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/* vi: set sw=4 ts=4: */
/*
* Program to load an ELF binary on a linux system, and run it
* after resolving ELF shared library symbols
*
* Copyright (C) 2004 by Joakim Tjernlund <joakim.tjernlund@lumentis.se>
* Copyright (C) 2000-2006 by Erik Andersen <andersen@codepoet.org>
* Copyright (c) 1994-2000 Eric Youngdale, Peter MacDonald,
* David Engel, Hongjiu Lu and Mitch D'Souza
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. The name of the above contributors may not be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/* Various symbol table handling functions, including symbol lookup */
/*
* This is the start of the linked list that describes all of the files present
* in the system with pointers to all of the symbol, string, and hash tables,
* as well as all of the other good stuff in the binary.
*/
struct elf_resolve *_dl_loaded_modules = NULL;
/*
* This is the list of modules that are loaded when the image is first
* started. As we add more via dlopen, they get added into other
* chains.
*/
struct dyn_elf *_dl_symbol_tables = NULL;
/*
* This is the list of modules that are loaded via dlopen. We may need
* to search these for RTLD_GLOBAL files.
*/
struct dyn_elf *_dl_handles = NULL;
/* This is the hash function that is used by the ELF linker to generate the
* hash table that each executable and library is required to have. We need
* it to decode the hash table. */
static inline Elf_Symndx _dl_elf_hash(const char *name)
{
unsigned long hash=0;
unsigned long tmp;
while (*name) {
hash = (hash << 4) + *name++;
tmp = hash & 0xf0000000;
/* The algorithm specified in the ELF ABI is as follows:
if (tmp != 0)
hash ^= tmp >> 24;
hash &= ~tmp;
But the following is equivalent and a lot
faster, especially on modern processors. */
hash ^= tmp;
hash ^= tmp >> 24;
}
return hash;
}
/*
* We call this function when we have just read an ELF library or executable.
* We add the relevant info to the symbol chain, so that we can resolve all
* externals properly.
*/
struct elf_resolve *_dl_add_elf_hash_table(const char *libname,
ElfW(Addr) loadaddr, unsigned long *dynamic_info, unsigned long dynamic_addr,
attribute_unused unsigned long dynamic_size)
{
Elf_Symndx *hash_addr;
struct elf_resolve *tpnt;
int i;
if (!_dl_loaded_modules) {
tpnt = _dl_loaded_modules = (struct elf_resolve *) _dl_malloc(sizeof(struct elf_resolve));
_dl_memset(tpnt, 0, sizeof(struct elf_resolve));
} else {
tpnt = _dl_loaded_modules;
while (tpnt->next)
tpnt = tpnt->next;
tpnt->next = (struct elf_resolve *) _dl_malloc(sizeof(struct elf_resolve));
_dl_memset(tpnt->next, 0, sizeof(struct elf_resolve));
tpnt->next->prev = tpnt;
tpnt = tpnt->next;
};
tpnt->next = NULL;
tpnt->init_flag = 0;
tpnt->libname = _dl_strdup(libname);
tpnt->dynamic_addr = (ElfW(Dyn) *)dynamic_addr;
tpnt->libtype = loaded_file;
if (dynamic_info[DT_HASH] != 0) {
hash_addr = (Elf_Symndx*)dynamic_info[DT_HASH];
tpnt->nbucket = *hash_addr++;
tpnt->nchain = *hash_addr++;
tpnt->elf_buckets = hash_addr;
hash_addr += tpnt->nbucket;
tpnt->chains = hash_addr;
}
tpnt->loadaddr = loadaddr;
for (i = 0; i < DYNAMIC_SIZE; i++)
tpnt->dynamic_info[i] = dynamic_info[i];
return tpnt;
}
/*
* This function resolves externals, and this is either called when we process
* relocations or when we call an entry in the PLT table for the first time.
*/
char *_dl_find_hash(const char *name, struct dyn_elf *rpnt, struct elf_resolve *mytpnt, int type_class)
{
struct elf_resolve *tpnt;
int si;
char *strtab;
ElfW(Sym) *symtab;
unsigned long elf_hash_number, hn;
const ElfW(Sym) *sym;
char *weak_result = NULL;
elf_hash_number = _dl_elf_hash(name);
for (; rpnt; rpnt = rpnt->next) {
tpnt = rpnt->dyn;
if (!(tpnt->rtld_flags & RTLD_GLOBAL) && mytpnt) {
if (mytpnt == tpnt)
;
else {
struct init_fini_list *tmp;
for (tmp = mytpnt->rtld_local; tmp; tmp = tmp->next) {
if (tmp->tpnt == tpnt)
break;
}
if (!tmp)
continue;
}
}
/* Don't search the executable when resolving a copy reloc. */
if ((type_class & ELF_RTYPE_CLASS_COPY) && tpnt->libtype == elf_executable)
continue;
/* Avoid calling .urem here. */
do_rem(hn, elf_hash_number, tpnt->nbucket);
symtab = (ElfW(Sym) *) (intptr_t) (tpnt->dynamic_info[DT_SYMTAB]);
strtab = (char *) (tpnt->dynamic_info[DT_STRTAB]);
for (si = tpnt->elf_buckets[hn]; si != STN_UNDEF; si = tpnt->chains[si]) {
sym = &symtab[si];
if (type_class & (sym->st_shndx == SHN_UNDEF))
continue;
if (_dl_strcmp(strtab + sym->st_name, name) != 0)
continue;
if (sym->st_value == 0)
continue;
if (ELF_ST_TYPE(sym->st_info) > STT_FUNC)
continue;
switch (ELF_ST_BIND(sym->st_info)) {
case STB_WEAK:
#if 0
/* Perhaps we should support old style weak symbol handling
* per what glibc does when you export LD_DYNAMIC_WEAK */
if (!weak_result)
weak_result = (char *)tpnt->loadaddr + sym->st_value;
break;
#endif
case STB_GLOBAL:
return (char*)tpnt->loadaddr + sym->st_value;
default: /* Local symbols not handled here */
break;
}
}
}
return weak_result;
}
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