500 lines
14 KiB
C
500 lines
14 KiB
C
/* $NetBSD: alpha_reloc.c,v 1.30 2007/02/23 01:17:11 matt Exp $ */
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/*
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* Copyright (c) 2001 Wasabi Systems, Inc.
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* All rights reserved.
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*
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* Written by Jason R. Thorpe for Wasabi Systems, Inc.
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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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed for the NetBSD Project by
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* Wasabi Systems, Inc.
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* 4. The name of Wasabi Systems, Inc. may not be used to endorse
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* or promote products derived from this software without specific prior
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* written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL WASABI SYSTEMS, INC
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* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*/
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/*
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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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#include <sys/cdefs.h>
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#ifndef lint
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__RCSID("$NetBSD: alpha_reloc.c,v 1.30 2007/02/23 01:17:11 matt Exp $");
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#endif /* not lint */
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <string.h>
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#include "rtld.h"
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#include "debug.h"
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#ifdef RTLD_DEBUG_ALPHA
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#define adbg(x) xprintf x
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#else
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#define adbg(x) /* nothing */
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#endif
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void _rtld_bind_start(void);
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void _rtld_bind_start_old(void);
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void _rtld_relocate_nonplt_self(Elf_Dyn *, Elf_Addr);
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caddr_t _rtld_bind(const Obj_Entry *, Elf_Word);
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static inline int _rtld_relocate_plt_object(const Obj_Entry *,
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const Elf_Rela *, Elf_Addr *);
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void
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_rtld_setup_pltgot(const Obj_Entry *obj)
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{
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uint32_t word0;
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/*
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* The PLTGOT on the Alpha looks like this:
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*
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* PLT HEADER
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* .
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* . 32 bytes
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* .
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* PLT ENTRY #0
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* .
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* . 12 bytes
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* .
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* PLT ENTRY #1
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* .
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* . 12 bytes
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* .
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* etc.
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*
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* The old-format entries look like (displacements filled in
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* by the linker):
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*
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* ldah $28, 0($31) # 0x279f0000
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* lda $28, 0($28) # 0x239c0000
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* br $31, plt0 # 0xc3e00000
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*
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* The new-format entries look like:
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*
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* br $28, plt0 # 0xc3800000
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* # 0x00000000
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* # 0x00000000
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*
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* What we do is fetch the first PLT entry and check to
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* see the first word of it matches the first word of the
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* old format. If so, we use a binding routine that can
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* handle the old format, otherwise we use a binding routine
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* that handles the new format.
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*
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* Note that this is done on a per-object basis, we can mix
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* and match shared objects build with both the old and new
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* linker.
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*/
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word0 = *(uint32_t *)(((char *) obj->pltgot) + 32);
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if ((word0 & 0xffff0000) == 0x279f0000) {
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/* Old PLT entry format. */
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adbg(("ALPHA: object %p has old PLT format\n", obj));
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obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start_old;
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obj->pltgot[3] = (Elf_Addr) obj;
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} else {
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/* New PLT entry format. */
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adbg(("ALPHA: object %p has new PLT format\n", obj));
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obj->pltgot[2] = (Elf_Addr) &_rtld_bind_start;
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obj->pltgot[3] = (Elf_Addr) obj;
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}
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__asm volatile("imb");
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}
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/*
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* It is possible for the compiler to emit relocations for unaligned data.
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* We handle this situation with these inlines.
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*/
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#define RELOC_ALIGNED_P(x) \
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(((uintptr_t)(x) & (sizeof(void *) - 1)) == 0)
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static inline Elf_Addr
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load_ptr(void *where)
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{
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Elf_Addr res;
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memcpy(&res, where, sizeof(res));
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return (res);
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}
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static inline void
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store_ptr(void *where, Elf_Addr val)
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{
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memcpy(where, &val, sizeof(val));
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}
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void
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_rtld_relocate_nonplt_self(Elf_Dyn *dynp, Elf_Addr relocbase)
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{
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const Elf_Rela *rela = 0, *relalim;
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Elf_Addr relasz = 0;
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Elf_Addr *where;
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for (; dynp->d_tag != DT_NULL; dynp++) {
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switch (dynp->d_tag) {
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case DT_RELA:
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rela = (const Elf_Rela *)(relocbase + dynp->d_un.d_ptr);
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break;
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case DT_RELASZ:
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relasz = dynp->d_un.d_val;
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break;
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}
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}
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relalim = (const Elf_Rela *)((caddr_t)rela + relasz);
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for (; rela < relalim; rela++) {
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where = (Elf_Addr *)(relocbase + rela->r_offset);
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/* XXX For some reason I see a few GLOB_DAT relocs here. */
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*where += (Elf_Addr)relocbase;
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}
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}
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int
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_rtld_relocate_nonplt_objects(const Obj_Entry *obj)
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{
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const Elf_Rela *rela;
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Elf_Addr target = -1;
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for (rela = obj->rela; rela < obj->relalim; rela++) {
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Elf_Addr *where;
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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Elf_Addr tmp;
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unsigned long symnum;
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where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
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symnum = ELF_R_SYM(rela->r_info);
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switch (ELF_R_TYPE(rela->r_info)) {
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case R_TYPE(NONE):
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break;
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case R_TYPE(REFQUAD):
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case R_TYPE(GLOB_DAT):
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def = _rtld_find_symdef(symnum, obj, &defobj, false);
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if (def == NULL)
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return -1;
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target = (Elf_Addr)(defobj->relocbase +
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def->st_value);
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tmp = target + rela->r_addend;
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if (__predict_true(RELOC_ALIGNED_P(where))) {
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if (*where != tmp)
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*where = tmp;
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} else {
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if (load_ptr(where) != tmp)
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store_ptr(where, tmp);
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}
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rdbg(("REFQUAD/GLOB_DAT %s in %s --> %p in %s",
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obj->strtab + obj->symtab[symnum].st_name,
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obj->path, (void *)tmp, defobj->path));
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break;
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case R_TYPE(RELATIVE):
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if (__predict_true(RELOC_ALIGNED_P(where)))
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*where += (Elf_Addr)obj->relocbase;
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else
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store_ptr(where,
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load_ptr(where) + (Elf_Addr)obj->relocbase);
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rdbg(("RELATIVE in %s --> %p", obj->path,
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(void *)*where));
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break;
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case R_TYPE(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
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* COPY relocation is not in a shared library. They
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* are allowed only in executable files.
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*/
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if (obj->isdynamic) {
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_rtld_error(
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"%s: Unexpected R_COPY relocation in shared library",
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obj->path);
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return -1;
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}
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rdbg(("COPY (avoid in main)"));
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break;
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default:
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rdbg(("sym = %lu, type = %lu, offset = %p, "
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"addend = %p, contents = %p, symbol = %s",
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symnum, (u_long)ELF_R_TYPE(rela->r_info),
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(void *)rela->r_offset, (void *)rela->r_addend,
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(void *)load_ptr(where),
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obj->strtab + obj->symtab[symnum].st_name));
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_rtld_error("%s: Unsupported relocation type %ld "
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"in non-PLT relocations\n",
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obj->path, (u_long) ELF_R_TYPE(rela->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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int
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_rtld_relocate_plt_lazy(const Obj_Entry *obj)
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{
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const Elf_Rela *rela;
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if (!obj->relocbase)
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return 0;
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for (rela = obj->pltrela; rela < obj->pltrelalim; rela++) {
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Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
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assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
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/* Just relocate the GOT slots pointing into the PLT */
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*where += (Elf_Addr)obj->relocbase;
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rdbg(("fixup !main in %s --> %p", obj->path, (void *)*where));
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}
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return 0;
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}
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static inline int
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_rtld_relocate_plt_object(const Obj_Entry *obj, const Elf_Rela *rela, Elf_Addr *tp)
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{
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Elf_Addr *where = (Elf_Addr *)(obj->relocbase + rela->r_offset);
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Elf_Addr new_value;
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const Elf_Sym *def;
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const Obj_Entry *defobj;
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Elf_Addr stubaddr;
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assert(ELF_R_TYPE(rela->r_info) == R_TYPE(JMP_SLOT));
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def = _rtld_find_symdef(ELF_R_SYM(rela->r_info), obj, &defobj, true);
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if (def == NULL)
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return -1;
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new_value = (Elf_Addr)(defobj->relocbase + def->st_value);
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rdbg(("bind now/fixup in %s --> old=%p new=%p",
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defobj->strtab + def->st_name, (void *)*where, (void *)new_value));
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if ((stubaddr = *where) != new_value) {
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int64_t delta, idisp;
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uint32_t insn[3], *stubptr;
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int insncnt;
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Elf_Addr pc;
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/* Point this GOT entry at the target. */
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*where = new_value;
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/*
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* Alpha shared objects may have multiple GOTs, each
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* of which may point to this entry in the PLT. But,
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* we only have a reference to the first GOT entry which
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* points to this PLT entry. In order to avoid having to
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* re-bind this call every time a non-first GOT entry is
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* used, we will attempt to patch up the PLT entry to
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* reference the target, rather than the binder.
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*
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* When the PLT stub gets control, PV contains the address
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* of the PLT entry. Each PLT entry has room for 3 insns.
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* If the displacement of the target from PV fits in a signed
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* 32-bit integer, we can simply add it to PV. Otherwise,
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* we must load the GOT entry itself into PV.
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*
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* Note if the shared object uses the old PLT format, then
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* we cannot patch up the PLT safely, and so we skip it
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* in that case[*].
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*
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* [*] Actually, if we're not doing lazy-binding, then
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* we *can* (and do) patch up this PLT entry; the PLTGOT
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* thunk won't yet point to any binder entry point, and
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* so this test will fail as it would for the new PLT
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* entry format.
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*/
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if (obj->pltgot[2] == (Elf_Addr) &_rtld_bind_start_old) {
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rdbg((" old PLT format"));
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goto out;
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}
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delta = new_value - stubaddr;
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rdbg((" stubaddr=%p, where-stubaddr=%ld, delta=%ld",
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(void *)stubaddr, (long)where - (long)stubaddr,
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(long)delta));
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insncnt = 0;
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if ((int32_t)delta == delta) {
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/*
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* We can adjust PV with an LDA, LDAH sequence.
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*
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* First, build an LDA insn to adjust the low 16
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* bits.
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*/
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insn[insncnt++] = 0x08 << 26 | 27 << 21 | 27 << 16 |
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(delta & 0xffff);
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rdbg((" LDA $27,%d($27)", (int16_t)delta));
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/*
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* Adjust the delta to account for the effects of
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* the LDA, including sign-extension.
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*/
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delta -= (int16_t)delta;
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if (delta != 0) {
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/*
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* Build an LDAH instruction to adjust the
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* high 16 bits.
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*/
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insn[insncnt++] = 0x09 << 26 | 27 << 21 |
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27 << 16 | ((delta >> 16) & 0xffff);
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rdbg((" LDAH $27,%d($27)",
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(int16_t)(delta >> 16)));
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}
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} else {
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int64_t dhigh;
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/* We must load the GOT entry. */
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delta = (Elf_Addr)where - stubaddr;
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/*
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* If the GOT entry is too far away from the PLT
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* entry, then we can't patch up the PLT entry.
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* This PLT entry will have to be bound for each
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* GOT entry except for the first one. This program
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* will still run, albeit very slowly. It is very
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* unlikely that this case will ever happen in
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* practice.
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*/
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if ((int32_t)delta != delta) {
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rdbg((" PLT stub too far from GOT to relocate"));
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goto out;
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}
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dhigh = delta - (int16_t)delta;
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if (dhigh != 0) {
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/*
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* Build an LDAH instruction to adjust the
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* high 16 bits.
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*/
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insn[insncnt++] = 0x09 << 26 | 27 << 21 |
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27 << 16 | ((dhigh >> 16) & 0xffff);
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rdbg((" LDAH $27,%d($27)",
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(int16_t)(dhigh >> 16)));
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}
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/* Build an LDQ to load the GOT entry. */
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insn[insncnt++] = 0x29 << 26 | 27 << 21 |
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27 << 16 | (delta & 0xffff);
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rdbg((" LDQ $27,%d($27)",
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(int16_t)delta));
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}
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/*
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* Now, build a JMP or BR insn to jump to the target. If
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* the displacement fits in a sign-extended 21-bit field,
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* we can use the more efficient BR insn. Otherwise, we
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* have to jump indirect through PV.
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*/
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pc = stubaddr + (4 * (insncnt + 1));
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idisp = (int64_t)(new_value - pc) >> 2;
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if (-0x100000 <= idisp && idisp < 0x100000) {
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insn[insncnt++] = 0x30 << 26 | 31 << 21 |
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(idisp & 0x1fffff);
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rdbg((" BR $31,%p", (void *)new_value));
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} else {
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insn[insncnt++] = 0x1a << 26 | 31 << 21 |
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27 << 16 | (idisp & 0x3fff);
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rdbg((" JMP $31,($27),%d",
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(int)(idisp & 0x3fff)));
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}
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/*
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* Fill in the tail of the PLT entry first, for reentrancy.
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* Until we have overwritten the first insn (an unconditional
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* branch), the remaining insns have no effect.
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*/
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stubptr = (uint32_t *)stubaddr;
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while (insncnt > 1) {
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insncnt--;
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stubptr[insncnt] = insn[insncnt];
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}
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/*
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* Commit the tail of the insn sequence to memory
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* before overwriting the first insn.
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*/
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__asm volatile("wmb" ::: "memory");
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stubptr[0] = insn[0];
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/*
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* I-stream will be sync'd when we either return from
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* the binder (lazy bind case) or when the PLTGOT thunk
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* is patched up (bind-now case).
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*/
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}
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out:
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if (tp)
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*tp = new_value;
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return 0;
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}
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caddr_t
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_rtld_bind(const Obj_Entry *obj, Elf_Word reloff)
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{
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const Elf_Rela *rela = (const Elf_Rela *)((caddr_t)obj->pltrela + reloff);
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Elf_Addr result;
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int err;
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err = _rtld_relocate_plt_object(obj, rela, &result);
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if (err)
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_rtld_die();
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return (caddr_t)result;
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}
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int
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_rtld_relocate_plt_objects(const Obj_Entry *obj)
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{
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const Elf_Rela *rela;
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for (rela = obj->pltrela; rela < obj->pltrelalim; rela++)
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if (_rtld_relocate_plt_object(obj, rela, NULL) < 0)
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return -1;
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return 0;
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}
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