1 /* Handle SVR4 shared libraries for GDB, the GNU Debugger.
2 Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
4 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 #ifndef SVR4_FETCH_LINK_MAP_OFFSETS
41 #define SVR4_FETCH_LINK_MAP_OFFSETS() svr4_fetch_link_map_offsets ()
44 static struct link_map_offsets *svr4_fetch_link_map_offsets (void);
45 static struct link_map_offsets *legacy_fetch_link_map_offsets (void);
46 static int svr4_have_link_map_offsets (void);
48 /* fetch_link_map_offsets_gdbarch_data is a handle used to obtain the
49 architecture specific link map offsets fetching function. */
51 static struct gdbarch_data *fetch_link_map_offsets_gdbarch_data;
53 /* legacy_svr4_fetch_link_map_offsets_hook is a pointer to a function
54 which is used to fetch link map offsets. It will only be set
55 by solib-legacy.c, if at all. */
57 struct link_map_offsets *(*legacy_svr4_fetch_link_map_offsets_hook)(void) = 0;
59 /* Link map info to include in an allocated so_list entry */
63 /* Pointer to copy of link map from inferior. The type is char *
64 rather than void *, so that we may use byte offsets to find the
65 various fields without the need for a cast. */
69 /* On SVR4 systems, a list of symbols in the dynamic linker where
70 GDB can try to place a breakpoint to monitor shared library
73 If none of these symbols are found, or other errors occur, then
74 SVR4 systems will fall back to using a symbol as the "startup
75 mapping complete" breakpoint address. */
77 static char *solib_break_names[] =
85 /* On the 64-bit PowerPC, the linker symbol with the same name as
86 the C function points to a function descriptor, not to the entry
87 point. The linker symbol whose name is the C function name
88 prefixed with a '.' points to the function's entry point. So
89 when we look through this table, we ignore symbols that point
90 into the data section (thus skipping the descriptor's symbol),
91 and eventually try this one, giving us the real entry point
98 #define BKPT_AT_SYMBOL 1
100 #if defined (BKPT_AT_SYMBOL)
101 static char *bkpt_names[] =
103 #ifdef SOLIB_BKPT_NAME
104 SOLIB_BKPT_NAME, /* Prefer configured name if it exists. */
113 static char *main_name_list[] =
119 /* Macro to extract an address from a solib structure. When GDB is
120 configured for some 32-bit targets (e.g. Solaris 2.7 sparc), BFD is
121 configured to handle 64-bit targets, so CORE_ADDR is 64 bits. We
122 have to extract only the significant bits of addresses to get the
123 right address when accessing the core file BFD.
125 Assume that the address is unsigned. */
127 #define SOLIB_EXTRACT_ADDRESS(MEMBER) \
128 extract_unsigned_integer (&(MEMBER), sizeof (MEMBER))
130 /* local data declarations */
132 /* link map access functions */
135 LM_ADDR (struct so_list *so)
137 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
139 return (CORE_ADDR) extract_signed_integer (so->lm_info->lm + lmo->l_addr_offset,
144 LM_NEXT (struct so_list *so)
146 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
148 /* Assume that the address is unsigned. */
149 return extract_unsigned_integer (so->lm_info->lm + lmo->l_next_offset,
154 LM_NAME (struct so_list *so)
156 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
158 /* Assume that the address is unsigned. */
159 return extract_unsigned_integer (so->lm_info->lm + lmo->l_name_offset,
164 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
166 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
168 /* Assume that the address is unsigned. */
169 return extract_unsigned_integer (so->lm_info->lm + lmo->l_prev_offset,
170 lmo->l_prev_size) == 0;
173 static CORE_ADDR debug_base; /* Base of dynamic linker structures */
174 static CORE_ADDR breakpoint_addr; /* Address where end bkpt is set */
176 /* Local function prototypes */
178 static int match_main (char *);
180 static CORE_ADDR bfd_lookup_symbol (bfd *, char *);
186 bfd_lookup_symbol -- lookup the value for a specific symbol
190 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
194 An expensive way to lookup the value of a single symbol for
195 bfd's that are only temporary anyway. This is used by the
196 shared library support to find the address of the debugger
197 interface structures in the shared library.
199 Note that 0 is specifically allowed as an error return (no
204 bfd_lookup_symbol (bfd *abfd, char *symname)
208 asymbol **symbol_table;
209 unsigned int number_of_symbols;
211 struct cleanup *back_to;
212 CORE_ADDR symaddr = 0;
214 storage_needed = bfd_get_symtab_upper_bound (abfd);
216 if (storage_needed > 0)
218 symbol_table = (asymbol **) xmalloc (storage_needed);
219 back_to = make_cleanup (xfree, symbol_table);
220 number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
222 for (i = 0; i < number_of_symbols; i++)
224 sym = *symbol_table++;
225 if (STREQ (sym->name, symname))
227 /* Bfd symbols are section relative. */
228 symaddr = sym->value + sym->section->vma;
232 do_cleanups (back_to);
238 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
239 have to check the dynamic string table too. */
241 storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);
243 if (storage_needed > 0)
245 symbol_table = (asymbol **) xmalloc (storage_needed);
246 back_to = make_cleanup (xfree, symbol_table);
247 number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table);
249 for (i = 0; i < number_of_symbols; i++)
251 sym = *symbol_table++;
252 if (STREQ (sym->name, symname))
254 /* Bfd symbols are section relative. */
255 symaddr = sym->value + sym->section->vma;
259 do_cleanups (back_to);
265 #ifdef HANDLE_SVR4_EXEC_EMULATORS
268 Solaris BCP (the part of Solaris which allows it to run SunOS4
269 a.out files) throws in another wrinkle. Solaris does not fill
270 in the usual a.out link map structures when running BCP programs,
271 the only way to get at them is via groping around in the dynamic
273 The dynamic linker and it's structures are located in the shared
274 C library, which gets run as the executable's "interpreter" by
277 Note that we can assume nothing about the process state at the time
278 we need to find these structures. We may be stopped on the first
279 instruction of the interpreter (C shared library), the first
280 instruction of the executable itself, or somewhere else entirely
281 (if we attached to the process for example).
284 static char *debug_base_symbols[] =
286 "r_debug", /* Solaris 2.3 */
287 "_r_debug", /* Solaris 2.1, 2.2 */
291 static int look_for_base (int, CORE_ADDR);
297 look_for_base -- examine file for each mapped address segment
301 static int look_for_base (int fd, CORE_ADDR baseaddr)
305 This function is passed to proc_iterate_over_mappings, which
306 causes it to get called once for each mapped address space, with
307 an open file descriptor for the file mapped to that space, and the
308 base address of that mapped space.
310 Our job is to find the debug base symbol in the file that this
311 fd is open on, if it exists, and if so, initialize the dynamic
312 linker structure base address debug_base.
314 Note that this is a computationally expensive proposition, since
315 we basically have to open a bfd on every call, so we specifically
316 avoid opening the exec file.
320 look_for_base (int fd, CORE_ADDR baseaddr)
323 CORE_ADDR address = 0;
326 /* If the fd is -1, then there is no file that corresponds to this
327 mapped memory segment, so skip it. Also, if the fd corresponds
328 to the exec file, skip it as well. */
332 && fdmatch (fileno ((FILE *) (exec_bfd->iostream)), fd)))
337 /* Try to open whatever random file this fd corresponds to. Note that
338 we have no way currently to find the filename. Don't gripe about
339 any problems we might have, just fail. */
341 if ((interp_bfd = bfd_fdopenr ("unnamed", gnutarget, fd)) == NULL)
345 if (!bfd_check_format (interp_bfd, bfd_object))
347 /* FIXME-leak: on failure, might not free all memory associated with
349 bfd_close (interp_bfd);
353 /* Now try to find our debug base symbol in this file, which we at
354 least know to be a valid ELF executable or shared library. */
356 for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
358 address = bfd_lookup_symbol (interp_bfd, *symbolp);
366 /* FIXME-leak: on failure, might not free all memory associated with
368 bfd_close (interp_bfd);
372 /* Eureka! We found the symbol. But now we may need to relocate it
373 by the base address. If the symbol's value is less than the base
374 address of the shared library, then it hasn't yet been relocated
375 by the dynamic linker, and we have to do it ourself. FIXME: Note
376 that we make the assumption that the first segment that corresponds
377 to the shared library has the base address to which the library
380 if (address < baseaddr)
384 debug_base = address;
385 /* FIXME-leak: on failure, might not free all memory associated with
387 bfd_close (interp_bfd);
390 #endif /* HANDLE_SVR4_EXEC_EMULATORS */
396 elf_locate_base -- locate the base address of dynamic linker structs
397 for SVR4 elf targets.
401 CORE_ADDR elf_locate_base (void)
405 For SVR4 elf targets the address of the dynamic linker's runtime
406 structure is contained within the dynamic info section in the
407 executable file. The dynamic section is also mapped into the
408 inferior address space. Because the runtime loader fills in the
409 real address before starting the inferior, we have to read in the
410 dynamic info section from the inferior address space.
411 If there are any errors while trying to find the address, we
412 silently return 0, otherwise the found address is returned.
417 elf_locate_base (void)
419 sec_ptr dyninfo_sect;
420 int dyninfo_sect_size;
421 CORE_ADDR dyninfo_addr;
426 /* Find the start address of the .dynamic section. */
427 dyninfo_sect = bfd_get_section_by_name (exec_bfd, ".dynamic");
428 if (dyninfo_sect == NULL)
430 dyninfo_addr = bfd_section_vma (exec_bfd, dyninfo_sect);
432 /* Read in .dynamic section, silently ignore errors. */
433 dyninfo_sect_size = bfd_section_size (exec_bfd, dyninfo_sect);
434 buf = alloca (dyninfo_sect_size);
435 if (target_read_memory (dyninfo_addr, buf, dyninfo_sect_size))
438 /* Find the DT_DEBUG entry in the the .dynamic section.
439 For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has
440 no DT_DEBUG entries. */
442 arch_size = bfd_get_arch_size (exec_bfd);
443 if (arch_size == -1) /* failure */
448 for (bufend = buf + dyninfo_sect_size;
450 buf += sizeof (Elf32_External_Dyn))
452 Elf32_External_Dyn *x_dynp = (Elf32_External_Dyn *) buf;
456 dyn_tag = bfd_h_get_32 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
457 if (dyn_tag == DT_NULL)
459 else if (dyn_tag == DT_DEBUG)
461 dyn_ptr = bfd_h_get_32 (exec_bfd,
462 (bfd_byte *) x_dynp->d_un.d_ptr);
465 else if (dyn_tag == DT_MIPS_RLD_MAP)
468 int pbuf_size = TARGET_PTR_BIT / HOST_CHAR_BIT;
470 pbuf = alloca (pbuf_size);
471 /* DT_MIPS_RLD_MAP contains a pointer to the address
472 of the dynamic link structure. */
473 dyn_ptr = bfd_h_get_32 (exec_bfd,
474 (bfd_byte *) x_dynp->d_un.d_ptr);
475 if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
477 return extract_unsigned_integer (pbuf, pbuf_size);
481 else /* 64-bit elf */
483 for (bufend = buf + dyninfo_sect_size;
485 buf += sizeof (Elf64_External_Dyn))
487 Elf64_External_Dyn *x_dynp = (Elf64_External_Dyn *) buf;
491 dyn_tag = bfd_h_get_64 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
492 if (dyn_tag == DT_NULL)
494 else if (dyn_tag == DT_DEBUG)
496 dyn_ptr = bfd_h_get_64 (exec_bfd,
497 (bfd_byte *) x_dynp->d_un.d_ptr);
500 else if (dyn_tag == DT_MIPS_RLD_MAP)
503 int pbuf_size = TARGET_PTR_BIT / HOST_CHAR_BIT;
505 pbuf = alloca (pbuf_size);
506 /* DT_MIPS_RLD_MAP contains a pointer to the address
507 of the dynamic link structure. */
508 dyn_ptr = bfd_h_get_64 (exec_bfd,
509 (bfd_byte *) x_dynp->d_un.d_ptr);
510 if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
512 return extract_unsigned_integer (pbuf, pbuf_size);
517 /* DT_DEBUG entry not found. */
525 locate_base -- locate the base address of dynamic linker structs
529 CORE_ADDR locate_base (void)
533 For both the SunOS and SVR4 shared library implementations, if the
534 inferior executable has been linked dynamically, there is a single
535 address somewhere in the inferior's data space which is the key to
536 locating all of the dynamic linker's runtime structures. This
537 address is the value of the debug base symbol. The job of this
538 function is to find and return that address, or to return 0 if there
539 is no such address (the executable is statically linked for example).
541 For SunOS, the job is almost trivial, since the dynamic linker and
542 all of it's structures are statically linked to the executable at
543 link time. Thus the symbol for the address we are looking for has
544 already been added to the minimal symbol table for the executable's
545 objfile at the time the symbol file's symbols were read, and all we
546 have to do is look it up there. Note that we explicitly do NOT want
547 to find the copies in the shared library.
549 The SVR4 version is a bit more complicated because the address
550 is contained somewhere in the dynamic info section. We have to go
551 to a lot more work to discover the address of the debug base symbol.
552 Because of this complexity, we cache the value we find and return that
553 value on subsequent invocations. Note there is no copy in the
554 executable symbol tables.
561 /* Check to see if we have a currently valid address, and if so, avoid
562 doing all this work again and just return the cached address. If
563 we have no cached address, try to locate it in the dynamic info
564 section for ELF executables. There's no point in doing any of this
565 though if we don't have some link map offsets to work with. */
567 if (debug_base == 0 && svr4_have_link_map_offsets ())
570 && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
571 debug_base = elf_locate_base ();
572 #ifdef HANDLE_SVR4_EXEC_EMULATORS
573 /* Try it the hard way for emulated executables. */
574 else if (!ptid_equal (inferior_ptid, null_ptid) && target_has_execution)
575 proc_iterate_over_mappings (look_for_base);
585 first_link_map_member -- locate first member in dynamic linker's map
589 static CORE_ADDR first_link_map_member (void)
593 Find the first element in the inferior's dynamic link map, and
594 return its address in the inferior. This function doesn't copy the
595 link map entry itself into our address space; current_sos actually
599 first_link_map_member (void)
602 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
603 char *r_map_buf = xmalloc (lmo->r_map_size);
604 struct cleanup *cleanups = make_cleanup (xfree, r_map_buf);
606 read_memory (debug_base + lmo->r_map_offset, r_map_buf, lmo->r_map_size);
608 /* Assume that the address is unsigned. */
609 lm = extract_unsigned_integer (r_map_buf, lmo->r_map_size);
611 /* FIXME: Perhaps we should validate the info somehow, perhaps by
612 checking r_version for a known version number, or r_state for
615 do_cleanups (cleanups);
624 open_symbol_file_object
628 void open_symbol_file_object (void *from_tty)
632 If no open symbol file, attempt to locate and open the main symbol
633 file. On SVR4 systems, this is the first link map entry. If its
634 name is here, we can open it. Useful when attaching to a process
635 without first loading its symbol file.
637 If FROM_TTYP dereferences to a non-zero integer, allow messages to
638 be printed. This parameter is a pointer rather than an int because
639 open_symbol_file_object() is called via catch_errors() and
640 catch_errors() requires a pointer argument. */
643 open_symbol_file_object (void *from_ttyp)
645 CORE_ADDR lm, l_name;
648 int from_tty = *(int *)from_ttyp;
649 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
650 char *l_name_buf = xmalloc (lmo->l_name_size);
651 struct cleanup *cleanups = make_cleanup (xfree, l_name_buf);
654 if (!query ("Attempt to reload symbols from process? "))
657 if ((debug_base = locate_base ()) == 0)
658 return 0; /* failed somehow... */
660 /* First link map member should be the executable. */
661 if ((lm = first_link_map_member ()) == 0)
662 return 0; /* failed somehow... */
664 /* Read address of name from target memory to GDB. */
665 read_memory (lm + lmo->l_name_offset, l_name_buf, lmo->l_name_size);
667 /* Convert the address to host format. Assume that the address is
669 l_name = extract_unsigned_integer (l_name_buf, lmo->l_name_size);
671 /* Free l_name_buf. */
672 do_cleanups (cleanups);
675 return 0; /* No filename. */
677 /* Now fetch the filename from target memory. */
678 target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode);
682 warning ("failed to read exec filename from attached file: %s",
683 safe_strerror (errcode));
687 make_cleanup (xfree, filename);
688 /* Have a pathname: read the symbol file. */
689 symbol_file_add_main (filename, from_tty);
696 current_sos -- build a list of currently loaded shared objects
700 struct so_list *current_sos ()
704 Build a list of `struct so_list' objects describing the shared
705 objects currently loaded in the inferior. This list does not
706 include an entry for the main executable file.
708 Note that we only gather information directly available from the
709 inferior --- we don't examine any of the shared library files
710 themselves. The declaration of `struct so_list' says which fields
711 we provide values for. */
713 static struct so_list *
714 svr4_current_sos (void)
717 struct so_list *head = 0;
718 struct so_list **link_ptr = &head;
720 /* Make sure we've looked up the inferior's dynamic linker's base
724 debug_base = locate_base ();
726 /* If we can't find the dynamic linker's base structure, this
727 must not be a dynamically linked executable. Hmm. */
732 /* Walk the inferior's link map list, and build our list of
733 `struct so_list' nodes. */
734 lm = first_link_map_member ();
737 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
739 = (struct so_list *) xmalloc (sizeof (struct so_list));
740 struct cleanup *old_chain = make_cleanup (xfree, new);
742 memset (new, 0, sizeof (*new));
744 new->lm_info = xmalloc (sizeof (struct lm_info));
745 make_cleanup (xfree, new->lm_info);
747 new->lm_info->lm = xmalloc (lmo->link_map_size);
748 make_cleanup (xfree, new->lm_info->lm);
749 memset (new->lm_info->lm, 0, lmo->link_map_size);
751 read_memory (lm, new->lm_info->lm, lmo->link_map_size);
755 /* For SVR4 versions, the first entry in the link map is for the
756 inferior executable, so we must ignore it. For some versions of
757 SVR4, it has no name. For others (Solaris 2.3 for example), it
758 does have a name, so we can no longer use a missing name to
759 decide when to ignore it. */
760 if (IGNORE_FIRST_LINK_MAP_ENTRY (new))
767 /* Extract this shared object's name. */
768 target_read_string (LM_NAME (new), &buffer,
769 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
772 warning ("current_sos: Can't read pathname for load map: %s\n",
773 safe_strerror (errcode));
777 strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
778 new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
780 strcpy (new->so_original_name, new->so_name);
783 /* If this entry has no name, or its name matches the name
784 for the main executable, don't include it in the list. */
785 if (! new->so_name[0]
786 || match_main (new->so_name))
792 link_ptr = &new->next;
796 discard_cleanups (old_chain);
802 /* Get the address of the link_map for a given OBJFILE. Loop through
803 the link maps, and return the address of the one corresponding to
804 the given objfile. Note that this function takes into account that
805 objfile can be the main executable, not just a shared library. The
806 main executable has always an empty name field in the linkmap. */
809 svr4_fetch_objfile_link_map (struct objfile *objfile)
813 if ((debug_base = locate_base ()) == 0)
814 return 0; /* failed somehow... */
816 /* Position ourselves on the first link map. */
817 lm = first_link_map_member ();
820 /* Get info on the layout of the r_debug and link_map structures. */
821 struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
824 struct lm_info objfile_lm_info;
825 struct cleanup *old_chain;
826 CORE_ADDR name_address;
827 char *l_name_buf = xmalloc (lmo->l_name_size);
828 old_chain = make_cleanup (xfree, l_name_buf);
830 /* Set up the buffer to contain the portion of the link_map
831 structure that gdb cares about. Note that this is not the
832 whole link_map structure. */
833 objfile_lm_info.lm = xmalloc (lmo->link_map_size);
834 make_cleanup (xfree, objfile_lm_info.lm);
835 memset (objfile_lm_info.lm, 0, lmo->link_map_size);
837 /* Read the link map into our internal structure. */
838 read_memory (lm, objfile_lm_info.lm, lmo->link_map_size);
840 /* Read address of name from target memory to GDB. */
841 read_memory (lm + lmo->l_name_offset, l_name_buf, lmo->l_name_size);
843 /* Extract this object's name. Assume that the address is
845 name_address = extract_unsigned_integer (l_name_buf, lmo->l_name_size);
846 target_read_string (name_address, &buffer,
847 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
848 make_cleanup (xfree, buffer);
851 warning ("svr4_fetch_objfile_link_map: Can't read pathname for load map: %s\n",
852 safe_strerror (errcode));
856 /* Is this the linkmap for the file we want? */
857 /* If the file is not a shared library and has no name,
858 we are sure it is the main executable, so we return that. */
859 if ((buffer && strcmp (buffer, objfile->name) == 0)
860 || (!(objfile->flags & OBJF_SHARED) && (strcmp (buffer, "") == 0)))
862 do_cleanups (old_chain);
866 /* Not the file we wanted, continue checking. Assume that the
867 address is unsigned. */
868 lm = extract_unsigned_integer (objfile_lm_info.lm + lmo->l_next_offset,
870 do_cleanups (old_chain);
875 /* On some systems, the only way to recognize the link map entry for
876 the main executable file is by looking at its name. Return
877 non-zero iff SONAME matches one of the known main executable names. */
880 match_main (char *soname)
884 for (mainp = main_name_list; *mainp != NULL; mainp++)
886 if (strcmp (soname, *mainp) == 0)
893 /* Return 1 if PC lies in the dynamic symbol resolution code of the
894 SVR4 run time loader. */
895 static CORE_ADDR interp_text_sect_low;
896 static CORE_ADDR interp_text_sect_high;
897 static CORE_ADDR interp_plt_sect_low;
898 static CORE_ADDR interp_plt_sect_high;
901 svr4_in_dynsym_resolve_code (CORE_ADDR pc)
903 return ((pc >= interp_text_sect_low && pc < interp_text_sect_high)
904 || (pc >= interp_plt_sect_low && pc < interp_plt_sect_high)
905 || in_plt_section (pc, NULL));
913 enable_break -- arrange for dynamic linker to hit breakpoint
917 int enable_break (void)
921 Both the SunOS and the SVR4 dynamic linkers have, as part of their
922 debugger interface, support for arranging for the inferior to hit
923 a breakpoint after mapping in the shared libraries. This function
924 enables that breakpoint.
926 For SunOS, there is a special flag location (in_debugger) which we
927 set to 1. When the dynamic linker sees this flag set, it will set
928 a breakpoint at a location known only to itself, after saving the
929 original contents of that place and the breakpoint address itself,
930 in it's own internal structures. When we resume the inferior, it
931 will eventually take a SIGTRAP when it runs into the breakpoint.
932 We handle this (in a different place) by restoring the contents of
933 the breakpointed location (which is only known after it stops),
934 chasing around to locate the shared libraries that have been
935 loaded, then resuming.
937 For SVR4, the debugger interface structure contains a member (r_brk)
938 which is statically initialized at the time the shared library is
939 built, to the offset of a function (_r_debug_state) which is guaran-
940 teed to be called once before mapping in a library, and again when
941 the mapping is complete. At the time we are examining this member,
942 it contains only the unrelocated offset of the function, so we have
943 to do our own relocation. Later, when the dynamic linker actually
944 runs, it relocates r_brk to be the actual address of _r_debug_state().
946 The debugger interface structure also contains an enumeration which
947 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
948 depending upon whether or not the library is being mapped or unmapped,
949 and then set to RT_CONSISTENT after the library is mapped/unmapped.
957 #ifdef BKPT_AT_SYMBOL
959 struct minimal_symbol *msymbol;
961 asection *interp_sect;
963 /* First, remove all the solib event breakpoints. Their addresses
964 may have changed since the last time we ran the program. */
965 remove_solib_event_breakpoints ();
967 interp_text_sect_low = interp_text_sect_high = 0;
968 interp_plt_sect_low = interp_plt_sect_high = 0;
970 /* Find the .interp section; if not found, warn the user and drop
971 into the old breakpoint at symbol code. */
972 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
975 unsigned int interp_sect_size;
977 CORE_ADDR load_addr = 0;
978 int load_addr_found = 0;
979 struct so_list *inferior_sos;
982 char *tmp_pathname = NULL;
983 CORE_ADDR sym_addr = 0;
985 /* Read the contents of the .interp section into a local buffer;
986 the contents specify the dynamic linker this program uses. */
987 interp_sect_size = bfd_section_size (exec_bfd, interp_sect);
988 buf = alloca (interp_sect_size);
989 bfd_get_section_contents (exec_bfd, interp_sect,
990 buf, 0, interp_sect_size);
992 /* Now we need to figure out where the dynamic linker was
993 loaded so that we can load its symbols and place a breakpoint
994 in the dynamic linker itself.
996 This address is stored on the stack. However, I've been unable
997 to find any magic formula to find it for Solaris (appears to
998 be trivial on GNU/Linux). Therefore, we have to try an alternate
999 mechanism to find the dynamic linker's base address. */
1001 tmp_fd = solib_open (buf, &tmp_pathname);
1003 tmp_bfd = bfd_fdopenr (tmp_pathname, gnutarget, tmp_fd);
1005 if (tmp_bfd == NULL)
1006 goto bkpt_at_symbol;
1008 /* Make sure the dynamic linker's really a useful object. */
1009 if (!bfd_check_format (tmp_bfd, bfd_object))
1011 warning ("Unable to grok dynamic linker %s as an object file", buf);
1012 bfd_close (tmp_bfd);
1013 goto bkpt_at_symbol;
1016 /* If the entry in _DYNAMIC for the dynamic linker has already
1017 been filled in, we can read its base address from there. */
1018 inferior_sos = svr4_current_sos ();
1021 /* Connected to a running target. Update our shared library table. */
1022 solib_add (NULL, 0, NULL, auto_solib_add);
1024 while (inferior_sos)
1026 if (strcmp (buf, inferior_sos->so_original_name) == 0)
1028 load_addr_found = 1;
1029 load_addr = LM_ADDR (inferior_sos);
1032 inferior_sos = inferior_sos->next;
1035 /* Otherwise we find the dynamic linker's base address by examining
1036 the current pc (which should point at the entry point for the
1037 dynamic linker) and subtracting the offset of the entry point. */
1038 if (!load_addr_found)
1039 load_addr = read_pc () - tmp_bfd->start_address;
1041 /* Record the relocated start and end address of the dynamic linker
1042 text and plt section for svr4_in_dynsym_resolve_code. */
1043 interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
1046 interp_text_sect_low =
1047 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1048 interp_text_sect_high =
1049 interp_text_sect_low + bfd_section_size (tmp_bfd, interp_sect);
1051 interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
1054 interp_plt_sect_low =
1055 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1056 interp_plt_sect_high =
1057 interp_plt_sect_low + bfd_section_size (tmp_bfd, interp_sect);
1060 /* Now try to set a breakpoint in the dynamic linker. */
1061 for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
1063 sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep);
1068 /* We're done with the temporary bfd. */
1069 bfd_close (tmp_bfd);
1073 create_solib_event_breakpoint (load_addr + sym_addr);
1077 /* For whatever reason we couldn't set a breakpoint in the dynamic
1078 linker. Warn and drop into the old code. */
1080 warning ("Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code.");
1083 /* Scan through the list of symbols, trying to look up the symbol and
1084 set a breakpoint there. Terminate loop when we/if we succeed. */
1086 breakpoint_addr = 0;
1087 for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
1089 msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
1090 if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
1092 create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol));
1097 /* Nothing good happened. */
1100 #endif /* BKPT_AT_SYMBOL */
1109 special_symbol_handling -- additional shared library symbol handling
1113 void special_symbol_handling ()
1117 Once the symbols from a shared object have been loaded in the usual
1118 way, we are called to do any system specific symbol handling that
1121 For SunOS4, this consisted of grunging around in the dynamic
1122 linkers structures to find symbol definitions for "common" symbols
1123 and adding them to the minimal symbol table for the runtime common
1126 However, for SVR4, there's nothing to do.
1131 svr4_special_symbol_handling (void)
1135 /* Relocate the main executable. This function should be called upon
1136 stopping the inferior process at the entry point to the program.
1137 The entry point from BFD is compared to the PC and if they are
1138 different, the main executable is relocated by the proper amount.
1140 As written it will only attempt to relocate executables which
1141 lack interpreter sections. It seems likely that only dynamic
1142 linker executables will get relocated, though it should work
1143 properly for a position-independent static executable as well. */
1146 svr4_relocate_main_executable (void)
1148 asection *interp_sect;
1149 CORE_ADDR pc = read_pc ();
1151 /* Decide if the objfile needs to be relocated. As indicated above,
1152 we will only be here when execution is stopped at the beginning
1153 of the program. Relocation is necessary if the address at which
1154 we are presently stopped differs from the start address stored in
1155 the executable AND there's no interpreter section. The condition
1156 regarding the interpreter section is very important because if
1157 there *is* an interpreter section, execution will begin there
1158 instead. When there is an interpreter section, the start address
1159 is (presumably) used by the interpreter at some point to start
1160 execution of the program.
1162 If there is an interpreter, it is normal for it to be set to an
1163 arbitrary address at the outset. The job of finding it is
1164 handled in enable_break().
1166 So, to summarize, relocations are necessary when there is no
1167 interpreter section and the start address obtained from the
1168 executable is different from the address at which GDB is
1171 [ The astute reader will note that we also test to make sure that
1172 the executable in question has the DYNAMIC flag set. It is my
1173 opinion that this test is unnecessary (undesirable even). It
1174 was added to avoid inadvertent relocation of an executable
1175 whose e_type member in the ELF header is not ET_DYN. There may
1176 be a time in the future when it is desirable to do relocations
1177 on other types of files as well in which case this condition
1178 should either be removed or modified to accomodate the new file
1179 type. (E.g, an ET_EXEC executable which has been built to be
1180 position-independent could safely be relocated by the OS if
1181 desired. It is true that this violates the ABI, but the ABI
1182 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1185 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
1186 if (interp_sect == NULL
1187 && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0
1188 && bfd_get_start_address (exec_bfd) != pc)
1190 struct cleanup *old_chain;
1191 struct section_offsets *new_offsets;
1193 CORE_ADDR displacement;
1195 /* It is necessary to relocate the objfile. The amount to
1196 relocate by is simply the address at which we are stopped
1197 minus the starting address from the executable.
1199 We relocate all of the sections by the same amount. This
1200 behavior is mandated by recent editions of the System V ABI.
1201 According to the System V Application Binary Interface,
1202 Edition 4.1, page 5-5:
1204 ... Though the system chooses virtual addresses for
1205 individual processes, it maintains the segments' relative
1206 positions. Because position-independent code uses relative
1207 addressesing between segments, the difference between
1208 virtual addresses in memory must match the difference
1209 between virtual addresses in the file. The difference
1210 between the virtual address of any segment in memory and
1211 the corresponding virtual address in the file is thus a
1212 single constant value for any one executable or shared
1213 object in a given process. This difference is the base
1214 address. One use of the base address is to relocate the
1215 memory image of the program during dynamic linking.
1217 The same language also appears in Edition 4.0 of the System V
1218 ABI and is left unspecified in some of the earlier editions. */
1220 displacement = pc - bfd_get_start_address (exec_bfd);
1223 new_offsets = xcalloc (symfile_objfile->num_sections,
1224 sizeof (struct section_offsets));
1225 old_chain = make_cleanup (xfree, new_offsets);
1227 for (i = 0; i < symfile_objfile->num_sections; i++)
1229 if (displacement != ANOFFSET (symfile_objfile->section_offsets, i))
1231 new_offsets->offsets[i] = displacement;
1235 objfile_relocate (symfile_objfile, new_offsets);
1237 do_cleanups (old_chain);
1245 svr4_solib_create_inferior_hook -- shared library startup support
1249 void svr4_solib_create_inferior_hook()
1253 When gdb starts up the inferior, it nurses it along (through the
1254 shell) until it is ready to execute it's first instruction. At this
1255 point, this function gets called via expansion of the macro
1256 SOLIB_CREATE_INFERIOR_HOOK.
1258 For SunOS executables, this first instruction is typically the
1259 one at "_start", or a similar text label, regardless of whether
1260 the executable is statically or dynamically linked. The runtime
1261 startup code takes care of dynamically linking in any shared
1262 libraries, once gdb allows the inferior to continue.
1264 For SVR4 executables, this first instruction is either the first
1265 instruction in the dynamic linker (for dynamically linked
1266 executables) or the instruction at "start" for statically linked
1267 executables. For dynamically linked executables, the system
1268 first exec's /lib/libc.so.N, which contains the dynamic linker,
1269 and starts it running. The dynamic linker maps in any needed
1270 shared libraries, maps in the actual user executable, and then
1271 jumps to "start" in the user executable.
1273 For both SunOS shared libraries, and SVR4 shared libraries, we
1274 can arrange to cooperate with the dynamic linker to discover the
1275 names of shared libraries that are dynamically linked, and the
1276 base addresses to which they are linked.
1278 This function is responsible for discovering those names and
1279 addresses, and saving sufficient information about them to allow
1280 their symbols to be read at a later time.
1284 Between enable_break() and disable_break(), this code does not
1285 properly handle hitting breakpoints which the user might have
1286 set in the startup code or in the dynamic linker itself. Proper
1287 handling will probably have to wait until the implementation is
1288 changed to use the "breakpoint handler function" method.
1290 Also, what if child has exit()ed? Must exit loop somehow.
1294 svr4_solib_create_inferior_hook (void)
1296 /* Relocate the main executable if necessary. */
1297 svr4_relocate_main_executable ();
1299 if (!svr4_have_link_map_offsets ())
1301 warning ("no shared library support for this OS / ABI");
1306 if (!enable_break ())
1308 warning ("shared library handler failed to enable breakpoint");
1312 #if defined(_SCO_DS)
1313 /* SCO needs the loop below, other systems should be using the
1314 special shared library breakpoints and the shared library breakpoint
1317 Now run the target. It will eventually hit the breakpoint, at
1318 which point all of the libraries will have been mapped in and we
1319 can go groveling around in the dynamic linker structures to find
1320 out what we need to know about them. */
1322 clear_proceed_status ();
1323 stop_soon = STOP_QUIETLY;
1324 stop_signal = TARGET_SIGNAL_0;
1327 target_resume (pid_to_ptid (-1), 0, stop_signal);
1328 wait_for_inferior ();
1330 while (stop_signal != TARGET_SIGNAL_TRAP);
1331 stop_soon = NO_STOP_QUIETLY;
1332 #endif /* defined(_SCO_DS) */
1336 svr4_clear_solib (void)
1342 svr4_free_so (struct so_list *so)
1344 xfree (so->lm_info->lm);
1345 xfree (so->lm_info);
1349 /* Clear any bits of ADDR that wouldn't fit in a target-format
1350 data pointer. "Data pointer" here refers to whatever sort of
1351 address the dynamic linker uses to manage its sections. At the
1352 moment, we don't support shared libraries on any processors where
1353 code and data pointers are different sizes.
1355 This isn't really the right solution. What we really need here is
1356 a way to do arithmetic on CORE_ADDR values that respects the
1357 natural pointer/address correspondence. (For example, on the MIPS,
1358 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1359 sign-extend the value. There, simply truncating the bits above
1360 TARGET_PTR_BIT, as we do below, is no good.) This should probably
1361 be a new gdbarch method or something. */
1363 svr4_truncate_ptr (CORE_ADDR addr)
1365 if (TARGET_PTR_BIT == sizeof (CORE_ADDR) * 8)
1366 /* We don't need to truncate anything, and the bit twiddling below
1367 will fail due to overflow problems. */
1370 return addr & (((CORE_ADDR) 1 << TARGET_PTR_BIT) - 1);
1375 svr4_relocate_section_addresses (struct so_list *so,
1376 struct section_table *sec)
1378 sec->addr = svr4_truncate_ptr (sec->addr + LM_ADDR (so));
1379 sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR (so));
1383 /* Fetch a link_map_offsets structure for native targets using struct
1384 definitions from link.h. See solib-legacy.c for the function
1385 which does the actual work.
1387 Note: For non-native targets (i.e. cross-debugging situations),
1388 a target specific fetch_link_map_offsets() function should be
1389 defined and registered via set_solib_svr4_fetch_link_map_offsets(). */
1391 static struct link_map_offsets *
1392 legacy_fetch_link_map_offsets (void)
1394 if (legacy_svr4_fetch_link_map_offsets_hook)
1395 return legacy_svr4_fetch_link_map_offsets_hook ();
1398 internal_error (__FILE__, __LINE__,
1399 "legacy_fetch_link_map_offsets called without legacy "
1400 "link_map support enabled.");
1405 /* Fetch a link_map_offsets structure using the method registered in the
1406 architecture vector. */
1408 static struct link_map_offsets *
1409 svr4_fetch_link_map_offsets (void)
1411 struct link_map_offsets *(*flmo)(void) =
1412 gdbarch_data (current_gdbarch, fetch_link_map_offsets_gdbarch_data);
1416 internal_error (__FILE__, __LINE__,
1417 "svr4_fetch_link_map_offsets: fetch_link_map_offsets "
1418 "method not defined for this architecture.");
1425 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1427 svr4_have_link_map_offsets (void)
1429 struct link_map_offsets *(*flmo)(void) =
1430 gdbarch_data (current_gdbarch, fetch_link_map_offsets_gdbarch_data);
1432 || (flmo == legacy_fetch_link_map_offsets
1433 && legacy_svr4_fetch_link_map_offsets_hook == NULL))
1439 /* set_solib_svr4_fetch_link_map_offsets() is intended to be called by
1440 a <arch>_gdbarch_init() function. It is used to establish an
1441 architecture specific link_map_offsets fetcher for the architecture
1445 set_solib_svr4_fetch_link_map_offsets (struct gdbarch *gdbarch,
1446 struct link_map_offsets *(*flmo) (void))
1448 set_gdbarch_data (gdbarch, fetch_link_map_offsets_gdbarch_data, flmo);
1451 /* Initialize the architecture-specific link_map_offsets fetcher.
1452 This is called after <arch>_gdbarch_init() has set up its `struct
1453 gdbarch' for the new architecture, and is only called if the
1454 link_map_offsets fetcher isn't already initialized (which is
1455 usually done by calling set_solib_svr4_fetch_link_map_offsets()
1456 above in <arch>_gdbarch_init()). Therefore we attempt to provide a
1457 reasonable alternative (for native targets anyway) if the
1458 <arch>_gdbarch_init() fails to call
1459 set_solib_svr4_fetch_link_map_offsets(). */
1462 init_fetch_link_map_offsets (struct gdbarch *gdbarch)
1464 return legacy_fetch_link_map_offsets;
1467 static struct target_so_ops svr4_so_ops;
1469 extern initialize_file_ftype _initialize_svr4_solib; /* -Wmissing-prototypes */
1472 _initialize_svr4_solib (void)
1474 fetch_link_map_offsets_gdbarch_data =
1475 register_gdbarch_data (init_fetch_link_map_offsets, 0);
1477 svr4_so_ops.relocate_section_addresses = svr4_relocate_section_addresses;
1478 svr4_so_ops.free_so = svr4_free_so;
1479 svr4_so_ops.clear_solib = svr4_clear_solib;
1480 svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook;
1481 svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling;
1482 svr4_so_ops.current_sos = svr4_current_sos;
1483 svr4_so_ops.open_symbol_file_object = open_symbol_file_object;
1484 svr4_so_ops.in_dynsym_resolve_code = svr4_in_dynsym_resolve_code;
1486 /* FIXME: Don't do this here. *_gdbarch_init() should set so_ops. */
1487 current_target_so_ops = &svr4_so_ops;