libexec/rtld-elf/map_object.c

   1 /*-
   2  * Copyright 1996-1998 John D. Polstra.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  *
  25  * $FreeBSD$
  26  */
  27
  28 #include <sys/param.h>
  29 #include <sys/mman.h>
  30 #include <sys/stat.h>
  31
  32 #include <errno.h>
  33 #include <stddef.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36 #include <unistd.h>
  37
  38 #include "debug.h"
  39 #include "rtld.h"
  40
  41 static Elf_Ehdr *get_elf_header(int, const char *);
  42 static int convert_flags(int); /* Elf flags -> mmap flags */
  43
  44 /*
  45  * Map a shared object into memory.  The "fd" argument is a file descriptor,
  46  * which must be open on the object and positioned at its beginning.
  47  * The "path" argument is a pathname that is used only for error messages.
  48  *
  49  * The return value is a pointer to a newly-allocated Obj_Entry structure
  50  * for the shared object.  Returns NULL on failure.
  51  */
  52 Obj_Entry *
  53 map_object(int fd, const char *path, const struct stat *sb)
  54 {
  55     Obj_Entry *obj;
  56     Elf_Ehdr *hdr;
  57     int i;
  58     Elf_Phdr *phdr;
  59     Elf_Phdr *phlimit;
  60     Elf_Phdr **segs;
  61     int nsegs;
  62     Elf_Phdr *phdyn;
  63     Elf_Phdr *phinterp;
  64     Elf_Phdr *phtls;
  65     caddr_t mapbase;
  66     caddr_t shlib_base;
  67     size_t mapsize;
  68     Elf_Addr base_vaddr;
  69     Elf_Addr base_vlimit;
  70     caddr_t base_addr;
  71     Elf_Off data_offset;
  72     Elf_Addr data_vaddr;
  73     Elf_Addr data_vlimit;
  74     caddr_t data_addr;
  75     int data_prot;
  76     int data_flags;
  77     Elf_Addr clear_vaddr;
  78     caddr_t clear_addr;
  79     caddr_t clear_page;
  80     Elf_Addr phdr_vaddr;
  81     size_t nclear, phsize;
  82     Elf_Addr bss_vaddr;
  83     Elf_Addr bss_vlimit;
  84     caddr_t bss_addr;
  85     Elf_Word stack_flags;
  86     Elf_Addr relro_page;
  87     size_t relro_size;
  88     Elf_Addr note_start;
  89     Elf_Addr note_end;
  90
  91     hdr = get_elf_header(fd, path);
  92     if (hdr == NULL)
  93         return (NULL);
  94
  95     if (__ld_sharedlib_base) {
  96         shlib_base = (void *)(intptr_t)strtoul(__ld_sharedlib_base, NULL, 0);
  97     } else {
  98         shlib_base = NULL;
  99     }
 100
 101     /*
 102      * Scan the program header entries, and save key information.
 103      *
 104      * We expect that the loadable segments are ordered by load address.
 105      */
 106     phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff);
 107     phsize  = hdr->e_phnum * sizeof (phdr[0]);
 108     phlimit = phdr + hdr->e_phnum;
 109     nsegs = -1;
 110     phdyn = phinterp = phtls = NULL;
 111     phdr_vaddr = 0;
 112     relro_page = 0;
 113     relro_size = 0;
 114     note_start = 0;
 115     note_end = 0;
 116     segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
 117     stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
 118     while (phdr < phlimit) {
 119         switch (phdr->p_type) {
 120
 121         case PT_INTERP:
 122             phinterp = phdr;
 123             break;
 124
 125         case PT_LOAD:
 126             segs[++nsegs] = phdr;
 127             if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) {
 128                 _rtld_error("%s: PT_LOAD segment %d not page-aligned",
 129                     path, nsegs);
 130                 goto error;
 131             }
 132             break;
 133
 134         case PT_PHDR:
 135             phdr_vaddr = phdr->p_vaddr;
 136             phsize = phdr->p_memsz;
 137             break;
 138
 139         case PT_DYNAMIC:
 140             phdyn = phdr;
 141             break;
 142
 143         case PT_TLS:
 144             phtls = phdr;
 145             break;
 146
 147         case PT_GNU_STACK:
 148             stack_flags = phdr->p_flags;
 149             break;
 150
 151         case PT_GNU_RELRO:
 152             relro_page = phdr->p_vaddr;
 153             relro_size = phdr->p_memsz;
 154             break;
 155
 156         case PT_NOTE:
 157             if (phdr->p_offset > PAGE_SIZE ||
 158               phdr->p_offset + phdr->p_filesz > PAGE_SIZE)
 159                 break;
 160             note_start = (Elf_Addr)(char *)hdr + phdr->p_offset;
 161             note_end = note_start + phdr->p_filesz;
 162             break;
 163         }
 164
 165         ++phdr;
 166     }
 167     if (phdyn == NULL) {
 168         _rtld_error("%s: object is not dynamically-linked", path);
 169         goto error;
 170     }
 171
 172     if (nsegs < 0) {
 173         _rtld_error("%s: too few PT_LOAD segments", path);
 174         goto error;
 175     }
 176
 177     /*
 178      * Map the entire address space of the object, to stake out our
 179      * contiguous region, and to establish the base address for relocation.
 180      */
 181     base_vaddr = trunc_page(segs[0]->p_vaddr);
 182     base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
 183     mapsize = base_vlimit - base_vaddr;
 184     base_addr = (caddr_t) base_vaddr;
 185
 186     if (base_addr == NULL && shlib_base) {
 187         size_t limit = 1024 * 256 * 1024;
 188         size_t offset;
 189
 190         for (offset = 0; offset < limit; offset += 256 * 1024) {
 191                 mapbase = mmap(shlib_base + offset, mapsize,
 192                                PROT_NONE,
 193                                MAP_ANON | MAP_PRIVATE | MAP_NOCORE |
 194                                MAP_TRYFIXED,
 195                                -1, 0);
 196                 if (mapbase != MAP_FAILED)
 197                         break;
 198         }
 199     } else {
 200         mapbase = mmap(base_addr, mapsize,
 201                        PROT_NONE,
 202                        MAP_ANON | MAP_PRIVATE | MAP_NOCORE,
 203                        -1, 0);
 204     }
 205     if (mapbase == (caddr_t) -1) {
 206         _rtld_error("%s: mmap of entire address space failed: %s",
 207           path, rtld_strerror(errno));
 208         goto error;
 209     }
 210     if (base_addr != NULL && mapbase != base_addr) {
 211         _rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
 212           path, base_addr, mapbase);
 213         goto error1;
 214     }
 215
 216     for (i = 0; i <= nsegs; i++) {
 217         /* Overlay the segment onto the proper region. */
 218         data_offset = trunc_page(segs[i]->p_offset);
 219         data_vaddr = trunc_page(segs[i]->p_vaddr);
 220         data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
 221         data_addr = mapbase + (data_vaddr - base_vaddr);
 222         data_prot = convert_prot(segs[i]->p_flags);
 223         data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
 224         if (mmap(data_addr, data_vlimit - data_vaddr, data_prot,
 225           data_flags, fd, data_offset) == (caddr_t) -1) {
 226             _rtld_error("%s: mmap of data failed: %s", path,
 227                 rtld_strerror(errno));
 228             goto error1;
 229         }
 230
 231         /* Do BSS setup */
 232         if (segs[i]->p_filesz != segs[i]->p_memsz) {
 233
 234             /* Clear any BSS in the last page of the segment. */
 235             clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
 236             clear_addr = mapbase + (clear_vaddr - base_vaddr);
 237             clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
 238
 239             if ((nclear = data_vlimit - clear_vaddr) > 0) {
 240                 /* Make sure the end of the segment is writable */
 241                 if ((data_prot & PROT_WRITE) == 0 && -1 ==
 242                      mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
 243                         _rtld_error("%s: mprotect failed: %s", path,
 244                             rtld_strerror(errno));
 245                         goto error1;
 246                 }
 247
 248                 memset(clear_addr, 0, nclear);
 249
 250                 /*
 251                  * reset the data protection back, enable the segment to be
 252                  * coredumped since we modified it.
 253                  */
 254                 if ((data_prot & PROT_WRITE) == 0) {
 255                     madvise(clear_page, PAGE_SIZE, MADV_CORE);
 256                     mprotect(clear_page, PAGE_SIZE, data_prot);
 257                 }
 258             }
 259
 260             /* Overlay the BSS segment onto the proper region. */
 261             bss_vaddr = data_vlimit;
 262             bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
 263             bss_addr = mapbase +  (bss_vaddr - base_vaddr);
 264             if (bss_vlimit > bss_vaddr) {       /* There is something to do */
 265                 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
 266                     data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) {
 267                     _rtld_error("%s: mmap of bss failed: %s", path,
 268                         rtld_strerror(errno));
 269                     goto error1;
 270                 }
 271             }
 272         }
 273
 274         if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
 275           (data_vlimit - data_vaddr + data_offset) >=
 276           (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
 277             phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
 278         }
 279     }
 280
 281     obj = obj_new();
 282     if (sb != NULL) {
 283         obj->dev = sb->st_dev;
 284         obj->ino = sb->st_ino;
 285     }
 286     obj->mapbase = mapbase;
 287     obj->mapsize = mapsize;
 288     obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
 289       base_vaddr;
 290     obj->vaddrbase = base_vaddr;
 291     obj->relocbase = mapbase - base_vaddr;
 292     obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
 293     if (hdr->e_entry != 0)
 294         obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry);
 295     if (phdr_vaddr != 0) {
 296         obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr);
 297     } else {
 298         obj->phdr = malloc(phsize);
 299         if (obj->phdr == NULL) {
 300             obj_free(obj);
 301             _rtld_error("%s: cannot allocate program header", path);
 302             goto error1;
 303         }
 304         memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize);
 305         obj->phdr_alloc = true;
 306     }
 307     obj->phsize = phsize;
 308     if (phinterp != NULL)
 309         obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
 310     if (phtls != NULL) {
 311         tls_dtv_generation++;
 312         obj->tlsindex = ++tls_max_index;
 313         obj->tlssize = phtls->p_memsz;
 314         obj->tlsalign = phtls->p_align;
 315         obj->tlsinitsize = phtls->p_filesz;
 316         obj->tlsinit = mapbase + phtls->p_vaddr;
 317     }
 318     obj->stack_flags = stack_flags;
 319     if (relro_size) {
 320         obj->relro_page = obj->relocbase + trunc_page(relro_page);
 321         obj->relro_size = round_page(relro_size);
 322     }
 323     if (note_start < note_end)
 324        digest_notes(obj, note_start, note_end);
 325     munmap(hdr, PAGE_SIZE);
 326     return (obj);
 327
 328 error1:
 329     munmap(mapbase, mapsize);
 330 error:
 331     munmap(hdr, PAGE_SIZE);
 332     return (NULL);
 333 }
 334
 335 static Elf_Ehdr *
 336 get_elf_header(int fd, const char *path)
 337 {
 338         Elf_Ehdr *hdr;
 339
 340         /* DragonFly mmap does not have MAP_PREFAULT_READ */
 341         hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE, fd, 0);
 342         if (hdr == (Elf_Ehdr *)MAP_FAILED) {
 343                 _rtld_error("%s: read error: %s", path, rtld_strerror(errno));
 344                 return (NULL);
 345         }
 346
 347         /* Make sure the file is valid */
 348         if (!IS_ELF(*hdr)) {
 349                 _rtld_error("%s: invalid file format", path);
 350                 goto error;
 351         }
 352         if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
 353             hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
 354                 _rtld_error("%s: unsupported file layout", path);
 355                 goto error;
 356         }
 357         if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
 358             hdr->e_version != EV_CURRENT) {
 359                 _rtld_error("%s: unsupported file version", path);
 360                 goto error;
 361         }
 362         if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
 363                 _rtld_error("%s: unsupported file type", path);
 364                 goto error;
 365         }
 366         if (hdr->e_machine != ELF_TARG_MACH) {
 367                 _rtld_error("%s: unsupported machine", path);
 368                 goto error;
 369         }
 370
 371         /*
 372          * We rely on the program header being in the first page.  This is
 373          * not strictly required by the ABI specification, but it seems to
 374          * always true in practice.  And, it simplifies things considerably.
 375          */
 376         if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
 377                 _rtld_error(
 378             "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
 379                 goto error;
 380         }
 381         if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) >
 382             (size_t)PAGE_SIZE) {
 383                 _rtld_error("%s: program header too large", path);
 384                 goto error;
 385         }
 386         return (hdr);
 387
 388 error:
 389         munmap(hdr, PAGE_SIZE);
 390         return (NULL);
 391 }
 392
 393 void
 394 obj_free(Obj_Entry *obj)
 395 {
 396     Objlist_Entry *elm;
 397
 398     if (obj->tls_done)
 399         free_tls_offset(obj);
 400     while (obj->needed != NULL) {
 401         Needed_Entry *needed = obj->needed;
 402         obj->needed = needed->next;
 403         free(needed);
 404     }
 405     while (!STAILQ_EMPTY(&obj->names)) {
 406         Name_Entry *entry = STAILQ_FIRST(&obj->names);
 407         STAILQ_REMOVE_HEAD(&obj->names, link);
 408         free(entry);
 409     }
 410     while (!STAILQ_EMPTY(&obj->dldags)) {
 411         elm = STAILQ_FIRST(&obj->dldags);
 412         STAILQ_REMOVE_HEAD(&obj->dldags, link);
 413         free(elm);
 414     }
 415     while (!STAILQ_EMPTY(&obj->dagmembers)) {
 416         elm = STAILQ_FIRST(&obj->dagmembers);
 417         STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
 418         free(elm);
 419     }
 420     if (obj->vertab)
 421         free(obj->vertab);
 422     if (obj->origin_path)
 423         free(obj->origin_path);
 424     if (obj->z_origin)
 425         free(obj->rpath);
 426     if (obj->priv)
 427         free(obj->priv);
 428     if (obj->path)
 429         free(obj->path);
 430     if (obj->phdr_alloc)
 431         free((void *)obj->phdr);
 432     free(obj);
 433 }
 434
 435 Obj_Entry *
 436 obj_new(void)
 437 {
 438     Obj_Entry *obj;
 439
 440     obj = CNEW(Obj_Entry);
 441     STAILQ_INIT(&obj->dldags);
 442     STAILQ_INIT(&obj->dagmembers);
 443     STAILQ_INIT(&obj->names);
 444     return obj;
 445 }
 446
 447 /*
 448  * Given a set of ELF protection flags, return the corresponding protection
 449  * flags for MMAP.
 450  */
 451 int
 452 convert_prot(int elfflags)
 453 {
 454     int prot = 0;
 455     if (elfflags & PF_R)
 456         prot |= PROT_READ;
 457     if (elfflags & PF_W)
 458         prot |= PROT_WRITE;
 459     if (elfflags & PF_X)
 460         prot |= PROT_EXEC;
 461     return prot;
 462 }
 463
 464 static int
 465 convert_flags(int elfflags)
 466 {
 467     int flags = MAP_PRIVATE; /* All mappings are private */
 468
 469     /*
 470      * Readonly mappings are marked "MAP_NOCORE", because they can be
 471      * reconstructed by a debugger.
 472      */
 473     if (!(elfflags & PF_W))
 474         flags |= MAP_NOCORE;
 475     return flags;
 476 }