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         gfp_t gfp_mask = GFP_KERNEL;
  36         void *p;
  37
  38         /* Silence the initial allocation */
  39         if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS))
  40                 gfp_mask |= __GFP_NOWARN;
  41
  42         p = __vmalloc_node_range(size, MODULE_ALIGN, module_alloc_base,
  43                                 module_alloc_base + MODULES_VSIZE,
  44                                 gfp_mask, PAGE_KERNEL_EXEC, 0,
  45                                 NUMA_NO_NODE, __builtin_return_address(0));
  46
  47         if (!p && IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
  48             !IS_ENABLED(CONFIG_KASAN))
  49                 /*
  50                  * KASAN can only deal with module allocations being served
  51                  * from the reserved module region, since the remainder of
  52                  * the vmalloc region is already backed by zero shadow pages,
  53                  * and punching holes into it is non-trivial. Since the module
  54                  * region is not randomized when KASAN is enabled, it is even
  55                  * less likely that the module region gets exhausted, so we
  56                  * can simply omit this fallback in that case.
  57                  */
  58                 p = __vmalloc_node_range(size, MODULE_ALIGN, VMALLOC_START,
  59                                 VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_EXEC, 0,
  60                                 NUMA_NO_NODE, __builtin_return_address(0));
  61
  62         if (p && (kasan_module_alloc(p, size) < 0)) {
  63                 vfree(p);
  64                 return NULL;
  65         }
  66
  67         return p;
  68 }
  69
  70 enum aarch64_reloc_op {
  71         RELOC_OP_NONE,
  72         RELOC_OP_ABS,
  73         RELOC_OP_PREL,
  74         RELOC_OP_PAGE,
  75 };
  76
  77 static u64 do_reloc(enum aarch64_reloc_op reloc_op, void *place, u64 val)
  78 {
  79         switch (reloc_op) {
  80         case RELOC_OP_ABS:
  81                 return val;
  82         case RELOC_OP_PREL:
  83                 return val - (u64)place;
  84         case RELOC_OP_PAGE:
  85                 return (val & ~0xfff) - ((u64)place & ~0xfff);
  86         case RELOC_OP_NONE:
  87                 return 0;
  88         }
  89
  90         pr_err("do_reloc: unknown relocation operation %d\n", reloc_op);
  91         return 0;
  92 }
  93
  94 static int reloc_data(enum aarch64_reloc_op op, void *place, u64 val, int len)
  95 {
  96         s64 sval = do_reloc(op, place, val);
  97
  98         switch (len) {
  99         case 16:
 100                 *(s16 *)place = sval;
 101                 if (sval < S16_MIN || sval > U16_MAX)
 102                         return -ERANGE;
 103                 break;
 104         case 32:
 105                 *(s32 *)place = sval;
 106                 if (sval < S32_MIN || sval > U32_MAX)
 107                         return -ERANGE;
 108                 break;
 109         case 64:
 110                 *(s64 *)place = sval;
 111                 break;
 112         default:
 113                 pr_err("Invalid length (%d) for data relocation\n", len);
 114                 return 0;
 115         }
 116         return 0;
 117 }
 118
 119 enum aarch64_insn_movw_imm_type {
 120         AARCH64_INSN_IMM_MOVNZ,
 121         AARCH64_INSN_IMM_MOVKZ,
 122 };
 123
 124 static int reloc_insn_movw(enum aarch64_reloc_op op, void *place, u64 val,
 125                            int lsb, enum aarch64_insn_movw_imm_type imm_type)
 126 {
 127         u64 imm;
 128         s64 sval;
 129         u32 insn = le32_to_cpu(*(u32 *)place);
 130
 131         sval = do_reloc(op, place, val);
 132         imm = sval >> lsb;
 133
 134         if (imm_type == AARCH64_INSN_IMM_MOVNZ) {
 135                 /*
 136                  * For signed MOVW relocations, we have to manipulate the
 137                  * instruction encoding depending on whether or not the
 138                  * immediate is less than zero.
 139                  */
 140                 insn &= ~(3 << 29);
 141                 if (sval >= 0) {
 142                         /* >=0: Set the instruction to MOVZ (opcode 10b). */
 143                         insn |= 2 << 29;
 144                 } else {
 145                         /*
 146                          * <0: Set the instruction to MOVN (opcode 00b).
 147                          *     Since we've masked the opcode already, we
 148                          *     don't need to do anything other than
 149                          *     inverting the new immediate field.
 150                          */
 151                         imm = ~imm;
 152                 }
 153         }
 154
 155         /* Update the instruction with the new encoding. */
 156         insn = aarch64_insn_encode_immediate(AARCH64_INSN_IMM_16, insn, imm);
 157         *(u32 *)place = cpu_to_le32(insn);
 158
 159         if (imm > U16_MAX)
 160                 return -ERANGE;
 161
 162         return 0;
 163 }
 164
 165 static int reloc_insn_imm(enum aarch64_reloc_op op, void *place, u64 val,
 166                           int lsb, int len, enum aarch64_insn_imm_type imm_type)
 167 {
 168         u64 imm, imm_mask;
 169         s64 sval;
 170         u32 insn = le32_to_cpu(*(u32 *)place);
 171
 172         /* Calculate the relocation value. */
 173         sval = do_reloc(op, place, val);
 174         sval >>= lsb;
 175
 176         /* Extract the value bits and shift them to bit 0. */
 177         imm_mask = (BIT(lsb + len) - 1) >> lsb;
 178         imm = sval & imm_mask;
 179
 180         /* Update the instruction's immediate field. */
 181         insn = aarch64_insn_encode_immediate(imm_type, insn, imm);
 182         *(u32 *)place = cpu_to_le32(insn);
 183
 184         /*
 185          * Extract the upper value bits (including the sign bit) and
 186          * shift them to bit 0.
 187          */
 188         sval = (s64)(sval & ~(imm_mask >> 1)) >> (len - 1);
 189
 190         /*
 191          * Overflow has occurred if the upper bits are not all equal to
 192          * the sign bit of the value.
 193          */
 194         if ((u64)(sval + 1) >= 2)
 195                 return -ERANGE;
 196
 197         return 0;
 198 }
 199
 200 int apply_relocate_add(Elf64_Shdr *sechdrs,
 201                        const char *strtab,
 202                        unsigned int symindex,
 203                        unsigned int relsec,
 204                        struct module *me)
 205 {
 206         unsigned int i;
 207         int ovf;
 208         bool overflow_check;
 209         Elf64_Sym *sym;
 210         void *loc;
 211         u64 val;
 212         Elf64_Rela *rel = (void *)sechdrs[relsec].sh_addr;
 213
 214         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 215                 /* loc corresponds to P in the AArch64 ELF document. */
 216                 loc = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 217                         + rel[i].r_offset;
 218
 219                 /* sym is the ELF symbol we're referring to. */
 220                 sym = (Elf64_Sym *)sechdrs[symindex].sh_addr
 221                         + ELF64_R_SYM(rel[i].r_info);
 222
 223                 /* val corresponds to (S + A) in the AArch64 ELF document. */
 224                 val = sym->st_value + rel[i].r_addend;
 225
 226                 /* Check for overflow by default. */
 227                 overflow_check = true;
 228
 229                 /* Perform the static relocation. */
 230                 switch (ELF64_R_TYPE(rel[i].r_info)) {
 231                 /* Null relocations. */
 232                 case R_ARM_NONE:
 233                 case R_AARCH64_NONE:
 234                         ovf = 0;
 235                         break;
 236
 237                 /* Data relocations. */
 238                 case R_AARCH64_ABS64:
 239                         overflow_check = false;
 240                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 64);
 241                         break;
 242                 case R_AARCH64_ABS32:
 243                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 32);
 244                         break;
 245                 case R_AARCH64_ABS16:
 246                         ovf = reloc_data(RELOC_OP_ABS, loc, val, 16);
 247                         break;
 248                 case R_AARCH64_PREL64:
 249                         overflow_check = false;
 250                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 64);
 251                         break;
 252                 case R_AARCH64_PREL32:
 253                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 32);
 254                         break;
 255                 case R_AARCH64_PREL16:
 256                         ovf = reloc_data(RELOC_OP_PREL, loc, val, 16);
 257                         break;
 258
 259                 /* MOVW instruction relocations. */
 260                 case R_AARCH64_MOVW_UABS_G0_NC:
 261                         overflow_check = false;
 262                 case R_AARCH64_MOVW_UABS_G0:
 263                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
 264                                               AARCH64_INSN_IMM_MOVKZ);
 265                         break;
 266                 case R_AARCH64_MOVW_UABS_G1_NC:
 267                         overflow_check = false;
 268                 case R_AARCH64_MOVW_UABS_G1:
 269                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
 270                                               AARCH64_INSN_IMM_MOVKZ);
 271                         break;
 272                 case R_AARCH64_MOVW_UABS_G2_NC:
 273                         overflow_check = false;
 274                 case R_AARCH64_MOVW_UABS_G2:
 275                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
 276                                               AARCH64_INSN_IMM_MOVKZ);
 277                         break;
 278                 case R_AARCH64_MOVW_UABS_G3:
 279                         /* We're using the top bits so we can't overflow. */
 280                         overflow_check = false;
 281                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 48,
 282                                               AARCH64_INSN_IMM_MOVKZ);
 283                         break;
 284                 case R_AARCH64_MOVW_SABS_G0:
 285                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 0,
 286                                               AARCH64_INSN_IMM_MOVNZ);
 287                         break;
 288                 case R_AARCH64_MOVW_SABS_G1:
 289                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 16,
 290                                               AARCH64_INSN_IMM_MOVNZ);
 291                         break;
 292                 case R_AARCH64_MOVW_SABS_G2:
 293                         ovf = reloc_insn_movw(RELOC_OP_ABS, loc, val, 32,
 294                                               AARCH64_INSN_IMM_MOVNZ);
 295                         break;
 296                 case R_AARCH64_MOVW_PREL_G0_NC:
 297                         overflow_check = false;
 298                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
 299                                               AARCH64_INSN_IMM_MOVKZ);
 300                         break;
 301                 case R_AARCH64_MOVW_PREL_G0:
 302                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 0,
 303                                               AARCH64_INSN_IMM_MOVNZ);
 304                         break;
 305                 case R_AARCH64_MOVW_PREL_G1_NC:
 306                         overflow_check = false;
 307                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
 308                                               AARCH64_INSN_IMM_MOVKZ);
 309                         break;
 310                 case R_AARCH64_MOVW_PREL_G1:
 311                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 16,
 312                                               AARCH64_INSN_IMM_MOVNZ);
 313                         break;
 314                 case R_AARCH64_MOVW_PREL_G2_NC:
 315                         overflow_check = false;
 316                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
 317                                               AARCH64_INSN_IMM_MOVKZ);
 318                         break;
 319                 case R_AARCH64_MOVW_PREL_G2:
 320                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 32,
 321                                               AARCH64_INSN_IMM_MOVNZ);
 322                         break;
 323                 case R_AARCH64_MOVW_PREL_G3:
 324                         /* We're using the top bits so we can't overflow. */
 325                         overflow_check = false;
 326                         ovf = reloc_insn_movw(RELOC_OP_PREL, loc, val, 48,
 327                                               AARCH64_INSN_IMM_MOVNZ);
 328                         break;
 329
 330                 /* Immediate instruction relocations. */
 331                 case R_AARCH64_LD_PREL_LO19:
 332                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
 333                                              AARCH64_INSN_IMM_19);
 334                         break;
 335                 case R_AARCH64_ADR_PREL_LO21:
 336                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 0, 21,
 337                                              AARCH64_INSN_IMM_ADR);
 338                         break;
 339 #ifndef CONFIG_ARM64_ERRATUM_843419
 340                 case R_AARCH64_ADR_PREL_PG_HI21_NC:
 341                         overflow_check = false;
 342                 case R_AARCH64_ADR_PREL_PG_HI21:
 343                         ovf = reloc_insn_imm(RELOC_OP_PAGE, loc, val, 12, 21,
 344                                              AARCH64_INSN_IMM_ADR);
 345                         break;
 346 #endif
 347                 case R_AARCH64_ADD_ABS_LO12_NC:
 348                 case R_AARCH64_LDST8_ABS_LO12_NC:
 349                         overflow_check = false;
 350                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 0, 12,
 351                                              AARCH64_INSN_IMM_12);
 352                         break;
 353                 case R_AARCH64_LDST16_ABS_LO12_NC:
 354                         overflow_check = false;
 355                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 1, 11,
 356                                              AARCH64_INSN_IMM_12);
 357                         break;
 358                 case R_AARCH64_LDST32_ABS_LO12_NC:
 359                         overflow_check = false;
 360                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 2, 10,
 361                                              AARCH64_INSN_IMM_12);
 362                         break;
 363                 case R_AARCH64_LDST64_ABS_LO12_NC:
 364                         overflow_check = false;
 365                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 3, 9,
 366                                              AARCH64_INSN_IMM_12);
 367                         break;
 368                 case R_AARCH64_LDST128_ABS_LO12_NC:
 369                         overflow_check = false;
 370                         ovf = reloc_insn_imm(RELOC_OP_ABS, loc, val, 4, 8,
 371                                              AARCH64_INSN_IMM_12);
 372                         break;
 373                 case R_AARCH64_TSTBR14:
 374                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 14,
 375                                              AARCH64_INSN_IMM_14);
 376                         break;
 377                 case R_AARCH64_CONDBR19:
 378                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 19,
 379                                              AARCH64_INSN_IMM_19);
 380                         break;
 381                 case R_AARCH64_JUMP26:
 382                 case R_AARCH64_CALL26:
 383                         ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2, 26,
 384                                              AARCH64_INSN_IMM_26);
 385
 386                         if (IS_ENABLED(CONFIG_ARM64_MODULE_PLTS) &&
 387                             ovf == -ERANGE) {
 388                                 val = module_emit_plt_entry(me, loc, &rel[i], sym);
 389                                 ovf = reloc_insn_imm(RELOC_OP_PREL, loc, val, 2,
 390                                                      26, AARCH64_INSN_IMM_26);
 391                         }
 392                         break;
 393
 394                 default:
 395                         pr_err("module %s: unsupported RELA relocation: %llu\n",
 396                                me->name, ELF64_R_TYPE(rel[i].r_info));
 397                         return -ENOEXEC;
 398                 }
 399
 400                 if (overflow_check && ovf == -ERANGE)
 401                         goto overflow;
 402
 403         }
 404
 405         return 0;
 406
 407 overflow:
 408         pr_err("module %s: overflow in relocation type %d val %Lx\n",
 409                me->name, (int)ELF64_R_TYPE(rel[i].r_info), val);
 410         return -ENOEXEC;
 411 }
 412
 413 int module_finalize(const Elf_Ehdr *hdr,
 414                     const Elf_Shdr *sechdrs,
 415                     struct module *me)
 416 {
 417         const Elf_Shdr *s, *se;
 418         const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 419
 420         for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++) {
 421                 if (strcmp(".altinstructions", secstrs + s->sh_name) == 0) {
 422                         apply_alternatives((void *)s->sh_addr, s->sh_size);
 423                         return 0;
 424                 }
 425         }
 426
 427         return 0;
 428 }