elf/dl-debug.c

   1 /* Communicate dynamic linker state to the debugger at runtime.
   2    Copyright (C) 1996, 1998,2000,2002,2004,2005,2006
   3         Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <ldsodefs.h>
  21
  22
  23 /* These are the members in the public `struct link_map' type.
  24    Sanity check that the internal type and the public type match.  */
  25 #define VERIFY_MEMBER(name) \
  26   (offsetof (struct link_map_public, name) == offsetof (struct link_map, name))
  27 extern const int verify_link_map_members[(VERIFY_MEMBER (l_addr)
  28                                           && VERIFY_MEMBER (l_name)
  29                                           && VERIFY_MEMBER (l_ld)
  30                                           && VERIFY_MEMBER (l_next)
  31                                           && VERIFY_MEMBER (l_prev))
  32                                          ? 1 : -1];
  33
  34 /* This structure communicates dl state to the debugger.  The debugger
  35    normally finds it via the DT_DEBUG entry in the dynamic section, but in
  36    a statically-linked program there is no dynamic section for the debugger
  37    to examine and it looks for this particular symbol name.  */
  38 struct r_debug _r_debug;
  39
  40
  41 /* Initialize _r_debug if it has not already been done.  The argument is
  42    the run-time load address of the dynamic linker, to be put in
  43    _r_debug.r_ldbase.  Returns the address of _r_debug.  */
  44
  45 struct r_debug *
  46 internal_function
  47 _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns)
  48 {
  49   struct r_debug *r;
  50
  51   if (ns == LM_ID_BASE)
  52     r = &_r_debug;
  53   else
  54     r = &GL(dl_ns)[ns]._ns_debug;
  55
  56   if (r->r_map == NULL || ldbase != 0)
  57     {
  58       /* Tell the debugger where to find the map of loaded objects.  */
  59       r->r_version = 1  /* R_DEBUG_VERSION XXX */;
  60       r->r_ldbase = ldbase ?: _r_debug.r_ldbase;
  61       r->r_map = (void *) GL(dl_ns)[ns]._ns_loaded;
  62       r->r_brk = (ElfW(Addr)) &_dl_debug_state;
  63     }
  64
  65   return r;
  66 }
  67
  68
  69 /* This function exists solely to have a breakpoint set on it by the
  70    debugger.  The debugger is supposed to find this function's address by
  71    examining the r_brk member of struct r_debug, but GDB 4.15 in fact looks
  72    for this particular symbol name in the PT_INTERP file.  */
  73 void
  74 _dl_debug_state (void)
  75 {
  76 }
  77 rtld_hidden_def (_dl_debug_state)