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9.2.2. Getting the Sources
Since the Linux kernel sources are available as a package, you can retrieve them by installing the linux-source-version package. The apt-cache search ^linux-source command should list the latest kernel version packaged by Kali. Note that the source code contained in these packages does not correspond precisely with that published by Linus Torvalds and the kernel developers4; like all distributions, Debian and Kali apply a number of patches, which might (or might not) find their way into the upstream version of Linux. These modifications include backports of fixes/fea- tures/drivers from newer kernel versions, new features not yet (entirely) merged in the upstream Linux tree, and sometimes even Debian or Kali specific changes.
The remainder of this section focuses on the 4.9 version of the Linux kernel, but the examples can, of course, be adapted to the particular version of the kernel that you want.
In this example, we assume that the linux-source-4.9 binary package has been installed. Note that we install a binary package containing the upstream sources but do not retrieve the Kali source package named linux.
# apt install linux-source-4.9 Reading package lists... Done Building dependency tree
Reading state information... Done
The following additional packages will be installed: bc libreadline7
Suggested packages:
libncurses-dev | ncurses-dev libqt4-dev
The following NEW packages will be installed: bc libreadline7 linux-source-4.9
0 upgraded, 3 newly installed, 0 to remove and 0 not upgraded. Need to get 95.4 MB of archives.
After this operation, 95.8 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
[...]
# ls /usr/src
linux-config-4.9 linux-patch-4.9-rt.patch.xz linux-source-4.9.tar.xz
# apt install linux-source-4.9 Reading package lists... Done Building dependency tree
Reading state information... Done
The following additional packages will be installed: bc libreadline7
Suggested packages:
libncurses-dev | ncurses-dev libqt4-dev
The following NEW packages will be installed: bc libreadline7 linux-source-4.9
0 upgraded, 3 newly installed, 0 to remove and 0 not upgraded. Need to get 95.4 MB of archives.
After this operation, 95.8 MB of additional disk space will be used.
Do you want to continue? [Y/n] y
[...]
# ls /usr/src
linux-config-4.9 linux-patch-4.9-rt.patch.xz linux-source-4.9.tar.xz
Notice that the package contains /usr/src/linux-source-4.9.tar.xz, a compressed archive of the kernel sources. You must extract these files in a new directory (not directly under /usr/src/,
4https://kernel.org/
since there is no need for special permissions to compile a Linux kernel). Instead, ~/kernel/ is more appropriate.
$ mkdir ~/kernel; cd ~/kernel
$ tar -xaf /usr/src/linux-source-4.9.tar.xz
$ mkdir ~/kernel; cd ~/kernel
$ tar -xaf /usr/src/linux-source-4.9.tar.xz