NetBSD/libexec/ld.elf_so/symbol.c

244 lines
6.8 KiB
C

/* $NetBSD: symbol.c,v 1.9 2000/07/26 02:07:36 mycroft Exp $ */
/*
* Copyright 1996 John D. Polstra.
* Copyright 1996 Matt Thomas <matt@3am-software.com>
* All rights reserved.
*
* 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. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Polstra.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
*/
/*
* Dynamic linker for ELF.
*
* John Polstra <jdp@polstra.com>.
*/
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <dirent.h>
#include "debug.h"
#include "rtld.h"
/*
* Hash function for symbol table lookup. Don't even think about changing
* this. It is specified by the System V ABI.
*/
unsigned long
_rtld_elf_hash(name)
const char *name;
{
const unsigned char *p = (const unsigned char *) name;
unsigned long h = 0;
unsigned long g;
while (*p != '\0') {
h = (h << 4) + *p++;
if ((g = h & 0xf0000000) != 0)
h ^= g >> 24;
h &= ~g;
}
return h;
}
const Elf_Sym *
_rtld_symlook_list(const char *name, unsigned long hash, Objlist *objlist,
const Obj_Entry **defobj_out, bool in_plt)
{
const Elf_Sym *symp;
const Elf_Sym *def;
const Obj_Entry *defobj;
const Objlist_Entry *elm;
def = NULL;
defobj = NULL;
for (elm = SIMPLEQ_FIRST(objlist); elm; elm = SIMPLEQ_NEXT(elm, link)) {
if (elm->obj->mark == _rtld_curmark)
continue;
elm->obj->mark = _rtld_curmark;
if ((symp = _rtld_symlook_obj(name, hash, elm->obj, in_plt))
!= NULL) {
if ((def == NULL) ||
(ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
def = symp;
defobj = elm->obj;
if (ELF_ST_BIND(def->st_info) != STB_WEAK)
break;
}
}
}
if (def != NULL)
*defobj_out = defobj;
return def;
}
/*
* Search the symbol table of a single shared object for a symbol of
* the given name. Returns a pointer to the symbol, or NULL if no
* definition was found.
*
* The symbol's hash value is passed in for efficiency reasons; that
* eliminates many recomputations of the hash value.
*/
const Elf_Sym *
_rtld_symlook_obj(name, hash, obj, in_plt)
const char *name;
unsigned long hash;
const Obj_Entry *obj;
bool in_plt;
{
unsigned long symnum = obj->buckets[hash % obj->nbuckets];
while (symnum != ELF_SYM_UNDEFINED) {
const Elf_Sym *symp;
const char *strp;
assert(symnum < obj->nchains);
symp = obj->symtab + symnum;
strp = obj->strtab + symp->st_name;
#if 0
assert(symp->st_name != 0);
#endif
if (strcmp(name, strp) == 0) {
if (symp->st_shndx != SHN_UNDEF
#if !defined(__mips__) /* Following doesn't work on MIPS? mhitch */
|| (!in_plt && symp->st_value != 0 &&
ELF_ST_TYPE(symp->st_info) == STT_FUNC)
#endif
) {
return symp;
}
}
symnum = obj->chains[symnum];
}
return NULL;
}
/*
* Given a symbol number in a referencing object, find the corresponding
* definition of the symbol. Returns a pointer to the symbol, or NULL if
* no definition was found. Returns a pointer to the Obj_Entry of the
* defining object via the reference parameter DEFOBJ_OUT.
*/
const Elf_Sym *
_rtld_find_symdef(obj_list, r_info, name, refobj, defobj_out, in_plt)
const Obj_Entry *obj_list;
Elf_Addr r_info;
const char *name;
Obj_Entry *refobj;
const Obj_Entry **defobj_out;
bool in_plt;
{
Elf_Addr symnum = ELF_R_SYM(r_info);
const Elf_Sym *ref = NULL;
const Elf_Sym *def;
const Elf_Sym *symp;
const Obj_Entry *obj;
const Obj_Entry *defobj;
const Objlist_Entry *elm;
unsigned long hash;
if (name == NULL) {
ref = refobj->symtab + symnum;
name = refobj->strtab + ref->st_name;
}
hash = _rtld_elf_hash(name);
def = NULL;
defobj = NULL;
_rtld_curmark++;
if (refobj->symbolic) { /* Look first in the referencing object */
symp = _rtld_symlook_obj(name, hash, refobj, in_plt);
refobj->mark = _rtld_curmark;
if (symp != NULL) {
def = symp;
defobj = refobj;
}
}
/* Search all objects loaded at program start up. */
if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
symp = _rtld_symlook_list(name, hash, &_rtld_list_main, &obj, in_plt);
if (symp != NULL &&
(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
def = symp;
defobj = obj;
}
}
/* Search all dlopened DAGs containing the referencing object. */
for (elm = SIMPLEQ_FIRST(&refobj->dldags); elm; elm = SIMPLEQ_NEXT(elm, link)) {
if (def != NULL && ELF_ST_BIND(def->st_info) != STB_WEAK)
break;
symp = _rtld_symlook_list(name, hash, &elm->obj->dagmembers, &obj,
in_plt);
if (symp != NULL &&
(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
def = symp;
defobj = obj;
}
}
/* Search all RTLD_GLOBAL objects. */
if (def == NULL || ELF_ST_BIND(def->st_info) == STB_WEAK) {
symp = _rtld_symlook_list(name, hash, &_rtld_list_global, &obj, in_plt);
if (symp != NULL &&
(def == NULL || ELF_ST_BIND(symp->st_info) != STB_WEAK)) {
def = symp;
defobj = obj;
}
}
/*
* If we found no definition and the reference is weak, treat the
* symbol as having the value zero.
*/
if (def == NULL && ELF_ST_BIND(ref->st_info) == STB_WEAK) {
def = &_rtld_sym_zero;
defobj = _rtld_objmain;
}
if (def != NULL)
*defobj_out = defobj;
else if (ELF_R_TYPE(r_info) != R_TYPE(NONE)) {
_rtld_error(
"%s: Undefined %ssymbol \"%s\" (reloc type = %d, symnum = %d)",
refobj->path, in_plt ? "PLT " : "", name,
ELF_R_TYPE(r_info), symnum);
}
return def;
}