1 /* Handle SVR4 shared libraries for GDB, the GNU Debugger.
3 Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
4 2001, 2003, 2004, 2005, 2006, 2007 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., 51 Franklin Street, Fifth Floor,
21 Boston, MA 02110-1301, USA. */
25 #include "elf/external.h"
26 #include "elf/common.h"
37 #include "gdb_assert.h"
41 #include "solib-svr4.h"
43 #include "bfd-target.h"
47 static struct link_map_offsets
*svr4_fetch_link_map_offsets (void);
48 static int svr4_have_link_map_offsets (void);
50 /* This hook is set to a function that provides native link map
51 offsets if the code in solib-legacy.c is linked in. */
52 struct link_map_offsets
*(*legacy_svr4_fetch_link_map_offsets_hook
) (void);
54 /* Link map info to include in an allocated so_list entry */
58 /* Pointer to copy of link map from inferior. The type is char *
59 rather than void *, so that we may use byte offsets to find the
60 various fields without the need for a cast. */
63 /* Amount by which addresses in the binary should be relocated to
64 match the inferior. This could most often be taken directly
65 from lm, but when prelinking is involved and the prelink base
66 address changes, we may need a different offset, we want to
67 warn about the difference and compute it only once. */
71 /* On SVR4 systems, a list of symbols in the dynamic linker where
72 GDB can try to place a breakpoint to monitor shared library
75 If none of these symbols are found, or other errors occur, then
76 SVR4 systems will fall back to using a symbol as the "startup
77 mapping complete" breakpoint address. */
79 static char *solib_break_names
[] =
87 /* On the 64-bit PowerPC, the linker symbol with the same name as
88 the C function points to a function descriptor, not to the entry
89 point. The linker symbol whose name is the C function name
90 prefixed with a '.' points to the function's entry point. So
91 when we look through this table, we ignore symbols that point
92 into the data section (thus skipping the descriptor's symbol),
93 and eventually try this one, giving us the real entry point
100 #define BKPT_AT_SYMBOL 1
102 #if defined (BKPT_AT_SYMBOL)
103 static char *bkpt_names
[] =
105 #ifdef SOLIB_BKPT_NAME
106 SOLIB_BKPT_NAME
, /* Prefer configured name if it exists. */
115 static char *main_name_list
[] =
121 /* link map access functions */
124 LM_ADDR_FROM_LINK_MAP (struct so_list
*so
)
126 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
128 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_addr_offset
,
129 builtin_type_void_data_ptr
);
133 HAS_LM_DYNAMIC_FROM_LINK_MAP ()
135 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
137 return lmo
->l_ld_offset
>= 0;
141 LM_DYNAMIC_FROM_LINK_MAP (struct so_list
*so
)
143 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
145 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_ld_offset
,
146 builtin_type_void_data_ptr
);
150 LM_ADDR_CHECK (struct so_list
*so
, bfd
*abfd
)
152 if (so
->lm_info
->l_addr
== (CORE_ADDR
)-1)
154 struct bfd_section
*dyninfo_sect
;
155 CORE_ADDR l_addr
, l_dynaddr
, dynaddr
, align
= 0x1000;
157 l_addr
= LM_ADDR_FROM_LINK_MAP (so
);
159 if (! abfd
|| ! HAS_LM_DYNAMIC_FROM_LINK_MAP ())
162 l_dynaddr
= LM_DYNAMIC_FROM_LINK_MAP (so
);
164 dyninfo_sect
= bfd_get_section_by_name (abfd
, ".dynamic");
165 if (dyninfo_sect
== NULL
)
168 dynaddr
= bfd_section_vma (abfd
, dyninfo_sect
);
170 if (dynaddr
+ l_addr
!= l_dynaddr
)
172 if (bfd_get_flavour (abfd
) == bfd_target_elf_flavour
)
174 Elf_Internal_Ehdr
*ehdr
= elf_tdata (abfd
)->elf_header
;
175 Elf_Internal_Phdr
*phdr
= elf_tdata (abfd
)->phdr
;
180 for (i
= 0; i
< ehdr
->e_phnum
; i
++)
181 if (phdr
[i
].p_type
== PT_LOAD
&& phdr
[i
].p_align
> align
)
182 align
= phdr
[i
].p_align
;
185 /* Turn it into a mask. */
188 /* If the changes match the alignment requirements, we
189 assume we're using a core file that was generated by the
190 same binary, just prelinked with a different base offset.
191 If it doesn't match, we may have a different binary, the
192 same binary with the dynamic table loaded at an unrelated
193 location, or anything, really. To avoid regressions,
194 don't adjust the base offset in the latter case, although
195 odds are that, if things really changed, debugging won't
197 if ((l_addr
& align
) == 0 && ((dynaddr
- l_dynaddr
) & align
) == 0)
199 l_addr
= l_dynaddr
- dynaddr
;
201 warning (_(".dynamic section for \"%s\" "
202 "is not at the expected address"), so
->so_name
);
203 warning (_("difference appears to be caused by prelink, "
204 "adjusting expectations"));
207 warning (_(".dynamic section for \"%s\" "
208 "is not at the expected address "
209 "(wrong library or version mismatch?)"), so
->so_name
);
213 so
->lm_info
->l_addr
= l_addr
;
216 return so
->lm_info
->l_addr
;
220 LM_NEXT (struct so_list
*so
)
222 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
224 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_next_offset
,
225 builtin_type_void_data_ptr
);
229 LM_NAME (struct so_list
*so
)
231 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
233 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_name_offset
,
234 builtin_type_void_data_ptr
);
238 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list
*so
)
240 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
242 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_prev_offset
,
243 builtin_type_void_data_ptr
) == 0;
246 static CORE_ADDR debug_base
; /* Base of dynamic linker structures */
247 static CORE_ADDR breakpoint_addr
; /* Address where end bkpt is set */
249 /* Validity flag for debug_loader_offset. */
250 static int debug_loader_offset_p
;
252 /* Load address for the dynamic linker, inferred. */
253 static CORE_ADDR debug_loader_offset
;
255 /* Name of the dynamic linker, valid if debug_loader_offset_p. */
256 static char *debug_loader_name
;
258 /* Local function prototypes */
260 static int match_main (char *);
262 static CORE_ADDR
bfd_lookup_symbol (bfd
*, char *, flagword
);
268 bfd_lookup_symbol -- lookup the value for a specific symbol
272 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname, flagword sect_flags)
276 An expensive way to lookup the value of a single symbol for
277 bfd's that are only temporary anyway. This is used by the
278 shared library support to find the address of the debugger
279 interface structures in the shared library.
281 If SECT_FLAGS is non-zero, only match symbols in sections whose
282 flags include all those in SECT_FLAGS.
284 Note that 0 is specifically allowed as an error return (no
289 bfd_lookup_symbol (bfd
*abfd
, char *symname
, flagword sect_flags
)
293 asymbol
**symbol_table
;
294 unsigned int number_of_symbols
;
296 struct cleanup
*back_to
;
297 CORE_ADDR symaddr
= 0;
299 storage_needed
= bfd_get_symtab_upper_bound (abfd
);
301 if (storage_needed
> 0)
303 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
304 back_to
= make_cleanup (xfree
, symbol_table
);
305 number_of_symbols
= bfd_canonicalize_symtab (abfd
, symbol_table
);
307 for (i
= 0; i
< number_of_symbols
; i
++)
309 sym
= *symbol_table
++;
310 if (strcmp (sym
->name
, symname
) == 0
311 && (sym
->section
->flags
& sect_flags
) == sect_flags
)
313 /* Bfd symbols are section relative. */
314 symaddr
= sym
->value
+ sym
->section
->vma
;
318 do_cleanups (back_to
);
324 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
325 have to check the dynamic string table too. */
327 storage_needed
= bfd_get_dynamic_symtab_upper_bound (abfd
);
329 if (storage_needed
> 0)
331 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
332 back_to
= make_cleanup (xfree
, symbol_table
);
333 number_of_symbols
= bfd_canonicalize_dynamic_symtab (abfd
, symbol_table
);
335 for (i
= 0; i
< number_of_symbols
; i
++)
337 sym
= *symbol_table
++;
339 if (strcmp (sym
->name
, symname
) == 0
340 && (sym
->section
->flags
& sect_flags
) == sect_flags
)
342 /* Bfd symbols are section relative. */
343 symaddr
= sym
->value
+ sym
->section
->vma
;
347 do_cleanups (back_to
);
357 elf_locate_base -- locate the base address of dynamic linker structs
358 for SVR4 elf targets.
362 CORE_ADDR elf_locate_base (void)
366 For SVR4 elf targets the address of the dynamic linker's runtime
367 structure is contained within the dynamic info section in the
368 executable file. The dynamic section is also mapped into the
369 inferior address space. Because the runtime loader fills in the
370 real address before starting the inferior, we have to read in the
371 dynamic info section from the inferior address space.
372 If there are any errors while trying to find the address, we
373 silently return 0, otherwise the found address is returned.
378 elf_locate_base (void)
380 struct bfd_section
*dyninfo_sect
;
381 int dyninfo_sect_size
;
382 CORE_ADDR dyninfo_addr
;
387 /* Find the start address of the .dynamic section. */
388 dyninfo_sect
= bfd_get_section_by_name (exec_bfd
, ".dynamic");
389 if (dyninfo_sect
== NULL
)
391 dyninfo_addr
= bfd_section_vma (exec_bfd
, dyninfo_sect
);
393 /* Read in .dynamic section, silently ignore errors. */
394 dyninfo_sect_size
= bfd_section_size (exec_bfd
, dyninfo_sect
);
395 buf
= alloca (dyninfo_sect_size
);
396 if (target_read_memory (dyninfo_addr
, buf
, dyninfo_sect_size
))
399 /* Find the DT_DEBUG entry in the the .dynamic section.
400 For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has
401 no DT_DEBUG entries. */
403 arch_size
= bfd_get_arch_size (exec_bfd
);
404 if (arch_size
== -1) /* failure */
409 for (bufend
= buf
+ dyninfo_sect_size
;
411 buf
+= sizeof (Elf32_External_Dyn
))
413 Elf32_External_Dyn
*x_dynp
= (Elf32_External_Dyn
*) buf
;
417 dyn_tag
= bfd_h_get_32 (exec_bfd
, (bfd_byte
*) x_dynp
->d_tag
);
418 if (dyn_tag
== DT_NULL
)
420 else if (dyn_tag
== DT_DEBUG
)
422 dyn_ptr
= bfd_h_get_32 (exec_bfd
,
423 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
426 else if (dyn_tag
== DT_MIPS_RLD_MAP
)
429 int pbuf_size
= TYPE_LENGTH (builtin_type_void_data_ptr
);
431 pbuf
= alloca (pbuf_size
);
432 /* DT_MIPS_RLD_MAP contains a pointer to the address
433 of the dynamic link structure. */
434 dyn_ptr
= bfd_h_get_32 (exec_bfd
,
435 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
436 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
438 return extract_typed_address (pbuf
, builtin_type_void_data_ptr
);
442 else /* 64-bit elf */
444 for (bufend
= buf
+ dyninfo_sect_size
;
446 buf
+= sizeof (Elf64_External_Dyn
))
448 Elf64_External_Dyn
*x_dynp
= (Elf64_External_Dyn
*) buf
;
452 dyn_tag
= bfd_h_get_64 (exec_bfd
, (bfd_byte
*) x_dynp
->d_tag
);
453 if (dyn_tag
== DT_NULL
)
455 else if (dyn_tag
== DT_DEBUG
)
457 dyn_ptr
= bfd_h_get_64 (exec_bfd
,
458 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
461 else if (dyn_tag
== DT_MIPS_RLD_MAP
)
464 int pbuf_size
= TYPE_LENGTH (builtin_type_void_data_ptr
);
466 pbuf
= alloca (pbuf_size
);
467 /* DT_MIPS_RLD_MAP contains a pointer to the address
468 of the dynamic link structure. */
469 dyn_ptr
= bfd_h_get_64 (exec_bfd
,
470 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
471 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
473 return extract_typed_address (pbuf
, builtin_type_void_data_ptr
);
478 /* DT_DEBUG entry not found. */
486 locate_base -- locate the base address of dynamic linker structs
490 CORE_ADDR locate_base (void)
494 For both the SunOS and SVR4 shared library implementations, if the
495 inferior executable has been linked dynamically, there is a single
496 address somewhere in the inferior's data space which is the key to
497 locating all of the dynamic linker's runtime structures. This
498 address is the value of the debug base symbol. The job of this
499 function is to find and return that address, or to return 0 if there
500 is no such address (the executable is statically linked for example).
502 For SunOS, the job is almost trivial, since the dynamic linker and
503 all of it's structures are statically linked to the executable at
504 link time. Thus the symbol for the address we are looking for has
505 already been added to the minimal symbol table for the executable's
506 objfile at the time the symbol file's symbols were read, and all we
507 have to do is look it up there. Note that we explicitly do NOT want
508 to find the copies in the shared library.
510 The SVR4 version is a bit more complicated because the address
511 is contained somewhere in the dynamic info section. We have to go
512 to a lot more work to discover the address of the debug base symbol.
513 Because of this complexity, we cache the value we find and return that
514 value on subsequent invocations. Note there is no copy in the
515 executable symbol tables.
522 /* Check to see if we have a currently valid address, and if so, avoid
523 doing all this work again and just return the cached address. If
524 we have no cached address, try to locate it in the dynamic info
525 section for ELF executables. There's no point in doing any of this
526 though if we don't have some link map offsets to work with. */
528 if (debug_base
== 0 && svr4_have_link_map_offsets ())
531 && bfd_get_flavour (exec_bfd
) == bfd_target_elf_flavour
)
532 debug_base
= elf_locate_base ();
537 /* Find the first element in the inferior's dynamic link map, and
538 return its address in the inferior.
540 FIXME: Perhaps we should validate the info somehow, perhaps by
541 checking r_version for a known version number, or r_state for
545 solib_svr4_r_map (void)
547 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
549 return read_memory_typed_address (debug_base
+ lmo
->r_map_offset
,
550 builtin_type_void_data_ptr
);
553 /* Find the link map for the dynamic linker (if it is not in the
554 normal list of loaded shared objects). */
557 solib_svr4_r_ldsomap (void)
559 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
562 /* Check version, and return zero if `struct r_debug' doesn't have
563 the r_ldsomap member. */
564 version
= read_memory_unsigned_integer (debug_base
+ lmo
->r_version_offset
,
565 lmo
->r_version_size
);
566 if (version
< 2 || lmo
->r_ldsomap_offset
== -1)
569 return read_memory_typed_address (debug_base
+ lmo
->r_ldsomap_offset
,
570 builtin_type_void_data_ptr
);
577 open_symbol_file_object
581 void open_symbol_file_object (void *from_tty)
585 If no open symbol file, attempt to locate and open the main symbol
586 file. On SVR4 systems, this is the first link map entry. If its
587 name is here, we can open it. Useful when attaching to a process
588 without first loading its symbol file.
590 If FROM_TTYP dereferences to a non-zero integer, allow messages to
591 be printed. This parameter is a pointer rather than an int because
592 open_symbol_file_object() is called via catch_errors() and
593 catch_errors() requires a pointer argument. */
596 open_symbol_file_object (void *from_ttyp
)
598 CORE_ADDR lm
, l_name
;
601 int from_tty
= *(int *)from_ttyp
;
602 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
603 int l_name_size
= TYPE_LENGTH (builtin_type_void_data_ptr
);
604 gdb_byte
*l_name_buf
= xmalloc (l_name_size
);
605 struct cleanup
*cleanups
= make_cleanup (xfree
, l_name_buf
);
608 if (!query ("Attempt to reload symbols from process? "))
611 if ((debug_base
= locate_base ()) == 0)
612 return 0; /* failed somehow... */
614 /* First link map member should be the executable. */
615 lm
= solib_svr4_r_map ();
617 return 0; /* failed somehow... */
619 /* Read address of name from target memory to GDB. */
620 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, l_name_size
);
622 /* Convert the address to host format. */
623 l_name
= extract_typed_address (l_name_buf
, builtin_type_void_data_ptr
);
625 /* Free l_name_buf. */
626 do_cleanups (cleanups
);
629 return 0; /* No filename. */
631 /* Now fetch the filename from target memory. */
632 target_read_string (l_name
, &filename
, SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
636 warning (_("failed to read exec filename from attached file: %s"),
637 safe_strerror (errcode
));
641 make_cleanup (xfree
, filename
);
642 /* Have a pathname: read the symbol file. */
643 symbol_file_add_main (filename
, from_tty
);
648 /* If no shared library information is available from the dynamic
649 linker, build a fallback list from other sources. */
651 static struct so_list
*
652 svr4_default_sos (void)
654 struct so_list
*head
= NULL
;
655 struct so_list
**link_ptr
= &head
;
657 if (debug_loader_offset_p
)
659 struct so_list
*new = XZALLOC (struct so_list
);
661 new->lm_info
= xmalloc (sizeof (struct lm_info
));
663 /* Nothing will ever check the cached copy of the link
664 map if we set l_addr. */
665 new->lm_info
->l_addr
= debug_loader_offset
;
666 new->lm_info
->lm
= NULL
;
668 strncpy (new->so_name
, debug_loader_name
, SO_NAME_MAX_PATH_SIZE
- 1);
669 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
670 strcpy (new->so_original_name
, new->so_name
);
673 link_ptr
= &new->next
;
681 current_sos -- build a list of currently loaded shared objects
685 struct so_list *current_sos ()
689 Build a list of `struct so_list' objects describing the shared
690 objects currently loaded in the inferior. This list does not
691 include an entry for the main executable file.
693 Note that we only gather information directly available from the
694 inferior --- we don't examine any of the shared library files
695 themselves. The declaration of `struct so_list' says which fields
696 we provide values for. */
698 static struct so_list
*
699 svr4_current_sos (void)
702 struct so_list
*head
= 0;
703 struct so_list
**link_ptr
= &head
;
704 CORE_ADDR ldsomap
= 0;
706 /* Make sure we've looked up the inferior's dynamic linker's base
710 debug_base
= locate_base ();
712 /* If we can't find the dynamic linker's base structure, this
713 must not be a dynamically linked executable. Hmm. */
715 return svr4_default_sos ();
718 /* Walk the inferior's link map list, and build our list of
719 `struct so_list' nodes. */
720 lm
= solib_svr4_r_map ();
724 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
725 struct so_list
*new = XZALLOC (struct so_list
);
726 struct cleanup
*old_chain
= make_cleanup (xfree
, new);
728 new->lm_info
= xmalloc (sizeof (struct lm_info
));
729 make_cleanup (xfree
, new->lm_info
);
731 new->lm_info
->l_addr
= (CORE_ADDR
)-1;
732 new->lm_info
->lm
= xzalloc (lmo
->link_map_size
);
733 make_cleanup (xfree
, new->lm_info
->lm
);
735 read_memory (lm
, new->lm_info
->lm
, lmo
->link_map_size
);
739 /* For SVR4 versions, the first entry in the link map is for the
740 inferior executable, so we must ignore it. For some versions of
741 SVR4, it has no name. For others (Solaris 2.3 for example), it
742 does have a name, so we can no longer use a missing name to
743 decide when to ignore it. */
744 if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap
== 0)
751 /* Extract this shared object's name. */
752 target_read_string (LM_NAME (new), &buffer
,
753 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
755 warning (_("Can't read pathname for load map: %s."),
756 safe_strerror (errcode
));
759 strncpy (new->so_name
, buffer
, SO_NAME_MAX_PATH_SIZE
- 1);
760 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
762 strcpy (new->so_original_name
, new->so_name
);
765 /* If this entry has no name, or its name matches the name
766 for the main executable, don't include it in the list. */
767 if (! new->so_name
[0]
768 || match_main (new->so_name
))
774 link_ptr
= &new->next
;
778 /* On Solaris, the dynamic linker is not in the normal list of
779 shared objects, so make sure we pick it up too. Having
780 symbol information for the dynamic linker is quite crucial
781 for skipping dynamic linker resolver code. */
782 if (lm
== 0 && ldsomap
== 0)
783 lm
= ldsomap
= solib_svr4_r_ldsomap ();
785 discard_cleanups (old_chain
);
789 return svr4_default_sos ();
794 /* Get the address of the link_map for a given OBJFILE. Loop through
795 the link maps, and return the address of the one corresponding to
796 the given objfile. Note that this function takes into account that
797 objfile can be the main executable, not just a shared library. The
798 main executable has always an empty name field in the linkmap. */
801 svr4_fetch_objfile_link_map (struct objfile
*objfile
)
805 if ((debug_base
= locate_base ()) == 0)
806 return 0; /* failed somehow... */
808 /* Position ourselves on the first link map. */
809 lm
= solib_svr4_r_map ();
812 /* Get info on the layout of the r_debug and link_map structures. */
813 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
816 struct lm_info objfile_lm_info
;
817 struct cleanup
*old_chain
;
818 CORE_ADDR name_address
;
819 int l_name_size
= TYPE_LENGTH (builtin_type_void_data_ptr
);
820 gdb_byte
*l_name_buf
= xmalloc (l_name_size
);
821 old_chain
= make_cleanup (xfree
, l_name_buf
);
823 /* Set up the buffer to contain the portion of the link_map
824 structure that gdb cares about. Note that this is not the
825 whole link_map structure. */
826 objfile_lm_info
.lm
= xzalloc (lmo
->link_map_size
);
827 make_cleanup (xfree
, objfile_lm_info
.lm
);
829 /* Read the link map into our internal structure. */
830 read_memory (lm
, objfile_lm_info
.lm
, lmo
->link_map_size
);
832 /* Read address of name from target memory to GDB. */
833 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, l_name_size
);
835 /* Extract this object's name. */
836 name_address
= extract_typed_address (l_name_buf
,
837 builtin_type_void_data_ptr
);
838 target_read_string (name_address
, &buffer
,
839 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
840 make_cleanup (xfree
, buffer
);
842 warning (_("Can't read pathname for load map: %s."),
843 safe_strerror (errcode
));
846 /* Is this the linkmap for the file we want? */
847 /* If the file is not a shared library and has no name,
848 we are sure it is the main executable, so we return that. */
849 if ((buffer
&& strcmp (buffer
, objfile
->name
) == 0)
850 || (!(objfile
->flags
& OBJF_SHARED
) && (strcmp (buffer
, "") == 0)))
852 do_cleanups (old_chain
);
856 /* Not the file we wanted, continue checking. */
857 lm
= extract_typed_address (objfile_lm_info
.lm
+ lmo
->l_next_offset
,
858 builtin_type_void_data_ptr
);
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
));
897 /* Given an executable's ABFD and target, compute the entry-point
901 exec_entry_point (struct bfd
*abfd
, struct target_ops
*targ
)
903 /* KevinB wrote ... for most targets, the address returned by
904 bfd_get_start_address() is the entry point for the start
905 function. But, for some targets, bfd_get_start_address() returns
906 the address of a function descriptor from which the entry point
907 address may be extracted. This address is extracted by
908 gdbarch_convert_from_func_ptr_addr(). The method
909 gdbarch_convert_from_func_ptr_addr() is the merely the identify
910 function for targets which don't use function descriptors. */
911 return gdbarch_convert_from_func_ptr_addr (current_gdbarch
,
912 bfd_get_start_address (abfd
),
920 enable_break -- arrange for dynamic linker to hit breakpoint
924 int enable_break (void)
928 Both the SunOS and the SVR4 dynamic linkers have, as part of their
929 debugger interface, support for arranging for the inferior to hit
930 a breakpoint after mapping in the shared libraries. This function
931 enables that breakpoint.
933 For SunOS, there is a special flag location (in_debugger) which we
934 set to 1. When the dynamic linker sees this flag set, it will set
935 a breakpoint at a location known only to itself, after saving the
936 original contents of that place and the breakpoint address itself,
937 in it's own internal structures. When we resume the inferior, it
938 will eventually take a SIGTRAP when it runs into the breakpoint.
939 We handle this (in a different place) by restoring the contents of
940 the breakpointed location (which is only known after it stops),
941 chasing around to locate the shared libraries that have been
942 loaded, then resuming.
944 For SVR4, the debugger interface structure contains a member (r_brk)
945 which is statically initialized at the time the shared library is
946 built, to the offset of a function (_r_debug_state) which is guaran-
947 teed to be called once before mapping in a library, and again when
948 the mapping is complete. At the time we are examining this member,
949 it contains only the unrelocated offset of the function, so we have
950 to do our own relocation. Later, when the dynamic linker actually
951 runs, it relocates r_brk to be the actual address of _r_debug_state().
953 The debugger interface structure also contains an enumeration which
954 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
955 depending upon whether or not the library is being mapped or unmapped,
956 and then set to RT_CONSISTENT after the library is mapped/unmapped.
964 #ifdef BKPT_AT_SYMBOL
966 struct minimal_symbol
*msymbol
;
968 asection
*interp_sect
;
970 /* First, remove all the solib event breakpoints. Their addresses
971 may have changed since the last time we ran the program. */
972 remove_solib_event_breakpoints ();
974 interp_text_sect_low
= interp_text_sect_high
= 0;
975 interp_plt_sect_low
= interp_plt_sect_high
= 0;
977 /* Find the .interp section; if not found, warn the user and drop
978 into the old breakpoint at symbol code. */
979 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
982 unsigned int interp_sect_size
;
984 CORE_ADDR load_addr
= 0;
985 int load_addr_found
= 0;
988 struct target_ops
*tmp_bfd_target
;
990 char *tmp_pathname
= NULL
;
991 CORE_ADDR sym_addr
= 0;
993 /* Read the contents of the .interp section into a local buffer;
994 the contents specify the dynamic linker this program uses. */
995 interp_sect_size
= bfd_section_size (exec_bfd
, interp_sect
);
996 buf
= alloca (interp_sect_size
);
997 bfd_get_section_contents (exec_bfd
, interp_sect
,
998 buf
, 0, interp_sect_size
);
1000 /* Now we need to figure out where the dynamic linker was
1001 loaded so that we can load its symbols and place a breakpoint
1002 in the dynamic linker itself.
1004 This address is stored on the stack. However, I've been unable
1005 to find any magic formula to find it for Solaris (appears to
1006 be trivial on GNU/Linux). Therefore, we have to try an alternate
1007 mechanism to find the dynamic linker's base address. */
1009 /* TODO drow/2006-09-12: This is somewhat fragile, because it
1010 relies on read_pc. On both Solaris and GNU/Linux we can use
1011 the AT_BASE auxilliary entry, which GDB now knows how to
1012 access, to find the base address. */
1014 tmp_fd
= solib_open (buf
, &tmp_pathname
);
1016 tmp_bfd
= bfd_fopen (tmp_pathname
, gnutarget
, FOPEN_RB
, tmp_fd
);
1018 if (tmp_bfd
== NULL
)
1019 goto bkpt_at_symbol
;
1021 /* Make sure the dynamic linker's really a useful object. */
1022 if (!bfd_check_format (tmp_bfd
, bfd_object
))
1024 warning (_("Unable to grok dynamic linker %s as an object file"), buf
);
1025 bfd_close (tmp_bfd
);
1026 goto bkpt_at_symbol
;
1029 /* Now convert the TMP_BFD into a target. That way target, as
1030 well as BFD operations can be used. Note that closing the
1031 target will also close the underlying bfd. */
1032 tmp_bfd_target
= target_bfd_reopen (tmp_bfd
);
1034 /* On a running target, we can get the dynamic linker's base
1035 address from the shared library table. */
1036 solib_add (NULL
, 0, NULL
, auto_solib_add
);
1037 so
= master_so_list ();
1040 if (strcmp (buf
, so
->so_original_name
) == 0)
1042 load_addr_found
= 1;
1043 load_addr
= LM_ADDR_CHECK (so
, tmp_bfd
);
1049 /* Otherwise we find the dynamic linker's base address by examining
1050 the current pc (which should point at the entry point for the
1051 dynamic linker) and subtracting the offset of the entry point. */
1052 if (!load_addr_found
)
1054 load_addr
= (read_pc ()
1055 - exec_entry_point (tmp_bfd
, tmp_bfd_target
));
1056 debug_loader_name
= xstrdup (buf
);
1057 debug_loader_offset_p
= 1;
1058 debug_loader_offset
= load_addr
;
1059 solib_add (NULL
, 0, NULL
, auto_solib_add
);
1062 /* Record the relocated start and end address of the dynamic linker
1063 text and plt section for svr4_in_dynsym_resolve_code. */
1064 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
1067 interp_text_sect_low
=
1068 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1069 interp_text_sect_high
=
1070 interp_text_sect_low
+ bfd_section_size (tmp_bfd
, interp_sect
);
1072 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
1075 interp_plt_sect_low
=
1076 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1077 interp_plt_sect_high
=
1078 interp_plt_sect_low
+ bfd_section_size (tmp_bfd
, interp_sect
);
1081 /* Now try to set a breakpoint in the dynamic linker. */
1082 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1084 /* On ABI's that use function descriptors, there are usually
1085 two linker symbols associated with each C function: one
1086 pointing at the actual entry point of the machine code,
1087 and one pointing at the function's descriptor. The
1088 latter symbol has the same name as the C function.
1090 What we're looking for here is the machine code entry
1091 point, so we are only interested in symbols in code
1093 sym_addr
= bfd_lookup_symbol (tmp_bfd
, *bkpt_namep
, SEC_CODE
);
1098 /* We're done with both the temporary bfd and target. Remember,
1099 closing the target closes the underlying bfd. */
1100 target_close (tmp_bfd_target
, 0);
1104 create_solib_event_breakpoint (load_addr
+ sym_addr
);
1108 /* For whatever reason we couldn't set a breakpoint in the dynamic
1109 linker. Warn and drop into the old code. */
1111 warning (_("Unable to find dynamic linker breakpoint function.\n"
1112 "GDB will be unable to debug shared library initializers\n"
1113 "and track explicitly loaded dynamic code."));
1116 /* Scan through the list of symbols, trying to look up the symbol and
1117 set a breakpoint there. Terminate loop when we/if we succeed. */
1119 breakpoint_addr
= 0;
1120 for (bkpt_namep
= bkpt_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1122 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
1123 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
1125 create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol
));
1130 /* Nothing good happened. */
1133 #endif /* BKPT_AT_SYMBOL */
1142 special_symbol_handling -- additional shared library symbol handling
1146 void special_symbol_handling ()
1150 Once the symbols from a shared object have been loaded in the usual
1151 way, we are called to do any system specific symbol handling that
1154 For SunOS4, this consisted of grunging around in the dynamic
1155 linkers structures to find symbol definitions for "common" symbols
1156 and adding them to the minimal symbol table for the runtime common
1159 However, for SVR4, there's nothing to do.
1164 svr4_special_symbol_handling (void)
1168 /* Relocate the main executable. This function should be called upon
1169 stopping the inferior process at the entry point to the program.
1170 The entry point from BFD is compared to the PC and if they are
1171 different, the main executable is relocated by the proper amount.
1173 As written it will only attempt to relocate executables which
1174 lack interpreter sections. It seems likely that only dynamic
1175 linker executables will get relocated, though it should work
1176 properly for a position-independent static executable as well. */
1179 svr4_relocate_main_executable (void)
1181 asection
*interp_sect
;
1182 CORE_ADDR pc
= read_pc ();
1184 /* Decide if the objfile needs to be relocated. As indicated above,
1185 we will only be here when execution is stopped at the beginning
1186 of the program. Relocation is necessary if the address at which
1187 we are presently stopped differs from the start address stored in
1188 the executable AND there's no interpreter section. The condition
1189 regarding the interpreter section is very important because if
1190 there *is* an interpreter section, execution will begin there
1191 instead. When there is an interpreter section, the start address
1192 is (presumably) used by the interpreter at some point to start
1193 execution of the program.
1195 If there is an interpreter, it is normal for it to be set to an
1196 arbitrary address at the outset. The job of finding it is
1197 handled in enable_break().
1199 So, to summarize, relocations are necessary when there is no
1200 interpreter section and the start address obtained from the
1201 executable is different from the address at which GDB is
1204 [ The astute reader will note that we also test to make sure that
1205 the executable in question has the DYNAMIC flag set. It is my
1206 opinion that this test is unnecessary (undesirable even). It
1207 was added to avoid inadvertent relocation of an executable
1208 whose e_type member in the ELF header is not ET_DYN. There may
1209 be a time in the future when it is desirable to do relocations
1210 on other types of files as well in which case this condition
1211 should either be removed or modified to accomodate the new file
1212 type. (E.g, an ET_EXEC executable which has been built to be
1213 position-independent could safely be relocated by the OS if
1214 desired. It is true that this violates the ABI, but the ABI
1215 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1218 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
1219 if (interp_sect
== NULL
1220 && (bfd_get_file_flags (exec_bfd
) & DYNAMIC
) != 0
1221 && (exec_entry_point (exec_bfd
, &exec_ops
) != pc
))
1223 struct cleanup
*old_chain
;
1224 struct section_offsets
*new_offsets
;
1226 CORE_ADDR displacement
;
1228 /* It is necessary to relocate the objfile. The amount to
1229 relocate by is simply the address at which we are stopped
1230 minus the starting address from the executable.
1232 We relocate all of the sections by the same amount. This
1233 behavior is mandated by recent editions of the System V ABI.
1234 According to the System V Application Binary Interface,
1235 Edition 4.1, page 5-5:
1237 ... Though the system chooses virtual addresses for
1238 individual processes, it maintains the segments' relative
1239 positions. Because position-independent code uses relative
1240 addressesing between segments, the difference between
1241 virtual addresses in memory must match the difference
1242 between virtual addresses in the file. The difference
1243 between the virtual address of any segment in memory and
1244 the corresponding virtual address in the file is thus a
1245 single constant value for any one executable or shared
1246 object in a given process. This difference is the base
1247 address. One use of the base address is to relocate the
1248 memory image of the program during dynamic linking.
1250 The same language also appears in Edition 4.0 of the System V
1251 ABI and is left unspecified in some of the earlier editions. */
1253 displacement
= pc
- exec_entry_point (exec_bfd
, &exec_ops
);
1256 new_offsets
= xcalloc (symfile_objfile
->num_sections
,
1257 sizeof (struct section_offsets
));
1258 old_chain
= make_cleanup (xfree
, new_offsets
);
1260 for (i
= 0; i
< symfile_objfile
->num_sections
; i
++)
1262 if (displacement
!= ANOFFSET (symfile_objfile
->section_offsets
, i
))
1264 new_offsets
->offsets
[i
] = displacement
;
1268 objfile_relocate (symfile_objfile
, new_offsets
);
1270 do_cleanups (old_chain
);
1278 svr4_solib_create_inferior_hook -- shared library startup support
1282 void svr4_solib_create_inferior_hook ()
1286 When gdb starts up the inferior, it nurses it along (through the
1287 shell) until it is ready to execute it's first instruction. At this
1288 point, this function gets called via expansion of the macro
1289 SOLIB_CREATE_INFERIOR_HOOK.
1291 For SunOS executables, this first instruction is typically the
1292 one at "_start", or a similar text label, regardless of whether
1293 the executable is statically or dynamically linked. The runtime
1294 startup code takes care of dynamically linking in any shared
1295 libraries, once gdb allows the inferior to continue.
1297 For SVR4 executables, this first instruction is either the first
1298 instruction in the dynamic linker (for dynamically linked
1299 executables) or the instruction at "start" for statically linked
1300 executables. For dynamically linked executables, the system
1301 first exec's /lib/libc.so.N, which contains the dynamic linker,
1302 and starts it running. The dynamic linker maps in any needed
1303 shared libraries, maps in the actual user executable, and then
1304 jumps to "start" in the user executable.
1306 For both SunOS shared libraries, and SVR4 shared libraries, we
1307 can arrange to cooperate with the dynamic linker to discover the
1308 names of shared libraries that are dynamically linked, and the
1309 base addresses to which they are linked.
1311 This function is responsible for discovering those names and
1312 addresses, and saving sufficient information about them to allow
1313 their symbols to be read at a later time.
1317 Between enable_break() and disable_break(), this code does not
1318 properly handle hitting breakpoints which the user might have
1319 set in the startup code or in the dynamic linker itself. Proper
1320 handling will probably have to wait until the implementation is
1321 changed to use the "breakpoint handler function" method.
1323 Also, what if child has exit()ed? Must exit loop somehow.
1327 svr4_solib_create_inferior_hook (void)
1329 /* Relocate the main executable if necessary. */
1330 svr4_relocate_main_executable ();
1332 if (!svr4_have_link_map_offsets ())
1334 warning (_("no shared library support for this OS / ABI"));
1339 if (!enable_break ())
1341 warning (_("shared library handler failed to enable breakpoint"));
1345 #if defined(_SCO_DS)
1346 /* SCO needs the loop below, other systems should be using the
1347 special shared library breakpoints and the shared library breakpoint
1350 Now run the target. It will eventually hit the breakpoint, at
1351 which point all of the libraries will have been mapped in and we
1352 can go groveling around in the dynamic linker structures to find
1353 out what we need to know about them. */
1355 clear_proceed_status ();
1356 stop_soon
= STOP_QUIETLY
;
1357 stop_signal
= TARGET_SIGNAL_0
;
1360 target_resume (pid_to_ptid (-1), 0, stop_signal
);
1361 wait_for_inferior ();
1363 while (stop_signal
!= TARGET_SIGNAL_TRAP
);
1364 stop_soon
= NO_STOP_QUIETLY
;
1365 #endif /* defined(_SCO_DS) */
1369 svr4_clear_solib (void)
1372 debug_loader_offset_p
= 0;
1373 debug_loader_offset
= 0;
1374 xfree (debug_loader_name
);
1375 debug_loader_name
= NULL
;
1379 svr4_free_so (struct so_list
*so
)
1381 xfree (so
->lm_info
->lm
);
1382 xfree (so
->lm_info
);
1386 /* Clear any bits of ADDR that wouldn't fit in a target-format
1387 data pointer. "Data pointer" here refers to whatever sort of
1388 address the dynamic linker uses to manage its sections. At the
1389 moment, we don't support shared libraries on any processors where
1390 code and data pointers are different sizes.
1392 This isn't really the right solution. What we really need here is
1393 a way to do arithmetic on CORE_ADDR values that respects the
1394 natural pointer/address correspondence. (For example, on the MIPS,
1395 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1396 sign-extend the value. There, simply truncating the bits above
1397 TARGET_PTR_BIT, as we do below, is no good.) This should probably
1398 be a new gdbarch method or something. */
1400 svr4_truncate_ptr (CORE_ADDR addr
)
1402 if (TARGET_PTR_BIT
== sizeof (CORE_ADDR
) * 8)
1403 /* We don't need to truncate anything, and the bit twiddling below
1404 will fail due to overflow problems. */
1407 return addr
& (((CORE_ADDR
) 1 << TARGET_PTR_BIT
) - 1);
1412 svr4_relocate_section_addresses (struct so_list
*so
,
1413 struct section_table
*sec
)
1415 sec
->addr
= svr4_truncate_ptr (sec
->addr
+ LM_ADDR_CHECK (so
,
1417 sec
->endaddr
= svr4_truncate_ptr (sec
->endaddr
+ LM_ADDR_CHECK (so
,
1422 /* Architecture-specific operations. */
1424 /* Per-architecture data key. */
1425 static struct gdbarch_data
*solib_svr4_data
;
1427 struct solib_svr4_ops
1429 /* Return a description of the layout of `struct link_map'. */
1430 struct link_map_offsets
*(*fetch_link_map_offsets
)(void);
1433 /* Return a default for the architecture-specific operations. */
1436 solib_svr4_init (struct obstack
*obstack
)
1438 struct solib_svr4_ops
*ops
;
1440 ops
= OBSTACK_ZALLOC (obstack
, struct solib_svr4_ops
);
1441 ops
->fetch_link_map_offsets
= legacy_svr4_fetch_link_map_offsets_hook
;
1445 /* Set the architecture-specific `struct link_map_offsets' fetcher for
1449 set_solib_svr4_fetch_link_map_offsets (struct gdbarch
*gdbarch
,
1450 struct link_map_offsets
*(*flmo
) (void))
1452 struct solib_svr4_ops
*ops
= gdbarch_data (gdbarch
, solib_svr4_data
);
1454 ops
->fetch_link_map_offsets
= flmo
;
1457 /* Fetch a link_map_offsets structure using the architecture-specific
1458 `struct link_map_offsets' fetcher. */
1460 static struct link_map_offsets
*
1461 svr4_fetch_link_map_offsets (void)
1463 struct solib_svr4_ops
*ops
= gdbarch_data (current_gdbarch
, solib_svr4_data
);
1465 gdb_assert (ops
->fetch_link_map_offsets
);
1466 return ops
->fetch_link_map_offsets ();
1469 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1472 svr4_have_link_map_offsets (void)
1474 struct solib_svr4_ops
*ops
= gdbarch_data (current_gdbarch
, solib_svr4_data
);
1475 return (ops
->fetch_link_map_offsets
!= NULL
);
1479 /* Most OS'es that have SVR4-style ELF dynamic libraries define a
1480 `struct r_debug' and a `struct link_map' that are binary compatible
1481 with the origional SVR4 implementation. */
1483 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1484 for an ILP32 SVR4 system. */
1486 struct link_map_offsets
*
1487 svr4_ilp32_fetch_link_map_offsets (void)
1489 static struct link_map_offsets lmo
;
1490 static struct link_map_offsets
*lmp
= NULL
;
1496 lmo
.r_version_offset
= 0;
1497 lmo
.r_version_size
= 4;
1498 lmo
.r_map_offset
= 4;
1499 lmo
.r_ldsomap_offset
= 20;
1501 /* Everything we need is in the first 20 bytes. */
1502 lmo
.link_map_size
= 20;
1503 lmo
.l_addr_offset
= 0;
1504 lmo
.l_name_offset
= 4;
1505 lmo
.l_ld_offset
= 8;
1506 lmo
.l_next_offset
= 12;
1507 lmo
.l_prev_offset
= 16;
1513 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1514 for an LP64 SVR4 system. */
1516 struct link_map_offsets
*
1517 svr4_lp64_fetch_link_map_offsets (void)
1519 static struct link_map_offsets lmo
;
1520 static struct link_map_offsets
*lmp
= NULL
;
1526 lmo
.r_version_offset
= 0;
1527 lmo
.r_version_size
= 4;
1528 lmo
.r_map_offset
= 8;
1529 lmo
.r_ldsomap_offset
= 40;
1531 /* Everything we need is in the first 40 bytes. */
1532 lmo
.link_map_size
= 40;
1533 lmo
.l_addr_offset
= 0;
1534 lmo
.l_name_offset
= 8;
1535 lmo
.l_ld_offset
= 16;
1536 lmo
.l_next_offset
= 24;
1537 lmo
.l_prev_offset
= 32;
1544 static struct target_so_ops svr4_so_ops
;
1546 extern initialize_file_ftype _initialize_svr4_solib
; /* -Wmissing-prototypes */
1549 _initialize_svr4_solib (void)
1551 solib_svr4_data
= gdbarch_data_register_pre_init (solib_svr4_init
);
1553 svr4_so_ops
.relocate_section_addresses
= svr4_relocate_section_addresses
;
1554 svr4_so_ops
.free_so
= svr4_free_so
;
1555 svr4_so_ops
.clear_solib
= svr4_clear_solib
;
1556 svr4_so_ops
.solib_create_inferior_hook
= svr4_solib_create_inferior_hook
;
1557 svr4_so_ops
.special_symbol_handling
= svr4_special_symbol_handling
;
1558 svr4_so_ops
.current_sos
= svr4_current_sos
;
1559 svr4_so_ops
.open_symbol_file_object
= open_symbol_file_object
;
1560 svr4_so_ops
.in_dynsym_resolve_code
= svr4_in_dynsym_resolve_code
;
1562 /* FIXME: Don't do this here. *_gdbarch_init() should set so_ops. */
1563 current_target_so_ops
= &svr4_so_ops
;