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, 2008, 2009, 2010
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 3 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, see <http://www.gnu.org/licenses/>. */
24 #include "elf/external.h"
25 #include "elf/common.h"
36 #include "gdbthread.h"
39 #include "gdb_assert.h"
43 #include "solib-svr4.h"
45 #include "bfd-target.h"
49 #include "exceptions.h"
51 static struct link_map_offsets
*svr4_fetch_link_map_offsets (void);
52 static int svr4_have_link_map_offsets (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. */
70 /* The target location of lm. */
74 /* On SVR4 systems, a list of symbols in the dynamic linker where
75 GDB can try to place a breakpoint to monitor shared library
78 If none of these symbols are found, or other errors occur, then
79 SVR4 systems will fall back to using a symbol as the "startup
80 mapping complete" breakpoint address. */
82 static char *solib_break_names
[] =
93 static char *bkpt_names
[] =
101 static char *main_name_list
[] =
107 /* Return non-zero if GDB_SO_NAME and INFERIOR_SO_NAME represent
108 the same shared library. */
111 svr4_same_1 (const char *gdb_so_name
, const char *inferior_so_name
)
113 if (strcmp (gdb_so_name
, inferior_so_name
) == 0)
116 /* On Solaris, when starting inferior we think that dynamic linker is
117 /usr/lib/ld.so.1, but later on, the table of loaded shared libraries
118 contains /lib/ld.so.1. Sometimes one file is a link to another, but
119 sometimes they have identical content, but are not linked to each
120 other. We don't restrict this check for Solaris, but the chances
121 of running into this situation elsewhere are very low. */
122 if (strcmp (gdb_so_name
, "/usr/lib/ld.so.1") == 0
123 && strcmp (inferior_so_name
, "/lib/ld.so.1") == 0)
126 /* Similarly, we observed the same issue with sparc64, but with
127 different locations. */
128 if (strcmp (gdb_so_name
, "/usr/lib/sparcv9/ld.so.1") == 0
129 && strcmp (inferior_so_name
, "/lib/sparcv9/ld.so.1") == 0)
136 svr4_same (struct so_list
*gdb
, struct so_list
*inferior
)
138 return (svr4_same_1 (gdb
->so_original_name
, inferior
->so_original_name
));
141 /* link map access functions */
144 LM_ADDR_FROM_LINK_MAP (struct so_list
*so
)
146 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
147 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
149 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_addr_offset
,
154 HAS_LM_DYNAMIC_FROM_LINK_MAP (void)
156 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
158 return lmo
->l_ld_offset
>= 0;
162 LM_DYNAMIC_FROM_LINK_MAP (struct so_list
*so
)
164 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
165 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
167 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_ld_offset
,
172 LM_ADDR_CHECK (struct so_list
*so
, bfd
*abfd
)
174 if (so
->lm_info
->l_addr
== (CORE_ADDR
)-1)
176 struct bfd_section
*dyninfo_sect
;
177 CORE_ADDR l_addr
, l_dynaddr
, dynaddr
, align
= 0x1000;
179 l_addr
= LM_ADDR_FROM_LINK_MAP (so
);
181 if (! abfd
|| ! HAS_LM_DYNAMIC_FROM_LINK_MAP ())
184 l_dynaddr
= LM_DYNAMIC_FROM_LINK_MAP (so
);
186 dyninfo_sect
= bfd_get_section_by_name (abfd
, ".dynamic");
187 if (dyninfo_sect
== NULL
)
190 dynaddr
= bfd_section_vma (abfd
, dyninfo_sect
);
192 if (dynaddr
+ l_addr
!= l_dynaddr
)
194 if (bfd_get_flavour (abfd
) == bfd_target_elf_flavour
)
196 Elf_Internal_Ehdr
*ehdr
= elf_tdata (abfd
)->elf_header
;
197 Elf_Internal_Phdr
*phdr
= elf_tdata (abfd
)->phdr
;
202 for (i
= 0; i
< ehdr
->e_phnum
; i
++)
203 if (phdr
[i
].p_type
== PT_LOAD
&& phdr
[i
].p_align
> align
)
204 align
= phdr
[i
].p_align
;
207 /* Turn it into a mask. */
210 /* If the changes match the alignment requirements, we
211 assume we're using a core file that was generated by the
212 same binary, just prelinked with a different base offset.
213 If it doesn't match, we may have a different binary, the
214 same binary with the dynamic table loaded at an unrelated
215 location, or anything, really. To avoid regressions,
216 don't adjust the base offset in the latter case, although
217 odds are that, if things really changed, debugging won't
219 if ((l_addr
& align
) == ((l_dynaddr
- dynaddr
) & align
))
221 l_addr
= l_dynaddr
- dynaddr
;
223 warning (_(".dynamic section for \"%s\" "
224 "is not at the expected address"), so
->so_name
);
225 warning (_("difference appears to be caused by prelink, "
226 "adjusting expectations"));
229 warning (_(".dynamic section for \"%s\" "
230 "is not at the expected address "
231 "(wrong library or version mismatch?)"), so
->so_name
);
235 so
->lm_info
->l_addr
= l_addr
;
238 return so
->lm_info
->l_addr
;
242 LM_NEXT (struct so_list
*so
)
244 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
245 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
247 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_next_offset
,
252 LM_NAME (struct so_list
*so
)
254 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
255 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
257 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_name_offset
,
262 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list
*so
)
264 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
265 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
267 /* Assume that everything is a library if the dynamic loader was loaded
268 late by a static executable. */
269 if (exec_bfd
&& bfd_get_section_by_name (exec_bfd
, ".dynamic") == NULL
)
272 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_prev_offset
,
276 /* Per pspace SVR4 specific data. */
280 CORE_ADDR debug_base
; /* Base of dynamic linker structures */
282 /* Validity flag for debug_loader_offset. */
283 int debug_loader_offset_p
;
285 /* Load address for the dynamic linker, inferred. */
286 CORE_ADDR debug_loader_offset
;
288 /* Name of the dynamic linker, valid if debug_loader_offset_p. */
289 char *debug_loader_name
;
291 /* Load map address for the main executable. */
292 CORE_ADDR main_lm_addr
;
294 CORE_ADDR interp_text_sect_low
;
295 CORE_ADDR interp_text_sect_high
;
296 CORE_ADDR interp_plt_sect_low
;
297 CORE_ADDR interp_plt_sect_high
;
300 /* Per-program-space data key. */
301 static const struct program_space_data
*solib_svr4_pspace_data
;
304 svr4_pspace_data_cleanup (struct program_space
*pspace
, void *arg
)
306 struct svr4_info
*info
;
308 info
= program_space_data (pspace
, solib_svr4_pspace_data
);
312 /* Get the current svr4 data. If none is found yet, add it now. This
313 function always returns a valid object. */
315 static struct svr4_info
*
318 struct svr4_info
*info
;
320 info
= program_space_data (current_program_space
, solib_svr4_pspace_data
);
324 info
= XZALLOC (struct svr4_info
);
325 set_program_space_data (current_program_space
, solib_svr4_pspace_data
, info
);
329 /* Local function prototypes */
331 static int match_main (char *);
333 static CORE_ADDR
bfd_lookup_symbol (bfd
*, char *);
339 bfd_lookup_symbol -- lookup the value for a specific symbol
343 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
347 An expensive way to lookup the value of a single symbol for
348 bfd's that are only temporary anyway. This is used by the
349 shared library support to find the address of the debugger
350 notification routine in the shared library.
352 The returned symbol may be in a code or data section; functions
353 will normally be in a code section, but may be in a data section
354 if this architecture uses function descriptors.
356 Note that 0 is specifically allowed as an error return (no
361 bfd_lookup_symbol (bfd
*abfd
, char *symname
)
365 asymbol
**symbol_table
;
366 unsigned int number_of_symbols
;
368 struct cleanup
*back_to
;
369 CORE_ADDR symaddr
= 0;
371 storage_needed
= bfd_get_symtab_upper_bound (abfd
);
373 if (storage_needed
> 0)
375 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
376 back_to
= make_cleanup (xfree
, symbol_table
);
377 number_of_symbols
= bfd_canonicalize_symtab (abfd
, symbol_table
);
379 for (i
= 0; i
< number_of_symbols
; i
++)
381 sym
= *symbol_table
++;
382 if (strcmp (sym
->name
, symname
) == 0
383 && (sym
->section
->flags
& (SEC_CODE
| SEC_DATA
)) != 0)
385 /* BFD symbols are section relative. */
386 symaddr
= sym
->value
+ sym
->section
->vma
;
390 do_cleanups (back_to
);
396 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
397 have to check the dynamic string table too. */
399 storage_needed
= bfd_get_dynamic_symtab_upper_bound (abfd
);
401 if (storage_needed
> 0)
403 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
404 back_to
= make_cleanup (xfree
, symbol_table
);
405 number_of_symbols
= bfd_canonicalize_dynamic_symtab (abfd
, symbol_table
);
407 for (i
= 0; i
< number_of_symbols
; i
++)
409 sym
= *symbol_table
++;
411 if (strcmp (sym
->name
, symname
) == 0
412 && (sym
->section
->flags
& (SEC_CODE
| SEC_DATA
)) != 0)
414 /* BFD symbols are section relative. */
415 symaddr
= sym
->value
+ sym
->section
->vma
;
419 do_cleanups (back_to
);
426 /* Read program header TYPE from inferior memory. The header is found
427 by scanning the OS auxillary vector.
429 Return a pointer to allocated memory holding the program header contents,
430 or NULL on failure. If sucessful, and unless P_SECT_SIZE is NULL, the
431 size of those contents is returned to P_SECT_SIZE. Likewise, the target
432 architecture size (32-bit or 64-bit) is returned to P_ARCH_SIZE. */
435 read_program_header (int type
, int *p_sect_size
, int *p_arch_size
)
437 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
438 CORE_ADDR at_phdr
, at_phent
, at_phnum
;
439 int arch_size
, sect_size
;
443 /* Get required auxv elements from target. */
444 if (target_auxv_search (¤t_target
, AT_PHDR
, &at_phdr
) <= 0)
446 if (target_auxv_search (¤t_target
, AT_PHENT
, &at_phent
) <= 0)
448 if (target_auxv_search (¤t_target
, AT_PHNUM
, &at_phnum
) <= 0)
450 if (!at_phdr
|| !at_phnum
)
453 /* Determine ELF architecture type. */
454 if (at_phent
== sizeof (Elf32_External_Phdr
))
456 else if (at_phent
== sizeof (Elf64_External_Phdr
))
461 /* Find .dynamic section via the PT_DYNAMIC PHDR. */
464 Elf32_External_Phdr phdr
;
467 /* Search for requested PHDR. */
468 for (i
= 0; i
< at_phnum
; i
++)
470 if (target_read_memory (at_phdr
+ i
* sizeof (phdr
),
471 (gdb_byte
*)&phdr
, sizeof (phdr
)))
474 if (extract_unsigned_integer ((gdb_byte
*)phdr
.p_type
,
475 4, byte_order
) == type
)
482 /* Retrieve address and size. */
483 sect_addr
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_vaddr
,
485 sect_size
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_memsz
,
490 Elf64_External_Phdr phdr
;
493 /* Search for requested PHDR. */
494 for (i
= 0; i
< at_phnum
; i
++)
496 if (target_read_memory (at_phdr
+ i
* sizeof (phdr
),
497 (gdb_byte
*)&phdr
, sizeof (phdr
)))
500 if (extract_unsigned_integer ((gdb_byte
*)phdr
.p_type
,
501 4, byte_order
) == type
)
508 /* Retrieve address and size. */
509 sect_addr
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_vaddr
,
511 sect_size
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_memsz
,
515 /* Read in requested program header. */
516 buf
= xmalloc (sect_size
);
517 if (target_read_memory (sect_addr
, buf
, sect_size
))
524 *p_arch_size
= arch_size
;
526 *p_sect_size
= sect_size
;
532 /* Return program interpreter string. */
534 find_program_interpreter (void)
536 gdb_byte
*buf
= NULL
;
538 /* If we have an exec_bfd, use its section table. */
540 && bfd_get_flavour (exec_bfd
) == bfd_target_elf_flavour
)
542 struct bfd_section
*interp_sect
;
544 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
545 if (interp_sect
!= NULL
)
547 CORE_ADDR sect_addr
= bfd_section_vma (exec_bfd
, interp_sect
);
548 int sect_size
= bfd_section_size (exec_bfd
, interp_sect
);
550 buf
= xmalloc (sect_size
);
551 bfd_get_section_contents (exec_bfd
, interp_sect
, buf
, 0, sect_size
);
555 /* If we didn't find it, use the target auxillary vector. */
557 buf
= read_program_header (PT_INTERP
, NULL
, NULL
);
563 /* Scan for DYNTAG in .dynamic section of ABFD. If DYNTAG is found 1 is
564 returned and the corresponding PTR is set. */
567 scan_dyntag (int dyntag
, bfd
*abfd
, CORE_ADDR
*ptr
)
569 int arch_size
, step
, sect_size
;
572 gdb_byte
*bufend
, *bufstart
, *buf
;
573 Elf32_External_Dyn
*x_dynp_32
;
574 Elf64_External_Dyn
*x_dynp_64
;
575 struct bfd_section
*sect
;
576 struct target_section
*target_section
;
581 if (bfd_get_flavour (abfd
) != bfd_target_elf_flavour
)
584 arch_size
= bfd_get_arch_size (abfd
);
588 /* Find the start address of the .dynamic section. */
589 sect
= bfd_get_section_by_name (abfd
, ".dynamic");
593 for (target_section
= current_target_sections
->sections
;
594 target_section
< current_target_sections
->sections_end
;
596 if (sect
== target_section
->the_bfd_section
)
598 gdb_assert (target_section
< current_target_sections
->sections_end
);
600 /* Read in .dynamic from the BFD. We will get the actual value
601 from memory later. */
602 sect_size
= bfd_section_size (abfd
, sect
);
603 buf
= bufstart
= alloca (sect_size
);
604 if (!bfd_get_section_contents (abfd
, sect
,
608 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
609 step
= (arch_size
== 32) ? sizeof (Elf32_External_Dyn
)
610 : sizeof (Elf64_External_Dyn
);
611 for (bufend
= buf
+ sect_size
;
617 x_dynp_32
= (Elf32_External_Dyn
*) buf
;
618 dyn_tag
= bfd_h_get_32 (abfd
, (bfd_byte
*) x_dynp_32
->d_tag
);
619 dyn_ptr
= bfd_h_get_32 (abfd
, (bfd_byte
*) x_dynp_32
->d_un
.d_ptr
);
623 x_dynp_64
= (Elf64_External_Dyn
*) buf
;
624 dyn_tag
= bfd_h_get_64 (abfd
, (bfd_byte
*) x_dynp_64
->d_tag
);
625 dyn_ptr
= bfd_h_get_64 (abfd
, (bfd_byte
*) x_dynp_64
->d_un
.d_ptr
);
627 if (dyn_tag
== DT_NULL
)
629 if (dyn_tag
== dyntag
)
631 /* If requested, try to read the runtime value of this .dynamic
635 struct type
*ptr_type
;
639 ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
640 ptr_addr
= target_section
->addr
+ (buf
- bufstart
) + arch_size
/ 8;
641 if (target_read_memory (ptr_addr
, ptr_buf
, arch_size
/ 8) == 0)
642 dyn_ptr
= extract_typed_address (ptr_buf
, ptr_type
);
652 /* Scan for DYNTAG in .dynamic section of the target's main executable,
653 found by consulting the OS auxillary vector. If DYNTAG is found 1 is
654 returned and the corresponding PTR is set. */
657 scan_dyntag_auxv (int dyntag
, CORE_ADDR
*ptr
)
659 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
660 int sect_size
, arch_size
, step
;
663 gdb_byte
*bufend
, *bufstart
, *buf
;
665 /* Read in .dynamic section. */
666 buf
= bufstart
= read_program_header (PT_DYNAMIC
, §_size
, &arch_size
);
670 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
671 step
= (arch_size
== 32) ? sizeof (Elf32_External_Dyn
)
672 : sizeof (Elf64_External_Dyn
);
673 for (bufend
= buf
+ sect_size
;
679 Elf32_External_Dyn
*dynp
= (Elf32_External_Dyn
*) buf
;
680 dyn_tag
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_tag
,
682 dyn_ptr
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_un
.d_ptr
,
687 Elf64_External_Dyn
*dynp
= (Elf64_External_Dyn
*) buf
;
688 dyn_tag
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_tag
,
690 dyn_ptr
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_un
.d_ptr
,
693 if (dyn_tag
== DT_NULL
)
696 if (dyn_tag
== dyntag
)
715 elf_locate_base -- locate the base address of dynamic linker structs
716 for SVR4 elf targets.
720 CORE_ADDR elf_locate_base (void)
724 For SVR4 elf targets the address of the dynamic linker's runtime
725 structure is contained within the dynamic info section in the
726 executable file. The dynamic section is also mapped into the
727 inferior address space. Because the runtime loader fills in the
728 real address before starting the inferior, we have to read in the
729 dynamic info section from the inferior address space.
730 If there are any errors while trying to find the address, we
731 silently return 0, otherwise the found address is returned.
736 elf_locate_base (void)
738 struct minimal_symbol
*msymbol
;
741 /* Look for DT_MIPS_RLD_MAP first. MIPS executables use this
742 instead of DT_DEBUG, although they sometimes contain an unused
744 if (scan_dyntag (DT_MIPS_RLD_MAP
, exec_bfd
, &dyn_ptr
)
745 || scan_dyntag_auxv (DT_MIPS_RLD_MAP
, &dyn_ptr
))
747 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
749 int pbuf_size
= TYPE_LENGTH (ptr_type
);
750 pbuf
= alloca (pbuf_size
);
751 /* DT_MIPS_RLD_MAP contains a pointer to the address
752 of the dynamic link structure. */
753 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
755 return extract_typed_address (pbuf
, ptr_type
);
759 if (scan_dyntag (DT_DEBUG
, exec_bfd
, &dyn_ptr
)
760 || scan_dyntag_auxv (DT_DEBUG
, &dyn_ptr
))
763 /* This may be a static executable. Look for the symbol
764 conventionally named _r_debug, as a last resort. */
765 msymbol
= lookup_minimal_symbol ("_r_debug", NULL
, symfile_objfile
);
767 return SYMBOL_VALUE_ADDRESS (msymbol
);
769 /* DT_DEBUG entry not found. */
777 locate_base -- locate the base address of dynamic linker structs
781 CORE_ADDR locate_base (struct svr4_info *)
785 For both the SunOS and SVR4 shared library implementations, if the
786 inferior executable has been linked dynamically, there is a single
787 address somewhere in the inferior's data space which is the key to
788 locating all of the dynamic linker's runtime structures. This
789 address is the value of the debug base symbol. The job of this
790 function is to find and return that address, or to return 0 if there
791 is no such address (the executable is statically linked for example).
793 For SunOS, the job is almost trivial, since the dynamic linker and
794 all of it's structures are statically linked to the executable at
795 link time. Thus the symbol for the address we are looking for has
796 already been added to the minimal symbol table for the executable's
797 objfile at the time the symbol file's symbols were read, and all we
798 have to do is look it up there. Note that we explicitly do NOT want
799 to find the copies in the shared library.
801 The SVR4 version is a bit more complicated because the address
802 is contained somewhere in the dynamic info section. We have to go
803 to a lot more work to discover the address of the debug base symbol.
804 Because of this complexity, we cache the value we find and return that
805 value on subsequent invocations. Note there is no copy in the
806 executable symbol tables.
811 locate_base (struct svr4_info
*info
)
813 /* Check to see if we have a currently valid address, and if so, avoid
814 doing all this work again and just return the cached address. If
815 we have no cached address, try to locate it in the dynamic info
816 section for ELF executables. There's no point in doing any of this
817 though if we don't have some link map offsets to work with. */
819 if (info
->debug_base
== 0 && svr4_have_link_map_offsets ())
820 info
->debug_base
= elf_locate_base ();
821 return info
->debug_base
;
824 /* Find the first element in the inferior's dynamic link map, and
825 return its address in the inferior.
827 FIXME: Perhaps we should validate the info somehow, perhaps by
828 checking r_version for a known version number, or r_state for
832 solib_svr4_r_map (struct svr4_info
*info
)
834 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
835 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
837 return read_memory_typed_address (info
->debug_base
+ lmo
->r_map_offset
,
841 /* Find r_brk from the inferior's debug base. */
844 solib_svr4_r_brk (struct svr4_info
*info
)
846 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
847 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
849 return read_memory_typed_address (info
->debug_base
+ lmo
->r_brk_offset
,
853 /* Find the link map for the dynamic linker (if it is not in the
854 normal list of loaded shared objects). */
857 solib_svr4_r_ldsomap (struct svr4_info
*info
)
859 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
860 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
861 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
864 /* Check version, and return zero if `struct r_debug' doesn't have
865 the r_ldsomap member. */
867 = read_memory_unsigned_integer (info
->debug_base
+ lmo
->r_version_offset
,
868 lmo
->r_version_size
, byte_order
);
869 if (version
< 2 || lmo
->r_ldsomap_offset
== -1)
872 return read_memory_typed_address (info
->debug_base
+ lmo
->r_ldsomap_offset
,
876 /* On Solaris systems with some versions of the dynamic linker,
877 ld.so's l_name pointer points to the SONAME in the string table
878 rather than into writable memory. So that GDB can find shared
879 libraries when loading a core file generated by gcore, ensure that
880 memory areas containing the l_name string are saved in the core
884 svr4_keep_data_in_core (CORE_ADDR vaddr
, unsigned long size
)
886 struct svr4_info
*info
;
889 struct cleanup
*old_chain
;
890 struct link_map_offsets
*lmo
;
893 info
= get_svr4_info ();
895 info
->debug_base
= 0;
897 if (!info
->debug_base
)
900 ldsomap
= solib_svr4_r_ldsomap (info
);
904 lmo
= svr4_fetch_link_map_offsets ();
905 new = XZALLOC (struct so_list
);
906 old_chain
= make_cleanup (xfree
, new);
907 new->lm_info
= xmalloc (sizeof (struct lm_info
));
908 make_cleanup (xfree
, new->lm_info
);
909 new->lm_info
->l_addr
= (CORE_ADDR
)-1;
910 new->lm_info
->lm_addr
= ldsomap
;
911 new->lm_info
->lm
= xzalloc (lmo
->link_map_size
);
912 make_cleanup (xfree
, new->lm_info
->lm
);
913 read_memory (ldsomap
, new->lm_info
->lm
, lmo
->link_map_size
);
914 lm_name
= LM_NAME (new);
915 do_cleanups (old_chain
);
917 return (lm_name
>= vaddr
&& lm_name
< vaddr
+ size
);
924 open_symbol_file_object
928 void open_symbol_file_object (void *from_tty)
932 If no open symbol file, attempt to locate and open the main symbol
933 file. On SVR4 systems, this is the first link map entry. If its
934 name is here, we can open it. Useful when attaching to a process
935 without first loading its symbol file.
937 If FROM_TTYP dereferences to a non-zero integer, allow messages to
938 be printed. This parameter is a pointer rather than an int because
939 open_symbol_file_object() is called via catch_errors() and
940 catch_errors() requires a pointer argument. */
943 open_symbol_file_object (void *from_ttyp
)
945 CORE_ADDR lm
, l_name
;
948 int from_tty
= *(int *)from_ttyp
;
949 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
950 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
951 int l_name_size
= TYPE_LENGTH (ptr_type
);
952 gdb_byte
*l_name_buf
= xmalloc (l_name_size
);
953 struct cleanup
*cleanups
= make_cleanup (xfree
, l_name_buf
);
954 struct svr4_info
*info
= get_svr4_info ();
957 if (!query (_("Attempt to reload symbols from process? ")))
960 /* Always locate the debug struct, in case it has moved. */
961 info
->debug_base
= 0;
962 if (locate_base (info
) == 0)
963 return 0; /* failed somehow... */
965 /* First link map member should be the executable. */
966 lm
= solib_svr4_r_map (info
);
968 return 0; /* failed somehow... */
970 /* Read address of name from target memory to GDB. */
971 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, l_name_size
);
973 /* Convert the address to host format. */
974 l_name
= extract_typed_address (l_name_buf
, ptr_type
);
976 /* Free l_name_buf. */
977 do_cleanups (cleanups
);
980 return 0; /* No filename. */
982 /* Now fetch the filename from target memory. */
983 target_read_string (l_name
, &filename
, SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
984 make_cleanup (xfree
, filename
);
988 warning (_("failed to read exec filename from attached file: %s"),
989 safe_strerror (errcode
));
993 /* Have a pathname: read the symbol file. */
994 symbol_file_add_main (filename
, from_tty
);
999 /* If no shared library information is available from the dynamic
1000 linker, build a fallback list from other sources. */
1002 static struct so_list
*
1003 svr4_default_sos (void)
1005 struct svr4_info
*info
= get_svr4_info ();
1007 struct so_list
*head
= NULL
;
1008 struct so_list
**link_ptr
= &head
;
1010 if (info
->debug_loader_offset_p
)
1012 struct so_list
*new = XZALLOC (struct so_list
);
1014 new->lm_info
= xmalloc (sizeof (struct lm_info
));
1016 /* Nothing will ever check the cached copy of the link
1017 map if we set l_addr. */
1018 new->lm_info
->l_addr
= info
->debug_loader_offset
;
1019 new->lm_info
->lm_addr
= 0;
1020 new->lm_info
->lm
= NULL
;
1022 strncpy (new->so_name
, info
->debug_loader_name
,
1023 SO_NAME_MAX_PATH_SIZE
- 1);
1024 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
1025 strcpy (new->so_original_name
, new->so_name
);
1028 link_ptr
= &new->next
;
1036 current_sos -- build a list of currently loaded shared objects
1040 struct so_list *current_sos ()
1044 Build a list of `struct so_list' objects describing the shared
1045 objects currently loaded in the inferior. This list does not
1046 include an entry for the main executable file.
1048 Note that we only gather information directly available from the
1049 inferior --- we don't examine any of the shared library files
1050 themselves. The declaration of `struct so_list' says which fields
1051 we provide values for. */
1053 static struct so_list
*
1054 svr4_current_sos (void)
1057 struct so_list
*head
= 0;
1058 struct so_list
**link_ptr
= &head
;
1059 CORE_ADDR ldsomap
= 0;
1060 struct svr4_info
*info
;
1062 info
= get_svr4_info ();
1064 /* Always locate the debug struct, in case it has moved. */
1065 info
->debug_base
= 0;
1068 /* If we can't find the dynamic linker's base structure, this
1069 must not be a dynamically linked executable. Hmm. */
1070 if (! info
->debug_base
)
1071 return svr4_default_sos ();
1073 /* Walk the inferior's link map list, and build our list of
1074 `struct so_list' nodes. */
1075 lm
= solib_svr4_r_map (info
);
1079 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
1080 struct so_list
*new = XZALLOC (struct so_list
);
1081 struct cleanup
*old_chain
= make_cleanup (xfree
, new);
1083 new->lm_info
= xmalloc (sizeof (struct lm_info
));
1084 make_cleanup (xfree
, new->lm_info
);
1086 new->lm_info
->l_addr
= (CORE_ADDR
)-1;
1087 new->lm_info
->lm_addr
= lm
;
1088 new->lm_info
->lm
= xzalloc (lmo
->link_map_size
);
1089 make_cleanup (xfree
, new->lm_info
->lm
);
1091 read_memory (lm
, new->lm_info
->lm
, lmo
->link_map_size
);
1095 /* For SVR4 versions, the first entry in the link map is for the
1096 inferior executable, so we must ignore it. For some versions of
1097 SVR4, it has no name. For others (Solaris 2.3 for example), it
1098 does have a name, so we can no longer use a missing name to
1099 decide when to ignore it. */
1100 if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap
== 0)
1102 info
->main_lm_addr
= new->lm_info
->lm_addr
;
1110 /* Extract this shared object's name. */
1111 target_read_string (LM_NAME (new), &buffer
,
1112 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
1114 warning (_("Can't read pathname for load map: %s."),
1115 safe_strerror (errcode
));
1118 strncpy (new->so_name
, buffer
, SO_NAME_MAX_PATH_SIZE
- 1);
1119 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
1120 strcpy (new->so_original_name
, new->so_name
);
1124 /* If this entry has no name, or its name matches the name
1125 for the main executable, don't include it in the list. */
1126 if (! new->so_name
[0]
1127 || match_main (new->so_name
))
1133 link_ptr
= &new->next
;
1137 /* On Solaris, the dynamic linker is not in the normal list of
1138 shared objects, so make sure we pick it up too. Having
1139 symbol information for the dynamic linker is quite crucial
1140 for skipping dynamic linker resolver code. */
1141 if (lm
== 0 && ldsomap
== 0)
1142 lm
= ldsomap
= solib_svr4_r_ldsomap (info
);
1144 discard_cleanups (old_chain
);
1148 return svr4_default_sos ();
1153 /* Get the address of the link_map for a given OBJFILE. */
1156 svr4_fetch_objfile_link_map (struct objfile
*objfile
)
1159 struct svr4_info
*info
= get_svr4_info ();
1161 /* Cause svr4_current_sos() to be run if it hasn't been already. */
1162 if (info
->main_lm_addr
== 0)
1163 solib_add (NULL
, 0, ¤t_target
, auto_solib_add
);
1165 /* svr4_current_sos() will set main_lm_addr for the main executable. */
1166 if (objfile
== symfile_objfile
)
1167 return info
->main_lm_addr
;
1169 /* The other link map addresses may be found by examining the list
1170 of shared libraries. */
1171 for (so
= master_so_list (); so
; so
= so
->next
)
1172 if (so
->objfile
== objfile
)
1173 return so
->lm_info
->lm_addr
;
1179 /* On some systems, the only way to recognize the link map entry for
1180 the main executable file is by looking at its name. Return
1181 non-zero iff SONAME matches one of the known main executable names. */
1184 match_main (char *soname
)
1188 for (mainp
= main_name_list
; *mainp
!= NULL
; mainp
++)
1190 if (strcmp (soname
, *mainp
) == 0)
1197 /* Return 1 if PC lies in the dynamic symbol resolution code of the
1198 SVR4 run time loader. */
1201 svr4_in_dynsym_resolve_code (CORE_ADDR pc
)
1203 struct svr4_info
*info
= get_svr4_info ();
1205 return ((pc
>= info
->interp_text_sect_low
1206 && pc
< info
->interp_text_sect_high
)
1207 || (pc
>= info
->interp_plt_sect_low
1208 && pc
< info
->interp_plt_sect_high
)
1209 || in_plt_section (pc
, NULL
));
1212 /* Given an executable's ABFD and target, compute the entry-point
1216 exec_entry_point (struct bfd
*abfd
, struct target_ops
*targ
)
1218 /* KevinB wrote ... for most targets, the address returned by
1219 bfd_get_start_address() is the entry point for the start
1220 function. But, for some targets, bfd_get_start_address() returns
1221 the address of a function descriptor from which the entry point
1222 address may be extracted. This address is extracted by
1223 gdbarch_convert_from_func_ptr_addr(). The method
1224 gdbarch_convert_from_func_ptr_addr() is the merely the identify
1225 function for targets which don't use function descriptors. */
1226 return gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1227 bfd_get_start_address (abfd
),
1235 enable_break -- arrange for dynamic linker to hit breakpoint
1239 int enable_break (void)
1243 Both the SunOS and the SVR4 dynamic linkers have, as part of their
1244 debugger interface, support for arranging for the inferior to hit
1245 a breakpoint after mapping in the shared libraries. This function
1246 enables that breakpoint.
1248 For SunOS, there is a special flag location (in_debugger) which we
1249 set to 1. When the dynamic linker sees this flag set, it will set
1250 a breakpoint at a location known only to itself, after saving the
1251 original contents of that place and the breakpoint address itself,
1252 in it's own internal structures. When we resume the inferior, it
1253 will eventually take a SIGTRAP when it runs into the breakpoint.
1254 We handle this (in a different place) by restoring the contents of
1255 the breakpointed location (which is only known after it stops),
1256 chasing around to locate the shared libraries that have been
1257 loaded, then resuming.
1259 For SVR4, the debugger interface structure contains a member (r_brk)
1260 which is statically initialized at the time the shared library is
1261 built, to the offset of a function (_r_debug_state) which is guaran-
1262 teed to be called once before mapping in a library, and again when
1263 the mapping is complete. At the time we are examining this member,
1264 it contains only the unrelocated offset of the function, so we have
1265 to do our own relocation. Later, when the dynamic linker actually
1266 runs, it relocates r_brk to be the actual address of _r_debug_state().
1268 The debugger interface structure also contains an enumeration which
1269 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
1270 depending upon whether or not the library is being mapped or unmapped,
1271 and then set to RT_CONSISTENT after the library is mapped/unmapped.
1275 enable_break (struct svr4_info
*info
, int from_tty
)
1277 struct minimal_symbol
*msymbol
;
1279 asection
*interp_sect
;
1280 gdb_byte
*interp_name
;
1283 /* First, remove all the solib event breakpoints. Their addresses
1284 may have changed since the last time we ran the program. */
1285 remove_solib_event_breakpoints ();
1287 info
->interp_text_sect_low
= info
->interp_text_sect_high
= 0;
1288 info
->interp_plt_sect_low
= info
->interp_plt_sect_high
= 0;
1290 /* If we already have a shared library list in the target, and
1291 r_debug contains r_brk, set the breakpoint there - this should
1292 mean r_brk has already been relocated. Assume the dynamic linker
1293 is the object containing r_brk. */
1295 solib_add (NULL
, from_tty
, ¤t_target
, auto_solib_add
);
1297 if (info
->debug_base
&& solib_svr4_r_map (info
) != 0)
1298 sym_addr
= solib_svr4_r_brk (info
);
1302 struct obj_section
*os
;
1304 sym_addr
= gdbarch_addr_bits_remove
1305 (target_gdbarch
, gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1309 os
= find_pc_section (sym_addr
);
1312 /* Record the relocated start and end address of the dynamic linker
1313 text and plt section for svr4_in_dynsym_resolve_code. */
1315 CORE_ADDR load_addr
;
1317 tmp_bfd
= os
->objfile
->obfd
;
1318 load_addr
= ANOFFSET (os
->objfile
->section_offsets
,
1319 os
->objfile
->sect_index_text
);
1321 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
1324 info
->interp_text_sect_low
=
1325 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1326 info
->interp_text_sect_high
=
1327 info
->interp_text_sect_low
1328 + bfd_section_size (tmp_bfd
, interp_sect
);
1330 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
1333 info
->interp_plt_sect_low
=
1334 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1335 info
->interp_plt_sect_high
=
1336 info
->interp_plt_sect_low
1337 + bfd_section_size (tmp_bfd
, interp_sect
);
1340 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1345 /* Find the program interpreter; if not found, warn the user and drop
1346 into the old breakpoint at symbol code. */
1347 interp_name
= find_program_interpreter ();
1350 CORE_ADDR load_addr
= 0;
1351 int load_addr_found
= 0;
1352 int loader_found_in_list
= 0;
1354 bfd
*tmp_bfd
= NULL
;
1355 struct target_ops
*tmp_bfd_target
;
1356 volatile struct gdb_exception ex
;
1360 /* Now we need to figure out where the dynamic linker was
1361 loaded so that we can load its symbols and place a breakpoint
1362 in the dynamic linker itself.
1364 This address is stored on the stack. However, I've been unable
1365 to find any magic formula to find it for Solaris (appears to
1366 be trivial on GNU/Linux). Therefore, we have to try an alternate
1367 mechanism to find the dynamic linker's base address. */
1369 TRY_CATCH (ex
, RETURN_MASK_ALL
)
1371 tmp_bfd
= solib_bfd_open (interp_name
);
1373 if (tmp_bfd
== NULL
)
1374 goto bkpt_at_symbol
;
1376 /* Now convert the TMP_BFD into a target. That way target, as
1377 well as BFD operations can be used. Note that closing the
1378 target will also close the underlying bfd. */
1379 tmp_bfd_target
= target_bfd_reopen (tmp_bfd
);
1381 /* On a running target, we can get the dynamic linker's base
1382 address from the shared library table. */
1383 so
= master_so_list ();
1386 if (svr4_same_1 (interp_name
, so
->so_original_name
))
1388 load_addr_found
= 1;
1389 loader_found_in_list
= 1;
1390 load_addr
= LM_ADDR_CHECK (so
, tmp_bfd
);
1396 /* If we were not able to find the base address of the loader
1397 from our so_list, then try using the AT_BASE auxilliary entry. */
1398 if (!load_addr_found
)
1399 if (target_auxv_search (¤t_target
, AT_BASE
, &load_addr
) > 0)
1400 load_addr_found
= 1;
1402 /* Otherwise we find the dynamic linker's base address by examining
1403 the current pc (which should point at the entry point for the
1404 dynamic linker) and subtracting the offset of the entry point.
1406 This is more fragile than the previous approaches, but is a good
1407 fallback method because it has actually been working well in
1409 if (!load_addr_found
)
1411 struct regcache
*regcache
1412 = get_thread_arch_regcache (inferior_ptid
, target_gdbarch
);
1413 load_addr
= (regcache_read_pc (regcache
)
1414 - exec_entry_point (tmp_bfd
, tmp_bfd_target
));
1417 if (!loader_found_in_list
)
1419 info
->debug_loader_name
= xstrdup (interp_name
);
1420 info
->debug_loader_offset_p
= 1;
1421 info
->debug_loader_offset
= load_addr
;
1422 solib_add (NULL
, from_tty
, ¤t_target
, auto_solib_add
);
1425 /* Record the relocated start and end address of the dynamic linker
1426 text and plt section for svr4_in_dynsym_resolve_code. */
1427 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
1430 info
->interp_text_sect_low
=
1431 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1432 info
->interp_text_sect_high
=
1433 info
->interp_text_sect_low
1434 + bfd_section_size (tmp_bfd
, interp_sect
);
1436 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
1439 info
->interp_plt_sect_low
=
1440 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1441 info
->interp_plt_sect_high
=
1442 info
->interp_plt_sect_low
1443 + bfd_section_size (tmp_bfd
, interp_sect
);
1446 /* Now try to set a breakpoint in the dynamic linker. */
1447 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1449 sym_addr
= bfd_lookup_symbol (tmp_bfd
, *bkpt_namep
);
1455 /* Convert 'sym_addr' from a function pointer to an address.
1456 Because we pass tmp_bfd_target instead of the current
1457 target, this will always produce an unrelocated value. */
1458 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1462 /* We're done with both the temporary bfd and target. Remember,
1463 closing the target closes the underlying bfd. */
1464 target_close (tmp_bfd_target
, 0);
1468 create_solib_event_breakpoint (target_gdbarch
, load_addr
+ sym_addr
);
1469 xfree (interp_name
);
1473 /* For whatever reason we couldn't set a breakpoint in the dynamic
1474 linker. Warn and drop into the old code. */
1476 xfree (interp_name
);
1477 warning (_("Unable to find dynamic linker breakpoint function.\n"
1478 "GDB will be unable to debug shared library initializers\n"
1479 "and track explicitly loaded dynamic code."));
1482 /* Scan through the lists of symbols, trying to look up the symbol and
1483 set a breakpoint there. Terminate loop when we/if we succeed. */
1485 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1487 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
1488 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
1490 sym_addr
= SYMBOL_VALUE_ADDRESS (msymbol
);
1491 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1494 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1499 for (bkpt_namep
= bkpt_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1501 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
1502 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
1504 sym_addr
= SYMBOL_VALUE_ADDRESS (msymbol
);
1505 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1508 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1519 special_symbol_handling -- additional shared library symbol handling
1523 void special_symbol_handling ()
1527 Once the symbols from a shared object have been loaded in the usual
1528 way, we are called to do any system specific symbol handling that
1531 For SunOS4, this consisted of grunging around in the dynamic
1532 linkers structures to find symbol definitions for "common" symbols
1533 and adding them to the minimal symbol table for the runtime common
1536 However, for SVR4, there's nothing to do.
1541 svr4_special_symbol_handling (void)
1545 /* Decide if the objfile needs to be relocated. As indicated above,
1546 we will only be here when execution is stopped at the beginning
1547 of the program. Relocation is necessary if the address at which
1548 we are presently stopped differs from the start address stored in
1549 the executable AND there's no interpreter section. The condition
1550 regarding the interpreter section is very important because if
1551 there *is* an interpreter section, execution will begin there
1552 instead. When there is an interpreter section, the start address
1553 is (presumably) used by the interpreter at some point to start
1554 execution of the program.
1556 If there is an interpreter, it is normal for it to be set to an
1557 arbitrary address at the outset. The job of finding it is
1558 handled in enable_break().
1560 So, to summarize, relocations are necessary when there is no
1561 interpreter section and the start address obtained from the
1562 executable is different from the address at which GDB is
1565 [ The astute reader will note that we also test to make sure that
1566 the executable in question has the DYNAMIC flag set. It is my
1567 opinion that this test is unnecessary (undesirable even). It
1568 was added to avoid inadvertent relocation of an executable
1569 whose e_type member in the ELF header is not ET_DYN. There may
1570 be a time in the future when it is desirable to do relocations
1571 on other types of files as well in which case this condition
1572 should either be removed or modified to accomodate the new file
1573 type. (E.g, an ET_EXEC executable which has been built to be
1574 position-independent could safely be relocated by the OS if
1575 desired. It is true that this violates the ABI, but the ABI
1576 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1580 svr4_static_exec_displacement (void)
1582 asection
*interp_sect
;
1583 struct regcache
*regcache
1584 = get_thread_arch_regcache (inferior_ptid
, target_gdbarch
);
1585 CORE_ADDR pc
= regcache_read_pc (regcache
);
1587 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
1588 if (interp_sect
== NULL
1589 && (bfd_get_file_flags (exec_bfd
) & DYNAMIC
) != 0
1590 && (exec_entry_point (exec_bfd
, &exec_ops
) != pc
))
1591 return pc
- exec_entry_point (exec_bfd
, &exec_ops
);
1596 /* We relocate all of the sections by the same amount. This
1597 behavior is mandated by recent editions of the System V ABI.
1598 According to the System V Application Binary Interface,
1599 Edition 4.1, page 5-5:
1601 ... Though the system chooses virtual addresses for
1602 individual processes, it maintains the segments' relative
1603 positions. Because position-independent code uses relative
1604 addressesing between segments, the difference between
1605 virtual addresses in memory must match the difference
1606 between virtual addresses in the file. The difference
1607 between the virtual address of any segment in memory and
1608 the corresponding virtual address in the file is thus a
1609 single constant value for any one executable or shared
1610 object in a given process. This difference is the base
1611 address. One use of the base address is to relocate the
1612 memory image of the program during dynamic linking.
1614 The same language also appears in Edition 4.0 of the System V
1615 ABI and is left unspecified in some of the earlier editions. */
1618 svr4_exec_displacement (void)
1621 CORE_ADDR entry_point
;
1623 if (exec_bfd
== NULL
)
1626 if (target_auxv_search (¤t_target
, AT_ENTRY
, &entry_point
) == 1)
1627 return entry_point
- exec_entry_point (exec_bfd
, ¤t_target
);
1629 return svr4_static_exec_displacement ();
1632 /* Relocate the main executable. This function should be called upon
1633 stopping the inferior process at the entry point to the program.
1634 The entry point from BFD is compared to the AT_ENTRY of AUXV and if they are
1635 different, the main executable is relocated by the proper amount. */
1638 svr4_relocate_main_executable (void)
1640 CORE_ADDR displacement
= svr4_exec_displacement ();
1642 /* Even if DISPLACEMENT is 0 still try to relocate it as this is a new
1643 difference of in-memory vs. in-file addresses and we could already
1644 relocate the executable at this function to improper address before. */
1646 if (symfile_objfile
)
1648 struct section_offsets
*new_offsets
;
1651 new_offsets
= alloca (symfile_objfile
->num_sections
1652 * sizeof (*new_offsets
));
1654 for (i
= 0; i
< symfile_objfile
->num_sections
; i
++)
1655 new_offsets
->offsets
[i
] = displacement
;
1657 objfile_relocate (symfile_objfile
, new_offsets
);
1663 for (asect
= exec_bfd
->sections
; asect
!= NULL
; asect
= asect
->next
)
1664 exec_set_section_address (bfd_get_filename (exec_bfd
), asect
->index
,
1665 (bfd_section_vma (exec_bfd
, asect
)
1674 svr4_solib_create_inferior_hook -- shared library startup support
1678 void svr4_solib_create_inferior_hook (int from_tty)
1682 When gdb starts up the inferior, it nurses it along (through the
1683 shell) until it is ready to execute it's first instruction. At this
1684 point, this function gets called via expansion of the macro
1685 SOLIB_CREATE_INFERIOR_HOOK.
1687 For SunOS executables, this first instruction is typically the
1688 one at "_start", or a similar text label, regardless of whether
1689 the executable is statically or dynamically linked. The runtime
1690 startup code takes care of dynamically linking in any shared
1691 libraries, once gdb allows the inferior to continue.
1693 For SVR4 executables, this first instruction is either the first
1694 instruction in the dynamic linker (for dynamically linked
1695 executables) or the instruction at "start" for statically linked
1696 executables. For dynamically linked executables, the system
1697 first exec's /lib/libc.so.N, which contains the dynamic linker,
1698 and starts it running. The dynamic linker maps in any needed
1699 shared libraries, maps in the actual user executable, and then
1700 jumps to "start" in the user executable.
1702 For both SunOS shared libraries, and SVR4 shared libraries, we
1703 can arrange to cooperate with the dynamic linker to discover the
1704 names of shared libraries that are dynamically linked, and the
1705 base addresses to which they are linked.
1707 This function is responsible for discovering those names and
1708 addresses, and saving sufficient information about them to allow
1709 their symbols to be read at a later time.
1713 Between enable_break() and disable_break(), this code does not
1714 properly handle hitting breakpoints which the user might have
1715 set in the startup code or in the dynamic linker itself. Proper
1716 handling will probably have to wait until the implementation is
1717 changed to use the "breakpoint handler function" method.
1719 Also, what if child has exit()ed? Must exit loop somehow.
1723 svr4_solib_create_inferior_hook (int from_tty
)
1725 struct inferior
*inf
;
1726 struct thread_info
*tp
;
1727 struct svr4_info
*info
;
1729 info
= get_svr4_info ();
1731 /* Relocate the main executable if necessary. */
1732 svr4_relocate_main_executable ();
1734 if (!svr4_have_link_map_offsets ())
1737 if (!enable_break (info
, from_tty
))
1740 #if defined(_SCO_DS)
1741 /* SCO needs the loop below, other systems should be using the
1742 special shared library breakpoints and the shared library breakpoint
1745 Now run the target. It will eventually hit the breakpoint, at
1746 which point all of the libraries will have been mapped in and we
1747 can go groveling around in the dynamic linker structures to find
1748 out what we need to know about them. */
1750 inf
= current_inferior ();
1751 tp
= inferior_thread ();
1753 clear_proceed_status ();
1754 inf
->stop_soon
= STOP_QUIETLY
;
1755 tp
->stop_signal
= TARGET_SIGNAL_0
;
1758 target_resume (pid_to_ptid (-1), 0, tp
->stop_signal
);
1759 wait_for_inferior (0);
1761 while (tp
->stop_signal
!= TARGET_SIGNAL_TRAP
);
1762 inf
->stop_soon
= NO_STOP_QUIETLY
;
1763 #endif /* defined(_SCO_DS) */
1767 svr4_clear_solib (void)
1769 struct svr4_info
*info
;
1771 info
= get_svr4_info ();
1772 info
->debug_base
= 0;
1773 info
->debug_loader_offset_p
= 0;
1774 info
->debug_loader_offset
= 0;
1775 xfree (info
->debug_loader_name
);
1776 info
->debug_loader_name
= NULL
;
1780 svr4_free_so (struct so_list
*so
)
1782 xfree (so
->lm_info
->lm
);
1783 xfree (so
->lm_info
);
1787 /* Clear any bits of ADDR that wouldn't fit in a target-format
1788 data pointer. "Data pointer" here refers to whatever sort of
1789 address the dynamic linker uses to manage its sections. At the
1790 moment, we don't support shared libraries on any processors where
1791 code and data pointers are different sizes.
1793 This isn't really the right solution. What we really need here is
1794 a way to do arithmetic on CORE_ADDR values that respects the
1795 natural pointer/address correspondence. (For example, on the MIPS,
1796 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1797 sign-extend the value. There, simply truncating the bits above
1798 gdbarch_ptr_bit, as we do below, is no good.) This should probably
1799 be a new gdbarch method or something. */
1801 svr4_truncate_ptr (CORE_ADDR addr
)
1803 if (gdbarch_ptr_bit (target_gdbarch
) == sizeof (CORE_ADDR
) * 8)
1804 /* We don't need to truncate anything, and the bit twiddling below
1805 will fail due to overflow problems. */
1808 return addr
& (((CORE_ADDR
) 1 << gdbarch_ptr_bit (target_gdbarch
)) - 1);
1813 svr4_relocate_section_addresses (struct so_list
*so
,
1814 struct target_section
*sec
)
1816 sec
->addr
= svr4_truncate_ptr (sec
->addr
+ LM_ADDR_CHECK (so
,
1818 sec
->endaddr
= svr4_truncate_ptr (sec
->endaddr
+ LM_ADDR_CHECK (so
,
1823 /* Architecture-specific operations. */
1825 /* Per-architecture data key. */
1826 static struct gdbarch_data
*solib_svr4_data
;
1828 struct solib_svr4_ops
1830 /* Return a description of the layout of `struct link_map'. */
1831 struct link_map_offsets
*(*fetch_link_map_offsets
)(void);
1834 /* Return a default for the architecture-specific operations. */
1837 solib_svr4_init (struct obstack
*obstack
)
1839 struct solib_svr4_ops
*ops
;
1841 ops
= OBSTACK_ZALLOC (obstack
, struct solib_svr4_ops
);
1842 ops
->fetch_link_map_offsets
= NULL
;
1846 /* Set the architecture-specific `struct link_map_offsets' fetcher for
1847 GDBARCH to FLMO. Also, install SVR4 solib_ops into GDBARCH. */
1850 set_solib_svr4_fetch_link_map_offsets (struct gdbarch
*gdbarch
,
1851 struct link_map_offsets
*(*flmo
) (void))
1853 struct solib_svr4_ops
*ops
= gdbarch_data (gdbarch
, solib_svr4_data
);
1855 ops
->fetch_link_map_offsets
= flmo
;
1857 set_solib_ops (gdbarch
, &svr4_so_ops
);
1860 /* Fetch a link_map_offsets structure using the architecture-specific
1861 `struct link_map_offsets' fetcher. */
1863 static struct link_map_offsets
*
1864 svr4_fetch_link_map_offsets (void)
1866 struct solib_svr4_ops
*ops
= gdbarch_data (target_gdbarch
, solib_svr4_data
);
1868 gdb_assert (ops
->fetch_link_map_offsets
);
1869 return ops
->fetch_link_map_offsets ();
1872 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1875 svr4_have_link_map_offsets (void)
1877 struct solib_svr4_ops
*ops
= gdbarch_data (target_gdbarch
, solib_svr4_data
);
1878 return (ops
->fetch_link_map_offsets
!= NULL
);
1882 /* Most OS'es that have SVR4-style ELF dynamic libraries define a
1883 `struct r_debug' and a `struct link_map' that are binary compatible
1884 with the origional SVR4 implementation. */
1886 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1887 for an ILP32 SVR4 system. */
1889 struct link_map_offsets
*
1890 svr4_ilp32_fetch_link_map_offsets (void)
1892 static struct link_map_offsets lmo
;
1893 static struct link_map_offsets
*lmp
= NULL
;
1899 lmo
.r_version_offset
= 0;
1900 lmo
.r_version_size
= 4;
1901 lmo
.r_map_offset
= 4;
1902 lmo
.r_brk_offset
= 8;
1903 lmo
.r_ldsomap_offset
= 20;
1905 /* Everything we need is in the first 20 bytes. */
1906 lmo
.link_map_size
= 20;
1907 lmo
.l_addr_offset
= 0;
1908 lmo
.l_name_offset
= 4;
1909 lmo
.l_ld_offset
= 8;
1910 lmo
.l_next_offset
= 12;
1911 lmo
.l_prev_offset
= 16;
1917 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1918 for an LP64 SVR4 system. */
1920 struct link_map_offsets
*
1921 svr4_lp64_fetch_link_map_offsets (void)
1923 static struct link_map_offsets lmo
;
1924 static struct link_map_offsets
*lmp
= NULL
;
1930 lmo
.r_version_offset
= 0;
1931 lmo
.r_version_size
= 4;
1932 lmo
.r_map_offset
= 8;
1933 lmo
.r_brk_offset
= 16;
1934 lmo
.r_ldsomap_offset
= 40;
1936 /* Everything we need is in the first 40 bytes. */
1937 lmo
.link_map_size
= 40;
1938 lmo
.l_addr_offset
= 0;
1939 lmo
.l_name_offset
= 8;
1940 lmo
.l_ld_offset
= 16;
1941 lmo
.l_next_offset
= 24;
1942 lmo
.l_prev_offset
= 32;
1949 struct target_so_ops svr4_so_ops
;
1951 /* Lookup global symbol for ELF DSOs linked with -Bsymbolic. Those DSOs have a
1952 different rule for symbol lookup. The lookup begins here in the DSO, not in
1953 the main executable. */
1955 static struct symbol
*
1956 elf_lookup_lib_symbol (const struct objfile
*objfile
,
1958 const char *linkage_name
,
1959 const domain_enum domain
)
1963 if (objfile
== symfile_objfile
)
1967 /* OBJFILE should have been passed as the non-debug one. */
1968 gdb_assert (objfile
->separate_debug_objfile_backlink
== NULL
);
1970 abfd
= objfile
->obfd
;
1973 if (abfd
== NULL
|| scan_dyntag (DT_SYMBOLIC
, abfd
, NULL
) != 1)
1976 return lookup_global_symbol_from_objfile
1977 (objfile
, name
, linkage_name
, domain
);
1980 extern initialize_file_ftype _initialize_svr4_solib
; /* -Wmissing-prototypes */
1983 _initialize_svr4_solib (void)
1985 solib_svr4_data
= gdbarch_data_register_pre_init (solib_svr4_init
);
1986 solib_svr4_pspace_data
1987 = register_program_space_data_with_cleanup (svr4_pspace_data_cleanup
);
1989 svr4_so_ops
.relocate_section_addresses
= svr4_relocate_section_addresses
;
1990 svr4_so_ops
.free_so
= svr4_free_so
;
1991 svr4_so_ops
.clear_solib
= svr4_clear_solib
;
1992 svr4_so_ops
.solib_create_inferior_hook
= svr4_solib_create_inferior_hook
;
1993 svr4_so_ops
.special_symbol_handling
= svr4_special_symbol_handling
;
1994 svr4_so_ops
.current_sos
= svr4_current_sos
;
1995 svr4_so_ops
.open_symbol_file_object
= open_symbol_file_object
;
1996 svr4_so_ops
.in_dynsym_resolve_code
= svr4_in_dynsym_resolve_code
;
1997 svr4_so_ops
.bfd_open
= solib_bfd_open
;
1998 svr4_so_ops
.lookup_lib_global_symbol
= elf_lookup_lib_symbol
;
1999 svr4_so_ops
.same
= svr4_same
;
2000 svr4_so_ops
.keep_data_in_core
= svr4_keep_data_in_core
;