1 /* Handle SVR4 shared libraries for GDB, the GNU Debugger.
3 Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999,
5 Free Software Foundation, Inc.
7 This file is part of GDB.
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 59 Temple Place - Suite 330,
22 Boston, MA 02111-1307, USA. */
26 #include "elf/external.h"
27 #include "elf/common.h"
39 #include "solib-svr4.h"
41 #include "bfd-target.h"
44 #ifndef SVR4_FETCH_LINK_MAP_OFFSETS
45 #define SVR4_FETCH_LINK_MAP_OFFSETS() svr4_fetch_link_map_offsets ()
48 static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
49 static struct link_map_offsets *legacy_fetch_link_map_offsets (void);
50 static int svr4_have_link_map_offsets (void);
52 /* fetch_link_map_offsets_gdbarch_data is a handle used to obtain the
53 architecture specific link map offsets fetching function. */
55 static struct gdbarch_data *fetch_link_map_offsets_gdbarch_data;
57 /* legacy_svr4_fetch_link_map_offsets_hook is a pointer to a function
58 which is used to fetch link map offsets. It will only be set
59 by solib-legacy.c, if at all. */
61 struct link_map_offsets *(*legacy_svr4_fetch_link_map_offsets_hook)(void) = 0;
63 /* Link map info to include in an allocated so_list entry */
67 /* Pointer to copy of link map from inferior. The type is char *
68 rather than void *, so that we may use byte offsets to find the
69 various fields without the need for a cast. */
73 /* On SVR4 systems, a list of symbols in the dynamic linker where
74 GDB can try to place a breakpoint to monitor shared library
77 If none of these symbols are found, or other errors occur, then
78 SVR4 systems will fall back to using a symbol as the "startup
79 mapping complete" breakpoint address. */
81 static char *solib_break_names[] =
89 /* On the 64-bit PowerPC, the linker symbol with the same name as
90 the C function points to a function descriptor, not to the entry
91 point. The linker symbol whose name is the C function name
92 prefixed with a '.' points to the function's entry point. So
93 when we look through this table, we ignore symbols that point
94 into the data section (thus skipping the descriptor's symbol),
95 and eventually try this one, giving us the real entry point
103 #define BKPT_AT_SYMBOL 1
105 #if defined (BKPT_AT_SYMBOL)
106 static char *bkpt_names[] =
108 #ifdef SOLIB_BKPT_NAME
109 SOLIB_BKPT_NAME, /* Prefer configured name if it exists. */
118 static char *main_name_list[] =
124 /* Macro to extract an address from a solib structure. When GDB is
125 configured for some 32-bit targets (e.g. Solaris 2.7 sparc), BFD is
126 configured to handle 64-bit targets, so CORE_ADDR is 64 bits. We
127 have to extract only the significant bits of addresses to get the
128 right address when accessing the core file BFD.
130 Assume that the address is unsigned. */
132 #define SOLIB_EXTRACT_ADDRESS(MEMBER) \
133 extract_unsigned_integer (&(MEMBER), sizeof (MEMBER))
135 /* local data declarations */
137 /* link map access functions */
140 LM_ADDR (struct so_list *so)
142 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
144 return (CORE_ADDR) extract_signed_integer (so->lm_info->lm + lmo->l_addr_offset,
149 LM_NEXT (struct so_list *so)
151 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
153 /* Assume that the address is unsigned. */
154 return extract_unsigned_integer (so->lm_info->lm + lmo->l_next_offset,
159 LM_NAME (struct so_list *so)
161 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
163 /* Assume that the address is unsigned. */
164 return extract_unsigned_integer (so->lm_info->lm + lmo->l_name_offset,
169 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
171 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
173 /* Assume that the address is unsigned. */
174 return extract_unsigned_integer (so->lm_info->lm + lmo->l_prev_offset,
175 lmo->l_prev_size) == 0;
178 static CORE_ADDR debug_base; /* Base of dynamic linker structures */
179 static CORE_ADDR breakpoint_addr; /* Address where end bkpt is set */
181 /* Local function prototypes */
183 static int match_main (char *);
185 static CORE_ADDR bfd_lookup_symbol (bfd *, char *, flagword);
191 bfd_lookup_symbol -- lookup the value for a specific symbol
195 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname, flagword sect_flags)
199 An expensive way to lookup the value of a single symbol for
200 bfd's that are only temporary anyway. This is used by the
201 shared library support to find the address of the debugger
202 interface structures in the shared library.
204 If SECT_FLAGS is non-zero, only match symbols in sections whose
205 flags include all those in SECT_FLAGS.
207 Note that 0 is specifically allowed as an error return (no
212 bfd_lookup_symbol (bfd *abfd, char *symname, flagword sect_flags)
216 asymbol **symbol_table;
217 unsigned int number_of_symbols;
219 struct cleanup *back_to;
220 CORE_ADDR symaddr = 0;
222 storage_needed = bfd_get_symtab_upper_bound (abfd);
224 if (storage_needed > 0)
226 symbol_table = (asymbol **) xmalloc (storage_needed);
227 back_to = make_cleanup (xfree, symbol_table);
228 number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
230 for (i = 0; i < number_of_symbols; i++)
232 sym = *symbol_table++;
233 if (strcmp (sym->name, symname) == 0
234 && (sym->section->flags & sect_flags) == sect_flags)
236 /* Bfd symbols are section relative. */
237 symaddr = sym->value + sym->section->vma;
241 do_cleanups (back_to);
247 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
248 have to check the dynamic string table too. */
250 storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);
252 if (storage_needed > 0)
254 symbol_table = (asymbol **) xmalloc (storage_needed);
255 back_to = make_cleanup (xfree, symbol_table);
256 number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table);
258 for (i = 0; i < number_of_symbols; i++)
260 sym = *symbol_table++;
262 if (strcmp (sym->name, symname) == 0
263 && (sym->section->flags & sect_flags) == sect_flags)
265 /* Bfd symbols are section relative. */
266 symaddr = sym->value + sym->section->vma;
270 do_cleanups (back_to);
276 #ifdef HANDLE_SVR4_EXEC_EMULATORS
279 Solaris BCP (the part of Solaris which allows it to run SunOS4
280 a.out files) throws in another wrinkle. Solaris does not fill
281 in the usual a.out link map structures when running BCP programs,
282 the only way to get at them is via groping around in the dynamic
284 The dynamic linker and it's structures are located in the shared
285 C library, which gets run as the executable's "interpreter" by
288 Note that we can assume nothing about the process state at the time
289 we need to find these structures. We may be stopped on the first
290 instruction of the interpreter (C shared library), the first
291 instruction of the executable itself, or somewhere else entirely
292 (if we attached to the process for example).
295 static char *debug_base_symbols[] =
297 "r_debug", /* Solaris 2.3 */
298 "_r_debug", /* Solaris 2.1, 2.2 */
302 static int look_for_base (int, CORE_ADDR);
308 look_for_base -- examine file for each mapped address segment
312 static int look_for_base (int fd, CORE_ADDR baseaddr)
316 This function is passed to proc_iterate_over_mappings, which
317 causes it to get called once for each mapped address space, with
318 an open file descriptor for the file mapped to that space, and the
319 base address of that mapped space.
321 Our job is to find the debug base symbol in the file that this
322 fd is open on, if it exists, and if so, initialize the dynamic
323 linker structure base address debug_base.
325 Note that this is a computationally expensive proposition, since
326 we basically have to open a bfd on every call, so we specifically
327 avoid opening the exec file.
331 look_for_base (int fd, CORE_ADDR baseaddr)
334 CORE_ADDR address = 0;
337 /* If the fd is -1, then there is no file that corresponds to this
338 mapped memory segment, so skip it. Also, if the fd corresponds
339 to the exec file, skip it as well. */
343 && fdmatch (fileno ((FILE *) (exec_bfd->iostream)), fd)))
348 /* Try to open whatever random file this fd corresponds to. Note that
349 we have no way currently to find the filename. Don't gripe about
350 any problems we might have, just fail. */
352 if ((interp_bfd = bfd_fdopenr ("unnamed", gnutarget, fd)) == NULL)
356 if (!bfd_check_format (interp_bfd, bfd_object))
358 /* FIXME-leak: on failure, might not free all memory associated with
360 bfd_close (interp_bfd);
364 /* Now try to find our debug base symbol in this file, which we at
365 least know to be a valid ELF executable or shared library. */
367 for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
369 address = bfd_lookup_symbol (interp_bfd, *symbolp, 0);
377 /* FIXME-leak: on failure, might not free all memory associated with
379 bfd_close (interp_bfd);
383 /* Eureka! We found the symbol. But now we may need to relocate it
384 by the base address. If the symbol's value is less than the base
385 address of the shared library, then it hasn't yet been relocated
386 by the dynamic linker, and we have to do it ourself. FIXME: Note
387 that we make the assumption that the first segment that corresponds
388 to the shared library has the base address to which the library
391 if (address < baseaddr)
395 debug_base = address;
396 /* FIXME-leak: on failure, might not free all memory associated with
398 bfd_close (interp_bfd);
401 #endif /* HANDLE_SVR4_EXEC_EMULATORS */
407 elf_locate_base -- locate the base address of dynamic linker structs
408 for SVR4 elf targets.
412 CORE_ADDR elf_locate_base (void)
416 For SVR4 elf targets the address of the dynamic linker's runtime
417 structure is contained within the dynamic info section in the
418 executable file. The dynamic section is also mapped into the
419 inferior address space. Because the runtime loader fills in the
420 real address before starting the inferior, we have to read in the
421 dynamic info section from the inferior address space.
422 If there are any errors while trying to find the address, we
423 silently return 0, otherwise the found address is returned.
428 elf_locate_base (void)
430 struct bfd_section *dyninfo_sect;
431 int dyninfo_sect_size;
432 CORE_ADDR dyninfo_addr;
437 /* Find the start address of the .dynamic section. */
438 dyninfo_sect = bfd_get_section_by_name (exec_bfd, ".dynamic");
439 if (dyninfo_sect == NULL)
441 dyninfo_addr = bfd_section_vma (exec_bfd, dyninfo_sect);
443 /* Read in .dynamic section, silently ignore errors. */
444 dyninfo_sect_size = bfd_section_size (exec_bfd, dyninfo_sect);
445 buf = alloca (dyninfo_sect_size);
446 if (target_read_memory (dyninfo_addr, buf, dyninfo_sect_size))
449 /* Find the DT_DEBUG entry in the the .dynamic section.
450 For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has
451 no DT_DEBUG entries. */
453 arch_size = bfd_get_arch_size (exec_bfd);
454 if (arch_size == -1) /* failure */
459 for (bufend = buf + dyninfo_sect_size;
461 buf += sizeof (Elf32_External_Dyn))
463 Elf32_External_Dyn *x_dynp = (Elf32_External_Dyn *) buf;
467 dyn_tag = bfd_h_get_32 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
468 if (dyn_tag == DT_NULL)
470 else if (dyn_tag == DT_DEBUG)
472 dyn_ptr = bfd_h_get_32 (exec_bfd,
473 (bfd_byte *) x_dynp->d_un.d_ptr);
476 else if (dyn_tag == DT_MIPS_RLD_MAP)
479 int pbuf_size = TARGET_PTR_BIT / HOST_CHAR_BIT;
481 pbuf = alloca (pbuf_size);
482 /* DT_MIPS_RLD_MAP contains a pointer to the address
483 of the dynamic link structure. */
484 dyn_ptr = bfd_h_get_32 (exec_bfd,
485 (bfd_byte *) x_dynp->d_un.d_ptr);
486 if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
488 return extract_unsigned_integer (pbuf, pbuf_size);
492 else /* 64-bit elf */
494 for (bufend = buf + dyninfo_sect_size;
496 buf += sizeof (Elf64_External_Dyn))
498 Elf64_External_Dyn *x_dynp = (Elf64_External_Dyn *) buf;
502 dyn_tag = bfd_h_get_64 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
503 if (dyn_tag == DT_NULL)
505 else if (dyn_tag == DT_DEBUG)
507 dyn_ptr = bfd_h_get_64 (exec_bfd,
508 (bfd_byte *) x_dynp->d_un.d_ptr);
511 else if (dyn_tag == DT_MIPS_RLD_MAP)
514 int pbuf_size = TARGET_PTR_BIT / HOST_CHAR_BIT;
516 pbuf = alloca (pbuf_size);
517 /* DT_MIPS_RLD_MAP contains a pointer to the address
518 of the dynamic link structure. */
519 dyn_ptr = bfd_h_get_64 (exec_bfd,
520 (bfd_byte *) x_dynp->d_un.d_ptr);
521 if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
523 return extract_unsigned_integer (pbuf, pbuf_size);
528 /* DT_DEBUG entry not found. */
536 locate_base -- locate the base address of dynamic linker structs
540 CORE_ADDR locate_base (void)
544 For both the SunOS and SVR4 shared library implementations, if the
545 inferior executable has been linked dynamically, there is a single
546 address somewhere in the inferior's data space which is the key to
547 locating all of the dynamic linker's runtime structures. This
548 address is the value of the debug base symbol. The job of this
549 function is to find and return that address, or to return 0 if there
550 is no such address (the executable is statically linked for example).
552 For SunOS, the job is almost trivial, since the dynamic linker and
553 all of it's structures are statically linked to the executable at
554 link time. Thus the symbol for the address we are looking for has
555 already been added to the minimal symbol table for the executable's
556 objfile at the time the symbol file's symbols were read, and all we
557 have to do is look it up there. Note that we explicitly do NOT want
558 to find the copies in the shared library.
560 The SVR4 version is a bit more complicated because the address
561 is contained somewhere in the dynamic info section. We have to go
562 to a lot more work to discover the address of the debug base symbol.
563 Because of this complexity, we cache the value we find and return that
564 value on subsequent invocations. Note there is no copy in the
565 executable symbol tables.
572 /* Check to see if we have a currently valid address, and if so, avoid
573 doing all this work again and just return the cached address. If
574 we have no cached address, try to locate it in the dynamic info
575 section for ELF executables. There's no point in doing any of this
576 though if we don't have some link map offsets to work with. */
578 if (debug_base == 0 && svr4_have_link_map_offsets ())
581 && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
582 debug_base = elf_locate_base ();
583 #ifdef HANDLE_SVR4_EXEC_EMULATORS
584 /* Try it the hard way for emulated executables. */
585 else if (!ptid_equal (inferior_ptid, null_ptid) && target_has_execution)
586 proc_iterate_over_mappings (look_for_base);
596 first_link_map_member -- locate first member in dynamic linker's map
600 static CORE_ADDR first_link_map_member (void)
604 Find the first element in the inferior's dynamic link map, and
605 return its address in the inferior. This function doesn't copy the
606 link map entry itself into our address space; current_sos actually
610 first_link_map_member (void)
613 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
614 char *r_map_buf = xmalloc (lmo->r_map_size);
615 struct cleanup *cleanups = make_cleanup (xfree, r_map_buf);
617 read_memory (debug_base + lmo->r_map_offset, r_map_buf, lmo->r_map_size);
619 /* Assume that the address is unsigned. */
620 lm = extract_unsigned_integer (r_map_buf, lmo->r_map_size);
622 /* FIXME: Perhaps we should validate the info somehow, perhaps by
623 checking r_version for a known version number, or r_state for
626 do_cleanups (cleanups);
635 open_symbol_file_object
639 void open_symbol_file_object (void *from_tty)
643 If no open symbol file, attempt to locate and open the main symbol
644 file. On SVR4 systems, this is the first link map entry. If its
645 name is here, we can open it. Useful when attaching to a process
646 without first loading its symbol file.
648 If FROM_TTYP dereferences to a non-zero integer, allow messages to
649 be printed. This parameter is a pointer rather than an int because
650 open_symbol_file_object() is called via catch_errors() and
651 catch_errors() requires a pointer argument. */
654 open_symbol_file_object (void *from_ttyp)
656 CORE_ADDR lm, l_name;
659 int from_tty = *(int *)from_ttyp;
660 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
661 char *l_name_buf = xmalloc (lmo->l_name_size);
662 struct cleanup *cleanups = make_cleanup (xfree, l_name_buf);
665 if (!query ("Attempt to reload symbols from process? "))
668 if ((debug_base = locate_base ()) == 0)
669 return 0; /* failed somehow... */
671 /* First link map member should be the executable. */
672 if ((lm = first_link_map_member ()) == 0)
673 return 0; /* failed somehow... */
675 /* Read address of name from target memory to GDB. */
676 read_memory (lm + lmo->l_name_offset, l_name_buf, lmo->l_name_size);
678 /* Convert the address to host format. Assume that the address is
680 l_name = extract_unsigned_integer (l_name_buf, lmo->l_name_size);
682 /* Free l_name_buf. */
683 do_cleanups (cleanups);
686 return 0; /* No filename. */
688 /* Now fetch the filename from target memory. */
689 target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode);
693 warning ("failed to read exec filename from attached file: %s",
694 safe_strerror (errcode));
698 make_cleanup (xfree, filename);
699 /* Have a pathname: read the symbol file. */
700 symbol_file_add_main (filename, from_tty);
707 current_sos -- build a list of currently loaded shared objects
711 struct so_list *current_sos ()
715 Build a list of `struct so_list' objects describing the shared
716 objects currently loaded in the inferior. This list does not
717 include an entry for the main executable file.
719 Note that we only gather information directly available from the
720 inferior --- we don't examine any of the shared library files
721 themselves. The declaration of `struct so_list' says which fields
722 we provide values for. */
724 static struct so_list *
725 svr4_current_sos (void)
728 struct so_list *head = 0;
729 struct so_list **link_ptr = &head;
731 /* Make sure we've looked up the inferior's dynamic linker's base
735 debug_base = locate_base ();
737 /* If we can't find the dynamic linker's base structure, this
738 must not be a dynamically linked executable. Hmm. */
743 /* Walk the inferior's link map list, and build our list of
744 `struct so_list' nodes. */
745 lm = first_link_map_member ();
748 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
750 = (struct so_list *) xmalloc (sizeof (struct so_list));
751 struct cleanup *old_chain = make_cleanup (xfree, new);
753 memset (new, 0, sizeof (*new));
755 new->lm_info = xmalloc (sizeof (struct lm_info));
756 make_cleanup (xfree, new->lm_info);
758 new->lm_info->lm = xmalloc (lmo->link_map_size);
759 make_cleanup (xfree, new->lm_info->lm);
760 memset (new->lm_info->lm, 0, lmo->link_map_size);
762 read_memory (lm, new->lm_info->lm, lmo->link_map_size);
766 /* For SVR4 versions, the first entry in the link map is for the
767 inferior executable, so we must ignore it. For some versions of
768 SVR4, it has no name. For others (Solaris 2.3 for example), it
769 does have a name, so we can no longer use a missing name to
770 decide when to ignore it. */
771 if (IGNORE_FIRST_LINK_MAP_ENTRY (new))
778 /* Extract this shared object's name. */
779 target_read_string (LM_NAME (new), &buffer,
780 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
783 warning ("current_sos: Can't read pathname for load map: %s\n",
784 safe_strerror (errcode));
788 strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
789 new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
791 strcpy (new->so_original_name, new->so_name);
794 /* If this entry has no name, or its name matches the name
795 for the main executable, don't include it in the list. */
796 if (! new->so_name[0]
797 || match_main (new->so_name))
803 link_ptr = &new->next;
807 discard_cleanups (old_chain);
813 /* Get the address of the link_map for a given OBJFILE. Loop through
814 the link maps, and return the address of the one corresponding to
815 the given objfile. Note that this function takes into account that
816 objfile can be the main executable, not just a shared library. The
817 main executable has always an empty name field in the linkmap. */
820 svr4_fetch_objfile_link_map (struct objfile *objfile)
824 if ((debug_base = locate_base ()) == 0)
825 return 0; /* failed somehow... */
827 /* Position ourselves on the first link map. */
828 lm = first_link_map_member ();
831 /* Get info on the layout of the r_debug and link_map structures. */
832 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
835 struct lm_info objfile_lm_info;
836 struct cleanup *old_chain;
837 CORE_ADDR name_address;
838 char *l_name_buf = xmalloc (lmo->l_name_size);
839 old_chain = make_cleanup (xfree, l_name_buf);
841 /* Set up the buffer to contain the portion of the link_map
842 structure that gdb cares about. Note that this is not the
843 whole link_map structure. */
844 objfile_lm_info.lm = xmalloc (lmo->link_map_size);
845 make_cleanup (xfree, objfile_lm_info.lm);
846 memset (objfile_lm_info.lm, 0, lmo->link_map_size);
848 /* Read the link map into our internal structure. */
849 read_memory (lm, objfile_lm_info.lm, lmo->link_map_size);
851 /* Read address of name from target memory to GDB. */
852 read_memory (lm + lmo->l_name_offset, l_name_buf, lmo->l_name_size);
854 /* Extract this object's name. Assume that the address is
856 name_address = extract_unsigned_integer (l_name_buf, lmo->l_name_size);
857 target_read_string (name_address, &buffer,
858 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
859 make_cleanup (xfree, buffer);
862 warning ("svr4_fetch_objfile_link_map: Can't read pathname for load map: %s\n",
863 safe_strerror (errcode));
867 /* Is this the linkmap for the file we want? */
868 /* If the file is not a shared library and has no name,
869 we are sure it is the main executable, so we return that. */
870 if ((buffer && strcmp (buffer, objfile->name) == 0)
871 || (!(objfile->flags & OBJF_SHARED) && (strcmp (buffer, "") == 0)))
873 do_cleanups (old_chain);
877 /* Not the file we wanted, continue checking. Assume that the
878 address is unsigned. */
879 lm = extract_unsigned_integer (objfile_lm_info.lm + lmo->l_next_offset,
881 do_cleanups (old_chain);
886 /* On some systems, the only way to recognize the link map entry for
887 the main executable file is by looking at its name. Return
888 non-zero iff SONAME matches one of the known main executable names. */
891 match_main (char *soname)
895 for (mainp = main_name_list; *mainp != NULL; mainp++)
897 if (strcmp (soname, *mainp) == 0)
904 /* Return 1 if PC lies in the dynamic symbol resolution code of the
905 SVR4 run time loader. */
906 static CORE_ADDR interp_text_sect_low;
907 static CORE_ADDR interp_text_sect_high;
908 static CORE_ADDR interp_plt_sect_low;
909 static CORE_ADDR interp_plt_sect_high;
912 svr4_in_dynsym_resolve_code (CORE_ADDR pc)
914 return ((pc >= interp_text_sect_low && pc < interp_text_sect_high)
915 || (pc >= interp_plt_sect_low && pc < interp_plt_sect_high)
916 || in_plt_section (pc, NULL));
919 /* Given an executable's ABFD and target, compute the entry-point
923 exec_entry_point (struct bfd *abfd, struct target_ops *targ)
925 /* KevinB wrote ... for most targets, the address returned by
926 bfd_get_start_address() is the entry point for the start
927 function. But, for some targets, bfd_get_start_address() returns
928 the address of a function descriptor from which the entry point
929 address may be extracted. This address is extracted by
930 gdbarch_convert_from_func_ptr_addr(). The method
931 gdbarch_convert_from_func_ptr_addr() is the merely the identify
932 function for targets which don't use function descriptors. */
933 return gdbarch_convert_from_func_ptr_addr (current_gdbarch,
934 bfd_get_start_address (abfd),
942 enable_break -- arrange for dynamic linker to hit breakpoint
946 int enable_break (void)
950 Both the SunOS and the SVR4 dynamic linkers have, as part of their
951 debugger interface, support for arranging for the inferior to hit
952 a breakpoint after mapping in the shared libraries. This function
953 enables that breakpoint.
955 For SunOS, there is a special flag location (in_debugger) which we
956 set to 1. When the dynamic linker sees this flag set, it will set
957 a breakpoint at a location known only to itself, after saving the
958 original contents of that place and the breakpoint address itself,
959 in it's own internal structures. When we resume the inferior, it
960 will eventually take a SIGTRAP when it runs into the breakpoint.
961 We handle this (in a different place) by restoring the contents of
962 the breakpointed location (which is only known after it stops),
963 chasing around to locate the shared libraries that have been
964 loaded, then resuming.
966 For SVR4, the debugger interface structure contains a member (r_brk)
967 which is statically initialized at the time the shared library is
968 built, to the offset of a function (_r_debug_state) which is guaran-
969 teed to be called once before mapping in a library, and again when
970 the mapping is complete. At the time we are examining this member,
971 it contains only the unrelocated offset of the function, so we have
972 to do our own relocation. Later, when the dynamic linker actually
973 runs, it relocates r_brk to be the actual address of _r_debug_state().
975 The debugger interface structure also contains an enumeration which
976 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
977 depending upon whether or not the library is being mapped or unmapped,
978 and then set to RT_CONSISTENT after the library is mapped/unmapped.
986 #ifdef BKPT_AT_SYMBOL
988 struct minimal_symbol *msymbol;
990 asection *interp_sect;
992 /* First, remove all the solib event breakpoints. Their addresses
993 may have changed since the last time we ran the program. */
994 remove_solib_event_breakpoints ();
996 interp_text_sect_low = interp_text_sect_high = 0;
997 interp_plt_sect_low = interp_plt_sect_high = 0;
999 /* Find the .interp section; if not found, warn the user and drop
1000 into the old breakpoint at symbol code. */
1001 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
1004 unsigned int interp_sect_size;
1006 CORE_ADDR load_addr = 0;
1007 int load_addr_found = 0;
1008 struct so_list *inferior_sos;
1009 bfd *tmp_bfd = NULL;
1010 struct target_ops *tmp_bfd_target;
1012 char *tmp_pathname = NULL;
1013 CORE_ADDR sym_addr = 0;
1015 /* Read the contents of the .interp section into a local buffer;
1016 the contents specify the dynamic linker this program uses. */
1017 interp_sect_size = bfd_section_size (exec_bfd, interp_sect);
1018 buf = alloca (interp_sect_size);
1019 bfd_get_section_contents (exec_bfd, interp_sect,
1020 buf, 0, interp_sect_size);
1022 /* Now we need to figure out where the dynamic linker was
1023 loaded so that we can load its symbols and place a breakpoint
1024 in the dynamic linker itself.
1026 This address is stored on the stack. However, I've been unable
1027 to find any magic formula to find it for Solaris (appears to
1028 be trivial on GNU/Linux). Therefore, we have to try an alternate
1029 mechanism to find the dynamic linker's base address. */
1031 tmp_fd = solib_open (buf, &tmp_pathname);
1033 tmp_bfd = bfd_fdopenr (tmp_pathname, gnutarget, tmp_fd);
1035 if (tmp_bfd == NULL)
1036 goto bkpt_at_symbol;
1038 /* Make sure the dynamic linker's really a useful object. */
1039 if (!bfd_check_format (tmp_bfd, bfd_object))
1041 warning ("Unable to grok dynamic linker %s as an object file", buf);
1042 bfd_close (tmp_bfd);
1043 goto bkpt_at_symbol;
1046 /* Now convert the TMP_BFD into a target. That way target, as
1047 well as BFD operations can be used. Note that closing the
1048 target will also close the underlying bfd. */
1049 tmp_bfd_target = target_bfd_reopen (tmp_bfd);
1051 /* If the entry in _DYNAMIC for the dynamic linker has already
1052 been filled in, we can read its base address from there. */
1053 inferior_sos = svr4_current_sos ();
1056 /* Connected to a running target. Update our shared library table. */
1057 solib_add (NULL, 0, NULL, auto_solib_add);
1059 while (inferior_sos)
1061 if (strcmp (buf, inferior_sos->so_original_name) == 0)
1063 load_addr_found = 1;
1064 load_addr = LM_ADDR (inferior_sos);
1067 inferior_sos = inferior_sos->next;
1070 /* Otherwise we find the dynamic linker's base address by examining
1071 the current pc (which should point at the entry point for the
1072 dynamic linker) and subtracting the offset of the entry point. */
1073 if (!load_addr_found)
1074 load_addr = (read_pc ()
1075 - exec_entry_point (tmp_bfd, tmp_bfd_target));
1077 /* Record the relocated start and end address of the dynamic linker
1078 text and plt section for svr4_in_dynsym_resolve_code. */
1079 interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
1082 interp_text_sect_low =
1083 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1084 interp_text_sect_high =
1085 interp_text_sect_low + bfd_section_size (tmp_bfd, interp_sect);
1087 interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
1090 interp_plt_sect_low =
1091 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1092 interp_plt_sect_high =
1093 interp_plt_sect_low + bfd_section_size (tmp_bfd, interp_sect);
1096 /* Now try to set a breakpoint in the dynamic linker. */
1097 for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
1099 /* On ABI's that use function descriptors, there are usually
1100 two linker symbols associated with each C function: one
1101 pointing at the actual entry point of the machine code,
1102 and one pointing at the function's descriptor. The
1103 latter symbol has the same name as the C function.
1105 What we're looking for here is the machine code entry
1106 point, so we are only interested in symbols in code
1108 sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep, SEC_CODE);
1113 /* We're done with both the temporary bfd and target. Remember,
1114 closing the target closes the underlying bfd. */
1115 target_close (tmp_bfd_target, 0);
1119 create_solib_event_breakpoint (load_addr + sym_addr);
1123 /* For whatever reason we couldn't set a breakpoint in the dynamic
1124 linker. Warn and drop into the old code. */
1126 warning ("Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code.");
1129 /* Scan through the list of symbols, trying to look up the symbol and
1130 set a breakpoint there. Terminate loop when we/if we succeed. */
1132 breakpoint_addr = 0;
1133 for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
1135 msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
1136 if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
1138 create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol));
1143 /* Nothing good happened. */
1146 #endif /* BKPT_AT_SYMBOL */
1155 special_symbol_handling -- additional shared library symbol handling
1159 void special_symbol_handling ()
1163 Once the symbols from a shared object have been loaded in the usual
1164 way, we are called to do any system specific symbol handling that
1167 For SunOS4, this consisted of grunging around in the dynamic
1168 linkers structures to find symbol definitions for "common" symbols
1169 and adding them to the minimal symbol table for the runtime common
1172 However, for SVR4, there's nothing to do.
1177 svr4_special_symbol_handling (void)
1181 /* Relocate the main executable. This function should be called upon
1182 stopping the inferior process at the entry point to the program.
1183 The entry point from BFD is compared to the PC and if they are
1184 different, the main executable is relocated by the proper amount.
1186 As written it will only attempt to relocate executables which
1187 lack interpreter sections. It seems likely that only dynamic
1188 linker executables will get relocated, though it should work
1189 properly for a position-independent static executable as well. */
1192 svr4_relocate_main_executable (void)
1194 asection *interp_sect;
1195 CORE_ADDR pc = read_pc ();
1197 /* Decide if the objfile needs to be relocated. As indicated above,
1198 we will only be here when execution is stopped at the beginning
1199 of the program. Relocation is necessary if the address at which
1200 we are presently stopped differs from the start address stored in
1201 the executable AND there's no interpreter section. The condition
1202 regarding the interpreter section is very important because if
1203 there *is* an interpreter section, execution will begin there
1204 instead. When there is an interpreter section, the start address
1205 is (presumably) used by the interpreter at some point to start
1206 execution of the program.
1208 If there is an interpreter, it is normal for it to be set to an
1209 arbitrary address at the outset. The job of finding it is
1210 handled in enable_break().
1212 So, to summarize, relocations are necessary when there is no
1213 interpreter section and the start address obtained from the
1214 executable is different from the address at which GDB is
1217 [ The astute reader will note that we also test to make sure that
1218 the executable in question has the DYNAMIC flag set. It is my
1219 opinion that this test is unnecessary (undesirable even). It
1220 was added to avoid inadvertent relocation of an executable
1221 whose e_type member in the ELF header is not ET_DYN. There may
1222 be a time in the future when it is desirable to do relocations
1223 on other types of files as well in which case this condition
1224 should either be removed or modified to accomodate the new file
1225 type. (E.g, an ET_EXEC executable which has been built to be
1226 position-independent could safely be relocated by the OS if
1227 desired. It is true that this violates the ABI, but the ABI
1228 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1231 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
1232 if (interp_sect == NULL
1233 && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0
1234 && (exec_entry_point (exec_bfd, &exec_ops) != pc))
1236 struct cleanup *old_chain;
1237 struct section_offsets *new_offsets;
1239 CORE_ADDR displacement;
1241 /* It is necessary to relocate the objfile. The amount to
1242 relocate by is simply the address at which we are stopped
1243 minus the starting address from the executable.
1245 We relocate all of the sections by the same amount. This
1246 behavior is mandated by recent editions of the System V ABI.
1247 According to the System V Application Binary Interface,
1248 Edition 4.1, page 5-5:
1250 ... Though the system chooses virtual addresses for
1251 individual processes, it maintains the segments' relative
1252 positions. Because position-independent code uses relative
1253 addressesing between segments, the difference between
1254 virtual addresses in memory must match the difference
1255 between virtual addresses in the file. The difference
1256 between the virtual address of any segment in memory and
1257 the corresponding virtual address in the file is thus a
1258 single constant value for any one executable or shared
1259 object in a given process. This difference is the base
1260 address. One use of the base address is to relocate the
1261 memory image of the program during dynamic linking.
1263 The same language also appears in Edition 4.0 of the System V
1264 ABI and is left unspecified in some of the earlier editions. */
1266 displacement = pc - exec_entry_point (exec_bfd, &exec_ops);
1269 new_offsets = xcalloc (symfile_objfile->num_sections,
1270 sizeof (struct section_offsets));
1271 old_chain = make_cleanup (xfree, new_offsets);
1273 for (i = 0; i < symfile_objfile->num_sections; i++)
1275 if (displacement != ANOFFSET (symfile_objfile->section_offsets, i))
1277 new_offsets->offsets[i] = displacement;
1281 objfile_relocate (symfile_objfile, new_offsets);
1283 do_cleanups (old_chain);
1291 svr4_solib_create_inferior_hook -- shared library startup support
1295 void svr4_solib_create_inferior_hook()
1299 When gdb starts up the inferior, it nurses it along (through the
1300 shell) until it is ready to execute it's first instruction. At this
1301 point, this function gets called via expansion of the macro
1302 SOLIB_CREATE_INFERIOR_HOOK.
1304 For SunOS executables, this first instruction is typically the
1305 one at "_start", or a similar text label, regardless of whether
1306 the executable is statically or dynamically linked. The runtime
1307 startup code takes care of dynamically linking in any shared
1308 libraries, once gdb allows the inferior to continue.
1310 For SVR4 executables, this first instruction is either the first
1311 instruction in the dynamic linker (for dynamically linked
1312 executables) or the instruction at "start" for statically linked
1313 executables. For dynamically linked executables, the system
1314 first exec's /lib/libc.so.N, which contains the dynamic linker,
1315 and starts it running. The dynamic linker maps in any needed
1316 shared libraries, maps in the actual user executable, and then
1317 jumps to "start" in the user executable.
1319 For both SunOS shared libraries, and SVR4 shared libraries, we
1320 can arrange to cooperate with the dynamic linker to discover the
1321 names of shared libraries that are dynamically linked, and the
1322 base addresses to which they are linked.
1324 This function is responsible for discovering those names and
1325 addresses, and saving sufficient information about them to allow
1326 their symbols to be read at a later time.
1330 Between enable_break() and disable_break(), this code does not
1331 properly handle hitting breakpoints which the user might have
1332 set in the startup code or in the dynamic linker itself. Proper
1333 handling will probably have to wait until the implementation is
1334 changed to use the "breakpoint handler function" method.
1336 Also, what if child has exit()ed? Must exit loop somehow.
1340 svr4_solib_create_inferior_hook (void)
1342 /* Relocate the main executable if necessary. */
1343 svr4_relocate_main_executable ();
1345 if (!svr4_have_link_map_offsets ())
1347 warning ("no shared library support for this OS / ABI");
1352 if (!enable_break ())
1354 warning ("shared library handler failed to enable breakpoint");
1358 #if defined(_SCO_DS)
1359 /* SCO needs the loop below, other systems should be using the
1360 special shared library breakpoints and the shared library breakpoint
1363 Now run the target. It will eventually hit the breakpoint, at
1364 which point all of the libraries will have been mapped in and we
1365 can go groveling around in the dynamic linker structures to find
1366 out what we need to know about them. */
1368 clear_proceed_status ();
1369 stop_soon = STOP_QUIETLY;
1370 stop_signal = TARGET_SIGNAL_0;
1373 target_resume (pid_to_ptid (-1), 0, stop_signal);
1374 wait_for_inferior ();
1376 while (stop_signal != TARGET_SIGNAL_TRAP);
1377 stop_soon = NO_STOP_QUIETLY;
1378 #endif /* defined(_SCO_DS) */
1382 svr4_clear_solib (void)
1388 svr4_free_so (struct so_list *so)
1390 xfree (so->lm_info->lm);
1391 xfree (so->lm_info);
1395 /* Clear any bits of ADDR that wouldn't fit in a target-format
1396 data pointer. "Data pointer" here refers to whatever sort of
1397 address the dynamic linker uses to manage its sections. At the
1398 moment, we don't support shared libraries on any processors where
1399 code and data pointers are different sizes.
1401 This isn't really the right solution. What we really need here is
1402 a way to do arithmetic on CORE_ADDR values that respects the
1403 natural pointer/address correspondence. (For example, on the MIPS,
1404 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1405 sign-extend the value. There, simply truncating the bits above
1406 TARGET_PTR_BIT, as we do below, is no good.) This should probably
1407 be a new gdbarch method or something. */
1409 svr4_truncate_ptr (CORE_ADDR addr)
1411 if (TARGET_PTR_BIT == sizeof (CORE_ADDR) * 8)
1412 /* We don't need to truncate anything, and the bit twiddling below
1413 will fail due to overflow problems. */
1416 return addr & (((CORE_ADDR) 1 << TARGET_PTR_BIT) - 1);
1421 svr4_relocate_section_addresses (struct so_list *so,
1422 struct section_table *sec)
1424 sec->addr = svr4_truncate_ptr (sec->addr + LM_ADDR (so));
1425 sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR (so));
1429 /* Fetch a link_map_offsets structure for native targets using struct
1430 definitions from link.h. See solib-legacy.c for the function
1431 which does the actual work.
1433 Note: For non-native targets (i.e. cross-debugging situations),
1434 a target specific fetch_link_map_offsets() function should be
1435 defined and registered via set_solib_svr4_fetch_link_map_offsets(). */
1437 static struct link_map_offsets *
1438 legacy_fetch_link_map_offsets (void)
1440 if (legacy_svr4_fetch_link_map_offsets_hook)
1441 return legacy_svr4_fetch_link_map_offsets_hook ();
1444 internal_error (__FILE__, __LINE__,
1445 "legacy_fetch_link_map_offsets called without legacy "
1446 "link_map support enabled.");
1451 /* Fetch a link_map_offsets structure using the method registered in the
1452 architecture vector. */
1454 static struct link_map_offsets *
1455 svr4_fetch_link_map_offsets (void)
1457 struct link_map_offsets *(*flmo)(void) =
1458 gdbarch_data (current_gdbarch, fetch_link_map_offsets_gdbarch_data);
1462 internal_error (__FILE__, __LINE__,
1463 "svr4_fetch_link_map_offsets: fetch_link_map_offsets "
1464 "method not defined for this architecture.");
1471 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1473 svr4_have_link_map_offsets (void)
1475 struct link_map_offsets *(*flmo)(void) =
1476 gdbarch_data (current_gdbarch, fetch_link_map_offsets_gdbarch_data);
1478 || (flmo == legacy_fetch_link_map_offsets
1479 && legacy_svr4_fetch_link_map_offsets_hook == NULL))
1485 /* set_solib_svr4_fetch_link_map_offsets() is intended to be called by
1486 a <arch>_gdbarch_init() function. It is used to establish an
1487 architecture specific link_map_offsets fetcher for the architecture
1491 set_solib_svr4_fetch_link_map_offsets (struct gdbarch *gdbarch,
1492 struct link_map_offsets *(*flmo) (void))
1494 set_gdbarch_data (gdbarch, fetch_link_map_offsets_gdbarch_data, flmo);
1497 /* Initialize the architecture-specific link_map_offsets fetcher.
1498 This is called after <arch>_gdbarch_init() has set up its `struct
1499 gdbarch' for the new architecture, and is only called if the
1500 link_map_offsets fetcher isn't already initialized (which is
1501 usually done by calling set_solib_svr4_fetch_link_map_offsets()
1502 above in <arch>_gdbarch_init()). Therefore we attempt to provide a
1503 reasonable alternative (for native targets anyway) if the
1504 <arch>_gdbarch_init() fails to call
1505 set_solib_svr4_fetch_link_map_offsets(). */
1508 init_fetch_link_map_offsets (struct gdbarch *gdbarch)
1510 return legacy_fetch_link_map_offsets;
1513 /* Most OS'es that have SVR4-style ELF dynamic libraries define a
1514 `struct r_debug' and a `struct link_map' that are binary compatible
1515 with the origional SVR4 implementation. */
1517 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1518 for an ILP32 SVR4 system. */
1520 struct link_map_offsets *
1521 svr4_ilp32_fetch_link_map_offsets (void)
1523 static struct link_map_offsets lmo;
1524 static struct link_map_offsets *lmp = NULL;
1530 /* Everything we need is in the first 8 bytes. */
1531 lmo.r_debug_size = 8;
1532 lmo.r_map_offset = 4;
1535 /* Everything we need is in the first 20 bytes. */
1536 lmo.link_map_size = 20;
1537 lmo.l_addr_offset = 0;
1538 lmo.l_addr_size = 4;
1539 lmo.l_name_offset = 4;
1540 lmo.l_name_size = 4;
1541 lmo.l_next_offset = 12;
1542 lmo.l_next_size = 4;
1543 lmo.l_prev_offset = 16;
1544 lmo.l_prev_size = 4;
1550 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1551 for an LP64 SVR4 system. */
1553 struct link_map_offsets *
1554 svr4_lp64_fetch_link_map_offsets (void)
1556 static struct link_map_offsets lmo;
1557 static struct link_map_offsets *lmp = NULL;
1563 /* Everything we need is in the first 16 bytes. */
1564 lmo.r_debug_size = 16;
1565 lmo.r_map_offset = 8;
1568 /* Everything we need is in the first 40 bytes. */
1569 lmo.link_map_size = 40;
1570 lmo.l_addr_offset = 0;
1571 lmo.l_addr_size = 8;
1572 lmo.l_name_offset = 8;
1573 lmo.l_name_size = 8;
1574 lmo.l_next_offset = 24;
1575 lmo.l_next_size = 8;
1576 lmo.l_prev_offset = 32;
1577 lmo.l_prev_size = 8;
1584 static struct target_so_ops svr4_so_ops;
1586 extern initialize_file_ftype _initialize_svr4_solib; /* -Wmissing-prototypes */
1589 _initialize_svr4_solib (void)
1591 fetch_link_map_offsets_gdbarch_data =
1592 register_gdbarch_data (init_fetch_link_map_offsets);
1594 svr4_so_ops.relocate_section_addresses = svr4_relocate_section_addresses;
1595 svr4_so_ops.free_so = svr4_free_so;
1596 svr4_so_ops.clear_solib = svr4_clear_solib;
1597 svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook;
1598 svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling;
1599 svr4_so_ops.current_sos = svr4_current_sos;
1600 svr4_so_ops.open_symbol_file_object = open_symbol_file_object;
1601 svr4_so_ops.in_dynsym_resolve_code = svr4_in_dynsym_resolve_code;
1603 /* FIXME: Don't do this here. *_gdbarch_init() should set so_ops. */
1604 current_target_so_ops = &svr4_so_ops;