sysdeps/mips/dl-trampoline.c

   1 /* PLT trampoline.  MIPS version.
   2    Copyright (C) 1996-2001, 2002, 2003, 2004, 2005
   3    Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5    Contributed by Kazumoto Kojima <kkojima@info.kanagawa-u.ac.jp>.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, write to the Free
  19    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  20    02111-1307 USA.  */
  21
  22 /*  FIXME: Profiling of shared libraries is not implemented yet.  */
  23
  24 #include <sysdep.h>
  25 #include <link.h>
  26 #include <elf.h>
  27 #include <ldsodefs.h>
  28 #include <dl-machine.h>
  29
  30 /* Get link map for callers object containing STUB_PC.  */
  31 static inline struct link_map *
  32 elf_machine_runtime_link_map (ElfW(Addr) gpreg, ElfW(Addr) stub_pc)
  33 {
  34   extern int _dl_mips_gnu_objects;
  35
  36   /* got[1] is reserved to keep its link map address for the shared
  37      object generated by the gnu linker.  If all are such objects, we
  38      can find the link map from current GPREG simply.  If not so, get
  39      the link map for caller's object containing STUB_PC.  */
  40
  41   if (_dl_mips_gnu_objects)
  42     {
  43       ElfW(Addr) *got = elf_mips_got_from_gpreg (gpreg);
  44       ElfW(Word) g1;
  45
  46       g1 = ((ElfW(Word) *) got)[1];
  47
  48       if ((g1 & ELF_MIPS_GNU_GOT1_MASK) != 0)
  49         {
  50           struct link_map *l =
  51             (struct link_map *) (g1 & ~ELF_MIPS_GNU_GOT1_MASK);
  52           ElfW(Addr) base, limit;
  53           const ElfW(Phdr) *p = l->l_phdr;
  54           ElfW(Half) this, nent = l->l_phnum;
  55
  56           /* For the common case of a stub being called from the containing
  57              object, STUB_PC will point to somewhere within the object that
  58              is described by the link map fetched via got[1].  Otherwise we
  59              have to scan all maps.  */
  60           for (this = 0; this < nent; this++)
  61             {
  62               if (p[this].p_type == PT_LOAD)
  63                 {
  64                   base = p[this].p_vaddr + l->l_addr;
  65                   limit = base + p[this].p_memsz;
  66                   if (stub_pc >= base && stub_pc < limit)
  67                     return l;
  68                 }
  69             }
  70         }
  71     }
  72
  73     struct link_map *l;
  74     Lmid_t nsid;
  75
  76     for (nsid = 0; nsid < DL_NNS; ++nsid)
  77       for (l = GL(dl_ns)[nsid]._ns_loaded; l != NULL; l = l->l_next)
  78         {
  79           ElfW(Addr) base, limit;
  80           const ElfW(Phdr) *p = l->l_phdr;
  81           ElfW(Half) this, nent = l->l_phnum;
  82
  83           for (this = 0; this < nent; ++this)
  84             {
  85               if (p[this].p_type == PT_LOAD)
  86                 {
  87                   base = p[this].p_vaddr + l->l_addr;
  88                   limit = base + p[this].p_memsz;
  89                   if (stub_pc >= base && stub_pc < limit)
  90                     return l;
  91                 }
  92             }
  93         }
  94
  95   _dl_signal_error (0, NULL, NULL, "cannot find runtime link map");
  96   return NULL;
  97 }
  98
  99 /* Define mips specific runtime resolver. The function __dl_runtime_resolve
 100    is called from assembler function _dl_runtime_resolve which converts
 101    special argument registers t7 ($15) and t8 ($24):
 102      t7  address to return to the caller of the function
 103      t8  index for this function symbol in .dynsym
 104    to usual c arguments.
 105
 106    Other architectures call fixup from dl-runtime.c in
 107    _dl_runtime_resolve.  MIPS instead calls __dl_runtime_resolve.  We
 108    have to use our own version because of the way the got section is
 109    treated on MIPS (we've also got ELF_MACHINE_PLT defined).  */
 110
 111 /* The flag _dl_mips_gnu_objects is set if all dynamic objects are
 112    generated by the gnu linker. */
 113 int _dl_mips_gnu_objects = 1;
 114
 115 #define VERSYMIDX(sym)  (DT_NUM + DT_THISPROCNUM + DT_VERSIONTAGIDX (sym))
 116
 117 /* This is called from assembly stubs below which the compiler can't see.  */
 118 static ElfW(Addr)
 119 __dl_runtime_resolve (ElfW(Word), ElfW(Word), ElfW(Addr), ElfW(Addr))
 120                   __attribute_used__;
 121
 122 static ElfW(Addr)
 123 __dl_runtime_resolve (ElfW(Word) sym_index,
 124                       ElfW(Word) return_address,
 125                       ElfW(Addr) old_gpreg,
 126                       ElfW(Addr) stub_pc)
 127 {
 128   struct link_map *l = elf_machine_runtime_link_map (old_gpreg, stub_pc);
 129   const ElfW(Sym) *const symtab
 130     = (const ElfW(Sym) *) D_PTR (l, l_info[DT_SYMTAB]);
 131   const char *strtab = (const void *) D_PTR (l, l_info[DT_STRTAB]);
 132   ElfW(Addr) *got
 133     = (ElfW(Addr) *) D_PTR (l, l_info[DT_PLTGOT]);
 134   const ElfW(Word) local_gotno
 135     = (const ElfW(Word)) l->l_info[DT_MIPS (LOCAL_GOTNO)]->d_un.d_val;
 136   const ElfW(Word) gotsym
 137     = (const ElfW(Word)) l->l_info[DT_MIPS (GOTSYM)]->d_un.d_val;
 138   const ElfW(Sym) *sym = &symtab[sym_index];
 139   struct link_map *sym_map;
 140   ElfW(Addr) value;
 141
 142   /* FIXME: The symbol versioning stuff is not tested yet.  */
 143   if (__builtin_expect (ELFW(ST_VISIBILITY) (sym->st_other), 0) == 0)
 144     {
 145       switch (l->l_info[VERSYMIDX (DT_VERSYM)] != NULL)
 146         {
 147         default:
 148           {
 149             const ElfW(Half) *vernum =
 150               (const void *) D_PTR (l, l_info[VERSYMIDX (DT_VERSYM)]);
 151             ElfW(Half) ndx = vernum[sym_index] & 0x7fff;
 152             const struct r_found_version *version = &l->l_versions[ndx];
 153
 154             if (version->hash != 0)
 155               {
 156                 sym_map = _dl_lookup_symbol_x (strtab + sym->st_name, l,
 157                                                &sym, l->l_scope, version,
 158                                                ELF_RTYPE_CLASS_PLT, 0, 0);
 159                 break;
 160               }
 161             /* Fall through.  */
 162           }
 163         case 0:
 164           sym_map = _dl_lookup_symbol_x (strtab + sym->st_name, l, &sym,
 165                                          l->l_scope, 0, ELF_RTYPE_CLASS_PLT,
 166                                          DL_LOOKUP_ADD_DEPENDENCY, 0);
 167         }
 168
 169       /* Currently value contains the base load address of the object
 170          that defines sym.  Now add in the symbol offset.  */
 171       value = (sym ? sym_map->l_addr + sym->st_value : 0);
 172     }
 173   else
 174     /* We already found the symbol.  The module (and therefore its load
 175        address) is also known.  */
 176     value = l->l_addr + sym->st_value;
 177
 178   /* Apply the relocation with that value.  */
 179   *(got + local_gotno + sym_index - gotsym) = value;
 180
 181   return value;
 182 }
 183
 184 #if _MIPS_SIM == _ABIO32
 185 #define ELF_DL_FRAME_SIZE 40
 186
 187 #define ELF_DL_SAVE_ARG_REGS "\
 188         sw      $15, 36($29)\n                                                \
 189         sw      $4, 16($29)\n                                                 \
 190         sw      $5, 20($29)\n                                                 \
 191         sw      $6, 24($29)\n                                                 \
 192         sw      $7, 28($29)\n                                                 \
 193 "
 194
 195 #define ELF_DL_RESTORE_ARG_REGS "\
 196         lw      $31, 36($29)\n                                                \
 197         lw      $4, 16($29)\n                                                 \
 198         lw      $5, 20($29)\n                                                 \
 199         lw      $6, 24($29)\n                                                 \
 200         lw      $7, 28($29)\n                                                 \
 201 "
 202
 203 /* The PLT resolver should also save and restore $2 and $3, which are used
 204    as arguments to MIPS16 stub functions.  */
 205 #define ELF_DL_PLT_FRAME_SIZE 48
 206
 207 #define ELF_DL_PLT_SAVE_ARG_REGS \
 208         ELF_DL_SAVE_ARG_REGS "\
 209         sw      $2, 40($29)\n                                                 \
 210         sw      $3, 44($29)\n                                                 \
 211 "
 212
 213 #define ELF_DL_PLT_RESTORE_ARG_REGS \
 214         ELF_DL_RESTORE_ARG_REGS "\
 215         lw      $2, 40($29)\n                                                 \
 216         lw      $3, 44($29)\n                                                 \
 217 "
 218
 219 #define IFABIO32(X) X
 220 #define IFNEWABI(X)
 221
 222 #else /* _MIPS_SIM == _ABIN32 || _MIPS_SIM == _ABI64 */
 223
 224 #define ELF_DL_FRAME_SIZE 80
 225
 226 #define ELF_DL_SAVE_ARG_REGS "\
 227         sd      $15, 72($29)\n                                                \
 228         sd      $4, 8($29)\n                                                  \
 229         sd      $5, 16($29)\n                                                 \
 230         sd      $6, 24($29)\n                                                 \
 231         sd      $7, 32($29)\n                                                 \
 232         sd      $8, 40($29)\n                                                 \
 233         sd      $9, 48($29)\n                                                 \
 234         sd      $10, 56($29)\n                                                \
 235         sd      $11, 64($29)\n                                                \
 236 "
 237
 238 #define ELF_DL_RESTORE_ARG_REGS "\
 239         ld      $31, 72($29)\n                                                \
 240         ld      $4, 8($29)\n                                                  \
 241         ld      $5, 16($29)\n                                                 \
 242         ld      $6, 24($29)\n                                                 \
 243         ld      $7, 32($29)\n                                                 \
 244         ld      $8, 40($29)\n                                                 \
 245         ld      $9, 48($29)\n                                                 \
 246         ld      $10, 56($29)\n                                                \
 247         ld      $11, 64($29)\n                                                \
 248 "
 249
 250 /* The PLT resolver should also save and restore $2 and $3, which are used
 251    as arguments to MIPS16 stub functions.  */
 252 #define ELF_DL_PLT_FRAME_SIZE 96
 253
 254 #define ELF_DL_PLT_SAVE_ARG_REGS \
 255         ELF_DL_SAVE_ARG_REGS "\
 256         sd      $2, 80($29)\n                                                 \
 257         sd      $3, 88($29)\n                                                 \
 258 "
 259
 260 #define ELF_DL_PLT_RESTORE_ARG_REGS \
 261         ELF_DL_RESTORE_ARG_REGS "\
 262         ld      $2, 80($29)\n                                                 \
 263         ld      $3, 88($29)\n                                                 \
 264 "
 265
 266 #define IFABIO32(X)
 267 #define IFNEWABI(X) X
 268
 269 #endif
 270
 271 asm ("\n\
 272         .text\n\
 273         .align  2\n\
 274         .globl  _dl_runtime_resolve\n\
 275         .type   _dl_runtime_resolve,@function\n\
 276         .ent    _dl_runtime_resolve\n\
 277 _dl_runtime_resolve:\n\
 278         .frame  $29, " STRINGXP(ELF_DL_FRAME_SIZE) ", $31\n\
 279         .set noreorder\n\
 280         # Save GP.\n\
 281         move    $3, $28\n\
 282         # Save arguments and sp value in stack.\n\
 283         " STRINGXP(PTR_SUBIU) "  $29, " STRINGXP(ELF_DL_FRAME_SIZE) "\n\
 284         # Modify t9 ($25) so as to point .cpload instruction.\n\
 285         " IFABIO32(STRINGXP(PTR_ADDIU) "        $25, 12\n") "\
 286         # Compute GP.\n\
 287         " STRINGXP(SETUP_GP) "\n\
 288         " STRINGXV(SETUP_GP64 (0, _dl_runtime_resolve)) "\n\
 289         .set reorder\n\
 290         # Save slot call pc.\n\
 291         move    $2, $31\n\
 292         " IFABIO32(STRINGXP(CPRESTORE(32))) "\n\
 293         " ELF_DL_SAVE_ARG_REGS "\
 294         move    $4, $24\n\
 295         move    $5, $15\n\
 296         move    $6, $3\n\
 297         move    $7, $2\n\
 298         jal     __dl_runtime_resolve\n\
 299         " ELF_DL_RESTORE_ARG_REGS "\
 300         " STRINGXP(RESTORE_GP64) "\n\
 301         " STRINGXP(PTR_ADDIU) " $29, " STRINGXP(ELF_DL_FRAME_SIZE) "\n\
 302         move    $25, $2\n\
 303         jr      $25\n\
 304         .end    _dl_runtime_resolve\n\
 305         .previous\n\
 306 ");
 307
 308 /* Assembler veneer called from the PLT header code when using PLTs.
 309
 310    Code in each PLT entry and the PLT header fills in the arguments to
 311    this function:
 312
 313    - $15 (o32 t7, n32/n64 t3) - caller's return address
 314    - $24 (t8) - PLT entry index
 315    - $25 (t9) - address of _dl_runtime_pltresolve
 316    - o32 $28 (gp), n32/n64 $14 (t2) - address of .got.plt
 317
 318    Different registers are used for .got.plt because the ABI was
 319    originally designed for o32, where gp was available (call
 320    clobbered).  On n32/n64 gp is call saved.
 321
 322    _dl_fixup needs:
 323
 324    - $4 (a0) - link map address
 325    - $5 (a1) - .rel.plt offset (== PLT entry index * 8)  */
 326
 327 asm ("\n\
 328         .text\n\
 329         .align  2\n\
 330         .globl  _dl_runtime_pltresolve\n\
 331         .type   _dl_runtime_pltresolve,@function\n\
 332         .ent    _dl_runtime_pltresolve\n\
 333 _dl_runtime_pltresolve:\n\
 334         .frame  $29, " STRINGXP(ELF_DL_PLT_FRAME_SIZE) ", $31\n\
 335         .set noreorder\n\
 336         # Save arguments and sp value in stack.\n\
 337         " STRINGXP(PTR_SUBIU) " $29, " STRINGXP(ELF_DL_PLT_FRAME_SIZE) "\n\
 338         " IFABIO32(STRINGXP(PTR_L) "    $13, " STRINGXP(PTRSIZE) "($28)") "\n\
 339         " IFNEWABI(STRINGXP(PTR_L) "    $13, " STRINGXP(PTRSIZE) "($14)") "\n\
 340         # Modify t9 ($25) so as to point .cpload instruction.\n\
 341         " IFABIO32(STRINGXP(PTR_ADDIU) "        $25, 12\n") "\
 342         # Compute GP.\n\
 343         " STRINGXP(SETUP_GP) "\n\
 344         " STRINGXV(SETUP_GP64 (0, _dl_runtime_pltresolve)) "\n\
 345         .set reorder\n\
 346         " IFABIO32(STRINGXP(CPRESTORE(32))) "\n\
 347         " ELF_DL_PLT_SAVE_ARG_REGS "\
 348         move    $4, $13\n\
 349         sll     $5, $24, " STRINGXP(PTRLOG) " + 1\n\
 350         jal     _dl_fixup\n\
 351         move    $25, $2\n\
 352         " ELF_DL_PLT_RESTORE_ARG_REGS "\
 353         " STRINGXP(RESTORE_GP64) "\n\
 354         " STRINGXP(PTR_ADDIU) " $29, " STRINGXP(ELF_DL_PLT_FRAME_SIZE) "\n\
 355         jr      $25\n\
 356         .end    _dl_runtime_pltresolve\n\
 357         .previous\n\
 358 ");
 359