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, module_alloc_base,
  38                                 module_alloc_base + MODULES_VSIZE,
  39                                 GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
  40                                 NUMA_NO_NODE, __builtin_return_address(0));
  41
  42         if (!p && IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
  43             !IS_ENABLED(CONFIG_KASAN))
  44                 /*
  45                  * KASAN can only deal with module allocations being served
  46                  * from the reserved module region, since the remainder of
  47                  * the vmalloc region is already backed by zero shadow pages,
  48                  * and punching holes into it is non-trivial. Since the module
  49                  * region is not randomized when KASAN is enabled, it is even
  50                  * less likely that the module region gets exhausted, so we
  51                  * can simply omit this fallback in that case.
  52                  */
  53                 p = __vmalloc_node_range(size, MODULE_ALIGN, VMALLOC_START,
  54                                 VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
  55                                 NUMA_NO_NODE, __builtin_return_address(0));
  56
  57         if (p && (kasan_module_alloc(p, size) < 0)) {
  58                 vfree(p);
  59                 return NULL;
  60         }
  61
  62         return p;
  63 }
  64
  65 enum aarch64_reloc_op {
  66         RELOC_OP_NONE,
  67         RELOC_OP_ABS,
  68         RELOC_OP_PREL,
  69         RELOC_OP_PAGE,
  70 };
  71
  72 static u64 do_reloc(enum aarch64_reloc_op reloc_op, void *place, u64 val)
  73 {
  74         switch (reloc_op) {
  75         case RELOC_OP_ABS:
  76                 return val;
  77         case RELOC_OP_PREL:
  78                 return val - (u64)place;
  79         case RELOC_OP_PAGE:
  80                 return (val & ~0xfff) - ((u64)place & ~0xfff);
  81         case RELOC_OP_NONE:
  82                 return 0;
  83         }
  84
  85         pr_err("do_reloc: unknown relocation operation %d\n", reloc_op);
  86         return 0;
  87 }
  88
  89 static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
  90 {
  91         s64 sval = do_reloc(op, place, val);
  92
  93         switch (len) {
  94         case 16:
  95                 *(s16 *)place = sval;
  96                 if (sval < S16_MIN || sval > U16_MAX)
  97                         return -ERANGE;
  98                 break;
  99         case 32:
 100                 *(s32 *)place = sval;
 101                 if (sval < S32_MIN || sval > U32_MAX)
 102                         return -ERANGE;
 103                 break;
 104         case 64:
 105                 *(s64 *)place = sval;
 106                 break;
 107         default:
 108                 pr_err("Invalid length (%d) for data relocation\n", len);
 109                 return 0;
 110         }
 111         return 0;
 112 }
 113
 114 enum aarch64_insn_movw_imm_type {
 115         AARCH64_INSN_IMM_MOVNZ,
 116         AARCH64_INSN_IMM_MOVKZ,
 117 };
 118
 119 static int reloc_insn_movw(enum aarch64_reloc_op op, void *place, u64 val,
 120                            int lsb, enum aarch64_insn_movw_imm_type imm_type)
 121 {
 122         u64 imm;
 123         s64 sval;
 124         u32 insn = le32_to_cpu(*(u32 *)place);
 125
 126         sval = do_reloc(op, place, val);
 127         imm = sval >> lsb;
 128
 129         if (imm_type == AARCH64_INSN_IMM_MOVNZ) {
 130                 /*
 131                  * For signed MOVW relocations, we have to manipulate the
 132                  * instruction encoding depending on whether or not the
 133                  * immediate is less than zero.
 134                  */
 135                 insn &= ~(3 << 29);
 136                 if (sval >= 0) {
 137                         /* >=0: Set the instruction to MOVZ (opcode 10b). */
 138                         insn |= 2 << 29;
 139                 } else {
 140                         /*
 141                          * <0: Set the instruction to MOVN (opcode 00b).
 142                          *     Since we've masked the opcode already, we
 143                          *     don't need to do anything other than
 144                          *     inverting the new immediate field.
 145                          */
 146                         imm = ~imm;
 147                 }
 148         }
 149
 150         /* Update the instruction with the new encoding. */
 151         insn = aarch64_insn_encode_immediate(AARCH64_INSN_IMM_16, insn, imm);
 152         *(u32 *)place = cpu_to_le32(insn);
 153
 154         if (imm > U16_MAX)
 155                 return -ERANGE;
 156
 157         return 0;
 158 }
 159
 160 static int reloc_insn_imm(enum aarch64_reloc_op op, void *place, u64 val,
 161                           int lsb, int len, enum aarch64_insn_imm_type imm_type)
 162 {
 163         u64 imm, imm_mask;
 164         s64 sval;
 165         u32 insn = le32_to_cpu(*(u32 *)place);
 166
 167         /* Calculate the relocation value. */
 168         sval = do_reloc(op, place, val);
 169         sval >>= lsb;
 170
 171         /* Extract the value bits and shift them to bit 0. */
 172         imm_mask = (BIT(lsb + len) - 1) >> lsb;
 173         imm = sval & imm_mask;
 174
 175         /* Update the instruction's immediate field. */
 176         insn = aarch64_insn_encode_immediate(imm_type, insn, imm);
 177         *(u32 *)place = cpu_to_le32(insn);
 178
 179         /*
 180          * Extract the upper value bits (including the sign bit) and
 181          * shift them to bit 0.
 182          */
 183         sval = (s64)(sval & ~(imm_mask >> 1)) >> (len - 1);
 184
 185         /*
 186          * Overflow has occurred if the upper bits are not all equal to
 187          * the sign bit of the value.
 188          */
 189         if ((u64)(sval + 1) >= 2)
 190                 return -ERANGE;
 191
 192         return 0;
 193 }
 194
 195 int apply_relocate_add(Elf64_Shdr *sechdrs,
 196                        const char *strtab,
 197                        unsigned int symindex,
 198                        unsigned int relsec,
 199                        struct module *me)
 200 {
 201         unsigned int i;
 202         int ovf;
 203         bool overflow_check;
 204         Elf64_Sym *sym;
 205         void *loc;
 206         u64 val;
 207         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 208
 209         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 210                 /* loc corresponds to P in the AArch64 ELF document. */
 211                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 212                         + rel[i].r_offset;
 213
 214                 /* sym is the ELF symbol we're referring to. */
 215                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 216                         + ELF64_R_SYM(rel[i].r_info);
 217
 218                 /* val corresponds to (S + A) in the AArch64 ELF document. */
 219                 val = sym->st_value + rel[i].r_addend;
 220
 221                 /* Check for overflow by default. */
 222                 overflow_check = true;
 223
 224                 /* Perform the static relocation. */
 225                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 226                 /* Null relocations. */
 227                 case R_ARM_NONE:
 228                 case R_AARCH64_NONE:
 229                         ovf = 0;
 230                         break;
 231
 232                 /* Data relocations. */
 233                 case R_AARCH64_ABS64:
 234                         overflow_check = false;
 235                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 64);
 236                         break;
 237                 case R_AARCH64_ABS32:
 238                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 32);
 239                         break;
 240                 case R_AARCH64_ABS16:
 241                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 16);
 242                         break;
 243                 case R_AARCH64_PREL64:
 244                         overflow_check = false;
 245                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 64);
 246                         break;
 247                 case R_AARCH64_PREL32:
 248                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 32);
 249                         break;
 250                 case R_AARCH64_PREL16:
 251                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 16);
 252                         break;
 253
 254                 /* MOVW instruction relocations. */
 255                 case R_AARCH64_MOVW_UABS_G0_NC:
 256                         overflow_check = false;
 257                 case R_AARCH64_MOVW_UABS_G0:
 258                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
 259                                               AARCH64_INSN_IMM_MOVKZ);
 260                         break;
 261                 case R_AARCH64_MOVW_UABS_G1_NC:
 262                         overflow_check = false;
 263                 case R_AARCH64_MOVW_UABS_G1:
 264                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
 265                                               AARCH64_INSN_IMM_MOVKZ);
 266                         break;
 267                 case R_AARCH64_MOVW_UABS_G2_NC:
 268                         overflow_check = false;
 269                 case R_AARCH64_MOVW_UABS_G2:
 270                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
 271                                               AARCH64_INSN_IMM_MOVKZ);
 272                         break;
 273                 case R_AARCH64_MOVW_UABS_G3:
 274                         /* We're using the top bits so we can't overflow. */
 275                         overflow_check = false;
 276                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 48,
 277                                               AARCH64_INSN_IMM_MOVKZ);
 278                         break;
 279                 case R_AARCH64_MOVW_SABS_G0:
 280                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
 281                                               AARCH64_INSN_IMM_MOVNZ);
 282                         break;
 283                 case R_AARCH64_MOVW_SABS_G1:
 284                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
 285                                               AARCH64_INSN_IMM_MOVNZ);
 286                         break;
 287                 case R_AARCH64_MOVW_SABS_G2:
 288                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
 289                                               AARCH64_INSN_IMM_MOVNZ);
 290                         break;
 291                 case R_AARCH64_MOVW_PREL_G0_NC:
 292                         overflow_check = false;
 293                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
 294                                               AARCH64_INSN_IMM_MOVKZ);
 295                         break;
 296                 case R_AARCH64_MOVW_PREL_G0:
 297                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
 298                                               AARCH64_INSN_IMM_MOVNZ);
 299                         break;
 300                 case R_AARCH64_MOVW_PREL_G1_NC:
 301                         overflow_check = false;
 302                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
 303                                               AARCH64_INSN_IMM_MOVKZ);
 304                         break;
 305                 case R_AARCH64_MOVW_PREL_G1:
 306                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
 307                                               AARCH64_INSN_IMM_MOVNZ);
 308                         break;
 309                 case R_AARCH64_MOVW_PREL_G2_NC:
 310                         overflow_check = false;
 311                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
 312                                               AARCH64_INSN_IMM_MOVKZ);
 313                         break;
 314                 case R_AARCH64_MOVW_PREL_G2:
 315                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
 316                                               AARCH64_INSN_IMM_MOVNZ);
 317                         break;
 318                 case R_AARCH64_MOVW_PREL_G3:
 319                         /* We're using the top bits so we can't overflow. */
 320                         overflow_check = false;
 321                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 48,
 322                                               AARCH64_INSN_IMM_MOVNZ);
 323                         break;
 324
 325                 /* Immediate instruction relocations. */
 326                 case R_AARCH64_LD_PREL_LO19:
 327                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
 328                                              AARCH64_INSN_IMM_19);
 329                         break;
 330                 case R_AARCH64_ADR_PREL_LO21:
 331                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
 332                                              AARCH64_INSN_IMM_ADR);
 333                         break;
 334 #ifndef CONFIG_ARM64_ERRATUM_843419
 335                 case R_AARCH64_ADR_PREL_PG_HI21_NC:
 336                         overflow_check = false;
 337                 case R_AARCH64_ADR_PREL_PG_HI21:
 338                         ovf = reloc_insn_imm(RELOC_OP_PAGE, loc, val, 12, 21,
 339                                              AARCH64_INSN_IMM_ADR);
 340                         break;
 341 #endif
 342                 case R_AARCH64_ADD_ABS_LO12_NC:
 343                 case R_AARCH64_LDST8_ABS_LO12_NC:
 344                         overflow_check = false;
 345                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 0, 12,
 346                                              AARCH64_INSN_IMM_12);
 347                         break;
 348                 case R_AARCH64_LDST16_ABS_LO12_NC:
 349                         overflow_check = false;
 350                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 1, 11,
 351                                              AARCH64_INSN_IMM_12);
 352                         break;
 353                 case R_AARCH64_LDST32_ABS_LO12_NC:
 354                         overflow_check = false;
 355                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 2, 10,
 356                                              AARCH64_INSN_IMM_12);
 357                         break;
 358                 case R_AARCH64_LDST64_ABS_LO12_NC:
 359                         overflow_check = false;
 360                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 3, 9,
 361                                              AARCH64_INSN_IMM_12);
 362                         break;
 363                 case R_AARCH64_LDST128_ABS_LO12_NC:
 364                         overflow_check = false;
 365                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 4, 8,
 366                                              AARCH64_INSN_IMM_12);
 367                         break;
 368                 case R_AARCH64_TSTBR14:
 369                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 14,
 370                                              AARCH64_INSN_IMM_14);
 371                         break;
 372                 case R_AARCH64_CONDBR19:
 373                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
 374                                              AARCH64_INSN_IMM_19);
 375                         break;
 376                 case R_AARCH64_JUMP26:
 377                 case R_AARCH64_CALL26:
 378                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
 379                                              AARCH64_INSN_IMM_26);
 380
 381                         if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
 382                             ovf == -ERANGE) {
 383                                 val = module_emit_plt_entry(me, &rel[i], sym);
 384                                 ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2,
 385                                                      26, AARCH64_INSN_IMM_26);
 386                         }
 387                         break;
 388
 389                 default:
 390                         pr_err("module %s: unsupported RELA relocation: %llu\n",
 391                                me->name, ELF64_R_TYPE(rel[i].r_info));
 392                         return -ENOEXEC;
 393                 }
 394
 395                 if (overflow_check && ovf == -ERANGE)
 396                         goto overflow;
 397
 398         }
 399
 400         return 0;
 401
 402 overflow:
 403         pr_err("module %s: overflow in relocation type %d val %Lx\n",
 404                me->name, (int)ELF64_R_TYPE(rel[i].r_info), val);
 405         return -ENOEXEC;
 406 }
 407
 408 int module_finalize(const Elf_Ehdr *hdr,
 409                     const Elf_Shdr *sechdrs,
 410                     struct module *me)
 411 {
 412         const Elf_Shdr *s, *se;
 413         const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 414
 415         for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++) {
 416                 if (strcmp(".altinstructions", secstrs + s->sh_name) == 0) {
 417                         apply_alternatives((void *)s->sh_addr, s->sh_size);
 418                         return 0;
 419                 }
 420         }
 421
 422         return 0;
 423 }