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 /* $FreeBSD: releng/5.0/sys/ddb/db_elf.c 103362 2002-09-15 22:28:39Z bde $ */ 2 /* $NetBSD: db_elf.c,v 1.4 1998/05/03 18:49:54 thorpej Exp $ */ 3 4 /*- 5 * Copyright (c) 1997 The NetBSD Foundation, Inc. 6 * All rights reserved. 7 * 8 * This code is derived from software contributed to The NetBSD Foundation 9 * by Jason R. Thorpe of the Numerical Aerospace Simulation Facility, 10 * NASA Ames Research Center. 11 * 12 * Redistribution and use in source and binary forms, with or without 13 * modification, are permitted provided that the following conditions 14 * are met: 15 * 1. Redistributions of source code must retain the above copyright 16 * notice, this list of conditions and the following disclaimer. 17 * 2. Redistributions in binary form must reproduce the above copyright 18 * notice, this list of conditions and the following disclaimer in the 19 * documentation and/or other materials provided with the distribution. 20 * 3. All advertising materials mentioning features or use of this software 21 * must display the following acknowledgement: 22 * This product includes software developed by the NetBSD 23 * Foundation, Inc. and its contributors. 24 * 4. Neither the name of The NetBSD Foundation nor the names of its 25 * contributors may be used to endorse or promote products derived 26 * from this software without specific prior written permission. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 29 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 30 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 31 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 32 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 33 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 34 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 35 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 36 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 37 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 38 * POSSIBILITY OF SUCH DAMAGE. 39 */ 40 41 #include "opt_ddb.h" 42 43 #ifdef DDB_NOKLDSYM 44 45 #include <sys/param.h> 46 #include <sys/systm.h> 47 48 #ifdef __i386__ 49 #include <machine/bootinfo.h> 50 #endif 51 52 #include <ddb/ddb.h> 53 #include <ddb/db_sym.h> 54 55 #include <machine/elf.h> 56 57 #ifndef _ALIGNED_POINTER 58 #define _ALIGNED_POINTER(ptr, type) 1 59 #endif 60 61 static char *db_elf_find_strtab(db_symtab_t *); 62 63 #define STAB_TO_SYMSTART(stab) ((Elf_Sym *)((stab)->start)) 64 #define STAB_TO_SYMEND(stab) ((Elf_Sym *)((stab)->end)) 65 #define STAB_TO_EHDR(stab) ((Elf_Ehdr *)((stab)->private)) 66 #define STAB_TO_SHDR(stab, e) ((Elf_Shdr *)((stab)->private + (e)->e_shoff)) 67 68 void X_db_sym_init(void *symtab, void *esymtab, char *name); 69 70 /* 71 * Find the symbol table and strings; tell ddb about them. 72 */ 73 void 74 X_db_sym_init(symtab, esymtab, name) 75 void *symtab; /* pointer to start of symbol table */ 76 void *esymtab; /* pointer to end of string table, 77 for checking - rounded up to integer 78 boundary */ 79 char *name; 80 { 81 Elf_Ehdr *elf; 82 Elf_Shdr *shp; 83 Elf_Sym *symp, *symtab_start, *symtab_end; 84 char *strtab_start, *strtab_end; 85 int i; 86 87 if (_ALIGNED_POINTER(symtab, long) == 0) { 88 printf("DDB: bad symbol table start address %p\n", symtab); 89 return; 90 } 91 92 symtab_start = symtab_end = NULL; 93 strtab_start = strtab_end = NULL; 94 95 /* 96 * The format of the symbols loaded by the boot program is: 97 * 98 * Elf exec header 99 * first section header 100 * . . . 101 * . . . 102 * last section header 103 * first symbol or string table section 104 * . . . 105 * . . . 106 * last symbol or string table section 107 */ 108 109 /* 110 * Validate the Elf header. 111 */ 112 elf = (Elf_Ehdr *)symtab; 113 if (elf->e_ident[EI_MAG0] != ELFMAG0 114 || elf->e_ident[EI_MAG1] != ELFMAG1 115 || elf->e_ident[EI_MAG2] != ELFMAG2 116 || elf->e_ident[EI_MAG3] != ELFMAG3) 117 goto badheader; 118 119 if (!ELF_MACHINE_OK(elf->e_machine)) 120 goto badheader; 121 122 /* 123 * We need to avoid the section header string table (small string 124 * table which names the sections). We do this by assuming that 125 * the following two conditions will be true: 126 * 127 * (1) .shstrtab will be smaller than one page. 128 * (2) .strtab will be larger than one page. 129 * 130 * When we encounter what we think is the .shstrtab, we change 131 * its section type Elf_sht_null so that it will be ignored 132 * later. 133 */ 134 shp = (Elf_Shdr *)((char*)symtab + elf->e_shoff); 135 for (i = 0; i < elf->e_shnum; i++) { 136 if (shp[i].sh_addr || i == elf->e_shstrndx) 137 continue; 138 switch (shp[i].sh_type) { 139 case SHT_STRTAB: 140 if (shp[i].sh_size < PAGE_SIZE) { 141 shp[i].sh_type = SHT_NULL; 142 continue; 143 } 144 if (strtab_start != NULL) 145 goto multiple_strtab; 146 strtab_start = (char *)symtab + shp[i].sh_offset; 147 strtab_end = (char *)symtab + shp[i].sh_offset + 148 shp[i].sh_size; 149 break; 150 151 case SHT_SYMTAB: 152 if (symtab_start != NULL) 153 goto multiple_symtab; 154 symtab_start = (Elf_Sym *)((char*)symtab + shp[i].sh_offset); 155 symtab_end = (Elf_Sym *)((char*)symtab + shp[i].sh_offset + 156 shp[i].sh_size); 157 break; 158 159 default: 160 /* Ignore all other sections. */ 161 break; 162 } 163 } 164 165 /* 166 * Now, sanity check the symbols against the string table. 167 */ 168 if (symtab_start == NULL || strtab_start == NULL || 169 _ALIGNED_POINTER(symtab_start, long) == 0 || 170 _ALIGNED_POINTER(strtab_start, long) == 0) 171 goto badheader; 172 for (symp = symtab_start; symp < symtab_end; symp++) 173 if (symp->st_name + strtab_start > strtab_end) 174 goto badheader; 175 176 /* 177 * Link the symbol table into the debugger. 178 */ 179 db_add_symbol_table((char *)symtab_start, 180 (char *)symtab_end, name, (char *)symtab); 181 printf("[ preserving %lu bytes of %s symbol table ]\n", 182 (u_long)roundup(((char*)esymtab - (char*)symtab), sizeof(u_long)), name); 183 return; 184 185 badheader: 186 printf("[ %s symbol table not valid ]\n", name); 187 return; 188 189 multiple_strtab: 190 printf("[ %s has multiple string tables ]\n", name); 191 return; 192 193 multiple_symtab: 194 printf("[ %s has multiple symbol tables ]\n", name); 195 return; 196 } 197 198 /* 199 * Internal helper function - return a pointer to the string table 200 * for the current symbol table. 201 */ 202 static char * 203 db_elf_find_strtab(stab) 204 db_symtab_t *stab; 205 { 206 Elf_Ehdr *elf = STAB_TO_EHDR(stab); 207 Elf_Shdr *shp = STAB_TO_SHDR(stab, elf); 208 int i; 209 210 for (i = 0; i < elf->e_shnum; i++) { 211 if (shp[i].sh_type == SHT_STRTAB 212 && !shp[i].sh_addr && i != elf->e_shstrndx) 213 return (stab->private + shp[i].sh_offset); 214 } 215 216 return (NULL); 217 } 218 219 /* 220 * Lookup the symbol with the given name. 221 */ 222 c_db_sym_t 223 X_db_lookup(stab, symstr) 224 db_symtab_t *stab; 225 const char *symstr; 226 { 227 Elf_Sym *symp, *symtab_start, *symtab_end; 228 char *strtab; 229 230 symtab_start = STAB_TO_SYMSTART(stab); 231 symtab_end = STAB_TO_SYMEND(stab); 232 233 strtab = db_elf_find_strtab(stab); 234 if (strtab == NULL) 235 return ((db_sym_t)0); 236 237 for (symp = symtab_start; symp < symtab_end; symp++) { 238 if (symp->st_name != 0 && 239 db_eqname(strtab + symp->st_name, symstr, 0)) 240 return ((db_sym_t)symp); 241 } 242 243 return ((db_sym_t)0); 244 } 245 246 /* 247 * Search for the symbol with the given address (matching within the 248 * provided threshold). 249 */ 250 c_db_sym_t 251 X_db_search_symbol(symtab, off, strategy, diffp) 252 db_symtab_t *symtab; 253 db_addr_t off; 254 db_strategy_t strategy; 255 db_expr_t *diffp; /* in/out */ 256 { 257 Elf_Sym *rsymp, *symp, *symtab_start, *symtab_end; 258 db_expr_t diff = *diffp; 259 260 symtab_start = STAB_TO_SYMSTART(symtab); 261 symtab_end = STAB_TO_SYMEND(symtab); 262 263 rsymp = NULL; 264 265 for (symp = symtab_start; symp < symtab_end; symp++) { 266 if (symp->st_name == 0) 267 continue; 268 if (off >= symp->st_value) { 269 if ((off - symp->st_value) < diff) { 270 diff = off - symp->st_value; 271 rsymp = symp; 272 if (diff == 0) { 273 if (strategy == DB_STGY_PROC && 274 ELF_ST_TYPE(symp->st_info) == 275 STT_FUNC && 276 ELF_ST_BIND(symp->st_info) != 277 STB_LOCAL) 278 break; 279 if (strategy == DB_STGY_ANY && 280 ELF_ST_BIND(symp->st_info) != 281 STB_LOCAL) 282 break; 283 } 284 } else if ((off - symp->st_value) == diff) { 285 if (rsymp == NULL) 286 rsymp = symp; 287 else if (ELF_ST_BIND(rsymp->st_info) == 288 STB_LOCAL && 289 ELF_ST_BIND(symp->st_info) != 290 STB_LOCAL) { 291 /* pick the external symbol */ 292 rsymp = symp; 293 } 294 } 295 } 296 } 297 298 if (rsymp == NULL) 299 *diffp = off; 300 else 301 *diffp = diff; 302 303 return ((db_sym_t)rsymp); 304 } 305 306 /* 307 * Return the name and value for a symbol. 308 */ 309 void 310 X_db_symbol_values(symtab, sym, namep, valuep) 311 db_symtab_t *symtab; 312 c_db_sym_t sym; 313 const char **namep; 314 db_expr_t *valuep; 315 { 316 const Elf_Sym *symp = (const Elf_Sym *)sym; 317 char *strtab; 318 319 if (namep) { 320 strtab = db_elf_find_strtab(symtab); 321 if (strtab == NULL) 322 *namep = NULL; 323 else 324 *namep = strtab + symp->st_name; 325 } 326 327 if (valuep) 328 *valuep = symp->st_value; 329 } 330 331 /* 332 * Return the file and line number of the current program counter 333 * if we can find the appropriate debugging symbol. 334 */ 335 boolean_t 336 X_db_line_at_pc(symtab, cursym, filename, linenum, off) 337 db_symtab_t *symtab; 338 c_db_sym_t cursym; 339 char **filename; 340 int *linenum; 341 db_expr_t off; 342 { 343 344 /* 345 * XXX We don't support this (yet). 346 */ 347 return (FALSE); 348 } 349 350 /* 351 * Returns the number of arguments to a function and their 352 * names if we can find the appropriate debugging symbol. 353 */ 354 boolean_t 355 X_db_sym_numargs(symtab, cursym, nargp, argnamep) 356 db_symtab_t *symtab; 357 c_db_sym_t cursym; 358 int *nargp; 359 char **argnamep; 360 { 361 362 /* 363 * XXX We don't support this (yet). 364 */ 365 return (FALSE); 366 } 367 368 /* 369 * Initialization routine for Elf files. 370 */ 371 372 #ifdef __i386__ 373 void *ksym_start, *ksym_end; 374 #else 375 extern void *ksym_start, *ksym_end; 376 #endif 377 378 void 379 kdb_init(void) 380 { 381 static Elf_Ehdr elf; 382 static Elf_Shdr sh[2]; 383 384 #ifdef __i386__ 385 ksym_start = (void *)bootinfo.bi_symtab; 386 ksym_end = (void *)bootinfo.bi_esymtab; 387 #endif 388 if (ksym_end <= ksym_start) 389 return; 390 391 /* 392 * The FreeBSD boot program doesn't actually load any headers, so 393 * fake just enough for the routines in this file to work. 394 */ 395 elf.e_ident[EI_MAG0] = ELFMAG0; 396 elf.e_ident[EI_MAG1] = ELFMAG1; 397 elf.e_ident[EI_MAG2] = ELFMAG2; 398 elf.e_ident[EI_MAG3] = ELFMAG3; 399 elf.e_machine = EM_486; 400 elf.e_shoff = (uintptr_t)(void *)&sh[0] - (uintptr_t)(void *)&elf; 401 sh[0].sh_type = SHT_SYMTAB; 402 sh[0].sh_offset = (uintptr_t)ksym_start + sizeof(long) - 403 (uintptr_t)(void *)&elf; 404 sh[0].sh_size = *(int *)ksym_start; 405 sh[1].sh_type = SHT_STRTAB; 406 sh[1].sh_offset = sh[0].sh_offset + sh[0].sh_size + sizeof(long); 407 sh[1].sh_size = (uintptr_t)ksym_end - (uintptr_t)ksym_start - 408 sizeof(long) - sh[0].sh_size - sizeof(long); 409 elf.e_shstrndx = -1; 410 elf.e_shnum = 2; 411 412 X_db_sym_init(&elf, ksym_end, "kernel"); 413 } 414 415 #endif /* DDB_NOKLDSYM */
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