1 /* Handle SVR4 shared libraries for GDB, the GNU Debugger.
3 Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999,
4 2000, 2001, 2003 Free Software Foundation, Inc.
6 This file is part of GDB.
8 This program is free software; you can redistribute it and/or modify
9 it under the terms of the GNU General Public License as published by
10 the Free Software Foundation; either version 2 of the License, or
11 (at your option) any later version.
13 This program is distributed in the hope that it will be useful,
14 but WITHOUT ANY WARRANTY; without even the implied warranty of
15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16 GNU General Public License for more details.
18 You should have received a copy of the GNU General Public License
19 along with this program; if not, write to the Free Software
20 Foundation, Inc., 59 Temple Place - Suite 330,
21 Boston, MA 02111-1307, USA. */
25 #include "elf/external.h"
26 #include "elf/common.h"
38 #include "solib-svr4.h"
40 #include "bfd-target.h"
43 #ifndef SVR4_FETCH_LINK_MAP_OFFSETS
44 #define SVR4_FETCH_LINK_MAP_OFFSETS() svr4_fetch_link_map_offsets ()
47 static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
48 static struct link_map_offsets *legacy_fetch_link_map_offsets (void);
49 static int svr4_have_link_map_offsets (void);
51 /* fetch_link_map_offsets_gdbarch_data is a handle used to obtain the
52 architecture specific link map offsets fetching function. */
54 static struct gdbarch_data *fetch_link_map_offsets_gdbarch_data;
56 /* legacy_svr4_fetch_link_map_offsets_hook is a pointer to a function
57 which is used to fetch link map offsets. It will only be set
58 by solib-legacy.c, if at all. */
60 struct link_map_offsets *(*legacy_svr4_fetch_link_map_offsets_hook)(void) = 0;
62 /* Link map info to include in an allocated so_list entry */
66 /* Pointer to copy of link map from inferior. The type is char *
67 rather than void *, so that we may use byte offsets to find the
68 various fields without the need for a cast. */
72 /* On SVR4 systems, a list of symbols in the dynamic linker where
73 GDB can try to place a breakpoint to monitor shared library
76 If none of these symbols are found, or other errors occur, then
77 SVR4 systems will fall back to using a symbol as the "startup
78 mapping complete" breakpoint address. */
80 static char *solib_break_names[] =
88 /* On the 64-bit PowerPC, the linker symbol with the same name as
89 the C function points to a function descriptor, not to the entry
90 point. The linker symbol whose name is the C function name
91 prefixed with a '.' points to the function's entry point. So
92 when we look through this table, we ignore symbols that point
93 into the data section (thus skipping the descriptor's symbol),
94 and eventually try this one, giving us the real entry point
101 #define BKPT_AT_SYMBOL 1
103 #if defined (BKPT_AT_SYMBOL)
104 static char *bkpt_names[] =
106 #ifdef SOLIB_BKPT_NAME
107 SOLIB_BKPT_NAME, /* Prefer configured name if it exists. */
116 static char *main_name_list[] =
122 /* Macro to extract an address from a solib structure. When GDB is
123 configured for some 32-bit targets (e.g. Solaris 2.7 sparc), BFD is
124 configured to handle 64-bit targets, so CORE_ADDR is 64 bits. We
125 have to extract only the significant bits of addresses to get the
126 right address when accessing the core file BFD.
128 Assume that the address is unsigned. */
130 #define SOLIB_EXTRACT_ADDRESS(MEMBER) \
131 extract_unsigned_integer (&(MEMBER), sizeof (MEMBER))
133 /* local data declarations */
135 /* link map access functions */
138 LM_ADDR (struct so_list *so)
140 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
142 return (CORE_ADDR) extract_signed_integer (so->lm_info->lm + lmo->l_addr_offset,
147 LM_NEXT (struct so_list *so)
149 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
151 /* Assume that the address is unsigned. */
152 return extract_unsigned_integer (so->lm_info->lm + lmo->l_next_offset,
157 LM_NAME (struct so_list *so)
159 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
161 /* Assume that the address is unsigned. */
162 return extract_unsigned_integer (so->lm_info->lm + lmo->l_name_offset,
167 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
169 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
171 /* Assume that the address is unsigned. */
172 return extract_unsigned_integer (so->lm_info->lm + lmo->l_prev_offset,
173 lmo->l_prev_size) == 0;
176 static CORE_ADDR debug_base; /* Base of dynamic linker structures */
177 static CORE_ADDR breakpoint_addr; /* Address where end bkpt is set */
179 /* Local function prototypes */
181 static int match_main (char *);
183 static CORE_ADDR bfd_lookup_symbol (bfd *, char *, flagword);
189 bfd_lookup_symbol -- lookup the value for a specific symbol
193 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname, flagword sect_flags)
197 An expensive way to lookup the value of a single symbol for
198 bfd's that are only temporary anyway. This is used by the
199 shared library support to find the address of the debugger
200 interface structures in the shared library.
202 If SECT_FLAGS is non-zero, only match symbols in sections whose
203 flags include all those in SECT_FLAGS.
205 Note that 0 is specifically allowed as an error return (no
210 bfd_lookup_symbol (bfd *abfd, char *symname, flagword sect_flags)
214 asymbol **symbol_table;
215 unsigned int number_of_symbols;
217 struct cleanup *back_to;
218 CORE_ADDR symaddr = 0;
220 storage_needed = bfd_get_symtab_upper_bound (abfd);
222 if (storage_needed > 0)
224 symbol_table = (asymbol **) xmalloc (storage_needed);
225 back_to = make_cleanup (xfree, symbol_table);
226 number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
228 for (i = 0; i < number_of_symbols; i++)
230 sym = *symbol_table++;
231 if (strcmp (sym->name, symname) == 0
232 && (sym->section->flags & sect_flags) == sect_flags)
234 /* Bfd symbols are section relative. */
235 symaddr = sym->value + sym->section->vma;
239 do_cleanups (back_to);
245 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
246 have to check the dynamic string table too. */
248 storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);
250 if (storage_needed > 0)
252 symbol_table = (asymbol **) xmalloc (storage_needed);
253 back_to = make_cleanup (xfree, symbol_table);
254 number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table);
256 for (i = 0; i < number_of_symbols; i++)
258 sym = *symbol_table++;
260 if (strcmp (sym->name, symname) == 0
261 && (sym->section->flags & sect_flags) == sect_flags)
263 /* Bfd symbols are section relative. */
264 symaddr = sym->value + sym->section->vma;
268 do_cleanups (back_to);
274 #ifdef HANDLE_SVR4_EXEC_EMULATORS
277 Solaris BCP (the part of Solaris which allows it to run SunOS4
278 a.out files) throws in another wrinkle. Solaris does not fill
279 in the usual a.out link map structures when running BCP programs,
280 the only way to get at them is via groping around in the dynamic
282 The dynamic linker and it's structures are located in the shared
283 C library, which gets run as the executable's "interpreter" by
286 Note that we can assume nothing about the process state at the time
287 we need to find these structures. We may be stopped on the first
288 instruction of the interpreter (C shared library), the first
289 instruction of the executable itself, or somewhere else entirely
290 (if we attached to the process for example).
293 static char *debug_base_symbols[] =
295 "r_debug", /* Solaris 2.3 */
296 "_r_debug", /* Solaris 2.1, 2.2 */
300 static int look_for_base (int, CORE_ADDR);
306 look_for_base -- examine file for each mapped address segment
310 static int look_for_base (int fd, CORE_ADDR baseaddr)
314 This function is passed to proc_iterate_over_mappings, which
315 causes it to get called once for each mapped address space, with
316 an open file descriptor for the file mapped to that space, and the
317 base address of that mapped space.
319 Our job is to find the debug base symbol in the file that this
320 fd is open on, if it exists, and if so, initialize the dynamic
321 linker structure base address debug_base.
323 Note that this is a computationally expensive proposition, since
324 we basically have to open a bfd on every call, so we specifically
325 avoid opening the exec file.
329 look_for_base (int fd, CORE_ADDR baseaddr)
332 CORE_ADDR address = 0;
335 /* If the fd is -1, then there is no file that corresponds to this
336 mapped memory segment, so skip it. Also, if the fd corresponds
337 to the exec file, skip it as well. */
341 && fdmatch (fileno ((FILE *) (exec_bfd->iostream)), fd)))
346 /* Try to open whatever random file this fd corresponds to. Note that
347 we have no way currently to find the filename. Don't gripe about
348 any problems we might have, just fail. */
350 if ((interp_bfd = bfd_fdopenr ("unnamed", gnutarget, fd)) == NULL)
354 if (!bfd_check_format (interp_bfd, bfd_object))
356 /* FIXME-leak: on failure, might not free all memory associated with
358 bfd_close (interp_bfd);
362 /* Now try to find our debug base symbol in this file, which we at
363 least know to be a valid ELF executable or shared library. */
365 for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
367 address = bfd_lookup_symbol (interp_bfd, *symbolp, 0);
375 /* FIXME-leak: on failure, might not free all memory associated with
377 bfd_close (interp_bfd);
381 /* Eureka! We found the symbol. But now we may need to relocate it
382 by the base address. If the symbol's value is less than the base
383 address of the shared library, then it hasn't yet been relocated
384 by the dynamic linker, and we have to do it ourself. FIXME: Note
385 that we make the assumption that the first segment that corresponds
386 to the shared library has the base address to which the library
389 if (address < baseaddr)
393 debug_base = address;
394 /* FIXME-leak: on failure, might not free all memory associated with
396 bfd_close (interp_bfd);
399 #endif /* HANDLE_SVR4_EXEC_EMULATORS */
405 elf_locate_base -- locate the base address of dynamic linker structs
406 for SVR4 elf targets.
410 CORE_ADDR elf_locate_base (void)
414 For SVR4 elf targets the address of the dynamic linker's runtime
415 structure is contained within the dynamic info section in the
416 executable file. The dynamic section is also mapped into the
417 inferior address space. Because the runtime loader fills in the
418 real address before starting the inferior, we have to read in the
419 dynamic info section from the inferior address space.
420 If there are any errors while trying to find the address, we
421 silently return 0, otherwise the found address is returned.
426 elf_locate_base (void)
428 struct bfd_section *dyninfo_sect;
429 int dyninfo_sect_size;
430 CORE_ADDR dyninfo_addr;
435 /* Find the start address of the .dynamic section. */
436 dyninfo_sect = bfd_get_section_by_name (exec_bfd, ".dynamic");
437 if (dyninfo_sect == NULL)
439 dyninfo_addr = bfd_section_vma (exec_bfd, dyninfo_sect);
441 /* Read in .dynamic section, silently ignore errors. */
442 dyninfo_sect_size = bfd_section_size (exec_bfd, dyninfo_sect);
443 buf = alloca (dyninfo_sect_size);
444 if (target_read_memory (dyninfo_addr, buf, dyninfo_sect_size))
447 /* Find the DT_DEBUG entry in the the .dynamic section.
448 For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has
449 no DT_DEBUG entries. */
451 arch_size = bfd_get_arch_size (exec_bfd);
452 if (arch_size == -1) /* failure */
457 for (bufend = buf + dyninfo_sect_size;
459 buf += sizeof (Elf32_External_Dyn))
461 Elf32_External_Dyn *x_dynp = (Elf32_External_Dyn *) buf;
465 dyn_tag = bfd_h_get_32 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
466 if (dyn_tag == DT_NULL)
468 else if (dyn_tag == DT_DEBUG)
470 dyn_ptr = bfd_h_get_32 (exec_bfd,
471 (bfd_byte *) x_dynp->d_un.d_ptr);
474 else if (dyn_tag == DT_MIPS_RLD_MAP)
477 int pbuf_size = TARGET_PTR_BIT / HOST_CHAR_BIT;
479 pbuf = alloca (pbuf_size);
480 /* DT_MIPS_RLD_MAP contains a pointer to the address
481 of the dynamic link structure. */
482 dyn_ptr = bfd_h_get_32 (exec_bfd,
483 (bfd_byte *) x_dynp->d_un.d_ptr);
484 if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
486 return extract_unsigned_integer (pbuf, pbuf_size);
490 else /* 64-bit elf */
492 for (bufend = buf + dyninfo_sect_size;
494 buf += sizeof (Elf64_External_Dyn))
496 Elf64_External_Dyn *x_dynp = (Elf64_External_Dyn *) buf;
500 dyn_tag = bfd_h_get_64 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
501 if (dyn_tag == DT_NULL)
503 else if (dyn_tag == DT_DEBUG)
505 dyn_ptr = bfd_h_get_64 (exec_bfd,
506 (bfd_byte *) x_dynp->d_un.d_ptr);
509 else if (dyn_tag == DT_MIPS_RLD_MAP)
512 int pbuf_size = TARGET_PTR_BIT / HOST_CHAR_BIT;
514 pbuf = alloca (pbuf_size);
515 /* DT_MIPS_RLD_MAP contains a pointer to the address
516 of the dynamic link structure. */
517 dyn_ptr = bfd_h_get_64 (exec_bfd,
518 (bfd_byte *) x_dynp->d_un.d_ptr);
519 if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
521 return extract_unsigned_integer (pbuf, pbuf_size);
526 /* DT_DEBUG entry not found. */
534 locate_base -- locate the base address of dynamic linker structs
538 CORE_ADDR locate_base (void)
542 For both the SunOS and SVR4 shared library implementations, if the
543 inferior executable has been linked dynamically, there is a single
544 address somewhere in the inferior's data space which is the key to
545 locating all of the dynamic linker's runtime structures. This
546 address is the value of the debug base symbol. The job of this
547 function is to find and return that address, or to return 0 if there
548 is no such address (the executable is statically linked for example).
550 For SunOS, the job is almost trivial, since the dynamic linker and
551 all of it's structures are statically linked to the executable at
552 link time. Thus the symbol for the address we are looking for has
553 already been added to the minimal symbol table for the executable's
554 objfile at the time the symbol file's symbols were read, and all we
555 have to do is look it up there. Note that we explicitly do NOT want
556 to find the copies in the shared library.
558 The SVR4 version is a bit more complicated because the address
559 is contained somewhere in the dynamic info section. We have to go
560 to a lot more work to discover the address of the debug base symbol.
561 Because of this complexity, we cache the value we find and return that
562 value on subsequent invocations. Note there is no copy in the
563 executable symbol tables.
570 /* Check to see if we have a currently valid address, and if so, avoid
571 doing all this work again and just return the cached address. If
572 we have no cached address, try to locate it in the dynamic info
573 section for ELF executables. There's no point in doing any of this
574 though if we don't have some link map offsets to work with. */
576 if (debug_base == 0 && svr4_have_link_map_offsets ())
579 && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
580 debug_base = elf_locate_base ();
581 #ifdef HANDLE_SVR4_EXEC_EMULATORS
582 /* Try it the hard way for emulated executables. */
583 else if (!ptid_equal (inferior_ptid, null_ptid) && target_has_execution)
584 proc_iterate_over_mappings (look_for_base);
594 first_link_map_member -- locate first member in dynamic linker's map
598 static CORE_ADDR first_link_map_member (void)
602 Find the first element in the inferior's dynamic link map, and
603 return its address in the inferior. This function doesn't copy the
604 link map entry itself into our address space; current_sos actually
608 first_link_map_member (void)
611 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
612 char *r_map_buf = xmalloc (lmo->r_map_size);
613 struct cleanup *cleanups = make_cleanup (xfree, r_map_buf);
615 read_memory (debug_base + lmo->r_map_offset, r_map_buf, lmo->r_map_size);
617 /* Assume that the address is unsigned. */
618 lm = extract_unsigned_integer (r_map_buf, lmo->r_map_size);
620 /* FIXME: Perhaps we should validate the info somehow, perhaps by
621 checking r_version for a known version number, or r_state for
624 do_cleanups (cleanups);
633 open_symbol_file_object
637 void open_symbol_file_object (void *from_tty)
641 If no open symbol file, attempt to locate and open the main symbol
642 file. On SVR4 systems, this is the first link map entry. If its
643 name is here, we can open it. Useful when attaching to a process
644 without first loading its symbol file.
646 If FROM_TTYP dereferences to a non-zero integer, allow messages to
647 be printed. This parameter is a pointer rather than an int because
648 open_symbol_file_object() is called via catch_errors() and
649 catch_errors() requires a pointer argument. */
652 open_symbol_file_object (void *from_ttyp)
654 CORE_ADDR lm, l_name;
657 int from_tty = *(int *)from_ttyp;
658 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
659 char *l_name_buf = xmalloc (lmo->l_name_size);
660 struct cleanup *cleanups = make_cleanup (xfree, l_name_buf);
663 if (!query ("Attempt to reload symbols from process? "))
666 if ((debug_base = locate_base ()) == 0)
667 return 0; /* failed somehow... */
669 /* First link map member should be the executable. */
670 if ((lm = first_link_map_member ()) == 0)
671 return 0; /* failed somehow... */
673 /* Read address of name from target memory to GDB. */
674 read_memory (lm + lmo->l_name_offset, l_name_buf, lmo->l_name_size);
676 /* Convert the address to host format. Assume that the address is
678 l_name = extract_unsigned_integer (l_name_buf, lmo->l_name_size);
680 /* Free l_name_buf. */
681 do_cleanups (cleanups);
684 return 0; /* No filename. */
686 /* Now fetch the filename from target memory. */
687 target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode);
691 warning ("failed to read exec filename from attached file: %s",
692 safe_strerror (errcode));
696 make_cleanup (xfree, filename);
697 /* Have a pathname: read the symbol file. */
698 symbol_file_add_main (filename, from_tty);
705 current_sos -- build a list of currently loaded shared objects
709 struct so_list *current_sos ()
713 Build a list of `struct so_list' objects describing the shared
714 objects currently loaded in the inferior. This list does not
715 include an entry for the main executable file.
717 Note that we only gather information directly available from the
718 inferior --- we don't examine any of the shared library files
719 themselves. The declaration of `struct so_list' says which fields
720 we provide values for. */
722 static struct so_list *
723 svr4_current_sos (void)
726 struct so_list *head = 0;
727 struct so_list **link_ptr = &head;
729 /* Make sure we've looked up the inferior's dynamic linker's base
733 debug_base = locate_base ();
735 /* If we can't find the dynamic linker's base structure, this
736 must not be a dynamically linked executable. Hmm. */
741 /* Walk the inferior's link map list, and build our list of
742 `struct so_list' nodes. */
743 lm = first_link_map_member ();
746 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
748 = (struct so_list *) xmalloc (sizeof (struct so_list));
749 struct cleanup *old_chain = make_cleanup (xfree, new);
751 memset (new, 0, sizeof (*new));
753 new->lm_info = xmalloc (sizeof (struct lm_info));
754 make_cleanup (xfree, new->lm_info);
756 new->lm_info->lm = xmalloc (lmo->link_map_size);
757 make_cleanup (xfree, new->lm_info->lm);
758 memset (new->lm_info->lm, 0, lmo->link_map_size);
760 read_memory (lm, new->lm_info->lm, lmo->link_map_size);
764 /* For SVR4 versions, the first entry in the link map is for the
765 inferior executable, so we must ignore it. For some versions of
766 SVR4, it has no name. For others (Solaris 2.3 for example), it
767 does have a name, so we can no longer use a missing name to
768 decide when to ignore it. */
769 if (IGNORE_FIRST_LINK_MAP_ENTRY (new))
776 /* Extract this shared object's name. */
777 target_read_string (LM_NAME (new), &buffer,
778 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
781 warning ("current_sos: Can't read pathname for load map: %s\n",
782 safe_strerror (errcode));
786 strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
787 new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
789 strcpy (new->so_original_name, new->so_name);
792 /* If this entry has no name, or its name matches the name
793 for the main executable, don't include it in the list. */
794 if (! new->so_name[0]
795 || match_main (new->so_name))
801 link_ptr = &new->next;
805 discard_cleanups (old_chain);
811 /* Get the address of the link_map for a given OBJFILE. Loop through
812 the link maps, and return the address of the one corresponding to
813 the given objfile. Note that this function takes into account that
814 objfile can be the main executable, not just a shared library. The
815 main executable has always an empty name field in the linkmap. */
818 svr4_fetch_objfile_link_map (struct objfile *objfile)
822 if ((debug_base = locate_base ()) == 0)
823 return 0; /* failed somehow... */
825 /* Position ourselves on the first link map. */
826 lm = first_link_map_member ();
829 /* Get info on the layout of the r_debug and link_map structures. */
830 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
833 struct lm_info objfile_lm_info;
834 struct cleanup *old_chain;
835 CORE_ADDR name_address;
836 char *l_name_buf = xmalloc (lmo->l_name_size);
837 old_chain = make_cleanup (xfree, l_name_buf);
839 /* Set up the buffer to contain the portion of the link_map
840 structure that gdb cares about. Note that this is not the
841 whole link_map structure. */
842 objfile_lm_info.lm = xmalloc (lmo->link_map_size);
843 make_cleanup (xfree, objfile_lm_info.lm);
844 memset (objfile_lm_info.lm, 0, lmo->link_map_size);
846 /* Read the link map into our internal structure. */
847 read_memory (lm, objfile_lm_info.lm, lmo->link_map_size);
849 /* Read address of name from target memory to GDB. */
850 read_memory (lm + lmo->l_name_offset, l_name_buf, lmo->l_name_size);
852 /* Extract this object's name. Assume that the address is
854 name_address = extract_unsigned_integer (l_name_buf, lmo->l_name_size);
855 target_read_string (name_address, &buffer,
856 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
857 make_cleanup (xfree, buffer);
860 warning ("svr4_fetch_objfile_link_map: Can't read pathname for load map: %s\n",
861 safe_strerror (errcode));
865 /* Is this the linkmap for the file we want? */
866 /* If the file is not a shared library and has no name,
867 we are sure it is the main executable, so we return that. */
868 if ((buffer && strcmp (buffer, objfile->name) == 0)
869 || (!(objfile->flags & OBJF_SHARED) && (strcmp (buffer, "") == 0)))
871 do_cleanups (old_chain);
875 /* Not the file we wanted, continue checking. Assume that the
876 address is unsigned. */
877 lm = extract_unsigned_integer (objfile_lm_info.lm + lmo->l_next_offset,
879 do_cleanups (old_chain);
884 /* On some systems, the only way to recognize the link map entry for
885 the main executable file is by looking at its name. Return
886 non-zero iff SONAME matches one of the known main executable names. */
889 match_main (char *soname)
893 for (mainp = main_name_list; *mainp != NULL; mainp++)
895 if (strcmp (soname, *mainp) == 0)
902 /* Return 1 if PC lies in the dynamic symbol resolution code of the
903 SVR4 run time loader. */
904 static CORE_ADDR interp_text_sect_low;
905 static CORE_ADDR interp_text_sect_high;
906 static CORE_ADDR interp_plt_sect_low;
907 static CORE_ADDR interp_plt_sect_high;
910 svr4_in_dynsym_resolve_code (CORE_ADDR pc)
912 return ((pc >= interp_text_sect_low && pc < interp_text_sect_high)
913 || (pc >= interp_plt_sect_low && pc < interp_plt_sect_high)
914 || in_plt_section (pc, NULL));
917 /* Given an executable's ABFD and target, compute the entry-point
921 exec_entry_point (struct bfd *abfd, struct target_ops *targ)
923 /* KevinB wrote ... for most targets, the address returned by
924 bfd_get_start_address() is the entry point for the start
925 function. But, for some targets, bfd_get_start_address() returns
926 the address of a function descriptor from which the entry point
927 address may be extracted. This address is extracted by
928 gdbarch_convert_from_func_ptr_addr(). The method
929 gdbarch_convert_from_func_ptr_addr() is the merely the identify
930 function for targets which don't use function descriptors. */
931 return gdbarch_convert_from_func_ptr_addr (current_gdbarch,
932 bfd_get_start_address (abfd),
940 enable_break -- arrange for dynamic linker to hit breakpoint
944 int enable_break (void)
948 Both the SunOS and the SVR4 dynamic linkers have, as part of their
949 debugger interface, support for arranging for the inferior to hit
950 a breakpoint after mapping in the shared libraries. This function
951 enables that breakpoint.
953 For SunOS, there is a special flag location (in_debugger) which we
954 set to 1. When the dynamic linker sees this flag set, it will set
955 a breakpoint at a location known only to itself, after saving the
956 original contents of that place and the breakpoint address itself,
957 in it's own internal structures. When we resume the inferior, it
958 will eventually take a SIGTRAP when it runs into the breakpoint.
959 We handle this (in a different place) by restoring the contents of
960 the breakpointed location (which is only known after it stops),
961 chasing around to locate the shared libraries that have been
962 loaded, then resuming.
964 For SVR4, the debugger interface structure contains a member (r_brk)
965 which is statically initialized at the time the shared library is
966 built, to the offset of a function (_r_debug_state) which is guaran-
967 teed to be called once before mapping in a library, and again when
968 the mapping is complete. At the time we are examining this member,
969 it contains only the unrelocated offset of the function, so we have
970 to do our own relocation. Later, when the dynamic linker actually
971 runs, it relocates r_brk to be the actual address of _r_debug_state().
973 The debugger interface structure also contains an enumeration which
974 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
975 depending upon whether or not the library is being mapped or unmapped,
976 and then set to RT_CONSISTENT after the library is mapped/unmapped.
984 #ifdef BKPT_AT_SYMBOL
986 struct minimal_symbol *msymbol;
988 asection *interp_sect;
990 /* First, remove all the solib event breakpoints. Their addresses
991 may have changed since the last time we ran the program. */
992 remove_solib_event_breakpoints ();
994 interp_text_sect_low = interp_text_sect_high = 0;
995 interp_plt_sect_low = interp_plt_sect_high = 0;
997 /* Find the .interp section; if not found, warn the user and drop
998 into the old breakpoint at symbol code. */
999 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
1002 unsigned int interp_sect_size;
1004 CORE_ADDR load_addr = 0;
1005 int load_addr_found = 0;
1006 struct so_list *inferior_sos;
1007 bfd *tmp_bfd = NULL;
1008 struct target_ops *tmp_bfd_target;
1010 char *tmp_pathname = NULL;
1011 CORE_ADDR sym_addr = 0;
1013 /* Read the contents of the .interp section into a local buffer;
1014 the contents specify the dynamic linker this program uses. */
1015 interp_sect_size = bfd_section_size (exec_bfd, interp_sect);
1016 buf = alloca (interp_sect_size);
1017 bfd_get_section_contents (exec_bfd, interp_sect,
1018 buf, 0, interp_sect_size);
1020 /* Now we need to figure out where the dynamic linker was
1021 loaded so that we can load its symbols and place a breakpoint
1022 in the dynamic linker itself.
1024 This address is stored on the stack. However, I've been unable
1025 to find any magic formula to find it for Solaris (appears to
1026 be trivial on GNU/Linux). Therefore, we have to try an alternate
1027 mechanism to find the dynamic linker's base address. */
1029 tmp_fd = solib_open (buf, &tmp_pathname);
1031 tmp_bfd = bfd_fdopenr (tmp_pathname, gnutarget, tmp_fd);
1033 if (tmp_bfd == NULL)
1034 goto bkpt_at_symbol;
1036 /* Make sure the dynamic linker's really a useful object. */
1037 if (!bfd_check_format (tmp_bfd, bfd_object))
1039 warning ("Unable to grok dynamic linker %s as an object file", buf);
1040 bfd_close (tmp_bfd);
1041 goto bkpt_at_symbol;
1044 /* Now convert the TMP_BFD into a target. That way target, as
1045 well as BFD operations can be used. Note that closing the
1046 target will also close the underlying bfd. */
1047 tmp_bfd_target = target_bfd_reopen (tmp_bfd);
1049 /* If the entry in _DYNAMIC for the dynamic linker has already
1050 been filled in, we can read its base address from there. */
1051 inferior_sos = svr4_current_sos ();
1054 /* Connected to a running target. Update our shared library table. */
1055 solib_add (NULL, 0, NULL, auto_solib_add);
1057 while (inferior_sos)
1059 if (strcmp (buf, inferior_sos->so_original_name) == 0)
1061 load_addr_found = 1;
1062 load_addr = LM_ADDR (inferior_sos);
1065 inferior_sos = inferior_sos->next;
1068 /* Otherwise we find the dynamic linker's base address by examining
1069 the current pc (which should point at the entry point for the
1070 dynamic linker) and subtracting the offset of the entry point. */
1071 if (!load_addr_found)
1072 load_addr = (read_pc ()
1073 - exec_entry_point (tmp_bfd, tmp_bfd_target));
1075 /* Record the relocated start and end address of the dynamic linker
1076 text and plt section for svr4_in_dynsym_resolve_code. */
1077 interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
1080 interp_text_sect_low =
1081 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1082 interp_text_sect_high =
1083 interp_text_sect_low + bfd_section_size (tmp_bfd, interp_sect);
1085 interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
1088 interp_plt_sect_low =
1089 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1090 interp_plt_sect_high =
1091 interp_plt_sect_low + bfd_section_size (tmp_bfd, interp_sect);
1094 /* Now try to set a breakpoint in the dynamic linker. */
1095 for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
1097 /* On ABI's that use function descriptors, there are usually
1098 two linker symbols associated with each C function: one
1099 pointing at the actual entry point of the machine code,
1100 and one pointing at the function's descriptor. The
1101 latter symbol has the same name as the C function.
1103 What we're looking for here is the machine code entry
1104 point, so we are only interested in symbols in code
1106 sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep, SEC_CODE);
1111 /* We're done with both the temporary bfd and target. Remember,
1112 closing the target closes the underlying bfd. */
1113 target_close (tmp_bfd_target, 0);
1117 create_solib_event_breakpoint (load_addr + sym_addr);
1121 /* For whatever reason we couldn't set a breakpoint in the dynamic
1122 linker. Warn and drop into the old code. */
1124 warning ("Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code.");
1127 /* Scan through the list of symbols, trying to look up the symbol and
1128 set a breakpoint there. Terminate loop when we/if we succeed. */
1130 breakpoint_addr = 0;
1131 for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
1133 msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
1134 if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
1136 create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol));
1141 /* Nothing good happened. */
1144 #endif /* BKPT_AT_SYMBOL */
1153 special_symbol_handling -- additional shared library symbol handling
1157 void special_symbol_handling ()
1161 Once the symbols from a shared object have been loaded in the usual
1162 way, we are called to do any system specific symbol handling that
1165 For SunOS4, this consisted of grunging around in the dynamic
1166 linkers structures to find symbol definitions for "common" symbols
1167 and adding them to the minimal symbol table for the runtime common
1170 However, for SVR4, there's nothing to do.
1175 svr4_special_symbol_handling (void)
1179 /* Relocate the main executable. This function should be called upon
1180 stopping the inferior process at the entry point to the program.
1181 The entry point from BFD is compared to the PC and if they are
1182 different, the main executable is relocated by the proper amount.
1184 As written it will only attempt to relocate executables which
1185 lack interpreter sections. It seems likely that only dynamic
1186 linker executables will get relocated, though it should work
1187 properly for a position-independent static executable as well. */
1190 svr4_relocate_main_executable (void)
1192 asection *interp_sect;
1193 CORE_ADDR pc = read_pc ();
1195 /* Decide if the objfile needs to be relocated. As indicated above,
1196 we will only be here when execution is stopped at the beginning
1197 of the program. Relocation is necessary if the address at which
1198 we are presently stopped differs from the start address stored in
1199 the executable AND there's no interpreter section. The condition
1200 regarding the interpreter section is very important because if
1201 there *is* an interpreter section, execution will begin there
1202 instead. When there is an interpreter section, the start address
1203 is (presumably) used by the interpreter at some point to start
1204 execution of the program.
1206 If there is an interpreter, it is normal for it to be set to an
1207 arbitrary address at the outset. The job of finding it is
1208 handled in enable_break().
1210 So, to summarize, relocations are necessary when there is no
1211 interpreter section and the start address obtained from the
1212 executable is different from the address at which GDB is
1215 [ The astute reader will note that we also test to make sure that
1216 the executable in question has the DYNAMIC flag set. It is my
1217 opinion that this test is unnecessary (undesirable even). It
1218 was added to avoid inadvertent relocation of an executable
1219 whose e_type member in the ELF header is not ET_DYN. There may
1220 be a time in the future when it is desirable to do relocations
1221 on other types of files as well in which case this condition
1222 should either be removed or modified to accomodate the new file
1223 type. (E.g, an ET_EXEC executable which has been built to be
1224 position-independent could safely be relocated by the OS if
1225 desired. It is true that this violates the ABI, but the ABI
1226 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1229 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
1230 if (interp_sect == NULL
1231 && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0
1232 && (exec_entry_point (exec_bfd, &exec_ops) != pc))
1234 struct cleanup *old_chain;
1235 struct section_offsets *new_offsets;
1237 CORE_ADDR displacement;
1239 /* It is necessary to relocate the objfile. The amount to
1240 relocate by is simply the address at which we are stopped
1241 minus the starting address from the executable.
1243 We relocate all of the sections by the same amount. This
1244 behavior is mandated by recent editions of the System V ABI.
1245 According to the System V Application Binary Interface,
1246 Edition 4.1, page 5-5:
1248 ... Though the system chooses virtual addresses for
1249 individual processes, it maintains the segments' relative
1250 positions. Because position-independent code uses relative
1251 addressesing between segments, the difference between
1252 virtual addresses in memory must match the difference
1253 between virtual addresses in the file. The difference
1254 between the virtual address of any segment in memory and
1255 the corresponding virtual address in the file is thus a
1256 single constant value for any one executable or shared
1257 object in a given process. This difference is the base
1258 address. One use of the base address is to relocate the
1259 memory image of the program during dynamic linking.
1261 The same language also appears in Edition 4.0 of the System V
1262 ABI and is left unspecified in some of the earlier editions. */
1264 displacement = pc - exec_entry_point (exec_bfd, &exec_ops);
1267 new_offsets = xcalloc (symfile_objfile->num_sections,
1268 sizeof (struct section_offsets));
1269 old_chain = make_cleanup (xfree, new_offsets);
1271 for (i = 0; i < symfile_objfile->num_sections; i++)
1273 if (displacement != ANOFFSET (symfile_objfile->section_offsets, i))
1275 new_offsets->offsets[i] = displacement;
1279 objfile_relocate (symfile_objfile, new_offsets);
1281 do_cleanups (old_chain);
1289 svr4_solib_create_inferior_hook -- shared library startup support
1293 void svr4_solib_create_inferior_hook()
1297 When gdb starts up the inferior, it nurses it along (through the
1298 shell) until it is ready to execute it's first instruction. At this
1299 point, this function gets called via expansion of the macro
1300 SOLIB_CREATE_INFERIOR_HOOK.
1302 For SunOS executables, this first instruction is typically the
1303 one at "_start", or a similar text label, regardless of whether
1304 the executable is statically or dynamically linked. The runtime
1305 startup code takes care of dynamically linking in any shared
1306 libraries, once gdb allows the inferior to continue.
1308 For SVR4 executables, this first instruction is either the first
1309 instruction in the dynamic linker (for dynamically linked
1310 executables) or the instruction at "start" for statically linked
1311 executables. For dynamically linked executables, the system
1312 first exec's /lib/libc.so.N, which contains the dynamic linker,
1313 and starts it running. The dynamic linker maps in any needed
1314 shared libraries, maps in the actual user executable, and then
1315 jumps to "start" in the user executable.
1317 For both SunOS shared libraries, and SVR4 shared libraries, we
1318 can arrange to cooperate with the dynamic linker to discover the
1319 names of shared libraries that are dynamically linked, and the
1320 base addresses to which they are linked.
1322 This function is responsible for discovering those names and
1323 addresses, and saving sufficient information about them to allow
1324 their symbols to be read at a later time.
1328 Between enable_break() and disable_break(), this code does not
1329 properly handle hitting breakpoints which the user might have
1330 set in the startup code or in the dynamic linker itself. Proper
1331 handling will probably have to wait until the implementation is
1332 changed to use the "breakpoint handler function" method.
1334 Also, what if child has exit()ed? Must exit loop somehow.
1338 svr4_solib_create_inferior_hook (void)
1340 /* Relocate the main executable if necessary. */
1341 svr4_relocate_main_executable ();
1343 if (!svr4_have_link_map_offsets ())
1345 warning ("no shared library support for this OS / ABI");
1350 if (!enable_break ())
1352 warning ("shared library handler failed to enable breakpoint");
1356 #if defined(_SCO_DS)
1357 /* SCO needs the loop below, other systems should be using the
1358 special shared library breakpoints and the shared library breakpoint
1361 Now run the target. It will eventually hit the breakpoint, at
1362 which point all of the libraries will have been mapped in and we
1363 can go groveling around in the dynamic linker structures to find
1364 out what we need to know about them. */
1366 clear_proceed_status ();
1367 stop_soon = STOP_QUIETLY;
1368 stop_signal = TARGET_SIGNAL_0;
1371 target_resume (pid_to_ptid (-1), 0, stop_signal);
1372 wait_for_inferior ();
1374 while (stop_signal != TARGET_SIGNAL_TRAP);
1375 stop_soon = NO_STOP_QUIETLY;
1376 #endif /* defined(_SCO_DS) */
1380 svr4_clear_solib (void)
1386 svr4_free_so (struct so_list *so)
1388 xfree (so->lm_info->lm);
1389 xfree (so->lm_info);
1393 /* Clear any bits of ADDR that wouldn't fit in a target-format
1394 data pointer. "Data pointer" here refers to whatever sort of
1395 address the dynamic linker uses to manage its sections. At the
1396 moment, we don't support shared libraries on any processors where
1397 code and data pointers are different sizes.
1399 This isn't really the right solution. What we really need here is
1400 a way to do arithmetic on CORE_ADDR values that respects the
1401 natural pointer/address correspondence. (For example, on the MIPS,
1402 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1403 sign-extend the value. There, simply truncating the bits above
1404 TARGET_PTR_BIT, as we do below, is no good.) This should probably
1405 be a new gdbarch method or something. */
1407 svr4_truncate_ptr (CORE_ADDR addr)
1409 if (TARGET_PTR_BIT == sizeof (CORE_ADDR) * 8)
1410 /* We don't need to truncate anything, and the bit twiddling below
1411 will fail due to overflow problems. */
1414 return addr & (((CORE_ADDR) 1 << TARGET_PTR_BIT) - 1);
1419 svr4_relocate_section_addresses (struct so_list *so,
1420 struct section_table *sec)
1422 sec->addr = svr4_truncate_ptr (sec->addr + LM_ADDR (so));
1423 sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR (so));
1427 /* Fetch a link_map_offsets structure for native targets using struct
1428 definitions from link.h. See solib-legacy.c for the function
1429 which does the actual work.
1431 Note: For non-native targets (i.e. cross-debugging situations),
1432 a target specific fetch_link_map_offsets() function should be
1433 defined and registered via set_solib_svr4_fetch_link_map_offsets(). */
1435 static struct link_map_offsets *
1436 legacy_fetch_link_map_offsets (void)
1438 if (legacy_svr4_fetch_link_map_offsets_hook)
1439 return legacy_svr4_fetch_link_map_offsets_hook ();
1442 internal_error (__FILE__, __LINE__,
1443 "legacy_fetch_link_map_offsets called without legacy "
1444 "link_map support enabled.");
1449 /* Fetch a link_map_offsets structure using the method registered in the
1450 architecture vector. */
1452 static struct link_map_offsets *
1453 svr4_fetch_link_map_offsets (void)
1455 struct link_map_offsets *(*flmo)(void) =
1456 gdbarch_data (current_gdbarch, fetch_link_map_offsets_gdbarch_data);
1460 internal_error (__FILE__, __LINE__,
1461 "svr4_fetch_link_map_offsets: fetch_link_map_offsets "
1462 "method not defined for this architecture.");
1469 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1471 svr4_have_link_map_offsets (void)
1473 struct link_map_offsets *(*flmo)(void) =
1474 gdbarch_data (current_gdbarch, fetch_link_map_offsets_gdbarch_data);
1476 || (flmo == legacy_fetch_link_map_offsets
1477 && legacy_svr4_fetch_link_map_offsets_hook == NULL))
1483 /* set_solib_svr4_fetch_link_map_offsets() is intended to be called by
1484 a <arch>_gdbarch_init() function. It is used to establish an
1485 architecture specific link_map_offsets fetcher for the architecture
1489 set_solib_svr4_fetch_link_map_offsets (struct gdbarch *gdbarch,
1490 struct link_map_offsets *(*flmo) (void))
1492 set_gdbarch_data (gdbarch, fetch_link_map_offsets_gdbarch_data, flmo);
1495 /* Initialize the architecture-specific link_map_offsets fetcher.
1496 This is called after <arch>_gdbarch_init() has set up its `struct
1497 gdbarch' for the new architecture, and is only called if the
1498 link_map_offsets fetcher isn't already initialized (which is
1499 usually done by calling set_solib_svr4_fetch_link_map_offsets()
1500 above in <arch>_gdbarch_init()). Therefore we attempt to provide a
1501 reasonable alternative (for native targets anyway) if the
1502 <arch>_gdbarch_init() fails to call
1503 set_solib_svr4_fetch_link_map_offsets(). */
1506 init_fetch_link_map_offsets (struct gdbarch *gdbarch)
1508 return legacy_fetch_link_map_offsets;
1511 static struct target_so_ops svr4_so_ops;
1513 extern initialize_file_ftype _initialize_svr4_solib; /* -Wmissing-prototypes */
1516 _initialize_svr4_solib (void)
1518 fetch_link_map_offsets_gdbarch_data =
1519 register_gdbarch_data (init_fetch_link_map_offsets);
1521 svr4_so_ops.relocate_section_addresses = svr4_relocate_section_addresses;
1522 svr4_so_ops.free_so = svr4_free_so;
1523 svr4_so_ops.clear_solib = svr4_clear_solib;
1524 svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook;
1525 svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling;
1526 svr4_so_ops.current_sos = svr4_current_sos;
1527 svr4_so_ops.open_symbol_file_object = open_symbol_file_object;
1528 svr4_so_ops.in_dynsym_resolve_code = svr4_in_dynsym_resolve_code;
1530 /* FIXME: Don't do this here. *_gdbarch_init() should set so_ops. */
1531 current_target_so_ops = &svr4_so_ops;