glibc/elf/dl-lookup.c

387 lines
12 KiB
C

/* Look up a symbol in the loaded objects.
Copyright (C) 1995, 1996, 1997 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 Library General Public License as
published by the Free Software Foundation; either version 2 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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <alloca.h>
#include <stddef.h>
#include <link.h>
#include <assert.h>
#include <string.h>
#include "dl-hash.h"
#include <dl-machine.h>
#define VERSTAG(tag) (DT_NUM + DT_PROCNUM + DT_VERSIONTAGIDX (tag))
/* We need this string more than once. */
static const char undefined_msg[] = "undefined symbol: ";
struct sym_val
{
ElfW(Addr) a;
const ElfW(Sym) *s;
};
#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; \
})
/* Inner part of the lookup functions. We return a value > 0 if we
found the symbol, the value 0 if nothing is found and < 0 if
something bad happened. */
static inline int
do_lookup (const char *undef_name, unsigned long int hash,
const ElfW(Sym) *ref, struct sym_val *result,
struct link_map *list[], size_t i, size_t n,
const char *reference_name, const struct r_found_version *version,
struct link_map *skip, int reloc_type)
{
struct link_map *map;
for (; i < n; ++i)
{
const ElfW(Sym) *symtab;
const char *strtab;
const ElfW(Half) *verstab;
ElfW(Symndx) symidx;
map = list[i];
/* Here come the extra test needed for `_dl_lookup_symbol_skip'. */
if (skip != NULL && map == skip)
continue;
/* Skip objects that could not be opened, which can occur in trace
mode. */
if (map->l_opencount == 0)
continue;
/* Don't search the executable when resolving a copy reloc. */
if (elf_machine_lookup_noexec_p (reloc_type) &&
map->l_type == lt_executable)
continue;
/* Skip objects without symbol tables. */
if (map->l_info[DT_SYMTAB] == NULL)
continue;
symtab = ((void *) map->l_addr + map->l_info[DT_SYMTAB]->d_un.d_ptr);
strtab = ((void *) map->l_addr + map->l_info[DT_STRTAB]->d_un.d_ptr);
if (map->l_nversions > 0 && map->l_info[VERSTAG (DT_VERSYM)] != NULL)
verstab = ((void *) map->l_addr
+ map->l_info[VERSTAG (DT_VERSYM)]->d_un.d_ptr);
else
verstab = NULL;
/* Search the appropriate hash bucket in this object's symbol table
for a definition for the same symbol name. */
for (symidx = map->l_buckets[hash % map->l_nbuckets];
symidx != STN_UNDEF;
symidx = map->l_chain[symidx])
{
const ElfW(Sym) *sym = &symtab[symidx];
if (sym->st_value == 0 || /* No value. */
(elf_machine_lookup_noplt_p (reloc_type) /* Reject PLT entry. */
&& sym->st_shndx == SHN_UNDEF))
continue;
if (ELFW(ST_TYPE) (sym->st_info) > STT_FUNC)
/* Ignore all but STT_NOTYPE, STT_OBJECT and STT_FUNC entries
since these are no code/data definitions. */
continue;
if (sym != ref && strcmp (strtab + sym->st_name, undef_name))
/* Not the symbol we are looking for. */
continue;
if (version == NULL)
{
/* No specific version is selected. When the object
file also does not define a version we have a match.
Otherwise we only accept the default version, i.e.,
the version which name is "". */
if (verstab != NULL)
{
ElfW(Half) ndx = verstab[symidx] & 0x7fff;
if (ndx > 2) /* map->l_versions[ndx].hash != 0) */
continue;
}
}
else
{
if (verstab == NULL)
{
/* We need a versioned system but haven't found any.
If this is the object which is referenced in the
verneed entry it is a bug in the library since a
symbol must not simply disappear. */
if (version->filename != NULL
&& _dl_name_match_p (version->filename, map))
return -2;
/* Otherwise we accept the symbol. */
}
else
{
/* We can match the version information or use the
default one if it is not hidden. */
ElfW(Half) ndx = verstab[symidx] & 0x7fff;
if ((map->l_versions[ndx].hash != version->hash
|| strcmp (map->l_versions[ndx].name, version->name))
&& (version->hidden || map->l_versions[ndx].hash
|| (verstab[symidx] & 0x8000)))
/* It's not the version we want. */
continue;
}
}
switch (ELFW(ST_BIND) (sym->st_info))
{
case STB_GLOBAL:
/* Global definition. Just what we need. */
result->s = sym;
result->a = map->l_addr;
return 1;
case STB_WEAK:
/* Weak definition. Use this value if we don't find
another. */
if (! result->s)
{
result->s = sym;
result->a = map->l_addr;
}
break;
default:
/* Local symbols are ignored. */
break;
}
/* There cannot be another entry for this symbol so stop here. */
break;
}
/* If this current map is the one mentioned in the verneed entry
and we have not found a weak entry, it is a bug. */
if (symidx == STN_UNDEF && version != NULL && version->filename != NULL
&& _dl_name_match_p (version->filename, map))
return -1;
}
/* We have not found anything until now. */
return 0;
}
/* Search loaded objects' symbol tables for a definition of the symbol
UNDEF_NAME. */
ElfW(Addr)
_dl_lookup_symbol (const char *undef_name, const ElfW(Sym) **ref,
struct link_map *symbol_scope[],
const char *reference_name,
int reloc_type)
{
const unsigned long int hash = _dl_elf_hash (undef_name);
struct sym_val current_value = { 0, NULL };
struct link_map **scope;
/* Search the relevant loaded objects for a definition. */
for (scope = symbol_scope; *scope; ++scope)
if (do_lookup (undef_name, hash, *ref, &current_value,
(*scope)->l_searchlist, 0, (*scope)->l_nsearchlist,
reference_name, NULL, NULL, reloc_type))
break;
if (current_value.s == NULL &&
(*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK))
/* We could find no value for a strong reference. */
_dl_signal_error (0, reference_name,
make_string (undefined_msg, undef_name));
*ref = current_value.s;
return current_value.a;
}
/* This function is nearly the same as `_dl_lookup_symbol' but it
skips in the first list all objects until SKIP_MAP is found. I.e.,
it only considers objects which were loaded after the described
object. If there are more search lists the object described by
SKIP_MAP is only skipped. */
ElfW(Addr)
_dl_lookup_symbol_skip (const char *undef_name, const ElfW(Sym) **ref,
struct link_map *symbol_scope[],
const char *reference_name,
struct link_map *skip_map)
{
const unsigned long int hash = _dl_elf_hash (undef_name);
struct sym_val current_value = { 0, NULL };
struct link_map **scope;
size_t i;
/* Search the relevant loaded objects for a definition. */
scope = symbol_scope;
for (i = 0; (*scope)->l_dupsearchlist[i] != skip_map; ++i)
assert (i < (*scope)->l_ndupsearchlist);
if (! do_lookup (undef_name, hash, *ref, &current_value,
(*scope)->l_dupsearchlist, i, (*scope)->l_ndupsearchlist,
reference_name, NULL, skip_map, 0))
while (*++scope)
if (do_lookup (undef_name, hash, *ref, &current_value,
(*scope)->l_dupsearchlist, 0, (*scope)->l_ndupsearchlist,
reference_name, NULL, skip_map, 0))
break;
*ref = current_value.s;
return current_value.a;
}
/* This function works like _dl_lookup_symbol but it takes an
additional arguement with the version number of the requested
symbol.
XXX We'll see whether we need this separate function. */
ElfW(Addr)
_dl_lookup_versioned_symbol (const char *undef_name, const ElfW(Sym) **ref,
struct link_map *symbol_scope[],
const char *reference_name,
const struct r_found_version *version,
int reloc_type)
{
extern char **_dl_argv;
const unsigned long int hash = _dl_elf_hash (undef_name);
struct sym_val current_value = { 0, NULL };
struct link_map **scope;
/* Search the relevant loaded objects for a definition. */
for (scope = symbol_scope; *scope; ++scope)
{
int res = do_lookup (undef_name, hash, *ref, &current_value,
(*scope)->l_searchlist, 0, (*scope)->l_nsearchlist,
reference_name, version, NULL, reloc_type);
if (res > 0)
break;
if (res < 0)
/* Oh, oh. The file named in the relocation entry does not
contain the needed symbol. */
_dl_signal_error (0, (*reference_name
? reference_name
: (_dl_argv[0] ?: "<main program>")),
make_string ("symbol ", undef_name, ", version ",
version->name,
" not defined in file ",
version->filename,
" with link time reference",
res == -2
? " (no version symbols)" : ""));
}
if (current_value.s == NULL &&
(*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK))
/* We could find no value for a strong reference. */
_dl_signal_error (0, reference_name,
make_string (undefined_msg, undef_name,
", version ", version->name ?: NULL));
*ref = current_value.s;
return current_value.a;
}
/* Similar to _dl_lookup_symbol_skip but takes an additional argument
with the version we are looking for. */
ElfW(Addr)
_dl_lookup_versioned_symbol_skip (const char *undef_name,
const ElfW(Sym) **ref,
struct link_map *symbol_scope[],
const char *reference_name,
const struct r_found_version *version,
struct link_map *skip_map)
{
const unsigned long int hash = _dl_elf_hash (undef_name);
struct sym_val current_value = { 0, NULL };
struct link_map **scope;
size_t i;
/* Search the relevant loaded objects for a definition. */
scope = symbol_scope;
for (i = 0; (*scope)->l_dupsearchlist[i] != skip_map; ++i)
assert (i < (*scope)->l_ndupsearchlist);
if (! do_lookup (undef_name, hash, *ref, &current_value,
(*scope)->l_dupsearchlist, i, (*scope)->l_ndupsearchlist,
reference_name, version, skip_map, 0))
while (*++scope)
if (do_lookup (undef_name, hash, *ref, &current_value,
(*scope)->l_dupsearchlist, 0, (*scope)->l_ndupsearchlist,
reference_name, version, skip_map, 0))
break;
if (current_value.s == NULL &&
(*ref == NULL || ELFW(ST_BIND) ((*ref)->st_info) != STB_WEAK))
{
/* We could find no value for a strong reference. */
const size_t len = strlen (undef_name);
char buf[sizeof undefined_msg + len];
__mempcpy (__mempcpy (buf, undefined_msg, sizeof undefined_msg - 1),
undef_name, len + 1);
_dl_signal_error (0, reference_name, buf);
}
*ref = current_value.s;
return current_value.a;
}
/* Cache the location of MAP's hash table. */
void
_dl_setup_hash (struct link_map *map)
{
ElfW(Symndx) *hash;
ElfW(Symndx) nchain;
if (!map->l_info[DT_HASH])
return;
hash = (void *)(map->l_addr + map->l_info[DT_HASH]->d_un.d_ptr);
map->l_nbuckets = *hash++;
nchain = *hash++;
map->l_buckets = hash;
hash += map->l_nbuckets;
map->l_chain = hash;
}