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
   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->psymbol_obstack, 0, 0, xmalloc,
 149                               xfree);
 150   obstack_specify_allocation (&objfile->symbol_obstack, 0, 0, xmalloc,
 151                               xfree);
 152   obstack_specify_allocation (&objfile->type_obstack, 0, 0, xmalloc,
 153                               xfree);
 154   objfile->name = mstrsave (objfile->md, "rt_common");
 155
 156   /* Add this file onto the tail of the linked list of other such files. */
 157
 158   objfile->next = NULL;
 159   if (object_files == NULL)
 160     object_files = objfile;
 161   else
 162     {
 163       for (last_one = object_files;
 164            last_one->next;
 165            last_one = last_one->next);
 166       last_one->next = objfile;
 167     }
 168
 169   rt_common_objfile = objfile;
 170 }
 171
 172 /* Read all dynamically loaded common symbol definitions from the inferior
 173    and put them into the minimal symbol table for the runtime common
 174    objfile.  */
 175
 176 static void
 177 solib_add_common_symbols (CORE_ADDR rtc_symp)
 178 {
 179   struct rtc_symb inferior_rtc_symb;
 180   struct nlist inferior_rtc_nlist;
 181   int len;
 182   char *name;
 183
 184   /* Remove any runtime common symbols from previous runs.  */
 185
 186   if (rt_common_objfile != NULL && rt_common_objfile->minimal_symbol_count)
 187     {
 188       obstack_free (&rt_common_objfile->symbol_obstack, 0);
 189       obstack_specify_allocation (&rt_common_objfile->symbol_obstack, 0, 0,
 190                                   xmalloc, xfree);
 191       rt_common_objfile->minimal_symbol_count = 0;
 192       rt_common_objfile->msymbols = NULL;
 193       terminate_minimal_symbol_table (rt_common_objfile);
 194     }
 195
 196   init_minimal_symbol_collection ();
 197   make_cleanup_discard_minimal_symbols ();
 198
 199   while (rtc_symp)
 200     {
 201       read_memory (rtc_symp,
 202                    (char *) &inferior_rtc_symb,
 203                    sizeof (inferior_rtc_symb));
 204       read_memory (SOLIB_EXTRACT_ADDRESS (inferior_rtc_symb.rtc_sp),
 205                    (char *) &inferior_rtc_nlist,
 206                    sizeof (inferior_rtc_nlist));
 207       if (inferior_rtc_nlist.n_type == N_COMM)
 208         {
 209           /* FIXME: The length of the symbol name is not available, but in the
 210              current implementation the common symbol is allocated immediately
 211              behind the name of the symbol. */
 212           len = inferior_rtc_nlist.n_value - inferior_rtc_nlist.n_un.n_strx;
 213
 214           name = xmalloc (len);
 215           read_memory (SOLIB_EXTRACT_ADDRESS (inferior_rtc_nlist.n_un.n_name),
 216                        name, len);
 217
 218           /* Allocate the runtime common objfile if necessary. */
 219           if (rt_common_objfile == NULL)
 220             allocate_rt_common_objfile ();
 221
 222           prim_record_minimal_symbol (name, inferior_rtc_nlist.n_value,
 223                                       mst_bss, rt_common_objfile);
 224           xfree (name);
 225         }
 226       rtc_symp = SOLIB_EXTRACT_ADDRESS (inferior_rtc_symb.rtc_next);
 227     }
 228
 229   /* Install any minimal symbols that have been collected as the current
 230      minimal symbols for the runtime common objfile.  */
 231
 232   install_minimal_symbols (rt_common_objfile);
 233 }
 234
 235
 236 /*
 237
 238    LOCAL FUNCTION
 239
 240    locate_base -- locate the base address of dynamic linker structs
 241
 242    SYNOPSIS
 243
 244    CORE_ADDR locate_base (void)
 245
 246    DESCRIPTION
 247
 248    For both the SunOS and SVR4 shared library implementations, if the
 249    inferior executable has been linked dynamically, there is a single
 250    address somewhere in the inferior's data space which is the key to
 251    locating all of the dynamic linker's runtime structures.  This
 252    address is the value of the debug base symbol.  The job of this
 253    function is to find and return that address, or to return 0 if there
 254    is no such address (the executable is statically linked for example).
 255
 256    For SunOS, the job is almost trivial, since the dynamic linker and
 257    all of it's structures are statically linked to the executable at
 258    link time.  Thus the symbol for the address we are looking for has
 259    already been added to the minimal symbol table for the executable's
 260    objfile at the time the symbol file's symbols were read, and all we
 261    have to do is look it up there.  Note that we explicitly do NOT want
 262    to find the copies in the shared library.
 263
 264    The SVR4 version is a bit more complicated because the address
 265    is contained somewhere in the dynamic info section.  We have to go
 266    to a lot more work to discover the address of the debug base symbol.
 267    Because of this complexity, we cache the value we find and return that
 268    value on subsequent invocations.  Note there is no copy in the
 269    executable symbol tables.
 270
 271  */
 272
 273 static CORE_ADDR
 274 locate_base (void)
 275 {
 276   struct minimal_symbol *msymbol;
 277   CORE_ADDR address = 0;
 278   char **symbolp;
 279
 280   /* For SunOS, we want to limit the search for the debug base symbol to the
 281      executable being debugged, since there is a duplicate named symbol in the
 282      shared library.  We don't want the shared library versions. */
 283
 284   for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
 285     {
 286       msymbol = lookup_minimal_symbol (*symbolp, NULL, symfile_objfile);
 287       if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
 288         {
 289           address = SYMBOL_VALUE_ADDRESS (msymbol);
 290           return (address);
 291         }
 292     }
 293   return (0);
 294 }
 295
 296 /*
 297
 298    LOCAL FUNCTION
 299
 300    first_link_map_member -- locate first member in dynamic linker's map
 301
 302    SYNOPSIS
 303
 304    static CORE_ADDR first_link_map_member (void)
 305
 306    DESCRIPTION
 307
 308    Find the first element in the inferior's dynamic link map, and
 309    return its address in the inferior.  This function doesn't copy the
 310    link map entry itself into our address space; current_sos actually
 311    does the reading.  */
 312
 313 static CORE_ADDR
 314 first_link_map_member (void)
 315 {
 316   CORE_ADDR lm = 0;
 317
 318   read_memory (debug_base, (char *) &dynamic_copy, sizeof (dynamic_copy));
 319   if (dynamic_copy.ld_version >= 2)
 320     {
 321       /* It is a version that we can deal with, so read in the secondary
 322          structure and find the address of the link map list from it. */
 323       read_memory (SOLIB_EXTRACT_ADDRESS (dynamic_copy.ld_un.ld_2),
 324                    (char *) &ld_2_copy, sizeof (struct link_dynamic_2));
 325       lm = SOLIB_EXTRACT_ADDRESS (ld_2_copy.ld_loaded);
 326     }
 327   return (lm);
 328 }
 329
 330 static int
 331 open_symbol_file_object (void *from_ttyp)
 332 {
 333   return 1;
 334 }
 335
 336
 337 /* LOCAL FUNCTION
 338
 339    current_sos -- build a list of currently loaded shared objects
 340
 341    SYNOPSIS
 342
 343    struct so_list *current_sos ()
 344
 345    DESCRIPTION
 346
 347    Build a list of `struct so_list' objects describing the shared
 348    objects currently loaded in the inferior.  This list does not
 349    include an entry for the main executable file.
 350
 351    Note that we only gather information directly available from the
 352    inferior --- we don't examine any of the shared library files
 353    themselves.  The declaration of `struct so_list' says which fields
 354    we provide values for.  */
 355
 356 static struct so_list *
 357 sunos_current_sos (void)
 358 {
 359   CORE_ADDR lm;
 360   struct so_list *head = 0;
 361   struct so_list **link_ptr = &head;
 362   int errcode;
 363   char *buffer;
 364
 365   /* Make sure we've looked up the inferior's dynamic linker's base
 366      structure.  */
 367   if (! debug_base)
 368     {
 369       debug_base = locate_base ();
 370
 371       /* If we can't find the dynamic linker's base structure, this
 372          must not be a dynamically linked executable.  Hmm.  */
 373       if (! debug_base)
 374         return 0;
 375     }
 376
 377   /* Walk the inferior's link map list, and build our list of
 378      `struct so_list' nodes.  */
 379   lm = first_link_map_member ();
 380   while (lm)
 381     {
 382       struct so_list *new
 383         = (struct so_list *) xmalloc (sizeof (struct so_list));
 384       struct cleanup *old_chain = make_cleanup (xfree, new);
 385
 386       memset (new, 0, sizeof (*new));
 387
 388       new->lm_info = xmalloc (sizeof (struct lm_info));
 389       make_cleanup (xfree, new->lm_info);
 390
 391       new->lm_info->lm = xmalloc (sizeof (struct link_map));
 392       make_cleanup (xfree, new->lm_info->lm);
 393       memset (new->lm_info->lm, 0, sizeof (struct link_map));
 394
 395       read_memory (lm, new->lm_info->lm, sizeof (struct link_map));
 396
 397       lm = LM_NEXT (new);
 398
 399       /* Extract this shared object's name.  */
 400       target_read_string (LM_NAME (new), &buffer,
 401                           SO_NAME_MAX_PATH_SIZE - 1, &errcode);
 402       if (errcode != 0)
 403         {
 404           warning ("current_sos: Can't read pathname for load map: %s\n",
 405                    safe_strerror (errcode));
 406         }
 407       else
 408         {
 409           strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
 410           new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
 411           xfree (buffer);
 412           strcpy (new->so_original_name, new->so_name);
 413         }
 414
 415       /* If this entry has no name, or its name matches the name
 416          for the main executable, don't include it in the list.  */
 417       if (! new->so_name[0]
 418           || match_main (new->so_name))
 419         free_so (new);
 420       else
 421         {
 422           new->next = 0;
 423           *link_ptr = new;
 424           link_ptr = &new->next;
 425         }
 426
 427       discard_cleanups (old_chain);
 428     }
 429
 430   return head;
 431 }
 432
 433
 434 /* On some systems, the only way to recognize the link map entry for
 435    the main executable file is by looking at its name.  Return
 436    non-zero iff SONAME matches one of the known main executable names.  */
 437
 438 static int
 439 match_main (char *soname)
 440 {
 441   char **mainp;
 442
 443   for (mainp = main_name_list; *mainp != NULL; mainp++)
 444     {
 445       if (strcmp (soname, *mainp) == 0)
 446         return (1);
 447     }
 448
 449   return (0);
 450 }
 451
 452
 453 static int
 454 sunos_in_dynsym_resolve_code (CORE_ADDR pc)
 455 {
 456   return 0;
 457 }
 458
 459 /*
 460
 461    LOCAL FUNCTION
 462
 463    disable_break -- remove the "mapping changed" breakpoint
 464
 465    SYNOPSIS
 466
 467    static int disable_break ()
 468
 469    DESCRIPTION
 470
 471    Removes the breakpoint that gets hit when the dynamic linker
 472    completes a mapping change.
 473
 474  */
 475
 476 static int
 477 disable_break (void)
 478 {
 479   CORE_ADDR breakpoint_addr;    /* Address where end bkpt is set */
 480
 481   int in_debugger = 0;
 482
 483   /* Read the debugger structure from the inferior to retrieve the
 484      address of the breakpoint and the original contents of the
 485      breakpoint address.  Remove the breakpoint by writing the original
 486      contents back. */
 487
 488   read_memory (debug_addr, (char *) &debug_copy, sizeof (debug_copy));
 489
 490   /* Set `in_debugger' to zero now. */
 491
 492   write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
 493
 494   breakpoint_addr = SOLIB_EXTRACT_ADDRESS (debug_copy.ldd_bp_addr);
 495   write_memory (breakpoint_addr, (char *) &debug_copy.ldd_bp_inst,
 496                 sizeof (debug_copy.ldd_bp_inst));
 497
 498   /* For the SVR4 version, we always know the breakpoint address.  For the
 499      SunOS version we don't know it until the above code is executed.
 500      Grumble if we are stopped anywhere besides the breakpoint address. */
 501
 502   if (stop_pc != breakpoint_addr)
 503     {
 504       warning ("stopped at unknown breakpoint while handling shared libraries");
 505     }
 506
 507   return 1;
 508 }
 509
 510
 511 /*
 512
 513    LOCAL FUNCTION
 514
 515    enable_break -- arrange for dynamic linker to hit breakpoint
 516
 517    SYNOPSIS
 518
 519    int enable_break (void)
 520
 521    DESCRIPTION
 522
 523    Both the SunOS and the SVR4 dynamic linkers have, as part of their
 524    debugger interface, support for arranging for the inferior to hit
 525    a breakpoint after mapping in the shared libraries.  This function
 526    enables that breakpoint.
 527
 528    For SunOS, there is a special flag location (in_debugger) which we
 529    set to 1.  When the dynamic linker sees this flag set, it will set
 530    a breakpoint at a location known only to itself, after saving the
 531    original contents of that place and the breakpoint address itself,
 532    in it's own internal structures.  When we resume the inferior, it
 533    will eventually take a SIGTRAP when it runs into the breakpoint.
 534    We handle this (in a different place) by restoring the contents of
 535    the breakpointed location (which is only known after it stops),
 536    chasing around to locate the shared libraries that have been
 537    loaded, then resuming.
 538
 539    For SVR4, the debugger interface structure contains a member (r_brk)
 540    which is statically initialized at the time the shared library is
 541    built, to the offset of a function (_r_debug_state) which is guaran-
 542    teed to be called once before mapping in a library, and again when
 543    the mapping is complete.  At the time we are examining this member,
 544    it contains only the unrelocated offset of the function, so we have
 545    to do our own relocation.  Later, when the dynamic linker actually
 546    runs, it relocates r_brk to be the actual address of _r_debug_state().
 547
 548    The debugger interface structure also contains an enumeration which
 549    is set to either RT_ADD or RT_DELETE prior to changing the mapping,
 550    depending upon whether or not the library is being mapped or unmapped,
 551    and then set to RT_CONSISTENT after the library is mapped/unmapped.
 552  */
 553
 554 static int
 555 enable_break (void)
 556 {
 557   int success = 0;
 558   int j;
 559   int in_debugger;
 560
 561   /* Get link_dynamic structure */
 562
 563   j = target_read_memory (debug_base, (char *) &dynamic_copy,
 564                           sizeof (dynamic_copy));
 565   if (j)
 566     {
 567       /* unreadable */
 568       return (0);
 569     }
 570
 571   /* Calc address of debugger interface structure */
 572
 573   debug_addr = SOLIB_EXTRACT_ADDRESS (dynamic_copy.ldd);
 574
 575   /* Calc address of `in_debugger' member of debugger interface structure */
 576
 577   flag_addr = debug_addr + (CORE_ADDR) ((char *) &debug_copy.ldd_in_debugger -
 578                                         (char *) &debug_copy);
 579
 580   /* Write a value of 1 to this member.  */
 581
 582   in_debugger = 1;
 583   write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
 584   success = 1;
 585
 586   return (success);
 587 }
 588
 589 /*
 590
 591    LOCAL FUNCTION
 592
 593    special_symbol_handling -- additional shared library symbol handling
 594
 595    SYNOPSIS
 596
 597    void special_symbol_handling ()
 598
 599    DESCRIPTION
 600
 601    Once the symbols from a shared object have been loaded in the usual
 602    way, we are called to do any system specific symbol handling that
 603    is needed.
 604
 605    For SunOS4, this consists of grunging around in the dynamic
 606    linkers structures to find symbol definitions for "common" symbols
 607    and adding them to the minimal symbol table for the runtime common
 608    objfile.
 609
 610  */
 611
 612 static void
 613 sunos_special_symbol_handling (void)
 614 {
 615   int j;
 616
 617   if (debug_addr == 0)
 618     {
 619       /* Get link_dynamic structure */
 620
 621       j = target_read_memory (debug_base, (char *) &dynamic_copy,
 622                               sizeof (dynamic_copy));
 623       if (j)
 624         {
 625           /* unreadable */
 626           return;
 627         }
 628
 629       /* Calc address of debugger interface structure */
 630       /* FIXME, this needs work for cross-debugging of core files
 631          (byteorder, size, alignment, etc).  */
 632
 633       debug_addr = SOLIB_EXTRACT_ADDRESS (dynamic_copy.ldd);
 634     }
 635
 636   /* Read the debugger structure from the inferior, just to make sure
 637      we have a current copy. */
 638
 639   j = target_read_memory (debug_addr, (char *) &debug_copy,
 640                           sizeof (debug_copy));
 641   if (j)
 642     return;                     /* unreadable */
 643
 644   /* Get common symbol definitions for the loaded object. */
 645
 646   if (debug_copy.ldd_cp)
 647     {
 648       solib_add_common_symbols (SOLIB_EXTRACT_ADDRESS (debug_copy.ldd_cp));
 649     }
 650 }
 651
 652 /* Relocate the main executable.  This function should be called upon
 653    stopping the inferior process at the entry point to the program.
 654    The entry point from BFD is compared to the PC and if they are
 655    different, the main executable is relocated by the proper amount.
 656
 657    As written it will only attempt to relocate executables which
 658    lack interpreter sections.  It seems likely that only dynamic
 659    linker executables will get relocated, though it should work
 660    properly for a position-independent static executable as well.  */
 661
 662 static void
 663 sunos_relocate_main_executable (void)
 664 {
 665   asection *interp_sect;
 666   CORE_ADDR pc = read_pc ();
 667
 668   /* Decide if the objfile needs to be relocated.  As indicated above,
 669      we will only be here when execution is stopped at the beginning
 670      of the program.  Relocation is necessary if the address at which
 671      we are presently stopped differs from the start address stored in
 672      the executable AND there's no interpreter section.  The condition
 673      regarding the interpreter section is very important because if
 674      there *is* an interpreter section, execution will begin there
 675      instead.  When there is an interpreter section, the start address
 676      is (presumably) used by the interpreter at some point to start
 677      execution of the program.
 678
 679      If there is an interpreter, it is normal for it to be set to an
 680      arbitrary address at the outset.  The job of finding it is
 681      handled in enable_break().
 682
 683      So, to summarize, relocations are necessary when there is no
 684      interpreter section and the start address obtained from the
 685      executable is different from the address at which GDB is
 686      currently stopped.
 687
 688      [ The astute reader will note that we also test to make sure that
 689        the executable in question has the DYNAMIC flag set.  It is my
 690        opinion that this test is unnecessary (undesirable even).  It
 691        was added to avoid inadvertent relocation of an executable
 692        whose e_type member in the ELF header is not ET_DYN.  There may
 693        be a time in the future when it is desirable to do relocations
 694        on other types of files as well in which case this condition
 695        should either be removed or modified to accomodate the new file
 696        type.  (E.g, an ET_EXEC executable which has been built to be
 697        position-independent could safely be relocated by the OS if
 698        desired.  It is true that this violates the ABI, but the ABI
 699        has been known to be bent from time to time.)  - Kevin, Nov 2000. ]
 700      */
 701
 702   interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
 703   if (interp_sect == NULL
 704       && (bfd_get_file_flags (exec_bfd) & DYNAMIC) != 0
 705       && bfd_get_start_address (exec_bfd) != pc)
 706     {
 707       struct cleanup *old_chain;
 708       struct section_offsets *new_offsets;
 709       int i, changed;
 710       CORE_ADDR displacement;
 711
 712       /* It is necessary to relocate the objfile.  The amount to
 713          relocate by is simply the address at which we are stopped
 714          minus the starting address from the executable.
 715
 716          We relocate all of the sections by the same amount.  This
 717          behavior is mandated by recent editions of the System V ABI.
 718          According to the System V Application Binary Interface,
 719          Edition 4.1, page 5-5:
 720
 721            ...  Though the system chooses virtual addresses for
 722            individual processes, it maintains the segments' relative
 723            positions.  Because position-independent code uses relative
 724            addressesing between segments, the difference between
 725            virtual addresses in memory must match the difference
 726            between virtual addresses in the file.  The difference
 727            between the virtual address of any segment in memory and
 728            the corresponding virtual address in the file is thus a
 729            single constant value for any one executable or shared
 730            object in a given process.  This difference is the base
 731            address.  One use of the base address is to relocate the
 732            memory image of the program during dynamic linking.
 733
 734          The same language also appears in Edition 4.0 of the System V
 735          ABI and is left unspecified in some of the earlier editions.  */
 736
 737       displacement = pc - bfd_get_start_address (exec_bfd);
 738       changed = 0;
 739
 740       new_offsets = xcalloc (symfile_objfile->num_sections,
 741                              sizeof (struct section_offsets));
 742       old_chain = make_cleanup (xfree, new_offsets);
 743
 744       for (i = 0; i < symfile_objfile->num_sections; i++)
 745         {
 746           if (displacement != ANOFFSET (symfile_objfile->section_offsets, i))
 747             changed = 1;
 748           new_offsets->offsets[i] = displacement;
 749         }
 750
 751       if (changed)
 752         objfile_relocate (symfile_objfile, new_offsets);
 753
 754       do_cleanups (old_chain);
 755     }
 756 }
 757
 758 /*
 759
 760    GLOBAL FUNCTION
 761
 762    sunos_solib_create_inferior_hook -- shared library startup support
 763
 764    SYNOPSIS
 765
 766    void sunos_solib_create_inferior_hook()
 767
 768    DESCRIPTION
 769
 770    When gdb starts up the inferior, it nurses it along (through the
 771    shell) until it is ready to execute it's first instruction.  At this
 772    point, this function gets called via expansion of the macro
 773    SOLIB_CREATE_INFERIOR_HOOK.
 774
 775    For SunOS executables, this first instruction is typically the
 776    one at "_start", or a similar text label, regardless of whether
 777    the executable is statically or dynamically linked.  The runtime
 778    startup code takes care of dynamically linking in any shared
 779    libraries, once gdb allows the inferior to continue.
 780
 781    For SVR4 executables, this first instruction is either the first
 782    instruction in the dynamic linker (for dynamically linked
 783    executables) or the instruction at "start" for statically linked
 784    executables.  For dynamically linked executables, the system
 785    first exec's /lib/libc.so.N, which contains the dynamic linker,
 786    and starts it running.  The dynamic linker maps in any needed
 787    shared libraries, maps in the actual user executable, and then
 788    jumps to "start" in the user executable.
 789
 790    For both SunOS shared libraries, and SVR4 shared libraries, we
 791    can arrange to cooperate with the dynamic linker to discover the
 792    names of shared libraries that are dynamically linked, and the
 793    base addresses to which they are linked.
 794
 795    This function is responsible for discovering those names and
 796    addresses, and saving sufficient information about them to allow
 797    their symbols to be read at a later time.
 798
 799    FIXME
 800
 801    Between enable_break() and disable_break(), this code does not
 802    properly handle hitting breakpoints which the user might have
 803    set in the startup code or in the dynamic linker itself.  Proper
 804    handling will probably have to wait until the implementation is
 805    changed to use the "breakpoint handler function" method.
 806
 807    Also, what if child has exit()ed?  Must exit loop somehow.
 808  */
 809
 810 static void
 811 sunos_solib_create_inferior_hook (void)
 812 {
 813   /* Relocate the main executable if necessary.  */
 814   sunos_relocate_main_executable ();
 815
 816   if ((debug_base = locate_base ()) == 0)
 817     {
 818       /* Can't find the symbol or the executable is statically linked. */
 819       return;
 820     }
 821
 822   if (!enable_break ())
 823     {
 824       warning ("shared library handler failed to enable breakpoint");
 825       return;
 826     }
 827
 828   /* SCO and SunOS need the loop below, other systems should be using the
 829      special shared library breakpoints and the shared library breakpoint
 830      service routine.
 831
 832      Now run the target.  It will eventually hit the breakpoint, at
 833      which point all of the libraries will have been mapped in and we
 834      can go groveling around in the dynamic linker structures to find
 835      out what we need to know about them. */
 836
 837   clear_proceed_status ();
 838   stop_soon = STOP_QUIETLY;
 839   stop_signal = TARGET_SIGNAL_0;
 840   do
 841     {
 842       target_resume (pid_to_ptid (-1), 0, stop_signal);
 843       wait_for_inferior ();
 844     }
 845   while (stop_signal != TARGET_SIGNAL_TRAP);
 846   stop_soon = NO_STOP_QUIETLY;
 847
 848   /* We are now either at the "mapping complete" breakpoint (or somewhere
 849      else, a condition we aren't prepared to deal with anyway), so adjust
 850      the PC as necessary after a breakpoint, disable the breakpoint, and
 851      add any shared libraries that were mapped in. */
 852
 853   if (DECR_PC_AFTER_BREAK)
 854     {
 855       stop_pc -= DECR_PC_AFTER_BREAK;
 856       write_register (PC_REGNUM, stop_pc);
 857     }
 858
 859   if (!disable_break ())
 860     {
 861       warning ("shared library handler failed to disable breakpoint");
 862     }
 863
 864   solib_add ((char *) 0, 0, (struct target_ops *) 0, auto_solib_add);
 865 }
 866
 867 static void
 868 sunos_clear_solib (void)
 869 {
 870   debug_base = 0;
 871 }
 872
 873 static void
 874 sunos_free_so (struct so_list *so)
 875 {
 876   xfree (so->lm_info->lm);
 877   xfree (so->lm_info);
 878 }
 879
 880 static void
 881 sunos_relocate_section_addresses (struct so_list *so,
 882                                  struct section_table *sec)
 883 {
 884   sec->addr += LM_ADDR (so);
 885   sec->endaddr += LM_ADDR (so);
 886 }
 887
 888 static struct target_so_ops sunos_so_ops;
 889
 890 void
 891 _initialize_sunos_solib (void)
 892 {
 893   sunos_so_ops.relocate_section_addresses = sunos_relocate_section_addresses;
 894   sunos_so_ops.free_so = sunos_free_so;
 895   sunos_so_ops.clear_solib = sunos_clear_solib;
 896   sunos_so_ops.solib_create_inferior_hook = sunos_solib_create_inferior_hook;
 897   sunos_so_ops.special_symbol_handling = sunos_special_symbol_handling;
 898   sunos_so_ops.current_sos = sunos_current_sos;
 899   sunos_so_ops.open_symbol_file_object = open_symbol_file_object;
 900   sunos_so_ops.in_dynsym_resolve_code = sunos_in_dynsym_resolve_code;
 901
 902   /* FIXME: Don't do this here.  *_gdbarch_init() should set so_ops. */
 903   current_target_so_ops = &sunos_so_ops;
 904 }