lib/livepatch/test_klp_state.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 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");