arch/x86/kernel/livepatch.c

   1 /*
   2  * livepatch.c - x86-specific Kernel Live Patching Core
   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 #include <linux/module.h>
  19 #include <linux/kallsyms.h>
  20 #include <linux/livepatch.h>
  21 #include <asm/text-patching.h>
  22
  23 /* Apply per-object alternatives. Based on x86 module_finalize() */
  24 void arch_klp_init_object_loaded(struct klp_patch *patch,
  25                                  struct klp_object *obj)
  26 {
  27         int cnt;
  28         struct klp_modinfo *info;
  29         Elf_Shdr *s, *alt = NULL, *para = NULL;
  30         void *aseg, *pseg;
  31         const char *objname;
  32         char sec_objname[MODULE_NAME_LEN];
  33         char secname[KSYM_NAME_LEN];
  34
  35         info = patch->mod->klp_info;
  36         objname = obj->name ? obj->name : "vmlinux";
  37
  38         /* See livepatch core code for BUILD_BUG_ON() explanation */
  39         BUILD_BUG_ON(MODULE_NAME_LEN < 56 || KSYM_NAME_LEN != 128);
  40
  41         for (s = info->sechdrs; s < info->sechdrs + info->hdr.e_shnum; s++) {
  42                 /* Apply per-object .klp.arch sections */
  43                 cnt = sscanf(info->secstrings + s->sh_name,
  44                              ".klp.arch.%55[^.].%127s",
  45                              sec_objname, secname);
  46                 if (cnt != 2)
  47                         continue;
  48                 if (strcmp(sec_objname, objname))
  49                         continue;
  50                 if (!strcmp(".altinstructions", secname))
  51                         alt = s;
  52                 if (!strcmp(".parainstructions", secname))
  53                         para = s;
  54         }
  55
  56         if (alt) {
  57                 aseg = (void *) alt->sh_addr;
  58                 apply_alternatives(aseg, aseg + alt->sh_size);
  59         }
  60
  61         if (para) {
  62                 pseg = (void *) para->sh_addr;
  63                 apply_paravirt(pseg, pseg + para->sh_size);
  64         }
  65 }