glibc/elf/dl-lookup.c

466 lines
14 KiB
C

/* Look up a symbol in the loaded objects.
Copyright (C) 1995-2002, 2003, 2004, 2005 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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <alloca.h>
#include <libintl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ldsodefs.h>
#include "dl-hash.h"
#include <dl-machine.h>
#include <bits/libc-lock.h>
#include <tls.h>
#include <assert.h>
#define VERSTAG(tag) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (tag))
/* We need this string more than once. */
static const char undefined_msg[] = "undefined symbol: ";
struct sym_val
{
const ElfW(Sym) *s;
struct link_map *m;
};
#define make_string(string, rest...) \
({ \
const char *all[] = { string, ## rest }; \
size_t len, cnt; \
char *result, *cp; \
\
len = 1; \
for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt) \
len += strlen (all[cnt]); \
\
cp = result = alloca (len); \
for (cnt = 0; cnt < sizeof (all) / sizeof (all[0]); ++cnt) \
cp = __stpcpy (cp, all[cnt]); \
\
result; \
})
/* Statistics function. */
#ifdef SHARED
# define bump_num_relocations() ++GL(dl_num_relocations)
#else
# define bump_num_relocations() ((void) 0)
#endif
/* The actual lookup code. */
#include "do-lookup.h"
/* Add extra dependency on MAP to UNDEF_MAP. */
static int
internal_function
add_dependency (struct link_map *undef_map, struct link_map *map)
{
struct link_map **list;
struct link_map *runp;
unsigned int act;
unsigned int i;
int result = 0;
/* Avoid self-references and references to objects which cannot be
unloaded anyway. */
if (undef_map == map)
return 0;
/* Make sure nobody can unload the object while we are at it. */
__rtld_lock_lock_recursive (GL(dl_load_lock));
/* Don't create cross-reference between modules which are
dynamically loaded by the same dlopen() call. */
if (undef_map->l_opencount == 0 && map->l_opencount == 0)
goto out;
/* Avoid references to objects which cannot be unloaded anyway. */
if (map->l_type != lt_loaded
|| (map->l_flags_1 & DF_1_NODELETE) != 0)
goto out;
/* If the object with the undefined reference cannot be removed ever
just make sure the same is true for the object which contains the
definition. */
if (undef_map->l_type != lt_loaded
|| (undef_map->l_flags_1 & DF_1_NODELETE) != 0)
{
++map->l_opencount;
map->l_flags_1 |= DF_1_NODELETE;
goto out;
}
/* Determine whether UNDEF_MAP already has a reference to MAP. First
look in the normal dependencies. */
if (undef_map->l_searchlist.r_list != NULL)
{
list = undef_map->l_initfini;
for (i = 0; list[i] != NULL; ++i)
if (list[i] == map)
goto out;
}
/* No normal dependency. See whether we already had to add it
to the special list of dynamic dependencies. */
list = undef_map->l_reldeps;
act = undef_map->l_reldepsact;
for (i = 0; i < act; ++i)
if (list[i] == map)
goto out;
/* The object is not yet in the dependency list. Before we add
it make sure just one more time the object we are about to
reference is still available. There is a brief period in
which the object could have been removed since we found the
definition. */
runp = GL(dl_ns)[undef_map->l_ns]._ns_loaded;
while (runp != NULL && runp != map)
runp = runp->l_next;
if (runp != NULL)
{
/* The object is still available. Add the reference now. */
if (__builtin_expect (act >= undef_map->l_reldepsmax, 0))
{
/* Allocate more memory for the dependency list. Since this
can never happen during the startup phase we can use
`realloc'. */
void *newp;
undef_map->l_reldepsmax += 5;
newp = realloc (undef_map->l_reldeps,
undef_map->l_reldepsmax
* sizeof (struct link_map *));
if (__builtin_expect (newp != NULL, 1))
undef_map->l_reldeps = (struct link_map **) newp;
else
/* Correct the addition. */
undef_map->l_reldepsmax -= 5;
}
/* If we didn't manage to allocate memory for the list this is
no fatal mistake. We simply increment the use counter of the
referenced object and don't record the dependencies. This
means this increment can never be reverted and the object
will never be unloaded. This is semantically the correct
behavior. */
if (__builtin_expect (act < undef_map->l_reldepsmax, 1))
undef_map->l_reldeps[undef_map->l_reldepsact++] = map;
if (map->l_searchlist.r_list != NULL)
/* And increment the counter in the referenced object. */
++map->l_opencount;
else
/* We have to bump the counts for all dependencies since so far
this object was only a normal or transitive dependency.
Now it might be closed with _dl_close() directly. */
for (list = map->l_initfini; *list != NULL; ++list)
++(*list)->l_opencount;
/* As if it is opened through _dl_open. */
++map->l_direct_opencount;
/* Display information if we are debugging. */
if (__builtin_expect (GLRO(dl_debug_mask) & DL_DEBUG_FILES, 0))
_dl_debug_printf ("\
\nfile=%s [%lu]; needed by %s [%lu] (relocation dependency)\n\n",
map->l_name[0] ? map->l_name : rtld_progname,
map->l_ns,
undef_map->l_name[0]
? undef_map->l_name : rtld_progname,
undef_map->l_ns);
}
else
/* Whoa, that was bad luck. We have to search again. */
result = -1;
out:
/* Release the lock. */
__rtld_lock_unlock_recursive (GL(dl_load_lock));
return result;
}
static void
internal_function
_dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
const ElfW(Sym) **ref, struct r_scope_elem *symbol_scope[],
struct sym_val *value,
const struct r_found_version *version, int type_class,
int protected);
/* Search loaded objects' symbol tables for a definition of the symbol
UNDEF_NAME, perhaps with a requested version for the symbol. */
lookup_t
internal_function
_dl_lookup_symbol_x (const char *undef_name, struct link_map *undef_map,
const ElfW(Sym) **ref,
struct r_scope_elem *symbol_scope[],
const struct r_found_version *version,
int type_class, int flags, struct link_map *skip_map)
{
const unsigned long int hash = _dl_elf_hash (undef_name);
struct sym_val current_value = { NULL, NULL };
struct r_scope_elem **scope = symbol_scope;
bump_num_relocations ();
/* No other flag than DL_LOOKUP_ADD_DEPENDENCY is allowed if we look
up a versioned symbol. */
assert (version == NULL || flags == 0 || flags == DL_LOOKUP_ADD_DEPENDENCY);
size_t i = 0;
if (__builtin_expect (skip_map != NULL, 0))
{
/* Search the relevant loaded objects for a definition. */
while ((*scope)->r_list[i] != skip_map)
++i;
assert (i < (*scope)->r_nlist);
}
/* Search the relevant loaded objects for a definition. */
for (size_t start = i; *scope != NULL; start = 0, ++scope)
{
int res = do_lookup_x (undef_name, hash, *ref, &current_value, *scope,
start, version, flags, skip_map, type_class);
if (res > 0)
break;
if (__builtin_expect (res, 0) < 0 && skip_map == NULL)
{
/* Oh, oh. The file named in the relocation entry does not
contain the needed symbol. This code is never reached
for unversioned lookups. */
assert (version != NULL);
const char *reference_name = undef_map ? undef_map->l_name : NULL;
/* XXX We cannot translate the message. */
_dl_signal_cerror (0, (reference_name[0]
? reference_name
: (rtld_progname ?: "<main program>")),
N_("relocation error"),
make_string ("symbol ", undef_name, ", version ",
version->name,
" not defined in file ",
version->filename,
" with link time reference",
res == -2
? " (no version symbols)" : ""));
*ref = NULL;
return 0;
}
}
if (__builtin_expect (current_value.s == NULL, 0))
{
if ((*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK)
&& skip_map == NULL)
{
/* We could find no value for a strong reference. */
const char *reference_name = undef_map ? undef_map->l_name : "";
const char *versionstr = version ? ", version " : "";
const char *versionname = (version && version->name
? version->name : "");
/* XXX We cannot translate the message. */
_dl_signal_cerror (0, (reference_name[0]
? reference_name
: (rtld_progname ?: "<main program>")),
N_("symbol lookup error"),
make_string (undefined_msg, undef_name,
versionstr, versionname));
}
*ref = NULL;
return 0;
}
int protected = (*ref
&& ELFW(ST_VISIBILITY) ((*ref)->st_other) == STV_PROTECTED);
if (__builtin_expect (protected != 0, 0))
{
/* It is very tricky. We need to figure out what value to
return for the protected symbol. */
if (type_class == ELF_RTYPE_CLASS_PLT)
{
if (current_value.s != NULL && current_value.m != undef_map)
{
current_value.s = *ref;
current_value.m = undef_map;
}
}
else
{
struct sym_val protected_value = { NULL, NULL };
for (scope = symbol_scope; *scope != NULL; i = 0, ++scope)
if (do_lookup_x (undef_name, hash, *ref, &protected_value,
*scope, i, version, flags, skip_map,
ELF_RTYPE_CLASS_PLT) != 0)
break;
if (protected_value.s != NULL && protected_value.m != undef_map)
{
current_value.s = *ref;
current_value.m = undef_map;
}
}
}
/* We have to check whether this would bind UNDEF_MAP to an object
in the global scope which was dynamically loaded. In this case
we have to prevent the latter from being unloaded unless the
UNDEF_MAP object is also unloaded. */
if (__builtin_expect (current_value.m->l_type == lt_loaded, 0)
/* Don't do this for explicit lookups as opposed to implicit
runtime lookups. */
&& (flags & DL_LOOKUP_ADD_DEPENDENCY) != 0
/* Add UNDEF_MAP to the dependencies. */
&& add_dependency (undef_map, current_value.m) < 0)
/* Something went wrong. Perhaps the object we tried to reference
was just removed. Try finding another definition. */
return _dl_lookup_symbol_x (undef_name, undef_map, ref,
symbol_scope, version, type_class,
flags, skip_map);
/* The object is used. */
current_value.m->l_used = 1;
if (__builtin_expect (GLRO(dl_debug_mask)
& (DL_DEBUG_BINDINGS|DL_DEBUG_PRELINK), 0))
_dl_debug_bindings (undef_name, undef_map, ref, symbol_scope,
&current_value, version, type_class, protected);
*ref = current_value.s;
return LOOKUP_VALUE (current_value.m);
}
/* Cache the location of MAP's hash table. */
void
internal_function
_dl_setup_hash (struct link_map *map)
{
Elf_Symndx *hash;
Elf_Symndx nchain;
if (!map->l_info[DT_HASH])
return;
hash = (void *) D_PTR (map, l_info[DT_HASH]);
map->l_nbuckets = *hash++;
nchain = *hash++;
map->l_buckets = hash;
hash += map->l_nbuckets;
map->l_chain = hash;
}
static void
internal_function
_dl_debug_bindings (const char *undef_name, struct link_map *undef_map,
const ElfW(Sym) **ref, struct r_scope_elem *symbol_scope[],
struct sym_val *value,
const struct r_found_version *version, int type_class,
int protected)
{
const char *reference_name = undef_map->l_name;
if (GLRO(dl_debug_mask) & DL_DEBUG_BINDINGS)
{
_dl_debug_printf ("binding file %s [%lu] to %s [%lu]: %s symbol `%s'",
(reference_name[0]
? reference_name
: (rtld_progname ?: "<main program>")),
undef_map->l_ns,
value->m->l_name[0] ? value->m->l_name : rtld_progname,
value->m->l_ns,
protected ? "protected" : "normal", undef_name);
if (version)
_dl_debug_printf_c (" [%s]\n", version->name);
else
_dl_debug_printf_c ("\n");
}
#ifdef SHARED
if (GLRO(dl_debug_mask) & DL_DEBUG_PRELINK)
{
int conflict = 0;
struct sym_val val = { NULL, NULL };
if ((GLRO(dl_trace_prelink_map) == NULL
|| GLRO(dl_trace_prelink_map) == GL(dl_ns)[LM_ID_BASE]._ns_loaded)
&& undef_map != GL(dl_ns)[LM_ID_BASE]._ns_loaded)
{
const unsigned long int hash = _dl_elf_hash (undef_name);
do_lookup_x (undef_name, hash, *ref, &val,
undef_map->l_local_scope[0], 0, version, 0, NULL,
type_class);
if (val.s != value->s || val.m != value->m)
conflict = 1;
}
# ifdef USE_TLS
if (value->s
&& (__builtin_expect (ELFW(ST_TYPE) (value->s->st_info)
== STT_TLS, 0)))
type_class = 4;
# endif
if (conflict
|| GLRO(dl_trace_prelink_map) == undef_map
|| GLRO(dl_trace_prelink_map) == NULL
|| type_class == 4)
{
_dl_printf ("%s 0x%0*Zx 0x%0*Zx -> 0x%0*Zx 0x%0*Zx ",
conflict ? "conflict" : "lookup",
(int) sizeof (ElfW(Addr)) * 2,
(size_t) undef_map->l_map_start,
(int) sizeof (ElfW(Addr)) * 2,
(size_t) (((ElfW(Addr)) *ref) - undef_map->l_map_start),
(int) sizeof (ElfW(Addr)) * 2,
(size_t) (value->s ? value->m->l_map_start : 0),
(int) sizeof (ElfW(Addr)) * 2,
(size_t) (value->s ? value->s->st_value : 0));
if (conflict)
_dl_printf ("x 0x%0*Zx 0x%0*Zx ",
(int) sizeof (ElfW(Addr)) * 2,
(size_t) (val.s ? val.m->l_map_start : 0),
(int) sizeof (ElfW(Addr)) * 2,
(size_t) (val.s ? val.s->st_value : 0));
_dl_printf ("/%x %s\n", type_class, undef_name);
}
}
#endif
}