sysdeps/generic/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  Stub version.
   2    Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If
  17    not, write to the Free Software Foundation, Inc.,
  18    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 #define ELF_MACHINE_NAME "stub"
  21
  22 #include <assert.h>
  23 #include <string.h>
  24 #include <link.h>
  25
  26
  27 /* Return nonzero iff E_MACHINE is compatible with the running host.  */
  28 static inline int
  29 elf_machine_matches_host (Elf32_Half e_machine)
  30 {
  31   switch (e_machine)
  32     {
  33     default:
  34       return 0;
  35     }
  36 }
  37
  38
  39 /* Return the link-time address of _DYNAMIC.  */
  40 static inline Elf32_Addr
  41 elf_machine_dynamic (void)
  42 {
  43 #error "Damn, no _DYNAMIC"
  44 }
  45
  46
  47 /* Return the run-time load address of the shared object.  */
  48 static inline Elf32_Addr
  49 elf_machine_load_address (void)
  50 {
  51 #error "Where am I?"
  52 }
  53
  54 /* Fixup a PLT entry to bounce directly to the function at VALUE.  */
  55
  56 static inline void
  57 elf_machine_fixup_plt (struct link_map *map, const Elf32_Rel *reloc,
  58                        Elf32_Addr *reloc_addr, Elf32_Addr value)
  59 {
  60   *reloc_addr = value;
  61 }
  62
  63 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
  64    LOADADDR is the load address of the object; INFO is an array indexed
  65    by DT_* of the .dynamic section info.  */
  66
  67 static inline void
  68 elf_machine_rel (Elf32_Addr loadaddr, Elf32_Dyn *info[DT_NUM],
  69                  const Elf32_Rel *reloc, const Elf32_Sym *sym,
  70                  Elf32_Addr (*resolve) (const Elf32_Sym **ref,
  71                                         Elf32_Addr reloc_addr,
  72                                         int noplt))
  73 {
  74   Elf32_Addr *const reloc_addr = (Elf32_Addr *) reloc->r_offset;
  75   Elf32_Addr loadbase;
  76
  77   switch (ELF32_R_TYPE (reloc->r_info))
  78     {
  79     case R_MACHINE_COPY:
  80       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
  81       memcpy (reloc_addr, (void *) (loadbase + sym->st_value), sym->st_size);
  82       break;
  83     default:
  84       assert (! "unexpected dynamic reloc type");
  85       break;
  86     }
  87 }
  88
  89
  90 static inline Elf32_Addr
  91 elf_machine_rela (Elf32_Addr loadaddr, Elf32_Dyn *info[DT_NUM],
  92                   const Elf32_Rel *reloc, const Elf32_Sym *sym,
  93                   Elf32_Addr (*resolve) (const Elf32_Sym **ref,
  94                                          Elf32_Addr reloc_addr,
  95                                          int noplt))
  96 {
  97   _dl_signal_error (0, "Elf32_Rela relocation requested -- unused on "
  98                     ELF_MACHINE_NAME);
  99 }
 100
 101
 102 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 103    PLT entries should not be allowed to define the value.  */
 104 #define elf_machine_pltrel_p(type) ((type) == R_???_JMP_SLOT)
 105
 106
 107 /* Set up the loaded object described by L so its unrelocated PLT
 108    entries will jump to the on-demand fixup code in dl-runtime.c.  */
 109
 110 static inline int
 111 elf_machine_runtime_setup (struct link_map *l, int lazy)
 112 {
 113   extern void _dl_runtime_resolve (Elf32_Word);
 114
 115   if (lazy)
 116     {
 117       /* The GOT entries for functions in the PLT have not yet been filled
 118          in.  Their initial contents will arrange when called to push an
 119          offset into the .rel.plt section, push _GLOBAL_OFFSET_TABLE_[1],
 120          and then jump to _GLOBAL_OFFSET_TABLE[2].  */
 121       Elf32_Addr *got = (Elf32_Addr *) l->l_info[DT_PLTGOT]->d_un.d_ptr;
 122       got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */
 123
 124       /* This function will get called to fix up the GOT entry indicated by
 125          the offset on the stack, and then jump to the resolved address.  */
 126       got[2] = (Elf32_Addr) &_dl_runtime_resolve;
 127     }
 128
 129   return lazy;
 130 }
 131
 132
 133 /* Initial entry point code for the dynamic linker.
 134    The C function `_dl_start' is the real entry point;
 135    its return value is the user program's entry point.  */
 136
 137 #define RTLD_START #error need some startup code