arch/mips/kernel/module.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  *
   4  *  Copyright (C) 2001 Rusty Russell.
   5  *  Copyright (C) 2003, 2004 Ralf Baechle (ralf@linux-mips.org)
   6  *  Copyright (C) 2005 Thiemo Seufer
   7  */
   8
   9 #undef DEBUG
  10
  11 #include <linux/extable.h>
  12 #include <linux/moduleloader.h>
  13 #include <linux/elf.h>
  14 #include <linux/mm.h>
  15 #include <linux/numa.h>
  16 #include <linux/vmalloc.h>
  17 #include <linux/slab.h>
  18 #include <linux/fs.h>
  19 #include <linux/string.h>
  20 #include <linux/kernel.h>
  21 #include <linux/spinlock.h>
  22 #include <linux/jump_label.h>
  23
  24
  25 struct mips_hi16 {
  26         struct mips_hi16 *next;
  27         Elf_Addr *addr;
  28         Elf_Addr value;
  29 };
  30
  31 static LIST_HEAD(dbe_list);
  32 static DEFINE_SPINLOCK(dbe_lock);
  33
  34 #ifdef MODULE_START
  35 void *module_alloc(unsigned long size)
  36 {
  37         return __vmalloc_node_range(size, 1, MODULE_START, MODULE_END,
  38                                 GFP_KERNEL, PAGE_KERNEL, 0, NUMA_NO_NODE,
  39                                 __builtin_return_address(0));
  40 }
  41 #endif
  42
  43 static int apply_r_mips_none(struct module *me, u32 *location,
  44                              u32 base, Elf_Addr v, bool rela)
  45 {
  46         return 0;
  47 }
  48
  49 static int apply_r_mips_32(struct module *me, u32 *location,
  50                            u32 base, Elf_Addr v, bool rela)
  51 {
  52         *location = base + v;
  53
  54         return 0;
  55 }
  56
  57 static int apply_r_mips_26(struct module *me, u32 *location,
  58                            u32 base, Elf_Addr v, bool rela)
  59 {
  60         if (v % 4) {
  61                 pr_err("module %s: dangerous R_MIPS_26 relocation\n",
  62                        me->name);
  63                 return -ENOEXEC;
  64         }
  65
  66         if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
  67                 pr_err("module %s: relocation overflow\n",
  68                        me->name);
  69                 return -ENOEXEC;
  70         }
  71
  72         *location = (*location & ~0x03ffffff) |
  73                     ((base + (v >> 2)) & 0x03ffffff);
  74
  75         return 0;
  76 }
  77
  78 static int apply_r_mips_hi16(struct module *me, u32 *location,
  79                              u32 base, Elf_Addr v, bool rela)
  80 {
  81         struct mips_hi16 *n;
  82
  83         if (rela) {
  84                 *location = (*location & 0xffff0000) |
  85                             ((((long long) v + 0x8000LL) >> 16) & 0xffff);
  86                 return 0;
  87         }
  88
  89         /*
  90          * We cannot relocate this one now because we don't know the value of
  91          * the carry we need to add.  Save the information, and let LO16 do the
  92          * actual relocation.
  93          */
  94         n = kmalloc(sizeof *n, GFP_KERNEL);
  95         if (!n)
  96                 return -ENOMEM;
  97
  98         n->addr = (Elf_Addr *)location;
  99         n->value = v;
 100         n->next = me->arch.r_mips_hi16_list;
 101         me->arch.r_mips_hi16_list = n;
 102
 103         return 0;
 104 }
 105
 106 static void free_relocation_chain(struct mips_hi16 *l)
 107 {
 108         struct mips_hi16 *next;
 109
 110         while (l) {
 111                 next = l->next;
 112                 kfree(l);
 113                 l = next;
 114         }
 115 }
 116
 117 static int apply_r_mips_lo16(struct module *me, u32 *location,
 118                              u32 base, Elf_Addr v, bool rela)
 119 {
 120         unsigned long insnlo = base;
 121         struct mips_hi16 *l;
 122         Elf_Addr val, vallo;
 123
 124         if (rela) {
 125                 *location = (*location & 0xffff0000) | (v & 0xffff);
 126                 return 0;
 127         }
 128
 129         /* Sign extend the addend we extract from the lo insn.  */
 130         vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;
 131
 132         if (me->arch.r_mips_hi16_list != NULL) {
 133                 l = me->arch.r_mips_hi16_list;
 134                 while (l != NULL) {
 135                         struct mips_hi16 *next;
 136                         unsigned long insn;
 137
 138                         /*
 139                          * The value for the HI16 had best be the same.
 140                          */
 141                         if (v != l->value)
 142                                 goto out_danger;
 143
 144                         /*
 145                          * Do the HI16 relocation.  Note that we actually don't
 146                          * need to know anything about the LO16 itself, except
 147                          * where to find the low 16 bits of the addend needed
 148                          * by the LO16.
 149                          */
 150                         insn = *l->addr;
 151                         val = ((insn & 0xffff) << 16) + vallo;
 152                         val += v;
 153
 154                         /*
 155                          * Account for the sign extension that will happen in
 156                          * the low bits.
 157                          */
 158                         val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;
 159
 160                         insn = (insn & ~0xffff) | val;
 161                         *l->addr = insn;
 162
 163                         next = l->next;
 164                         kfree(l);
 165                         l = next;
 166                 }
 167
 168                 me->arch.r_mips_hi16_list = NULL;
 169         }
 170
 171         /*
 172          * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
 173          */
 174         val = v + vallo;
 175         insnlo = (insnlo & ~0xffff) | (val & 0xffff);
 176         *location = insnlo;
 177
 178         return 0;
 179
 180 out_danger:
 181         free_relocation_chain(l);
 182         me->arch.r_mips_hi16_list = NULL;
 183
 184         pr_err("module %s: dangerous R_MIPS_LO16 relocation\n", me->name);
 185
 186         return -ENOEXEC;
 187 }
 188
 189 static int apply_r_mips_pc(struct module *me, u32 *location, u32 base,
 190                            Elf_Addr v, unsigned int bits)
 191 {
 192         unsigned long mask = GENMASK(bits - 1, 0);
 193         unsigned long se_bits;
 194         long offset;
 195
 196         if (v % 4) {
 197                 pr_err("module %s: dangerous R_MIPS_PC%u relocation\n",
 198                        me->name, bits);
 199                 return -ENOEXEC;
 200         }
 201
 202         /* retrieve & sign extend implicit addend if any */
 203         offset = base & mask;
 204         offset |= (offset & BIT(bits - 1)) ? ~mask : 0;
 205
 206         offset += ((long)v - (long)location) >> 2;
 207
 208         /* check the sign bit onwards are identical - ie. we didn't overflow */
 209         se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
 210         if ((offset & ~mask) != (se_bits & ~mask)) {
 211                 pr_err("module %s: relocation overflow\n", me->name);
 212                 return -ENOEXEC;
 213         }
 214
 215         *location = (*location & ~mask) | (offset & mask);
 216
 217         return 0;
 218 }
 219
 220 static int apply_r_mips_pc16(struct module *me, u32 *location,
 221                              u32 base, Elf_Addr v, bool rela)
 222 {
 223         return apply_r_mips_pc(me, location, base, v, 16);
 224 }
 225
 226 static int apply_r_mips_pc21(struct module *me, u32 *location,
 227                              u32 base, Elf_Addr v, bool rela)
 228 {
 229         return apply_r_mips_pc(me, location, base, v, 21);
 230 }
 231
 232 static int apply_r_mips_pc26(struct module *me, u32 *location,
 233                              u32 base, Elf_Addr v, bool rela)
 234 {
 235         return apply_r_mips_pc(me, location, base, v, 26);
 236 }
 237
 238 static int apply_r_mips_64(struct module *me, u32 *location,
 239                            u32 base, Elf_Addr v, bool rela)
 240 {
 241         if (WARN_ON(!rela))
 242                 return -EINVAL;
 243
 244         *(Elf_Addr *)location = v;
 245
 246         return 0;
 247 }
 248
 249 static int apply_r_mips_higher(struct module *me, u32 *location,
 250                                u32 base, Elf_Addr v, bool rela)
 251 {
 252         if (WARN_ON(!rela))
 253                 return -EINVAL;
 254
 255         *location = (*location & 0xffff0000) |
 256                     ((((long long)v + 0x80008000LL) >> 32) & 0xffff);
 257
 258         return 0;
 259 }
 260
 261 static int apply_r_mips_highest(struct module *me, u32 *location,
 262                                 u32 base, Elf_Addr v, bool rela)
 263 {
 264         if (WARN_ON(!rela))
 265                 return -EINVAL;
 266
 267         *location = (*location & 0xffff0000) |
 268                     ((((long long)v + 0x800080008000LL) >> 48) & 0xffff);
 269
 270         return 0;
 271 }
 272
 273 /**
 274  * reloc_handler() - Apply a particular relocation to a module
 275  * @me: the module to apply the reloc to
 276  * @location: the address at which the reloc is to be applied
 277  * @base: the existing value at location for REL-style; 0 for RELA-style
 278  * @v: the value of the reloc, with addend for RELA-style
 279  *
 280  * Each implemented reloc_handler function applies a particular type of
 281  * relocation to the module @me. Relocs that may be found in either REL or RELA
 282  * variants can be handled by making use of the @base & @v parameters which are
 283  * set to values which abstract the difference away from the particular reloc
 284  * implementations.
 285  *
 286  * Return: 0 upon success, else -ERRNO
 287  */
 288 typedef int (*reloc_handler)(struct module *me, u32 *location,
 289                              u32 base, Elf_Addr v, bool rela);
 290
 291 /* The handlers for known reloc types */
 292 static reloc_handler reloc_handlers[] = {
 293         [R_MIPS_NONE]           = apply_r_mips_none,
 294         [R_MIPS_32]             = apply_r_mips_32,
 295         [R_MIPS_26]             = apply_r_mips_26,
 296         [R_MIPS_HI16]           = apply_r_mips_hi16,
 297         [R_MIPS_LO16]           = apply_r_mips_lo16,
 298         [R_MIPS_PC16]           = apply_r_mips_pc16,
 299         [R_MIPS_64]             = apply_r_mips_64,
 300         [R_MIPS_HIGHER]         = apply_r_mips_higher,
 301         [R_MIPS_HIGHEST]        = apply_r_mips_highest,
 302         [R_MIPS_PC21_S2]        = apply_r_mips_pc21,
 303         [R_MIPS_PC26_S2]        = apply_r_mips_pc26,
 304 };
 305
 306 static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
 307                             unsigned int symindex, unsigned int relsec,
 308                             struct module *me, bool rela)
 309 {
 310         union {
 311                 Elf_Mips_Rel *rel;
 312                 Elf_Mips_Rela *rela;
 313         } r;
 314         reloc_handler handler;
 315         Elf_Sym *sym;
 316         u32 *location, base;
 317         unsigned int i, type;
 318         Elf_Addr v;
 319         int err = 0;
 320         size_t reloc_sz;
 321
 322         pr_debug("Applying relocate section %u to %u\n", relsec,
 323                sechdrs[relsec].sh_info);
 324
 325         r.rel = (void *)sechdrs[relsec].sh_addr;
 326         reloc_sz = rela ? sizeof(*r.rela) : sizeof(*r.rel);
 327         me->arch.r_mips_hi16_list = NULL;
 328         for (i = 0; i < sechdrs[relsec].sh_size / reloc_sz; i++) {
 329                 /* This is where to make the change */
 330                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 331                         + r.rel->r_offset;
 332                 /* This is the symbol it is referring to */
 333                 sym = (Elf_Sym *)sechdrs[symindex].sh_addr
 334                         + ELF_MIPS_R_SYM(*r.rel);
 335                 if (sym->st_value >= -MAX_ERRNO) {
 336                         /* Ignore unresolved weak symbol */
 337                         if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
 338                                 continue;
 339                         pr_warn("%s: Unknown symbol %s\n",
 340                                 me->name, strtab + sym->st_name);
 341                         err = -ENOENT;
 342                         goto out;
 343                 }
 344
 345                 type = ELF_MIPS_R_TYPE(*r.rel);
 346                 if (type < ARRAY_SIZE(reloc_handlers))
 347                         handler = reloc_handlers[type];
 348                 else
 349                         handler = NULL;
 350
 351                 if (!handler) {
 352                         pr_err("%s: Unknown relocation type %u\n",
 353                                me->name, type);
 354                         err = -EINVAL;
 355                         goto out;
 356                 }
 357
 358                 if (rela) {
 359                         v = sym->st_value + r.rela->r_addend;
 360                         base = 0;
 361                         r.rela = &r.rela[1];
 362                 } else {
 363                         v = sym->st_value;
 364                         base = *location;
 365                         r.rel = &r.rel[1];
 366                 }
 367
 368                 err = handler(me, location, base, v, rela);
 369                 if (err)
 370                         goto out;
 371         }
 372
 373 out:
 374         /*
 375          * Normally the hi16 list should be deallocated at this point. A
 376          * malformed binary however could contain a series of R_MIPS_HI16
 377          * relocations not followed by a R_MIPS_LO16 relocation, or if we hit
 378          * an error processing a reloc we might have gotten here before
 379          * reaching the R_MIPS_LO16. In either case, free up the list and
 380          * return an error.
 381          */
 382         if (me->arch.r_mips_hi16_list) {
 383                 free_relocation_chain(me->arch.r_mips_hi16_list);
 384                 me->arch.r_mips_hi16_list = NULL;
 385                 err = err ?: -ENOEXEC;
 386         }
 387
 388         return err;
 389 }
 390
 391 int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
 392                    unsigned int symindex, unsigned int relsec,
 393                    struct module *me)
 394 {
 395         return __apply_relocate(sechdrs, strtab, symindex, relsec, me, false);
 396 }
 397
 398 #ifdef CONFIG_MODULES_USE_ELF_RELA
 399 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 400                        unsigned int symindex, unsigned int relsec,
 401                        struct module *me)
 402 {
 403         return __apply_relocate(sechdrs, strtab, symindex, relsec, me, true);
 404 }
 405 #endif /* CONFIG_MODULES_USE_ELF_RELA */
 406
 407 /* Given an address, look for it in the module exception tables. */
 408 const struct exception_table_entry *search_module_dbetables(unsigned long addr)
 409 {
 410         unsigned long flags;
 411         const struct exception_table_entry *e = NULL;
 412         struct mod_arch_specific *dbe;
 413
 414         spin_lock_irqsave(&dbe_lock, flags);
 415         list_for_each_entry(dbe, &dbe_list, dbe_list) {
 416                 e = search_extable(dbe->dbe_start,
 417                                    dbe->dbe_end - dbe->dbe_start, addr);
 418                 if (e)
 419                         break;
 420         }
 421         spin_unlock_irqrestore(&dbe_lock, flags);
 422
 423         /* Now, if we found one, we are running inside it now, hence
 424            we cannot unload the module, hence no refcnt needed. */
 425         return e;
 426 }
 427
 428 /* Put in dbe list if necessary. */
 429 int module_finalize(const Elf_Ehdr *hdr,
 430                     const Elf_Shdr *sechdrs,
 431                     struct module *me)
 432 {
 433         const Elf_Shdr *s;
 434         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 435
 436         /* Make jump label nops. */
 437         jump_label_apply_nops(me);
 438
 439         INIT_LIST_HEAD(&me->arch.dbe_list);
 440         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 441                 if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
 442                         continue;
 443                 me->arch.dbe_start = (void *)s->sh_addr;
 444                 me->arch.dbe_end = (void *)s->sh_addr + s->sh_size;
 445                 spin_lock_irq(&dbe_lock);
 446                 list_add(&me->arch.dbe_list, &dbe_list);
 447                 spin_unlock_irq(&dbe_lock);
 448         }
 449         return 0;
 450 }
 451
 452 void module_arch_cleanup(struct module *mod)
 453 {
 454         spin_lock_irq(&dbe_lock);
 455         list_del(&mod->arch.dbe_list);
 456         spin_unlock_irq(&dbe_lock);
 457 }