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;
246 printf_unfiltered (_("Using PIC (Position Independent Code) "
247 "prelink displacement %s for \"%s\".\n"),
248 paddress (target_gdbarch, l_addr),
252 warning (_(".dynamic section for \"%s\" "
253 "is not at the expected address "
254 "(wrong library or version mismatch?)"), so->so_name);
258 so->lm_info->l_addr = l_addr;
261 return so->lm_info->l_addr;
265 LM_NEXT (struct so_list *so)
267 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
268 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
270 return extract_typed_address (so->lm_info->lm + lmo->l_next_offset,
275 LM_PREV (struct so_list *so)
277 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
278 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
280 return extract_typed_address (so->lm_info->lm + lmo->l_prev_offset,
285 LM_NAME (struct so_list *so)
287 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
288 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
290 return extract_typed_address (so->lm_info->lm + lmo->l_name_offset,
295 IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
297 /* Assume that everything is a library if the dynamic loader was loaded
298 late by a static executable. */
299 if (exec_bfd && bfd_get_section_by_name (exec_bfd, ".dynamic") == NULL)
302 return LM_PREV (so) == 0;
305 /* Per pspace SVR4 specific data. */
309 CORE_ADDR debug_base; /* Base of dynamic linker structures */
311 /* Validity flag for debug_loader_offset. */
312 int debug_loader_offset_p;
314 /* Load address for the dynamic linker, inferred. */
315 CORE_ADDR debug_loader_offset;
317 /* Name of the dynamic linker, valid if debug_loader_offset_p. */
318 char *debug_loader_name;
320 /* Load map address for the main executable. */
321 CORE_ADDR main_lm_addr;
323 CORE_ADDR interp_text_sect_low;
324 CORE_ADDR interp_text_sect_high;
325 CORE_ADDR interp_plt_sect_low;
326 CORE_ADDR interp_plt_sect_high;
329 /* Per-program-space data key. */
330 static const struct program_space_data *solib_svr4_pspace_data;
333 svr4_pspace_data_cleanup (struct program_space *pspace, void *arg)
335 struct svr4_info *info;
337 info = program_space_data (pspace, solib_svr4_pspace_data);
341 /* Get the current svr4 data. If none is found yet, add it now. This
342 function always returns a valid object. */
344 static struct svr4_info *
347 struct svr4_info *info;
349 info = program_space_data (current_program_space, solib_svr4_pspace_data);
353 info = XZALLOC (struct svr4_info);
354 set_program_space_data (current_program_space, solib_svr4_pspace_data, info);
358 /* Local function prototypes */
360 static int match_main (char *);
362 static CORE_ADDR bfd_lookup_symbol (bfd *, char *);
368 bfd_lookup_symbol -- lookup the value for a specific symbol
372 CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
376 An expensive way to lookup the value of a single symbol for
377 bfd's that are only temporary anyway. This is used by the
378 shared library support to find the address of the debugger
379 notification routine in the shared library.
381 The returned symbol may be in a code or data section; functions
382 will normally be in a code section, but may be in a data section
383 if this architecture uses function descriptors.
385 Note that 0 is specifically allowed as an error return (no
390 bfd_lookup_symbol (bfd *abfd, char *symname)
394 asymbol **symbol_table;
395 unsigned int number_of_symbols;
397 struct cleanup *back_to;
398 CORE_ADDR symaddr = 0;
400 storage_needed = bfd_get_symtab_upper_bound (abfd);
402 if (storage_needed > 0)
404 symbol_table = (asymbol **) xmalloc (storage_needed);
405 back_to = make_cleanup (xfree, symbol_table);
406 number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
408 for (i = 0; i < number_of_symbols; i++)
410 sym = *symbol_table++;
411 if (strcmp (sym->name, symname) == 0
412 && (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
414 /* BFD symbols are section relative. */
415 symaddr = sym->value + sym->section->vma;
419 do_cleanups (back_to);
425 /* On FreeBSD, the dynamic linker is stripped by default. So we'll
426 have to check the dynamic string table too. */
428 storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);
430 if (storage_needed > 0)
432 symbol_table = (asymbol **) xmalloc (storage_needed);
433 back_to = make_cleanup (xfree, symbol_table);
434 number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table);
436 for (i = 0; i < number_of_symbols; i++)
438 sym = *symbol_table++;
440 if (strcmp (sym->name, symname) == 0
441 && (sym->section->flags & (SEC_CODE | SEC_DATA)) != 0)
443 /* BFD symbols are section relative. */
444 symaddr = sym->value + sym->section->vma;
448 do_cleanups (back_to);
455 /* Read program header TYPE from inferior memory. The header is found
456 by scanning the OS auxillary vector.
458 If TYPE == -1, return the program headers instead of the contents of
461 Return a pointer to allocated memory holding the program header contents,
462 or NULL on failure. If sucessful, and unless P_SECT_SIZE is NULL, the
463 size of those contents is returned to P_SECT_SIZE. Likewise, the target
464 architecture size (32-bit or 64-bit) is returned to P_ARCH_SIZE. */
467 read_program_header (int type, int *p_sect_size, int *p_arch_size)
469 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
470 CORE_ADDR at_phdr, at_phent, at_phnum;
471 int arch_size, sect_size;
475 /* Get required auxv elements from target. */
476 if (target_auxv_search (¤t_target, AT_PHDR, &at_phdr) <= 0)
478 if (target_auxv_search (¤t_target, AT_PHENT, &at_phent) <= 0)
480 if (target_auxv_search (¤t_target, AT_PHNUM, &at_phnum) <= 0)
482 if (!at_phdr || !at_phnum)
485 /* Determine ELF architecture type. */
486 if (at_phent == sizeof (Elf32_External_Phdr))
488 else if (at_phent == sizeof (Elf64_External_Phdr))
493 /* Find the requested segment. */
497 sect_size = at_phent * at_phnum;
499 else if (arch_size == 32)
501 Elf32_External_Phdr phdr;
504 /* Search for requested PHDR. */
505 for (i = 0; i < at_phnum; i++)
507 if (target_read_memory (at_phdr + i * sizeof (phdr),
508 (gdb_byte *)&phdr, sizeof (phdr)))
511 if (extract_unsigned_integer ((gdb_byte *)phdr.p_type,
512 4, byte_order) == type)
519 /* Retrieve address and size. */
520 sect_addr = extract_unsigned_integer ((gdb_byte *)phdr.p_vaddr,
522 sect_size = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz,
527 Elf64_External_Phdr phdr;
530 /* Search for requested PHDR. */
531 for (i = 0; i < at_phnum; i++)
533 if (target_read_memory (at_phdr + i * sizeof (phdr),
534 (gdb_byte *)&phdr, sizeof (phdr)))
537 if (extract_unsigned_integer ((gdb_byte *)phdr.p_type,
538 4, byte_order) == type)
545 /* Retrieve address and size. */
546 sect_addr = extract_unsigned_integer ((gdb_byte *)phdr.p_vaddr,
548 sect_size = extract_unsigned_integer ((gdb_byte *)phdr.p_memsz,
552 /* Read in requested program header. */
553 buf = xmalloc (sect_size);
554 if (target_read_memory (sect_addr, buf, sect_size))
561 *p_arch_size = arch_size;
563 *p_sect_size = sect_size;
569 /* Return program interpreter string. */
571 find_program_interpreter (void)
573 gdb_byte *buf = NULL;
575 /* If we have an exec_bfd, use its section table. */
577 && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
579 struct bfd_section *interp_sect;
581 interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
582 if (interp_sect != NULL)
584 int sect_size = bfd_section_size (exec_bfd, interp_sect);
586 buf = xmalloc (sect_size);
587 bfd_get_section_contents (exec_bfd, interp_sect, buf, 0, sect_size);
591 /* If we didn't find it, use the target auxillary vector. */
593 buf = read_program_header (PT_INTERP, NULL, NULL);
599 /* Scan for DYNTAG in .dynamic section of ABFD. If DYNTAG is found 1 is
600 returned and the corresponding PTR is set. */
603 scan_dyntag (int dyntag, bfd *abfd, CORE_ADDR *ptr)
605 int arch_size, step, sect_size;
607 CORE_ADDR dyn_ptr, dyn_addr;
608 gdb_byte *bufend, *bufstart, *buf;
609 Elf32_External_Dyn *x_dynp_32;
610 Elf64_External_Dyn *x_dynp_64;
611 struct bfd_section *sect;
612 struct target_section *target_section;
617 if (bfd_get_flavour (abfd) != bfd_target_elf_flavour)
620 arch_size = bfd_get_arch_size (abfd);
624 /* Find the start address of the .dynamic section. */
625 sect = bfd_get_section_by_name (abfd, ".dynamic");
629 for (target_section = current_target_sections->sections;
630 target_section < current_target_sections->sections_end;
632 if (sect == target_section->the_bfd_section)
634 if (target_section < current_target_sections->sections_end)
635 dyn_addr = target_section->addr;
638 /* ABFD may come from OBJFILE acting only as a symbol file without being
639 loaded into the target (see add_symbol_file_command). This case is
640 such fallback to the file VMA address without the possibility of
641 having the section relocated to its actual in-memory address. */
643 dyn_addr = bfd_section_vma (abfd, sect);
646 /* Read in .dynamic from the BFD. We will get the actual value
647 from memory later. */
648 sect_size = bfd_section_size (abfd, sect);
649 buf = bufstart = alloca (sect_size);
650 if (!bfd_get_section_contents (abfd, sect,
654 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
655 step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
656 : sizeof (Elf64_External_Dyn);
657 for (bufend = buf + sect_size;
663 x_dynp_32 = (Elf32_External_Dyn *) buf;
664 dyn_tag = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_tag);
665 dyn_ptr = bfd_h_get_32 (abfd, (bfd_byte *) x_dynp_32->d_un.d_ptr);
669 x_dynp_64 = (Elf64_External_Dyn *) buf;
670 dyn_tag = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_tag);
671 dyn_ptr = bfd_h_get_64 (abfd, (bfd_byte *) x_dynp_64->d_un.d_ptr);
673 if (dyn_tag == DT_NULL)
675 if (dyn_tag == dyntag)
677 /* If requested, try to read the runtime value of this .dynamic
681 struct type *ptr_type;
685 ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
686 ptr_addr = dyn_addr + (buf - bufstart) + arch_size / 8;
687 if (target_read_memory (ptr_addr, ptr_buf, arch_size / 8) == 0)
688 dyn_ptr = extract_typed_address (ptr_buf, ptr_type);
698 /* Scan for DYNTAG in .dynamic section of the target's main executable,
699 found by consulting the OS auxillary vector. If DYNTAG is found 1 is
700 returned and the corresponding PTR is set. */
703 scan_dyntag_auxv (int dyntag, CORE_ADDR *ptr)
705 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
706 int sect_size, arch_size, step;
709 gdb_byte *bufend, *bufstart, *buf;
711 /* Read in .dynamic section. */
712 buf = bufstart = read_program_header (PT_DYNAMIC, §_size, &arch_size);
716 /* Iterate over BUF and scan for DYNTAG. If found, set PTR and return. */
717 step = (arch_size == 32) ? sizeof (Elf32_External_Dyn)
718 : sizeof (Elf64_External_Dyn);
719 for (bufend = buf + sect_size;
725 Elf32_External_Dyn *dynp = (Elf32_External_Dyn *) buf;
727 dyn_tag = extract_unsigned_integer ((gdb_byte *) dynp->d_tag,
729 dyn_ptr = extract_unsigned_integer ((gdb_byte *) dynp->d_un.d_ptr,
734 Elf64_External_Dyn *dynp = (Elf64_External_Dyn *) buf;
736 dyn_tag = extract_unsigned_integer ((gdb_byte *) dynp->d_tag,
738 dyn_ptr = extract_unsigned_integer ((gdb_byte *) dynp->d_un.d_ptr,
741 if (dyn_tag == DT_NULL)
744 if (dyn_tag == dyntag)
763 elf_locate_base -- locate the base address of dynamic linker structs
764 for SVR4 elf targets.
768 CORE_ADDR elf_locate_base (void)
772 For SVR4 elf targets the address of the dynamic linker's runtime
773 structure is contained within the dynamic info section in the
774 executable file. The dynamic section is also mapped into the
775 inferior address space. Because the runtime loader fills in the
776 real address before starting the inferior, we have to read in the
777 dynamic info section from the inferior address space.
778 If there are any errors while trying to find the address, we
779 silently return 0, otherwise the found address is returned.
784 elf_locate_base (void)
786 struct minimal_symbol *msymbol;
789 /* Look for DT_MIPS_RLD_MAP first. MIPS executables use this
790 instead of DT_DEBUG, although they sometimes contain an unused
792 if (scan_dyntag (DT_MIPS_RLD_MAP, exec_bfd, &dyn_ptr)
793 || scan_dyntag_auxv (DT_MIPS_RLD_MAP, &dyn_ptr))
795 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
797 int pbuf_size = TYPE_LENGTH (ptr_type);
799 pbuf = alloca (pbuf_size);
800 /* DT_MIPS_RLD_MAP contains a pointer to the address
801 of the dynamic link structure. */
802 if (target_read_memory (dyn_ptr, pbuf, pbuf_size))
804 return extract_typed_address (pbuf, ptr_type);
808 if (scan_dyntag (DT_DEBUG, exec_bfd, &dyn_ptr)
809 || scan_dyntag_auxv (DT_DEBUG, &dyn_ptr))
812 /* This may be a static executable. Look for the symbol
813 conventionally named _r_debug, as a last resort. */
814 msymbol = lookup_minimal_symbol ("_r_debug", NULL, symfile_objfile);
816 return SYMBOL_VALUE_ADDRESS (msymbol);
818 /* DT_DEBUG entry not found. */
826 locate_base -- locate the base address of dynamic linker structs
830 CORE_ADDR locate_base (struct svr4_info *)
834 For both the SunOS and SVR4 shared library implementations, if the
835 inferior executable has been linked dynamically, there is a single
836 address somewhere in the inferior's data space which is the key to
837 locating all of the dynamic linker's runtime structures. This
838 address is the value of the debug base symbol. The job of this
839 function is to find and return that address, or to return 0 if there
840 is no such address (the executable is statically linked for example).
842 For SunOS, the job is almost trivial, since the dynamic linker and
843 all of it's structures are statically linked to the executable at
844 link time. Thus the symbol for the address we are looking for has
845 already been added to the minimal symbol table for the executable's
846 objfile at the time the symbol file's symbols were read, and all we
847 have to do is look it up there. Note that we explicitly do NOT want
848 to find the copies in the shared library.
850 The SVR4 version is a bit more complicated because the address
851 is contained somewhere in the dynamic info section. We have to go
852 to a lot more work to discover the address of the debug base symbol.
853 Because of this complexity, we cache the value we find and return that
854 value on subsequent invocations. Note there is no copy in the
855 executable symbol tables.
860 locate_base (struct svr4_info *info)
862 /* Check to see if we have a currently valid address, and if so, avoid
863 doing all this work again and just return the cached address. If
864 we have no cached address, try to locate it in the dynamic info
865 section for ELF executables. There's no point in doing any of this
866 though if we don't have some link map offsets to work with. */
868 if (info->debug_base == 0 && svr4_have_link_map_offsets ())
869 info->debug_base = elf_locate_base ();
870 return info->debug_base;
873 /* Find the first element in the inferior's dynamic link map, and
874 return its address in the inferior. Return zero if the address
875 could not be determined.
877 FIXME: Perhaps we should validate the info somehow, perhaps by
878 checking r_version for a known version number, or r_state for
882 solib_svr4_r_map (struct svr4_info *info)
884 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
885 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
887 volatile struct gdb_exception ex;
889 TRY_CATCH (ex, RETURN_MASK_ERROR)
891 addr = read_memory_typed_address (info->debug_base + lmo->r_map_offset,
894 exception_print (gdb_stderr, ex);
898 /* Find r_brk from the inferior's debug base. */
901 solib_svr4_r_brk (struct svr4_info *info)
903 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
904 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
906 return read_memory_typed_address (info->debug_base + lmo->r_brk_offset,
910 /* Find the link map for the dynamic linker (if it is not in the
911 normal list of loaded shared objects). */
914 solib_svr4_r_ldsomap (struct svr4_info *info)
916 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
917 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
918 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
921 /* Check version, and return zero if `struct r_debug' doesn't have
922 the r_ldsomap member. */
924 = read_memory_unsigned_integer (info->debug_base + lmo->r_version_offset,
925 lmo->r_version_size, byte_order);
926 if (version < 2 || lmo->r_ldsomap_offset == -1)
929 return read_memory_typed_address (info->debug_base + lmo->r_ldsomap_offset,
933 /* On Solaris systems with some versions of the dynamic linker,
934 ld.so's l_name pointer points to the SONAME in the string table
935 rather than into writable memory. So that GDB can find shared
936 libraries when loading a core file generated by gcore, ensure that
937 memory areas containing the l_name string are saved in the core
941 svr4_keep_data_in_core (CORE_ADDR vaddr, unsigned long size)
943 struct svr4_info *info;
946 struct cleanup *old_chain;
947 struct link_map_offsets *lmo;
950 info = get_svr4_info ();
952 info->debug_base = 0;
954 if (!info->debug_base)
957 ldsomap = solib_svr4_r_ldsomap (info);
961 lmo = svr4_fetch_link_map_offsets ();
962 new = XZALLOC (struct so_list);
963 old_chain = make_cleanup (xfree, new);
964 new->lm_info = xmalloc (sizeof (struct lm_info));
965 make_cleanup (xfree, new->lm_info);
966 new->lm_info->l_addr = (CORE_ADDR)-1;
967 new->lm_info->lm_addr = ldsomap;
968 new->lm_info->lm = xzalloc (lmo->link_map_size);
969 make_cleanup (xfree, new->lm_info->lm);
970 read_memory (ldsomap, new->lm_info->lm, lmo->link_map_size);
971 lm_name = LM_NAME (new);
972 do_cleanups (old_chain);
974 return (lm_name >= vaddr && lm_name < vaddr + size);
981 open_symbol_file_object
985 void open_symbol_file_object (void *from_tty)
989 If no open symbol file, attempt to locate and open the main symbol
990 file. On SVR4 systems, this is the first link map entry. If its
991 name is here, we can open it. Useful when attaching to a process
992 without first loading its symbol file.
994 If FROM_TTYP dereferences to a non-zero integer, allow messages to
995 be printed. This parameter is a pointer rather than an int because
996 open_symbol_file_object() is called via catch_errors() and
997 catch_errors() requires a pointer argument. */
1000 open_symbol_file_object (void *from_ttyp)
1002 CORE_ADDR lm, l_name;
1005 int from_tty = *(int *)from_ttyp;
1006 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
1007 struct type *ptr_type = builtin_type (target_gdbarch)->builtin_data_ptr;
1008 int l_name_size = TYPE_LENGTH (ptr_type);
1009 gdb_byte *l_name_buf = xmalloc (l_name_size);
1010 struct cleanup *cleanups = make_cleanup (xfree, l_name_buf);
1011 struct svr4_info *info = get_svr4_info ();
1013 if (symfile_objfile)
1014 if (!query (_("Attempt to reload symbols from process? ")))
1017 /* Always locate the debug struct, in case it has moved. */
1018 info->debug_base = 0;
1019 if (locate_base (info) == 0)
1020 return 0; /* failed somehow... */
1022 /* First link map member should be the executable. */
1023 lm = solib_svr4_r_map (info);
1025 return 0; /* failed somehow... */
1027 /* Read address of name from target memory to GDB. */
1028 read_memory (lm + lmo->l_name_offset, l_name_buf, l_name_size);
1030 /* Convert the address to host format. */
1031 l_name = extract_typed_address (l_name_buf, ptr_type);
1033 /* Free l_name_buf. */
1034 do_cleanups (cleanups);
1037 return 0; /* No filename. */
1039 /* Now fetch the filename from target memory. */
1040 target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode);
1041 make_cleanup (xfree, filename);
1045 warning (_("failed to read exec filename from attached file: %s"),
1046 safe_strerror (errcode));
1050 /* Have a pathname: read the symbol file. */
1051 symbol_file_add_main (filename, from_tty);
1056 /* If no shared library information is available from the dynamic
1057 linker, build a fallback list from other sources. */
1059 static struct so_list *
1060 svr4_default_sos (void)
1062 struct svr4_info *info = get_svr4_info ();
1064 struct so_list *head = NULL;
1065 struct so_list **link_ptr = &head;
1067 if (info->debug_loader_offset_p)
1069 struct so_list *new = XZALLOC (struct so_list);
1071 new->lm_info = xmalloc (sizeof (struct lm_info));
1073 /* Nothing will ever check the cached copy of the link
1074 map if we set l_addr. */
1075 new->lm_info->l_addr = info->debug_loader_offset;
1076 new->lm_info->lm_addr = 0;
1077 new->lm_info->lm = NULL;
1079 strncpy (new->so_name, info->debug_loader_name,
1080 SO_NAME_MAX_PATH_SIZE - 1);
1081 new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
1082 strcpy (new->so_original_name, new->so_name);
1085 link_ptr = &new->next;
1093 current_sos -- build a list of currently loaded shared objects
1097 struct so_list *current_sos ()
1101 Build a list of `struct so_list' objects describing the shared
1102 objects currently loaded in the inferior. This list does not
1103 include an entry for the main executable file.
1105 Note that we only gather information directly available from the
1106 inferior --- we don't examine any of the shared library files
1107 themselves. The declaration of `struct so_list' says which fields
1108 we provide values for. */
1110 static struct so_list *
1111 svr4_current_sos (void)
1113 CORE_ADDR lm, prev_lm;
1114 struct so_list *head = 0;
1115 struct so_list **link_ptr = &head;
1116 CORE_ADDR ldsomap = 0;
1117 struct svr4_info *info;
1119 info = get_svr4_info ();
1121 /* Always locate the debug struct, in case it has moved. */
1122 info->debug_base = 0;
1125 /* If we can't find the dynamic linker's base structure, this
1126 must not be a dynamically linked executable. Hmm. */
1127 if (! info->debug_base)
1128 return svr4_default_sos ();
1130 /* Walk the inferior's link map list, and build our list of
1131 `struct so_list' nodes. */
1133 lm = solib_svr4_r_map (info);
1137 struct link_map_offsets *lmo = svr4_fetch_link_map_offsets ();
1138 struct so_list *new = XZALLOC (struct so_list);
1139 struct cleanup *old_chain = make_cleanup (xfree, new);
1142 new->lm_info = xmalloc (sizeof (struct lm_info));
1143 make_cleanup (xfree, new->lm_info);
1145 new->lm_info->l_addr = (CORE_ADDR)-1;
1146 new->lm_info->lm_addr = lm;
1147 new->lm_info->lm = xzalloc (lmo->link_map_size);
1148 make_cleanup (xfree, new->lm_info->lm);
1150 read_memory (lm, new->lm_info->lm, lmo->link_map_size);
1152 next_lm = LM_NEXT (new);
1154 if (LM_PREV (new) != prev_lm)
1156 warning (_("Corrupted shared library list"));
1161 /* For SVR4 versions, the first entry in the link map is for the
1162 inferior executable, so we must ignore it. For some versions of
1163 SVR4, it has no name. For others (Solaris 2.3 for example), it
1164 does have a name, so we can no longer use a missing name to
1165 decide when to ignore it. */
1166 else if (IGNORE_FIRST_LINK_MAP_ENTRY (new) && ldsomap == 0)
1168 info->main_lm_addr = new->lm_info->lm_addr;
1176 /* Extract this shared object's name. */
1177 target_read_string (LM_NAME (new), &buffer,
1178 SO_NAME_MAX_PATH_SIZE - 1, &errcode);
1180 warning (_("Can't read pathname for load map: %s."),
1181 safe_strerror (errcode));
1184 strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
1185 new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
1186 strcpy (new->so_original_name, new->so_name);
1190 /* If this entry has no name, or its name matches the name
1191 for the main executable, don't include it in the list. */
1192 if (! new->so_name[0]
1193 || match_main (new->so_name))
1199 link_ptr = &new->next;
1206 /* On Solaris, the dynamic linker is not in the normal list of
1207 shared objects, so make sure we pick it up too. Having
1208 symbol information for the dynamic linker is quite crucial
1209 for skipping dynamic linker resolver code. */
1210 if (lm == 0 && ldsomap == 0)
1212 lm = ldsomap = solib_svr4_r_ldsomap (info);
1216 discard_cleanups (old_chain);
1220 return svr4_default_sos ();
1225 /* Get the address of the link_map for a given OBJFILE. */
1228 svr4_fetch_objfile_link_map (struct objfile *objfile)
1231 struct svr4_info *info = get_svr4_info ();
1233 /* Cause svr4_current_sos() to be run if it hasn't been already. */
1234 if (info->main_lm_addr == 0)
1235 solib_add (NULL, 0, ¤t_target, auto_solib_add);
1237 /* svr4_current_sos() will set main_lm_addr for the main executable. */
1238 if (objfile == symfile_objfile)
1239 return info->main_lm_addr;
1241 /* The other link map addresses may be found by examining the list
1242 of shared libraries. */
1243 for (so = master_so_list (); so; so = so->next)
1244 if (so->objfile == objfile)
1245 return so->lm_info->lm_addr;
1251 /* On some systems, the only way to recognize the link map entry for
1252 the main executable file is by looking at its name. Return
1253 non-zero iff SONAME matches one of the known main executable names. */
1256 match_main (char *soname)
1260 for (mainp = main_name_list; *mainp != NULL; mainp++)
1262 if (strcmp (soname, *mainp) == 0)
1269 /* Return 1 if PC lies in the dynamic symbol resolution code of the
1270 SVR4 run time loader. */
1273 svr4_in_dynsym_resolve_code (CORE_ADDR pc)
1275 struct svr4_info *info = get_svr4_info ();
1277 return ((pc >= info->interp_text_sect_low
1278 && pc < info->interp_text_sect_high)
1279 || (pc >= info->interp_plt_sect_low
1280 && pc < info->interp_plt_sect_high)
1281 || in_plt_section (pc, NULL));
1284 /* Given an executable's ABFD and target, compute the entry-point
1288 exec_entry_point (struct bfd *abfd, struct target_ops *targ)
1290 /* KevinB wrote ... for most targets, the address returned by
1291 bfd_get_start_address() is the entry point for the start
1292 function. But, for some targets, bfd_get_start_address() returns
1293 the address of a function descriptor from which the entry point
1294 address may be extracted. This address is extracted by
1295 gdbarch_convert_from_func_ptr_addr(). The method
1296 gdbarch_convert_from_func_ptr_addr() is the merely the identify
1297 function for targets which don't use function descriptors. */
1298 return gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1299 bfd_get_start_address (abfd),
1307 enable_break -- arrange for dynamic linker to hit breakpoint
1311 int enable_break (void)
1315 Both the SunOS and the SVR4 dynamic linkers have, as part of their
1316 debugger interface, support for arranging for the inferior to hit
1317 a breakpoint after mapping in the shared libraries. This function
1318 enables that breakpoint.
1320 For SunOS, there is a special flag location (in_debugger) which we
1321 set to 1. When the dynamic linker sees this flag set, it will set
1322 a breakpoint at a location known only to itself, after saving the
1323 original contents of that place and the breakpoint address itself,
1324 in it's own internal structures. When we resume the inferior, it
1325 will eventually take a SIGTRAP when it runs into the breakpoint.
1326 We handle this (in a different place) by restoring the contents of
1327 the breakpointed location (which is only known after it stops),
1328 chasing around to locate the shared libraries that have been
1329 loaded, then resuming.
1331 For SVR4, the debugger interface structure contains a member (r_brk)
1332 which is statically initialized at the time the shared library is
1333 built, to the offset of a function (_r_debug_state) which is guaran-
1334 teed to be called once before mapping in a library, and again when
1335 the mapping is complete. At the time we are examining this member,
1336 it contains only the unrelocated offset of the function, so we have
1337 to do our own relocation. Later, when the dynamic linker actually
1338 runs, it relocates r_brk to be the actual address of _r_debug_state().
1340 The debugger interface structure also contains an enumeration which
1341 is set to either RT_ADD or RT_DELETE prior to changing the mapping,
1342 depending upon whether or not the library is being mapped or unmapped,
1343 and then set to RT_CONSISTENT after the library is mapped/unmapped.
1347 enable_break (struct svr4_info *info, int from_tty)
1349 struct minimal_symbol *msymbol;
1351 asection *interp_sect;
1352 gdb_byte *interp_name;
1355 info->interp_text_sect_low = info->interp_text_sect_high = 0;
1356 info->interp_plt_sect_low = info->interp_plt_sect_high = 0;
1358 /* If we already have a shared library list in the target, and
1359 r_debug contains r_brk, set the breakpoint there - this should
1360 mean r_brk has already been relocated. Assume the dynamic linker
1361 is the object containing r_brk. */
1363 solib_add (NULL, from_tty, ¤t_target, auto_solib_add);
1365 if (info->debug_base && solib_svr4_r_map (info) != 0)
1366 sym_addr = solib_svr4_r_brk (info);
1370 struct obj_section *os;
1372 sym_addr = gdbarch_addr_bits_remove
1373 (target_gdbarch, gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1377 /* On at least some versions of Solaris there's a dynamic relocation
1378 on _r_debug.r_brk and SYM_ADDR may not be relocated yet, e.g., if
1379 we get control before the dynamic linker has self-relocated.
1380 Check if SYM_ADDR is in a known section, if it is assume we can
1381 trust its value. This is just a heuristic though, it could go away
1382 or be replaced if it's getting in the way.
1384 On ARM we need to know whether the ISA of rtld_db_dlactivity (or
1385 however it's spelled in your particular system) is ARM or Thumb.
1386 That knowledge is encoded in the address, if it's Thumb the low bit
1387 is 1. However, we've stripped that info above and it's not clear
1388 what all the consequences are of passing a non-addr_bits_remove'd
1389 address to create_solib_event_breakpoint. The call to
1390 find_pc_section verifies we know about the address and have some
1391 hope of computing the right kind of breakpoint to use (via
1392 symbol info). It does mean that GDB needs to be pointed at a
1393 non-stripped version of the dynamic linker in order to obtain
1394 information it already knows about. Sigh. */
1396 os = find_pc_section (sym_addr);
1399 /* Record the relocated start and end address of the dynamic linker
1400 text and plt section for svr4_in_dynsym_resolve_code. */
1402 CORE_ADDR load_addr;
1404 tmp_bfd = os->objfile->obfd;
1405 load_addr = ANOFFSET (os->objfile->section_offsets,
1406 os->objfile->sect_index_text);
1408 interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
1411 info->interp_text_sect_low =
1412 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1413 info->interp_text_sect_high =
1414 info->interp_text_sect_low
1415 + bfd_section_size (tmp_bfd, interp_sect);
1417 interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
1420 info->interp_plt_sect_low =
1421 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1422 info->interp_plt_sect_high =
1423 info->interp_plt_sect_low
1424 + bfd_section_size (tmp_bfd, interp_sect);
1427 create_solib_event_breakpoint (target_gdbarch, sym_addr);
1432 /* Find the program interpreter; if not found, warn the user and drop
1433 into the old breakpoint at symbol code. */
1434 interp_name = find_program_interpreter ();
1437 CORE_ADDR load_addr = 0;
1438 int load_addr_found = 0;
1439 int loader_found_in_list = 0;
1441 bfd *tmp_bfd = NULL;
1442 struct target_ops *tmp_bfd_target;
1443 volatile struct gdb_exception ex;
1447 /* Now we need to figure out where the dynamic linker was
1448 loaded so that we can load its symbols and place a breakpoint
1449 in the dynamic linker itself.
1451 This address is stored on the stack. However, I've been unable
1452 to find any magic formula to find it for Solaris (appears to
1453 be trivial on GNU/Linux). Therefore, we have to try an alternate
1454 mechanism to find the dynamic linker's base address. */
1456 TRY_CATCH (ex, RETURN_MASK_ALL)
1458 tmp_bfd = solib_bfd_open (interp_name);
1460 if (tmp_bfd == NULL)
1461 goto bkpt_at_symbol;
1463 /* Now convert the TMP_BFD into a target. That way target, as
1464 well as BFD operations can be used. Note that closing the
1465 target will also close the underlying bfd. */
1466 tmp_bfd_target = target_bfd_reopen (tmp_bfd);
1468 /* On a running target, we can get the dynamic linker's base
1469 address from the shared library table. */
1470 so = master_so_list ();
1473 if (svr4_same_1 (interp_name, so->so_original_name))
1475 load_addr_found = 1;
1476 loader_found_in_list = 1;
1477 load_addr = LM_ADDR_CHECK (so, tmp_bfd);
1483 /* If we were not able to find the base address of the loader
1484 from our so_list, then try using the AT_BASE auxilliary entry. */
1485 if (!load_addr_found)
1486 if (target_auxv_search (¤t_target, AT_BASE, &load_addr) > 0)
1488 int addr_bit = gdbarch_addr_bit (target_gdbarch);
1490 /* Ensure LOAD_ADDR has proper sign in its possible upper bits so
1491 that `+ load_addr' will overflow CORE_ADDR width not creating
1492 invalid addresses like 0x101234567 for 32bit inferiors on 64bit
1495 if (addr_bit < (sizeof (CORE_ADDR) * HOST_CHAR_BIT))
1497 CORE_ADDR space_size = (CORE_ADDR) 1 << addr_bit;
1498 CORE_ADDR tmp_entry_point = exec_entry_point (tmp_bfd,
1501 gdb_assert (load_addr < space_size);
1503 /* TMP_ENTRY_POINT exceeding SPACE_SIZE would be for prelinked
1504 64bit ld.so with 32bit executable, it should not happen. */
1506 if (tmp_entry_point < space_size
1507 && tmp_entry_point + load_addr >= space_size)
1508 load_addr -= space_size;
1511 load_addr_found = 1;
1514 /* Otherwise we find the dynamic linker's base address by examining
1515 the current pc (which should point at the entry point for the
1516 dynamic linker) and subtracting the offset of the entry point.
1518 This is more fragile than the previous approaches, but is a good
1519 fallback method because it has actually been working well in
1521 if (!load_addr_found)
1523 struct regcache *regcache
1524 = get_thread_arch_regcache (inferior_ptid, target_gdbarch);
1526 load_addr = (regcache_read_pc (regcache)
1527 - exec_entry_point (tmp_bfd, tmp_bfd_target));
1530 if (!loader_found_in_list)
1532 info->debug_loader_name = xstrdup (interp_name);
1533 info->debug_loader_offset_p = 1;
1534 info->debug_loader_offset = load_addr;
1535 solib_add (NULL, from_tty, ¤t_target, auto_solib_add);
1538 /* Record the relocated start and end address of the dynamic linker
1539 text and plt section for svr4_in_dynsym_resolve_code. */
1540 interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
1543 info->interp_text_sect_low =
1544 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1545 info->interp_text_sect_high =
1546 info->interp_text_sect_low
1547 + bfd_section_size (tmp_bfd, interp_sect);
1549 interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
1552 info->interp_plt_sect_low =
1553 bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
1554 info->interp_plt_sect_high =
1555 info->interp_plt_sect_low
1556 + bfd_section_size (tmp_bfd, interp_sect);
1559 /* Now try to set a breakpoint in the dynamic linker. */
1560 for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
1562 sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep);
1568 /* Convert 'sym_addr' from a function pointer to an address.
1569 Because we pass tmp_bfd_target instead of the current
1570 target, this will always produce an unrelocated value. */
1571 sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1575 /* We're done with both the temporary bfd and target. Remember,
1576 closing the target closes the underlying bfd. */
1577 target_close (tmp_bfd_target, 0);
1581 create_solib_event_breakpoint (target_gdbarch, load_addr + sym_addr);
1582 xfree (interp_name);
1586 /* For whatever reason we couldn't set a breakpoint in the dynamic
1587 linker. Warn and drop into the old code. */
1589 xfree (interp_name);
1590 warning (_("Unable to find dynamic linker breakpoint function.\n"
1591 "GDB will be unable to debug shared library initializers\n"
1592 "and track explicitly loaded dynamic code."));
1595 /* Scan through the lists of symbols, trying to look up the symbol and
1596 set a breakpoint there. Terminate loop when we/if we succeed. */
1598 for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
1600 msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
1601 if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
1603 sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
1604 sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1607 create_solib_event_breakpoint (target_gdbarch, sym_addr);
1612 for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
1614 msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
1615 if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
1617 sym_addr = SYMBOL_VALUE_ADDRESS (msymbol);
1618 sym_addr = gdbarch_convert_from_func_ptr_addr (target_gdbarch,
1621 create_solib_event_breakpoint (target_gdbarch, sym_addr);
1632 special_symbol_handling -- additional shared library symbol handling
1636 void special_symbol_handling ()
1640 Once the symbols from a shared object have been loaded in the usual
1641 way, we are called to do any system specific symbol handling that
1644 For SunOS4, this consisted of grunging around in the dynamic
1645 linkers structures to find symbol definitions for "common" symbols
1646 and adding them to the minimal symbol table for the runtime common
1649 However, for SVR4, there's nothing to do.
1654 svr4_special_symbol_handling (void)
1658 /* Read the ELF program headers from ABFD. Return the contents and
1659 set *PHDRS_SIZE to the size of the program headers. */
1662 read_program_headers_from_bfd (bfd *abfd, int *phdrs_size)
1664 Elf_Internal_Ehdr *ehdr;
1667 ehdr = elf_elfheader (abfd);
1669 *phdrs_size = ehdr->e_phnum * ehdr->e_phentsize;
1670 if (*phdrs_size == 0)
1673 buf = xmalloc (*phdrs_size);
1674 if (bfd_seek (abfd, ehdr->e_phoff, SEEK_SET) != 0
1675 || bfd_bread (buf, *phdrs_size, abfd) != *phdrs_size)
1684 /* Return 1 and fill *DISPLACEMENTP with detected PIE offset of inferior
1685 exec_bfd. Otherwise return 0.
1687 We relocate all of the sections by the same amount. This
1688 behavior is mandated by recent editions of the System V ABI.
1689 According to the System V Application Binary Interface,
1690 Edition 4.1, page 5-5:
1692 ... Though the system chooses virtual addresses for
1693 individual processes, it maintains the segments' relative
1694 positions. Because position-independent code uses relative
1695 addressesing between segments, the difference between
1696 virtual addresses in memory must match the difference
1697 between virtual addresses in the file. The difference
1698 between the virtual address of any segment in memory and
1699 the corresponding virtual address in the file is thus a
1700 single constant value for any one executable or shared
1701 object in a given process. This difference is the base
1702 address. One use of the base address is to relocate the
1703 memory image of the program during dynamic linking.
1705 The same language also appears in Edition 4.0 of the System V
1706 ABI and is left unspecified in some of the earlier editions.
1708 Decide if the objfile needs to be relocated. As indicated above, we will
1709 only be here when execution is stopped. But during attachment PC can be at
1710 arbitrary address therefore regcache_read_pc can be misleading (contrary to
1711 the auxv AT_ENTRY value). Moreover for executable with interpreter section
1712 regcache_read_pc would point to the interpreter and not the main executable.
1714 So, to summarize, relocations are necessary when the start address obtained
1715 from the executable is different from the address in auxv AT_ENTRY entry.
1717 [ The astute reader will note that we also test to make sure that
1718 the executable in question has the DYNAMIC flag set. It is my
1719 opinion that this test is unnecessary (undesirable even). It
1720 was added to avoid inadvertent relocation of an executable
1721 whose e_type member in the ELF header is not ET_DYN. There may
1722 be a time in the future when it is desirable to do relocations
1723 on other types of files as well in which case this condition
1724 should either be removed or modified to accomodate the new file
1725 type. - Kevin, Nov 2000. ] */
1728 svr4_exec_displacement (CORE_ADDR *displacementp)
1730 /* ENTRY_POINT is a possible function descriptor - before
1731 a call to gdbarch_convert_from_func_ptr_addr. */
1732 CORE_ADDR entry_point, displacement;
1734 if (exec_bfd == NULL)
1737 /* Therefore for ELF it is ET_EXEC and not ET_DYN. Both shared libraries
1738 being executed themselves and PIE (Position Independent Executable)
1739 executables are ET_DYN. */
1741 if ((bfd_get_file_flags (exec_bfd) & DYNAMIC) == 0)
1744 if (target_auxv_search (¤t_target, AT_ENTRY, &entry_point) <= 0)
1747 displacement = entry_point - bfd_get_start_address (exec_bfd);
1749 /* Verify the DISPLACEMENT candidate complies with the required page
1750 alignment. It is cheaper than the program headers comparison below. */
1752 if (bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
1754 const struct elf_backend_data *elf = get_elf_backend_data (exec_bfd);
1756 /* p_align of PT_LOAD segments does not specify any alignment but
1757 only congruency of addresses:
1758 p_offset % p_align == p_vaddr % p_align
1759 Kernel is free to load the executable with lower alignment. */
1761 if ((displacement & (elf->minpagesize - 1)) != 0)
1765 /* Verify that the auxilliary vector describes the same file as exec_bfd, by
1766 comparing their program headers. If the program headers in the auxilliary
1767 vector do not match the program headers in the executable, then we are
1768 looking at a different file than the one used by the kernel - for
1769 instance, "gdb program" connected to "gdbserver :PORT ld.so program". */
1771 if (bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
1773 /* Be optimistic and clear OK only if GDB was able to verify the headers
1774 really do not match. */
1775 int phdrs_size, phdrs2_size, ok = 1;
1776 gdb_byte *buf, *buf2;
1779 buf = read_program_header (-1, &phdrs_size, &arch_size);
1780 buf2 = read_program_headers_from_bfd (exec_bfd, &phdrs2_size);
1781 if (buf != NULL && buf2 != NULL)
1783 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch);
1785 /* We are dealing with three different addresses. EXEC_BFD
1786 represents current address in on-disk file. target memory content
1787 may be different from EXEC_BFD as the file may have been prelinked
1788 to a different address after the executable has been loaded.
1789 Moreover the address of placement in target memory can be
1790 different from what the program headers in target memory say - this
1793 Detected DISPLACEMENT covers both the offsets of PIE placement and
1794 possible new prelink performed after start of the program. Here
1795 relocate BUF and BUF2 just by the EXEC_BFD vs. target memory
1796 content offset for the verification purpose. */
1798 if (phdrs_size != phdrs2_size
1799 || bfd_get_arch_size (exec_bfd) != arch_size)
1801 else if (arch_size == 32 && phdrs_size >= sizeof (Elf32_External_Phdr)
1802 && phdrs_size % sizeof (Elf32_External_Phdr) == 0)
1804 Elf_Internal_Ehdr *ehdr2 = elf_tdata (exec_bfd)->elf_header;
1805 Elf_Internal_Phdr *phdr2 = elf_tdata (exec_bfd)->phdr;
1806 CORE_ADDR displacement = 0;
1809 /* DISPLACEMENT could be found more easily by the difference of
1810 ehdr2->e_entry. But we haven't read the ehdr yet, and we
1811 already have enough information to compute that displacement
1812 with what we've read. */
1814 for (i = 0; i < ehdr2->e_phnum; i++)
1815 if (phdr2[i].p_type == PT_LOAD)
1817 Elf32_External_Phdr *phdrp;
1818 gdb_byte *buf_vaddr_p, *buf_paddr_p;
1819 CORE_ADDR vaddr, paddr;
1820 CORE_ADDR displacement_vaddr = 0;
1821 CORE_ADDR displacement_paddr = 0;
1823 phdrp = &((Elf32_External_Phdr *) buf)[i];
1824 buf_vaddr_p = (gdb_byte *) &phdrp->p_vaddr;
1825 buf_paddr_p = (gdb_byte *) &phdrp->p_paddr;
1827 vaddr = extract_unsigned_integer (buf_vaddr_p, 4,
1829 displacement_vaddr = vaddr - phdr2[i].p_vaddr;
1831 paddr = extract_unsigned_integer (buf_paddr_p, 4,
1833 displacement_paddr = paddr - phdr2[i].p_paddr;
1835 if (displacement_vaddr == displacement_paddr)
1836 displacement = displacement_vaddr;
1841 /* Now compare BUF and BUF2 with optional DISPLACEMENT. */
1843 for (i = 0; i < phdrs_size / sizeof (Elf32_External_Phdr); i++)
1845 Elf32_External_Phdr *phdrp;
1846 Elf32_External_Phdr *phdr2p;
1847 gdb_byte *buf_vaddr_p, *buf_paddr_p;
1848 CORE_ADDR vaddr, paddr;
1850 phdrp = &((Elf32_External_Phdr *) buf)[i];
1851 buf_vaddr_p = (gdb_byte *) &phdrp->p_vaddr;
1852 buf_paddr_p = (gdb_byte *) &phdrp->p_paddr;
1853 phdr2p = &((Elf32_External_Phdr *) buf2)[i];
1855 /* PT_GNU_STACK is an exception by being never relocated by
1856 prelink as its addresses are always zero. */
1858 if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
1861 /* Check also other adjustment combinations - PR 11786. */
1863 vaddr = extract_unsigned_integer (buf_vaddr_p, 4, byte_order);
1864 vaddr -= displacement;
1865 store_unsigned_integer (buf_vaddr_p, 4, byte_order, vaddr);
1867 paddr = extract_unsigned_integer (buf_paddr_p, 4, byte_order);
1868 paddr -= displacement;
1869 store_unsigned_integer (buf_paddr_p, 4, byte_order, paddr);
1871 if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
1878 else if (arch_size == 64 && phdrs_size >= sizeof (Elf64_External_Phdr)
1879 && phdrs_size % sizeof (Elf64_External_Phdr) == 0)
1881 Elf_Internal_Ehdr *ehdr2 = elf_tdata (exec_bfd)->elf_header;
1882 Elf_Internal_Phdr *phdr2 = elf_tdata (exec_bfd)->phdr;
1883 CORE_ADDR displacement = 0;
1886 /* DISPLACEMENT could be found more easily by the difference of
1887 ehdr2->e_entry. But we haven't read the ehdr yet, and we
1888 already have enough information to compute that displacement
1889 with what we've read. */
1891 for (i = 0; i < ehdr2->e_phnum; i++)
1892 if (phdr2[i].p_type == PT_LOAD)
1894 Elf64_External_Phdr *phdrp;
1895 gdb_byte *buf_vaddr_p, *buf_paddr_p;
1896 CORE_ADDR vaddr, paddr;
1897 CORE_ADDR displacement_vaddr = 0;
1898 CORE_ADDR displacement_paddr = 0;
1900 phdrp = &((Elf64_External_Phdr *) buf)[i];
1901 buf_vaddr_p = (gdb_byte *) &phdrp->p_vaddr;
1902 buf_paddr_p = (gdb_byte *) &phdrp->p_paddr;
1904 vaddr = extract_unsigned_integer (buf_vaddr_p, 8,
1906 displacement_vaddr = vaddr - phdr2[i].p_vaddr;
1908 paddr = extract_unsigned_integer (buf_paddr_p, 8,
1910 displacement_paddr = paddr - phdr2[i].p_paddr;
1912 if (displacement_vaddr == displacement_paddr)
1913 displacement = displacement_vaddr;
1918 /* Now compare BUF and BUF2 with optional DISPLACEMENT. */
1920 for (i = 0; i < phdrs_size / sizeof (Elf64_External_Phdr); i++)
1922 Elf64_External_Phdr *phdrp;
1923 Elf64_External_Phdr *phdr2p;
1924 gdb_byte *buf_vaddr_p, *buf_paddr_p;
1925 CORE_ADDR vaddr, paddr;
1927 phdrp = &((Elf64_External_Phdr *) buf)[i];
1928 buf_vaddr_p = (gdb_byte *) &phdrp->p_vaddr;
1929 buf_paddr_p = (gdb_byte *) &phdrp->p_paddr;
1930 phdr2p = &((Elf64_External_Phdr *) buf2)[i];
1932 /* PT_GNU_STACK is an exception by being never relocated by
1933 prelink as its addresses are always zero. */
1935 if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
1938 /* Check also other adjustment combinations - PR 11786. */
1940 vaddr = extract_unsigned_integer (buf_vaddr_p, 8, byte_order);
1941 vaddr -= displacement;
1942 store_unsigned_integer (buf_vaddr_p, 8, byte_order, vaddr);
1944 paddr = extract_unsigned_integer (buf_paddr_p, 8, byte_order);
1945 paddr -= displacement;
1946 store_unsigned_integer (buf_paddr_p, 8, byte_order, paddr);
1948 if (memcmp (phdrp, phdr2p, sizeof (*phdrp)) == 0)
1968 /* It can be printed repeatedly as there is no easy way to check
1969 the executable symbols/file has been already relocated to
1972 printf_unfiltered (_("Using PIE (Position Independent Executable) "
1973 "displacement %s for \"%s\".\n"),
1974 paddress (target_gdbarch, displacement),
1975 bfd_get_filename (exec_bfd));
1978 *displacementp = displacement;
1982 /* Relocate the main executable. This function should be called upon
1983 stopping the inferior process at the entry point to the program.
1984 The entry point from BFD is compared to the AT_ENTRY of AUXV and if they are
1985 different, the main executable is relocated by the proper amount. */
1988 svr4_relocate_main_executable (void)
1990 CORE_ADDR displacement;
1992 if (symfile_objfile)
1996 /* Remote target may have already set specific offsets by `qOffsets'
1997 which should be preferred. */
1999 for (i = 0; i < symfile_objfile->num_sections; i++)
2000 if (ANOFFSET (symfile_objfile->section_offsets, i) != 0)
2004 if (! svr4_exec_displacement (&displacement))
2007 /* Even DISPLACEMENT 0 is a valid new difference of in-memory vs. in-file
2010 if (symfile_objfile)
2012 struct section_offsets *new_offsets;
2015 new_offsets = alloca (symfile_objfile->num_sections
2016 * sizeof (*new_offsets));
2018 for (i = 0; i < symfile_objfile->num_sections; i++)
2019 new_offsets->offsets[i] = displacement;
2021 objfile_relocate (symfile_objfile, new_offsets);
2027 for (asect = exec_bfd->sections; asect != NULL; asect = asect->next)
2028 exec_set_section_address (bfd_get_filename (exec_bfd), asect->index,
2029 (bfd_section_vma (exec_bfd, asect)
2038 svr4_solib_create_inferior_hook -- shared library startup support
2042 void svr4_solib_create_inferior_hook (int from_tty)
2046 When gdb starts up the inferior, it nurses it along (through the
2047 shell) until it is ready to execute it's first instruction. At this
2048 point, this function gets called via expansion of the macro
2049 SOLIB_CREATE_INFERIOR_HOOK.
2051 For SunOS executables, this first instruction is typically the
2052 one at "_start", or a similar text label, regardless of whether
2053 the executable is statically or dynamically linked. The runtime
2054 startup code takes care of dynamically linking in any shared
2055 libraries, once gdb allows the inferior to continue.
2057 For SVR4 executables, this first instruction is either the first
2058 instruction in the dynamic linker (for dynamically linked
2059 executables) or the instruction at "start" for statically linked
2060 executables. For dynamically linked executables, the system
2061 first exec's /lib/libc.so.N, which contains the dynamic linker,
2062 and starts it running. The dynamic linker maps in any needed
2063 shared libraries, maps in the actual user executable, and then
2064 jumps to "start" in the user executable.
2066 For both SunOS shared libraries, and SVR4 shared libraries, we
2067 can arrange to cooperate with the dynamic linker to discover the
2068 names of shared libraries that are dynamically linked, and the
2069 base addresses to which they are linked.
2071 This function is responsible for discovering those names and
2072 addresses, and saving sufficient information about them to allow
2073 their symbols to be read at a later time.
2077 Between enable_break() and disable_break(), this code does not
2078 properly handle hitting breakpoints which the user might have
2079 set in the startup code or in the dynamic linker itself. Proper
2080 handling will probably have to wait until the implementation is
2081 changed to use the "breakpoint handler function" method.
2083 Also, what if child has exit()ed? Must exit loop somehow.
2087 svr4_solib_create_inferior_hook (int from_tty)
2089 #if defined(_SCO_DS)
2090 struct inferior *inf;
2091 struct thread_info *tp;
2092 #endif /* defined(_SCO_DS) */
2093 struct svr4_info *info;
2095 info = get_svr4_info ();
2097 /* Relocate the main executable if necessary. */
2098 svr4_relocate_main_executable ();
2100 if (!svr4_have_link_map_offsets ())
2103 if (!enable_break (info, from_tty))
2106 #if defined(_SCO_DS)
2107 /* SCO needs the loop below, other systems should be using the
2108 special shared library breakpoints and the shared library breakpoint
2111 Now run the target. It will eventually hit the breakpoint, at
2112 which point all of the libraries will have been mapped in and we
2113 can go groveling around in the dynamic linker structures to find
2114 out what we need to know about them. */
2116 inf = current_inferior ();
2117 tp = inferior_thread ();
2119 clear_proceed_status ();
2120 inf->stop_soon = STOP_QUIETLY;
2121 tp->stop_signal = TARGET_SIGNAL_0;
2124 target_resume (pid_to_ptid (-1), 0, tp->stop_signal);
2125 wait_for_inferior (0);
2127 while (tp->stop_signal != TARGET_SIGNAL_TRAP);
2128 inf->stop_soon = NO_STOP_QUIETLY;
2129 #endif /* defined(_SCO_DS) */
2133 svr4_clear_solib (void)
2135 struct svr4_info *info;
2137 info = get_svr4_info ();
2138 info->debug_base = 0;
2139 info->debug_loader_offset_p = 0;
2140 info->debug_loader_offset = 0;
2141 xfree (info->debug_loader_name);
2142 info->debug_loader_name = NULL;
2146 svr4_free_so (struct so_list *so)
2148 xfree (so->lm_info->lm);
2149 xfree (so->lm_info);
2153 /* Clear any bits of ADDR that wouldn't fit in a target-format
2154 data pointer. "Data pointer" here refers to whatever sort of
2155 address the dynamic linker uses to manage its sections. At the
2156 moment, we don't support shared libraries on any processors where
2157 code and data pointers are different sizes.
2159 This isn't really the right solution. What we really need here is
2160 a way to do arithmetic on CORE_ADDR values that respects the
2161 natural pointer/address correspondence. (For example, on the MIPS,
2162 converting a 32-bit pointer to a 64-bit CORE_ADDR requires you to
2163 sign-extend the value. There, simply truncating the bits above
2164 gdbarch_ptr_bit, as we do below, is no good.) This should probably
2165 be a new gdbarch method or something. */
2167 svr4_truncate_ptr (CORE_ADDR addr)
2169 if (gdbarch_ptr_bit (target_gdbarch) == sizeof (CORE_ADDR) * 8)
2170 /* We don't need to truncate anything, and the bit twiddling below
2171 will fail due to overflow problems. */
2174 return addr & (((CORE_ADDR) 1 << gdbarch_ptr_bit (target_gdbarch)) - 1);
2179 svr4_relocate_section_addresses (struct so_list *so,
2180 struct target_section *sec)
2182 sec->addr = svr4_truncate_ptr (sec->addr + LM_ADDR_CHECK (so,
2184 sec->endaddr = svr4_truncate_ptr (sec->endaddr + LM_ADDR_CHECK (so,
2189 /* Architecture-specific operations. */
2191 /* Per-architecture data key. */
2192 static struct gdbarch_data *solib_svr4_data;
2194 struct solib_svr4_ops
2196 /* Return a description of the layout of `struct link_map'. */
2197 struct link_map_offsets *(*fetch_link_map_offsets)(void);
2200 /* Return a default for the architecture-specific operations. */
2203 solib_svr4_init (struct obstack *obstack)
2205 struct solib_svr4_ops *ops;
2207 ops = OBSTACK_ZALLOC (obstack, struct solib_svr4_ops);
2208 ops->fetch_link_map_offsets = NULL;
2212 /* Set the architecture-specific `struct link_map_offsets' fetcher for
2213 GDBARCH to FLMO. Also, install SVR4 solib_ops into GDBARCH. */
2216 set_solib_svr4_fetch_link_map_offsets (struct gdbarch *gdbarch,
2217 struct link_map_offsets *(*flmo) (void))
2219 struct solib_svr4_ops *ops = gdbarch_data (gdbarch, solib_svr4_data);
2221 ops->fetch_link_map_offsets = flmo;
2223 set_solib_ops (gdbarch, &svr4_so_ops);
2226 /* Fetch a link_map_offsets structure using the architecture-specific
2227 `struct link_map_offsets' fetcher. */
2229 static struct link_map_offsets *
2230 svr4_fetch_link_map_offsets (void)
2232 struct solib_svr4_ops *ops = gdbarch_data (target_gdbarch, solib_svr4_data);
2234 gdb_assert (ops->fetch_link_map_offsets);
2235 return ops->fetch_link_map_offsets ();
2238 /* Return 1 if a link map offset fetcher has been defined, 0 otherwise. */
2241 svr4_have_link_map_offsets (void)
2243 struct solib_svr4_ops *ops = gdbarch_data (target_gdbarch, solib_svr4_data);
2245 return (ops->fetch_link_map_offsets != NULL);
2249 /* Most OS'es that have SVR4-style ELF dynamic libraries define a
2250 `struct r_debug' and a `struct link_map' that are binary compatible
2251 with the origional SVR4 implementation. */
2253 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
2254 for an ILP32 SVR4 system. */
2256 struct link_map_offsets *
2257 svr4_ilp32_fetch_link_map_offsets (void)
2259 static struct link_map_offsets lmo;
2260 static struct link_map_offsets *lmp = NULL;
2266 lmo.r_version_offset = 0;
2267 lmo.r_version_size = 4;
2268 lmo.r_map_offset = 4;
2269 lmo.r_brk_offset = 8;
2270 lmo.r_ldsomap_offset = 20;
2272 /* Everything we need is in the first 20 bytes. */
2273 lmo.link_map_size = 20;
2274 lmo.l_addr_offset = 0;
2275 lmo.l_name_offset = 4;
2276 lmo.l_ld_offset = 8;
2277 lmo.l_next_offset = 12;
2278 lmo.l_prev_offset = 16;
2284 /* Fetch (and possibly build) an appropriate `struct link_map_offsets'
2285 for an LP64 SVR4 system. */
2287 struct link_map_offsets *
2288 svr4_lp64_fetch_link_map_offsets (void)
2290 static struct link_map_offsets lmo;
2291 static struct link_map_offsets *lmp = NULL;
2297 lmo.r_version_offset = 0;
2298 lmo.r_version_size = 4;
2299 lmo.r_map_offset = 8;
2300 lmo.r_brk_offset = 16;
2301 lmo.r_ldsomap_offset = 40;
2303 /* Everything we need is in the first 40 bytes. */
2304 lmo.link_map_size = 40;
2305 lmo.l_addr_offset = 0;
2306 lmo.l_name_offset = 8;
2307 lmo.l_ld_offset = 16;
2308 lmo.l_next_offset = 24;
2309 lmo.l_prev_offset = 32;
2316 struct target_so_ops svr4_so_ops;
2318 /* Lookup global symbol for ELF DSOs linked with -Bsymbolic. Those DSOs have a
2319 different rule for symbol lookup. The lookup begins here in the DSO, not in
2320 the main executable. */
2322 static struct symbol *
2323 elf_lookup_lib_symbol (const struct objfile *objfile,
2325 const domain_enum domain)
2329 if (objfile == symfile_objfile)
2333 /* OBJFILE should have been passed as the non-debug one. */
2334 gdb_assert (objfile->separate_debug_objfile_backlink == NULL);
2336 abfd = objfile->obfd;
2339 if (abfd == NULL || scan_dyntag (DT_SYMBOLIC, abfd, NULL) != 1)
2342 return lookup_global_symbol_from_objfile (objfile, name, domain);
2345 extern initialize_file_ftype _initialize_svr4_solib; /* -Wmissing-prototypes */
2348 _initialize_svr4_solib (void)
2350 solib_svr4_data = gdbarch_data_register_pre_init (solib_svr4_init);
2351 solib_svr4_pspace_data
2352 = register_program_space_data_with_cleanup (svr4_pspace_data_cleanup);
2354 svr4_so_ops.relocate_section_addresses = svr4_relocate_section_addresses;
2355 svr4_so_ops.free_so = svr4_free_so;
2356 svr4_so_ops.clear_solib = svr4_clear_solib;
2357 svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook;
2358 svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling;
2359 svr4_so_ops.current_sos = svr4_current_sos;
2360 svr4_so_ops.open_symbol_file_object = open_symbol_file_object;
2361 svr4_so_ops.in_dynsym_resolve_code = svr4_in_dynsym_resolve_code;
2362 svr4_so_ops.bfd_open = solib_bfd_open;
2363 svr4_so_ops.lookup_lib_global_symbol = elf_lookup_lib_symbol;
2364 svr4_so_ops.same = svr4_same;
2365 svr4_so_ops.keep_data_in_core = svr4_keep_data_in_core;