235 lines
6.9 KiB
C
235 lines
6.9 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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if (!klp_have_reliable_stack() && !patch.immediate) {
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/*
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* WARNING: Be very careful when using 'patch.immediate' in
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* your patches. It's ok to use it for simple patches like
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* this, but for more complex patches which change function
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* semantics, locking semantics, or data structures, it may not
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* be safe. Use of this option will also prevent removal of
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* the patch.
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*
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* See Documentation/livepatch/livepatch.txt for more details.
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*/
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patch.immediate = true;
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pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n");
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}
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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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