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_Rela *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 ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0) :
 114                   /* RESOLVE is null during bootstrap relocation.  */
 115                   map->l_addr);
 116       *reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 117                      + reloc->r_addend);
 118       break;
 119     case R_68K_RELATIVE:
 120       *reloc_addr = map->l_addr + reloc->r_addend;
 121       break;
 122     case R_68K_PC8:
 123       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 124       *(char *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 125                               + reloc->r_addend
 126                               - (Elf32_Addr) reloc_addr);
 127       break;
 128     case R_68K_PC16:
 129       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 130       *(short *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 131                                + reloc->r_addend
 132                                - (Elf32_Addr) reloc_addr);
 133       break;
 134     case R_68K_PC32:
 135       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 136       *reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 137                      + reloc->r_addend
 138                      - (Elf32_Addr) reloc_addr);
 139       break;
 140     case R_68K_NONE:            /* Alright, Wilbur.  */
 141       break;
 142     default:
 143       assert (! "unexpected dynamic reloc type");
 144       break;
 145     }
 146 }
 147
 148 static inline void
 149 elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
 150 {
 151   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
 152   switch (ELF32_R_TYPE (reloc->r_info))
 153     {
 154     case R_68K_NONE:
 155       break;
 156     case R_68K_JMP_SLOT:
 157       *reloc_addr += map->l_addr;
 158       break;
 159     default:
 160       assert (! "unexpected PLT reloc type");
 161       break;
 162     }
 163 }
 164
 165 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 166    PLT entries should not be allowed to define the value.  */
 167 #define elf_machine_pltrel_p(type) ((type) == R_68K_JMP_SLOT)
 168
 169 /* The m68k never uses Elf32_Rel relocations.  */
 170 #define ELF_MACHINE_NO_REL 1
 171
 172
 173 /* Set up the loaded object described by L so its unrelocated PLT
 174    entries will jump to the on-demand fixup code in dl-runtime.c.  */
 175
 176 static inline void
 177 elf_machine_runtime_setup (struct link_map *l, int lazy)
 178 {
 179   Elf32_Addr *got;
 180   extern void _dl_runtime_resolve (Elf32_Word);
 181
 182   if (l->l_info[DT_JMPREL] && lazy)
 183     {
 184       /* The GOT entries for functions in the PLT have not yet been
 185          filled in.  Their initial contents will arrange when called
 186          to push an offset into the .rela.plt section, push
 187          _GLOBAL_OFFSET_TABLE_[1], and then jump to
 188          _GLOBAL_OFFSET_TABLE_[2].  */
 189       got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
 190       got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */
 191       /* This function will get called to fix up the GOT entry
 192          indicated by the offset on the stack, and then jump to the
 193          resolved address.  */
 194       got[2] = (Elf32_Addr) &_dl_runtime_resolve;
 195     }
 196
 197   /* This code is used in dl-runtime.c to call the `fixup' function
 198      and then redirect to the address it returns.  */
 199 #define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 200 | Trampoline for _dl_runtime_resolver
 201         .globl _dl_runtime_resolve
 202         .type _dl_runtime_resolve, @function
 203 _dl_runtime_resolve:
 204         | Save %a0 (struct return address) and %a1.
 205         move.l %a0, -(%sp)
 206         move.l %a1, -(%sp)
 207         | Call the real address resolver.
 208         jbsr fixup
 209         | Restore register %a0 and %a1.
 210         move.l (%sp)+, %a1
 211         move.l (%sp)+, %a0
 212         | Pop parameters
 213         addq.l #8, %sp
 214         | Call real function.
 215         jmp (%d0)
 216         .size _dl_runtime_resolve, . - _dl_runtime_resolve
 217 ");
 218 #define ELF_MACHINE_RUNTIME_FIXUP_ARGS long int save_a0, long int save_a1
 219 /* The PLT uses Elf32_Rela relocs.  */
 220 #define elf_machine_relplt elf_machine_rela
 221 }
 222
 223
 224 /* Mask identifying addresses reserved for the user program,
 225    where the dynamic linker should not map anything.  */
 226 #define ELF_MACHINE_USER_ADDRESS_MASK   0x80000000UL
 227
 228 /* Initial entry point code for the dynamic linker.
 229    The C function `_dl_start' is the real entry point;
 230    its return value is the user program's entry point.  */
 231
 232 #define RTLD_START asm ("\
 233 .text
 234 .globl _start
 235 .globl _dl_start_user
 236 _start:
 237         move.l %sp, -(%sp)
 238         jbsr _dl_start
 239         addq.l #4, %sp
 240 _dl_start_user:
 241         | Save the user entry point address in %a4.
 242         move.l %d0, %a4
 243         | Point %a5 at the GOT.
 244         lea _GLOBAL_OFFSET_TABLE_@GOTPC(%pc), %a5
 245         | See if we were run as a command with the executable file
 246         | name as an extra leading argument.
 247         move.l ([_dl_skip_args@GOT, %a5]), %d0
 248         jeq 0f
 249         | Pop the original argument count
 250         move.l (%sp)+, %d1
 251         | Subtract _dl_skip_args from it.
 252         sub.l %d0, %d1
 253         | Adjust the stack pointer to skip _dl_skip_args words.
 254         lea (%sp, %d0*4), %sp
 255         | Push back the modified argument count.
 256         move.l %d1, -(%sp)
 257 0:      | Push _dl_default_scope[2] as argument in _dl_init_next call below.
 258         move.l ([_dl_default_scope@GOT, %a5]), %d2
 259 0:      move.l (%d2, 8), -(%sp)
 260         | Call _dl_init_next to return the address of an initializer
 261         | function to run.
 262         bsr.l _dl_init_next@PLTPC
 263         add.l #4, %sp | Pop argument.
 264         | Check for zero return, when out of initializers.
 265         tst.l %d0
 266         jeq 1f
 267         | Call the shared object initializer function.
 268         | NOTE: We depend only on the registers (%d2, %a4 and %a5)
 269         | and the return address pushed by this call;
 270         | the initializer is called with the stack just
 271         | as it appears on entry, and it is free to move
 272         | the stack around, as long as it winds up jumping to
 273         | the return address on the top of the stack.
 274         move.l %d0, %a0
 275         jsr (%a0)
 276         | Loop to call _dl_init_next for the next initializer.
 277         jra 0b
 278 1:      | Pass our finalizer function to the user in %a1.
 279         move.l _dl_fini@GOT(%a5), %a1
 280         | Initialize %fp with the stack pointer.
 281         move.l %sp, %fp
 282         | Jump to the user's entry point.
 283         jmp (%a4)");