Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_elf.c
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1 /* $NetBSD: db_elf.c,v 1.4 1998/05/03 18:49:54 thorpej Exp $ */ 2 /*- 3 * Copyright (c) 1997 The NetBSD Foundation, Inc. 4 * All rights reserved. 5 * 6 * This code is derived from software contributed to The NetBSD Foundation 7 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 8 * NASA Ames Research Center. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the NetBSD 21 * Foundation, Inc. and its contributors. 22 * 4. Neither the name of The NetBSD Foundation nor the names of its 23 * contributors may be used to endorse or promote products derived 24 * from this software without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 27 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 28 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 29 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 30 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 31 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 32 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 33 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 34 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 35 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 36 * POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 __FBSDID("$FreeBSD: releng/5.2/sys/ddb/db_elf.c 120543 2003-09-28 06:02:33Z bde $"); 41 42 #include "opt_ddb.h" 43 44 #ifdef DDB_NOKLDSYM 45 46 #include <sys/param.h> 47 #include <sys/systm.h> 48 49 #ifdef __i386__ 50 #include <machine/bootinfo.h> 51 #endif 52 53 #include <ddb/ddb.h> 54 #include <ddb/db_sym.h> 55 56 #include <machine/elf.h> 57 58 #ifndef _ALIGNED_POINTER 59 #define _ALIGNED_POINTER(ptr, type) 1 60 #endif 61 62 static char *db_elf_find_strtab(db_symtab_t *); 63 64 #define STAB_TO_SYMSTART(stab) ((Elf_Sym *)((stab)->start)) 65 #define STAB_TO_SYMEND(stab) ((Elf_Sym *)((stab)->end)) 66 #define STAB_TO_EHDR(stab) ((Elf_Ehdr *)((stab)->private)) 67 #define STAB_TO_SHDR(stab, e) ((Elf_Shdr *)((stab)->private + (e)->e_shoff)) 68 69 void X_db_sym_init(void *symtab, void *esymtab, char *name); 70 71 /* 72 * Find the symbol table and strings; tell ddb about them. 73 */ 74 void 75 X_db_sym_init(symtab, esymtab, name) 76 void *symtab; /* pointer to start of symbol table */ 77 void *esymtab; /* pointer to end of string table, 78 for checking - rounded up to integer 79 boundary */ 80 char *name; 81 { 82 Elf_Ehdr *elf; 83 Elf_Shdr *shp; 84 Elf_Sym *symp, *symtab_start, *symtab_end; 85 char *strtab_start, *strtab_end; 86 int i; 87 88 if (_ALIGNED_POINTER(symtab, long) == 0) { 89 printf("DDB: bad symbol table start address %p\n", symtab); 90 return; 91 } 92 93 symtab_start = symtab_end = NULL; 94 strtab_start = strtab_end = NULL; 95 96 /* 97 * The format of the symbols loaded by the boot program is: 98 * 99 * Elf exec header 100 * first section header 101 * . . . 102 * . . . 103 * last section header 104 * first symbol or string table section 105 * . . . 106 * . . . 107 * last symbol or string table section 108 */ 109 110 /* 111 * Validate the Elf header. 112 */ 113 elf = (Elf_Ehdr *)symtab; 114 if (elf->e_ident[EI_MAG0] != ELFMAG0 115 || elf->e_ident[EI_MAG1] != ELFMAG1 116 || elf->e_ident[EI_MAG2] != ELFMAG2 117 || elf->e_ident[EI_MAG3] != ELFMAG3) 118 goto badheader; 119 120 if (!ELF_MACHINE_OK(elf->e_machine)) 121 goto badheader; 122 123 /* 124 * We need to avoid the section header string table (small string 125 * table which names the sections). We do this by assuming that 126 * the following two conditions will be true: 127 * 128 * (1) .shstrtab will be smaller than one page. 129 * (2) .strtab will be larger than one page. 130 * 131 * When we encounter what we think is the .shstrtab, we change 132 * its section type Elf_sht_null so that it will be ignored 133 * later. 134 */ 135 shp = (Elf_Shdr *)((char*)symtab + elf->e_shoff); 136 for (i = 0; i < elf->e_shnum; i++) { 137 if (shp[i].sh_addr || i == elf->e_shstrndx) 138 continue; 139 switch (shp[i].sh_type) { 140 case SHT_STRTAB: 141 if (shp[i].sh_size < PAGE_SIZE) { 142 shp[i].sh_type = SHT_NULL; 143 continue; 144 } 145 if (strtab_start != NULL) 146 goto multiple_strtab; 147 strtab_start = (char *)symtab + shp[i].sh_offset; 148 strtab_end = (char *)symtab + shp[i].sh_offset + 149 shp[i].sh_size; 150 break; 151 152 case SHT_SYMTAB: 153 if (symtab_start != NULL) 154 goto multiple_symtab; 155 symtab_start = (Elf_Sym *)((char*)symtab + shp[i].sh_offset); 156 symtab_end = (Elf_Sym *)((char*)symtab + shp[i].sh_offset + 157 shp[i].sh_size); 158 break; 159 160 default: 161 /* Ignore all other sections. */ 162 break; 163 } 164 } 165 166 /* 167 * Now, sanity check the symbols against the string table. 168 */ 169 if (symtab_start == NULL || strtab_start == NULL || 170 _ALIGNED_POINTER(symtab_start, long) == 0 || 171 _ALIGNED_POINTER(strtab_start, long) == 0) 172 goto badheader; 173 for (symp = symtab_start; symp < symtab_end; symp++) 174 if (symp->st_name + strtab_start > strtab_end) 175 goto badheader; 176 177 /* 178 * Link the symbol table into the debugger. 179 */ 180 db_add_symbol_table((char *)symtab_start, 181 (char *)symtab_end, name, (char *)symtab); 182 printf("[ preserving %lu bytes of %s symbol table ]\n", 183 (u_long)roundup(((char*)esymtab - (char*)symtab), sizeof(u_long)), name); 184 return; 185 186 badheader: 187 printf("[ %s symbol table not valid ]\n", name); 188 return; 189 190 multiple_strtab: 191 printf("[ %s has multiple string tables ]\n", name); 192 return; 193 194 multiple_symtab: 195 printf("[ %s has multiple symbol tables ]\n", name); 196 return; 197 } 198 199 /* 200 * Internal helper function - return a pointer to the string table 201 * for the current symbol table. 202 */ 203 static char * 204 db_elf_find_strtab(stab) 205 db_symtab_t *stab; 206 { 207 Elf_Ehdr *elf = STAB_TO_EHDR(stab); 208 Elf_Shdr *shp = STAB_TO_SHDR(stab, elf); 209 int i; 210 211 for (i = 0; i < elf->e_shnum; i++) { 212 if (shp[i].sh_type == SHT_STRTAB 213 && !shp[i].sh_addr && i != elf->e_shstrndx) 214 return (stab->private + shp[i].sh_offset); 215 } 216 217 return (NULL); 218 } 219 220 /* 221 * Lookup the symbol with the given name. 222 */ 223 c_db_sym_t 224 X_db_lookup(stab, symstr) 225 db_symtab_t *stab; 226 const char *symstr; 227 { 228 Elf_Sym *symp, *symtab_start, *symtab_end; 229 char *strtab; 230 231 symtab_start = STAB_TO_SYMSTART(stab); 232 symtab_end = STAB_TO_SYMEND(stab); 233 234 strtab = db_elf_find_strtab(stab); 235 if (strtab == NULL) 236 return ((db_sym_t)0); 237 238 for (symp = symtab_start; symp < symtab_end; symp++) { 239 if (symp->st_name != 0 && 240 db_eqname(strtab + symp->st_name, symstr, 0)) 241 return ((db_sym_t)symp); 242 } 243 244 return ((db_sym_t)0); 245 } 246 247 /* 248 * Search for the symbol with the given address (matching within the 249 * provided threshold). 250 */ 251 c_db_sym_t 252 X_db_search_symbol(symtab, off, strategy, diffp) 253 db_symtab_t *symtab; 254 db_addr_t off; 255 db_strategy_t strategy; 256 db_expr_t *diffp; /* in/out */ 257 { 258 Elf_Sym *rsymp, *symp, *symtab_start, *symtab_end; 259 db_expr_t diff = *diffp; 260 261 symtab_start = STAB_TO_SYMSTART(symtab); 262 symtab_end = STAB_TO_SYMEND(symtab); 263 264 rsymp = NULL; 265 266 for (symp = symtab_start; symp < symtab_end; symp++) { 267 if (symp->st_name == 0) 268 continue; 269 if (ELF_ST_TYPE(symp->st_info) != STT_OBJECT && 270 ELF_ST_TYPE(symp->st_info) != STT_FUNC && 271 ELF_ST_TYPE(symp->st_info) != STT_NOTYPE) 272 continue; 273 274 if (off >= symp->st_value) { 275 if ((off - symp->st_value) < diff) { 276 diff = off - symp->st_value; 277 rsymp = symp; 278 if (diff == 0) { 279 if (strategy == DB_STGY_PROC && 280 ELF_ST_TYPE(symp->st_info) == 281 STT_FUNC && 282 ELF_ST_BIND(symp->st_info) != 283 STB_LOCAL) 284 break; 285 if (strategy == DB_STGY_ANY && 286 ELF_ST_BIND(symp->st_info) != 287 STB_LOCAL) 288 break; 289 } 290 } else if ((off - symp->st_value) == diff) { 291 if (rsymp == NULL) 292 rsymp = symp; 293 else if (ELF_ST_BIND(rsymp->st_info) == 294 STB_LOCAL && 295 ELF_ST_BIND(symp->st_info) != 296 STB_LOCAL) { 297 /* pick the external symbol */ 298 rsymp = symp; 299 } 300 } 301 } 302 } 303 304 if (rsymp == NULL) 305 *diffp = off; 306 else 307 *diffp = diff; 308 309 return ((db_sym_t)rsymp); 310 } 311 312 /* 313 * Return the name and value for a symbol. 314 */ 315 void 316 X_db_symbol_values(symtab, sym, namep, valuep) 317 db_symtab_t *symtab; 318 c_db_sym_t sym; 319 const char **namep; 320 db_expr_t *valuep; 321 { 322 const Elf_Sym *symp = (const Elf_Sym *)sym; 323 char *strtab; 324 325 if (namep) { 326 strtab = db_elf_find_strtab(symtab); 327 if (strtab == NULL) 328 *namep = NULL; 329 else 330 *namep = strtab + symp->st_name; 331 } 332 333 if (valuep) 334 *valuep = symp->st_value; 335 } 336 337 /* 338 * Return the file and line number of the current program counter 339 * if we can find the appropriate debugging symbol. 340 */ 341 boolean_t 342 X_db_line_at_pc(symtab, cursym, filename, linenum, off) 343 db_symtab_t *symtab; 344 c_db_sym_t cursym; 345 char **filename; 346 int *linenum; 347 db_expr_t off; 348 { 349 350 /* 351 * XXX We don't support this (yet). 352 */ 353 return (FALSE); 354 } 355 356 /* 357 * Returns the number of arguments to a function and their 358 * names if we can find the appropriate debugging symbol. 359 */ 360 boolean_t 361 X_db_sym_numargs(symtab, cursym, nargp, argnamep) 362 db_symtab_t *symtab; 363 c_db_sym_t cursym; 364 int *nargp; 365 char **argnamep; 366 { 367 368 /* 369 * XXX We don't support this (yet). 370 */ 371 return (FALSE); 372 } 373 374 /* 375 * Initialization routine for Elf files. 376 */ 377 378 #ifdef __i386__ 379 void *ksym_start, *ksym_end; 380 #else 381 extern void *ksym_start, *ksym_end; 382 #endif 383 384 void 385 kdb_init(void) 386 { 387 static Elf_Ehdr elf; 388 static Elf_Shdr sh[2]; 389 390 #ifdef __i386__ 391 ksym_start = (void *)bootinfo.bi_symtab; 392 ksym_end = (void *)bootinfo.bi_esymtab; 393 #endif 394 if (ksym_end <= ksym_start) 395 return; 396 397 /* 398 * The FreeBSD boot program doesn't actually load any headers, so 399 * fake just enough for the routines in this file to work. 400 */ 401 elf.e_ident[EI_MAG0] = ELFMAG0; 402 elf.e_ident[EI_MAG1] = ELFMAG1; 403 elf.e_ident[EI_MAG2] = ELFMAG2; 404 elf.e_ident[EI_MAG3] = ELFMAG3; 405 elf.e_machine = EM_486; 406 elf.e_shoff = (uintptr_t)(void *)&sh[0] - (uintptr_t)(void *)&elf; 407 sh[0].sh_type = SHT_SYMTAB; 408 sh[0].sh_offset = (uintptr_t)ksym_start + sizeof(long) - 409 (uintptr_t)(void *)&elf; 410 sh[0].sh_size = *(int *)ksym_start; 411 sh[1].sh_type = SHT_STRTAB; 412 sh[1].sh_offset = sh[0].sh_offset + sh[0].sh_size + sizeof(long); 413 sh[1].sh_size = (uintptr_t)ksym_end - (uintptr_t)ksym_start - 414 sizeof(long) - sh[0].sh_size - sizeof(long); 415 elf.e_shstrndx = -1; 416 elf.e_shnum = 2; 417 418 X_db_sym_init(&elf, ksym_end, "kernel"); 419 } 420 421 #endif /* DDB_NOKLDSYM */
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