1 /* Common target-dependent code for ppc64 GDB, the GNU debugger. 2 3 Copyright (C) 1986-2020 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 "infrun.h" 24 #include "ppc-tdep.h" 25 #include "ppc64-tdep.h" 26 #include "elf-bfd.h" 27 28 /* Macros for matching instructions. Note that, since all the 29 operands are masked off before they're or-ed into the instruction, 30 you can use -1 to make masks. */ 31 32 #define insn_d(opcd, rts, ra, d) \ 33 ((((unsigned (opcd)) & 0x3f) << 26) \ 34 | (((unsigned (rts)) & 0x1f) << 21) \ 35 | (((unsigned (ra)) & 0x1f) << 16) \ 36 | ((unsigned (d)) & 0xffff)) 37 38 #define insn_ds(opcd, rts, ra, d, xo) \ 39 ((((unsigned (opcd)) & 0x3f) << 26) \ 40 | (((unsigned (rts)) & 0x1f) << 21) \ 41 | (((unsigned (ra)) & 0x1f) << 16) \ 42 | ((unsigned (d)) & 0xfffc) \ 43 | ((unsigned (xo)) & 0x3)) 44 45 #define insn_xfx(opcd, rts, spr, xo) \ 46 ((((unsigned (opcd)) & 0x3f) << 26) \ 47 | (((unsigned (rts)) & 0x1f) << 21) \ 48 | (((unsigned (spr)) & 0x1f) << 16) \ 49 | (((unsigned (spr)) & 0x3e0) << 6) \ 50 | (((unsigned (xo)) & 0x3ff) << 1)) 51 52 /* PLT_OFF is the TOC-relative offset of a 64-bit PowerPC PLT entry. 53 Return the function's entry point. */ 54 55 static CORE_ADDR 56 ppc64_plt_entry_point (struct frame_info *frame, CORE_ADDR plt_off) 57 { 58 struct gdbarch *gdbarch = get_frame_arch (frame); 59 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); 60 struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch); 61 CORE_ADDR tocp; 62 63 if (execution_direction == EXEC_REVERSE) 64 { 65 /* If executing in reverse, r2 will have been stored to the stack. */ 66 CORE_ADDR sp = get_frame_register_unsigned (frame, 67 tdep->ppc_gp0_regnum + 1); 68 unsigned int sp_off = tdep->elf_abi == POWERPC_ELF_V1 ? 40 : 24; 69 tocp = read_memory_unsigned_integer (sp + sp_off, 8, byte_order); 70 } 71 else 72 tocp = get_frame_register_unsigned (frame, tdep->ppc_gp0_regnum + 2); 73 74 /* The first word of the PLT entry is the function entry point. */ 75 return read_memory_unsigned_integer (tocp + plt_off, 8, byte_order); 76 } 77 78 /* Patterns for the standard linkage functions. These are built by 79 build_plt_stub in bfd/elf64-ppc.c. */ 80 81 /* Old ELFv1 PLT call stub. */ 82 83 static const struct ppc_insn_pattern ppc64_standard_linkage1[] = 84 { 85 /* addis r12, r2, <any> */ 86 { insn_d (-1, -1, -1, 0), insn_d (15, 12, 2, 0), 0 }, 87 88 /* std r2, 40(r1) */ 89 { (unsigned) -1, insn_ds (62, 2, 1, 40, 0), 0 }, 90 91 /* ld r11, <any>(r12) */ 92 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 0 }, 93 94 /* addis r12, r12, 1 <optional> */ 95 { insn_d (-1, -1, -1, -1), insn_d (15, 12, 12, 1), 1 }, 96 97 /* ld r2, <any>(r12) */ 98 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 12, 0, 0), 0 }, 99 100 /* addis r12, r12, 1 <optional> */ 101 { insn_d (-1, -1, -1, -1), insn_d (15, 12, 12, 1), 1 }, 102 103 /* mtctr r11 */ 104 { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 }, 105 106 /* ld r11, <any>(r12) <optional> */ 107 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 1 }, 108 109 /* bctr */ 110 { (unsigned) -1, 0x4e800420, 0 }, 111 112 { 0, 0, 0 } 113 }; 114 115 /* ELFv1 PLT call stub to access PLT entries more than +/- 32k from r2. 116 Also supports older stub with different placement of std 2,40(1), 117 a stub that omits the std 2,40(1), and both versions of power7 118 thread safety read barriers. Note that there are actually two more 119 instructions following "cmpldi r2, 0", "bnectr+" and "b <glink_i>", 120 but there isn't any need to match them. */ 121 122 static const struct ppc_insn_pattern ppc64_standard_linkage2[] = 123 { 124 /* std r2, 40(r1) <optional> */ 125 { (unsigned) -1, insn_ds (62, 2, 1, 40, 0), 1 }, 126 127 /* addis r12, r2, <any> */ 128 { insn_d (-1, -1, -1, 0), insn_d (15, 12, 2, 0), 0 }, 129 130 /* std r2, 40(r1) <optional> */ 131 { (unsigned) -1, insn_ds (62, 2, 1, 40, 0), 1 }, 132 133 /* ld r11, <any>(r12) */ 134 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 0 }, 135 136 /* addi r12, r12, <any> <optional> */ 137 { insn_d (-1, -1, -1, 0), insn_d (14, 12, 12, 0), 1 }, 138 139 /* mtctr r11 */ 140 { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 }, 141 142 /* xor r11, r11, r11 <optional> */ 143 { (unsigned) -1, 0x7d6b5a78, 1 }, 144 145 /* add r12, r12, r11 <optional> */ 146 { (unsigned) -1, 0x7d8c5a14, 1 }, 147 148 /* ld r2, <any>(r12) */ 149 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 12, 0, 0), 0 }, 150 151 /* ld r11, <any>(r12) <optional> */ 152 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 12, 0, 0), 1 }, 153 154 /* bctr <optional> */ 155 { (unsigned) -1, 0x4e800420, 1 }, 156 157 /* cmpldi r2, 0 <optional> */ 158 { (unsigned) -1, 0x28220000, 1 }, 159 160 { 0, 0, 0 } 161 }; 162 163 /* ELFv1 PLT call stub to access PLT entries within +/- 32k of r2. */ 164 165 static const struct ppc_insn_pattern ppc64_standard_linkage3[] = 166 { 167 /* std r2, 40(r1) <optional> */ 168 { (unsigned) -1, insn_ds (62, 2, 1, 40, 0), 1 }, 169 170 /* ld r11, <any>(r2) */ 171 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 2, 0, 0), 0 }, 172 173 /* addi r2, r2, <any> <optional> */ 174 { insn_d (-1, -1, -1, 0), insn_d (14, 2, 2, 0), 1 }, 175 176 /* mtctr r11 */ 177 { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 11, 9, 467), 0 }, 178 179 /* xor r11, r11, r11 <optional> */ 180 { (unsigned) -1, 0x7d6b5a78, 1 }, 181 182 /* add r2, r2, r11 <optional> */ 183 { (unsigned) -1, 0x7c425a14, 1 }, 184 185 /* ld r11, <any>(r2) <optional> */ 186 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 2, 0, 0), 1 }, 187 188 /* ld r2, <any>(r2) */ 189 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 2, 0, 0), 0 }, 190 191 /* bctr <optional> */ 192 { (unsigned) -1, 0x4e800420, 1 }, 193 194 /* cmpldi r2, 0 <optional> */ 195 { (unsigned) -1, 0x28220000, 1 }, 196 197 { 0, 0, 0 } 198 }; 199 200 /* ELFv1 PLT call stub to access PLT entries more than +/- 32k from r2. 201 A more modern variant of ppc64_standard_linkage2 differing in 202 register usage. */ 203 204 static const struct ppc_insn_pattern ppc64_standard_linkage4[] = 205 { 206 /* std r2, 40(r1) <optional> */ 207 { (unsigned) -1, insn_ds (62, 2, 1, 40, 0), 1 }, 208 209 /* addis r11, r2, <any> */ 210 { insn_d (-1, -1, -1, 0), insn_d (15, 11, 2, 0), 0 }, 211 212 /* ld r12, <any>(r11) */ 213 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 11, 0, 0), 0 }, 214 215 /* addi r11, r11, <any> <optional> */ 216 { insn_d (-1, -1, -1, 0), insn_d (14, 11, 11, 0), 1 }, 217 218 /* mtctr r12 */ 219 { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 }, 220 221 /* xor r2, r12, r12 <optional> */ 222 { (unsigned) -1, 0x7d826278, 1 }, 223 224 /* add r11, r11, r2 <optional> */ 225 { (unsigned) -1, 0x7d6b1214, 1 }, 226 227 /* ld r2, <any>(r11) */ 228 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 11, 0, 0), 0 }, 229 230 /* ld r11, <any>(r11) <optional> */ 231 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 11, 0, 0), 1 }, 232 233 /* bctr <optional> */ 234 { (unsigned) -1, 0x4e800420, 1 }, 235 236 /* cmpldi r2, 0 <optional> */ 237 { (unsigned) -1, 0x28220000, 1 }, 238 239 { 0, 0, 0 } 240 }; 241 242 /* ELFv1 PLT call stub to access PLT entries within +/- 32k of r2. 243 A more modern variant of ppc64_standard_linkage3 differing in 244 register usage. */ 245 246 static const struct ppc_insn_pattern ppc64_standard_linkage5[] = 247 { 248 /* std r2, 40(r1) <optional> */ 249 { (unsigned) -1, insn_ds (62, 2, 1, 40, 0), 1 }, 250 251 /* ld r12, <any>(r2) */ 252 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 2, 0, 0), 0 }, 253 254 /* addi r2, r2, <any> <optional> */ 255 { insn_d (-1, -1, -1, 0), insn_d (14, 2, 2, 0), 1 }, 256 257 /* mtctr r12 */ 258 { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 }, 259 260 /* xor r11, r12, r12 <optional> */ 261 { (unsigned) -1, 0x7d8b6278, 1 }, 262 263 /* add r2, r2, r11 <optional> */ 264 { (unsigned) -1, 0x7c425a14, 1 }, 265 266 /* ld r11, <any>(r2) <optional> */ 267 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 11, 2, 0, 0), 1 }, 268 269 /* ld r2, <any>(r2) */ 270 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 2, 2, 0, 0), 0 }, 271 272 /* bctr <optional> */ 273 { (unsigned) -1, 0x4e800420, 1 }, 274 275 /* cmpldi r2, 0 <optional> */ 276 { (unsigned) -1, 0x28220000, 1 }, 277 278 { 0, 0, 0 } 279 }; 280 281 /* ELFv2 PLT call stub to access PLT entries more than +/- 32k from r2. */ 282 283 static const struct ppc_insn_pattern ppc64_standard_linkage6[] = 284 { 285 /* std r2, 24(r1) <optional> */ 286 { (unsigned) -1, insn_ds (62, 2, 1, 24, 0), 1 }, 287 288 /* addis r11, r2, <any> */ 289 { insn_d (-1, -1, -1, 0), insn_d (15, 11, 2, 0), 0 }, 290 291 /* ld r12, <any>(r11) */ 292 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 11, 0, 0), 0 }, 293 294 /* mtctr r12 */ 295 { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 }, 296 297 /* bctr */ 298 { (unsigned) -1, 0x4e800420, 0 }, 299 300 { 0, 0, 0 } 301 }; 302 303 /* ELFv2 PLT call stub to access PLT entries within +/- 32k of r2. */ 304 305 static const struct ppc_insn_pattern ppc64_standard_linkage7[] = 306 { 307 /* std r2, 24(r1) <optional> */ 308 { (unsigned) -1, insn_ds (62, 2, 1, 24, 0), 1 }, 309 310 /* ld r12, <any>(r2) */ 311 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 2, 0, 0), 0 }, 312 313 /* mtctr r12 */ 314 { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 }, 315 316 /* bctr */ 317 { (unsigned) -1, 0x4e800420, 0 }, 318 319 { 0, 0, 0 } 320 }; 321 322 /* ELFv2 PLT call stub to access PLT entries more than +/- 32k from r2, 323 supporting fusion. */ 324 325 static const struct ppc_insn_pattern ppc64_standard_linkage8[] = 326 { 327 /* std r2, 24(r1) <optional> */ 328 { (unsigned) -1, insn_ds (62, 2, 1, 24, 0), 1 }, 329 330 /* addis r12, r2, <any> */ 331 { insn_d (-1, -1, -1, 0), insn_d (15, 12, 2, 0), 0 }, 332 333 /* ld r12, <any>(r12) */ 334 { insn_ds (-1, -1, -1, 0, -1), insn_ds (58, 12, 12, 0, 0), 0 }, 335 336 /* mtctr r12 */ 337 { insn_xfx (-1, -1, -1, -1), insn_xfx (31, 12, 9, 467), 0 }, 338 339 /* bctr */ 340 { (unsigned) -1, 0x4e800420, 0 }, 341 342 { 0, 0, 0 } 343 }; 344 345 /* When the dynamic linker is doing lazy symbol resolution, the first 346 call to a function in another object will go like this: 347 348 - The user's function calls the linkage function: 349 350 100003d4: 4b ff ff ad bl 10000380 <nnnn.plt_call.printf> 351 100003d8: e8 41 00 28 ld r2,40(r1) 352 353 - The linkage function loads the entry point and toc pointer from 354 the function descriptor in the PLT, and jumps to it: 355 356 <nnnn.plt_call.printf>: 357 10000380: f8 41 00 28 std r2,40(r1) 358 10000384: e9 62 80 78 ld r11,-32648(r2) 359 10000388: 7d 69 03 a6 mtctr r11 360 1000038c: e8 42 80 80 ld r2,-32640(r2) 361 10000390: 28 22 00 00 cmpldi r2,0 362 10000394: 4c e2 04 20 bnectr+ 363 10000398: 48 00 03 a0 b 10000738 <printf@plt> 364 365 - But since this is the first time that PLT entry has been used, it 366 sends control to its glink entry. That loads the number of the 367 PLT entry and jumps to the common glink0 code: 368 369 <printf@plt>: 370 10000738: 38 00 00 01 li r0,1 371 1000073c: 4b ff ff bc b 100006f8 <__glink_PLTresolve> 372 373 - The common glink0 code then transfers control to the dynamic 374 linker's fixup code: 375 376 100006f0: 0000000000010440 .quad plt0 - (. + 16) 377 <__glink_PLTresolve>: 378 100006f8: 7d 88 02 a6 mflr r12 379 100006fc: 42 9f 00 05 bcl 20,4*cr7+so,10000700 380 10000700: 7d 68 02 a6 mflr r11 381 10000704: e8 4b ff f0 ld r2,-16(r11) 382 10000708: 7d 88 03 a6 mtlr r12 383 1000070c: 7d 82 5a 14 add r12,r2,r11 384 10000710: e9 6c 00 00 ld r11,0(r12) 385 10000714: e8 4c 00 08 ld r2,8(r12) 386 10000718: 7d 69 03 a6 mtctr r11 387 1000071c: e9 6c 00 10 ld r11,16(r12) 388 10000720: 4e 80 04 20 bctr 389 390 Eventually, this code will figure out how to skip all of this, 391 including the dynamic linker. At the moment, we just get through 392 the linkage function. */ 393 394 /* If the current thread is about to execute a series of instructions 395 matching the ppc64_standard_linkage pattern, and INSN is the result 396 from that pattern match, return the code address to which the 397 standard linkage function will send them. (This doesn't deal with 398 dynamic linker lazy symbol resolution stubs.) */ 399 400 static CORE_ADDR 401 ppc64_standard_linkage1_target (struct frame_info *frame, unsigned int *insn) 402 { 403 CORE_ADDR plt_off = ((ppc_insn_d_field (insn[0]) << 16) 404 + ppc_insn_ds_field (insn[2])); 405 406 return ppc64_plt_entry_point (frame, plt_off); 407 } 408 409 static CORE_ADDR 410 ppc64_standard_linkage2_target (struct frame_info *frame, unsigned int *insn) 411 { 412 CORE_ADDR plt_off = ((ppc_insn_d_field (insn[1]) << 16) 413 + ppc_insn_ds_field (insn[3])); 414 415 return ppc64_plt_entry_point (frame, plt_off); 416 } 417 418 static CORE_ADDR 419 ppc64_standard_linkage3_target (struct frame_info *frame, unsigned int *insn) 420 { 421 CORE_ADDR plt_off = ppc_insn_ds_field (insn[1]); 422 423 return ppc64_plt_entry_point (frame, plt_off); 424 } 425 426 static CORE_ADDR 427 ppc64_standard_linkage4_target (struct frame_info *frame, unsigned int *insn) 428 { 429 CORE_ADDR plt_off = ((ppc_insn_d_field (insn[1]) << 16) 430 + ppc_insn_ds_field (insn[2])); 431 432 return ppc64_plt_entry_point (frame, plt_off); 433 } 434 435 436 /* Given that we've begun executing a call trampoline at PC, return 437 the entry point of the function the trampoline will go to. 438 439 When the execution direction is EXEC_REVERSE, scan backward to 440 check whether we are in the middle of a PLT stub. */ 441 442 static CORE_ADDR 443 ppc64_skip_trampoline_code_1 (struct frame_info *frame, CORE_ADDR pc) 444 { 445 #define MAX(a,b) ((a) > (b) ? (a) : (b)) 446 unsigned int insns[MAX (MAX (MAX (ARRAY_SIZE (ppc64_standard_linkage1), 447 ARRAY_SIZE (ppc64_standard_linkage2)), 448 MAX (ARRAY_SIZE (ppc64_standard_linkage3), 449 ARRAY_SIZE (ppc64_standard_linkage4))), 450 MAX (MAX (ARRAY_SIZE (ppc64_standard_linkage5), 451 ARRAY_SIZE (ppc64_standard_linkage6)), 452 MAX (ARRAY_SIZE (ppc64_standard_linkage7), 453 ARRAY_SIZE (ppc64_standard_linkage8)))) 454 - 1]; 455 CORE_ADDR target; 456 int scan_limit, i; 457 458 scan_limit = 1; 459 /* When reverse-debugging, scan backward to check whether we are 460 in the middle of trampoline code. */ 461 if (execution_direction == EXEC_REVERSE) 462 scan_limit = ARRAY_SIZE (insns) - 1; 463 464 for (i = 0; i < scan_limit; i++) 465 { 466 if (i < ARRAY_SIZE (ppc64_standard_linkage8) - 1 467 && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage8, insns)) 468 pc = ppc64_standard_linkage4_target (frame, insns); 469 else if (i < ARRAY_SIZE (ppc64_standard_linkage7) - 1 470 && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage7, 471 insns)) 472 pc = ppc64_standard_linkage3_target (frame, insns); 473 else if (i < ARRAY_SIZE (ppc64_standard_linkage6) - 1 474 && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage6, 475 insns)) 476 pc = ppc64_standard_linkage4_target (frame, insns); 477 else if (i < ARRAY_SIZE (ppc64_standard_linkage5) - 1 478 && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage5, 479 insns) 480 && (insns[8] != 0 || insns[9] != 0)) 481 pc = ppc64_standard_linkage3_target (frame, insns); 482 else if (i < ARRAY_SIZE (ppc64_standard_linkage4) - 1 483 && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage4, 484 insns) 485 && (insns[9] != 0 || insns[10] != 0)) 486 pc = ppc64_standard_linkage4_target (frame, insns); 487 else if (i < ARRAY_SIZE (ppc64_standard_linkage3) - 1 488 && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage3, 489 insns) 490 && (insns[8] != 0 || insns[9] != 0)) 491 pc = ppc64_standard_linkage3_target (frame, insns); 492 else if (i < ARRAY_SIZE (ppc64_standard_linkage2) - 1 493 && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage2, 494 insns) 495 && (insns[10] != 0 || insns[11] != 0)) 496 pc = ppc64_standard_linkage2_target (frame, insns); 497 else if (i < ARRAY_SIZE (ppc64_standard_linkage1) - 1 498 && ppc_insns_match_pattern (frame, pc, ppc64_standard_linkage1, 499 insns)) 500 pc = ppc64_standard_linkage1_target (frame, insns); 501 else 502 { 503 /* Scan backward one more instructions if doesn't match. */ 504 pc -= 4; 505 continue; 506 } 507 508 /* The PLT descriptor will either point to the already resolved target 509 address, or else to a glink stub. As the latter carry synthetic @plt 510 symbols, find_solib_trampoline_target should be able to resolve them. */ 511 target = find_solib_trampoline_target (frame, pc); 512 return target ? target : pc; 513 } 514 515 return 0; 516 } 517 518 /* Wrapper of ppc64_skip_trampoline_code_1 checking also 519 ppc_elfv2_skip_entrypoint. */ 520 521 CORE_ADDR 522 ppc64_skip_trampoline_code (struct frame_info *frame, CORE_ADDR pc) 523 { 524 struct gdbarch *gdbarch = get_frame_arch (frame); 525 526 pc = ppc64_skip_trampoline_code_1 (frame, pc); 527 if (pc != 0 && gdbarch_skip_entrypoint_p (gdbarch)) 528 pc = gdbarch_skip_entrypoint (gdbarch, pc); 529 return pc; 530 } 531 532 /* Support for convert_from_func_ptr_addr (ARCH, ADDR, TARG) on PPC64 533 GNU/Linux. 534 535 Usually a function pointer's representation is simply the address 536 of the function. On GNU/Linux on the PowerPC however, a function 537 pointer may be a pointer to a function descriptor. 538 539 For PPC64, a function descriptor is a TOC entry, in a data section, 540 which contains three words: the first word is the address of the 541 function, the second word is the TOC pointer (r2), and the third word 542 is the static chain value. 543 544 Throughout GDB it is currently assumed that a function pointer contains 545 the address of the function, which is not easy to fix. In addition, the 546 conversion of a function address to a function pointer would 547 require allocation of a TOC entry in the inferior's memory space, 548 with all its drawbacks. To be able to call C++ virtual methods in 549 the inferior (which are called via function pointers), 550 find_function_addr uses this function to get the function address 551 from a function pointer. 552 553 If ADDR points at what is clearly a function descriptor, transform 554 it into the address of the corresponding function, if needed. Be 555 conservative, otherwise GDB will do the transformation on any 556 random addresses such as occur when there is no symbol table. */ 557 558 CORE_ADDR 559 ppc64_convert_from_func_ptr_addr (struct gdbarch *gdbarch, 560 CORE_ADDR addr, 561 struct target_ops *targ) 562 { 563 enum bfd_endian byte_order = gdbarch_byte_order (gdbarch); 564 struct target_section *s = target_section_by_addr (targ, addr); 565 566 /* Check if ADDR points to a function descriptor. */ 567 if (s && strcmp (s->the_bfd_section->name, ".opd") == 0) 568 { 569 /* There may be relocations that need to be applied to the .opd 570 section. Unfortunately, this function may be called at a time 571 where these relocations have not yet been performed -- this can 572 happen for example shortly after a library has been loaded with 573 dlopen, but ld.so has not yet applied the relocations. 574 575 To cope with both the case where the relocation has been applied, 576 and the case where it has not yet been applied, we do *not* read 577 the (maybe) relocated value from target memory, but we instead 578 read the non-relocated value from the BFD, and apply the relocation 579 offset manually. 580 581 This makes the assumption that all .opd entries are always relocated 582 by the same offset the section itself was relocated. This should 583 always be the case for GNU/Linux executables and shared libraries. 584 Note that other kind of object files (e.g. those added via 585 add-symbol-files) will currently never end up here anyway, as this 586 function accesses *target* sections only; only the main exec and 587 shared libraries are ever added to the target. */ 588 589 gdb_byte buf[8]; 590 int res; 591 592 res = bfd_get_section_contents (s->the_bfd_section->owner, 593 s->the_bfd_section, 594 &buf, addr - s->addr, 8); 595 if (res != 0) 596 return (extract_unsigned_integer (buf, 8, byte_order) 597 - bfd_section_vma (s->the_bfd_section) + s->addr); 598 } 599 600 return addr; 601 } 602 603 /* A synthetic 'dot' symbols on ppc64 has the udata.p entry pointing 604 back to the original ELF symbol it was derived from. Get the size 605 from that symbol. */ 606 607 void 608 ppc64_elf_make_msymbol_special (asymbol *sym, struct minimal_symbol *msym) 609 { 610 if ((sym->flags & BSF_SYNTHETIC) != 0 && sym->udata.p != NULL) 611 { 612 elf_symbol_type *elf_sym = (elf_symbol_type *) sym->udata.p; 613 SET_MSYMBOL_SIZE (msym, elf_sym->internal_elf_sym.st_size); 614 } 615 } 616