234 lines
7.6 KiB
C
234 lines
7.6 KiB
C
/* On-demand PLT fixup for shared objects.
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Copyright (C) 1995-1999, 2000, 2001 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA. */
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#include <alloca.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <ldsodefs.h>
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#include "dynamic-link.h"
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#ifndef __attribute_used__
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#define __attribute_used__
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#endif
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#if !defined ELF_MACHINE_NO_RELA || ELF_MACHINE_NO_REL
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# define PLTREL ElfW(Rela)
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#else
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# define PLTREL ElfW(Rel)
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#endif
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#ifndef VERSYMIDX
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# define VERSYMIDX(sym) (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (sym))
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#endif
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/* This function is called through a special trampoline from the PLT the
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first time each PLT entry is called. We must perform the relocation
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specified in the PLT of the given shared object, and return the resolved
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function address to the trampoline, which will restart the original call
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to that address. Future calls will bounce directly from the PLT to the
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function. */
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#ifndef ELF_MACHINE_NO_PLT
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static ElfW(Addr) __attribute__ ((regparm (2), used))
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fixup (
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# ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
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ELF_MACHINE_RUNTIME_FIXUP_ARGS,
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# endif
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/* GKM FIXME: Fix trampoline to pass bounds so we can do
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without the `__unbounded' qualifier. */
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struct link_map *__unbounded l, ElfW(Word) reloc_offset)
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{
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const ElfW(Sym) *const symtab
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= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
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const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
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const PLTREL *const reloc
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= (const void *) (D_PTR (l, l_info[DT_JMPREL]) + reloc_offset);
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const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
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void *const rel_addr = (void *)(l->l_addr + reloc->r_offset);
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lookup_t result;
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ElfW(Addr) value;
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/* The use of `alloca' here looks ridiculous but it helps. The goal is
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to prevent the function from being inlined and thus optimized out.
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There is no official way to do this so we use this trick. gcc never
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inlines functions which use `alloca'. */
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alloca (sizeof (int));
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/* Sanity check that we're really looking at a PLT relocation. */
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assert (ELFW(R_TYPE)(reloc->r_info) == ELF_MACHINE_JMP_SLOT);
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/* Look up the target symbol. If the normal lookup rules are not
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used don't look in the global scope. */
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if (__builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
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{
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switch (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
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{
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default:
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{
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const ElfW(Half) *vernum =
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(const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
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ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)];
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const struct r_found_version *version = &l->l_versions[ndx];
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if (version->hash != 0)
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{
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result = _dl_lookup_versioned_symbol (strtab + sym->st_name,
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l, &sym, l->l_scope,
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version,
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ELF_RTYPE_CLASS_PLT, 0);
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break;
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}
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}
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case 0:
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result = _dl_lookup_symbol (strtab + sym->st_name, l, &sym,
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l->l_scope, ELF_RTYPE_CLASS_PLT, 0);
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}
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/* Currently result contains the base load address (or link map)
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of the object that defines sym. Now add in the symbol
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offset. */
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value = (sym ? LOOKUP_VALUE_ADDRESS (result) + sym->st_value : 0);
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}
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else
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{
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/* We already found the symbol. The module (and therefore its load
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address) is also known. */
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value = l->l_addr + sym->st_value;
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#ifdef DL_LOOKUP_RETURNS_MAP
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result = l;
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#endif
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}
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/* And now perhaps the relocation addend. */
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value = elf_machine_plt_value (l, reloc, value);
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/* Finally, fix up the plt itself. */
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if (__builtin_expect (_dl_bind_not, 0))
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return value;
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return elf_machine_fixup_plt (l, result, reloc, rel_addr, value);
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}
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#endif
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#if !defined PROF && !defined ELF_MACHINE_NO_PLT && !__BOUNDED_POINTERS__
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static ElfW(Addr) __attribute__ ((regparm (3), used))
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profile_fixup (
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#ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
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ELF_MACHINE_RUNTIME_FIXUP_ARGS,
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#endif
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struct link_map *l, ElfW(Word) reloc_offset, ElfW(Addr) retaddr)
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{
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void (*mcount_fct) (ElfW(Addr), ElfW(Addr)) = _dl_mcount;
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ElfW(Addr) *resultp;
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lookup_t result;
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ElfW(Addr) value;
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/* The use of `alloca' here looks ridiculous but it helps. The goal is
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to prevent the function from being inlined, and thus optimized out.
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There is no official way to do this so we use this trick. gcc never
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inlines functions which use `alloca'. */
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alloca (sizeof (int));
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/* This is the address in the array where we store the result of previous
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relocations. */
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resultp = &l->l_reloc_result[reloc_offset / sizeof (PLTREL)];
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value = *resultp;
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if (value == 0)
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{
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/* This is the first time we have to relocate this object. */
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const ElfW(Sym) *const symtab
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= (const void *) D_PTR (l, l_info[DT_SYMTAB]);
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const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
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const PLTREL *const reloc
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= (const void *) (D_PTR (l, l_info[DT_JMPREL]) + reloc_offset);
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const ElfW(Sym) *sym = &symtab[ELFW(R_SYM) (reloc->r_info)];
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/* Sanity check that we're really looking at a PLT relocation. */
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assert (ELFW(R_TYPE)(reloc->r_info) == ELF_MACHINE_JMP_SLOT);
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/* Look up the target symbol. If the symbol is marked STV_PROTECTED
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don't look in the global scope. */
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if (__builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
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{
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switch (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
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{
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default:
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{
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const ElfW(Half) *vernum =
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(const void *) D_PTR (l,l_info[VERSYMIDX (DT_VERSYM)]);
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ElfW(Half) ndx = vernum[ELFW(R_SYM) (reloc->r_info)];
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const struct r_found_version *version = &l->l_versions[ndx];
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if (version->hash != 0)
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{
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result = _dl_lookup_versioned_symbol(strtab + sym->st_name,
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l, &sym, l->l_scope,
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version,
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ELF_RTYPE_CLASS_PLT,
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0);
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break;
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}
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}
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case 0:
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result = _dl_lookup_symbol (strtab + sym->st_name, l, &sym,
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l->l_scope, ELF_RTYPE_CLASS_PLT, 0);
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}
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/* Currently result contains the base load address (or link map)
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of the object that defines sym. Now add in the symbol
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offset. */
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value = (sym ? LOOKUP_VALUE_ADDRESS (result) + sym->st_value : 0);
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}
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else
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{
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/* We already found the symbol. The module (and therefore its load
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address) is also known. */
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value = l->l_addr + sym->st_value;
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#ifdef DL_LOOKUP_RETURNS_MAP
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result = l;
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#endif
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}
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/* And now perhaps the relocation addend. */
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value = elf_machine_plt_value (l, reloc, value);
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/* Store the result for later runs. */
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if (__builtin_expect (! _dl_bind_not, 1))
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*resultp = value;
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}
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(*mcount_fct) (retaddr, value);
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return value;
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}
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#endif /* PROF && ELF_MACHINE_NO_PLT */
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/* This macro is defined in dl-machine.h to define the entry point called
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by the PLT. The `fixup' function above does the real work, but a little
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more twiddling is needed to get the stack right and jump to the address
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finally resolved. */
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ELF_MACHINE_RUNTIME_TRAMPOLINE
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