Josh Poimboeuf | c349cdca | 2017-02-13 19:42:37 -0600 | [diff] [blame^] | 1 | /* |
| 2 | * patch.c - livepatch patching functions |
| 3 | * |
| 4 | * Copyright (C) 2014 Seth Jennings <sjenning@redhat.com> |
| 5 | * Copyright (C) 2014 SUSE |
| 6 | * Copyright (C) 2015 Josh Poimboeuf <jpoimboe@redhat.com> |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or |
| 9 | * modify it under the terms of the GNU General Public License |
| 10 | * as published by the Free Software Foundation; either version 2 |
| 11 | * of the License, or (at your option) any later version. |
| 12 | * |
| 13 | * This program is distributed in the hope that it will be useful, |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 16 | * GNU General Public License for more details. |
| 17 | * |
| 18 | * You should have received a copy of the GNU General Public License |
| 19 | * along with this program; if not, see <http://www.gnu.org/licenses/>. |
| 20 | */ |
| 21 | |
| 22 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 23 | |
| 24 | #include <linux/livepatch.h> |
| 25 | #include <linux/list.h> |
| 26 | #include <linux/ftrace.h> |
| 27 | #include <linux/rculist.h> |
| 28 | #include <linux/slab.h> |
| 29 | #include <linux/bug.h> |
| 30 | #include <linux/printk.h> |
| 31 | #include "patch.h" |
| 32 | |
| 33 | static LIST_HEAD(klp_ops); |
| 34 | |
| 35 | struct klp_ops *klp_find_ops(unsigned long old_addr) |
| 36 | { |
| 37 | struct klp_ops *ops; |
| 38 | struct klp_func *func; |
| 39 | |
| 40 | list_for_each_entry(ops, &klp_ops, node) { |
| 41 | func = list_first_entry(&ops->func_stack, struct klp_func, |
| 42 | stack_node); |
| 43 | if (func->old_addr == old_addr) |
| 44 | return ops; |
| 45 | } |
| 46 | |
| 47 | return NULL; |
| 48 | } |
| 49 | |
| 50 | static void notrace klp_ftrace_handler(unsigned long ip, |
| 51 | unsigned long parent_ip, |
| 52 | struct ftrace_ops *fops, |
| 53 | struct pt_regs *regs) |
| 54 | { |
| 55 | struct klp_ops *ops; |
| 56 | struct klp_func *func; |
| 57 | |
| 58 | ops = container_of(fops, struct klp_ops, fops); |
| 59 | |
| 60 | rcu_read_lock(); |
| 61 | func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, |
| 62 | stack_node); |
| 63 | if (WARN_ON_ONCE(!func)) |
| 64 | goto unlock; |
| 65 | |
| 66 | klp_arch_set_pc(regs, (unsigned long)func->new_func); |
| 67 | unlock: |
| 68 | rcu_read_unlock(); |
| 69 | } |
| 70 | |
| 71 | /* |
| 72 | * Convert a function address into the appropriate ftrace location. |
| 73 | * |
| 74 | * Usually this is just the address of the function, but on some architectures |
| 75 | * it's more complicated so allow them to provide a custom behaviour. |
| 76 | */ |
| 77 | #ifndef klp_get_ftrace_location |
| 78 | static unsigned long klp_get_ftrace_location(unsigned long faddr) |
| 79 | { |
| 80 | return faddr; |
| 81 | } |
| 82 | #endif |
| 83 | |
| 84 | static void klp_unpatch_func(struct klp_func *func) |
| 85 | { |
| 86 | struct klp_ops *ops; |
| 87 | |
| 88 | if (WARN_ON(!func->patched)) |
| 89 | return; |
| 90 | if (WARN_ON(!func->old_addr)) |
| 91 | return; |
| 92 | |
| 93 | ops = klp_find_ops(func->old_addr); |
| 94 | if (WARN_ON(!ops)) |
| 95 | return; |
| 96 | |
| 97 | if (list_is_singular(&ops->func_stack)) { |
| 98 | unsigned long ftrace_loc; |
| 99 | |
| 100 | ftrace_loc = klp_get_ftrace_location(func->old_addr); |
| 101 | if (WARN_ON(!ftrace_loc)) |
| 102 | return; |
| 103 | |
| 104 | WARN_ON(unregister_ftrace_function(&ops->fops)); |
| 105 | WARN_ON(ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0)); |
| 106 | |
| 107 | list_del_rcu(&func->stack_node); |
| 108 | list_del(&ops->node); |
| 109 | kfree(ops); |
| 110 | } else { |
| 111 | list_del_rcu(&func->stack_node); |
| 112 | } |
| 113 | |
| 114 | func->patched = false; |
| 115 | } |
| 116 | |
| 117 | static int klp_patch_func(struct klp_func *func) |
| 118 | { |
| 119 | struct klp_ops *ops; |
| 120 | int ret; |
| 121 | |
| 122 | if (WARN_ON(!func->old_addr)) |
| 123 | return -EINVAL; |
| 124 | |
| 125 | if (WARN_ON(func->patched)) |
| 126 | return -EINVAL; |
| 127 | |
| 128 | ops = klp_find_ops(func->old_addr); |
| 129 | if (!ops) { |
| 130 | unsigned long ftrace_loc; |
| 131 | |
| 132 | ftrace_loc = klp_get_ftrace_location(func->old_addr); |
| 133 | if (!ftrace_loc) { |
| 134 | pr_err("failed to find location for function '%s'\n", |
| 135 | func->old_name); |
| 136 | return -EINVAL; |
| 137 | } |
| 138 | |
| 139 | ops = kzalloc(sizeof(*ops), GFP_KERNEL); |
| 140 | if (!ops) |
| 141 | return -ENOMEM; |
| 142 | |
| 143 | ops->fops.func = klp_ftrace_handler; |
| 144 | ops->fops.flags = FTRACE_OPS_FL_SAVE_REGS | |
| 145 | FTRACE_OPS_FL_DYNAMIC | |
| 146 | FTRACE_OPS_FL_IPMODIFY; |
| 147 | |
| 148 | list_add(&ops->node, &klp_ops); |
| 149 | |
| 150 | INIT_LIST_HEAD(&ops->func_stack); |
| 151 | list_add_rcu(&func->stack_node, &ops->func_stack); |
| 152 | |
| 153 | ret = ftrace_set_filter_ip(&ops->fops, ftrace_loc, 0, 0); |
| 154 | if (ret) { |
| 155 | pr_err("failed to set ftrace filter for function '%s' (%d)\n", |
| 156 | func->old_name, ret); |
| 157 | goto err; |
| 158 | } |
| 159 | |
| 160 | ret = register_ftrace_function(&ops->fops); |
| 161 | if (ret) { |
| 162 | pr_err("failed to register ftrace handler for function '%s' (%d)\n", |
| 163 | func->old_name, ret); |
| 164 | ftrace_set_filter_ip(&ops->fops, ftrace_loc, 1, 0); |
| 165 | goto err; |
| 166 | } |
| 167 | |
| 168 | |
| 169 | } else { |
| 170 | list_add_rcu(&func->stack_node, &ops->func_stack); |
| 171 | } |
| 172 | |
| 173 | func->patched = true; |
| 174 | |
| 175 | return 0; |
| 176 | |
| 177 | err: |
| 178 | list_del_rcu(&func->stack_node); |
| 179 | list_del(&ops->node); |
| 180 | kfree(ops); |
| 181 | return ret; |
| 182 | } |
| 183 | |
| 184 | void klp_unpatch_object(struct klp_object *obj) |
| 185 | { |
| 186 | struct klp_func *func; |
| 187 | |
| 188 | klp_for_each_func(obj, func) |
| 189 | if (func->patched) |
| 190 | klp_unpatch_func(func); |
| 191 | |
| 192 | obj->patched = false; |
| 193 | } |
| 194 | |
| 195 | int klp_patch_object(struct klp_object *obj) |
| 196 | { |
| 197 | struct klp_func *func; |
| 198 | int ret; |
| 199 | |
| 200 | if (WARN_ON(obj->patched)) |
| 201 | return -EINVAL; |
| 202 | |
| 203 | klp_for_each_func(obj, func) { |
| 204 | ret = klp_patch_func(func); |
| 205 | if (ret) { |
| 206 | klp_unpatch_object(obj); |
| 207 | return ret; |
| 208 | } |
| 209 | } |
| 210 | obj->patched = true; |
| 211 | |
| 212 | return 0; |
| 213 | } |