d5b537d01a
the Makefile, and move it down into the architecture-specific subdirectories. Eliminate an asm() statement for the i386. Make the dynamic linker work if it is built as an executable instead of as a shared library. See i386/Makefile.inc to find out how to do it. Note, this change is not enabled and it might never be enabled. But it might be useful in the future. Building the dynamic linker as an executable should make it start up faster, because it won't have any relocations. But in practice I suspect the difference is negligible.
323 lines
8.7 KiB
C
323 lines
8.7 KiB
C
/*-
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* Copyright 1996-1998 John D. Polstra.
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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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*
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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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* $Id: reloc.c,v 1.3 1998/09/11 18:30:55 dfr Exp $
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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 <sys/param.h>
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#include <sys/mman.h>
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#include <dlfcn.h>
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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 "debug.h"
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#include "rtld.h"
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/*
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* Debugging support.
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*/
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#define assert(cond) ((cond) ? (void) 0 :\
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(msg("oops: " __XSTRING(__LINE__) "\n"), abort()))
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#define msg(s) (write(1, s, strlen(s)))
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#define trace() msg("trace: " __XSTRING(__LINE__) "\n");
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extern Elf_Dyn _DYNAMIC;
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/* Relocate a non-PLT object with addend. */
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static int
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reloc_non_plt_obj(Obj_Entry *obj_rtld, 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_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 = find_symdef(ELF_R_SYM(rela->r_info), obj,
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&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 +
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def->st_value) + *where + rela->r_addend;
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if (*where != tmp_value)
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*where = tmp_value;
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}
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break;
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case R_ALPHA_GLOB_DAT: {
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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def = find_symdef(ELF_R_SYM(rela->r_info), obj,
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&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 +
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def->st_value + rela->r_addend))
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*where = (Elf_Addr) (defobj->relocbase +
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def->st_value + rela->r_addend);
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}
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break;
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case R_ALPHA_RELATIVE: {
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if (obj != obj_rtld ||
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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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}
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break;
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case R_ALPHA_COPY: {
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/*
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* These are deferred until all other relocations
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* have been done. All we do here is make sure
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* that the COPY relocation is not in a shared
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* library. They are allowed only in executable
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* files.
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*/
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if (!obj->mainprog) {
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_rtld_error("%s: Unexpected R_COPY "
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" relocation in shared library",
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obj->path);
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return -1;
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}
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}
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break;
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default:
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_rtld_error("%s: Unsupported relocation type %d"
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" in non-PLT relocations\n", obj->path,
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ELF_R_TYPE(rela->r_info));
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return -1;
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}
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return(0);
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}
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/* Process the non-PLT relocations. */
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int
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reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld)
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{
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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const Elf_Rela *relalim;
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const Elf_Rela *rela;
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/* Perform relocations without addend if there are any: */
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rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize);
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for (rel = obj->rel; obj->rel != NULL && rel < rellim; rel++) {
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Elf_Rela locrela;
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locrela.r_info = rel->r_info;
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locrela.r_offset = rel->r_offset;
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locrela.r_addend = 0;
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if (reloc_non_plt_obj(obj_rtld, obj, &locrela))
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return -1;
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}
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/* Perform relocations with addend if there are any: */
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relalim = (const Elf_Rela *) ((caddr_t) obj->rela + obj->relasize);
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for (rela = obj->rela; obj->rela != NULL && rela < relalim; rela++) {
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if (reloc_non_plt_obj(obj_rtld, obj, rela))
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return -1;
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}
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return 0;
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}
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/* Process the PLT relocations. */
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int
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reloc_plt(Obj_Entry *obj, bool bind_now)
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{
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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const Elf_Rela *relalim;
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const Elf_Rela *rela;
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/* Process the PLT relocations without addend if there are any. */
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rellim = (const Elf_Rel *) ((caddr_t) obj->pltrel + obj->pltrelsize);
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if (bind_now) {
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/* Fully resolve procedure addresses now */
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for (rel = obj->pltrel; obj->pltrel != NULL && rel < rellim;
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rel++) {
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Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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assert(ELF_R_TYPE(rel->r_info) == R_ALPHA_JMP_SLOT);
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def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true);
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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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} else { /* Just relocate the GOT slots pointing into the PLT */
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for (rel = obj->pltrel; obj->pltrel != NULL && rel < rellim;
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rel++) {
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Elf_Addr *where = (Elf_Addr *)
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(obj->relocbase + rel->r_offset);
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*where += (Elf_Addr) obj->relocbase;
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}
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}
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/* Process the PLT relocations with addend if there are any. */
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relalim = (const Elf_Rela *) ((caddr_t) obj->pltrela +
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obj->pltrelasize);
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if (bind_now) {
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/* Fully resolve procedure addresses now */
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for (rela = obj->pltrela; obj->pltrela != NULL && rela < relalim;
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rela++) {
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Elf_Addr *where = (Elf_Addr *) (obj->relocbase +
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rela->r_offset);
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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_ALPHA_JMP_SLOT);
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def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, true);
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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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} else { /* Just relocate the GOT slots pointing into the PLT */
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for (rela = obj->pltrela; obj->pltrela != NULL && rela < relalim;
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rela++) {
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Elf_Addr *where = (Elf_Addr *)
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(obj->relocbase + rela->r_offset);
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*where += (Elf_Addr) obj->relocbase;
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}
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}
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return 0;
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}
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/* Process an R_ALPHA_COPY relocation. */
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static int
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do_copy_relocation(Obj_Entry *dstobj, const Elf_Rela *rela)
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{
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void *dstaddr;
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const Elf_Sym *dstsym;
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const char *name;
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unsigned long hash;
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size_t 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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dstaddr = (void *) (dstobj->relocbase + rela->r_offset);
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dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info);
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name = dstobj->strtab + dstsym->st_name;
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hash = elf_hash(name);
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size = dstsym->st_size;
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for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next)
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if ((srcsym = 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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/*
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* Process the special R_ALPHA_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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do_copy_relocations(Obj_Entry *dstobj)
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{
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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const Elf_Rela *relalim;
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const Elf_Rela *rela;
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assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */
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rellim = (const Elf_Rel *) ((caddr_t) dstobj->rel + dstobj->relsize);
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for (rel = dstobj->rel; dstobj->rel != NULL && rel < rellim; rel++) {
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if (ELF_R_TYPE(rel->r_info) == R_ALPHA_COPY) {
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Elf_Rela locrela;
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locrela.r_info = rel->r_info;
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locrela.r_offset = rel->r_offset;
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locrela.r_addend = 0;
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if (do_copy_relocation(dstobj, &locrela))
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return -1;
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}
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}
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relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela +
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dstobj->relasize);
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for (rela = dstobj->rela; dstobj->rela != NULL && rela < relalim;
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rela++) {
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if (ELF_R_TYPE(rela->r_info) == R_ALPHA_COPY) {
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if (do_copy_relocation(dstobj, rela))
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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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/* Initialize the special PLT entries. */
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void
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init_pltgot(Obj_Entry *obj)
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{
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if (obj->pltgot != NULL &&
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(obj->pltrelsize != 0 || obj->pltrelasize != 0)) {
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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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}
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}
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