NetBSD-5.0.2/libexec/ld.elf_so/arch/alpha/alpha_reloc.c
/* $NetBSD: alpha_reloc.c,v 1.31 2008/07/24 04:39:25 matt Exp $ */
/*
* Copyright (c) 2001 Wasabi Systems, Inc.
* All rights reserved.
*
* Written by Jason R. Thorpe for Wasabi Systems, Inc.
*
* 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 for the NetBSD Project by
* Wasabi Systems, Inc.
* 4. The name of Wasabi Systems, Inc. may not be used to endorse
* or promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``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 WASABI SYSTEMS, INC
* 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.
*/
/*
* 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.
*/
#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: alpha_reloc.c,v 1.31 2008/07/24 04:39:25 matt Exp $");
#endif /* not lint */
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include "rtld.h"
#include "debug.h"
#ifdef RTLD_DEBUG_ALPHA
#define adbg(x) xprintf x
#else
#define adbg(x) /* nothing */
#endif
void _rtld_bind_start(void);
void _rtld_bind_start_old(void);
void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
caddr_t _rtld_bind(const Obj_Entry *, Elf_Word);
static inline int _rtld_relocate_plt_object(const Obj_Entry *,
const Elf_Rela *, Elf_Addr *);
void
_rtld_setup_pltgot(const Obj_Entry *obj)
{
uint32_t word0;
/*
* The PLTGOT on the Alpha looks like this:
*
* PLT HEADER
* .
* . 32 bytes
* .
* PLT ENTRY #0
* .
* . 12 bytes
* .
* PLT ENTRY #1
* .
* . 12 bytes
* .
* etc.
*
* The old-format entries look like (displacements filled in
* by the linker):
*
* ldah $28, 0($31) # 0x279f0000
* lda $28, 0($28) # 0x239c0000
* br $31, plt0 # 0xc3e00000
*
* The new-format entries look like:
*
* br $28, plt0 # 0xc3800000
* # 0x00000000
* # 0x00000000
*
* What we do is fetch the first PLT entry and check to
* see the first word of it matches the first word of the
* old format. If so, we use a binding routine that can
* handle the old format, otherwise we use a binding routine
* that handles the new format.
*
* Note that this is done on a per-object basis, we can mix
* and match shared objects build with both the old and new
* linker.
*/
word0 = *(uint32_t *)(((char *) obj->pltgot) + 32);
if ((word0 & 0xffff0000) == 0x279f0000) {
/* Old PLT entry format. */
adbg(("ALPHA: object %p has old PLT format\n", obj));
obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start_old;
obj->pltgot[3] = (Elf_Addr) obj;
} else {
/* New PLT entry format. */
adbg(("ALPHA: object %p has new PLT format\n", obj));
obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
obj->pltgot[3] = (Elf_Addr) obj;
}
__asm volatile("imb");
}
/*
* It is possible for the compiler to emit relocations for unaligned data.
* We handle this situation with these inlines.
*/
#define RELOC_ALIGNED_P(x) \
(((uintptr_t)(x) & (sizeof(void *) - 1)) == 0)
static inline Elf_Addr
load_ptr(void *where)
{
Elf_Addr res;
memcpy(&res, where, sizeof(res));
return (res);
}
static inline void
store_ptr(void *where, Elf_Addr val)
{
memcpy(where, &val, sizeof(val));
}
void
_rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
{
const Elf_Rela *rela = 0, *relalim;
Elf_Addr relasz = 0;
Elf_Addr *where;
for (; dynp->d_tag != DT_NULL; dynp++) {
switch (dynp->d_tag) {
case DT_RELA:
rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr);
break;
case DT_RELASZ:
relasz = dynp->d_un.d_val;
break;
}
}
relalim = (const Elf_Rela *)((caddr_t)rela + relasz);
for (; rela < relalim; rela++) {
where = (Elf_Addr *)(relocbase + rela->r_offset);
/* XXX For some reason I see a few GLOB_DAT relocs here. */
*where += (Elf_Addr)relocbase;
}
}
int
_rtld_relocate_nonplt_objects(const Obj_Entry *obj)
{
const Elf_Rela *rela;
Elf_Addr target = -1;
for (rela = obj->rela; rela < obj->relalim; rela++) {
Elf_Addr *where;
const Elf_Sym *def;
const Obj_Entry *defobj;
Elf_Addr tmp;
unsigned long symnum;
where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
symnum = ELF_R_SYM(rela->r_info);
switch (ELF_R_TYPE(rela->r_info)) {
case R_TYPE(NONE):
break;
case R_TYPE(REFQUAD):
case R_TYPE(GLOB_DAT):
def = _rtld_find_symdef(symnum, obj, &defobj, false);
if (def == NULL)
return -1;
target = (Elf_Addr)(defobj->relocbase +
def->st_value);
tmp = target + rela->r_addend;
if (__predict_true(RELOC_ALIGNED_P(where))) {
if (*where != tmp)
*where = tmp;
} else {
if (load_ptr(where) != tmp)
store_ptr(where, tmp);
}
rdbg(("REFQUAD/GLOB_DAT %s in %s --> %p in %s",
obj->strtab + obj->symtab[symnum].st_name,
obj->path, (void *)tmp, defobj->path));
break;
case R_TYPE(RELATIVE):
if (__predict_true(RELOC_ALIGNED_P(where)))
*where += (Elf_Addr)obj->relocbase;
else
store_ptr(where,
load_ptr(where) + (Elf_Addr)obj->relocbase);
rdbg(("RELATIVE in %s --> %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->isdynamic) {
_rtld_error(
"%s: Unexpected R_COPY relocation in shared library",
obj->path);
return -1;
}
rdbg(("COPY (avoid in main)"));
break;
default:
rdbg(("sym = %lu, type = %lu, offset = %p, "
"addend = %p, contents = %p, symbol = %s",
symnum, (u_long)ELF_R_TYPE(rela->r_info),
(void *)rela->r_offset, (void *)rela->r_addend,
(void *)load_ptr(where),
obj->strtab + obj->symtab[symnum].st_name));
_rtld_error("%s: Unsupported relocation type %ld "
"in non-PLT relocations\n",
obj->path, (u_long) ELF_R_TYPE(rela->r_info));
return -1;
}
}
return 0;
}
int
_rtld_relocate_plt_lazy(const Obj_Entry *obj)
{
const Elf_Rela *rela;
if (!obj->relocbase)
return 0;
for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) {
Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
/* Just relocate the GOT slots pointing into the PLT */
*where += (Elf_Addr)obj->relocbase;
rdbg(("fixup !main in %s --> %p", obj->path, (void *)*where));
}
return 0;
}
static inline int
_rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp)
{
Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
Elf_Addr new_value;
const Elf_Sym *def;
const Obj_Entry *defobj;
Elf_Addr stubaddr;
assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
def = _rtld_find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, true);
if (def == NULL)
return -1;
new_value = (Elf_Addr)(defobj->relocbase + def->st_value);
rdbg(("bind now/fixup in %s --> old=%p new=%p",
defobj->strtab + def->st_name, (void *)*where, (void *)new_value));
if ((stubaddr = *where) != new_value) {
int64_t delta, idisp;
uint32_t insn[3], *stubptr;
int insncnt;
Elf_Addr pc;
/* Point this GOT entry at the target. */
*where = new_value;
/*
* Alpha shared objects may have multiple GOTs, each
* of which may point to this entry in the PLT. But,
* we only have a reference to the first GOT entry which
* points to this PLT entry. In order to avoid having to
* re-bind this call every time a non-first GOT entry is
* used, we will attempt to patch up the PLT entry to
* reference the target, rather than the binder.
*
* When the PLT stub gets control, PV contains the address
* of the PLT entry. Each PLT entry has room for 3 insns.
* If the displacement of the target from PV fits in a signed
* 32-bit integer, we can simply add it to PV. Otherwise,
* we must load the GOT entry itself into PV.
*
* Note if the shared object uses the old PLT format, then
* we cannot patch up the PLT safely, and so we skip it
* in that case[*].
*
* [*] Actually, if we're not doing lazy-binding, then
* we *can* (and do) patch up this PLT entry; the PLTGOT
* thunk won't yet point to any binder entry point, and
* so this test will fail as it would for the new PLT
* entry format.
*/
if (obj->pltgot[2] == (Elf_Addr) &_rtld_bind_start_old) {
rdbg((" old PLT format"));
goto out;
}
delta = new_value - stubaddr;
rdbg((" stubaddr=%p, where-stubaddr=%ld, delta=%ld",
(void *)stubaddr, (long)where - (long)stubaddr,
(long)delta));
insncnt = 0;
if ((int32_t)delta == delta) {
/*
* We can adjust PV with an LDA, LDAH sequence.
*
* First, build an LDA insn to adjust the low 16
* bits.
*/
insn[insncnt++] = 0x08 << 26 | 27 << 21 | 27 << 16 |
(delta & 0xffff);
rdbg((" 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.
*/
insn[insncnt++] = 0x09 << 26 | 27 << 21 |
27 << 16 | ((delta >> 16) & 0xffff);
rdbg((" LDAH $27,%d($27)",
(int16_t)(delta >> 16)));
}
} else {
int64_t dhigh;
/* We must load the GOT entry. */
delta = (Elf_Addr)where - stubaddr;
/*
* If the GOT entry is too far away from the PLT
* entry, then we can't patch up the PLT entry.
* This PLT entry will have to be bound for each
* GOT entry except for the first one. This program
* will still run, albeit very slowly. It is very
* unlikely that this case will ever happen in
* practice.
*/
if ((int32_t)delta != delta) {
rdbg((" PLT stub too far from GOT to relocate"));
goto out;
}
dhigh = delta - (int16_t)delta;
if (dhigh != 0) {
/*
* Build an LDAH instruction to adjust the
* high 16 bits.
*/
insn[insncnt++] = 0x09 << 26 | 27 << 21 |
27 << 16 | ((dhigh >> 16) & 0xffff);
rdbg((" LDAH $27,%d($27)",
(int16_t)(dhigh >> 16)));
}
/* Build an LDQ to load the GOT entry. */
insn[insncnt++] = 0x29 << 26 | 27 << 21 |
27 << 16 | (delta & 0xffff);
rdbg((" LDQ $27,%d($27)",
(int16_t)delta));
}
/*
* Now, build a JMP or BR insn to jump to the target. If
* the displacement fits in a sign-extended 21-bit field,
* we can use the more efficient BR insn. Otherwise, we
* have to jump indirect through PV.
*/
pc = stubaddr + (4 * (insncnt + 1));
idisp = (int64_t)(new_value - pc) >> 2;
if (-0x100000 <= idisp && idisp < 0x100000) {
insn[insncnt++] = 0x30 << 26 | 31 << 21 |
(idisp & 0x1fffff);
rdbg((" BR $31,%p", (void *)new_value));
} else {
insn[insncnt++] = 0x1a << 26 | 31 << 21 |
27 << 16 | (idisp & 0x3fff);
rdbg((" JMP $31,($27),%d",
(int)(idisp & 0x3fff)));
}
/*
* Fill in the tail of the PLT entry first, for reentrancy.
* Until we have overwritten the first insn (an unconditional
* branch), the remaining insns have no effect.
*/
stubptr = (uint32_t *)stubaddr;
while (insncnt > 1) {
insncnt--;
stubptr[insncnt] = insn[insncnt];
}
/*
* Commit the tail of the insn sequence to memory
* before overwriting the first insn.
*/
__asm volatile("wmb" ::: "memory");
stubptr[0] = insn[0];
/*
* I-stream will be sync'd when we either return from
* the binder (lazy bind case) or when the PLTGOT thunk
* is patched up (bind-now case).
*/
}
out:
if (tp)
*tp = new_value;
return 0;
}
caddr_t
_rtld_bind(const Obj_Entry *obj, Elf_Word reloff)
{
const Elf_Rela *rela = (const Elf_Rela *)((caddr_t)obj->pltrela + reloff);
Elf_Addr result;
int err;
err = _rtld_relocate_plt_object(obj, rela, &result);
if (err || result == 0)
_rtld_die();
return (caddr_t)result;
}
int
_rtld_relocate_plt_objects(const Obj_Entry *obj)
{
const Elf_Rela *rela;
for (rela = obj->pltrela; rela < obj->pltrelalim; rela++)
if (_rtld_relocate_plt_object(obj, rela, NULL) < 0)
return -1;
return 0;
}