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196 lines
5.5 KiB
196 lines
5.5 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* |
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* Copyright (C) 2017 Joe Lawrence <[email protected]> |
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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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return klp_enable_patch(&patch); |
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} |
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static void livepatch_callbacks_demo_exit(void) |
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{ |
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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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