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
  37 #if 0
  38 #define DEBUGP(fmt, ...)                                \
  39         printk(KERN_DEBUG fmt, ##__VA_ARGS__)
  40 #else
  41 #define DEBUGP(fmt, ...)                                \
  42 do {                                                    \
  43         if (0)                                          \
  44                 printk(KERN_DEBUG fmt, ##__VA_ARGS__);  \
  45 } while (0)
  46 #endif
  47
  48 #ifdef CONFIG_RANDOMIZE_BASE
  49 static unsigned long module_load_offset;
  50 static int randomize_modules = 1;
  51
  52 /* Mutex protects the module_load_offset. */
  53 static DEFINE_MUTEX(module_kaslr_mutex);
  54
  55 static int __init parse_nokaslr(char *p)
  56 {
  57         randomize_modules = 0;
  58         return 0;
  59 }
  60 early_param("nokaslr", parse_nokaslr);
  61
  62 static unsigned long int get_module_load_offset(void)
  63 {
  64         if (randomize_modules) {
  65                 mutex_lock(&module_kaslr_mutex);
  66                 /*
  67                  * Calculate the module_load_offset the first time this
  68                  * code is called. Once calculated it stays the same until
  69                  * reboot.
  70                  */
  71                 if (module_load_offset == 0)
  72                         module_load_offset =
  73                                 (get_random_int() % 1024 + 1) * PAGE_SIZE;
  74                 mutex_unlock(&module_kaslr_mutex);
  75         }
  76         return module_load_offset;
  77 }
  78 #else
  79 static unsigned long int get_module_load_offset(void)
  80 {
  81         return 0;
  82 }
  83 #endif
  84
  85 void *module_alloc(unsigned long size)
  86 {
  87         void *p;
  88
  89         if (PAGE_ALIGN(size) > MODULES_LEN)
  90                 return NULL;
  91
  92         p = __vmalloc_node_range(size, MODULE_ALIGN,
  93                                     MODULES_VADDR + get_module_load_offset(),
  94                                     MODULES_END, GFP_KERNEL | __GFP_HIGHMEM,
  95                                     PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
  96                                     __builtin_return_address(0));
  97         if (p && (kasan_module_alloc(p, size) < 0)) {
  98                 vfree(p);
  99                 return NULL;
 100         }
 101
 102         return p;
 103 }
 104
 105 #ifdef CONFIG_X86_32
 106 int apply_relocate(Elf32_Shdr *sechdrs,
 107                    const char *strtab,
 108                    unsigned int symindex,
 109                    unsigned int relsec,
 110                    struct module *me)
 111 {
 112         unsigned int i;
 113         Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
 114         Elf32_Sym *sym;
 115         uint32_t *location;
 116
 117         DEBUGP("Applying relocate section %u to %u\n",
 118                relsec, sechdrs[relsec].sh_info);
 119         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 120                 /* This is where to make the change */
 121                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 122                         + rel[i].r_offset;
 123                 /* This is the symbol it is referring to.  Note that all
 124                    undefined symbols have been resolved.  */
 125                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 126                         + ELF32_R_SYM(rel[i].r_info);
 127
 128                 switch (ELF32_R_TYPE(rel[i].r_info)) {
 129                 case R_386_32:
 130                         /* We add the value into the location given */
 131                         *location += sym->st_value;
 132                         break;
 133                 case R_386_PC32:
 134                         /* Add the value, subtract its position */
 135                         *location += sym->st_value - (uint32_t)location;
 136                         break;
 137                 default:
 138                         pr_err("%s: Unknown relocation: %u\n",
 139                                me->name, ELF32_R_TYPE(rel[i].r_info));
 140                         return -ENOEXEC;
 141                 }
 142         }
 143         return 0;
 144 }
 145 #else /*X86_64*/
 146 int apply_relocate_add(Elf64_Shdr *sechdrs,
 147                    const char *strtab,
 148                    unsigned int symindex,
 149                    unsigned int relsec,
 150                    struct module *me)
 151 {
 152         unsigned int i;
 153         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 154         Elf64_Sym *sym;
 155         void *loc;
 156         u64 val;
 157
 158         DEBUGP("Applying relocate section %u to %u\n",
 159                relsec, sechdrs[relsec].sh_info);
 160         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 161                 /* This is where to make the change */
 162                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 163                         + rel[i].r_offset;
 164
 165                 /* This is the symbol it is referring to.  Note that all
 166                    undefined symbols have been resolved.  */
 167                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 168                         + ELF64_R_SYM(rel[i].r_info);
 169
 170                 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 171                        (int)ELF64_R_TYPE(rel[i].r_info),
 172                        sym->st_value, rel[i].r_addend, (u64)loc);
 173
 174                 val = sym->st_value + rel[i].r_addend;
 175
 176                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 177                 case R_X86_64_NONE:
 178                         break;
 179                 case R_X86_64_64:
 180                         *(u64 *)loc = val;
 181                         break;
 182                 case R_X86_64_32:
 183                         *(u32 *)loc = val;
 184                         if (val != *(u32 *)loc)
 185                                 goto overflow;
 186                         break;
 187                 case R_X86_64_32S:
 188                         *(s32 *)loc = val;
 189                         if ((s64)val != *(s32 *)loc)
 190                                 goto overflow;
 191                         break;
 192                 case R_X86_64_PC32:
 193                         val -= (u64)loc;
 194                         *(u32 *)loc = val;
 195 #if 0
 196                         if ((s64)val != *(s32 *)loc)
 197                                 goto overflow;
 198 #endif
 199                         break;
 200                 default:
 201                         pr_err("%s: Unknown rela relocation: %llu\n",
 202                                me->name, ELF64_R_TYPE(rel[i].r_info));
 203                         return -ENOEXEC;
 204                 }
 205         }
 206         return 0;
 207
 208 overflow:
 209         pr_err("overflow in relocation type %d val %Lx\n",
 210                (int)ELF64_R_TYPE(rel[i].r_info), val);
 211         pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 212                me->name);
 213         return -ENOEXEC;
 214 }
 215 #endif
 216
 217 int module_finalize(const Elf_Ehdr *hdr,
 218                     const Elf_Shdr *sechdrs,
 219                     struct module *me)
 220 {
 221         const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
 222                 *para = NULL;
 223         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 224
 225         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 226                 if (!strcmp(".text", secstrings + s->sh_name))
 227                         text = s;
 228                 if (!strcmp(".altinstructions", secstrings + s->sh_name))
 229                         alt = s;
 230                 if (!strcmp(".smp_locks", secstrings + s->sh_name))
 231                         locks = s;
 232                 if (!strcmp(".parainstructions", secstrings + s->sh_name))
 233                         para = s;
 234         }
 235
 236         if (alt) {
 237                 /* patch .altinstructions */
 238                 void *aseg = (void *)alt->sh_addr;
 239                 apply_alternatives(aseg, aseg + alt->sh_size);
 240         }
 241         if (locks && text) {
 242                 void *lseg = (void *)locks->sh_addr;
 243                 void *tseg = (void *)text->sh_addr;
 244                 alternatives_smp_module_add(me, me->name,
 245                                             lseg, lseg + locks->sh_size,
 246                                             tseg, tseg + text->sh_size);
 247         }
 248
 249         if (para) {
 250                 void *pseg = (void *)para->sh_addr;
 251                 apply_paravirt(pseg, pseg + para->sh_size);
 252         }
 253
 254         /* make jump label nops */
 255         jump_label_apply_nops(me);
 256
 257         return 0;
 258 }
 259
 260 void module_arch_cleanup(struct module *mod)
 261 {
 262         alternatives_smp_module_del(mod);
 263 }