kern/dl.c

   1 /* dl.c - loadable module support */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2002, 2003, 2004, 2005  Free Software Foundation, Inc.
   5  *
   6  *  GRUB is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  *  You should have received a copy of the GNU General Public License
  17  *  along with GRUB; if not, write to the Free Software
  18  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  19  */
  20
  21 #include <config.h>
  22 #include <grub/elf.h>
  23 #include <grub/dl.h>
  24 #include <grub/misc.h>
  25 #include <grub/mm.h>
  26 #include <grub/err.h>
  27 #include <grub/types.h>
  28 #include <grub/symbol.h>
  29 #include <grub/file.h>
  30 #include <grub/env.h>
  31 #include <grub/cache.h>
  32
  33 #if GRUB_CPU_SIZEOF_VOID_P == 4
  34
  35 typedef Elf32_Word Elf_Word;
  36 typedef Elf32_Addr Elf_Addr;
  37 typedef Elf32_Ehdr Elf_Ehdr;
  38 typedef Elf32_Shdr Elf_Shdr;
  39 typedef Elf32_Sym Elf_Sym;
  40
  41 # define ELF_ST_BIND(val)       ELF32_ST_BIND (val)
  42 # define ELF_ST_TYPE(val)       ELF32_ST_TYPE (val)
  43
  44 #elif GRUB_CPU_SIZEOF_VOID_P == 8
  45
  46 typedef Elf64_Word Elf_Word;
  47 typedef Elf64_Addr Elf_Addr;
  48 typedef Elf64_Ehdr Elf_Ehdr;
  49 typedef Elf64_Shdr Elf_Shdr;
  50 typedef Elf64_Sym Elf_Sym;
  51
  52 # define ELF_ST_BIND(val)       ELF64_ST_BIND (val)
  53 # define ELF_ST_TYPE(val)       ELF64_ST_TYPE (val)
  54
  55 #endif
  56
  57 \f
  58
  59 struct grub_dl_list
  60 {
  61   struct grub_dl_list *next;
  62   grub_dl_t mod;
  63 };
  64 typedef struct grub_dl_list *grub_dl_list_t;
  65
  66 static grub_dl_list_t grub_dl_head;
  67
  68 static grub_err_t
  69 grub_dl_add (grub_dl_t mod)
  70 {
  71   grub_dl_list_t l;
  72
  73   if (grub_dl_get (mod->name))
  74     return grub_error (GRUB_ERR_BAD_MODULE,
  75                        "`%s' is already loaded", mod->name);
  76
  77   l = (grub_dl_list_t) grub_malloc (sizeof (*l));
  78   if (! l)
  79     return grub_errno;
  80
  81   l->mod = mod;
  82   l->next = grub_dl_head;
  83   grub_dl_head = l;
  84
  85   return GRUB_ERR_NONE;
  86 }
  87
  88 static void
  89 grub_dl_remove (grub_dl_t mod)
  90 {
  91   grub_dl_list_t *p, q;
  92
  93   for (p = &grub_dl_head, q = *p; q; p = &q->next, q = *p)
  94     if (q->mod == mod)
  95       {
  96         *p = q->next;
  97         grub_free (q);
  98         return;
  99       }
 100 }
 101
 102 grub_dl_t
 103 grub_dl_get (const char *name)
 104 {
 105   grub_dl_list_t l;
 106
 107   for (l = grub_dl_head; l; l = l->next)
 108     if (grub_strcmp (name, l->mod->name) == 0)
 109       return l->mod;
 110
 111   return 0;
 112 }
 113
 114 void
 115 grub_dl_iterate (int (*hook) (grub_dl_t mod))
 116 {
 117   grub_dl_list_t l;
 118
 119   for (l = grub_dl_head; l; l = l->next)
 120     if (hook (l->mod))
 121       break;
 122 }
 123
 124 \f
 125
 126 struct grub_symbol
 127 {
 128   struct grub_symbol *next;
 129   const char *name;
 130   void *addr;
 131   grub_dl_t mod;        /* The module to which this symbol belongs.  */
 132 };
 133 typedef struct grub_symbol *grub_symbol_t;
 134
 135 /* The size of the symbol table.  */
 136 #define GRUB_SYMTAB_SIZE        509
 137
 138 /* The symbol table (using an open-hash).  */
 139 static struct grub_symbol *grub_symtab[GRUB_SYMTAB_SIZE];
 140
 141 /* Simple hash function.  */
 142 static unsigned
 143 grub_symbol_hash (const char *s)
 144 {
 145   unsigned key = 0;
 146
 147   while (*s)
 148     key = key * 65599 + *s++;
 149
 150   return (key + (key >> 5)) % GRUB_SYMTAB_SIZE;
 151 }
 152
 153 /* Resolve the symbol name NAME and return the address.
 154    Return NULL, if not found.  */
 155 void *
 156 grub_dl_resolve_symbol (const char *name)
 157 {
 158   grub_symbol_t sym;
 159
 160   for (sym = grub_symtab[grub_symbol_hash (name)]; sym; sym = sym->next)
 161     if (grub_strcmp (sym->name, name) == 0)
 162       return sym->addr;
 163
 164   return 0;
 165 }
 166
 167 /* Register a symbol with the name NAME and the address ADDR.  */
 168 grub_err_t
 169 grub_dl_register_symbol (const char *name, void *addr, grub_dl_t mod)
 170 {
 171   grub_symbol_t sym;
 172   unsigned k;
 173
 174   sym = (grub_symbol_t) grub_malloc (sizeof (*sym));
 175   if (! sym)
 176     return grub_errno;
 177
 178   if (mod)
 179     {
 180       sym->name = grub_strdup (name);
 181       if (! sym->name)
 182         {
 183           grub_free (sym);
 184           return grub_errno;
 185         }
 186     }
 187   else
 188     sym->name = name;
 189
 190   sym->addr = addr;
 191   sym->mod = mod;
 192
 193   k = grub_symbol_hash (name);
 194   sym->next = grub_symtab[k];
 195   grub_symtab[k] = sym;
 196
 197   return GRUB_ERR_NONE;
 198 }
 199
 200 /* Unregister all the symbols defined in the module MOD.  */
 201 static void
 202 grub_dl_unregister_symbols (grub_dl_t mod)
 203 {
 204   unsigned i;
 205
 206   if (! mod)
 207     grub_fatal ("core symbols cannot be unregistered");
 208
 209   for (i = 0; i < GRUB_SYMTAB_SIZE; i++)
 210     {
 211       grub_symbol_t sym, *p, q;
 212
 213       for (p = &grub_symtab[i], sym = *p; sym; sym = q)
 214         {
 215           q = sym->next;
 216           if (sym->mod == mod)
 217             {
 218               *p = q;
 219               grub_free ((void *) sym->name);
 220               grub_free (sym);
 221             }
 222           else
 223             p = &sym->next;
 224         }
 225     }
 226 }
 227
 228 /* Return the address of a section whose index is N.  */
 229 static void *
 230 grub_dl_get_section_addr (grub_dl_t mod, unsigned n)
 231 {
 232   grub_dl_segment_t seg;
 233
 234   for (seg = mod->segment; seg; seg = seg->next)
 235     if (seg->section == n)
 236       return seg->addr;
 237
 238   return 0;
 239 }
 240
 241 /* Check if EHDR is a valid ELF header.  */
 242 grub_err_t
 243 grub_dl_check_header (void *ehdr, grub_size_t size)
 244 {
 245   Elf_Ehdr *e = ehdr;
 246
 247   /* Check the header size.  */
 248   if (size < sizeof (Elf_Ehdr))
 249     return grub_error (GRUB_ERR_BAD_OS, "ELF header smaller than expected");
 250
 251   /* Check the magic numbers.  */
 252   if (grub_arch_dl_check_header (ehdr)
 253       || e->e_ident[EI_MAG0] != ELFMAG0
 254       || e->e_ident[EI_MAG1] != ELFMAG1
 255       || e->e_ident[EI_MAG2] != ELFMAG2
 256       || e->e_ident[EI_MAG3] != ELFMAG3
 257       || e->e_ident[EI_VERSION] != EV_CURRENT
 258       || e->e_version != EV_CURRENT)
 259     return grub_error (GRUB_ERR_BAD_OS, "invalid arch independent ELF magic");
 260
 261   return GRUB_ERR_NONE;
 262 }
 263
 264 /* Load all segments from memory specified by E.  */
 265 static grub_err_t
 266 grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e)
 267 {
 268   unsigned i;
 269   Elf_Shdr *s;
 270
 271   for (i = 0, s = (Elf_Shdr *)((char *) e + e->e_shoff);
 272        i < e->e_shnum;
 273        i++, s = (Elf_Shdr *)((char *) s + e->e_shentsize))
 274     {
 275       if (s->sh_flags & SHF_ALLOC)
 276         {
 277           grub_dl_segment_t seg;
 278
 279           seg = (grub_dl_segment_t) grub_malloc (sizeof (*seg));
 280           if (! seg)
 281             return grub_errno;
 282
 283           if (s->sh_size)
 284             {
 285               void *addr;
 286
 287               addr = grub_memalign (s->sh_addralign, s->sh_size);
 288               if (! addr)
 289                 {
 290                   grub_free (seg);
 291                   return grub_errno;
 292                 }
 293
 294               switch (s->sh_type)
 295                 {
 296                 case SHT_PROGBITS:
 297                   grub_memcpy (addr, (char *) e + s->sh_offset, s->sh_size);
 298                   break;
 299                 case SHT_NOBITS:
 300                   grub_memset (addr, 0, s->sh_size);
 301                   break;
 302                 }
 303
 304               seg->addr = addr;
 305             }
 306           else
 307             seg->addr = 0;
 308
 309           seg->size = s->sh_size;
 310           seg->section = i;
 311           seg->next = mod->segment;
 312           mod->segment = seg;
 313         }
 314     }
 315
 316   return GRUB_ERR_NONE;
 317 }
 318
 319 static grub_err_t
 320 grub_dl_resolve_symbols (grub_dl_t mod, Elf_Ehdr *e)
 321 {
 322   unsigned i;
 323   Elf_Shdr *s;
 324   Elf_Sym *sym;
 325   const char *str;
 326   Elf_Word size, entsize;
 327
 328   for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
 329        i < e->e_shnum;
 330        i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
 331     if (s->sh_type == SHT_SYMTAB)
 332       break;
 333
 334   if (i == e->e_shnum)
 335     return grub_error (GRUB_ERR_BAD_MODULE, "no symbol table");
 336
 337   sym = (Elf_Sym *) ((char *) e + s->sh_offset);
 338   size = s->sh_size;
 339   entsize = s->sh_entsize;
 340
 341   s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shentsize * s->sh_link);
 342   str = (char *) e + s->sh_offset;
 343
 344   for (i = 0;
 345        i < size / entsize;
 346        i++, sym = (Elf_Sym *) ((char *) sym + entsize))
 347     {
 348       unsigned char type = ELF_ST_TYPE (sym->st_info);
 349       unsigned char bind = ELF_ST_BIND (sym->st_info);
 350       const char *name = str + sym->st_name;
 351
 352       switch (type)
 353         {
 354         case STT_NOTYPE:
 355           /* Resolve a global symbol.  */
 356           if (sym->st_name != 0 && sym->st_shndx == 0)
 357             {
 358               sym->st_value = (Elf_Addr) grub_dl_resolve_symbol (name);
 359               if (! sym->st_value)
 360                 return grub_error (GRUB_ERR_BAD_MODULE,
 361                                    "the symbol `%s' not found", name);
 362             }
 363           else
 364             sym->st_value = 0;
 365           break;
 366
 367         case STT_OBJECT:
 368           sym->st_value += (Elf_Addr) grub_dl_get_section_addr (mod,
 369                                                                 sym->st_shndx);
 370           if (bind != STB_LOCAL)
 371             if (grub_dl_register_symbol (name, (void *) sym->st_value, mod))
 372               return grub_errno;
 373           break;
 374
 375         case STT_FUNC:
 376           sym->st_value += (Elf_Addr) grub_dl_get_section_addr (mod,
 377                                                                 sym->st_shndx);
 378           if (bind != STB_LOCAL)
 379             if (grub_dl_register_symbol (name, (void *) sym->st_value, mod))
 380               return grub_errno;
 381
 382           if (grub_strcmp (name, "grub_mod_init") == 0)
 383             mod->init = (void (*) (grub_dl_t)) sym->st_value;
 384           else if (grub_strcmp (name, "grub_mod_fini") == 0)
 385             mod->fini = (void (*) (void)) sym->st_value;
 386           break;
 387
 388         case STT_SECTION:
 389           sym->st_value = (Elf_Addr) grub_dl_get_section_addr (mod,
 390                                                                sym->st_shndx);
 391           break;
 392
 393         case STT_FILE:
 394           sym->st_value = 0;
 395           break;
 396
 397         default:
 398           return grub_error (GRUB_ERR_BAD_MODULE,
 399                              "unknown symbol type `%d'", (int) type);
 400         }
 401     }
 402
 403   return GRUB_ERR_NONE;
 404 }
 405
 406 static void
 407 grub_dl_call_init (grub_dl_t mod)
 408 {
 409   if (mod->init)
 410     (mod->init) (mod);
 411 }
 412
 413 static grub_err_t
 414 grub_dl_resolve_name (grub_dl_t mod, Elf_Ehdr *e)
 415 {
 416   Elf_Shdr *s;
 417   const char *str;
 418   unsigned i;
 419
 420   s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
 421   str = (char *) e + s->sh_offset;
 422
 423   for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
 424        i < e->e_shnum;
 425        i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
 426     if (grub_strcmp (str + s->sh_name, ".modname") == 0)
 427       {
 428         mod->name = grub_strdup ((char *) e + s->sh_offset);
 429         if (! mod->name)
 430           return grub_errno;
 431         break;
 432       }
 433
 434   if (i == e->e_shnum)
 435     return grub_error (GRUB_ERR_BAD_MODULE, "no module name found");
 436
 437   return GRUB_ERR_NONE;
 438 }
 439
 440 static grub_err_t
 441 grub_dl_resolve_dependencies (grub_dl_t mod, Elf_Ehdr *e)
 442 {
 443   Elf_Shdr *s;
 444   const char *str;
 445   unsigned i;
 446
 447   s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
 448   str = (char *) e + s->sh_offset;
 449
 450   for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
 451        i < e->e_shnum;
 452        i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
 453     if (grub_strcmp (str + s->sh_name, ".moddeps") == 0)
 454       {
 455         const char *name = (char *) e + s->sh_offset;
 456         const char *max = name + s->sh_size;
 457
 458         while (name < max)
 459           {
 460             grub_dl_t m;
 461             grub_dl_dep_t dep;
 462
 463             m = grub_dl_load (name);
 464             if (! m)
 465               return grub_errno;
 466
 467             grub_dl_ref (m);
 468
 469             dep = (grub_dl_dep_t) grub_malloc (sizeof (*dep));
 470             if (! dep)
 471               return grub_errno;
 472
 473             dep->mod = m;
 474             dep->next = mod->dep;
 475             mod->dep = dep;
 476
 477             name += grub_strlen (name) + 1;
 478           }
 479       }
 480
 481   return GRUB_ERR_NONE;
 482 }
 483
 484 int
 485 grub_dl_ref (grub_dl_t mod)
 486 {
 487   grub_dl_dep_t dep;
 488
 489   for (dep = mod->dep; dep; dep = dep->next)
 490     grub_dl_ref (dep->mod);
 491
 492   return ++mod->ref_count;
 493 }
 494
 495 int
 496 grub_dl_unref (grub_dl_t mod)
 497 {
 498   grub_dl_dep_t dep;
 499
 500   for (dep = mod->dep; dep; dep = dep->next)
 501     grub_dl_unref (dep->mod);
 502
 503   return --mod->ref_count;
 504 }
 505
 506 static void
 507 grub_dl_flush_cache (grub_dl_t mod)
 508 {
 509   grub_dl_segment_t seg;
 510
 511   for (seg = mod->segment; seg; seg = seg->next) {
 512     if (seg->size) {
 513       grub_dprintf ("modules", "flushing 0x%x bytes at %p\n", seg->size,
 514                     seg->addr);
 515       grub_arch_sync_caches (seg->addr, seg->size);
 516     }
 517   }
 518 }
 519
 520 /* Load a module from core memory.  */
 521 grub_dl_t
 522 grub_dl_load_core (void *addr, grub_size_t size)
 523 {
 524   Elf_Ehdr *e;
 525   grub_dl_t mod;
 526
 527   grub_dprintf ("modules", "module at %p, size 0x%x\n", addr, size);
 528   e = addr;
 529   if (grub_dl_check_header (e, size))
 530     return 0;
 531
 532   if (e->e_type != ET_REL)
 533     {
 534       grub_error (GRUB_ERR_BAD_MODULE, "invalid ELF file type");
 535       return 0;
 536     }
 537
 538   /* Make sure that every section is within the core.  */
 539   if (size < e->e_shoff + e->e_shentsize * e->e_shnum)
 540     {
 541       grub_error (GRUB_ERR_BAD_OS, "ELF sections outside core");
 542       return 0;
 543     }
 544
 545   mod = (grub_dl_t) grub_malloc (sizeof (*mod));
 546   if (! mod)
 547     return 0;
 548
 549   mod->name = 0;
 550   mod->ref_count = 1;
 551   mod->dep = 0;
 552   mod->segment = 0;
 553   mod->init = 0;
 554   mod->fini = 0;
 555
 556   grub_dprintf ("modules", "relocating to %p\n", mod);
 557   if (grub_dl_resolve_name (mod, e)
 558       || grub_dl_resolve_dependencies (mod, e)
 559       || grub_dl_load_segments (mod, e)
 560       || grub_dl_resolve_symbols (mod, e)
 561       || grub_arch_dl_relocate_symbols (mod, e))
 562     {
 563       mod->fini = 0;
 564       grub_dl_unload (mod);
 565       return 0;
 566     }
 567
 568   grub_dl_flush_cache (mod);
 569
 570   grub_dprintf ("modules", "module name: %s\n", mod->name);
 571   grub_dprintf ("modules", "init function: %p\n", mod->init);
 572   grub_dl_call_init (mod);
 573
 574   if (grub_dl_add (mod))
 575     {
 576       grub_dl_unload (mod);
 577       return 0;
 578     }
 579
 580   return mod;
 581 }
 582
 583 /* Load a module from the file FILENAME.  */
 584 grub_dl_t
 585 grub_dl_load_file (const char *filename)
 586 {
 587   grub_file_t file;
 588   grub_ssize_t size;
 589   void *core = 0;
 590   grub_dl_t mod = 0;
 591
 592   file = grub_file_open (filename);
 593   if (! file)
 594     return 0;
 595
 596   size = grub_file_size (file);
 597   core = grub_malloc (size);
 598   if (! core)
 599     goto failed;
 600
 601   if (grub_file_read (file, core, size) != (int) size)
 602     goto failed;
 603
 604   mod = grub_dl_load_core (core, size);
 605   if (! mod)
 606     goto failed;
 607
 608   mod->ref_count = 0;
 609
 610  failed:
 611   grub_file_close (file);
 612   grub_free (core);
 613
 614   return mod;
 615 }
 616
 617 /* Load a module using a symbolic name.  */
 618 grub_dl_t
 619 grub_dl_load (const char *name)
 620 {
 621   char *filename;
 622   grub_dl_t mod;
 623   char *grub_dl_dir = grub_env_get ("prefix");
 624
 625   mod = grub_dl_get (name);
 626   if (mod)
 627     return mod;
 628
 629   if (! grub_dl_dir)
 630     grub_fatal ("module dir is not initialized yet");
 631
 632   filename = (char *) grub_malloc (grub_strlen (grub_dl_dir) + 1
 633                                    + grub_strlen (name) + 4 + 1);
 634   if (! filename)
 635     return 0;
 636
 637   grub_sprintf (filename, "%s/%s.mod", grub_dl_dir, name);
 638   mod = grub_dl_load_file (filename);
 639   grub_free (filename);
 640
 641   if (! mod)
 642     return 0;
 643
 644   if (grub_strcmp (mod->name, name) != 0)
 645     grub_error (GRUB_ERR_BAD_MODULE, "mismatched names");
 646
 647   return mod;
 648 }
 649
 650 /* Unload the module MOD.  */
 651 int
 652 grub_dl_unload (grub_dl_t mod)
 653 {
 654   grub_dl_dep_t dep, depn;
 655   grub_dl_segment_t seg, segn;
 656
 657   if (mod->ref_count > 0)
 658     return 0;
 659
 660   if (mod->fini)
 661     (mod->fini) ();
 662
 663   grub_dl_remove (mod);
 664   grub_dl_unregister_symbols (mod);
 665
 666   for (dep = mod->dep; dep; dep = depn)
 667     {
 668       depn = dep->next;
 669
 670       if (! grub_dl_unref (dep->mod))
 671         grub_dl_unload (dep->mod);
 672
 673       grub_free (dep);
 674     }
 675
 676   for (seg = mod->segment; seg; seg = segn)
 677     {
 678       segn = seg->next;
 679       grub_free (seg->addr);
 680       grub_free (seg);
 681     }
 682
 683   grub_free (mod->name);
 684   grub_free (mod);
 685   return 1;
 686 }
 687
 688 /* Unload unneeded modules.  */
 689 void
 690 grub_dl_unload_unneeded (void)
 691 {
 692   /* Because grub_dl_remove modifies the list of modules, this
 693      implementation is tricky.  */
 694   grub_dl_list_t p = grub_dl_head;
 695
 696   while (p)
 697     {
 698       if (grub_dl_unload (p->mod))
 699         {
 700           p = grub_dl_head;
 701           continue;
 702         }
 703
 704       p = p->next;
 705     }
 706 }
 707
 708 /* Unload all modules.  */
 709 void
 710 grub_dl_unload_all (void)
 711 {
 712   while (grub_dl_head)
 713     {
 714       grub_dl_list_t p;
 715
 716       grub_dl_unload_unneeded ();
 717
 718       /* Force to decrement the ref count. This will purge pre-loaded
 719          modules and manually inserted modules.  */
 720       for (p = grub_dl_head; p; p = p->next)
 721         p->mod->ref_count--;
 722     }
 723 }