elf/dl-debug.c

   1 /* Communicate dynamic linker state to the debugger at runtime.
   2    Copyright (C) 1996-2020 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <ldsodefs.h>
  20
  21
  22 /* These are the members in the public `struct link_map' type.
  23    Sanity check that the internal type and the public type match.  */
  24 #define VERIFY_MEMBER(name) \
  25   (offsetof (struct link_map_public, name) == offsetof (struct link_map, name))
  26 extern const int verify_link_map_members[(VERIFY_MEMBER (l_addr)
  27                                           && VERIFY_MEMBER (l_name)
  28                                           && VERIFY_MEMBER (l_ld)
  29                                           && VERIFY_MEMBER (l_next)
  30                                           && VERIFY_MEMBER (l_prev))
  31                                          ? 1 : -1];
  32
  33 /* This structure communicates dl state to the debugger.  The debugger
  34    normally finds it via the DT_DEBUG entry in the dynamic section, but in
  35    a statically-linked program there is no dynamic section for the debugger
  36    to examine and it looks for this particular symbol name.  */
  37 struct r_debug _r_debug;
  38
  39
  40 /* Initialize _r_debug if it has not already been done.  The argument is
  41    the run-time load address of the dynamic linker, to be put in
  42    _r_debug.r_ldbase.  Returns the address of _r_debug.  */
  43
  44 struct r_debug *
  45 _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns)
  46 {
  47   struct r_debug *r;
  48
  49   if (ns == LM_ID_BASE)
  50     r = &_r_debug;
  51   else
  52     r = &GL(dl_ns)[ns]._ns_debug;
  53
  54   if (r->r_map == NULL || ldbase != 0)
  55     {
  56       /* Tell the debugger where to find the map of loaded objects.  */
  57       r->r_version = 1  /* R_DEBUG_VERSION XXX */;
  58       r->r_ldbase = ldbase ?: _r_debug.r_ldbase;
  59       r->r_map = (void *) GL(dl_ns)[ns]._ns_loaded;
  60       r->r_brk = (ElfW(Addr)) &_dl_debug_state;
  61     }
  62
  63   return r;
  64 }
  65
  66
  67 /* This function exists solely to have a breakpoint set on it by the
  68    debugger.  The debugger is supposed to find this function's address by
  69    examining the r_brk member of struct r_debug, but GDB 4.15 in fact looks
  70    for this particular symbol name in the PT_INTERP file.  */
  71 void
  72 _dl_debug_state (void)
  73 {
  74 }
  75 rtld_hidden_def (_dl_debug_state)