gdb/i386-linux-nat.c

   1 /* Native-dependent code for Linux/x86.
   2    Copyright 1999, 2000, 2001 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include "defs.h"
  22 #include "inferior.h"
  23 #include "gdbcore.h"
  24 #include "regcache.h"
  25
  26 #include <sys/ptrace.h>
  27 #include <sys/user.h>
  28 #include <sys/procfs.h>
  29
  30 #ifdef HAVE_SYS_REG_H
  31 #include <sys/reg.h>
  32 #endif
  33
  34 /* Prototypes for supply_gregset etc.  */
  35 #include "gregset.h"
  36
  37 /* Prototypes for i387_supply_fsave etc.  */
  38 #include "i387-nat.h"
  39
  40 /* Prototypes for local functions.  */
  41 static void dummy_sse_values (void);
  42
  43 /* On Linux, threads are implemented as pseudo-processes, in which
  44    case we may be tracing more than one process at a time.  In that
  45    case, inferior_pid will contain the main process ID and the
  46    individual thread (process) ID mashed together.  These macros are
  47    used to separate them out.  These definitions should be overridden
  48    if thread support is included.  */
  49
  50 #if !defined (PIDGET)   /* Default definition for PIDGET/TIDGET.  */
  51 #define PIDGET(PID)     PID
  52 #define TIDGET(PID)     0
  53 #endif
  54 \f
  55
  56 /* The register sets used in Linux ELF core-dumps are identical to the
  57    register sets in `struct user' that is used for a.out core-dumps,
  58    and is also used by `ptrace'.  The corresponding types are
  59    `elf_gregset_t' for the general-purpose registers (with
  60    `elf_greg_t' the type of a single GP register) and `elf_fpregset_t'
  61    for the floating-point registers.
  62
  63    Those types used to be available under the names `gregset_t' and
  64    `fpregset_t' too, and this file used those names in the past.  But
  65    those names are now used for the register sets used in the
  66    `mcontext_t' type, and have a different size and layout.  */
  67
  68 /* Mapping between the general-purpose registers in `struct user'
  69    format and GDB's register array layout.  */
  70 static int regmap[] =
  71 {
  72   EAX, ECX, EDX, EBX,
  73   UESP, EBP, ESI, EDI,
  74   EIP, EFL, CS, SS,
  75   DS, ES, FS, GS
  76 };
  77
  78 /* Which ptrace request retrieves which registers?
  79    These apply to the corresponding SET requests as well.  */
  80 #define GETREGS_SUPPLIES(regno) \
  81   (0 <= (regno) && (regno) <= 15)
  82 #define GETFPREGS_SUPPLIES(regno) \
  83   (FP0_REGNUM <= (regno) && (regno) <= LAST_FPU_CTRL_REGNUM)
  84 #define GETFPXREGS_SUPPLIES(regno) \
  85   (FP0_REGNUM <= (regno) && (regno) <= MXCSR_REGNUM)
  86
  87 /* Does the current host support the GETREGS request?  */
  88 int have_ptrace_getregs =
  89 #ifdef HAVE_PTRACE_GETREGS
  90   1
  91 #else
  92   0
  93 #endif
  94 ;
  95
  96 /* Does the current host support the GETFPXREGS request?  The header
  97    file may or may not define it, and even if it is defined, the
  98    kernel will return EIO if it's running on a pre-SSE processor.
  99
 100    My instinct is to attach this to some architecture- or
 101    target-specific data structure, but really, a particular GDB
 102    process can only run on top of one kernel at a time.  So it's okay
 103    for this to be a simple variable.  */
 104 int have_ptrace_getfpxregs =
 105 #ifdef HAVE_PTRACE_GETFPXREGS
 106   1
 107 #else
 108   0
 109 #endif
 110 ;
 111 \f
 112
 113 /* Fetching registers directly from the U area, one at a time.  */
 114
 115 /* FIXME: kettenis/2000-03-05: This duplicates code from `inptrace.c'.
 116    The problem is that we define FETCH_INFERIOR_REGISTERS since we
 117    want to use our own versions of {fetch,store}_inferior_registers
 118    that use the GETREGS request.  This means that the code in
 119    `infptrace.c' is #ifdef'd out.  But we need to fall back on that
 120    code when GDB is running on top of a kernel that doesn't support
 121    the GETREGS request.  I want to avoid changing `infptrace.c' right
 122    now.  */
 123
 124 #ifndef PT_READ_U
 125 #define PT_READ_U PTRACE_PEEKUSR
 126 #endif
 127 #ifndef PT_WRITE_U
 128 #define PT_WRITE_U PTRACE_POKEUSR
 129 #endif
 130
 131 /* Default the type of the ptrace transfer to int.  */
 132 #ifndef PTRACE_XFER_TYPE
 133 #define PTRACE_XFER_TYPE int
 134 #endif
 135
 136 /* Registers we shouldn't try to fetch.  */
 137 #define OLD_CANNOT_FETCH_REGISTER(regno) ((regno) >= NUM_GREGS)
 138
 139 /* Fetch one register.  */
 140
 141 static void
 142 fetch_register (int regno)
 143 {
 144   /* This isn't really an address.  But ptrace thinks of it as one.  */
 145   CORE_ADDR regaddr;
 146   char mess[128];               /* For messages */
 147   register int i;
 148   unsigned int offset;          /* Offset of registers within the u area.  */
 149   char buf[MAX_REGISTER_RAW_SIZE];
 150   int tid;
 151
 152   if (OLD_CANNOT_FETCH_REGISTER (regno))
 153     {
 154       memset (buf, '\0', REGISTER_RAW_SIZE (regno));    /* Supply zeroes */
 155       supply_register (regno, buf);
 156       return;
 157     }
 158
 159   /* Overload thread id onto process id */
 160   if ((tid = TIDGET (inferior_pid)) == 0)
 161     tid = inferior_pid;         /* no thread id, just use process id */
 162
 163   offset = U_REGS_OFFSET;
 164
 165   regaddr = register_addr (regno, offset);
 166   for (i = 0; i < REGISTER_RAW_SIZE (regno); i += sizeof (PTRACE_XFER_TYPE))
 167     {
 168       errno = 0;
 169       *(PTRACE_XFER_TYPE *) & buf[i] = ptrace (PT_READ_U, tid,
 170                                                (PTRACE_ARG3_TYPE) regaddr, 0);
 171       regaddr += sizeof (PTRACE_XFER_TYPE);
 172       if (errno != 0)
 173         {
 174           sprintf (mess, "reading register %s (#%d)",
 175                    REGISTER_NAME (regno), regno);
 176           perror_with_name (mess);
 177         }
 178     }
 179   supply_register (regno, buf);
 180 }
 181
 182 /* Fetch register values from the inferior.
 183    If REGNO is negative, do this for all registers.
 184    Otherwise, REGNO specifies which register (so we can save time). */
 185
 186 void
 187 old_fetch_inferior_registers (int regno)
 188 {
 189   if (regno >= 0)
 190     {
 191       fetch_register (regno);
 192     }
 193   else
 194     {
 195       for (regno = 0; regno < NUM_REGS; regno++)
 196         {
 197           fetch_register (regno);
 198         }
 199     }
 200 }
 201
 202 /* Registers we shouldn't try to store.  */
 203 #define OLD_CANNOT_STORE_REGISTER(regno) ((regno) >= NUM_GREGS)
 204
 205 /* Store one register. */
 206
 207 static void
 208 store_register (int regno)
 209 {
 210   /* This isn't really an address.  But ptrace thinks of it as one.  */
 211   CORE_ADDR regaddr;
 212   char mess[128];               /* For messages */
 213   register int i;
 214   unsigned int offset;          /* Offset of registers within the u area.  */
 215   int tid;
 216
 217   if (OLD_CANNOT_STORE_REGISTER (regno))
 218     {
 219       return;
 220     }
 221
 222   /* Overload thread id onto process id */
 223   if ((tid = TIDGET (inferior_pid)) == 0)
 224     tid = inferior_pid;         /* no thread id, just use process id */
 225
 226   offset = U_REGS_OFFSET;
 227
 228   regaddr = register_addr (regno, offset);
 229   for (i = 0; i < REGISTER_RAW_SIZE (regno); i += sizeof (PTRACE_XFER_TYPE))
 230     {
 231       errno = 0;
 232       ptrace (PT_WRITE_U, tid, (PTRACE_ARG3_TYPE) regaddr,
 233               *(PTRACE_XFER_TYPE *) & registers[REGISTER_BYTE (regno) + i]);
 234       regaddr += sizeof (PTRACE_XFER_TYPE);
 235       if (errno != 0)
 236         {
 237           sprintf (mess, "writing register %s (#%d)",
 238                    REGISTER_NAME (regno), regno);
 239           perror_with_name (mess);
 240         }
 241     }
 242 }
 243
 244 /* Store our register values back into the inferior.
 245    If REGNO is negative, do this for all registers.
 246    Otherwise, REGNO specifies which register (so we can save time).  */
 247
 248 void
 249 old_store_inferior_registers (int regno)
 250 {
 251   if (regno >= 0)
 252     {
 253       store_register (regno);
 254     }
 255   else
 256     {
 257       for (regno = 0; regno < NUM_REGS; regno++)
 258         {
 259           store_register (regno);
 260         }
 261     }
 262 }
 263 \f
 264
 265 /* Transfering the general-purpose registers between GDB, inferiors
 266    and core files.  */
 267
 268 /* Fill GDB's register array with the general-purpose register values
 269    in *GREGSETP.  */
 270
 271 void
 272 supply_gregset (elf_gregset_t *gregsetp)
 273 {
 274   elf_greg_t *regp = (elf_greg_t *) gregsetp;
 275   int i;
 276
 277   for (i = 0; i < NUM_GREGS; i++)
 278     supply_register (i, (char *) (regp + regmap[i]));
 279 }
 280
 281 /* Fill register REGNO (if it is a general-purpose register) in
 282    *GREGSETPS with the value in GDB's register array.  If REGNO is -1,
 283    do this for all registers.  */
 284
 285 void
 286 fill_gregset (elf_gregset_t *gregsetp, int regno)
 287 {
 288   elf_greg_t *regp = (elf_greg_t *) gregsetp;
 289   int i;
 290
 291   for (i = 0; i < NUM_GREGS; i++)
 292     if ((regno == -1 || regno == i))
 293       *(regp + regmap[i]) = *(elf_greg_t *) &registers[REGISTER_BYTE (i)];
 294 }
 295
 296 #ifdef HAVE_PTRACE_GETREGS
 297
 298 /* Fetch all general-purpose registers from process/thread TID and
 299    store their values in GDB's register array.  */
 300
 301 static void
 302 fetch_regs (int tid)
 303 {
 304   elf_gregset_t regs;
 305
 306   if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
 307     {
 308       if (errno == EIO)
 309         {
 310           /* The kernel we're running on doesn't support the GETREGS
 311              request.  Reset `have_ptrace_getregs'.  */
 312           have_ptrace_getregs = 0;
 313           return;
 314         }
 315
 316       perror_with_name ("Couldn't get registers");
 317     }
 318
 319   supply_gregset (&regs);
 320 }
 321
 322 /* Store all valid general-purpose registers in GDB's register array
 323    into the process/thread specified by TID.  */
 324
 325 static void
 326 store_regs (int tid, int regno)
 327 {
 328   elf_gregset_t regs;
 329
 330   if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
 331     perror_with_name ("Couldn't get registers");
 332
 333   fill_gregset (&regs, regno);
 334
 335   if (ptrace (PTRACE_SETREGS, tid, 0, (int) &regs) < 0)
 336     perror_with_name ("Couldn't write registers");
 337 }
 338
 339 #else
 340
 341 static void fetch_regs (int tid) {}
 342 static void store_regs (int tid, int regno) {}
 343
 344 #endif
 345 \f
 346
 347 /* Transfering floating-point registers between GDB, inferiors and cores.  */
 348
 349 /* Fill GDB's register array with the floating-point register values in
 350    *FPREGSETP.  */
 351
 352 void
 353 supply_fpregset (elf_fpregset_t *fpregsetp)
 354 {
 355   i387_supply_fsave ((char *) fpregsetp);
 356   dummy_sse_values ();
 357 }
 358
 359 /* Fill register REGNO (if it is a floating-point register) in
 360    *FPREGSETP with the value in GDB's register array.  If REGNO is -1,
 361    do this for all registers.  */
 362
 363 void
 364 fill_fpregset (elf_fpregset_t *fpregsetp, int regno)
 365 {
 366   i387_fill_fsave ((char *) fpregsetp, regno);
 367 }
 368
 369 #ifdef HAVE_PTRACE_GETREGS
 370
 371 /* Fetch all floating-point registers from process/thread TID and store
 372    thier values in GDB's register array.  */
 373
 374 static void
 375 fetch_fpregs (int tid)
 376 {
 377   elf_fpregset_t fpregs;
 378
 379   if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
 380     perror_with_name ("Couldn't get floating point status");
 381
 382   supply_fpregset (&fpregs);
 383 }
 384
 385 /* Store all valid floating-point registers in GDB's register array
 386    into the process/thread specified by TID.  */
 387
 388 static void
 389 store_fpregs (int tid, int regno)
 390 {
 391   elf_fpregset_t fpregs;
 392
 393   if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
 394     perror_with_name ("Couldn't get floating point status");
 395
 396   fill_fpregset (&fpregs, regno);
 397
 398   if (ptrace (PTRACE_SETFPREGS, tid, 0, (int) &fpregs) < 0)
 399     perror_with_name ("Couldn't write floating point status");
 400 }
 401
 402 #else
 403
 404 static void fetch_fpregs (int tid) {}
 405 static void store_fpregs (int tid, int regno) {}
 406
 407 #endif
 408 \f
 409
 410 /* Transfering floating-point and SSE registers to and from GDB.  */
 411
 412 #ifdef HAVE_PTRACE_GETFPXREGS
 413
 414 /* Fill GDB's register array with the floating-point and SSE register
 415    values in *FPXREGSETP.  */
 416
 417 static void
 418 supply_fpxregset (elf_fpxregset_t *fpxregsetp)
 419 {
 420   i387_supply_fxsave ((char *) fpxregsetp);
 421 }
 422
 423 /* Fill register REGNO (if it is a floating-point or SSE register) in
 424    *FPXREGSETP with the value in GDB's register array.  If REGNO is
 425    -1, do this for all registers.  */
 426
 427 static void
 428 fill_fpxregset (elf_fpxregset_t *fpxregsetp, int regno)
 429 {
 430   i387_fill_fxsave ((char *) fpxregsetp, regno);
 431 }
 432
 433 /* Fetch all registers covered by the PTRACE_GETFPXREGS request from
 434    process/thread TID and store their values in GDB's register array.
 435    Return non-zero if successful, zero otherwise.  */
 436
 437 static int
 438 fetch_fpxregs (int tid)
 439 {
 440   elf_fpxregset_t fpxregs;
 441
 442   if (! have_ptrace_getfpxregs)
 443     return 0;
 444
 445   if (ptrace (PTRACE_GETFPXREGS, tid, 0, (int) &fpxregs) < 0)
 446     {
 447       if (errno == EIO)
 448         {
 449           have_ptrace_getfpxregs = 0;
 450           return 0;
 451         }
 452
 453       perror_with_name ("Couldn't read floating-point and SSE registers");
 454     }
 455
 456   supply_fpxregset (&fpxregs);
 457   return 1;
 458 }
 459
 460 /* Store all valid registers in GDB's register array covered by the
 461    PTRACE_SETFPXREGS request into the process/thread specified by TID.
 462    Return non-zero if successful, zero otherwise.  */
 463
 464 static int
 465 store_fpxregs (int tid, int regno)
 466 {
 467   elf_fpxregset_t fpxregs;
 468
 469   if (! have_ptrace_getfpxregs)
 470     return 0;
 471
 472   if (ptrace (PTRACE_GETFPXREGS, tid, 0, &fpxregs) == -1)
 473     {
 474       if (errno == EIO)
 475         {
 476           have_ptrace_getfpxregs = 0;
 477           return 0;
 478         }
 479
 480       perror_with_name ("Couldn't read floating-point and SSE registers");
 481     }
 482
 483   fill_fpxregset (&fpxregs, regno);
 484
 485   if (ptrace (PTRACE_SETFPXREGS, tid, 0, &fpxregs) == -1)
 486     perror_with_name ("Couldn't write floating-point and SSE registers");
 487
 488   return 1;
 489 }
 490
 491 /* Fill the XMM registers in the register array with dummy values.  For
 492    cases where we don't have access to the XMM registers.  I think
 493    this is cleaner than printing a warning.  For a cleaner solution,
 494    we should gdbarchify the i386 family.  */
 495
 496 static void
 497 dummy_sse_values (void)
 498 {
 499   /* C doesn't have a syntax for NaN's, so write it out as an array of
 500      longs.  */
 501   static long dummy[4] = { 0xffffffff, 0xffffffff, 0xffffffff, 0xffffffff };
 502   static long mxcsr = 0x1f80;
 503   int reg;
 504
 505   for (reg = 0; reg < 8; reg++)
 506     supply_register (XMM0_REGNUM + reg, (char *) dummy);
 507   supply_register (MXCSR_REGNUM, (char *) &mxcsr);
 508 }
 509
 510 #else
 511
 512 static int fetch_fpxregs (int tid) { return 0; }
 513 static int store_fpxregs (int tid, int regno) { return 0; }
 514 static void dummy_sse_values (void) {}
 515
 516 #endif /* HAVE_PTRACE_GETFPXREGS */
 517 \f
 518
 519 /* Transferring arbitrary registers between GDB and inferior.  */
 520
 521 /* Check if register REGNO in the child process is accessible.
 522    If we are accessing registers directly via the U area, only the
 523    general-purpose registers are available.
 524    All registers should be accessible if we have GETREGS support.  */
 525
 526 int
 527 cannot_fetch_register (int regno)
 528 {
 529   if (! have_ptrace_getregs)
 530     return OLD_CANNOT_FETCH_REGISTER (regno);
 531   return 0;
 532 }
 533 int
 534 cannot_store_register (int regno)
 535 {
 536   if (! have_ptrace_getregs)
 537     return OLD_CANNOT_STORE_REGISTER (regno);
 538   return 0;
 539 }
 540
 541 /* Fetch register REGNO from the child process.  If REGNO is -1, do
 542    this for all registers (including the floating point and SSE
 543    registers).  */
 544
 545 void
 546 fetch_inferior_registers (int regno)
 547 {
 548   int tid;
 549
 550   /* Use the old method of peeking around in `struct user' if the
 551      GETREGS request isn't available.  */
 552   if (! have_ptrace_getregs)
 553     {
 554       old_fetch_inferior_registers (regno);
 555       return;
 556     }
 557
 558   /* Linux LWP ID's are process ID's.  */
 559   if ((tid = TIDGET (inferior_pid)) == 0)
 560     tid = inferior_pid;         /* Not a threaded program.  */
 561
 562   /* Use the PTRACE_GETFPXREGS request whenever possible, since it
 563      transfers more registers in one system call, and we'll cache the
 564      results.  But remember that fetch_fpxregs can fail, and return
 565      zero.  */
 566   if (regno == -1)
 567     {
 568       fetch_regs (tid);
 569
 570       /* The call above might reset `have_ptrace_getregs'.  */
 571       if (! have_ptrace_getregs)
 572         {
 573           old_fetch_inferior_registers (-1);
 574           return;
 575         }
 576
 577       if (fetch_fpxregs (tid))
 578         return;
 579       fetch_fpregs (tid);
 580       return;
 581     }
 582
 583   if (GETREGS_SUPPLIES (regno))
 584     {
 585       fetch_regs (tid);
 586       return;
 587     }
 588
 589   if (GETFPXREGS_SUPPLIES (regno))
 590     {
 591       if (fetch_fpxregs (tid))
 592         return;
 593
 594       /* Either our processor or our kernel doesn't support the SSE
 595          registers, so read the FP registers in the traditional way,
 596          and fill the SSE registers with dummy values.  It would be
 597          more graceful to handle differences in the register set using
 598          gdbarch.  Until then, this will at least make things work
 599          plausibly.  */
 600       fetch_fpregs (tid);
 601       return;
 602     }
 603
 604   internal_error (__FILE__, __LINE__,
 605                   "Got request for bad register number %d.", regno);
 606 }
 607
 608 /* Store register REGNO back into the child process.  If REGNO is -1,
 609    do this for all registers (including the floating point and SSE
 610    registers).  */
 611 void
 612 store_inferior_registers (int regno)
 613 {
 614   int tid;
 615
 616   /* Use the old method of poking around in `struct user' if the
 617      SETREGS request isn't available.  */
 618   if (! have_ptrace_getregs)
 619     {
 620       old_store_inferior_registers (regno);
 621       return;
 622     }
 623
 624   /* Linux LWP ID's are process ID's.  */
 625   if ((tid = TIDGET (inferior_pid)) == 0)
 626     tid = inferior_pid;         /* Not a threaded program.  */
 627
 628   /* Use the PTRACE_SETFPXREGS requests whenever possible, since it
 629      transfers more registers in one system call.  But remember that
 630      store_fpxregs can fail, and return zero.  */
 631   if (regno == -1)
 632     {
 633       store_regs (tid, regno);
 634       if (store_fpxregs (tid, regno))
 635         return;
 636       store_fpregs (tid, regno);
 637       return;
 638     }
 639
 640   if (GETREGS_SUPPLIES (regno))
 641     {
 642       store_regs (tid, regno);
 643       return;
 644     }
 645
 646   if (GETFPXREGS_SUPPLIES (regno))
 647     {
 648       if (store_fpxregs (tid, regno))
 649         return;
 650
 651       /* Either our processor or our kernel doesn't support the SSE
 652          registers, so just write the FP registers in the traditional
 653          way.  */
 654       store_fpregs (tid, regno);
 655       return;
 656     }
 657
 658   internal_error (__FILE__, __LINE__,
 659                   "Got request to store bad register number %d.", regno);
 660 }
 661 \f
 662
 663 /* Interpreting register set info found in core files.  */
 664
 665 /* Provide registers to GDB from a core file.
 666
 667    (We can't use the generic version of this function in
 668    core-regset.c, because Linux has *three* different kinds of
 669    register set notes.  core-regset.c would have to call
 670    supply_fpxregset, which most platforms don't have.)
 671
 672    CORE_REG_SECT points to an array of bytes, which are the contents
 673    of a `note' from a core file which BFD thinks might contain
 674    register contents.  CORE_REG_SIZE is its size.
 675
 676    WHICH says which register set corelow suspects this is:
 677      0 --- the general-purpose register set, in elf_gregset_t format
 678      2 --- the floating-point register set, in elf_fpregset_t format
 679      3 --- the extended floating-point register set, in elf_fpxregset_t format
 680
 681    REG_ADDR isn't used on Linux.  */
 682
 683 static void
 684 fetch_core_registers (char *core_reg_sect, unsigned core_reg_size,
 685                       int which, CORE_ADDR reg_addr)
 686 {
 687   elf_gregset_t gregset;
 688   elf_fpregset_t fpregset;
 689
 690   switch (which)
 691     {
 692     case 0:
 693       if (core_reg_size != sizeof (gregset))
 694         warning ("Wrong size gregset in core file.");
 695       else
 696         {
 697           memcpy (&gregset, core_reg_sect, sizeof (gregset));
 698           supply_gregset (&gregset);
 699         }
 700       break;
 701
 702     case 2:
 703       if (core_reg_size != sizeof (fpregset))
 704         warning ("Wrong size fpregset in core file.");
 705       else
 706         {
 707           memcpy (&fpregset, core_reg_sect, sizeof (fpregset));
 708           supply_fpregset (&fpregset);
 709         }
 710       break;
 711
 712 #ifdef HAVE_PTRACE_GETFPXREGS
 713       {
 714         elf_fpxregset_t fpxregset;
 715
 716       case 3:
 717         if (core_reg_size != sizeof (fpxregset))
 718           warning ("Wrong size fpxregset in core file.");
 719         else
 720           {
 721             memcpy (&fpxregset, core_reg_sect, sizeof (fpxregset));
 722             supply_fpxregset (&fpxregset);
 723           }
 724         break;
 725       }
 726 #endif
 727
 728     default:
 729       /* We've covered all the kinds of registers we know about here,
 730          so this must be something we wouldn't know what to do with
 731          anyway.  Just ignore it.  */
 732       break;
 733     }
 734 }
 735 \f
 736
 737 /* The instruction for a Linux system call is:
 738        int $0x80
 739    or 0xcd 0x80.  */
 740
 741 static const unsigned char linux_syscall[] = { 0xcd, 0x80 };
 742
 743 #define LINUX_SYSCALL_LEN (sizeof linux_syscall)
 744
 745 /* The system call number is stored in the %eax register.  */
 746 #define LINUX_SYSCALL_REGNUM 0  /* %eax */
 747
 748 /* We are specifically interested in the sigreturn and rt_sigreturn
 749    system calls.  */
 750
 751 #ifndef SYS_sigreturn
 752 #define SYS_sigreturn           0x77
 753 #endif
 754 #ifndef SYS_rt_sigreturn
 755 #define SYS_rt_sigreturn        0xad
 756 #endif
 757
 758 /* Offset to saved processor flags, from <asm/sigcontext.h>.  */
 759 #define LINUX_SIGCONTEXT_EFLAGS_OFFSET (64)
 760
 761 /* Resume execution of the inferior process.
 762    If STEP is nonzero, single-step it.
 763    If SIGNAL is nonzero, give it that signal.  */
 764
 765 void
 766 child_resume (int pid, int step, enum target_signal signal)
 767 {
 768   int request = PTRACE_CONT;
 769
 770   if (pid == -1)
 771     /* Resume all threads.  */
 772     /* I think this only gets used in the non-threaded case, where "resume
 773        all threads" and "resume inferior_pid" are the same.  */
 774     pid = inferior_pid;
 775
 776   if (step)
 777     {
 778       CORE_ADDR pc = read_pc_pid (pid);
 779       unsigned char buf[LINUX_SYSCALL_LEN];
 780
 781       request = PTRACE_SINGLESTEP;
 782
 783       /* Returning from a signal trampoline is done by calling a
 784          special system call (sigreturn or rt_sigreturn, see
 785          i386-linux-tdep.c for more information).  This system call
 786          restores the registers that were saved when the signal was
 787          raised, including %eflags.  That means that single-stepping
 788          won't work.  Instead, we'll have to modify the signal context
 789          that's about to be restored, and set the trace flag there.  */
 790
 791       /* First check if PC is at a system call.  */
 792       if (read_memory_nobpt (pc, (char *) buf, LINUX_SYSCALL_LEN) == 0
 793           && memcmp (buf, linux_syscall, LINUX_SYSCALL_LEN) == 0)
 794         {
 795           int syscall = read_register_pid (LINUX_SYSCALL_REGNUM, pid);
 796
 797           /* Then check the system call number.  */
 798           if (syscall == SYS_sigreturn || syscall == SYS_rt_sigreturn)
 799             {
 800               CORE_ADDR sp = read_register (SP_REGNUM);
 801               CORE_ADDR addr = sp;
 802               unsigned long int eflags;
 803
 804               if (syscall == SYS_rt_sigreturn)
 805                 addr = read_memory_integer (sp + 8, 4) + 20;
 806
 807               /* Set the trace flag in the context that's about to be
 808                  restored.  */
 809               addr += LINUX_SIGCONTEXT_EFLAGS_OFFSET;
 810               read_memory (addr, (char *) &eflags, 4);
 811               eflags |= 0x0100;
 812               write_memory (addr, (char *) &eflags, 4);
 813             }
 814         }
 815     }
 816
 817   if (ptrace (request, pid, 0, target_signal_to_host (signal)) == -1)
 818     perror_with_name ("ptrace");
 819 }
 820 \f
 821
 822 /* Register that we are able to handle Linux ELF core file formats.  */
 823
 824 static struct core_fns linux_elf_core_fns =
 825 {
 826   bfd_target_elf_flavour,               /* core_flavour */
 827   default_check_format,                 /* check_format */
 828   default_core_sniffer,                 /* core_sniffer */
 829   fetch_core_registers,                 /* core_read_registers */
 830   NULL                                  /* next */
 831 };
 832
 833 void
 834 _initialize_i386_linux_nat (void)
 835 {
 836   add_core_fns (&linux_elf_core_fns);
 837 }