563a44c171
rtld on x86 to be hidden. This is a micro-optimization, which allows intrinsic references inside rtld to be handled without indirection through PLT. The visibility of rtld symbols for other objects in the symbol namespace is controlled by a version script. Reviewed by: kan, jilles Sponsored by: The FreeBSD Foundation MFC after: 2 weeks
441 lines
11 KiB
C
441 lines
11 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 <machine/segments.h>
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#include <machine/sysarch.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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#include "rtld_tls.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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size_t size;
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const void *srcaddr;
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const Elf_Sym *srcsym;
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const Obj_Entry *srcobj, *defobj;
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SymLook req;
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int res;
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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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size = dstsym->st_size;
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symlook_init(&req, name);
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req.ventry = fetch_ventry(dstobj, ELF_R_SYM(rel->r_info));
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req.flags = SYMLOOK_EARLY;
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for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next) {
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res = symlook_obj(&req, srcobj);
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if (res == 0) {
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srcsym = req.sym_out;
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defobj = req.defobj_out;
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break;
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}
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}
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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 *) (defobj->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, int flags,
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RtldLockState *lockstate)
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{
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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SymCache *cache;
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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Elf_Addr *where, symval, add;
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int r;
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r = -1;
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/*
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* The dynamic loader may be called from a thread, we have
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* limited amounts of stack available so we cannot use alloca().
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*/
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if (obj != obj_rtld) {
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cache = calloc(obj->dynsymcount, sizeof(SymCache));
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/* No need to check for NULL here */
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} else
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cache = NULL;
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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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switch (ELF_R_TYPE(rel->r_info)) {
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case R_386_32:
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case R_386_PC32:
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case R_386_GLOB_DAT:
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case R_386_TLS_TPOFF:
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case R_386_TLS_TPOFF32:
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case R_386_TLS_DTPMOD32:
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case R_386_TLS_DTPOFF32:
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def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
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flags, cache, lockstate);
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if (def == NULL)
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goto done;
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if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
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switch (ELF_R_TYPE(rel->r_info)) {
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case R_386_32:
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case R_386_PC32:
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case R_386_GLOB_DAT:
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if ((flags & SYMLOOK_IFUNC) == 0) {
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obj->non_plt_gnu_ifunc = true;
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continue;
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}
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symval = (Elf_Addr)rtld_resolve_ifunc(
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defobj, def);
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break;
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case R_386_TLS_TPOFF:
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case R_386_TLS_TPOFF32:
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case R_386_TLS_DTPMOD32:
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case R_386_TLS_DTPOFF32:
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_rtld_error("%s: IFUNC for TLS reloc",
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obj->path);
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goto done;
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}
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} else {
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if ((flags & SYMLOOK_IFUNC) != 0)
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continue;
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symval = (Elf_Addr)defobj->relocbase +
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def->st_value;
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}
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break;
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default:
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if ((flags & SYMLOOK_IFUNC) != 0)
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continue;
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break;
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}
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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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*where += symval;
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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
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* see this type of relocation. But the
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* binutils-2.6 tools sometimes generate it.
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*/
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*where += symval - (Elf_Addr)where;
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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
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* relocations have been done. All we do here
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* is make sure that the COPY relocation is
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* 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 "
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"relocation in shared library", obj->path);
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goto done;
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}
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break;
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case R_386_GLOB_DAT:
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*where = symval;
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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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case R_386_TLS_TPOFF:
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case R_386_TLS_TPOFF32:
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/*
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* We lazily allocate offsets for static TLS
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* as we see the first relocation that
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* references the TLS block. This allows us to
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* support (small amounts of) static TLS in
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* dynamically loaded modules. If we run out
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* of space, we generate an error.
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*/
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if (!defobj->tls_done) {
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if (!allocate_tls_offset((Obj_Entry*) defobj)) {
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_rtld_error("%s: No space available "
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"for static Thread Local Storage",
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obj->path);
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goto done;
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}
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}
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add = (Elf_Addr)(def->st_value - defobj->tlsoffset);
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if (ELF_R_TYPE(rel->r_info) == R_386_TLS_TPOFF)
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*where += add;
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else
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*where -= add;
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break;
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case R_386_TLS_DTPMOD32:
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*where += (Elf_Addr)defobj->tlsindex;
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break;
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case R_386_TLS_DTPOFF32:
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*where += (Elf_Addr) def->st_value;
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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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goto done;
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}
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}
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r = 0;
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done:
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free(cache);
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return (r);
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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)
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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/*, val*/;
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switch (ELF_R_TYPE(rel->r_info)) {
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case 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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break;
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case R_386_IRELATIVE:
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obj->irelative = true;
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break;
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default:
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_rtld_error("Unknown relocation type %x in PLT",
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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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/* Relocate the jump slots in an object. */
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int
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reloc_jmpslots(Obj_Entry *obj, int flags, RtldLockState *lockstate)
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{
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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if (obj->jmpslots_done)
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return 0;
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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, target;
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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switch (ELF_R_TYPE(rel->r_info)) {
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case R_386_JMP_SLOT:
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where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
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def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
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SYMLOOK_IN_PLT | flags, NULL, lockstate);
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if (def == NULL)
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return (-1);
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if (ELF_ST_TYPE(def->st_info) == STT_GNU_IFUNC) {
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obj->gnu_ifunc = true;
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continue;
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}
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target = (Elf_Addr)(defobj->relocbase + def->st_value);
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reloc_jmpslot(where, target, defobj, obj, rel);
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break;
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case R_386_IRELATIVE:
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break;
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default:
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_rtld_error("Unknown relocation type %x in PLT",
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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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obj->jmpslots_done = true;
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return 0;
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}
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int
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reloc_iresolve(Obj_Entry *obj, RtldLockState *lockstate)
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{
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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Elf_Addr *where, target;
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if (!obj->irelative)
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return (0);
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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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switch (ELF_R_TYPE(rel->r_info)) {
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case R_386_IRELATIVE:
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where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
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lock_release(rtld_bind_lock, lockstate);
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target = ((Elf_Addr (*)(void))(obj->relocbase + *where))();
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wlock_acquire(rtld_bind_lock, lockstate);
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*where = target;
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break;
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}
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}
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obj->irelative = false;
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return (0);
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}
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int
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reloc_gnu_ifunc(Obj_Entry *obj, int flags, RtldLockState *lockstate)
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{
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const Elf_Rel *rellim;
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const Elf_Rel *rel;
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if (!obj->gnu_ifunc)
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return (0);
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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, target;
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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switch (ELF_R_TYPE(rel->r_info)) {
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case R_386_JMP_SLOT:
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where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
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def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj,
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SYMLOOK_IN_PLT | flags, NULL, lockstate);
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if (def == NULL)
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return (-1);
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if (ELF_ST_TYPE(def->st_info) != STT_GNU_IFUNC)
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continue;
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lock_release(rtld_bind_lock, lockstate);
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target = (Elf_Addr)rtld_resolve_ifunc(defobj, def);
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wlock_acquire(rtld_bind_lock, lockstate);
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reloc_jmpslot(where, target, defobj, obj, rel);
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break;
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}
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}
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obj->gnu_ifunc = false;
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return (0);
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}
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void
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allocate_initial_tls(Obj_Entry *objs)
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{
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void* tls;
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/*
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* Fix the size of the static TLS block by using the maximum
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* offset allocated so far and adding a bit for dynamic modules to
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* use.
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*/
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tls_static_space = tls_last_offset + RTLD_STATIC_TLS_EXTRA;
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tls = allocate_tls(objs, NULL, 3*sizeof(Elf_Addr), sizeof(Elf_Addr));
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i386_set_gsbase(tls);
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}
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/* GNU ABI */
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__attribute__((__regparm__(1)))
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void *___tls_get_addr(tls_index *ti)
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{
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Elf_Addr** segbase;
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__asm __volatile("movl %%gs:0, %0" : "=r" (segbase));
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return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset);
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}
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/* Sun ABI */
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void *__tls_get_addr(tls_index *ti)
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{
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Elf_Addr** segbase;
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__asm __volatile("movl %%gs:0, %0" : "=r" (segbase));
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return tls_get_addr_common(&segbase[1], ti->ti_module, ti->ti_offset);
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}
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