90 lines
3.2 KiB
C
90 lines
3.2 KiB
C
/* On-demand PLT fixup for shared objects.
|
|
Copyright (C) 1995, 1996 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Library General Public License as
|
|
published by the Free Software Foundation; either version 2 of the
|
|
License, or (at your option) any later version.
|
|
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
Library General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Library General Public
|
|
License along with the GNU C Library; see the file COPYING.LIB. If
|
|
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
|
|
Cambridge, MA 02139, USA. */
|
|
|
|
#include <link.h>
|
|
#include "dynamic-link.h"
|
|
|
|
/* Figure out the right type, Rel or Rela. */
|
|
#define elf_machine_rel 1
|
|
#define elf_machine_rela 2
|
|
#if elf_machine_relplt == elf_machine_rel
|
|
#define PLTREL Elf32_Rel
|
|
#elif elf_machine_relplt == elf_machine_rela
|
|
#define PLTREL Elf32_Rela
|
|
#else
|
|
#error "dl-machine.h bug: elf_machine_relplt not rel or rela"
|
|
#endif
|
|
#undef elf_machine_rel
|
|
#undef elf_machine_rela
|
|
|
|
/* We need to define the function as a local symbol so that the reference
|
|
in the trampoline code will be a local PC-relative call. Tell the
|
|
compiler not to worry that the function appears not to be called. */
|
|
|
|
static Elf32_Addr fixup (
|
|
#ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
|
|
ELF_MACHINE_RUNTIME_FIXUP_ARGS,
|
|
#endif
|
|
struct link_map *l, Elf32_Word reloc_offset)
|
|
__attribute__ ((unused));
|
|
|
|
/* This function is called through a special trampoline from the PLT the
|
|
first time each PLT entry is called. We must perform the relocation
|
|
specified in the PLT of the given shared object, and return the resolved
|
|
function address to the trampoline, which will restart the original call
|
|
to that address. Future calls will bounce directly from the PLT to the
|
|
function. */
|
|
|
|
static Elf32_Addr
|
|
fixup (
|
|
#ifdef ELF_MACHINE_RUNTIME_FIXUP_ARGS
|
|
ELF_MACHINE_RUNTIME_FIXUP_ARGS,
|
|
#endif
|
|
struct link_map *l, Elf32_Word reloc_offset)
|
|
{
|
|
const Elf32_Sym *const symtab
|
|
= (const Elf32_Sym *) (l->l_addr + l->l_info[DT_SYMTAB]->d_un.d_ptr);
|
|
const char *strtab =
|
|
(const char *) (l->l_addr + l->l_info[DT_STRTAB]->d_un.d_ptr);
|
|
|
|
const PLTREL *const reloc
|
|
= (const void *) (l->l_addr + l->l_info[DT_JMPREL]->d_un.d_ptr +
|
|
reloc_offset);
|
|
|
|
Elf32_Addr resolve (const Elf32_Sym **ref,
|
|
Elf32_Addr reloc_addr, int noplt)
|
|
{
|
|
return _dl_lookup_symbol (strtab + (*ref)->st_name, ref, _dl_loaded,
|
|
l->l_name, reloc_addr, noplt);
|
|
}
|
|
|
|
/* Perform the specified relocation. */
|
|
elf_machine_relplt (l, reloc, &symtab[ELF32_R_SYM (reloc->r_info)], resolve);
|
|
|
|
return *(Elf32_Addr *) (l->l_addr + reloc->r_offset);
|
|
}
|
|
|
|
|
|
/* This macro is defined in dl-machine.h to define the entry point called
|
|
by the PLT. The `fixup' function above does the real work, but a little
|
|
more twiddling is needed to get the stack right and jump to the address
|
|
finally resolved. */
|
|
|
|
ELF_MACHINE_RUNTIME_TRAMPOLINE
|