d0807da78e
Immediate flag has been used to disable per-task consistency and patch
all tasks immediately. It could be useful if the patch doesn't change any
function or data semantics.
However, it causes problems on its own. The consistency problem is
currently broken with respect to immediate patches.
func a
patches 1i
2i
3
When the patch 3 is applied, only 2i function is checked (by stack
checking facility). There might be a task sleeping in 1i though. Such
task is migrated to 3, because we do not check 1i in
klp_check_stack_func() at all.
Coming atomic replace feature would be easier to implement and more
reliable without immediate.
Thus, remove immediate feature completely and save us from the problems.
Note that force feature has the similar problem. However it is
considered as a last resort. If used, administrator should not apply any
new live patches and should plan for reboot into an updated kernel.
The architectures would now need to provide HAVE_RELIABLE_STACKTRACE to
fully support livepatch.
Signed-off-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
219 lines
6.3 KiB
C
219 lines
6.3 KiB
C
/*
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* Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* livepatch-callbacks-demo.c - (un)patching callbacks livepatch demo
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*
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*
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* Purpose
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* -------
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*
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* Demonstration of registering livepatch (un)patching callbacks.
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*
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*
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* Usage
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* -----
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*
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* Step 1 - load the simple module
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*
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* insmod samples/livepatch/livepatch-callbacks-mod.ko
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*
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*
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* Step 2 - load the demonstration livepatch (with callbacks)
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*
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* insmod samples/livepatch/livepatch-callbacks-demo.ko
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*
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*
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* Step 3 - cleanup
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*
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* echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled
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* rmmod livepatch_callbacks_demo
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* rmmod livepatch_callbacks_mod
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*
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* Watch dmesg output to see livepatch enablement, callback execution
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* and patching operations for both vmlinux and module targets.
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*
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* NOTE: swap the insmod order of livepatch-callbacks-mod.ko and
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* livepatch-callbacks-demo.ko to observe what happens when a
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* target module is loaded after a livepatch with callbacks.
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*
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* NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch
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* callback return status. Try setting up a non-zero status
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* such as -19 (-ENODEV):
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*
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* # Load demo livepatch, vmlinux is patched
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* insmod samples/livepatch/livepatch-callbacks-demo.ko
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*
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* # Setup next pre-patch callback to return -ENODEV
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* echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret
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*
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* # Module loader refuses to load the target module
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* insmod samples/livepatch/livepatch-callbacks-mod.ko
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* insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device
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*
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* NOTE: There is a second target module,
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* livepatch-callbacks-busymod.ko, available for experimenting
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* with livepatch (un)patch callbacks. This module contains
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* a 'sleep_secs' parameter that parks the module on one of the
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* functions that the livepatch demo module wants to patch.
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* Modifying this value and tweaking the order of module loads can
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* effectively demonstrate stalled patch transitions:
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*
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* # Load a target module, let it park on 'busymod_work_func' for
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* # thirty seconds
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* insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30
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*
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* # Meanwhile load the livepatch
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* insmod samples/livepatch/livepatch-callbacks-demo.ko
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*
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* # ... then load and unload another target module while the
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* # transition is in progress
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* insmod samples/livepatch/livepatch-callbacks-mod.ko
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* rmmod samples/livepatch/livepatch-callbacks-mod.ko
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*
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* # Finally cleanup
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* echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled
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* rmmod samples/livepatch/livepatch-callbacks-demo.ko
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/livepatch.h>
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static int pre_patch_ret;
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module_param(pre_patch_ret, int, 0644);
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MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)");
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static const char *const module_state[] = {
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[MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state",
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[MODULE_STATE_COMING] = "[MODULE_STATE_COMING] Full formed, running module_init",
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[MODULE_STATE_GOING] = "[MODULE_STATE_GOING] Going away",
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[MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up",
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};
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static void callback_info(const char *callback, struct klp_object *obj)
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{
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if (obj->mod)
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pr_info("%s: %s -> %s\n", callback, obj->mod->name,
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module_state[obj->mod->state]);
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else
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pr_info("%s: vmlinux\n", callback);
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}
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/* Executed on object patching (ie, patch enablement) */
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static int pre_patch_callback(struct klp_object *obj)
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{
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callback_info(__func__, obj);
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return pre_patch_ret;
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}
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/* Executed on object unpatching (ie, patch disablement) */
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static void post_patch_callback(struct klp_object *obj)
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{
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callback_info(__func__, obj);
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}
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/* Executed on object unpatching (ie, patch disablement) */
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static void pre_unpatch_callback(struct klp_object *obj)
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{
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callback_info(__func__, obj);
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}
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/* Executed on object unpatching (ie, patch disablement) */
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static void post_unpatch_callback(struct klp_object *obj)
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{
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callback_info(__func__, obj);
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}
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static void patched_work_func(struct work_struct *work)
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{
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pr_info("%s\n", __func__);
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}
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static struct klp_func no_funcs[] = {
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{ }
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};
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static struct klp_func busymod_funcs[] = {
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{
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.old_name = "busymod_work_func",
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.new_func = patched_work_func,
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}, { }
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};
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static struct klp_object objs[] = {
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{
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.name = NULL, /* vmlinux */
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.funcs = no_funcs,
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.callbacks = {
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.pre_patch = pre_patch_callback,
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.post_patch = post_patch_callback,
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.pre_unpatch = pre_unpatch_callback,
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.post_unpatch = post_unpatch_callback,
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},
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}, {
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.name = "livepatch_callbacks_mod",
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.funcs = no_funcs,
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.callbacks = {
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.pre_patch = pre_patch_callback,
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.post_patch = post_patch_callback,
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.pre_unpatch = pre_unpatch_callback,
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.post_unpatch = post_unpatch_callback,
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},
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}, {
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.name = "livepatch_callbacks_busymod",
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.funcs = busymod_funcs,
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.callbacks = {
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.pre_patch = pre_patch_callback,
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.post_patch = post_patch_callback,
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.pre_unpatch = pre_unpatch_callback,
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.post_unpatch = post_unpatch_callback,
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},
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}, { }
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};
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static struct klp_patch patch = {
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.mod = THIS_MODULE,
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.objs = objs,
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};
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static int livepatch_callbacks_demo_init(void)
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{
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int ret;
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ret = klp_register_patch(&patch);
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if (ret)
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return ret;
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ret = klp_enable_patch(&patch);
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if (ret) {
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WARN_ON(klp_unregister_patch(&patch));
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return ret;
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}
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return 0;
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}
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static void livepatch_callbacks_demo_exit(void)
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{
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WARN_ON(klp_unregister_patch(&patch));
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}
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module_init(livepatch_callbacks_demo_init);
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module_exit(livepatch_callbacks_demo_exit);
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MODULE_LICENSE("GPL");
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MODULE_INFO(livepatch, "Y");
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