[v5,2/4] deb-pkg: split debug symbols in their own package

This can reduce almost 3 times the size of the linux-image package,
while keeping the debug symbols available for this particular build, in
their own package.

This mimics the way kernels are built in debian, ubuntu, or with
make-kpkg, and comes at the price of a small slowdown in the building of
packages.

Signed-off-by: Anisse Astier <anisse@astier.eu>
Cc: Ben Hutchings <ben@decadent.org.uk>
---
 scripts/package/builddeb | 50 +++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 49 insertions(+), 1 deletion(-)

On Fri, Jun 14, 2013 at 11:46:55AM +0200, Anisse Astier wrote:
> This can reduce almost 3 times the size of the linux-image package,
> while keeping the debug symbols available for this particular build, in
> their own package.
> 
> This mimics the way kernels are built in debian, ubuntu, or with
> make-kpkg, and comes at the price of a small slowdown in the building of
> packages.
> 
> Signed-off-by: Anisse Astier <anisse@astier.eu>
> Cc: Ben Hutchings <ben@decadent.org.uk>
Acked-by: maximilian attems <max@stro.at>
> ---
>  scripts/package/builddeb | 50 +++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 49 insertions(+), 1 deletion(-)
> 
> diff --git a/scripts/package/builddeb b/scripts/package/builddeb
> index 6f21ad8..7c5703a 100644
> --- a/scripts/package/builddeb
> +++ b/scripts/package/builddeb
> @@ -78,17 +78,21 @@ tmpdir="$objtree/debian/tmp"
>  fwdir="$objtree/debian/fwtmp"
>  kernel_headers_dir="$objtree/debian/hdrtmp"
>  libc_headers_dir="$objtree/debian/headertmp"
> +dbg_dir="$objtree/debian/dbgtmp"
>  packagename=linux-image-$version
>  fwpackagename=linux-firmware-image
>  kernel_headers_packagename=linux-headers-$version
>  libc_headers_packagename=linux-libc-dev
> +dbg_packagename=$packagename-dbg
>  
>  if [ "$ARCH" = "um" ] ; then
>  	packagename=user-mode-linux-$version
>  fi
>  
> +BUILD_DEBUG="$(grep -s '^CONFIG_DEBUG_INFO=y' $KCONFIG_CONFIG || true)"
> +
>  # Setup the directory structure
> -rm -rf "$tmpdir" "$fwdir" "$kernel_headers_dir" "$libc_headers_dir"
> +rm -rf "$tmpdir" "$fwdir" "$kernel_headers_dir" "$libc_headers_dir" "$dbg_dir"
>  mkdir -m 755 -p "$tmpdir/DEBIAN"
>  mkdir -p  "$tmpdir/lib" "$tmpdir/boot" "$tmpdir/usr/share/doc/$packagename"
>  mkdir -m 755 -p "$fwdir/DEBIAN"
> @@ -101,6 +105,10 @@ mkdir -p "$kernel_headers_dir/lib/modules/$version/"
>  if [ "$ARCH" = "um" ] ; then
>  	mkdir -p "$tmpdir/usr/lib/uml/modules/$version" "$tmpdir/usr/bin"
>  fi
> +if [ -n "$BUILD_DEBUG" ] ; then
> +	mkdir -p "$dbg_dir/usr/share/doc/$dbg_packagename"
> +	mkdir -m 755 -p "$dbg_dir/DEBIAN"
> +fi
>  
>  # Build and install the kernel
>  if [ "$ARCH" = "um" ] ; then
> @@ -128,6 +136,20 @@ if grep -q '^CONFIG_MODULES=y' $KCONFIG_CONFIG ; then
>  		mv "$tmpdir/lib/modules/$version"/* "$tmpdir/usr/lib/uml/modules/$version/"
>  		rmdir "$tmpdir/lib/modules/$version"
>  	fi
> +	if [ -n "$BUILD_DEBUG" ] ; then
> +		(
> +			cd $tmpdir
> +			for module in $(find lib/modules/ -name *.ko); do
> +				mkdir -p $(dirname $dbg_dir/usr/lib/debug/$module)
> +				# only keep debug symbols in the debug file
> +				objcopy --only-keep-debug $module $dbg_dir/usr/lib/debug/$module
> +				# strip original module from debug symbols
> +				objcopy --strip-debug $module
> +				# then add a link to those
> +				objcopy --add-gnu-debuglink=$dbg_dir/usr/lib/debug/$module $module
> +			done
> +		)
> +	fi
>  fi
>  
>  if [ "$ARCH" != "um" ]; then
> @@ -299,4 +321,30 @@ fi
>  
>  create_package "$packagename" "$tmpdir"
>  
> +if [ -n "$BUILD_DEBUG" ] ; then
> +	# Build debug package
> +	# Different tools want the image in different locations
> +	# perf
> +	mkdir -p $dbg_dir/usr/lib/debug/lib/modules/$version/
> +	cp vmlinux $dbg_dir/usr/lib/debug/lib/modules/$version/
> +	# systemtap
> +	mkdir -p $dbg_dir/usr/lib/debug/boot/
> +	ln -s ../lib/modules/$version/vmlinux $dbg_dir/usr/lib/debug/boot/vmlinux-$version
> +	# kdump-tools
> +	ln -s lib/modules/$version/vmlinux $dbg_dir/usr/lib/debug/vmlinux-$version
> +
> +	cat <<EOF >> debian/control
> +
> +Package: $dbg_packagename
> +Section: debug
> +Provides: linux-debug, linux-debug-$version
> +Architecture: any
> +Description: Linux kernel debugging symbols for $version
> + This package will come in handy if you need to debug the kernel. It provides
> + all the necessary debug symbols for the kernel and its modules.
> +EOF
> +
> +	create_package "$dbg_packagename" "$dbg_dir"
> +fi
> +
>  exit 0
> -- 
> 1.8.3.rc1
>

On Fri, 2013-06-14 at 11:46 +0200, Anisse Astier wrote:
> This can reduce almost 3 times the size of the linux-image package,
> while keeping the debug symbols available for this particular build, in
> their own package.
> 
> This mimics the way kernels are built in debian, ubuntu, or with
> make-kpkg, and comes at the price of a small slowdown in the building of
> packages.
[...]
> @@ -128,6 +136,20 @@ if grep -q '^CONFIG_MODULES=y' $KCONFIG_CONFIG ; then
>  		mv "$tmpdir/lib/modules/$version"/* "$tmpdir/usr/lib/uml/modules/$version/"
>  		rmdir "$tmpdir/lib/modules/$version"
>  	fi
> +	if [ -n "$BUILD_DEBUG" ] ; then
> +		(
> +			cd $tmpdir
> +			for module in $(find lib/modules/ -name *.ko); do
[...]

Can shells generally cope with the list this produces for, say, an
allmodconfig build?  My instinct would be to use xargs and while, but
I'm willing to believe that this does work.

Ben.

On Sat, 15 Jun 2013 05:03:15 +0100, Ben Hutchings <ben@decadent.org.uk> wrote :

> On Fri, 2013-06-14 at 11:46 +0200, Anisse Astier wrote:
> > This can reduce almost 3 times the size of the linux-image package,
> > while keeping the debug symbols available for this particular build, in
> > their own package.
> > 
> > This mimics the way kernels are built in debian, ubuntu, or with
> > make-kpkg, and comes at the price of a small slowdown in the building of
> > packages.
> [...]
> > @@ -128,6 +136,20 @@ if grep -q '^CONFIG_MODULES=y' $KCONFIG_CONFIG ; then
> >  		mv "$tmpdir/lib/modules/$version"/* "$tmpdir/usr/lib/uml/modules/$version/"
> >  		rmdir "$tmpdir/lib/modules/$version"
> >  	fi
> > +	if [ -n "$BUILD_DEBUG" ] ; then
> > +		(
> > +			cd $tmpdir
> > +			for module in $(find lib/modules/ -name *.ko); do
> [...]
> 
> Can shells generally cope with the list this produces for, say, an
> allmodconfig build?  My instinct would be to use xargs and while, but
> I'm willing to believe that this does work.

Did a quick test with an allmodconfig. It has 4038 modules. I'm pretty
sure it should work.

In bash 4.2.37, "for i in $(seq 50000000); do  :; done" does work,
although it ends up eating 5GB of memory.

Anisse