osfmk/kern/symbols.c

   1 /*
   2  * Copyright (c) 2006 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 /*-
  30  * Copyright (c) 2004 Networks Associates Technology, Inc.
  31  * All rights reserved.
  32  *
  33  * Redistribution and use in source and binary forms, with or without
  34  * modification, are permitted provided that the following conditions
  35  * are met:
  36  * 1. Redistributions of source code must retain the above copyright
  37  *    notice, this list of conditions and the following disclaimer.
  38  * 2. Redistributions in binary form must reproduce the above copyright
  39  *    notice, this list of conditions and the following disclaimer in the
  40  *    documentation and/or other materials provided with the distribution.
  41  *
  42  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  43  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  44  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  45  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  46  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  47  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  48  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  49  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  50  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  51  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  52  * SUCH DAMAGE.
  53  */
  54
  55 #include <mach/mach_types.h>
  56 #include <mach-o/mach_header.h>
  57 #include <mach-o/nlist.h>
  58 #include <mach/kmod.h>
  59 #include <libsa/stdlib.h>
  60 #include <kern/misc_protos.h>
  61
  62 static const struct nlist *
  63 syms_find(const struct nlist *syms, int nsyms, vm_offset_t addr,
  64     vm_offset_t *ofs)
  65 {
  66         const struct nlist *best = 0;
  67         int                 i;
  68
  69         for (i = 0; i < nsyms; i++) {
  70                 int st = syms[i].n_type & N_TYPE;
  71
  72                 if (st == N_SECT || st == N_ABS) {
  73                         if (syms[i].n_value == addr) {
  74                                 *ofs = 0;
  75                                 return (syms+i);
  76                         }
  77                         else if (syms[i].n_value < addr &&
  78                                  (best == 0 ||
  79                                   (syms[i].n_value > best->n_value))) {
  80                                 *ofs = addr - syms[i].n_value;
  81                                 best = syms+i;
  82                         }
  83                 }
  84         }
  85
  86         return (best);
  87 }
  88
  89 static const char *
  90 syms_getname(const struct symtab_command *sc, const char *ss,
  91              const struct nlist *sp)
  92 {
  93         if (sp->n_un.n_strx == 0)
  94                 return ("");
  95         else if ((unsigned)sp->n_un.n_strx > sc->strsize)
  96                 return ("*bad string*");
  97         else
  98                 return (ss + sp->n_un.n_strx);
  99 }
 100
 101 /* Search for a symbol in the given object file, which must either
 102  * have a LINKEDIT segment or have been read directly into memory
 103  * and isload passed as 1.
 104
 105  * If mh has a LINKEDIT segment, an object file loaded in the normal
 106  * way will have the symbol table available at the load address.
 107  */
 108
 109 static const char *
 110 syms_nameforaddr1(const struct mach_header *mh, int isload,
 111     vm_offset_t addr, vm_offset_t *ofs)
 112 {
 113         const struct symtab_command  *sc = NULL;
 114         const struct segment_command *le = NULL;
 115         const struct segment_command *p;
 116         const struct segment_command *sym = NULL;
 117         const struct nlist           *syms;
 118         const char                   *strings;
 119         unsigned int                  i;
 120
 121         p = (const struct segment_command *) (&mh[1]);
 122
 123         for (i = 0; i < mh->ncmds; i++) {
 124                 if (p->cmd == LC_SYMTAB)
 125                         sc = (const struct symtab_command *) p;
 126                 else if (p->cmd == LC_SEGMENT &&
 127                     !strncmp(p->segname, "__LINKEDIT", sizeof(p->segname)))
 128                         le = p;
 129
 130                 /* only try to find a name for an address that came from
 131                  * a text section.
 132                  */
 133                 if (p->cmd == LC_SEGMENT &&
 134                     addr >= p->vmaddr && addr < p->vmaddr + p->vmsize) {
 135                         unsigned int j;
 136
 137                         const struct section *sp = (const struct section *)
 138                             (((const char *) p) + sizeof(struct segment_command));
 139
 140                         for (j = 0; j < p->nsects; j++) {
 141                                 if (addr >= sp[j].addr &&
 142                                     addr <  sp[j].addr + sp[j].size &&
 143                                     !strncmp (sp[j].sectname, "__text",
 144                                                 sizeof(sp[j].sectname))) {
 145                                         sym = p;
 146                                         break;
 147                                 }
 148                         }
 149                 }
 150                 p = (const struct segment_command *)
 151                         (((const char *) p) + p->cmdsize);
 152         }
 153
 154         if (sc == 0 || sym == NULL)
 155                 return (NULL);
 156
 157         if (!isload) {
 158                 syms = (const struct nlist *) (((const char *) mh) + sc->symoff);
 159                 strings = ((const char *) mh) + sc->stroff;
 160         }
 161         else if (le) {
 162                 syms = (const struct nlist *) le->vmaddr;
 163                 strings = (const char *)
 164                         (le->vmaddr + sc->nsyms * sizeof(struct nlist));
 165         } else
 166                 return (NULL);
 167
 168         const struct nlist *sp = syms_find(syms, sc->nsyms, addr, ofs);
 169         if (sp)
 170                 return syms_getname(sc, strings, sp);
 171
 172         return (NULL);
 173 }
 174
 175 extern struct mach_header  _mh_execute_header;
 176 extern kmod_info_t        *kmod;
 177
 178 /* Search for a symbol and return the name, offset, and module in which the
 179  * address was found. A null module means the kernel itself.
 180  */
 181
 182 const char *
 183 syms_nameforaddr(vm_offset_t addr, vm_offset_t *ofs, kmod_info_t **km)
 184 {
 185         const char  *name = NULL;
 186
 187         name = syms_nameforaddr1(&_mh_execute_header, 1, addr, ofs);
 188         if (name) {
 189                 *km = NULL;
 190                 return (name);
 191         }
 192
 193         return (NULL);
 194 }
 195
 196
 197 /* Format the results of calling syms_nameforaddr into a single string.
 198  * The buffer must be at least 13 bytes long; 80 is recommended.
 199  */
 200
 201 int
 202 syms_formataddr(vm_offset_t addr, char *out, vm_offset_t outsize)
 203 {
 204         vm_offset_t  ofs;
 205         kmod_info_t *k = NULL;
 206         const char  *name;
 207
 208         name = syms_nameforaddr(addr, &ofs, &k);
 209
 210         if (ofs > 0x100000)
 211                 name = NULL;
 212
 213         if (name != NULL) {
 214                 if (k != NULL)
 215                         snprintf(out, outsize, "0x%08X <%s:%s + %d>", addr,
 216                             k->name, name, ofs);
 217                 else
 218                         snprintf(out, outsize, "0x%08X <%s + %d>", addr, name,
 219                             ofs);
 220
 221                 return (1);
 222         }
 223         else {
 224                 snprintf(out, outsize, "0x%08X", addr);
 225                 return (0);
 226         }
 227 }