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/text-patching.h>
  35 #include <asm/page.h>
  36 #include <asm/pgtable.h>
  37 #include <asm/setup.h>
  38
  39 #if 0
  40 #define DEBUGP(fmt, ...)                                \
  41         printk(KERN_DEBUG fmt, ##__VA_ARGS__)
  42 #else
  43 #define DEBUGP(fmt, ...)                                \
  44 do {                                                    \
  45         if (0)                                          \
  46                 printk(KERN_DEBUG fmt, ##__VA_ARGS__);  \
  47 } while (0)
  48 #endif
  49
  50 #ifdef CONFIG_RANDOMIZE_BASE
  51 static unsigned long module_load_offset;
  52
  53 /* Mutex protects the module_load_offset. */
  54 static DEFINE_MUTEX(module_kaslr_mutex);
  55
  56 static unsigned long int get_module_load_offset(void)
  57 {
  58         if (kaslr_enabled()) {
  59                 mutex_lock(&module_kaslr_mutex);
  60                 /*
  61                  * Calculate the module_load_offset the first time this
  62                  * code is called. Once calculated it stays the same until
  63                  * reboot.
  64                  */
  65                 if (module_load_offset == 0)
  66                         module_load_offset =
  67                                 (get_random_int() % 1024 + 1) * PAGE_SIZE;
  68                 mutex_unlock(&module_kaslr_mutex);
  69         }
  70         return module_load_offset;
  71 }
  72 #else
  73 static unsigned long int get_module_load_offset(void)
  74 {
  75         return 0;
  76 }
  77 #endif
  78
  79 void *module_alloc(unsigned long size)
  80 {
  81         void *p;
  82
  83         if (PAGE_ALIGN(size) > MODULES_LEN)
  84                 return NULL;
  85
  86         p = __vmalloc_node_range(size, MODULE_ALIGN,
  87                                     MODULES_VADDR + get_module_load_offset(),
  88                                     MODULES_END, GFP_KERNEL | __GFP_HIGHMEM,
  89                                     PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE,
  90                                     __builtin_return_address(0));
  91         if (p && (kasan_module_alloc(p, size) < 0)) {
  92                 vfree(p);
  93                 return NULL;
  94         }
  95
  96         return p;
  97 }
  98
  99 #ifdef CONFIG_X86_32
 100 int apply_relocate(Elf32_Shdr *sechdrs,
 101                    const char *strtab,
 102                    unsigned int symindex,
 103                    unsigned int relsec,
 104                    struct module *me)
 105 {
 106         unsigned int i;
 107         Elf32_Rel *rel = (void *)sechdrs[relsec].sh_addr;
 108         Elf32_Sym *sym;
 109         uint32_t *location;
 110
 111         DEBUGP("Applying relocate section %u to %u\n",
 112                relsec, sechdrs[relsec].sh_info);
 113         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 114                 /* This is where to make the change */
 115                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 116                         + rel[i].r_offset;
 117                 /* This is the symbol it is referring to.  Note that all
 118                    undefined symbols have been resolved.  */
 119                 sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
 120                         + ELF32_R_SYM(rel[i].r_info);
 121
 122                 switch (ELF32_R_TYPE(rel[i].r_info)) {
 123                 case R_386_32:
 124                         /* We add the value into the location given */
 125                         *location += sym->st_value;
 126                         break;
 127                 case R_386_PC32:
 128                 case R_386_PLT32:
 129                         /* Add the value, subtract its position */
 130                         *location += sym->st_value - (uint32_t)location;
 131                         break;
 132                 default:
 133                         pr_err("%s: Unknown relocation: %u\n",
 134                                me->name, ELF32_R_TYPE(rel[i].r_info));
 135                         return -ENOEXEC;
 136                 }
 137         }
 138         return 0;
 139 }
 140 #else /*X86_64*/
 141 int apply_relocate_add(Elf64_Shdr *sechdrs,
 142                    const char *strtab,
 143                    unsigned int symindex,
 144                    unsigned int relsec,
 145                    struct module *me)
 146 {
 147         unsigned int i;
 148         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 149         Elf64_Sym *sym;
 150         void *loc;
 151         u64 val;
 152
 153         DEBUGP("Applying relocate section %u to %u\n",
 154                relsec, sechdrs[relsec].sh_info);
 155         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 156                 /* This is where to make the change */
 157                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 158                         + rel[i].r_offset;
 159
 160                 /* This is the symbol it is referring to.  Note that all
 161                    undefined symbols have been resolved.  */
 162                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 163                         + ELF64_R_SYM(rel[i].r_info);
 164
 165                 DEBUGP("type %d st_value %Lx r_addend %Lx loc %Lx\n",
 166                        (int)ELF64_R_TYPE(rel[i].r_info),
 167                        sym->st_value, rel[i].r_addend, (u64)loc);
 168
 169                 val = sym->st_value + rel[i].r_addend;
 170
 171                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 172                 case R_X86_64_NONE:
 173                         break;
 174                 case R_X86_64_64:
 175                         if (*(u64 *)loc != 0)
 176                                 goto invalid_relocation;
 177                         *(u64 *)loc = val;
 178                         break;
 179                 case R_X86_64_32:
 180                         if (*(u32 *)loc != 0)
 181                                 goto invalid_relocation;
 182                         *(u32 *)loc = val;
 183                         if (val != *(u32 *)loc)
 184                                 goto overflow;
 185                         break;
 186                 case R_X86_64_32S:
 187                         if (*(s32 *)loc != 0)
 188                                 goto invalid_relocation;
 189                         *(s32 *)loc = val;
 190                         if ((s64)val != *(s32 *)loc)
 191                                 goto overflow;
 192                         break;
 193                 case R_X86_64_PC32:
 194                 case R_X86_64_PLT32:
 195                         if (*(u32 *)loc != 0)
 196                                 goto invalid_relocation;
 197                         val -= (u64)loc;
 198                         *(u32 *)loc = val;
 199 #if 0
 200                         if ((s64)val != *(s32 *)loc)
 201                                 goto overflow;
 202 #endif
 203                         break;
 204                 default:
 205                         pr_err("%s: Unknown rela relocation: %llu\n",
 206                                me->name, ELF64_R_TYPE(rel[i].r_info));
 207                         return -ENOEXEC;
 208                 }
 209         }
 210         return 0;
 211
 212 invalid_relocation:
 213         pr_err("x86/modules: Skipping invalid relocation target, existing value is nonzero for type %d, loc %p, val %Lx\n",
 214                (int)ELF64_R_TYPE(rel[i].r_info), loc, val);
 215         return -ENOEXEC;
 216
 217 overflow:
 218         pr_err("overflow in relocation type %d val %Lx\n",
 219                (int)ELF64_R_TYPE(rel[i].r_info), val);
 220         pr_err("`%s' likely not compiled with -mcmodel=kernel\n",
 221                me->name);
 222         return -ENOEXEC;
 223 }
 224 #endif
 225
 226 int module_finalize(const Elf_Ehdr *hdr,
 227                     const Elf_Shdr *sechdrs,
 228                     struct module *me)
 229 {
 230         const Elf_Shdr *s, *text = NULL, *alt = NULL, *locks = NULL,
 231                 *para = NULL;
 232         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 233
 234         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 235                 if (!strcmp(".text", secstrings + s->sh_name))
 236                         text = s;
 237                 if (!strcmp(".altinstructions", secstrings + s->sh_name))
 238                         alt = s;
 239                 if (!strcmp(".smp_locks", secstrings + s->sh_name))
 240                         locks = s;
 241                 if (!strcmp(".parainstructions", secstrings + s->sh_name))
 242                         para = s;
 243         }
 244
 245         if (alt) {
 246                 /* patch .altinstructions */
 247                 void *aseg = (void *)alt->sh_addr;
 248                 apply_alternatives(aseg, aseg + alt->sh_size);
 249         }
 250         if (locks && text) {
 251                 void *lseg = (void *)locks->sh_addr;
 252                 void *tseg = (void *)text->sh_addr;
 253                 alternatives_smp_module_add(me, me->name,
 254                                             lseg, lseg + locks->sh_size,
 255                                             tseg, tseg + text->sh_size);
 256         }
 257
 258         if (para) {
 259                 void *pseg = (void *)para->sh_addr;
 260                 apply_paravirt(pseg, pseg + para->sh_size);
 261         }
 262
 263         /* make jump label nops */
 264         jump_label_apply_nops(me);
 265
 266         return 0;
 267 }
 268
 269 void module_arch_cleanup(struct module *mod)
 270 {
 271         alternatives_smp_module_del(mod);
 272 }