libexec/ld.elf_so/map_object.c

   1 /*      $NetBSD: map_object.c,v 1.53 2014/10/30 07:53:41 martin Exp $    */
   2
   3 /*
   4  * Copyright 1996 John D. Polstra.
   5  * Copyright 1996 Matt Thomas <matt@3am-software.com>
   6  * Copyright 2002 Charles M. Hannum <root@ihack.net>
   7  * All rights reserved.
   8  *
   9  * Redistribution and use in source and binary forms, with or without
  10  * modification, are permitted provided that the following conditions
  11  * are met:
  12  * 1. Redistributions of source code must retain the above copyright
  13  *    notice, this list of conditions and the following disclaimer.
  14  * 2. Redistributions in binary form must reproduce the above copyright
  15  *    notice, this list of conditions and the following disclaimer in the
  16  *    documentation and/or other materials provided with the distribution.
  17  * 3. All advertising materials mentioning features or use of this software
  18  *    must display the following acknowledgement:
  19  *      This product includes software developed by John Polstra.
  20  * 4. The name of the author may not be used to endorse or promote products
  21  *    derived from this software without specific prior written permission.
  22  *
  23  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  24  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  25  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  26  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  27  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  28  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  29  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  30  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  31  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  32  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #ifndef lint
  37 __RCSID("$NetBSD: map_object.c,v 1.53 2014/10/30 07:53:41 martin Exp $");
  38 #endif /* not lint */
  39
  40 #include <errno.h>
  41 #include <stddef.h>
  42 #include <stdlib.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45 #include <sys/stat.h>
  46 #include <sys/types.h>
  47 #include <sys/mman.h>
  48
  49 #include "debug.h"
  50 #include "rtld.h"
  51
  52 static int protflags(int);      /* Elf flags -> mmap protection */
  53
  54 #define EA_UNDEF                (~(Elf_Addr)0)
  55
  56 /*
  57  * Map a shared object into memory.  The argument is a file descriptor,
  58  * which must be open on the object and positioned at its beginning.
  59  *
  60  * The return value is a pointer to a newly-allocated Obj_Entry structure
  61  * for the shared object.  Returns NULL on failure.
  62  */
  63 Obj_Entry *
  64 _rtld_map_object(const char *path, int fd, const struct stat *sb)
  65 {
  66         Obj_Entry       *obj;
  67         Elf_Ehdr        *ehdr;
  68         Elf_Phdr        *phdr;
  69 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
  70         Elf_Phdr        *phtls;
  71 #endif
  72         size_t           phsize;
  73         Elf_Phdr        *phlimit;
  74         Elf_Phdr        *segs[2];
  75         int              nsegs;
  76         caddr_t          mapbase = MAP_FAILED;
  77         size_t           mapsize = 0;
  78         int              mapflags;
  79         Elf_Off          base_offset;
  80 #ifdef MAP_ALIGNED
  81         Elf_Addr         base_alignment;
  82 #endif
  83         Elf_Addr         base_vaddr;
  84         Elf_Addr         base_vlimit;
  85         Elf_Addr         text_vlimit;
  86         int              text_flags;
  87         caddr_t          base_addr;
  88         Elf_Off          data_offset;
  89         Elf_Addr         data_vaddr;
  90         Elf_Addr         data_vlimit;
  91         int              data_flags;
  92         caddr_t          data_addr;
  93 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
  94         Elf_Addr         tls_vaddr = 0; /* Noise GCC */
  95 #endif
  96         Elf_Addr         phdr_vaddr;
  97         size_t           phdr_memsz;
  98 #if defined(__minix) && (defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II))
  99         caddr_t          gap_addr;
 100         size_t           gap_size;
 101 #endif /* defined(__minix) */
 102         int i;
 103 #ifdef RTLD_LOADER
 104         Elf_Addr         clear_vaddr;
 105         caddr_t          clear_addr;
 106         size_t           nclear;
 107 #endif
 108
 109         if (sb != NULL && sb->st_size < (off_t)sizeof (Elf_Ehdr)) {
 110                 _rtld_error("%s: not ELF file (too short)", path);
 111                 return NULL;
 112         }
 113
 114         obj = _rtld_obj_new();
 115         obj->path = xstrdup(path);
 116         obj->pathlen = strlen(path);
 117         if (sb != NULL) {
 118                 obj->dev = sb->st_dev;
 119                 obj->ino = sb->st_ino;
 120         }
 121
 122         ehdr = mmap(NULL, _rtld_pagesz, PROT_READ, MAP_FILE | MAP_SHARED, fd,
 123             (off_t)0);
 124         obj->ehdr = ehdr;
 125         if (ehdr == MAP_FAILED) {
 126                 _rtld_error("%s: read error: %s", path, xstrerror(errno));
 127                 goto bad;
 128         }
 129         /* Make sure the file is valid */
 130         if (memcmp(ELFMAG, ehdr->e_ident, SELFMAG) != 0) {
 131                 _rtld_error("%s: not ELF file (magic number bad)", path);
 132                 goto bad;
 133         }
 134         if (ehdr->e_ident[EI_CLASS] != ELFCLASS) {
 135                 _rtld_error("%s: invalid ELF class %x; expected %x", path,
 136                     ehdr->e_ident[EI_CLASS], ELFCLASS);
 137                 goto bad;
 138         }
 139         /* Elf_e_ident includes class */
 140         if (ehdr->e_ident[EI_VERSION] != EV_CURRENT ||
 141             ehdr->e_version != EV_CURRENT ||
 142             ehdr->e_ident[EI_DATA] != ELFDEFNNAME(MACHDEP_ENDIANNESS)) {
 143                 _rtld_error("%s: unsupported file version", path);
 144                 goto bad;
 145         }
 146         if (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) {
 147                 _rtld_error("%s: unsupported file type", path);
 148                 goto bad;
 149         }
 150         switch (ehdr->e_machine) {
 151                 ELFDEFNNAME(MACHDEP_ID_CASES)
 152         default:
 153                 _rtld_error("%s: unsupported machine", path);
 154                 goto bad;
 155         }
 156
 157         /*
 158          * We rely on the program header being in the first page.  This is
 159          * not strictly required by the ABI specification, but it seems to
 160          * always true in practice.  And, it simplifies things considerably.
 161          */
 162         assert(ehdr->e_phentsize == sizeof(Elf_Phdr));
 163         assert(ehdr->e_phoff + ehdr->e_phnum * sizeof(Elf_Phdr) <=
 164             _rtld_pagesz);
 165
 166         /*
 167          * Scan the program header entries, and save key information.
 168          *
 169          * We rely on there being exactly two load segments, text and data,
 170          * in that order.
 171          */
 172         phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff);
 173 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
 174         phtls = NULL;
 175 #endif
 176         phsize = ehdr->e_phnum * sizeof(phdr[0]);
 177         obj->phdr = NULL;
 178         phdr_vaddr = EA_UNDEF;
 179         phdr_memsz = 0;
 180         phlimit = phdr + ehdr->e_phnum;
 181         nsegs = 0;
 182         while (phdr < phlimit) {
 183                 switch (phdr->p_type) {
 184                 case PT_INTERP:
 185                         obj->interp = (void *)(uintptr_t)phdr->p_vaddr;
 186                         dbg(("%s: PT_INTERP %p", obj->path, obj->interp));
 187                         break;
 188
 189                 case PT_LOAD:
 190                         if (nsegs < 2)
 191                                 segs[nsegs] = phdr;
 192                         ++nsegs;
 193
 194                         dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_LOAD",
 195                             (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
 196                         break;
 197
 198                 case PT_PHDR:
 199                         phdr_vaddr = phdr->p_vaddr;
 200                         phdr_memsz = phdr->p_memsz;
 201                         dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_PHDR",
 202                             (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
 203                         break;
 204
 205                 case PT_DYNAMIC:
 206                         obj->dynamic = (void *)(uintptr_t)phdr->p_vaddr;
 207                         dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_DYNAMIC",
 208                             (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
 209                         break;
 210
 211 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
 212                 case PT_TLS:
 213                         phtls = phdr;
 214                         dbg(("%s: %s %p phsize %" PRImemsz, obj->path, "PT_TLS",
 215                             (void *)(uintptr_t)phdr->p_vaddr, phdr->p_memsz));
 216                         break;
 217 #endif
 218 #ifdef __ARM_EABI__
 219                 case PT_ARM_EXIDX:
 220                         obj->exidx_start = (void *)(uintptr_t)phdr->p_vaddr;
 221                         obj->exidx_sz = phdr->p_memsz;
 222                         break;
 223 #endif
 224                 }
 225
 226                 ++phdr;
 227         }
 228         phdr = (Elf_Phdr *) ((caddr_t)ehdr + ehdr->e_phoff);
 229         obj->entry = (void *)(uintptr_t)ehdr->e_entry;
 230         if (!obj->dynamic) {
 231                 _rtld_error("%s: not dynamically linked", path);
 232                 goto bad;
 233         }
 234         if (nsegs != 2) {
 235                 _rtld_error("%s: wrong number of segments (%d != 2)", path,
 236                     nsegs);
 237                 goto bad;
 238         }
 239
 240         /*
 241          * Map the entire address space of the object as a file
 242          * region to stake out our contiguous region and establish a
 243          * base for relocation.  We use a file mapping so that
 244          * the kernel will give us whatever alignment is appropriate
 245          * for the platform we're running on.
 246          *
 247          * We map it using the text protection, map the data segment
 248          * into the right place, then map an anon segment for the bss
 249          * and unmap the gaps left by padding to alignment.
 250          */
 251
 252 #ifdef MAP_ALIGNED
 253         base_alignment = segs[0]->p_align;
 254 #endif
 255         base_offset = round_down(segs[0]->p_offset);
 256         base_vaddr = round_down(segs[0]->p_vaddr);
 257         base_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_memsz);
 258         text_vlimit = round_up(segs[0]->p_vaddr + segs[0]->p_memsz);
 259         text_flags = protflags(segs[0]->p_flags);
 260         data_offset = round_down(segs[1]->p_offset);
 261         data_vaddr = round_down(segs[1]->p_vaddr);
 262         data_vlimit = round_up(segs[1]->p_vaddr + segs[1]->p_filesz);
 263         data_flags = protflags(segs[1]->p_flags);
 264 #ifdef RTLD_LOADER
 265         clear_vaddr = segs[1]->p_vaddr + segs[1]->p_filesz;
 266 #endif
 267
 268         obj->textsize = text_vlimit - base_vaddr;
 269         obj->vaddrbase = base_vaddr;
 270         obj->isdynamic = ehdr->e_type == ET_DYN;
 271
 272 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
 273         if (phtls != NULL) {
 274                 ++_rtld_tls_dtv_generation;
 275                 obj->tlsindex = ++_rtld_tls_max_index;
 276                 obj->tlssize = phtls->p_memsz;
 277                 obj->tlsalign = phtls->p_align;
 278                 obj->tlsinitsize = phtls->p_filesz;
 279                 tls_vaddr = phtls->p_vaddr;
 280         }
 281 #endif
 282
 283         obj->phdr_loaded = false;
 284         for (i = 0; i < nsegs; i++) {
 285                 if (phdr_vaddr != EA_UNDEF &&
 286                     segs[i]->p_vaddr <= phdr_vaddr &&
 287                     segs[i]->p_memsz >= phdr_memsz) {
 288                         obj->phdr_loaded = true;
 289                         break;
 290                 }
 291                 if (segs[i]->p_offset <= ehdr->e_phoff &&
 292                     segs[i]->p_memsz >= phsize) {
 293                         phdr_vaddr = segs[i]->p_vaddr + ehdr->e_phoff;
 294                         phdr_memsz = phsize;
 295                         obj->phdr_loaded = true;
 296                         break;
 297                 }
 298         }
 299         if (obj->phdr_loaded) {
 300                 obj->phdr = (void *)(uintptr_t)phdr_vaddr;
 301                 obj->phsize = phdr_memsz;
 302         } else {
 303                 Elf_Phdr *buf;
 304                 buf = xmalloc(phsize);
 305                 if (buf == NULL) {
 306                         _rtld_error("%s: cannot allocate program header", path);
 307                         goto bad;
 308                 }
 309                 memcpy(buf, phdr, phsize);
 310                 obj->phdr = buf;
 311                 obj->phsize = phsize;
 312         }
 313         dbg(("%s: phdr %p phsize %zu (%s)", obj->path, obj->phdr, obj->phsize,
 314              obj->phdr_loaded ? "loaded" : "allocated"));
 315
 316         /* Unmap header if it overlaps the first load section. */
 317         if (base_offset < _rtld_pagesz) {
 318                 munmap(ehdr, _rtld_pagesz);
 319                 obj->ehdr = MAP_FAILED;
 320         }
 321
 322         /*
 323          * Calculate log2 of the base section alignment.
 324          */
 325         mapflags = 0;
 326 #ifdef MAP_ALIGNED
 327         if (base_alignment > _rtld_pagesz) {
 328                 unsigned int log2 = 0;
 329                 for (; base_alignment > 1; base_alignment >>= 1)
 330                         log2++;
 331                 mapflags = MAP_ALIGNED(log2);
 332         }
 333 #endif
 334
 335 #ifdef RTLD_LOADER
 336         base_addr = obj->isdynamic ? NULL : (caddr_t)base_vaddr;
 337 #else
 338         base_addr = NULL;
 339 #endif
 340         mapsize = base_vlimit - base_vaddr;
 341         mapbase = mmap(base_addr, mapsize, text_flags,
 342             mapflags | MAP_FILE | MAP_PRIVATE, fd, base_offset);
 343         if (mapbase == MAP_FAILED) {
 344                 _rtld_error("mmap of entire address space failed: %s",
 345                     xstrerror(errno));
 346                 goto bad;
 347         }
 348
 349         /* Overlay the data segment onto the proper region. */
 350         data_addr = mapbase + (data_vaddr - base_vaddr);
 351         if (mmap(data_addr, data_vlimit - data_vaddr, data_flags,
 352             MAP_FILE | MAP_PRIVATE | MAP_FIXED, fd, data_offset) ==
 353             MAP_FAILED) {
 354                 _rtld_error("mmap of data failed: %s", xstrerror(errno));
 355                 goto bad;
 356         }
 357
 358         /* Overlay the bss segment onto the proper region. */
 359 #if defined(__minix)
 360         /* MINIX's mmap is strict and refuses 0-bytes mappings. */
 361         if (0 < base_vlimit - data_vlimit)
 362 #endif /*defined(__minix) */
 363         if (mmap(mapbase + data_vlimit - base_vaddr, base_vlimit - data_vlimit,
 364             data_flags, MAP_ANON | MAP_PRIVATE | MAP_FIXED, -1, 0) ==
 365             MAP_FAILED) {
 366                 _rtld_error("mmap of bss failed: %s", xstrerror(errno));
 367                 goto bad;
 368         }
 369
 370         /* Unmap the gap between the text and data. */
 371 #if !defined(__minix)
 372         gap_addr = mapbase + round_up(text_vlimit - base_vaddr);
 373         gap_size = data_addr - gap_addr;
 374         if (gap_size != 0 && mprotect(gap_addr, gap_size, PROT_NONE) == -1) {
 375                 _rtld_error("mprotect of text -> data gap failed: %s",
 376                     xstrerror(errno));
 377                 goto bad;
 378         }
 379 #endif /* !defined(__minix) */
 380
 381 #ifdef RTLD_LOADER
 382         /* Clear any BSS in the last page of the data segment. */
 383         clear_addr = mapbase + (clear_vaddr - base_vaddr);
 384         if ((nclear = data_vlimit - clear_vaddr) > 0)
 385                 memset(clear_addr, 0, nclear);
 386
 387         /* Non-file portion of BSS mapped above. */
 388 #endif
 389
 390 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
 391         if (phtls != NULL)
 392                 obj->tlsinit = mapbase + tls_vaddr;
 393 #endif
 394
 395         obj->mapbase = mapbase;
 396         obj->mapsize = mapsize;
 397         obj->relocbase = mapbase - base_vaddr;
 398
 399         if (obj->dynamic)
 400                 obj->dynamic = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->dynamic);
 401         if (obj->entry)
 402                 obj->entry = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->entry);
 403         if (obj->interp)
 404                 obj->interp = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->interp);
 405         if (obj->phdr_loaded)
 406                 obj->phdr =  (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->phdr);
 407 #ifdef __ARM_EABI__
 408         if (obj->exidx_start)
 409                 obj->exidx_start = (void *)(obj->relocbase + (Elf_Addr)(uintptr_t)obj->exidx_start);
 410 #endif
 411
 412         return obj;
 413
 414 bad:
 415         if (obj->ehdr != MAP_FAILED)
 416                 munmap(obj->ehdr, _rtld_pagesz);
 417         if (mapbase != MAP_FAILED)
 418                 munmap(mapbase, mapsize);
 419         _rtld_obj_free(obj);
 420         return NULL;
 421 }
 422
 423 void
 424 _rtld_obj_free(Obj_Entry *obj)
 425 {
 426         Objlist_Entry *elm;
 427         Name_Entry *entry;
 428
 429 #if defined(__HAVE_TLS_VARIANT_I) || defined(__HAVE_TLS_VARIANT_II)
 430         if (obj->tls_done)
 431                 _rtld_tls_offset_free(obj);
 432 #endif
 433         xfree(obj->path);
 434         while (obj->needed != NULL) {
 435                 Needed_Entry *needed = obj->needed;
 436                 obj->needed = needed->next;
 437                 xfree(needed);
 438         }
 439         while ((entry = SIMPLEQ_FIRST(&obj->names)) != NULL) {
 440                 SIMPLEQ_REMOVE_HEAD(&obj->names, link);
 441                 xfree(entry);
 442         }
 443         while ((elm = SIMPLEQ_FIRST(&obj->dldags)) != NULL) {
 444                 SIMPLEQ_REMOVE_HEAD(&obj->dldags, link);
 445                 xfree(elm);
 446         }
 447         while ((elm = SIMPLEQ_FIRST(&obj->dagmembers)) != NULL) {
 448                 SIMPLEQ_REMOVE_HEAD(&obj->dagmembers, link);
 449                 xfree(elm);
 450         }
 451         if (!obj->phdr_loaded)
 452                 xfree((void *)(uintptr_t)obj->phdr);
 453 #ifdef COMBRELOC
 454         _rtld_combreloc_reset(obj);
 455 #endif
 456         xfree(obj);
 457 }
 458
 459 Obj_Entry *
 460 _rtld_obj_new(void)
 461 {
 462         Obj_Entry *obj;
 463
 464         obj = CNEW(Obj_Entry);
 465         SIMPLEQ_INIT(&obj->names);
 466         SIMPLEQ_INIT(&obj->dldags);
 467         SIMPLEQ_INIT(&obj->dagmembers);
 468         return obj;
 469 }
 470
 471 /*
 472  * Given a set of ELF protection flags, return the corresponding protection
 473  * flags for MMAP.
 474  */
 475 static int
 476 protflags(int elfflags)
 477 {
 478         int prot = 0;
 479
 480         if (elfflags & PF_R)
 481                 prot |= PROT_READ;
 482 #ifdef RTLD_LOADER
 483         if (elfflags & PF_W)
 484                 prot |= PROT_WRITE;
 485 #endif
 486         if (elfflags & PF_X)
 487                 prot |= PROT_EXEC;
 488 #if defined(__minix)
 489         /* Minix has to map it writable so we can do relocations
 490          * as we don't have mprotect() yet.
 491          */
 492         prot |= PROT_WRITE;
 493 #endif /* defined(__minix) */
 494         return prot;
 495 }