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1 /* Handle Darwin shared libraries for GDB, the GNU Debugger.
2
3 Copyright (C) 2009-2020 Free Software Foundation, Inc.
4
5 This file is part of GDB.
6
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
11
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
16
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>. */
19
20 #include "defs.h"
21
22 #include "symtab.h"
23 #include "bfd.h"
24 #include "symfile.h"
25 #include "objfiles.h"
26 #include "gdbcore.h"
27 #include "target.h"
28 #include "inferior.h"
29 #include "regcache.h"
30 #include "gdbthread.h"
31 #include "gdb_bfd.h"
32
33 #include "solist.h"
34 #include "solib.h"
35 #include "solib-svr4.h"
36
37 #include "bfd-target.h"
38 #include "elf-bfd.h"
39 #include "exec.h"
40 #include "auxv.h"
41 #include "mach-o.h"
42 #include "mach-o/external.h"
43
44 struct gdb_dyld_image_info
45 {
46 /* Base address (which corresponds to the Mach-O header). */
47 CORE_ADDR mach_header;
48 /* Image file path. */
49 CORE_ADDR file_path;
50 /* st.m_time of image file. */
51 unsigned long mtime;
52 };
53
54 /* Content of inferior dyld_all_image_infos structure.
55 See /usr/include/mach-o/dyld_images.h for the documentation. */
56 struct gdb_dyld_all_image_infos
57 {
58 /* Version (1). */
59 unsigned int version;
60 /* Number of images. */
61 unsigned int count;
62 /* Image description. */
63 CORE_ADDR info;
64 /* Notifier (function called when a library is added or removed). */
65 CORE_ADDR notifier;
66 };
67
68 /* Current all_image_infos version. */
69 #define DYLD_VERSION_MIN 1
70 #define DYLD_VERSION_MAX 15
71
72 /* Per PSPACE specific data. */
73 struct darwin_info
74 {
75 /* Address of structure dyld_all_image_infos in inferior. */
76 CORE_ADDR all_image_addr = 0;
77
78 /* Gdb copy of dyld_all_info_infos. */
79 struct gdb_dyld_all_image_infos all_image {};
80 };
81
82 /* Per-program-space data key. */
83 static program_space_key<darwin_info> solib_darwin_pspace_data;
84
85 /* Get the current darwin data. If none is found yet, add it now. This
86 function always returns a valid object. */
87
88 static struct darwin_info *
89 get_darwin_info (void)
90 {
91 struct darwin_info *info;
92
93 info = solib_darwin_pspace_data.get (current_program_space);
94 if (info != NULL)
95 return info;
96
97 return solib_darwin_pspace_data.emplace (current_program_space);
98 }
99
100 /* Return non-zero if the version in dyld_all_image is known. */
101
102 static int
103 darwin_dyld_version_ok (const struct darwin_info *info)
104 {
105 return info->all_image.version >= DYLD_VERSION_MIN
106 && info->all_image.version <= DYLD_VERSION_MAX;
107 }
108
109 /* Read dyld_all_image from inferior. */
110
111 static void
112 darwin_load_image_infos (struct darwin_info *info)
113 {
114 gdb_byte buf[24];
115 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
116 struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
117 int len;
118
119 /* If the structure address is not known, don't continue. */
120 if (info->all_image_addr == 0)
121 return;
122
123 /* The structure has 4 fields: version (4 bytes), count (4 bytes),
124 info (pointer) and notifier (pointer). */
125 len = 4 + 4 + 2 * TYPE_LENGTH (ptr_type);
126 gdb_assert (len <= sizeof (buf));
127 memset (&info->all_image, 0, sizeof (info->all_image));
128
129 /* Read structure raw bytes from target. */
130 if (target_read_memory (info->all_image_addr, buf, len))
131 return;
132
133 /* Extract the fields. */
134 info->all_image.version = extract_unsigned_integer (buf, 4, byte_order);
135 if (!darwin_dyld_version_ok (info))
136 return;
137
138 info->all_image.count = extract_unsigned_integer (buf + 4, 4, byte_order);
139 info->all_image.info = extract_typed_address (buf + 8, ptr_type);
140 info->all_image.notifier = extract_typed_address
141 (buf + 8 + TYPE_LENGTH (ptr_type), ptr_type);
142 }
143
144 /* Link map info to include in an allocated so_list entry. */
145
146 struct lm_info_darwin : public lm_info_base
147 {
148 /* The target location of lm. */
149 CORE_ADDR lm_addr = 0;
150 };
151
152 /* Lookup the value for a specific symbol. */
153
154 static CORE_ADDR
155 lookup_symbol_from_bfd (bfd *abfd, const char *symname)
156 {
157 long storage_needed;
158 asymbol **symbol_table;
159 unsigned int number_of_symbols;
160 unsigned int i;
161 CORE_ADDR symaddr = 0;
162
163 storage_needed = bfd_get_symtab_upper_bound (abfd);
164
165 if (storage_needed <= 0)
166 return 0;
167
168 symbol_table = (asymbol **) xmalloc (storage_needed);
169 number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
170
171 for (i = 0; i < number_of_symbols; i++)
172 {
173 asymbol *sym = symbol_table[i];
174
175 if (strcmp (sym->name, symname) == 0
176 && (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
177 {
178 /* BFD symbols are section relative. */
179 symaddr = sym->value + sym->section->vma;
180 break;
181 }
182 }
183 xfree (symbol_table);
184
185 return symaddr;
186 }
187
188 /* Return program interpreter string. */
189
190 static char *
191 find_program_interpreter (void)
192 {
193 char *buf = NULL;
194
195 /* If we have an exec_bfd, get the interpreter from the load commands. */
196 if (exec_bfd)
197 {
198 bfd_mach_o_load_command *cmd;
199
200 if (bfd_mach_o_lookup_command (exec_bfd,
201 BFD_MACH_O_LC_LOAD_DYLINKER, &cmd) == 1)
202 return cmd->command.dylinker.name_str;
203 }
204
205 /* If we didn't find it, read from memory.
206 FIXME: todo. */
207 return buf;
208 }
209
210 /* Not used. I don't see how the main symbol file can be found: the
211 interpreter name is needed and it is known from the executable file.
212 Note that darwin-nat.c implements pid_to_exec_file. */
213
214 static int
215 open_symbol_file_object (int from_tty)
216 {
217 return 0;
218 }
219
220 /* Build a list of currently loaded shared objects. See solib-svr4.c. */
221
222 static struct so_list *
223 darwin_current_sos (void)
224 {
225 struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
226 enum bfd_endian byte_order = type_byte_order (ptr_type);
227 int ptr_len = TYPE_LENGTH (ptr_type);
228 unsigned int image_info_size;
229 struct so_list *head = NULL;
230 struct so_list *tail = NULL;
231 int i;
232 struct darwin_info *info = get_darwin_info ();
233
234 /* Be sure image infos are loaded. */
235 darwin_load_image_infos (info);
236
237 if (!darwin_dyld_version_ok (info))
238 return NULL;
239
240 image_info_size = ptr_len * 3;
241
242 /* Read infos for each solib.
243 The first entry was rumored to be the executable itself, but this is not
244 true when a large number of shared libraries are used (table expanded ?).
245 We now check all entries, but discard executable images. */
246 for (i = 0; i < info->all_image.count; i++)
247 {
248 CORE_ADDR iinfo = info->all_image.info + i * image_info_size;
249 gdb_byte buf[image_info_size];
250 CORE_ADDR load_addr;
251 CORE_ADDR path_addr;
252 struct mach_o_header_external hdr;
253 unsigned long hdr_val;
254 gdb::unique_xmalloc_ptr<char> file_path;
255 int errcode;
256
257 /* Read image info from inferior. */
258 if (target_read_memory (iinfo, buf, image_info_size))
259 break;
260
261 load_addr = extract_typed_address (buf, ptr_type);
262 path_addr = extract_typed_address (buf + ptr_len, ptr_type);
263
264 /* Read Mach-O header from memory. */
265 if (target_read_memory (load_addr, (gdb_byte *) &hdr, sizeof (hdr) - 4))
266 break;
267 /* Discard wrong magic numbers. Shouldn't happen. */
268 hdr_val = extract_unsigned_integer
269 (hdr.magic, sizeof (hdr.magic), byte_order);
270 if (hdr_val != BFD_MACH_O_MH_MAGIC && hdr_val != BFD_MACH_O_MH_MAGIC_64)
271 continue;
272 /* Discard executable. Should happen only once. */
273 hdr_val = extract_unsigned_integer
274 (hdr.filetype, sizeof (hdr.filetype), byte_order);
275 if (hdr_val == BFD_MACH_O_MH_EXECUTE)
276 continue;
277
278 target_read_string (path_addr, &file_path,
279 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
280 if (errcode)
281 break;
282
283 /* Create and fill the new so_list element. */
284 gdb::unique_xmalloc_ptr<struct so_list> newobj (XCNEW (struct so_list));
285
286 lm_info_darwin *li = new lm_info_darwin;
287 newobj->lm_info = li;
288
289 strncpy (newobj->so_name, file_path.get (), SO_NAME_MAX_PATH_SIZE - 1);
290 newobj->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
291 strcpy (newobj->so_original_name, newobj->so_name);
292 li->lm_addr = load_addr;
293
294 if (head == NULL)
295 head = newobj.get ();
296 else
297 tail->next = newobj.get ();
298 tail = newobj.release ();
299 }
300
301 return head;
302 }
303
304 /* Check LOAD_ADDR points to a Mach-O executable header. Return LOAD_ADDR
305 in case of success, 0 in case of failure. */
306
307 static CORE_ADDR
308 darwin_validate_exec_header (CORE_ADDR load_addr)
309 {
310 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
311 struct mach_o_header_external hdr;
312 unsigned long hdr_val;
313
314 /* Read Mach-O header from memory. */
315 if (target_read_memory (load_addr, (gdb_byte *) &hdr, sizeof (hdr) - 4))
316 return 0;
317
318 /* Discard wrong magic numbers. Shouldn't happen. */
319 hdr_val = extract_unsigned_integer
320 (hdr.magic, sizeof (hdr.magic), byte_order);
321 if (hdr_val != BFD_MACH_O_MH_MAGIC && hdr_val != BFD_MACH_O_MH_MAGIC_64)
322 return 0;
323
324 /* Check executable. */
325 hdr_val = extract_unsigned_integer
326 (hdr.filetype, sizeof (hdr.filetype), byte_order);
327 if (hdr_val == BFD_MACH_O_MH_EXECUTE)
328 return load_addr;
329
330 return 0;
331 }
332
333 /* Get the load address of the executable using dyld list of images.
334 We assume that the dyld info are correct (which is wrong if the target
335 is stopped at the first instruction). */
336
337 static CORE_ADDR
338 darwin_read_exec_load_addr_from_dyld (struct darwin_info *info)
339 {
340 struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
341 int ptr_len = TYPE_LENGTH (ptr_type);
342 unsigned int image_info_size = ptr_len * 3;
343 int i;
344
345 /* Read infos for each solib. One of them should be the executable. */
346 for (i = 0; i < info->all_image.count; i++)
347 {
348 CORE_ADDR iinfo = info->all_image.info + i * image_info_size;
349 gdb_byte buf[image_info_size];
350 CORE_ADDR load_addr;
351
352 /* Read image info from inferior. */
353 if (target_read_memory (iinfo, buf, image_info_size))
354 break;
355
356 load_addr = extract_typed_address (buf, ptr_type);
357 if (darwin_validate_exec_header (load_addr) == load_addr)
358 return load_addr;
359 }
360
361 return 0;
362 }
363
364 /* Get the load address of the executable when the PC is at the dyld
365 entry point using parameter passed by the kernel (at SP). */
366
367 static CORE_ADDR
368 darwin_read_exec_load_addr_at_init (struct darwin_info *info)
369 {
370 struct gdbarch *gdbarch = target_gdbarch ();
371 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
372 int addr_size = gdbarch_addr_bit (gdbarch) / 8;
373 ULONGEST load_ptr_addr;
374 ULONGEST load_addr;
375 gdb_byte buf[8];
376
377 /* Get SP. */
378 if (regcache_cooked_read_unsigned (get_current_regcache (),
379 gdbarch_sp_regnum (gdbarch),
380 &load_ptr_addr) != REG_VALID)
381 return 0;
382
383 /* Read value at SP (image load address). */
384 if (target_read_memory (load_ptr_addr, buf, addr_size))
385 return 0;
386
387 load_addr = extract_unsigned_integer (buf, addr_size, byte_order);
388
389 return darwin_validate_exec_header (load_addr);
390 }
391
392 /* Return 1 if PC lies in the dynamic symbol resolution code of the
393 run time loader. */
394
395 static int
396 darwin_in_dynsym_resolve_code (CORE_ADDR pc)
397 {
398 return 0;
399 }
400
401 /* A wrapper for bfd_mach_o_fat_extract that handles reference
402 counting properly. This will either return NULL, or return a new
403 reference to a BFD. */
404
405 static gdb_bfd_ref_ptr
406 gdb_bfd_mach_o_fat_extract (bfd *abfd, bfd_format format,
407 const bfd_arch_info_type *arch)
408 {
409 bfd *result = bfd_mach_o_fat_extract (abfd, format, arch);
410
411 if (result == NULL)
412 return NULL;
413
414 if (result == abfd)
415 gdb_bfd_ref (result);
416 else
417 gdb_bfd_mark_parent (result, abfd);
418
419 return gdb_bfd_ref_ptr (result);
420 }
421
422 /* Return the BFD for the program interpreter. */
423
424 static gdb_bfd_ref_ptr
425 darwin_get_dyld_bfd ()
426 {
427 char *interp_name;
428
429 /* This method doesn't work with an attached process. */
430 if (current_inferior ()->attach_flag)
431 return NULL;
432
433 /* Find the program interpreter. */
434 interp_name = find_program_interpreter ();
435 if (!interp_name)
436 return NULL;
437
438 /* Create a bfd for the interpreter. */
439 gdb_bfd_ref_ptr dyld_bfd (gdb_bfd_open (interp_name, gnutarget));
440 if (dyld_bfd != NULL)
441 {
442 gdb_bfd_ref_ptr sub
443 (gdb_bfd_mach_o_fat_extract (dyld_bfd.get (), bfd_object,
444 gdbarch_bfd_arch_info (target_gdbarch ())));
445 dyld_bfd = sub;
446 }
447 return dyld_bfd;
448 }
449
450 /* Extract dyld_all_image_addr when the process was just created, assuming the
451 current PC is at the entry of the dynamic linker. */
452
453 static void
454 darwin_solib_get_all_image_info_addr_at_init (struct darwin_info *info)
455 {
456 CORE_ADDR load_addr = 0;
457 gdb_bfd_ref_ptr dyld_bfd = darwin_get_dyld_bfd ();
458
459 if (dyld_bfd == NULL)
460 return;
461
462 /* We find the dynamic linker's base address by examining
463 the current pc (which should point at the entry point for the
464 dynamic linker) and subtracting the offset of the entry point. */
465 load_addr = (regcache_read_pc (get_current_regcache ())
466 - bfd_get_start_address (dyld_bfd.get ()));
467
468 /* Now try to set a breakpoint in the dynamic linker. */
469 info->all_image_addr =
470 lookup_symbol_from_bfd (dyld_bfd.get (), "_dyld_all_image_infos");
471
472 if (info->all_image_addr == 0)
473 return;
474
475 info->all_image_addr += load_addr;
476 }
477
478 /* Extract dyld_all_image_addr reading it from
479 TARGET_OBJECT_DARWIN_DYLD_INFO. */
480
481 static void
482 darwin_solib_read_all_image_info_addr (struct darwin_info *info)
483 {
484 gdb_byte buf[8];
485 LONGEST len;
486 struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
487
488 /* Sanity check. */
489 if (TYPE_LENGTH (ptr_type) > sizeof (buf))
490 return;
491
492 len = target_read (current_top_target (), TARGET_OBJECT_DARWIN_DYLD_INFO,
493 NULL, buf, 0, TYPE_LENGTH (ptr_type));
494 if (len <= 0)
495 return;
496
497 /* The use of BIG endian is intended, as BUF is a raw stream of bytes. This
498 makes the support of remote protocol easier. */
499 info->all_image_addr = extract_unsigned_integer (buf, len, BFD_ENDIAN_BIG);
500 }
501
502 /* Shared library startup support. See documentation in solib-svr4.c. */
503
504 static void
505 darwin_solib_create_inferior_hook (int from_tty)
506 {
507 struct darwin_info *info = get_darwin_info ();
508 CORE_ADDR load_addr;
509
510 info->all_image_addr = 0;
511
512 darwin_solib_read_all_image_info_addr (info);
513
514 if (info->all_image_addr == 0)
515 darwin_solib_get_all_image_info_addr_at_init (info);
516
517 if (info->all_image_addr == 0)
518 return;
519
520 darwin_load_image_infos (info);
521
522 if (!darwin_dyld_version_ok (info))
523 {
524 warning (_("unhandled dyld version (%d)"), info->all_image.version);
525 return;
526 }
527
528 if (info->all_image.count != 0)
529 {
530 /* Possible relocate the main executable (PIE). */
531 load_addr = darwin_read_exec_load_addr_from_dyld (info);
532 }
533 else
534 {
535 /* Possible issue:
536 Do not break on the notifier if dyld is not initialized (deduced from
537 count == 0). In that case, dyld hasn't relocated itself and the
538 notifier may point to a wrong address. */
539
540 load_addr = darwin_read_exec_load_addr_at_init (info);
541 }
542
543 if (load_addr != 0 && symfile_objfile != NULL)
544 {
545 CORE_ADDR vmaddr;
546
547 /* Find the base address of the executable. */
548 vmaddr = bfd_mach_o_get_base_address (exec_bfd);
549
550 /* Relocate. */
551 if (vmaddr != load_addr)
552 objfile_rebase (symfile_objfile, load_addr - vmaddr);
553 }
554
555 /* Set solib notifier (to reload list of shared libraries). */
556 CORE_ADDR notifier = info->all_image.notifier;
557
558 if (info->all_image.count == 0)
559 {
560 /* Dyld hasn't yet relocated itself, so the notifier address may
561 be incorrect (as it has to be relocated). */
562 CORE_ADDR start = bfd_get_start_address (exec_bfd);
563 if (start == 0)
564 notifier = 0;
565 else
566 {
567 gdb_bfd_ref_ptr dyld_bfd = darwin_get_dyld_bfd ();
568 if (dyld_bfd != NULL)
569 {
570 CORE_ADDR dyld_bfd_start_address;
571 CORE_ADDR dyld_relocated_base_address;
572 CORE_ADDR pc;
573
574 dyld_bfd_start_address = bfd_get_start_address (dyld_bfd.get());
575
576 /* We find the dynamic linker's base address by examining
577 the current pc (which should point at the entry point
578 for the dynamic linker) and subtracting the offset of
579 the entry point. */
580
581 pc = regcache_read_pc (get_current_regcache ());
582 dyld_relocated_base_address = pc - dyld_bfd_start_address;
583
584 /* We get the proper notifier relocated address by
585 adding the dyld relocated base address to the current
586 notifier offset value. */
587
588 notifier += dyld_relocated_base_address;
589 }
590 }
591 }
592
593 /* Add the breakpoint which is hit by dyld when the list of solib is
594 modified. */
595 if (notifier != 0)
596 create_solib_event_breakpoint (target_gdbarch (), notifier);
597 }
598
599 static void
600 darwin_clear_solib (void)
601 {
602 struct darwin_info *info = get_darwin_info ();
603
604 info->all_image_addr = 0;
605 info->all_image.version = 0;
606 }
607
608 static void
609 darwin_free_so (struct so_list *so)
610 {
611 lm_info_darwin *li = (lm_info_darwin *) so->lm_info;
612
613 delete li;
614 }
615
616 /* The section table is built from bfd sections using bfd VMAs.
617 Relocate these VMAs according to solib info. */
618
619 static void
620 darwin_relocate_section_addresses (struct so_list *so,
621 struct target_section *sec)
622 {
623 lm_info_darwin *li = (lm_info_darwin *) so->lm_info;
624
625 sec->addr += li->lm_addr;
626 sec->endaddr += li->lm_addr;
627
628 /* Best effort to set addr_high/addr_low. This is used only by
629 'info sharedlibary'. */
630 if (so->addr_high == 0)
631 {
632 so->addr_low = sec->addr;
633 so->addr_high = sec->endaddr;
634 }
635 if (sec->endaddr > so->addr_high)
636 so->addr_high = sec->endaddr;
637 if (sec->addr < so->addr_low)
638 so->addr_low = sec->addr;
639 }
640 \f
641 static gdb_bfd_ref_ptr
642 darwin_bfd_open (const char *pathname)
643 {
644 int found_file;
645
646 /* Search for shared library file. */
647 gdb::unique_xmalloc_ptr<char> found_pathname
648 = solib_find (pathname, &found_file);
649 if (found_pathname == NULL)
650 perror_with_name (pathname);
651
652 /* Open bfd for shared library. */
653 gdb_bfd_ref_ptr abfd (solib_bfd_fopen (found_pathname.get (), found_file));
654
655 gdb_bfd_ref_ptr res
656 (gdb_bfd_mach_o_fat_extract (abfd.get (), bfd_object,
657 gdbarch_bfd_arch_info (target_gdbarch ())));
658 if (res == NULL)
659 error (_("`%s': not a shared-library: %s"),
660 bfd_get_filename (abfd.get ()), bfd_errmsg (bfd_get_error ()));
661
662 /* The current filename for fat-binary BFDs is a name generated
663 by BFD, usually a string containing the name of the architecture.
664 Reset its value to the actual filename. */
665 bfd_set_filename (res.get (), pathname);
666
667 return res;
668 }
669
670 struct target_so_ops darwin_so_ops;
671
672 void _initialize_darwin_solib ();
673 void
674 _initialize_darwin_solib ()
675 {
676 darwin_so_ops.relocate_section_addresses = darwin_relocate_section_addresses;
677 darwin_so_ops.free_so = darwin_free_so;
678 darwin_so_ops.clear_solib = darwin_clear_solib;
679 darwin_so_ops.solib_create_inferior_hook = darwin_solib_create_inferior_hook;
680 darwin_so_ops.current_sos = darwin_current_sos;
681 darwin_so_ops.open_symbol_file_object = open_symbol_file_object;
682 darwin_so_ops.in_dynsym_resolve_code = darwin_in_dynsym_resolve_code;
683 darwin_so_ops.bfd_open = darwin_bfd_open;
684 }