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   obstack_specify_allocation (&objfile->symbol_obstack, 0, 0, xmalloc,
 151                               xfree);
 152
 153   objfile->name = mstrsave (objfile->md, "rt_common");
 154
 155   /* Add this file onto the tail of the linked list of other such files. */
 156
 157   objfile->next = NULL;
 158   if (object_files == NULL)
 159     object_files = objfile;
 160   else
 161     {
 162       for (last_one = object_files;
 163            last_one->next;
 164            last_one = last_one->next);
 165       last_one->next = objfile;
 166     }
 167
 168   rt_common_objfile = objfile;
 169 }
 170
 171 /* Read all dynamically loaded common symbol definitions from the inferior
 172    and put them into the minimal symbol table for the runtime common
 173    objfile.  */
 174
 175 static void
 176 solib_add_common_symbols (CORE_ADDR rtc_symp)
 177 {
 178   struct rtc_symb inferior_rtc_symb;
 179   struct nlist inferior_rtc_nlist;
 180   int len;
 181   char *name;
 182
 183   /* Remove any runtime common symbols from previous runs.  */
 184
 185   if (rt_common_objfile != NULL && rt_common_objfile->minimal_symbol_count)
 186     {
 187       obstack_free (&rt_common_objfile->symbol_obstack, 0);
 188       obstack_specify_allocation (&rt_common_objfile->symbol_obstack, 0, 0,
 189                                   xmalloc, xfree);
 190       rt_common_objfile->minimal_symbol_count = 0;
 191       rt_common_objfile->msymbols = NULL;
 192       terminate_minimal_symbol_table (rt_common_objfile);
 193     }
 194
 195   init_minimal_symbol_collection ();
 196   make_cleanup_discard_minimal_symbols ();
 197
 198   while (rtc_symp)
 199     {
 200       read_memory (rtc_symp,
 201                    (char *) &inferior_rtc_symb,
 202                    sizeof (inferior_rtc_symb));
 203       read_memory (SOLIB_EXTRACT_ADDRESS (inferior_rtc_symb.rtc_sp),
 204                    (char *) &inferior_rtc_nlist,
 205                    sizeof (inferior_rtc_nlist));
 206       if (inferior_rtc_nlist.n_type == N_COMM)
 207         {
 208           /* FIXME: The length of the symbol name is not available, but in the
 209              current implementation the common symbol is allocated immediately
 210              behind the name of the symbol. */
 211           len = inferior_rtc_nlist.n_value - inferior_rtc_nlist.n_un.n_strx;
 212
 213           name = xmalloc (len);
 214           read_memory (SOLIB_EXTRACT_ADDRESS (inferior_rtc_nlist.n_un.n_name),
 215                        name, len);
 216
 217           /* Allocate the runtime common objfile if necessary. */
 218           if (rt_common_objfile == NULL)
 219             allocate_rt_common_objfile ();
 220
 221           prim_record_minimal_symbol (name, inferior_rtc_nlist.n_value,
 222                                       mst_bss, rt_common_objfile);
 223           xfree (name);
 224         }
 225       rtc_symp = SOLIB_EXTRACT_ADDRESS (inferior_rtc_symb.rtc_next);
 226     }
 227
 228   /* Install any minimal symbols that have been collected as the current
 229      minimal symbols for the runtime common objfile.  */
 230
 231   install_minimal_symbols (rt_common_objfile);
 232 }
 233
 234
 235 /*
 236
 237    LOCAL FUNCTION
 238
 239    locate_base -- locate the base address of dynamic linker structs
 240
 241    SYNOPSIS
 242
 243    CORE_ADDR locate_base (void)
 244
 245    DESCRIPTION
 246
 247    For both the SunOS and SVR4 shared library implementations, if the
 248    inferior executable has been linked dynamically, there is a single
 249    address somewhere in the inferior's data space which is the key to
 250    locating all of the dynamic linker's runtime structures.  This
 251    address is the value of the debug base symbol.  The job of this
 252    function is to find and return that address, or to return 0 if there
 253    is no such address (the executable is statically linked for example).
 254
 255    For SunOS, the job is almost trivial, since the dynamic linker and
 256    all of it's structures are statically linked to the executable at
 257    link time.  Thus the symbol for the address we are looking for has
 258    already been added to the minimal symbol table for the executable's
 259    objfile at the time the symbol file's symbols were read, and all we
 260    have to do is look it up there.  Note that we explicitly do NOT want
 261    to find the copies in the shared library.
 262
 263    The SVR4 version is a bit more complicated because the address
 264    is contained somewhere in the dynamic info section.  We have to go
 265    to a lot more work to discover the address of the debug base symbol.
 266    Because of this complexity, we cache the value we find and return that
 267    value on subsequent invocations.  Note there is no copy in the
 268    executable symbol tables.
 269
 270  */
 271
 272 static CORE_ADDR
 273 locate_base (void)
 274 {
 275   struct minimal_symbol *msymbol;
 276   CORE_ADDR address = 0;
 277   char **symbolp;
 278
 279   /* For SunOS, we want to limit the search for the debug base symbol to the
 280      executable being debugged, since there is a duplicate named symbol in the
 281      shared library.  We don't want the shared library versions. */
 282
 283   for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
 284     {
 285       msymbol = lookup_minimal_symbol (*symbolp, NULL, symfile_objfile);
 286       if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
 287         {
 288           address = SYMBOL_VALUE_ADDRESS (msymbol);
 289           return (address);
 290         }
 291     }
 292   return (0);
 293 }
 294
 295 /*
 296
 297    LOCAL FUNCTION
 298
 299    first_link_map_member -- locate first member in dynamic linker's map
 300
 301    SYNOPSIS
 302
 303    static CORE_ADDR first_link_map_member (void)
 304
 305    DESCRIPTION
 306
 307    Find the first element in the inferior's dynamic link map, and
 308    return its address in the inferior.  This function doesn't copy the
 309    link map entry itself into our address space; current_sos actually
 310    does the reading.  */
 311
 312 static CORE_ADDR
 313 first_link_map_member (void)
 314 {
 315   CORE_ADDR lm = 0;
 316
 317   read_memory (debug_base, (char *) &dynamic_copy, sizeof (dynamic_copy));
 318   if (dynamic_copy.ld_version >= 2)
 319     {
 320       /* It is a version that we can deal with, so read in the secondary
 321          structure and find the address of the link map list from it. */
 322       read_memory (SOLIB_EXTRACT_ADDRESS (dynamic_copy.ld_un.ld_2),
 323                    (char *) &ld_2_copy, sizeof (struct link_dynamic_2));
 324       lm = SOLIB_EXTRACT_ADDRESS (ld_2_copy.ld_loaded);
 325     }
 326   return (lm);
 327 }
 328
 329 static int
 330 open_symbol_file_object (void *from_ttyp)
 331 {
 332   return 1;
 333 }
 334
 335
 336 /* LOCAL FUNCTION
 337
 338    current_sos -- build a list of currently loaded shared objects
 339
 340    SYNOPSIS
 341
 342    struct so_list *current_sos ()
 343
 344    DESCRIPTION
 345
 346    Build a list of `struct so_list' objects describing the shared
 347    objects currently loaded in the inferior.  This list does not
 348    include an entry for the main executable file.
 349
 350    Note that we only gather information directly available from the
 351    inferior --- we don't examine any of the shared library files
 352    themselves.  The declaration of `struct so_list' says which fields
 353    we provide values for.  */
 354
 355 static struct so_list *
 356 sunos_current_sos (void)
 357 {
 358   CORE_ADDR lm;
 359   struct so_list *head = 0;
 360   struct so_list **link_ptr = &head;
 361   int errcode;
 362   char *buffer;
 363
 364   /* Make sure we've looked up the inferior's dynamic linker's base
 365      structure.  */
 366   if (! debug_base)
 367     {
 368       debug_base = locate_base ();
 369
 370       /* If we can't find the dynamic linker's base structure, this
 371          must not be a dynamically linked executable.  Hmm.  */
 372       if (! debug_base)
 373         return 0;
 374     }
 375
 376   /* Walk the inferior's link map list, and build our list of
 377      `struct so_list' nodes.  */
 378   lm = first_link_map_member ();
 379   while (lm)
 380     {
 381       struct so_list *new
 382         = (struct so_list *) xmalloc (sizeof (struct so_list));
 383       struct cleanup *old_chain = make_cleanup (xfree, new);
 384
 385       memset (new, 0, sizeof (*new));
 386
 387       new->lm_info = xmalloc (sizeof (struct lm_info));
 388       make_cleanup (xfree, new->lm_info);
 389
 390       new->lm_info->lm = xmalloc (sizeof (struct link_map));
 391       make_cleanup (xfree, new->lm_info->lm);
 392       memset (new->lm_info->lm, 0, sizeof (struct link_map));
 393
 394       read_memory (lm, new->lm_info->lm, sizeof (struct link_map));
 395
 396       lm = LM_NEXT (new);
 397
 398       /* Extract this shared object's name.  */
 399       target_read_string (LM_NAME (new), &buffer,
 400                           SO_NAME_MAX_PATH_SIZE - 1, &errcode);
 401       if (errcode != 0)
 402         {
 403           warning ("current_sos: Can't read pathname for load map: %s\n",
 404                    safe_strerror (errcode));
 405         }
 406       else
 407         {
 408           strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
 409           new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
 410           xfree (buffer);
 411           strcpy (new->so_original_name, new->so_name);
 412         }
 413
 414       /* If this entry has no name, or its name matches the name
 415          for the main executable, don't include it in the list.  */
 416       if (! new->so_name[0]
 417           || match_main (new->so_name))
 418         free_so (new);
 419       else
 420         {
 421           new->next = 0;
 422           *link_ptr = new;
 423           link_ptr = &new->next;
 424         }
 425
 426       discard_cleanups (old_chain);
 427     }
 428
 429   return head;
 430 }
 431
 432
 433 /* On some systems, the only way to recognize the link map entry for
 434    the main executable file is by looking at its name.  Return
 435    non-zero iff SONAME matches one of the known main executable names.  */
 436
 437 static int
 438 match_main (char *soname)
 439 {
 440   char **mainp;
 441
 442   for (mainp = main_name_list; *mainp != NULL; mainp++)
 443     {
 444       if (strcmp (soname, *mainp) == 0)
 445         return (1);
 446     }
 447
 448   return (0);
 449 }
 450
 451
 452 static int
 453 sunos_in_dynsym_resolve_code (CORE_ADDR pc)
 454 {
 455   return 0;
 456 }
 457
 458 /*
 459
 460    LOCAL FUNCTION
 461
 462    disable_break -- remove the "mapping changed" breakpoint
 463
 464    SYNOPSIS
 465
 466    static int disable_break ()
 467
 468    DESCRIPTION
 469
 470    Removes the breakpoint that gets hit when the dynamic linker
 471    completes a mapping change.
 472
 473  */
 474
 475 static int
 476 disable_break (void)
 477 {
 478   CORE_ADDR breakpoint_addr;    /* Address where end bkpt is set */
 479
 480   int in_debugger = 0;
 481
 482   /* Read the debugger structure from the inferior to retrieve the
 483      address of the breakpoint and the original contents of the
 484      breakpoint address.  Remove the breakpoint by writing the original
 485      contents back. */
 486
 487   read_memory (debug_addr, (char *) &debug_copy, sizeof (debug_copy));
 488
 489   /* Set `in_debugger' to zero now. */
 490
 491   write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
 492
 493   breakpoint_addr = SOLIB_EXTRACT_ADDRESS (debug_copy.ldd_bp_addr);
 494   write_memory (breakpoint_addr, (char *) &debug_copy.ldd_bp_inst,
 495                 sizeof (debug_copy.ldd_bp_inst));
 496
 497   /* For the SVR4 version, we always know the breakpoint address.  For the
 498      SunOS version we don't know it until the above code is executed.
 499      Grumble if we are stopped anywhere besides the breakpoint address. */
 500
 501   if (stop_pc != breakpoint_addr)
 502     {
 503       warning ("stopped at unknown breakpoint while handling shared libraries");
 504     }
 505
 506   return 1;
 507 }
 508
 509
 510 /*
 511
 512    LOCAL FUNCTION
 513
 514    enable_break -- arrange for dynamic linker to hit breakpoint
 515
 516    SYNOPSIS
 517
 518    int enable_break (void)
 519
 520    DESCRIPTION
 521
 522    Both the SunOS and the SVR4 dynamic linkers have, as part of their
 523    debugger interface, support for arranging for the inferior to hit
 524    a breakpoint after mapping in the shared libraries.  This function
 525    enables that breakpoint.
 526
 527    For SunOS, there is a special flag location (in_debugger) which we
 528    set to 1.  When the dynamic linker sees this flag set, it will set
 529    a breakpoint at a location known only to itself, after saving the
 530    original contents of that place and the breakpoint address itself,
 531    in it's own internal structures.  When we resume the inferior, it
 532    will eventually take a SIGTRAP when it runs into the breakpoint.
 533    We handle this (in a different place) by restoring the contents of
 534    the breakpointed location (which is only known after it stops),
 535    chasing around to locate the shared libraries that have been
 536    loaded, then resuming.
 537
 538    For SVR4, the debugger interface structure contains a member (r_brk)
 539    which is statically initialized at the time the shared library is
 540    built, to the offset of a function (_r_debug_state) which is guaran-
 541    teed to be called once before mapping in a library, and again when
 542    the mapping is complete.  At the time we are examining this member,
 543    it contains only the unrelocated offset of the function, so we have
 544    to do our own relocation.  Later, when the dynamic linker actually
 545    runs, it relocates r_brk to be the actual address of _r_debug_state().
 546
 547    The debugger interface structure also contains an enumeration which
 548    is set to either RT_ADD or RT_DELETE prior to changing the mapping,
 549    depending upon whether or not the library is being mapped or unmapped,
 550    and then set to RT_CONSISTENT after the library is mapped/unmapped.
 551  */
 552
 553 static int
 554 enable_break (void)
 555 {
 556   int success = 0;
 557   int j;
 558   int in_debugger;
 559
 560   /* Get link_dynamic structure */
 561
 562   j = target_read_memory (debug_base, (char *) &dynamic_copy,
 563                           sizeof (dynamic_copy));
 564   if (j)
 565     {
 566       /* unreadable */
 567       return (0);
 568     }
 569
 570   /* Calc address of debugger interface structure */
 571
 572   debug_addr = SOLIB_EXTRACT_ADDRESS (dynamic_copy.ldd);
 573
 574   /* Calc address of `in_debugger' member of debugger interface structure */
 575
 576   flag_addr = debug_addr + (CORE_ADDR) ((char *) &debug_copy.ldd_in_debugger -
 577                                         (char *) &debug_copy);
 578
 579   /* Write a value of 1 to this member.  */
 580
 581   in_debugger = 1;
 582   write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
 583   success = 1;
 584
 585   return (success);
 586 }
 587
 588 /*
 589
 590    LOCAL FUNCTION
 591
 592    special_symbol_handling -- additional shared library symbol handling
 593
 594    SYNOPSIS
 595
 596    void special_symbol_handling ()
 597
 598    DESCRIPTION
 599
 600    Once the symbols from a shared object have been loaded in the usual
 601    way, we are called to do any system specific symbol handling that
 602    is needed.
 603
 604    For SunOS4, this consists of grunging around in the dynamic
 605    linkers structures to find symbol definitions for "common" symbols
 606    and adding them to the minimal symbol table for the runtime common
 607    objfile.
 608
 609  */
 610
 611 static void
 612 sunos_special_symbol_handling (void)
 613 {
 614   int j;
 615
 616   if (debug_addr == 0)
 617     {
 618       /* Get link_dynamic structure */
 619
 620       j = target_read_memory (debug_base, (char *) &dynamic_copy,
 621                               sizeof (dynamic_copy));
 622       if (j)
 623         {
 624           /* unreadable */
 625           return;
 626         }
 627
 628       /* Calc address of debugger interface structure */
 629       /* FIXME, this needs work for cross-debugging of core files
 630          (byteorder, size, alignment, etc).  */
 631
 632       debug_addr = SOLIB_EXTRACT_ADDRESS (dynamic_copy.ldd);
 633     }
 634
 635   /* Read the debugger structure from the inferior, just to make sure
 636      we have a current copy. */
 637
 638   j = target_read_memory (debug_addr, (char *) &debug_copy,
 639                           sizeof (debug_copy));
 640   if (j)
 641     return;                     /* unreadable */
 642
 643   /* Get common symbol definitions for the loaded object. */
 644
 645   if (debug_copy.ldd_cp)
 646     {
 647       solib_add_common_symbols (SOLIB_EXTRACT_ADDRESS (debug_copy.ldd_cp));
 648     }
 649 }
 650
 651 /* Relocate the main executable.  This function should be called upon
 652    stopping the inferior process at the entry point to the program.
 653    The entry point from BFD is compared to the PC and if they are
 654    different, the main executable is relocated by the proper amount.
 655
 656    As written it will only attempt to relocate executables which
 657    lack interpreter sections.  It seems likely that only dynamic
 658    linker executables will get relocated, though it should work
 659    properly for a position-independent static executable as well.  */
 660
 661 static void
 662 sunos_relocate_main_executable (void)
 663 {
 664   asection *interp_sect;
 665   CORE_ADDR pc = read_pc ();
 666
 667   /* Decide if the objfile needs to be relocated.  As indicated above,
 668      we will only be here when execution is stopped at the beginning
 669      of the program.  Relocation is necessary if the address at which
 670      we are presently stopped differs from the start address stored in
 671      the executable AND there's no interpreter section.  The condition
 672      regarding the interpreter section is very important because if
 673      there *is* an interpreter section, execution will begin there
 674      instead.  When there is an interpreter section, the start address
 675      is (presumably) used by the interpreter at some point to start
 676      execution of the program.
 677
 678      If there is an interpreter, it is normal for it to be set to an
 679      arbitrary address at the outset.  The job of finding it is
 680      handled in enable_break().
 681
 682      So, to summarize, relocations are necessary when there is no
 683      interpreter section and the start address obtained from the
 684      executable is different from the address at which GDB is
 685      currently stopped.
 686
 687      [ The astute reader will note that we also test to make sure that
 688        the executable in question has the DYNAMIC flag set.  It is my
 689        opinion that this test is unnecessary (undesirable even).  It
 690        was added to avoid inadvertent relocation of an executable
 691        whose e_type member in the ELF header is not ET_DYN.  There may
 692        be a time in the future when it is desirable to do relocations
 693        on other types of files as well in which case this condition
 694        should either be removed or modified to accomodate the new file
 695        type.  (E.g, an ET_EXEC executable which has been built to be
 696        position-independent could safely be relocated by the OS if
 697        desired.  It is true that this violates the ABI, but the ABI
 698        has been known to be bent from time to time.)  - Kevin, Nov 2000. ]
 699      */
 700
 701   interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
 702   if (interp_sect == NULL
 703       && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0
 704       && bfd_get_start_address (exec_bfd) != pc)
 705     {
 706       struct cleanup *old_chain;
 707       struct section_offsets *new_offsets;
 708       int i, changed;
 709       CORE_ADDR displacement;
 710
 711       /* It is necessary to relocate the objfile.  The amount to
 712          relocate by is simply the address at which we are stopped
 713          minus the starting address from the executable.
 714
 715          We relocate all of the sections by the same amount.  This
 716          behavior is mandated by recent editions of the System V ABI.
 717          According to the System V Application Binary Interface,
 718          Edition 4.1, page 5-5:
 719
 720            ...  Though the system chooses virtual addresses for
 721            individual processes, it maintains the segments' relative
 722            positions.  Because position-independent code uses relative
 723            addressesing between segments, the difference between
 724            virtual addresses in memory must match the difference
 725            between virtual addresses in the file.  The difference
 726            between the virtual address of any segment in memory and
 727            the corresponding virtual address in the file is thus a
 728            single constant value for any one executable or shared
 729            object in a given process.  This difference is the base
 730            address.  One use of the base address is to relocate the
 731            memory image of the program during dynamic linking.
 732
 733          The same language also appears in Edition 4.0 of the System V
 734          ABI and is left unspecified in some of the earlier editions.  */
 735
 736       displacement = pc - bfd_get_start_address (exec_bfd);
 737       changed = 0;
 738
 739       new_offsets = xcalloc (symfile_objfile->num_sections,
 740                              sizeof (struct section_offsets));
 741       old_chain = make_cleanup (xfree, new_offsets);
 742
 743       for (i = 0; i < symfile_objfile->num_sections; i++)
 744         {
 745           if (displacement != ANOFFSET (symfile_objfile->section_offsets, i))
 746             changed = 1;
 747           new_offsets->offsets[i] = displacement;
 748         }
 749
 750       if (changed)
 751         objfile_relocate (symfile_objfile, new_offsets);
 752
 753       do_cleanups (old_chain);
 754     }
 755 }
 756
 757 /*
 758
 759    GLOBAL FUNCTION
 760
 761    sunos_solib_create_inferior_hook -- shared library startup support
 762
 763    SYNOPSIS
 764
 765    void sunos_solib_create_inferior_hook()
 766
 767    DESCRIPTION
 768
 769    When gdb starts up the inferior, it nurses it along (through the
 770    shell) until it is ready to execute it's first instruction.  At this
 771    point, this function gets called via expansion of the macro
 772    SOLIB_CREATE_INFERIOR_HOOK.
 773
 774    For SunOS executables, this first instruction is typically the
 775    one at "_start", or a similar text label, regardless of whether
 776    the executable is statically or dynamically linked.  The runtime
 777    startup code takes care of dynamically linking in any shared
 778    libraries, once gdb allows the inferior to continue.
 779
 780    For SVR4 executables, this first instruction is either the first
 781    instruction in the dynamic linker (for dynamically linked
 782    executables) or the instruction at "start" for statically linked
 783    executables.  For dynamically linked executables, the system
 784    first exec's /lib/libc.so.N, which contains the dynamic linker,
 785    and starts it running.  The dynamic linker maps in any needed
 786    shared libraries, maps in the actual user executable, and then
 787    jumps to "start" in the user executable.
 788
 789    For both SunOS shared libraries, and SVR4 shared libraries, we
 790    can arrange to cooperate with the dynamic linker to discover the
 791    names of shared libraries that are dynamically linked, and the
 792    base addresses to which they are linked.
 793
 794    This function is responsible for discovering those names and
 795    addresses, and saving sufficient information about them to allow
 796    their symbols to be read at a later time.
 797
 798    FIXME
 799
 800    Between enable_break() and disable_break(), this code does not
 801    properly handle hitting breakpoints which the user might have
 802    set in the startup code or in the dynamic linker itself.  Proper
 803    handling will probably have to wait until the implementation is
 804    changed to use the "breakpoint handler function" method.
 805
 806    Also, what if child has exit()ed?  Must exit loop somehow.
 807  */
 808
 809 static void
 810 sunos_solib_create_inferior_hook (void)
 811 {
 812   /* Relocate the main executable if necessary.  */
 813   sunos_relocate_main_executable ();
 814
 815   if ((debug_base = locate_base ()) == 0)
 816     {
 817       /* Can't find the symbol or the executable is statically linked. */
 818       return;
 819     }
 820
 821   if (!enable_break ())
 822     {
 823       warning ("shared library handler failed to enable breakpoint");
 824       return;
 825     }
 826
 827   /* SCO and SunOS need the loop below, other systems should be using the
 828      special shared library breakpoints and the shared library breakpoint
 829      service routine.
 830
 831      Now run the target.  It will eventually hit the breakpoint, at
 832      which point all of the libraries will have been mapped in and we
 833      can go groveling around in the dynamic linker structures to find
 834      out what we need to know about them. */
 835
 836   clear_proceed_status ();
 837   stop_soon = STOP_QUIETLY;
 838   stop_signal = TARGET_SIGNAL_0;
 839   do
 840     {
 841       target_resume (pid_to_ptid (-1), 0, stop_signal);
 842       wait_for_inferior ();
 843     }
 844   while (stop_signal != TARGET_SIGNAL_TRAP);
 845   stop_soon = NO_STOP_QUIETLY;
 846
 847   /* We are now either at the "mapping complete" breakpoint (or somewhere
 848      else, a condition we aren't prepared to deal with anyway), so adjust
 849      the PC as necessary after a breakpoint, disable the breakpoint, and
 850      add any shared libraries that were mapped in. */
 851
 852   if (DECR_PC_AFTER_BREAK)
 853     {
 854       stop_pc -= DECR_PC_AFTER_BREAK;
 855       write_register (PC_REGNUM, stop_pc);
 856     }
 857
 858   if (!disable_break ())
 859     {
 860       warning ("shared library handler failed to disable breakpoint");
 861     }
 862
 863   solib_add ((char *) 0, 0, (struct target_ops *) 0, auto_solib_add);
 864 }
 865
 866 static void
 867 sunos_clear_solib (void)
 868 {
 869   debug_base = 0;
 870 }
 871
 872 static void
 873 sunos_free_so (struct so_list *so)
 874 {
 875   xfree (so->lm_info->lm);
 876   xfree (so->lm_info);
 877 }
 878
 879 static void
 880 sunos_relocate_section_addresses (struct so_list *so,
 881                                  struct section_table *sec)
 882 {
 883   sec->addr += LM_ADDR (so);
 884   sec->endaddr += LM_ADDR (so);
 885 }
 886
 887 static struct target_so_ops sunos_so_ops;
 888
 889 void
 890 _initialize_sunos_solib (void)
 891 {
 892   sunos_so_ops.relocate_section_addresses = sunos_relocate_section_addresses;
 893   sunos_so_ops.free_so = sunos_free_so;
 894   sunos_so_ops.clear_solib = sunos_clear_solib;
 895   sunos_so_ops.solib_create_inferior_hook = sunos_solib_create_inferior_hook;
 896   sunos_so_ops.special_symbol_handling = sunos_special_symbol_handling;
 897   sunos_so_ops.current_sos = sunos_current_sos;
 898   sunos_so_ops.open_symbol_file_object = open_symbol_file_object;
 899   sunos_so_ops.in_dynsym_resolve_code = sunos_in_dynsym_resolve_code;
 900
 901   /* FIXME: Don't do this here.  *_gdbarch_init() should set so_ops. */
 902   current_target_so_ops = &sunos_so_ops;
 903 }