arch/mips/kernel/module.c

   1 /*
   2  *  This program is free software; you can redistribute it and/or modify
   3  *  it under the terms of the GNU General Public License as published by
   4  *  the Free Software Foundation; either version 2 of the License, or
   5  *  (at your option) any later version.
   6  *
   7  *  This program is distributed in the hope that it will be useful,
   8  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
   9  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  10  *  GNU General Public License for more details.
  11  *
  12  *  You should have received a copy of the GNU General Public License
  13  *  along with this program; if not, write to the Free Software
  14  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  15  *
  16  *  Copyright (C) 2001 Rusty Russell.
  17  *  Copyright (C) 2003, 2004 Ralf Baechle (ralf@linux-mips.org)
  18  *  Copyright (C) 2005 Thiemo Seufer
  19  */
  20
  21 #undef DEBUG
  22
  23 #include <linux/extable.h>
  24 #include <linux/moduleloader.h>
  25 #include <linux/elf.h>
  26 #include <linux/mm.h>
  27 #include <linux/numa.h>
  28 #include <linux/vmalloc.h>
  29 #include <linux/slab.h>
  30 #include <linux/fs.h>
  31 #include <linux/string.h>
  32 #include <linux/kernel.h>
  33 #include <linux/spinlock.h>
  34 #include <linux/jump_label.h>
  35
  36 #include <asm/pgtable.h>        /* MODULE_START */
  37
  38 struct mips_hi16 {
  39         struct mips_hi16 *next;
  40         Elf_Addr *addr;
  41         Elf_Addr value;
  42 };
  43
  44 static LIST_HEAD(dbe_list);
  45 static DEFINE_SPINLOCK(dbe_lock);
  46
  47 #ifdef MODULE_START
  48 void *module_alloc(unsigned long size)
  49 {
  50         return __vmalloc_node_range(size, 1, MODULE_START, MODULE_END,
  51                                 GFP_KERNEL, PAGE_KERNEL, 0, NUMA_NO_NODE,
  52                                 __builtin_return_address(0));
  53 }
  54 #endif
  55
  56 int apply_r_mips_none(struct module *me, u32 *location, Elf_Addr v)
  57 {
  58         return 0;
  59 }
  60
  61 static int apply_r_mips_32_rel(struct module *me, u32 *location, Elf_Addr v)
  62 {
  63         *location += v;
  64
  65         return 0;
  66 }
  67
  68 static int apply_r_mips_26_rel(struct module *me, u32 *location, Elf_Addr v)
  69 {
  70         if (v % 4) {
  71                 pr_err("module %s: dangerous R_MIPS_26 REL relocation\n",
  72                        me->name);
  73                 return -ENOEXEC;
  74         }
  75
  76         if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
  77                 pr_err("module %s: relocation overflow\n",
  78                        me->name);
  79                 return -ENOEXEC;
  80         }
  81
  82         *location = (*location & ~0x03ffffff) |
  83                     ((*location + (v >> 2)) & 0x03ffffff);
  84
  85         return 0;
  86 }
  87
  88 static int apply_r_mips_hi16_rel(struct module *me, u32 *location, Elf_Addr v)
  89 {
  90         struct mips_hi16 *n;
  91
  92         /*
  93          * We cannot relocate this one now because we don't know the value of
  94          * the carry we need to add.  Save the information, and let LO16 do the
  95          * actual relocation.
  96          */
  97         n = kmalloc(sizeof *n, GFP_KERNEL);
  98         if (!n)
  99                 return -ENOMEM;
 100
 101         n->addr = (Elf_Addr *)location;
 102         n->value = v;
 103         n->next = me->arch.r_mips_hi16_list;
 104         me->arch.r_mips_hi16_list = n;
 105
 106         return 0;
 107 }
 108
 109 static void free_relocation_chain(struct mips_hi16 *l)
 110 {
 111         struct mips_hi16 *next;
 112
 113         while (l) {
 114                 next = l->next;
 115                 kfree(l);
 116                 l = next;
 117         }
 118 }
 119
 120 static int apply_r_mips_lo16_rel(struct module *me, u32 *location, Elf_Addr v)
 121 {
 122         unsigned long insnlo = *location;
 123         struct mips_hi16 *l;
 124         Elf_Addr val, vallo;
 125
 126         /* Sign extend the addend we extract from the lo insn.  */
 127         vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;
 128
 129         if (me->arch.r_mips_hi16_list != NULL) {
 130                 l = me->arch.r_mips_hi16_list;
 131                 while (l != NULL) {
 132                         struct mips_hi16 *next;
 133                         unsigned long insn;
 134
 135                         /*
 136                          * The value for the HI16 had best be the same.
 137                          */
 138                         if (v != l->value)
 139                                 goto out_danger;
 140
 141                         /*
 142                          * Do the HI16 relocation.  Note that we actually don't
 143                          * need to know anything about the LO16 itself, except
 144                          * where to find the low 16 bits of the addend needed
 145                          * by the LO16.
 146                          */
 147                         insn = *l->addr;
 148                         val = ((insn & 0xffff) << 16) + vallo;
 149                         val += v;
 150
 151                         /*
 152                          * Account for the sign extension that will happen in
 153                          * the low bits.
 154                          */
 155                         val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;
 156
 157                         insn = (insn & ~0xffff) | val;
 158                         *l->addr = insn;
 159
 160                         next = l->next;
 161                         kfree(l);
 162                         l = next;
 163                 }
 164
 165                 me->arch.r_mips_hi16_list = NULL;
 166         }
 167
 168         /*
 169          * Ok, we're done with the HI16 relocs.  Now deal with the LO16.
 170          */
 171         val = v + vallo;
 172         insnlo = (insnlo & ~0xffff) | (val & 0xffff);
 173         *location = insnlo;
 174
 175         return 0;
 176
 177 out_danger:
 178         free_relocation_chain(l);
 179         me->arch.r_mips_hi16_list = NULL;
 180
 181         pr_err("module %s: dangerous R_MIPS_LO16 REL relocation\n", me->name);
 182
 183         return -ENOEXEC;
 184 }
 185
 186 static int apply_r_mips_pc_rel(struct module *me, u32 *location, Elf_Addr v,
 187                                unsigned bits)
 188 {
 189         unsigned long mask = GENMASK(bits - 1, 0);
 190         unsigned long se_bits;
 191         long offset;
 192
 193         if (v % 4) {
 194                 pr_err("module %s: dangerous R_MIPS_PC%u REL relocation\n",
 195                        me->name, bits);
 196                 return -ENOEXEC;
 197         }
 198
 199         /* retrieve & sign extend implicit addend */
 200         offset = *location & mask;
 201         offset |= (offset & BIT(bits - 1)) ? ~mask : 0;
 202
 203         offset += ((long)v - (long)location) >> 2;
 204
 205         /* check the sign bit onwards are identical - ie. we didn't overflow */
 206         se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
 207         if ((offset & ~mask) != (se_bits & ~mask)) {
 208                 pr_err("module %s: relocation overflow\n", me->name);
 209                 return -ENOEXEC;
 210         }
 211
 212         *location = (*location & ~mask) | (offset & mask);
 213
 214         return 0;
 215 }
 216
 217 static int apply_r_mips_pc16_rel(struct module *me, u32 *location, Elf_Addr v)
 218 {
 219         return apply_r_mips_pc_rel(me, location, v, 16);
 220 }
 221
 222 static int apply_r_mips_pc21_rel(struct module *me, u32 *location, Elf_Addr v)
 223 {
 224         return apply_r_mips_pc_rel(me, location, v, 21);
 225 }
 226
 227 static int apply_r_mips_pc26_rel(struct module *me, u32 *location, Elf_Addr v)
 228 {
 229         return apply_r_mips_pc_rel(me, location, v, 26);
 230 }
 231
 232 static int (*reloc_handlers_rel[]) (struct module *me, u32 *location,
 233                                 Elf_Addr v) = {
 234         [R_MIPS_NONE]           = apply_r_mips_none,
 235         [R_MIPS_32]             = apply_r_mips_32_rel,
 236         [R_MIPS_26]             = apply_r_mips_26_rel,
 237         [R_MIPS_HI16]           = apply_r_mips_hi16_rel,
 238         [R_MIPS_LO16]           = apply_r_mips_lo16_rel,
 239         [R_MIPS_PC16]           = apply_r_mips_pc16_rel,
 240         [R_MIPS_PC21_S2]        = apply_r_mips_pc21_rel,
 241         [R_MIPS_PC26_S2]        = apply_r_mips_pc26_rel,
 242 };
 243
 244 int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
 245                    unsigned int symindex, unsigned int relsec,
 246                    struct module *me)
 247 {
 248         Elf_Mips_Rel *rel = (void *) sechdrs[relsec].sh_addr;
 249         int (*handler)(struct module *me, u32 *location, Elf_Addr v);
 250         Elf_Sym *sym;
 251         u32 *location;
 252         unsigned int i, type;
 253         Elf_Addr v;
 254         int res;
 255
 256         pr_debug("Applying relocate section %u to %u\n", relsec,
 257                sechdrs[relsec].sh_info);
 258
 259         me->arch.r_mips_hi16_list = NULL;
 260         for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
 261                 /* This is where to make the change */
 262                 location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
 263                         + rel[i].r_offset;
 264                 /* This is the symbol it is referring to */
 265                 sym = (Elf_Sym *)sechdrs[symindex].sh_addr
 266                         + ELF_MIPS_R_SYM(rel[i]);
 267                 if (sym->st_value >= -MAX_ERRNO) {
 268                         /* Ignore unresolved weak symbol */
 269                         if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
 270                                 continue;
 271                         pr_warn("%s: Unknown symbol %s\n",
 272                                 me->name, strtab + sym->st_name);
 273                         return -ENOENT;
 274                 }
 275
 276                 type = ELF_MIPS_R_TYPE(rel[i]);
 277
 278                 if (type < ARRAY_SIZE(reloc_handlers_rel))
 279                         handler = reloc_handlers_rel[type];
 280                 else
 281                         handler = NULL;
 282
 283                 if (!handler) {
 284                         pr_err("%s: Unknown relocation type %u\n",
 285                                me->name, type);
 286                         return -EINVAL;
 287                 }
 288
 289                 v = sym->st_value;
 290                 res = handler(me, location, v);
 291                 if (res)
 292                         return res;
 293         }
 294
 295         /*
 296          * Normally the hi16 list should be deallocated at this point.  A
 297          * malformed binary however could contain a series of R_MIPS_HI16
 298          * relocations not followed by a R_MIPS_LO16 relocation.  In that
 299          * case, free up the list and return an error.
 300          */
 301         if (me->arch.r_mips_hi16_list) {
 302                 free_relocation_chain(me->arch.r_mips_hi16_list);
 303                 me->arch.r_mips_hi16_list = NULL;
 304
 305                 return -ENOEXEC;
 306         }
 307
 308         return 0;
 309 }
 310
 311 /* Given an address, look for it in the module exception tables. */
 312 const struct exception_table_entry *search_module_dbetables(unsigned long addr)
 313 {
 314         unsigned long flags;
 315         const struct exception_table_entry *e = NULL;
 316         struct mod_arch_specific *dbe;
 317
 318         spin_lock_irqsave(&dbe_lock, flags);
 319         list_for_each_entry(dbe, &dbe_list, dbe_list) {
 320                 e = search_extable(dbe->dbe_start,
 321                                    dbe->dbe_end - dbe->dbe_start, addr);
 322                 if (e)
 323                         break;
 324         }
 325         spin_unlock_irqrestore(&dbe_lock, flags);
 326
 327         /* Now, if we found one, we are running inside it now, hence
 328            we cannot unload the module, hence no refcnt needed. */
 329         return e;
 330 }
 331
 332 /* Put in dbe list if necessary. */
 333 int module_finalize(const Elf_Ehdr *hdr,
 334                     const Elf_Shdr *sechdrs,
 335                     struct module *me)
 336 {
 337         const Elf_Shdr *s;
 338         char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 339
 340         /* Make jump label nops. */
 341         jump_label_apply_nops(me);
 342
 343         INIT_LIST_HEAD(&me->arch.dbe_list);
 344         for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
 345                 if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
 346                         continue;
 347                 me->arch.dbe_start = (void *)s->sh_addr;
 348                 me->arch.dbe_end = (void *)s->sh_addr + s->sh_size;
 349                 spin_lock_irq(&dbe_lock);
 350                 list_add(&me->arch.dbe_list, &dbe_list);
 351                 spin_unlock_irq(&dbe_lock);
 352         }
 353         return 0;
 354 }
 355
 356 void module_arch_cleanup(struct module *mod)
 357 {
 358         spin_lock_irq(&dbe_lock);
 359         list_del(&mod->arch.dbe_list);
 360         spin_unlock_irq(&dbe_lock);
 361 }