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
;
239 warning (_(".dynamic section for \"%s\" "
240 "is not at the expected address"), so
->so_name
);
241 warning (_("difference appears to be caused by prelink, "
242 "adjusting expectations"));
246 warning (_(".dynamic section for \"%s\" "
247 "is not at the expected address "
248 "(wrong library or version mismatch?)"), so
->so_name
);
252 so
->lm_info
->l_addr
= l_addr
;
255 return so
->lm_info
->l_addr
;
259 LM_NEXT (struct so_list
*so
)
261 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
262 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
264 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_next_offset
,
269 LM_NAME (struct so_list
*so
)
271 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
272 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
274 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_name_offset
,
279 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list
*so
)
281 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
282 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
284 /* Assume that everything is a library if the dynamic loader was loaded
285 late by a static executable. */
286 if (exec_bfd
&& bfd_get_section_by_name (exec_bfd
, ".dynamic") == NULL
)
289 return extract_typed_address (so
->lm_info
->lm
+ lmo
->l_prev_offset
,
293 /* Per pspace SVR4 specific data. */
297 CORE_ADDR debug_base
; /* Base of dynamic linker structures */
299 /* Validity flag for debug_loader_offset. */
300 int debug_loader_offset_p
;
302 /* Load address for the dynamic linker, inferred. */
303 CORE_ADDR debug_loader_offset
;
305 /* Name of the dynamic linker, valid if debug_loader_offset_p. */
306 char *debug_loader_name
;
308 /* Load map address for the main executable. */
309 CORE_ADDR main_lm_addr
;
311 CORE_ADDR interp_text_sect_low
;
312 CORE_ADDR interp_text_sect_high
;
313 CORE_ADDR interp_plt_sect_low
;
314 CORE_ADDR interp_plt_sect_high
;
317 /* Per-program-space data key. */
318 static const struct program_space_data
*solib_svr4_pspace_data
;
321 svr4_pspace_data_cleanup (struct program_space
*pspace
, void *arg
)
323 struct svr4_info
*info
;
325 info
= program_space_data (pspace
, solib_svr4_pspace_data
);
329 /* Get the current svr4 data. If none is found yet, add it now. This
330 function always returns a valid object. */
332 static struct svr4_info
*
335 struct svr4_info
*info
;
337 info
= program_space_data (current_program_space
, solib_svr4_pspace_data
);
341 info
= XZALLOC (struct svr4_info
);
342 set_program_space_data (current_program_space
, solib_svr4_pspace_data
, info
);
346 /* Local function prototypes */
348 static int match_main (char *);
350 static CORE_ADDR
bfd_lookup_symbol (bfd
*, char *);
356 bfd_lookup_symbol -- lookup the value for a specific symbol
360 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
364 An expensive way to lookup the value of a single symbol for
365 bfd's that are only temporary anyway. This is used by the
366 shared library support to find the address of the debugger
367 notification routine in the shared library.
369 The returned symbol may be in a code or data section; functions
370 will normally be in a code section, but may be in a data section
371 if this architecture uses function descriptors.
373 Note that 0 is specifically allowed as an error return (no
378 bfd_lookup_symbol (bfd
*abfd
, char *symname
)
382 asymbol
**symbol_table
;
383 unsigned int number_of_symbols
;
385 struct cleanup
*back_to
;
386 CORE_ADDR symaddr
= 0;
388 storage_needed
= bfd_get_symtab_upper_bound (abfd
);
390 if (storage_needed
> 0)
392 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
393 back_to
= make_cleanup (xfree
, symbol_table
);
394 number_of_symbols
= bfd_canonicalize_symtab (abfd
, symbol_table
);
396 for (i
= 0; i
< number_of_symbols
; i
++)
398 sym
= *symbol_table
++;
399 if (strcmp (sym
->name
, symname
) == 0
400 && (sym
->section
->flags
& (SEC_CODE
| SEC_DATA
)) != 0)
402 /* BFD symbols are section relative. */
403 symaddr
= sym
->value
+ sym
->section
->vma
;
407 do_cleanups (back_to
);
413 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
414 have to check the dynamic string table too. */
416 storage_needed
= bfd_get_dynamic_symtab_upper_bound (abfd
);
418 if (storage_needed
> 0)
420 symbol_table
= (asymbol
**) xmalloc (storage_needed
);
421 back_to
= make_cleanup (xfree
, symbol_table
);
422 number_of_symbols
= bfd_canonicalize_dynamic_symtab (abfd
, symbol_table
);
424 for (i
= 0; i
< number_of_symbols
; i
++)
426 sym
= *symbol_table
++;
428 if (strcmp (sym
->name
, symname
) == 0
429 && (sym
->section
->flags
& (SEC_CODE
| SEC_DATA
)) != 0)
431 /* BFD symbols are section relative. */
432 symaddr
= sym
->value
+ sym
->section
->vma
;
436 do_cleanups (back_to
);
443 /* Read program header TYPE from inferior memory. The header is found
444 by scanning the OS auxillary vector.
446 Return a pointer to allocated memory holding the program header contents,
447 or NULL on failure. If sucessful, and unless P_SECT_SIZE is NULL, the
448 size of those contents is returned to P_SECT_SIZE. Likewise, the target
449 architecture size (32-bit or 64-bit) is returned to P_ARCH_SIZE. */
452 read_program_header (int type
, int *p_sect_size
, int *p_arch_size
)
454 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
455 CORE_ADDR at_phdr
, at_phent
, at_phnum
;
456 int arch_size
, sect_size
;
460 /* Get required auxv elements from target. */
461 if (target_auxv_search (¤t_target
, AT_PHDR
, &at_phdr
) <= 0)
463 if (target_auxv_search (¤t_target
, AT_PHENT
, &at_phent
) <= 0)
465 if (target_auxv_search (¤t_target
, AT_PHNUM
, &at_phnum
) <= 0)
467 if (!at_phdr
|| !at_phnum
)
470 /* Determine ELF architecture type. */
471 if (at_phent
== sizeof (Elf32_External_Phdr
))
473 else if (at_phent
== sizeof (Elf64_External_Phdr
))
478 /* Find .dynamic section via the PT_DYNAMIC PHDR. */
481 Elf32_External_Phdr phdr
;
484 /* Search for requested PHDR. */
485 for (i
= 0; i
< at_phnum
; i
++)
487 if (target_read_memory (at_phdr
+ i
* sizeof (phdr
),
488 (gdb_byte
*)&phdr
, sizeof (phdr
)))
491 if (extract_unsigned_integer ((gdb_byte
*)phdr
.p_type
,
492 4, byte_order
) == type
)
499 /* Retrieve address and size. */
500 sect_addr
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_vaddr
,
502 sect_size
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_memsz
,
507 Elf64_External_Phdr phdr
;
510 /* Search for requested PHDR. */
511 for (i
= 0; i
< at_phnum
; i
++)
513 if (target_read_memory (at_phdr
+ i
* sizeof (phdr
),
514 (gdb_byte
*)&phdr
, sizeof (phdr
)))
517 if (extract_unsigned_integer ((gdb_byte
*)phdr
.p_type
,
518 4, byte_order
) == type
)
525 /* Retrieve address and size. */
526 sect_addr
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_vaddr
,
528 sect_size
= extract_unsigned_integer ((gdb_byte
*)phdr
.p_memsz
,
532 /* Read in requested program header. */
533 buf
= xmalloc (sect_size
);
534 if (target_read_memory (sect_addr
, buf
, sect_size
))
541 *p_arch_size
= arch_size
;
543 *p_sect_size
= sect_size
;
549 /* Return program interpreter string. */
551 find_program_interpreter (void)
553 gdb_byte
*buf
= NULL
;
555 /* If we have an exec_bfd, use its section table. */
557 && bfd_get_flavour (exec_bfd
) == bfd_target_elf_flavour
)
559 struct bfd_section
*interp_sect
;
561 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
562 if (interp_sect
!= NULL
)
564 CORE_ADDR sect_addr
= bfd_section_vma (exec_bfd
, interp_sect
);
565 int sect_size
= bfd_section_size (exec_bfd
, interp_sect
);
567 buf
= xmalloc (sect_size
);
568 bfd_get_section_contents (exec_bfd
, interp_sect
, buf
, 0, sect_size
);
572 /* If we didn't find it, use the target auxillary vector. */
574 buf
= read_program_header (PT_INTERP
, NULL
, NULL
);
580 /* Scan for DYNTAG in .dynamic section of ABFD. If DYNTAG is found 1 is
581 returned and the corresponding PTR is set. */
584 scan_dyntag (int dyntag
, bfd
*abfd
, CORE_ADDR
*ptr
)
586 int arch_size
, step
, sect_size
;
588 CORE_ADDR dyn_ptr
, dyn_addr
;
589 gdb_byte
*bufend
, *bufstart
, *buf
;
590 Elf32_External_Dyn
*x_dynp_32
;
591 Elf64_External_Dyn
*x_dynp_64
;
592 struct bfd_section
*sect
;
593 struct target_section
*target_section
;
598 if (bfd_get_flavour (abfd
) != bfd_target_elf_flavour
)
601 arch_size
= bfd_get_arch_size (abfd
);
605 /* Find the start address of the .dynamic section. */
606 sect
= bfd_get_section_by_name (abfd
, ".dynamic");
610 for (target_section
= current_target_sections
->sections
;
611 target_section
< current_target_sections
->sections_end
;
613 if (sect
== target_section
->the_bfd_section
)
615 if (target_section
< current_target_sections
->sections_end
)
616 dyn_addr
= target_section
->addr
;
619 /* ABFD may come from OBJFILE acting only as a symbol file without being
620 loaded into the target (see add_symbol_file_command). This case is
621 such fallback to the file VMA address without the possibility of
622 having the section relocated to its actual in-memory address. */
624 dyn_addr
= bfd_section_vma (abfd
, sect
);
627 /* Read in .dynamic from the BFD. We will get the actual value
628 from memory later. */
629 sect_size
= bfd_section_size (abfd
, sect
);
630 buf
= bufstart
= alloca (sect_size
);
631 if (!bfd_get_section_contents (abfd
, sect
,
635 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
636 step
= (arch_size
== 32) ? sizeof (Elf32_External_Dyn
)
637 : sizeof (Elf64_External_Dyn
);
638 for (bufend
= buf
+ sect_size
;
644 x_dynp_32
= (Elf32_External_Dyn
*) buf
;
645 dyn_tag
= bfd_h_get_32 (abfd
, (bfd_byte
*) x_dynp_32
->d_tag
);
646 dyn_ptr
= bfd_h_get_32 (abfd
, (bfd_byte
*) x_dynp_32
->d_un
.d_ptr
);
650 x_dynp_64
= (Elf64_External_Dyn
*) buf
;
651 dyn_tag
= bfd_h_get_64 (abfd
, (bfd_byte
*) x_dynp_64
->d_tag
);
652 dyn_ptr
= bfd_h_get_64 (abfd
, (bfd_byte
*) x_dynp_64
->d_un
.d_ptr
);
654 if (dyn_tag
== DT_NULL
)
656 if (dyn_tag
== dyntag
)
658 /* If requested, try to read the runtime value of this .dynamic
662 struct type
*ptr_type
;
666 ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
667 ptr_addr
= dyn_addr
+ (buf
- bufstart
) + arch_size
/ 8;
668 if (target_read_memory (ptr_addr
, ptr_buf
, arch_size
/ 8) == 0)
669 dyn_ptr
= extract_typed_address (ptr_buf
, ptr_type
);
679 /* Scan for DYNTAG in .dynamic section of the target's main executable,
680 found by consulting the OS auxillary vector. If DYNTAG is found 1 is
681 returned and the corresponding PTR is set. */
684 scan_dyntag_auxv (int dyntag
, CORE_ADDR
*ptr
)
686 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
687 int sect_size
, arch_size
, step
;
690 gdb_byte
*bufend
, *bufstart
, *buf
;
692 /* Read in .dynamic section. */
693 buf
= bufstart
= read_program_header (PT_DYNAMIC
, §_size
, &arch_size
);
697 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
698 step
= (arch_size
== 32) ? sizeof (Elf32_External_Dyn
)
699 : sizeof (Elf64_External_Dyn
);
700 for (bufend
= buf
+ sect_size
;
706 Elf32_External_Dyn
*dynp
= (Elf32_External_Dyn
*) buf
;
707 dyn_tag
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_tag
,
709 dyn_ptr
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_un
.d_ptr
,
714 Elf64_External_Dyn
*dynp
= (Elf64_External_Dyn
*) buf
;
715 dyn_tag
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_tag
,
717 dyn_ptr
= extract_unsigned_integer ((gdb_byte
*) dynp
->d_un
.d_ptr
,
720 if (dyn_tag
== DT_NULL
)
723 if (dyn_tag
== dyntag
)
742 elf_locate_base -- locate the base address of dynamic linker structs
743 for SVR4 elf targets.
747 CORE_ADDR elf_locate_base (void)
751 For SVR4 elf targets the address of the dynamic linker's runtime
752 structure is contained within the dynamic info section in the
753 executable file. The dynamic section is also mapped into the
754 inferior address space. Because the runtime loader fills in the
755 real address before starting the inferior, we have to read in the
756 dynamic info section from the inferior address space.
757 If there are any errors while trying to find the address, we
758 silently return 0, otherwise the found address is returned.
763 elf_locate_base (void)
765 struct minimal_symbol
*msymbol
;
768 /* Look for DT_MIPS_RLD_MAP first. MIPS executables use this
769 instead of DT_DEBUG, although they sometimes contain an unused
771 if (scan_dyntag (DT_MIPS_RLD_MAP
, exec_bfd
, &dyn_ptr
)
772 || scan_dyntag_auxv (DT_MIPS_RLD_MAP
, &dyn_ptr
))
774 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
776 int pbuf_size
= TYPE_LENGTH (ptr_type
);
777 pbuf
= alloca (pbuf_size
);
778 /* DT_MIPS_RLD_MAP contains a pointer to the address
779 of the dynamic link structure. */
780 if (target_read_memory (dyn_ptr
, pbuf
, pbuf_size
))
782 return extract_typed_address (pbuf
, ptr_type
);
786 if (scan_dyntag (DT_DEBUG
, exec_bfd
, &dyn_ptr
)
787 || scan_dyntag_auxv (DT_DEBUG
, &dyn_ptr
))
790 /* This may be a static executable. Look for the symbol
791 conventionally named _r_debug, as a last resort. */
792 msymbol
= lookup_minimal_symbol ("_r_debug", NULL
, symfile_objfile
);
794 return SYMBOL_VALUE_ADDRESS (msymbol
);
796 /* DT_DEBUG entry not found. */
804 locate_base -- locate the base address of dynamic linker structs
808 CORE_ADDR locate_base (struct svr4_info *)
812 For both the SunOS and SVR4 shared library implementations, if the
813 inferior executable has been linked dynamically, there is a single
814 address somewhere in the inferior's data space which is the key to
815 locating all of the dynamic linker's runtime structures. This
816 address is the value of the debug base symbol. The job of this
817 function is to find and return that address, or to return 0 if there
818 is no such address (the executable is statically linked for example).
820 For SunOS, the job is almost trivial, since the dynamic linker and
821 all of it's structures are statically linked to the executable at
822 link time. Thus the symbol for the address we are looking for has
823 already been added to the minimal symbol table for the executable's
824 objfile at the time the symbol file's symbols were read, and all we
825 have to do is look it up there. Note that we explicitly do NOT want
826 to find the copies in the shared library.
828 The SVR4 version is a bit more complicated because the address
829 is contained somewhere in the dynamic info section. We have to go
830 to a lot more work to discover the address of the debug base symbol.
831 Because of this complexity, we cache the value we find and return that
832 value on subsequent invocations. Note there is no copy in the
833 executable symbol tables.
838 locate_base (struct svr4_info
*info
)
840 /* Check to see if we have a currently valid address, and if so, avoid
841 doing all this work again and just return the cached address. If
842 we have no cached address, try to locate it in the dynamic info
843 section for ELF executables. There's no point in doing any of this
844 though if we don't have some link map offsets to work with. */
846 if (info
->debug_base
== 0 && svr4_have_link_map_offsets ())
847 info
->debug_base
= elf_locate_base ();
848 return info
->debug_base
;
851 /* Find the first element in the inferior's dynamic link map, and
852 return its address in the inferior.
854 FIXME: Perhaps we should validate the info somehow, perhaps by
855 checking r_version for a known version number, or r_state for
859 solib_svr4_r_map (struct svr4_info
*info
)
861 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
862 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
864 return read_memory_typed_address (info
->debug_base
+ lmo
->r_map_offset
,
868 /* Find r_brk from the inferior's debug base. */
871 solib_svr4_r_brk (struct svr4_info
*info
)
873 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
874 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
876 return read_memory_typed_address (info
->debug_base
+ lmo
->r_brk_offset
,
880 /* Find the link map for the dynamic linker (if it is not in the
881 normal list of loaded shared objects). */
884 solib_svr4_r_ldsomap (struct svr4_info
*info
)
886 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
887 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
888 enum bfd_endian byte_order
= gdbarch_byte_order (target_gdbarch
);
891 /* Check version, and return zero if `struct r_debug' doesn't have
892 the r_ldsomap member. */
894 = read_memory_unsigned_integer (info
->debug_base
+ lmo
->r_version_offset
,
895 lmo
->r_version_size
, byte_order
);
896 if (version
< 2 || lmo
->r_ldsomap_offset
== -1)
899 return read_memory_typed_address (info
->debug_base
+ lmo
->r_ldsomap_offset
,
903 /* On Solaris systems with some versions of the dynamic linker,
904 ld.so's l_name pointer points to the SONAME in the string table
905 rather than into writable memory. So that GDB can find shared
906 libraries when loading a core file generated by gcore, ensure that
907 memory areas containing the l_name string are saved in the core
911 svr4_keep_data_in_core (CORE_ADDR vaddr
, unsigned long size
)
913 struct svr4_info
*info
;
916 struct cleanup
*old_chain
;
917 struct link_map_offsets
*lmo
;
920 info
= get_svr4_info ();
922 info
->debug_base
= 0;
924 if (!info
->debug_base
)
927 ldsomap
= solib_svr4_r_ldsomap (info
);
931 lmo
= svr4_fetch_link_map_offsets ();
932 new = XZALLOC (struct so_list
);
933 old_chain
= make_cleanup (xfree
, new);
934 new->lm_info
= xmalloc (sizeof (struct lm_info
));
935 make_cleanup (xfree
, new->lm_info
);
936 new->lm_info
->l_addr
= (CORE_ADDR
)-1;
937 new->lm_info
->lm_addr
= ldsomap
;
938 new->lm_info
->lm
= xzalloc (lmo
->link_map_size
);
939 make_cleanup (xfree
, new->lm_info
->lm
);
940 read_memory (ldsomap
, new->lm_info
->lm
, lmo
->link_map_size
);
941 lm_name
= LM_NAME (new);
942 do_cleanups (old_chain
);
944 return (lm_name
>= vaddr
&& lm_name
< vaddr
+ size
);
951 open_symbol_file_object
955 void open_symbol_file_object (void *from_tty)
959 If no open symbol file, attempt to locate and open the main symbol
960 file. On SVR4 systems, this is the first link map entry. If its
961 name is here, we can open it. Useful when attaching to a process
962 without first loading its symbol file.
964 If FROM_TTYP dereferences to a non-zero integer, allow messages to
965 be printed. This parameter is a pointer rather than an int because
966 open_symbol_file_object() is called via catch_errors() and
967 catch_errors() requires a pointer argument. */
970 open_symbol_file_object (void *from_ttyp
)
972 CORE_ADDR lm
, l_name
;
975 int from_tty
= *(int *)from_ttyp
;
976 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
977 struct type
*ptr_type
= builtin_type (target_gdbarch
)->builtin_data_ptr
;
978 int l_name_size
= TYPE_LENGTH (ptr_type
);
979 gdb_byte
*l_name_buf
= xmalloc (l_name_size
);
980 struct cleanup
*cleanups
= make_cleanup (xfree
, l_name_buf
);
981 struct svr4_info
*info
= get_svr4_info ();
984 if (!query (_("Attempt to reload symbols from process? ")))
987 /* Always locate the debug struct, in case it has moved. */
988 info
->debug_base
= 0;
989 if (locate_base (info
) == 0)
990 return 0; /* failed somehow... */
992 /* First link map member should be the executable. */
993 lm
= solib_svr4_r_map (info
);
995 return 0; /* failed somehow... */
997 /* Read address of name from target memory to GDB. */
998 read_memory (lm
+ lmo
->l_name_offset
, l_name_buf
, l_name_size
);
1000 /* Convert the address to host format. */
1001 l_name
= extract_typed_address (l_name_buf
, ptr_type
);
1003 /* Free l_name_buf. */
1004 do_cleanups (cleanups
);
1007 return 0; /* No filename. */
1009 /* Now fetch the filename from target memory. */
1010 target_read_string (l_name
, &filename
, SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
1011 make_cleanup (xfree
, filename
);
1015 warning (_("failed to read exec filename from attached file: %s"),
1016 safe_strerror (errcode
));
1020 /* Have a pathname: read the symbol file. */
1021 symbol_file_add_main (filename
, from_tty
);
1026 /* If no shared library information is available from the dynamic
1027 linker, build a fallback list from other sources. */
1029 static struct so_list
*
1030 svr4_default_sos (void)
1032 struct svr4_info
*info
= get_svr4_info ();
1034 struct so_list
*head
= NULL
;
1035 struct so_list
**link_ptr
= &head
;
1037 if (info
->debug_loader_offset_p
)
1039 struct so_list
*new = XZALLOC (struct so_list
);
1041 new->lm_info
= xmalloc (sizeof (struct lm_info
));
1043 /* Nothing will ever check the cached copy of the link
1044 map if we set l_addr. */
1045 new->lm_info
->l_addr
= info
->debug_loader_offset
;
1046 new->lm_info
->lm_addr
= 0;
1047 new->lm_info
->lm
= NULL
;
1049 strncpy (new->so_name
, info
->debug_loader_name
,
1050 SO_NAME_MAX_PATH_SIZE
- 1);
1051 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
1052 strcpy (new->so_original_name
, new->so_name
);
1055 link_ptr
= &new->next
;
1063 current_sos -- build a list of currently loaded shared objects
1067 struct so_list *current_sos ()
1071 Build a list of `struct so_list' objects describing the shared
1072 objects currently loaded in the inferior. This list does not
1073 include an entry for the main executable file.
1075 Note that we only gather information directly available from the
1076 inferior --- we don't examine any of the shared library files
1077 themselves. The declaration of `struct so_list' says which fields
1078 we provide values for. */
1080 static struct so_list
*
1081 svr4_current_sos (void)
1084 struct so_list
*head
= 0;
1085 struct so_list
**link_ptr
= &head
;
1086 CORE_ADDR ldsomap
= 0;
1087 struct svr4_info
*info
;
1089 info
= get_svr4_info ();
1091 /* Always locate the debug struct, in case it has moved. */
1092 info
->debug_base
= 0;
1095 /* If we can't find the dynamic linker's base structure, this
1096 must not be a dynamically linked executable. Hmm. */
1097 if (! info
->debug_base
)
1098 return svr4_default_sos ();
1100 /* Walk the inferior's link map list, and build our list of
1101 `struct so_list' nodes. */
1102 lm
= solib_svr4_r_map (info
);
1106 struct link_map_offsets
*lmo
= svr4_fetch_link_map_offsets ();
1107 struct so_list
*new = XZALLOC (struct so_list
);
1108 struct cleanup
*old_chain
= make_cleanup (xfree
, new);
1110 new->lm_info
= xmalloc (sizeof (struct lm_info
));
1111 make_cleanup (xfree
, new->lm_info
);
1113 new->lm_info
->l_addr
= (CORE_ADDR
)-1;
1114 new->lm_info
->lm_addr
= lm
;
1115 new->lm_info
->lm
= xzalloc (lmo
->link_map_size
);
1116 make_cleanup (xfree
, new->lm_info
->lm
);
1118 read_memory (lm
, new->lm_info
->lm
, lmo
->link_map_size
);
1122 /* For SVR4 versions, the first entry in the link map is for the
1123 inferior executable, so we must ignore it. For some versions of
1124 SVR4, it has no name. For others (Solaris 2.3 for example), it
1125 does have a name, so we can no longer use a missing name to
1126 decide when to ignore it. */
1127 if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap
== 0)
1129 info
->main_lm_addr
= new->lm_info
->lm_addr
;
1137 /* Extract this shared object's name. */
1138 target_read_string (LM_NAME (new), &buffer
,
1139 SO_NAME_MAX_PATH_SIZE
- 1, &errcode
);
1141 warning (_("Can't read pathname for load map: %s."),
1142 safe_strerror (errcode
));
1145 strncpy (new->so_name
, buffer
, SO_NAME_MAX_PATH_SIZE
- 1);
1146 new->so_name
[SO_NAME_MAX_PATH_SIZE
- 1] = '\0';
1147 strcpy (new->so_original_name
, new->so_name
);
1151 /* If this entry has no name, or its name matches the name
1152 for the main executable, don't include it in the list. */
1153 if (! new->so_name
[0]
1154 || match_main (new->so_name
))
1160 link_ptr
= &new->next
;
1164 /* On Solaris, the dynamic linker is not in the normal list of
1165 shared objects, so make sure we pick it up too. Having
1166 symbol information for the dynamic linker is quite crucial
1167 for skipping dynamic linker resolver code. */
1168 if (lm
== 0 && ldsomap
== 0)
1169 lm
= ldsomap
= solib_svr4_r_ldsomap (info
);
1171 discard_cleanups (old_chain
);
1175 return svr4_default_sos ();
1180 /* Get the address of the link_map for a given OBJFILE. */
1183 svr4_fetch_objfile_link_map (struct objfile
*objfile
)
1186 struct svr4_info
*info
= get_svr4_info ();
1188 /* Cause svr4_current_sos() to be run if it hasn't been already. */
1189 if (info
->main_lm_addr
== 0)
1190 solib_add (NULL
, 0, ¤t_target
, auto_solib_add
);
1192 /* svr4_current_sos() will set main_lm_addr for the main executable. */
1193 if (objfile
== symfile_objfile
)
1194 return info
->main_lm_addr
;
1196 /* The other link map addresses may be found by examining the list
1197 of shared libraries. */
1198 for (so
= master_so_list (); so
; so
= so
->next
)
1199 if (so
->objfile
== objfile
)
1200 return so
->lm_info
->lm_addr
;
1206 /* On some systems, the only way to recognize the link map entry for
1207 the main executable file is by looking at its name. Return
1208 non-zero iff SONAME matches one of the known main executable names. */
1211 match_main (char *soname
)
1215 for (mainp
= main_name_list
; *mainp
!= NULL
; mainp
++)
1217 if (strcmp (soname
, *mainp
) == 0)
1224 /* Return 1 if PC lies in the dynamic symbol resolution code of the
1225 SVR4 run time loader. */
1228 svr4_in_dynsym_resolve_code (CORE_ADDR pc
)
1230 struct svr4_info
*info
= get_svr4_info ();
1232 return ((pc
>= info
->interp_text_sect_low
1233 && pc
< info
->interp_text_sect_high
)
1234 || (pc
>= info
->interp_plt_sect_low
1235 && pc
< info
->interp_plt_sect_high
)
1236 || in_plt_section (pc
, NULL
));
1239 /* Given an executable's ABFD and target, compute the entry-point
1243 exec_entry_point (struct bfd
*abfd
, struct target_ops
*targ
)
1245 /* KevinB wrote ... for most targets, the address returned by
1246 bfd_get_start_address() is the entry point for the start
1247 function. But, for some targets, bfd_get_start_address() returns
1248 the address of a function descriptor from which the entry point
1249 address may be extracted. This address is extracted by
1250 gdbarch_convert_from_func_ptr_addr(). The method
1251 gdbarch_convert_from_func_ptr_addr() is the merely the identify
1252 function for targets which don't use function descriptors. */
1253 return gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1254 bfd_get_start_address (abfd
),
1262 enable_break -- arrange for dynamic linker to hit breakpoint
1266 int enable_break (void)
1270 Both the SunOS and the SVR4 dynamic linkers have, as part of their
1271 debugger interface, support for arranging for the inferior to hit
1272 a breakpoint after mapping in the shared libraries. This function
1273 enables that breakpoint.
1275 For SunOS, there is a special flag location (in_debugger) which we
1276 set to 1. When the dynamic linker sees this flag set, it will set
1277 a breakpoint at a location known only to itself, after saving the
1278 original contents of that place and the breakpoint address itself,
1279 in it's own internal structures. When we resume the inferior, it
1280 will eventually take a SIGTRAP when it runs into the breakpoint.
1281 We handle this (in a different place) by restoring the contents of
1282 the breakpointed location (which is only known after it stops),
1283 chasing around to locate the shared libraries that have been
1284 loaded, then resuming.
1286 For SVR4, the debugger interface structure contains a member (r_brk)
1287 which is statically initialized at the time the shared library is
1288 built, to the offset of a function (_r_debug_state) which is guaran-
1289 teed to be called once before mapping in a library, and again when
1290 the mapping is complete. At the time we are examining this member,
1291 it contains only the unrelocated offset of the function, so we have
1292 to do our own relocation. Later, when the dynamic linker actually
1293 runs, it relocates r_brk to be the actual address of _r_debug_state().
1295 The debugger interface structure also contains an enumeration which
1296 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
1297 depending upon whether or not the library is being mapped or unmapped,
1298 and then set to RT_CONSISTENT after the library is mapped/unmapped.
1302 enable_break (struct svr4_info
*info
, int from_tty
)
1304 struct minimal_symbol
*msymbol
;
1306 asection
*interp_sect
;
1307 gdb_byte
*interp_name
;
1310 /* First, remove all the solib event breakpoints. Their addresses
1311 may have changed since the last time we ran the program. */
1312 remove_solib_event_breakpoints ();
1314 info
->interp_text_sect_low
= info
->interp_text_sect_high
= 0;
1315 info
->interp_plt_sect_low
= info
->interp_plt_sect_high
= 0;
1317 /* If we already have a shared library list in the target, and
1318 r_debug contains r_brk, set the breakpoint there - this should
1319 mean r_brk has already been relocated. Assume the dynamic linker
1320 is the object containing r_brk. */
1322 solib_add (NULL
, from_tty
, ¤t_target
, auto_solib_add
);
1324 if (info
->debug_base
&& solib_svr4_r_map (info
) != 0)
1325 sym_addr
= solib_svr4_r_brk (info
);
1329 struct obj_section
*os
;
1331 sym_addr
= gdbarch_addr_bits_remove
1332 (target_gdbarch
, gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1336 /* On at least some versions of Solaris there's a dynamic relocation
1337 on _r_debug.r_brk and SYM_ADDR may not be relocated yet, e.g., if
1338 we get control before the dynamic linker has self-relocated.
1339 Check if SYM_ADDR is in a known section, if it is assume we can
1340 trust its value. This is just a heuristic though, it could go away
1341 or be replaced if it's getting in the way.
1343 On ARM we need to know whether the ISA of rtld_db_dlactivity (or
1344 however it's spelled in your particular system) is ARM or Thumb.
1345 That knowledge is encoded in the address, if it's Thumb the low bit
1346 is 1. However, we've stripped that info above and it's not clear
1347 what all the consequences are of passing a non-addr_bits_remove'd
1348 address to create_solib_event_breakpoint. The call to
1349 find_pc_section verifies we know about the address and have some
1350 hope of computing the right kind of breakpoint to use (via
1351 symbol info). It does mean that GDB needs to be pointed at a
1352 non-stripped version of the dynamic linker in order to obtain
1353 information it already knows about. Sigh. */
1355 os
= find_pc_section (sym_addr
);
1358 /* Record the relocated start and end address of the dynamic linker
1359 text and plt section for svr4_in_dynsym_resolve_code. */
1361 CORE_ADDR load_addr
;
1363 tmp_bfd
= os
->objfile
->obfd
;
1364 load_addr
= ANOFFSET (os
->objfile
->section_offsets
,
1365 os
->objfile
->sect_index_text
);
1367 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
1370 info
->interp_text_sect_low
=
1371 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1372 info
->interp_text_sect_high
=
1373 info
->interp_text_sect_low
1374 + bfd_section_size (tmp_bfd
, interp_sect
);
1376 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
1379 info
->interp_plt_sect_low
=
1380 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1381 info
->interp_plt_sect_high
=
1382 info
->interp_plt_sect_low
1383 + bfd_section_size (tmp_bfd
, interp_sect
);
1386 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1391 /* Find the program interpreter; if not found, warn the user and drop
1392 into the old breakpoint at symbol code. */
1393 interp_name
= find_program_interpreter ();
1396 CORE_ADDR load_addr
= 0;
1397 int load_addr_found
= 0;
1398 int loader_found_in_list
= 0;
1400 bfd
*tmp_bfd
= NULL
;
1401 struct target_ops
*tmp_bfd_target
;
1402 volatile struct gdb_exception ex
;
1406 /* Now we need to figure out where the dynamic linker was
1407 loaded so that we can load its symbols and place a breakpoint
1408 in the dynamic linker itself.
1410 This address is stored on the stack. However, I've been unable
1411 to find any magic formula to find it for Solaris (appears to
1412 be trivial on GNU/Linux). Therefore, we have to try an alternate
1413 mechanism to find the dynamic linker's base address. */
1415 TRY_CATCH (ex
, RETURN_MASK_ALL
)
1417 tmp_bfd
= solib_bfd_open (interp_name
);
1419 if (tmp_bfd
== NULL
)
1420 goto bkpt_at_symbol
;
1422 /* Now convert the TMP_BFD into a target. That way target, as
1423 well as BFD operations can be used. Note that closing the
1424 target will also close the underlying bfd. */
1425 tmp_bfd_target
= target_bfd_reopen (tmp_bfd
);
1427 /* On a running target, we can get the dynamic linker's base
1428 address from the shared library table. */
1429 so
= master_so_list ();
1432 if (svr4_same_1 (interp_name
, so
->so_original_name
))
1434 load_addr_found
= 1;
1435 loader_found_in_list
= 1;
1436 load_addr
= LM_ADDR_CHECK (so
, tmp_bfd
);
1442 /* If we were not able to find the base address of the loader
1443 from our so_list, then try using the AT_BASE auxilliary entry. */
1444 if (!load_addr_found
)
1445 if (target_auxv_search (¤t_target
, AT_BASE
, &load_addr
) > 0)
1446 load_addr_found
= 1;
1448 /* Otherwise we find the dynamic linker's base address by examining
1449 the current pc (which should point at the entry point for the
1450 dynamic linker) and subtracting the offset of the entry point.
1452 This is more fragile than the previous approaches, but is a good
1453 fallback method because it has actually been working well in
1455 if (!load_addr_found
)
1457 struct regcache
*regcache
1458 = get_thread_arch_regcache (inferior_ptid
, target_gdbarch
);
1459 load_addr
= (regcache_read_pc (regcache
)
1460 - exec_entry_point (tmp_bfd
, tmp_bfd_target
));
1463 if (!loader_found_in_list
)
1465 info
->debug_loader_name
= xstrdup (interp_name
);
1466 info
->debug_loader_offset_p
= 1;
1467 info
->debug_loader_offset
= load_addr
;
1468 solib_add (NULL
, from_tty
, ¤t_target
, auto_solib_add
);
1471 /* Record the relocated start and end address of the dynamic linker
1472 text and plt section for svr4_in_dynsym_resolve_code. */
1473 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".text");
1476 info
->interp_text_sect_low
=
1477 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1478 info
->interp_text_sect_high
=
1479 info
->interp_text_sect_low
1480 + bfd_section_size (tmp_bfd
, interp_sect
);
1482 interp_sect
= bfd_get_section_by_name (tmp_bfd
, ".plt");
1485 info
->interp_plt_sect_low
=
1486 bfd_section_vma (tmp_bfd
, interp_sect
) + load_addr
;
1487 info
->interp_plt_sect_high
=
1488 info
->interp_plt_sect_low
1489 + bfd_section_size (tmp_bfd
, interp_sect
);
1492 /* Now try to set a breakpoint in the dynamic linker. */
1493 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1495 sym_addr
= bfd_lookup_symbol (tmp_bfd
, *bkpt_namep
);
1501 /* Convert 'sym_addr' from a function pointer to an address.
1502 Because we pass tmp_bfd_target instead of the current
1503 target, this will always produce an unrelocated value. */
1504 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1508 /* We're done with both the temporary bfd and target. Remember,
1509 closing the target closes the underlying bfd. */
1510 target_close (tmp_bfd_target
, 0);
1514 create_solib_event_breakpoint (target_gdbarch
, load_addr
+ sym_addr
);
1515 xfree (interp_name
);
1519 /* For whatever reason we couldn't set a breakpoint in the dynamic
1520 linker. Warn and drop into the old code. */
1522 xfree (interp_name
);
1523 warning (_("Unable to find dynamic linker breakpoint function.\n"
1524 "GDB will be unable to debug shared library initializers\n"
1525 "and track explicitly loaded dynamic code."));
1528 /* Scan through the lists of symbols, trying to look up the symbol and
1529 set a breakpoint there. Terminate loop when we/if we succeed. */
1531 for (bkpt_namep
= solib_break_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1533 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
1534 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
1536 sym_addr
= SYMBOL_VALUE_ADDRESS (msymbol
);
1537 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1540 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1545 for (bkpt_namep
= bkpt_names
; *bkpt_namep
!= NULL
; bkpt_namep
++)
1547 msymbol
= lookup_minimal_symbol (*bkpt_namep
, NULL
, symfile_objfile
);
1548 if ((msymbol
!= NULL
) && (SYMBOL_VALUE_ADDRESS (msymbol
) != 0))
1550 sym_addr
= SYMBOL_VALUE_ADDRESS (msymbol
);
1551 sym_addr
= gdbarch_convert_from_func_ptr_addr (target_gdbarch
,
1554 create_solib_event_breakpoint (target_gdbarch
, sym_addr
);
1565 special_symbol_handling -- additional shared library symbol handling
1569 void special_symbol_handling ()
1573 Once the symbols from a shared object have been loaded in the usual
1574 way, we are called to do any system specific symbol handling that
1577 For SunOS4, this consisted of grunging around in the dynamic
1578 linkers structures to find symbol definitions for "common" symbols
1579 and adding them to the minimal symbol table for the runtime common
1582 However, for SVR4, there's nothing to do.
1587 svr4_special_symbol_handling (void)
1589 svr4_relocate_main_executable ();
1592 /* Decide if the objfile needs to be relocated. As indicated above,
1593 we will only be here when execution is stopped at the beginning
1594 of the program. Relocation is necessary if the address at which
1595 we are presently stopped differs from the start address stored in
1596 the executable AND there's no interpreter section. The condition
1597 regarding the interpreter section is very important because if
1598 there *is* an interpreter section, execution will begin there
1599 instead. When there is an interpreter section, the start address
1600 is (presumably) used by the interpreter at some point to start
1601 execution of the program.
1603 If there is an interpreter, it is normal for it to be set to an
1604 arbitrary address at the outset. The job of finding it is
1605 handled in enable_break().
1607 So, to summarize, relocations are necessary when there is no
1608 interpreter section and the start address obtained from the
1609 executable is different from the address at which GDB is
1612 [ The astute reader will note that we also test to make sure that
1613 the executable in question has the DYNAMIC flag set. It is my
1614 opinion that this test is unnecessary (undesirable even). It
1615 was added to avoid inadvertent relocation of an executable
1616 whose e_type member in the ELF header is not ET_DYN. There may
1617 be a time in the future when it is desirable to do relocations
1618 on other types of files as well in which case this condition
1619 should either be removed or modified to accomodate the new file
1620 type. (E.g, an ET_EXEC executable which has been built to be
1621 position-independent could safely be relocated by the OS if
1622 desired. It is true that this violates the ABI, but the ABI
1623 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1627 svr4_static_exec_displacement (void)
1629 asection
*interp_sect
;
1630 struct regcache
*regcache
1631 = get_thread_arch_regcache (inferior_ptid
, target_gdbarch
);
1632 CORE_ADDR pc
= regcache_read_pc (regcache
);
1634 interp_sect
= bfd_get_section_by_name (exec_bfd
, ".interp");
1635 if (interp_sect
== NULL
1636 && (bfd_get_file_flags (exec_bfd
) & DYNAMIC
) != 0
1637 && (exec_entry_point (exec_bfd
, &exec_ops
) != pc
))
1638 return pc
- exec_entry_point (exec_bfd
, &exec_ops
);
1643 /* We relocate all of the sections by the same amount. This
1644 behavior is mandated by recent editions of the System V ABI.
1645 According to the System V Application Binary Interface,
1646 Edition 4.1, page 5-5:
1648 ... Though the system chooses virtual addresses for
1649 individual processes, it maintains the segments' relative
1650 positions. Because position-independent code uses relative
1651 addressesing between segments, the difference between
1652 virtual addresses in memory must match the difference
1653 between virtual addresses in the file. The difference
1654 between the virtual address of any segment in memory and
1655 the corresponding virtual address in the file is thus a
1656 single constant value for any one executable or shared
1657 object in a given process. This difference is the base
1658 address. One use of the base address is to relocate the
1659 memory image of the program during dynamic linking.
1661 The same language also appears in Edition 4.0 of the System V
1662 ABI and is left unspecified in some of the earlier editions. */
1665 svr4_exec_displacement (void)
1668 /* ENTRY_POINT is a possible function descriptor - before
1669 a call to gdbarch_convert_from_func_ptr_addr. */
1670 CORE_ADDR entry_point
;
1672 if (exec_bfd
== NULL
)
1675 if (target_auxv_search (¤t_target
, AT_ENTRY
, &entry_point
) == 1)
1676 return entry_point
- bfd_get_start_address (exec_bfd
);
1678 return svr4_static_exec_displacement ();
1681 /* Relocate the main executable. This function should be called upon
1682 stopping the inferior process at the entry point to the program.
1683 The entry point from BFD is compared to the AT_ENTRY of AUXV and if they are
1684 different, the main executable is relocated by the proper amount. */
1687 svr4_relocate_main_executable (void)
1689 CORE_ADDR displacement
= svr4_exec_displacement ();
1691 /* Even if DISPLACEMENT is 0 still try to relocate it as this is a new
1692 difference of in-memory vs. in-file addresses and we could already
1693 relocate the executable at this function to improper address before. */
1695 if (symfile_objfile
)
1697 struct section_offsets
*new_offsets
;
1700 new_offsets
= alloca (symfile_objfile
->num_sections
1701 * sizeof (*new_offsets
));
1703 for (i
= 0; i
< symfile_objfile
->num_sections
; i
++)
1704 new_offsets
->offsets
[i
] = displacement
;
1706 objfile_relocate (symfile_objfile
, new_offsets
);
1712 for (asect
= exec_bfd
->sections
; asect
!= NULL
; asect
= asect
->next
)
1713 exec_set_section_address (bfd_get_filename (exec_bfd
), asect
->index
,
1714 (bfd_section_vma (exec_bfd
, asect
)
1723 svr4_solib_create_inferior_hook -- shared library startup support
1727 void svr4_solib_create_inferior_hook (int from_tty)
1731 When gdb starts up the inferior, it nurses it along (through the
1732 shell) until it is ready to execute it's first instruction. At this
1733 point, this function gets called via expansion of the macro
1734 SOLIB_CREATE_INFERIOR_HOOK.
1736 For SunOS executables, this first instruction is typically the
1737 one at "_start", or a similar text label, regardless of whether
1738 the executable is statically or dynamically linked. The runtime
1739 startup code takes care of dynamically linking in any shared
1740 libraries, once gdb allows the inferior to continue.
1742 For SVR4 executables, this first instruction is either the first
1743 instruction in the dynamic linker (for dynamically linked
1744 executables) or the instruction at "start" for statically linked
1745 executables. For dynamically linked executables, the system
1746 first exec's /lib/libc.so.N, which contains the dynamic linker,
1747 and starts it running. The dynamic linker maps in any needed
1748 shared libraries, maps in the actual user executable, and then
1749 jumps to "start" in the user executable.
1751 For both SunOS shared libraries, and SVR4 shared libraries, we
1752 can arrange to cooperate with the dynamic linker to discover the
1753 names of shared libraries that are dynamically linked, and the
1754 base addresses to which they are linked.
1756 This function is responsible for discovering those names and
1757 addresses, and saving sufficient information about them to allow
1758 their symbols to be read at a later time.
1762 Between enable_break() and disable_break(), this code does not
1763 properly handle hitting breakpoints which the user might have
1764 set in the startup code or in the dynamic linker itself. Proper
1765 handling will probably have to wait until the implementation is
1766 changed to use the "breakpoint handler function" method.
1768 Also, what if child has exit()ed? Must exit loop somehow.
1772 svr4_solib_create_inferior_hook (int from_tty
)
1774 struct inferior
*inf
;
1775 struct thread_info
*tp
;
1776 struct svr4_info
*info
;
1778 info
= get_svr4_info ();
1780 /* Relocate the main executable if necessary. */
1781 if (current_inferior ()->attach_flag
== 0)
1782 svr4_relocate_main_executable ();
1784 if (!svr4_have_link_map_offsets ())
1787 if (!enable_break (info
, from_tty
))
1790 #if defined(_SCO_DS)
1791 /* SCO needs the loop below, other systems should be using the
1792 special shared library breakpoints and the shared library breakpoint
1795 Now run the target. It will eventually hit the breakpoint, at
1796 which point all of the libraries will have been mapped in and we
1797 can go groveling around in the dynamic linker structures to find
1798 out what we need to know about them. */
1800 inf
= current_inferior ();
1801 tp
= inferior_thread ();
1803 clear_proceed_status ();
1804 inf
->stop_soon
= STOP_QUIETLY
;
1805 tp
->stop_signal
= TARGET_SIGNAL_0
;
1808 target_resume (pid_to_ptid (-1), 0, tp
->stop_signal
);
1809 wait_for_inferior (0);
1811 while (tp
->stop_signal
!= TARGET_SIGNAL_TRAP
);
1812 inf
->stop_soon
= NO_STOP_QUIETLY
;
1813 #endif /* defined(_SCO_DS) */
1817 svr4_clear_solib (void)
1819 struct svr4_info
*info
;
1821 info
= get_svr4_info ();
1822 info
->debug_base
= 0;
1823 info
->debug_loader_offset_p
= 0;
1824 info
->debug_loader_offset
= 0;
1825 xfree (info
->debug_loader_name
);
1826 info
->debug_loader_name
= NULL
;
1830 svr4_free_so (struct so_list
*so
)
1832 xfree (so
->lm_info
->lm
);
1833 xfree (so
->lm_info
);
1837 /* Clear any bits of ADDR that wouldn't fit in a target-format
1838 data pointer. "Data pointer" here refers to whatever sort of
1839 address the dynamic linker uses to manage its sections. At the
1840 moment, we don't support shared libraries on any processors where
1841 code and data pointers are different sizes.
1843 This isn't really the right solution. What we really need here is
1844 a way to do arithmetic on CORE_ADDR values that respects the
1845 natural pointer/address correspondence. (For example, on the MIPS,
1846 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1847 sign-extend the value. There, simply truncating the bits above
1848 gdbarch_ptr_bit, as we do below, is no good.) This should probably
1849 be a new gdbarch method or something. */
1851 svr4_truncate_ptr (CORE_ADDR addr
)
1853 if (gdbarch_ptr_bit (target_gdbarch
) == sizeof (CORE_ADDR
) * 8)
1854 /* We don't need to truncate anything, and the bit twiddling below
1855 will fail due to overflow problems. */
1858 return addr
& (((CORE_ADDR
) 1 << gdbarch_ptr_bit (target_gdbarch
)) - 1);
1863 svr4_relocate_section_addresses (struct so_list
*so
,
1864 struct target_section
*sec
)
1866 sec
->addr
= svr4_truncate_ptr (sec
->addr
+ LM_ADDR_CHECK (so
,
1868 sec
->endaddr
= svr4_truncate_ptr (sec
->endaddr
+ LM_ADDR_CHECK (so
,
1873 /* Architecture-specific operations. */
1875 /* Per-architecture data key. */
1876 static struct gdbarch_data
*solib_svr4_data
;
1878 struct solib_svr4_ops
1880 /* Return a description of the layout of `struct link_map'. */
1881 struct link_map_offsets
*(*fetch_link_map_offsets
)(void);
1884 /* Return a default for the architecture-specific operations. */
1887 solib_svr4_init (struct obstack
*obstack
)
1889 struct solib_svr4_ops
*ops
;
1891 ops
= OBSTACK_ZALLOC (obstack
, struct solib_svr4_ops
);
1892 ops
->fetch_link_map_offsets
= NULL
;
1896 /* Set the architecture-specific `struct link_map_offsets' fetcher for
1897 GDBARCH to FLMO. Also, install SVR4 solib_ops into GDBARCH. */
1900 set_solib_svr4_fetch_link_map_offsets (struct gdbarch
*gdbarch
,
1901 struct link_map_offsets
*(*flmo
) (void))
1903 struct solib_svr4_ops
*ops
= gdbarch_data (gdbarch
, solib_svr4_data
);
1905 ops
->fetch_link_map_offsets
= flmo
;
1907 set_solib_ops (gdbarch
, &svr4_so_ops
);
1910 /* Fetch a link_map_offsets structure using the architecture-specific
1911 `struct link_map_offsets' fetcher. */
1913 static struct link_map_offsets
*
1914 svr4_fetch_link_map_offsets (void)
1916 struct solib_svr4_ops
*ops
= gdbarch_data (target_gdbarch
, solib_svr4_data
);
1918 gdb_assert (ops
->fetch_link_map_offsets
);
1919 return ops
->fetch_link_map_offsets ();
1922 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1925 svr4_have_link_map_offsets (void)
1927 struct solib_svr4_ops
*ops
= gdbarch_data (target_gdbarch
, solib_svr4_data
);
1928 return (ops
->fetch_link_map_offsets
!= NULL
);
1932 /* Most OS'es that have SVR4-style ELF dynamic libraries define a
1933 `struct r_debug' and a `struct link_map' that are binary compatible
1934 with the origional SVR4 implementation. */
1936 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1937 for an ILP32 SVR4 system. */
1939 struct link_map_offsets
*
1940 svr4_ilp32_fetch_link_map_offsets (void)
1942 static struct link_map_offsets lmo
;
1943 static struct link_map_offsets
*lmp
= NULL
;
1949 lmo
.r_version_offset
= 0;
1950 lmo
.r_version_size
= 4;
1951 lmo
.r_map_offset
= 4;
1952 lmo
.r_brk_offset
= 8;
1953 lmo
.r_ldsomap_offset
= 20;
1955 /* Everything we need is in the first 20 bytes. */
1956 lmo
.link_map_size
= 20;
1957 lmo
.l_addr_offset
= 0;
1958 lmo
.l_name_offset
= 4;
1959 lmo
.l_ld_offset
= 8;
1960 lmo
.l_next_offset
= 12;
1961 lmo
.l_prev_offset
= 16;
1967 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1968 for an LP64 SVR4 system. */
1970 struct link_map_offsets
*
1971 svr4_lp64_fetch_link_map_offsets (void)
1973 static struct link_map_offsets lmo
;
1974 static struct link_map_offsets
*lmp
= NULL
;
1980 lmo
.r_version_offset
= 0;
1981 lmo
.r_version_size
= 4;
1982 lmo
.r_map_offset
= 8;
1983 lmo
.r_brk_offset
= 16;
1984 lmo
.r_ldsomap_offset
= 40;
1986 /* Everything we need is in the first 40 bytes. */
1987 lmo
.link_map_size
= 40;
1988 lmo
.l_addr_offset
= 0;
1989 lmo
.l_name_offset
= 8;
1990 lmo
.l_ld_offset
= 16;
1991 lmo
.l_next_offset
= 24;
1992 lmo
.l_prev_offset
= 32;
1999 struct target_so_ops svr4_so_ops
;
2001 /* Lookup global symbol for ELF DSOs linked with -Bsymbolic. Those DSOs have a
2002 different rule for symbol lookup. The lookup begins here in the DSO, not in
2003 the main executable. */
2005 static struct symbol
*
2006 elf_lookup_lib_symbol (const struct objfile
*objfile
,
2008 const char *linkage_name
,
2009 const domain_enum domain
)
2013 if (objfile
== symfile_objfile
)
2017 /* OBJFILE should have been passed as the non-debug one. */
2018 gdb_assert (objfile
->separate_debug_objfile_backlink
== NULL
);
2020 abfd
= objfile
->obfd
;
2023 if (abfd
== NULL
|| scan_dyntag (DT_SYMBOLIC
, abfd
, NULL
) != 1)
2026 return lookup_global_symbol_from_objfile
2027 (objfile
, name
, linkage_name
, domain
);
2030 extern initialize_file_ftype _initialize_svr4_solib
; /* -Wmissing-prototypes */
2033 _initialize_svr4_solib (void)
2035 solib_svr4_data
= gdbarch_data_register_pre_init (solib_svr4_init
);
2036 solib_svr4_pspace_data
2037 = register_program_space_data_with_cleanup (svr4_pspace_data_cleanup
);
2039 svr4_so_ops
.relocate_section_addresses
= svr4_relocate_section_addresses
;
2040 svr4_so_ops
.free_so
= svr4_free_so
;
2041 svr4_so_ops
.clear_solib
= svr4_clear_solib
;
2042 svr4_so_ops
.solib_create_inferior_hook
= svr4_solib_create_inferior_hook
;
2043 svr4_so_ops
.special_symbol_handling
= svr4_special_symbol_handling
;
2044 svr4_so_ops
.current_sos
= svr4_current_sos
;
2045 svr4_so_ops
.open_symbol_file_object
= open_symbol_file_object
;
2046 svr4_so_ops
.in_dynsym_resolve_code
= svr4_in_dynsym_resolve_code
;
2047 svr4_so_ops
.bfd_open
= solib_bfd_open
;
2048 svr4_so_ops
.lookup_lib_global_symbol
= elf_lookup_lib_symbol
;
2049 svr4_so_ops
.same
= svr4_same
;
2050 svr4_so_ops
.keep_data_in_core
= svr4_keep_data_in_core
;