FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_elf.c
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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