Reorganize solib.c.

1 files changed, 1586 insertions, 0 deletions

diff --git a/gdb/solib-svr4.c b/gdb/solib-svr4.c
new file mode 100644
index 00000000000..13fea47e52d
--- /dev/null
+++ b/gdb/solib-svr4.c
@@ -0,0 +1,1586 @@
+/* Handle SunOS and SVR4 shared libraries for GDB, the GNU Debugger.
+   Copyright 1990, 91, 92, 93, 94, 95, 96, 98, 1999, 2000
+   Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#define _SYSCALL32	/* for Sparc64 cross Sparc32 */
+#include "defs.h"
+
+
+#include <sys/types.h>
+#include <signal.h>
+#include "gdb_string.h"
+#include <sys/param.h>
+#include <fcntl.h>
+
+#ifndef SVR4_SHARED_LIBS
+ /* SunOS shared libs need the nlist structure.  */
+#include <a.out.h>
+#else
+#include "elf/external.h"
+#endif
+
+#ifdef HAVE_LINK_H
+#include <link.h>
+#endif
+
+#include "symtab.h"
+#include "bfd.h"
+#include "symfile.h"
+#include "objfiles.h"
+#include "gdbcore.h"
+#include "command.h"
+#include "target.h"
+#include "frame.h"
+#include "gdb_regex.h"
+#include "inferior.h"
+#include "environ.h"
+#include "language.h"
+#include "gdbcmd.h"
+
+#include "solist.h"
+#include "solib-svr4.h"
+
+/* Link map info to include in an allocated so_list entry */
+
+struct lm_info
+  {
+    /* Pointer to copy of link map from inferior.  The type is char *
+       rather than void *, so that we may use byte offsets to find the
+       various fields without the need for a cast.  */
+    char *lm;
+  };
+
+/* On SVR4 systems, a list of symbols in the dynamic linker where
+   GDB can try to place a breakpoint to monitor shared library
+   events.
+
+   If none of these symbols are found, or other errors occur, then
+   SVR4 systems will fall back to using a symbol as the "startup
+   mapping complete" breakpoint address.  */
+
+#ifdef SVR4_SHARED_LIBS
+static char *solib_break_names[] =
+{
+  "r_debug_state",
+  "_r_debug_state",
+  "_dl_debug_state",
+  "rtld_db_dlactivity",
+  NULL
+};
+#endif
+
+#define BKPT_AT_SYMBOL 1
+
+#if defined (BKPT_AT_SYMBOL) && defined (SVR4_SHARED_LIBS)
+static char *bkpt_names[] =
+{
+#ifdef SOLIB_BKPT_NAME
+  SOLIB_BKPT_NAME,		/* Prefer configured name if it exists. */
+#endif
+  "_start",
+  "main",
+  NULL
+};
+#endif
+
+/* Symbols which are used to locate the base of the link map structures. */
+
+#ifndef SVR4_SHARED_LIBS
+static char *debug_base_symbols[] =
+{
+  "_DYNAMIC",
+  "_DYNAMIC__MGC",
+  NULL
+};
+#endif
+
+static char *main_name_list[] =
+{
+  "main_$main",
+  NULL
+};
+
+
+/* Fetch (and possibly build) an appropriate link_map_offsets structure
+   for native targets using struct definitions from link.h.  */
+
+struct link_map_offsets *
+default_svr4_fetch_link_map_offsets (void)
+{
+#ifdef HAVE_LINK_H
+  static struct link_map_offsets lmo;
+  static struct link_map_offsets *lmp = 0;
+#if defined (HAVE_STRUCT_LINK_MAP32)
+  static struct link_map_offsets lmo32;
+  static struct link_map_offsets *lmp32 = 0;
+#endif
+
+#ifndef offsetof
+#define offsetof(TYPE, MEMBER) ((unsigned long) &((TYPE *)0)->MEMBER)
+#endif
+#define fieldsize(TYPE, MEMBER) (sizeof (((TYPE *)0)->MEMBER))
+
+  if (lmp == 0)
+    {
+      lmp = &lmo;
+
+#ifdef SVR4_SHARED_LIBS
+      lmo.r_debug_size = sizeof (struct r_debug);
+
+      lmo.r_map_offset = offsetof (struct r_debug, r_map);
+      lmo.r_map_size = fieldsize (struct r_debug, r_map);
+
+      lmo.link_map_size = sizeof (struct link_map);
+
+      lmo.l_addr_offset = offsetof (struct link_map, l_addr);
+      lmo.l_addr_size = fieldsize (struct link_map, l_addr);
+
+      lmo.l_next_offset = offsetof (struct link_map, l_next);
+      lmo.l_next_size = fieldsize (struct link_map, l_next);
+
+      lmo.l_prev_offset = offsetof (struct link_map, l_prev);
+      lmo.l_prev_size = fieldsize (struct link_map, l_prev);
+
+      lmo.l_name_offset = offsetof (struct link_map, l_name);
+      lmo.l_name_size = fieldsize (struct link_map, l_name);
+#else /* !SVR4_SHARED_LIBS */
+      lmo.link_map_size = sizeof (struct link_map);
+
+      lmo.l_addr_offset = offsetof (struct link_map, lm_addr);
+      lmo.l_addr_size = fieldsize (struct link_map, lm_addr);
+
+      lmo.l_next_offset = offsetof (struct link_map, lm_next);
+      lmo.l_next_size = fieldsize (struct link_map, lm_next);
+
+      lmo.l_name_offset = offsetof (struct link_map, lm_name);
+      lmo.l_name_size = fieldsize (struct link_map, lm_name);
+#endif /* SVR4_SHARED_LIBS */
+    }
+
+#if defined (HAVE_STRUCT_LINK_MAP32)
+  if (lmp32 == 0)
+    {
+      lmp32 = &lmo32;
+
+      lmo32.r_debug_size = sizeof (struct r_debug32);
+
+      lmo32.r_map_offset = offsetof (struct r_debug32, r_map);
+      lmo32.r_map_size = fieldsize (struct r_debug32, r_map);
+
+      lmo32.link_map_size = sizeof (struct link_map32);
+
+      lmo32.l_addr_offset = offsetof (struct link_map32, l_addr);
+      lmo32.l_addr_size = fieldsize (struct link_map32, l_addr);
+
+      lmo32.l_next_offset = offsetof (struct link_map32, l_next);
+      lmo32.l_next_size = fieldsize (struct link_map32, l_next);
+
+      lmo32.l_prev_offset = offsetof (struct link_map32, l_prev);
+      lmo32.l_prev_size = fieldsize (struct link_map32, l_prev);
+
+      lmo32.l_name_offset = offsetof (struct link_map32, l_name);
+      lmo32.l_name_size = fieldsize (struct link_map32, l_name);
+    }
+#endif /* defined (HAVE_STRUCT_LINK_MAP32) */
+
+#if defined (HAVE_STRUCT_LINK_MAP32)
+  if (bfd_get_arch_size (exec_bfd) == 32)
+    return lmp32;
+  else
+#endif
+    return lmp;
+
+#else
+
+  internal_error ("default_svr4_fetch_link_map_offsets called without HAVE_LINK_H defined.");
+  return 0;
+
+#endif /* HAVE_LINK_H */
+}
+
+/* Macro to extract an address from a solib structure.
+   When GDB is configured for some 32-bit targets (e.g. Solaris 2.7
+   sparc), BFD is configured to handle 64-bit targets, so CORE_ADDR is
+   64 bits.  We have to extract only the significant bits of addresses
+   to get the right address when accessing the core file BFD.  */
+
+#define SOLIB_EXTRACT_ADDRESS(MEMBER) \
+	extract_address (&(MEMBER), sizeof (MEMBER))
+
+/* local data declarations */
+
+#ifndef SVR4_SHARED_LIBS
+
+/* NOTE: converted the macros LM_ADDR, LM_NEXT, LM_NAME and
+   IGNORE_FIRST_LINK_MAP_ENTRY into functions (see below).
+   MVS, June 2000  */
+
+static struct link_dynamic dynamic_copy;
+static struct link_dynamic_2 ld_2_copy;
+static struct ld_debug debug_copy;
+static CORE_ADDR debug_addr;
+static CORE_ADDR flag_addr;
+
+#endif /* !SVR4_SHARED_LIBS */
+
+/* link map access functions */
+
+static CORE_ADDR
+LM_ADDR (struct so_list *so)
+{
+  struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
+
+  return extract_address (so->lm_info->lm + lmo->l_addr_offset, lmo->l_addr_size);
+}
+
+static CORE_ADDR
+LM_NEXT (struct so_list *so)
+{
+  struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
+
+  return extract_address (so->lm_info->lm + lmo->l_next_offset, lmo->l_next_size);
+}
+
+static CORE_ADDR
+LM_NAME (struct so_list *so)
+{
+  struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
+
+  return extract_address (so->lm_info->lm + lmo->l_name_offset, lmo->l_name_size);
+}
+
+#ifndef SVR4_SHARED_LIBS
+
+static int 
+IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
+{
+  return 0;
+}
+
+#else /* SVR4_SHARED_LIBS */
+
+static int
+IGNORE_FIRST_LINK_MAP_ENTRY (struct so_list *so)
+{
+  struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
+
+  return extract_address (so->lm_info->lm + lmo->l_prev_offset,
+                          lmo->l_prev_size) == 0;
+}
+
+#endif /* !SVR4_SHARED_LIBS */
+
+
+static CORE_ADDR debug_base;	/* Base of dynamic linker structures */
+static CORE_ADDR breakpoint_addr;	/* Address where end bkpt is set */
+
+/* Local function prototypes */
+
+static int match_main (char *);
+
+/* If non-zero, this is a prefix that will be added to the front of the name
+   shared libraries with an absolute filename for loading.  */
+static char *solib_absolute_prefix = NULL;
+
+/* If non-empty, this is a search path for loading non-absolute shared library
+   symbol files.  This takes precedence over the environment variables PATH
+   and LD_LIBRARY_PATH.  */
+static char *solib_search_path = NULL;
+
+
+#ifndef SVR4_SHARED_LIBS
+
+/* Allocate the runtime common object file.  */
+
+static void
+allocate_rt_common_objfile (void)
+{
+  struct objfile *objfile;
+  struct objfile *last_one;
+
+  objfile = (struct objfile *) xmalloc (sizeof (struct objfile));
+  memset (objfile, 0, sizeof (struct objfile));
+  objfile->md = NULL;
+  obstack_specify_allocation (&objfile->psymbol_cache.cache, 0, 0,
+			      xmalloc, free);
+  obstack_specify_allocation (&objfile->psymbol_obstack, 0, 0, xmalloc,
+			      free);
+  obstack_specify_allocation (&objfile->symbol_obstack, 0, 0, xmalloc,
+			      free);
+  obstack_specify_allocation (&objfile->type_obstack, 0, 0, xmalloc,
+			      free);
+  objfile->name = mstrsave (objfile->md, "rt_common");
+
+  /* Add this file onto the tail of the linked list of other such files. */
+
+  objfile->next = NULL;
+  if (object_files == NULL)
+    object_files = objfile;
+  else
+    {
+      for (last_one = object_files;
+	   last_one->next;
+	   last_one = last_one->next);
+      last_one->next = objfile;
+    }
+
+  rt_common_objfile = objfile;
+}
+
+/* Read all dynamically loaded common symbol definitions from the inferior
+   and put them into the minimal symbol table for the runtime common
+   objfile.  */
+
+static void
+solib_add_common_symbols (CORE_ADDR rtc_symp)
+{
+  struct rtc_symb inferior_rtc_symb;
+  struct nlist inferior_rtc_nlist;
+  int len;
+  char *name;
+
+  /* Remove any runtime common symbols from previous runs.  */
+
+  if (rt_common_objfile != NULL && rt_common_objfile->minimal_symbol_count)
+    {
+      obstack_free (&rt_common_objfile->symbol_obstack, 0);
+      obstack_specify_allocation (&rt_common_objfile->symbol_obstack, 0, 0,
+				  xmalloc, free);
+      rt_common_objfile->minimal_symbol_count = 0;
+      rt_common_objfile->msymbols = NULL;
+    }
+
+  init_minimal_symbol_collection ();
+  make_cleanup_discard_minimal_symbols ();
+
+  while (rtc_symp)
+    {
+      read_memory (rtc_symp,
+		   (char *) &inferior_rtc_symb,
+		   sizeof (inferior_rtc_symb));
+      read_memory (SOLIB_EXTRACT_ADDRESS (inferior_rtc_symb.rtc_sp),
+		   (char *) &inferior_rtc_nlist,
+		   sizeof (inferior_rtc_nlist));
+      if (inferior_rtc_nlist.n_type == N_COMM)
+	{
+	  /* FIXME: The length of the symbol name is not available, but in the
+	     current implementation the common symbol is allocated immediately
+	     behind the name of the symbol. */
+	  len = inferior_rtc_nlist.n_value - inferior_rtc_nlist.n_un.n_strx;
+
+	  name = xmalloc (len);
+	  read_memory (SOLIB_EXTRACT_ADDRESS (inferior_rtc_nlist.n_un.n_name),
+		       name, len);
+
+	  /* Allocate the runtime common objfile if necessary. */
+	  if (rt_common_objfile == NULL)
+	    allocate_rt_common_objfile ();
+
+	  prim_record_minimal_symbol (name, inferior_rtc_nlist.n_value,
+				      mst_bss, rt_common_objfile);
+	  free (name);
+	}
+      rtc_symp = SOLIB_EXTRACT_ADDRESS (inferior_rtc_symb.rtc_next);
+    }
+
+  /* Install any minimal symbols that have been collected as the current
+     minimal symbols for the runtime common objfile.  */
+
+  install_minimal_symbols (rt_common_objfile);
+}
+
+#endif /* SVR4_SHARED_LIBS */
+
+
+#ifdef SVR4_SHARED_LIBS
+
+static CORE_ADDR bfd_lookup_symbol (bfd *, char *);
+
+/*
+
+   LOCAL FUNCTION
+
+   bfd_lookup_symbol -- lookup the value for a specific symbol
+
+   SYNOPSIS
+
+   CORE_ADDR bfd_lookup_symbol (bfd *abfd, char *symname)
+
+   DESCRIPTION
+
+   An expensive way to lookup the value of a single symbol for
+   bfd's that are only temporary anyway.  This is used by the
+   shared library support to find the address of the debugger
+   interface structures in the shared library.
+
+   Note that 0 is specifically allowed as an error return (no
+   such symbol).
+ */
+
+static CORE_ADDR
+bfd_lookup_symbol (bfd *abfd, char *symname)
+{
+  unsigned int storage_needed;
+  asymbol *sym;
+  asymbol **symbol_table;
+  unsigned int number_of_symbols;
+  unsigned int i;
+  struct cleanup *back_to;
+  CORE_ADDR symaddr = 0;
+
+  storage_needed = bfd_get_symtab_upper_bound (abfd);
+
+  if (storage_needed > 0)
+    {
+      symbol_table = (asymbol **) xmalloc (storage_needed);
+      back_to = make_cleanup (free, (PTR) symbol_table);
+      number_of_symbols = bfd_canonicalize_symtab (abfd, symbol_table);
+
+      for (i = 0; i < number_of_symbols; i++)
+	{
+	  sym = *symbol_table++;
+	  if (STREQ (sym->name, symname))
+	    {
+	      /* Bfd symbols are section relative. */
+	      symaddr = sym->value + sym->section->vma;
+	      break;
+	    }
+	}
+      do_cleanups (back_to);
+    }
+
+  if (symaddr)
+    return symaddr;
+
+  /* On FreeBSD, the dynamic linker is stripped by default.  So we'll
+     have to check the dynamic string table too.  */
+
+  storage_needed = bfd_get_dynamic_symtab_upper_bound (abfd);
+
+  if (storage_needed > 0)
+    {
+      symbol_table = (asymbol **) xmalloc (storage_needed);
+      back_to = make_cleanup (free, (PTR) symbol_table);
+      number_of_symbols = bfd_canonicalize_dynamic_symtab (abfd, symbol_table);
+
+      for (i = 0; i < number_of_symbols; i++)
+	{
+	  sym = *symbol_table++;
+	  if (STREQ (sym->name, symname))
+	    {
+	      /* Bfd symbols are section relative. */
+	      symaddr = sym->value + sym->section->vma;
+	      break;
+	    }
+	}
+      do_cleanups (back_to);
+    }
+
+  return symaddr;
+}
+
+#ifdef HANDLE_SVR4_EXEC_EMULATORS
+
+/*
+   Solaris BCP (the part of Solaris which allows it to run SunOS4
+   a.out files) throws in another wrinkle. Solaris does not fill
+   in the usual a.out link map structures when running BCP programs,
+   the only way to get at them is via groping around in the dynamic
+   linker.
+   The dynamic linker and it's structures are located in the shared
+   C library, which gets run as the executable's "interpreter" by
+   the kernel.
+
+   Note that we can assume nothing about the process state at the time
+   we need to find these structures.  We may be stopped on the first
+   instruction of the interpreter (C shared library), the first
+   instruction of the executable itself, or somewhere else entirely
+   (if we attached to the process for example).
+ */
+
+static char *debug_base_symbols[] =
+{
+  "r_debug",			/* Solaris 2.3 */
+  "_r_debug",			/* Solaris 2.1, 2.2 */
+  NULL
+};
+
+static int look_for_base (int, CORE_ADDR);
+
+/*
+
+   LOCAL FUNCTION
+
+   look_for_base -- examine file for each mapped address segment
+
+   SYNOPSYS
+
+   static int look_for_base (int fd, CORE_ADDR baseaddr)
+
+   DESCRIPTION
+
+   This function is passed to proc_iterate_over_mappings, which
+   causes it to get called once for each mapped address space, with
+   an open file descriptor for the file mapped to that space, and the
+   base address of that mapped space.
+
+   Our job is to find the debug base symbol in the file that this
+   fd is open on, if it exists, and if so, initialize the dynamic
+   linker structure base address debug_base.
+
+   Note that this is a computationally expensive proposition, since
+   we basically have to open a bfd on every call, so we specifically
+   avoid opening the exec file.
+ */
+
+static int
+look_for_base (int fd, CORE_ADDR baseaddr)
+{
+  bfd *interp_bfd;
+  CORE_ADDR address = 0;
+  char **symbolp;
+
+  /* If the fd is -1, then there is no file that corresponds to this
+     mapped memory segment, so skip it.  Also, if the fd corresponds
+     to the exec file, skip it as well. */
+
+  if (fd == -1
+      || (exec_bfd != NULL
+	  && fdmatch (fileno ((FILE *) (exec_bfd->iostream)), fd)))
+    {
+      return (0);
+    }
+
+  /* Try to open whatever random file this fd corresponds to.  Note that
+     we have no way currently to find the filename.  Don't gripe about
+     any problems we might have, just fail. */
+
+  if ((interp_bfd = bfd_fdopenr ("unnamed", gnutarget, fd)) == NULL)
+    {
+      return (0);
+    }
+  if (!bfd_check_format (interp_bfd, bfd_object))
+    {
+      /* FIXME-leak: on failure, might not free all memory associated with
+         interp_bfd.  */
+      bfd_close (interp_bfd);
+      return (0);
+    }
+
+  /* Now try to find our debug base symbol in this file, which we at
+     least know to be a valid ELF executable or shared library. */
+
+  for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
+    {
+      address = bfd_lookup_symbol (interp_bfd, *symbolp);
+      if (address != 0)
+	{
+	  break;
+	}
+    }
+  if (address == 0)
+    {
+      /* FIXME-leak: on failure, might not free all memory associated with
+         interp_bfd.  */
+      bfd_close (interp_bfd);
+      return (0);
+    }
+
+  /* Eureka!  We found the symbol.  But now we may need to relocate it
+     by the base address.  If the symbol's value is less than the base
+     address of the shared library, then it hasn't yet been relocated
+     by the dynamic linker, and we have to do it ourself.  FIXME: Note
+     that we make the assumption that the first segment that corresponds
+     to the shared library has the base address to which the library
+     was relocated. */
+
+  if (address < baseaddr)
+    {
+      address += baseaddr;
+    }
+  debug_base = address;
+  /* FIXME-leak: on failure, might not free all memory associated with
+     interp_bfd.  */
+  bfd_close (interp_bfd);
+  return (1);
+}
+#endif /* HANDLE_SVR4_EXEC_EMULATORS */
+
+/*
+
+   LOCAL FUNCTION
+
+   elf_locate_base -- locate the base address of dynamic linker structs
+   for SVR4 elf targets.
+
+   SYNOPSIS
+
+   CORE_ADDR elf_locate_base (void)
+
+   DESCRIPTION
+
+   For SVR4 elf targets the address of the dynamic linker's runtime
+   structure is contained within the dynamic info section in the
+   executable file.  The dynamic section is also mapped into the
+   inferior address space.  Because the runtime loader fills in the
+   real address before starting the inferior, we have to read in the
+   dynamic info section from the inferior address space.
+   If there are any errors while trying to find the address, we
+   silently return 0, otherwise the found address is returned.
+
+ */
+
+static CORE_ADDR
+elf_locate_base (void)
+{
+  sec_ptr dyninfo_sect;
+  int dyninfo_sect_size;
+  CORE_ADDR dyninfo_addr;
+  char *buf;
+  char *bufend;
+  int arch_size;
+
+  /* Find the start address of the .dynamic section.  */
+  dyninfo_sect = bfd_get_section_by_name (exec_bfd, ".dynamic");
+  if (dyninfo_sect == NULL)
+    return 0;
+  dyninfo_addr = bfd_section_vma (exec_bfd, dyninfo_sect);
+
+  /* Read in .dynamic section, silently ignore errors.  */
+  dyninfo_sect_size = bfd_section_size (exec_bfd, dyninfo_sect);
+  buf = alloca (dyninfo_sect_size);
+  if (target_read_memory (dyninfo_addr, buf, dyninfo_sect_size))
+    return 0;
+
+  /* Find the DT_DEBUG entry in the the .dynamic section.
+     For mips elf we look for DT_MIPS_RLD_MAP, mips elf apparently has
+     no DT_DEBUG entries.  */
+
+  arch_size = bfd_get_arch_size (exec_bfd);
+  if (arch_size == -1)	/* failure */
+    return 0;
+
+  if (arch_size == 32)
+    { /* 32-bit elf */
+      for (bufend = buf + dyninfo_sect_size;
+	   buf < bufend;
+	   buf += sizeof (Elf32_External_Dyn))
+	{
+	  Elf32_External_Dyn *x_dynp = (Elf32_External_Dyn *) buf;
+	  long dyn_tag;
+	  CORE_ADDR dyn_ptr;
+
+	  dyn_tag = bfd_h_get_32 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
+	  if (dyn_tag == DT_NULL)
+	    break;
+	  else if (dyn_tag == DT_DEBUG)
+	    {
+	      dyn_ptr = bfd_h_get_32 (exec_bfd, 
+				      (bfd_byte *) x_dynp->d_un.d_ptr);
+	      return dyn_ptr;
+	    }
+#ifdef DT_MIPS_RLD_MAP
+	  else if (dyn_tag == DT_MIPS_RLD_MAP)
+	    {
+	      char *pbuf;
+
+	      pbuf = alloca (TARGET_PTR_BIT / HOST_CHAR_BIT);
+	      /* DT_MIPS_RLD_MAP contains a pointer to the address
+		 of the dynamic link structure.  */
+	      dyn_ptr = bfd_h_get_32 (exec_bfd, 
+				      (bfd_byte *) x_dynp->d_un.d_ptr);
+	      if (target_read_memory (dyn_ptr, pbuf, sizeof (pbuf)))
+		return 0;
+	      return extract_unsigned_integer (pbuf, sizeof (pbuf));
+	    }
+#endif
+	}
+    }
+  else /* 64-bit elf */
+    {
+      for (bufend = buf + dyninfo_sect_size;
+	   buf < bufend;
+	   buf += sizeof (Elf64_External_Dyn))
+	{
+	  Elf64_External_Dyn *x_dynp = (Elf64_External_Dyn *) buf;
+	  long dyn_tag;
+	  CORE_ADDR dyn_ptr;
+
+	  dyn_tag = bfd_h_get_64 (exec_bfd, (bfd_byte *) x_dynp->d_tag);
+	  if (dyn_tag == DT_NULL)
+	    break;
+	  else if (dyn_tag == DT_DEBUG)
+	    {
+	      dyn_ptr = bfd_h_get_64 (exec_bfd, 
+				      (bfd_byte *) x_dynp->d_un.d_ptr);
+	      return dyn_ptr;
+	    }
+	}
+    }
+
+  /* DT_DEBUG entry not found.  */
+  return 0;
+}
+
+#endif /* SVR4_SHARED_LIBS */
+
+/*
+
+   LOCAL FUNCTION
+
+   locate_base -- locate the base address of dynamic linker structs
+
+   SYNOPSIS
+
+   CORE_ADDR locate_base (void)
+
+   DESCRIPTION
+
+   For both the SunOS and SVR4 shared library implementations, if the
+   inferior executable has been linked dynamically, there is a single
+   address somewhere in the inferior's data space which is the key to
+   locating all of the dynamic linker's runtime structures.  This
+   address is the value of the debug base symbol.  The job of this
+   function is to find and return that address, or to return 0 if there
+   is no such address (the executable is statically linked for example).
+
+   For SunOS, the job is almost trivial, since the dynamic linker and
+   all of it's structures are statically linked to the executable at
+   link time.  Thus the symbol for the address we are looking for has
+   already been added to the minimal symbol table for the executable's
+   objfile at the time the symbol file's symbols were read, and all we
+   have to do is look it up there.  Note that we explicitly do NOT want
+   to find the copies in the shared library.
+
+   The SVR4 version is a bit more complicated because the address
+   is contained somewhere in the dynamic info section.  We have to go
+   to a lot more work to discover the address of the debug base symbol.
+   Because of this complexity, we cache the value we find and return that
+   value on subsequent invocations.  Note there is no copy in the
+   executable symbol tables.
+
+ */
+
+static CORE_ADDR
+locate_base (void)
+{
+
+#ifndef SVR4_SHARED_LIBS
+
+  struct minimal_symbol *msymbol;
+  CORE_ADDR address = 0;
+  char **symbolp;
+
+  /* For SunOS, we want to limit the search for the debug base symbol to the
+     executable being debugged, since there is a duplicate named symbol in the
+     shared library.  We don't want the shared library versions. */
+
+  for (symbolp = debug_base_symbols; *symbolp != NULL; symbolp++)
+    {
+      msymbol = lookup_minimal_symbol (*symbolp, NULL, symfile_objfile);
+      if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
+	{
+	  address = SYMBOL_VALUE_ADDRESS (msymbol);
+	  return (address);
+	}
+    }
+  return (0);
+
+#else /* SVR4_SHARED_LIBS */
+
+  /* Check to see if we have a currently valid address, and if so, avoid
+     doing all this work again and just return the cached address.  If
+     we have no cached address, try to locate it in the dynamic info
+     section for ELF executables.  */
+
+  if (debug_base == 0)
+    {
+      if (exec_bfd != NULL
+	  && bfd_get_flavour (exec_bfd) == bfd_target_elf_flavour)
+	debug_base = elf_locate_base ();
+#ifdef HANDLE_SVR4_EXEC_EMULATORS
+      /* Try it the hard way for emulated executables.  */
+      else if (inferior_pid != 0 && target_has_execution)
+	proc_iterate_over_mappings (look_for_base);
+#endif
+    }
+  return (debug_base);
+
+#endif /* !SVR4_SHARED_LIBS */
+
+}
+
+/*
+
+   LOCAL FUNCTION
+
+   first_link_map_member -- locate first member in dynamic linker's map
+
+   SYNOPSIS
+
+   static CORE_ADDR first_link_map_member (void)
+
+   DESCRIPTION
+
+   Find the first element in the inferior's dynamic link map, and
+   return its address in the inferior.  This function doesn't copy the
+   link map entry itself into our address space; current_sos actually
+   does the reading.  */
+
+static CORE_ADDR
+first_link_map_member (void)
+{
+  CORE_ADDR lm = 0;
+
+#ifndef SVR4_SHARED_LIBS
+
+  read_memory (debug_base, (char *) &dynamic_copy, sizeof (dynamic_copy));
+  if (dynamic_copy.ld_version >= 2)
+    {
+      /* It is a version that we can deal with, so read in the secondary
+         structure and find the address of the link map list from it. */
+      read_memory (SOLIB_EXTRACT_ADDRESS (dynamic_copy.ld_un.ld_2),
+		   (char *) &ld_2_copy, sizeof (struct link_dynamic_2));
+      lm = SOLIB_EXTRACT_ADDRESS (ld_2_copy.ld_loaded);
+    }
+
+#else /* SVR4_SHARED_LIBS */
+  struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
+  char *r_map_buf = xmalloc (lmo->r_map_size);
+  struct cleanup *cleanups = make_cleanup (free, r_map_buf);
+
+  read_memory (debug_base + lmo->r_map_offset, r_map_buf, lmo->r_map_size);
+
+  lm = extract_address (r_map_buf, lmo->r_map_size);
+
+  /* FIXME:  Perhaps we should validate the info somehow, perhaps by
+     checking r_version for a known version number, or r_state for
+     RT_CONSISTENT. */
+
+  do_cleanups (cleanups);
+
+#endif /* !SVR4_SHARED_LIBS */
+
+  return (lm);
+}
+
+#ifdef SVR4_SHARED_LIBS
+/*
+
+  LOCAL FUNCTION
+
+  open_symbol_file_object
+
+  SYNOPSIS
+
+  void open_symbol_file_object (void *from_tty)
+
+  DESCRIPTION
+
+  If no open symbol file, attempt to locate and open the main symbol
+  file.  On SVR4 systems, this is the first link map entry.  If its
+  name is here, we can open it.  Useful when attaching to a process
+  without first loading its symbol file.
+
+  If FROM_TTYP dereferences to a non-zero integer, allow messages to
+  be printed.  This parameter is a pointer rather than an int because
+  open_symbol_file_object() is called via catch_errors() and
+  catch_errors() requires a pointer argument. */
+
+static int
+open_symbol_file_object (void *from_ttyp)
+{
+  CORE_ADDR lm, l_name;
+  char *filename;
+  int errcode;
+  int from_tty = *(int *)from_ttyp;
+  struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
+  char *l_name_buf = xmalloc (lmo->l_name_size);
+  struct cleanup *cleanups = make_cleanup (free, l_name_buf);
+
+  if (symfile_objfile)
+    if (!query ("Attempt to reload symbols from process? "))
+      return 0;
+
+  if ((debug_base = locate_base ()) == 0)
+    return 0;	/* failed somehow... */
+
+  /* First link map member should be the executable.  */
+  if ((lm = first_link_map_member ()) == 0)
+    return 0;	/* failed somehow... */
+
+  /* Read address of name from target memory to GDB.  */
+  read_memory (lm + lmo->l_name_offset, l_name_buf, lmo->l_name_size);
+
+  /* Convert the address to host format.  */
+  l_name = extract_address (l_name_buf, lmo->l_name_size);
+
+  /* Free l_name_buf.  */
+  do_cleanups (cleanups);
+
+  if (l_name == 0)
+    return 0;		/* No filename.  */
+
+  /* Now fetch the filename from target memory.  */
+  target_read_string (l_name, &filename, SO_NAME_MAX_PATH_SIZE - 1, &errcode);
+
+  if (errcode)
+    {
+      warning ("failed to read exec filename from attached file: %s",
+	       safe_strerror (errcode));
+      return 0;
+    }
+
+  make_cleanup (free, filename);
+  /* Have a pathname: read the symbol file.  */
+  symbol_file_command (filename, from_tty);
+
+  return 1;
+}
+#else
+
+static int
+open_symbol_file_object (int *from_ttyp)
+{
+  return 1;
+}
+
+#endif /* SVR4_SHARED_LIBS */
+
+
+/* LOCAL FUNCTION
+
+   current_sos -- build a list of currently loaded shared objects
+
+   SYNOPSIS
+
+   struct so_list *current_sos ()
+
+   DESCRIPTION
+
+   Build a list of `struct so_list' objects describing the shared
+   objects currently loaded in the inferior.  This list does not
+   include an entry for the main executable file.
+
+   Note that we only gather information directly available from the
+   inferior --- we don't examine any of the shared library files
+   themselves.  The declaration of `struct so_list' says which fields
+   we provide values for.  */
+
+static struct so_list *
+svr4_current_sos (void)
+{
+  CORE_ADDR lm;
+  struct so_list *head = 0;
+  struct so_list **link_ptr = &head;
+
+  /* Make sure we've looked up the inferior's dynamic linker's base
+     structure.  */
+  if (! debug_base)
+    {
+      debug_base = locate_base ();
+
+      /* If we can't find the dynamic linker's base structure, this
+	 must not be a dynamically linked executable.  Hmm.  */
+      if (! debug_base)
+	return 0;
+    }
+
+  /* Walk the inferior's link map list, and build our list of
+     `struct so_list' nodes.  */
+  lm = first_link_map_member ();  
+  while (lm)
+    {
+      struct link_map_offsets *lmo = SVR4_FETCH_LINK_MAP_OFFSETS ();
+      struct so_list *new
+	= (struct so_list *) xmalloc (sizeof (struct so_list));
+      struct cleanup *old_chain = make_cleanup (free, new);
+
+      memset (new, 0, sizeof (*new));
+
+      new->lm_info = xmalloc (sizeof (struct lm_info));
+      make_cleanup (free, new->lm_info);
+
+      new->lm_info->lm = xmalloc (lmo->link_map_size);
+      make_cleanup (free, new->lm_info->lm);
+      memset (new->lm_info->lm, 0, lmo->link_map_size);
+
+      read_memory (lm, new->lm_info->lm, lmo->link_map_size);
+
+      lm = LM_NEXT (new);
+
+      /* For SVR4 versions, the first entry in the link map is for the
+         inferior executable, so we must ignore it.  For some versions of
+         SVR4, it has no name.  For others (Solaris 2.3 for example), it
+         does have a name, so we can no longer use a missing name to
+         decide when to ignore it. */
+      if (IGNORE_FIRST_LINK_MAP_ENTRY (new))
+	free_so (new);
+      else
+	{
+	  int errcode;
+	  char *buffer;
+
+	  /* Extract this shared object's name.  */
+	  target_read_string (LM_NAME (new), &buffer,
+			      SO_NAME_MAX_PATH_SIZE - 1, &errcode);
+	  if (errcode != 0)
+	    {
+	      warning ("current_sos: Can't read pathname for load map: %s\n",
+		       safe_strerror (errcode));
+	    }
+	  else
+	    {
+	      strncpy (new->so_name, buffer, SO_NAME_MAX_PATH_SIZE - 1);
+	      new->so_name[SO_NAME_MAX_PATH_SIZE - 1] = '\0';
+	      free (buffer);
+	      strcpy (new->so_original_name, new->so_name);
+	    }
+
+	  /* If this entry has no name, or its name matches the name
+	     for the main executable, don't include it in the list.  */
+	  if (! new->so_name[0]
+	      || match_main (new->so_name))
+	    free_so (new);
+	  else
+	    {
+	      new->next = 0;
+	      *link_ptr = new;
+	      link_ptr = &new->next;
+	    }
+	}
+
+      discard_cleanups (old_chain);
+    }
+
+  return head;
+}
+
+
+/* On some systems, the only way to recognize the link map entry for
+   the main executable file is by looking at its name.  Return
+   non-zero iff SONAME matches one of the known main executable names.  */
+
+static int
+match_main (char *soname)
+{
+  char **mainp;
+
+  for (mainp = main_name_list; *mainp != NULL; mainp++)
+    {
+      if (strcmp (soname, *mainp) == 0)
+	return (1);
+    }
+
+  return (0);
+}
+
+
+#ifdef SVR4_SHARED_LIBS
+
+/* Return 1 if PC lies in the dynamic symbol resolution code of the
+   SVR4 run time loader.  */
+
+static CORE_ADDR interp_text_sect_low;
+static CORE_ADDR interp_text_sect_high;
+static CORE_ADDR interp_plt_sect_low;
+static CORE_ADDR interp_plt_sect_high;
+
+int
+in_svr4_dynsym_resolve_code (CORE_ADDR pc)
+{
+  return ((pc >= interp_text_sect_low && pc < interp_text_sect_high)
+	  || (pc >= interp_plt_sect_low && pc < interp_plt_sect_high)
+	  || in_plt_section (pc, NULL));
+}
+#endif
+
+/*
+
+   LOCAL FUNCTION
+
+   disable_break -- remove the "mapping changed" breakpoint
+
+   SYNOPSIS
+
+   static int disable_break ()
+
+   DESCRIPTION
+
+   Removes the breakpoint that gets hit when the dynamic linker
+   completes a mapping change.
+
+ */
+
+#ifndef SVR4_SHARED_LIBS
+
+static int
+disable_break (void)
+{
+  int status = 1;
+
+  int in_debugger = 0;
+
+  /* Read the debugger structure from the inferior to retrieve the
+     address of the breakpoint and the original contents of the
+     breakpoint address.  Remove the breakpoint by writing the original
+     contents back. */
+
+  read_memory (debug_addr, (char *) &debug_copy, sizeof (debug_copy));
+
+  /* Set `in_debugger' to zero now. */
+
+  write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
+
+  breakpoint_addr = SOLIB_EXTRACT_ADDRESS (debug_copy.ldd_bp_addr);
+  write_memory (breakpoint_addr, (char *) &debug_copy.ldd_bp_inst,
+		sizeof (debug_copy.ldd_bp_inst));
+
+  /* For the SVR4 version, we always know the breakpoint address.  For the
+     SunOS version we don't know it until the above code is executed.
+     Grumble if we are stopped anywhere besides the breakpoint address. */
+
+  if (stop_pc != breakpoint_addr)
+    {
+      warning ("stopped at unknown breakpoint while handling shared libraries");
+    }
+
+  return (status);
+}
+
+#endif /* #ifdef SVR4_SHARED_LIBS */
+
+/*
+
+   LOCAL FUNCTION
+
+   enable_break -- arrange for dynamic linker to hit breakpoint
+
+   SYNOPSIS
+
+   int enable_break (void)
+
+   DESCRIPTION
+
+   Both the SunOS and the SVR4 dynamic linkers have, as part of their
+   debugger interface, support for arranging for the inferior to hit
+   a breakpoint after mapping in the shared libraries.  This function
+   enables that breakpoint.
+
+   For SunOS, there is a special flag location (in_debugger) which we
+   set to 1.  When the dynamic linker sees this flag set, it will set
+   a breakpoint at a location known only to itself, after saving the
+   original contents of that place and the breakpoint address itself,
+   in it's own internal structures.  When we resume the inferior, it
+   will eventually take a SIGTRAP when it runs into the breakpoint.
+   We handle this (in a different place) by restoring the contents of
+   the breakpointed location (which is only known after it stops),
+   chasing around to locate the shared libraries that have been
+   loaded, then resuming.
+
+   For SVR4, the debugger interface structure contains a member (r_brk)
+   which is statically initialized at the time the shared library is
+   built, to the offset of a function (_r_debug_state) which is guaran-
+   teed to be called once before mapping in a library, and again when
+   the mapping is complete.  At the time we are examining this member,
+   it contains only the unrelocated offset of the function, so we have
+   to do our own relocation.  Later, when the dynamic linker actually
+   runs, it relocates r_brk to be the actual address of _r_debug_state().
+
+   The debugger interface structure also contains an enumeration which
+   is set to either RT_ADD or RT_DELETE prior to changing the mapping,
+   depending upon whether or not the library is being mapped or unmapped,
+   and then set to RT_CONSISTENT after the library is mapped/unmapped.
+ */
+
+static int
+enable_break (void)
+{
+  int success = 0;
+
+#ifndef SVR4_SHARED_LIBS
+
+  int j;
+  int in_debugger;
+
+  /* Get link_dynamic structure */
+
+  j = target_read_memory (debug_base, (char *) &dynamic_copy,
+			  sizeof (dynamic_copy));
+  if (j)
+    {
+      /* unreadable */
+      return (0);
+    }
+
+  /* Calc address of debugger interface structure */
+
+  debug_addr = SOLIB_EXTRACT_ADDRESS (dynamic_copy.ldd);
+
+  /* Calc address of `in_debugger' member of debugger interface structure */
+
+  flag_addr = debug_addr + (CORE_ADDR) ((char *) &debug_copy.ldd_in_debugger -
+					(char *) &debug_copy);
+
+  /* Write a value of 1 to this member.  */
+
+  in_debugger = 1;
+  write_memory (flag_addr, (char *) &in_debugger, sizeof (in_debugger));
+  success = 1;
+
+#else /* SVR4_SHARED_LIBS */
+
+#ifdef BKPT_AT_SYMBOL
+
+  struct minimal_symbol *msymbol;
+  char **bkpt_namep;
+  asection *interp_sect;
+
+  /* First, remove all the solib event breakpoints.  Their addresses
+     may have changed since the last time we ran the program.  */
+  remove_solib_event_breakpoints ();
+
+#ifdef SVR4_SHARED_LIBS
+  interp_text_sect_low = interp_text_sect_high = 0;
+  interp_plt_sect_low = interp_plt_sect_high = 0;
+
+  /* Find the .interp section; if not found, warn the user and drop
+     into the old breakpoint at symbol code.  */
+  interp_sect = bfd_get_section_by_name (exec_bfd, ".interp");
+  if (interp_sect)
+    {
+      unsigned int interp_sect_size;
+      char *buf;
+      CORE_ADDR load_addr;
+      bfd *tmp_bfd;
+      CORE_ADDR sym_addr = 0;
+
+      /* Read the contents of the .interp section into a local buffer;
+         the contents specify the dynamic linker this program uses.  */
+      interp_sect_size = bfd_section_size (exec_bfd, interp_sect);
+      buf = alloca (interp_sect_size);
+      bfd_get_section_contents (exec_bfd, interp_sect,
+				buf, 0, interp_sect_size);
+
+      /* Now we need to figure out where the dynamic linker was
+         loaded so that we can load its symbols and place a breakpoint
+         in the dynamic linker itself.
+
+         This address is stored on the stack.  However, I've been unable
+         to find any magic formula to find it for Solaris (appears to
+         be trivial on GNU/Linux).  Therefore, we have to try an alternate
+         mechanism to find the dynamic linker's base address.  */
+      tmp_bfd = bfd_openr (buf, gnutarget);
+      if (tmp_bfd == NULL)
+	goto bkpt_at_symbol;
+
+      /* Make sure the dynamic linker's really a useful object.  */
+      if (!bfd_check_format (tmp_bfd, bfd_object))
+	{
+	  warning ("Unable to grok dynamic linker %s as an object file", buf);
+	  bfd_close (tmp_bfd);
+	  goto bkpt_at_symbol;
+	}
+
+      /* We find the dynamic linker's base address by examining the
+         current pc (which point at the entry point for the dynamic
+         linker) and subtracting the offset of the entry point.  */
+      load_addr = read_pc () - tmp_bfd->start_address;
+
+      /* Record the relocated start and end address of the dynamic linker
+         text and plt section for in_svr4_dynsym_resolve_code.  */
+      interp_sect = bfd_get_section_by_name (tmp_bfd, ".text");
+      if (interp_sect)
+	{
+	  interp_text_sect_low =
+	    bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
+	  interp_text_sect_high =
+	    interp_text_sect_low + bfd_section_size (tmp_bfd, interp_sect);
+	}
+      interp_sect = bfd_get_section_by_name (tmp_bfd, ".plt");
+      if (interp_sect)
+	{
+	  interp_plt_sect_low =
+	    bfd_section_vma (tmp_bfd, interp_sect) + load_addr;
+	  interp_plt_sect_high =
+	    interp_plt_sect_low + bfd_section_size (tmp_bfd, interp_sect);
+	}
+
+      /* Now try to set a breakpoint in the dynamic linker.  */
+      for (bkpt_namep = solib_break_names; *bkpt_namep != NULL; bkpt_namep++)
+	{
+	  sym_addr = bfd_lookup_symbol (tmp_bfd, *bkpt_namep);
+	  if (sym_addr != 0)
+	    break;
+	}
+
+      /* We're done with the temporary bfd.  */
+      bfd_close (tmp_bfd);
+
+      if (sym_addr != 0)
+	{
+	  create_solib_event_breakpoint (load_addr + sym_addr);
+	  return 1;
+	}
+
+      /* For whatever reason we couldn't set a breakpoint in the dynamic
+         linker.  Warn and drop into the old code.  */
+    bkpt_at_symbol:
+      warning ("Unable to find dynamic linker breakpoint function.\nGDB will be unable to debug shared library initializers\nand track explicitly loaded dynamic code.");
+    }
+#endif
+
+  /* Scan through the list of symbols, trying to look up the symbol and
+     set a breakpoint there.  Terminate loop when we/if we succeed. */
+
+  breakpoint_addr = 0;
+  for (bkpt_namep = bkpt_names; *bkpt_namep != NULL; bkpt_namep++)
+    {
+      msymbol = lookup_minimal_symbol (*bkpt_namep, NULL, symfile_objfile);
+      if ((msymbol != NULL) && (SYMBOL_VALUE_ADDRESS (msymbol) != 0))
+	{
+	  create_solib_event_breakpoint (SYMBOL_VALUE_ADDRESS (msymbol));
+	  return 1;
+	}
+    }
+
+  /* Nothing good happened.  */
+  success = 0;
+
+#endif /* BKPT_AT_SYMBOL */
+
+#endif /* !SVR4_SHARED_LIBS */
+
+  return (success);
+}
+
+/*
+
+   LOCAL FUNCTION
+
+   special_symbol_handling -- additional shared library symbol handling
+
+   SYNOPSIS
+
+   void special_symbol_handling ()
+
+   DESCRIPTION
+
+   Once the symbols from a shared object have been loaded in the usual
+   way, we are called to do any system specific symbol handling that 
+   is needed.
+
+   For SunOS4, this consists of grunging around in the dynamic
+   linkers structures to find symbol definitions for "common" symbols
+   and adding them to the minimal symbol table for the runtime common
+   objfile.
+
+ */
+
+static void
+svr4_special_symbol_handling (void)
+{
+#ifndef SVR4_SHARED_LIBS
+  int j;
+
+  if (debug_addr == 0)
+    {
+      /* Get link_dynamic structure */
+
+      j = target_read_memory (debug_base, (char *) &dynamic_copy,
+			      sizeof (dynamic_copy));
+      if (j)
+	{
+	  /* unreadable */
+	  return;
+	}
+
+      /* Calc address of debugger interface structure */
+      /* FIXME, this needs work for cross-debugging of core files
+         (byteorder, size, alignment, etc).  */
+
+      debug_addr = SOLIB_EXTRACT_ADDRESS (dynamic_copy.ldd);
+    }
+
+  /* Read the debugger structure from the inferior, just to make sure
+     we have a current copy. */
+
+  j = target_read_memory (debug_addr, (char *) &debug_copy,
+			  sizeof (debug_copy));
+  if (j)
+    return;			/* unreadable */
+
+  /* Get common symbol definitions for the loaded object. */
+
+  if (debug_copy.ldd_cp)
+    {
+      solib_add_common_symbols (SOLIB_EXTRACT_ADDRESS (debug_copy.ldd_cp));
+    }
+
+#endif /* !SVR4_SHARED_LIBS */
+}
+
+/*
+
+   GLOBAL FUNCTION
+
+   svr4_solib_create_inferior_hook -- shared library startup support
+
+   SYNOPSIS
+
+   void svr4_solib_create_inferior_hook()
+
+   DESCRIPTION
+
+   When gdb starts up the inferior, it nurses it along (through the
+   shell) until it is ready to execute it's first instruction.  At this
+   point, this function gets called via expansion of the macro
+   SOLIB_CREATE_INFERIOR_HOOK.
+
+   For SunOS executables, this first instruction is typically the
+   one at "_start", or a similar text label, regardless of whether
+   the executable is statically or dynamically linked.  The runtime
+   startup code takes care of dynamically linking in any shared
+   libraries, once gdb allows the inferior to continue.
+
+   For SVR4 executables, this first instruction is either the first
+   instruction in the dynamic linker (for dynamically linked
+   executables) or the instruction at "start" for statically linked
+   executables.  For dynamically linked executables, the system
+   first exec's /lib/libc.so.N, which contains the dynamic linker,
+   and starts it running.  The dynamic linker maps in any needed
+   shared libraries, maps in the actual user executable, and then
+   jumps to "start" in the user executable.
+
+   For both SunOS shared libraries, and SVR4 shared libraries, we
+   can arrange to cooperate with the dynamic linker to discover the
+   names of shared libraries that are dynamically linked, and the
+   base addresses to which they are linked.
+
+   This function is responsible for discovering those names and
+   addresses, and saving sufficient information about them to allow
+   their symbols to be read at a later time.
+
+   FIXME
+
+   Between enable_break() and disable_break(), this code does not
+   properly handle hitting breakpoints which the user might have
+   set in the startup code or in the dynamic linker itself.  Proper
+   handling will probably have to wait until the implementation is
+   changed to use the "breakpoint handler function" method.
+
+   Also, what if child has exit()ed?  Must exit loop somehow.
+ */
+
+void
+svr4_solib_create_inferior_hook (void)
+{
+  /* If we are using the BKPT_AT_SYMBOL code, then we don't need the base
+     yet.  In fact, in the case of a SunOS4 executable being run on
+     Solaris, we can't get it yet.  current_sos will get it when it needs
+     it.  */
+#if !(defined (SVR4_SHARED_LIBS) && defined (BKPT_AT_SYMBOL))
+  if ((debug_base = locate_base ()) == 0)
+    {
+      /* Can't find the symbol or the executable is statically linked. */
+      return;
+    }
+#endif
+
+  if (!enable_break ())
+    {
+      warning ("shared library handler failed to enable breakpoint");
+      return;
+    }
+
+#if !defined(SVR4_SHARED_LIBS) || defined(_SCO_DS)
+  /* SCO and SunOS need the loop below, other systems should be using the
+     special shared library breakpoints and the shared library breakpoint
+     service routine.
+
+     Now run the target.  It will eventually hit the breakpoint, at
+     which point all of the libraries will have been mapped in and we
+     can go groveling around in the dynamic linker structures to find
+     out what we need to know about them. */
+
+  clear_proceed_status ();
+  stop_soon_quietly = 1;
+  stop_signal = TARGET_SIGNAL_0;
+  do
+    {
+      target_resume (-1, 0, stop_signal);
+      wait_for_inferior ();
+    }
+  while (stop_signal != TARGET_SIGNAL_TRAP);
+  stop_soon_quietly = 0;
+
+#if !defined(_SCO_DS)
+  /* We are now either at the "mapping complete" breakpoint (or somewhere
+     else, a condition we aren't prepared to deal with anyway), so adjust
+     the PC as necessary after a breakpoint, disable the breakpoint, and
+     add any shared libraries that were mapped in. */
+
+  if (DECR_PC_AFTER_BREAK)
+    {
+      stop_pc -= DECR_PC_AFTER_BREAK;
+      write_register (PC_REGNUM, stop_pc);
+    }
+
+  if (!disable_break ())
+    {
+      warning ("shared library handler failed to disable breakpoint");
+    }
+
+  if (auto_solib_add)
+    solib_add ((char *) 0, 0, (struct target_ops *) 0);
+#endif /* ! _SCO_DS */
+#endif
+}
+
+static void
+svr4_clear_solib (void)
+{
+  debug_base = 0;
+}
+
+static void
+svr4_free_so (struct so_list *so)
+{
+  free (so->lm_info->lm);
+  free (so->lm_info);
+}
+
+static struct target_so_ops svr4_so_ops;
+
+void
+_initialize_svr4_solib (void)
+{
+  svr4_so_ops.lm_addr = LM_ADDR;
+  svr4_so_ops.free_so = svr4_free_so;
+  svr4_so_ops.clear_solib = svr4_clear_solib;
+  svr4_so_ops.solib_create_inferior_hook = svr4_solib_create_inferior_hook;
+  svr4_so_ops.special_symbol_handling = svr4_special_symbol_handling;
+  svr4_so_ops.current_sos = svr4_current_sos;
+  svr4_so_ops.open_symbol_file_object = open_symbol_file_object;
+
+  /* FIXME: Don't do this here.  *_gdbarch_init() should set so_ops. */
+  current_target_so_ops = &svr4_so_ops;
+}
+