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
[] =
87 #define BKPT_AT_SYMBOL 1
89 #if defined (BKPT_AT_SYMBOL)
90 static char *bkpt_names
[] =
92 #ifdef SOLIB_BKPT_NAME
93 SOLIB_BKPT_NAME
, /* Prefer configured name if it exists. */
102 static char *main_name_list
[] =
108 /* Macro to extract an address from a solib structure. When GDB is
109 configured for some 32-bit targets (e.g. Solaris 2.7 sparc), BFD is
110 configured to handle 64-bit targets, so CORE_ADDR is 64 bits. We
111 have to extract only the significant bits of addresses to get the
112 right address when accessing the core file BFD.
114 Assume that the address is unsigned. */
116 #define SOLIB_EXTRACT_ADDRESS(MEMBER) \
117 extract_unsigned_integer (&(MEMBER), sizeof (MEMBER))
119 /* local data declarations */
121 /* link map access functions */
124 LM_ADDR (struct so_list
*so
)
126 struct link_map_offsets
*lmo
= SVR4_FETCH_LINK_MAP_OFFSETS ();
128 return (CORE_ADDR
) extract_signed_integer (so
->lm_info
->lm
+ lmo
->l_addr_offset
,
133 LM_NEXT (struct so_list
*so
)
135 struct link_map_offsets
*lmo
= SVR4_FETCH_LINK_MAP_OFFSETS ();
137 /* Assume that the address is unsigned. */
138 return extract_unsigned_integer (so
->lm_info
->lm
+ lmo
->l_next_offset
,
143 LM_NAME (struct so_list
*so
)
145 struct link_map_offsets
*lmo
= SVR4_FETCH_LINK_MAP_OFFSETS ();
147 /* Assume that the address is unsigned. */
148 return extract_unsigned_integer (so
->lm_info
->lm
+ lmo
->l_name_offset
,
153 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list
*so
)
155 struct link_map_offsets
*lmo
= SVR4_FETCH_LINK_MAP_OFFSETS ();
157 /* Assume that the address is unsigned. */
158 return extract_unsigned_integer (so
->lm_info
->lm
+ lmo
->l_prev_offset
,
159 lmo
->l_prev_size
) == 0;
162 static CORE_ADDR debug_base
; /* Base of dynamic linker structures */
163 static CORE_ADDR breakpoint_addr
; /* Address where end bkpt is set */
165 /* Local function prototypes */
167 static int match_main (char *);
169 static CORE_ADDR
bfd_lookup_symbol (bfd
*, char *);
175 bfd_lookup_symbol -- lookup the value for a specific symbol
179 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
183 An expensive way to lookup the value of a single symbol for
184 bfd's that are only temporary anyway. This is used by the
185 shared library support to find the address of the debugger
186 interface structures in the shared library.
188 Note that 0 is specifically allowed as an error return (no
193 bfd_lookup_symbol (bfd
*abfd
, char *symname
)
197 asymbol
**symbol_table
;
198 unsigned int number_of_symbols
;
200 struct cleanup
*back_to
;
201 CORE_ADDR symaddr
= 0;
203 storage_needed
= bfd_get_symtab_upper_bound (abfd
);
205 if (storage_needed
> 0)
207 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
208 back_to
= make_cleanup (xfree
, symbol_table
);
209 number_of_symbols
= bfd_canonicalize_symtab (abfd
, symbol_table
);
211 for (i
= 0; i
< number_of_symbols
; i
++)
213 sym
= *symbol_table
++;
214 if (STREQ (sym
->name
, symname
))
216 /* Bfd symbols are section relative. */
217 symaddr
= sym
->value
+ sym
->section
->vma
;
221 do_cleanups (back_to
);
227 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
228 have to check the dynamic string table too. */
230 storage_needed
= bfd_get_dynamic_symtab_upper_bound (abfd
);
232 if (storage_needed
> 0)
234 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
235 back_to
= make_cleanup (xfree
, symbol_table
);
236 number_of_symbols
= bfd_canonicalize_dynamic_symtab (abfd
, symbol_table
);
238 for (i
= 0; i
< number_of_symbols
; i
++)
240 sym
= *symbol_table
++;
241 if (STREQ (sym
->name
, symname
))
243 /* Bfd symbols are section relative. */
244 symaddr
= sym
->value
+ sym
->section
->vma
;
248 do_cleanups (back_to
);
254 #ifdef HANDLE_SVR4_EXEC_EMULATORS
257 Solaris BCP (the part of Solaris which allows it to run SunOS4
258 a.out files) throws in another wrinkle. Solaris does not fill
259 in the usual a.out link map structures when running BCP programs,
260 the only way to get at them is via groping around in the dynamic
262 The dynamic linker and it's structures are located in the shared
263 C library, which gets run as the executable's "interpreter" by
266 Note that we can assume nothing about the process state at the time
267 we need to find these structures. We may be stopped on the first
268 instruction of the interpreter (C shared library), the first
269 instruction of the executable itself, or somewhere else entirely
270 (if we attached to the process for example).
273 static char *debug_base_symbols
[] =
275 "r_debug", /* Solaris 2.3 */
276 "_r_debug", /* Solaris 2.1, 2.2 */
280 static int look_for_base (int, CORE_ADDR
);
286 look_for_base -- examine file for each mapped address segment
290 static int look_for_base (int fd, CORE_ADDR baseaddr)
294 This function is passed to proc_iterate_over_mappings, which
295 causes it to get called once for each mapped address space, with
296 an open file descriptor for the file mapped to that space, and the
297 base address of that mapped space.
299 Our job is to find the debug base symbol in the file that this
300 fd is open on, if it exists, and if so, initialize the dynamic
301 linker structure base address debug_base.
303 Note that this is a computationally expensive proposition, since
304 we basically have to open a bfd on every call, so we specifically
305 avoid opening the exec file.
309 look_for_base (int fd
, CORE_ADDR baseaddr
)
312 CORE_ADDR address
= 0;
315 /* If the fd is -1, then there is no file that corresponds to this
316 mapped memory segment, so skip it. Also, if the fd corresponds
317 to the exec file, skip it as well. */
321 && fdmatch (fileno ((FILE *) (exec_bfd
->iostream
)), fd
)))
326 /* Try to open whatever random file this fd corresponds to. Note that
327 we have no way currently to find the filename. Don't gripe about
328 any problems we might have, just fail. */
330 if ((interp_bfd
= bfd_fdopenr ("unnamed", gnutarget
, fd
)) == NULL
)
334 if (!bfd_check_format (interp_bfd
, bfd_object
))
336 /* FIXME-leak: on failure, might not free all memory associated with
338 bfd_close (interp_bfd
);
342 /* Now try to find our debug base symbol in this file, which we at
343 least know to be a valid ELF executable or shared library. */
345 for (symbolp
= debug_base_symbols
; *symbolp
!= NULL
; symbolp
++)
347 address
= bfd_lookup_symbol (interp_bfd
, *symbolp
);
355 /* FIXME-leak: on failure, might not free all memory associated with
357 bfd_close (interp_bfd
);
361 /* Eureka! We found the symbol. But now we may need to relocate it
362 by the base address. If the symbol's value is less than the base
363 address of the shared library, then it hasn't yet been relocated
364 by the dynamic linker, and we have to do it ourself. FIXME: Note
365 that we make the assumption that the first segment that corresponds
366 to the shared library has the base address to which the library
369 if (address
< baseaddr
)
373 debug_base
= address
;
374 /* FIXME-leak: on failure, might not free all memory associated with
376 bfd_close (interp_bfd
);
379 #endif /* HANDLE_SVR4_EXEC_EMULATORS */
385 elf_locate_base -- locate the base address of dynamic linker structs
386 for SVR4 elf targets.
390 CORE_ADDR elf_locate_base (void)
394 For SVR4 elf targets the address of the dynamic linker's runtime
395 structure is contained within the dynamic info section in the
396 executable file. The dynamic section is also mapped into the
397 inferior address space. Because the runtime loader fills in the
398 real address before starting the inferior, we have to read in the
399 dynamic info section from the inferior address space.
400 If there are any errors while trying to find the address, we
401 silently return 0, otherwise the found address is returned.
406 elf_locate_base (void)
408 sec_ptr dyninfo_sect
;
409 int dyninfo_sect_size
;
410 CORE_ADDR dyninfo_addr
;
415 /* Find the start address of the .dynamic section. */
416 dyninfo_sect
= bfd_get_section_by_name (exec_bfd
, ".dynamic");
417 if (dyninfo_sect
== NULL
)
419 dyninfo_addr
= bfd_section_vma (exec_bfd
, dyninfo_sect
);
421 /* Read in .dynamic section, silently ignore errors. */
422 dyninfo_sect_size
= bfd_section_size (exec_bfd
, dyninfo_sect
);
423 buf
= alloca (dyninfo_sect_size
);
424 if (target_read_memory (dyninfo_addr
, buf
, dyninfo_sect_size
))
427 /* Find the DT_DEBUG entry in the the .dynamic section.
428 For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has
429 no DT_DEBUG entries. */
431 arch_size
= bfd_get_arch_size (exec_bfd
);
432 if (arch_size
== -1) /* failure */
437 for (bufend
= buf
+ dyninfo_sect_size
;
439 buf
+= sizeof (Elf32_External_Dyn
))
441 Elf32_External_Dyn
*x_dynp
= (Elf32_External_Dyn
*) buf
;
445 dyn_tag
= bfd_h_get_32 (exec_bfd
, (bfd_byte
*) x_dynp
->d_tag
);
446 if (dyn_tag
== DT_NULL
)
448 else if (dyn_tag
== DT_DEBUG
)
450 dyn_ptr
= bfd_h_get_32 (exec_bfd
,
451 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
454 else if (dyn_tag
== DT_MIPS_RLD_MAP
)
457 int pbuf_size
= TARGET_PTR_BIT
/ HOST_CHAR_BIT
;
459 pbuf
= alloca (pbuf_size
);
460 /* DT_MIPS_RLD_MAP contains a pointer to the address
461 of the dynamic link structure. */
462 dyn_ptr
= bfd_h_get_32 (exec_bfd
,
463 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
464 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
466 return extract_unsigned_integer (pbuf
, pbuf_size
);
470 else /* 64-bit elf */
472 for (bufend
= buf
+ dyninfo_sect_size
;
474 buf
+= sizeof (Elf64_External_Dyn
))
476 Elf64_External_Dyn
*x_dynp
= (Elf64_External_Dyn
*) buf
;
480 dyn_tag
= bfd_h_get_64 (exec_bfd
, (bfd_byte
*) x_dynp
->d_tag
);
481 if (dyn_tag
== DT_NULL
)
483 else if (dyn_tag
== DT_DEBUG
)
485 dyn_ptr
= bfd_h_get_64 (exec_bfd
,
486 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
489 else if (dyn_tag
== DT_MIPS_RLD_MAP
)
492 int pbuf_size
= TARGET_PTR_BIT
/ HOST_CHAR_BIT
;
494 pbuf
= alloca (pbuf_size
);
495 /* DT_MIPS_RLD_MAP contains a pointer to the address
496 of the dynamic link structure. */
497 dyn_ptr
= bfd_h_get_64 (exec_bfd
,
498 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
499 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
501 return extract_unsigned_integer (pbuf
, pbuf_size
);
506 /* DT_DEBUG entry not found. */
514 locate_base -- locate the base address of dynamic linker structs
518 CORE_ADDR locate_base (void)
522 For both the SunOS and SVR4 shared library implementations, if the
523 inferior executable has been linked dynamically, there is a single
524 address somewhere in the inferior's data space which is the key to
525 locating all of the dynamic linker's runtime structures. This
526 address is the value of the debug base symbol. The job of this
527 function is to find and return that address, or to return 0 if there
528 is no such address (the executable is statically linked for example).
530 For SunOS, the job is almost trivial, since the dynamic linker and
531 all of it's structures are statically linked to the executable at
532 link time. Thus the symbol for the address we are looking for has
533 already been added to the minimal symbol table for the executable's
534 objfile at the time the symbol file's symbols were read, and all we
535 have to do is look it up there. Note that we explicitly do NOT want
536 to find the copies in the shared library.
538 The SVR4 version is a bit more complicated because the address
539 is contained somewhere in the dynamic info section. We have to go
540 to a lot more work to discover the address of the debug base symbol.
541 Because of this complexity, we cache the value we find and return that
542 value on subsequent invocations. Note there is no copy in the
543 executable symbol tables.
550 /* Check to see if we have a currently valid address, and if so, avoid
551 doing all this work again and just return the cached address. If
552 we have no cached address, try to locate it in the dynamic info
553 section for ELF executables. There's no point in doing any of this
554 though if we don't have some link map offsets to work with. */
556 if (debug_base
== 0 && svr4_have_link_map_offsets ())
559 && bfd_get_flavour (exec_bfd
) == bfd_target_elf_flavour
)
560 debug_base
= elf_locate_base ();
561 #ifdef HANDLE_SVR4_EXEC_EMULATORS
562 /* Try it the hard way for emulated executables. */
563 else if (!ptid_equal (inferior_ptid
, null_ptid
) && target_has_execution
)
564 proc_iterate_over_mappings (look_for_base
);
574 first_link_map_member -- locate first member in dynamic linker's map
578 static CORE_ADDR first_link_map_member (void)
582 Find the first element in the inferior's dynamic link map, and
583 return its address in the inferior. This function doesn't copy the
584 link map entry itself into our address space; current_sos actually
588 first_link_map_member (void)
591 struct link_map_offsets
*lmo
= SVR4_FETCH_LINK_MAP_OFFSETS ();
592 char *r_map_buf
= xmalloc (lmo
->r_map_size
);
593 struct cleanup
*cleanups
= make_cleanup (xfree
, r_map_buf
);
595 read_memory (debug_base
+ lmo
->r_map_offset
, r_map_buf
, lmo
->r_map_size
);
597 /* Assume that the address is unsigned. */
598 lm
= extract_unsigned_integer (r_map_buf
, lmo
->r_map_size
);
600 /* FIXME: Perhaps we should validate the info somehow, perhaps by
601 checking r_version for a known version number, or r_state for
604 do_cleanups (cleanups
);
613 open_symbol_file_object
617 void open_symbol_file_object (void *from_tty)
621 If no open symbol file, attempt to locate and open the main symbol
622 file. On SVR4 systems, this is the first link map entry. If its
623 name is here, we can open it. Useful when attaching to a process
624 without first loading its symbol file.
626 If FROM_TTYP dereferences to a non-zero integer, allow messages to
627 be printed. This parameter is a pointer rather than an int because
628 open_symbol_file_object() is called via catch_errors() and
629 catch_errors() requires a pointer argument. */
632 open_symbol_file_object (void *from_ttyp
)
634 CORE_ADDR lm
, l_name
;
637 int from_tty
= *(int *)from_ttyp
;
638 struct link_map_offsets
*lmo
= SVR4_FETCH_LINK_MAP_OFFSETS ();
639 char *l_name_buf
= xmalloc (lmo
->l_name_size
);
640 struct cleanup
*cleanups
= make_cleanup (xfree
, l_name_buf
);
643 if (!query ("Attempt to reload symbols from process? "))
646 if ((debug_base
= locate_base ()) == 0)
647 return 0; /* failed somehow... */
649 /* First link map member should be the executable. */
650 if ((lm
= first_link_map_member ()) == 0)
651 return 0; /* failed somehow... */
653 /* Read address of name from target memory to GDB. */
654 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, lmo
->l_name_size
);
656 /* Convert the address to host format. Assume that the address is
658 l_name
= extract_unsigned_integer (l_name_buf
, lmo
->l_name_size
);
660 /* Free l_name_buf. */
661 do_cleanups (cleanups
);
664 return 0; /* No filename. */
666 /* Now fetch the filename from target memory. */
667 target_read_string (l_name
, &filename
, SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
671 warning ("failed to read exec filename from attached file: %s",
672 safe_strerror (errcode
));
676 make_cleanup (xfree
, filename
);
677 /* Have a pathname: read the symbol file. */
678 symbol_file_add_main (filename
, from_tty
);
685 current_sos -- build a list of currently loaded shared objects
689 struct so_list *current_sos ()
693 Build a list of `struct so_list' objects describing the shared
694 objects currently loaded in the inferior. This list does not
695 include an entry for the main executable file.
697 Note that we only gather information directly available from the
698 inferior --- we don't examine any of the shared library files
699 themselves. The declaration of `struct so_list' says which fields
700 we provide values for. */
702 static struct so_list
*
703 svr4_current_sos (void)
706 struct so_list
*head
= 0;
707 struct so_list
**link_ptr
= &head
;
709 /* Make sure we've looked up the inferior's dynamic linker's base
713 debug_base
= locate_base ();
715 /* If we can't find the dynamic linker's base structure, this
716 must not be a dynamically linked executable. Hmm. */
721 /* Walk the inferior's link map list, and build our list of
722 `struct so_list' nodes. */
723 lm
= first_link_map_member ();
726 struct link_map_offsets
*lmo
= SVR4_FETCH_LINK_MAP_OFFSETS ();
728 = (struct so_list
*) xmalloc (sizeof (struct so_list
));
729 struct cleanup
*old_chain
= make_cleanup (xfree
, new);
731 memset (new, 0, sizeof (*new));
733 new->lm_info
= xmalloc (sizeof (struct lm_info
));
734 make_cleanup (xfree
, new->lm_info
);
736 new->lm_info
->lm
= xmalloc (lmo
->link_map_size
);
737 make_cleanup (xfree
, new->lm_info
->lm
);
738 memset (new->lm_info
->lm
, 0, lmo
->link_map_size
);
740 read_memory (lm
, new->lm_info
->lm
, lmo
->link_map_size
);
744 /* For SVR4 versions, the first entry in the link map is for the
745 inferior executable, so we must ignore it. For some versions of
746 SVR4, it has no name. For others (Solaris 2.3 for example), it
747 does have a name, so we can no longer use a missing name to
748 decide when to ignore it. */
749 if (IGNORE_FIRST_LINK_MAP_ENTRY (new))
756 /* Extract this shared object's name. */
757 target_read_string (LM_NAME (new), &buffer
,
758 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
761 warning ("current_sos: Can't read pathname for load map: %s\n",
762 safe_strerror (errcode
));
766 strncpy (new->so_name
, buffer
, SO_NAME_MAX_PATH_SIZE
- 1);
767 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
769 strcpy (new->so_original_name
, new->so_name
);
772 /* If this entry has no name, or its name matches the name
773 for the main executable, don't include it in the list. */
774 if (! new->so_name
[0]
775 || match_main (new->so_name
))
781 link_ptr
= &new->next
;
785 discard_cleanups (old_chain
);
791 /* Get the address of the link_map for a given OBJFILE. Loop through
792 the link maps, and return the address of the one corresponding to
793 the given objfile. Note that this function takes into account that
794 objfile can be the main executable, not just a shared library. The
795 main executable has always an empty name field in the linkmap. */
798 svr4_fetch_objfile_link_map (struct objfile
*objfile
)
802 if ((debug_base
= locate_base ()) == 0)
803 return 0; /* failed somehow... */
805 /* Position ourselves on the first link map. */
806 lm
= first_link_map_member ();
809 /* Get info on the layout of the r_debug and link_map structures. */
810 struct link_map_offsets
*lmo
= SVR4_FETCH_LINK_MAP_OFFSETS ();
813 struct lm_info objfile_lm_info
;
814 struct cleanup
*old_chain
;
815 CORE_ADDR name_address
;
816 char *l_name_buf
= xmalloc (lmo
->l_name_size
);
817 old_chain
= make_cleanup (xfree
, l_name_buf
);
819 /* Set up the buffer to contain the portion of the link_map
820 structure that gdb cares about. Note that this is not the
821 whole link_map structure. */
822 objfile_lm_info
.lm
= xmalloc (lmo
->link_map_size
);
823 make_cleanup (xfree
, objfile_lm_info
.lm
);
824 memset (objfile_lm_info
.lm
, 0, lmo
->link_map_size
);
826 /* Read the link map into our internal structure. */
827 read_memory (lm
, objfile_lm_info
.lm
, lmo
->link_map_size
);
829 /* Read address of name from target memory to GDB. */
830 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, lmo
->l_name_size
);
832 /* Extract this object's name. Assume that the address is
834 name_address
= extract_unsigned_integer (l_name_buf
, lmo
->l_name_size
);
835 target_read_string (name_address
, &buffer
,
836 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
837 make_cleanup (xfree
, buffer
);
840 warning ("svr4_fetch_objfile_link_map: Can't read pathname for load map: %s\n",
841 safe_strerror (errcode
));
845 /* Is this the linkmap for the file we want? */
846 /* If the file is not a shared library and has no name,
847 we are sure it is the main executable, so we return that. */
848 if ((buffer
&& strcmp (buffer
, objfile
->name
) == 0)
849 || (!(objfile
->flags
& OBJF_SHARED
) && (strcmp (buffer
, "") == 0)))
851 do_cleanups (old_chain
);
855 /* Not the file we wanted, continue checking. Assume that the
856 address is unsigned. */
857 lm
= extract_unsigned_integer (objfile_lm_info
.lm
+ lmo
->l_next_offset
,
859 do_cleanups (old_chain
);
864 /* On some systems, the only way to recognize the link map entry for
865 the main executable file is by looking at its name. Return
866 non-zero iff SONAME matches one of the known main executable names. */
869 match_main (char *soname
)
873 for (mainp
= main_name_list
; *mainp
!= NULL
; mainp
++)
875 if (strcmp (soname
, *mainp
) == 0)
882 /* Return 1 if PC lies in the dynamic symbol resolution code of the
883 SVR4 run time loader. */
884 static CORE_ADDR interp_text_sect_low
;
885 static CORE_ADDR interp_text_sect_high
;
886 static CORE_ADDR interp_plt_sect_low
;
887 static CORE_ADDR interp_plt_sect_high
;
890 svr4_in_dynsym_resolve_code (CORE_ADDR pc
)
892 return ((pc
>= interp_text_sect_low
&& pc
< interp_text_sect_high
)
893 || (pc
>= interp_plt_sect_low
&& pc
< interp_plt_sect_high
)
894 || in_plt_section (pc
, NULL
));
902 enable_break -- arrange for dynamic linker to hit breakpoint
906 int enable_break (void)
910 Both the SunOS and the SVR4 dynamic linkers have, as part of their
911 debugger interface, support for arranging for the inferior to hit
912 a breakpoint after mapping in the shared libraries. This function
913 enables that breakpoint.
915 For SunOS, there is a special flag location (in_debugger) which we
916 set to 1. When the dynamic linker sees this flag set, it will set
917 a breakpoint at a location known only to itself, after saving the
918 original contents of that place and the breakpoint address itself,
919 in it's own internal structures. When we resume the inferior, it
920 will eventually take a SIGTRAP when it runs into the breakpoint.
921 We handle this (in a different place) by restoring the contents of
922 the breakpointed location (which is only known after it stops),
923 chasing around to locate the shared libraries that have been
924 loaded, then resuming.
926 For SVR4, the debugger interface structure contains a member (r_brk)
927 which is statically initialized at the time the shared library is
928 built, to the offset of a function (_r_debug_state) which is guaran-
929 teed to be called once before mapping in a library, and again when
930 the mapping is complete. At the time we are examining this member,
931 it contains only the unrelocated offset of the function, so we have
932 to do our own relocation. Later, when the dynamic linker actually
933 runs, it relocates r_brk to be the actual address of _r_debug_state().
935 The debugger interface structure also contains an enumeration which
936 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
937 depending upon whether or not the library is being mapped or unmapped,
938 and then set to RT_CONSISTENT after the library is mapped/unmapped.
946 #ifdef BKPT_AT_SYMBOL
948 struct minimal_symbol
*msymbol
;
950 asection
*interp_sect
;
952 /* First, remove all the solib event breakpoints. Their addresses
953 may have changed since the last time we ran the program. */
954 remove_solib_event_breakpoints ();
956 interp_text_sect_low
= interp_text_sect_high
= 0;
957 interp_plt_sect_low
= interp_plt_sect_high
= 0;
959 /* Find the .interp section; if not found, warn the user and drop
960 into the old breakpoint at symbol code. */
961 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
964 unsigned int interp_sect_size
;
966 CORE_ADDR load_addr
= 0;
967 int load_addr_found
= 0;
968 struct so_list
*inferior_sos
;
971 char *tmp_pathname
= NULL
;
972 CORE_ADDR sym_addr
= 0;
974 /* Read the contents of the .interp section into a local buffer;
975 the contents specify the dynamic linker this program uses. */
976 interp_sect_size
= bfd_section_size (exec_bfd
, interp_sect
);
977 buf
= alloca (interp_sect_size
);
978 bfd_get_section_contents (exec_bfd
, interp_sect
,
979 buf
, 0, interp_sect_size
);
981 /* Now we need to figure out where the dynamic linker was
982 loaded so that we can load its symbols and place a breakpoint
983 in the dynamic linker itself.
985 This address is stored on the stack. However, I've been unable
986 to find any magic formula to find it for Solaris (appears to
987 be trivial on GNU/Linux). Therefore, we have to try an alternate
988 mechanism to find the dynamic linker's base address. */
990 tmp_fd
= solib_open (buf
, &tmp_pathname
);
992 tmp_bfd
= bfd_fdopenr (tmp_pathname
, gnutarget
, tmp_fd
);
997 /* Make sure the dynamic linker's really a useful object. */
998 if (!bfd_check_format (tmp_bfd
, bfd_object
))
1000 warning ("Unable to grok dynamic linker %s as an object file", buf
);
1001 bfd_close (tmp_bfd
);
1002 goto bkpt_at_symbol
;
1005 /* If the entry in _DYNAMIC for the dynamic linker has already
1006 been filled in, we can read its base address from there. */
1007 inferior_sos
= svr4_current_sos ();
1010 /* Connected to a running target. Update our shared library table. */
1011 solib_add (NULL
, 0, NULL
, auto_solib_add
);
1013 while (inferior_sos
)
1015 if (strcmp (buf
, inferior_sos
->so_original_name
) == 0)
1017 load_addr_found
= 1;
1018 load_addr
= LM_ADDR (inferior_sos
);
1021 inferior_sos
= inferior_sos
->next
;
1024 /* Otherwise we find the dynamic linker's base address by examining
1025 the current pc (which should point at the entry point for the
1026 dynamic linker) and subtracting the offset of the entry point. */
1027 if (!load_addr_found
)
1028 load_addr
= read_pc () - tmp_bfd
->start_address
;
1030 /* Record the relocated start and end address of the dynamic linker
1031 text and plt section for svr4_in_dynsym_resolve_code. */
1032 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
1035 interp_text_sect_low
=
1036 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1037 interp_text_sect_high
=
1038 interp_text_sect_low
+ bfd_section_size (tmp_bfd
, interp_sect
);
1040 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
1043 interp_plt_sect_low
=
1044 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1045 interp_plt_sect_high
=
1046 interp_plt_sect_low
+ bfd_section_size (tmp_bfd
, interp_sect
);
1049 /* Now try to set a breakpoint in the dynamic linker. */
1050 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1052 sym_addr
= bfd_lookup_symbol (tmp_bfd
, *bkpt_namep
);
1057 /* We're done with the temporary bfd. */
1058 bfd_close (tmp_bfd
);
1062 create_solib_event_breakpoint (load_addr
+ sym_addr
);
1066 /* For whatever reason we couldn't set a breakpoint in the dynamic
1067 linker. Warn and drop into the old code. */
1069 warning ("Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code.");
1072 /* Scan through the list of symbols, trying to look up the symbol and
1073 set a breakpoint there. Terminate loop when we/if we succeed. */
1075 breakpoint_addr
= 0;
1076 for (bkpt_namep
= bkpt_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1078 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
1079 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
1081 create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol
));
1086 /* Nothing good happened. */
1089 #endif /* BKPT_AT_SYMBOL */
1098 special_symbol_handling -- additional shared library symbol handling
1102 void special_symbol_handling ()
1106 Once the symbols from a shared object have been loaded in the usual
1107 way, we are called to do any system specific symbol handling that
1110 For SunOS4, this consisted of grunging around in the dynamic
1111 linkers structures to find symbol definitions for "common" symbols
1112 and adding them to the minimal symbol table for the runtime common
1115 However, for SVR4, there's nothing to do.
1120 svr4_special_symbol_handling (void)
1124 /* Relocate the main executable. This function should be called upon
1125 stopping the inferior process at the entry point to the program.
1126 The entry point from BFD is compared to the PC and if they are
1127 different, the main executable is relocated by the proper amount.
1129 As written it will only attempt to relocate executables which
1130 lack interpreter sections. It seems likely that only dynamic
1131 linker executables will get relocated, though it should work
1132 properly for a position-independent static executable as well. */
1135 svr4_relocate_main_executable (void)
1137 asection
*interp_sect
;
1138 CORE_ADDR pc
= read_pc ();
1140 /* Decide if the objfile needs to be relocated. As indicated above,
1141 we will only be here when execution is stopped at the beginning
1142 of the program. Relocation is necessary if the address at which
1143 we are presently stopped differs from the start address stored in
1144 the executable AND there's no interpreter section. The condition
1145 regarding the interpreter section is very important because if
1146 there *is* an interpreter section, execution will begin there
1147 instead. When there is an interpreter section, the start address
1148 is (presumably) used by the interpreter at some point to start
1149 execution of the program.
1151 If there is an interpreter, it is normal for it to be set to an
1152 arbitrary address at the outset. The job of finding it is
1153 handled in enable_break().
1155 So, to summarize, relocations are necessary when there is no
1156 interpreter section and the start address obtained from the
1157 executable is different from the address at which GDB is
1160 [ The astute reader will note that we also test to make sure that
1161 the executable in question has the DYNAMIC flag set. It is my
1162 opinion that this test is unnecessary (undesirable even). It
1163 was added to avoid inadvertent relocation of an executable
1164 whose e_type member in the ELF header is not ET_DYN. There may
1165 be a time in the future when it is desirable to do relocations
1166 on other types of files as well in which case this condition
1167 should either be removed or modified to accomodate the new file
1168 type. (E.g, an ET_EXEC executable which has been built to be
1169 position-independent could safely be relocated by the OS if
1170 desired. It is true that this violates the ABI, but the ABI
1171 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1174 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
1175 if (interp_sect
== NULL
1176 && (bfd_get_file_flags (exec_bfd
) & DYNAMIC
) != 0
1177 && bfd_get_start_address (exec_bfd
) != pc
)
1179 struct cleanup
*old_chain
;
1180 struct section_offsets
*new_offsets
;
1182 CORE_ADDR displacement
;
1184 /* It is necessary to relocate the objfile. The amount to
1185 relocate by is simply the address at which we are stopped
1186 minus the starting address from the executable.
1188 We relocate all of the sections by the same amount. This
1189 behavior is mandated by recent editions of the System V ABI.
1190 According to the System V Application Binary Interface,
1191 Edition 4.1, page 5-5:
1193 ... Though the system chooses virtual addresses for
1194 individual processes, it maintains the segments' relative
1195 positions. Because position-independent code uses relative
1196 addressesing between segments, the difference between
1197 virtual addresses in memory must match the difference
1198 between virtual addresses in the file. The difference
1199 between the virtual address of any segment in memory and
1200 the corresponding virtual address in the file is thus a
1201 single constant value for any one executable or shared
1202 object in a given process. This difference is the base
1203 address. One use of the base address is to relocate the
1204 memory image of the program during dynamic linking.
1206 The same language also appears in Edition 4.0 of the System V
1207 ABI and is left unspecified in some of the earlier editions. */
1209 displacement
= pc
- bfd_get_start_address (exec_bfd
);
1212 new_offsets
= xcalloc (symfile_objfile
->num_sections
,
1213 sizeof (struct section_offsets
));
1214 old_chain
= make_cleanup (xfree
, new_offsets
);
1216 for (i
= 0; i
< symfile_objfile
->num_sections
; i
++)
1218 if (displacement
!= ANOFFSET (symfile_objfile
->section_offsets
, i
))
1220 new_offsets
->offsets
[i
] = displacement
;
1224 objfile_relocate (symfile_objfile
, new_offsets
);
1226 do_cleanups (old_chain
);
1234 svr4_solib_create_inferior_hook -- shared library startup support
1238 void svr4_solib_create_inferior_hook()
1242 When gdb starts up the inferior, it nurses it along (through the
1243 shell) until it is ready to execute it's first instruction. At this
1244 point, this function gets called via expansion of the macro
1245 SOLIB_CREATE_INFERIOR_HOOK.
1247 For SunOS executables, this first instruction is typically the
1248 one at "_start", or a similar text label, regardless of whether
1249 the executable is statically or dynamically linked. The runtime
1250 startup code takes care of dynamically linking in any shared
1251 libraries, once gdb allows the inferior to continue.
1253 For SVR4 executables, this first instruction is either the first
1254 instruction in the dynamic linker (for dynamically linked
1255 executables) or the instruction at "start" for statically linked
1256 executables. For dynamically linked executables, the system
1257 first exec's /lib/libc.so.N, which contains the dynamic linker,
1258 and starts it running. The dynamic linker maps in any needed
1259 shared libraries, maps in the actual user executable, and then
1260 jumps to "start" in the user executable.
1262 For both SunOS shared libraries, and SVR4 shared libraries, we
1263 can arrange to cooperate with the dynamic linker to discover the
1264 names of shared libraries that are dynamically linked, and the
1265 base addresses to which they are linked.
1267 This function is responsible for discovering those names and
1268 addresses, and saving sufficient information about them to allow
1269 their symbols to be read at a later time.
1273 Between enable_break() and disable_break(), this code does not
1274 properly handle hitting breakpoints which the user might have
1275 set in the startup code or in the dynamic linker itself. Proper
1276 handling will probably have to wait until the implementation is
1277 changed to use the "breakpoint handler function" method.
1279 Also, what if child has exit()ed? Must exit loop somehow.
1283 svr4_solib_create_inferior_hook (void)
1285 /* Relocate the main executable if necessary. */
1286 svr4_relocate_main_executable ();
1288 if (!svr4_have_link_map_offsets ())
1290 warning ("no shared library support for this OS / ABI");
1295 if (!enable_break ())
1297 warning ("shared library handler failed to enable breakpoint");
1301 #if defined(_SCO_DS)
1302 /* SCO needs the loop below, other systems should be using the
1303 special shared library breakpoints and the shared library breakpoint
1306 Now run the target. It will eventually hit the breakpoint, at
1307 which point all of the libraries will have been mapped in and we
1308 can go groveling around in the dynamic linker structures to find
1309 out what we need to know about them. */
1311 clear_proceed_status ();
1312 stop_soon
= STOP_QUIETLY
;
1313 stop_signal
= TARGET_SIGNAL_0
;
1316 target_resume (pid_to_ptid (-1), 0, stop_signal
);
1317 wait_for_inferior ();
1319 while (stop_signal
!= TARGET_SIGNAL_TRAP
);
1320 stop_soon
= NO_STOP_QUIETLY
;
1321 #endif /* defined(_SCO_DS) */
1325 svr4_clear_solib (void)
1331 svr4_free_so (struct so_list
*so
)
1333 xfree (so
->lm_info
->lm
);
1334 xfree (so
->lm_info
);
1338 /* Clear any bits of ADDR that wouldn't fit in a target-format
1339 data pointer. "Data pointer" here refers to whatever sort of
1340 address the dynamic linker uses to manage its sections. At the
1341 moment, we don't support shared libraries on any processors where
1342 code and data pointers are different sizes.
1344 This isn't really the right solution. What we really need here is
1345 a way to do arithmetic on CORE_ADDR values that respects the
1346 natural pointer/address correspondence. (For example, on the MIPS,
1347 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1348 sign-extend the value. There, simply truncating the bits above
1349 TARGET_PTR_BIT, as we do below, is no good.) This should probably
1350 be a new gdbarch method or something. */
1352 svr4_truncate_ptr (CORE_ADDR addr
)
1354 if (TARGET_PTR_BIT
== sizeof (CORE_ADDR
) * 8)
1355 /* We don't need to truncate anything, and the bit twiddling below
1356 will fail due to overflow problems. */
1359 return addr
& (((CORE_ADDR
) 1 << TARGET_PTR_BIT
) - 1);
1364 svr4_relocate_section_addresses (struct so_list
*so
,
1365 struct section_table
*sec
)
1367 sec
->addr
= svr4_truncate_ptr (sec
->addr
+ LM_ADDR (so
));
1368 sec
->endaddr
= svr4_truncate_ptr (sec
->endaddr
+ LM_ADDR (so
));
1372 /* Fetch a link_map_offsets structure for native targets using struct
1373 definitions from link.h. See solib-legacy.c for the function
1374 which does the actual work.
1376 Note: For non-native targets (i.e. cross-debugging situations),
1377 a target specific fetch_link_map_offsets() function should be
1378 defined and registered via set_solib_svr4_fetch_link_map_offsets(). */
1380 static struct link_map_offsets
*
1381 legacy_fetch_link_map_offsets (void)
1383 if (legacy_svr4_fetch_link_map_offsets_hook
)
1384 return legacy_svr4_fetch_link_map_offsets_hook ();
1387 internal_error (__FILE__
, __LINE__
,
1388 "legacy_fetch_link_map_offsets called without legacy "
1389 "link_map support enabled.");
1394 /* Fetch a link_map_offsets structure using the method registered in the
1395 architecture vector. */
1397 static struct link_map_offsets
*
1398 svr4_fetch_link_map_offsets (void)
1400 struct link_map_offsets
*(*flmo
)(void) =
1401 gdbarch_data (current_gdbarch
, fetch_link_map_offsets_gdbarch_data
);
1405 internal_error (__FILE__
, __LINE__
,
1406 "svr4_fetch_link_map_offsets: fetch_link_map_offsets "
1407 "method not defined for this architecture.");
1414 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1416 svr4_have_link_map_offsets (void)
1418 struct link_map_offsets
*(*flmo
)(void) =
1419 gdbarch_data (current_gdbarch
, fetch_link_map_offsets_gdbarch_data
);
1421 || (flmo
== legacy_fetch_link_map_offsets
1422 && legacy_svr4_fetch_link_map_offsets_hook
== NULL
))
1428 /* set_solib_svr4_fetch_link_map_offsets() is intended to be called by
1429 a <arch>_gdbarch_init() function. It is used to establish an
1430 architecture specific link_map_offsets fetcher for the architecture
1434 set_solib_svr4_fetch_link_map_offsets (struct gdbarch
*gdbarch
,
1435 struct link_map_offsets
*(*flmo
) (void))
1437 set_gdbarch_data (gdbarch
, fetch_link_map_offsets_gdbarch_data
, flmo
);
1440 /* Initialize the architecture-specific link_map_offsets fetcher.
1441 This is called after <arch>_gdbarch_init() has set up its `struct
1442 gdbarch' for the new architecture, and is only called if the
1443 link_map_offsets fetcher isn't already initialized (which is
1444 usually done by calling set_solib_svr4_fetch_link_map_offsets()
1445 above in <arch>_gdbarch_init()). Therefore we attempt to provide a
1446 reasonable alternative (for native targets anyway) if the
1447 <arch>_gdbarch_init() fails to call
1448 set_solib_svr4_fetch_link_map_offsets(). */
1451 init_fetch_link_map_offsets (struct gdbarch
*gdbarch
)
1453 return legacy_fetch_link_map_offsets
;
1456 static struct target_so_ops svr4_so_ops
;
1458 extern initialize_file_ftype _initialize_svr4_solib
; /* -Wmissing-prototypes */
1461 _initialize_svr4_solib (void)
1463 fetch_link_map_offsets_gdbarch_data
=
1464 register_gdbarch_data (init_fetch_link_map_offsets
, 0);
1466 svr4_so_ops
.relocate_section_addresses
= svr4_relocate_section_addresses
;
1467 svr4_so_ops
.free_so
= svr4_free_so
;
1468 svr4_so_ops
.clear_solib
= svr4_clear_solib
;
1469 svr4_so_ops
.solib_create_inferior_hook
= svr4_solib_create_inferior_hook
;
1470 svr4_so_ops
.special_symbol_handling
= svr4_special_symbol_handling
;
1471 svr4_so_ops
.current_sos
= svr4_current_sos
;
1472 svr4_so_ops
.open_symbol_file_object
= open_symbol_file_object
;
1473 svr4_so_ops
.in_dynsym_resolve_code
= svr4_in_dynsym_resolve_code
;
1475 /* FIXME: Don't do this here. *_gdbarch_init() should set so_ops. */
1476 current_target_so_ops
= &svr4_so_ops
;