NetBSD/libexec/ld.elf_so/symbol.c

172 lines
4.9 KiB
C

/* $NetBSD: symbol.c,v 1.1 1996/12/16 20:38:06 cgd 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(
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;
}
/*
* 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(
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 != Elf_eshn_undefined
|| (!in_plt && symp->st_value != 0 &&
ELF_SYM_TYPE(symp->st_info) == Elf_estt_func)) {
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(
const Obj_Entry *obj_list,
Elf_Word r_info,
const char *name,
const Obj_Entry *refobj,
const Obj_Entry **defobj_out,
bool in_plt)
{
Elf_Word symnum = ELF_R_SYM(r_info);
const Elf_Sym *ref;
const Obj_Entry *obj;
unsigned long hash;
if (name == NULL) {
ref = refobj->symtab + symnum;
name = refobj->strtab + ref->st_name;
}
hash = _rtld_elf_hash(name);
if (refobj->symbolic) { /* Look first in the referencing object */
const Elf_Sym *def = _rtld_symlook_obj(name, hash, refobj, in_plt);
if (def != NULL) {
*defobj_out = refobj;
return def;
}
}
/*
* Look in all loaded objects. Skip the referencing object, if
* we have already searched it.
*/
for (obj = obj_list; obj != NULL; obj = obj->next) {
if (obj != refobj || !refobj->symbolic) {
const Elf_Sym *def = _rtld_symlook_obj(name, hash, obj, in_plt);
if (def != NULL) {
*defobj_out = obj;
return def;
}
}
}
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 NULL;
}