docs: kernel_abi.py: fix command injection

The kernel-abi directive passes its argument straight to the shell.
This is unfortunate and unnecessary.

Let's always use paths relative to $srctree/Documentation/ and use
subprocess.check_call() instead of subprocess.Popen(shell=True).

This also makes the code shorter.

Link: https://fosstodon.org/@jani/111676532203641247
Reported-by: Jani Nikula <jani.nikula@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20231231235959.3342928-2-vegard.nossum@oracle.com

docs: ABI: make it parse ABI/stable as ReST-compatible files

Now that the stable ABI files are compatible with ReST,
parse them without converting complex descriptions as literal
blocks nor escaping special characters.

Please notice that escaping special characters will probably
be needed at descriptions, at least for the asterisk character.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/59ccbaa75ff05f23e701dd9a0bbe118e9343a553.1604042072.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

docs: add ABI documentation to the admin-guide book

As we don't want a generic Sphinx extension to execute commands,
change the one proposed to Markus to call the abi_book.pl
script.

Use a script to parse the Documentation/ABI directory and output
it at the admin-guide.

Acked-by: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/5651482b06500e69a1acdf92152f90a203e6521d.1604042072.git.mchehab+huawei@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>