These binary packages represent builds of the mainline or stable Linux kernel tree at the commit below:
v4.1-rc4 (e26081808edadfd257c6c9d81014e3b25e9a6118)
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 v4.1-rc4
and apply the following patches on top in the order below:
0001-base-packaging.patch
0002-debian-changelog.patch
0003-configs-based-on-Ubuntu-4.1.0-1.1.patch
This is summarised in the SOURCES file included with these binaries.
For further information see: http://wiki.ubuntu.com/Kernel/MainlineBuilds