From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755679AbaFWNbj (ORCPT ); Mon, 23 Jun 2014 09:31:39 -0400 Received: from ip4-83-240-18-248.cust.nbox.cz ([83.240.18.248]:60761 "EHLO ip4-83-240-18-248.cust.nbox.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754838AbaFWN3j (ORCPT ); Mon, 23 Jun 2014 09:29:39 -0400 From: Jiri Slaby To: linux-kernel@vger.kernel.org Cc: jirislaby@gmail.com, Vojtech Pavlik , Jiri Kosina , Jiri Slaby , Udo Seidel Subject: [PATCH 06/21] kgr: add Documentation Date: Mon, 23 Jun 2014 15:29:20 +0200 Message-Id: <1403530175-29217-6-git-send-email-jslaby@suse.cz> X-Mailer: git-send-email 2.0.0 In-Reply-To: <1403530175-29217-1-git-send-email-jslaby@suse.cz> References: <1403530175-29217-1-git-send-email-jslaby@suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is a text provided by Udo and polished. Signed-off-by: Jiri Slaby Cc: Udo Seidel --- Documentation/kgraft.txt | 44 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 44 insertions(+) create mode 100644 Documentation/kgraft.txt diff --git a/Documentation/kgraft.txt b/Documentation/kgraft.txt new file mode 100644 index 000000000000..476beaf35c62 --- /dev/null +++ b/Documentation/kgraft.txt @@ -0,0 +1,44 @@ +Live Kernel Patching with kGraft +-------------------------------- + +Written by Udo Seidel +Based on the Blog entry by Vojtech Pavlik +Updated by Jiri Slaby + +June 2014 + +kGraft's developement was started by the SUSE Labs. kGraft builds on +technologies and ideas that are already present in the kernel: ftrace [1] and +its mcount-based reserved space in function headers [2], the INT3/IPI-NMI +patching also used in jump labels [3], and RCU-like update of code that does +not require stopping the kernel. + +A kGraft patch is a kernel module and fully relies on the in-kernel module +loader to link the new code with the kernel. Thanks to all that, the design +can be nicely minimalistic. + +While kGraft is, by choice, limited to replacing whole functions and constants +they reference, this does not limit the set of code patches that can be +applied significantly. + +Use +--- + +1) Build a kernel with CONFIG_KGRAFT enabled +2) Create a module with a patch + * Look at samples/kgraft/kgraft_patcher.c for an example +3) Insert the module from 2) into the booted kernel from 1) +4) All processes need to enter the kernel to acknowledge the new state + * This can be done e.g. by sending a non-fatal signal to all processes + * Check /proc/*/kgr_in_progress to check who still needs to be poked +5) You should see "kgr succeeded" in dmesg now + +Enjoy your patched system! + + +References +---------- + +[1] Documentation/trace/ftrace.txt +[2] Documentation/trace/ftrace-design.txt +[3] Documentation/static-keys.txt -- 2.0.0