1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (C) 2019 SUSE 3 4 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 5 6 #include <linux/slab.h> 7 #include <linux/module.h> 8 #include <linux/kernel.h> 9 #include <linux/printk.h> 10 #include <linux/livepatch.h> 11 12 #define CONSOLE_LOGLEVEL_STATE 1 13 /* Version 2 supports migration. */ 14 #define CONSOLE_LOGLEVEL_STATE_VERSION 2 15 16 static const char *const module_state[] = { 17 [MODULE_STATE_LIVE] = "[MODULE_STATE_LIVE] Normal state", 18 [MODULE_STATE_COMING] = "[MODULE_STATE_COMING] Full formed, running module_init", 19 [MODULE_STATE_GOING] = "[MODULE_STATE_GOING] Going away", 20 [MODULE_STATE_UNFORMED] = "[MODULE_STATE_UNFORMED] Still setting it up", 21 }; 22 23 static void callback_info(const char *callback, struct klp_object *obj) 24 { 25 if (obj->mod) 26 pr_info("%s: %s -> %s\n", callback, obj->mod->name, 27 module_state[obj->mod->state]); 28 else 29 pr_info("%s: vmlinux\n", callback); 30 } 31 32 static struct klp_patch patch; 33 34 static int allocate_loglevel_state(void) 35 { 36 struct klp_state *loglevel_state, *prev_loglevel_state; 37 38 prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE); 39 if (prev_loglevel_state) { 40 pr_info("%s: space to store console_loglevel already allocated\n", 41 __func__); 42 return 0; 43 } 44 45 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE); 46 if (!loglevel_state) 47 return -EINVAL; 48 49 loglevel_state->data = kzalloc(sizeof(console_loglevel), GFP_KERNEL); 50 if (!loglevel_state->data) 51 return -ENOMEM; 52 53 pr_info("%s: allocating space to store console_loglevel\n", 54 __func__); 55 return 0; 56 } 57 58 static void fix_console_loglevel(void) 59 { 60 struct klp_state *loglevel_state, *prev_loglevel_state; 61 62 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE); 63 if (!loglevel_state) 64 return; 65 66 prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE); 67 if (prev_loglevel_state) { 68 pr_info("%s: taking over the console_loglevel change\n", 69 __func__); 70 loglevel_state->data = prev_loglevel_state->data; 71 return; 72 } 73 74 pr_info("%s: fixing console_loglevel\n", __func__); 75 *(int *)loglevel_state->data = console_loglevel; 76 console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH; 77 } 78 79 static void restore_console_loglevel(void) 80 { 81 struct klp_state *loglevel_state, *prev_loglevel_state; 82 83 prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE); 84 if (prev_loglevel_state) { 85 pr_info("%s: passing the console_loglevel change back to the old livepatch\n", 86 __func__); 87 return; 88 } 89 90 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE); 91 if (!loglevel_state) 92 return; 93 94 pr_info("%s: restoring console_loglevel\n", __func__); 95 console_loglevel = *(int *)loglevel_state->data; 96 } 97 98 static void free_loglevel_state(void) 99 { 100 struct klp_state *loglevel_state, *prev_loglevel_state; 101 102 prev_loglevel_state = klp_get_prev_state(CONSOLE_LOGLEVEL_STATE); 103 if (prev_loglevel_state) { 104 pr_info("%s: keeping space to store console_loglevel\n", 105 __func__); 106 return; 107 } 108 109 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE); 110 if (!loglevel_state) 111 return; 112 113 pr_info("%s: freeing space for the stored console_loglevel\n", 114 __func__); 115 kfree(loglevel_state->data); 116 } 117 118 /* Executed on object patching (ie, patch enablement) */ 119 static int pre_patch_callback(struct klp_object *obj) 120 { 121 callback_info(__func__, obj); 122 return allocate_loglevel_state(); 123 } 124 125 /* Executed on object unpatching (ie, patch disablement) */ 126 static void post_patch_callback(struct klp_object *obj) 127 { 128 callback_info(__func__, obj); 129 fix_console_loglevel(); 130 } 131 132 /* Executed on object unpatching (ie, patch disablement) */ 133 static void pre_unpatch_callback(struct klp_object *obj) 134 { 135 callback_info(__func__, obj); 136 restore_console_loglevel(); 137 } 138 139 /* Executed on object unpatching (ie, patch disablement) */ 140 static void post_unpatch_callback(struct klp_object *obj) 141 { 142 callback_info(__func__, obj); 143 free_loglevel_state(); 144 } 145 146 static struct klp_func no_funcs[] = { 147 {} 148 }; 149 150 static struct klp_object objs[] = { 151 { 152 .name = NULL, /* vmlinux */ 153 .funcs = no_funcs, 154 .callbacks = { 155 .pre_patch = pre_patch_callback, 156 .post_patch = post_patch_callback, 157 .pre_unpatch = pre_unpatch_callback, 158 .post_unpatch = post_unpatch_callback, 159 }, 160 }, { } 161 }; 162 163 static struct klp_state states[] = { 164 { 165 .id = CONSOLE_LOGLEVEL_STATE, 166 .version = CONSOLE_LOGLEVEL_STATE_VERSION, 167 }, { } 168 }; 169 170 static struct klp_patch patch = { 171 .mod = THIS_MODULE, 172 .objs = objs, 173 .states = states, 174 .replace = true, 175 }; 176 177 static int test_klp_callbacks_demo_init(void) 178 { 179 return klp_enable_patch(&patch); 180 } 181 182 static void test_klp_callbacks_demo_exit(void) 183 { 184 } 185 186 module_init(test_klp_callbacks_demo_init); 187 module_exit(test_klp_callbacks_demo_exit); 188 MODULE_LICENSE("GPL"); 189 MODULE_INFO(livepatch, "Y"); 190 MODULE_AUTHOR("Petr Mladek <pmladek@suse.com>"); 191 MODULE_DESCRIPTION("Livepatch test: system state modification"); 192