arch/x86/kernel/module.c

   1 /*  Kernel module help for x86.
   2     Copyright (C) 2001 Rusty Russell.
   3
   4     This program is free software; you can redistribute it and/or modify
   5     it under the terms of the GNU General Public License as published by
   6     the Free Software Foundation; either version 2 of the License, or
   7     (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, write to the Free Software
  16     Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  17 */
  18
  19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21 #include <linux/moduleloader.h>
  22 #include <linux/elf.h>
  23 #include <linux/vmalloc.h>
  24 #include <linux/fs.h>
  25 #include <linux/string.h>
  26 #include <linux/kernel.h>
  27 #include <linux/bug.h>
  28 #include <linux/mm.h>
  29 #include <linux/gfp.h>
  30 #include <linux/jump_label.h>
  31 #include <linux/random.h>
  32
  33 #include <asm/page.h>
  34 #include <asm/pgtable.h>
  35
  36 #if 0
  37 #define DEBUGP(fmt, ...)                                \
  38         printk(KERN_DEBUG fmt, ##__VA_ARGS__)
  39 #else
  40 #define DEBUGP(fmt, ...)                                \
  41 do {                                                    \
  42         if (0)                                          \
  43                 printk(KERN_DEBUG fmt, ##__VA_ARGS__);  \
  44 } while (0)
  45 #endif
  46
  47 #ifdef CONFIG_RANDOMIZE_BASE
  48 static unsigned long module_load_offset;
  49 static int randomize_modules = 1;
  50
  51 /* Mutex protects the module_load_offset. */
  52 static DEFINE_MUTEX(module_kaslr_mutex);
  53
  54 static int __init parse_nokaslr(char *p)
  55 {
  56         randomize_modules = 0;
  57         return 0;
  58 }
  59 early_param("nokaslr", parse_nokaslr);
  60
  61 static unsigned long int get_module_load_offset(void)
  62 {
  63         if (randomize_modules) {
  64                 mutex_lock(&module_kaslr_mutex);
  65                 /*
  66                  * Calculate the module_load_offset the first time this
  67                  * code is called. Once calculated it stays the same until
  68                  * reboot.
  69                  */
  70                 if (module_load_offset == 0)
  71                         module_load_offset =
  72                                 (get_random_int() % 1024 + 1) * PAGE_SIZE;
  73                 mutex_unlock(&module_kaslr_mutex);
  74         }
  75         return module_load_offset;
  76 }
  77 #else
  78 static unsigned long int get_module_load_offset(void)
  79 {
  80         return 0;
  81 }
  82 #endif
  83
  84 void *module_alloc(unsigned long size)
  85 {
  86         if (PAGE_ALIGN(size) > MODULES_LEN)
  87                 return NULL;
  88         return __vmalloc_node_range(size, 1,
  89                                     MODULES_VADDR + get_module_load_offset(),
  90                                     MODULES_END, GFP_KERNEL | __GFP_HIGHMEM,
  91                                     PAGE_KERNEL_EXEC, NUMA_NO_NODE,
  92                                     __builtin_return_address(0));
  93 }
  94
  95 #ifdef CONFIG_X86_32
  96 int apply_relocate(Elf32_Shdr *sechdrs,
  97                    const char *strtab,
  98                    unsigned int symindex,
  99                    unsigned int relsec,
 100                    struct module *me)
 101 {
 102         unsigned int i;
 103         Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
 104         Elf32_Sym *sym;
 105         uint32_t *location;
 106
 107         DEBUGP("Applying relocate section %u to %u\n",
 108                relsec, sechdrs[relsec].sh_info);
 109         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 110                 /* This is where to make the change */
 111                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 112                         + rel[i].r_offset;
 113                 /* This is the symbol it is referring to.  Note that all
 114                    undefined symbols have been resolved.  */
 115                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 116                         + ELF32_R_SYM(rel[i].r_info);
 117
 118                 switch (ELF32_R_TYPE(rel[i].r_info)) {
 119                 case R_386_32:
 120                         /* We add the value into the location given */
 121                         *location += sym->st_value;
 122                         break;
 123                 case R_386_PC32:
 124                         /* Add the value, subtract its position */
 125                         *location += sym->st_value - (uint32_t)location;
 126                         break;
 127                 default:
 128                         pr_err("%s: Unknown relocation: %u\n",
 129                                me->name, ELF32_R_TYPE(rel[i].r_info));
 130                         return -ENOEXEC;
 131                 }
 132         }
 133         return 0;
 134 }
 135 #else /*X86_64*/
 136 int apply_relocate_add(Elf64_Shdr *sechdrs,
 137                    const char *strtab,
 138                    unsigned int symindex,
 139                    unsigned int relsec,
 140                    struct module *me)
 141 {
 142         unsigned int i;
 143         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 144         Elf64_Sym *sym;
 145         void *loc;
 146         u64 val;
 147
 148         DEBUGP("Applying relocate section %u to %u\n",
 149                relsec, sechdrs[relsec].sh_info);
 150         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 151                 /* This is where to make the change */
 152                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 153                         + rel[i].r_offset;
 154
 155                 /* This is the symbol it is referring to.  Note that all
 156                    undefined symbols have been resolved.  */
 157                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 158                         + ELF64_R_SYM(rel[i].r_info);
 159
 160                 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 161                        (int)ELF64_R_TYPE(rel[i].r_info),
 162                        sym->st_value, rel[i].r_addend, (u64)loc);
 163
 164                 val = sym->st_value + rel[i].r_addend;
 165
 166                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 167                 case R_X86_64_NONE:
 168                         break;
 169                 case R_X86_64_64:
 170                         *(u64 *)loc = val;
 171                         break;
 172                 case R_X86_64_32:
 173                         *(u32 *)loc = val;
 174                         if (val != *(u32 *)loc)
 175                                 goto overflow;
 176                         break;
 177                 case R_X86_64_32S:
 178                         *(s32 *)loc = val;
 179                         if ((s64)val != *(s32 *)loc)
 180                                 goto overflow;
 181                         break;
 182                 case R_X86_64_PC32:
 183                         val -= (u64)loc;
 184                         *(u32 *)loc = val;
 185 #if 0
 186                         if ((s64)val != *(s32 *)loc)
 187                                 goto overflow;
 188 #endif
 189                         break;
 190                 default:
 191                         pr_err("%s: Unknown rela relocation: %llu\n",
 192                                me->name, ELF64_R_TYPE(rel[i].r_info));
 193                         return -ENOEXEC;
 194                 }
 195         }
 196         return 0;
 197
 198 overflow:
 199         pr_err("overflow in relocation type %d val %Lx\n",
 200                (int)ELF64_R_TYPE(rel[i].r_info), val);
 201         pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 202                me->name);
 203         return -ENOEXEC;
 204 }
 205 #endif
 206
 207 int module_finalize(const Elf_Ehdr *hdr,
 208                     const Elf_Shdr *sechdrs,
 209                     struct module *me)
 210 {
 211         const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
 212                 *para = NULL;
 213         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 214
 215         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 216                 if (!strcmp(".text", secstrings + s->sh_name))
 217                         text = s;
 218                 if (!strcmp(".altinstructions", secstrings + s->sh_name))
 219                         alt = s;
 220                 if (!strcmp(".smp_locks", secstrings + s->sh_name))
 221                         locks = s;
 222                 if (!strcmp(".parainstructions", secstrings + s->sh_name))
 223                         para = s;
 224         }
 225
 226         if (alt) {
 227                 /* patch .altinstructions */
 228                 void *aseg = (void *)alt->sh_addr;
 229                 apply_alternatives(aseg, aseg + alt->sh_size);
 230         }
 231         if (locks && text) {
 232                 void *lseg = (void *)locks->sh_addr;
 233                 void *tseg = (void *)text->sh_addr;
 234                 alternatives_smp_module_add(me, me->name,
 235                                             lseg, lseg + locks->sh_size,
 236                                             tseg, tseg + text->sh_size);
 237         }
 238
 239         if (para) {
 240                 void *pseg = (void *)para->sh_addr;
 241                 apply_paravirt(pseg, pseg + para->sh_size);
 242         }
 243
 244         /* make jump label nops */
 245         jump_label_apply_nops(me);
 246
 247         return 0;
 248 }
 249
 250 void module_arch_cleanup(struct module *mod)
 251 {
 252         alternatives_smp_module_del(mod);
 253 }