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;
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 CORE_ADDR align = 0x1000;
197 CORE_ADDR minpagesize = align;
199 if (bfd_get_flavour (abfd) == bfd_target_elf_flavour)
201 Elf_Internal_Ehdr *ehdr = elf_tdata (abfd)->elf_header;
202 Elf_Internal_Phdr *phdr = elf_tdata (abfd)->phdr;
207 for (i = 0; i < ehdr->e_phnum; i++)
208 if (phdr[i].p_type == PT_LOAD && phdr[i].p_align > align)
209 align = phdr[i].p_align;
211 minpagesize = get_elf_backend_data (abfd)->minpagesize;
214 /* Turn it into a mask. */
217 /* If the changes match the alignment requirements, we
218 assume we're using a core file that was generated by the
219 same binary, just prelinked with a different base offset.
220 If it doesn't match, we may have a different binary, the
221 same binary with the dynamic table loaded at an unrelated
222 location, or anything, really. To avoid regressions,
223 don't adjust the base offset in the latter case, although
224 odds are that, if things really changed, debugging won't
227 One could expect more the condition
228 ((l_addr & align) == 0 && ((l_dynaddr - dynaddr) & align) == 0)
229 but the one below is relaxed for PPC. The PPC kernel supports
230 either 4k or 64k page sizes. To be prepared for 64k pages,
231 PPC ELF files are built using an alignment requirement of 64k.
232 However, when running on a kernel supporting 4k pages, the memory
233 mapping of the library may not actually happen on a 64k boundary!
235 (In the usual case where (l_addr & align) == 0, this check is
236 equivalent to the possibly expected check above.)
238 Even on PPC it must be zero-aligned at least for MINPAGESIZE. */
240 if ((l_addr & (minpagesize - 1)) == 0
241 && (l_addr & align) == ((l_dynaddr - dynaddr) & align))
243 l_addr = l_dynaddr - dynaddr;
247 warning (_(".dynamic section for \"%s\" "
248 "is not at the expected address"), so->so_name);
249 warning (_("difference appears to be caused by prelink, "
250 "adjusting expectations"));
254 warning (_(".dynamic section for \"%s\" "
255 "is not at the expected address "
256 "(wrong library or version mismatch?)"), so->so_name);
260 so->lm_info->l_addr = l_addr;
263 return so->lm_info->l_addr;
267 LM_NEXT (struct so_list *so)
269 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
270 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
272 return extract_typed_address (so->lm_info->lm + lmo->l_next_offset,
277 LM_NAME (struct so_list *so)
279 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
280 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
282 return extract_typed_address (so->lm_info->lm + lmo->l_name_offset,
287 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
289 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
290 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
292 /* Assume that everything is a library if the dynamic loader was loaded
293 late by a static executable. */
294 if (exec_bfd && bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
297 return extract_typed_address (so->lm_info->lm + lmo->l_prev_offset,
301 /* Per pspace SVR4 specific data. */
305 CORE_ADDR debug_base; /* Base of dynamic linker structures */
307 /* Validity flag for debug_loader_offset. */
308 int debug_loader_offset_p;
310 /* Load address for the dynamic linker, inferred. */
311 CORE_ADDR debug_loader_offset;
313 /* Name of the dynamic linker, valid if debug_loader_offset_p. */
314 char *debug_loader_name;
316 /* Load map address for the main executable. */
317 CORE_ADDR main_lm_addr;
319 CORE_ADDR interp_text_sect_low;
320 CORE_ADDR interp_text_sect_high;
321 CORE_ADDR interp_plt_sect_low;
322 CORE_ADDR interp_plt_sect_high;
325 /* Per-program-space data key. */
326 static const struct program_space_data *solib_svr4_pspace_data;
329 svr4_pspace_data_cleanup (struct program_space *pspace, void *arg)
331 struct svr4_info *info;
333 info = program_space_data (pspace, solib_svr4_pspace_data);
337 /* Get the current svr4 data. If none is found yet, add it now. This
338 function always returns a valid object. */
340 static struct svr4_info *
343 struct svr4_info *info;
345 info = program_space_data (current_program_space, solib_svr4_pspace_data);
349 info = XZALLOC (struct svr4_info);
350 set_program_space_data (current_program_space, solib_svr4_pspace_data, info);
354 /* Local function prototypes */
356 static int match_main (char *);
358 static CORE_ADDR bfd_lookup_symbol (bfd *, char *);
364 bfd_lookup_symbol -- lookup the value for a specific symbol
368 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
372 An expensive way to lookup the value of a single symbol for
373 bfd's that are only temporary anyway. This is used by the
374 shared library support to find the address of the debugger
375 notification routine in the shared library.
377 The returned symbol may be in a code or data section; functions
378 will normally be in a code section, but may be in a data section
379 if this architecture uses function descriptors.
381 Note that 0 is specifically allowed as an error return (no
386 bfd_lookup_symbol (bfd *abfd, char *symname)
390 asymbol **symbol_table;
391 unsigned int number_of_symbols;
393 struct cleanup *back_to;
394 CORE_ADDR symaddr = 0;
396 storage_needed = bfd_get_symtab_upper_bound (abfd);
398 if (storage_needed > 0)
400 symbol_table = (asymbol **) xmalloc (storage_needed);
401 back_to = make_cleanup (xfree, symbol_table);
402 number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
404 for (i = 0; i < number_of_symbols; i++)
406 sym = *symbol_table++;
407 if (strcmp (sym->name, symname) == 0
408 && (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
410 /* BFD symbols are section relative. */
411 symaddr = sym->value + sym->section->vma;
415 do_cleanups (back_to);
421 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
422 have to check the dynamic string table too. */
424 storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);
426 if (storage_needed > 0)
428 symbol_table = (asymbol **) xmalloc (storage_needed);
429 back_to = make_cleanup (xfree, symbol_table);
430 number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table);
432 for (i = 0; i < number_of_symbols; i++)
434 sym = *symbol_table++;
436 if (strcmp (sym->name, symname) == 0
437 && (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
439 /* BFD symbols are section relative. */
440 symaddr = sym->value + sym->section->vma;
444 do_cleanups (back_to);
451 /* Read program header TYPE from inferior memory. The header is found
452 by scanning the OS auxillary vector.
454 Return a pointer to allocated memory holding the program header contents,
455 or NULL on failure. If sucessful, and unless P_SECT_SIZE is NULL, the
456 size of those contents is returned to P_SECT_SIZE. Likewise, the target
457 architecture size (32-bit or 64-bit) is returned to P_ARCH_SIZE. */
460 read_program_header (int type, int *p_sect_size, int *p_arch_size)
462 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
463 CORE_ADDR at_phdr, at_phent, at_phnum;
464 int arch_size, sect_size;
468 /* Get required auxv elements from target. */
469 if (target_auxv_search (¤t_target, AT_PHDR, &at_phdr) <= 0)
471 if (target_auxv_search (¤t_target, AT_PHENT, &at_phent) <= 0)
473 if (target_auxv_search (¤t_target, AT_PHNUM, &at_phnum) <= 0)
475 if (!at_phdr || !at_phnum)
478 /* Determine ELF architecture type. */
479 if (at_phent == sizeof (Elf32_External_Phdr))
481 else if (at_phent == sizeof (Elf64_External_Phdr))
486 /* Find .dynamic section via the PT_DYNAMIC PHDR. */
489 Elf32_External_Phdr phdr;
492 /* Search for requested PHDR. */
493 for (i = 0; i < at_phnum; i++)
495 if (target_read_memory (at_phdr + i * sizeof (phdr),
496 (gdb_byte *)&phdr, sizeof (phdr)))
499 if (extract_unsigned_integer ((gdb_byte *)phdr.p_type,
500 4, byte_order) == type)
507 /* Retrieve address and size. */
508 sect_addr = extract_unsigned_integer ((gdb_byte *)phdr.p_vaddr,
510 sect_size = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz,
515 Elf64_External_Phdr phdr;
518 /* Search for requested PHDR. */
519 for (i = 0; i < at_phnum; i++)
521 if (target_read_memory (at_phdr + i * sizeof (phdr),
522 (gdb_byte *)&phdr, sizeof (phdr)))
525 if (extract_unsigned_integer ((gdb_byte *)phdr.p_type,
526 4, byte_order) == type)
533 /* Retrieve address and size. */
534 sect_addr = extract_unsigned_integer ((gdb_byte *)phdr.p_vaddr,
536 sect_size = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz,
540 /* Read in requested program header. */
541 buf = xmalloc (sect_size);
542 if (target_read_memory (sect_addr, buf, sect_size))
549 *p_arch_size = arch_size;
551 *p_sect_size = sect_size;
557 /* Return program interpreter string. */
559 find_program_interpreter (void)
561 gdb_byte *buf = NULL;
563 /* If we have an exec_bfd, use its section table. */
565 && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
567 struct bfd_section *interp_sect;
569 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
570 if (interp_sect != NULL)
572 CORE_ADDR sect_addr = bfd_section_vma (exec_bfd, interp_sect);
573 int sect_size = bfd_section_size (exec_bfd, interp_sect);
575 buf = xmalloc (sect_size);
576 bfd_get_section_contents (exec_bfd, interp_sect, buf, 0, sect_size);
580 /* If we didn't find it, use the target auxillary vector. */
582 buf = read_program_header (PT_INTERP, NULL, NULL);
588 /* Scan for DYNTAG in .dynamic section of ABFD. If DYNTAG is found 1 is
589 returned and the corresponding PTR is set. */
592 scan_dyntag (int dyntag, bfd *abfd, CORE_ADDR *ptr)
594 int arch_size, step, sect_size;
596 CORE_ADDR dyn_ptr, dyn_addr;
597 gdb_byte *bufend, *bufstart, *buf;
598 Elf32_External_Dyn *x_dynp_32;
599 Elf64_External_Dyn *x_dynp_64;
600 struct bfd_section *sect;
601 struct target_section *target_section;
606 if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
609 arch_size = bfd_get_arch_size (abfd);
613 /* Find the start address of the .dynamic section. */
614 sect = bfd_get_section_by_name (abfd, ".dynamic");
618 for (target_section = current_target_sections->sections;
619 target_section < current_target_sections->sections_end;
621 if (sect == target_section->the_bfd_section)
623 if (target_section < current_target_sections->sections_end)
624 dyn_addr = target_section->addr;
627 /* ABFD may come from OBJFILE acting only as a symbol file without being
628 loaded into the target (see add_symbol_file_command). This case is
629 such fallback to the file VMA address without the possibility of
630 having the section relocated to its actual in-memory address. */
632 dyn_addr = bfd_section_vma (abfd, sect);
635 /* Read in .dynamic from the BFD. We will get the actual value
636 from memory later. */
637 sect_size = bfd_section_size (abfd, sect);
638 buf = bufstart = alloca (sect_size);
639 if (!bfd_get_section_contents (abfd, sect,
643 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
644 step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
645 : sizeof (Elf64_External_Dyn);
646 for (bufend = buf + sect_size;
652 x_dynp_32 = (Elf32_External_Dyn *) buf;
653 dyn_tag = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_tag);
654 dyn_ptr = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_un.d_ptr);
658 x_dynp_64 = (Elf64_External_Dyn *) buf;
659 dyn_tag = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_tag);
660 dyn_ptr = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_un.d_ptr);
662 if (dyn_tag == DT_NULL)
664 if (dyn_tag == dyntag)
666 /* If requested, try to read the runtime value of this .dynamic
670 struct type *ptr_type;
674 ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
675 ptr_addr = dyn_addr + (buf - bufstart) + arch_size / 8;
676 if (target_read_memory (ptr_addr, ptr_buf, arch_size / 8) == 0)
677 dyn_ptr = extract_typed_address (ptr_buf, ptr_type);
687 /* Scan for DYNTAG in .dynamic section of the target's main executable,
688 found by consulting the OS auxillary vector. If DYNTAG is found 1 is
689 returned and the corresponding PTR is set. */
692 scan_dyntag_auxv (int dyntag, CORE_ADDR *ptr)
694 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
695 int sect_size, arch_size, step;
698 gdb_byte *bufend, *bufstart, *buf;
700 /* Read in .dynamic section. */
701 buf = bufstart = read_program_header (PT_DYNAMIC, §_size, &arch_size);
705 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
706 step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
707 : sizeof (Elf64_External_Dyn);
708 for (bufend = buf + sect_size;
714 Elf32_External_Dyn *dynp = (Elf32_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,
722 Elf64_External_Dyn *dynp = (Elf64_External_Dyn *) buf;
723 dyn_tag = extract_unsigned_integer ((gdb_byte *) dynp->d_tag,
725 dyn_ptr = extract_unsigned_integer ((gdb_byte *) dynp->d_un.d_ptr,
728 if (dyn_tag == DT_NULL)
731 if (dyn_tag == dyntag)
750 elf_locate_base -- locate the base address of dynamic linker structs
751 for SVR4 elf targets.
755 CORE_ADDR elf_locate_base (void)
759 For SVR4 elf targets the address of the dynamic linker's runtime
760 structure is contained within the dynamic info section in the
761 executable file. The dynamic section is also mapped into the
762 inferior address space. Because the runtime loader fills in the
763 real address before starting the inferior, we have to read in the
764 dynamic info section from the inferior address space.
765 If there are any errors while trying to find the address, we
766 silently return 0, otherwise the found address is returned.
771 elf_locate_base (void)
773 struct minimal_symbol *msymbol;
776 /* Look for DT_MIPS_RLD_MAP first. MIPS executables use this
777 instead of DT_DEBUG, although they sometimes contain an unused
779 if (scan_dyntag (DT_MIPS_RLD_MAP, exec_bfd, &dyn_ptr)
780 || scan_dyntag_auxv (DT_MIPS_RLD_MAP, &dyn_ptr))
782 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
784 int pbuf_size = TYPE_LENGTH (ptr_type);
785 pbuf = alloca (pbuf_size);
786 /* DT_MIPS_RLD_MAP contains a pointer to the address
787 of the dynamic link structure. */
788 if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
790 return extract_typed_address (pbuf, ptr_type);
794 if (scan_dyntag (DT_DEBUG, exec_bfd, &dyn_ptr)
795 || scan_dyntag_auxv (DT_DEBUG, &dyn_ptr))
798 /* This may be a static executable. Look for the symbol
799 conventionally named _r_debug, as a last resort. */
800 msymbol = lookup_minimal_symbol ("_r_debug", NULL, symfile_objfile);
802 return SYMBOL_VALUE_ADDRESS (msymbol);
804 /* DT_DEBUG entry not found. */
812 locate_base -- locate the base address of dynamic linker structs
816 CORE_ADDR locate_base (struct svr4_info *)
820 For both the SunOS and SVR4 shared library implementations, if the
821 inferior executable has been linked dynamically, there is a single
822 address somewhere in the inferior's data space which is the key to
823 locating all of the dynamic linker's runtime structures. This
824 address is the value of the debug base symbol. The job of this
825 function is to find and return that address, or to return 0 if there
826 is no such address (the executable is statically linked for example).
828 For SunOS, the job is almost trivial, since the dynamic linker and
829 all of it's structures are statically linked to the executable at
830 link time. Thus the symbol for the address we are looking for has
831 already been added to the minimal symbol table for the executable's
832 objfile at the time the symbol file's symbols were read, and all we
833 have to do is look it up there. Note that we explicitly do NOT want
834 to find the copies in the shared library.
836 The SVR4 version is a bit more complicated because the address
837 is contained somewhere in the dynamic info section. We have to go
838 to a lot more work to discover the address of the debug base symbol.
839 Because of this complexity, we cache the value we find and return that
840 value on subsequent invocations. Note there is no copy in the
841 executable symbol tables.
846 locate_base (struct svr4_info *info)
848 /* Check to see if we have a currently valid address, and if so, avoid
849 doing all this work again and just return the cached address. If
850 we have no cached address, try to locate it in the dynamic info
851 section for ELF executables. There's no point in doing any of this
852 though if we don't have some link map offsets to work with. */
854 if (info->debug_base == 0 && svr4_have_link_map_offsets ())
855 info->debug_base = elf_locate_base ();
856 return info->debug_base;
859 /* Find the first element in the inferior's dynamic link map, and
860 return its address in the inferior.
862 FIXME: Perhaps we should validate the info somehow, perhaps by
863 checking r_version for a known version number, or r_state for
867 solib_svr4_r_map (struct svr4_info *info)
869 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
870 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
872 return read_memory_typed_address (info->debug_base + lmo->r_map_offset,
876 /* Find r_brk from the inferior's debug base. */
879 solib_svr4_r_brk (struct svr4_info *info)
881 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
882 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
884 return read_memory_typed_address (info->debug_base + lmo->r_brk_offset,
888 /* Find the link map for the dynamic linker (if it is not in the
889 normal list of loaded shared objects). */
892 solib_svr4_r_ldsomap (struct svr4_info *info)
894 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
895 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
896 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
899 /* Check version, and return zero if `struct r_debug' doesn't have
900 the r_ldsomap member. */
902 = read_memory_unsigned_integer (info->debug_base + lmo->r_version_offset,
903 lmo->r_version_size, byte_order);
904 if (version < 2 || lmo->r_ldsomap_offset == -1)
907 return read_memory_typed_address (info->debug_base + lmo->r_ldsomap_offset,
911 /* On Solaris systems with some versions of the dynamic linker,
912 ld.so's l_name pointer points to the SONAME in the string table
913 rather than into writable memory. So that GDB can find shared
914 libraries when loading a core file generated by gcore, ensure that
915 memory areas containing the l_name string are saved in the core
919 svr4_keep_data_in_core (CORE_ADDR vaddr, unsigned long size)
921 struct svr4_info *info;
924 struct cleanup *old_chain;
925 struct link_map_offsets *lmo;
928 info = get_svr4_info ();
930 info->debug_base = 0;
932 if (!info->debug_base)
935 ldsomap = solib_svr4_r_ldsomap (info);
939 lmo = svr4_fetch_link_map_offsets ();
940 new = XZALLOC (struct so_list);
941 old_chain = make_cleanup (xfree, new);
942 new->lm_info = xmalloc (sizeof (struct lm_info));
943 make_cleanup (xfree, new->lm_info);
944 new->lm_info->l_addr = (CORE_ADDR)-1;
945 new->lm_info->lm_addr = ldsomap;
946 new->lm_info->lm = xzalloc (lmo->link_map_size);
947 make_cleanup (xfree, new->lm_info->lm);
948 read_memory (ldsomap, new->lm_info->lm, lmo->link_map_size);
949 lm_name = LM_NAME (new);
950 do_cleanups (old_chain);
952 return (lm_name >= vaddr && lm_name < vaddr + size);
959 open_symbol_file_object
963 void open_symbol_file_object (void *from_tty)
967 If no open symbol file, attempt to locate and open the main symbol
968 file. On SVR4 systems, this is the first link map entry. If its
969 name is here, we can open it. Useful when attaching to a process
970 without first loading its symbol file.
972 If FROM_TTYP dereferences to a non-zero integer, allow messages to
973 be printed. This parameter is a pointer rather than an int because
974 open_symbol_file_object() is called via catch_errors() and
975 catch_errors() requires a pointer argument. */
978 open_symbol_file_object (void *from_ttyp)
980 CORE_ADDR lm, l_name;
983 int from_tty = *(int *)from_ttyp;
984 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
985 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
986 int l_name_size = TYPE_LENGTH (ptr_type);
987 gdb_byte *l_name_buf = xmalloc (l_name_size);
988 struct cleanup *cleanups = make_cleanup (xfree, l_name_buf);
989 struct svr4_info *info = get_svr4_info ();
992 if (!query (_("Attempt to reload symbols from process? ")))
995 /* Always locate the debug struct, in case it has moved. */
996 info->debug_base = 0;
997 if (locate_base (info) == 0)
998 return 0; /* failed somehow... */
1000 /* First link map member should be the executable. */
1001 lm = solib_svr4_r_map (info);
1003 return 0; /* failed somehow... */
1005 /* Read address of name from target memory to GDB. */
1006 read_memory (lm + lmo->l_name_offset, l_name_buf, l_name_size);
1008 /* Convert the address to host format. */
1009 l_name = extract_typed_address (l_name_buf, ptr_type);
1011 /* Free l_name_buf. */
1012 do_cleanups (cleanups);
1015 return 0; /* No filename. */
1017 /* Now fetch the filename from target memory. */
1018 target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode);
1019 make_cleanup (xfree, filename);
1023 warning (_("failed to read exec filename from attached file: %s"),
1024 safe_strerror (errcode));
1028 /* Have a pathname: read the symbol file. */
1029 symbol_file_add_main (filename, from_tty);
1034 /* If no shared library information is available from the dynamic
1035 linker, build a fallback list from other sources. */
1037 static struct so_list *
1038 svr4_default_sos (void)
1040 struct svr4_info *info = get_svr4_info ();
1042 struct so_list *head = NULL;
1043 struct so_list **link_ptr = &head;
1045 if (info->debug_loader_offset_p)
1047 struct so_list *new = XZALLOC (struct so_list);
1049 new->lm_info = xmalloc (sizeof (struct lm_info));
1051 /* Nothing will ever check the cached copy of the link
1052 map if we set l_addr. */
1053 new->lm_info->l_addr = info->debug_loader_offset;
1054 new->lm_info->lm_addr = 0;
1055 new->lm_info->lm = NULL;
1057 strncpy (new->so_name, info->debug_loader_name,
1058 SO_NAME_MAX_PATH_SIZE - 1);
1059 new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
1060 strcpy (new->so_original_name, new->so_name);
1063 link_ptr = &new->next;
1071 current_sos -- build a list of currently loaded shared objects
1075 struct so_list *current_sos ()
1079 Build a list of `struct so_list' objects describing the shared
1080 objects currently loaded in the inferior. This list does not
1081 include an entry for the main executable file.
1083 Note that we only gather information directly available from the
1084 inferior --- we don't examine any of the shared library files
1085 themselves. The declaration of `struct so_list' says which fields
1086 we provide values for. */
1088 static struct so_list *
1089 svr4_current_sos (void)
1092 struct so_list *head = 0;
1093 struct so_list **link_ptr = &head;
1094 CORE_ADDR ldsomap = 0;
1095 struct svr4_info *info;
1097 info = get_svr4_info ();
1099 /* Always locate the debug struct, in case it has moved. */
1100 info->debug_base = 0;
1103 /* If we can't find the dynamic linker's base structure, this
1104 must not be a dynamically linked executable. Hmm. */
1105 if (! info->debug_base)
1106 return svr4_default_sos ();
1108 /* Walk the inferior's link map list, and build our list of
1109 `struct so_list' nodes. */
1110 lm = solib_svr4_r_map (info);
1114 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
1115 struct so_list *new = XZALLOC (struct so_list);
1116 struct cleanup *old_chain = make_cleanup (xfree, new);
1118 new->lm_info = xmalloc (sizeof (struct lm_info));
1119 make_cleanup (xfree, new->lm_info);
1121 new->lm_info->l_addr = (CORE_ADDR)-1;
1122 new->lm_info->lm_addr = lm;
1123 new->lm_info->lm = xzalloc (lmo->link_map_size);
1124 make_cleanup (xfree, new->lm_info->lm);
1126 read_memory (lm, new->lm_info->lm, lmo->link_map_size);
1130 /* For SVR4 versions, the first entry in the link map is for the
1131 inferior executable, so we must ignore it. For some versions of
1132 SVR4, it has no name. For others (Solaris 2.3 for example), it
1133 does have a name, so we can no longer use a missing name to
1134 decide when to ignore it. */
1135 if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap == 0)
1137 info->main_lm_addr = new->lm_info->lm_addr;
1145 /* Extract this shared object's name. */
1146 target_read_string (LM_NAME (new), &buffer,
1147 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
1149 warning (_("Can't read pathname for load map: %s."),
1150 safe_strerror (errcode));
1153 strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
1154 new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
1155 strcpy (new->so_original_name, new->so_name);
1159 /* If this entry has no name, or its name matches the name
1160 for the main executable, don't include it in the list. */
1161 if (! new->so_name[0]
1162 || match_main (new->so_name))
1168 link_ptr = &new->next;
1172 /* On Solaris, the dynamic linker is not in the normal list of
1173 shared objects, so make sure we pick it up too. Having
1174 symbol information for the dynamic linker is quite crucial
1175 for skipping dynamic linker resolver code. */
1176 if (lm == 0 && ldsomap == 0)
1177 lm = ldsomap = solib_svr4_r_ldsomap (info);
1179 discard_cleanups (old_chain);
1183 return svr4_default_sos ();
1188 /* Get the address of the link_map for a given OBJFILE. */
1191 svr4_fetch_objfile_link_map (struct objfile *objfile)
1194 struct svr4_info *info = get_svr4_info ();
1196 /* Cause svr4_current_sos() to be run if it hasn't been already. */
1197 if (info->main_lm_addr == 0)
1198 solib_add (NULL, 0, ¤t_target, auto_solib_add);
1200 /* svr4_current_sos() will set main_lm_addr for the main executable. */
1201 if (objfile == symfile_objfile)
1202 return info->main_lm_addr;
1204 /* The other link map addresses may be found by examining the list
1205 of shared libraries. */
1206 for (so = master_so_list (); so; so = so->next)
1207 if (so->objfile == objfile)
1208 return so->lm_info->lm_addr;
1214 /* On some systems, the only way to recognize the link map entry for
1215 the main executable file is by looking at its name. Return
1216 non-zero iff SONAME matches one of the known main executable names. */
1219 match_main (char *soname)
1223 for (mainp = main_name_list; *mainp != NULL; mainp++)
1225 if (strcmp (soname, *mainp) == 0)
1232 /* Return 1 if PC lies in the dynamic symbol resolution code of the
1233 SVR4 run time loader. */
1236 svr4_in_dynsym_resolve_code (CORE_ADDR pc)
1238 struct svr4_info *info = get_svr4_info ();
1240 return ((pc >= info->interp_text_sect_low
1241 && pc < info->interp_text_sect_high)
1242 || (pc >= info->interp_plt_sect_low
1243 && pc < info->interp_plt_sect_high)
1244 || in_plt_section (pc, NULL));
1247 /* Given an executable's ABFD and target, compute the entry-point
1251 exec_entry_point (struct bfd *abfd, struct target_ops *targ)
1253 /* KevinB wrote ... for most targets, the address returned by
1254 bfd_get_start_address() is the entry point for the start
1255 function. But, for some targets, bfd_get_start_address() returns
1256 the address of a function descriptor from which the entry point
1257 address may be extracted. This address is extracted by
1258 gdbarch_convert_from_func_ptr_addr(). The method
1259 gdbarch_convert_from_func_ptr_addr() is the merely the identify
1260 function for targets which don't use function descriptors. */
1261 return gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1262 bfd_get_start_address (abfd),
1270 enable_break -- arrange for dynamic linker to hit breakpoint
1274 int enable_break (void)
1278 Both the SunOS and the SVR4 dynamic linkers have, as part of their
1279 debugger interface, support for arranging for the inferior to hit
1280 a breakpoint after mapping in the shared libraries. This function
1281 enables that breakpoint.
1283 For SunOS, there is a special flag location (in_debugger) which we
1284 set to 1. When the dynamic linker sees this flag set, it will set
1285 a breakpoint at a location known only to itself, after saving the
1286 original contents of that place and the breakpoint address itself,
1287 in it's own internal structures. When we resume the inferior, it
1288 will eventually take a SIGTRAP when it runs into the breakpoint.
1289 We handle this (in a different place) by restoring the contents of
1290 the breakpointed location (which is only known after it stops),
1291 chasing around to locate the shared libraries that have been
1292 loaded, then resuming.
1294 For SVR4, the debugger interface structure contains a member (r_brk)
1295 which is statically initialized at the time the shared library is
1296 built, to the offset of a function (_r_debug_state) which is guaran-
1297 teed to be called once before mapping in a library, and again when
1298 the mapping is complete. At the time we are examining this member,
1299 it contains only the unrelocated offset of the function, so we have
1300 to do our own relocation. Later, when the dynamic linker actually
1301 runs, it relocates r_brk to be the actual address of _r_debug_state().
1303 The debugger interface structure also contains an enumeration which
1304 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
1305 depending upon whether or not the library is being mapped or unmapped,
1306 and then set to RT_CONSISTENT after the library is mapped/unmapped.
1310 enable_break (struct svr4_info *info, int from_tty)
1312 struct minimal_symbol *msymbol;
1314 asection *interp_sect;
1315 gdb_byte *interp_name;
1318 /* First, remove all the solib event breakpoints. Their addresses
1319 may have changed since the last time we ran the program. */
1320 remove_solib_event_breakpoints ();
1322 info->interp_text_sect_low = info->interp_text_sect_high = 0;
1323 info->interp_plt_sect_low = info->interp_plt_sect_high = 0;
1325 /* If we already have a shared library list in the target, and
1326 r_debug contains r_brk, set the breakpoint there - this should
1327 mean r_brk has already been relocated. Assume the dynamic linker
1328 is the object containing r_brk. */
1330 solib_add (NULL, from_tty, ¤t_target, auto_solib_add);
1332 if (info->debug_base && solib_svr4_r_map (info) != 0)
1333 sym_addr = solib_svr4_r_brk (info);
1337 struct obj_section *os;
1339 sym_addr = gdbarch_addr_bits_remove
1340 (target_gdbarch, gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1344 /* On at least some versions of Solaris there's a dynamic relocation
1345 on _r_debug.r_brk and SYM_ADDR may not be relocated yet, e.g., if
1346 we get control before the dynamic linker has self-relocated.
1347 Check if SYM_ADDR is in a known section, if it is assume we can
1348 trust its value. This is just a heuristic though, it could go away
1349 or be replaced if it's getting in the way.
1351 On ARM we need to know whether the ISA of rtld_db_dlactivity (or
1352 however it's spelled in your particular system) is ARM or Thumb.
1353 That knowledge is encoded in the address, if it's Thumb the low bit
1354 is 1. However, we've stripped that info above and it's not clear
1355 what all the consequences are of passing a non-addr_bits_remove'd
1356 address to create_solib_event_breakpoint. The call to
1357 find_pc_section verifies we know about the address and have some
1358 hope of computing the right kind of breakpoint to use (via
1359 symbol info). It does mean that GDB needs to be pointed at a
1360 non-stripped version of the dynamic linker in order to obtain
1361 information it already knows about. Sigh. */
1363 os = find_pc_section (sym_addr);
1366 /* Record the relocated start and end address of the dynamic linker
1367 text and plt section for svr4_in_dynsym_resolve_code. */
1369 CORE_ADDR load_addr;
1371 tmp_bfd = os->objfile->obfd;
1372 load_addr = ANOFFSET (os->objfile->section_offsets,
1373 os->objfile->sect_index_text);
1375 interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
1378 info->interp_text_sect_low =
1379 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1380 info->interp_text_sect_high =
1381 info->interp_text_sect_low
1382 + bfd_section_size (tmp_bfd, interp_sect);
1384 interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
1387 info->interp_plt_sect_low =
1388 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1389 info->interp_plt_sect_high =
1390 info->interp_plt_sect_low
1391 + bfd_section_size (tmp_bfd, interp_sect);
1394 create_solib_event_breakpoint (target_gdbarch, sym_addr);
1399 /* Find the program interpreter; if not found, warn the user and drop
1400 into the old breakpoint at symbol code. */
1401 interp_name = find_program_interpreter ();
1404 CORE_ADDR load_addr = 0;
1405 int load_addr_found = 0;
1406 int loader_found_in_list = 0;
1408 bfd *tmp_bfd = NULL;
1409 struct target_ops *tmp_bfd_target;
1410 volatile struct gdb_exception ex;
1414 /* Now we need to figure out where the dynamic linker was
1415 loaded so that we can load its symbols and place a breakpoint
1416 in the dynamic linker itself.
1418 This address is stored on the stack. However, I've been unable
1419 to find any magic formula to find it for Solaris (appears to
1420 be trivial on GNU/Linux). Therefore, we have to try an alternate
1421 mechanism to find the dynamic linker's base address. */
1423 TRY_CATCH (ex, RETURN_MASK_ALL)
1425 tmp_bfd = solib_bfd_open (interp_name);
1427 if (tmp_bfd == NULL)
1428 goto bkpt_at_symbol;
1430 /* Now convert the TMP_BFD into a target. That way target, as
1431 well as BFD operations can be used. Note that closing the
1432 target will also close the underlying bfd. */
1433 tmp_bfd_target = target_bfd_reopen (tmp_bfd);
1435 /* On a running target, we can get the dynamic linker's base
1436 address from the shared library table. */
1437 so = master_so_list ();
1440 if (svr4_same_1 (interp_name, so->so_original_name))
1442 load_addr_found = 1;
1443 loader_found_in_list = 1;
1444 load_addr = LM_ADDR_CHECK (so, tmp_bfd);
1450 /* If we were not able to find the base address of the loader
1451 from our so_list, then try using the AT_BASE auxilliary entry. */
1452 if (!load_addr_found)
1453 if (target_auxv_search (¤t_target, AT_BASE, &load_addr) > 0)
1454 load_addr_found = 1;
1456 /* Otherwise we find the dynamic linker's base address by examining
1457 the current pc (which should point at the entry point for the
1458 dynamic linker) and subtracting the offset of the entry point.
1460 This is more fragile than the previous approaches, but is a good
1461 fallback method because it has actually been working well in
1463 if (!load_addr_found)
1465 struct regcache *regcache
1466 = get_thread_arch_regcache (inferior_ptid, target_gdbarch);
1467 load_addr = (regcache_read_pc (regcache)
1468 - exec_entry_point (tmp_bfd, tmp_bfd_target));
1471 if (!loader_found_in_list)
1473 info->debug_loader_name = xstrdup (interp_name);
1474 info->debug_loader_offset_p = 1;
1475 info->debug_loader_offset = load_addr;
1476 solib_add (NULL, from_tty, ¤t_target, auto_solib_add);
1479 /* Record the relocated start and end address of the dynamic linker
1480 text and plt section for svr4_in_dynsym_resolve_code. */
1481 interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
1484 info->interp_text_sect_low =
1485 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1486 info->interp_text_sect_high =
1487 info->interp_text_sect_low
1488 + bfd_section_size (tmp_bfd, interp_sect);
1490 interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
1493 info->interp_plt_sect_low =
1494 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1495 info->interp_plt_sect_high =
1496 info->interp_plt_sect_low
1497 + bfd_section_size (tmp_bfd, interp_sect);
1500 /* Now try to set a breakpoint in the dynamic linker. */
1501 for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
1503 sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep);
1509 /* Convert 'sym_addr' from a function pointer to an address.
1510 Because we pass tmp_bfd_target instead of the current
1511 target, this will always produce an unrelocated value. */
1512 sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1516 /* We're done with both the temporary bfd and target. Remember,
1517 closing the target closes the underlying bfd. */
1518 target_close (tmp_bfd_target, 0);
1522 create_solib_event_breakpoint (target_gdbarch, load_addr + sym_addr);
1523 xfree (interp_name);
1527 /* For whatever reason we couldn't set a breakpoint in the dynamic
1528 linker. Warn and drop into the old code. */
1530 xfree (interp_name);
1531 warning (_("Unable to find dynamic linker breakpoint function.\n"
1532 "GDB will be unable to debug shared library initializers\n"
1533 "and track explicitly loaded dynamic code."));
1536 /* Scan through the lists of symbols, trying to look up the symbol and
1537 set a breakpoint there. Terminate loop when we/if we succeed. */
1539 for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
1541 msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
1542 if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
1544 sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
1545 sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1548 create_solib_event_breakpoint (target_gdbarch, sym_addr);
1553 for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
1555 msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
1556 if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
1558 sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
1559 sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1562 create_solib_event_breakpoint (target_gdbarch, sym_addr);
1573 special_symbol_handling -- additional shared library symbol handling
1577 void special_symbol_handling ()
1581 Once the symbols from a shared object have been loaded in the usual
1582 way, we are called to do any system specific symbol handling that
1585 For SunOS4, this consisted of grunging around in the dynamic
1586 linkers structures to find symbol definitions for "common" symbols
1587 and adding them to the minimal symbol table for the runtime common
1590 However, for SVR4, there's nothing to do.
1595 svr4_special_symbol_handling (void)
1597 svr4_relocate_main_executable ();
1600 /* Decide if the objfile needs to be relocated. As indicated above,
1601 we will only be here when execution is stopped at the beginning
1602 of the program. Relocation is necessary if the address at which
1603 we are presently stopped differs from the start address stored in
1604 the executable AND there's no interpreter section. The condition
1605 regarding the interpreter section is very important because if
1606 there *is* an interpreter section, execution will begin there
1607 instead. When there is an interpreter section, the start address
1608 is (presumably) used by the interpreter at some point to start
1609 execution of the program.
1611 If there is an interpreter, it is normal for it to be set to an
1612 arbitrary address at the outset. The job of finding it is
1613 handled in enable_break().
1615 So, to summarize, relocations are necessary when there is no
1616 interpreter section and the start address obtained from the
1617 executable is different from the address at which GDB is
1620 [ The astute reader will note that we also test to make sure that
1621 the executable in question has the DYNAMIC flag set. It is my
1622 opinion that this test is unnecessary (undesirable even). It
1623 was added to avoid inadvertent relocation of an executable
1624 whose e_type member in the ELF header is not ET_DYN. There may
1625 be a time in the future when it is desirable to do relocations
1626 on other types of files as well in which case this condition
1627 should either be removed or modified to accomodate the new file
1628 type. (E.g, an ET_EXEC executable which has been built to be
1629 position-independent could safely be relocated by the OS if
1630 desired. It is true that this violates the ABI, but the ABI
1631 has been known to be bent from time to time.) - Kevin, Nov 2000. ]
1635 svr4_static_exec_displacement (void)
1637 asection *interp_sect;
1638 struct regcache *regcache
1639 = get_thread_arch_regcache (inferior_ptid, target_gdbarch);
1640 CORE_ADDR pc = regcache_read_pc (regcache);
1642 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
1643 if (interp_sect == NULL
1644 && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0
1645 && (exec_entry_point (exec_bfd, &exec_ops) != pc))
1646 return pc - exec_entry_point (exec_bfd, &exec_ops);
1651 /* We relocate all of the sections by the same amount. This
1652 behavior is mandated by recent editions of the System V ABI.
1653 According to the System V Application Binary Interface,
1654 Edition 4.1, page 5-5:
1656 ... Though the system chooses virtual addresses for
1657 individual processes, it maintains the segments' relative
1658 positions. Because position-independent code uses relative
1659 addressesing between segments, the difference between
1660 virtual addresses in memory must match the difference
1661 between virtual addresses in the file. The difference
1662 between the virtual address of any segment in memory and
1663 the corresponding virtual address in the file is thus a
1664 single constant value for any one executable or shared
1665 object in a given process. This difference is the base
1666 address. One use of the base address is to relocate the
1667 memory image of the program during dynamic linking.
1669 The same language also appears in Edition 4.0 of the System V
1670 ABI and is left unspecified in some of the earlier editions. */
1673 svr4_exec_displacement (void)
1676 /* ENTRY_POINT is a possible function descriptor - before
1677 a call to gdbarch_convert_from_func_ptr_addr. */
1678 CORE_ADDR entry_point;
1680 if (exec_bfd == NULL)
1683 if (target_auxv_search (¤t_target, AT_ENTRY, &entry_point) == 1)
1684 return entry_point - bfd_get_start_address (exec_bfd);
1686 return svr4_static_exec_displacement ();
1689 /* Relocate the main executable. This function should be called upon
1690 stopping the inferior process at the entry point to the program.
1691 The entry point from BFD is compared to the AT_ENTRY of AUXV and if they are
1692 different, the main executable is relocated by the proper amount. */
1695 svr4_relocate_main_executable (void)
1697 CORE_ADDR displacement = svr4_exec_displacement ();
1699 /* Even if DISPLACEMENT is 0 still try to relocate it as this is a new
1700 difference of in-memory vs. in-file addresses and we could already
1701 relocate the executable at this function to improper address before. */
1703 if (symfile_objfile)
1705 struct section_offsets *new_offsets;
1708 new_offsets = alloca (symfile_objfile->num_sections
1709 * sizeof (*new_offsets));
1711 for (i = 0; i < symfile_objfile->num_sections; i++)
1712 new_offsets->offsets[i] = displacement;
1714 objfile_relocate (symfile_objfile, new_offsets);
1720 for (asect = exec_bfd->sections; asect != NULL; asect = asect->next)
1721 exec_set_section_address (bfd_get_filename (exec_bfd), asect->index,
1722 (bfd_section_vma (exec_bfd, asect)
1731 svr4_solib_create_inferior_hook -- shared library startup support
1735 void svr4_solib_create_inferior_hook (int from_tty)
1739 When gdb starts up the inferior, it nurses it along (through the
1740 shell) until it is ready to execute it's first instruction. At this
1741 point, this function gets called via expansion of the macro
1742 SOLIB_CREATE_INFERIOR_HOOK.
1744 For SunOS executables, this first instruction is typically the
1745 one at "_start", or a similar text label, regardless of whether
1746 the executable is statically or dynamically linked. The runtime
1747 startup code takes care of dynamically linking in any shared
1748 libraries, once gdb allows the inferior to continue.
1750 For SVR4 executables, this first instruction is either the first
1751 instruction in the dynamic linker (for dynamically linked
1752 executables) or the instruction at "start" for statically linked
1753 executables. For dynamically linked executables, the system
1754 first exec's /lib/libc.so.N, which contains the dynamic linker,
1755 and starts it running. The dynamic linker maps in any needed
1756 shared libraries, maps in the actual user executable, and then
1757 jumps to "start" in the user executable.
1759 For both SunOS shared libraries, and SVR4 shared libraries, we
1760 can arrange to cooperate with the dynamic linker to discover the
1761 names of shared libraries that are dynamically linked, and the
1762 base addresses to which they are linked.
1764 This function is responsible for discovering those names and
1765 addresses, and saving sufficient information about them to allow
1766 their symbols to be read at a later time.
1770 Between enable_break() and disable_break(), this code does not
1771 properly handle hitting breakpoints which the user might have
1772 set in the startup code or in the dynamic linker itself. Proper
1773 handling will probably have to wait until the implementation is
1774 changed to use the "breakpoint handler function" method.
1776 Also, what if child has exit()ed? Must exit loop somehow.
1780 svr4_solib_create_inferior_hook (int from_tty)
1782 struct inferior *inf;
1783 struct thread_info *tp;
1784 struct svr4_info *info;
1786 info = get_svr4_info ();
1788 /* Relocate the main executable if necessary. */
1789 if (current_inferior ()->attach_flag == 0)
1790 svr4_relocate_main_executable ();
1792 if (!svr4_have_link_map_offsets ())
1795 if (!enable_break (info, from_tty))
1798 #if defined(_SCO_DS)
1799 /* SCO needs the loop below, other systems should be using the
1800 special shared library breakpoints and the shared library breakpoint
1803 Now run the target. It will eventually hit the breakpoint, at
1804 which point all of the libraries will have been mapped in and we
1805 can go groveling around in the dynamic linker structures to find
1806 out what we need to know about them. */
1808 inf = current_inferior ();
1809 tp = inferior_thread ();
1811 clear_proceed_status ();
1812 inf->stop_soon = STOP_QUIETLY;
1813 tp->stop_signal = TARGET_SIGNAL_0;
1816 target_resume (pid_to_ptid (-1), 0, tp->stop_signal);
1817 wait_for_inferior (0);
1819 while (tp->stop_signal != TARGET_SIGNAL_TRAP);
1820 inf->stop_soon = NO_STOP_QUIETLY;
1821 #endif /* defined(_SCO_DS) */
1825 svr4_clear_solib (void)
1827 struct svr4_info *info;
1829 info = get_svr4_info ();
1830 info->debug_base = 0;
1831 info->debug_loader_offset_p = 0;
1832 info->debug_loader_offset = 0;
1833 xfree (info->debug_loader_name);
1834 info->debug_loader_name = NULL;
1838 svr4_free_so (struct so_list *so)
1840 xfree (so->lm_info->lm);
1841 xfree (so->lm_info);
1845 /* Clear any bits of ADDR that wouldn't fit in a target-format
1846 data pointer. "Data pointer" here refers to whatever sort of
1847 address the dynamic linker uses to manage its sections. At the
1848 moment, we don't support shared libraries on any processors where
1849 code and data pointers are different sizes.
1851 This isn't really the right solution. What we really need here is
1852 a way to do arithmetic on CORE_ADDR values that respects the
1853 natural pointer/address correspondence. (For example, on the MIPS,
1854 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
1855 sign-extend the value. There, simply truncating the bits above
1856 gdbarch_ptr_bit, as we do below, is no good.) This should probably
1857 be a new gdbarch method or something. */
1859 svr4_truncate_ptr (CORE_ADDR addr)
1861 if (gdbarch_ptr_bit (target_gdbarch) == sizeof (CORE_ADDR) * 8)
1862 /* We don't need to truncate anything, and the bit twiddling below
1863 will fail due to overflow problems. */
1866 return addr & (((CORE_ADDR) 1 << gdbarch_ptr_bit (target_gdbarch)) - 1);
1871 svr4_relocate_section_addresses (struct so_list *so,
1872 struct target_section *sec)
1874 sec->addr = svr4_truncate_ptr (sec->addr + LM_ADDR_CHECK (so,
1876 sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR_CHECK (so,
1881 /* Architecture-specific operations. */
1883 /* Per-architecture data key. */
1884 static struct gdbarch_data *solib_svr4_data;
1886 struct solib_svr4_ops
1888 /* Return a description of the layout of `struct link_map'. */
1889 struct link_map_offsets *(*fetch_link_map_offsets)(void);
1892 /* Return a default for the architecture-specific operations. */
1895 solib_svr4_init (struct obstack *obstack)
1897 struct solib_svr4_ops *ops;
1899 ops = OBSTACK_ZALLOC (obstack, struct solib_svr4_ops);
1900 ops->fetch_link_map_offsets = NULL;
1904 /* Set the architecture-specific `struct link_map_offsets' fetcher for
1905 GDBARCH to FLMO. Also, install SVR4 solib_ops into GDBARCH. */
1908 set_solib_svr4_fetch_link_map_offsets (struct gdbarch *gdbarch,
1909 struct link_map_offsets *(*flmo) (void))
1911 struct solib_svr4_ops *ops = gdbarch_data (gdbarch, solib_svr4_data);
1913 ops->fetch_link_map_offsets = flmo;
1915 set_solib_ops (gdbarch, &svr4_so_ops);
1918 /* Fetch a link_map_offsets structure using the architecture-specific
1919 `struct link_map_offsets' fetcher. */
1921 static struct link_map_offsets *
1922 svr4_fetch_link_map_offsets (void)
1924 struct solib_svr4_ops *ops = gdbarch_data (target_gdbarch, solib_svr4_data);
1926 gdb_assert (ops->fetch_link_map_offsets);
1927 return ops->fetch_link_map_offsets ();
1930 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
1933 svr4_have_link_map_offsets (void)
1935 struct solib_svr4_ops *ops = gdbarch_data (target_gdbarch, solib_svr4_data);
1936 return (ops->fetch_link_map_offsets != NULL);
1940 /* Most OS'es that have SVR4-style ELF dynamic libraries define a
1941 `struct r_debug' and a `struct link_map' that are binary compatible
1942 with the origional SVR4 implementation. */
1944 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1945 for an ILP32 SVR4 system. */
1947 struct link_map_offsets *
1948 svr4_ilp32_fetch_link_map_offsets (void)
1950 static struct link_map_offsets lmo;
1951 static struct link_map_offsets *lmp = NULL;
1957 lmo.r_version_offset = 0;
1958 lmo.r_version_size = 4;
1959 lmo.r_map_offset = 4;
1960 lmo.r_brk_offset = 8;
1961 lmo.r_ldsomap_offset = 20;
1963 /* Everything we need is in the first 20 bytes. */
1964 lmo.link_map_size = 20;
1965 lmo.l_addr_offset = 0;
1966 lmo.l_name_offset = 4;
1967 lmo.l_ld_offset = 8;
1968 lmo.l_next_offset = 12;
1969 lmo.l_prev_offset = 16;
1975 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
1976 for an LP64 SVR4 system. */
1978 struct link_map_offsets *
1979 svr4_lp64_fetch_link_map_offsets (void)
1981 static struct link_map_offsets lmo;
1982 static struct link_map_offsets *lmp = NULL;
1988 lmo.r_version_offset = 0;
1989 lmo.r_version_size = 4;
1990 lmo.r_map_offset = 8;
1991 lmo.r_brk_offset = 16;
1992 lmo.r_ldsomap_offset = 40;
1994 /* Everything we need is in the first 40 bytes. */
1995 lmo.link_map_size = 40;
1996 lmo.l_addr_offset = 0;
1997 lmo.l_name_offset = 8;
1998 lmo.l_ld_offset = 16;
1999 lmo.l_next_offset = 24;
2000 lmo.l_prev_offset = 32;
2007 struct target_so_ops svr4_so_ops;
2009 /* Lookup global symbol for ELF DSOs linked with -Bsymbolic. Those DSOs have a
2010 different rule for symbol lookup. The lookup begins here in the DSO, not in
2011 the main executable. */
2013 static struct symbol *
2014 elf_lookup_lib_symbol (const struct objfile *objfile,
2016 const char *linkage_name,
2017 const domain_enum domain)
2021 if (objfile == symfile_objfile)
2025 /* OBJFILE should have been passed as the non-debug one. */
2026 gdb_assert (objfile->separate_debug_objfile_backlink == NULL);
2028 abfd = objfile->obfd;
2031 if (abfd == NULL || scan_dyntag (DT_SYMBOLIC, abfd, NULL) != 1)
2034 return lookup_global_symbol_from_objfile
2035 (objfile, name, linkage_name, domain);
2038 extern initialize_file_ftype _initialize_svr4_solib; /* -Wmissing-prototypes */
2041 _initialize_svr4_solib (void)
2043 solib_svr4_data = gdbarch_data_register_pre_init (solib_svr4_init);
2044 solib_svr4_pspace_data
2045 = register_program_space_data_with_cleanup (svr4_pspace_data_cleanup);
2047 svr4_so_ops.relocate_section_addresses = svr4_relocate_section_addresses;
2048 svr4_so_ops.free_so = svr4_free_so;
2049 svr4_so_ops.clear_solib = svr4_clear_solib;
2050 svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook;
2051 svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling;
2052 svr4_so_ops.current_sos = svr4_current_sos;
2053 svr4_so_ops.open_symbol_file_object = open_symbol_file_object;
2054 svr4_so_ops.in_dynsym_resolve_code = svr4_in_dynsym_resolve_code;
2055 svr4_so_ops.bfd_open = solib_bfd_open;
2056 svr4_so_ops.lookup_lib_global_symbol = elf_lookup_lib_symbol;
2057 svr4_so_ops.same = svr4_same;
2058 svr4_so_ops.keep_data_in_core = svr4_keep_data_in_core;