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 <sys/param.h>
  26
  27 #include <assert.h>
  28
  29 /* Return nonzero iff E_MACHINE is compatible with the running host.  */
  30 static inline int
  31 elf_machine_matches_host (Elf32_Half e_machine)
  32 {
  33   switch (e_machine)
  34     {
  35     case EM_68K:
  36       return 1;
  37     default:
  38       return 0;
  39     }
  40 }
  41
  42
  43 /* Return the link-time address of _DYNAMIC.  Conveniently, this is the
  44    first element of the GOT.  This must be inlined in a function which
  45    uses global data.  */
  46 static inline Elf32_Addr
  47 elf_machine_dynamic (void)
  48 {
  49   register Elf32_Addr *got asm ("%a5");
  50   return *got;
  51 }
  52
  53
  54 /* Return the run-time load address of the shared object.  */
  55 static inline Elf32_Addr
  56 elf_machine_load_address (void)
  57 {
  58   Elf32_Addr addr;
  59   asm (".Lhere: lea .Lhere(%%pc), %0\n"
  60        "        sub.l %#.Lhere, %0"
  61        : "=a" (addr));
  62   return addr;
  63 }
  64
  65 /* The `subl' insn above will contain an R_68K_RELATIVE relocation
  66    entry intended to insert the run-time address of the label `.Lhere'.
  67    This will be the first relocation in the text of the dynamic
  68    linker; we skip it to avoid trying to modify read-only text in this
  69    early stage.  */
  70 #define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \
  71   ((dynamic_info)[DT_RELA]->d_un.d_ptr += sizeof (Elf32_Rela), \
  72    (dynamic_info)[DT_RELASZ]->d_un.d_val -= sizeof (Elf32_Rela))
  73
  74
  75 /* Set up the loaded object described by L so its unrelocated PLT
  76    entries will jump to the on-demand fixup code in dl-runtime.c.  */
  77
  78 static inline int
  79 elf_machine_runtime_setup (struct link_map *l, int lazy)
  80 {
  81   Elf32_Addr *got;
  82   extern void _dl_runtime_resolve (Elf32_Word);
  83
  84   if (l->l_info[DT_JMPREL] && lazy)
  85     {
  86       /* The GOT entries for functions in the PLT have not yet been
  87          filled in.  Their initial contents will arrange when called
  88          to push an offset into the .rela.plt section, push
  89          _GLOBAL_OFFSET_TABLE_[1], and then jump to
  90          _GLOBAL_OFFSET_TABLE_[2].  */
  91       got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
  92       got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */
  93       /* This function will get called to fix up the GOT entry
  94          indicated by the offset on the stack, and then jump to the
  95          resolved address.  */
  96       got[2] = (Elf32_Addr) &_dl_runtime_resolve;
  97     }
  98
  99   return lazy;
 100 }
 101
 102 /* This code is used in dl-runtime.c to call the `fixup' function
 103    and then redirect to the address it returns.  */
 104 #define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 105 | Trampoline for _dl_runtime_resolver
 106         .globl _dl_runtime_resolve
 107         .type _dl_runtime_resolve, @function
 108 _dl_runtime_resolve:
 109         | Save %a0 (struct return address) and %a1.
 110         move.l %a0, -(%sp)
 111         move.l %a1, -(%sp)
 112         | Call the real address resolver.
 113         jbsr fixup
 114         | Restore register %a0 and %a1.
 115         move.l (%sp)+, %a1
 116         move.l (%sp)+, %a0
 117         | Pop parameters
 118         addq.l #8, %sp
 119         | Call real function.
 120         jmp (%d0)
 121         .size _dl_runtime_resolve, . - _dl_runtime_resolve
 122 ");
 123 #define ELF_MACHINE_RUNTIME_FIXUP_ARGS long int save_a0, long int save_a1
 124 /* The PLT uses Elf32_Rela relocs.  */
 125 #define elf_machine_relplt elf_machine_rela
 126
 127
 128 /* Mask identifying addresses reserved for the user program,
 129    where the dynamic linker should not map anything.  */
 130 #define ELF_MACHINE_USER_ADDRESS_MASK   0x80000000UL
 131
 132 /* Initial entry point code for the dynamic linker.
 133    The C function `_dl_start' is the real entry point;
 134    its return value is the user program's entry point.  */
 135
 136 #define RTLD_START asm ("\
 137 .text
 138 .globl _start
 139 .globl _dl_start_user
 140 _start:
 141         move.l %sp, -(%sp)
 142         jbsr _dl_start
 143         addq.l #4, %sp
 144 _dl_start_user:
 145         | Save the user entry point address in %a4.
 146         move.l %d0, %a4
 147         | Point %a5 at the GOT.
 148         lea _GLOBAL_OFFSET_TABLE_@GOTPC(%pc), %a5
 149         | See if we were run as a command with the executable file
 150         | name as an extra leading argument.
 151         move.l ([_dl_skip_args@GOT, %a5]), %d0
 152         jeq 0f
 153         | Pop the original argument count
 154         move.l (%sp)+, %d1
 155         | Subtract _dl_skip_args from it.
 156         sub.l %d0, %d1
 157         | Adjust the stack pointer to skip _dl_skip_args words.
 158         lea (%sp, %d0*4), %sp
 159         | Push back the modified argument count.
 160         move.l %d1, -(%sp)
 161 0:      | Push _dl_default_scope[2] as argument in _dl_init_next call below.
 162         move.l ([_dl_default_scope@GOT, %a5], 8), %d2
 163 0:      move.l %d2, -(%sp)
 164         | Call _dl_init_next to return the address of an initializer
 165         | function to run.
 166         bsr.l _dl_init_next@PLTPC
 167         add.l #4, %sp | Pop argument.
 168         | Check for zero return, when out of initializers.
 169         tst.l %d0
 170         jeq 1f
 171         | Call the shared object initializer function.
 172         | NOTE: We depend only on the registers (%d2, %a4 and %a5)
 173         | and the return address pushed by this call;
 174         | the initializer is called with the stack just
 175         | as it appears on entry, and it is free to move
 176         | the stack around, as long as it winds up jumping to
 177         | the return address on the top of the stack.
 178         move.l %d0, %a0
 179         jsr (%a0)
 180         | Loop to call _dl_init_next for the next initializer.
 181         jra 0b
 182 1:      | Clear the startup flag.
 183         clr.l _dl_starting_up@GOT(%a5)
 184         | Pass our finalizer function to the user in %a1.
 185         move.l _dl_fini@GOT(%a5), %a1
 186         | Initialize %fp with the stack pointer.
 187         move.l %sp, %fp
 188         | Jump to the user's entry point.
 189         jmp (%a4)");
 190
 191 /* Nonzero iff TYPE describes a relocation that should
 192    skip the executable when looking up the symbol value.  */
 193 #define elf_machine_lookup_noexec_p(type) ((type) == R_68K_COPY)
 194
 195 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 196    PLT entries should not be allowed to define the value.  */
 197 #define elf_machine_lookup_noplt_p(type) ((type) == R_68K_JMP_SLOT)
 198
 199 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 200 #define ELF_MACHINE_RELOC_NOPLT R_68K_JMP_SLOT
 201
 202 /* The m68k never uses Elf32_Rel relocations.  */
 203 #define ELF_MACHINE_NO_REL 1
 204
 205 #endif /* !dl_machine_h */
 206
 207 #ifdef RESOLVE
 208
 209 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 210    MAP is the object containing the reloc.  */
 211
 212 static inline void
 213 elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 214                   const Elf32_Sym *sym, const struct r_found_version *version)
 215 {
 216   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
 217
 218   if (ELF32_R_TYPE (reloc->r_info) == R_68K_RELATIVE)
 219     *reloc_addr = map->l_addr + reloc->r_addend;
 220   else
 221     {
 222       const Elf32_Sym *const refsym = sym;
 223       Elf32_Addr value = RESOLVE (&sym, version, ELF32_R_TYPE (reloc->r_info));
 224       if (sym)
 225         value += sym->st_value;
 226
 227       switch (ELF32_R_TYPE (reloc->r_info))
 228         {
 229         case R_68K_COPY:
 230           if (sym == NULL)
 231             /* This can happen in trace mode if an object could not be
 232                found.  */
 233             break;
 234           if (sym->st_size > refsym->st_size
 235               || (_dl_verbose && sym->st_size < refsym->st_size))
 236             {
 237               extern char **_dl_argv;
 238               const char *strtab;
 239
 240               strtab = ((void *) map->l_addr
 241                         + map->l_info[DT_STRTAB]->d_un.d_ptr);
 242               _dl_sysdep_error (_dl_argv[0] ?: "<program name unknown>",
 243                                 ": Symbol `", strtab + refsym->st_name,
 244                                 "' has different size in shared object, "
 245                                 "consider re-linking\n", NULL);
 246             }
 247           memcpy (reloc_addr, (void *) value, MIN (sym->st_size,
 248                                                    refsym->st_size));
 249           break;
 250         case R_68K_GLOB_DAT:
 251         case R_68K_JMP_SLOT:
 252           *reloc_addr = value;
 253           break;
 254         case R_68K_8:
 255           *(char *) reloc_addr = value + reloc->r_addend;
 256           break;
 257         case R_68K_16:
 258           *(short *) reloc_addr = value + reloc->r_addend;
 259           break;
 260         case R_68K_32:
 261           *reloc_addr = value + reloc->r_addend;
 262           break;
 263         case R_68K_PC8:
 264           *(char *) reloc_addr
 265             = value + reloc->r_addend - (Elf32_Addr) reloc_addr;
 266           break;
 267         case R_68K_PC16:
 268           *(short *) reloc_addr
 269             = value + reloc->r_addend - (Elf32_Addr) reloc_addr;
 270           break;
 271         case R_68K_PC32:
 272           *reloc_addr = value + reloc->r_addend - (Elf32_Addr) reloc_addr;
 273           break;
 274         case R_68K_NONE:                /* Alright, Wilbur.  */
 275           break;
 276         default:
 277           assert (! "unexpected dynamic reloc type");
 278           break;
 279         }
 280     }
 281 }
 282
 283 static inline void
 284 elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
 285 {
 286   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
 287   switch (ELF32_R_TYPE (reloc->r_info))
 288     {
 289     case R_68K_JMP_SLOT:
 290       *reloc_addr += map->l_addr;
 291       break;
 292     default:
 293       assert (! "unexpected PLT reloc type");
 294       break;
 295     }
 296 }
 297
 298 #endif /* RESOLVE */