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 #include <asm/pgtable.h>        /* MODULE_START */
  25
  26 struct mips_hi16 {
  27         struct mips_hi16 *next;
  28         Elf_Addr *addr;
  29         Elf_Addr value;
  30 };
  31
  32 static LIST_HEAD(dbe_list);
  33 static DEFINE_SPINLOCK(dbe_lock);
  34
  35 #ifdef MODULE_START
  36 void *module_alloc(unsigned long size)
  37 {
  38         return __vmalloc_node_range(size, 1, MODULE_START, MODULE_END,
  39                                 GFP_KERNEL, PAGE_KERNEL, 0, NUMA_NO_NODE,
  40                                 __builtin_return_address(0));
  41 }
  42 #endif
  43
  44 static int apply_r_mips_none(struct module *me, u32 *location,
  45                              u32 base, Elf_Addr v, bool rela)
  46 {
  47         return 0;
  48 }
  49
  50 static int apply_r_mips_32(struct module *me, u32 *location,
  51                            u32 base, Elf_Addr v, bool rela)
  52 {
  53         *location = base + v;
  54
  55         return 0;
  56 }
  57
  58 static int apply_r_mips_26(struct module *me, u32 *location,
  59                            u32 base, Elf_Addr v, bool rela)
  60 {
  61         if (v % 4) {
  62                 pr_err("module %s: dangerous R_MIPS_26 relocation\n",
  63                        me->name);
  64                 return -ENOEXEC;
  65         }
  66
  67         if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
  68                 pr_err("module %s: relocation overflow\n",
  69                        me->name);
  70                 return -ENOEXEC;
  71         }
  72
  73         *location = (*location & ~0x03ffffff) |
  74                     ((base + (v >> 2)) & 0x03ffffff);
  75
  76         return 0;
  77 }
  78
  79 static int apply_r_mips_hi16(struct module *me, u32 *location,
  80                              u32 base, Elf_Addr v, bool rela)
  81 {
  82         struct mips_hi16 *n;
  83
  84         if (rela) {
  85                 *location = (*location & 0xffff0000) |
  86                             ((((long long) v + 0x8000LL) >> 16) & 0xffff);
  87                 return 0;
  88         }
  89
  90         /*
  91          * We cannot relocate this one now because we don't know the value of
  92          * the carry we need to add.  Save the information, and let LO16 do the
  93          * actual relocation.
  94          */
  95         n = kmalloc(sizeof *n, GFP_KERNEL);
  96         if (!n)
  97                 return -ENOMEM;
  98
  99         n->addr = (Elf_Addr *)location;
 100         n->value = v;
 101         n->next = me->arch.r_mips_hi16_list;
 102         me->arch.r_mips_hi16_list = n;
 103
 104         return 0;
 105 }
 106
 107 static void free_relocation_chain(struct mips_hi16 *l)
 108 {
 109         struct mips_hi16 *next;
 110
 111         while (l) {
 112                 next = l->next;
 113                 kfree(l);
 114                 l = next;
 115         }
 116 }
 117
 118 static int apply_r_mips_lo16(struct module *me, u32 *location,
 119                              u32 base, Elf_Addr v, bool rela)
 120 {
 121         unsigned long insnlo = base;
 122         struct mips_hi16 *l;
 123         Elf_Addr val, vallo;
 124
 125         if (rela) {
 126                 *location = (*location & 0xffff0000) | (v & 0xffff);
 127                 return 0;
 128         }
 129
 130         /* Sign extend the addend we extract from the lo insn.  */
 131         vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;
 132
 133         if (me->arch.r_mips_hi16_list != NULL) {
 134                 l = me->arch.r_mips_hi16_list;
 135                 while (l != NULL) {
 136                         struct mips_hi16 *next;
 137                         unsigned long insn;
 138
 139                         /*
 140                          * The value for the HI16 had best be the same.
 141                          */
 142                         if (v != l->value)
 143                                 goto out_danger;
 144
 145                         /*
 146                          * Do the HI16 relocation.  Note that we actually don't
 147                          * need to know anything about the LO16 itself, except
 148                          * where to find the low 16 bits of the addend needed
 149                          * by the LO16.
 150                          */
 151                         insn = *l->addr;
 152                         val = ((insn & 0xffff) << 16) + vallo;
 153                         val += v;
 154
 155                         /*
 156                          * Account for the sign extension that will happen in
 157                          * the low bits.
 158                          */
 159                         val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;
 160
 161                         insn = (insn & ~0xffff) | val;
 162                         *l->addr = insn;
 163
 164                         next = l->next;
 165                         kfree(l);
 166                         l = next;
 167                 }
 168
 169                 me->arch.r_mips_hi16_list = NULL;
 170         }
 171
 172         /*
 173          * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
 174          */
 175         val = v + vallo;
 176         insnlo = (insnlo & ~0xffff) | (val & 0xffff);
 177         *location = insnlo;
 178
 179         return 0;
 180
 181 out_danger:
 182         free_relocation_chain(l);
 183         me->arch.r_mips_hi16_list = NULL;
 184
 185         pr_err("module %s: dangerous R_MIPS_LO16 relocation\n", me->name);
 186
 187         return -ENOEXEC;
 188 }
 189
 190 static int apply_r_mips_pc(struct module *me, u32 *location, u32 base,
 191                            Elf_Addr v, unsigned int bits)
 192 {
 193         unsigned long mask = GENMASK(bits - 1, 0);
 194         unsigned long se_bits;
 195         long offset;
 196
 197         if (v % 4) {
 198                 pr_err("module %s: dangerous R_MIPS_PC%u relocation\n",
 199                        me->name, bits);
 200                 return -ENOEXEC;
 201         }
 202
 203         /* retrieve & sign extend implicit addend if any */
 204         offset = base & mask;
 205         offset |= (offset & BIT(bits - 1)) ? ~mask : 0;
 206
 207         offset += ((long)v - (long)location) >> 2;
 208
 209         /* check the sign bit onwards are identical - ie. we didn't overflow */
 210         se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
 211         if ((offset & ~mask) != (se_bits & ~mask)) {
 212                 pr_err("module %s: relocation overflow\n", me->name);
 213                 return -ENOEXEC;
 214         }
 215
 216         *location = (*location & ~mask) | (offset & mask);
 217
 218         return 0;
 219 }
 220
 221 static int apply_r_mips_pc16(struct module *me, u32 *location,
 222                              u32 base, Elf_Addr v, bool rela)
 223 {
 224         return apply_r_mips_pc(me, location, base, v, 16);
 225 }
 226
 227 static int apply_r_mips_pc21(struct module *me, u32 *location,
 228                              u32 base, Elf_Addr v, bool rela)
 229 {
 230         return apply_r_mips_pc(me, location, base, v, 21);
 231 }
 232
 233 static int apply_r_mips_pc26(struct module *me, u32 *location,
 234                              u32 base, Elf_Addr v, bool rela)
 235 {
 236         return apply_r_mips_pc(me, location, base, v, 26);
 237 }
 238
 239 static int apply_r_mips_64(struct module *me, u32 *location,
 240                            u32 base, Elf_Addr v, bool rela)
 241 {
 242         if (WARN_ON(!rela))
 243                 return -EINVAL;
 244
 245         *(Elf_Addr *)location = v;
 246
 247         return 0;
 248 }
 249
 250 static int apply_r_mips_higher(struct module *me, u32 *location,
 251                                u32 base, Elf_Addr v, bool rela)
 252 {
 253         if (WARN_ON(!rela))
 254                 return -EINVAL;
 255
 256         *location = (*location & 0xffff0000) |
 257                     ((((long long)v + 0x80008000LL) >> 32) & 0xffff);
 258
 259         return 0;
 260 }
 261
 262 static int apply_r_mips_highest(struct module *me, u32 *location,
 263                                 u32 base, Elf_Addr v, bool rela)
 264 {
 265         if (WARN_ON(!rela))
 266                 return -EINVAL;
 267
 268         *location = (*location & 0xffff0000) |
 269                     ((((long long)v + 0x800080008000LL) >> 48) & 0xffff);
 270
 271         return 0;
 272 }
 273
 274 /**
 275  * reloc_handler() - Apply a particular relocation to a module
 276  * @me: the module to apply the reloc to
 277  * @location: the address at which the reloc is to be applied
 278  * @base: the existing value at location for REL-style; 0 for RELA-style
 279  * @v: the value of the reloc, with addend for RELA-style
 280  *
 281  * Each implemented reloc_handler function applies a particular type of
 282  * relocation to the module @me. Relocs that may be found in either REL or RELA
 283  * variants can be handled by making use of the @base & @v parameters which are
 284  * set to values which abstract the difference away from the particular reloc
 285  * implementations.
 286  *
 287  * Return: 0 upon success, else -ERRNO
 288  */
 289 typedef int (*reloc_handler)(struct module *me, u32 *location,
 290                              u32 base, Elf_Addr v, bool rela);
 291
 292 /* The handlers for known reloc types */
 293 static reloc_handler reloc_handlers[] = {
 294         [R_MIPS_NONE]           = apply_r_mips_none,
 295         [R_MIPS_32]             = apply_r_mips_32,
 296         [R_MIPS_26]             = apply_r_mips_26,
 297         [R_MIPS_HI16]           = apply_r_mips_hi16,
 298         [R_MIPS_LO16]           = apply_r_mips_lo16,
 299         [R_MIPS_PC16]           = apply_r_mips_pc16,
 300         [R_MIPS_64]             = apply_r_mips_64,
 301         [R_MIPS_HIGHER]         = apply_r_mips_higher,
 302         [R_MIPS_HIGHEST]        = apply_r_mips_highest,
 303         [R_MIPS_PC21_S2]        = apply_r_mips_pc21,
 304         [R_MIPS_PC26_S2]        = apply_r_mips_pc26,
 305 };
 306
 307 static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
 308                             unsigned int symindex, unsigned int relsec,
 309                             struct module *me, bool rela)
 310 {
 311         union {
 312                 Elf_Mips_Rel *rel;
 313                 Elf_Mips_Rela *rela;
 314         } r;
 315         reloc_handler handler;
 316         Elf_Sym *sym;
 317         u32 *location, base;
 318         unsigned int i, type;
 319         Elf_Addr v;
 320         int err = 0;
 321         size_t reloc_sz;
 322
 323         pr_debug("Applying relocate section %u to %u\n", relsec,
 324                sechdrs[relsec].sh_info);
 325
 326         r.rel = (void *)sechdrs[relsec].sh_addr;
 327         reloc_sz = rela ? sizeof(*r.rela) : sizeof(*r.rel);
 328         me->arch.r_mips_hi16_list = NULL;
 329         for (i = 0; i < sechdrs[relsec].sh_size / reloc_sz; i++) {
 330                 /* This is where to make the change */
 331                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 332                         + r.rel->r_offset;
 333                 /* This is the symbol it is referring to */
 334                 sym = (Elf_Sym *)sechdrs[symindex].sh_addr
 335                         + ELF_MIPS_R_SYM(*r.rel);
 336                 if (sym->st_value >= -MAX_ERRNO) {
 337                         /* Ignore unresolved weak symbol */
 338                         if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
 339                                 continue;
 340                         pr_warn("%s: Unknown symbol %s\n",
 341                                 me->name, strtab + sym->st_name);
 342                         err = -ENOENT;
 343                         goto out;
 344                 }
 345
 346                 type = ELF_MIPS_R_TYPE(*r.rel);
 347                 if (type < ARRAY_SIZE(reloc_handlers))
 348                         handler = reloc_handlers[type];
 349                 else
 350                         handler = NULL;
 351
 352                 if (!handler) {
 353                         pr_err("%s: Unknown relocation type %u\n",
 354                                me->name, type);
 355                         err = -EINVAL;
 356                         goto out;
 357                 }
 358
 359                 if (rela) {
 360                         v = sym->st_value + r.rela->r_addend;
 361                         base = 0;
 362                         r.rela = &r.rela[1];
 363                 } else {
 364                         v = sym->st_value;
 365                         base = *location;
 366                         r.rel = &r.rel[1];
 367                 }
 368
 369                 err = handler(me, location, base, v, rela);
 370                 if (err)
 371                         goto out;
 372         }
 373
 374 out:
 375         /*
 376          * Normally the hi16 list should be deallocated at this point. A
 377          * malformed binary however could contain a series of R_MIPS_HI16
 378          * relocations not followed by a R_MIPS_LO16 relocation, or if we hit
 379          * an error processing a reloc we might have gotten here before
 380          * reaching the R_MIPS_LO16. In either case, free up the list and
 381          * return an error.
 382          */
 383         if (me->arch.r_mips_hi16_list) {
 384                 free_relocation_chain(me->arch.r_mips_hi16_list);
 385                 me->arch.r_mips_hi16_list = NULL;
 386                 err = err ?: -ENOEXEC;
 387         }
 388
 389         return err;
 390 }
 391
 392 int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
 393                    unsigned int symindex, unsigned int relsec,
 394                    struct module *me)
 395 {
 396         return __apply_relocate(sechdrs, strtab, symindex, relsec, me, false);
 397 }
 398
 399 #ifdef CONFIG_MODULES_USE_ELF_RELA
 400 int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
 401                        unsigned int symindex, unsigned int relsec,
 402                        struct module *me)
 403 {
 404         return __apply_relocate(sechdrs, strtab, symindex, relsec, me, true);
 405 }
 406 #endif /* CONFIG_MODULES_USE_ELF_RELA */
 407
 408 /* Given an address, look for it in the module exception tables. */
 409 const struct exception_table_entry *search_module_dbetables(unsigned long addr)
 410 {
 411         unsigned long flags;
 412         const struct exception_table_entry *e = NULL;
 413         struct mod_arch_specific *dbe;
 414
 415         spin_lock_irqsave(&dbe_lock, flags);
 416         list_for_each_entry(dbe, &dbe_list, dbe_list) {
 417                 e = search_extable(dbe->dbe_start,
 418                                    dbe->dbe_end - dbe->dbe_start, addr);
 419                 if (e)
 420                         break;
 421         }
 422         spin_unlock_irqrestore(&dbe_lock, flags);
 423
 424         /* Now, if we found one, we are running inside it now, hence
 425            we cannot unload the module, hence no refcnt needed. */
 426         return e;
 427 }
 428
 429 /* Put in dbe list if necessary. */
 430 int module_finalize(const Elf_Ehdr *hdr,
 431                     const Elf_Shdr *sechdrs,
 432                     struct module *me)
 433 {
 434         const Elf_Shdr *s;
 435         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 436
 437         /* Make jump label nops. */
 438         jump_label_apply_nops(me);
 439
 440         INIT_LIST_HEAD(&me->arch.dbe_list);
 441         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 442                 if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
 443                         continue;
 444                 me->arch.dbe_start = (void *)s->sh_addr;
 445                 me->arch.dbe_end = (void *)s->sh_addr + s->sh_size;
 446                 spin_lock_irq(&dbe_lock);
 447                 list_add(&me->arch.dbe_list, &dbe_list);
 448                 spin_unlock_irq(&dbe_lock);
 449         }
 450         return 0;
 451 }
 452
 453 void module_arch_cleanup(struct module *mod)
 454 {
 455         spin_lock_irq(&dbe_lock);
 456         list_del(&mod->arch.dbe_list);
 457         spin_unlock_irq(&dbe_lock);
 458 }