kern/dl.c

   1 /* dl.c - loadable module support */
   2 /*
   3  *  GRUB  --  GRand Unified Bootloader
   4  *  Copyright (C) 2002, 2003, 2004  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_HOST_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_HOST_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 /* Load all segments from memory specified by E.  */
 242 static grub_err_t
 243 grub_dl_load_segments (grub_dl_t mod, const Elf_Ehdr *e)
 244 {
 245   unsigned i;
 246   Elf_Shdr *s;
 247
 248   for (i = 0, s = (Elf_Shdr *)((char *) e + e->e_shoff);
 249        i < e->e_shnum;
 250        i++, s = (Elf_Shdr *)((char *) s + e->e_shentsize))
 251     {
 252       if (s->sh_flags & SHF_ALLOC)
 253         {
 254           grub_dl_segment_t seg;
 255
 256           seg = (grub_dl_segment_t) grub_malloc (sizeof (*seg));
 257           if (! seg)
 258             return grub_errno;
 259
 260           if (s->sh_size)
 261             {
 262               void *addr;
 263
 264               addr = grub_memalign (s->sh_addralign, s->sh_size);
 265               if (! addr)
 266                 {
 267                   grub_free (seg);
 268                   return grub_errno;
 269                 }
 270
 271               switch (s->sh_type)
 272                 {
 273                 case SHT_PROGBITS:
 274                   grub_memcpy (addr, (char *) e + s->sh_offset, s->sh_size);
 275                   break;
 276                 case SHT_NOBITS:
 277                   grub_memset (addr, 0, s->sh_size);
 278                   break;
 279                 }
 280
 281               seg->addr = addr;
 282             }
 283           else
 284             seg->addr = 0;
 285
 286           seg->size = s->sh_size;
 287           seg->section = i;
 288           seg->next = mod->segment;
 289           mod->segment = seg;
 290         }
 291     }
 292
 293   return GRUB_ERR_NONE;
 294 }
 295
 296 static grub_err_t
 297 grub_dl_resolve_symbols (grub_dl_t mod, Elf_Ehdr *e)
 298 {
 299   unsigned i;
 300   Elf_Shdr *s;
 301   Elf_Sym *sym;
 302   const char *str;
 303   Elf_Word size, entsize;
 304
 305   for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
 306        i < e->e_shnum;
 307        i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
 308     if (s->sh_type == SHT_SYMTAB)
 309       break;
 310
 311   if (i == e->e_shnum)
 312     return grub_error (GRUB_ERR_BAD_MODULE, "no symbol table");
 313
 314   sym = (Elf_Sym *) ((char *) e + s->sh_offset);
 315   size = s->sh_size;
 316   entsize = s->sh_entsize;
 317
 318   s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shentsize * s->sh_link);
 319   str = (char *) e + s->sh_offset;
 320
 321   for (i = 0;
 322        i < size / entsize;
 323        i++, sym = (Elf_Sym *) ((char *) sym + entsize))
 324     {
 325       unsigned char type = ELF_ST_TYPE (sym->st_info);
 326       unsigned char bind = ELF_ST_BIND (sym->st_info);
 327       const char *name = str + sym->st_name;
 328
 329       switch (type)
 330         {
 331         case STT_NOTYPE:
 332           /* Resolve a global symbol.  */
 333           if (sym->st_name != 0 && sym->st_shndx == 0)
 334             {
 335               sym->st_value = (Elf_Addr) grub_dl_resolve_symbol (name);
 336               if (! sym->st_value)
 337                 return grub_error (GRUB_ERR_BAD_MODULE,
 338                                    "the symbol `%s' not found", name);
 339             }
 340           else
 341             sym->st_value = 0;
 342           break;
 343
 344         case STT_OBJECT:
 345           sym->st_value += (Elf_Addr) grub_dl_get_section_addr (mod,
 346                                                                 sym->st_shndx);
 347           if (bind != STB_LOCAL)
 348             if (grub_dl_register_symbol (name, (void *) sym->st_value, mod))
 349               return grub_errno;
 350           break;
 351
 352         case STT_FUNC:
 353           sym->st_value += (Elf_Addr) grub_dl_get_section_addr (mod,
 354                                                                 sym->st_shndx);
 355           if (bind != STB_LOCAL)
 356             if (grub_dl_register_symbol (name, (void *) sym->st_value, mod))
 357               return grub_errno;
 358
 359           if (grub_strcmp (name, "grub_mod_init") == 0)
 360             mod->init = (void (*) (grub_dl_t)) sym->st_value;
 361           else if (grub_strcmp (name, "grub_mod_fini") == 0)
 362             mod->fini = (void (*) (void)) sym->st_value;
 363           break;
 364
 365         case STT_SECTION:
 366           sym->st_value = (Elf_Addr) grub_dl_get_section_addr (mod,
 367                                                                sym->st_shndx);
 368           break;
 369
 370         case STT_FILE:
 371           sym->st_value = 0;
 372           break;
 373
 374         default:
 375           return grub_error (GRUB_ERR_BAD_MODULE,
 376                              "unknown symbol type `%d'", (int) type);
 377         }
 378     }
 379
 380   return GRUB_ERR_NONE;
 381 }
 382
 383 static void
 384 grub_dl_call_init (grub_dl_t mod)
 385 {
 386   if (mod->init)
 387     (mod->init) (mod);
 388 }
 389
 390 static grub_err_t
 391 grub_dl_resolve_name (grub_dl_t mod, Elf_Ehdr *e)
 392 {
 393   Elf_Shdr *s;
 394   const char *str;
 395   unsigned i;
 396
 397   s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
 398   str = (char *) e + s->sh_offset;
 399
 400   for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
 401        i < e->e_shnum;
 402        i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
 403     if (grub_strcmp (str + s->sh_name, ".modname") == 0)
 404       {
 405         mod->name = grub_strdup ((char *) e + s->sh_offset);
 406         if (! mod->name)
 407           return grub_errno;
 408         break;
 409       }
 410
 411   if (i == e->e_shnum)
 412     return grub_error (GRUB_ERR_BAD_MODULE, "no module name found");
 413
 414   return GRUB_ERR_NONE;
 415 }
 416
 417 static grub_err_t
 418 grub_dl_resolve_dependencies (grub_dl_t mod, Elf_Ehdr *e)
 419 {
 420   Elf_Shdr *s;
 421   const char *str;
 422   unsigned i;
 423
 424   s = (Elf_Shdr *) ((char *) e + e->e_shoff + e->e_shstrndx * e->e_shentsize);
 425   str = (char *) e + s->sh_offset;
 426
 427   for (i = 0, s = (Elf_Shdr *) ((char *) e + e->e_shoff);
 428        i < e->e_shnum;
 429        i++, s = (Elf_Shdr *) ((char *) s + e->e_shentsize))
 430     if (grub_strcmp (str + s->sh_name, ".moddeps") == 0)
 431       {
 432         const char *name = (char *) e + s->sh_offset;
 433         const char *max = name + s->sh_size;
 434
 435         while (name < max)
 436           {
 437             grub_dl_t m;
 438             grub_dl_dep_t dep;
 439
 440             m = grub_dl_load (name);
 441             if (! m)
 442               return grub_errno;
 443
 444             grub_dl_ref (m);
 445
 446             dep = (grub_dl_dep_t) grub_malloc (sizeof (*dep));
 447             if (! dep)
 448               return grub_errno;
 449
 450             dep->mod = m;
 451             dep->next = mod->dep;
 452             mod->dep = dep;
 453
 454             name += grub_strlen (name) + 1;
 455           }
 456       }
 457
 458   return GRUB_ERR_NONE;
 459 }
 460
 461 int
 462 grub_dl_ref (grub_dl_t mod)
 463 {
 464   grub_dl_dep_t dep;
 465
 466   for (dep = mod->dep; dep; dep = dep->next)
 467     grub_dl_ref (dep->mod);
 468
 469   return ++mod->ref_count;
 470 }
 471
 472 int
 473 grub_dl_unref (grub_dl_t mod)
 474 {
 475   grub_dl_dep_t dep;
 476
 477   for (dep = mod->dep; dep; dep = dep->next)
 478     grub_dl_unref (dep->mod);
 479
 480   return --mod->ref_count;
 481 }
 482
 483 static void
 484 grub_dl_flush_cache (grub_dl_t mod)
 485 {
 486   grub_dl_segment_t seg;
 487
 488   for (seg = mod->segment; seg; seg = seg->next)
 489     grub_arch_sync_caches (seg->addr, seg->size);
 490 }
 491
 492 /* Load a module from core memory.  */
 493 grub_dl_t
 494 grub_dl_load_core (void *addr, grub_size_t size)
 495 {
 496   Elf_Ehdr *e;
 497   grub_dl_t mod;
 498
 499   e = addr;
 500   if (! grub_arch_dl_check_header (e, size))
 501     {
 502       grub_error (GRUB_ERR_BAD_MODULE, "invalid ELF header");
 503       return 0;
 504     }
 505
 506   mod = (grub_dl_t) grub_malloc (sizeof (*mod));
 507   if (! mod)
 508     return 0;
 509
 510   mod->name = 0;
 511   mod->ref_count = 1;
 512   mod->dep = 0;
 513   mod->segment = 0;
 514   mod->init = 0;
 515   mod->fini = 0;
 516
 517   if (grub_dl_resolve_name (mod, e)
 518       || grub_dl_resolve_dependencies (mod, e)
 519       || grub_dl_load_segments (mod, e)
 520       || grub_dl_resolve_symbols (mod, e)
 521       || grub_arch_dl_relocate_symbols (mod, e))
 522     {
 523       mod->fini = 0;
 524       grub_dl_unload (mod);
 525       return 0;
 526     }
 527
 528   grub_dl_flush_cache (mod);
 529
 530   grub_dl_call_init (mod);
 531
 532   if (grub_dl_add (mod))
 533     {
 534       grub_dl_unload (mod);
 535       return 0;
 536     }
 537
 538   return mod;
 539 }
 540
 541 /* Load a module from the file FILENAME.  */
 542 grub_dl_t
 543 grub_dl_load_file (const char *filename)
 544 {
 545   grub_file_t file;
 546   grub_ssize_t size;
 547   void *core = 0;
 548   grub_dl_t mod = 0;
 549
 550   file = grub_file_open (filename);
 551   if (! file)
 552     return 0;
 553
 554   size = grub_file_size (file);
 555   core = grub_malloc (size);
 556   if (! core)
 557     goto failed;
 558
 559   if (grub_file_read (file, core, size) != (int) size)
 560     goto failed;
 561
 562   mod = grub_dl_load_core (core, size);
 563   mod->ref_count = 0;
 564
 565  failed:
 566   grub_file_close (file);
 567   grub_free (core);
 568
 569   return mod;
 570 }
 571
 572 /* Load a module using a symbolic name.  */
 573 grub_dl_t
 574 grub_dl_load (const char *name)
 575 {
 576   char *filename;
 577   grub_dl_t mod;
 578   char *grub_dl_dir = grub_env_get ("prefix");
 579
 580   mod = grub_dl_get (name);
 581   if (mod)
 582     return mod;
 583
 584   if (! grub_dl_dir)
 585     grub_fatal ("module dir is not initialized yet");
 586
 587   filename = (char *) grub_malloc (grub_strlen (grub_dl_dir) + 1
 588                                    + grub_strlen (name) + 4 + 1);
 589   if (! filename)
 590     return 0;
 591
 592   grub_sprintf (filename, "%s/%s.mod", grub_dl_dir, name);
 593   mod = grub_dl_load_file (filename);
 594   grub_free (filename);
 595
 596   if (! mod)
 597     return 0;
 598
 599   if (grub_strcmp (mod->name, name) != 0)
 600     grub_error (GRUB_ERR_BAD_MODULE, "mismatched names");
 601
 602   return mod;
 603 }
 604
 605 /* Unload the module MOD.  */
 606 int
 607 grub_dl_unload (grub_dl_t mod)
 608 {
 609   grub_dl_dep_t dep, depn;
 610   grub_dl_segment_t seg, segn;
 611
 612   if (mod->ref_count > 0)
 613     return 0;
 614
 615   if (mod->fini)
 616     (mod->fini) ();
 617
 618   grub_dl_remove (mod);
 619   grub_dl_unregister_symbols (mod);
 620
 621   for (dep = mod->dep; dep; dep = depn)
 622     {
 623       depn = dep->next;
 624
 625       if (! grub_dl_unref (dep->mod))
 626         grub_dl_unload (dep->mod);
 627
 628       grub_free (dep);
 629     }
 630
 631   for (seg = mod->segment; seg; seg = segn)
 632     {
 633       segn = seg->next;
 634       grub_free (seg->addr);
 635       grub_free (seg);
 636     }
 637
 638   grub_free (mod->name);
 639   grub_free (mod);
 640   return 1;
 641 }
 642
 643 /* Unload unneeded modules.  */
 644 void
 645 grub_dl_unload_unneeded (void)
 646 {
 647   /* Because grub_dl_remove modifies the list of modules, this
 648      implementation is tricky.  */
 649   grub_dl_list_t p = grub_dl_head;
 650
 651   while (p)
 652     {
 653       if (grub_dl_unload (p->mod))
 654         {
 655           p = grub_dl_head;
 656           continue;
 657         }
 658
 659       p = p->next;
 660     }
 661 }
 662
 663 /* Unload all modules.  */
 664 void
 665 grub_dl_unload_all (void)
 666 {
 667   while (grub_dl_head)
 668     {
 669       grub_dl_list_t p;
 670
 671       grub_dl_unload_unneeded ();
 672
 673       /* Force to decrement the ref count. This will purge pre-loaded
 674          modules and manually inserted modules.  */
 675       for (p = grub_dl_head; p; p = p->next)
 676         p->mod->ref_count--;
 677     }
 678 }