arch/arm64/kernel/module.c

   1 /*
   2  * AArch64 loadable module support.
   3  *
   4  * Copyright (C) 2012 ARM Limited
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17  *
  18  * Author: Will Deacon <will.deacon@arm.com>
  19  */
  20
  21 #include <linux/bitops.h>
  22 #include <linux/elf.h>
  23 #include <linux/gfp.h>
  24 #include <linux/kasan.h>
  25 #include <linux/kernel.h>
  26 #include <linux/mm.h>
  27 #include <linux/moduleloader.h>
  28 #include <linux/vmalloc.h>
  29 #include <asm/alternative.h>
  30 #include <asm/insn.h>
  31 #include <asm/sections.h>
  32
  33 void *module_alloc(unsigned long size)
  34 {
  35         void *p;
  36
  37         p = __vmalloc_node_range(size, MODULE_ALIGN, MODULES_VADDR, MODULES_END,
  38                                 GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
  39                                 NUMA_NO_NODE, __builtin_return_address(0));
  40
  41         if (p && (kasan_module_alloc(p, size) < 0)) {
  42                 vfree(p);
  43                 return NULL;
  44         }
  45
  46         return p;
  47 }
  48
  49 enum aarch64_reloc_op {
  50         RELOC_OP_NONE,
  51         RELOC_OP_ABS,
  52         RELOC_OP_PREL,
  53         RELOC_OP_PAGE,
  54 };
  55
  56 static u64 do_reloc(enum aarch64_reloc_op reloc_op, void *place, u64 val)
  57 {
  58         switch (reloc_op) {
  59         case RELOC_OP_ABS:
  60                 return val;
  61         case RELOC_OP_PREL:
  62                 return val - (u64)place;
  63         case RELOC_OP_PAGE:
  64                 return (val & ~0xfff) - ((u64)place & ~0xfff);
  65         case RELOC_OP_NONE:
  66                 return 0;
  67         }
  68
  69         pr_err("do_reloc: unknown relocation operation %d\n", reloc_op);
  70         return 0;
  71 }
  72
  73 static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
  74 {
  75         s64 sval = do_reloc(op, place, val);
  76
  77         switch (len) {
  78         case 16:
  79                 *(s16 *)place = sval;
  80                 if (sval < S16_MIN || sval > U16_MAX)
  81                         return -ERANGE;
  82                 break;
  83         case 32:
  84                 *(s32 *)place = sval;
  85                 if (sval < S32_MIN || sval > U32_MAX)
  86                         return -ERANGE;
  87                 break;
  88         case 64:
  89                 *(s64 *)place = sval;
  90                 break;
  91         default:
  92                 pr_err("Invalid length (%d) for data relocation\n", len);
  93                 return 0;
  94         }
  95         return 0;
  96 }
  97
  98 enum aarch64_insn_movw_imm_type {
  99         AARCH64_INSN_IMM_MOVNZ,
 100         AARCH64_INSN_IMM_MOVKZ,
 101 };
 102
 103 static int reloc_insn_movw(enum aarch64_reloc_op op, void *place, u64 val,
 104                            int lsb, enum aarch64_insn_movw_imm_type imm_type)
 105 {
 106         u64 imm;
 107         s64 sval;
 108         u32 insn = le32_to_cpu(*(u32 *)place);
 109
 110         sval = do_reloc(op, place, val);
 111         imm = sval >> lsb;
 112
 113         if (imm_type == AARCH64_INSN_IMM_MOVNZ) {
 114                 /*
 115                  * For signed MOVW relocations, we have to manipulate the
 116                  * instruction encoding depending on whether or not the
 117                  * immediate is less than zero.
 118                  */
 119                 insn &= ~(3 << 29);
 120                 if (sval >= 0) {
 121                         /* >=0: Set the instruction to MOVZ (opcode 10b). */
 122                         insn |= 2 << 29;
 123                 } else {
 124                         /*
 125                          * <0: Set the instruction to MOVN (opcode 00b).
 126                          *     Since we've masked the opcode already, we
 127                          *     don't need to do anything other than
 128                          *     inverting the new immediate field.
 129                          */
 130                         imm = ~imm;
 131                 }
 132         }
 133
 134         /* Update the instruction with the new encoding. */
 135         insn = aarch64_insn_encode_immediate(AARCH64_INSN_IMM_16, insn, imm);
 136         *(u32 *)place = cpu_to_le32(insn);
 137
 138         if (imm > U16_MAX)
 139                 return -ERANGE;
 140
 141         return 0;
 142 }
 143
 144 static int reloc_insn_imm(enum aarch64_reloc_op op, void *place, u64 val,
 145                           int lsb, int len, enum aarch64_insn_imm_type imm_type)
 146 {
 147         u64 imm, imm_mask;
 148         s64 sval;
 149         u32 insn = le32_to_cpu(*(u32 *)place);
 150
 151         /* Calculate the relocation value. */
 152         sval = do_reloc(op, place, val);
 153         sval >>= lsb;
 154
 155         /* Extract the value bits and shift them to bit 0. */
 156         imm_mask = (BIT(lsb + len) - 1) >> lsb;
 157         imm = sval & imm_mask;
 158
 159         /* Update the instruction's immediate field. */
 160         insn = aarch64_insn_encode_immediate(imm_type, insn, imm);
 161         *(u32 *)place = cpu_to_le32(insn);
 162
 163         /*
 164          * Extract the upper value bits (including the sign bit) and
 165          * shift them to bit 0.
 166          */
 167         sval = (s64)(sval & ~(imm_mask >> 1)) >> (len - 1);
 168
 169         /*
 170          * Overflow has occurred if the upper bits are not all equal to
 171          * the sign bit of the value.
 172          */
 173         if ((u64)(sval + 1) >= 2)
 174                 return -ERANGE;
 175
 176         return 0;
 177 }
 178
 179 int apply_relocate_add(Elf64_Shdr *sechdrs,
 180                        const char *strtab,
 181                        unsigned int symindex,
 182                        unsigned int relsec,
 183                        struct module *me)
 184 {
 185         unsigned int i;
 186         int ovf;
 187         bool overflow_check;
 188         Elf64_Sym *sym;
 189         void *loc;
 190         u64 val;
 191         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 192
 193         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 194                 /* loc corresponds to P in the AArch64 ELF document. */
 195                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 196                         + rel[i].r_offset;
 197
 198                 /* sym is the ELF symbol we're referring to. */
 199                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 200                         + ELF64_R_SYM(rel[i].r_info);
 201
 202                 /* val corresponds to (S + A) in the AArch64 ELF document. */
 203                 val = sym->st_value + rel[i].r_addend;
 204
 205                 /* Check for overflow by default. */
 206                 overflow_check = true;
 207
 208                 /* Perform the static relocation. */
 209                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 210                 /* Null relocations. */
 211                 case R_ARM_NONE:
 212                 case R_AARCH64_NONE:
 213                         ovf = 0;
 214                         break;
 215
 216                 /* Data relocations. */
 217                 case R_AARCH64_ABS64:
 218                         overflow_check = false;
 219                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 64);
 220                         break;
 221                 case R_AARCH64_ABS32:
 222                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 32);
 223                         break;
 224                 case R_AARCH64_ABS16:
 225                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 16);
 226                         break;
 227                 case R_AARCH64_PREL64:
 228                         overflow_check = false;
 229                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 64);
 230                         break;
 231                 case R_AARCH64_PREL32:
 232                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 32);
 233                         break;
 234                 case R_AARCH64_PREL16:
 235                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 16);
 236                         break;
 237
 238                 /* MOVW instruction relocations. */
 239                 case R_AARCH64_MOVW_UABS_G0_NC:
 240                         overflow_check = false;
 241                 case R_AARCH64_MOVW_UABS_G0:
 242                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
 243                                               AARCH64_INSN_IMM_MOVKZ);
 244                         break;
 245                 case R_AARCH64_MOVW_UABS_G1_NC:
 246                         overflow_check = false;
 247                 case R_AARCH64_MOVW_UABS_G1:
 248                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
 249                                               AARCH64_INSN_IMM_MOVKZ);
 250                         break;
 251                 case R_AARCH64_MOVW_UABS_G2_NC:
 252                         overflow_check = false;
 253                 case R_AARCH64_MOVW_UABS_G2:
 254                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
 255                                               AARCH64_INSN_IMM_MOVKZ);
 256                         break;
 257                 case R_AARCH64_MOVW_UABS_G3:
 258                         /* We're using the top bits so we can't overflow. */
 259                         overflow_check = false;
 260                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 48,
 261                                               AARCH64_INSN_IMM_MOVKZ);
 262                         break;
 263                 case R_AARCH64_MOVW_SABS_G0:
 264                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
 265                                               AARCH64_INSN_IMM_MOVNZ);
 266                         break;
 267                 case R_AARCH64_MOVW_SABS_G1:
 268                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
 269                                               AARCH64_INSN_IMM_MOVNZ);
 270                         break;
 271                 case R_AARCH64_MOVW_SABS_G2:
 272                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
 273                                               AARCH64_INSN_IMM_MOVNZ);
 274                         break;
 275                 case R_AARCH64_MOVW_PREL_G0_NC:
 276                         overflow_check = false;
 277                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
 278                                               AARCH64_INSN_IMM_MOVKZ);
 279                         break;
 280                 case R_AARCH64_MOVW_PREL_G0:
 281                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
 282                                               AARCH64_INSN_IMM_MOVNZ);
 283                         break;
 284                 case R_AARCH64_MOVW_PREL_G1_NC:
 285                         overflow_check = false;
 286                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
 287                                               AARCH64_INSN_IMM_MOVKZ);
 288                         break;
 289                 case R_AARCH64_MOVW_PREL_G1:
 290                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
 291                                               AARCH64_INSN_IMM_MOVNZ);
 292                         break;
 293                 case R_AARCH64_MOVW_PREL_G2_NC:
 294                         overflow_check = false;
 295                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
 296                                               AARCH64_INSN_IMM_MOVKZ);
 297                         break;
 298                 case R_AARCH64_MOVW_PREL_G2:
 299                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
 300                                               AARCH64_INSN_IMM_MOVNZ);
 301                         break;
 302                 case R_AARCH64_MOVW_PREL_G3:
 303                         /* We're using the top bits so we can't overflow. */
 304                         overflow_check = false;
 305                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 48,
 306                                               AARCH64_INSN_IMM_MOVNZ);
 307                         break;
 308
 309                 /* Immediate instruction relocations. */
 310                 case R_AARCH64_LD_PREL_LO19:
 311                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
 312                                              AARCH64_INSN_IMM_19);
 313                         break;
 314                 case R_AARCH64_ADR_PREL_LO21:
 315                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
 316                                              AARCH64_INSN_IMM_ADR);
 317                         break;
 318 #ifndef CONFIG_ARM64_ERRATUM_843419
 319                 case R_AARCH64_ADR_PREL_PG_HI21_NC:
 320                         overflow_check = false;
 321                 case R_AARCH64_ADR_PREL_PG_HI21:
 322                         ovf = reloc_insn_imm(RELOC_OP_PAGE, loc, val, 12, 21,
 323                                              AARCH64_INSN_IMM_ADR);
 324                         break;
 325 #endif
 326                 case R_AARCH64_ADD_ABS_LO12_NC:
 327                 case R_AARCH64_LDST8_ABS_LO12_NC:
 328                         overflow_check = false;
 329                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 0, 12,
 330                                              AARCH64_INSN_IMM_12);
 331                         break;
 332                 case R_AARCH64_LDST16_ABS_LO12_NC:
 333                         overflow_check = false;
 334                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 1, 11,
 335                                              AARCH64_INSN_IMM_12);
 336                         break;
 337                 case R_AARCH64_LDST32_ABS_LO12_NC:
 338                         overflow_check = false;
 339                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 2, 10,
 340                                              AARCH64_INSN_IMM_12);
 341                         break;
 342                 case R_AARCH64_LDST64_ABS_LO12_NC:
 343                         overflow_check = false;
 344                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 3, 9,
 345                                              AARCH64_INSN_IMM_12);
 346                         break;
 347                 case R_AARCH64_LDST128_ABS_LO12_NC:
 348                         overflow_check = false;
 349                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 4, 8,
 350                                              AARCH64_INSN_IMM_12);
 351                         break;
 352                 case R_AARCH64_TSTBR14:
 353                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 14,
 354                                              AARCH64_INSN_IMM_14);
 355                         break;
 356                 case R_AARCH64_CONDBR19:
 357                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
 358                                              AARCH64_INSN_IMM_19);
 359                         break;
 360                 case R_AARCH64_JUMP26:
 361                 case R_AARCH64_CALL26:
 362                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
 363                                              AARCH64_INSN_IMM_26);
 364                         break;
 365
 366                 default:
 367                         pr_err("module %s: unsupported RELA relocation: %llu\n",
 368                                me->name, ELF64_R_TYPE(rel[i].r_info));
 369                         return -ENOEXEC;
 370                 }
 371
 372                 if (overflow_check && ovf == -ERANGE)
 373                         goto overflow;
 374
 375         }
 376
 377         return 0;
 378
 379 overflow:
 380         pr_err("module %s: overflow in relocation type %d val %Lx\n",
 381                me->name, (int)ELF64_R_TYPE(rel[i].r_info), val);
 382         return -ENOEXEC;
 383 }
 384
 385 int module_finalize(const Elf_Ehdr *hdr,
 386                     const Elf_Shdr *sechdrs,
 387                     struct module *me)
 388 {
 389         const Elf_Shdr *s, *se;
 390         const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 391
 392         for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++) {
 393                 if (strcmp(".altinstructions", secstrs + s->sh_name) == 0) {
 394                         apply_alternatives((void *)s->sh_addr, s->sh_size);
 395                         return 0;
 396                 }
 397         }
 398
 399         return 0;
 400 }