sysdeps/sparc/dl-machine.h

   1 /* Machine-dependent ELF dynamic relocation inline functions.  SPARC 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.,
  18    59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  19
  20 #define ELF_MACHINE_NAME "sparc"
  21
  22 #include <assert.h>
  23 #include <string.h>
  24 #include <link.h>
  25
  26
  27 /* Some SPARC opcodes we need to use for self-modifying code.  */
  28 #define OPCODE_NOP      0x01000000 /* nop */
  29 #define OPCODE_CALL     0x04000000 /* call ?; add PC-rel word address */
  30 #define OPCODE_SETHI_G1 0x03000000 /* sethi ?, %g1; add value>>10 */
  31 #define OPCODE_JMP_G1   0x81c06000 /* jmp %g1+?; add lo 10 bits of value */
  32 #define OPCODE_SAVE_SP64 0x9de3bfc0 /* save %sp, -64, %sp */
  33
  34
  35 /* Return nonzero iff E_MACHINE is compatible with the running host.  */
  36 static inline int
  37 elf_machine_matches_host (Elf32_Half e_machine)
  38 {
  39   switch (e_machine)
  40     {
  41     case EM_SPARC:
  42       return 1;
  43     default:
  44       return 0;
  45     }
  46 }
  47
  48
  49 /* Return the link-time address of _DYNAMIC.  Conveniently, this is the
  50    first element of the GOT.  This must be inlined in a function which
  51    uses global data.  */
  52 static inline Elf32_Addr
  53 elf_machine_dynamic (void)
  54 {
  55   register Elf32_Addr *got asm ("%l7");
  56   return *got;
  57 }
  58
  59
  60 /* Return the run-time load address of the shared object.  */
  61 static inline Elf32_Addr
  62 elf_machine_load_address (void)
  63 {
  64   Elf32_Addr addr;
  65 ???
  66   return addr;
  67 }
  68
  69 /* The `subl' insn above will contain an R_68K_RELATIVE relocation
  70    entry intended to insert the run-time address of the label `here'.
  71    This will be the first relocation in the text of the dynamic
  72    linker; we skip it to avoid trying to modify read-only text in this
  73    early stage.  */
  74 #define ELF_MACHINE_BEFORE_RTLD_RELOC(dynamic_info) \
  75   ((dynamic_info)[DT_RELA]->d_un.d_ptr += sizeof (Elf32_Rela), \
  76    (dynamic_info)[DT_RELASZ]->d_un.d_val -= sizeof (Elf32_Rela))
  77
  78 /* Perform the relocation specified by RELOC and SYM (which is fully resolved).
  79    MAP is the object containing the reloc.  */
  80
  81 static inline void
  82 elf_machine_rela (struct link_map *map,
  83                   const Elf32_Rela *reloc, const Elf32_Sym *sym,
  84                   Elf32_Addr (*resolve) (const Elf32_Sym **ref,
  85                                          Elf32_Addr reloc_addr,
  86                                          int noplt))
  87 {
  88   Elf32_Addr *const reloc_addr = (void *) (map->l_addr + reloc->r_offset);
  89   Elf32_Addr loadbase;
  90
  91   switch (ELF32_R_TYPE (reloc->r_info))
  92     {
  93     case R_SPARC_COPY:
  94       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
  95       memcpy (reloc_addr, (void *) (loadbase + sym->st_value), sym->st_size);
  96       break;
  97     case R_SPARC_GLOB_DAT:
  98     case R_SPARC_32:
  99       loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0) :
 100                   /* RESOLVE is null during bootstrap relocation.  */
 101                   map->l_addr);
 102       *reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 103                      + reloc->r_addend);
 104       break;
 105     case R_SPARC_JMP_SLOT:
 106       loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 1) :
 107                   /* RESOLVE is null during bootstrap relocation.  */
 108                   map->l_addr);
 109       {
 110         Elf32_Addr value = ((sym ? (loadbase + sym->st_value) : 0)
 111                             + reloc->r_addend);
 112         reloc_addr[1] = OPCODE_SETHI | (value >> 10);
 113         reloc_addr[2] = OPCODE_JMP_G1 | (value & 0x3ff);
 114       }
 115       break;
 116     case R_SPARC_8:
 117       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 118       *(char *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 119                               + reloc->r_addend);
 120       break;
 121     case R_SPARC_16:
 122       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 123       *(short *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 124                                + reloc->r_addend);
 125       break;
 126     case R_SPARC_32:
 127       loadbase = (resolve ? (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0) :
 128                   /* RESOLVE is null during bootstrap relocation.  */
 129                   map->l_addr);
 130       break;
 131     case R_SPARC_RELATIVE:
 132       *reloc_addr = map->l_addr + reloc->r_addend;
 133       break;
 134     case R_SPARC_DISP8:
 135       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 136       *(char *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 137                               + reloc->r_addend
 138                               - (Elf32_Addr) reloc_addr);
 139       break;
 140     case R_SPARC_DISP16:
 141       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 142       *(short *) reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 143                                + reloc->r_addend
 144                                - (Elf32_Addr) reloc_addr);
 145       break;
 146     case R_SPARC_DISP32:
 147       loadbase = (*resolve) (&sym, (Elf32_Addr) reloc_addr, 0);
 148       *reloc_addr = ((sym ? (loadbase + sym->st_value) : 0)
 149                      + reloc->r_addend
 150                      - (Elf32_Addr) reloc_addr);
 151       break;
 152     case R_SPARC_NONE:          /* Alright, Wilbur.  */
 153       break;
 154     default:
 155       assert (! "unexpected dynamic reloc type");
 156       break;
 157     }
 158 }
 159
 160 static inline void
 161 elf_machine_lazy_rel (struct link_map *map, const Elf32_Rela *reloc)
 162 {
 163   switch (ELF32_R_TYPE (reloc->r_info))
 164     {
 165     case R_SPARC_NONE:
 166       break;
 167     case R_SPARC_JMP_SLOT:
 168       break;
 169     default:
 170       assert (! "unexpected PLT reloc type");
 171       break;
 172     }
 173 }
 174
 175 /* Nonzero iff TYPE describes relocation of a PLT entry, so
 176    PLT entries should not be allowed to define the value.  */
 177 #define elf_machine_pltrel_p(type) ((type) == R_SPARC_JMP_SLOT)
 178
 179 /* The SPARC never uses Elf32_Rel relocations.  */
 180 #define ELF_MACHINE_NO_REL 1
 181
 182
 183 /* Set up the loaded object described by L so its unrelocated PLT
 184    entries will jump to the on-demand fixup code in dl-runtime.c.  */
 185
 186 static inline void
 187 elf_machine_runtime_setup (struct link_map *l, int lazy)
 188 {
 189   Elf32_Addr *plt;
 190   extern void _dl_runtime_resolve (Elf32_Word);
 191
 192   if (l->l_info[DT_JMPREL] && lazy)
 193     {
 194       /* The entries for functions in the PLT have not yet been filled in.
 195          Their initial contents will arrange when called to set the high 22
 196          bits of %g1 with an offset into the .rela.plt section and jump to
 197          the beginning of the PLT.  */
 198       plt = (Elf32_Addr *) (l->l_addr + l->l_info[DT_PLTGOT]->d_un.d_ptr);
 199
 200       /* The beginning of the PLT does:
 201
 202                 save %sp, -64, %sp
 203          pltpc: call _dl_runtime_resolve
 204                 nop
 205                 .word MAP
 206
 207          This saves the register window containing the arguments, and the
 208          PC value (pltpc) implicitly saved in %o7 by the call points near the
 209          location where we store the link_map pointer for this object.  */
 210
 211       plt[0] = OPCODE_SAVE_SP64; /* save %sp, -64, %sp */
 212       /* Construct PC-relative word address.  */
 213       plt[1] = OPCODE_CALL | (((Elf32_Addr) &_dl_runtime_resolve -
 214                                (Elf32_Addr) &plt[1]) >> 2);
 215       plt[2] = OPCODE_NOP;      /* Fill call delay slot.  */
 216       plt[3] = l;
 217     }
 218
 219   /* This code is used in dl-runtime.c to call the `fixup' function
 220      and then redirect to the address it returns.  */
 221 #define ELF_MACHINE_RUNTIME_TRAMPOLINE asm ("\
 222 | Trampoline for _dl_runtime_resolver
 223         .globl _dl_runtime_resolve
 224         .type _dl_runtime_resolve, @function
 225 _dl_runtime_resolve:
 226         | Pass two args to fixup: the PLT address computed from the PC saved
 227         | in the PLT's call insn, and the reloc offset passed in %g1.
 228         ld [%o7 + 8], %o1       | Second arg, loaded from PLTPC[2].
 229         call fixup
 230         shrl %g1, 22, %o0       | First arg, set in delay slot of call.
 231         | Jump to the real function.
 232         jmpl %o0, %g0
 233         | In the delay slot of that jump, restore the register window
 234         | saved by the first insn of the PLT.
 235         restore
 236         .size _dl_runtime_resolve, . - _dl_runtime_resolve
 237 ");
 238 /* The PLT uses Elf32_Rela relocs.  */
 239 #define elf_machine_relplt elf_machine_rela
 240 }
 241
 242
 243 /* Mask identifying addresses reserved for the user program,
 244    where the dynamic linker should not map anything.  */
 245 #define ELF_MACHINE_USER_ADDRESS_MASK   ???
 246
 247 /* Initial entry point code for the dynamic linker.
 248    The C function `_dl_start' is the real entry point;
 249    its return value is the user program's entry point.  */
 250
 251 #define RTLD_START asm (???)