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/* Communicate dynamic linker state to the debugger at runtime.
Copyright (C) 1996-2025 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <assert.h>
#include <ldsodefs.h>
/* These are the members in the public `struct link_map' type.
Sanity check that the internal type and the public type match. */
#define VERIFY_MEMBER(name) \
(offsetof (struct link_map_public, name) == offsetof (struct link_map, name))
extern const int verify_link_map_members[(VERIFY_MEMBER (l_addr)
&& VERIFY_MEMBER (l_name)
&& VERIFY_MEMBER (l_ld)
&& VERIFY_MEMBER (l_next)
&& VERIFY_MEMBER (l_prev))
? 1 : -1];
#ifdef SHARED
/* r_debug structs for secondary namespaces. The first namespace is
handled separately because its r_debug structure must overlap with
the public _r_debug symbol, so the first array element corresponds
to LM_ID_BASE + 1. See elf/dl-debug-symbols.S. */
struct r_debug_extended _r_debug_array[DL_NNS - 1];
/* If not null, pointer to the _r_debug in the main executable. */
static struct r_debug *_r_debug_main;
void
_dl_debug_post_relocate (struct link_map *main_map)
{
/* Perform a full symbol search in all objects, to maintain
compatibility if interposed _r_debug definitions. The lookup
cannot fail because there is a definition in ld.so, and this
function is only called if the ld.so search scope is not empty. */
const ElfW(Sym) *sym = NULL;
lookup_t result =_dl_lookup_symbol_x ("_r_debug", main_map, &sym,
main_map->l_scope, NULL, 0, 0, NULL);
if (sym->st_size >= sizeof (struct r_debug))
{
struct r_debug *main_r_debug = DL_SYMBOL_ADDRESS (result, sym);
if (main_r_debug != &_r_debug_extended.base)
{
/* The extended version of the struct is not available in
the main executable because a copy relocation has been
used. r_map etc. have already been copied as part of the
copy relocation processing. */
main_r_debug->r_version = 1;
/* Record that dual updates of the initial link map are
required. */
_r_debug_main = main_r_debug;
}
}
}
/* Return the r_debug object for the namespace NS. */
static inline struct r_debug_extended *
get_rdebug (Lmid_t ns)
{
if (ns == LM_ID_BASE)
return &_r_debug_extended;
else
return &_r_debug_array[ns - 1];
}
#else /* !SHARED */
static inline struct r_debug_extended *
get_rdebug (Lmid_t ns)
{
return &_r_debug_extended; /* There is just one namespace. */
}
#endif /* !SHARED */
/* Update the `r_map' member and return the address of `struct r_debug'
of the namespace NS. */
struct r_debug *
_dl_debug_update (Lmid_t ns)
{
struct r_debug_extended *r = get_rdebug (ns);
if (r->base.r_map == NULL)
atomic_store_release (&r->base.r_map,
(void *) GL(dl_ns)[ns]._ns_loaded);
return &r->base;
}
void
_dl_debug_change_state (struct r_debug *r, int state)
{
atomic_store_release (&r->r_state, state);
#ifdef SHARED
if (r == &_r_debug_extended.base && _r_debug_main != NULL)
/* Update the copy-relocation of _r_debug. */
atomic_store_release (&_r_debug_main->r_state, state);
#endif
_dl_debug_state ();
}
/* Initialize _r_debug_extended for the namespace NS. LDBASE is the
run-time load address of the dynamic linker, to be put in
_r_debug_extended.r_ldbase. Return the address of _r_debug. */
struct r_debug *
_dl_debug_initialize (ElfW(Addr) ldbase, Lmid_t ns)
{
struct r_debug_extended *r = get_rdebug (ns);
if (r->base.r_brk == 0)
{
/* Tell the debugger where to find the map of loaded objects.
This function is called from dlopen. Initialize the namespace
only once. */
r->base.r_ldbase = ldbase ?: _r_debug_extended.base.r_ldbase;
r->base.r_brk = (ElfW(Addr)) &_dl_debug_state;
#ifdef SHARED
/* Add the new namespace to the linked list. This assumes that
namespaces are allocated in increasing order. After a
namespace is initialized, r_brk becomes non-zero. A
namespace becomes empty (r_map == NULL) when it is unused.
But it is never removed from the linked list. */
if (ns != LM_ID_BASE)
{
r->base.r_version = 2;
if (ns - 1 == LM_ID_BASE)
{
atomic_store_release (&_r_debug_extended.r_next, r);
/* Now there are multiple namespaces. Note that this
deliberately does not update the copy in the main
executable (if it exists). */
atomic_store_release (&_r_debug_extended.base.r_version, 2);
}
else
/* Update r_debug_extended of the previous namespace. */
atomic_store_release (&_r_debug_array[ns - 2].r_next, r);
}
else
#endif /* SHARED */
r->base.r_version = 1;
}
if (r->base.r_map == NULL)
{
struct link_map_public *l = (void *) GL(dl_ns)[ns]._ns_loaded;
atomic_store_release (&r->base.r_map, l);
#ifdef SHARED
if (ns == LM_ID_BASE && _r_debug_main != NULL)
/* Update the copy-relocation of _r_debug. */
atomic_store_release (&_r_debug_main->r_map, l);
#endif
}
return &r->base;
}
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