kbuild: deb-pkg: use build ID instead of debug link for dbg package

There are two ways of managing separate debug info files:

 [1] The executable contains the .gnu_debuglink section, which specifies
     the name and the CRC of the separate debug info file.

 [2] The executable contains a build ID, and the corresponding debug info
     file is placed in the .build-id directory.

We could do both, but the former, which 'make deb-pkg' currently does,
results in complicated installation steps because we need to manually
strip the debug sections, create debug links, and re-sign the modules.
Besides, it is not working with module compression.

This commit abandons the approach [1], and instead opts for [2].

Debian kernel commit de26137e2a9f ("Drop not needed extra step to add
debug links") also stopped adding debug links.

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

diff --git a/scripts/package/builddeb b/scripts/package/builddeb
index 436d55a83ab070cd888ad20092c386319aac7be7..cc8c7a807fcc2d6c1b7392f043b194c944a8650f 100755 (executable)
--- a/scripts/package/builddeb
+++ b/scripts/package/builddeb
@@ -49,7 +49,7 @@ install_linux_image () {
                ${MAKE} -f ${srctree}/Makefile INSTALL_DTBS_PATH="${pdir}/usr/lib/linux-image-${KERNELRELEASE}" dtbs_install
        fi
 
-       ${MAKE} -f ${srctree}/Makefile INSTALL_MOD_PATH="${pdir}" modules_install
+       ${MAKE} -f ${srctree}/Makefile INSTALL_MOD_PATH="${pdir}" INSTALL_MOD_STRIP=1 modules_install
        rm -f "${pdir}/lib/modules/${KERNELRELEASE}/build"
 
        # Install the kernel
@@ -110,25 +110,21 @@ install_linux_image () {
 
 install_linux_image_dbg () {
        pdir=$1
-       image_pdir=$2
 
        rm -rf ${pdir}
 
-       for module in $(find ${image_pdir}/lib/modules/ -name *.ko -printf '%P\n'); do
-               module=lib/modules/${module}
-               mkdir -p $(dirname ${pdir}/usr/lib/debug/${module})
-               # only keep debug symbols in the debug file
-               ${OBJCOPY} --only-keep-debug ${image_pdir}/${module} ${pdir}/usr/lib/debug/${module}
-               # strip original module from debug symbols
-               ${OBJCOPY} --strip-debug ${image_pdir}/${module}
-               # then add a link to those
-               ${OBJCOPY} --add-gnu-debuglink=${pdir}/usr/lib/debug/${module} ${image_pdir}/${module}
-       done
+       # Parse modules.order directly because 'make modules_install' may sign,
+       # compress modules, and then run unneeded depmod.
+       while read -r mod; do
+               mod="${mod%.o}.ko"
+               dbg="${pdir}/usr/lib/debug/lib/modules/${KERNELRELEASE}/kernel/${mod}"
+               buildid=$("${READELF}" -n "${mod}" | sed -n 's@^.*Build ID: \(..\)\(.*\)@\1/\2@p')
+               link="${pdir}/usr/lib/debug/.build-id/${buildid}.debug"
 
-       # re-sign stripped modules
-       if is_enabled CONFIG_MODULE_SIG_ALL; then
-               ${MAKE} -f ${srctree}/Makefile INSTALL_MOD_PATH="${image_pdir}" modules_sign
-       fi
+               mkdir -p "${dbg%/*}" "${link%/*}"
+               "${OBJCOPY}" --only-keep-debug "${mod}" "${dbg}"
+               ln -sf --relative "${dbg}" "${link}"
+       done < modules.order
 
        # Build debug package
        # Different tools want the image in different locations
@@ -176,9 +172,7 @@ for package in ${packages_enabled}
 do
        case ${package} in
        *-dbg)
-               # This must be done after linux-image, that is, we expect the
-               # debug package appears after linux-image in debian/control.
-               install_linux_image_dbg debian/linux-image-dbg debian/linux-image;;
+               install_linux_image_dbg debian/linux-image-dbg;;
        linux-image-*|user-mode-linux-*)
                install_linux_image debian/linux-image ${package};;
        linux-libc-dev)