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Diffstat (limited to 'samples/livepatch/livepatch-callbacks-demo.c')
| -rw-r--r-- | samples/livepatch/livepatch-callbacks-demo.c | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/samples/livepatch/livepatch-callbacks-demo.c b/samples/livepatch/livepatch-callbacks-demo.c new file mode 100644 index 0000000..3d115bd --- /dev/null +++ b/samples/livepatch/livepatch-callbacks-demo.c @@ -0,0 +1,234 @@ +/* + * Copyright (C) 2017 Joe Lawrence <joe.lawrence@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/>. + */ + +/* + * livepatch-callbacks-demo.c - (un)patching callbacks livepatch demo + * + * + * Purpose + * ------- + * + * Demonstration of registering livepatch (un)patching callbacks. + * + * + * Usage + * ----- + * + * Step 1 - load the simple module + * + * insmod samples/livepatch/livepatch-callbacks-mod.ko + * + * + * Step 2 - load the demonstration livepatch (with callbacks) + * + * insmod samples/livepatch/livepatch-callbacks-demo.ko + * + * + * Step 3 - cleanup + * + * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled + * rmmod livepatch_callbacks_demo + * rmmod livepatch_callbacks_mod + * + * Watch dmesg output to see livepatch enablement, callback execution + * and patching operations for both vmlinux and module targets. + * + * NOTE: swap the insmod order of livepatch-callbacks-mod.ko and + * livepatch-callbacks-demo.ko to observe what happens when a + * target module is loaded after a livepatch with callbacks. + * + * NOTE: 'pre_patch_ret' is a module parameter that sets the pre-patch + * callback return status. Try setting up a non-zero status + * such as -19 (-ENODEV): + * + * # Load demo livepatch, vmlinux is patched + * insmod samples/livepatch/livepatch-callbacks-demo.ko + * + * # Setup next pre-patch callback to return -ENODEV + * echo -19 > /sys/module/livepatch_callbacks_demo/parameters/pre_patch_ret + * + * # Module loader refuses to load the target module + * insmod samples/livepatch/livepatch-callbacks-mod.ko + * insmod: ERROR: could not insert module samples/livepatch/livepatch-callbacks-mod.ko: No such device + * + * NOTE: There is a second target module, + * livepatch-callbacks-busymod.ko, available for experimenting + * with livepatch (un)patch callbacks. This module contains + * a 'sleep_secs' parameter that parks the module on one of the + * functions that the livepatch demo module wants to patch. + * Modifying this value and tweaking the order of module loads can + * effectively demonstrate stalled patch transitions: + * + * # Load a target module, let it park on 'busymod_work_func' for + * # thirty seconds + * insmod samples/livepatch/livepatch-callbacks-busymod.ko sleep_secs=30 + * + * # Meanwhile load the livepatch + * insmod samples/livepatch/livepatch-callbacks-demo.ko + * + * # ... then load and unload another target module while the + * # transition is in progress + * insmod samples/livepatch/livepatch-callbacks-mod.ko + * rmmod samples/livepatch/livepatch-callbacks-mod.ko + * + * # Finally cleanup + * echo 0 > /sys/kernel/livepatch/livepatch_callbacks_demo/enabled + * rmmod samples/livepatch/livepatch-callbacks-demo.ko + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt + +#include <linux/module.h> +#include <linux/kernel.h> +#include <linux/livepatch.h> + +static int pre_patch_ret; +module_param(pre_patch_ret, int, 0644); +MODULE_PARM_DESC(pre_patch_ret, "pre_patch_ret (default=0)"); + +static const char *const module_state[] = { + [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state", + [MODULE_STATE_COMING] = "[MODULE_STATE_COMING] Full formed, running module_init", + [MODULE_STATE_GOING] = "[MODULE_STATE_GOING] Going away", + [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up", +}; + +static void callback_info(const char *callback, struct klp_object *obj) +{ + if (obj->mod) + pr_info("%s: %s -> %s\n", callback, obj->mod->name, + module_state[obj->mod->state]); + else + pr_info("%s: vmlinux\n", callback); +} + +/* Executed on object patching (ie, patch enablement) */ +static int pre_patch_callback(struct klp_object *obj) +{ + callback_info(__func__, obj); + return pre_patch_ret; +} + +/* Executed on object unpatching (ie, patch disablement) */ +static void post_patch_callback(struct klp_object *obj) +{ + callback_info(__func__, obj); +} + +/* Executed on object unpatching (ie, patch disablement) */ +static void pre_unpatch_callback(struct klp_object *obj) +{ + callback_info(__func__, obj); +} + +/* Executed on object unpatching (ie, patch disablement) */ +static void post_unpatch_callback(struct klp_object *obj) +{ + callback_info(__func__, obj); +} + +static void patched_work_func(struct work_struct *work) +{ + pr_info("%s\n", __func__); +} + +static struct klp_func no_funcs[] = { + { } +}; + +static struct klp_func busymod_funcs[] = { + { + .old_name = "busymod_work_func", + .new_func = patched_work_func, + }, { } +}; + +static struct klp_object objs[] = { + { + .name = NULL, /* vmlinux */ + .funcs = no_funcs, + .callbacks = { + .pre_patch = pre_patch_callback, + .post_patch = post_patch_callback, + .pre_unpatch = pre_unpatch_callback, + .post_unpatch = post_unpatch_callback, + }, + }, { + .name = "livepatch_callbacks_mod", + .funcs = no_funcs, + .callbacks = { + .pre_patch = pre_patch_callback, + .post_patch = post_patch_callback, + .pre_unpatch = pre_unpatch_callback, + .post_unpatch = post_unpatch_callback, + }, + }, { + .name = "livepatch_callbacks_busymod", + .funcs = busymod_funcs, + .callbacks = { + .pre_patch = pre_patch_callback, + .post_patch = post_patch_callback, + .pre_unpatch = pre_unpatch_callback, + .post_unpatch = post_unpatch_callback, + }, + }, { } +}; + +static struct klp_patch patch = { + .mod = THIS_MODULE, + .objs = objs, +}; + +static int livepatch_callbacks_demo_init(void) +{ + int ret; + + if (!klp_have_reliable_stack() && !patch.immediate) { + /* + * WARNING: Be very careful when using 'patch.immediate' in + * your patches. It's ok to use it for simple patches like + * this, but for more complex patches which change function + * semantics, locking semantics, or data structures, it may not + * be safe. Use of this option will also prevent removal of + * the patch. + * + * See Documentation/livepatch/livepatch.txt for more details. + */ + patch.immediate = true; + pr_notice("The consistency model isn't supported for your architecture. Bypassing safety mechanisms and applying the patch immediately.\n"); + } + + 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_callbacks_demo_exit(void) +{ + WARN_ON(klp_unregister_patch(&patch)); +} + +module_init(livepatch_callbacks_demo_init); +module_exit(livepatch_callbacks_demo_exit); +MODULE_LICENSE("GPL"); +MODULE_INFO(livepatch, "Y"); |
