Comment 3 for bug 1840704

Test Build 3) New behavior if ZFS modules are built with debug symbols

goal: show zfs debug symbols are correctly built and packaged into non-debug & debug packages.

- test packaging
- zfs built with debug symbols
- zfs modules present in debug package
- extra modules *have* .gnu_debuglink section

Test packaging, debug symbols *enabled* in zfs-dkms:

Modules are built with debug symbols, copied to debug package directory,
and stripped before being copied into strip/non-debug package directory.

 II: dkms-build installing zfs into /home/ubuntu/dbgsym/unstable/debian/linux-image-unsigned-5.3.0-8-generic-dbgsym/usr/lib/debug/lib/modules/5.3.0-8-generic/kernel/zfs (debug symbols)
 copying zavl.ko
 stripping zavl.ko
 copying znvpair.ko
 stripping znvpair.ko
 copying zunicode.ko
 stripping zunicode.ko
 copying zcommon.ko
 stripping zcommon.ko
 copying zfs.ko
 stripping zfs.ko
 copying icp.ko
 stripping icp.ko
 copying zlua.ko
 stripping zlua.ko
 copying spl.ko
 stripping spl.ko
 II: dkms-build installing zfs into /home/ubuntu/dbgsym/unstable/debian/linux-modules-5.3.0-8-generic/lib/modules/5.3.0-8-generic/kernel/zfs
 signing zavl.ko
 signing znvpair.ko
 signing zunicode.ko
 signing zcommon.ko
 signing zfs.ko
 signing icp.ko
 signing zlua.ko
 signing spl.ko
 II: dkms-build build zfs complete

The ZFS modules are now present in the debug package:

 $ dpkg-deb -x linux-image-unsigned-5.3.0-8-generic-dbgsym_5.3.0-8.9_amd64.ddeb ddeb-test-enabled

 $ ls -1 ddeb-test-enabled/usr/lib/debug/lib/modules/5.3.0-8-generic/kernel/zfs/
 icp.ko
 spl.ko
 zavl.ko
 zcommon.ko
 zfs.ko
 zlua.ko
 znvpair.ko
 zunicode.ko

And now all modules in 'linux-modules' have the '.gnu_debuglink' section:

 $ dpkg-deb -x linux-modules-5.3.0-8-generic_5.3.0-8.9_amd64.deb deb-modules
 $ find deb-modules/ -name '*.ko' | while read ko; do objdump -h -j .gnu_debuglink $ko >/dev/null 2>&1 || echo "Module without debug link '$ko'"; done
 $

The build log no longer shows ZFS modules as missing debug symbols:

 $ grep WARNING build.log
          echo "WARNING: Missing debug symbols for module '$module'."; \
 WARNING: Missing debug symbols for module '/lib/modules/5.3.0-8-generic/kernel/virtualbox-guest/vboxguest.ko'.
 WARNING: Missing debug symbols for module '/lib/modules/5.3.0-8-generic/kernel/virtualbox-guest/vboxsf.ko'.
 $

The only modules in 'linux-modules-extra' without that continue to be virtualbox modules:

 $ dpkg-deb -x linux-modules-extra-5.3.0-8-generic_5.3.0-8.9_amd64.deb deb-modules-extra
 $ find deb-modules-extra/ -name '*.ko' | while read ko; do objdump -h -j .gnu_debuglink $ko >/dev/null 2>&1 || echo "Module without debug link '$ko'"; done
 Module without debug link 'deb-modules-extra/lib/modules/5.3.0-8-generic/kernel/virtualbox-guest/vboxguest.ko'
 Module without debug link 'deb-modules-extra/lib/modules/5.3.0-8-generic/kernel/virtualbox-guest/vboxsf.ko'
 $

As reflected in the kernel build log.

 $ grep WARNING build.log
          echo "WARNING: Missing debug symbols for module '$module'."; \
 WARNING: Missing debug symbols for module '/lib/modules/5.3.0-8-generic/kernel/virtualbox-guest/vboxguest.ko'.
 WARNING: Missing debug symbols for module '/lib/modules/5.3.0-8-generic/kernel/virtualbox-guest/vboxsf.ko'.