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livepatch: samples: add sample live patching module
Add a sample live patching module. Signed-off-by: Seth Jennings <sjenning@redhat.com> Reviewed-by: Miroslav Benes <mbenes@suse.cz> Reviewed-by: Petr Mladek <pmladek@suse.cz> Reviewed-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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# Makefile for Linux samples code | ||
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obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ \ | ||
obj-$(CONFIG_SAMPLES) += kobject/ kprobes/ trace_events/ livepatch/ \ | ||
hw_breakpoint/ kfifo/ kdb/ hidraw/ rpmsg/ seccomp/ |
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obj-$(CONFIG_SAMPLE_LIVE_PATCHING) += livepatch-sample.o |
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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/>. | ||
*/ | ||
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#include <linux/module.h> | ||
#include <linux/kernel.h> | ||
#include <linux/livepatch.h> | ||
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/* | ||
* 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> | ||
*/ | ||
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#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; | ||
} | ||
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static struct klp_func funcs[] = { | ||
{ | ||
.old_name = "cmdline_proc_show", | ||
.new_func = livepatch_cmdline_proc_show, | ||
}, { } | ||
}; | ||
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static struct klp_object objs[] = { | ||
{ | ||
/* name being NULL means vmlinux */ | ||
.funcs = funcs, | ||
}, { } | ||
}; | ||
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static struct klp_patch patch = { | ||
.mod = THIS_MODULE, | ||
.objs = objs, | ||
}; | ||
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static int livepatch_init(void) | ||
{ | ||
int ret; | ||
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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; | ||
} | ||
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static void livepatch_exit(void) | ||
{ | ||
WARN_ON(klp_disable_patch(&patch)); | ||
WARN_ON(klp_unregister_patch(&patch)); | ||
} | ||
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module_init(livepatch_init); | ||
module_exit(livepatch_exit); | ||
MODULE_LICENSE("GPL"); |