lib/libc/gen/nlist.c

   1 /*
   2  * Copyright (c) 1989, 1993
   3  *      The Regents of the University of California.  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  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  *      $FreeBSD: src/lib/libc/gen/nlist.c,v 1.12.2.1 2001/07/11 23:59:09 obrien Exp $
  30  *
  31  * @(#)nlist.c  8.1 (Berkeley) 6/4/93
  32  */
  33
  34 #include "namespace.h"
  35 #include <sys/param.h>
  36 #include <sys/mman.h>
  37 #include <sys/stat.h>
  38 #include <sys/file.h>
  39
  40 #include <errno.h>
  41 #include <a.out.h>
  42 #include <stdio.h>
  43 #include <string.h>
  44 #include <unistd.h>
  45 #include "un-namespace.h"
  46
  47 #define _NLIST_DO_AOUT
  48 #define _NLIST_DO_ELF
  49
  50 #ifdef _NLIST_DO_ELF
  51 #include <machine/elf.h>
  52 #include <elf-hints.h>
  53 #endif
  54
  55 int     __fdnlist(int, struct nlist *);
  56 int     __aout_fdnlist(int, struct nlist *);
  57 int     __elf_fdnlist(int, struct nlist *);
  58
  59 int
  60 nlist(const char *name, struct nlist *list)
  61 {
  62         int fd, n;
  63
  64         fd = _open(name, O_RDONLY | O_CLOEXEC, 0);
  65         if (fd < 0)
  66                 return (-1);
  67         n = __fdnlist(fd, list);
  68         _close(fd);
  69         return (n);
  70 }
  71
  72 static struct nlist_handlers {
  73         int     (*fn)(int fd, struct nlist *list);
  74 } nlist_fn[] = {
  75 #ifdef _NLIST_DO_AOUT
  76         { __aout_fdnlist },
  77 #endif
  78 #ifdef _NLIST_DO_ELF
  79         { __elf_fdnlist },
  80 #endif
  81 };
  82
  83 int
  84 __fdnlist(int fd, struct nlist *list)
  85 {
  86         int n = -1;
  87         size_t i;
  88
  89         for (i = 0; i < NELEM(nlist_fn); i++) {
  90                 n = (nlist_fn[i].fn)(fd, list);
  91                 if (n != -1)
  92                         break;
  93         }
  94         return (n);
  95 }
  96
  97 #define ISLAST(p)       (p->n_un.n_name == 0 || p->n_un.n_name[0] == 0)
  98
  99 #ifdef _NLIST_DO_AOUT
 100 int
 101 __aout_fdnlist(int fd, struct nlist *list)
 102 {
 103         struct nlist *p, *symtab;
 104         caddr_t strtab, a_out_mmap;
 105         off_t stroff, symoff;
 106         u_long symsize;
 107         int nent;
 108         struct exec * exec;
 109         struct stat st;
 110
 111         /* check that file is at least as large as struct exec! */
 112         if ((_fstat(fd, &st) < 0) || (st.st_size < sizeof(struct exec)))
 113                 return (-1);
 114
 115         /* Check for files too large to mmap. */
 116         if (st.st_size > SIZE_T_MAX) {
 117                 errno = EFBIG;
 118                 return (-1);
 119         }
 120
 121         /*
 122          * Map the whole a.out file into our address space.
 123          * We then find the string table withing this area.
 124          * We do not just mmap the string table, as it probably
 125          * does not start at a page boundary - we save ourselves a
 126          * lot of nastiness by mmapping the whole file.
 127          *
 128          * This gives us an easy way to randomly access all the strings,
 129          * without making the memory allocation permanent as with
 130          * malloc/free (i.e., munmap will return it to the system).
 131          */
 132         a_out_mmap = mmap(NULL, (size_t)st.st_size, PROT_READ, MAP_PRIVATE, fd, (off_t)0);
 133         if (a_out_mmap == MAP_FAILED)
 134                 return (-1);
 135
 136         exec = (struct exec *)a_out_mmap;
 137         if (N_BADMAG(*exec)) {
 138                 munmap(a_out_mmap, (size_t)st.st_size);
 139                 return (-1);
 140         }
 141
 142         symoff = N_SYMOFF(*exec);
 143         symsize = exec->a_syms;
 144         stroff = symoff + symsize;
 145
 146         /* find the string table in our mmapped area */
 147         strtab = a_out_mmap + stroff;
 148         symtab = (struct nlist *)(a_out_mmap + symoff);
 149
 150         /*
 151          * clean out any left-over information for all valid entries.
 152          * Type and value defined to be 0 if not found; historical
 153          * versions cleared other and desc as well.  Also figure out
 154          * the largest string length so don't read any more of the
 155          * string table than we have to.
 156          *
 157          * XXX clearing anything other than n_type and n_value violates
 158          * the semantics given in the man page.
 159          */
 160         nent = 0;
 161         for (p = list; !ISLAST(p); ++p) {
 162                 p->n_type = 0;
 163                 p->n_other = 0;
 164                 p->n_desc = 0;
 165                 p->n_value = 0;
 166                 ++nent;
 167         }
 168
 169         while (symsize > 0) {
 170                 int soff;
 171
 172                 symsize-= sizeof(struct nlist);
 173                 soff = symtab->n_un.n_strx;
 174
 175
 176                 if (soff != 0 && (symtab->n_type & N_STAB) == 0)
 177                         for (p = list; !ISLAST(p); p++)
 178                                 if (!strcmp(&strtab[soff], p->n_un.n_name)) {
 179                                         p->n_value = symtab->n_value;
 180                                         p->n_type = symtab->n_type;
 181                                         p->n_desc = symtab->n_desc;
 182                                         p->n_other = symtab->n_other;
 183                                         if (--nent <= 0)
 184                                                 break;
 185                                 }
 186                 symtab++;
 187         }
 188         munmap(a_out_mmap, (size_t)st.st_size);
 189         return (nent);
 190 }
 191 #endif
 192
 193 #ifdef _NLIST_DO_ELF
 194 static void     elf_sym_to_nlist(struct nlist *, Elf_Sym *, Elf_Shdr *, int);
 195
 196 /*
 197  * __elf_is_okay__ - Determine if ehdr really
 198  * is ELF and valid for the target platform.
 199  *
 200  * WARNING:  This is NOT a ELF ABI function and
 201  * as such it's use should be restricted.
 202  */
 203 static int
 204 __elf_is_okay__(Elf_Ehdr *ehdr)
 205 {
 206         int retval = 0;
 207         /*
 208          * We need to check magic, class size, endianess,
 209          * and version before we look at the rest of the
 210          * Elf_Ehdr structure.  These few elements are
 211          * represented in a machine independant fashion.
 212          */
 213         if (IS_ELF(*ehdr) &&
 214             ehdr->e_ident[EI_CLASS] == ELF_TARG_CLASS &&
 215             ehdr->e_ident[EI_DATA] == ELF_TARG_DATA &&
 216             ehdr->e_ident[EI_VERSION] == ELF_TARG_VER) {
 217
 218                 /* Now check the machine dependant header */
 219                 if (ehdr->e_machine == ELF_TARG_MACH &&
 220                     ehdr->e_version == ELF_TARG_VER)
 221                         retval = 1;
 222         }
 223         return retval;
 224 }
 225
 226 int
 227 __elf_fdnlist(int fd, struct nlist *list)
 228 {
 229         struct nlist *p;
 230         Elf_Off symoff = 0, symstroff = 0;
 231         Elf_Word symsize = 0, symstrsize = 0;
 232         Elf_Sword cc, i;
 233         int nent = -1;
 234         int errsave;
 235         Elf_Sym sbuf[1024];
 236         Elf_Sym *s;
 237         Elf_Ehdr ehdr;
 238         char *strtab = NULL;
 239         Elf_Shdr *shdr = NULL;
 240         Elf_Word shdr_size;
 241         void *base;
 242         struct stat st;
 243
 244         /* Make sure obj is OK */
 245         if (lseek(fd, (off_t)0, SEEK_SET) == -1 ||
 246             _read(fd, &ehdr, sizeof(Elf_Ehdr)) != sizeof(Elf_Ehdr) ||
 247             !__elf_is_okay__(&ehdr) ||
 248             _fstat(fd, &st) < 0)
 249                 return (-1);
 250
 251         /* calculate section header table size */
 252         shdr_size = ehdr.e_shentsize * ehdr.e_shnum;
 253
 254 #ifndef __x86_64__
 255         /* Make sure it's not too big to mmap */
 256         if (shdr_size > SIZE_T_MAX) {
 257                 errno = EFBIG;
 258                 return (-1);
 259         }
 260 #endif
 261
 262         /* mmap section header table */
 263         base = mmap(NULL, (size_t)shdr_size, PROT_READ, 0, fd,
 264             (off_t)ehdr.e_shoff);
 265         if (base == MAP_FAILED)
 266                 return (-1);
 267         shdr = (Elf_Shdr *)base;
 268
 269         /*
 270          * Find the symbol table entry and it's corresponding
 271          * string table entry.  Version 1.1 of the ABI states
 272          * that there is only one symbol table but that this
 273          * could change in the future.
 274          */
 275         for (i = 0; i < ehdr.e_shnum; i++) {
 276                 if (shdr[i].sh_type == SHT_SYMTAB) {
 277                         symoff = shdr[i].sh_offset;
 278                         symsize = shdr[i].sh_size;
 279                         symstroff = shdr[shdr[i].sh_link].sh_offset;
 280                         symstrsize = shdr[shdr[i].sh_link].sh_size;
 281                         break;
 282                 }
 283         }
 284
 285 #ifndef __x86_64__
 286         /* Check for files too large to mmap. */
 287         if (symstrsize > SIZE_T_MAX) {
 288                 errno = EFBIG;
 289                 goto done;
 290         }
 291 #endif
 292
 293         /*
 294          * Map string table into our address space.  This gives us
 295          * an easy way to randomly access all the strings, without
 296          * making the memory allocation permanent as with malloc/free
 297          * (i.e., munmap will return it to the system).
 298          */
 299         base = mmap(NULL, (size_t)symstrsize, PROT_READ, 0, fd,
 300             (off_t)symstroff);
 301         if (base == MAP_FAILED)
 302                 goto done;
 303         strtab = (char *)base;
 304
 305         /*
 306          * clean out any left-over information for all valid entries.
 307          * Type and value defined to be 0 if not found; historical
 308          * versions cleared other and desc as well.  Also figure out
 309          * the largest string length so don't read any more of the
 310          * string table than we have to.
 311          *
 312          * XXX clearing anything other than n_type and n_value violates
 313          * the semantics given in the man page.
 314          */
 315         nent = 0;
 316         for (p = list; !ISLAST(p); ++p) {
 317                 p->n_type = 0;
 318                 p->n_other = 0;
 319                 p->n_desc = 0;
 320                 p->n_value = 0;
 321                 ++nent;
 322         }
 323
 324         /* Don't process any further if object is stripped. */
 325         if (symoff == 0)
 326                 goto done;
 327
 328         if (lseek(fd, (off_t) symoff, SEEK_SET) == -1) {
 329                 nent = -1;
 330                 goto done;
 331         }
 332
 333         while (symsize > 0 && nent > 0) {
 334                 cc = MIN(symsize, sizeof(sbuf));
 335                 if (_read(fd, sbuf, cc) != cc)
 336                         break;
 337                 symsize -= cc;
 338                 for (s = sbuf; cc > 0 && nent > 0; ++s, cc -= sizeof(*s)) {
 339                         char *name;
 340                         struct nlist *p_local;
 341
 342                         name = strtab + s->st_name;
 343                         if (name[0] == '\0')
 344                                 continue;
 345                         for (p_local = list; !ISLAST(p_local); p_local++) {
 346                                 if ((p_local->n_un.n_name[0] == '_' &&
 347                                     strcmp(name, p_local->n_un.n_name+1) == 0)
 348                                     || strcmp(name, p_local->n_un.n_name) == 0) {
 349                                         elf_sym_to_nlist(p_local, s, shdr,
 350                                             ehdr.e_shnum);
 351                                         if (--nent <= 0)
 352                                                 break;
 353                                 }
 354                         }
 355                 }
 356         }
 357 done:
 358         errsave = errno;
 359         if (strtab != NULL)
 360                 munmap(strtab, symstrsize);
 361         if (shdr != NULL)
 362                 munmap(shdr, shdr_size);
 363         errno = errsave;
 364         return (nent);
 365 }
 366
 367 /*
 368  * Convert an Elf_Sym into an nlist structure.  This fills in only the
 369  * n_value and n_type members.
 370  */
 371 static void
 372 elf_sym_to_nlist(struct nlist *nl, Elf_Sym *s, Elf_Shdr *shdr, int shnum)
 373 {
 374         nl->n_value = s->st_value;
 375
 376         switch (s->st_shndx) {
 377         case SHN_UNDEF:
 378         case SHN_COMMON:
 379                 nl->n_type = N_UNDF;
 380                 break;
 381         case SHN_ABS:
 382                 nl->n_type = ELF_ST_TYPE(s->st_info) == STT_FILE ?
 383                     N_FN : N_ABS;
 384                 break;
 385         default:
 386                 if (s->st_shndx >= shnum)
 387                         nl->n_type = N_UNDF;
 388                 else {
 389                         Elf_Shdr *sh = shdr + s->st_shndx;
 390
 391                         nl->n_type = sh->sh_type == SHT_PROGBITS ?
 392                             (sh->sh_flags & SHF_WRITE ? N_DATA : N_TEXT) :
 393                             (sh->sh_type == SHT_NOBITS ? N_BSS : N_UNDF);
 394                 }
 395                 break;
 396         }
 397
 398         if (ELF_ST_BIND(s->st_info) == STB_GLOBAL ||
 399             ELF_ST_BIND(s->st_info) == STB_WEAK)
 400                 nl->n_type |= N_EXT;
 401 }
 402 #endif /* _NLIST_DO_ELF */