lib/livepatch/test_klp_state2.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 // Copyright (C) 2019 SUSE
0003
0004 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0005
0006 #include <linux/slab.h>
0007 #include <linux/module.h>
0008 #include <linux/kernel.h>
0009 #include <linux/printk.h>
0010 #include <linux/livepatch.h>
0011
0012 #define CONSOLE_LOGLEVEL_STATE 1
0013 /* Version 2 supports migration. */
0014 #define CONSOLE_LOGLEVEL_STATE_VERSION 2
0015
0016 static const char *const module_state[] = {
0017     [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state",
0018     [MODULE_STATE_COMING]   = "[MODULE_STATE_COMING] Full formed, running module_init",
0019     [MODULE_STATE_GOING]    = "[MODULE_STATE_GOING] Going away",
0020     [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up",
0021 };
0022
0023 static void callback_info(const char *callback, struct klp_object *obj)
0024 {
0025     if (obj->mod)
0026         pr_info("%s: %s -> %s\n", callback, obj->mod->name,
0027             module_state[obj->mod->state]);
0028     else
0029         pr_info("%s: vmlinux\n", callback);
0030 }
0031
0032 static struct klp_patch patch;
0033
0034 static int allocate_loglevel_state(void)
0035 {
0036     struct klp_state *loglevel_state, *prev_loglevel_state;
0037
0038     prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE);
0039     if (prev_loglevel_state) {
0040         pr_info("%s: space to store console_loglevel already allocated\n",
0041         __func__);
0042         return 0;
0043     }
0044
0045     loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
0046     if (!loglevel_state)
0047         return -EINVAL;
0048
0049     loglevel_state->data = kzalloc(sizeof(console_loglevel), GFP_KERNEL);
0050     if (!loglevel_state->data)
0051         return -ENOMEM;
0052
0053     pr_info("%s: allocating space to store console_loglevel\n",
0054         __func__);
0055     return 0;
0056 }
0057
0058 static void fix_console_loglevel(void)
0059 {
0060     struct klp_state *loglevel_state, *prev_loglevel_state;
0061
0062     loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
0063     if (!loglevel_state)
0064         return;
0065
0066     prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE);
0067     if (prev_loglevel_state) {
0068         pr_info("%s: taking over the console_loglevel change\n",
0069         __func__);
0070         loglevel_state->data = prev_loglevel_state->data;
0071         return;
0072     }
0073
0074     pr_info("%s: fixing console_loglevel\n", __func__);
0075     *(int *)loglevel_state->data = console_loglevel;
0076     console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH;
0077 }
0078
0079 static void restore_console_loglevel(void)
0080 {
0081     struct klp_state *loglevel_state, *prev_loglevel_state;
0082
0083     prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE);
0084     if (prev_loglevel_state) {
0085         pr_info("%s: passing the console_loglevel change back to the old livepatch\n",
0086         __func__);
0087         return;
0088     }
0089
0090     loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
0091     if (!loglevel_state)
0092         return;
0093
0094     pr_info("%s: restoring console_loglevel\n", __func__);
0095     console_loglevel = *(int *)loglevel_state->data;
0096 }
0097
0098 static void free_loglevel_state(void)
0099 {
0100     struct klp_state *loglevel_state, *prev_loglevel_state;
0101
0102     prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE);
0103     if (prev_loglevel_state) {
0104         pr_info("%s: keeping space to store console_loglevel\n",
0105         __func__);
0106         return;
0107     }
0108
0109     loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE);
0110     if (!loglevel_state)
0111         return;
0112
0113     pr_info("%s: freeing space for the stored console_loglevel\n",
0114         __func__);
0115     kfree(loglevel_state->data);
0116 }
0117
0118 /* Executed on object patching (ie, patch enablement) */
0119 static int pre_patch_callback(struct klp_object *obj)
0120 {
0121     callback_info(__func__, obj);
0122     return allocate_loglevel_state();
0123 }
0124
0125 /* Executed on object unpatching (ie, patch disablement) */
0126 static void post_patch_callback(struct klp_object *obj)
0127 {
0128     callback_info(__func__, obj);
0129     fix_console_loglevel();
0130 }
0131
0132 /* Executed on object unpatching (ie, patch disablement) */
0133 static void pre_unpatch_callback(struct klp_object *obj)
0134 {
0135     callback_info(__func__, obj);
0136     restore_console_loglevel();
0137 }
0138
0139 /* Executed on object unpatching (ie, patch disablement) */
0140 static void post_unpatch_callback(struct klp_object *obj)
0141 {
0142     callback_info(__func__, obj);
0143     free_loglevel_state();
0144 }
0145
0146 static struct klp_func no_funcs[] = {
0147     {}
0148 };
0149
0150 static struct klp_object objs[] = {
0151     {
0152         .name = NULL,   /* vmlinux */
0153         .funcs = no_funcs,
0154         .callbacks = {
0155             .pre_patch = pre_patch_callback,
0156             .post_patch = post_patch_callback,
0157             .pre_unpatch = pre_unpatch_callback,
0158             .post_unpatch = post_unpatch_callback,
0159         },
0160     }, { }
0161 };
0162
0163 static struct klp_state states[] = {
0164     {
0165         .id = CONSOLE_LOGLEVEL_STATE,
0166         .version = CONSOLE_LOGLEVEL_STATE_VERSION,
0167     }, { }
0168 };
0169
0170 static struct klp_patch patch = {
0171     .mod = THIS_MODULE,
0172     .objs = objs,
0173     .states = states,
0174     .replace = true,
0175 };
0176
0177 static int test_klp_callbacks_demo_init(void)
0178 {
0179     return klp_enable_patch(&patch);
0180 }
0181
0182 static void test_klp_callbacks_demo_exit(void)
0183 {
0184 }
0185
0186 module_init(test_klp_callbacks_demo_init);
0187 module_exit(test_klp_callbacks_demo_exit);
0188 MODULE_LICENSE("GPL");
0189 MODULE_INFO(livepatch, "Y");
0190 MODULE_AUTHOR("Petr Mladek <pmladek@suse.com>");
0191 MODULE_DESCRIPTION("Livepatch test: system state modification");