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);
53 static void svr4_relocate_main_executable (void);
55 /* Link map info to include in an allocated so_list entry */
59 /* Pointer to copy of link map from inferior. The type is char *
60 rather than void *, so that we may use byte offsets to find the
61 various fields without the need for a cast. */
64 /* Amount by which addresses in the binary should be relocated to
65 match the inferior. This could most often be taken directly
66 from lm, but when prelinking is involved and the prelink base
67 address changes, we may need a different offset, we want to
68 warn about the difference and compute it only once. */
71 /* The target location of lm. */
75 /* On SVR4 systems, a list of symbols in the dynamic linker where
76 GDB can try to place a breakpoint to monitor shared library
79 If none of these symbols are found, or other errors occur, then
80 SVR4 systems will fall back to using a symbol as the "startup
81 mapping complete" breakpoint address. */
83 static char *solib_break_names
[] =
89 "__dl_rtld_db_dlactivity",
95 static char *bkpt_names
[] =
103 static char *main_name_list
[] =
109 /* Return non-zero if GDB_SO_NAME and INFERIOR_SO_NAME represent
110 the same shared library. */
113 svr4_same_1 (const char *gdb_so_name
, const char *inferior_so_name
)
115 if (strcmp (gdb_so_name
, inferior_so_name
) == 0)
118 /* On Solaris, when starting inferior we think that dynamic linker is
119 /usr/lib/ld.so.1, but later on, the table of loaded shared libraries
120 contains /lib/ld.so.1. Sometimes one file is a link to another, but
121 sometimes they have identical content, but are not linked to each
122 other. We don't restrict this check for Solaris, but the chances
123 of running into this situation elsewhere are very low. */
124 if (strcmp (gdb_so_name
, "/usr/lib/ld.so.1") == 0
125 && strcmp (inferior_so_name
, "/lib/ld.so.1") == 0)
128 /* Similarly, we observed the same issue with sparc64, but with
129 different locations. */
130 if (strcmp (gdb_so_name
, "/usr/lib/sparcv9/ld.so.1") == 0
131 && strcmp (inferior_so_name
, "/lib/sparcv9/ld.so.1") == 0)
138 svr4_same (struct so_list
*gdb
, struct so_list
*inferior
)
140 return (svr4_same_1 (gdb
->so_original_name
, inferior
->so_original_name
));
143 /* link map access functions */
146 LM_ADDR_FROM_LINK_MAP (struct so_list
*so
)
148 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
149 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
151 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_addr_offset
,
156 HAS_LM_DYNAMIC_FROM_LINK_MAP (void)
158 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
160 return lmo
->l_ld_offset
>= 0;
164 LM_DYNAMIC_FROM_LINK_MAP (struct so_list
*so
)
166 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
167 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
169 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_ld_offset
,
174 LM_ADDR_CHECK (struct so_list
*so
, bfd
*abfd
)
176 if (so
->lm_info
->l_addr
== (CORE_ADDR
)-1)
178 struct bfd_section
*dyninfo_sect
;
179 CORE_ADDR l_addr
, l_dynaddr
, dynaddr
, align
= 0x1000;
181 l_addr
= LM_ADDR_FROM_LINK_MAP (so
);
183 if (! abfd
|| ! HAS_LM_DYNAMIC_FROM_LINK_MAP ())
186 l_dynaddr
= LM_DYNAMIC_FROM_LINK_MAP (so
);
188 dyninfo_sect
= bfd_get_section_by_name (abfd
, ".dynamic");
189 if (dyninfo_sect
== NULL
)
192 dynaddr
= bfd_section_vma (abfd
, dyninfo_sect
);
194 if (dynaddr
+ l_addr
!= l_dynaddr
)
196 if (bfd_get_flavour (abfd
) == bfd_target_elf_flavour
)
198 Elf_Internal_Ehdr
*ehdr
= elf_tdata (abfd
)->elf_header
;
199 Elf_Internal_Phdr
*phdr
= elf_tdata (abfd
)->phdr
;
204 for (i
= 0; i
< ehdr
->e_phnum
; i
++)
205 if (phdr
[i
].p_type
== PT_LOAD
&& phdr
[i
].p_align
> align
)
206 align
= phdr
[i
].p_align
;
209 /* Turn it into a mask. */
212 /* If the changes match the alignment requirements, we
213 assume we're using a core file that was generated by the
214 same binary, just prelinked with a different base offset.
215 If it doesn't match, we may have a different binary, the
216 same binary with the dynamic table loaded at an unrelated
217 location, or anything, really. To avoid regressions,
218 don't adjust the base offset in the latter case, although
219 odds are that, if things really changed, debugging won't
222 One could expect more the condition
223 ((l_addr & align) == 0 && ((l_dynaddr - dynaddr) & align) == 0)
224 but the one below is relaxed for PPC. The PPC kernel supports
225 either 4k or 64k page sizes. To be prepared for 64k pages,
226 PPC ELF files are built using an alignment requirement of 64k.
227 However, when running on a kernel supporting 4k pages, the memory
228 mapping of the library may not actually happen on a 64k boundary!
230 (In the usual case where (l_addr & align) == 0, this check is
231 equivalent to the possibly expected check above.) */
233 if ((l_addr
& align
) == ((l_dynaddr
- dynaddr
) & align
))
235 l_addr
= l_dynaddr
- dynaddr
;
237 warning (_(".dynamic section for \"%s\" "
238 "is not at the expected address"), so
->so_name
);
239 warning (_("difference appears to be caused by prelink, "
240 "adjusting expectations"));
243 warning (_(".dynamic section for \"%s\" "
244 "is not at the expected address "
245 "(wrong library or version mismatch?)"), so
->so_name
);
249 so
->lm_info
->l_addr
= l_addr
;
252 return so
->lm_info
->l_addr
;
256 LM_NEXT (struct so_list
*so
)
258 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
259 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
261 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_next_offset
,
266 LM_NAME (struct so_list
*so
)
268 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
269 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
271 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_name_offset
,
276 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list
*so
)
278 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
279 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
281 /* Assume that everything is a library if the dynamic loader was loaded
282 late by a static executable. */
283 if (exec_bfd
&& bfd_get_section_by_name (exec_bfd
, ".dynamic") == NULL
)
286 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_prev_offset
,
290 /* Per pspace SVR4 specific data. */
294 CORE_ADDR debug_base
; /* Base of dynamic linker structures */
296 /* Validity flag for debug_loader_offset. */
297 int debug_loader_offset_p
;
299 /* Load address for the dynamic linker, inferred. */
300 CORE_ADDR debug_loader_offset
;
302 /* Name of the dynamic linker, valid if debug_loader_offset_p. */
303 char *debug_loader_name
;
305 /* Load map address for the main executable. */
306 CORE_ADDR main_lm_addr
;
308 CORE_ADDR interp_text_sect_low
;
309 CORE_ADDR interp_text_sect_high
;
310 CORE_ADDR interp_plt_sect_low
;
311 CORE_ADDR interp_plt_sect_high
;
314 /* Per-program-space data key. */
315 static const struct program_space_data
*solib_svr4_pspace_data
;
318 svr4_pspace_data_cleanup (struct program_space
*pspace
, void *arg
)
320 struct svr4_info
*info
;
322 info
= program_space_data (pspace
, solib_svr4_pspace_data
);
326 /* Get the current svr4 data. If none is found yet, add it now. This
327 function always returns a valid object. */
329 static struct svr4_info
*
332 struct svr4_info
*info
;
334 info
= program_space_data (current_program_space
, solib_svr4_pspace_data
);
338 info
= XZALLOC (struct svr4_info
);
339 set_program_space_data (current_program_space
, solib_svr4_pspace_data
, info
);
343 /* Local function prototypes */
345 static int match_main (char *);
347 static CORE_ADDR
bfd_lookup_symbol (bfd
*, char *);
353 bfd_lookup_symbol -- lookup the value for a specific symbol
357 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
361 An expensive way to lookup the value of a single symbol for
362 bfd's that are only temporary anyway. This is used by the
363 shared library support to find the address of the debugger
364 notification routine in the shared library.
366 The returned symbol may be in a code or data section; functions
367 will normally be in a code section, but may be in a data section
368 if this architecture uses function descriptors.
370 Note that 0 is specifically allowed as an error return (no
375 bfd_lookup_symbol (bfd
*abfd
, char *symname
)
379 asymbol
**symbol_table
;
380 unsigned int number_of_symbols
;
382 struct cleanup
*back_to
;
383 CORE_ADDR symaddr
= 0;
385 storage_needed
= bfd_get_symtab_upper_bound (abfd
);
387 if (storage_needed
> 0)
389 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
390 back_to
= make_cleanup (xfree
, symbol_table
);
391 number_of_symbols
= bfd_canonicalize_symtab (abfd
, symbol_table
);
393 for (i
= 0; i
< number_of_symbols
; i
++)
395 sym
= *symbol_table
++;
396 if (strcmp (sym
->name
, symname
) == 0
397 && (sym
->section
->flags
& (SEC_CODE
| SEC_DATA
)) != 0)
399 /* BFD symbols are section relative. */
400 symaddr
= sym
->value
+ sym
->section
->vma
;
404 do_cleanups (back_to
);
410 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
411 have to check the dynamic string table too. */
413 storage_needed
= bfd_get_dynamic_symtab_upper_bound (abfd
);
415 if (storage_needed
> 0)
417 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
418 back_to
= make_cleanup (xfree
, symbol_table
);
419 number_of_symbols
= bfd_canonicalize_dynamic_symtab (abfd
, symbol_table
);
421 for (i
= 0; i
< number_of_symbols
; i
++)
423 sym
= *symbol_table
++;
425 if (strcmp (sym
->name
, symname
) == 0
426 && (sym
->section
->flags
& (SEC_CODE
| SEC_DATA
)) != 0)
428 /* BFD symbols are section relative. */
429 symaddr
= sym
->value
+ sym
->section
->vma
;
433 do_cleanups (back_to
);
440 /* Read program header TYPE from inferior memory. The header is found
441 by scanning the OS auxillary vector.
443 Return a pointer to allocated memory holding the program header contents,
444 or NULL on failure. If sucessful, and unless P_SECT_SIZE is NULL, the
445 size of those contents is returned to P_SECT_SIZE. Likewise, the target
446 architecture size (32-bit or 64-bit) is returned to P_ARCH_SIZE. */
449 read_program_header (int type
, int *p_sect_size
, int *p_arch_size
)
451 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
452 CORE_ADDR at_phdr
, at_phent
, at_phnum
;
453 int arch_size
, sect_size
;
457 /* Get required auxv elements from target. */
458 if (target_auxv_search (¤t_target
, AT_PHDR
, &at_phdr
) <= 0)
460 if (target_auxv_search (¤t_target
, AT_PHENT
, &at_phent
) <= 0)
462 if (target_auxv_search (¤t_target
, AT_PHNUM
, &at_phnum
) <= 0)
464 if (!at_phdr
|| !at_phnum
)
467 /* Determine ELF architecture type. */
468 if (at_phent
== sizeof (Elf32_External_Phdr
))
470 else if (at_phent
== sizeof (Elf64_External_Phdr
))
475 /* Find .dynamic section via the PT_DYNAMIC PHDR. */
478 Elf32_External_Phdr phdr
;
481 /* Search for requested PHDR. */
482 for (i
= 0; i
< at_phnum
; i
++)
484 if (target_read_memory (at_phdr
+ i
* sizeof (phdr
),
485 (gdb_byte
*)&phdr
, sizeof (phdr
)))
488 if (extract_unsigned_integer ((gdb_byte
*)phdr
.p_type
,
489 4, byte_order
) == type
)
496 /* Retrieve address and size. */
497 sect_addr
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_vaddr
,
499 sect_size
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_memsz
,
504 Elf64_External_Phdr phdr
;
507 /* Search for requested PHDR. */
508 for (i
= 0; i
< at_phnum
; i
++)
510 if (target_read_memory (at_phdr
+ i
* sizeof (phdr
),
511 (gdb_byte
*)&phdr
, sizeof (phdr
)))
514 if (extract_unsigned_integer ((gdb_byte
*)phdr
.p_type
,
515 4, byte_order
) == type
)
522 /* Retrieve address and size. */
523 sect_addr
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_vaddr
,
525 sect_size
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_memsz
,
529 /* Read in requested program header. */
530 buf
= xmalloc (sect_size
);
531 if (target_read_memory (sect_addr
, buf
, sect_size
))
538 *p_arch_size
= arch_size
;
540 *p_sect_size
= sect_size
;
546 /* Return program interpreter string. */
548 find_program_interpreter (void)
550 gdb_byte
*buf
= NULL
;
552 /* If we have an exec_bfd, use its section table. */
554 && bfd_get_flavour (exec_bfd
) == bfd_target_elf_flavour
)
556 struct bfd_section
*interp_sect
;
558 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
559 if (interp_sect
!= NULL
)
561 CORE_ADDR sect_addr
= bfd_section_vma (exec_bfd
, interp_sect
);
562 int sect_size
= bfd_section_size (exec_bfd
, interp_sect
);
564 buf
= xmalloc (sect_size
);
565 bfd_get_section_contents (exec_bfd
, interp_sect
, buf
, 0, sect_size
);
569 /* If we didn't find it, use the target auxillary vector. */
571 buf
= read_program_header (PT_INTERP
, NULL
, NULL
);
577 /* Scan for DYNTAG in .dynamic section of ABFD. If DYNTAG is found 1 is
578 returned and the corresponding PTR is set. */
581 scan_dyntag (int dyntag
, bfd
*abfd
, CORE_ADDR
*ptr
)
583 int arch_size
, step
, sect_size
;
585 CORE_ADDR dyn_ptr
, dyn_addr
;
586 gdb_byte
*bufend
, *bufstart
, *buf
;
587 Elf32_External_Dyn
*x_dynp_32
;
588 Elf64_External_Dyn
*x_dynp_64
;
589 struct bfd_section
*sect
;
590 struct target_section
*target_section
;
595 if (bfd_get_flavour (abfd
) != bfd_target_elf_flavour
)
598 arch_size
= bfd_get_arch_size (abfd
);
602 /* Find the start address of the .dynamic section. */
603 sect
= bfd_get_section_by_name (abfd
, ".dynamic");
607 for (target_section
= current_target_sections
->sections
;
608 target_section
< current_target_sections
->sections_end
;
610 if (sect
== target_section
->the_bfd_section
)
612 if (target_section
< current_target_sections
->sections_end
)
613 dyn_addr
= target_section
->addr
;
616 /* ABFD may come from OBJFILE acting only as a symbol file without being
617 loaded into the target (see add_symbol_file_command). This case is
618 such fallback to the file VMA address without the possibility of
619 having the section relocated to its actual in-memory address. */
621 dyn_addr
= bfd_section_vma (abfd
, sect
);
624 /* Read in .dynamic from the BFD. We will get the actual value
625 from memory later. */
626 sect_size
= bfd_section_size (abfd
, sect
);
627 buf
= bufstart
= alloca (sect_size
);
628 if (!bfd_get_section_contents (abfd
, sect
,
632 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
633 step
= (arch_size
== 32) ? sizeof (Elf32_External_Dyn
)
634 : sizeof (Elf64_External_Dyn
);
635 for (bufend
= buf
+ sect_size
;
641 x_dynp_32
= (Elf32_External_Dyn
*) buf
;
642 dyn_tag
= bfd_h_get_32 (abfd
, (bfd_byte
*) x_dynp_32
->d_tag
);
643 dyn_ptr
= bfd_h_get_32 (abfd
, (bfd_byte
*) x_dynp_32
->d_un
.d_ptr
);
647 x_dynp_64
= (Elf64_External_Dyn
*) buf
;
648 dyn_tag
= bfd_h_get_64 (abfd
, (bfd_byte
*) x_dynp_64
->d_tag
);
649 dyn_ptr
= bfd_h_get_64 (abfd
, (bfd_byte
*) x_dynp_64
->d_un
.d_ptr
);
651 if (dyn_tag
== DT_NULL
)
653 if (dyn_tag
== dyntag
)
655 /* If requested, try to read the runtime value of this .dynamic
659 struct type
*ptr_type
;
663 ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
664 ptr_addr
= dyn_addr
+ (buf
- bufstart
) + arch_size
/ 8;
665 if (target_read_memory (ptr_addr
, ptr_buf
, arch_size
/ 8) == 0)
666 dyn_ptr
= extract_typed_address (ptr_buf
, ptr_type
);
676 /* Scan for DYNTAG in .dynamic section of the target's main executable,
677 found by consulting the OS auxillary vector. If DYNTAG is found 1 is
678 returned and the corresponding PTR is set. */
681 scan_dyntag_auxv (int dyntag
, CORE_ADDR
*ptr
)
683 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
684 int sect_size
, arch_size
, step
;
687 gdb_byte
*bufend
, *bufstart
, *buf
;
689 /* Read in .dynamic section. */
690 buf
= bufstart
= read_program_header (PT_DYNAMIC
, §_size
, &arch_size
);
694 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
695 step
= (arch_size
== 32) ? sizeof (Elf32_External_Dyn
)
696 : sizeof (Elf64_External_Dyn
);
697 for (bufend
= buf
+ sect_size
;
703 Elf32_External_Dyn
*dynp
= (Elf32_External_Dyn
*) buf
;
704 dyn_tag
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_tag
,
706 dyn_ptr
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_un
.d_ptr
,
711 Elf64_External_Dyn
*dynp
= (Elf64_External_Dyn
*) buf
;
712 dyn_tag
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_tag
,
714 dyn_ptr
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_un
.d_ptr
,
717 if (dyn_tag
== DT_NULL
)
720 if (dyn_tag
== dyntag
)
739 elf_locate_base -- locate the base address of dynamic linker structs
740 for SVR4 elf targets.
744 CORE_ADDR elf_locate_base (void)
748 For SVR4 elf targets the address of the dynamic linker's runtime
749 structure is contained within the dynamic info section in the
750 executable file. The dynamic section is also mapped into the
751 inferior address space. Because the runtime loader fills in the
752 real address before starting the inferior, we have to read in the
753 dynamic info section from the inferior address space.
754 If there are any errors while trying to find the address, we
755 silently return 0, otherwise the found address is returned.
760 elf_locate_base (void)
762 struct minimal_symbol
*msymbol
;
765 /* Look for DT_MIPS_RLD_MAP first. MIPS executables use this
766 instead of DT_DEBUG, although they sometimes contain an unused
768 if (scan_dyntag (DT_MIPS_RLD_MAP
, exec_bfd
, &dyn_ptr
)
769 || scan_dyntag_auxv (DT_MIPS_RLD_MAP
, &dyn_ptr
))
771 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
773 int pbuf_size
= TYPE_LENGTH (ptr_type
);
774 pbuf
= alloca (pbuf_size
);
775 /* DT_MIPS_RLD_MAP contains a pointer to the address
776 of the dynamic link structure. */
777 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
779 return extract_typed_address (pbuf
, ptr_type
);
783 if (scan_dyntag (DT_DEBUG
, exec_bfd
, &dyn_ptr
)
784 || scan_dyntag_auxv (DT_DEBUG
, &dyn_ptr
))
787 /* This may be a static executable. Look for the symbol
788 conventionally named _r_debug, as a last resort. */
789 msymbol
= lookup_minimal_symbol ("_r_debug", NULL
, symfile_objfile
);
791 return SYMBOL_VALUE_ADDRESS (msymbol
);
793 /* DT_DEBUG entry not found. */
801 locate_base -- locate the base address of dynamic linker structs
805 CORE_ADDR locate_base (struct svr4_info *)
809 For both the SunOS and SVR4 shared library implementations, if the
810 inferior executable has been linked dynamically, there is a single
811 address somewhere in the inferior's data space which is the key to
812 locating all of the dynamic linker's runtime structures. This
813 address is the value of the debug base symbol. The job of this
814 function is to find and return that address, or to return 0 if there
815 is no such address (the executable is statically linked for example).
817 For SunOS, the job is almost trivial, since the dynamic linker and
818 all of it's structures are statically linked to the executable at
819 link time. Thus the symbol for the address we are looking for has
820 already been added to the minimal symbol table for the executable's
821 objfile at the time the symbol file's symbols were read, and all we
822 have to do is look it up there. Note that we explicitly do NOT want
823 to find the copies in the shared library.
825 The SVR4 version is a bit more complicated because the address
826 is contained somewhere in the dynamic info section. We have to go
827 to a lot more work to discover the address of the debug base symbol.
828 Because of this complexity, we cache the value we find and return that
829 value on subsequent invocations. Note there is no copy in the
830 executable symbol tables.
835 locate_base (struct svr4_info
*info
)
837 /* Check to see if we have a currently valid address, and if so, avoid
838 doing all this work again and just return the cached address. If
839 we have no cached address, try to locate it in the dynamic info
840 section for ELF executables. There's no point in doing any of this
841 though if we don't have some link map offsets to work with. */
843 if (info
->debug_base
== 0 && svr4_have_link_map_offsets ())
844 info
->debug_base
= elf_locate_base ();
845 return info
->debug_base
;
848 /* Find the first element in the inferior's dynamic link map, and
849 return its address in the inferior.
851 FIXME: Perhaps we should validate the info somehow, perhaps by
852 checking r_version for a known version number, or r_state for
856 solib_svr4_r_map (struct svr4_info
*info
)
858 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
859 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
861 return read_memory_typed_address (info
->debug_base
+ lmo
->r_map_offset
,
865 /* Find r_brk from the inferior's debug base. */
868 solib_svr4_r_brk (struct svr4_info
*info
)
870 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
871 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
873 return read_memory_typed_address (info
->debug_base
+ lmo
->r_brk_offset
,
877 /* Find the link map for the dynamic linker (if it is not in the
878 normal list of loaded shared objects). */
881 solib_svr4_r_ldsomap (struct svr4_info
*info
)
883 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
884 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
885 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
888 /* Check version, and return zero if `struct r_debug' doesn't have
889 the r_ldsomap member. */
891 = read_memory_unsigned_integer (info
->debug_base
+ lmo
->r_version_offset
,
892 lmo
->r_version_size
, byte_order
);
893 if (version
< 2 || lmo
->r_ldsomap_offset
== -1)
896 return read_memory_typed_address (info
->debug_base
+ lmo
->r_ldsomap_offset
,
900 /* On Solaris systems with some versions of the dynamic linker,
901 ld.so's l_name pointer points to the SONAME in the string table
902 rather than into writable memory. So that GDB can find shared
903 libraries when loading a core file generated by gcore, ensure that
904 memory areas containing the l_name string are saved in the core
908 svr4_keep_data_in_core (CORE_ADDR vaddr
, unsigned long size
)
910 struct svr4_info
*info
;
913 struct cleanup
*old_chain
;
914 struct link_map_offsets
*lmo
;
917 info
= get_svr4_info ();
919 info
->debug_base
= 0;
921 if (!info
->debug_base
)
924 ldsomap
= solib_svr4_r_ldsomap (info
);
928 lmo
= svr4_fetch_link_map_offsets ();
929 new = XZALLOC (struct so_list
);
930 old_chain
= make_cleanup (xfree
, new);
931 new->lm_info
= xmalloc (sizeof (struct lm_info
));
932 make_cleanup (xfree
, new->lm_info
);
933 new->lm_info
->l_addr
= (CORE_ADDR
)-1;
934 new->lm_info
->lm_addr
= ldsomap
;
935 new->lm_info
->lm
= xzalloc (lmo
->link_map_size
);
936 make_cleanup (xfree
, new->lm_info
->lm
);
937 read_memory (ldsomap
, new->lm_info
->lm
, lmo
->link_map_size
);
938 lm_name
= LM_NAME (new);
939 do_cleanups (old_chain
);
941 return (lm_name
>= vaddr
&& lm_name
< vaddr
+ size
);
948 open_symbol_file_object
952 void open_symbol_file_object (void *from_tty)
956 If no open symbol file, attempt to locate and open the main symbol
957 file. On SVR4 systems, this is the first link map entry. If its
958 name is here, we can open it. Useful when attaching to a process
959 without first loading its symbol file.
961 If FROM_TTYP dereferences to a non-zero integer, allow messages to
962 be printed. This parameter is a pointer rather than an int because
963 open_symbol_file_object() is called via catch_errors() and
964 catch_errors() requires a pointer argument. */
967 open_symbol_file_object (void *from_ttyp
)
969 CORE_ADDR lm
, l_name
;
972 int from_tty
= *(int *)from_ttyp
;
973 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
974 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
975 int l_name_size
= TYPE_LENGTH (ptr_type
);
976 gdb_byte
*l_name_buf
= xmalloc (l_name_size
);
977 struct cleanup
*cleanups
= make_cleanup (xfree
, l_name_buf
);
978 struct svr4_info
*info
= get_svr4_info ();
981 if (!query (_("Attempt to reload symbols from process? ")))
984 /* Always locate the debug struct, in case it has moved. */
985 info
->debug_base
= 0;
986 if (locate_base (info
) == 0)
987 return 0; /* failed somehow... */
989 /* First link map member should be the executable. */
990 lm
= solib_svr4_r_map (info
);
992 return 0; /* failed somehow... */
994 /* Read address of name from target memory to GDB. */
995 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, l_name_size
);
997 /* Convert the address to host format. */
998 l_name
= extract_typed_address (l_name_buf
, ptr_type
);
1000 /* Free l_name_buf. */
1001 do_cleanups (cleanups
);
1004 return 0; /* No filename. */
1006 /* Now fetch the filename from target memory. */
1007 target_read_string (l_name
, &filename
, SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
1008 make_cleanup (xfree
, filename
);
1012 warning (_("failed to read exec filename from attached file: %s"),
1013 safe_strerror (errcode
));
1017 /* Have a pathname: read the symbol file. */
1018 symbol_file_add_main (filename
, from_tty
);
1023 /* If no shared library information is available from the dynamic
1024 linker, build a fallback list from other sources. */
1026 static struct so_list
*
1027 svr4_default_sos (void)
1029 struct svr4_info
*info
= get_svr4_info ();
1031 struct so_list
*head
= NULL
;
1032 struct so_list
**link_ptr
= &head
;
1034 if (info
->debug_loader_offset_p
)
1036 struct so_list
*new = XZALLOC (struct so_list
);
1038 new->lm_info
= xmalloc (sizeof (struct lm_info
));
1040 /* Nothing will ever check the cached copy of the link
1041 map if we set l_addr. */
1042 new->lm_info
->l_addr
= info
->debug_loader_offset
;
1043 new->lm_info
->lm_addr
= 0;
1044 new->lm_info
->lm
= NULL
;
1046 strncpy (new->so_name
, info
->debug_loader_name
,
1047 SO_NAME_MAX_PATH_SIZE
- 1);
1048 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
1049 strcpy (new->so_original_name
, new->so_name
);
1052 link_ptr
= &new->next
;
1060 current_sos -- build a list of currently loaded shared objects
1064 struct so_list *current_sos ()
1068 Build a list of `struct so_list' objects describing the shared
1069 objects currently loaded in the inferior. This list does not
1070 include an entry for the main executable file.
1072 Note that we only gather information directly available from the
1073 inferior --- we don't examine any of the shared library files
1074 themselves. The declaration of `struct so_list' says which fields
1075 we provide values for. */
1077 static struct so_list
*
1078 svr4_current_sos (void)
1081 struct so_list
*head
= 0;
1082 struct so_list
**link_ptr
= &head
;
1083 CORE_ADDR ldsomap
= 0;
1084 struct svr4_info
*info
;
1086 info
= get_svr4_info ();
1088 /* Always locate the debug struct, in case it has moved. */
1089 info
->debug_base
= 0;
1092 /* If we can't find the dynamic linker's base structure, this
1093 must not be a dynamically linked executable. Hmm. */
1094 if (! info
->debug_base
)
1095 return svr4_default_sos ();
1097 /* Walk the inferior's link map list, and build our list of
1098 `struct so_list' nodes. */
1099 lm
= solib_svr4_r_map (info
);
1103 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
1104 struct so_list
*new = XZALLOC (struct so_list
);
1105 struct cleanup
*old_chain
= make_cleanup (xfree
, new);
1107 new->lm_info
= xmalloc (sizeof (struct lm_info
));
1108 make_cleanup (xfree
, new->lm_info
);
1110 new->lm_info
->l_addr
= (CORE_ADDR
)-1;
1111 new->lm_info
->lm_addr
= lm
;
1112 new->lm_info
->lm
= xzalloc (lmo
->link_map_size
);
1113 make_cleanup (xfree
, new->lm_info
->lm
);
1115 read_memory (lm
, new->lm_info
->lm
, lmo
->link_map_size
);
1119 /* For SVR4 versions, the first entry in the link map is for the
1120 inferior executable, so we must ignore it. For some versions of
1121 SVR4, it has no name. For others (Solaris 2.3 for example), it
1122 does have a name, so we can no longer use a missing name to
1123 decide when to ignore it. */
1124 if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap
== 0)
1126 info
->main_lm_addr
= new->lm_info
->lm_addr
;
1134 /* Extract this shared object's name. */
1135 target_read_string (LM_NAME (new), &buffer
,
1136 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
1138 warning (_("Can't read pathname for load map: %s."),
1139 safe_strerror (errcode
));
1142 strncpy (new->so_name
, buffer
, SO_NAME_MAX_PATH_SIZE
- 1);
1143 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
1144 strcpy (new->so_original_name
, new->so_name
);
1148 /* If this entry has no name, or its name matches the name
1149 for the main executable, don't include it in the list. */
1150 if (! new->so_name
[0]
1151 || match_main (new->so_name
))
1157 link_ptr
= &new->next
;
1161 /* On Solaris, the dynamic linker is not in the normal list of
1162 shared objects, so make sure we pick it up too. Having
1163 symbol information for the dynamic linker is quite crucial
1164 for skipping dynamic linker resolver code. */
1165 if (lm
== 0 && ldsomap
== 0)
1166 lm
= ldsomap
= solib_svr4_r_ldsomap (info
);
1168 discard_cleanups (old_chain
);
1172 return svr4_default_sos ();
1177 /* Get the address of the link_map for a given OBJFILE. */
1180 svr4_fetch_objfile_link_map (struct objfile
*objfile
)
1183 struct svr4_info
*info
= get_svr4_info ();
1185 /* Cause svr4_current_sos() to be run if it hasn't been already. */
1186 if (info
->main_lm_addr
== 0)
1187 solib_add (NULL
, 0, ¤t_target
, auto_solib_add
);
1189 /* svr4_current_sos() will set main_lm_addr for the main executable. */
1190 if (objfile
== symfile_objfile
)
1191 return info
->main_lm_addr
;
1193 /* The other link map addresses may be found by examining the list
1194 of shared libraries. */
1195 for (so
= master_so_list (); so
; so
= so
->next
)
1196 if (so
->objfile
== objfile
)
1197 return so
->lm_info
->lm_addr
;
1203 /* On some systems, the only way to recognize the link map entry for
1204 the main executable file is by looking at its name. Return
1205 non-zero iff SONAME matches one of the known main executable names. */
1208 match_main (char *soname
)
1212 for (mainp
= main_name_list
; *mainp
!= NULL
; mainp
++)
1214 if (strcmp (soname
, *mainp
) == 0)
1221 /* Return 1 if PC lies in the dynamic symbol resolution code of the
1222 SVR4 run time loader. */
1225 svr4_in_dynsym_resolve_code (CORE_ADDR pc
)
1227 struct svr4_info
*info
= get_svr4_info ();
1229 return ((pc
>= info
->interp_text_sect_low
1230 && pc
< info
->interp_text_sect_high
)
1231 || (pc
>= info
->interp_plt_sect_low
1232 && pc
< info
->interp_plt_sect_high
)
1233 || in_plt_section (pc
, NULL
));
1236 /* Given an executable's ABFD and target, compute the entry-point
1240 exec_entry_point (struct bfd
*abfd
, struct target_ops
*targ
)
1242 /* KevinB wrote ... for most targets, the address returned by
1243 bfd_get_start_address() is the entry point for the start
1244 function. But, for some targets, bfd_get_start_address() returns
1245 the address of a function descriptor from which the entry point
1246 address may be extracted. This address is extracted by
1247 gdbarch_convert_from_func_ptr_addr(). The method
1248 gdbarch_convert_from_func_ptr_addr() is the merely the identify
1249 function for targets which don't use function descriptors. */
1250 return gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1251 bfd_get_start_address (abfd
),
1259 enable_break -- arrange for dynamic linker to hit breakpoint
1263 int enable_break (void)
1267 Both the SunOS and the SVR4 dynamic linkers have, as part of their
1268 debugger interface, support for arranging for the inferior to hit
1269 a breakpoint after mapping in the shared libraries. This function
1270 enables that breakpoint.
1272 For SunOS, there is a special flag location (in_debugger) which we
1273 set to 1. When the dynamic linker sees this flag set, it will set
1274 a breakpoint at a location known only to itself, after saving the
1275 original contents of that place and the breakpoint address itself,
1276 in it's own internal structures. When we resume the inferior, it
1277 will eventually take a SIGTRAP when it runs into the breakpoint.
1278 We handle this (in a different place) by restoring the contents of
1279 the breakpointed location (which is only known after it stops),
1280 chasing around to locate the shared libraries that have been
1281 loaded, then resuming.
1283 For SVR4, the debugger interface structure contains a member (r_brk)
1284 which is statically initialized at the time the shared library is
1285 built, to the offset of a function (_r_debug_state) which is guaran-
1286 teed to be called once before mapping in a library, and again when
1287 the mapping is complete. At the time we are examining this member,
1288 it contains only the unrelocated offset of the function, so we have
1289 to do our own relocation. Later, when the dynamic linker actually
1290 runs, it relocates r_brk to be the actual address of _r_debug_state().
1292 The debugger interface structure also contains an enumeration which
1293 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
1294 depending upon whether or not the library is being mapped or unmapped,
1295 and then set to RT_CONSISTENT after the library is mapped/unmapped.
1299 enable_break (struct svr4_info
*info
, int from_tty
)
1301 struct minimal_symbol
*msymbol
;
1303 asection
*interp_sect
;
1304 gdb_byte
*interp_name
;
1307 /* First, remove all the solib event breakpoints. Their addresses
1308 may have changed since the last time we ran the program. */
1309 remove_solib_event_breakpoints ();
1311 info
->interp_text_sect_low
= info
->interp_text_sect_high
= 0;
1312 info
->interp_plt_sect_low
= info
->interp_plt_sect_high
= 0;
1314 /* If we already have a shared library list in the target, and
1315 r_debug contains r_brk, set the breakpoint there - this should
1316 mean r_brk has already been relocated. Assume the dynamic linker
1317 is the object containing r_brk. */
1319 solib_add (NULL
, from_tty
, ¤t_target
, auto_solib_add
);
1321 if (info
->debug_base
&& solib_svr4_r_map (info
) != 0)
1322 sym_addr
= solib_svr4_r_brk (info
);
1326 struct obj_section
*os
;
1328 sym_addr
= gdbarch_addr_bits_remove
1329 (target_gdbarch
, gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1333 /* On at least some versions of Solaris there's a dynamic relocation
1334 on _r_debug.r_brk and SYM_ADDR may not be relocated yet, e.g., if
1335 we get control before the dynamic linker has self-relocated.
1336 Check if SYM_ADDR is in a known section, if it is assume we can
1337 trust its value. This is just a heuristic though, it could go away
1338 or be replaced if it's getting in the way.
1340 On ARM we need to know whether the ISA of rtld_db_dlactivity (or
1341 however it's spelled in your particular system) is ARM or Thumb.
1342 That knowledge is encoded in the address, if it's Thumb the low bit
1343 is 1. However, we've stripped that info above and it's not clear
1344 what all the consequences are of passing a non-addr_bits_remove'd
1345 address to create_solib_event_breakpoint. The call to
1346 find_pc_section verifies we know about the address and have some
1347 hope of computing the right kind of breakpoint to use (via
1348 symbol info). It does mean that GDB needs to be pointed at a
1349 non-stripped version of the dynamic linker in order to obtain
1350 information it already knows about. Sigh. */
1352 os
= find_pc_section (sym_addr
);
1355 /* Record the relocated start and end address of the dynamic linker
1356 text and plt section for svr4_in_dynsym_resolve_code. */
1358 CORE_ADDR load_addr
;
1360 tmp_bfd
= os
->objfile
->obfd
;
1361 load_addr
= ANOFFSET (os
->objfile
->section_offsets
,
1362 os
->objfile
->sect_index_text
);
1364 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
1367 info
->interp_text_sect_low
=
1368 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1369 info
->interp_text_sect_high
=
1370 info
->interp_text_sect_low
1371 + bfd_section_size (tmp_bfd
, interp_sect
);
1373 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
1376 info
->interp_plt_sect_low
=
1377 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1378 info
->interp_plt_sect_high
=
1379 info
->interp_plt_sect_low
1380 + bfd_section_size (tmp_bfd
, interp_sect
);
1383 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1388 /* Find the program interpreter; if not found, warn the user and drop
1389 into the old breakpoint at symbol code. */
1390 interp_name
= find_program_interpreter ();
1393 CORE_ADDR load_addr
= 0;
1394 int load_addr_found
= 0;
1395 int loader_found_in_list
= 0;
1397 bfd
*tmp_bfd
= NULL
;
1398 struct target_ops
*tmp_bfd_target
;
1399 volatile struct gdb_exception ex
;
1403 /* Now we need to figure out where the dynamic linker was
1404 loaded so that we can load its symbols and place a breakpoint
1405 in the dynamic linker itself.
1407 This address is stored on the stack. However, I've been unable
1408 to find any magic formula to find it for Solaris (appears to
1409 be trivial on GNU/Linux). Therefore, we have to try an alternate
1410 mechanism to find the dynamic linker's base address. */
1412 TRY_CATCH (ex
, RETURN_MASK_ALL
)
1414 tmp_bfd
= solib_bfd_open (interp_name
);
1416 if (tmp_bfd
== NULL
)
1417 goto bkpt_at_symbol
;
1419 /* Now convert the TMP_BFD into a target. That way target, as
1420 well as BFD operations can be used. Note that closing the
1421 target will also close the underlying bfd. */
1422 tmp_bfd_target
= target_bfd_reopen (tmp_bfd
);
1424 /* On a running target, we can get the dynamic linker's base
1425 address from the shared library table. */
1426 so
= master_so_list ();
1429 if (svr4_same_1 (interp_name
, so
->so_original_name
))
1431 load_addr_found
= 1;
1432 loader_found_in_list
= 1;
1433 load_addr
= LM_ADDR_CHECK (so
, tmp_bfd
);
1439 /* If we were not able to find the base address of the loader
1440 from our so_list, then try using the AT_BASE auxilliary entry. */
1441 if (!load_addr_found
)
1442 if (target_auxv_search (¤t_target
, AT_BASE
, &load_addr
) > 0)
1443 load_addr_found
= 1;
1445 /* Otherwise we find the dynamic linker's base address by examining
1446 the current pc (which should point at the entry point for the
1447 dynamic linker) and subtracting the offset of the entry point.
1449 This is more fragile than the previous approaches, but is a good
1450 fallback method because it has actually been working well in
1452 if (!load_addr_found
)
1454 struct regcache
*regcache
1455 = get_thread_arch_regcache (inferior_ptid
, target_gdbarch
);
1456 load_addr
= (regcache_read_pc (regcache
)
1457 - exec_entry_point (tmp_bfd
, tmp_bfd_target
));
1460 if (!loader_found_in_list
)
1462 info
->debug_loader_name
= xstrdup (interp_name
);
1463 info
->debug_loader_offset_p
= 1;
1464 info
->debug_loader_offset
= load_addr
;
1465 solib_add (NULL
, from_tty
, ¤t_target
, auto_solib_add
);
1468 /* Record the relocated start and end address of the dynamic linker
1469 text and plt section for svr4_in_dynsym_resolve_code. */
1470 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
1473 info
->interp_text_sect_low
=
1474 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1475 info
->interp_text_sect_high
=
1476 info
->interp_text_sect_low
1477 + bfd_section_size (tmp_bfd
, interp_sect
);
1479 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
1482 info
->interp_plt_sect_low
=
1483 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1484 info
->interp_plt_sect_high
=
1485 info
->interp_plt_sect_low
1486 + bfd_section_size (tmp_bfd
, interp_sect
);
1489 /* Now try to set a breakpoint in the dynamic linker. */
1490 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1492 sym_addr
= bfd_lookup_symbol (tmp_bfd
, *bkpt_namep
);
1498 /* Convert 'sym_addr' from a function pointer to an address.
1499 Because we pass tmp_bfd_target instead of the current
1500 target, this will always produce an unrelocated value. */
1501 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1505 /* We're done with both the temporary bfd and target. Remember,
1506 closing the target closes the underlying bfd. */
1507 target_close (tmp_bfd_target
, 0);
1511 create_solib_event_breakpoint (target_gdbarch
, load_addr
+ sym_addr
);
1512 xfree (interp_name
);
1516 /* For whatever reason we couldn't set a breakpoint in the dynamic
1517 linker. Warn and drop into the old code. */
1519 xfree (interp_name
);
1520 warning (_("Unable to find dynamic linker breakpoint function.\n"
1521 "GDB will be unable to debug shared library initializers\n"
1522 "and track explicitly loaded dynamic code."));
1525 /* Scan through the lists of symbols, trying to look up the symbol and
1526 set a breakpoint there. Terminate loop when we/if we succeed. */
1528 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1530 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
1531 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
1533 sym_addr
= SYMBOL_VALUE_ADDRESS (msymbol
);
1534 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1537 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1542 for (bkpt_namep
= bkpt_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1544 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
1545 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
1547 sym_addr
= SYMBOL_VALUE_ADDRESS (msymbol
);
1548 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1551 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1562 special_symbol_handling -- additional shared library symbol handling
1566 void special_symbol_handling ()
1570 Once the symbols from a shared object have been loaded in the usual
1571 way, we are called to do any system specific symbol handling that
1574 For SunOS4, this consisted of grunging around in the dynamic
1575 linkers structures to find symbol definitions for "common" symbols
1576 and adding them to the minimal symbol table for the runtime common
1579 However, for SVR4, there's nothing to do.
1584 svr4_special_symbol_handling (void)
1586 svr4_relocate_main_executable ();
1589 /* Decide if the objfile needs to be relocated. As indicated above,
1590 we will only be here when execution is stopped at the beginning
1591 of the program. Relocation is necessary if the address at which
1592 we are presently stopped differs from the start address stored in
1593 the executable AND there's no interpreter section. The condition
1594 regarding the interpreter section is very important because if
1595 there *is* an interpreter section, execution will begin there
1596 instead. When there is an interpreter section, the start address
1597 is (presumably) used by the interpreter at some point to start
1598 execution of the program.
1600 If there is an interpreter, it is normal for it to be set to an
1601 arbitrary address at the outset. The job of finding it is
1602 handled in enable_break().
1604 So, to summarize, relocations are necessary when there is no
1605 interpreter section and the start address obtained from the
1606 executable is different from the address at which GDB is
1609 [ The astute reader will note that we also test to make sure that
1610 the executable in question has the DYNAMIC flag set. It is my
1611 opinion that this test is unnecessary (undesirable even). It
1612 was added to avoid inadvertent relocation of an executable
1613 whose e_type member in the ELF header is not ET_DYN. There may
1614 be a time in the future when it is desirable to do relocations
1615 on other types of files as well in which case this condition
1616 should either be removed or modified to accomodate the new file
1617 type. (E.g, an ET_EXEC executable which has been built to be
1618 position-independent could safely be relocated by the OS if
1619 desired. It is true that this violates the ABI, but the ABI
1620 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1624 svr4_static_exec_displacement (void)
1626 asection
*interp_sect
;
1627 struct regcache
*regcache
1628 = get_thread_arch_regcache (inferior_ptid
, target_gdbarch
);
1629 CORE_ADDR pc
= regcache_read_pc (regcache
);
1631 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
1632 if (interp_sect
== NULL
1633 && (bfd_get_file_flags (exec_bfd
) & DYNAMIC
) != 0
1634 && (exec_entry_point (exec_bfd
, &exec_ops
) != pc
))
1635 return pc
- exec_entry_point (exec_bfd
, &exec_ops
);
1640 /* We relocate all of the sections by the same amount. This
1641 behavior is mandated by recent editions of the System V ABI.
1642 According to the System V Application Binary Interface,
1643 Edition 4.1, page 5-5:
1645 ... Though the system chooses virtual addresses for
1646 individual processes, it maintains the segments' relative
1647 positions. Because position-independent code uses relative
1648 addressesing between segments, the difference between
1649 virtual addresses in memory must match the difference
1650 between virtual addresses in the file. The difference
1651 between the virtual address of any segment in memory and
1652 the corresponding virtual address in the file is thus a
1653 single constant value for any one executable or shared
1654 object in a given process. This difference is the base
1655 address. One use of the base address is to relocate the
1656 memory image of the program during dynamic linking.
1658 The same language also appears in Edition 4.0 of the System V
1659 ABI and is left unspecified in some of the earlier editions. */
1662 svr4_exec_displacement (void)
1665 /* ENTRY_POINT is a possible function descriptor - before
1666 a call to gdbarch_convert_from_func_ptr_addr. */
1667 CORE_ADDR entry_point
;
1669 if (exec_bfd
== NULL
)
1672 if (target_auxv_search (¤t_target
, AT_ENTRY
, &entry_point
) == 1)
1673 return entry_point
- bfd_get_start_address (exec_bfd
);
1675 return svr4_static_exec_displacement ();
1678 /* Relocate the main executable. This function should be called upon
1679 stopping the inferior process at the entry point to the program.
1680 The entry point from BFD is compared to the AT_ENTRY of AUXV and if they are
1681 different, the main executable is relocated by the proper amount. */
1684 svr4_relocate_main_executable (void)
1686 CORE_ADDR displacement
= svr4_exec_displacement ();
1688 /* Even if DISPLACEMENT is 0 still try to relocate it as this is a new
1689 difference of in-memory vs. in-file addresses and we could already
1690 relocate the executable at this function to improper address before. */
1692 if (symfile_objfile
)
1694 struct section_offsets
*new_offsets
;
1697 new_offsets
= alloca (symfile_objfile
->num_sections
1698 * sizeof (*new_offsets
));
1700 for (i
= 0; i
< symfile_objfile
->num_sections
; i
++)
1701 new_offsets
->offsets
[i
] = displacement
;
1703 objfile_relocate (symfile_objfile
, new_offsets
);
1709 for (asect
= exec_bfd
->sections
; asect
!= NULL
; asect
= asect
->next
)
1710 exec_set_section_address (bfd_get_filename (exec_bfd
), asect
->index
,
1711 (bfd_section_vma (exec_bfd
, asect
)
1720 svr4_solib_create_inferior_hook -- shared library startup support
1724 void svr4_solib_create_inferior_hook (int from_tty)
1728 When gdb starts up the inferior, it nurses it along (through the
1729 shell) until it is ready to execute it's first instruction. At this
1730 point, this function gets called via expansion of the macro
1731 SOLIB_CREATE_INFERIOR_HOOK.
1733 For SunOS executables, this first instruction is typically the
1734 one at "_start", or a similar text label, regardless of whether
1735 the executable is statically or dynamically linked. The runtime
1736 startup code takes care of dynamically linking in any shared
1737 libraries, once gdb allows the inferior to continue.
1739 For SVR4 executables, this first instruction is either the first
1740 instruction in the dynamic linker (for dynamically linked
1741 executables) or the instruction at "start" for statically linked
1742 executables. For dynamically linked executables, the system
1743 first exec's /lib/libc.so.N, which contains the dynamic linker,
1744 and starts it running. The dynamic linker maps in any needed
1745 shared libraries, maps in the actual user executable, and then
1746 jumps to "start" in the user executable.
1748 For both SunOS shared libraries, and SVR4 shared libraries, we
1749 can arrange to cooperate with the dynamic linker to discover the
1750 names of shared libraries that are dynamically linked, and the
1751 base addresses to which they are linked.
1753 This function is responsible for discovering those names and
1754 addresses, and saving sufficient information about them to allow
1755 their symbols to be read at a later time.
1759 Between enable_break() and disable_break(), this code does not
1760 properly handle hitting breakpoints which the user might have
1761 set in the startup code or in the dynamic linker itself. Proper
1762 handling will probably have to wait until the implementation is
1763 changed to use the "breakpoint handler function" method.
1765 Also, what if child has exit()ed? Must exit loop somehow.
1769 svr4_solib_create_inferior_hook (int from_tty
)
1771 struct inferior
*inf
;
1772 struct thread_info
*tp
;
1773 struct svr4_info
*info
;
1775 info
= get_svr4_info ();
1777 /* Relocate the main executable if necessary. */
1778 if (current_inferior ()->attach_flag
== 0)
1779 svr4_relocate_main_executable ();
1781 if (!svr4_have_link_map_offsets ())
1784 if (!enable_break (info
, from_tty
))
1787 #if defined(_SCO_DS)
1788 /* SCO needs the loop below, other systems should be using the
1789 special shared library breakpoints and the shared library breakpoint
1792 Now run the target. It will eventually hit the breakpoint, at
1793 which point all of the libraries will have been mapped in and we
1794 can go groveling around in the dynamic linker structures to find
1795 out what we need to know about them. */
1797 inf
= current_inferior ();
1798 tp
= inferior_thread ();
1800 clear_proceed_status ();
1801 inf
->stop_soon
= STOP_QUIETLY
;
1802 tp
->stop_signal
= TARGET_SIGNAL_0
;
1805 target_resume (pid_to_ptid (-1), 0, tp
->stop_signal
);
1806 wait_for_inferior (0);
1808 while (tp
->stop_signal
!= TARGET_SIGNAL_TRAP
);
1809 inf
->stop_soon
= NO_STOP_QUIETLY
;
1810 #endif /* defined(_SCO_DS) */
1814 svr4_clear_solib (void)
1816 struct svr4_info
*info
;
1818 info
= get_svr4_info ();
1819 info
->debug_base
= 0;
1820 info
->debug_loader_offset_p
= 0;
1821 info
->debug_loader_offset
= 0;
1822 xfree (info
->debug_loader_name
);
1823 info
->debug_loader_name
= NULL
;
1827 svr4_free_so (struct so_list
*so
)
1829 xfree (so
->lm_info
->lm
);
1830 xfree (so
->lm_info
);
1834 /* Clear any bits of ADDR that wouldn't fit in a target-format
1835 data pointer. "Data pointer" here refers to whatever sort of
1836 address the dynamic linker uses to manage its sections. At the
1837 moment, we don't support shared libraries on any processors where
1838 code and data pointers are different sizes.
1840 This isn't really the right solution. What we really need here is
1841 a way to do arithmetic on CORE_ADDR values that respects the
1842 natural pointer/address correspondence. (For example, on the MIPS,
1843 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1844 sign-extend the value. There, simply truncating the bits above
1845 gdbarch_ptr_bit, as we do below, is no good.) This should probably
1846 be a new gdbarch method or something. */
1848 svr4_truncate_ptr (CORE_ADDR addr
)
1850 if (gdbarch_ptr_bit (target_gdbarch
) == sizeof (CORE_ADDR
) * 8)
1851 /* We don't need to truncate anything, and the bit twiddling below
1852 will fail due to overflow problems. */
1855 return addr
& (((CORE_ADDR
) 1 << gdbarch_ptr_bit (target_gdbarch
)) - 1);
1860 svr4_relocate_section_addresses (struct so_list
*so
,
1861 struct target_section
*sec
)
1863 sec
->addr
= svr4_truncate_ptr (sec
->addr
+ LM_ADDR_CHECK (so
,
1865 sec
->endaddr
= svr4_truncate_ptr (sec
->endaddr
+ LM_ADDR_CHECK (so
,
1870 /* Architecture-specific operations. */
1872 /* Per-architecture data key. */
1873 static struct gdbarch_data
*solib_svr4_data
;
1875 struct solib_svr4_ops
1877 /* Return a description of the layout of `struct link_map'. */
1878 struct link_map_offsets
*(*fetch_link_map_offsets
)(void);
1881 /* Return a default for the architecture-specific operations. */
1884 solib_svr4_init (struct obstack
*obstack
)
1886 struct solib_svr4_ops
*ops
;
1888 ops
= OBSTACK_ZALLOC (obstack
, struct solib_svr4_ops
);
1889 ops
->fetch_link_map_offsets
= NULL
;
1893 /* Set the architecture-specific `struct link_map_offsets' fetcher for
1894 GDBARCH to FLMO. Also, install SVR4 solib_ops into GDBARCH. */
1897 set_solib_svr4_fetch_link_map_offsets (struct gdbarch
*gdbarch
,
1898 struct link_map_offsets
*(*flmo
) (void))
1900 struct solib_svr4_ops
*ops
= gdbarch_data (gdbarch
, solib_svr4_data
);
1902 ops
->fetch_link_map_offsets
= flmo
;
1904 set_solib_ops (gdbarch
, &svr4_so_ops
);
1907 /* Fetch a link_map_offsets structure using the architecture-specific
1908 `struct link_map_offsets' fetcher. */
1910 static struct link_map_offsets
*
1911 svr4_fetch_link_map_offsets (void)
1913 struct solib_svr4_ops
*ops
= gdbarch_data (target_gdbarch
, solib_svr4_data
);
1915 gdb_assert (ops
->fetch_link_map_offsets
);
1916 return ops
->fetch_link_map_offsets ();
1919 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1922 svr4_have_link_map_offsets (void)
1924 struct solib_svr4_ops
*ops
= gdbarch_data (target_gdbarch
, solib_svr4_data
);
1925 return (ops
->fetch_link_map_offsets
!= NULL
);
1929 /* Most OS'es that have SVR4-style ELF dynamic libraries define a
1930 `struct r_debug' and a `struct link_map' that are binary compatible
1931 with the origional SVR4 implementation. */
1933 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1934 for an ILP32 SVR4 system. */
1936 struct link_map_offsets
*
1937 svr4_ilp32_fetch_link_map_offsets (void)
1939 static struct link_map_offsets lmo
;
1940 static struct link_map_offsets
*lmp
= NULL
;
1946 lmo
.r_version_offset
= 0;
1947 lmo
.r_version_size
= 4;
1948 lmo
.r_map_offset
= 4;
1949 lmo
.r_brk_offset
= 8;
1950 lmo
.r_ldsomap_offset
= 20;
1952 /* Everything we need is in the first 20 bytes. */
1953 lmo
.link_map_size
= 20;
1954 lmo
.l_addr_offset
= 0;
1955 lmo
.l_name_offset
= 4;
1956 lmo
.l_ld_offset
= 8;
1957 lmo
.l_next_offset
= 12;
1958 lmo
.l_prev_offset
= 16;
1964 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1965 for an LP64 SVR4 system. */
1967 struct link_map_offsets
*
1968 svr4_lp64_fetch_link_map_offsets (void)
1970 static struct link_map_offsets lmo
;
1971 static struct link_map_offsets
*lmp
= NULL
;
1977 lmo
.r_version_offset
= 0;
1978 lmo
.r_version_size
= 4;
1979 lmo
.r_map_offset
= 8;
1980 lmo
.r_brk_offset
= 16;
1981 lmo
.r_ldsomap_offset
= 40;
1983 /* Everything we need is in the first 40 bytes. */
1984 lmo
.link_map_size
= 40;
1985 lmo
.l_addr_offset
= 0;
1986 lmo
.l_name_offset
= 8;
1987 lmo
.l_ld_offset
= 16;
1988 lmo
.l_next_offset
= 24;
1989 lmo
.l_prev_offset
= 32;
1996 struct target_so_ops svr4_so_ops
;
1998 /* Lookup global symbol for ELF DSOs linked with -Bsymbolic. Those DSOs have a
1999 different rule for symbol lookup. The lookup begins here in the DSO, not in
2000 the main executable. */
2002 static struct symbol
*
2003 elf_lookup_lib_symbol (const struct objfile
*objfile
,
2005 const char *linkage_name
,
2006 const domain_enum domain
)
2010 if (objfile
== symfile_objfile
)
2014 /* OBJFILE should have been passed as the non-debug one. */
2015 gdb_assert (objfile
->separate_debug_objfile_backlink
== NULL
);
2017 abfd
= objfile
->obfd
;
2020 if (abfd
== NULL
|| scan_dyntag (DT_SYMBOLIC
, abfd
, NULL
) != 1)
2023 return lookup_global_symbol_from_objfile
2024 (objfile
, name
, linkage_name
, domain
);
2027 extern initialize_file_ftype _initialize_svr4_solib
; /* -Wmissing-prototypes */
2030 _initialize_svr4_solib (void)
2032 solib_svr4_data
= gdbarch_data_register_pre_init (solib_svr4_init
);
2033 solib_svr4_pspace_data
2034 = register_program_space_data_with_cleanup (svr4_pspace_data_cleanup
);
2036 svr4_so_ops
.relocate_section_addresses
= svr4_relocate_section_addresses
;
2037 svr4_so_ops
.free_so
= svr4_free_so
;
2038 svr4_so_ops
.clear_solib
= svr4_clear_solib
;
2039 svr4_so_ops
.solib_create_inferior_hook
= svr4_solib_create_inferior_hook
;
2040 svr4_so_ops
.special_symbol_handling
= svr4_special_symbol_handling
;
2041 svr4_so_ops
.current_sos
= svr4_current_sos
;
2042 svr4_so_ops
.open_symbol_file_object
= open_symbol_file_object
;
2043 svr4_so_ops
.in_dynsym_resolve_code
= svr4_in_dynsym_resolve_code
;
2044 svr4_so_ops
.bfd_open
= solib_bfd_open
;
2045 svr4_so_ops
.lookup_lib_global_symbol
= elf_lookup_lib_symbol
;
2046 svr4_so_ops
.same
= svr4_same
;
2047 svr4_so_ops
.keep_data_in_core
= svr4_keep_data_in_core
;