Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2017 Joe Lawrence <joe.lawrence@redhat.com> |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or |
| 5 | * modify it under the terms of the GNU General Public License |
| 6 | * as published by the Free Software Foundation; either version 2 |
| 7 | * of the License, or (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | * GNU General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, see <http://www.gnu.org/licenses/>. |
| 16 | */ |
| 17 | |
| 18 | /* |
| 19 | * livepatch-shadow-fix2.c - Shadow variables, livepatch demo |
| 20 | * |
| 21 | * Purpose |
| 22 | * ------- |
| 23 | * |
| 24 | * Adds functionality to livepatch-shadow-mod's in-flight data |
| 25 | * structures through a shadow variable. The livepatch patches a |
| 26 | * routine that periodically inspects data structures, incrementing a |
| 27 | * per-data-structure counter, creating the counter if needed. |
| 28 | * |
| 29 | * |
| 30 | * Usage |
| 31 | * ----- |
| 32 | * |
| 33 | * This module is not intended to be standalone. See the "Usage" |
| 34 | * section of livepatch-shadow-mod.c. |
| 35 | */ |
| 36 | |
| 37 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 38 | |
| 39 | #include <linux/module.h> |
| 40 | #include <linux/kernel.h> |
| 41 | #include <linux/livepatch.h> |
| 42 | #include <linux/slab.h> |
| 43 | |
| 44 | /* Shadow variable enums */ |
| 45 | #define SV_LEAK 1 |
| 46 | #define SV_COUNTER 2 |
| 47 | |
| 48 | struct dummy { |
| 49 | struct list_head list; |
| 50 | unsigned long jiffies_expire; |
| 51 | }; |
| 52 | |
| 53 | bool livepatch_fix2_dummy_check(struct dummy *d, unsigned long jiffies) |
| 54 | { |
| 55 | int *shadow_count; |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 56 | |
| 57 | /* |
| 58 | * Patch: handle in-flight dummy structures, if they do not |
| 59 | * already have a SV_COUNTER shadow variable, then attach a |
| 60 | * new one. |
| 61 | */ |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 62 | shadow_count = klp_shadow_get_or_alloc(d, SV_COUNTER, |
Petr Mladek | e91c2518 | 2018-04-16 13:36:46 +0200 | [diff] [blame] | 63 | sizeof(*shadow_count), GFP_NOWAIT, |
| 64 | NULL, NULL); |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 65 | if (shadow_count) |
| 66 | *shadow_count += 1; |
| 67 | |
| 68 | return time_after(jiffies, d->jiffies_expire); |
| 69 | } |
| 70 | |
Petr Mladek | 3b2c77d | 2018-04-16 13:36:47 +0200 | [diff] [blame^] | 71 | static void livepatch_fix2_dummy_leak_dtor(void *obj, void *shadow_data) |
| 72 | { |
| 73 | void *d = obj; |
| 74 | void **shadow_leak = shadow_data; |
| 75 | |
| 76 | kfree(*shadow_leak); |
| 77 | pr_info("%s: dummy @ %p, prevented leak @ %p\n", |
| 78 | __func__, d, *shadow_leak); |
| 79 | } |
| 80 | |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 81 | void livepatch_fix2_dummy_free(struct dummy *d) |
| 82 | { |
Petr Mladek | 3b2c77d | 2018-04-16 13:36:47 +0200 | [diff] [blame^] | 83 | void **shadow_leak; |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 84 | int *shadow_count; |
| 85 | |
| 86 | /* Patch: copy the memory leak patch from the fix1 module. */ |
| 87 | shadow_leak = klp_shadow_get(d, SV_LEAK); |
Petr Mladek | 3b2c77d | 2018-04-16 13:36:47 +0200 | [diff] [blame^] | 88 | if (shadow_leak) |
| 89 | klp_shadow_free(d, SV_LEAK, livepatch_fix2_dummy_leak_dtor); |
| 90 | else |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 91 | pr_info("%s: dummy @ %p leaked!\n", __func__, d); |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 92 | |
| 93 | /* |
| 94 | * Patch: fetch the SV_COUNTER shadow variable and display |
| 95 | * the final count. Detach the shadow variable. |
| 96 | */ |
| 97 | shadow_count = klp_shadow_get(d, SV_COUNTER); |
| 98 | if (shadow_count) { |
| 99 | pr_info("%s: dummy @ %p, check counter = %d\n", |
| 100 | __func__, d, *shadow_count); |
Petr Mladek | 3b2c77d | 2018-04-16 13:36:47 +0200 | [diff] [blame^] | 101 | klp_shadow_free(d, SV_COUNTER, NULL); |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 102 | } |
| 103 | |
| 104 | kfree(d); |
| 105 | } |
| 106 | |
| 107 | static struct klp_func funcs[] = { |
| 108 | { |
| 109 | .old_name = "dummy_check", |
| 110 | .new_func = livepatch_fix2_dummy_check, |
| 111 | }, |
| 112 | { |
| 113 | .old_name = "dummy_free", |
| 114 | .new_func = livepatch_fix2_dummy_free, |
| 115 | }, { } |
| 116 | }; |
| 117 | |
| 118 | static struct klp_object objs[] = { |
| 119 | { |
| 120 | .name = "livepatch_shadow_mod", |
| 121 | .funcs = funcs, |
| 122 | }, { } |
| 123 | }; |
| 124 | |
| 125 | static struct klp_patch patch = { |
| 126 | .mod = THIS_MODULE, |
| 127 | .objs = objs, |
| 128 | }; |
| 129 | |
| 130 | static int livepatch_shadow_fix2_init(void) |
| 131 | { |
| 132 | int ret; |
| 133 | |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 134 | ret = klp_register_patch(&patch); |
| 135 | if (ret) |
| 136 | return ret; |
| 137 | ret = klp_enable_patch(&patch); |
| 138 | if (ret) { |
| 139 | WARN_ON(klp_unregister_patch(&patch)); |
| 140 | return ret; |
| 141 | } |
| 142 | return 0; |
| 143 | } |
| 144 | |
| 145 | static void livepatch_shadow_fix2_exit(void) |
| 146 | { |
| 147 | /* Cleanup any existing SV_COUNTER shadow variables */ |
Petr Mladek | 3b2c77d | 2018-04-16 13:36:47 +0200 | [diff] [blame^] | 148 | klp_shadow_free_all(SV_COUNTER, NULL); |
Joe Lawrence | 439e727 | 2017-08-31 16:37:41 -0400 | [diff] [blame] | 149 | |
| 150 | WARN_ON(klp_unregister_patch(&patch)); |
| 151 | } |
| 152 | |
| 153 | module_init(livepatch_shadow_fix2_init); |
| 154 | module_exit(livepatch_shadow_fix2_exit); |
| 155 | MODULE_LICENSE("GPL"); |
| 156 | MODULE_INFO(livepatch, "Y"); |