lib/livepatch/test_klp_state2.c

   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");