livepatch: samples: add sample live patching module (13d1cf7e) · Commits · e / devices / android_kernel_sony_msm8998

MAINTAINERS

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		@@ -5795,6 +5795,7 @@ F: include/linux/livepatch.h
		F: arch/x86/include/asm/livepatch.h
		F: arch/x86/kernel/livepatch.c
		F: Documentation/ABI/testing/sysfs-kernel-livepatch
		F: samples/livepatch/
		L: live-patching@vger.kernel.org

		LLC (802.2)

samples/Kconfig

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		@@ -63,4 +63,11 @@ config SAMPLE_RPMSG_CLIENT
		to communicate with an AMP-configured remote processor over
		the rpmsg bus.

		config SAMPLE_LIVE_PATCHING
		tristate "Build live patching sample -- loadable modules only"
		depends on LIVE_PATCHING && m
		help
		Builds a sample live patch that replaces the procfs handler
		for /proc/cmdline to print "this has been live patched".

		endif # SAMPLES

samples/Makefile

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		# Makefile for Linux samples code

		obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ \
		obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ livepatch/ \
		hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/

samples/livepatch/Makefile

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		obj-$(CONFIG_SAMPLE_LIVE_PATCHING) += livepatch-sample.o

samples/livepatch/livepatch-sample.c

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		/*
		* livepatch-sample.c - Kernel Live Patching Sample Module
		*
		* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
		*
		* This program is free software; you can redistribute it and/or
		* modify it under the terms of the GNU General Public License
		* as published by the Free Software Foundation; either version 2
		* of the License, or (at your option) any later version.
		*
		* This program is distributed in the hope that it will be useful,
		* but WITHOUT ANY WARRANTY; without even the implied warranty of
		* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
		* GNU General Public License for more details.
		*
		* You should have received a copy of the GNU General Public License
		* along with this program; if not, see <http://www.gnu.org/licenses/>.
		*/

		#include <linux/module.h>
		#include <linux/kernel.h>
		#include <linux/livepatch.h>

		/*
		* This (dumb) live patch overrides the function that prints the
		* kernel boot cmdline when /proc/cmdline is read.
		*
		* Example:
		* $ cat /proc/cmdline
		* <your cmdline>
		* $ insmod livepatch-sample.ko
		* $ cat /proc/cmdline
		* this has been live patched
		* $ echo 0 > /sys/kernel/livepatch/klp_sample/enabled
		* <your cmdline>
		*/

		#include <linux/seq_file.h>
		static int livepatch_cmdline_proc_show(struct seq_file m, void v)
		{
		seq_printf(m, "%s\n", "this has been live patched");
		return 0;
		}

		static struct klp_func funcs[] = {
		{
		.old_name = "cmdline_proc_show",
		.new_func = livepatch_cmdline_proc_show,
		}, { }
		};

		static struct klp_object objs[] = {
		{
		/* name being NULL means vmlinux */
		.funcs = funcs,
		}, { }
		};

		static struct klp_patch patch = {
		.mod = THIS_MODULE,
		.objs = objs,
		};

		static int livepatch_init(void)
		{
		int ret;

		ret = klp_register_patch(&patch);
		if (ret)
		return ret;
		ret = klp_enable_patch(&patch);
		if (ret) {
		WARN_ON(klp_unregister_patch(&patch));
		return ret;
		}
		return 0;
		}

		static void livepatch_exit(void)
		{
		WARN_ON(klp_disable_patch(&patch));
		WARN_ON(klp_unregister_patch(&patch));
		}

		module_init(livepatch_init);
		module_exit(livepatch_exit);
		MODULE_LICENSE("GPL");