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  * 4. 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
  30 #if defined(LIBC_SCCS) && !defined(lint)
  31 static char sccsid[] = "@(#)nlist.c     8.1 (Berkeley) 6/4/93";
  32 #endif /* LIBC_SCCS and not lint */
  33 #include <sys/cdefs.h>
  34 __FBSDID("$FreeBSD$");
  35
  36 #include "namespace.h"
  37 #include <sys/param.h>
  38 #include <sys/mman.h>
  39 #include <sys/stat.h>
  40 #include <sys/file.h>
  41 #include <arpa/inet.h>
  42
  43 #include <errno.h>
  44 #include <a.out.h>
  45 #include <stdio.h>
  46 #include <string.h>
  47 #include <unistd.h>
  48 #include "un-namespace.h"
  49
  50 /* i386 is the only current FreeBSD architecture that used a.out format. */
  51 #ifdef __i386__
  52 #define _NLIST_DO_AOUT
  53 #endif
  54 #define _NLIST_DO_ELF
  55
  56 #ifdef _NLIST_DO_ELF
  57 #include <machine/elf.h>
  58 #include <elf-hints.h>
  59 #endif
  60
  61 int __fdnlist(int, struct nlist *);
  62 int __aout_fdnlist(int, struct nlist *);
  63 int __elf_fdnlist(int, struct nlist *);
  64 int __elf_is_okay__(Elf_Ehdr *);
  65
  66 int
  67 nlist(const char *name, struct nlist *list)
  68 {
  69         int fd, n;
  70
  71         fd = _open(name, O_RDONLY | O_CLOEXEC, 0);
  72         if (fd < 0)
  73                 return (-1);
  74         n = __fdnlist(fd, list);
  75         (void)_close(fd);
  76         return (n);
  77 }
  78
  79 static struct nlist_handlers {
  80         int     (*fn)(int fd, struct nlist *list);
  81 } nlist_fn[] = {
  82 #ifdef _NLIST_DO_AOUT
  83         { __aout_fdnlist },
  84 #endif
  85 #ifdef _NLIST_DO_ELF
  86         { __elf_fdnlist },
  87 #endif
  88 };
  89
  90 int
  91 __fdnlist(int fd, struct nlist *list)
  92 {
  93         int n = -1;
  94         unsigned int i;
  95
  96         for (i = 0; i < sizeof(nlist_fn) / sizeof(nlist_fn[0]); i++) {
  97                 n = (nlist_fn[i].fn)(fd, list);
  98                 if (n != -1)
  99                         break;
 100         }
 101         return (n);
 102 }
 103
 104 #define ISLAST(p)       (p->n_un.n_name == 0 || p->n_un.n_name[0] == 0)
 105
 106 #ifdef _NLIST_DO_AOUT
 107 int
 108 __aout_fdnlist(int fd, struct nlist *list)
 109 {
 110         struct nlist *p, *symtab;
 111         caddr_t strtab, a_out_mmap;
 112         off_t stroff, symoff;
 113         u_long symsize;
 114         int nent;
 115         struct exec * exec;
 116         struct stat st;
 117
 118         /* check that file is at least as large as struct exec! */
 119         if ((_fstat(fd, &st) < 0) || (st.st_size < sizeof(struct exec)))
 120                 return (-1);
 121
 122         /* Check for files too large to mmap. */
 123         if (st.st_size > SIZE_T_MAX) {
 124                 errno = EFBIG;
 125                 return (-1);
 126         }
 127
 128         /*
 129          * Map the whole a.out file into our address space.
 130          * We then find the string table withing this area.
 131          * We do not just mmap the string table, as it probably
 132          * does not start at a page boundary - we save ourselves a
 133          * lot of nastiness by mmapping the whole file.
 134          *
 135          * This gives us an easy way to randomly access all the strings,
 136          * without making the memory allocation permanent as with
 137          * malloc/free (i.e., munmap will return it to the system).
 138          */
 139         a_out_mmap = mmap(NULL, (size_t)st.st_size, PROT_READ, MAP_PRIVATE, fd, (off_t)0);
 140         if (a_out_mmap == MAP_FAILED)
 141                 return (-1);
 142
 143         exec = (struct exec *)a_out_mmap;
 144         if (N_BADMAG(*exec)) {
 145                 munmap(a_out_mmap, (size_t)st.st_size);
 146                 return (-1);
 147         }
 148
 149         symoff = N_SYMOFF(*exec);
 150         symsize = exec->a_syms;
 151         stroff = symoff + symsize;
 152
 153         /* find the string table in our mmapped area */
 154         strtab = a_out_mmap + stroff;
 155         symtab = (struct nlist *)(a_out_mmap + symoff);
 156
 157         /*
 158          * clean out any left-over information for all valid entries.
 159          * Type and value defined to be 0 if not found; historical
 160          * versions cleared other and desc as well.  Also figure out
 161          * the largest string length so don't read any more of the
 162          * string table than we have to.
 163          *
 164          * XXX clearing anything other than n_type and n_value violates
 165          * the semantics given in the man page.
 166          */
 167         nent = 0;
 168         for (p = list; !ISLAST(p); ++p) {
 169                 p->n_type = 0;
 170                 p->n_other = 0;
 171                 p->n_desc = 0;
 172                 p->n_value = 0;
 173                 ++nent;
 174         }
 175
 176         while (symsize > 0) {
 177                 int soff;
 178
 179                 symsize-= sizeof(struct nlist);
 180                 soff = symtab->n_un.n_strx;
 181
 182
 183                 if (soff != 0 && (symtab->n_type & N_STAB) == 0)
 184                         for (p = list; !ISLAST(p); p++)
 185                                 if (!strcmp(&strtab[soff], p->n_un.n_name)) {
 186                                         p->n_value = symtab->n_value;
 187                                         p->n_type = symtab->n_type;
 188                                         p->n_desc = symtab->n_desc;
 189                                         p->n_other = symtab->n_other;
 190                                         if (--nent <= 0)
 191                                                 break;
 192                                 }
 193                 symtab++;
 194         }
 195         munmap(a_out_mmap, (size_t)st.st_size);
 196         return (nent);
 197 }
 198 #endif
 199
 200 #ifdef _NLIST_DO_ELF
 201 static void elf_sym_to_nlist(struct nlist *, Elf_Sym *, Elf_Shdr *, int);
 202
 203 /*
 204  * __elf_is_okay__ - Determine if ehdr really
 205  * is ELF and valid for the target platform.
 206  *
 207  * WARNING:  This is NOT an ELF ABI function and
 208  * as such its use should be restricted.
 209  */
 210 int
 211 __elf_is_okay__(Elf_Ehdr *ehdr)
 212 {
 213         int retval = 0;
 214         /*
 215          * We need to check magic, class size, endianess,
 216          * and version before we look at the rest of the
 217          * Elf_Ehdr structure.  These few elements are
 218          * represented in a machine independant fashion.
 219          */
 220         if (IS_ELF(*ehdr) &&
 221             ehdr->e_ident[EI_CLASS] == ELF_TARG_CLASS &&
 222             ehdr->e_ident[EI_DATA] == ELF_TARG_DATA &&
 223             ehdr->e_ident[EI_VERSION] == ELF_TARG_VER) {
 224
 225                 /* Now check the machine dependant header */
 226                 if (ehdr->e_machine == ELF_TARG_MACH &&
 227                     ehdr->e_version == ELF_TARG_VER)
 228                         retval = 1;
 229         }
 230         return retval;
 231 }
 232
 233 int
 234 __elf_fdnlist(int fd, struct nlist *list)
 235 {
 236         struct nlist *p;
 237         Elf_Off symoff = 0, symstroff = 0;
 238         Elf_Size symsize = 0, symstrsize = 0;
 239         Elf_Ssize cc, i;
 240         int nent = -1;
 241         int errsave;
 242         Elf_Sym sbuf[1024];
 243         Elf_Sym *s;
 244         Elf_Ehdr ehdr;
 245         char *strtab = NULL;
 246         Elf_Shdr *shdr = NULL;
 247         Elf_Size shdr_size;
 248         void *base;
 249         struct stat st;
 250
 251         /* Make sure obj is OK */
 252         if (lseek(fd, (off_t)0, SEEK_SET) == -1 ||
 253             _read(fd, &ehdr, sizeof(Elf_Ehdr)) != sizeof(Elf_Ehdr) ||
 254             !__elf_is_okay__(&ehdr) ||
 255             _fstat(fd, &st) < 0)
 256                 return (-1);
 257
 258         /* calculate section header table size */
 259         shdr_size = ehdr.e_shentsize * ehdr.e_shnum;
 260
 261         /* Make sure it's not too big to mmap */
 262         if (shdr_size > SIZE_T_MAX) {
 263                 errno = EFBIG;
 264                 return (-1);
 265         }
 266
 267         /* mmap section header table */
 268         base = mmap(NULL, (size_t)shdr_size, PROT_READ, MAP_PRIVATE, fd,
 269             (off_t)ehdr.e_shoff);
 270         if (base == MAP_FAILED)
 271                 return (-1);
 272         shdr = (Elf_Shdr *)base;
 273
 274         /*
 275          * Find the symbol table entry and it's corresponding
 276          * string table entry.  Version 1.1 of the ABI states
 277          * that there is only one symbol table but that this
 278          * could change in the future.
 279          */
 280         for (i = 0; i < ehdr.e_shnum; i++) {
 281                 if (shdr[i].sh_type == SHT_SYMTAB) {
 282                         symoff = shdr[i].sh_offset;
 283                         symsize = shdr[i].sh_size;
 284                         symstroff = shdr[shdr[i].sh_link].sh_offset;
 285                         symstrsize = shdr[shdr[i].sh_link].sh_size;
 286                         break;
 287                 }
 288         }
 289
 290         /* Check for files too large to mmap. */
 291         if (symstrsize > SIZE_T_MAX) {
 292                 errno = EFBIG;
 293                 goto done;
 294         }
 295         /*
 296          * Map string table into our address space.  This gives us
 297          * an easy way to randomly access all the strings, without
 298          * making the memory allocation permanent as with malloc/free
 299          * (i.e., munmap will return it to the system).
 300          */
 301         base = mmap(NULL, (size_t)symstrsize, PROT_READ, MAP_PRIVATE, fd,
 302             (off_t)symstroff);
 303         if (base == MAP_FAILED)
 304                 goto done;
 305         strtab = (char *)base;
 306
 307         /*
 308          * clean out any left-over information for all valid entries.
 309          * Type and value defined to be 0 if not found; historical
 310          * versions cleared other and desc as well.  Also figure out
 311          * the largest string length so don't read any more of the
 312          * string table than we have to.
 313          *
 314          * XXX clearing anything other than n_type and n_value violates
 315          * the semantics given in the man page.
 316          */
 317         nent = 0;
 318         for (p = list; !ISLAST(p); ++p) {
 319                 p->n_type = 0;
 320                 p->n_other = 0;
 321                 p->n_desc = 0;
 322                 p->n_value = 0;
 323                 ++nent;
 324         }
 325
 326         /* Don't process any further if object is stripped. */
 327         if (symoff == 0)
 328                 goto done;
 329
 330         if (lseek(fd, (off_t) symoff, SEEK_SET) == -1) {
 331                 nent = -1;
 332                 goto done;
 333         }
 334
 335         while (symsize > 0 && nent > 0) {
 336                 cc = MIN(symsize, sizeof(sbuf));
 337                 if (_read(fd, sbuf, cc) != cc)
 338                         break;
 339                 symsize -= cc;
 340                 for (s = sbuf; cc > 0 && nent > 0; ++s, cc -= sizeof(*s)) {
 341                         char *name;
 342                         struct nlist *p;
 343
 344                         name = strtab + s->st_name;
 345                         if (name[0] == '\0')
 346                                 continue;
 347                         for (p = list; !ISLAST(p); p++) {
 348                                 if ((p->n_un.n_name[0] == '_' &&
 349                                     strcmp(name, p->n_un.n_name+1) == 0)
 350                                     || strcmp(name, p->n_un.n_name) == 0) {
 351                                         elf_sym_to_nlist(p, s, shdr,
 352                                             ehdr.e_shnum);
 353                                         if (--nent <= 0)
 354                                                 break;
 355                                 }
 356                         }
 357                 }
 358         }
 359   done:
 360         errsave = errno;
 361         if (strtab != NULL)
 362                 munmap(strtab, symstrsize);
 363         if (shdr != NULL)
 364                 munmap(shdr, shdr_size);
 365         errno = errsave;
 366         return (nent);
 367 }
 368
 369 /*
 370  * Convert an Elf_Sym into an nlist structure.  This fills in only the
 371  * n_value and n_type members.
 372  */
 373 static void
 374 elf_sym_to_nlist(struct nlist *nl, Elf_Sym *s, Elf_Shdr *shdr, int shnum)
 375 {
 376         nl->n_value = s->st_value;
 377
 378         switch (s->st_shndx) {
 379         case SHN_UNDEF:
 380         case SHN_COMMON:
 381                 nl->n_type = N_UNDF;
 382                 break;
 383         case SHN_ABS:
 384                 nl->n_type = ELF_ST_TYPE(s->st_info) == STT_FILE ?
 385                     N_FN : N_ABS;
 386                 break;
 387         default:
 388                 if (s->st_shndx >= shnum)
 389                         nl->n_type = N_UNDF;
 390                 else {
 391                         Elf_Shdr *sh = shdr + s->st_shndx;
 392
 393                         nl->n_type = sh->sh_type == SHT_PROGBITS ?
 394                             (sh->sh_flags & SHF_WRITE ? N_DATA : N_TEXT) :
 395                             (sh->sh_type == SHT_NOBITS ? N_BSS : N_UNDF);
 396                 }
 397                 break;
 398         }
 399
 400         if (ELF_ST_BIND(s->st_info) == STB_GLOBAL ||
 401             ELF_ST_BIND(s->st_info) == STB_WEAK)
 402                 nl->n_type |= N_EXT;
 403 }
 404 #endif /* _NLIST_DO_ELF */