479 lines
13 KiB
C
479 lines
13 KiB
C
/* $NetBSD: reloc.c,v 1.2 1998/03/25 04:13:01 mhitch Exp $ */
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/*
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* Copyright 1996 John D. Polstra.
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* Copyright 1996 Matt Thomas <matt@3am-software.com>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by John Polstra.
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* 4. The name of the author may not be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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* Dynamic linker for ELF.
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*
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* John Polstra <jdp@polstra.com>.
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*/
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#include <err.h>
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#include <errno.h>
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#include <fcntl.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <sys/types.h>
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#include <sys/mman.h>
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#include <dirent.h>
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#include "debug.h"
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#include "rtld.h"
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#ifdef __alpha__
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static int
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_rtld_do_copy_relocation(
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const Obj_Entry *dstobj,
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const Elf_RelA *rela)
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{
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void *dstaddr = (void *) (dstobj->relocbase + rela->r_offset);
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const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info);
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const char *name = dstobj->strtab + dstsym->st_name;
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unsigned long hash = _rtld_elf_hash(name);
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size_t size = dstsym->st_size;
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const void *srcaddr;
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const Elf_Sym *srcsym;
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Obj_Entry *srcobj;
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for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next)
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if ((srcsym = _rtld_symlook_obj(name, hash, srcobj, false)) != NULL)
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break;
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if (srcobj == NULL) {
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_rtld_error("Undefined symbol \"%s\" referenced from COPY"
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" relocation in %s", name, dstobj->path);
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return -1;
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}
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srcaddr = (const void *) (srcobj->relocbase + srcsym->st_value);
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memcpy(dstaddr, srcaddr, size);
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return 0;
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}
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#endif /* __alpha__ */
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/*
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* Process the special R_xxx_COPY relocations in the main program. These
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* copy data from a shared object into a region in the main program's BSS
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* segment.
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*
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* Returns 0 on success, -1 on failure.
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*/
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int
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_rtld_do_copy_relocations(
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const Obj_Entry *dstobj)
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{
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assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */
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#ifdef __alpha__ /* jrs */
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if (dstobj->rel != NULL) {
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const Elf_Rel *rel;
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for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) {
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if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) {
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Elf_RelA ourrela;
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ourrela.r_info = rel->r_info;
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ourrela.r_offset = rel->r_offset;
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ourrela.r_addend = 0;
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if (_rtld_do_copy_relocation(dstobj, &ourrela) < 0)
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return -1;
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}
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}
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}
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if (dstobj->rela != NULL) {
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const Elf_RelA *rela;
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for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) {
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if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) {
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if (_rtld_do_copy_relocation(dstobj, rela) < 0)
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return -1;
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}
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}
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}
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#endif /* jrs */
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return 0;
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}
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static int
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_rtld_relocate_nonplt_object(
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const Obj_Entry *obj,
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const Elf_RelA *rela)
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{
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Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rela->r_offset);
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switch (ELF_R_TYPE(rela->r_info)) {
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case R_TYPE(NONE):
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break;
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#ifdef __i386__
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case R_386_GOT32: {
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false);
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if (def == NULL)
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return -1;
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if (*where != (Elf_Addr) (defobj->relocbase + def->st_value + rela->r_addend))
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*where = (Elf_Addr) (defobj->relocbase + def->st_value + rela->r_addend);
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break;
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}
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case R_386_PC32:
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/*
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* I don't think the dynamic linker should ever see this
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* type of relocation. But the binutils-2.6 tools sometimes
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* generate it.
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*/
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{
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false);
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if (def == NULL)
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return -1;
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*where += (Elf_Addr) (defobj->relocbase + def->st_value)
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- (Elf_Addr) where;
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break;
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}
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#endif
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#ifdef __alpha__
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case R_ALPHA_REFQUAD: {
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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Elf_Addr tmp_value;
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def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false);
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if (def == NULL)
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return -1;
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tmp_value = (Elf_Addr) (defobj->relocbase + def->st_value)
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+ *where + rela->r_addend;
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if (*where != tmp_value)
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*where = tmp_value;
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break;
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}
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/*#endif*/
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case R_TYPE(GLOB_DAT):
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{
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, false);
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if (def == NULL)
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return -1;
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if (*where != (Elf_Addr) (defobj->relocbase + def->st_value))
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*where = (Elf_Addr) (defobj->relocbase + def->st_value);
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break;
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}
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case R_TYPE(RELATIVE): {
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extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
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extern Elf_Dyn _DYNAMIC;
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if (obj != &_rtld_objself ||
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(caddr_t)where < (caddr_t)_GLOBAL_OFFSET_TABLE_ ||
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(caddr_t)where >= (caddr_t)&_DYNAMIC)
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*where += (Elf_Addr) obj->relocbase;
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break;
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}
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case R_TYPE(COPY): {
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/*
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* These are deferred until all other relocations have
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* been done. All we do here is make sure that the COPY
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* relocation is not in a shared library. They are allowed
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* only in executable files.
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*/
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if (!obj->mainprog) {
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_rtld_error("%s: Unexpected R_COPY relocation in shared library",
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obj->path);
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return -1;
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}
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break;
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}
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#endif /* __alpha__ */
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#ifdef __mips__
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case R_TYPE(REL32): {
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/* 32-bit PC-relative reference */
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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def = obj->symtab + ELF_R_SYM(rela->r_info);
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if (ELF_SYM_BIND(def->st_info) == Elf_estb_local &&
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(ELF_SYM_TYPE(def->st_info) == Elf_estt_section ||
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ELF_SYM_TYPE(def->st_info) == Elf_estt_notype)) {
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*where += (Elf_Addr) obj->relocbase;
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} else {
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/* XXX maybe do something re: bootstrapping? */
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def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
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&defobj, false);
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if (def == NULL)
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return -1;
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*where += (Elf_Addr)(defobj->relocbase + def->st_value);
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}
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break;
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}
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#endif /* mips */
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default: {
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, true);
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dbg("sym = %d, type = %d, offset = %p, addend = %p, contents = %p, symbol = %s",
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ELF_R_SYM(rela->r_info), ELF_R_TYPE(rela->r_info),
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rela->r_offset, rela->r_addend, *where,
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def ? defobj->strtab + def->st_name : "??");
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_rtld_error("%s: Unsupported relocation type %d in non-PLT relocations\n",
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obj->path, ELF_R_TYPE(rela->r_info));
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return -1;
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}
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}
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return 0;
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}
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static int
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_rtld_relocate_plt_object(
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const Obj_Entry *obj,
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const Elf_RelA *rela,
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bool bind_now)
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{
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Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rela->r_offset);
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Elf_Addr new_value;
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/* Fully resolve procedure addresses now */
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#if defined(__alpha__) /* (jrs) */
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if (bind_now || obj->pltgot == NULL) {
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
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def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj, &defobj, true);
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if (def == NULL)
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return -1;
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new_value = (Elf_Addr) (defobj->relocbase + def->st_value);
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#if 0
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dbg("fixup %s in %s --> %p in %s",
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defobj->strtab + def->st_name, obj->path,
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new_value, defobj->path);
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#endif
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} else
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#endif /* __alpha__ (jrs) */
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if (!obj->mainprog) {
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/* Just relocate the GOT slots pointing into the PLT */
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new_value = *where + (Elf_Addr) (obj->relocbase);
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} else {
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return 0;
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}
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/*
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* Since this page is probably copy-on-write, let's not write
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* it unless we really really have to.
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*/
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if (*where != new_value)
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*where = new_value;
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return 0;
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}
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caddr_t
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_rtld_bind(
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const Obj_Entry *obj,
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Elf_Word reloff)
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{
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const Elf_RelA *rela;
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Elf_RelA ourrela;
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if (obj->pltrel != NULL) {
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ourrela.r_info = ((const Elf_Rel *) ((caddr_t) obj->pltrel + reloff))->r_info;
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ourrela.r_offset = ((const Elf_Rel *) ((caddr_t) obj->pltrel + reloff))->r_offset;
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rela = &ourrela;
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} else {
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rela = (const Elf_RelA *) ((caddr_t) obj->pltrela + reloff);
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}
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if (_rtld_relocate_plt_object(obj, rela, true) < 0)
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_rtld_die();
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return *(caddr_t *)(obj->relocbase + rela->r_offset);
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}
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/*
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* Relocate newly-loaded shared objects. The argument is a pointer to
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* the Obj_Entry for the first such object. All objects from the first
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* to the end of the list of objects are relocated. Returns 0 on success,
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* or -1 on failure.
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*/
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int
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_rtld_relocate_objects(
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Obj_Entry *first,
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bool bind_now)
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{
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Obj_Entry *obj;
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int ok = 1;
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for (obj = first; obj != NULL; obj = obj->next) {
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if (obj->nbuckets == 0 || obj->nchains == 0
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|| obj->buckets == NULL || obj->symtab == NULL
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|| obj->strtab == NULL) {
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_rtld_error("%s: Shared object has no run-time symbol table",
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obj->path);
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return -1;
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}
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dbg(" relocating %s (%d/%d rel/rela, %d/%d plt rel/rela)",
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obj->path,
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obj->rellim - obj->rel, obj->relalim - obj->rela,
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obj->pltrellim - obj->pltrel, obj->pltrelalim - obj->pltrela);
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if (obj->textrel) {
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/* There are relocations to the write-protected text segment. */
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if (mprotect(obj->mapbase, obj->textsize,
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PROT_READ|PROT_WRITE|PROT_EXEC) == -1) {
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_rtld_error("%s: Cannot write-enable text segment: %s",
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obj->path, xstrerror(errno));
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return -1;
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}
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}
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if (obj->rel != NULL) {
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/* Process the non-PLT relocations. */
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const Elf_Rel *rel;
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for (rel = obj->rel; rel < obj->rellim; ++rel) {
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Elf_RelA ourrela;
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ourrela.r_info = rel->r_info;
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ourrela.r_offset = rel->r_offset;
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#if defined(__mips__)
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/* rel->r_offset is not valid on mips? */
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if (ELF_R_TYPE(ourrela.r_info) == R_TYPE(NONE))
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ourrela.r_addend = 0;
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else
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#endif
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ourrela.r_addend = *(Elf_Word *) (obj->relocbase + rel->r_offset);
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if (_rtld_relocate_nonplt_object(obj, &ourrela) < 0)
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ok = 0;
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}
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}
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if (obj->rela != NULL) {
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/* Process the non-PLT relocations. */
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const Elf_RelA *rela;
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for (rela = obj->rela; rela < obj->relalim; ++rela) {
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if (_rtld_relocate_nonplt_object(obj, rela) < 0)
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ok = 0;
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}
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}
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if (obj->textrel) { /* Re-protected the text segment. */
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if (mprotect(obj->mapbase, obj->textsize,
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PROT_READ|PROT_EXEC) == -1) {
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_rtld_error("%s: Cannot write-protect text segment: %s",
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obj->path, xstrerror(errno));
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return -1;
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}
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}
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/* Process the PLT relocations. */
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if (obj->pltrel != NULL) {
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const Elf_Rel *rel;
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for (rel = obj->pltrel; rel < obj->pltrellim; ++rel) {
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Elf_RelA ourrela;
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ourrela.r_info = rel->r_info;
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ourrela.r_offset = rel->r_offset;
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ourrela.r_addend = *(Elf_Word *) (obj->relocbase + rel->r_offset);
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if (_rtld_relocate_plt_object(obj, &ourrela, bind_now) < 0)
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ok = 0;
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}
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}
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if (obj->pltrela != NULL) {
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const Elf_RelA *rela;
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for (rela = obj->pltrela; rela < obj->pltrelalim; ++rela) {
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if (_rtld_relocate_plt_object(obj, rela, bind_now) < 0)
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ok = 0;
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}
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}
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if (!ok)
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return -1;
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/* Set some sanity-checking numbers in the Obj_Entry. */
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obj->magic = RTLD_MAGIC;
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obj->version = RTLD_VERSION;
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/* Fill in the dynamic linker entry points. */
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obj->dlopen = _rtld_dlopen;
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obj->dlsym = _rtld_dlsym;
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obj->dlerror = _rtld_dlerror;
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obj->dlclose = _rtld_dlclose;
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/* Set the special PLTGOT entries. */
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if (obj->pltgot != NULL) {
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#if defined(__i386__)
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obj->pltgot[1] = (Elf_Addr) obj;
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obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
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#endif
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#if defined(__alpha__)
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/* This function will be called to perform the relocation. */
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obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
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/* Identify this shared object */
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obj->pltgot[3] = (Elf_Addr) obj;
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#endif
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#if defined(__mips__)
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_rtld_relocate_mips_got(obj);
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obj->pltgot[0] = (Elf_Addr) &_rtld_bind_start;
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/* XXX only if obj->pltgot[1] & 0x80000000 ?? */
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obj->pltgot[1] |= (Elf_Addr) obj;
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#endif
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}
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}
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return 0;
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}
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