FreeBSD-5.3/libexec/rtld-elf/alpha/reloc.c
/*-
* Copyright 1996, 1997, 1998, 1999 John D. Polstra.
* 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.
*
* 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.
*
* $FreeBSD: src/libexec/rtld-elf/alpha/reloc.c,v 1.19 2004/08/03 08:50:59 dfr Exp $
*/
/*
* Dynamic linker for ELF.
*
* John Polstra <jdp@polstra.com>.
*/
#include <sys/param.h>
#include <sys/mman.h>
#include <dlfcn.h>
#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 "debug.h"
#include "rtld.h"
extern Elf_Dyn _GOT_END_;
/*
* Macros for loading/storing unaligned 64-bit values. These are
* needed because relocations can point to unaligned data. This
* occurs in the DWARF2 exception frame tables generated by the
* compiler, for instance.
*
* We don't use these when relocating jump slots and GOT entries,
* since they are guaranteed to be aligned.
*/
#define load64(p) ({ \
Elf_Addr __res; \
__asm__("ldq_u %0,%1" : "=r"(__res) : "m"(*(p))); \
__res; })
#define store64(p, v) \
__asm__("stq_u %1,%0" : "=m"(*(p)) : "r"(v))
/* Relocate a non-PLT object with addend. */
static int
reloc_non_plt_obj(Obj_Entry *obj_rtld, Obj_Entry *obj, const Elf_Rela *rela,
SymCache *cache)
{
Elf_Addr *where = (Elf_Addr *) (obj->relocbase + rela->r_offset);
switch (ELF_R_TYPE(rela->r_info)) {
case R_ALPHA_NONE:
break;
case R_ALPHA_REFQUAD: {
const Elf_Sym *def;
const Obj_Entry *defobj;
def = find_symdef(ELF_R_SYM(rela->r_info), obj,
&defobj, false, cache);
if (def == NULL)
return -1;
store64(where,
(Elf_Addr) (defobj->relocbase + def->st_value) +
load64(where) + rela->r_addend);
}
break;
case R_ALPHA_GLOB_DAT: {
const Elf_Sym *def;
const Obj_Entry *defobj;
Elf_Addr val;
def = find_symdef(ELF_R_SYM(rela->r_info), obj,
&defobj, false, cache);
if (def == NULL)
return -1;
val = (Elf_Addr) (defobj->relocbase + def->st_value +
rela->r_addend);
if (load64(where) != val)
store64(where, val);
}
break;
case R_ALPHA_RELATIVE: {
if (obj != obj_rtld ||
(caddr_t)where < (caddr_t)_GLOBAL_OFFSET_TABLE_ ||
(caddr_t)where >= (caddr_t)&_GOT_END_)
store64(where,
load64(where) + (Elf_Addr) obj->relocbase);
}
break;
case R_ALPHA_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;
}
}
break;
default:
_rtld_error("%s: Unsupported relocation type %d"
" in non-PLT relocations\n", obj->path,
ELF_R_TYPE(rela->r_info));
return -1;
}
return(0);
}
/* Process the non-PLT relocations. */
int
reloc_non_plt(Obj_Entry *obj, Obj_Entry *obj_rtld)
{
const Elf_Rel *rellim;
const Elf_Rel *rel;
const Elf_Rela *relalim;
const Elf_Rela *rela;
SymCache *cache;
int bytes = obj->nchains * sizeof(SymCache);
int r = -1;
/*
* The dynamic loader may be called from a thread, we have
* limited amounts of stack available so we cannot use alloca().
*/
cache = mmap(NULL, bytes, PROT_READ|PROT_WRITE, MAP_ANON, -1, 0);
if (cache == MAP_FAILED)
cache = NULL;
/* Perform relocations without addend if there are any: */
rellim = (const Elf_Rel *) ((caddr_t) obj->rel + obj->relsize);
for (rel = obj->rel; obj->rel != NULL && rel < rellim; rel++) {
Elf_Rela locrela;
locrela.r_info = rel->r_info;
locrela.r_offset = rel->r_offset;
locrela.r_addend = 0;
if (reloc_non_plt_obj(obj_rtld, obj, &locrela, cache))
goto done;
}
/* Perform relocations with addend if there are any: */
relalim = (const Elf_Rela *) ((caddr_t) obj->rela + obj->relasize);
for (rela = obj->rela; obj->rela != NULL && rela < relalim; rela++) {
if (reloc_non_plt_obj(obj_rtld, obj, rela, cache))
goto done;
}
r = 0;
done:
if (cache)
munmap(cache, bytes);
return(r);
}
/* Process the PLT relocations. */
int
reloc_plt(Obj_Entry *obj)
{
/* All PLT relocations are the same kind: either Elf_Rel or Elf_Rela. */
if (obj->pltrelsize != 0) {
const Elf_Rel *rellim;
const Elf_Rel *rel;
rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize);
for (rel = obj->pltrel; rel < rellim; rel++) {
Elf_Addr *where;
assert(ELF_R_TYPE(rel->r_info) == R_ALPHA_JMP_SLOT);
/* Relocate the GOT slot pointing into the PLT. */
where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
*where += (Elf_Addr)obj->relocbase;
}
} else {
const Elf_Rela *relalim;
const Elf_Rela *rela;
relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
for (rela = obj->pltrela; rela < relalim; rela++) {
Elf_Addr *where;
assert(ELF_R_TYPE(rela->r_info) == R_ALPHA_JMP_SLOT);
/* Relocate the GOT slot pointing into the PLT. */
where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
*where += (Elf_Addr)obj->relocbase;
}
}
return 0;
}
/* Relocate the jump slots in an object. */
int
reloc_jmpslots(Obj_Entry *obj)
{
if (obj->jmpslots_done)
return 0;
/* All PLT relocations are the same kind: either Elf_Rel or Elf_Rela. */
if (obj->pltrelsize != 0) {
const Elf_Rel *rellim;
const Elf_Rel *rel;
rellim = (const Elf_Rel *)((char *)obj->pltrel + obj->pltrelsize);
for (rel = obj->pltrel; rel < rellim; rel++) {
Elf_Addr *where;
const Elf_Sym *def;
const Obj_Entry *defobj;
assert(ELF_R_TYPE(rel->r_info) == R_ALPHA_JMP_SLOT);
where = (Elf_Addr *)(obj->relocbase + rel->r_offset);
def = find_symdef(ELF_R_SYM(rel->r_info), obj, &defobj, true,
NULL);
if (def == NULL)
return -1;
reloc_jmpslot(where,
(Elf_Addr)(defobj->relocbase + def->st_value),
defobj, obj, rel);
}
} else {
const Elf_Rela *relalim;
const Elf_Rela *rela;
relalim = (const Elf_Rela *)((char *)obj->pltrela + obj->pltrelasize);
for (rela = obj->pltrela; rela < relalim; rela++) {
Elf_Addr *where;
const Elf_Sym *def;
const Obj_Entry *defobj;
assert(ELF_R_TYPE(rela->r_info) == R_ALPHA_JMP_SLOT);
where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
def = find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, true,
NULL);
if (def == NULL)
return -1;
reloc_jmpslot(where,
(Elf_Addr)(defobj->relocbase + def->st_value),
defobj, obj, (Elf_Rel *)rela);
}
}
obj->jmpslots_done = true;
return 0;
}
/* Fixup the jump slot at "where" to transfer control to "target". */
Elf_Addr
reloc_jmpslot(Elf_Addr *where, Elf_Addr target, const Obj_Entry *obj,
const Obj_Entry *refobj, const Elf_Rel *rel)
{
Elf_Addr stubaddr;
dbg(" reloc_jmpslot: where=%p, target=%p", (void *)where, (void *)target);
stubaddr = *where;
if (stubaddr != target) {
int64_t delta;
u_int32_t inst[3];
int instct;
Elf_Addr pc;
int64_t idisp;
u_int32_t *stubptr;
/* Point this GOT entry directly at the target. */
*where = target;
/*
* There may be multiple GOT tables, each with an entry
* pointing to the stub in the PLT. But we can only find and
* fix up the first GOT entry. So we must rewrite the stub as
* well, to perform a call to the target if it is executed.
*
* When the stub gets control, register pv ($27) contains its
* address. We adjust its value so that it points to the
* target, and then jump indirect through it.
*
* Each PLT entry has room for 3 instructions. If the
* adjustment amount fits in a signed 32-bit integer, we can
* simply add it to register pv. Otherwise we must load the
* GOT entry itself into the pv register.
*/
delta = target - stubaddr;
dbg(" stubaddr=%p, where-stubaddr=%ld, delta=%ld", (void *)stubaddr,
(long)where - (long)stubaddr, (long)delta);
instct = 0;
if ((int32_t)delta == delta) {
/*
* We can adjust pv with a LDA, LDAH sequence.
*
* First build an LDA instruction to adjust the low 16 bits.
*/
inst[instct++] = 0x08 << 26 | 27 << 21 | 27 << 16 |
(delta & 0xffff);
dbg(" LDA $27,%d($27)", (int16_t)delta);
/*
* Adjust the delta to account for the effects of the LDA,
* including sign-extension.
*/
delta -= (int16_t)delta;
if (delta != 0) {
/* Build an LDAH instruction to adjust the high 16 bits. */
inst[instct++] = 0x09 << 26 | 27 << 21 | 27 << 16 |
(delta >> 16 & 0xffff);
dbg(" LDAH $27,%d($27)", (int16_t)(delta >> 16));
}
} else {
int64_t dhigh;
/* We must load the GOT entry from memory. */
delta = (Elf_Addr)where - stubaddr;
/*
* If the GOT entry is too far away from the PLT entry,
* then punt. This PLT entry will have to be looked up
* manually for all GOT entries except the first one.
* The program will still run, albeit very slowly. It's
* extremely unlikely that this case could ever arise in
* practice, but we might as well handle it correctly if
* it does.
*/
if ((int32_t)delta != delta) {
dbg(" PLT stub too far from GOT to relocate");
return target;
}
dhigh = delta - (int16_t)delta;
if (dhigh != 0) {
/* Build an LDAH instruction to adjust the high 16 bits. */
inst[instct++] = 0x09 << 26 | 27 << 21 | 27 << 16 |
(dhigh >> 16 & 0xffff);
dbg(" LDAH $27,%d($27)", (int16_t)(dhigh >> 16));
}
/* Build an LDQ to load the GOT entry. */
inst[instct++] = 0x29 << 26 | 27 << 21 | 27 << 16 |
(delta & 0xffff);
dbg(" LDQ $27,%d($27)", (int16_t)delta);
}
/*
* Build a JMP or BR instruction to jump to the target. If
* the instruction displacement fits in a sign-extended 21-bit
* field, we can use the more efficient BR instruction.
* Otherwise we have to jump indirect through the pv register.
*/
pc = stubaddr + 4 * (instct + 1);
idisp = (int64_t)(target - pc) >> 2;
if (-0x100000 <= idisp && idisp < 0x100000) {
inst[instct++] = 0x30 << 26 | 31 << 21 | (idisp & 0x1fffff);
dbg(" BR $31,%p", (void *)target);
} else {
inst[instct++] = 0x1a << 26 | 31 << 21 | 27 << 16 |
(idisp & 0x3fff);
dbg(" JMP $31,($27),%d", (int)(idisp & 0x3fff));
}
/*
* Fill in the tail of the PLT entry first for reentrancy.
* Until we have overwritten the first instruction (an
* unconditional branch), the remaining instructions have no
* effect.
*/
stubptr = (u_int32_t *)stubaddr;
while (instct > 1) {
instct--;
stubptr[instct] = inst[instct];
}
/*
* Commit the tail of the instruction sequence to memory
* before overwriting the first instruction.
*/
__asm__ __volatile__("wmb" : : : "memory");
stubptr[0] = inst[0];
}
return target;
}
/* Process an R_ALPHA_COPY relocation. */
static int
do_copy_relocation(Obj_Entry *dstobj, const Elf_Rela *rela)
{
void *dstaddr;
const Elf_Sym *dstsym;
const char *name;
unsigned long hash;
size_t size;
const void *srcaddr;
const Elf_Sym *srcsym;
Obj_Entry *srcobj;
dstaddr = (void *) (dstobj->relocbase + rela->r_offset);
dstsym = dstobj->symtab + ELF_R_SYM(rela->r_info);
name = dstobj->strtab + dstsym->st_name;
hash = elf_hash(name);
size = dstsym->st_size;
for (srcobj = dstobj->next; srcobj != NULL; srcobj = srcobj->next)
if ((srcsym = 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);
memcpy(dstaddr, srcaddr, size);
return 0;
}
/*
* Process the special R_ALPHA_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
do_copy_relocations(Obj_Entry *dstobj)
{
const Elf_Rel *rellim;
const Elf_Rel *rel;
const Elf_Rela *relalim;
const Elf_Rela *rela;
assert(dstobj->mainprog); /* COPY relocations are invalid elsewhere */
rellim = (const Elf_Rel *) ((caddr_t) dstobj->rel + dstobj->relsize);
for (rel = dstobj->rel; dstobj->rel != NULL && rel < rellim; rel++) {
if (ELF_R_TYPE(rel->r_info) == R_ALPHA_COPY) {
Elf_Rela locrela;
locrela.r_info = rel->r_info;
locrela.r_offset = rel->r_offset;
locrela.r_addend = 0;
if (do_copy_relocation(dstobj, &locrela))
return -1;
}
}
relalim = (const Elf_Rela *) ((caddr_t) dstobj->rela +
dstobj->relasize);
for (rela = dstobj->rela; dstobj->rela != NULL && rela < relalim;
rela++) {
if (ELF_R_TYPE(rela->r_info) == R_ALPHA_COPY) {
if (do_copy_relocation(dstobj, rela))
return -1;
}
}
return 0;
}
/* Initialize the special PLT entries. */
void
init_pltgot(Obj_Entry *obj)
{
u_int32_t *pltgot;
if (obj->pltgot != NULL &&
(obj->pltrelsize != 0 || obj->pltrelasize != 0)) {
/*
* This function will be called to perform the relocation.
* Look for the ldah instruction from the old PLT format since
* that will tell us what format we are trying to relocate.
*/
pltgot = (u_int32_t *) obj->pltgot;
if ((pltgot[8] & 0xffff0000) == 0x279f0000)
obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start_old;
else
obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
/* Identify this shared object */
obj->pltgot[3] = (Elf_Addr) obj;
}
}
void
allocate_initial_tls(Obj_Entry *list)
{
void *tls;
/*
* Fix the size of the static TLS block by using the maximum
* offset allocated so far and adding a bit for dynamic modules to
* use.
*/
tls_static_space = tls_last_offset + tls_last_size + RTLD_STATIC_TLS_EXTRA;
tls = allocate_tls(list, 0, 16, 16);
alpha_pal_wrunique((u_int64_t) tls);
}
void *__tls_get_addr(tls_index* ti)
{
Elf_Addr** tp = (Elf_Addr**) alpha_pal_rdunique();
return tls_get_addr_common(tp, ti->ti_module, ti->ti_offset);
}