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 ("lea _dl_start(%%pc), %0\n\t"
  60        "sub.l _dl_start@GOTPC(%%pc), %0"
  61        : "=a" (addr));
  62   return addr;
  63 }
  64
  65
  66 /* Set up the loaded object described by L so its unrelocated PLT
  67    entries will jump to the on-demand fixup code in dl-runtime.c.  */
  68
  69 static inline int
  70 elf_machine_runtime_setup (struct link_map *l, int lazy, int profile)
  71 {
  72   Elf32_Addr *got;
  73   extern void _dl_runtime_resolve (Elf32_Word);
  74   extern void _dl_runtime_profile (Elf32_Word);
  75
  76   if (l->l_info[DT_JMPREL] && lazy)
  77     {
  78       /* The GOT entries for functions in the PLT have not yet been
  79          filled in.  Their initial contents will arrange when called
  80          to push an offset into the .rela.plt section, push
  81          _GLOBAL_OFFSET_TABLE_[1], and then jump to
  82          _GLOBAL_OFFSET_TABLE_[2].  */
  83       got = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
  84       got[1] = (Elf32_Addr) l;  /* Identify this shared object.  */
  85
  86       /* The got[2] entry contains the address of a function which gets
  87          called to get the address of a so far unresolved function and
  88          jump to it.  The profiling extension of the dynamic linker allows
  89          to intercept the calls to collect information.  In this case we
  90          don't store the address in the GOT so that all future calls also
  91          end in this function.  */
  92       if (profile)
  93         {
  94           got[2] = (Elf32_Addr) &_dl_runtime_profile;
  95           /* Say that we really want profiling and the timers are started.  */
  96           _dl_profile_map = l;
  97         }
  98       else
  99         /* This function will get called to fix up the GOT entry indicated by
 100            the offset on the stack, and then jump to the resolved address.  */
 101         got[2] = (Elf32_Addr) &_dl_runtime_resolve;
 102     }
 103
 104   return lazy;
 105 }
 106
 107 /* This code is used in dl-runtime.c to call the `fixup' function
 108    and then redirect to the address it returns.  */
 109 #define TRAMPOLINE_TEMPLATE(tramp_name, fixup_name) \
 110 "| Trampoline for " #fixup_name "
 111         .globl " #tramp_name "
 112         .type " #tramp_name ", @function
 113 " #tramp_name ":
 114         | Save %a0 (struct return address) and %a1.
 115         move.l %a0, -(%sp)
 116         move.l %a1, -(%sp)
 117         | Call the real address resolver.
 118         jbsr " #fixup_name "
 119         | Restore register %a0 and %a1.
 120         move.l (%sp)+, %a1
 121         move.l (%sp)+, %a0
 122         | Pop parameters
 123         addq.l #8, %sp
 124         | Call real function.
 125         jmp (%d0)
 126         .size " #tramp_name ", . - " #tramp_name "\n"
 127 #ifndef PROF
 128 #define ELF_MACHINE_RUNTIME_TRAMPOLINE \
 129 asm (TRAMPOLINE_TEMPLATE (_dl_runtime_resolve, fixup) \
 130      TRAMPOLINE_TEMPLATE (_dl_runtime_profile, profile_fixup));
 131 #else
 132 #define ELF_MACHINE_RUNTIME_TRAMPOLINE \
 133 asm (TRAMPOLINE_TEMPLATE (_dl_runtime_resolve, fixup) \
 134      ".globl _dl_runtime_profile\n" \
 135      ".set _dl_runtime_profile, _dl_runtime_resolve");
 136 #endif
 137 #define ELF_MACHINE_RUNTIME_FIXUP_ARGS long int save_a0, long int save_a1
 138
 139
 140 /* Mask identifying addresses reserved for the user program,
 141    where the dynamic linker should not map anything.  */
 142 #define ELF_MACHINE_USER_ADDRESS_MASK   0x80000000UL
 143
 144 /* Initial entry point code for the dynamic linker.
 145    The C function `_dl_start' is the real entry point;
 146    its return value is the user program's entry point.  */
 147
 148 #define RTLD_START asm ("\
 149         .text
 150         .globl _start
 151         .type _start,@function
 152 _start:
 153         move.l %sp, -(%sp)
 154         jbsr _dl_start
 155         addq.l #4, %sp
 156
 157         .globl _dl_start_user
 158         .type _dl_start_user,@function
 159 _dl_start_user:
 160         | Save the user entry point address in %a4.
 161         move.l %d0, %a4
 162         | Point %a5 at the GOT.
 163         lea _GLOBAL_OFFSET_TABLE_@GOTPC(%pc), %a5
 164         | See if we were run as a command with the executable file
 165         | name as an extra leading argument.
 166         move.l ([_dl_skip_args@GOT, %a5]), %d0
 167         jeq 0f
 168         | Pop the original argument count
 169         move.l (%sp)+, %d1
 170         | Subtract _dl_skip_args from it.
 171         sub.l %d0, %d1
 172         | Adjust the stack pointer to skip _dl_skip_args words.
 173         lea (%sp, %d0*4), %sp
 174         | Push back the modified argument count.
 175         move.l %d1, -(%sp)
 176 0:      | Push _dl_default_scope[2] as argument in _dl_init_next call below.
 177         move.l ([_dl_default_scope@GOT, %a5], 8), %d2
 178 0:      move.l %d2, -(%sp)
 179         | Call _dl_init_next to return the address of an initializer
 180         | function to run.
 181         bsr.l _dl_init_next@PLTPC
 182         add.l #4, %sp | Pop argument.
 183         | Check for zero return, when out of initializers.
 184         tst.l %d0
 185         jeq 1f
 186         | Call the shared object initializer function.
 187         | NOTE: We depend only on the registers (%d2, %a4 and %a5)
 188         | and the return address pushed by this call;
 189         | the initializer is called with the stack just
 190         | as it appears on entry, and it is free to move
 191         | the stack around, as long as it winds up jumping to
 192         | the return address on the top of the stack.
 193         move.l %d0, %a0
 194         jsr (%a0)
 195         | Loop to call _dl_init_next for the next initializer.
 196         jra 0b
 197 1:      | Clear the startup flag.
 198         clr.l _dl_starting_up@GOT(%a5)
 199         | Pass our finalizer function to the user in %a1.
 200         move.l _dl_fini@GOT(%a5), %a1
 201         | Initialize %fp with the stack pointer.
 202         move.l %sp, %fp
 203         | Jump to the user's entry point.
 204         jmp (%a4)
 205         .size _dl_start_user, . - _dl_start_user
 206         .previous");
 207
 208 /* Nonzero iff TYPE describes a relocation that should
 209    skip the executable when looking up the symbol value.  */
 210 #define elf_machine_lookup_noexec_p(type) ((type) == R_68K_COPY)
 211
 212 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 213    PLT entries should not be allowed to define the value.  */
 214 #define elf_machine_lookup_noplt_p(type) ((type) == R_68K_JMP_SLOT)
 215
 216 /* A reloc type used for ld.so cmdline arg lookups to reject PLT entries.  */
 217 #define ELF_MACHINE_JMP_SLOT    R_68K_JMP_SLOT
 218
 219 /* The m68k never uses Elf32_Rel relocations.  */
 220 #define ELF_MACHINE_NO_REL 1
 221
 222 static inline void
 223 elf_machine_fixup_plt (struct link_map *map, const Elf32_Rela *reloc,
 224                        Elf32_Addr *reloc_addr, Elf32_Addr value)
 225 {
 226   *reloc_addr = value;
 227 }
 228
 229 /* Return the final value of a plt relocation.  On the m68k the JMP_SLOT
 230    relocation ignores the addend.  */
 231 static inline Elf32_Addr
 232 elf_machine_plt_value (struct link_map *map, const Elf32_Rela *reloc,
 233                        Elf32_Addr value)
 234 {
 235   return value;
 236 }
 237
 238 #endif /* !dl_machine_h */
 239
 240 #ifdef RESOLVE
 241
 242 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
 243    MAP is the object containing the reloc.  */
 244
 245 static inline void
 246 elf_machine_rela (struct link_map *map, const Elf32_Rela *reloc,
 247                   const Elf32_Sym *sym, const struct r_found_version *version,
 248                   Elf32_Addr *const reloc_addr)
 249 {
 250   if (ELF32_R_TYPE (reloc->r_info) == R_68K_RELATIVE)
 251     *reloc_addr = map->l_addr + reloc->r_addend;
 252   else
 253     {
 254       const Elf32_Sym *const refsym = sym;
 255       Elf32_Addr value = RESOLVE (&sym, version, ELF32_R_TYPE (reloc->r_info));
 256       if (sym)
 257         value += sym->st_value;
 258
 259       switch (ELF32_R_TYPE (reloc->r_info))
 260         {
 261         case R_68K_COPY:
 262           if (sym == NULL)
 263             /* This can happen in trace mode if an object could not be
 264                found.  */
 265             break;
 266           if (sym->st_size > refsym->st_size
 267               || (_dl_verbose && sym->st_size < refsym->st_size))
 268             {
 269               extern char **_dl_argv;
 270               const char *strtab;
 271
 272               strtab = ((void *) map->l_addr
 273                         + map->l_info[DT_STRTAB]->d_un.d_ptr);
 274               _dl_sysdep_error (_dl_argv[0] ?: "<program name unknown>",
 275                                 ": Symbol `", strtab + refsym->st_name,
 276                                 "' has different size in shared object, "
 277                                 "consider re-linking\n", NULL);
 278             }
 279           memcpy (reloc_addr, (void *) value, MIN (sym->st_size,
 280                                                    refsym->st_size));
 281           break;
 282         case R_68K_GLOB_DAT:
 283         case R_68K_JMP_SLOT:
 284           *reloc_addr = value;
 285           break;
 286         case R_68K_8:
 287           *(char *) reloc_addr = value + reloc->r_addend;
 288           break;
 289         case R_68K_16:
 290           *(short *) reloc_addr = value + reloc->r_addend;
 291           break;
 292         case R_68K_32:
 293           *reloc_addr = value + reloc->r_addend;
 294           break;
 295         case R_68K_PC8:
 296           *(char *) reloc_addr
 297             = value + reloc->r_addend - (Elf32_Addr) reloc_addr;
 298           break;
 299         case R_68K_PC16:
 300           *(short *) reloc_addr
 301             = value + reloc->r_addend - (Elf32_Addr) reloc_addr;
 302           break;
 303         case R_68K_PC32:
 304           *reloc_addr = value + reloc->r_addend - (Elf32_Addr) reloc_addr;
 305           break;
 306         case R_68K_NONE:                /* Alright, Wilbur.  */
 307           break;
 308         default:
 309           assert (! "unexpected dynamic reloc type");
 310           break;
 311         }
 312     }
 313 }
 314
 315 static inline void
 316 elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
 317 {
 318   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
 319   switch (ELF32_R_TYPE (reloc->r_info))
 320     {
 321     case R_68K_JMP_SLOT:
 322       *reloc_addr += map->l_addr;
 323       break;
 324     default:
 325       assert (! "unexpected PLT reloc type");
 326       break;
 327     }
 328 }
 329
 330 #endif /* RESOLVE */