5cc87d66a8
functions to be used by the dynamic linker. This can be called by threads packages at start-up time. I will add the call to libc_r soon. Also add a default locking method that is used up until dllockinit() is called. The default method works by blocking SIGVTALRM, SIGPROF, and SIGALRM in critical sections. It is based on the observation that most user-space threads packages implement thread preemption with one of these signals (usually SIGVTALRM). The dynamic linker has never been reentrant, but it became less reentrant in revision 1.34 of "src/libexec/rtld-elf/rtld.c". Starting with that revision, multiple threads each doing lazy binding could interfere with each other. The usual symptom was that a symbol was falsely reported as undefined at start-up time. It was rare but not unseen. This commit fixes it.
234 lines
6.0 KiB
C
234 lines
6.0 KiB
C
/*-
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* Copyright 1996, 1997, 1998, 1999 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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* $FreeBSD$
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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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* Process the special R_386_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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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; rel < rellim; rel++) {
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if (ELF_R_TYPE(rel->r_info) == R_386_COPY) {
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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 + rel->r_offset);
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dstsym = dstobj->symtab + ELF_R_SYM(rel->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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}
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}
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return 0;
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}
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/* Initialize the special GOT 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->pltgot[1] = (Elf_Addr) obj;
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obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
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}
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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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rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize);
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for (rel = obj->rel; rel < rellim; rel++) {
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Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rel->r_offset);
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switch (ELF_R_TYPE(rel->r_info)) {
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case R_386_NONE:
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break;
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case R_386_32:
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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 = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
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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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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 = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
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false);
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if (def == NULL)
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return -1;
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*where +=
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(Elf_Addr) (defobj->relocbase + def->st_value) -
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(Elf_Addr) where;
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}
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break;
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case R_386_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_386_COPY relocation"
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" in shared library", obj->path);
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return -1;
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}
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break;
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case R_386_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 = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
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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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case R_386_RELATIVE:
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*where += (Elf_Addr) obj->relocbase;
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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(rel->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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/* 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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rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize);
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for (rel = obj->pltrel; rel < rellim; rel++) {
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Elf_Addr *where;
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assert(ELF_R_TYPE(rel->r_info) == R_386_JMP_SLOT);
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/* Relocate the GOT slot pointing into the PLT. */
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where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
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*where += (Elf_Addr)obj->relocbase;
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if (bind_now) { /* Fully resolve the procedure address. */
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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(rel->r_info), obj, &defobj, true);
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if (def == NULL)
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return -1;
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reloc_jmpslot(where,
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(Elf_Addr)(defobj->relocbase + def->st_value));
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}
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}
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return 0;
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}
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