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 1 does not support migration. */ 14 #define CONSOLE_LOGLEVEL_STATE_VERSION 1 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; 37 38 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE); 39 if (!loglevel_state) 40 return -EINVAL; 41 42 loglevel_state->data = kzalloc(sizeof(console_loglevel), GFP_KERNEL); 43 if (!loglevel_state->data) 44 return -ENOMEM; 45 46 pr_info("%s: allocating space to store console_loglevel\n", 47 __func__); 48 return 0; 49 } 50 51 static void fix_console_loglevel(void) 52 { 53 struct klp_state *loglevel_state; 54 55 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE); 56 if (!loglevel_state) 57 return; 58 59 pr_info("%s: fixing console_loglevel\n", __func__); 60 *(int *)loglevel_state->data = console_loglevel; 61 console_loglevel = CONSOLE_LOGLEVEL_MOTORMOUTH; 62 } 63 64 static void restore_console_loglevel(void) 65 { 66 struct klp_state *loglevel_state; 67 68 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE); 69 if (!loglevel_state) 70 return; 71 72 pr_info("%s: restoring console_loglevel\n", __func__); 73 console_loglevel = *(int *)loglevel_state->data; 74 } 75 76 static void free_loglevel_state(void) 77 { 78 struct klp_state *loglevel_state; 79 80 loglevel_state = klp_get_state(&patch, CONSOLE_LOGLEVEL_STATE); 81 if (!loglevel_state) 82 return; 83 84 pr_info("%s: freeing space for the stored console_loglevel\n", 85 __func__); 86 kfree(loglevel_state->data); 87 } 88 89 /* Executed on object patching (ie, patch enablement) */ 90 static int pre_patch_callback(struct klp_object *obj) 91 { 92 callback_info(__func__, obj); 93 return allocate_loglevel_state(); 94 } 95 96 /* Executed on object unpatching (ie, patch disablement) */ 97 static void post_patch_callback(struct klp_object *obj) 98 { 99 callback_info(__func__, obj); 100 fix_console_loglevel(); 101 } 102 103 /* Executed on object unpatching (ie, patch disablement) */ 104 static void pre_unpatch_callback(struct klp_object *obj) 105 { 106 callback_info(__func__, obj); 107 restore_console_loglevel(); 108 } 109 110 /* Executed on object unpatching (ie, patch disablement) */ 111 static void post_unpatch_callback(struct klp_object *obj) 112 { 113 callback_info(__func__, obj); 114 free_loglevel_state(); 115 } 116 117 static struct klp_func no_funcs[] = { 118 {} 119 }; 120 121 static struct klp_object objs[] = { 122 { 123 .name = NULL, /* vmlinux */ 124 .funcs = no_funcs, 125 .callbacks = { 126 .pre_patch = pre_patch_callback, 127 .post_patch = post_patch_callback, 128 .pre_unpatch = pre_unpatch_callback, 129 .post_unpatch = post_unpatch_callback, 130 }, 131 }, { } 132 }; 133 134 static struct klp_state states[] = { 135 { 136 .id = CONSOLE_LOGLEVEL_STATE, 137 .version = CONSOLE_LOGLEVEL_STATE_VERSION, 138 }, { } 139 }; 140 141 static struct klp_patch patch = { 142 .mod = THIS_MODULE, 143 .objs = objs, 144 .states = states, 145 .replace = true, 146 }; 147 148 static int test_klp_callbacks_demo_init(void) 149 { 150 return klp_enable_patch(&patch); 151 } 152 153 static void test_klp_callbacks_demo_exit(void) 154 { 155 } 156 157 module_init(test_klp_callbacks_demo_init); 158 module_exit(test_klp_callbacks_demo_exit); 159 MODULE_LICENSE("GPL"); 160 MODULE_INFO(livepatch, "Y"); 161 MODULE_AUTHOR("Petr Mladek <pmladek@suse.com>"); 162 MODULE_DESCRIPTION("Livepatch test: system state modification"); 163