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