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NetBSD/libexec/ld.elf_so/reloc.c

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/* $NetBSD: reloc.c,v 1.19 1999/03/13 20:00:14 christos Exp $ */
/*
* Copyright 1996 John D. Polstra.
* Copyright 1996 Matt Thomas <matt@3am-software.com>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Polstra.
* 4. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
/*
* Dynamic linker for ELF.
*
* John Polstra <jdp@polstra.com>.
*/
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <dirent.h>
#include "debug.h"
#include "rtld.h"
#ifndef RTLD_INHIBIT_COPY_RELOCS
static int _rtld_do_copy_relocation __P((const Obj_Entry *, const Elf_RelA *,
bool));
/*
* XXX: These don't work for the alpha and i386; don't know about powerpc
* The alpha and the i386 avoid the problem by compiling everything PIC.
* These relocation are supposed to be writing the address of the
* function to be called on the bss.rel or bss.rela segment, but:
* - st_size == 0
* - on the i386 at least the call instruction is a direct call
* not an indirect call.
*/
static int
_rtld_do_copy_relocation(dstobj, rela, dodebug)
const Obj_Entry *dstobj;
const Elf_RelA *rela;
bool dodebug;
{
void *dstaddr = (void *)(dstobj->relocbase + rela->r_offset);
const Elf_Sym *dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info);
const char *name = dstobj->strtab + dstsym->st_name;
unsigned long hash = _rtld_elf_hash(name);
size_t size = dstsym->st_size;
const void *srcaddr;
const Elf_Sym *srcsym;
Obj_Entry *srcobj;
for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next)
if ((srcsym = _rtld_symlook_obj(name, hash, srcobj,
false)) != NULL)
break;
if (srcobj == NULL) {
_rtld_error("Undefined symbol \"%s\" referenced from COPY"
" relocation in %s", name, dstobj->path);
return (-1);
}
srcaddr = (const void *)(srcobj->relocbase + srcsym->st_value);
(void)memcpy(dstaddr, srcaddr, size);
rdbg(dodebug, ("COPY %s %s %s --> src=%p dst=%p *dst= %p size %ld",
dstobj->path, srcobj->path, name, (void *)srcaddr,
(void *)dstaddr, (void *)*(long *)dstaddr, (long)size));
return (0);
}
#endif /* RTLD_INHIBIT_COPY_RELOCS */
/*
* Process the special R_xxx_COPY relocations in the main program. These
* copy data from a shared object into a region in the main program's BSS
* segment.
*
* Returns 0 on success, -1 on failure.
*/
int
_rtld_do_copy_relocations(dstobj, dodebug)
const Obj_Entry *dstobj;
bool dodebug;
{
#ifndef RTLD_INHIBIT_COPY_RELOCS
/* COPY relocations are invalid elsewhere */
assert(dstobj->mainprog);
if (dstobj->rel != NULL) {
const Elf_Rel *rel;
for (rel = dstobj->rel; rel < dstobj->rellim; ++rel) {
if (ELF_R_TYPE(rel->r_info) == R_TYPE(COPY)) {
Elf_RelA ourrela;
ourrela.r_info = rel->r_info;
ourrela.r_offset = rel->r_offset;
ourrela.r_addend = 0;
if (_rtld_do_copy_relocation(dstobj,
&ourrela, dodebug) < 0)
return (-1);
}
}
}
if (dstobj->rela != NULL) {
const Elf_RelA *rela;
for (rela = dstobj->rela; rela < dstobj->relalim; ++rela) {
if (ELF_R_TYPE(rela->r_info) == R_TYPE(COPY)) {
if (_rtld_do_copy_relocation(dstobj, rela,
dodebug) < 0)
return (-1);
}
}
}
#endif /* RTLD_INHIBIT_COPY_RELOCS */
return (0);
}
#ifndef __sparc__
int
_rtld_relocate_nonplt_object(obj, rela, dodebug)
const Obj_Entry *obj;
const Elf_RelA *rela;
bool dodebug;
{
Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
const Elf_Sym *def;
const Obj_Entry *defobj;
#if defined(__i386__) || defined(__alpha__)
extern Elf_Addr _GLOBAL_OFFSET_TABLE_[];
extern Elf_Dyn _DYNAMIC;
#endif
#if defined(__i386__) || defined(__alpha__) || defined(__powerpc__)
Elf_Addr tmp;
#endif
switch (ELF_R_TYPE(rela->r_info)) {
case R_TYPE(NONE):
break;
#ifdef __i386__
case R_TYPE(GOT32):
def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
&defobj, false);
if (def == NULL)
return -1;
tmp = (Elf_Addr)(defobj->relocbase + def->st_value);
if (*where != tmp)
*where = tmp;
rdbg(dodebug, ("GOT32 %s in %s --> %p in %s",
defobj->strtab + def->st_name, obj->path,
(void *)*where, defobj->path));
break;
case R_TYPE(PC32):
/*
* I don't think the dynamic linker should ever see this
* type of relocation. But the binutils-2.6 tools sometimes
* generate it.
*/
def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
&defobj, false);
if (def == NULL)
return -1;
*where += (Elf_Addr)(defobj->relocbase + def->st_value) -
(Elf_Addr)where;
rdbg(dodebug, ("PC32 %s in %s --> %p in %s",
defobj->strtab + def->st_name, obj->path,
(void *)*where, defobj->path));
break;
case R_TYPE(32):
def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
&defobj, false);
if (def == NULL)
return -1;
*where += (Elf_Addr)(defobj->relocbase + def->st_value);
rdbg(dodebug, ("32 %s in %s --> %p in %s",
defobj->strtab + def->st_name, obj->path,
(void *)*where, defobj->path));
break;
#endif /* __i386__ */
#ifdef __alpha__
case R_TYPE(REFQUAD):
def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
&defobj, false);
if (def == NULL)
return -1;
tmp = (Elf_Addr)(defobj->relocbase + def->st_value) +
*where + rela->r_addend;
if (*where != tmp)
*where = tmp;
rdbg(dodebug, ("REFQUAD %s in %s --> %p in %s",
defobj->strtab + def->st_name, obj->path,
(void *)*where, defobj->path));
break;
#endif /* __alpha__ */
#if defined(__i386__) || defined(__alpha__)
case R_TYPE(GLOB_DAT):
def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
&defobj, false);
if (def == NULL)
return -1;
if (*where != (Elf_Addr)(defobj->relocbase + def->st_value))
*where = (Elf_Addr)(defobj->relocbase + def->st_value);
rdbg(dodebug, ("GLOB_DAT %s in %s --> %p in %s",
defobj->strtab + def->st_name, obj->path,
(void *)*where, defobj->path));
break;
case R_TYPE(RELATIVE):
if (!dodebug ||
(caddr_t)where < (caddr_t)_GLOBAL_OFFSET_TABLE_ ||
(caddr_t)where >= (caddr_t)&_DYNAMIC) {
*where += (Elf_Addr)obj->relocbase;
rdbg(dodebug, ("RELATIVE in %s --> %p", obj->path,
(void *)*where));
}
else
rdbg(dodebug, ("RELATIVE in %s stays at %p",
obj->path, (void *)*where));
break;
case R_TYPE(COPY):
/*
* These are deferred until all other relocations have
* been done. All we do here is make sure that the COPY
* relocation is not in a shared library. They are allowed
* only in executable files.
*/
if (!obj->mainprog) {
_rtld_error(
"%s: Unexpected R_COPY relocation in shared library",
obj->path);
return -1;
}
rdbg(dodebug, ("COPY (avoid in main)"));
break;
#endif /* __i386__ || __alpha__ */
#ifdef __mips__
case R_TYPE(REL32):
/* 32-bit PC-relative reference */
def = obj->symtab + ELF_R_SYM(rela->r_info);
if (ELF_SYM_BIND(def->st_info) == Elf_estb_local &&
(ELF_SYM_TYPE(def->st_info) == Elf_estt_section ||
ELF_SYM_TYPE(def->st_info) == Elf_estt_notype)) {
*where += (Elf_Addr)obj->relocbase;
rdbg(dodebug, ("REL32 in %s --> %p", obj->path,
(void *)*where));
} else {
/* XXX maybe do something re: bootstrapping? */
def = _rtld_find_symdef(_rtld_objlist, rela->r_info,
NULL, obj, &defobj, false);
if (def == NULL)
return -1;
*where += (Elf_Addr)(defobj->relocbase + def->st_value);
rdbg(dodebug, ("REL32 %s in %s --> %p in %s",
defobj->strtab + def->st_name, obj->path,
(void *)*where, defobj->path));
}
break;
#endif /* __mips__ */
#ifdef __powerpc__
case R_TYPE(32): /* word32 S + A */
case R_TYPE(GLOB_DAT): /* word32 S + A */
def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
&defobj, false);
if (def == NULL)
return -1;
tmp = (Elf_Addr)(defobj->relocbase + def->st_value +
rela->r_addend);
if (*where != tmp)
*where = tmp;
rdbg(dodebug, ("32/GLOB_DAT %s in %s --> %p in %s",
defobj->strtab + def->st_name, obj->path,
(void *)*where, defobj->path));
break;
case R_TYPE(COPY):
rdbg(dodebug, ("COPY"));
break;
case R_TYPE(JMP_SLOT):
rdbg(dodebug, ("JMP_SLOT"));
break;
case R_TYPE(RELATIVE): /* word32 B + A */
tmp = (Elf_Addr)(obj->relocbase + rela->r_addend);
if (obj == &_rtld_objself && *where == tmp)
break; /* GOT - already done */
*where = tmp;
rdbg(dodebug, ("RELATIVE in %s --> %p", obj->path,
(void *)*where));
break;
#endif /* __powerpc__ */
default:
def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
&defobj, true);
rdbg(dodebug, ("sym = %lu, type = %lu, offset = %p, "
"addend = %p, contents = %p, symbol = %s",
(u_long)ELF_R_SYM(rela->r_info),
(u_long)ELF_R_TYPE(rela->r_info),
(void *)rela->r_offset, (void *)rela->r_addend,
(void *)*where,
def ? defobj->strtab + def->st_name : "??"));
_rtld_error("%s: Unsupported relocation type %d"
"in non-PLT relocations\n",
obj->path, ELF_R_TYPE(rela->r_info));
return -1;
}
return 0;
}
int
_rtld_relocate_plt_object(obj, rela, addrp, bind_now, dodebug)
const Obj_Entry *obj;
const Elf_RelA *rela;
caddr_t *addrp;
bool bind_now;
bool dodebug;
{
Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
Elf_Addr new_value;
/* Fully resolve procedure addresses now */
#if defined(__powerpc__)
return _rtld_reloc_powerpc_plt(obj, rela, bind_now);
#endif
#if defined(__alpha__) || defined(__i386__)
if (bind_now || obj->pltgot == NULL) {
const Elf_Sym *def;
const Obj_Entry *defobj;
assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
def = _rtld_find_symdef(_rtld_objlist, rela->r_info, NULL, obj,
&defobj, true);
if (def == NULL)
return -1;
new_value = (Elf_Addr)(defobj->relocbase + def->st_value);
rdbg(dodebug, ("bind now %d/fixup in %s --> old=%p new=%p",
(int)bind_now,
defobj->strtab + def->st_name,
(void *)*where, (void *)new_value));
} else
#endif /* __alpha__ || __i386__ */
if (!obj->mainprog) {
/* Just relocate the GOT slots pointing into the PLT */
new_value = *where + (Elf_Addr)(obj->relocbase);
rdbg(dodebug, ("fixup !main in %s --> %p", obj->path,
(void *)*where));
} else {
return 0;
}
/*
* Since this page is probably copy-on-write, let's not write
* it unless we really really have to.
*/
if (*where != new_value)
*where = new_value;
if (addrp != NULL)
*addrp = *(caddr_t *)(obj->relocbase + rela->r_offset);
return 0;
}
#endif /* __sparc__ */
caddr_t
_rtld_bind(obj, reloff)
const Obj_Entry *obj;
Elf_Word reloff;
{
const Elf_RelA *rela;
Elf_RelA ourrela;
caddr_t addr;
if (obj->pltrel != NULL) {
const Elf_Rel *rel;
rel = (const Elf_Rel *)((caddr_t) obj->pltrel + reloff);
ourrela.r_info = rel->r_info;
ourrela.r_offset = rel->r_offset;
rela = &ourrela;
} else {
rela = (const Elf_RelA *)((caddr_t) obj->pltrela + reloff);
}
if (_rtld_relocate_plt_object(obj, rela, &addr, true, true) < 0)
_rtld_die();
return addr;
}
/*
* Relocate newly-loaded shared objects. The argument is a pointer to
* the Obj_Entry for the first such object. All objects from the first
* to the end of the list of objects are relocated. Returns 0 on success,
* or -1 on failure.
*/
int
_rtld_relocate_objects(first, bind_now, dodebug)
Obj_Entry *first;
bool bind_now;
bool dodebug;
{
Obj_Entry *obj;
int ok = 1;
for (obj = first; obj != NULL; obj = obj->next) {
if (obj->nbuckets == 0 || obj->nchains == 0 ||
obj->buckets == NULL || obj->symtab == NULL ||
obj->strtab == NULL) {
_rtld_error("%s: Shared object has no run-time"
" symbol table", obj->path);
return -1;
}
rdbg(dodebug, (" relocating %s (%ld/%ld rel/rela, "
"%ld/%ld plt rel/rela)",
obj->path,
(long)(obj->rellim - obj->rel),
(long)(obj->relalim - obj->rela),
(long)(obj->pltrellim - obj->pltrel),
(long)(obj->pltrelalim - obj->pltrela)));
if (obj->textrel) {
/*
* There are relocations to the write-protected text
* segment.
*/
if (mprotect(obj->mapbase, obj->textsize,
PROT_READ | PROT_WRITE | PROT_EXEC) == -1) {
_rtld_error("%s: Cannot write-enable text "
"segment: %s", obj->path, xstrerror(errno));
return -1;
}
}
if (obj->rel != NULL) {
/* Process the non-PLT relocations. */
const Elf_Rel *rel;
for (rel = obj->rel; rel < obj->rellim; ++rel) {
Elf_RelA ourrela;
ourrela.r_info = rel->r_info;
ourrela.r_offset = rel->r_offset;
#if defined(__mips__)
/* rel->r_offset is not valid on mips? */
if (ELF_R_TYPE(ourrela.r_info) == R_TYPE(NONE))
ourrela.r_addend = 0;
else
#endif
ourrela.r_addend =
*(Elf_Word *)(obj->relocbase +
rel->r_offset);
if (_rtld_relocate_nonplt_object(obj, &ourrela,
dodebug) < 0)
ok = 0;
}
}
if (obj->rela != NULL) {
/* Process the non-PLT relocations. */
const Elf_RelA *rela;
for (rela = obj->rela; rela < obj->relalim; ++rela) {
if (_rtld_relocate_nonplt_object(obj, rela,
dodebug) < 0)
ok = 0;
}
}
if (obj->textrel) { /* Re-protected the text segment. */
if (mprotect(obj->mapbase, obj->textsize,
PROT_READ | PROT_EXEC) == -1) {
_rtld_error("%s: Cannot write-protect text "
"segment: %s", obj->path, xstrerror(errno));
return -1;
}
}
/* Process the PLT relocations. */
if (obj->pltrel != NULL) {
const Elf_Rel *rel;
for (rel = obj->pltrel; rel < obj->pltrellim; ++rel) {
Elf_RelA ourrela;
ourrela.r_info = rel->r_info;
ourrela.r_offset = rel->r_offset;
ourrela.r_addend =
*(Elf_Word *)(obj->relocbase +
rel->r_offset);
if (_rtld_relocate_plt_object(obj, &ourrela,
NULL, bind_now, dodebug) < 0)
ok = 0;
}
}
if (obj->pltrela != NULL) {
const Elf_RelA *rela;
for (rela = obj->pltrela; rela < obj->pltrelalim;
++rela) {
if (_rtld_relocate_plt_object(obj, rela,
NULL, bind_now, dodebug) < 0)
ok = 0;
}
}
if (!ok)
return -1;
/* Set some sanity-checking numbers in the Obj_Entry. */
obj->magic = RTLD_MAGIC;
obj->version = RTLD_VERSION;
/* Fill in the dynamic linker entry points. */
obj->dlopen = _rtld_dlopen;
obj->dlsym = _rtld_dlsym;
obj->dlerror = _rtld_dlerror;
obj->dlclose = _rtld_dlclose;
/* Set the special PLTGOT entries. */
if (obj->pltgot != NULL) {
#if defined(__i386__)
obj->pltgot[1] = (Elf_Addr) obj;
obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start;
#endif
#if defined(__alpha__)
/*
* This function will be called to perform the
* relocation.
*/
obj->pltgot[2] = (Elf_Addr) & _rtld_bind_start;
/* Identify this shared object */
obj->pltgot[3] = (Elf_Addr) obj;
#endif
#if defined(__mips__)
_rtld_relocate_mips_got(obj);
obj->pltgot[0] = (Elf_Addr) & _rtld_bind_start;
/* XXX only if obj->pltgot[1] & 0x80000000 ?? */
obj->pltgot[1] |= (Elf_Addr) obj;
#endif
#if defined(__powerpc__)
_rtld_setup_powerpc_plt(obj);
#endif
#if defined(__sparc__)
/*
* PLTGOT is the PLT on the sparc.
* The first entry holds the call the dynamic linker.
* We construct a `call' sequence that transfers
* to `_rtld_bind_start()'.
* The second entry holds the object identification.
* Note: each PLT entry is three words long.
*/
#define SAVE 0x9de3bfc0 /* i.e. `save %sp,-64,%sp' */
#define CALL 0x40000000
#define NOP 0x01000000
obj->pltgot[0] = SAVE;
obj->pltgot[1] = CALL |
((Elf_Addr)&_rtld_bind_start -
(Elf_Addr)&obj->pltgot[1]) >> 2;
obj->pltgot[2] = NOP;
obj->pltgot[3] = (Elf_Addr) obj;
#endif
}
}
return 0;
}
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