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, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <ldsodefs.h>
  22
  23
  24 /* These are the members in the public `struct link_map' type.
  25    Sanity check that the internal type and the public type match.  */
  26 #define VERIFY_MEMBER(name) \
  27   (offsetof (struct link_map_public, name) == offsetof (struct link_map, name))
  28 extern const int verify_link_map_members[(VERIFY_MEMBER (l_addr)
  29                                           && VERIFY_MEMBER (l_name)
  30                                           && VERIFY_MEMBER (l_ld)
  31                                           && VERIFY_MEMBER (l_next)
  32                                           && VERIFY_MEMBER (l_prev))
  33                                          ? 1 : -1];
  34
  35 /* This structure communicates dl state to the debugger.  The debugger
  36    normally finds it via the DT_DEBUG entry in the dynamic section, but in
  37    a statically-linked program there is no dynamic section for the debugger
  38    to examine and it looks for this particular symbol name.  */
  39 struct r_debug _r_debug;
  40
  41
  42 /* Initialize _r_debug if it has not already been done.  The argument is
  43    the run-time load address of the dynamic linker, to be put in
  44    _r_debug.r_ldbase.  Returns the address of _r_debug.  */
  45
  46 struct r_debug *
  47 internal_function
  48 _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns)
  49 {
  50   struct r_debug *r;
  51
  52   if (ns == LM_ID_BASE)
  53     r = &_r_debug;
  54   else
  55     r = &GL(dl_ns)[ns]._ns_debug;
  56
  57   if (r->r_brk == 0 || ldbase != 0)
  58     {
  59       /* Tell the debugger where to find the map of loaded objects.  */
  60       r->r_version = 1  /* R_DEBUG_VERSION XXX */;
  61       r->r_ldbase = ldbase ?: _r_debug.r_ldbase;
  62       r->r_map = (void *) GL(dl_ns)[ns]._ns_loaded;
  63       r->r_brk = (ElfW(Addr)) &_dl_debug_state;
  64     }
  65
  66   return r;
  67 }
  68
  69
  70 /* This function exists solely to have a breakpoint set on it by the
  71    debugger.  The debugger is supposed to find this function's address by
  72    examining the r_brk member of struct r_debug, but GDB 4.15 in fact looks
  73    for this particular symbol name in the PT_INTERP file.  */
  74 void
  75 _dl_debug_state (void)
  76 {
  77 }
  78 rtld_hidden_def (_dl_debug_state)