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                 case R_386_PLT32:
 128                         /* Add the value, subtract its position */
 129                         *location += sym->st_value - (uint32_t)location;
 130                         break;
 131                 default:
 132                         pr_err("%s: Unknown relocation: %u\n",
 133                                me->name, ELF32_R_TYPE(rel[i].r_info));
 134                         return -ENOEXEC;
 135                 }
 136         }
 137         return 0;
 138 }
 139 #else /*X86_64*/
 140 int apply_relocate_add(Elf64_Shdr *sechdrs,
 141                    const char *strtab,
 142                    unsigned int symindex,
 143                    unsigned int relsec,
 144                    struct module *me)
 145 {
 146         unsigned int i;
 147         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 148         Elf64_Sym *sym;
 149         void *loc;
 150         u64 val;
 151
 152         DEBUGP("Applying relocate section %u to %u\n",
 153                relsec, sechdrs[relsec].sh_info);
 154         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 155                 /* This is where to make the change */
 156                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 157                         + rel[i].r_offset;
 158
 159                 /* This is the symbol it is referring to.  Note that all
 160                    undefined symbols have been resolved.  */
 161                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 162                         + ELF64_R_SYM(rel[i].r_info);
 163
 164                 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 165                        (int)ELF64_R_TYPE(rel[i].r_info),
 166                        sym->st_value, rel[i].r_addend, (u64)loc);
 167
 168                 val = sym->st_value + rel[i].r_addend;
 169
 170                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 171                 case R_X86_64_NONE:
 172                         break;
 173                 case R_X86_64_64:
 174                         if (*(u64 *)loc != 0)
 175                                 goto invalid_relocation;
 176                         *(u64 *)loc = val;
 177                         break;
 178                 case R_X86_64_32:
 179                         if (*(u32 *)loc != 0)
 180                                 goto invalid_relocation;
 181                         *(u32 *)loc = val;
 182                         if (val != *(u32 *)loc)
 183                                 goto overflow;
 184                         break;
 185                 case R_X86_64_32S:
 186                         if (*(s32 *)loc != 0)
 187                                 goto invalid_relocation;
 188                         *(s32 *)loc = val;
 189                         if ((s64)val != *(s32 *)loc)
 190                                 goto overflow;
 191                         break;
 192                 case R_X86_64_PC32:
 193                 case R_X86_64_PLT32:
 194                         if (*(u32 *)loc != 0)
 195                                 goto invalid_relocation;
 196                         val -= (u64)loc;
 197                         *(u32 *)loc = val;
 198 #if 0
 199                         if ((s64)val != *(s32 *)loc)
 200                                 goto overflow;
 201 #endif
 202                         break;
 203                 default:
 204                         pr_err("%s: Unknown rela relocation: %llu\n",
 205                                me->name, ELF64_R_TYPE(rel[i].r_info));
 206                         return -ENOEXEC;
 207                 }
 208         }
 209         return 0;
 210
 211 invalid_relocation:
 212         pr_err("x86/modules: Skipping invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
 213                (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
 214         return -ENOEXEC;
 215
 216 overflow:
 217         pr_err("overflow in relocation type %d val %Lx\n",
 218                (int)ELF64_R_TYPE(rel[i].r_info), val);
 219         pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 220                me->name);
 221         return -ENOEXEC;
 222 }
 223 #endif
 224
 225 int module_finalize(const Elf_Ehdr *hdr,
 226                     const Elf_Shdr *sechdrs,
 227                     struct module *me)
 228 {
 229         const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
 230                 *para = NULL;
 231         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 232
 233         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 234                 if (!strcmp(".text", secstrings + s->sh_name))
 235                         text = s;
 236                 if (!strcmp(".altinstructions", secstrings + s->sh_name))
 237                         alt = s;
 238                 if (!strcmp(".smp_locks", secstrings + s->sh_name))
 239                         locks = s;
 240                 if (!strcmp(".parainstructions", secstrings + s->sh_name))
 241                         para = s;
 242         }
 243
 244         if (alt) {
 245                 /* patch .altinstructions */
 246                 void *aseg = (void *)alt->sh_addr;
 247                 apply_alternatives(aseg, aseg + alt->sh_size);
 248         }
 249         if (locks && text) {
 250                 void *lseg = (void *)locks->sh_addr;
 251                 void *tseg = (void *)text->sh_addr;
 252                 alternatives_smp_module_add(me, me->name,
 253                                             lseg, lseg + locks->sh_size,
 254                                             tseg, tseg + text->sh_size);
 255         }
 256
 257         if (para) {
 258                 void *pseg = (void *)para->sh_addr;
 259                 apply_paravirt(pseg, pseg + para->sh_size);
 260         }
 261
 262         /* make jump label nops */
 263         jump_label_apply_nops(me);
 264
 265         return 0;
 266 }
 267
 268 void module_arch_cleanup(struct module *mod)
 269 {
 270         alternatives_smp_module_del(mod);
 271 }