1 /* Handle SVR4 shared libraries for GDB, the GNU Debugger.
3 Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999,
4 2000, 2001, 2003, 2004, 2005
5 Free Software Foundation, Inc.
7 This file is part of GDB.
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 59 Temple Place - Suite 330,
22 Boston, MA 02111-1307, USA. */
26 #include "elf/external.h"
27 #include "elf/common.h"
38 #include "gdb_assert.h"
42 #include "solib-svr4.h"
44 #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. */
64 /* On SVR4 systems, a list of symbols in the dynamic linker where
65 GDB can try to place a breakpoint to monitor shared library
68 If none of these symbols are found, or other errors occur, then
69 SVR4 systems will fall back to using a symbol as the "startup
70 mapping complete" breakpoint address. */
72 static char *solib_break_names
[] =
80 /* On the 64-bit PowerPC, the linker symbol with the same name as
81 the C function points to a function descriptor, not to the entry
82 point. The linker symbol whose name is the C function name
83 prefixed with a '.' points to the function's entry point. So
84 when we look through this table, we ignore symbols that point
85 into the data section (thus skipping the descriptor's symbol),
86 and eventually try this one, giving us the real entry point
93 #define BKPT_AT_SYMBOL 1
95 #if defined (BKPT_AT_SYMBOL)
96 static char *bkpt_names
[] =
98 #ifdef SOLIB_BKPT_NAME
99 SOLIB_BKPT_NAME
, /* Prefer configured name if it exists. */
108 static char *main_name_list
[] =
114 /* Macro to extract an address from a solib structure. When GDB is
115 configured for some 32-bit targets (e.g. Solaris 2.7 sparc), BFD is
116 configured to handle 64-bit targets, so CORE_ADDR is 64 bits. We
117 have to extract only the significant bits of addresses to get the
118 right address when accessing the core file BFD.
120 Assume that the address is unsigned. */
122 #define SOLIB_EXTRACT_ADDRESS(MEMBER) \
123 extract_unsigned_integer (&(MEMBER), sizeof (MEMBER))
125 /* local data declarations */
127 /* link map access functions */
130 LM_ADDR (struct so_list
*so
)
132 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
134 return (CORE_ADDR
) extract_signed_integer (so
->lm_info
->lm
+ lmo
->l_addr_offset
,
139 LM_NEXT (struct so_list
*so
)
141 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
143 /* Assume that the address is unsigned. */
144 return extract_unsigned_integer (so
->lm_info
->lm
+ lmo
->l_next_offset
,
149 LM_NAME (struct so_list
*so
)
151 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
153 /* Assume that the address is unsigned. */
154 return extract_unsigned_integer (so
->lm_info
->lm
+ lmo
->l_name_offset
,
159 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list
*so
)
161 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
163 /* Assume that the address is unsigned. */
164 return extract_unsigned_integer (so
->lm_info
->lm
+ lmo
->l_prev_offset
,
165 lmo
->l_prev_size
) == 0;
168 static CORE_ADDR debug_base
; /* Base of dynamic linker structures */
169 static CORE_ADDR breakpoint_addr
; /* Address where end bkpt is set */
171 /* Local function prototypes */
173 static int match_main (char *);
175 static CORE_ADDR
bfd_lookup_symbol (bfd
*, char *, flagword
);
181 bfd_lookup_symbol -- lookup the value for a specific symbol
185 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname, flagword sect_flags)
189 An expensive way to lookup the value of a single symbol for
190 bfd's that are only temporary anyway. This is used by the
191 shared library support to find the address of the debugger
192 interface structures in the shared library.
194 If SECT_FLAGS is non-zero, only match symbols in sections whose
195 flags include all those in SECT_FLAGS.
197 Note that 0 is specifically allowed as an error return (no
202 bfd_lookup_symbol (bfd
*abfd
, char *symname
, flagword sect_flags
)
206 asymbol
**symbol_table
;
207 unsigned int number_of_symbols
;
209 struct cleanup
*back_to
;
210 CORE_ADDR symaddr
= 0;
212 storage_needed
= bfd_get_symtab_upper_bound (abfd
);
214 if (storage_needed
> 0)
216 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
217 back_to
= make_cleanup (xfree
, symbol_table
);
218 number_of_symbols
= bfd_canonicalize_symtab (abfd
, symbol_table
);
220 for (i
= 0; i
< number_of_symbols
; i
++)
222 sym
= *symbol_table
++;
223 if (strcmp (sym
->name
, symname
) == 0
224 && (sym
->section
->flags
& sect_flags
) == sect_flags
)
226 /* Bfd symbols are section relative. */
227 symaddr
= sym
->value
+ sym
->section
->vma
;
231 do_cleanups (back_to
);
237 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
238 have to check the dynamic string table too. */
240 storage_needed
= bfd_get_dynamic_symtab_upper_bound (abfd
);
242 if (storage_needed
> 0)
244 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
245 back_to
= make_cleanup (xfree
, symbol_table
);
246 number_of_symbols
= bfd_canonicalize_dynamic_symtab (abfd
, symbol_table
);
248 for (i
= 0; i
< number_of_symbols
; i
++)
250 sym
= *symbol_table
++;
252 if (strcmp (sym
->name
, symname
) == 0
253 && (sym
->section
->flags
& sect_flags
) == sect_flags
)
255 /* Bfd symbols are section relative. */
256 symaddr
= sym
->value
+ sym
->section
->vma
;
260 do_cleanups (back_to
);
270 elf_locate_base -- locate the base address of dynamic linker structs
271 for SVR4 elf targets.
275 CORE_ADDR elf_locate_base (void)
279 For SVR4 elf targets the address of the dynamic linker's runtime
280 structure is contained within the dynamic info section in the
281 executable file. The dynamic section is also mapped into the
282 inferior address space. Because the runtime loader fills in the
283 real address before starting the inferior, we have to read in the
284 dynamic info section from the inferior address space.
285 If there are any errors while trying to find the address, we
286 silently return 0, otherwise the found address is returned.
291 elf_locate_base (void)
293 struct bfd_section
*dyninfo_sect
;
294 int dyninfo_sect_size
;
295 CORE_ADDR dyninfo_addr
;
300 /* Find the start address of the .dynamic section. */
301 dyninfo_sect
= bfd_get_section_by_name (exec_bfd
, ".dynamic");
302 if (dyninfo_sect
== NULL
)
304 dyninfo_addr
= bfd_section_vma (exec_bfd
, dyninfo_sect
);
306 /* Read in .dynamic section, silently ignore errors. */
307 dyninfo_sect_size
= bfd_section_size (exec_bfd
, dyninfo_sect
);
308 buf
= alloca (dyninfo_sect_size
);
309 if (target_read_memory (dyninfo_addr
, buf
, dyninfo_sect_size
))
312 /* Find the DT_DEBUG entry in the the .dynamic section.
313 For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has
314 no DT_DEBUG entries. */
316 arch_size
= bfd_get_arch_size (exec_bfd
);
317 if (arch_size
== -1) /* failure */
322 for (bufend
= buf
+ dyninfo_sect_size
;
324 buf
+= sizeof (Elf32_External_Dyn
))
326 Elf32_External_Dyn
*x_dynp
= (Elf32_External_Dyn
*) buf
;
330 dyn_tag
= bfd_h_get_32 (exec_bfd
, (bfd_byte
*) x_dynp
->d_tag
);
331 if (dyn_tag
== DT_NULL
)
333 else if (dyn_tag
== DT_DEBUG
)
335 dyn_ptr
= bfd_h_get_32 (exec_bfd
,
336 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
339 else if (dyn_tag
== DT_MIPS_RLD_MAP
)
342 int pbuf_size
= TARGET_PTR_BIT
/ HOST_CHAR_BIT
;
344 pbuf
= alloca (pbuf_size
);
345 /* DT_MIPS_RLD_MAP contains a pointer to the address
346 of the dynamic link structure. */
347 dyn_ptr
= bfd_h_get_32 (exec_bfd
,
348 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
349 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
351 return extract_unsigned_integer (pbuf
, pbuf_size
);
355 else /* 64-bit elf */
357 for (bufend
= buf
+ dyninfo_sect_size
;
359 buf
+= sizeof (Elf64_External_Dyn
))
361 Elf64_External_Dyn
*x_dynp
= (Elf64_External_Dyn
*) buf
;
365 dyn_tag
= bfd_h_get_64 (exec_bfd
, (bfd_byte
*) x_dynp
->d_tag
);
366 if (dyn_tag
== DT_NULL
)
368 else if (dyn_tag
== DT_DEBUG
)
370 dyn_ptr
= bfd_h_get_64 (exec_bfd
,
371 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
374 else if (dyn_tag
== DT_MIPS_RLD_MAP
)
377 int pbuf_size
= TARGET_PTR_BIT
/ HOST_CHAR_BIT
;
379 pbuf
= alloca (pbuf_size
);
380 /* DT_MIPS_RLD_MAP contains a pointer to the address
381 of the dynamic link structure. */
382 dyn_ptr
= bfd_h_get_64 (exec_bfd
,
383 (bfd_byte
*) x_dynp
->d_un
.d_ptr
);
384 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
386 return extract_unsigned_integer (pbuf
, pbuf_size
);
391 /* DT_DEBUG entry not found. */
399 locate_base -- locate the base address of dynamic linker structs
403 CORE_ADDR locate_base (void)
407 For both the SunOS and SVR4 shared library implementations, if the
408 inferior executable has been linked dynamically, there is a single
409 address somewhere in the inferior's data space which is the key to
410 locating all of the dynamic linker's runtime structures. This
411 address is the value of the debug base symbol. The job of this
412 function is to find and return that address, or to return 0 if there
413 is no such address (the executable is statically linked for example).
415 For SunOS, the job is almost trivial, since the dynamic linker and
416 all of it's structures are statically linked to the executable at
417 link time. Thus the symbol for the address we are looking for has
418 already been added to the minimal symbol table for the executable's
419 objfile at the time the symbol file's symbols were read, and all we
420 have to do is look it up there. Note that we explicitly do NOT want
421 to find the copies in the shared library.
423 The SVR4 version is a bit more complicated because the address
424 is contained somewhere in the dynamic info section. We have to go
425 to a lot more work to discover the address of the debug base symbol.
426 Because of this complexity, we cache the value we find and return that
427 value on subsequent invocations. Note there is no copy in the
428 executable symbol tables.
435 /* Check to see if we have a currently valid address, and if so, avoid
436 doing all this work again and just return the cached address. If
437 we have no cached address, try to locate it in the dynamic info
438 section for ELF executables. There's no point in doing any of this
439 though if we don't have some link map offsets to work with. */
441 if (debug_base
== 0 && svr4_have_link_map_offsets ())
444 && bfd_get_flavour (exec_bfd
) == bfd_target_elf_flavour
)
445 debug_base
= elf_locate_base ();
454 first_link_map_member -- locate first member in dynamic linker's map
458 static CORE_ADDR first_link_map_member (void)
462 Find the first element in the inferior's dynamic link map, and
463 return its address in the inferior. This function doesn't copy the
464 link map entry itself into our address space; current_sos actually
468 first_link_map_member (void)
471 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
472 gdb_byte
*r_map_buf
= xmalloc (lmo
->r_map_size
);
473 struct cleanup
*cleanups
= make_cleanup (xfree
, r_map_buf
);
475 read_memory (debug_base
+ lmo
->r_map_offset
, r_map_buf
, lmo
->r_map_size
);
477 /* Assume that the address is unsigned. */
478 lm
= extract_unsigned_integer (r_map_buf
, lmo
->r_map_size
);
480 /* FIXME: Perhaps we should validate the info somehow, perhaps by
481 checking r_version for a known version number, or r_state for
484 do_cleanups (cleanups
);
493 open_symbol_file_object
497 void open_symbol_file_object (void *from_tty)
501 If no open symbol file, attempt to locate and open the main symbol
502 file. On SVR4 systems, this is the first link map entry. If its
503 name is here, we can open it. Useful when attaching to a process
504 without first loading its symbol file.
506 If FROM_TTYP dereferences to a non-zero integer, allow messages to
507 be printed. This parameter is a pointer rather than an int because
508 open_symbol_file_object() is called via catch_errors() and
509 catch_errors() requires a pointer argument. */
512 open_symbol_file_object (void *from_ttyp
)
514 CORE_ADDR lm
, l_name
;
517 int from_tty
= *(int *)from_ttyp
;
518 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
519 gdb_byte
*l_name_buf
= xmalloc (lmo
->l_name_size
);
520 struct cleanup
*cleanups
= make_cleanup (xfree
, l_name_buf
);
523 if (!query ("Attempt to reload symbols from process? "))
526 if ((debug_base
= locate_base ()) == 0)
527 return 0; /* failed somehow... */
529 /* First link map member should be the executable. */
530 if ((lm
= first_link_map_member ()) == 0)
531 return 0; /* failed somehow... */
533 /* Read address of name from target memory to GDB. */
534 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, lmo
->l_name_size
);
536 /* Convert the address to host format. Assume that the address is
538 l_name
= extract_unsigned_integer (l_name_buf
, lmo
->l_name_size
);
540 /* Free l_name_buf. */
541 do_cleanups (cleanups
);
544 return 0; /* No filename. */
546 /* Now fetch the filename from target memory. */
547 target_read_string (l_name
, &filename
, SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
551 warning (_("failed to read exec filename from attached file: %s"),
552 safe_strerror (errcode
));
556 make_cleanup (xfree
, filename
);
557 /* Have a pathname: read the symbol file. */
558 symbol_file_add_main (filename
, from_tty
);
565 current_sos -- build a list of currently loaded shared objects
569 struct so_list *current_sos ()
573 Build a list of `struct so_list' objects describing the shared
574 objects currently loaded in the inferior. This list does not
575 include an entry for the main executable file.
577 Note that we only gather information directly available from the
578 inferior --- we don't examine any of the shared library files
579 themselves. The declaration of `struct so_list' says which fields
580 we provide values for. */
582 static struct so_list
*
583 svr4_current_sos (void)
586 struct so_list
*head
= 0;
587 struct so_list
**link_ptr
= &head
;
589 /* Make sure we've looked up the inferior's dynamic linker's base
593 debug_base
= locate_base ();
595 /* If we can't find the dynamic linker's base structure, this
596 must not be a dynamically linked executable. Hmm. */
601 /* Walk the inferior's link map list, and build our list of
602 `struct so_list' nodes. */
603 lm
= first_link_map_member ();
606 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
608 = (struct so_list
*) xmalloc (sizeof (struct so_list
));
609 struct cleanup
*old_chain
= make_cleanup (xfree
, new);
611 memset (new, 0, sizeof (*new));
613 new->lm_info
= xmalloc (sizeof (struct lm_info
));
614 make_cleanup (xfree
, new->lm_info
);
616 new->lm_info
->lm
= xmalloc (lmo
->link_map_size
);
617 make_cleanup (xfree
, new->lm_info
->lm
);
618 memset (new->lm_info
->lm
, 0, lmo
->link_map_size
);
620 read_memory (lm
, new->lm_info
->lm
, lmo
->link_map_size
);
624 /* For SVR4 versions, the first entry in the link map is for the
625 inferior executable, so we must ignore it. For some versions of
626 SVR4, it has no name. For others (Solaris 2.3 for example), it
627 does have a name, so we can no longer use a missing name to
628 decide when to ignore it. */
629 if (IGNORE_FIRST_LINK_MAP_ENTRY (new))
636 /* Extract this shared object's name. */
637 target_read_string (LM_NAME (new), &buffer
,
638 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
640 warning (_("Can't read pathname for load map: %s."),
641 safe_strerror (errcode
));
644 strncpy (new->so_name
, buffer
, SO_NAME_MAX_PATH_SIZE
- 1);
645 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
647 strcpy (new->so_original_name
, new->so_name
);
650 /* If this entry has no name, or its name matches the name
651 for the main executable, don't include it in the list. */
652 if (! new->so_name
[0]
653 || match_main (new->so_name
))
659 link_ptr
= &new->next
;
663 discard_cleanups (old_chain
);
669 /* Get the address of the link_map for a given OBJFILE. Loop through
670 the link maps, and return the address of the one corresponding to
671 the given objfile. Note that this function takes into account that
672 objfile can be the main executable, not just a shared library. The
673 main executable has always an empty name field in the linkmap. */
676 svr4_fetch_objfile_link_map (struct objfile
*objfile
)
680 if ((debug_base
= locate_base ()) == 0)
681 return 0; /* failed somehow... */
683 /* Position ourselves on the first link map. */
684 lm
= first_link_map_member ();
687 /* Get info on the layout of the r_debug and link_map structures. */
688 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
691 struct lm_info objfile_lm_info
;
692 struct cleanup
*old_chain
;
693 CORE_ADDR name_address
;
694 gdb_byte
*l_name_buf
= xmalloc (lmo
->l_name_size
);
695 old_chain
= make_cleanup (xfree
, l_name_buf
);
697 /* Set up the buffer to contain the portion of the link_map
698 structure that gdb cares about. Note that this is not the
699 whole link_map structure. */
700 objfile_lm_info
.lm
= xmalloc (lmo
->link_map_size
);
701 make_cleanup (xfree
, objfile_lm_info
.lm
);
702 memset (objfile_lm_info
.lm
, 0, lmo
->link_map_size
);
704 /* Read the link map into our internal structure. */
705 read_memory (lm
, objfile_lm_info
.lm
, lmo
->link_map_size
);
707 /* Read address of name from target memory to GDB. */
708 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, lmo
->l_name_size
);
710 /* Extract this object's name. Assume that the address is
712 name_address
= extract_unsigned_integer (l_name_buf
, lmo
->l_name_size
);
713 target_read_string (name_address
, &buffer
,
714 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
715 make_cleanup (xfree
, buffer
);
717 warning (_("Can't read pathname for load map: %s."),
718 safe_strerror (errcode
));
721 /* Is this the linkmap for the file we want? */
722 /* If the file is not a shared library and has no name,
723 we are sure it is the main executable, so we return that. */
724 if ((buffer
&& strcmp (buffer
, objfile
->name
) == 0)
725 || (!(objfile
->flags
& OBJF_SHARED
) && (strcmp (buffer
, "") == 0)))
727 do_cleanups (old_chain
);
731 /* Not the file we wanted, continue checking. Assume that the
732 address is unsigned. */
733 lm
= extract_unsigned_integer (objfile_lm_info
.lm
+ lmo
->l_next_offset
,
735 do_cleanups (old_chain
);
740 /* On some systems, the only way to recognize the link map entry for
741 the main executable file is by looking at its name. Return
742 non-zero iff SONAME matches one of the known main executable names. */
745 match_main (char *soname
)
749 for (mainp
= main_name_list
; *mainp
!= NULL
; mainp
++)
751 if (strcmp (soname
, *mainp
) == 0)
758 /* Return 1 if PC lies in the dynamic symbol resolution code of the
759 SVR4 run time loader. */
760 static CORE_ADDR interp_text_sect_low
;
761 static CORE_ADDR interp_text_sect_high
;
762 static CORE_ADDR interp_plt_sect_low
;
763 static CORE_ADDR interp_plt_sect_high
;
766 svr4_in_dynsym_resolve_code (CORE_ADDR pc
)
768 return ((pc
>= interp_text_sect_low
&& pc
< interp_text_sect_high
)
769 || (pc
>= interp_plt_sect_low
&& pc
< interp_plt_sect_high
)
770 || in_plt_section (pc
, NULL
));
773 /* Given an executable's ABFD and target, compute the entry-point
777 exec_entry_point (struct bfd
*abfd
, struct target_ops
*targ
)
779 /* KevinB wrote ... for most targets, the address returned by
780 bfd_get_start_address() is the entry point for the start
781 function. But, for some targets, bfd_get_start_address() returns
782 the address of a function descriptor from which the entry point
783 address may be extracted. This address is extracted by
784 gdbarch_convert_from_func_ptr_addr(). The method
785 gdbarch_convert_from_func_ptr_addr() is the merely the identify
786 function for targets which don't use function descriptors. */
787 return gdbarch_convert_from_func_ptr_addr (current_gdbarch
,
788 bfd_get_start_address (abfd
),
796 enable_break -- arrange for dynamic linker to hit breakpoint
800 int enable_break (void)
804 Both the SunOS and the SVR4 dynamic linkers have, as part of their
805 debugger interface, support for arranging for the inferior to hit
806 a breakpoint after mapping in the shared libraries. This function
807 enables that breakpoint.
809 For SunOS, there is a special flag location (in_debugger) which we
810 set to 1. When the dynamic linker sees this flag set, it will set
811 a breakpoint at a location known only to itself, after saving the
812 original contents of that place and the breakpoint address itself,
813 in it's own internal structures. When we resume the inferior, it
814 will eventually take a SIGTRAP when it runs into the breakpoint.
815 We handle this (in a different place) by restoring the contents of
816 the breakpointed location (which is only known after it stops),
817 chasing around to locate the shared libraries that have been
818 loaded, then resuming.
820 For SVR4, the debugger interface structure contains a member (r_brk)
821 which is statically initialized at the time the shared library is
822 built, to the offset of a function (_r_debug_state) which is guaran-
823 teed to be called once before mapping in a library, and again when
824 the mapping is complete. At the time we are examining this member,
825 it contains only the unrelocated offset of the function, so we have
826 to do our own relocation. Later, when the dynamic linker actually
827 runs, it relocates r_brk to be the actual address of _r_debug_state().
829 The debugger interface structure also contains an enumeration which
830 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
831 depending upon whether or not the library is being mapped or unmapped,
832 and then set to RT_CONSISTENT after the library is mapped/unmapped.
840 #ifdef BKPT_AT_SYMBOL
842 struct minimal_symbol
*msymbol
;
844 asection
*interp_sect
;
846 /* First, remove all the solib event breakpoints. Their addresses
847 may have changed since the last time we ran the program. */
848 remove_solib_event_breakpoints ();
850 interp_text_sect_low
= interp_text_sect_high
= 0;
851 interp_plt_sect_low
= interp_plt_sect_high
= 0;
853 /* Find the .interp section; if not found, warn the user and drop
854 into the old breakpoint at symbol code. */
855 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
858 unsigned int interp_sect_size
;
860 CORE_ADDR load_addr
= 0;
861 int load_addr_found
= 0;
864 struct target_ops
*tmp_bfd_target
;
866 char *tmp_pathname
= NULL
;
867 CORE_ADDR sym_addr
= 0;
869 /* Read the contents of the .interp section into a local buffer;
870 the contents specify the dynamic linker this program uses. */
871 interp_sect_size
= bfd_section_size (exec_bfd
, interp_sect
);
872 buf
= alloca (interp_sect_size
);
873 bfd_get_section_contents (exec_bfd
, interp_sect
,
874 buf
, 0, interp_sect_size
);
876 /* Now we need to figure out where the dynamic linker was
877 loaded so that we can load its symbols and place a breakpoint
878 in the dynamic linker itself.
880 This address is stored on the stack. However, I've been unable
881 to find any magic formula to find it for Solaris (appears to
882 be trivial on GNU/Linux). Therefore, we have to try an alternate
883 mechanism to find the dynamic linker's base address. */
885 tmp_fd
= solib_open (buf
, &tmp_pathname
);
887 tmp_bfd
= bfd_fopen (tmp_pathname
, gnutarget
, FOPEN_RB
, tmp_fd
);
892 /* Make sure the dynamic linker's really a useful object. */
893 if (!bfd_check_format (tmp_bfd
, bfd_object
))
895 warning (_("Unable to grok dynamic linker %s as an object file"), buf
);
900 /* Now convert the TMP_BFD into a target. That way target, as
901 well as BFD operations can be used. Note that closing the
902 target will also close the underlying bfd. */
903 tmp_bfd_target
= target_bfd_reopen (tmp_bfd
);
905 /* On a running target, we can get the dynamic linker's base
906 address from the shared library table. */
907 solib_add (NULL
, 0, NULL
, auto_solib_add
);
908 so
= master_so_list ();
911 if (strcmp (buf
, so
->so_original_name
) == 0)
914 load_addr
= LM_ADDR (so
);
920 /* Otherwise we find the dynamic linker's base address by examining
921 the current pc (which should point at the entry point for the
922 dynamic linker) and subtracting the offset of the entry point. */
923 if (!load_addr_found
)
924 load_addr
= (read_pc ()
925 - exec_entry_point (tmp_bfd
, tmp_bfd_target
));
927 /* Record the relocated start and end address of the dynamic linker
928 text and plt section for svr4_in_dynsym_resolve_code. */
929 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
932 interp_text_sect_low
=
933 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
934 interp_text_sect_high
=
935 interp_text_sect_low
+ bfd_section_size (tmp_bfd
, interp_sect
);
937 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
940 interp_plt_sect_low
=
941 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
942 interp_plt_sect_high
=
943 interp_plt_sect_low
+ bfd_section_size (tmp_bfd
, interp_sect
);
946 /* Now try to set a breakpoint in the dynamic linker. */
947 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
949 /* On ABI's that use function descriptors, there are usually
950 two linker symbols associated with each C function: one
951 pointing at the actual entry point of the machine code,
952 and one pointing at the function's descriptor. The
953 latter symbol has the same name as the C function.
955 What we're looking for here is the machine code entry
956 point, so we are only interested in symbols in code
958 sym_addr
= bfd_lookup_symbol (tmp_bfd
, *bkpt_namep
, SEC_CODE
);
963 /* We're done with both the temporary bfd and target. Remember,
964 closing the target closes the underlying bfd. */
965 target_close (tmp_bfd_target
, 0);
969 create_solib_event_breakpoint (load_addr
+ sym_addr
);
973 /* For whatever reason we couldn't set a breakpoint in the dynamic
974 linker. Warn and drop into the old code. */
976 warning (_("Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code."));
979 /* Scan through the list of symbols, trying to look up the symbol and
980 set a breakpoint there. Terminate loop when we/if we succeed. */
983 for (bkpt_namep
= bkpt_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
985 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
986 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
988 create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol
));
993 /* Nothing good happened. */
996 #endif /* BKPT_AT_SYMBOL */
1005 special_symbol_handling -- additional shared library symbol handling
1009 void special_symbol_handling ()
1013 Once the symbols from a shared object have been loaded in the usual
1014 way, we are called to do any system specific symbol handling that
1017 For SunOS4, this consisted of grunging around in the dynamic
1018 linkers structures to find symbol definitions for "common" symbols
1019 and adding them to the minimal symbol table for the runtime common
1022 However, for SVR4, there's nothing to do.
1027 svr4_special_symbol_handling (void)
1031 /* Relocate the main executable. This function should be called upon
1032 stopping the inferior process at the entry point to the program.
1033 The entry point from BFD is compared to the PC and if they are
1034 different, the main executable is relocated by the proper amount.
1036 As written it will only attempt to relocate executables which
1037 lack interpreter sections. It seems likely that only dynamic
1038 linker executables will get relocated, though it should work
1039 properly for a position-independent static executable as well. */
1042 svr4_relocate_main_executable (void)
1044 asection
*interp_sect
;
1045 CORE_ADDR pc
= read_pc ();
1047 /* Decide if the objfile needs to be relocated. As indicated above,
1048 we will only be here when execution is stopped at the beginning
1049 of the program. Relocation is necessary if the address at which
1050 we are presently stopped differs from the start address stored in
1051 the executable AND there's no interpreter section. The condition
1052 regarding the interpreter section is very important because if
1053 there *is* an interpreter section, execution will begin there
1054 instead. When there is an interpreter section, the start address
1055 is (presumably) used by the interpreter at some point to start
1056 execution of the program.
1058 If there is an interpreter, it is normal for it to be set to an
1059 arbitrary address at the outset. The job of finding it is
1060 handled in enable_break().
1062 So, to summarize, relocations are necessary when there is no
1063 interpreter section and the start address obtained from the
1064 executable is different from the address at which GDB is
1067 [ The astute reader will note that we also test to make sure that
1068 the executable in question has the DYNAMIC flag set. It is my
1069 opinion that this test is unnecessary (undesirable even). It
1070 was added to avoid inadvertent relocation of an executable
1071 whose e_type member in the ELF header is not ET_DYN. There may
1072 be a time in the future when it is desirable to do relocations
1073 on other types of files as well in which case this condition
1074 should either be removed or modified to accomodate the new file
1075 type. (E.g, an ET_EXEC executable which has been built to be
1076 position-independent could safely be relocated by the OS if
1077 desired. It is true that this violates the ABI, but the ABI
1078 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1081 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
1082 if (interp_sect
== NULL
1083 && (bfd_get_file_flags (exec_bfd
) & DYNAMIC
) != 0
1084 && (exec_entry_point (exec_bfd
, &exec_ops
) != pc
))
1086 struct cleanup
*old_chain
;
1087 struct section_offsets
*new_offsets
;
1089 CORE_ADDR displacement
;
1091 /* It is necessary to relocate the objfile. The amount to
1092 relocate by is simply the address at which we are stopped
1093 minus the starting address from the executable.
1095 We relocate all of the sections by the same amount. This
1096 behavior is mandated by recent editions of the System V ABI.
1097 According to the System V Application Binary Interface,
1098 Edition 4.1, page 5-5:
1100 ... Though the system chooses virtual addresses for
1101 individual processes, it maintains the segments' relative
1102 positions. Because position-independent code uses relative
1103 addressesing between segments, the difference between
1104 virtual addresses in memory must match the difference
1105 between virtual addresses in the file. The difference
1106 between the virtual address of any segment in memory and
1107 the corresponding virtual address in the file is thus a
1108 single constant value for any one executable or shared
1109 object in a given process. This difference is the base
1110 address. One use of the base address is to relocate the
1111 memory image of the program during dynamic linking.
1113 The same language also appears in Edition 4.0 of the System V
1114 ABI and is left unspecified in some of the earlier editions. */
1116 displacement
= pc
- exec_entry_point (exec_bfd
, &exec_ops
);
1119 new_offsets
= xcalloc (symfile_objfile
->num_sections
,
1120 sizeof (struct section_offsets
));
1121 old_chain
= make_cleanup (xfree
, new_offsets
);
1123 for (i
= 0; i
< symfile_objfile
->num_sections
; i
++)
1125 if (displacement
!= ANOFFSET (symfile_objfile
->section_offsets
, i
))
1127 new_offsets
->offsets
[i
] = displacement
;
1131 objfile_relocate (symfile_objfile
, new_offsets
);
1133 do_cleanups (old_chain
);
1141 svr4_solib_create_inferior_hook -- shared library startup support
1145 void svr4_solib_create_inferior_hook ()
1149 When gdb starts up the inferior, it nurses it along (through the
1150 shell) until it is ready to execute it's first instruction. At this
1151 point, this function gets called via expansion of the macro
1152 SOLIB_CREATE_INFERIOR_HOOK.
1154 For SunOS executables, this first instruction is typically the
1155 one at "_start", or a similar text label, regardless of whether
1156 the executable is statically or dynamically linked. The runtime
1157 startup code takes care of dynamically linking in any shared
1158 libraries, once gdb allows the inferior to continue.
1160 For SVR4 executables, this first instruction is either the first
1161 instruction in the dynamic linker (for dynamically linked
1162 executables) or the instruction at "start" for statically linked
1163 executables. For dynamically linked executables, the system
1164 first exec's /lib/libc.so.N, which contains the dynamic linker,
1165 and starts it running. The dynamic linker maps in any needed
1166 shared libraries, maps in the actual user executable, and then
1167 jumps to "start" in the user executable.
1169 For both SunOS shared libraries, and SVR4 shared libraries, we
1170 can arrange to cooperate with the dynamic linker to discover the
1171 names of shared libraries that are dynamically linked, and the
1172 base addresses to which they are linked.
1174 This function is responsible for discovering those names and
1175 addresses, and saving sufficient information about them to allow
1176 their symbols to be read at a later time.
1180 Between enable_break() and disable_break(), this code does not
1181 properly handle hitting breakpoints which the user might have
1182 set in the startup code or in the dynamic linker itself. Proper
1183 handling will probably have to wait until the implementation is
1184 changed to use the "breakpoint handler function" method.
1186 Also, what if child has exit()ed? Must exit loop somehow.
1190 svr4_solib_create_inferior_hook (void)
1192 /* Relocate the main executable if necessary. */
1193 svr4_relocate_main_executable ();
1195 if (!svr4_have_link_map_offsets ())
1197 warning (_("no shared library support for this OS / ABI"));
1202 if (!enable_break ())
1204 warning (_("shared library handler failed to enable breakpoint"));
1208 #if defined(_SCO_DS)
1209 /* SCO needs the loop below, other systems should be using the
1210 special shared library breakpoints and the shared library breakpoint
1213 Now run the target. It will eventually hit the breakpoint, at
1214 which point all of the libraries will have been mapped in and we
1215 can go groveling around in the dynamic linker structures to find
1216 out what we need to know about them. */
1218 clear_proceed_status ();
1219 stop_soon
= STOP_QUIETLY
;
1220 stop_signal
= TARGET_SIGNAL_0
;
1223 target_resume (pid_to_ptid (-1), 0, stop_signal
);
1224 wait_for_inferior ();
1226 while (stop_signal
!= TARGET_SIGNAL_TRAP
);
1227 stop_soon
= NO_STOP_QUIETLY
;
1228 #endif /* defined(_SCO_DS) */
1232 svr4_clear_solib (void)
1238 svr4_free_so (struct so_list
*so
)
1240 xfree (so
->lm_info
->lm
);
1241 xfree (so
->lm_info
);
1245 /* Clear any bits of ADDR that wouldn't fit in a target-format
1246 data pointer. "Data pointer" here refers to whatever sort of
1247 address the dynamic linker uses to manage its sections. At the
1248 moment, we don't support shared libraries on any processors where
1249 code and data pointers are different sizes.
1251 This isn't really the right solution. What we really need here is
1252 a way to do arithmetic on CORE_ADDR values that respects the
1253 natural pointer/address correspondence. (For example, on the MIPS,
1254 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1255 sign-extend the value. There, simply truncating the bits above
1256 TARGET_PTR_BIT, as we do below, is no good.) This should probably
1257 be a new gdbarch method or something. */
1259 svr4_truncate_ptr (CORE_ADDR addr
)
1261 if (TARGET_PTR_BIT
== sizeof (CORE_ADDR
) * 8)
1262 /* We don't need to truncate anything, and the bit twiddling below
1263 will fail due to overflow problems. */
1266 return addr
& (((CORE_ADDR
) 1 << TARGET_PTR_BIT
) - 1);
1271 svr4_relocate_section_addresses (struct so_list
*so
,
1272 struct section_table
*sec
)
1274 sec
->addr
= svr4_truncate_ptr (sec
->addr
+ LM_ADDR (so
));
1275 sec
->endaddr
= svr4_truncate_ptr (sec
->endaddr
+ LM_ADDR (so
));
1279 /* Architecture-specific operations. */
1281 /* Per-architecture data key. */
1282 static struct gdbarch_data
*solib_svr4_data
;
1284 struct solib_svr4_ops
1286 /* Return a description of the layout of `struct link_map'. */
1287 struct link_map_offsets
*(*fetch_link_map_offsets
)(void);
1290 /* Return a default for the architecture-specific operations. */
1293 solib_svr4_init (struct obstack
*obstack
)
1295 struct solib_svr4_ops
*ops
;
1297 ops
= OBSTACK_ZALLOC (obstack
, struct solib_svr4_ops
);
1298 ops
->fetch_link_map_offsets
= legacy_svr4_fetch_link_map_offsets_hook
;
1302 /* Set the architecture-specific `struct link_map_offsets' fetcher for
1306 set_solib_svr4_fetch_link_map_offsets (struct gdbarch
*gdbarch
,
1307 struct link_map_offsets
*(*flmo
) (void))
1309 struct solib_svr4_ops
*ops
= gdbarch_data (gdbarch
, solib_svr4_data
);
1311 ops
->fetch_link_map_offsets
= flmo
;
1314 /* Fetch a link_map_offsets structure using the architecture-specific
1315 `struct link_map_offsets' fetcher. */
1317 static struct link_map_offsets
*
1318 svr4_fetch_link_map_offsets (void)
1320 struct solib_svr4_ops
*ops
= gdbarch_data (current_gdbarch
, solib_svr4_data
);
1322 gdb_assert (ops
->fetch_link_map_offsets
);
1323 return ops
->fetch_link_map_offsets ();
1326 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1329 svr4_have_link_map_offsets (void)
1331 struct solib_svr4_ops
*ops
= gdbarch_data (current_gdbarch
, solib_svr4_data
);
1332 return (ops
->fetch_link_map_offsets
!= NULL
);
1336 /* Most OS'es that have SVR4-style ELF dynamic libraries define a
1337 `struct r_debug' and a `struct link_map' that are binary compatible
1338 with the origional SVR4 implementation. */
1340 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1341 for an ILP32 SVR4 system. */
1343 struct link_map_offsets
*
1344 svr4_ilp32_fetch_link_map_offsets (void)
1346 static struct link_map_offsets lmo
;
1347 static struct link_map_offsets
*lmp
= NULL
;
1353 /* Everything we need is in the first 8 bytes. */
1354 lmo
.r_debug_size
= 8;
1355 lmo
.r_map_offset
= 4;
1358 /* Everything we need is in the first 20 bytes. */
1359 lmo
.link_map_size
= 20;
1360 lmo
.l_addr_offset
= 0;
1361 lmo
.l_addr_size
= 4;
1362 lmo
.l_name_offset
= 4;
1363 lmo
.l_name_size
= 4;
1364 lmo
.l_next_offset
= 12;
1365 lmo
.l_next_size
= 4;
1366 lmo
.l_prev_offset
= 16;
1367 lmo
.l_prev_size
= 4;
1373 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1374 for an LP64 SVR4 system. */
1376 struct link_map_offsets
*
1377 svr4_lp64_fetch_link_map_offsets (void)
1379 static struct link_map_offsets lmo
;
1380 static struct link_map_offsets
*lmp
= NULL
;
1386 /* Everything we need is in the first 16 bytes. */
1387 lmo
.r_debug_size
= 16;
1388 lmo
.r_map_offset
= 8;
1391 /* Everything we need is in the first 40 bytes. */
1392 lmo
.link_map_size
= 40;
1393 lmo
.l_addr_offset
= 0;
1394 lmo
.l_addr_size
= 8;
1395 lmo
.l_name_offset
= 8;
1396 lmo
.l_name_size
= 8;
1397 lmo
.l_next_offset
= 24;
1398 lmo
.l_next_size
= 8;
1399 lmo
.l_prev_offset
= 32;
1400 lmo
.l_prev_size
= 8;
1407 static struct target_so_ops svr4_so_ops
;
1409 extern initialize_file_ftype _initialize_svr4_solib
; /* -Wmissing-prototypes */
1412 _initialize_svr4_solib (void)
1414 solib_svr4_data
= gdbarch_data_register_pre_init (solib_svr4_init
);
1416 svr4_so_ops
.relocate_section_addresses
= svr4_relocate_section_addresses
;
1417 svr4_so_ops
.free_so
= svr4_free_so
;
1418 svr4_so_ops
.clear_solib
= svr4_clear_solib
;
1419 svr4_so_ops
.solib_create_inferior_hook
= svr4_solib_create_inferior_hook
;
1420 svr4_so_ops
.special_symbol_handling
= svr4_special_symbol_handling
;
1421 svr4_so_ops
.current_sos
= svr4_current_sos
;
1422 svr4_so_ops
.open_symbol_file_object
= open_symbol_file_object
;
1423 svr4_so_ops
.in_dynsym_resolve_code
= svr4_in_dynsym_resolve_code
;
1425 /* FIXME: Don't do this here. *_gdbarch_init() should set so_ops. */
1426 current_target_so_ops
= &svr4_so_ops
;