bootstrap/elfloader.c

   1 /*
   2  Copyright (C) 2006-2011 The AROS Development Team. All rights reserved.
   3  $Id$
   4
   5  Desc: ELF loader extracted from our internal_load_seg_elf in dos.library.
   6  Lang: English
   7  */
   8
   9 #include <inttypes.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13
  14 /* Define this wrapper here, before loading AROS headers,
  15  * so that the defines in <aros/system.h> do not
  16  * confuse GCC's built-in substitutions for strcmp().
  17  */
  18 static inline int Strcmp(const char *a, const char *b) { return strcmp(a, b); }
  19
  20 #include <dos/elf.h>
  21 #include <libraries/debug.h>
  22
  23 #include <elfloader.h>
  24 #include <runtime.h>
  25
  26 #define D(x)
  27 #define DREL(x)
  28 #define DSYM(x)
  29
  30 /* Use own definitions because we may be compiled as 32-bit code but build structures for 64-bit code */
  31 struct ELF_ModuleInfo_t
  32 {
  33     elf_uintptr_t  Next;
  34     elf_uintptr_t  Name;
  35     unsigned short Type;
  36     unsigned short Pad0;        /* On i386 we have different alignment, so do explicit padding */
  37 #ifdef ELF_64BIT
  38     unsigned int   Pad1;
  39 #endif
  40     elf_uintptr_t  eh;
  41     elf_uintptr_t  sh;
  42 };
  43
  44 /* Our own definition of struct KernelBSS, to avoid excessive castings */
  45 struct KernelBSS_t
  46 {
  47     elf_uintptr_t addr;
  48     elf_uintptr_t len;
  49 };
  50
  51 static elf_uintptr_t SysBase_ptr = 0;
  52
  53 /*
  54  * Test for correct ELF header here
  55  */
  56 static char *check_header(struct elfheader *eh)
  57 {
  58     if (eh->ident[0] != 0x7f || eh->ident[1] != 'E'  ||
  59         eh->ident[2] != 'L'  || eh->ident[3] != 'F')
  60         return "Not a ELF file";
  61
  62     if (eh->type != ET_REL || eh->machine != AROS_ELF_MACHINE)
  63         return "Wrong object type or wrong architecture";
  64
  65     /* No error */
  66     return NULL;
  67 }
  68
  69 /*
  70  * Get the memory for chunk and load it
  71  */
  72 static void *load_hunk(void *file, struct sheader *sh, void *addr, struct KernelBSS_t **bss_tracker)
  73 {
  74     uintptr_t align;
  75
  76     /* empty chunk? Who cares :) */
  77     if (!sh->size)
  78         return addr;
  79
  80     D(kprintf("[ELF Loader] Chunk (%ld bytes, align=%ld (%p) @ ", sh->size, sh->addralign, (void *)sh->addralign));
  81     align = sh->addralign - 1;
  82     addr = (char *)(((uintptr_t)addr + align) & ~align);
  83
  84     D(kprintf("%p\n", addr));
  85     sh->addr = (elf_ptr_t)(uintptr_t)addr;
  86
  87     /* copy block of memory from ELF file if it exists */
  88     if (sh->type != SHT_NOBITS)
  89     {
  90         if (read_block(file, sh->offset, (void *)(uintptr_t)sh->addr, sh->size))
  91             return NULL;
  92     }
  93     else
  94     {
  95         memset(addr, 0, sh->size);
  96
  97         (*bss_tracker)->addr = (uintptr_t)addr;
  98         (*bss_tracker)->len = sh->size;
  99         (*bss_tracker)++;
 100     }
 101
 102     return addr + sh->size;
 103 }
 104
 105 static void *copy_data(void *src, void *addr, uintptr_t len)
 106 {
 107     memcpy(addr, src, len);
 108     return addr + len;
 109 }
 110
 111 /* Perform relocations of given section */
 112 static int relocate(struct elfheader *eh, struct sheader *sh, long shrel_idx, elf_uintptr_t DefSysBase)
 113 {
 114     struct sheader *shrel    = &sh[shrel_idx];
 115     struct sheader *shsymtab = &sh[shrel->link];
 116     struct sheader *toreloc  = &sh[shrel->info];
 117
 118     struct symbol *symtab   = (struct symbol *)(uintptr_t)shsymtab->addr;
 119     struct relo   *rel      = (struct relo *)(uintptr_t)shrel->addr;
 120     /* Early cast to uintptr_t omits __udivdi3 call in x86-64 native bootstrap */
 121     unsigned int numrel = (uintptr_t)shrel->size / (uintptr_t)shrel->entsize;
 122     unsigned int i;
 123
 124     struct symbol *SysBase_sym = NULL;
 125
 126     /*
 127      * Ignore relocs if the target section has no allocation. that can happen
 128      * eg. with a .debug PROGBITS and a .rel.debug section
 129      */
 130     if (!(toreloc->flags & SHF_ALLOC))
 131         return 1;
 132
 133     DREL(kprintf("[ELF Loader] performing %d relocations\n", numrel));
 134
 135     for (i=0; i<numrel; i++, rel++)
 136     {
 137         struct symbol *sym = &symtab[ELF_R_SYM(rel->info)];
 138         uintptr_t *p = (void *)(uintptr_t)toreloc->addr + rel->offset;
 139         const char *name = (const char *)(uintptr_t)sh[shsymtab->link].addr + sym->name;
 140         elf_uintptr_t s;
 141
 142 #ifdef __arm__
 143         /*
 144          * R_ARM_V4BX are actually special marks for the linker.
 145          * They even never have a target (shindex == SHN_UNDEF),
 146          * so we simply ignore them before doing any checks.
 147          */
 148         if (ELF_R_TYPE(rel->info) == R_ARM_V4BX)
 149             continue;
 150 #endif
 151
 152         switch (sym->shindex)
 153         {
 154         case SHN_UNDEF:
 155             if (Strcmp(name, "SysBase") == 0) {
 156                 if (!SysBase_ptr)
 157                 {
 158                     SysBase_ptr = DefSysBase;
 159                     D(kprintf("[ELF Loader] SysBase pointer set to default %p\n", (void *)SysBase_ptr));
 160                 }
 161
 162                 s = SysBase_ptr;
 163             } else {
 164                 kprintf("[ELF Loader] Undefined symbol '%s'\n", name);
 165                 return 0;
 166             }
 167             break;
 168
 169         case SHN_COMMON:
 170             kprintf("[ELF Loader] COMMON symbol '%s'\n", name);
 171             return 0;
 172
 173         case SHN_ABS:
 174             if (SysBase_sym == NULL)
 175             {
 176                 if (Strcmp(name, "SysBase") == 0)
 177                 {
 178                     DREL(kprintf("[ELF Loader] got SysBase\n"));
 179                     SysBase_sym = sym;
 180                 }
 181             }
 182
 183             if (SysBase_sym == sym)
 184             {
 185                 if (!SysBase_ptr)
 186                 {
 187                     SysBase_ptr = DefSysBase;
 188                     D(kprintf("[ELF Loader] SysBase pointer set to default %p\n", (void *)SysBase_ptr));
 189                 }
 190
 191                 s = SysBase_ptr;
 192             }
 193             else
 194                 s = sym->value;
 195             break;
 196
 197         default:
 198             s = (uintptr_t)sh[sym->shindex].addr + sym->value;
 199
 200             if (!SysBase_ptr)
 201             {
 202                 /*
 203                  * The first global data symbol named SysBase becomes global SysBase.
 204                  * The idea behind: the first module (kernel.resource) contains global
 205                  * SysBase variable and all other modules are linked to it.
 206                  */
 207                 if (sym->info == ELF_S_INFO(STB_GLOBAL, STT_OBJECT))
 208                 {
 209                     if (Strcmp(name, "SysBase") == 0)
 210                     {
 211                         SysBase_ptr = s;
 212                         D(kprintf("[ELF Loader] SysBase pointer set to %p\n", (void *)SysBase_ptr));
 213                     }
 214                 }
 215             }
 216         }
 217
 218         DREL(kprintf("[ELF Loader] Relocating symbol %s type ", sym->name ? name : "<unknown>"));
 219         switch (ELF_R_TYPE(rel->info))
 220         {
 221 #ifdef ELF_64BIT
 222         case R_X86_64_64: /* 64bit direct/absolute */
 223             *(uint64_t *)p = s + rel->addend;
 224             break;
 225
 226         case R_X86_64_PC32: /* PC relative 32 bit signed */
 227             *(uint32_t *)p = s + rel->addend - (uintptr_t) p;
 228             break;
 229
 230         case R_X86_64_32:
 231             *(uint32_t *)p = (uint64_t)s + (uint64_t)rel->addend;
 232             break;
 233
 234         case R_X86_64_32S:
 235             *(int32_t *)p = (int64_t)s + (int64_t)rel->addend;
 236             break;
 237
 238         case R_X86_64_NONE: /* No reloc */
 239             break;
 240 #else
 241 #ifdef __i386__
 242         case R_386_32: /* 32bit absolute */
 243             DREL(kprintf("R_386_32"));
 244             *p += s;
 245             break;
 246
 247         case R_386_PC32: /* 32bit PC relative */
 248             DREL(kprintf("R_386_PC32"));
 249             *p += (s - (uintptr_t)p);
 250             break;
 251
 252         case R_386_NONE:
 253             DREL(kprintf("R_386_NONE"));
 254             break;
 255 #endif
 256 #endif
 257 #ifdef __mc68000__
 258         case R_68K_32:
 259             *p = s + rel->addend;
 260             break;
 261
 262         case R_68K_PC32:
 263             *p = s + rel->addend - (uint32_t)p;
 264             break;
 265
 266         case R_68k_NONE:
 267             break;
 268 #endif
 269 #if defined(__ppc__) || defined(__powerpc__)
 270         case R_PPC_ADDR32:
 271             *p = s + rel->addend;
 272             break;
 273
 274         case R_PPC_ADDR16_LO:
 275         {
 276             unsigned short *c = (unsigned short *) p;
 277             *c = (s + rel->addend) & 0xffff;
 278         }
 279         break;
 280
 281         case R_PPC_ADDR16_HA:
 282         {
 283             unsigned short *c = (unsigned short *) p;
 284             uint32_t temp = s + rel->addend;
 285             *c = temp >> 16;
 286             if ((temp & 0x8000) != 0)
 287                 (*c)++;
 288         }
 289         break;
 290
 291         case R_PPC_REL16_LO:
 292         {
 293             unsigned short *c = (unsigned short *) p;
 294             *c = (s + rel->addend - (uint32_t)p) & 0xffff;
 295         }
 296         break;
 297
 298         case R_PPC_REL16_HA:
 299         {
 300             unsigned short *c = (unsigned short *) p;
 301             uint32_t temp = s + rel->addend - (uint32_t)p;
 302             *c = temp >> 16;
 303             if ((temp & 0x8000) != 0)
 304                         (*c)++;
 305         }
 306         break;
 307
 308         case R_PPC_REL24:
 309             *p &= ~0x3fffffc;
 310             *p |= (s + rel->addend - (uint32_t)p) & 0x3fffffc;
 311             break;
 312
 313         case R_PPC_REL32:
 314             *p = s + rel->addend - (uint32_t)p;
 315             break;
 316
 317         case R_PPC_NONE:
 318             break;
 319 #endif
 320 #ifdef __arm__
 321         case R_ARM_CALL:
 322         case R_ARM_JUMP24:
 323         case R_ARM_PC24:
 324         case R_ARM_PREL31:
 325             {
 326                 /* On ARM the 24 bit offset is shifted by 2 to the right */
 327                 signed long offset = (*p & 0x00ffffff) << 2;
 328                 /* If highest bit set, make offset negative */
 329                 if (offset & 0x02000000)
 330                     offset -= 0x04000000;
 331
 332                 offset += s - (uint32_t)p;
 333
 334                 offset >>= 2;
 335                 *p &= 0xff000000;
 336                 *p |= offset & 0x00ffffff;
 337             }
 338             break;
 339
 340         case R_ARM_MOVW_ABS_NC:
 341         case R_ARM_MOVT_ABS:
 342             {
 343                 signed long offset = *p;
 344                 offset = ((offset & 0xf0000) >> 4) | (offset & 0xfff);
 345                 offset = (offset ^ 0x8000) - 0x8000;
 346
 347                 offset += s;
 348
 349                 if (ELF_R_TYPE(rel->info) == R_ARM_MOVT_ABS)
 350                     offset >>= 16;
 351
 352                 *p &= 0xfff0f000;
 353                 *p |= ((offset & 0xf000) << 4) | (offset & 0x0fff);
 354             }
 355             break;
 356
 357         case R_ARM_ABS32:
 358             *p += s;
 359             break;
 360
 361         case R_ARM_NONE:
 362             break;
 363 #endif
 364         default:
 365             kprintf("[ELF Loader] Unrecognized relocation type %d %ld\n", i, (long)ELF_R_TYPE(rel->info));
 366             return 0;
 367         }
 368         DREL(kprintf(" -> %p\n", *p));
 369     }
 370     return 1;
 371 }
 372
 373 int GetKernelSize(struct ELFNode *FirstELF, unsigned long *ro_size, unsigned long *rw_size, unsigned long *bss_size)
 374 {
 375     struct ELFNode *n;
 376     unsigned long ksize = 0;
 377     unsigned long rwsize = 0;
 378     unsigned long bsize = sizeof(struct KernelBSS_t);
 379     unsigned short i;
 380
 381     kprintf("[ELF Loader] Calculating kickstart size...\n");
 382
 383     for (n = FirstELF; n; n = n->Next)
 384     {
 385         void *file;
 386         char *errstr = NULL;
 387         unsigned int err;
 388
 389         D(kprintf("[ELF Loader] Checking file %s\n", n->Name));
 390
 391         file = open_file(n, &err);
 392         if (err)
 393         {
 394             DisplayError("Failed to open file %s!\n", n->Name);
 395             return 0;
 396         }
 397
 398         /* Check the header of ELF file */
 399         n->eh = load_block(file, 0, sizeof(struct elfheader), &err);
 400         if (err)
 401         {
 402             errstr = "Failed to read file header";
 403         }
 404         else
 405         {
 406             errstr = check_header(n->eh);
 407             if (!errstr)
 408             {
 409                 n->sh = load_block(file, n->eh->shoff, n->eh->shnum * n->eh->shentsize, &err);
 410                 if (err)
 411                 {
 412                     errstr = "Failed to read section headers";
 413                 }
 414             }
 415         }
 416
 417         close_file(file);
 418         if (errstr)
 419         {
 420             DisplayError("%s: %s\n", n->Name, errstr);
 421             return 0;
 422         }
 423
 424         /*
 425          * Debug data for the module includes:
 426          * - Module descriptor (struct ELF_ModuleInfo_t)
 427          * - ELF file header
 428          * - ELF section header
 429          * - File name
 430          * - One empty pointer for alignment
 431          */
 432         ksize += (sizeof(struct ELF_ModuleInfo_t) + sizeof(struct elfheader) + n->eh->shnum * n->eh->shentsize  +
 433                   strlen(n->Name) + sizeof(void *));
 434
 435         /* Go through all sections and calculate kernel size */
 436         for(i = 0; i < n->eh->shnum; i++)
 437         {
 438             /* Ignore sections with zero lengths */
 439             if (!n->sh[i].size)
 440                 continue;
 441
 442             /*
 443              * We will load:
 444              * - Actual code and data (allocated sections)
 445              * - String tables (for debug data)
 446              * - Symbol tables (for debug data)
 447              */
 448             if ((n->sh[i].flags & SHF_ALLOC) || (n->sh[i].type == SHT_STRTAB) || (n->sh[i].type == SHT_SYMTAB))
 449             {
 450                 /* Add maximum space for alignment */
 451                 unsigned long s = n->sh[i].size + n->sh[i].addralign - 1;
 452
 453                 if (n->sh[i].flags & SHF_WRITE)
 454                     rwsize += s;
 455                 else
 456                     ksize += s;
 457
 458                 if (n->sh[i].type == SHT_NOBITS)
 459                     bsize += sizeof(struct KernelBSS_t);
 460             }
 461         }
 462     }
 463
 464     *ro_size = ksize;
 465     *rw_size = rwsize;
 466
 467     if (bss_size)
 468         *bss_size = bsize;
 469
 470     kprintf("[ELF Loader] Code %lu bytes, data %lu bytes, BSS array %lu bytes\n", ksize, rwsize, bsize);
 471
 472     return 1;
 473 }
 474
 475 /*
 476  * This function loads the listed modules.
 477  * It expects that ELF and section header pointers in the list are already set up by GetKernelSize().
 478  *
 479  * (elf_ptr_t)(uintptr_t) double-casting is needed because in some cases elf_ptr_t is an UQUAD,
 480  * while in most cases it's a pointer (see dos/elf.h).
 481  */
 482 int LoadKernel(struct ELFNode *FirstELF, void *ptr_ro, void *ptr_rw, void *tracker, uintptr_t DefSysBase,
 483                void **kick_end, kernel_entry_fun_t *kernel_entry, struct ELF_ModuleInfo **kernel_debug)
 484 {
 485     struct ELFNode *n;
 486     unsigned int i;
 487     unsigned char need_entry = 1;
 488     struct ELF_ModuleInfo_t *mod;
 489     struct ELF_ModuleInfo_t *prev_mod = NULL;
 490
 491     kprintf("[ELF Loader] Loading kickstart...\n");
 492
 493     for (n = FirstELF; n; n = n->Next)
 494     {
 495         void *file;
 496         unsigned int err;
 497
 498         kprintf("[ELF Loader] Code %p, Data %p, Module %s...\n", ptr_ro, ptr_rw, n->Name);
 499
 500         file = open_file(n, &err);
 501         if (err)
 502         {
 503             DisplayError("Failed to open file %s!\n", n->Name);
 504             return 0;
 505         }
 506
 507         /* Iterate over the section header in order to load some hunks */
 508         for (i=0; i < n->eh->shnum; i++)
 509         {
 510             struct sheader *sh = n->sh;
 511
 512             D(kprintf("[ELF Loader] Section %u... ", i));
 513
 514             if ((sh[i].flags & SHF_ALLOC) || (sh[i].type == SHT_STRTAB) || (sh[i].type == SHT_SYMTAB))
 515             {
 516                 /* Does the section require memory allcation? */
 517                 D(kprintf("Allocated section\n"));
 518
 519                 if (sh[i].flags & SHF_WRITE)
 520                 {
 521                     ptr_rw = load_hunk(file, &sh[i], (void *)ptr_rw, (struct KernelBSS_t **)&tracker);
 522                     if (!ptr_rw)
 523                     {
 524                         DisplayError("%s: Error loading hunk %u!\n", n->Name, i);
 525                         return 0;
 526                     }
 527                 }
 528                 else
 529                 {
 530                     ptr_ro = load_hunk(file, &sh[i], (void *)ptr_ro, (struct KernelBSS_t **)&tracker);
 531                     if (!ptr_ro)
 532                     {
 533                         DisplayError("%s: Error loading hunk %u!\n", n->Name, i);
 534                         return 0;
 535                     }
 536                 }
 537
 538                 /* Remember address of the first code section, this is our entry point */
 539                 if ((sh[i].flags & SHF_EXECINSTR) && need_entry)
 540                 {
 541                     *kernel_entry = (void *)(uintptr_t)sh[i].addr;
 542                     need_entry = 0;
 543                 }
 544             }
 545                 D(else kprintf("Ignored\n");)
 546
 547             D(kprintf("[ELF Loader] Section address: %p, size: %lu\n", sh[i].addr, sh[i].size));
 548         }
 549
 550         /* For every loaded section perform relocations */
 551         D(kprintf("[ELF Loader] Relocating...\n"));
 552         for (i=0; i < n->eh->shnum; i++)
 553         {
 554             struct sheader *sh = n->sh;
 555
 556             if ((sh[i].type == AROS_ELF_REL) && sh[sh[i].info].addr)
 557             {
 558                 sh[i].addr = (elf_ptr_t)(uintptr_t)load_block(file, sh[i].offset, sh[i].size, &err);
 559                 if (err)
 560                 {
 561                     DisplayError("%s: Failed to load relocation section %u\n", n->Name, i);
 562                     return 0;
 563                 }
 564
 565                 if (!relocate(n->eh, sh, i, (uintptr_t)DefSysBase))
 566                 {
 567                     DisplayError("%s: Relocation error in section %u!\n", n->Name, i);
 568                     return 0;
 569                 }
 570
 571                 free_block((void *)(uintptr_t)sh[i].addr);
 572                 sh[i].addr = (elf_ptr_t)0;
 573             }
 574         }
 575
 576         close_file(file);
 577
 578         D(kprintf("[ELF Loader] Adding module debug information...\n"));
 579
 580         /* Align our pointer */
 581         ptr_ro = (void *)(((uintptr_t)ptr_ro + sizeof(void *)) & ~(sizeof(void *) - 1));
 582
 583         /* Allocate module descriptor */
 584         mod = ptr_ro;
 585         ptr_ro += sizeof(struct ELF_ModuleInfo_t);
 586         mod->Next = 0;
 587         mod->Type = DEBUG_ELF;
 588
 589         /* Copy ELF header */
 590         mod->eh  = (uintptr_t)ptr_ro;
 591         ptr_ro = copy_data(n->eh, ptr_ro, sizeof(struct elfheader));
 592
 593         /* Copy section header */
 594         mod->sh = (uintptr_t)ptr_ro;
 595         ptr_ro = copy_data(n->sh, ptr_ro, n->eh->shnum * n->eh->shentsize);
 596
 597         /* Copy module name */
 598         mod->Name = (uintptr_t)ptr_ro;
 599         ptr_ro = copy_data(n->Name, ptr_ro, strlen(n->Name) + 1);
 600
 601         /* Link the module descriptor with previous one */
 602         if (prev_mod)
 603             prev_mod->Next = (uintptr_t)mod;
 604         else
 605             *kernel_debug = (struct ELF_ModuleInfo *)mod;
 606         prev_mod = mod;
 607
 608         free_block(n->sh);
 609         free_block(n->eh);
 610     }
 611
 612     /* Terminate the array of BSS sections */
 613     ((struct KernelBSS_t *)tracker)->addr = 0;
 614     ((struct KernelBSS_t *)tracker)->len  = 0;
 615
 616     /* Return end of kickstart read-only area if requested */
 617     if (kick_end)
 618         *kick_end = ptr_ro;
 619
 620     return 1;
 621 }