sys/ddb/db_elf.c

   1 /*      $NetBSD: db_elf.c,v 1.26 2009/03/07 22:02:17 ad Exp $   */
   2
   3 /*-
   4  * Copyright (c) 1997, 2009 The NetBSD Foundation, Inc.
   5  * All rights reserved.
   6  *
   7  * This code is derived from software contributed to The NetBSD Foundation
   8  * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility,
   9  * NASA Ames Research Center, and by Andrew Doran.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions and the following disclaimer.
  16  * 2. Redistributions in binary form must reproduce the above copyright
  17  *    notice, this list of conditions and the following disclaimer in the
  18  *    documentation and/or other materials provided with the distribution.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
  21  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
  22  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  23  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
  24  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  25  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  26  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  27  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  28  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  29  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  30  * POSSIBILITY OF SUCH DAMAGE.
  31  */
  32
  33 #include <sys/cdefs.h>
  34 __KERNEL_RCSID(0, "$NetBSD: db_elf.c,v 1.26 2009/03/07 22:02:17 ad Exp $");
  35
  36 #include <sys/param.h>
  37 #include <sys/systm.h>
  38 #include <sys/proc.h>
  39
  40 #include <ddb/ddb.h>
  41
  42 #include <machine/pmap.h>
  43 #include <machine/vmparam.h>
  44
  45 #ifdef DB_ELF_SYMBOLS
  46
  47 #ifndef DB_ELFSIZE
  48 #error Must define DB_ELFSIZE!
  49 #endif
  50
  51 #define ELFSIZE         DB_ELFSIZE
  52
  53 #include <sys/exec_elf.h>
  54
  55 static char     *db_elf_find_strtab(db_symtab_t *);
  56
  57 #define STAB_TO_SYMSTART(stab)  ((Elf_Sym *)((stab)->start))
  58 #define STAB_TO_SYMEND(stab)    ((Elf_Sym *)((stab)->end))
  59 #define STAB_TO_EHDR(stab)      ((Elf_Ehdr *)((stab)->private))
  60 #define STAB_TO_SHDR(stab, e)   ((Elf_Shdr *)((stab)->private + (e)->e_shoff))
  61
  62 static bool db_elf_sym_init(int, void *, void *, const char *);
  63 static db_sym_t db_elf_lookup(db_symtab_t *, const char *);
  64 static db_sym_t db_elf_search_symbol(db_symtab_t *, db_addr_t, db_strategy_t,
  65                     db_expr_t *);
  66 static void     db_elf_symbol_values(db_symtab_t *, db_sym_t, const char **,
  67                     db_expr_t *);
  68 static bool db_elf_line_at_pc(db_symtab_t *, db_sym_t, char **, int *,
  69                     db_expr_t);
  70 static bool db_elf_sym_numargs(db_symtab_t *, db_sym_t, int *, char **);
  71 static void     db_elf_forall(db_symtab_t *, db_forall_func_t db_forall_func,
  72                     void *);
  73
  74 const db_symformat_t db_symformat_elf = {
  75         "ELF",
  76         db_elf_sym_init,
  77         db_elf_lookup,
  78         db_elf_search_symbol,
  79         db_elf_symbol_values,
  80         db_elf_line_at_pc,
  81         db_elf_sym_numargs,
  82         db_elf_forall
  83 };
  84
  85 static db_symtab_t db_symtabs;
  86
  87 /*
  88  * Add symbol table, with given name, to symbol tables.
  89  */
  90 static int
  91 db_add_symbol_table(char *start, char *end, const char *name, char *ref)
  92 {
  93
  94         db_symtabs.start = start;
  95         db_symtabs.end = end;
  96         db_symtabs.name = name;
  97         db_symtabs.private = ref;
  98
  99         return(0);
 100 }
 101
 102 /*
 103  * Find the symbol table and strings; tell ddb about them.
 104  */
 105 static bool
 106 db_elf_sym_init(
 107         int symsize,            /* size of symbol table */
 108         void *symtab,           /* pointer to start of symbol table */
 109         void *esymtab,          /* pointer to end of string table,
 110                                    for checking - rounded up to integer
 111                                    boundary */
 112         const char *name
 113 )
 114 {
 115         Elf_Ehdr *elf;
 116         Elf_Shdr *shp;
 117         Elf_Sym *symp, *symtab_start, *symtab_end;
 118         char *strtab_start, *strtab_end;
 119         int i, j;
 120
 121         if (ALIGNED_POINTER(symtab, long) == 0) {
 122                 printf("[ %s symbol table has bad start address %p ]\n",
 123                     name, symtab);
 124                 return (false);
 125         }
 126
 127         symtab_start = symtab_end = NULL;
 128         strtab_start = strtab_end = NULL;
 129
 130         /*
 131          * The format of the symbols loaded by the boot program is:
 132          *
 133          *      Elf exec header
 134          *      first section header
 135          *      . . .
 136          *      . . .
 137          *      last section header
 138          *      first symbol or string table section
 139          *      . . .
 140          *      . . .
 141          *      last symbol or string table section
 142          */
 143
 144         /*
 145          * Validate the Elf header.
 146          */
 147         elf = (Elf_Ehdr *)symtab;
 148         if (memcmp(elf->e_ident, ELFMAG, SELFMAG) != 0 ||
 149             elf->e_ident[EI_CLASS] != ELFCLASS)
 150                 goto badheader;
 151
 152         switch (elf->e_machine) {
 153
 154         ELFDEFNNAME(MACHDEP_ID_CASES)
 155
 156         default:
 157                 goto badheader;
 158         }
 159
 160         /*
 161          * Find the first (and, we hope, only) SHT_SYMTAB section in
 162          * the file, and the SHT_STRTAB section that goes with it.
 163          */
 164         if (elf->e_shoff == 0)
 165                 goto badheader;
 166         shp = (Elf_Shdr *)((char *)symtab + elf->e_shoff);
 167         for (i = 0; i < elf->e_shnum; i++) {
 168                 if (shp[i].sh_type == SHT_SYMTAB) {
 169                         if (shp[i].sh_offset == 0)
 170                                 continue;
 171                         /* Got the symbol table. */
 172                         symtab_start = (Elf_Sym *)((char *)symtab +
 173                             shp[i].sh_offset);
 174                         symtab_end = (Elf_Sym *)((char *)symtab +
 175                             shp[i].sh_offset + shp[i].sh_size);
 176                         /* Find the string table to go with it. */
 177                         j = shp[i].sh_link;
 178                         if (shp[j].sh_offset == 0)
 179                                 continue;
 180                         strtab_start = (char *)symtab + shp[j].sh_offset;
 181                         strtab_end = (char *)symtab + shp[j].sh_offset +
 182                             shp[j].sh_size;
 183                         /* There should only be one symbol table. */
 184                         break;
 185                 }
 186         }
 187
 188         /*
 189          * Now, sanity check the symbols against the string table.
 190          */
 191         if (symtab_start == NULL || strtab_start == NULL ||
 192             ALIGNED_POINTER(symtab_start, long) == 0 ||
 193             ALIGNED_POINTER(strtab_start, long) == 0)
 194                 goto badheader;
 195         for (symp = symtab_start; symp < symtab_end; symp++)
 196                 if (symp->st_name + strtab_start > strtab_end)
 197                         goto badheader;
 198
 199         /*
 200          * Link the symbol table into the debugger.
 201          */
 202         if (db_add_symbol_table((char *)symtab_start,
 203             (char *)symtab_end, name, (char *)symtab) != -1) {
 204                 return (true);
 205         }
 206
 207         return (false);
 208
 209  badheader:
 210         printf("[ %s ELF symbol table not valid ]\n", name);
 211         return (false);
 212 }
 213
 214 /*
 215  * Internal helper function - return a pointer to the string table
 216  * for the current symbol table.
 217  */
 218 static char *
 219 db_elf_find_strtab(db_symtab_t *stab)
 220 {
 221         Elf_Ehdr *elf = STAB_TO_EHDR(stab);
 222         Elf_Shdr *shp = STAB_TO_SHDR(stab, elf);
 223         int i;
 224
 225         stab = &db_symtabs;
 226
 227         /*
 228          * We don't load ELF header for ELF modules.
 229          * Find out if this is a loadable module. If so,
 230          * string table comes right after symbol table.
 231          */
 232         if ((Elf_Sym *)elf == STAB_TO_SYMSTART(stab)) {
 233                 return ((char *)STAB_TO_SYMEND(stab));
 234         }
 235         for (i = 0; i < elf->e_shnum; i++) {
 236                 if (shp[i].sh_type == SHT_SYMTAB)
 237                         return ((char*)elf + shp[shp[i].sh_link].sh_offset);
 238         }
 239
 240         return (NULL);
 241 }
 242
 243 /*
 244  * Lookup the symbol with the given name.
 245  */
 246 static db_sym_t
 247 db_elf_lookup(db_symtab_t *stab, const char *symstr)
 248 {
 249         Elf_Sym *symp, *symtab_start, *symtab_end;
 250         char *strtab;
 251
 252         stab = &db_symtabs;
 253
 254         symtab_start = STAB_TO_SYMSTART(stab);
 255         symtab_end = STAB_TO_SYMEND(stab);
 256
 257         strtab = db_elf_find_strtab(stab);
 258         if (strtab == NULL)
 259                 return ((db_sym_t)0);
 260
 261         for (symp = symtab_start; symp < symtab_end; symp++) {
 262                 if (symp->st_name != 0 &&
 263                     db_eqname(strtab + symp->st_name, symstr, 0))
 264                         return ((db_sym_t)symp);
 265         }
 266
 267         return ((db_sym_t)0);
 268 }
 269
 270 /*
 271  * Search for the symbol with the given address (matching within the
 272  * provided threshold).
 273  */
 274 static db_sym_t
 275 db_elf_search_symbol(db_symtab_t *symtab, db_addr_t off, db_strategy_t strategy,
 276     db_expr_t *diffp)
 277 {
 278         Elf_Sym *rsymp, *symp, *symtab_start, *symtab_end;
 279         db_addr_t diff = *diffp;
 280
 281         symtab = &db_symtabs;
 282
 283         symtab_start = STAB_TO_SYMSTART(symtab);
 284         symtab_end = STAB_TO_SYMEND(symtab);
 285
 286         rsymp = NULL;
 287
 288         for (symp = symtab_start; symp < symtab_end; symp++) {
 289                 if (symp->st_name == 0)
 290                         continue;
 291
 292 #if 0
 293                 /* This prevents me from seeing anythin in locore.s -- eeh */
 294                 if (ELF_ST_TYPE(symp->st_info) != STT_OBJECT &&
 295                     ELF_ST_TYPE(symp->st_info) != STT_FUNC)
 296                         continue;
 297 #endif
 298
 299                 if (off >= symp->st_value) {
 300                         if (off - symp->st_value < diff) {
 301                                 diff = off - symp->st_value;
 302                                 rsymp = symp;
 303                                 if (diff == 0) {
 304                                         if (strategy == DB_STGY_PROC &&
 305                                             ELFDEFNNAME(ST_TYPE)(symp->st_info)
 306                                               == STT_FUNC &&
 307                                             ELFDEFNNAME(ST_BIND)(symp->st_info)
 308                                               != STB_LOCAL)
 309                                                 break;
 310                                         if (strategy == DB_STGY_ANY &&
 311                                             ELFDEFNNAME(ST_BIND)(symp->st_info)
 312                                               != STB_LOCAL)
 313                                                 break;
 314                                 }
 315                         } else if (off - symp->st_value == diff) {
 316                                 if (rsymp == NULL)
 317                                         rsymp = symp;
 318                                 else if (ELFDEFNNAME(ST_BIND)(rsymp->st_info)
 319                                       == STB_LOCAL &&
 320                                     ELFDEFNNAME(ST_BIND)(symp->st_info)
 321                                       != STB_LOCAL) {
 322                                         /* pick the external symbol */
 323                                         rsymp = symp;
 324                                 }
 325                         }
 326                 }
 327         }
 328
 329         if (rsymp == NULL)
 330                 *diffp = off;
 331         else
 332                 *diffp = diff;
 333
 334         return ((db_sym_t)rsymp);
 335 }
 336
 337 /*
 338  * Return the name and value for a symbol.
 339  */
 340 static void
 341 db_elf_symbol_values(db_symtab_t *symtab, db_sym_t sym, const char **namep,
 342     db_expr_t *valuep)
 343 {
 344         Elf_Sym *symp = (Elf_Sym *)sym;
 345         char *strtab;
 346
 347         symtab = &db_symtabs;
 348
 349         if (namep) {
 350                 strtab = db_elf_find_strtab(symtab);
 351                 if (strtab == NULL)
 352                         *namep = NULL;
 353                 else
 354                         *namep = strtab + symp->st_name;
 355         }
 356
 357         if (valuep)
 358                 *valuep = symp->st_value;
 359 }
 360
 361 /*
 362  * Return the file and line number of the current program counter
 363  * if we can find the appropriate debugging symbol.
 364  */
 365 static bool
 366 db_elf_line_at_pc(db_symtab_t *symtab, db_sym_t cursym, char **filename, int *linenum, db_expr_t off)
 367 {
 368
 369         /*
 370          * XXX We don't support this (yet).
 371          */
 372         return (false);
 373 }
 374
 375 /*
 376  * Returns the number of arguments to a function and their
 377  * names if we can find the appropriate debugging symbol.
 378  */
 379 static bool
 380 db_elf_sym_numargs(db_symtab_t *symtab, db_sym_t cursym, int *nargp,
 381     char **argnamep)
 382 {
 383
 384         /*
 385          * XXX We don't support this (yet).
 386          */
 387         return (false);
 388 }
 389
 390 static void
 391 db_elf_forall(db_symtab_t *stab, db_forall_func_t db_forall_func, void *arg)
 392 {
 393         char *strtab;
 394         static char suffix[2];
 395         Elf_Sym *symp, *symtab_start, *symtab_end;
 396
 397         stab = &db_symtabs;
 398
 399         symtab_start = STAB_TO_SYMSTART(stab);
 400         symtab_end = STAB_TO_SYMEND(stab);
 401
 402         strtab = db_elf_find_strtab(stab);
 403         if (strtab == NULL)
 404                 return;
 405
 406         for (symp = symtab_start; symp < symtab_end; symp++)
 407                 if (symp->st_name != 0) {
 408                         suffix[1] = '\0';
 409                         switch (ELFDEFNNAME(ST_TYPE)(symp->st_info)) {
 410                         case STT_OBJECT:
 411                                 suffix[0] = '+';
 412                                 break;
 413                         case STT_FUNC:
 414                                 suffix[0] = '*';
 415                                 break;
 416                         case STT_SECTION:
 417                                 suffix[0] = '&';
 418                                 break;
 419                         case STT_FILE:
 420                                 suffix[0] = '/';
 421                                 break;
 422                         default:
 423                                 suffix[0] = '\0';
 424                         }
 425                         (*db_forall_func)(stab, (db_sym_t)symp,
 426                             strtab + symp->st_name, suffix, 0, arg);
 427                 }
 428         return;
 429 }
 430 #endif /* DB_ELF_SYMBOLS */