sysdeps/m68k/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  m68k version.
   2 Copyright (C) 1996 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., 675 Mass Ave,
  18 Cambridge, MA 02139, USA.  */
  19
  20 #define ELF_MACHINE_NAME "m68k"
  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     case EM_68K:
  34       return 1;
  35     default:
  36       return 0;
  37     }
  38 }
  39
  40
  41 /* Return the run-time address of the _GLOBAL_OFFSET_TABLE_.
  42    Must be inlined in a function which uses global data.  */
  43 static inline Elf32_Addr *
  44 elf_machine_got (void)
  45 {
  46   register Elf32_Addr *got asm ("%a5");
  47   return got;
  48 }
  49
  50
  51 /* Return the run-time load address of the shared object.  */
  52 static inline Elf32_Addr
  53 elf_machine_load_address (void)
  54 {
  55   Elf32_Addr addr;
  56   asm ("here:   lea here(%%pc), %0\n"
  57        "        sub.l %#here, %0"
  58        : "=a" (addr));
  59   return addr;
  60 }
  61
  62 /* The `subl' insn above will contain an R_68K_RELATIVE relocation
  63    entry intended to insert the run-time address of the label `here'.
  64    This will be the first relocation in the text of the dynamic
  65    linker; we skip it to avoid trying to modify read-only text in this
  66    early stage.  */
  67 #define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \
  68   ((dynamic_info)[DT_RELA]->d_un.d_ptr += sizeof (Elf32_Rela), \
  69    (dynamic_info)[DT_RELASZ]->d_un.d_val -= sizeof (Elf32_Rela))
  70
  71 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
  72    MAP is the object containing the reloc.  */
  73
  74 static inline void
  75 elf_machine_rela (struct link_map *map,
  76                   const Elf32_Rel *reloc, const Elf32_Sym *sym,
  77                   Elf32_Addr (*resolve) (const Elf32_Sym **ref,
  78                                          Elf32_Addr reloc_addr,
  79                                          int noplt))
  80 {
  81   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
  82   Elf32_Addr loadbase;
  83
  84   switch (ELF32_R_TYPE (reloc->r_info))
  85     {
  86     case R_68K_COPY:
  87       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
  88       memcpy (reloc_addr, (void *) (loadbase + sym->st_value), sym->st_size);
  89       break;
  90     case R_68K_GLOB_DAT:
  91       loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0) :
  92                   /* RESOLVE is null during bootstrap relocation.  */
  93                   map->l_addr);
  94       *reloc_addr = sym ? (loadbase + sym->st_value) : 0;
  95       break;
  96     case R_68K_JMP_SLOT:
  97       loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 1) :
  98                   /* RESOLVE is null during bootstrap relocation.  */
  99                   map->l_addr);
 100       *reloc_addr = sym ? (loadbase + sym->st_value) : 0;
 101       break;
 102     case R_68K_8:
 103       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 104       *(char *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 105                               + reloc->r_addend);
 106       break;
 107     case R_68K_16:
 108       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 109       *(short *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 110                                + reloc->r_addend);
 111       break;
 112     case R_68K_32:
 113       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 114       *reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 115                      + reloc->r_addend);
 116       break;
 117     case R_68K_RELATIVE:
 118       *reloc_addr = map->l_addr + reloc->r_addend;
 119       break;
 120     case R_68K_PC8:
 121       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 122       *(char *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 123                               + reloc->r_addend
 124                               - (Elf32_Addr) reloc_addr);
 125       break;
 126     case R_68K_PC16:
 127       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 128       *(short *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 129                                + reloc->r_addend
 130                                - (Elf32_Addr) reloc_addr);
 131       break;
 132     case R_68K_PC32:
 133       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 134       *reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 135                      + reloc->r_addend
 136                      - (Elf32_Addr) reloc_addr);
 137       break;
 138     case R_68K_NONE:            /* Alright, Wilbur.  */
 139       break;
 140     default:
 141       assert (! "unexpected dynamic reloc type");
 142       break;
 143     }
 144 }
 145
 146 static inline void
 147 elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
 148 {
 149   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
 150   switch (ELF32_R_TYPE (reloc->r_info))
 151     {
 152     case R_68K_NONE:
 153       break;
 154     case R_68K_JMP_SLOT:
 155       *reloc_addr += map->l_addr;
 156       break;
 157     default:
 158       assert (! "unexpected PLT reloc type");
 159       break;
 160     }
 161 }
 162
 163 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 164    PLT entries should not be allowed to define the value.  */
 165 #define elf_machine_pltrel_p(type) ((type) == R_68K_JMP_SLOT)
 166
 167 /* The m68k never uses Elf32_Rel relocations.  */
 168 #define ELF_MACHINE_NO_REL 1
 169
 170
 171 /* Set up the loaded object described by L so its unrelocated PLT
 172    entries will jump to the on-demand fixup code in dl-runtime.c.  */
 173
 174 static inline void
 175 elf_machine_runtime_setup (struct link_map *l, int lazy)
 176 {
 177   Elf32_Addr *got;
 178   extern void _dl_runtime_resolve (Elf32_Word);
 179
 180   if (l->l_info[DT_JMPREL] && lazy)
 181     {
 182       /* The GOT entries for functions in the PLT have not yet been
 183          filled in.  Their initial contents will arrange when called
 184          to push an offset into the .rela.plt section, push
 185          _GLOBAL_OFFSET_TABLE_[1], and then jump to
 186          _GLOBAL_OFFSET_TABLE_[2].  */
 187       got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
 188       got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */
 189       /* This function will get called to fix up the GOT entry
 190          indicated by the offset on the stack, and then jump to the
 191          resolved address.  */
 192       got[2] = (Elf32_Addr) &_dl_runtime_resolve;
 193     }
 194
 195   /* This code is used in dl-runtime.c to call the `fixup' function
 196      and then redirect to the address it returns.  */
 197 #define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 198 | Trampoline for _dl_runtime_resolver
 199         .globl _dl_runtime_resolve
 200         .type _dl_runtime_resolve, @function
 201 _dl_runtime_resolve:
 202         | Save %a0 (struct return address) and %a1.
 203         move.l %a0, -(%sp)
 204         move.l %a1, -(%sp)
 205         | Call the real address resolver.
 206         jbsr fixup
 207         | Restore register %a0 and %a1.
 208         move.l (%sp)+, %a1
 209         move.l (%sp)+, %a0
 210         | Pop parameters
 211         addq.l #8, %sp
 212         | Call real function.
 213         jmp (%d0)
 214         .size _dl_runtime_resolve, . - _dl_runtime_resolve
 215 ");
 216 #define ELF_MACHINE_RUNTIME_FIXUP_ARGS long int save_a0, long int save_a1
 217 /* The PLT uses Elf32_Rela relocs.  */
 218 #define elf_machine_relplt elf_machine_rela
 219 }
 220
 221
 222 /* Mask identifying addresses reserved for the user program,
 223    where the dynamic linker should not map anything.  */
 224 #define ELF_MACHINE_USER_ADDRESS_MASK   0x80000000UL
 225
 226 /* Initial entry point code for the dynamic linker.
 227    The C function `_dl_start' is the real entry point;
 228    its return value is the user program's entry point.  */
 229
 230 #define RTLD_START asm ("\
 231 .text
 232 .globl _start
 233 .globl _dl_start_user
 234 _start:
 235         jbsr _dl_start
 236 _dl_start_user:
 237         | Save the user entry point address in %a4.
 238         move.l %d0, %a4
 239         | Point %a5 at the GOT.
 240         lea _GLOBAL_OFFSET_TABLE_@GOTPC(%pc), %a5
 241         | See if we were run as a command with the executable file
 242         | name as an extra leading argument.
 243         move.l ([_dl_skip_args@GOT, %a5]), %d0
 244         jeq 0f
 245         | Pop the original argument count
 246         move.l (%sp)+, %d1
 247         | Subtract _dl_skip_args from it.
 248         sub.l %d0, %d1
 249         | Adjust the stack pointer to skip _dl_skip_args words.
 250         lea (%sp, %d0*4), %sp
 251         | Push back the modified argument count.
 252         move.l %d1, -(%sp)
 253         | Push _dl_loaded as argument in _dl_init_next call below.
 254         move.l ([_dl_loaded@GOT, %a5]), %d2
 255 0:      move.l %d2, -(%sp)
 256         | Call _dl_init_next to return the address of an initializer
 257         | function to run.
 258         bsr.l _dl_init_next@PLTPC
 259         add.l #4, %sp | Pop argument.
 260         | Check for zero return, when out of initializers.
 261         tst.l %d0
 262         jeq 1f
 263         | Call the shared object initializer function.
 264         | NOTE: We depend only on the registers (%d2, %a4 and %a5)
 265         | and the return address pushed by this call;
 266         | the initializer is called with the stack just
 267         | as it appears on entry, and it is free to move
 268         | the stack around, as long as it winds up jumping to
 269         | the return address on the top of the stack.
 270         move.l %d0, %a0
 271         jsr (%a0)
 272         | Loop to call _dl_init_next for the next initializer.
 273         jra 0b
 274 1:      | Pass our finalizer function to the user in %a1.
 275         move.l _dl_fini@GOT(%a5), %a1
 276         | Initialize %fp with the stack pointer.
 277         move.l %sp, %fp
 278         | Jump to the user's entry point.
 279         jmp (%a4)");