kernel/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/kasan.h>
  28 #include <linux/bug.h>
  29 #include <linux/mm.h>
  30 #include <linux/gfp.h>
  31 #include <linux/jump_label.h>
  32 #include <linux/random.h>
  33
  34 #include <asm/page.h>
  35 #include <asm/pgtable.h>
  36 #include <asm/setup.h>
  37
  38 #if 0
  39 #define DEBUGP(fmt, ...)                                \
  40         printk(KERN_DEBUG fmt, ##__VA_ARGS__)
  41 #else
  42 #define DEBUGP(fmt, ...)                                \
  43 do {                                                    \
  44         if (0)                                          \
  45                 printk(KERN_DEBUG fmt, ##__VA_ARGS__);  \
  46 } while (0)
  47 #endif
  48
  49 #ifdef CONFIG_RANDOMIZE_BASE
  50 static unsigned long module_load_offset;
  51
  52 /* Mutex protects the module_load_offset. */
  53 static DEFINE_MUTEX(module_kaslr_mutex);
  54
  55 static unsigned long int get_module_load_offset(void)
  56 {
  57         if (kaslr_enabled()) {
  58                 mutex_lock(&module_kaslr_mutex);
  59                 /*
  60                  * Calculate the module_load_offset the first time this
  61                  * code is called. Once calculated it stays the same until
  62                  * reboot.
  63                  */
  64                 if (module_load_offset == 0)
  65                         module_load_offset =
  66                                 (get_random_int() % 1024 + 1) * PAGE_SIZE;
  67                 mutex_unlock(&module_kaslr_mutex);
  68         }
  69         return module_load_offset;
  70 }
  71 #else
  72 static unsigned long int get_module_load_offset(void)
  73 {
  74         return 0;
  75 }
  76 #endif
  77
  78 void *module_alloc(unsigned long size)
  79 {
  80         void *p;
  81
  82         if (PAGE_ALIGN(size) > MODULES_LEN)
  83                 return NULL;
  84
  85         p = __vmalloc_node_range(size, MODULE_ALIGN,
  86                                     MODULES_VADDR + get_module_load_offset(),
  87                                     MODULES_END, GFP_KERNEL | __GFP_HIGHMEM,
  88                                     PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
  89                                     __builtin_return_address(0));
  90         if (p && (kasan_module_alloc(p, size) < 0)) {
  91                 vfree(p);
  92                 return NULL;
  93         }
  94
  95         return p;
  96 }
  97
  98 #ifdef CONFIG_X86_32
  99 int apply_relocate(Elf32_Shdr *sechdrs,
 100                    const char *strtab,
 101                    unsigned int symindex,
 102                    unsigned int relsec,
 103                    struct module *me)
 104 {
 105         unsigned int i;
 106         Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
 107         Elf32_Sym *sym;
 108         uint32_t *location;
 109
 110         DEBUGP("Applying relocate section %u to %u\n",
 111                relsec, sechdrs[relsec].sh_info);
 112         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 113                 /* This is where to make the change */
 114                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 115                         + rel[i].r_offset;
 116                 /* This is the symbol it is referring to.  Note that all
 117                    undefined symbols have been resolved.  */
 118                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 119                         + ELF32_R_SYM(rel[i].r_info);
 120
 121                 switch (ELF32_R_TYPE(rel[i].r_info)) {
 122                 case R_386_32:
 123                         /* We add the value into the location given */
 124                         *location += sym->st_value;
 125                         break;
 126                 case R_386_PC32:
 127                         /* Add the value, subtract its position */
 128                         *location += sym->st_value - (uint32_t)location;
 129                         break;
 130                 default:
 131                         pr_err("%s: Unknown relocation: %u\n",
 132                                me->name, ELF32_R_TYPE(rel[i].r_info));
 133                         return -ENOEXEC;
 134                 }
 135         }
 136         return 0;
 137 }
 138 #else /*X86_64*/
 139 int apply_relocate_add(Elf64_Shdr *sechdrs,
 140                    const char *strtab,
 141                    unsigned int symindex,
 142                    unsigned int relsec,
 143                    struct module *me)
 144 {
 145         unsigned int i;
 146         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 147         Elf64_Sym *sym;
 148         void *loc;
 149         u64 val;
 150
 151         DEBUGP("Applying relocate section %u to %u\n",
 152                relsec, sechdrs[relsec].sh_info);
 153         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 154                 /* This is where to make the change */
 155                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 156                         + rel[i].r_offset;
 157
 158                 /* This is the symbol it is referring to.  Note that all
 159                    undefined symbols have been resolved.  */
 160                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 161                         + ELF64_R_SYM(rel[i].r_info);
 162
 163                 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 164                        (int)ELF64_R_TYPE(rel[i].r_info),
 165                        sym->st_value, rel[i].r_addend, (u64)loc);
 166
 167                 val = sym->st_value + rel[i].r_addend;
 168
 169                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 170                 case R_X86_64_NONE:
 171                         break;
 172                 case R_X86_64_64:
 173                         *(u64 *)loc = val;
 174                         break;
 175                 case R_X86_64_32:
 176                         *(u32 *)loc = val;
 177                         if (val != *(u32 *)loc)
 178                                 goto overflow;
 179                         break;
 180                 case R_X86_64_32S:
 181                         *(s32 *)loc = val;
 182                         if ((s64)val != *(s32 *)loc)
 183                                 goto overflow;
 184                         break;
 185                 case R_X86_64_PC32:
 186                         val -= (u64)loc;
 187                         *(u32 *)loc = val;
 188 #if 0
 189                         if ((s64)val != *(s32 *)loc)
 190                                 goto overflow;
 191 #endif
 192                         break;
 193                 default:
 194                         pr_err("%s: Unknown rela relocation: %llu\n",
 195                                me->name, ELF64_R_TYPE(rel[i].r_info));
 196                         return -ENOEXEC;
 197                 }
 198         }
 199         return 0;
 200
 201 overflow:
 202         pr_err("overflow in relocation type %d val %Lx\n",
 203                (int)ELF64_R_TYPE(rel[i].r_info), val);
 204         pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 205                me->name);
 206         return -ENOEXEC;
 207 }
 208 #endif
 209
 210 int module_finalize(const Elf_Ehdr *hdr,
 211                     const Elf_Shdr *sechdrs,
 212                     struct module *me)
 213 {
 214         const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
 215                 *para = NULL;
 216         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 217
 218         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 219                 if (!strcmp(".text", secstrings + s->sh_name))
 220                         text = s;
 221                 if (!strcmp(".altinstructions", secstrings + s->sh_name))
 222                         alt = s;
 223                 if (!strcmp(".smp_locks", secstrings + s->sh_name))
 224                         locks = s;
 225                 if (!strcmp(".parainstructions", secstrings + s->sh_name))
 226                         para = s;
 227         }
 228
 229         if (alt) {
 230                 /* patch .altinstructions */
 231                 void *aseg = (void *)alt->sh_addr;
 232                 apply_alternatives(aseg, aseg + alt->sh_size);
 233         }
 234         if (locks && text) {
 235                 void *lseg = (void *)locks->sh_addr;
 236                 void *tseg = (void *)text->sh_addr;
 237                 alternatives_smp_module_add(me, me->name,
 238                                             lseg, lseg + locks->sh_size,
 239                                             tseg, tseg + text->sh_size);
 240         }
 241
 242         if (para) {
 243                 void *pseg = (void *)para->sh_addr;
 244                 apply_paravirt(pseg, pseg + para->sh_size);
 245         }
 246
 247         /* make jump label nops */
 248         jump_label_apply_nops(me);
 249
 250         return 0;
 251 }
 252
 253 void module_arch_cleanup(struct module *mod)
 254 {
 255         alternatives_smp_module_del(mod);
 256 }