1  /* Communicate dynamic linker state to the debugger at runtime.
       2     Copyright (C) 1996-2023 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  /* Update the `r_map' member and return the address of `struct r_debug'
      34     of the namespace NS. */
      35  
      36  struct r_debug *
      37  _dl_debug_update (Lmid_t ns)
      38  {
      39    struct r_debug_extended *r;
      40    if (ns == LM_ID_BASE)
      41      r = &_r_debug_extended;
      42    else
      43      r = &GL(dl_ns)[ns]._ns_debug;
      44    if (r->base.r_map == NULL)
      45      atomic_store_release (&r->base.r_map,
      46  			  (void *) GL(dl_ns)[ns]._ns_loaded);
      47    return &r->base;
      48  }
      49  
      50  /* Initialize _r_debug_extended for the namespace NS.  LDBASE is the
      51     run-time load address of the dynamic linker, to be put in
      52     _r_debug_extended.r_ldbase.  Return the address of _r_debug.  */
      53  
      54  struct r_debug *
      55  _dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns)
      56  {
      57    struct r_debug_extended *r, **pp = NULL;
      58  
      59    if (ns == LM_ID_BASE)
      60      {
      61        r = &_r_debug_extended;
      62        /* Initialize r_version to 1.  */
      63        if (_r_debug_extended.base.r_version == 0)
      64  	_r_debug_extended.base.r_version = 1;
      65      }
      66    else if (DL_NNS > 1)
      67      {
      68        r = &GL(dl_ns)[ns]._ns_debug;
      69        if (r->base.r_brk == 0)
      70  	{
      71  	  /* Add the new namespace to the linked list.  After a namespace
      72  	     is initialized, r_brk becomes non-zero.  A namespace becomes
      73  	     empty (r_map == NULL) when it is unused.  But it is never
      74  	     removed from the linked list.  */
      75  	  struct r_debug_extended *p;
      76  	  for (pp = &_r_debug_extended.r_next;
      77  	       (p = *pp) != NULL;
      78  	       pp = &p->r_next)
      79  	    ;
      80  
      81  	  r->base.r_version = 2;
      82  	}
      83      }
      84  
      85    if (r->base.r_brk == 0)
      86      {
      87        /* Tell the debugger where to find the map of loaded objects.
      88  	 This function is called from dlopen.  Initialize the namespace
      89  	 only once.  */
      90        r->base.r_ldbase = ldbase ?: _r_debug_extended.base.r_ldbase;
      91        r->base.r_brk = (ElfW(Addr)) &_dl_debug_state;
      92        r->r_next = NULL;
      93      }
      94  
      95    if (r->base.r_map == NULL)
      96      atomic_store_release (&r->base.r_map,
      97  			  (void *) GL(dl_ns)[ns]._ns_loaded);
      98  
      99    if (pp != NULL)
     100      {
     101        atomic_store_release (pp, r);
     102        /* Bump r_version to 2 for the new namespace.  */
     103        atomic_store_release (&_r_debug_extended.base.r_version, 2);
     104      }
     105  
     106    return &r->base;
     107  }
     108  
     109  
     110  /* This function exists solely to have a breakpoint set on it by the
     111     debugger.  The debugger is supposed to find this function's address by
     112     examining the r_brk member of struct r_debug, but GDB 4.15 in fact looks
     113     for this particular symbol name in the PT_INTERP file.  */
     114  void
     115  _dl_debug_state (void)
     116  {
     117  }
     118  rtld_hidden_def (_dl_debug_state)