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- /* Run an ELF binary on a linux system.
- Copyright (C) 1993-1996, Eric Youngdale.
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 2, or (at your option)
- any later version.
- This program 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 General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software
- Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
- /* Various symbol table handling functions, including symbol lookup */
- #include "string.h"
- #include "dlfcn.h"
- #include "hash.h"
- #include "linuxelf.h"
- #include "syscall.h"
- #include "string.h"
- #include "sysdep.h"
- /*
- * 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.
- */
- unsigned long _dl_elf_hash(const char *name)
- {
- unsigned long hash = 0;
- unsigned long tmp;
- while (*name) {
- hash = (hash << 4) + *name++;
- if ((tmp = hash & 0xf0000000))
- hash ^= tmp >> 24;
- hash &= ~tmp;
- };
- return hash;
- }
- /*
- * Check to see if a library has already been added to the hash chain.
- */
- struct elf_resolve *_dl_check_hashed_files(char *libname)
- {
- struct elf_resolve *tpnt;
- int len = _dl_strlen(libname);
- for (tpnt = _dl_loaded_modules; tpnt; tpnt = tpnt->next) {
- if (_dl_strncmp(tpnt->libname, libname, len) == 0 &&
- (tpnt->libname[len] == '\0' || tpnt->libname[len] == '.'))
- return tpnt;
- }
- return NULL;
- }
- /*
- * 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(char *libname,
- char *loadaddr, unsigned long *dynamic_info, unsigned long dynamic_addr,
- unsigned long dynamic_size)
- {
- unsigned long *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(*tpnt));
- } 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(*(tpnt->next)));
- tpnt->next->prev = tpnt;
- tpnt = tpnt->next;
- };
- tpnt->next = NULL;
- tpnt->init_flag = 0;
- tpnt->libname = _dl_strdup(libname);
- tpnt->dynamic_addr = dynamic_addr;
- tpnt->dynamic_size = dynamic_size;
- tpnt->libtype = loaded_file;
- if (dynamic_info[DT_HASH] != 0) {
- hash_addr = (unsigned long *) (dynamic_info[DT_HASH] + loadaddr);
- 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 < 24; 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(char *name, struct dyn_elf *rpnt1,
- unsigned long instr_addr, struct elf_resolve *f_tpnt, int copyrel)
- {
- struct elf_resolve *tpnt;
- int si;
- char *pnt;
- int pass;
- char *strtab;
- Elf32_Sym *symtab;
- unsigned long elf_hash_number, hn;
- char *weak_result;
- struct elf_resolve *first_def;
- struct dyn_elf *rpnt, first;
- char *data_result = 0; /* nakao */
- weak_result = 0;
- elf_hash_number = _dl_elf_hash(name);
- /* A quick little hack to make sure that any symbol in the executable
- will be preferred to one in a shared library. This is necessary so
- that any shared library data symbols referenced in the executable
- will be seen at the same address by the executable, shared libraries
- and dynamically loaded code. -Rob Ryan (robr@cmu.edu) */
- if (!copyrel && rpnt1) {
- first = (*_dl_symbol_tables);
- first.next = rpnt1;
- rpnt1 = (&first);
- }
- /*
- * The passes are so that we can first search the regular symbols
- * for whatever module was specified, and then search anything
- * loaded with RTLD_GLOBAL. When pass is 1, it means we are just
- * starting the first dlopened module, and anything above that
- * is just the next one in the chain.
- */
- for (pass = 0; (1 == 1); pass++) {
- /*
- * If we are just starting to search for RTLD_GLOBAL, setup
- * the pointer for the start of the search.
- */
- if (pass == 1) {
- rpnt1 = _dl_handles;
- }
- /*
- * Anything after this, we need to skip to the next module.
- */
- else if (pass >= 2) {
- rpnt1 = rpnt1->next_handle;
- }
- /*
- * Make sure we still have a module, and make sure that this
- * module was loaded with RTLD_GLOBAL.
- */
- if (pass != 0) {
- if (rpnt1 == NULL)
- break;
- if ((rpnt1->flags & RTLD_GLOBAL) == 0)
- continue;
- }
- for (rpnt = (rpnt1 ? rpnt1 : _dl_symbol_tables); rpnt; rpnt = rpnt->next) {
- tpnt = rpnt->dyn;
- /*
- * The idea here is that if we are using dlsym, we want to
- * first search the entire chain loaded from dlopen, and
- * return a result from that if we found anything. If this
- * fails, then we continue the search into the stuff loaded
- * when the image was activated. For normal lookups, we start
- * with rpnt == NULL, so we should never hit this.
- */
- if (tpnt->libtype == elf_executable && weak_result != 0) {
- break;
- }
- /*
- * Avoid calling .urem here.
- */
- do_rem(hn, elf_hash_number, tpnt->nbucket);
- symtab = (Elf32_Sym *) (tpnt->dynamic_info[DT_SYMTAB] + tpnt->loadaddr);
- strtab = (char *) (tpnt->dynamic_info[DT_STRTAB] + tpnt->loadaddr);
- /*
- * This crap is required because the first instance of a
- * symbol on the chain will be used for all symbol references.
- * Thus this instance must be resolved to an address that
- * contains the actual function,
- */
- first_def = NULL;
- for (si = tpnt->elf_buckets[hn]; si; si = tpnt->chains[si]) {
- pnt = strtab + symtab[si].st_name;
- if (_dl_strcmp(pnt, name) == 0 &&
- (ELF32_ST_TYPE(symtab[si].st_info) == STT_FUNC ||
- ELF32_ST_TYPE(symtab[si].st_info) == STT_NOTYPE ||
- ELF32_ST_TYPE(symtab[si].st_info) == STT_OBJECT) &&
- symtab[si].st_value != 0) {
- /* Here we make sure that we find a module where the symbol is
- * actually defined.
- */
- if (f_tpnt) {
- if (!first_def)
- first_def = tpnt;
- if (first_def == f_tpnt
- && symtab[si].st_shndx == 0)
- continue;
- }
- switch (ELF32_ST_BIND(symtab[si].st_info)) {
- case STB_GLOBAL:
- if (tpnt->libtype != elf_executable &&
- ELF32_ST_TYPE(symtab[si].st_info)
- == STT_NOTYPE)
- { /* nakao */
- data_result = tpnt->loadaddr +
- symtab[si].st_value; /* nakao */
- break; /* nakao */
- } else /* nakao */
- return tpnt->loadaddr + symtab[si].st_value;
- case STB_WEAK:
- if (!weak_result)
- weak_result =
- tpnt->loadaddr + symtab[si].st_value;
- break;
- default: /* Do local symbols need to be examined? */
- break;
- }
- }
- }
- }
- }
- if (data_result)
- return data_result; /* nakao */
- return weak_result;
- }
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