gdb/i386-linux-nat.c

   1 /* Native-dependent code for GNU/Linux i386.
   2
   3    Copyright (C) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,
   4    2009, 2010 Free Software Foundation, Inc.
   5
   6    This file is part of GDB.
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  20
  21 #include "defs.h"
  22 #include "i386-nat.h"
  23 #include "inferior.h"
  24 #include "gdbcore.h"
  25 #include "regcache.h"
  26 #include "target.h"
  27 #include "linux-nat.h"
  28
  29 #include "gdb_assert.h"
  30 #include "gdb_string.h"
  31 #include <sys/ptrace.h>
  32 #include <sys/user.h>
  33 #include <sys/procfs.h>
  34
  35 #ifdef HAVE_SYS_REG_H
  36 #include <sys/reg.h>
  37 #endif
  38
  39 #ifndef ORIG_EAX
  40 #define ORIG_EAX -1
  41 #endif
  42
  43 #ifdef HAVE_SYS_DEBUGREG_H
  44 #include <sys/debugreg.h>
  45 #endif
  46
  47 #ifndef DR_FIRSTADDR
  48 #define DR_FIRSTADDR 0
  49 #endif
  50
  51 #ifndef DR_LASTADDR
  52 #define DR_LASTADDR 3
  53 #endif
  54
  55 #ifndef DR_STATUS
  56 #define DR_STATUS 6
  57 #endif
  58
  59 #ifndef DR_CONTROL
  60 #define DR_CONTROL 7
  61 #endif
  62
  63 /* Prototypes for supply_gregset etc.  */
  64 #include "gregset.h"
  65
  66 #include "i387-tdep.h"
  67 #include "i386-tdep.h"
  68 #include "i386-linux-tdep.h"
  69
  70 /* Defines ps_err_e, struct ps_prochandle.  */
  71 #include "gdb_proc_service.h"
  72 \f
  73
  74 /* The register sets used in GNU/Linux ELF core-dumps are identical to
  75    the register sets in `struct user' that is used for a.out
  76    core-dumps, and is also used by `ptrace'.  The corresponding types
  77    are `elf_gregset_t' for the general-purpose registers (with
  78    `elf_greg_t' the type of a single GP register) and `elf_fpregset_t'
  79    for the floating-point registers.
  80
  81    Those types used to be available under the names `gregset_t' and
  82    `fpregset_t' too, and this file used those names in the past.  But
  83    those names are now used for the register sets used in the
  84    `mcontext_t' type, and have a different size and layout.  */
  85
  86 /* Mapping between the general-purpose registers in `struct user'
  87    format and GDB's register array layout.  */
  88 static int regmap[] =
  89 {
  90   EAX, ECX, EDX, EBX,
  91   UESP, EBP, ESI, EDI,
  92   EIP, EFL, CS, SS,
  93   DS, ES, FS, GS,
  94   -1, -1, -1, -1,               /* st0, st1, st2, st3 */
  95   -1, -1, -1, -1,               /* st4, st5, st6, st7 */
  96   -1, -1, -1, -1,               /* fctrl, fstat, ftag, fiseg */
  97   -1, -1, -1, -1,               /* fioff, foseg, fooff, fop */
  98   -1, -1, -1, -1,               /* xmm0, xmm1, xmm2, xmm3 */
  99   -1, -1, -1, -1,               /* xmm4, xmm5, xmm6, xmm6 */
 100   -1,                           /* mxcsr */
 101   ORIG_EAX
 102 };
 103
 104 /* Which ptrace request retrieves which registers?
 105    These apply to the corresponding SET requests as well.  */
 106
 107 #define GETREGS_SUPPLIES(regno) \
 108   ((0 <= (regno) && (regno) <= 15) || (regno) == I386_LINUX_ORIG_EAX_REGNUM)
 109
 110 #define GETFPXREGS_SUPPLIES(regno) \
 111   (I386_ST0_REGNUM <= (regno) && (regno) < I386_SSE_NUM_REGS)
 112
 113 /* Does the current host support the GETREGS request?  */
 114 int have_ptrace_getregs =
 115 #ifdef HAVE_PTRACE_GETREGS
 116   1
 117 #else
 118   0
 119 #endif
 120 ;
 121
 122 /* Does the current host support the GETFPXREGS request?  The header
 123    file may or may not define it, and even if it is defined, the
 124    kernel will return EIO if it's running on a pre-SSE processor.
 125
 126    My instinct is to attach this to some architecture- or
 127    target-specific data structure, but really, a particular GDB
 128    process can only run on top of one kernel at a time.  So it's okay
 129    for this to be a simple variable.  */
 130 int have_ptrace_getfpxregs =
 131 #ifdef HAVE_PTRACE_GETFPXREGS
 132   1
 133 #else
 134   0
 135 #endif
 136 ;
 137 \f
 138
 139 /* Accessing registers through the U area, one at a time.  */
 140
 141 /* Fetch one register.  */
 142
 143 static void
 144 fetch_register (struct regcache *regcache, int regno)
 145 {
 146   int tid;
 147   int val;
 148
 149   gdb_assert (!have_ptrace_getregs);
 150   if (regmap[regno] == -1)
 151     {
 152       regcache_raw_supply (regcache, regno, NULL);
 153       return;
 154     }
 155
 156   /* GNU/Linux LWP ID's are process ID's.  */
 157   tid = TIDGET (inferior_ptid);
 158   if (tid == 0)
 159     tid = PIDGET (inferior_ptid); /* Not a threaded program.  */
 160
 161   errno = 0;
 162   val = ptrace (PTRACE_PEEKUSER, tid, 4 * regmap[regno], 0);
 163   if (errno != 0)
 164     error (_("Couldn't read register %s (#%d): %s."),
 165            gdbarch_register_name (get_regcache_arch (regcache), regno),
 166            regno, safe_strerror (errno));
 167
 168   regcache_raw_supply (regcache, regno, &val);
 169 }
 170
 171 /* Store one register. */
 172
 173 static void
 174 store_register (const struct regcache *regcache, int regno)
 175 {
 176   int tid;
 177   int val;
 178
 179   gdb_assert (!have_ptrace_getregs);
 180   if (regmap[regno] == -1)
 181     return;
 182
 183   /* GNU/Linux LWP ID's are process ID's.  */
 184   tid = TIDGET (inferior_ptid);
 185   if (tid == 0)
 186     tid = PIDGET (inferior_ptid); /* Not a threaded program.  */
 187
 188   errno = 0;
 189   regcache_raw_collect (regcache, regno, &val);
 190   ptrace (PTRACE_POKEUSER, tid, 4 * regmap[regno], val);
 191   if (errno != 0)
 192     error (_("Couldn't write register %s (#%d): %s."),
 193            gdbarch_register_name (get_regcache_arch (regcache), regno),
 194            regno, safe_strerror (errno));
 195 }
 196 \f
 197
 198 /* Transfering the general-purpose registers between GDB, inferiors
 199    and core files.  */
 200
 201 /* Fill GDB's register array with the general-purpose register values
 202    in *GREGSETP.  */
 203
 204 void
 205 supply_gregset (struct regcache *regcache, const elf_gregset_t *gregsetp)
 206 {
 207   const elf_greg_t *regp = (const elf_greg_t *) gregsetp;
 208   int i;
 209
 210   for (i = 0; i < I386_NUM_GREGS; i++)
 211     regcache_raw_supply (regcache, i, regp + regmap[i]);
 212
 213   if (I386_LINUX_ORIG_EAX_REGNUM
 214         < gdbarch_num_regs (get_regcache_arch (regcache)))
 215     regcache_raw_supply (regcache, I386_LINUX_ORIG_EAX_REGNUM,
 216                          regp + ORIG_EAX);
 217 }
 218
 219 /* Fill register REGNO (if it is a general-purpose register) in
 220    *GREGSETPS with the value in GDB's register array.  If REGNO is -1,
 221    do this for all registers.  */
 222
 223 void
 224 fill_gregset (const struct regcache *regcache,
 225               elf_gregset_t *gregsetp, int regno)
 226 {
 227   elf_greg_t *regp = (elf_greg_t *) gregsetp;
 228   int i;
 229
 230   for (i = 0; i < I386_NUM_GREGS; i++)
 231     if (regno == -1 || regno == i)
 232       regcache_raw_collect (regcache, i, regp + regmap[i]);
 233
 234   if ((regno == -1 || regno == I386_LINUX_ORIG_EAX_REGNUM)
 235       && I386_LINUX_ORIG_EAX_REGNUM
 236            < gdbarch_num_regs (get_regcache_arch (regcache)))
 237     regcache_raw_collect (regcache, I386_LINUX_ORIG_EAX_REGNUM,
 238                           regp + ORIG_EAX);
 239 }
 240
 241 #ifdef HAVE_PTRACE_GETREGS
 242
 243 /* Fetch all general-purpose registers from process/thread TID and
 244    store their values in GDB's register array.  */
 245
 246 static void
 247 fetch_regs (struct regcache *regcache, int tid)
 248 {
 249   elf_gregset_t regs;
 250   elf_gregset_t *regs_p = &regs;
 251
 252   if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
 253     {
 254       if (errno == EIO)
 255         {
 256           /* The kernel we're running on doesn't support the GETREGS
 257              request.  Reset `have_ptrace_getregs'.  */
 258           have_ptrace_getregs = 0;
 259           return;
 260         }
 261
 262       perror_with_name (_("Couldn't get registers"));
 263     }
 264
 265   supply_gregset (regcache, (const elf_gregset_t *) regs_p);
 266 }
 267
 268 /* Store all valid general-purpose registers in GDB's register array
 269    into the process/thread specified by TID.  */
 270
 271 static void
 272 store_regs (const struct regcache *regcache, int tid, int regno)
 273 {
 274   elf_gregset_t regs;
 275
 276   if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
 277     perror_with_name (_("Couldn't get registers"));
 278
 279   fill_gregset (regcache, &regs, regno);
 280
 281   if (ptrace (PTRACE_SETREGS, tid, 0, (int) &regs) < 0)
 282     perror_with_name (_("Couldn't write registers"));
 283 }
 284
 285 #else
 286
 287 static void fetch_regs (struct regcache *regcache, int tid) {}
 288 static void store_regs (const struct regcache *regcache, int tid, int regno) {}
 289
 290 #endif
 291 \f
 292
 293 /* Transfering floating-point registers between GDB, inferiors and cores.  */
 294
 295 /* Fill GDB's register array with the floating-point register values in
 296    *FPREGSETP.  */
 297
 298 void
 299 supply_fpregset (struct regcache *regcache, const elf_fpregset_t *fpregsetp)
 300 {
 301   i387_supply_fsave (regcache, -1, fpregsetp);
 302 }
 303
 304 /* Fill register REGNO (if it is a floating-point register) in
 305    *FPREGSETP with the value in GDB's register array.  If REGNO is -1,
 306    do this for all registers.  */
 307
 308 void
 309 fill_fpregset (const struct regcache *regcache,
 310                elf_fpregset_t *fpregsetp, int regno)
 311 {
 312   i387_collect_fsave (regcache, regno, fpregsetp);
 313 }
 314
 315 #ifdef HAVE_PTRACE_GETREGS
 316
 317 /* Fetch all floating-point registers from process/thread TID and store
 318    thier values in GDB's register array.  */
 319
 320 static void
 321 fetch_fpregs (struct regcache *regcache, int tid)
 322 {
 323   elf_fpregset_t fpregs;
 324
 325   if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
 326     perror_with_name (_("Couldn't get floating point status"));
 327
 328   supply_fpregset (regcache, (const elf_fpregset_t *) &fpregs);
 329 }
 330
 331 /* Store all valid floating-point registers in GDB's register array
 332    into the process/thread specified by TID.  */
 333
 334 static void
 335 store_fpregs (const struct regcache *regcache, int tid, int regno)
 336 {
 337   elf_fpregset_t fpregs;
 338
 339   if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
 340     perror_with_name (_("Couldn't get floating point status"));
 341
 342   fill_fpregset (regcache, &fpregs, regno);
 343
 344   if (ptrace (PTRACE_SETFPREGS, tid, 0, (int) &fpregs) < 0)
 345     perror_with_name (_("Couldn't write floating point status"));
 346 }
 347
 348 #else
 349
 350 static void fetch_fpregs (struct regcache *regcache, int tid) {}
 351 static void store_fpregs (const struct regcache *regcache, int tid, int regno) {}
 352
 353 #endif
 354 \f
 355
 356 /* Transfering floating-point and SSE registers to and from GDB.  */
 357
 358 #ifdef HAVE_PTRACE_GETFPXREGS
 359
 360 /* Fill GDB's register array with the floating-point and SSE register
 361    values in *FPXREGSETP.  */
 362
 363 void
 364 supply_fpxregset (struct regcache *regcache,
 365                   const elf_fpxregset_t *fpxregsetp)
 366 {
 367   i387_supply_fxsave (regcache, -1, fpxregsetp);
 368 }
 369
 370 /* Fill register REGNO (if it is a floating-point or SSE register) in
 371    *FPXREGSETP with the value in GDB's register array.  If REGNO is
 372    -1, do this for all registers.  */
 373
 374 void
 375 fill_fpxregset (const struct regcache *regcache,
 376                 elf_fpxregset_t *fpxregsetp, int regno)
 377 {
 378   i387_collect_fxsave (regcache, regno, fpxregsetp);
 379 }
 380
 381 /* Fetch all registers covered by the PTRACE_GETFPXREGS request from
 382    process/thread TID and store their values in GDB's register array.
 383    Return non-zero if successful, zero otherwise.  */
 384
 385 static int
 386 fetch_fpxregs (struct regcache *regcache, int tid)
 387 {
 388   elf_fpxregset_t fpxregs;
 389
 390   if (! have_ptrace_getfpxregs)
 391     return 0;
 392
 393   if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
 394     {
 395       if (errno == EIO)
 396         {
 397           have_ptrace_getfpxregs = 0;
 398           return 0;
 399         }
 400
 401       perror_with_name (_("Couldn't read floating-point and SSE registers"));
 402     }
 403
 404   supply_fpxregset (regcache, (const elf_fpxregset_t *) &fpxregs);
 405   return 1;
 406 }
 407
 408 /* Store all valid registers in GDB's register array covered by the
 409    PTRACE_SETFPXREGS request into the process/thread specified by TID.
 410    Return non-zero if successful, zero otherwise.  */
 411
 412 static int
 413 store_fpxregs (const struct regcache *regcache, int tid, int regno)
 414 {
 415   elf_fpxregset_t fpxregs;
 416
 417   if (! have_ptrace_getfpxregs)
 418     return 0;
 419
 420   if (ptrace (PTRACE_GETFPXREGS, tid, 0, &fpxregs) == -1)
 421     {
 422       if (errno == EIO)
 423         {
 424           have_ptrace_getfpxregs = 0;
 425           return 0;
 426         }
 427
 428       perror_with_name (_("Couldn't read floating-point and SSE registers"));
 429     }
 430
 431   fill_fpxregset (regcache, &fpxregs, regno);
 432
 433   if (ptrace (PTRACE_SETFPXREGS, tid, 0, &fpxregs) == -1)
 434     perror_with_name (_("Couldn't write floating-point and SSE registers"));
 435
 436   return 1;
 437 }
 438
 439 #else
 440
 441 static int fetch_fpxregs (struct regcache *regcache, int tid) { return 0; }
 442 static int store_fpxregs (const struct regcache *regcache, int tid, int regno) { return 0; }
 443
 444 #endif /* HAVE_PTRACE_GETFPXREGS */
 445 \f
 446
 447 /* Transferring arbitrary registers between GDB and inferior.  */
 448
 449 /* Fetch register REGNO from the child process.  If REGNO is -1, do
 450    this for all registers (including the floating point and SSE
 451    registers).  */
 452
 453 static void
 454 i386_linux_fetch_inferior_registers (struct target_ops *ops,
 455                                      struct regcache *regcache, int regno)
 456 {
 457   int tid;
 458
 459   /* Use the old method of peeking around in `struct user' if the
 460      GETREGS request isn't available.  */
 461   if (!have_ptrace_getregs)
 462     {
 463       int i;
 464
 465       for (i = 0; i < gdbarch_num_regs (get_regcache_arch (regcache)); i++)
 466         if (regno == -1 || regno == i)
 467           fetch_register (regcache, i);
 468
 469       return;
 470     }
 471
 472   /* GNU/Linux LWP ID's are process ID's.  */
 473   tid = TIDGET (inferior_ptid);
 474   if (tid == 0)
 475     tid = PIDGET (inferior_ptid); /* Not a threaded program.  */
 476
 477   /* Use the PTRACE_GETFPXREGS request whenever possible, since it
 478      transfers more registers in one system call, and we'll cache the
 479      results.  But remember that fetch_fpxregs can fail, and return
 480      zero.  */
 481   if (regno == -1)
 482     {
 483       fetch_regs (regcache, tid);
 484
 485       /* The call above might reset `have_ptrace_getregs'.  */
 486       if (!have_ptrace_getregs)
 487         {
 488           i386_linux_fetch_inferior_registers (ops, regcache, regno);
 489           return;
 490         }
 491
 492       if (fetch_fpxregs (regcache, tid))
 493         return;
 494       fetch_fpregs (regcache, tid);
 495       return;
 496     }
 497
 498   if (GETREGS_SUPPLIES (regno))
 499     {
 500       fetch_regs (regcache, tid);
 501       return;
 502     }
 503
 504   if (GETFPXREGS_SUPPLIES (regno))
 505     {
 506       if (fetch_fpxregs (regcache, tid))
 507         return;
 508
 509       /* Either our processor or our kernel doesn't support the SSE
 510          registers, so read the FP registers in the traditional way,
 511          and fill the SSE registers with dummy values.  It would be
 512          more graceful to handle differences in the register set using
 513          gdbarch.  Until then, this will at least make things work
 514          plausibly.  */
 515       fetch_fpregs (regcache, tid);
 516       return;
 517     }
 518
 519   internal_error (__FILE__, __LINE__,
 520                   _("Got request for bad register number %d."), regno);
 521 }
 522
 523 /* Store register REGNO back into the child process.  If REGNO is -1,
 524    do this for all registers (including the floating point and SSE
 525    registers).  */
 526 static void
 527 i386_linux_store_inferior_registers (struct target_ops *ops,
 528                                      struct regcache *regcache, int regno)
 529 {
 530   int tid;
 531
 532   /* Use the old method of poking around in `struct user' if the
 533      SETREGS request isn't available.  */
 534   if (!have_ptrace_getregs)
 535     {
 536       int i;
 537
 538       for (i = 0; i < gdbarch_num_regs (get_regcache_arch (regcache)); i++)
 539         if (regno == -1 || regno == i)
 540           store_register (regcache, i);
 541
 542       return;
 543     }
 544
 545   /* GNU/Linux LWP ID's are process ID's.  */
 546   tid = TIDGET (inferior_ptid);
 547   if (tid == 0)
 548     tid = PIDGET (inferior_ptid); /* Not a threaded program.  */
 549
 550   /* Use the PTRACE_SETFPXREGS requests whenever possible, since it
 551      transfers more registers in one system call.  But remember that
 552      store_fpxregs can fail, and return zero.  */
 553   if (regno == -1)
 554     {
 555       store_regs (regcache, tid, regno);
 556       if (store_fpxregs (regcache, tid, regno))
 557         return;
 558       store_fpregs (regcache, tid, regno);
 559       return;
 560     }
 561
 562   if (GETREGS_SUPPLIES (regno))
 563     {
 564       store_regs (regcache, tid, regno);
 565       return;
 566     }
 567
 568   if (GETFPXREGS_SUPPLIES (regno))
 569     {
 570       if (store_fpxregs (regcache, tid, regno))
 571         return;
 572
 573       /* Either our processor or our kernel doesn't support the SSE
 574          registers, so just write the FP registers in the traditional
 575          way.  */
 576       store_fpregs (regcache, tid, regno);
 577       return;
 578     }
 579
 580   internal_error (__FILE__, __LINE__,
 581                   _("Got request to store bad register number %d."), regno);
 582 }
 583 \f
 584
 585 /* Support for debug registers.  */
 586
 587 static unsigned long i386_linux_dr[DR_CONTROL + 1];
 588
 589 /* Get debug register REGNUM value from only the one LWP of PTID.  */
 590
 591 static unsigned long
 592 i386_linux_dr_get (ptid_t ptid, int regnum)
 593 {
 594   int tid;
 595   unsigned long value;
 596
 597   tid = TIDGET (ptid);
 598   if (tid == 0)
 599     tid = PIDGET (ptid);
 600
 601   /* FIXME: kettenis/2001-03-27: Calling perror_with_name if the
 602      ptrace call fails breaks debugging remote targets.  The correct
 603      way to fix this is to add the hardware breakpoint and watchpoint
 604      stuff to the target vector.  For now, just return zero if the
 605      ptrace call fails.  */
 606   errno = 0;
 607   value = ptrace (PTRACE_PEEKUSER, tid,
 608                   offsetof (struct user, u_debugreg[regnum]), 0);
 609   if (errno != 0)
 610 #if 0
 611     perror_with_name (_("Couldn't read debug register"));
 612 #else
 613     return 0;
 614 #endif
 615
 616   return value;
 617 }
 618
 619 /* Set debug register REGNUM to VALUE in only the one LWP of PTID.  */
 620
 621 static void
 622 i386_linux_dr_set (ptid_t ptid, int regnum, unsigned long value)
 623 {
 624   int tid;
 625
 626   tid = TIDGET (ptid);
 627   if (tid == 0)
 628     tid = PIDGET (ptid);
 629
 630   errno = 0;
 631   ptrace (PTRACE_POKEUSER, tid,
 632           offsetof (struct user, u_debugreg[regnum]), value);
 633   if (errno != 0)
 634     perror_with_name (_("Couldn't write debug register"));
 635 }
 636
 637 /* Set DR_CONTROL to ADDR in all LWPs of LWP_LIST.  */
 638
 639 static void
 640 i386_linux_dr_set_control (unsigned long control)
 641 {
 642   struct lwp_info *lp;
 643   ptid_t ptid;
 644
 645   i386_linux_dr[DR_CONTROL] = control;
 646   ALL_LWPS (lp, ptid)
 647     i386_linux_dr_set (ptid, DR_CONTROL, control);
 648 }
 649
 650 /* Set address REGNUM (zero based) to ADDR in all LWPs of LWP_LIST.  */
 651
 652 static void
 653 i386_linux_dr_set_addr (int regnum, CORE_ADDR addr)
 654 {
 655   struct lwp_info *lp;
 656   ptid_t ptid;
 657
 658   gdb_assert (regnum >= 0 && regnum <= DR_LASTADDR - DR_FIRSTADDR);
 659
 660   i386_linux_dr[DR_FIRSTADDR + regnum] = addr;
 661   ALL_LWPS (lp, ptid)
 662     i386_linux_dr_set (ptid, DR_FIRSTADDR + regnum, addr);
 663 }
 664
 665 /* Set address REGNUM (zero based) to zero in all LWPs of LWP_LIST.  */
 666
 667 static void
 668 i386_linux_dr_reset_addr (int regnum)
 669 {
 670   i386_linux_dr_set_addr (regnum, 0);
 671 }
 672
 673 /* Get DR_STATUS from only the one LWP of INFERIOR_PTID.  */
 674
 675 static unsigned long
 676 i386_linux_dr_get_status (void)
 677 {
 678   return i386_linux_dr_get (inferior_ptid, DR_STATUS);
 679 }
 680
 681 /* Unset MASK bits in DR_STATUS in all LWPs of LWP_LIST.  */
 682
 683 static void
 684 i386_linux_dr_unset_status (unsigned long mask)
 685 {
 686   struct lwp_info *lp;
 687   ptid_t ptid;
 688
 689   ALL_LWPS (lp, ptid)
 690     {
 691       unsigned long value;
 692
 693       value = i386_linux_dr_get (ptid, DR_STATUS);
 694       value &= ~mask;
 695       i386_linux_dr_set (ptid, DR_STATUS, value);
 696     }
 697 }
 698
 699 static void
 700 i386_linux_new_thread (ptid_t ptid)
 701 {
 702   int i;
 703
 704   for (i = DR_FIRSTADDR; i <= DR_LASTADDR; i++)
 705     i386_linux_dr_set (ptid, i, i386_linux_dr[i]);
 706
 707   i386_linux_dr_set (ptid, DR_CONTROL, i386_linux_dr[DR_CONTROL]);
 708 }
 709 \f
 710
 711 /* Called by libthread_db.  Returns a pointer to the thread local
 712    storage (or its descriptor).  */
 713
 714 ps_err_e
 715 ps_get_thread_area (const struct ps_prochandle *ph,
 716                     lwpid_t lwpid, int idx, void **base)
 717 {
 718   /* NOTE: cagney/2003-08-26: The definition of this buffer is found
 719      in the kernel header <asm-i386/ldt.h>.  It, after padding, is 4 x
 720      4 byte integers in size: `entry_number', `base_addr', `limit',
 721      and a bunch of status bits.
 722
 723      The values returned by this ptrace call should be part of the
 724      regcache buffer, and ps_get_thread_area should channel its
 725      request through the regcache.  That way remote targets could
 726      provide the value using the remote protocol and not this direct
 727      call.
 728
 729      Is this function needed?  I'm guessing that the `base' is the
 730      address of a a descriptor that libthread_db uses to find the
 731      thread local address base that GDB needs.  Perhaps that
 732      descriptor is defined by the ABI.  Anyway, given that
 733      libthread_db calls this function without prompting (gdb
 734      requesting tls base) I guess it needs info in there anyway.  */
 735   unsigned int desc[4];
 736   gdb_assert (sizeof (int) == 4);
 737
 738 #ifndef PTRACE_GET_THREAD_AREA
 739 #define PTRACE_GET_THREAD_AREA 25
 740 #endif
 741
 742   if (ptrace (PTRACE_GET_THREAD_AREA, lwpid,
 743               (void *) idx, (unsigned long) &desc) < 0)
 744     return PS_ERR;
 745
 746   *(int *)base = desc[1];
 747   return PS_OK;
 748 }
 749 \f
 750
 751 /* The instruction for a GNU/Linux system call is:
 752        int $0x80
 753    or 0xcd 0x80.  */
 754
 755 static const unsigned char linux_syscall[] = { 0xcd, 0x80 };
 756
 757 #define LINUX_SYSCALL_LEN (sizeof linux_syscall)
 758
 759 /* The system call number is stored in the %eax register.  */
 760 #define LINUX_SYSCALL_REGNUM I386_EAX_REGNUM
 761
 762 /* We are specifically interested in the sigreturn and rt_sigreturn
 763    system calls.  */
 764
 765 #ifndef SYS_sigreturn
 766 #define SYS_sigreturn           0x77
 767 #endif
 768 #ifndef SYS_rt_sigreturn
 769 #define SYS_rt_sigreturn        0xad
 770 #endif
 771
 772 /* Offset to saved processor flags, from <asm/sigcontext.h>.  */
 773 #define LINUX_SIGCONTEXT_EFLAGS_OFFSET (64)
 774
 775 /* Resume execution of the inferior process.
 776    If STEP is nonzero, single-step it.
 777    If SIGNAL is nonzero, give it that signal.  */
 778
 779 static void
 780 i386_linux_resume (struct target_ops *ops,
 781                    ptid_t ptid, int step, enum target_signal signal)
 782 {
 783   int pid = PIDGET (ptid);
 784
 785   int request;
 786
 787   if (catch_syscall_enabled () > 0)
 788    request = PTRACE_SYSCALL;
 789   else
 790     request = PTRACE_CONT;
 791
 792   if (step)
 793     {
 794       struct regcache *regcache = get_thread_regcache (pid_to_ptid (pid));
 795       struct gdbarch *gdbarch = get_regcache_arch (regcache);
 796       enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
 797       ULONGEST pc;
 798       gdb_byte buf[LINUX_SYSCALL_LEN];
 799
 800       request = PTRACE_SINGLESTEP;
 801
 802       regcache_cooked_read_unsigned (regcache,
 803                                      gdbarch_pc_regnum (gdbarch), &pc);
 804
 805       /* Returning from a signal trampoline is done by calling a
 806          special system call (sigreturn or rt_sigreturn, see
 807          i386-linux-tdep.c for more information).  This system call
 808          restores the registers that were saved when the signal was
 809          raised, including %eflags.  That means that single-stepping
 810          won't work.  Instead, we'll have to modify the signal context
 811          that's about to be restored, and set the trace flag there.  */
 812
 813       /* First check if PC is at a system call.  */
 814       if (target_read_memory (pc, buf, LINUX_SYSCALL_LEN) == 0
 815           && memcmp (buf, linux_syscall, LINUX_SYSCALL_LEN) == 0)
 816         {
 817           ULONGEST syscall;
 818           regcache_cooked_read_unsigned (regcache,
 819                                          LINUX_SYSCALL_REGNUM, &syscall);
 820
 821           /* Then check the system call number.  */
 822           if (syscall == SYS_sigreturn || syscall == SYS_rt_sigreturn)
 823             {
 824               ULONGEST sp, addr;
 825               unsigned long int eflags;
 826
 827               regcache_cooked_read_unsigned (regcache, I386_ESP_REGNUM, &sp);
 828               if (syscall == SYS_rt_sigreturn)
 829                 addr = read_memory_integer (sp + 8, 4, byte_order) + 20;
 830               else
 831                 addr = sp;
 832
 833               /* Set the trace flag in the context that's about to be
 834                  restored.  */
 835               addr += LINUX_SIGCONTEXT_EFLAGS_OFFSET;
 836               read_memory (addr, (gdb_byte *) &eflags, 4);
 837               eflags |= 0x0100;
 838               write_memory (addr, (gdb_byte *) &eflags, 4);
 839             }
 840         }
 841     }
 842
 843   if (ptrace (request, pid, 0, target_signal_to_host (signal)) == -1)
 844     perror_with_name (("ptrace"));
 845 }
 846
 847 static void (*super_post_startup_inferior) (ptid_t ptid);
 848
 849 static void
 850 i386_linux_child_post_startup_inferior (ptid_t ptid)
 851 {
 852   i386_cleanup_dregs ();
 853   super_post_startup_inferior (ptid);
 854 }
 855
 856 /* Get Linux/x86 target description from running target.  */
 857
 858 static const struct target_desc *
 859 i386_linux_read_description (struct target_ops *ops)
 860 {
 861   return tdesc_i386_linux;
 862 }
 863
 864 void
 865 _initialize_i386_linux_nat (void)
 866 {
 867   struct target_ops *t;
 868
 869   /* Fill in the generic GNU/Linux methods.  */
 870   t = linux_target ();
 871
 872   i386_use_watchpoints (t);
 873
 874   i386_dr_low.set_control = i386_linux_dr_set_control;
 875   i386_dr_low.set_addr = i386_linux_dr_set_addr;
 876   i386_dr_low.reset_addr = i386_linux_dr_reset_addr;
 877   i386_dr_low.get_status = i386_linux_dr_get_status;
 878   i386_dr_low.unset_status = i386_linux_dr_unset_status;
 879   i386_set_debug_register_length (4);
 880
 881   /* Override the default ptrace resume method.  */
 882   t->to_resume = i386_linux_resume;
 883
 884   /* Override the GNU/Linux inferior startup hook.  */
 885   super_post_startup_inferior = t->to_post_startup_inferior;
 886   t->to_post_startup_inferior = i386_linux_child_post_startup_inferior;
 887
 888   /* Add our register access methods.  */
 889   t->to_fetch_registers = i386_linux_fetch_inferior_registers;
 890   t->to_store_registers = i386_linux_store_inferior_registers;
 891
 892   t->to_read_description = i386_linux_read_description;
 893
 894   /* Register the target.  */
 895   linux_nat_add_target (t);
 896   linux_nat_set_new_thread (t, i386_linux_new_thread);
 897 }