gdb/solib-sunos.c

   1 /* Handle SunOS shared libraries for GDB, the GNU Debugger.
   2    Copyright 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1998, 1999, 2000,
   3    2001, 2004
   4    Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 2 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program; if not, write to the Free Software
  20    Foundation, Inc., 59 Temple Place - Suite 330,
  21    Boston, MA 02111-1307, USA.  */
  22
  23 #include "defs.h"
  24
  25 #include <sys/types.h>
  26 #include <signal.h>
  27 #include "gdb_string.h"
  28 #include <sys/param.h>
  29 #include <fcntl.h>
  30
  31  /* SunOS shared libs need the nlist structure.  */
  32 #include <a.out.h>
  33 #include <link.h>
  34
  35 #include "symtab.h"
  36 #include "bfd.h"
  37 #include "symfile.h"
  38 #include "objfiles.h"
  39 #include "gdbcore.h"
  40 #include "inferior.h"
  41 #include "solist.h"
  42 #include "bcache.h"
  43 #include "regcache.h"
  44
  45 /* Link map info to include in an allocated so_list entry */
  46
  47 struct lm_info
  48   {
  49     /* Pointer to copy of link map from inferior.  The type is char *
  50        rather than void *, so that we may use byte offsets to find the
  51        various fields without the need for a cast.  */
  52     char *lm;
  53   };
  54
  55
  56 /* Symbols which are used to locate the base of the link map structures. */
  57
  58 static char *debug_base_symbols[] =
  59 {
  60   "_DYNAMIC",
  61   "_DYNAMIC__MGC",
  62   NULL
  63 };
  64
  65 static char *main_name_list[] =
  66 {
  67   "main_$main",
  68   NULL
  69 };
  70
  71 /* Macro to extract an address from a solib structure.  When GDB is
  72    configured for some 32-bit targets (e.g. Solaris 2.7 sparc), BFD is
  73    configured to handle 64-bit targets, so CORE_ADDR is 64 bits.  We
  74    have to extract only the significant bits of addresses to get the
  75    right address when accessing the core file BFD.
  76
  77    Assume that the address is unsigned.  */
  78
  79 #define SOLIB_EXTRACT_ADDRESS(MEMBER) \
  80         extract_unsigned_integer (&(MEMBER), sizeof (MEMBER))
  81
  82 /* local data declarations */
  83
  84 static struct link_dynamic dynamic_copy;
  85 static struct link_dynamic_2 ld_2_copy;
  86 static struct ld_debug debug_copy;
  87 static CORE_ADDR debug_addr;
  88 static CORE_ADDR flag_addr;
  89
  90 #ifndef offsetof
  91 #define offsetof(TYPE, MEMBER) ((unsigned long) &((TYPE *)0)->MEMBER)
  92 #endif
  93 #define fieldsize(TYPE, MEMBER) (sizeof (((TYPE *)0)->MEMBER))
  94
  95 /* link map access functions */
  96
  97 static CORE_ADDR
  98 LM_ADDR (struct so_list *so)
  99 {
 100   int lm_addr_offset = offsetof (struct link_map, lm_addr);
 101   int lm_addr_size = fieldsize (struct link_map, lm_addr);
 102
 103   return (CORE_ADDR) extract_signed_integer (so->lm_info->lm + lm_addr_offset,
 104                                              lm_addr_size);
 105 }
 106
 107 static CORE_ADDR
 108 LM_NEXT (struct so_list *so)
 109 {
 110   int lm_next_offset = offsetof (struct link_map, lm_next);
 111   int lm_next_size = fieldsize (struct link_map, lm_next);
 112
 113   /* Assume that the address is unsigned.  */
 114   return extract_unsigned_integer (so->lm_info->lm + lm_next_offset,
 115                                    lm_next_size);
 116 }
 117
 118 static CORE_ADDR
 119 LM_NAME (struct so_list *so)
 120 {
 121   int lm_name_offset = offsetof (struct link_map, lm_name);
 122   int lm_name_size = fieldsize (struct link_map, lm_name);
 123
 124   /* Assume that the address is unsigned.  */
 125   return extract_unsigned_integer (so->lm_info->lm + lm_name_offset,
 126                                    lm_name_size);
 127 }
 128
 129 static CORE_ADDR debug_base;    /* Base of dynamic linker structures */
 130
 131 /* Local function prototypes */
 132
 133 static int match_main (char *);
 134
 135 /* Allocate the runtime common object file.  */
 136
 137 static void
 138 allocate_rt_common_objfile (void)
 139 {
 140   struct objfile *objfile;
 141   struct objfile *last_one;
 142
 143   objfile = (struct objfile *) xmalloc (sizeof (struct objfile));
 144   memset (objfile, 0, sizeof (struct objfile));
 145   objfile->md = NULL;
 146   objfile->psymbol_cache = bcache_xmalloc ();
 147   objfile->macro_cache = bcache_xmalloc ();
 148   obstack_specify_allocation (&objfile->objfile_obstack, 0, 0, xmalloc,
 149                               xfree);
 150   objfile->name = mstrsave (objfile->md, "rt_common");
 151
 152   /* Add this file onto the tail of the linked list of other such files. */
 153
 154   objfile->next = NULL;
 155   if (object_files == NULL)
 156     object_files = objfile;
 157   else
 158     {
 159       for (last_one = object_files;
 160            last_one->next;
 161            last_one = last_one->next);
 162       last_one->next = objfile;
 163     }
 164
 165   rt_common_objfile = objfile;
 166 }
 167
 168 /* Read all dynamically loaded common symbol definitions from the inferior
 169    and put them into the minimal symbol table for the runtime common
 170    objfile.  */
 171
 172 static void
 173 solib_add_common_symbols (CORE_ADDR rtc_symp)
 174 {
 175   struct rtc_symb inferior_rtc_symb;
 176   struct nlist inferior_rtc_nlist;
 177   int len;
 178   char *name;
 179
 180   /* Remove any runtime common symbols from previous runs.  */
 181
 182   if (rt_common_objfile != NULL && rt_common_objfile->minimal_symbol_count)
 183     {
 184       obstack_free (&rt_common_objfile->objfile_obstack, 0);
 185       obstack_specify_allocation (&rt_common_objfile->objfile_obstack, 0, 0,
 186                                   xmalloc, xfree);
 187       rt_common_objfile->minimal_symbol_count = 0;
 188       rt_common_objfile->msymbols = NULL;
 189       terminate_minimal_symbol_table (rt_common_objfile);
 190     }
 191
 192   init_minimal_symbol_collection ();
 193   make_cleanup_discard_minimal_symbols ();
 194
 195   while (rtc_symp)
 196     {
 197       read_memory (rtc_symp,
 198                    (char *) &inferior_rtc_symb,
 199                    sizeof (inferior_rtc_symb));
 200       read_memory (SOLIB_EXTRACT_ADDRESS (inferior_rtc_symb.rtc_sp),
 201                    (char *) &inferior_rtc_nlist,
 202                    sizeof (inferior_rtc_nlist));
 203       if (inferior_rtc_nlist.n_type == N_COMM)
 204         {
 205           /* FIXME: The length of the symbol name is not available, but in the
 206              current implementation the common symbol is allocated immediately
 207              behind the name of the symbol. */
 208           len = inferior_rtc_nlist.n_value - inferior_rtc_nlist.n_un.n_strx;
 209
 210           name = xmalloc (len);
 211           read_memory (SOLIB_EXTRACT_ADDRESS (inferior_rtc_nlist.n_un.n_name),
 212                        name, len);
 213
 214           /* Allocate the runtime common objfile if necessary. */
 215           if (rt_common_objfile == NULL)
 216             allocate_rt_common_objfile ();
 217
 218           prim_record_minimal_symbol (name, inferior_rtc_nlist.n_value,
 219                                       mst_bss, rt_common_objfile);
 220           xfree (name);
 221         }
 222       rtc_symp = SOLIB_EXTRACT_ADDRESS (inferior_rtc_symb.rtc_next);
 223     }
 224
 225   /* Install any minimal symbols that have been collected as the current
 226      minimal symbols for the runtime common objfile.  */
 227
 228   install_minimal_symbols (rt_common_objfile);
 229 }
 230
 231
 232 /*
 233
 234    LOCAL FUNCTION
 235
 236    locate_base -- locate the base address of dynamic linker structs
 237
 238    SYNOPSIS
 239
 240    CORE_ADDR locate_base (void)
 241
 242    DESCRIPTION
 243
 244    For both the SunOS and SVR4 shared library implementations, if the
 245    inferior executable has been linked dynamically, there is a single
 246    address somewhere in the inferior's data space which is the key to
 247    locating all of the dynamic linker's runtime structures.  This
 248    address is the value of the debug base symbol.  The job of this
 249    function is to find and return that address, or to return 0 if there
 250    is no such address (the executable is statically linked for example).
 251
 252    For SunOS, the job is almost trivial, since the dynamic linker and
 253    all of it's structures are statically linked to the executable at
 254    link time.  Thus the symbol for the address we are looking for has
 255    already been added to the minimal symbol table for the executable's
 256    objfile at the time the symbol file's symbols were read, and all we
 257    have to do is look it up there.  Note that we explicitly do NOT want
 258    to find the copies in the shared library.
 259
 260    The SVR4 version is a bit more complicated because the address
 261    is contained somewhere in the dynamic info section.  We have to go
 262    to a lot more work to discover the address of the debug base symbol.
 263    Because of this complexity, we cache the value we find and return that
 264    value on subsequent invocations.  Note there is no copy in the
 265    executable symbol tables.
 266
 267  */
 268
 269 static CORE_ADDR
 270 locate_base (void)
 271 {
 272   struct minimal_symbol *msymbol;
 273   CORE_ADDR address = 0;
 274   char **symbolp;
 275
 276   /* For SunOS, we want to limit the search for the debug base symbol to the
 277      executable being debugged, since there is a duplicate named symbol in the
 278      shared library.  We don't want the shared library versions. */
 279
 280   for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
 281     {
 282       msymbol = lookup_minimal_symbol (*symbolp, NULL, symfile_objfile);
 283       if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
 284         {
 285           address = SYMBOL_VALUE_ADDRESS (msymbol);
 286           return (address);
 287         }
 288     }
 289   return (0);
 290 }
 291
 292 /*
 293
 294    LOCAL FUNCTION
 295
 296    first_link_map_member -- locate first member in dynamic linker's map
 297
 298    SYNOPSIS
 299
 300    static CORE_ADDR first_link_map_member (void)
 301
 302    DESCRIPTION
 303
 304    Find the first element in the inferior's dynamic link map, and
 305    return its address in the inferior.  This function doesn't copy the
 306    link map entry itself into our address space; current_sos actually
 307    does the reading.  */
 308
 309 static CORE_ADDR
 310 first_link_map_member (void)
 311 {
 312   CORE_ADDR lm = 0;
 313
 314   read_memory (debug_base, (char *) &dynamic_copy, sizeof (dynamic_copy));
 315   if (dynamic_copy.ld_version >= 2)
 316     {
 317       /* It is a version that we can deal with, so read in the secondary
 318          structure and find the address of the link map list from it. */
 319       read_memory (SOLIB_EXTRACT_ADDRESS (dynamic_copy.ld_un.ld_2),
 320                    (char *) &ld_2_copy, sizeof (struct link_dynamic_2));
 321       lm = SOLIB_EXTRACT_ADDRESS (ld_2_copy.ld_loaded);
 322     }
 323   return (lm);
 324 }
 325
 326 static int
 327 open_symbol_file_object (void *from_ttyp)
 328 {
 329   return 1;
 330 }
 331
 332
 333 /* LOCAL FUNCTION
 334
 335    current_sos -- build a list of currently loaded shared objects
 336
 337    SYNOPSIS
 338
 339    struct so_list *current_sos ()
 340
 341    DESCRIPTION
 342
 343    Build a list of `struct so_list' objects describing the shared
 344    objects currently loaded in the inferior.  This list does not
 345    include an entry for the main executable file.
 346
 347    Note that we only gather information directly available from the
 348    inferior --- we don't examine any of the shared library files
 349    themselves.  The declaration of `struct so_list' says which fields
 350    we provide values for.  */
 351
 352 static struct so_list *
 353 sunos_current_sos (void)
 354 {
 355   CORE_ADDR lm;
 356   struct so_list *head = 0;
 357   struct so_list **link_ptr = &head;
 358   int errcode;
 359   char *buffer;
 360
 361   /* Make sure we've looked up the inferior's dynamic linker's base
 362      structure.  */
 363   if (! debug_base)
 364     {
 365       debug_base = locate_base ();
 366
 367       /* If we can't find the dynamic linker's base structure, this
 368          must not be a dynamically linked executable.  Hmm.  */
 369       if (! debug_base)
 370         return 0;
 371     }
 372
 373   /* Walk the inferior's link map list, and build our list of
 374      `struct so_list' nodes.  */
 375   lm = first_link_map_member ();
 376   while (lm)
 377     {
 378       struct so_list *new
 379         = (struct so_list *) xmalloc (sizeof (struct so_list));
 380       struct cleanup *old_chain = make_cleanup (xfree, new);
 381
 382       memset (new, 0, sizeof (*new));
 383
 384       new->lm_info = xmalloc (sizeof (struct lm_info));
 385       make_cleanup (xfree, new->lm_info);
 386
 387       new->lm_info->lm = xmalloc (sizeof (struct link_map));
 388       make_cleanup (xfree, new->lm_info->lm);
 389       memset (new->lm_info->lm, 0, sizeof (struct link_map));
 390
 391       read_memory (lm, new->lm_info->lm, sizeof (struct link_map));
 392
 393       lm = LM_NEXT (new);
 394
 395       /* Extract this shared object's name.  */
 396       target_read_string (LM_NAME (new), &buffer,
 397                           SO_NAME_MAX_PATH_SIZE - 1, &errcode);
 398       if (errcode != 0)
 399         {
 400           warning ("current_sos: Can't read pathname for load map: %s\n",
 401                    safe_strerror (errcode));
 402         }
 403       else
 404         {
 405           strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
 406           new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
 407           xfree (buffer);
 408           strcpy (new->so_original_name, new->so_name);
 409         }
 410
 411       /* If this entry has no name, or its name matches the name
 412          for the main executable, don't include it in the list.  */
 413       if (! new->so_name[0]
 414           || match_main (new->so_name))
 415         free_so (new);
 416       else
 417         {
 418           new->next = 0;
 419           *link_ptr = new;
 420           link_ptr = &new->next;
 421         }
 422
 423       discard_cleanups (old_chain);
 424     }
 425
 426   return head;
 427 }
 428
 429
 430 /* On some systems, the only way to recognize the link map entry for
 431    the main executable file is by looking at its name.  Return
 432    non-zero iff SONAME matches one of the known main executable names.  */
 433
 434 static int
 435 match_main (char *soname)
 436 {
 437   char **mainp;
 438
 439   for (mainp = main_name_list; *mainp != NULL; mainp++)
 440     {
 441       if (strcmp (soname, *mainp) == 0)
 442         return (1);
 443     }
 444
 445   return (0);
 446 }
 447
 448
 449 static int
 450 sunos_in_dynsym_resolve_code (CORE_ADDR pc)
 451 {
 452   return 0;
 453 }
 454
 455 /*
 456
 457    LOCAL FUNCTION
 458
 459    disable_break -- remove the "mapping changed" breakpoint
 460
 461    SYNOPSIS
 462
 463    static int disable_break ()
 464
 465    DESCRIPTION
 466
 467    Removes the breakpoint that gets hit when the dynamic linker
 468    completes a mapping change.
 469
 470  */
 471
 472 static int
 473 disable_break (void)
 474 {
 475   CORE_ADDR breakpoint_addr;    /* Address where end bkpt is set */
 476
 477   int in_debugger = 0;
 478
 479   /* Read the debugger structure from the inferior to retrieve the
 480      address of the breakpoint and the original contents of the
 481      breakpoint address.  Remove the breakpoint by writing the original
 482      contents back. */
 483
 484   read_memory (debug_addr, (char *) &debug_copy, sizeof (debug_copy));
 485
 486   /* Set `in_debugger' to zero now. */
 487
 488   write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
 489
 490   breakpoint_addr = SOLIB_EXTRACT_ADDRESS (debug_copy.ldd_bp_addr);
 491   write_memory (breakpoint_addr, (char *) &debug_copy.ldd_bp_inst,
 492                 sizeof (debug_copy.ldd_bp_inst));
 493
 494   /* For the SVR4 version, we always know the breakpoint address.  For the
 495      SunOS version we don't know it until the above code is executed.
 496      Grumble if we are stopped anywhere besides the breakpoint address. */
 497
 498   if (stop_pc != breakpoint_addr)
 499     {
 500       warning ("stopped at unknown breakpoint while handling shared libraries");
 501     }
 502
 503   return 1;
 504 }
 505
 506
 507 /*
 508
 509    LOCAL FUNCTION
 510
 511    enable_break -- arrange for dynamic linker to hit breakpoint
 512
 513    SYNOPSIS
 514
 515    int enable_break (void)
 516
 517    DESCRIPTION
 518
 519    Both the SunOS and the SVR4 dynamic linkers have, as part of their
 520    debugger interface, support for arranging for the inferior to hit
 521    a breakpoint after mapping in the shared libraries.  This function
 522    enables that breakpoint.
 523
 524    For SunOS, there is a special flag location (in_debugger) which we
 525    set to 1.  When the dynamic linker sees this flag set, it will set
 526    a breakpoint at a location known only to itself, after saving the
 527    original contents of that place and the breakpoint address itself,
 528    in it's own internal structures.  When we resume the inferior, it
 529    will eventually take a SIGTRAP when it runs into the breakpoint.
 530    We handle this (in a different place) by restoring the contents of
 531    the breakpointed location (which is only known after it stops),
 532    chasing around to locate the shared libraries that have been
 533    loaded, then resuming.
 534
 535    For SVR4, the debugger interface structure contains a member (r_brk)
 536    which is statically initialized at the time the shared library is
 537    built, to the offset of a function (_r_debug_state) which is guaran-
 538    teed to be called once before mapping in a library, and again when
 539    the mapping is complete.  At the time we are examining this member,
 540    it contains only the unrelocated offset of the function, so we have
 541    to do our own relocation.  Later, when the dynamic linker actually
 542    runs, it relocates r_brk to be the actual address of _r_debug_state().
 543
 544    The debugger interface structure also contains an enumeration which
 545    is set to either RT_ADD or RT_DELETE prior to changing the mapping,
 546    depending upon whether or not the library is being mapped or unmapped,
 547    and then set to RT_CONSISTENT after the library is mapped/unmapped.
 548  */
 549
 550 static int
 551 enable_break (void)
 552 {
 553   int success = 0;
 554   int j;
 555   int in_debugger;
 556
 557   /* Get link_dynamic structure */
 558
 559   j = target_read_memory (debug_base, (char *) &dynamic_copy,
 560                           sizeof (dynamic_copy));
 561   if (j)
 562     {
 563       /* unreadable */
 564       return (0);
 565     }
 566
 567   /* Calc address of debugger interface structure */
 568
 569   debug_addr = SOLIB_EXTRACT_ADDRESS (dynamic_copy.ldd);
 570
 571   /* Calc address of `in_debugger' member of debugger interface structure */
 572
 573   flag_addr = debug_addr + (CORE_ADDR) ((char *) &debug_copy.ldd_in_debugger -
 574                                         (char *) &debug_copy);
 575
 576   /* Write a value of 1 to this member.  */
 577
 578   in_debugger = 1;
 579   write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
 580   success = 1;
 581
 582   return (success);
 583 }
 584
 585 /*
 586
 587    LOCAL FUNCTION
 588
 589    special_symbol_handling -- additional shared library symbol handling
 590
 591    SYNOPSIS
 592
 593    void special_symbol_handling ()
 594
 595    DESCRIPTION
 596
 597    Once the symbols from a shared object have been loaded in the usual
 598    way, we are called to do any system specific symbol handling that
 599    is needed.
 600
 601    For SunOS4, this consists of grunging around in the dynamic
 602    linkers structures to find symbol definitions for "common" symbols
 603    and adding them to the minimal symbol table for the runtime common
 604    objfile.
 605
 606  */
 607
 608 static void
 609 sunos_special_symbol_handling (void)
 610 {
 611   int j;
 612
 613   if (debug_addr == 0)
 614     {
 615       /* Get link_dynamic structure */
 616
 617       j = target_read_memory (debug_base, (char *) &dynamic_copy,
 618                               sizeof (dynamic_copy));
 619       if (j)
 620         {
 621           /* unreadable */
 622           return;
 623         }
 624
 625       /* Calc address of debugger interface structure */
 626       /* FIXME, this needs work for cross-debugging of core files
 627          (byteorder, size, alignment, etc).  */
 628
 629       debug_addr = SOLIB_EXTRACT_ADDRESS (dynamic_copy.ldd);
 630     }
 631
 632   /* Read the debugger structure from the inferior, just to make sure
 633      we have a current copy. */
 634
 635   j = target_read_memory (debug_addr, (char *) &debug_copy,
 636                           sizeof (debug_copy));
 637   if (j)
 638     return;                     /* unreadable */
 639
 640   /* Get common symbol definitions for the loaded object. */
 641
 642   if (debug_copy.ldd_cp)
 643     {
 644       solib_add_common_symbols (SOLIB_EXTRACT_ADDRESS (debug_copy.ldd_cp));
 645     }
 646 }
 647
 648 /* Relocate the main executable.  This function should be called upon
 649    stopping the inferior process at the entry point to the program.
 650    The entry point from BFD is compared to the PC and if they are
 651    different, the main executable is relocated by the proper amount.
 652
 653    As written it will only attempt to relocate executables which
 654    lack interpreter sections.  It seems likely that only dynamic
 655    linker executables will get relocated, though it should work
 656    properly for a position-independent static executable as well.  */
 657
 658 static void
 659 sunos_relocate_main_executable (void)
 660 {
 661   asection *interp_sect;
 662   CORE_ADDR pc = read_pc ();
 663
 664   /* Decide if the objfile needs to be relocated.  As indicated above,
 665      we will only be here when execution is stopped at the beginning
 666      of the program.  Relocation is necessary if the address at which
 667      we are presently stopped differs from the start address stored in
 668      the executable AND there's no interpreter section.  The condition
 669      regarding the interpreter section is very important because if
 670      there *is* an interpreter section, execution will begin there
 671      instead.  When there is an interpreter section, the start address
 672      is (presumably) used by the interpreter at some point to start
 673      execution of the program.
 674
 675      If there is an interpreter, it is normal for it to be set to an
 676      arbitrary address at the outset.  The job of finding it is
 677      handled in enable_break().
 678
 679      So, to summarize, relocations are necessary when there is no
 680      interpreter section and the start address obtained from the
 681      executable is different from the address at which GDB is
 682      currently stopped.
 683
 684      [ The astute reader will note that we also test to make sure that
 685        the executable in question has the DYNAMIC flag set.  It is my
 686        opinion that this test is unnecessary (undesirable even).  It
 687        was added to avoid inadvertent relocation of an executable
 688        whose e_type member in the ELF header is not ET_DYN.  There may
 689        be a time in the future when it is desirable to do relocations
 690        on other types of files as well in which case this condition
 691        should either be removed or modified to accomodate the new file
 692        type.  (E.g, an ET_EXEC executable which has been built to be
 693        position-independent could safely be relocated by the OS if
 694        desired.  It is true that this violates the ABI, but the ABI
 695        has been known to be bent from time to time.)  - Kevin, Nov 2000. ]
 696      */
 697
 698   interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
 699   if (interp_sect == NULL
 700       && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0
 701       && bfd_get_start_address (exec_bfd) != pc)
 702     {
 703       struct cleanup *old_chain;
 704       struct section_offsets *new_offsets;
 705       int i, changed;
 706       CORE_ADDR displacement;
 707
 708       /* It is necessary to relocate the objfile.  The amount to
 709          relocate by is simply the address at which we are stopped
 710          minus the starting address from the executable.
 711
 712          We relocate all of the sections by the same amount.  This
 713          behavior is mandated by recent editions of the System V ABI.
 714          According to the System V Application Binary Interface,
 715          Edition 4.1, page 5-5:
 716
 717            ...  Though the system chooses virtual addresses for
 718            individual processes, it maintains the segments' relative
 719            positions.  Because position-independent code uses relative
 720            addressesing between segments, the difference between
 721            virtual addresses in memory must match the difference
 722            between virtual addresses in the file.  The difference
 723            between the virtual address of any segment in memory and
 724            the corresponding virtual address in the file is thus a
 725            single constant value for any one executable or shared
 726            object in a given process.  This difference is the base
 727            address.  One use of the base address is to relocate the
 728            memory image of the program during dynamic linking.
 729
 730          The same language also appears in Edition 4.0 of the System V
 731          ABI and is left unspecified in some of the earlier editions.  */
 732
 733       displacement = pc - bfd_get_start_address (exec_bfd);
 734       changed = 0;
 735
 736       new_offsets = xcalloc (symfile_objfile->num_sections,
 737                              sizeof (struct section_offsets));
 738       old_chain = make_cleanup (xfree, new_offsets);
 739
 740       for (i = 0; i < symfile_objfile->num_sections; i++)
 741         {
 742           if (displacement != ANOFFSET (symfile_objfile->section_offsets, i))
 743             changed = 1;
 744           new_offsets->offsets[i] = displacement;
 745         }
 746
 747       if (changed)
 748         objfile_relocate (symfile_objfile, new_offsets);
 749
 750       do_cleanups (old_chain);
 751     }
 752 }
 753
 754 /*
 755
 756    GLOBAL FUNCTION
 757
 758    sunos_solib_create_inferior_hook -- shared library startup support
 759
 760    SYNOPSIS
 761
 762    void sunos_solib_create_inferior_hook()
 763
 764    DESCRIPTION
 765
 766    When gdb starts up the inferior, it nurses it along (through the
 767    shell) until it is ready to execute it's first instruction.  At this
 768    point, this function gets called via expansion of the macro
 769    SOLIB_CREATE_INFERIOR_HOOK.
 770
 771    For SunOS executables, this first instruction is typically the
 772    one at "_start", or a similar text label, regardless of whether
 773    the executable is statically or dynamically linked.  The runtime
 774    startup code takes care of dynamically linking in any shared
 775    libraries, once gdb allows the inferior to continue.
 776
 777    For SVR4 executables, this first instruction is either the first
 778    instruction in the dynamic linker (for dynamically linked
 779    executables) or the instruction at "start" for statically linked
 780    executables.  For dynamically linked executables, the system
 781    first exec's /lib/libc.so.N, which contains the dynamic linker,
 782    and starts it running.  The dynamic linker maps in any needed
 783    shared libraries, maps in the actual user executable, and then
 784    jumps to "start" in the user executable.
 785
 786    For both SunOS shared libraries, and SVR4 shared libraries, we
 787    can arrange to cooperate with the dynamic linker to discover the
 788    names of shared libraries that are dynamically linked, and the
 789    base addresses to which they are linked.
 790
 791    This function is responsible for discovering those names and
 792    addresses, and saving sufficient information about them to allow
 793    their symbols to be read at a later time.
 794
 795    FIXME
 796
 797    Between enable_break() and disable_break(), this code does not
 798    properly handle hitting breakpoints which the user might have
 799    set in the startup code or in the dynamic linker itself.  Proper
 800    handling will probably have to wait until the implementation is
 801    changed to use the "breakpoint handler function" method.
 802
 803    Also, what if child has exit()ed?  Must exit loop somehow.
 804  */
 805
 806 static void
 807 sunos_solib_create_inferior_hook (void)
 808 {
 809   /* Relocate the main executable if necessary.  */
 810   sunos_relocate_main_executable ();
 811
 812   if ((debug_base = locate_base ()) == 0)
 813     {
 814       /* Can't find the symbol or the executable is statically linked. */
 815       return;
 816     }
 817
 818   if (!enable_break ())
 819     {
 820       warning ("shared library handler failed to enable breakpoint");
 821       return;
 822     }
 823
 824   /* SCO and SunOS need the loop below, other systems should be using the
 825      special shared library breakpoints and the shared library breakpoint
 826      service routine.
 827
 828      Now run the target.  It will eventually hit the breakpoint, at
 829      which point all of the libraries will have been mapped in and we
 830      can go groveling around in the dynamic linker structures to find
 831      out what we need to know about them. */
 832
 833   clear_proceed_status ();
 834   stop_soon = STOP_QUIETLY;
 835   stop_signal = TARGET_SIGNAL_0;
 836   do
 837     {
 838       target_resume (pid_to_ptid (-1), 0, stop_signal);
 839       wait_for_inferior ();
 840     }
 841   while (stop_signal != TARGET_SIGNAL_TRAP);
 842   stop_soon = NO_STOP_QUIETLY;
 843
 844   /* We are now either at the "mapping complete" breakpoint (or somewhere
 845      else, a condition we aren't prepared to deal with anyway), so adjust
 846      the PC as necessary after a breakpoint, disable the breakpoint, and
 847      add any shared libraries that were mapped in. */
 848
 849   if (DECR_PC_AFTER_BREAK)
 850     {
 851       stop_pc -= DECR_PC_AFTER_BREAK;
 852       write_register (PC_REGNUM, stop_pc);
 853     }
 854
 855   if (!disable_break ())
 856     {
 857       warning ("shared library handler failed to disable breakpoint");
 858     }
 859
 860   solib_add ((char *) 0, 0, (struct target_ops *) 0, auto_solib_add);
 861 }
 862
 863 static void
 864 sunos_clear_solib (void)
 865 {
 866   debug_base = 0;
 867 }
 868
 869 static void
 870 sunos_free_so (struct so_list *so)
 871 {
 872   xfree (so->lm_info->lm);
 873   xfree (so->lm_info);
 874 }
 875
 876 static void
 877 sunos_relocate_section_addresses (struct so_list *so,
 878                                  struct section_table *sec)
 879 {
 880   sec->addr += LM_ADDR (so);
 881   sec->endaddr += LM_ADDR (so);
 882 }
 883
 884 static struct target_so_ops sunos_so_ops;
 885
 886 void
 887 _initialize_sunos_solib (void)
 888 {
 889   sunos_so_ops.relocate_section_addresses = sunos_relocate_section_addresses;
 890   sunos_so_ops.free_so = sunos_free_so;
 891   sunos_so_ops.clear_solib = sunos_clear_solib;
 892   sunos_so_ops.solib_create_inferior_hook = sunos_solib_create_inferior_hook;
 893   sunos_so_ops.special_symbol_handling = sunos_special_symbol_handling;
 894   sunos_so_ops.current_sos = sunos_current_sos;
 895   sunos_so_ops.open_symbol_file_object = open_symbol_file_object;
 896   sunos_so_ops.in_dynsym_resolve_code = sunos_in_dynsym_resolve_code;
 897
 898   /* FIXME: Don't do this here.  *_gdbarch_init() should set so_ops. */
 899   current_target_so_ops = &sunos_so_ops;
 900 }