sysdeps/m68k/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  m68k version.
   2    Copyright (C) 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 #ifndef dl_machine_h
  21 #define dl_machine_h
  22
  23 #define ELF_MACHINE_NAME "m68k"
  24
  25 #include <assert.h>
  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 link-time address of _DYNAMIC.  Conveniently, this is the
  42    first element of the GOT.  This must be inlined in a function which
  43    uses global data.  */
  44 static inline Elf32_Addr
  45 elf_machine_dynamic (void)
  46 {
  47   register Elf32_Addr *got asm ("%a5");
  48   return *got;
  49 }
  50
  51
  52 /* Return the run-time load address of the shared object.  */
  53 static inline Elf32_Addr
  54 elf_machine_load_address (void)
  55 {
  56   Elf32_Addr addr;
  57   asm ("here:   lea here(%%pc), %0\n"
  58        "        sub.l %#here, %0"
  59        : "=a" (addr));
  60   return addr;
  61 }
  62
  63 /* The `subl' insn above will contain an R_68K_RELATIVE relocation
  64    entry intended to insert the run-time address of the label `here'.
  65    This will be the first relocation in the text of the dynamic
  66    linker; we skip it to avoid trying to modify read-only text in this
  67    early stage.  */
  68 #define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \
  69   ((dynamic_info)[DT_RELA]->d_un.d_ptr += sizeof (Elf32_Rela), \
  70    (dynamic_info)[DT_RELASZ]->d_un.d_val -= sizeof (Elf32_Rela))
  71
  72
  73 /* Set up the loaded object described by L so its unrelocated PLT
  74    entries will jump to the on-demand fixup code in dl-runtime.c.  */
  75
  76 static inline int
  77 elf_machine_runtime_setup (struct link_map *l, int lazy)
  78 {
  79   Elf32_Addr *got;
  80   extern void _dl_runtime_resolve (Elf32_Word);
  81
  82   if (l->l_info[DT_JMPREL] && lazy)
  83     {
  84       /* The GOT entries for functions in the PLT have not yet been
  85          filled in.  Their initial contents will arrange when called
  86          to push an offset into the .rela.plt section, push
  87          _GLOBAL_OFFSET_TABLE_[1], and then jump to
  88          _GLOBAL_OFFSET_TABLE_[2].  */
  89       got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
  90       got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */
  91       /* This function will get called to fix up the GOT entry
  92          indicated by the offset on the stack, and then jump to the
  93          resolved address.  */
  94       got[2] = (Elf32_Addr) &_dl_runtime_resolve;
  95     }
  96
  97   return lazy;
  98 }
  99 /* This code is used in dl-runtime.c to call the `fixup' function
 100    and then redirect to the address it returns.  */
 101 #define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 102 | Trampoline for _dl_runtime_resolver
 103         .globl _dl_runtime_resolve
 104         .type _dl_runtime_resolve, @function
 105 _dl_runtime_resolve:
 106         | Save %a0 (struct return address) and %a1.
 107         move.l %a0, -(%sp)
 108         move.l %a1, -(%sp)
 109         | Call the real address resolver.
 110         jbsr fixup
 111         | Restore register %a0 and %a1.
 112         move.l (%sp)+, %a1
 113         move.l (%sp)+, %a0
 114         | Pop parameters
 115         addq.l #8, %sp
 116         | Call real function.
 117         jmp (%d0)
 118         .size _dl_runtime_resolve, . - _dl_runtime_resolve
 119 ");
 120 #define ELF_MACHINE_RUNTIME_FIXUP_ARGS long int save_a0, long int save_a1
 121 /* The PLT uses Elf32_Rela relocs.  */
 122 #define elf_machine_relplt elf_machine_rela
 123
 124
 125 /* Mask identifying addresses reserved for the user program,
 126    where the dynamic linker should not map anything.  */
 127 #define ELF_MACHINE_USER_ADDRESS_MASK   0x80000000UL
 128
 129 /* Initial entry point code for the dynamic linker.
 130    The C function `_dl_start' is the real entry point;
 131    its return value is the user program's entry point.  */
 132
 133 #define RTLD_START asm ("\
 134 .text
 135 .globl _start
 136 .globl _dl_start_user
 137 _start:
 138         move.l %sp, -(%sp)
 139         jbsr _dl_start
 140         addq.l #4, %sp
 141 _dl_start_user:
 142         | Save the user entry point address in %a4.
 143         move.l %d0, %a4
 144         | Point %a5 at the GOT.
 145         lea _GLOBAL_OFFSET_TABLE_@GOTPC(%pc), %a5
 146         | See if we were run as a command with the executable file
 147         | name as an extra leading argument.
 148         move.l ([_dl_skip_args@GOT, %a5]), %d0
 149         jeq 0f
 150         | Pop the original argument count
 151         move.l (%sp)+, %d1
 152         | Subtract _dl_skip_args from it.
 153         sub.l %d0, %d1
 154         | Adjust the stack pointer to skip _dl_skip_args words.
 155         lea (%sp, %d0*4), %sp
 156         | Push back the modified argument count.
 157         move.l %d1, -(%sp)
 158 0:      | Push _dl_default_scope[2] as argument in _dl_init_next call below.
 159         move.l ([_dl_default_scope@GOT, %a5], 8), %d2
 160 0:      move.l %d2, -(%sp)
 161         | Call _dl_init_next to return the address of an initializer
 162         | function to run.
 163         bsr.l _dl_init_next@PLTPC
 164         add.l #4, %sp | Pop argument.
 165         | Check for zero return, when out of initializers.
 166         tst.l %d0
 167         jeq 1f
 168         | Call the shared object initializer function.
 169         | NOTE: We depend only on the registers (%d2, %a4 and %a5)
 170         | and the return address pushed by this call;
 171         | the initializer is called with the stack just
 172         | as it appears on entry, and it is free to move
 173         | the stack around, as long as it winds up jumping to
 174         | the return address on the top of the stack.
 175         move.l %d0, %a0
 176         jsr (%a0)
 177         | Loop to call _dl_init_next for the next initializer.
 178         jra 0b
 179 1:      | Clear the startup flag.
 180         clr.l _dl_starting_up@GOT(%a5)
 181         | Pass our finalizer function to the user in %a1.
 182         move.l _dl_fini@GOT(%a5), %a1
 183         | Initialize %fp with the stack pointer.
 184         move.l %sp, %fp
 185         | Jump to the user's entry point.
 186         jmp (%a4)");
 187
 188 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 189    PLT entries should not be allowed to define the value.  */
 190 #define elf_machine_pltrel_p(type) ((type) == R_68K_JMP_SLOT)
 191
 192 /* The m68k never uses Elf32_Rel relocations.  */
 193 #define ELF_MACHINE_NO_REL 1
 194
 195 #endif /* !dl_machine_h */
 196
 197 #ifdef RESOLVE
 198
 199 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 200    MAP is the object containing the reloc.  */
 201
 202 static inline void
 203 elf_machine_rela (struct link_map *map,
 204                   const Elf32_Rela *reloc, const Elf32_Sym *sym)
 205 {
 206   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
 207   Elf32_Addr loadbase;
 208
 209   switch (ELF32_R_TYPE (reloc->r_info))
 210     {
 211     case R_68K_COPY:
 212       loadbase = RESOLVE (&sym, DL_LOOKUP_NOEXEC);
 213       memcpy (reloc_addr, (void *) (loadbase + sym->st_value), sym->st_size);
 214       break;
 215     case R_68K_GLOB_DAT:
 216       loadbase = RESOLVE (&sym, 0);
 217       *reloc_addr = sym ? (loadbase + sym->st_value) : 0;
 218       break;
 219     case R_68K_JMP_SLOT:
 220       loadbase = RESOLVE (&sym, DL_LOOKUP_NOPLT);
 221       *reloc_addr = sym ? (loadbase + sym->st_value) : 0;
 222       break;
 223     case R_68K_8:
 224       loadbase = RESOLVE (&sym, 0);
 225       *(char *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 226                               + reloc->r_addend);
 227       break;
 228     case R_68K_16:
 229       loadbase = RESOLVE (&sym, 0);
 230       *(short *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 231                                + reloc->r_addend);
 232       break;
 233     case R_68K_32:
 234       loadbase = RESOLVE (&sym, 0);
 235       *reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 236                      + reloc->r_addend);
 237       break;
 238     case R_68K_RELATIVE:
 239       *reloc_addr = map->l_addr + reloc->r_addend;
 240       break;
 241     case R_68K_PC8:
 242       loadbase = RESOLVE (&sym, 0);
 243       *(char *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 244                               + reloc->r_addend - (Elf32_Addr) reloc_addr);
 245       break;
 246     case R_68K_PC16:
 247       loadbase = RESOLVE (&sym, 0);
 248       *(short *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 249                                + reloc->r_addend - (Elf32_Addr) reloc_addr);
 250       break;
 251     case R_68K_PC32:
 252       loadbase = RESOLVE (&sym, 0);
 253       *reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 254                      + reloc->r_addend - (Elf32_Addr) reloc_addr);
 255       break;
 256     case R_68K_NONE:            /* Alright, Wilbur.  */
 257       break;
 258     default:
 259       assert (! "unexpected dynamic reloc type");
 260       break;
 261     }
 262 }
 263
 264 static inline void
 265 elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
 266 {
 267   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
 268   switch (ELF32_R_TYPE (reloc->r_info))
 269     {
 270     case R_68K_JMP_SLOT:
 271       *reloc_addr += map->l_addr;
 272       break;
 273     default:
 274       assert (! "unexpected PLT reloc type");
 275       break;
 276     }
 277 }
 278
 279 #endif /* RESOLVE */