gdb/ppc64-tdep.c

   1 /* Common target-dependent code for ppc64 GDB, the GNU debugger.
   2
   3    Copyright (C) 1986-2014 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program 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
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "frame.h"
  22 #include "gdbcore.h"
  23 #include "ppc-tdep.h"
  24 #include "ppc64-tdep.h"
  25 #include "elf-bfd.h"
  26
  27 /* Macros for matching instructions.  Note that, since all the
  28    operands are masked off before they're or-ed into the instruction,
  29    you can use -1 to make masks.  */
  30
  31 #define insn_d(opcd, rts, ra, d)                \
  32   ((((opcd) & 0x3f) << 26)                      \
  33    | (((rts) & 0x1f) << 21)                     \
  34    | (((ra) & 0x1f) << 16)                      \
  35    | ((d) & 0xffff))
  36
  37 #define insn_ds(opcd, rts, ra, d, xo)           \
  38   ((((opcd) & 0x3f) << 26)                      \
  39    | (((rts) & 0x1f) << 21)                     \
  40    | (((ra) & 0x1f) << 16)                      \
  41    | ((d) & 0xfffc)                             \
  42    | ((xo) & 0x3))
  43
  44 #define insn_xfx(opcd, rts, spr, xo)            \
  45   ((((opcd) & 0x3f) << 26)                      \
  46    | (((rts) & 0x1f) << 21)                     \
  47    | (((spr) & 0x1f) << 16)                     \
  48    | (((spr) & 0x3e0) << 6)                     \
  49    | (((xo) & 0x3ff) << 1))
  50
  51 /* If PLT is the address of a 64-bit PowerPC PLT entry,
  52    return the function's entry point.  */
  53
  54 static CORE_ADDR
  55 ppc64_plt_entry_point (struct gdbarch *gdbarch, CORE_ADDR plt)
  56 {
  57   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
  58   /* The first word of the PLT entry is the function entry point.  */
  59   return (CORE_ADDR) read_memory_unsigned_integer (plt, 8, byte_order);
  60 }
  61
  62 /* Patterns for the standard linkage functions.  These are built by
  63    build_plt_stub in bfd/elf64-ppc.c.  */
  64
  65 /* Old ELFv1 PLT call stub.  */
  66
  67 static struct ppc_insn_pattern ppc64_standard_linkage1[] =
  68   {
  69     /* addis r12, r2, <any> */
  70     { insn_d (-1, -1, -1, 0), insn_d (15, 12, 2, 0), 0 },
  71
  72     /* std r2, 40(r1) */
  73     { -1, insn_ds (62, 2, 1, 40, 0), 0 },
  74
  75     /* ld r11, <any>(r12) */
  76     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 0 },
  77
  78     /* addis r12, r12, 1 <optional> */
  79     { insn_d (-1, -1, -1, -1), insn_d (15, 12, 12, 1), 1 },
  80
  81     /* ld r2, <any>(r12) */
  82     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 12, 0, 0), 0 },
  83
  84     /* addis r12, r12, 1 <optional> */
  85     { insn_d (-1, -1, -1, -1), insn_d (15, 12, 12, 1), 1 },
  86
  87     /* mtctr r11 */
  88     { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 },
  89
  90     /* ld r11, <any>(r12) <optional> */
  91     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 1 },
  92
  93     /* bctr */
  94     { -1, 0x4e800420, 0 },
  95
  96     { 0, 0, 0 }
  97   };
  98
  99 /* ELFv1 PLT call stub to access PLT entries more than +/- 32k from r2.
 100    Also supports older stub with different placement of std 2,40(1),
 101    a stub that omits the std 2,40(1), and both versions of power7
 102    thread safety read barriers.  Note that there are actually two more
 103    instructions following "cmpldi r2, 0", "bnectr+" and "b <glink_i>",
 104    but there isn't any need to match them.  */
 105
 106 static struct ppc_insn_pattern ppc64_standard_linkage2[] =
 107   {
 108     /* std r2, 40(r1) <optional> */
 109     { -1, insn_ds (62, 2, 1, 40, 0), 1 },
 110
 111     /* addis r12, r2, <any> */
 112     { insn_d (-1, -1, -1, 0), insn_d (15, 12, 2, 0), 0 },
 113
 114     /* std r2, 40(r1) <optional> */
 115     { -1, insn_ds (62, 2, 1, 40, 0), 1 },
 116
 117     /* ld r11, <any>(r12) */
 118     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 0 },
 119
 120     /* addi r12, r12, <any> <optional> */
 121     { insn_d (-1, -1, -1, 0), insn_d (14, 12, 12, 0), 1 },
 122
 123     /* mtctr r11 */
 124     { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 },
 125
 126     /* xor r11, r11, r11 <optional> */
 127     { -1, 0x7d6b5a78, 1 },
 128
 129     /* add r12, r12, r11 <optional> */
 130     { -1, 0x7d8c5a14, 1 },
 131
 132     /* ld r2, <any>(r12) */
 133     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 12, 0, 0), 0 },
 134
 135     /* ld r11, <any>(r12) <optional> */
 136     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 1 },
 137
 138     /* bctr <optional> */
 139     { -1, 0x4e800420, 1 },
 140
 141     /* cmpldi r2, 0 <optional> */
 142     { -1, 0x28220000, 1 },
 143
 144     { 0, 0, 0 }
 145   };
 146
 147 /* ELFv1 PLT call stub to access PLT entries within +/- 32k of r2.  */
 148
 149 static struct ppc_insn_pattern ppc64_standard_linkage3[] =
 150   {
 151     /* std r2, 40(r1) <optional> */
 152     { -1, insn_ds (62, 2, 1, 40, 0), 1 },
 153
 154     /* ld r11, <any>(r2) */
 155     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 2, 0, 0), 0 },
 156
 157     /* addi r2, r2, <any> <optional> */
 158     { insn_d (-1, -1, -1, 0), insn_d (14, 2, 2, 0), 1 },
 159
 160     /* mtctr r11 */
 161     { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 },
 162
 163     /* xor r11, r11, r11 <optional> */
 164     { -1, 0x7d6b5a78, 1 },
 165
 166     /* add r2, r2, r11 <optional> */
 167     { -1, 0x7c425a14, 1 },
 168
 169     /* ld r11, <any>(r2) <optional> */
 170     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 2, 0, 0), 1 },
 171
 172     /* ld r2, <any>(r2) */
 173     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 2, 0, 0), 0 },
 174
 175     /* bctr <optional> */
 176     { -1, 0x4e800420, 1 },
 177
 178     /* cmpldi r2, 0 <optional> */
 179     { -1, 0x28220000, 1 },
 180
 181     { 0, 0, 0 }
 182   };
 183
 184 /* ELFv1 PLT call stub to access PLT entries more than +/- 32k from r2.
 185    A more modern variant of ppc64_standard_linkage2 differing in
 186    register usage.  */
 187
 188 static struct ppc_insn_pattern ppc64_standard_linkage4[] =
 189   {
 190     /* std r2, 40(r1) <optional> */
 191     { -1, insn_ds (62, 2, 1, 40, 0), 1 },
 192
 193     /* addis r11, r2, <any> */
 194     { insn_d (-1, -1, -1, 0), insn_d (15, 11, 2, 0), 0 },
 195
 196     /* ld r12, <any>(r11) */
 197     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 11, 0, 0), 0 },
 198
 199     /* addi r11, r11, <any> <optional> */
 200     { insn_d (-1, -1, -1, 0), insn_d (14, 11, 11, 0), 1 },
 201
 202     /* mtctr r12 */
 203     { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 },
 204
 205     /* xor r2, r12, r12 <optional> */
 206     { -1, 0x7d826278, 1 },
 207
 208     /* add r11, r11, r2 <optional> */
 209     { -1, 0x7d6b1214, 1 },
 210
 211     /* ld r2, <any>(r11) */
 212     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 11, 0, 0), 0 },
 213
 214     /* ld r11, <any>(r11) <optional> */
 215     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 11, 0, 0), 1 },
 216
 217     /* bctr <optional> */
 218     { -1, 0x4e800420, 1 },
 219
 220     /* cmpldi r2, 0 <optional> */
 221     { -1, 0x28220000, 1 },
 222
 223     { 0, 0, 0 }
 224   };
 225
 226 /* ELFv1 PLT call stub to access PLT entries within +/- 32k of r2.
 227    A more modern variant of ppc64_standard_linkage3 differing in
 228    register usage.  */
 229
 230 static struct ppc_insn_pattern ppc64_standard_linkage5[] =
 231   {
 232     /* std r2, 40(r1) <optional> */
 233     { -1, insn_ds (62, 2, 1, 40, 0), 1 },
 234
 235     /* ld r12, <any>(r2) */
 236     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 2, 0, 0), 0 },
 237
 238     /* addi r2, r2, <any> <optional> */
 239     { insn_d (-1, -1, -1, 0), insn_d (14, 2, 2, 0), 1 },
 240
 241     /* mtctr r12 */
 242     { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 },
 243
 244     /* xor r11, r12, r12 <optional> */
 245     { -1, 0x7d8b6278, 1 },
 246
 247     /* add r2, r2, r11 <optional> */
 248     { -1, 0x7c425a14, 1 },
 249
 250     /* ld r11, <any>(r2) <optional> */
 251     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 2, 0, 0), 1 },
 252
 253     /* ld r2, <any>(r2) */
 254     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 2, 0, 0), 0 },
 255
 256     /* bctr <optional> */
 257     { -1, 0x4e800420, 1 },
 258
 259     /* cmpldi r2, 0 <optional> */
 260     { -1, 0x28220000, 1 },
 261
 262     { 0, 0, 0 }
 263   };
 264
 265 /* ELFv2 PLT call stub to access PLT entries more than +/- 32k from r2.  */
 266
 267 static struct ppc_insn_pattern ppc64_standard_linkage6[] =
 268   {
 269     /* std r2, 24(r1) <optional> */
 270     { -1, insn_ds (62, 2, 1, 24, 0), 1 },
 271
 272     /* addis r11, r2, <any> */
 273     { insn_d (-1, -1, -1, 0), insn_d (15, 11, 2, 0), 0 },
 274
 275     /* ld r12, <any>(r11) */
 276     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 11, 0, 0), 0 },
 277
 278     /* mtctr r12 */
 279     { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 },
 280
 281     /* bctr */
 282     { -1, 0x4e800420, 0 },
 283
 284     { 0, 0, 0 }
 285   };
 286
 287 /* ELFv2 PLT call stub to access PLT entries within +/- 32k of r2.  */
 288
 289 static struct ppc_insn_pattern ppc64_standard_linkage7[] =
 290   {
 291     /* std r2, 24(r1) <optional> */
 292     { -1, insn_ds (62, 2, 1, 24, 0), 1 },
 293
 294     /* ld r12, <any>(r2) */
 295     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 2, 0, 0), 0 },
 296
 297     /* mtctr r12 */
 298     { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 },
 299
 300     /* bctr */
 301     { -1, 0x4e800420, 0 },
 302
 303     { 0, 0, 0 }
 304   };
 305
 306 /* ELFv2 PLT call stub to access PLT entries more than +/- 32k from r2,
 307    supporting fusion.  */
 308
 309 static struct ppc_insn_pattern ppc64_standard_linkage8[] =
 310   {
 311     /* std r2, 24(r1) <optional> */
 312     { -1, insn_ds (62, 2, 1, 24, 0), 1 },
 313
 314     /* addis r12, r2, <any> */
 315     { insn_d (-1, -1, -1, 0), insn_d (15, 12, 2, 0), 0 },
 316
 317     /* ld r12, <any>(r12) */
 318     { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 12, 0, 0), 0 },
 319
 320     /* mtctr r12 */
 321     { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 },
 322
 323     /* bctr */
 324     { -1, 0x4e800420, 0 },
 325
 326     { 0, 0, 0 }
 327   };
 328
 329 /* When the dynamic linker is doing lazy symbol resolution, the first
 330    call to a function in another object will go like this:
 331
 332    - The user's function calls the linkage function:
 333
 334         100003d4:   4b ff ff ad     bl      10000380 <nnnn.plt_call.printf>
 335         100003d8:   e8 41 00 28     ld      r2,40(r1)
 336
 337    - The linkage function loads the entry point and toc pointer from
 338      the function descriptor in the PLT, and jumps to it:
 339
 340      <nnnn.plt_call.printf>:
 341         10000380:   f8 41 00 28     std     r2,40(r1)
 342         10000384:   e9 62 80 78     ld      r11,-32648(r2)
 343         10000388:   7d 69 03 a6     mtctr   r11
 344         1000038c:   e8 42 80 80     ld      r2,-32640(r2)
 345         10000390:   28 22 00 00     cmpldi  r2,0
 346         10000394:   4c e2 04 20     bnectr+
 347         10000398:   48 00 03 a0     b       10000738 <printf@plt>
 348
 349    - But since this is the first time that PLT entry has been used, it
 350      sends control to its glink entry.  That loads the number of the
 351      PLT entry and jumps to the common glink0 code:
 352
 353      <printf@plt>:
 354         10000738:   38 00 00 01     li      r0,1
 355         1000073c:   4b ff ff bc     b       100006f8 <__glink_PLTresolve>
 356
 357    - The common glink0 code then transfers control to the dynamic
 358      linker's fixup code:
 359
 360         100006f0:   0000000000010440 .quad plt0 - (. + 16)
 361      <__glink_PLTresolve>:
 362         100006f8:   7d 88 02 a6     mflr    r12
 363         100006fc:   42 9f 00 05     bcl     20,4*cr7+so,10000700
 364         10000700:   7d 68 02 a6     mflr    r11
 365         10000704:   e8 4b ff f0     ld      r2,-16(r11)
 366         10000708:   7d 88 03 a6     mtlr    r12
 367         1000070c:   7d 82 5a 14     add     r12,r2,r11
 368         10000710:   e9 6c 00 00     ld      r11,0(r12)
 369         10000714:   e8 4c 00 08     ld      r2,8(r12)
 370         10000718:   7d 69 03 a6     mtctr   r11
 371         1000071c:   e9 6c 00 10     ld      r11,16(r12)
 372         10000720:   4e 80 04 20     bctr
 373
 374    Eventually, this code will figure out how to skip all of this,
 375    including the dynamic linker.  At the moment, we just get through
 376    the linkage function.  */
 377
 378 /* If the current thread is about to execute a series of instructions
 379    at PC matching the ppc64_standard_linkage pattern, and INSN is the result
 380    from that pattern match, return the code address to which the
 381    standard linkage function will send them.  (This doesn't deal with
 382    dynamic linker lazy symbol resolution stubs.)  */
 383
 384 static CORE_ADDR
 385 ppc64_standard_linkage1_target (struct frame_info *frame,
 386                                 CORE_ADDR pc, unsigned int *insn)
 387 {
 388   struct gdbarch *gdbarch = get_frame_arch (frame);
 389   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 390
 391   /* The address of the PLT entry this linkage function references.  */
 392   CORE_ADDR plt
 393     = ((CORE_ADDR) get_frame_register_unsigned (frame,
 394                                                 tdep->ppc_gp0_regnum + 2)
 395        + (ppc_insn_d_field (insn[0]) << 16)
 396        + ppc_insn_ds_field (insn[2]));
 397
 398   return ppc64_plt_entry_point (gdbarch, plt);
 399 }
 400
 401 static CORE_ADDR
 402 ppc64_standard_linkage2_target (struct frame_info *frame,
 403                                 CORE_ADDR pc, unsigned int *insn)
 404 {
 405   struct gdbarch *gdbarch = get_frame_arch (frame);
 406   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 407
 408   /* The address of the PLT entry this linkage function references.  */
 409   CORE_ADDR plt
 410     = ((CORE_ADDR) get_frame_register_unsigned (frame,
 411                                                 tdep->ppc_gp0_regnum + 2)
 412        + (ppc_insn_d_field (insn[1]) << 16)
 413        + ppc_insn_ds_field (insn[3]));
 414
 415   return ppc64_plt_entry_point (gdbarch, plt);
 416 }
 417
 418 static CORE_ADDR
 419 ppc64_standard_linkage3_target (struct frame_info *frame,
 420                                 CORE_ADDR pc, unsigned int *insn)
 421 {
 422   struct gdbarch *gdbarch = get_frame_arch (frame);
 423   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 424
 425   /* The address of the PLT entry this linkage function references.  */
 426   CORE_ADDR plt
 427     = ((CORE_ADDR) get_frame_register_unsigned (frame,
 428                                                 tdep->ppc_gp0_regnum + 2)
 429        + ppc_insn_ds_field (insn[1]));
 430
 431   return ppc64_plt_entry_point (gdbarch, plt);
 432 }
 433
 434 static CORE_ADDR
 435 ppc64_standard_linkage4_target (struct frame_info *frame,
 436                                 CORE_ADDR pc, unsigned int *insn)
 437 {
 438   struct gdbarch *gdbarch = get_frame_arch (frame);
 439   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 440
 441   CORE_ADDR plt
 442     = ((CORE_ADDR) get_frame_register_unsigned (frame, tdep->ppc_gp0_regnum + 2)
 443        + (ppc_insn_d_field (insn[1]) << 16)
 444        + ppc_insn_ds_field (insn[2]));
 445
 446   return ppc64_plt_entry_point (gdbarch, plt);
 447 }
 448
 449
 450 /* Given that we've begun executing a call trampoline at PC, return
 451    the entry point of the function the trampoline will go to.  */
 452
 453 CORE_ADDR
 454 ppc64_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc)
 455 {
 456 #define MAX(a,b) ((a) > (b) ? (a) : (b))
 457   unsigned int insns[MAX (MAX (MAX (ARRAY_SIZE (ppc64_standard_linkage1),
 458                                     ARRAY_SIZE (ppc64_standard_linkage2)),
 459                                MAX (ARRAY_SIZE (ppc64_standard_linkage3),
 460                                     ARRAY_SIZE (ppc64_standard_linkage4))),
 461                           MAX (MAX (ARRAY_SIZE (ppc64_standard_linkage5),
 462                                     ARRAY_SIZE (ppc64_standard_linkage6)),
 463                                MAX (ARRAY_SIZE (ppc64_standard_linkage7),
 464                                     ARRAY_SIZE (ppc64_standard_linkage8))))
 465                      - 1];
 466   CORE_ADDR target;
 467
 468   if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage8, insns))
 469     pc = ppc64_standard_linkage4_target (frame, pc, insns);
 470   else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage7, insns))
 471     pc = ppc64_standard_linkage3_target (frame, pc, insns);
 472   else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage6, insns))
 473     pc = ppc64_standard_linkage4_target (frame, pc, insns);
 474   else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage5, insns)
 475            && (insns[8] != 0 || insns[9] != 0))
 476     pc = ppc64_standard_linkage3_target (frame, pc, insns);
 477   else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage4, insns)
 478            && (insns[9] != 0 || insns[10] != 0))
 479     pc = ppc64_standard_linkage4_target (frame, pc, insns);
 480   else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage3, insns)
 481            && (insns[8] != 0 || insns[9] != 0))
 482     pc = ppc64_standard_linkage3_target (frame, pc, insns);
 483   else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage2, insns)
 484            && (insns[10] != 0 || insns[11] != 0))
 485     pc = ppc64_standard_linkage2_target (frame, pc, insns);
 486   else if (ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage1, insns))
 487     pc = ppc64_standard_linkage1_target (frame, pc, insns);
 488   else
 489     return 0;
 490
 491   /* The PLT descriptor will either point to the already resolved target
 492      address, or else to a glink stub.  As the latter carry synthetic @plt
 493      symbols, find_solib_trampoline_target should be able to resolve them.  */
 494   target = find_solib_trampoline_target (frame, pc);
 495   return target ? target : pc;
 496 }
 497
 498 /* Support for convert_from_func_ptr_addr (ARCH, ADDR, TARG) on PPC64
 499    GNU/Linux.
 500
 501    Usually a function pointer's representation is simply the address
 502    of the function.  On GNU/Linux on the PowerPC however, a function
 503    pointer may be a pointer to a function descriptor.
 504
 505    For PPC64, a function descriptor is a TOC entry, in a data section,
 506    which contains three words: the first word is the address of the
 507    function, the second word is the TOC pointer (r2), and the third word
 508    is the static chain value.
 509
 510    Throughout GDB it is currently assumed that a function pointer contains
 511    the address of the function, which is not easy to fix.  In addition, the
 512    conversion of a function address to a function pointer would
 513    require allocation of a TOC entry in the inferior's memory space,
 514    with all its drawbacks.  To be able to call C++ virtual methods in
 515    the inferior (which are called via function pointers),
 516    find_function_addr uses this function to get the function address
 517    from a function pointer.
 518
 519    If ADDR points at what is clearly a function descriptor, transform
 520    it into the address of the corresponding function, if needed.  Be
 521    conservative, otherwise GDB will do the transformation on any
 522    random addresses such as occur when there is no symbol table.  */
 523
 524 CORE_ADDR
 525 ppc64_convert_from_func_ptr_addr (struct gdbarch *gdbarch,
 526                                         CORE_ADDR addr,
 527                                         struct target_ops *targ)
 528 {
 529   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 530   struct target_section *s = target_section_by_addr (targ, addr);
 531
 532   /* Check if ADDR points to a function descriptor.  */
 533   if (s && strcmp (s->the_bfd_section->name, ".opd") == 0)
 534     {
 535       /* There may be relocations that need to be applied to the .opd
 536          section.  Unfortunately, this function may be called at a time
 537          where these relocations have not yet been performed -- this can
 538          happen for example shortly after a library has been loaded with
 539          dlopen, but ld.so has not yet applied the relocations.
 540
 541          To cope with both the case where the relocation has been applied,
 542          and the case where it has not yet been applied, we do *not* read
 543          the (maybe) relocated value from target memory, but we instead
 544          read the non-relocated value from the BFD, and apply the relocation
 545          offset manually.
 546
 547          This makes the assumption that all .opd entries are always relocated
 548          by the same offset the section itself was relocated.  This should
 549          always be the case for GNU/Linux executables and shared libraries.
 550          Note that other kind of object files (e.g. those added via
 551          add-symbol-files) will currently never end up here anyway, as this
 552          function accesses *target* sections only; only the main exec and
 553          shared libraries are ever added to the target.  */
 554
 555       gdb_byte buf[8];
 556       int res;
 557
 558       res = bfd_get_section_contents (s->the_bfd_section->owner,
 559                                       s->the_bfd_section,
 560                                       &buf, addr - s->addr, 8);
 561       if (res != 0)
 562         return extract_unsigned_integer (buf, 8, byte_order)
 563                 - bfd_section_vma (s->bfd, s->the_bfd_section) + s->addr;
 564    }
 565
 566   return addr;
 567 }
 568
 569 /* A synthetic 'dot' symbols on ppc64 has the udata.p entry pointing
 570    back to the original ELF symbol it was derived from.  Get the size
 571    from that symbol.  */
 572
 573 void
 574 ppc64_elf_make_msymbol_special (asymbol *sym, struct minimal_symbol *msym)
 575 {
 576   if ((sym->flags & BSF_SYNTHETIC) != 0 && sym->udata.p != NULL)
 577     {
 578       elf_symbol_type *elf_sym = (elf_symbol_type *) sym->udata.p;
 579       SET_MSYMBOL_SIZE (msym, elf_sym->internal_elf_sym.st_size);
 580     }
 581 }