f "${tmpdir}/include/generated/utsversion.h"
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# shellcheck disable=SC2154 # srctree is passed as an env variable
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sed "s:^${srctree}/::" "${srclist}" | tar -c -f - -C "${srctree}" -T - | tar -xf - -C "${tmpdir}"
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tar -c -f - -T "${objlist}" | tar -xf - -C "${tmpdir}"
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# Remove comments except SDPX lines
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# Use a temporary file to store directory contents to prevent find/xargs from
···
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tar "${KBUILD_BUILD_TIMESTAMP:+--mtime=$KBUILD_BUILD_TIMESTAMP}" \
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--owner=0 --group=0 --sort=name --numeric-owner --mode=u=rw,go=r,a+X \
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-I $XZ -cf $tarfile -C "${tmpdir}/" . > /dev/null
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echo $headers_md5 > kernel/kheaders.md5
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echo "$this_file_md5" >> kernel/kheaders.md5
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echo "$(md5sum $tarfile | cut -d ' ' -f1)" >> kernel/kheaders.md5
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rm -rf "${tmpdir}"