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_prot(int);   /* Elf flags -> mmap protection */
  43 static int convert_flags(int); /* Elf flags -> mmap flags */
  44
  45 /*
  46  * Map a shared object into memory.  The "fd" argument is a file descriptor,
  47  * which must be open on the object and positioned at its beginning.
  48  * The "path" argument is a pathname that is used only for error messages.
  49  *
  50  * The return value is a pointer to a newly-allocated Obj_Entry structure
  51  * for the shared object.  Returns NULL on failure.
  52  */
  53 Obj_Entry *
  54 map_object(int fd, const char *path, const struct stat *sb)
  55 {
  56     Obj_Entry *obj;
  57     Elf_Ehdr *hdr;
  58     int i;
  59     Elf_Phdr *phdr;
  60     Elf_Phdr *phlimit;
  61     Elf_Phdr **segs;
  62     int nsegs;
  63     Elf_Phdr *phdyn;
  64     Elf_Phdr *phinterp;
  65     Elf_Phdr *phtls;
  66     caddr_t mapbase;
  67     caddr_t shlib_base;
  68     size_t mapsize;
  69     Elf_Addr base_vaddr;
  70     Elf_Addr base_vlimit;
  71     caddr_t base_addr;
  72     Elf_Off data_offset;
  73     Elf_Addr data_vaddr;
  74     Elf_Addr data_vlimit;
  75     caddr_t data_addr;
  76     int data_prot;
  77     int data_flags;
  78     Elf_Addr clear_vaddr;
  79     caddr_t clear_addr;
  80     caddr_t clear_page;
  81     Elf_Addr phdr_vaddr;
  82     size_t nclear, phsize;
  83     Elf_Addr bss_vaddr;
  84     Elf_Addr bss_vlimit;
  85     caddr_t bss_addr;
  86     Elf_Word stack_flags;
  87     Elf_Addr relro_page;
  88     size_t relro_size;
  89     Elf_Addr note_start;
  90     Elf_Addr note_end;
  91
  92     hdr = get_elf_header(fd, path);
  93     if (hdr == NULL)
  94         return (NULL);
  95
  96     if (__ld_sharedlib_base) {
  97         shlib_base = (void *)(intptr_t)strtoul(__ld_sharedlib_base, NULL, 0);
  98     } else {
  99         shlib_base = NULL;
 100     }
 101
 102     /*
 103      * Scan the program header entries, and save key information.
 104      *
 105      * We expect that the loadable segments are ordered by load address.
 106      */
 107     phdr = (Elf_Phdr *) ((char *)hdr + hdr->e_phoff);
 108     phsize  = hdr->e_phnum * sizeof (phdr[0]);
 109     phlimit = phdr + hdr->e_phnum;
 110     nsegs = -1;
 111     phdyn = phinterp = phtls = NULL;
 112     phdr_vaddr = 0;
 113     relro_page = 0;
 114     relro_size = 0;
 115     note_start = 0;
 116     note_end = 0;
 117     segs = alloca(sizeof(segs[0]) * hdr->e_phnum);
 118     stack_flags = RTLD_DEFAULT_STACK_PF_EXEC | PF_R | PF_W;
 119     while (phdr < phlimit) {
 120         switch (phdr->p_type) {
 121
 122         case PT_INTERP:
 123             phinterp = phdr;
 124             break;
 125
 126         case PT_LOAD:
 127             segs[++nsegs] = phdr;
 128             if ((segs[nsegs]->p_align & (PAGE_SIZE - 1)) != 0) {
 129                 _rtld_error("%s: PT_LOAD segment %d not page-aligned",
 130                     path, nsegs);
 131                 goto error;
 132             }
 133             break;
 134
 135         case PT_PHDR:
 136             phdr_vaddr = phdr->p_vaddr;
 137             phsize = phdr->p_memsz;
 138             break;
 139
 140         case PT_DYNAMIC:
 141             phdyn = phdr;
 142             break;
 143
 144         case PT_TLS:
 145             phtls = phdr;
 146             break;
 147
 148         case PT_GNU_STACK:
 149             stack_flags = phdr->p_flags;
 150             break;
 151
 152         case PT_GNU_RELRO:
 153             relro_page = phdr->p_vaddr;
 154             relro_size = phdr->p_memsz;
 155             break;
 156
 157         case PT_NOTE:
 158             if (phdr->p_offset > PAGE_SIZE ||
 159               phdr->p_offset + phdr->p_filesz > PAGE_SIZE)
 160                 break;
 161             note_start = (Elf_Addr)(char *)hdr + phdr->p_offset;
 162             note_end = note_start + phdr->p_filesz;
 163             break;
 164         }
 165
 166         ++phdr;
 167     }
 168     if (phdyn == NULL) {
 169         _rtld_error("%s: object is not dynamically-linked", path);
 170         goto error;
 171     }
 172
 173     if (nsegs < 0) {
 174         _rtld_error("%s: too few PT_LOAD segments", path);
 175         goto error;
 176     }
 177
 178     /*
 179      * Map the entire address space of the object, to stake out our
 180      * contiguous region, and to establish the base address for relocation.
 181      */
 182     base_vaddr = trunc_page(segs[0]->p_vaddr);
 183     base_vlimit = round_page(segs[nsegs]->p_vaddr + segs[nsegs]->p_memsz);
 184     mapsize = base_vlimit - base_vaddr;
 185     base_addr = (caddr_t) base_vaddr;
 186
 187     if (base_addr == NULL && shlib_base) {
 188         size_t limit = 1024 * 256 * 1024;
 189         size_t offset;
 190
 191         for (offset = 0; offset < limit; offset += 256 * 1024) {
 192                 mapbase = mmap(shlib_base + offset, mapsize,
 193                                PROT_NONE,
 194                                MAP_ANON | MAP_PRIVATE | MAP_NOCORE |
 195                                MAP_TRYFIXED,
 196                                -1, 0);
 197                 if (mapbase != MAP_FAILED)
 198                         break;
 199         }
 200     } else {
 201         mapbase = mmap(base_addr, mapsize,
 202                        PROT_NONE,
 203                        MAP_ANON | MAP_PRIVATE | MAP_NOCORE,
 204                        -1, 0);
 205     }
 206     if (mapbase == (caddr_t) -1) {
 207         _rtld_error("%s: mmap of entire address space failed: %s",
 208           path, rtld_strerror(errno));
 209         goto error;
 210     }
 211     if (base_addr != NULL && mapbase != base_addr) {
 212         _rtld_error("%s: mmap returned wrong address: wanted %p, got %p",
 213           path, base_addr, mapbase);
 214         goto error1;
 215     }
 216
 217     for (i = 0; i <= nsegs; i++) {
 218         /* Overlay the segment onto the proper region. */
 219         data_offset = trunc_page(segs[i]->p_offset);
 220         data_vaddr = trunc_page(segs[i]->p_vaddr);
 221         data_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_filesz);
 222         data_addr = mapbase + (data_vaddr - base_vaddr);
 223         data_prot = convert_prot(segs[i]->p_flags);
 224         data_flags = convert_flags(segs[i]->p_flags) | MAP_FIXED;
 225         if (mmap(data_addr, data_vlimit - data_vaddr, data_prot,
 226           data_flags, fd, data_offset) == (caddr_t) -1) {
 227             _rtld_error("%s: mmap of data failed: %s", path,
 228                 rtld_strerror(errno));
 229             goto error1;
 230         }
 231
 232         /* Do BSS setup */
 233         if (segs[i]->p_filesz != segs[i]->p_memsz) {
 234
 235             /* Clear any BSS in the last page of the segment. */
 236             clear_vaddr = segs[i]->p_vaddr + segs[i]->p_filesz;
 237             clear_addr = mapbase + (clear_vaddr - base_vaddr);
 238             clear_page = mapbase + (trunc_page(clear_vaddr) - base_vaddr);
 239
 240             if ((nclear = data_vlimit - clear_vaddr) > 0) {
 241                 /* Make sure the end of the segment is writable */
 242                 if ((data_prot & PROT_WRITE) == 0 && -1 ==
 243                      mprotect(clear_page, PAGE_SIZE, data_prot|PROT_WRITE)) {
 244                         _rtld_error("%s: mprotect failed: %s", path,
 245                             rtld_strerror(errno));
 246                         goto error1;
 247                 }
 248
 249                 memset(clear_addr, 0, nclear);
 250
 251                 /*
 252                  * reset the data protection back, enable the segment to be
 253                  * coredumped since we modified it.
 254                  */
 255                 if ((data_prot & PROT_WRITE) == 0) {
 256                     madvise(clear_page, PAGE_SIZE, MADV_CORE);
 257                     mprotect(clear_page, PAGE_SIZE, data_prot);
 258                 }
 259             }
 260
 261             /* Overlay the BSS segment onto the proper region. */
 262             bss_vaddr = data_vlimit;
 263             bss_vlimit = round_page(segs[i]->p_vaddr + segs[i]->p_memsz);
 264             bss_addr = mapbase +  (bss_vaddr - base_vaddr);
 265             if (bss_vlimit > bss_vaddr) {       /* There is something to do */
 266                 if (mmap(bss_addr, bss_vlimit - bss_vaddr, data_prot,
 267                     data_flags | MAP_ANON, -1, 0) == (caddr_t)-1) {
 268                     _rtld_error("%s: mmap of bss failed: %s", path,
 269                         rtld_strerror(errno));
 270                     goto error1;
 271                 }
 272             }
 273         }
 274
 275         if (phdr_vaddr == 0 && data_offset <= hdr->e_phoff &&
 276           (data_vlimit - data_vaddr + data_offset) >=
 277           (hdr->e_phoff + hdr->e_phnum * sizeof (Elf_Phdr))) {
 278             phdr_vaddr = data_vaddr + hdr->e_phoff - data_offset;
 279         }
 280     }
 281
 282     obj = obj_new();
 283     if (sb != NULL) {
 284         obj->dev = sb->st_dev;
 285         obj->ino = sb->st_ino;
 286     }
 287     obj->mapbase = mapbase;
 288     obj->mapsize = mapsize;
 289     obj->textsize = round_page(segs[0]->p_vaddr + segs[0]->p_memsz) -
 290       base_vaddr;
 291     obj->vaddrbase = base_vaddr;
 292     obj->relocbase = mapbase - base_vaddr;
 293     obj->dynamic = (const Elf_Dyn *) (obj->relocbase + phdyn->p_vaddr);
 294     if (hdr->e_entry != 0)
 295         obj->entry = (caddr_t) (obj->relocbase + hdr->e_entry);
 296     if (phdr_vaddr != 0) {
 297         obj->phdr = (const Elf_Phdr *) (obj->relocbase + phdr_vaddr);
 298     } else {
 299         obj->phdr = malloc(phsize);
 300         if (obj->phdr == NULL) {
 301             obj_free(obj);
 302             _rtld_error("%s: cannot allocate program header", path);
 303             goto error1;
 304         }
 305         memcpy((char *)obj->phdr, (char *)hdr + hdr->e_phoff, phsize);
 306         obj->phdr_alloc = true;
 307     }
 308     obj->phsize = phsize;
 309     if (phinterp != NULL)
 310         obj->interp = (const char *) (obj->relocbase + phinterp->p_vaddr);
 311     if (phtls != NULL) {
 312         tls_dtv_generation++;
 313         obj->tlsindex = ++tls_max_index;
 314         obj->tlssize = phtls->p_memsz;
 315         obj->tlsalign = phtls->p_align;
 316         obj->tlsinitsize = phtls->p_filesz;
 317         obj->tlsinit = mapbase + phtls->p_vaddr;
 318     }
 319     obj->stack_flags = stack_flags;
 320     if (relro_size) {
 321         obj->relro_page = obj->relocbase + trunc_page(relro_page);
 322         obj->relro_size = round_page(relro_size);
 323     }
 324     if (note_start < note_end)
 325        digest_notes(obj, note_start, note_end);
 326     munmap(hdr, PAGE_SIZE);
 327     return (obj);
 328
 329 error1:
 330     munmap(mapbase, mapsize);
 331 error:
 332     munmap(hdr, PAGE_SIZE);
 333     return (NULL);
 334 }
 335
 336 static Elf_Ehdr *
 337 get_elf_header(int fd, const char *path)
 338 {
 339         Elf_Ehdr *hdr;
 340
 341         /* DragonFly mmap does not have MAP_PREFAULT_READ */
 342         hdr = mmap(NULL, PAGE_SIZE, PROT_READ, MAP_PRIVATE, fd, 0);
 343         if (hdr == (Elf_Ehdr *)MAP_FAILED) {
 344                 _rtld_error("%s: read error: %s", path, rtld_strerror(errno));
 345                 return (NULL);
 346         }
 347
 348         /* Make sure the file is valid */
 349         if (!IS_ELF(*hdr)) {
 350                 _rtld_error("%s: invalid file format", path);
 351                 goto error;
 352         }
 353         if (hdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
 354             hdr->e_ident[EI_DATA] != ELF_TARG_DATA) {
 355                 _rtld_error("%s: unsupported file layout", path);
 356                 goto error;
 357         }
 358         if (hdr->e_ident[EI_VERSION] != EV_CURRENT ||
 359             hdr->e_version != EV_CURRENT) {
 360                 _rtld_error("%s: unsupported file version", path);
 361                 goto error;
 362         }
 363         if (hdr->e_type != ET_EXEC && hdr->e_type != ET_DYN) {
 364                 _rtld_error("%s: unsupported file type", path);
 365                 goto error;
 366         }
 367         if (hdr->e_machine != ELF_TARG_MACH) {
 368                 _rtld_error("%s: unsupported machine", path);
 369                 goto error;
 370         }
 371
 372         /*
 373          * We rely on the program header being in the first page.  This is
 374          * not strictly required by the ABI specification, but it seems to
 375          * always true in practice.  And, it simplifies things considerably.
 376          */
 377         if (hdr->e_phentsize != sizeof(Elf_Phdr)) {
 378                 _rtld_error(
 379             "%s: invalid shared object: e_phentsize != sizeof(Elf_Phdr)", path);
 380                 goto error;
 381         }
 382         if (hdr->e_phoff + hdr->e_phnum * sizeof(Elf_Phdr) >
 383             (size_t)PAGE_SIZE) {
 384                 _rtld_error("%s: program header too large", path);
 385                 goto error;
 386         }
 387         return (hdr);
 388
 389 error:
 390         munmap(hdr, PAGE_SIZE);
 391         return (NULL);
 392 }
 393
 394 void
 395 obj_free(Obj_Entry *obj)
 396 {
 397     Objlist_Entry *elm;
 398
 399     if (obj->tls_done)
 400         free_tls_offset(obj);
 401     while (obj->needed != NULL) {
 402         Needed_Entry *needed = obj->needed;
 403         obj->needed = needed->next;
 404         free(needed);
 405     }
 406     while (!STAILQ_EMPTY(&obj->names)) {
 407         Name_Entry *entry = STAILQ_FIRST(&obj->names);
 408         STAILQ_REMOVE_HEAD(&obj->names, link);
 409         free(entry);
 410     }
 411     while (!STAILQ_EMPTY(&obj->dldags)) {
 412         elm = STAILQ_FIRST(&obj->dldags);
 413         STAILQ_REMOVE_HEAD(&obj->dldags, link);
 414         free(elm);
 415     }
 416     while (!STAILQ_EMPTY(&obj->dagmembers)) {
 417         elm = STAILQ_FIRST(&obj->dagmembers);
 418         STAILQ_REMOVE_HEAD(&obj->dagmembers, link);
 419         free(elm);
 420     }
 421     if (obj->vertab)
 422         free(obj->vertab);
 423     if (obj->origin_path)
 424         free(obj->origin_path);
 425     if (obj->z_origin)
 426         free(obj->rpath);
 427     if (obj->priv)
 428         free(obj->priv);
 429     if (obj->path)
 430         free(obj->path);
 431     if (obj->phdr_alloc)
 432         free((void *)obj->phdr);
 433     free(obj);
 434 }
 435
 436 Obj_Entry *
 437 obj_new(void)
 438 {
 439     Obj_Entry *obj;
 440
 441     obj = CNEW(Obj_Entry);
 442     STAILQ_INIT(&obj->dldags);
 443     STAILQ_INIT(&obj->dagmembers);
 444     STAILQ_INIT(&obj->names);
 445     return obj;
 446 }
 447
 448 /*
 449  * Given a set of ELF protection flags, return the corresponding protection
 450  * flags for MMAP.
 451  */
 452 static int
 453 convert_prot(int elfflags)
 454 {
 455     int prot = 0;
 456     if (elfflags & PF_R)
 457         prot |= PROT_READ;
 458     if (elfflags & PF_W)
 459         prot |= PROT_WRITE;
 460     if (elfflags & PF_X)
 461         prot |= PROT_EXEC;
 462     return prot;
 463 }
 464
 465 static int
 466 convert_flags(int elfflags)
 467 {
 468     int flags = MAP_PRIVATE; /* All mappings are private */
 469
 470     /*
 471      * Readonly mappings are marked "MAP_NOCORE", because they can be
 472      * reconstructed by a debugger.
 473      */
 474     if (!(elfflags & PF_W))
 475         flags |= MAP_NOCORE;
 476     return flags;
 477 }