gdb/i386-linux-nat.c

   1 /* Native-dependent code for GNU/Linux x86.
   2
   3    Copyright 1999, 2000, 2001, 2002, 2003 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 2 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, write to the Free Software
  19    Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #include "defs.h"
  23 #include "inferior.h"
  24 #include "gdbcore.h"
  25 #include "regcache.h"
  26 #include "linux-nat.h"
  27
  28 #include "gdb_assert.h"
  29 #include "gdb_string.h"
  30 #include <sys/ptrace.h>
  31 #include <sys/user.h>
  32 #include <sys/procfs.h>
  33
  34 #ifdef HAVE_SYS_REG_H
  35 #include <sys/reg.h>
  36 #endif
  37
  38 #ifndef ORIG_EAX
  39 #define ORIG_EAX -1
  40 #endif
  41
  42 #ifdef HAVE_SYS_DEBUGREG_H
  43 #include <sys/debugreg.h>
  44 #endif
  45
  46 #ifndef DR_FIRSTADDR
  47 #define DR_FIRSTADDR 0
  48 #endif
  49
  50 #ifndef DR_LASTADDR
  51 #define DR_LASTADDR 3
  52 #endif
  53
  54 #ifndef DR_STATUS
  55 #define DR_STATUS 6
  56 #endif
  57
  58 #ifndef DR_CONTROL
  59 #define DR_CONTROL 7
  60 #endif
  61
  62 /* Prototypes for supply_gregset etc.  */
  63 #include "gregset.h"
  64
  65 /* Prototypes for i387_supply_fsave etc.  */
  66 #include "i387-tdep.h"
  67
  68 /* Defines for XMM0_REGNUM etc. */
  69 #include "i386-tdep.h"
  70
  71 /* Defines I386_LINUX_ORIG_EAX_REGNUM.  */
  72 #include "i386-linux-tdep.h"
  73
  74 /* Defines ps_err_e, struct ps_prochandle.  */
  75 #include "gdb_proc_service.h"
  76
  77 /* Prototypes for local functions.  */
  78 static void dummy_sse_values (void);
  79 \f
  80
  81 /* The register sets used in GNU/Linux ELF core-dumps are identical to
  82    the register sets in `struct user' that is used for a.out
  83    core-dumps, and is also used by `ptrace'.  The corresponding types
  84    are `elf_gregset_t' for the general-purpose registers (with
  85    `elf_greg_t' the type of a single GP register) and `elf_fpregset_t'
  86    for the floating-point registers.
  87
  88    Those types used to be available under the names `gregset_t' and
  89    `fpregset_t' too, and this file used those names in the past.  But
  90    those names are now used for the register sets used in the
  91    `mcontext_t' type, and have a different size and layout.  */
  92
  93 /* Mapping between the general-purpose registers in `struct user'
  94    format and GDB's register array layout.  */
  95 static int regmap[] =
  96 {
  97   EAX, ECX, EDX, EBX,
  98   UESP, EBP, ESI, EDI,
  99   EIP, EFL, CS, SS,
 100   DS, ES, FS, GS,
 101   -1, -1, -1, -1,               /* st0, st1, st2, st3 */
 102   -1, -1, -1, -1,               /* st4, st5, st6, st7 */
 103   -1, -1, -1, -1,               /* fctrl, fstat, ftag, fiseg */
 104   -1, -1, -1, -1,               /* fioff, foseg, fooff, fop */
 105   -1, -1, -1, -1,               /* xmm0, xmm1, xmm2, xmm3 */
 106   -1, -1, -1, -1,               /* xmm4, xmm5, xmm6, xmm6 */
 107   -1,                           /* mxcsr */
 108   ORIG_EAX
 109 };
 110
 111 /* Which ptrace request retrieves which registers?
 112    These apply to the corresponding SET requests as well.  */
 113
 114 #define GETREGS_SUPPLIES(regno) \
 115   ((0 <= (regno) && (regno) <= 15) || (regno) == I386_LINUX_ORIG_EAX_REGNUM)
 116
 117 #define GETFPREGS_SUPPLIES(regno) \
 118   (FP0_REGNUM <= (regno) && (regno) <= LAST_FPU_CTRL_REGNUM)
 119
 120 #define GETFPXREGS_SUPPLIES(regno) \
 121   (FP0_REGNUM <= (regno) && (regno) <= MXCSR_REGNUM)
 122
 123 /* Does the current host support the GETREGS request?  */
 124 int have_ptrace_getregs =
 125 #ifdef HAVE_PTRACE_GETREGS
 126   1
 127 #else
 128   0
 129 #endif
 130 ;
 131
 132 /* Does the current host support the GETFPXREGS request?  The header
 133    file may or may not define it, and even if it is defined, the
 134    kernel will return EIO if it's running on a pre-SSE processor.
 135
 136    My instinct is to attach this to some architecture- or
 137    target-specific data structure, but really, a particular GDB
 138    process can only run on top of one kernel at a time.  So it's okay
 139    for this to be a simple variable.  */
 140 int have_ptrace_getfpxregs =
 141 #ifdef HAVE_PTRACE_GETFPXREGS
 142   1
 143 #else
 144   0
 145 #endif
 146 ;
 147 \f
 148
 149 /* Support for the user struct.  */
 150
 151 /* Return the address of register REGNUM.  BLOCKEND is the value of
 152    u.u_ar0, which should point to the registers.  */
 153
 154 CORE_ADDR
 155 register_u_addr (CORE_ADDR blockend, int regnum)
 156 {
 157   return (blockend + 4 * regmap[regnum]);
 158 }
 159
 160 /* Return the size of the user struct.  */
 161
 162 int
 163 kernel_u_size (void)
 164 {
 165   return (sizeof (struct user));
 166 }
 167 \f
 168
 169 /* Accessing registers through the U area, one at a time.  */
 170
 171 /* Fetch one register.  */
 172
 173 static void
 174 fetch_register (int regno)
 175 {
 176   int tid;
 177   int val;
 178
 179   gdb_assert (!have_ptrace_getregs);
 180   if (cannot_fetch_register (regno))
 181     {
 182       supply_register (regno, NULL);
 183       return;
 184     }
 185
 186   /* GNU/Linux LWP ID's are process ID's.  */
 187   tid = TIDGET (inferior_ptid);
 188   if (tid == 0)
 189     tid = PIDGET (inferior_ptid); /* Not a threaded program.  */
 190
 191   errno = 0;
 192   val = ptrace (PTRACE_PEEKUSER, tid, register_addr (regno, 0), 0);
 193   if (errno != 0)
 194     error ("Couldn't read register %s (#%d): %s.", REGISTER_NAME (regno),
 195            regno, safe_strerror (errno));
 196
 197   supply_register (regno, &val);
 198 }
 199
 200 /* Store one register. */
 201
 202 static void
 203 store_register (int regno)
 204 {
 205   int tid;
 206   int val;
 207
 208   gdb_assert (!have_ptrace_getregs);
 209   if (cannot_store_register (regno))
 210     return;
 211
 212   /* GNU/Linux LWP ID's are process ID's.  */
 213   tid = TIDGET (inferior_ptid);
 214   if (tid == 0)
 215     tid = PIDGET (inferior_ptid); /* Not a threaded program.  */
 216
 217   errno = 0;
 218   regcache_collect (regno, &val);
 219   ptrace (PTRACE_POKEUSER, tid, register_addr (regno, 0), val);
 220   if (errno != 0)
 221     error ("Couldn't write register %s (#%d): %s.", REGISTER_NAME (regno),
 222            regno, safe_strerror (errno));
 223 }
 224 \f
 225
 226 /* Transfering the general-purpose registers between GDB, inferiors
 227    and core files.  */
 228
 229 /* Fill GDB's register array with the general-purpose register values
 230    in *GREGSETP.  */
 231
 232 void
 233 supply_gregset (elf_gregset_t *gregsetp)
 234 {
 235   elf_greg_t *regp = (elf_greg_t *) gregsetp;
 236   int i;
 237
 238   for (i = 0; i < I386_NUM_GREGS; i++)
 239     supply_register (i, regp + regmap[i]);
 240
 241   if (I386_LINUX_ORIG_EAX_REGNUM < NUM_REGS)
 242     supply_register (I386_LINUX_ORIG_EAX_REGNUM, regp + ORIG_EAX);
 243 }
 244
 245 /* Fill register REGNO (if it is a general-purpose register) in
 246    *GREGSETPS with the value in GDB's register array.  If REGNO is -1,
 247    do this for all registers.  */
 248
 249 void
 250 fill_gregset (elf_gregset_t *gregsetp, int regno)
 251 {
 252   elf_greg_t *regp = (elf_greg_t *) gregsetp;
 253   int i;
 254
 255   for (i = 0; i < I386_NUM_GREGS; i++)
 256     if (regno == -1 || regno == i)
 257       regcache_collect (i, regp + regmap[i]);
 258
 259   if ((regno == -1 || regno == I386_LINUX_ORIG_EAX_REGNUM)
 260       && I386_LINUX_ORIG_EAX_REGNUM < NUM_REGS)
 261     regcache_collect (I386_LINUX_ORIG_EAX_REGNUM, regp + ORIG_EAX);
 262 }
 263
 264 #ifdef HAVE_PTRACE_GETREGS
 265
 266 /* Fetch all general-purpose registers from process/thread TID and
 267    store their values in GDB's register array.  */
 268
 269 static void
 270 fetch_regs (int tid)
 271 {
 272   elf_gregset_t regs;
 273
 274   if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
 275     {
 276       if (errno == EIO)
 277         {
 278           /* The kernel we're running on doesn't support the GETREGS
 279              request.  Reset `have_ptrace_getregs'.  */
 280           have_ptrace_getregs = 0;
 281           return;
 282         }
 283
 284       perror_with_name ("Couldn't get registers");
 285     }
 286
 287   supply_gregset (&regs);
 288 }
 289
 290 /* Store all valid general-purpose registers in GDB's register array
 291    into the process/thread specified by TID.  */
 292
 293 static void
 294 store_regs (int tid, int regno)
 295 {
 296   elf_gregset_t regs;
 297
 298   if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
 299     perror_with_name ("Couldn't get registers");
 300
 301   fill_gregset (&regs, regno);
 302
 303   if (ptrace (PTRACE_SETREGS, tid, 0, (int) &regs) < 0)
 304     perror_with_name ("Couldn't write registers");
 305 }
 306
 307 #else
 308
 309 static void fetch_regs (int tid) {}
 310 static void store_regs (int tid, int regno) {}
 311
 312 #endif
 313 \f
 314
 315 /* Transfering floating-point registers between GDB, inferiors and cores.  */
 316
 317 /* Fill GDB's register array with the floating-point register values in
 318    *FPREGSETP.  */
 319
 320 void
 321 supply_fpregset (elf_fpregset_t *fpregsetp)
 322 {
 323   i387_supply_fsave (current_regcache, -1, fpregsetp);
 324   dummy_sse_values ();
 325 }
 326
 327 /* Fill register REGNO (if it is a floating-point register) in
 328    *FPREGSETP with the value in GDB's register array.  If REGNO is -1,
 329    do this for all registers.  */
 330
 331 void
 332 fill_fpregset (elf_fpregset_t *fpregsetp, int regno)
 333 {
 334   i387_fill_fsave ((char *) fpregsetp, regno);
 335 }
 336
 337 #ifdef HAVE_PTRACE_GETREGS
 338
 339 /* Fetch all floating-point registers from process/thread TID and store
 340    thier values in GDB's register array.  */
 341
 342 static void
 343 fetch_fpregs (int tid)
 344 {
 345   elf_fpregset_t fpregs;
 346
 347   if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
 348     perror_with_name ("Couldn't get floating point status");
 349
 350   supply_fpregset (&fpregs);
 351 }
 352
 353 /* Store all valid floating-point registers in GDB's register array
 354    into the process/thread specified by TID.  */
 355
 356 static void
 357 store_fpregs (int tid, int regno)
 358 {
 359   elf_fpregset_t fpregs;
 360
 361   if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
 362     perror_with_name ("Couldn't get floating point status");
 363
 364   fill_fpregset (&fpregs, regno);
 365
 366   if (ptrace (PTRACE_SETFPREGS, tid, 0, (int) &fpregs) < 0)
 367     perror_with_name ("Couldn't write floating point status");
 368 }
 369
 370 #else
 371
 372 static void fetch_fpregs (int tid) {}
 373 static void store_fpregs (int tid, int regno) {}
 374
 375 #endif
 376 \f
 377
 378 /* Transfering floating-point and SSE registers to and from GDB.  */
 379
 380 #ifdef HAVE_PTRACE_GETFPXREGS
 381
 382 /* Fill GDB's register array with the floating-point and SSE register
 383    values in *FPXREGSETP.  */
 384
 385 void
 386 supply_fpxregset (elf_fpxregset_t *fpxregsetp)
 387 {
 388   i387_supply_fxsave (current_regcache, -1, fpxregsetp);
 389 }
 390
 391 /* Fill register REGNO (if it is a floating-point or SSE register) in
 392    *FPXREGSETP with the value in GDB's register array.  If REGNO is
 393    -1, do this for all registers.  */
 394
 395 void
 396 fill_fpxregset (elf_fpxregset_t *fpxregsetp, int regno)
 397 {
 398   i387_fill_fxsave ((char *) fpxregsetp, regno);
 399 }
 400
 401 /* Fetch all registers covered by the PTRACE_GETFPXREGS request from
 402    process/thread TID and store their values in GDB's register array.
 403    Return non-zero if successful, zero otherwise.  */
 404
 405 static int
 406 fetch_fpxregs (int tid)
 407 {
 408   elf_fpxregset_t fpxregs;
 409
 410   if (! have_ptrace_getfpxregs)
 411     return 0;
 412
 413   if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
 414     {
 415       if (errno == EIO)
 416         {
 417           have_ptrace_getfpxregs = 0;
 418           return 0;
 419         }
 420
 421       perror_with_name ("Couldn't read floating-point and SSE registers");
 422     }
 423
 424   supply_fpxregset (&fpxregs);
 425   return 1;
 426 }
 427
 428 /* Store all valid registers in GDB's register array covered by the
 429    PTRACE_SETFPXREGS request into the process/thread specified by TID.
 430    Return non-zero if successful, zero otherwise.  */
 431
 432 static int
 433 store_fpxregs (int tid, int regno)
 434 {
 435   elf_fpxregset_t fpxregs;
 436
 437   if (! have_ptrace_getfpxregs)
 438     return 0;
 439
 440   if (ptrace (PTRACE_GETFPXREGS, tid, 0, &fpxregs) == -1)
 441     {
 442       if (errno == EIO)
 443         {
 444           have_ptrace_getfpxregs = 0;
 445           return 0;
 446         }
 447
 448       perror_with_name ("Couldn't read floating-point and SSE registers");
 449     }
 450
 451   fill_fpxregset (&fpxregs, regno);
 452
 453   if (ptrace (PTRACE_SETFPXREGS, tid, 0, &fpxregs) == -1)
 454     perror_with_name ("Couldn't write floating-point and SSE registers");
 455
 456   return 1;
 457 }
 458
 459 /* Fill the XMM registers in the register array with dummy values.  For
 460    cases where we don't have access to the XMM registers.  I think
 461    this is cleaner than printing a warning.  For a cleaner solution,
 462    we should gdbarchify the i386 family.  */
 463
 464 static void
 465 dummy_sse_values (void)
 466 {
 467   struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);
 468   /* C doesn't have a syntax for NaN's, so write it out as an array of
 469      longs.  */
 470   static long dummy[4] = { 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff };
 471   static long mxcsr = 0x1f80;
 472   int reg;
 473
 474   for (reg = 0; reg < tdep->num_xmm_regs; reg++)
 475     supply_register (XMM0_REGNUM + reg, (char *) dummy);
 476   if (tdep->num_xmm_regs > 0)
 477     supply_register (MXCSR_REGNUM, (char *) &mxcsr);
 478 }
 479
 480 #else
 481
 482 static int fetch_fpxregs (int tid) { return 0; }
 483 static int store_fpxregs (int tid, int regno) { return 0; }
 484 static void dummy_sse_values (void) {}
 485
 486 #endif /* HAVE_PTRACE_GETFPXREGS */
 487 \f
 488
 489 /* Transferring arbitrary registers between GDB and inferior.  */
 490
 491 /* Check if register REGNO in the child process is accessible.
 492    If we are accessing registers directly via the U area, only the
 493    general-purpose registers are available.
 494    All registers should be accessible if we have GETREGS support.  */
 495
 496 int
 497 cannot_fetch_register (int regno)
 498 {
 499   gdb_assert (regno >= 0 && regno < NUM_REGS);
 500   return (!have_ptrace_getregs && regmap[regno] == -1);
 501 }
 502
 503 int
 504 cannot_store_register (int regno)
 505 {
 506   gdb_assert (regno >= 0 && regno < NUM_REGS);
 507   return (!have_ptrace_getregs && regmap[regno] == -1);
 508 }
 509
 510 /* Fetch register REGNO from the child process.  If REGNO is -1, do
 511    this for all registers (including the floating point and SSE
 512    registers).  */
 513
 514 void
 515 fetch_inferior_registers (int regno)
 516 {
 517   int tid;
 518
 519   /* Use the old method of peeking around in `struct user' if the
 520      GETREGS request isn't available.  */
 521   if (!have_ptrace_getregs)
 522     {
 523       int i;
 524
 525       for (i = 0; i < NUM_REGS; i++)
 526         if (regno == -1 || regno == i)
 527           fetch_register (i);
 528
 529       return;
 530     }
 531
 532   /* GNU/Linux LWP ID's are process ID's.  */
 533   tid = TIDGET (inferior_ptid);
 534   if (tid == 0)
 535     tid = PIDGET (inferior_ptid); /* Not a threaded program.  */
 536
 537   /* Use the PTRACE_GETFPXREGS request whenever possible, since it
 538      transfers more registers in one system call, and we'll cache the
 539      results.  But remember that fetch_fpxregs can fail, and return
 540      zero.  */
 541   if (regno == -1)
 542     {
 543       fetch_regs (tid);
 544
 545       /* The call above might reset `have_ptrace_getregs'.  */
 546       if (!have_ptrace_getregs)
 547         {
 548           fetch_inferior_registers (regno);
 549           return;
 550         }
 551
 552       if (fetch_fpxregs (tid))
 553         return;
 554       fetch_fpregs (tid);
 555       return;
 556     }
 557
 558   if (GETREGS_SUPPLIES (regno))
 559     {
 560       fetch_regs (tid);
 561       return;
 562     }
 563
 564   if (GETFPXREGS_SUPPLIES (regno))
 565     {
 566       if (fetch_fpxregs (tid))
 567         return;
 568
 569       /* Either our processor or our kernel doesn't support the SSE
 570          registers, so read the FP registers in the traditional way,
 571          and fill the SSE registers with dummy values.  It would be
 572          more graceful to handle differences in the register set using
 573          gdbarch.  Until then, this will at least make things work
 574          plausibly.  */
 575       fetch_fpregs (tid);
 576       return;
 577     }
 578
 579   internal_error (__FILE__, __LINE__,
 580                   "Got request for bad register number %d.", regno);
 581 }
 582
 583 /* Store register REGNO back into the child process.  If REGNO is -1,
 584    do this for all registers (including the floating point and SSE
 585    registers).  */
 586 void
 587 store_inferior_registers (int regno)
 588 {
 589   int tid;
 590
 591   /* Use the old method of poking around in `struct user' if the
 592      SETREGS request isn't available.  */
 593   if (!have_ptrace_getregs)
 594     {
 595       int i;
 596
 597       for (i = 0; i < NUM_REGS; i++)
 598         if (regno == -1 || regno == i)
 599           store_register (i);
 600
 601       return;
 602     }
 603
 604   /* GNU/Linux LWP ID's are process ID's.  */
 605   tid = TIDGET (inferior_ptid);
 606   if (tid == 0)
 607     tid = PIDGET (inferior_ptid); /* Not a threaded program.  */
 608
 609   /* Use the PTRACE_SETFPXREGS requests whenever possible, since it
 610      transfers more registers in one system call.  But remember that
 611      store_fpxregs can fail, and return zero.  */
 612   if (regno == -1)
 613     {
 614       store_regs (tid, regno);
 615       if (store_fpxregs (tid, regno))
 616         return;
 617       store_fpregs (tid, regno);
 618       return;
 619     }
 620
 621   if (GETREGS_SUPPLIES (regno))
 622     {
 623       store_regs (tid, regno);
 624       return;
 625     }
 626
 627   if (GETFPXREGS_SUPPLIES (regno))
 628     {
 629       if (store_fpxregs (tid, regno))
 630         return;
 631
 632       /* Either our processor or our kernel doesn't support the SSE
 633          registers, so just write the FP registers in the traditional
 634          way.  */
 635       store_fpregs (tid, regno);
 636       return;
 637     }
 638
 639   internal_error (__FILE__, __LINE__,
 640                   "Got request to store bad register number %d.", regno);
 641 }
 642 \f
 643
 644 /* Support for debug registers.  */
 645
 646 static unsigned long
 647 i386_linux_dr_get (int regnum)
 648 {
 649   int tid;
 650   unsigned long value;
 651
 652   /* FIXME: kettenis/2001-01-29: It's not clear what we should do with
 653      multi-threaded processes here.  For now, pretend there is just
 654      one thread.  */
 655   tid = PIDGET (inferior_ptid);
 656
 657   /* FIXME: kettenis/2001-03-27: Calling perror_with_name if the
 658      ptrace call fails breaks debugging remote targets.  The correct
 659      way to fix this is to add the hardware breakpoint and watchpoint
 660      stuff to the target vectore.  For now, just return zero if the
 661      ptrace call fails.  */
 662   errno = 0;
 663   value = ptrace (PTRACE_PEEKUSER, tid,
 664                   offsetof (struct user, u_debugreg[regnum]), 0);
 665   if (errno != 0)
 666 #if 0
 667     perror_with_name ("Couldn't read debug register");
 668 #else
 669     return 0;
 670 #endif
 671
 672   return value;
 673 }
 674
 675 static void
 676 i386_linux_dr_set (int regnum, unsigned long value)
 677 {
 678   int tid;
 679
 680   /* FIXME: kettenis/2001-01-29: It's not clear what we should do with
 681      multi-threaded processes here.  For now, pretend there is just
 682      one thread.  */
 683   tid = PIDGET (inferior_ptid);
 684
 685   errno = 0;
 686   ptrace (PTRACE_POKEUSER, tid,
 687           offsetof (struct user, u_debugreg[regnum]), value);
 688   if (errno != 0)
 689     perror_with_name ("Couldn't write debug register");
 690 }
 691
 692 void
 693 i386_linux_dr_set_control (unsigned long control)
 694 {
 695   i386_linux_dr_set (DR_CONTROL, control);
 696 }
 697
 698 void
 699 i386_linux_dr_set_addr (int regnum, CORE_ADDR addr)
 700 {
 701   gdb_assert (regnum >= 0 && regnum <= DR_LASTADDR - DR_FIRSTADDR);
 702
 703   i386_linux_dr_set (DR_FIRSTADDR + regnum, addr);
 704 }
 705
 706 void
 707 i386_linux_dr_reset_addr (int regnum)
 708 {
 709   gdb_assert (regnum >= 0 && regnum <= DR_LASTADDR - DR_FIRSTADDR);
 710
 711   i386_linux_dr_set (DR_FIRSTADDR + regnum, 0L);
 712 }
 713
 714 unsigned long
 715 i386_linux_dr_get_status (void)
 716 {
 717   return i386_linux_dr_get (DR_STATUS);
 718 }
 719 \f
 720
 721 /* Called by libthread_db.  Returns a pointer to the thread local
 722    storage (or its descriptor).  */
 723
 724 ps_err_e
 725 ps_get_thread_area (const struct ps_prochandle *ph,
 726                     lwpid_t lwpid, int idx, void **base)
 727 {
 728   /* NOTE: cagney/2003-08-26: The definition of this buffer is found
 729      in the kernel header <asm-i386/ldt.h>.  It, after padding, is 4 x
 730      4 byte integers in size: `entry_number', `base_addr', `limit',
 731      and a bunch of status bits.
 732
 733      The values returned by this ptrace call should be part of the
 734      regcache buffer, and ps_get_thread_area should channel its
 735      request through the regcache.  That way remote targets could
 736      provide the value using the remote protocol and not this direct
 737      call.
 738
 739      Is this function needed?  I'm guessing that the `base' is the
 740      address of a a descriptor that libthread_db uses to find the
 741      thread local address base that GDB needs.  Perhaphs that
 742      descriptor is defined by the ABI.  Anyway, given that
 743      libthread_db calls this function without prompting (gdb
 744      requesting tls base) I guess it needs info in there anyway.  */
 745   unsigned int desc[4];
 746   gdb_assert (sizeof (int) == 4);
 747
 748 #ifndef PTRACE_GET_THREAD_AREA
 749 #define PTRACE_GET_THREAD_AREA 25
 750 #endif
 751
 752   if (ptrace (PTRACE_GET_THREAD_AREA, lwpid,
 753               (void *) idx, (unsigned long) &desc) < 0)
 754     return PS_ERR;
 755
 756   *(int *)base = desc[1];
 757   return PS_OK;
 758 }
 759 \f
 760
 761 /* The instruction for a GNU/Linux system call is:
 762        int $0x80
 763    or 0xcd 0x80.  */
 764
 765 static const unsigned char linux_syscall[] = { 0xcd, 0x80 };
 766
 767 #define LINUX_SYSCALL_LEN (sizeof linux_syscall)
 768
 769 /* The system call number is stored in the %eax register.  */
 770 #define LINUX_SYSCALL_REGNUM 0  /* %eax */
 771
 772 /* We are specifically interested in the sigreturn and rt_sigreturn
 773    system calls.  */
 774
 775 #ifndef SYS_sigreturn
 776 #define SYS_sigreturn           0x77
 777 #endif
 778 #ifndef SYS_rt_sigreturn
 779 #define SYS_rt_sigreturn        0xad
 780 #endif
 781
 782 /* Offset to saved processor flags, from <asm/sigcontext.h>.  */
 783 #define LINUX_SIGCONTEXT_EFLAGS_OFFSET (64)
 784
 785 /* Resume execution of the inferior process.
 786    If STEP is nonzero, single-step it.
 787    If SIGNAL is nonzero, give it that signal.  */
 788
 789 void
 790 child_resume (ptid_t ptid, int step, enum target_signal signal)
 791 {
 792   int pid = PIDGET (ptid);
 793
 794   int request = PTRACE_CONT;
 795
 796   if (pid == -1)
 797     /* Resume all threads.  */
 798     /* I think this only gets used in the non-threaded case, where "resume
 799        all threads" and "resume inferior_ptid" are the same.  */
 800     pid = PIDGET (inferior_ptid);
 801
 802   if (step)
 803     {
 804       CORE_ADDR pc = read_pc_pid (pid_to_ptid (pid));
 805       unsigned char buf[LINUX_SYSCALL_LEN];
 806
 807       request = PTRACE_SINGLESTEP;
 808
 809       /* Returning from a signal trampoline is done by calling a
 810          special system call (sigreturn or rt_sigreturn, see
 811          i386-linux-tdep.c for more information).  This system call
 812          restores the registers that were saved when the signal was
 813          raised, including %eflags.  That means that single-stepping
 814          won't work.  Instead, we'll have to modify the signal context
 815          that's about to be restored, and set the trace flag there.  */
 816
 817       /* First check if PC is at a system call.  */
 818       if (read_memory_nobpt (pc, (char *) buf, LINUX_SYSCALL_LEN) == 0
 819           && memcmp (buf, linux_syscall, LINUX_SYSCALL_LEN) == 0)
 820         {
 821           int syscall = read_register_pid (LINUX_SYSCALL_REGNUM,
 822                                            pid_to_ptid (pid));
 823
 824           /* Then check the system call number.  */
 825           if (syscall == SYS_sigreturn || syscall == SYS_rt_sigreturn)
 826             {
 827               CORE_ADDR sp = read_register (I386_ESP_REGNUM);
 828               CORE_ADDR addr = sp;
 829               unsigned long int eflags;
 830
 831               if (syscall == SYS_rt_sigreturn)
 832                 addr = read_memory_integer (sp + 8, 4) + 20;
 833
 834               /* Set the trace flag in the context that's about to be
 835                  restored.  */
 836               addr += LINUX_SIGCONTEXT_EFLAGS_OFFSET;
 837               read_memory (addr, (char *) &eflags, 4);
 838               eflags |= 0x0100;
 839               write_memory (addr, (char *) &eflags, 4);
 840             }
 841         }
 842     }
 843
 844   if (ptrace (request, pid, 0, target_signal_to_host (signal)) == -1)
 845     perror_with_name ("ptrace");
 846 }
 847
 848 void
 849 child_post_startup_inferior (ptid_t ptid)
 850 {
 851   i386_cleanup_dregs ();
 852   linux_child_post_startup_inferior (ptid);
 853 }