These binary packages represent builds of the mainline or stable Linux kernel tree at the commit below:
v4.3-rc1 (6ff33f3902c3b1c5d0db6b1e2c70b6d76fba357f)
To obtain the source from which they are built fetch the commit below:
git://git.launchpad.net/~ubuntu-kernel-test/ubuntu/+source/linux/+git/mainline-crack v4.3-rc1
and apply the following patches on top in the order below:
0001-base-packaging.patch
0002-debian-changelog.patch
0003-configs-based-on-Ubuntu-4.3.0-0.1.patch
This is summarised in the SOURCES file included with these binaries.
For further information see: http://wiki.ubuntu.com/Kernel/MainlineBuilds