gdb/m68klinux-nat.c

   1 /* Motorola m68k native support for GNU/Linux.
   2
   3    Copyright 1996, 1998, 2000, 2001, 2002 Free Software Foundation,
   4    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 2 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, write to the Free Software
  20    Foundation, Inc., 59 Temple Place - Suite 330,
  21    Boston, MA 02111-1307, USA.  */
  22
  23 #include "defs.h"
  24 #include "frame.h"
  25 #include "inferior.h"
  26 #include "language.h"
  27 #include "gdbcore.h"
  28 #include "regcache.h"
  29
  30 #ifdef USG
  31 #include <sys/types.h>
  32 #endif
  33
  34 #include <sys/param.h>
  35 #include <sys/dir.h>
  36 #include <signal.h>
  37 #include <sys/ptrace.h>
  38 #include <sys/user.h>
  39 #include <sys/ioctl.h>
  40 #include <fcntl.h>
  41 #include <sys/procfs.h>
  42
  43 #ifdef HAVE_SYS_REG_H
  44 #include <sys/reg.h>
  45 #endif
  46
  47 #include <sys/file.h>
  48 #include "gdb_stat.h"
  49
  50 #include "floatformat.h"
  51
  52 #include "target.h"
  53 \f
  54
  55 /* This table must line up with REGISTER_NAMES in tm-m68k.h */
  56 static const int regmap[] =
  57 {
  58   PT_D0, PT_D1, PT_D2, PT_D3, PT_D4, PT_D5, PT_D6, PT_D7,
  59   PT_A0, PT_A1, PT_A2, PT_A3, PT_A4, PT_A5, PT_A6, PT_USP,
  60   PT_SR, PT_PC,
  61   /* PT_FP0, ..., PT_FP7 */
  62   21, 24, 27, 30, 33, 36, 39, 42,
  63   /* PT_FPCR, PT_FPSR, PT_FPIAR */
  64   45, 46, 47
  65 };
  66
  67 /* Which ptrace request retrieves which registers?
  68    These apply to the corresponding SET requests as well.  */
  69 #define NUM_GREGS (18)
  70 #define MAX_NUM_REGS (NUM_GREGS + 11)
  71
  72 int
  73 getregs_supplies (int regno)
  74 {
  75   return 0 <= regno && regno < NUM_GREGS;
  76 }
  77
  78 int
  79 getfpregs_supplies (int regno)
  80 {
  81   return FP0_REGNUM <= regno && regno <= FPI_REGNUM;
  82 }
  83
  84 /* Does the current host support the GETREGS request?  */
  85 int have_ptrace_getregs =
  86 #ifdef HAVE_PTRACE_GETREGS
  87   1
  88 #else
  89   0
  90 #endif
  91 ;
  92
  93 \f
  94
  95 /* BLOCKEND is the value of u.u_ar0, and points to the place where GS
  96    is stored.  */
  97
  98 int
  99 m68k_linux_register_u_addr (int blockend, int regnum)
 100 {
 101   return (blockend + 4 * regmap[regnum]);
 102 }
 103 \f
 104
 105 /* Fetching registers directly from the U area, one at a time.  */
 106
 107 /* FIXME: This duplicates code from `inptrace.c'.  The problem is that we
 108    define FETCH_INFERIOR_REGISTERS since we want to use our own versions
 109    of {fetch,store}_inferior_registers that use the GETREGS request.  This
 110    means that the code in `infptrace.c' is #ifdef'd out.  But we need to
 111    fall back on that code when GDB is running on top of a kernel that
 112    doesn't support the GETREGS request.  */
 113
 114 #ifndef PT_READ_U
 115 #define PT_READ_U PTRACE_PEEKUSR
 116 #endif
 117 #ifndef PT_WRITE_U
 118 #define PT_WRITE_U PTRACE_POKEUSR
 119 #endif
 120
 121 /* Default the type of the ptrace transfer to int.  */
 122 #ifndef PTRACE_XFER_TYPE
 123 #define PTRACE_XFER_TYPE int
 124 #endif
 125
 126 /* Fetch one register.  */
 127
 128 static void
 129 fetch_register (int regno)
 130 {
 131   /* This isn't really an address.  But ptrace thinks of it as one.  */
 132   CORE_ADDR regaddr;
 133   char mess[128];               /* For messages */
 134   register int i;
 135   unsigned int offset;          /* Offset of registers within the u area.  */
 136   char buf[MAX_REGISTER_RAW_SIZE];
 137   int tid;
 138
 139   if (CANNOT_FETCH_REGISTER (regno))
 140     {
 141       memset (buf, '\0', REGISTER_RAW_SIZE (regno));    /* Supply zeroes */
 142       supply_register (regno, buf);
 143       return;
 144     }
 145
 146   /* Overload thread id onto process id */
 147   if ((tid = TIDGET (inferior_ptid)) == 0)
 148     tid = PIDGET (inferior_ptid);       /* no thread id, just use process id */
 149
 150   offset = U_REGS_OFFSET;
 151
 152   regaddr = register_addr (regno, offset);
 153   for (i = 0; i < REGISTER_RAW_SIZE (regno); i += sizeof (PTRACE_XFER_TYPE))
 154     {
 155       errno = 0;
 156       *(PTRACE_XFER_TYPE *) & buf[i] = ptrace (PT_READ_U, tid,
 157                                                (PTRACE_ARG3_TYPE) regaddr, 0);
 158       regaddr += sizeof (PTRACE_XFER_TYPE);
 159       if (errno != 0)
 160         {
 161           sprintf (mess, "reading register %s (#%d)",
 162                    REGISTER_NAME (regno), regno);
 163           perror_with_name (mess);
 164         }
 165     }
 166   supply_register (regno, buf);
 167 }
 168
 169 /* Fetch register values from the inferior.
 170    If REGNO is negative, do this for all registers.
 171    Otherwise, REGNO specifies which register (so we can save time). */
 172
 173 void
 174 old_fetch_inferior_registers (int regno)
 175 {
 176   if (regno >= 0)
 177     {
 178       fetch_register (regno);
 179     }
 180   else
 181     {
 182       for (regno = 0; regno < NUM_REGS; regno++)
 183         {
 184           fetch_register (regno);
 185         }
 186     }
 187 }
 188
 189 /* Store one register. */
 190
 191 static void
 192 store_register (int regno)
 193 {
 194   /* This isn't really an address.  But ptrace thinks of it as one.  */
 195   CORE_ADDR regaddr;
 196   char mess[128];               /* For messages */
 197   register int i;
 198   unsigned int offset;          /* Offset of registers within the u area.  */
 199   int tid;
 200   char *buf = alloca (MAX_REGISTER_RAW_SIZE);
 201
 202   if (CANNOT_STORE_REGISTER (regno))
 203     {
 204       return;
 205     }
 206
 207   /* Overload thread id onto process id */
 208   if ((tid = TIDGET (inferior_ptid)) == 0)
 209     tid = PIDGET (inferior_ptid);       /* no thread id, just use process id */
 210
 211   offset = U_REGS_OFFSET;
 212
 213   regaddr = register_addr (regno, offset);
 214
 215   /* Put the contents of regno into a local buffer */
 216   regcache_collect (regno, buf);
 217
 218   /* Store the local buffer into the inferior a chunk at the time. */
 219   for (i = 0; i < REGISTER_RAW_SIZE (regno); i += sizeof (PTRACE_XFER_TYPE))
 220     {
 221       errno = 0;
 222       ptrace (PT_WRITE_U, tid, (PTRACE_ARG3_TYPE) regaddr,
 223               *(PTRACE_XFER_TYPE *) (buf + i));
 224       regaddr += sizeof (PTRACE_XFER_TYPE);
 225       if (errno != 0)
 226         {
 227           sprintf (mess, "writing register %s (#%d)",
 228                    REGISTER_NAME (regno), regno);
 229           perror_with_name (mess);
 230         }
 231     }
 232 }
 233
 234 /* Store our register values back into the inferior.
 235    If REGNO is negative, do this for all registers.
 236    Otherwise, REGNO specifies which register (so we can save time).  */
 237
 238 void
 239 old_store_inferior_registers (int regno)
 240 {
 241   if (regno >= 0)
 242     {
 243       store_register (regno);
 244     }
 245   else
 246     {
 247       for (regno = 0; regno < NUM_REGS; regno++)
 248         {
 249           store_register (regno);
 250         }
 251     }
 252 }
 253 \f
 254 /*  Given a pointer to a general register set in /proc format
 255    (elf_gregset_t *), unpack the register contents and supply
 256    them as gdb's idea of the current register values. */
 257
 258
 259 /* Note both m68k-tdep.c and m68klinux-nat.c contain definitions
 260    for supply_gregset and supply_fpregset. The definitions
 261    in m68k-tdep.c are valid if USE_PROC_FS is defined. Otherwise,
 262    the definitions in m68klinux-nat.c will be used. This is a
 263    bit of a hack. The supply_* routines do not belong in
 264    *_tdep.c files. But, there are several lynx ports that currently
 265    depend on these definitions. */
 266
 267 #ifndef USE_PROC_FS
 268
 269 /* Prototypes for supply_gregset etc. */
 270 #include "gregset.h"
 271
 272 void
 273 supply_gregset (elf_gregset_t *gregsetp)
 274 {
 275   elf_greg_t *regp = (elf_greg_t *) gregsetp;
 276   int regi;
 277
 278   for (regi = D0_REGNUM; regi <= SP_REGNUM; regi++)
 279     supply_register (regi, (char *) &regp[regmap[regi]]);
 280   supply_register (PS_REGNUM, (char *) &regp[PT_SR]);
 281   supply_register (PC_REGNUM, (char *) &regp[PT_PC]);
 282 }
 283
 284 /* Fill register REGNO (if it is a general-purpose register) in
 285    *GREGSETPS with the value in GDB's register array.  If REGNO is -1,
 286    do this for all registers.  */
 287 void
 288 fill_gregset (elf_gregset_t *gregsetp, int regno)
 289 {
 290   elf_greg_t *regp = (elf_greg_t *) gregsetp;
 291   int i;
 292
 293   for (i = 0; i < NUM_GREGS; i++)
 294     if ((regno == -1 || regno == i))
 295       regcache_collect (i, regp + regmap[i]);
 296 }
 297
 298 #ifdef HAVE_PTRACE_GETREGS
 299
 300 /* Fetch all general-purpose registers from process/thread TID and
 301    store their values in GDB's register array.  */
 302
 303 static void
 304 fetch_regs (int tid)
 305 {
 306   elf_gregset_t regs;
 307
 308   if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
 309     {
 310       if (errno == EIO)
 311         {
 312           /* The kernel we're running on doesn't support the GETREGS
 313              request.  Reset `have_ptrace_getregs'.  */
 314           have_ptrace_getregs = 0;
 315           return;
 316         }
 317
 318       perror_with_name ("Couldn't get registers");
 319     }
 320
 321   supply_gregset (&regs);
 322 }
 323
 324 /* Store all valid general-purpose registers in GDB's register array
 325    into the process/thread specified by TID.  */
 326
 327 static void
 328 store_regs (int tid, int regno)
 329 {
 330   elf_gregset_t regs;
 331
 332   if (ptrace (PTRACE_GETREGS, tid, 0, (int) &regs) < 0)
 333     perror_with_name ("Couldn't get registers");
 334
 335   fill_gregset (&regs, regno);
 336
 337   if (ptrace (PTRACE_SETREGS, tid, 0, (int) &regs) < 0)
 338     perror_with_name ("Couldn't write registers");
 339 }
 340
 341 #else
 342
 343 static void fetch_regs (int tid) {}
 344 static void store_regs (int tid, int regno) {}
 345
 346 #endif
 347
 348 \f
 349 /* Transfering floating-point registers between GDB, inferiors and cores.  */
 350
 351 /* What is the address of fpN within the floating-point register set F?  */
 352 #define FPREG_ADDR(f, n) ((char *) &(f)->fpregs[(n) * 3])
 353
 354 /* Fill GDB's register array with the floating-point register values in
 355    *FPREGSETP.  */
 356
 357 void
 358 supply_fpregset (elf_fpregset_t *fpregsetp)
 359 {
 360   int regi;
 361
 362   for (regi = FP0_REGNUM; regi < FPC_REGNUM; regi++)
 363     supply_register (regi, FPREG_ADDR (fpregsetp, regi - FP0_REGNUM));
 364   supply_register (FPC_REGNUM, (char *) &fpregsetp->fpcntl[0]);
 365   supply_register (FPS_REGNUM, (char *) &fpregsetp->fpcntl[1]);
 366   supply_register (FPI_REGNUM, (char *) &fpregsetp->fpcntl[2]);
 367 }
 368
 369 /* Fill register REGNO (if it is a floating-point register) in
 370    *FPREGSETP with the value in GDB's register array.  If REGNO is -1,
 371    do this for all registers.  */
 372
 373 void
 374 fill_fpregset (elf_fpregset_t *fpregsetp, int regno)
 375 {
 376   int i;
 377
 378   /* Fill in the floating-point registers.  */
 379   for (i = FP0_REGNUM; i < FP0_REGNUM + 8; i++)
 380     if (regno == -1 || regno == i)
 381       regcache_collect (regno, FPREG_ADDR (fpregsetp, regno - FP0_REGNUM));
 382
 383   /* Fill in the floating-point control registers.  */
 384   for (i = FPC_REGNUM; i <= FPI_REGNUM; i++)
 385     if (regno == -1 || regno == i)
 386       regcache_collect (regno, (char *) &fpregsetp->fpcntl[regno - FPC_REGNUM]);
 387 }
 388
 389 #ifdef HAVE_PTRACE_GETREGS
 390
 391 /* Fetch all floating-point registers from process/thread TID and store
 392    thier values in GDB's register array.  */
 393
 394 static void
 395 fetch_fpregs (int tid)
 396 {
 397   elf_fpregset_t fpregs;
 398
 399   if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
 400     perror_with_name ("Couldn't get floating point status");
 401
 402   supply_fpregset (&fpregs);
 403 }
 404
 405 /* Store all valid floating-point registers in GDB's register array
 406    into the process/thread specified by TID.  */
 407
 408 static void
 409 store_fpregs (int tid, int regno)
 410 {
 411   elf_fpregset_t fpregs;
 412
 413   if (ptrace (PTRACE_GETFPREGS, tid, 0, (int) &fpregs) < 0)
 414     perror_with_name ("Couldn't get floating point status");
 415
 416   fill_fpregset (&fpregs, regno);
 417
 418   if (ptrace (PTRACE_SETFPREGS, tid, 0, (int) &fpregs) < 0)
 419     perror_with_name ("Couldn't write floating point status");
 420 }
 421
 422 #else
 423
 424 static void fetch_fpregs (int tid) {}
 425 static void store_fpregs (int tid, int regno) {}
 426
 427 #endif
 428
 429 #endif
 430 \f
 431 /* Transferring arbitrary registers between GDB and inferior.  */
 432
 433 /* Fetch register REGNO from the child process.  If REGNO is -1, do
 434    this for all registers (including the floating point and SSE
 435    registers).  */
 436
 437 void
 438 fetch_inferior_registers (int regno)
 439 {
 440   int tid;
 441
 442   /* Use the old method of peeking around in `struct user' if the
 443      GETREGS request isn't available.  */
 444   if (! have_ptrace_getregs)
 445     {
 446       old_fetch_inferior_registers (regno);
 447       return;
 448     }
 449
 450   /* GNU/Linux LWP ID's are process ID's.  */
 451   if ((tid = TIDGET (inferior_ptid)) == 0)
 452     tid = PIDGET (inferior_ptid);               /* Not a threaded program.  */
 453
 454   /* Use the PTRACE_GETFPXREGS request whenever possible, since it
 455      transfers more registers in one system call, and we'll cache the
 456      results.  But remember that fetch_fpxregs can fail, and return
 457      zero.  */
 458   if (regno == -1)
 459     {
 460       fetch_regs (tid);
 461
 462       /* The call above might reset `have_ptrace_getregs'.  */
 463       if (! have_ptrace_getregs)
 464         {
 465           old_fetch_inferior_registers (-1);
 466           return;
 467         }
 468
 469       fetch_fpregs (tid);
 470       return;
 471     }
 472
 473   if (getregs_supplies (regno))
 474     {
 475       fetch_regs (tid);
 476       return;
 477     }
 478
 479   if (getfpregs_supplies (regno))
 480     {
 481       fetch_fpregs (tid);
 482       return;
 483     }
 484
 485   internal_error (__FILE__, __LINE__,
 486                   "Got request for bad register number %d.", regno);
 487 }
 488
 489 /* Store register REGNO back into the child process.  If REGNO is -1,
 490    do this for all registers (including the floating point and SSE
 491    registers).  */
 492 void
 493 store_inferior_registers (int regno)
 494 {
 495   int tid;
 496
 497   /* Use the old method of poking around in `struct user' if the
 498      SETREGS request isn't available.  */
 499   if (! have_ptrace_getregs)
 500     {
 501       old_store_inferior_registers (regno);
 502       return;
 503     }
 504
 505   /* GNU/Linux LWP ID's are process ID's.  */
 506   if ((tid = TIDGET (inferior_ptid)) == 0)
 507     tid = PIDGET (inferior_ptid);       /* Not a threaded program.  */
 508
 509   /* Use the PTRACE_SETFPREGS requests whenever possible, since it
 510      transfers more registers in one system call.  But remember that
 511      store_fpregs can fail, and return zero.  */
 512   if (regno == -1)
 513     {
 514       store_regs (tid, regno);
 515       store_fpregs (tid, regno);
 516       return;
 517     }
 518
 519   if (getregs_supplies (regno))
 520     {
 521       store_regs (tid, regno);
 522       return;
 523     }
 524
 525   if (getfpregs_supplies (regno))
 526     {
 527       store_fpregs (tid, regno);
 528       return;
 529     }
 530
 531   internal_error (__FILE__, __LINE__,
 532                   "Got request to store bad register number %d.", regno);
 533 }
 534 \f
 535 /* Interpreting register set info found in core files.  */
 536
 537 /* Provide registers to GDB from a core file.
 538
 539    (We can't use the generic version of this function in
 540    core-regset.c, because we need to use elf_gregset_t instead of
 541    gregset_t.)
 542
 543    CORE_REG_SECT points to an array of bytes, which are the contents
 544    of a `note' from a core file which BFD thinks might contain
 545    register contents.  CORE_REG_SIZE is its size.
 546
 547    WHICH says which register set corelow suspects this is:
 548      0 --- the general-purpose register set, in elf_gregset_t format
 549      2 --- the floating-point register set, in elf_fpregset_t format
 550
 551    REG_ADDR isn't used on GNU/Linux.  */
 552
 553 static void
 554 fetch_core_registers (char *core_reg_sect, unsigned core_reg_size,
 555                       int which, CORE_ADDR reg_addr)
 556 {
 557   elf_gregset_t gregset;
 558   elf_fpregset_t fpregset;
 559
 560   switch (which)
 561     {
 562     case 0:
 563       if (core_reg_size != sizeof (gregset))
 564         warning ("Wrong size gregset in core file.");
 565       else
 566         {
 567           memcpy (&gregset, core_reg_sect, sizeof (gregset));
 568           supply_gregset (&gregset);
 569         }
 570       break;
 571
 572     case 2:
 573       if (core_reg_size != sizeof (fpregset))
 574         warning ("Wrong size fpregset in core file.");
 575       else
 576         {
 577           memcpy (&fpregset, core_reg_sect, sizeof (fpregset));
 578           supply_fpregset (&fpregset);
 579         }
 580       break;
 581
 582     default:
 583       /* We've covered all the kinds of registers we know about here,
 584          so this must be something we wouldn't know what to do with
 585          anyway.  Just ignore it.  */
 586       break;
 587     }
 588 }
 589 \f
 590
 591 int
 592 kernel_u_size (void)
 593 {
 594   return (sizeof (struct user));
 595 }
 596 \f
 597 /* Check whether insn1 and insn2 are parts of a signal trampoline.  */
 598
 599 #define IS_SIGTRAMP(insn1, insn2)                                       \
 600   (/* addaw #20,sp; moveq #119,d0; trap #0 */                           \
 601    (insn1 == 0xdefc0014 && insn2 == 0x70774e40)                         \
 602    /* moveq #119,d0; trap #0 */                                         \
 603    || insn1 == 0x70774e40)
 604
 605 #define IS_RT_SIGTRAMP(insn1, insn2)                                    \
 606   (/* movel #173,d0; trap #0 */                                         \
 607    (insn1 == 0x203c0000 && insn2 == 0x00ad4e40)                         \
 608    /* moveq #82,d0; notb d0; trap #0 */                                 \
 609    || (insn1 == 0x70524600 && (insn2 >> 16) == 0x4e40))
 610
 611 /* Return non-zero if PC points into the signal trampoline.  For the sake
 612    of m68k_linux_frame_saved_pc we also distinguish between non-RT and RT
 613    signal trampolines.  */
 614
 615 int
 616 m68k_linux_in_sigtramp (CORE_ADDR pc)
 617 {
 618   CORE_ADDR sp;
 619   char buf[12];
 620   unsigned long insn0, insn1, insn2;
 621
 622   if (read_memory_nobpt (pc - 4, buf, sizeof (buf)))
 623     return 0;
 624   insn1 = extract_unsigned_integer (buf + 4, 4);
 625   insn2 = extract_unsigned_integer (buf + 8, 4);
 626   if (IS_SIGTRAMP (insn1, insn2))
 627     return 1;
 628   if (IS_RT_SIGTRAMP (insn1, insn2))
 629     return 2;
 630
 631   insn0 = extract_unsigned_integer (buf, 4);
 632   if (IS_SIGTRAMP (insn0, insn1))
 633     return 1;
 634   if (IS_RT_SIGTRAMP (insn0, insn1))
 635     return 2;
 636
 637   insn0 = (insn0 << 16) | (insn1 >> 16);
 638   insn1 = (insn1 << 16) | (insn2 >> 16);
 639   if (IS_SIGTRAMP (insn0, insn1))
 640     return 1;
 641   if (IS_RT_SIGTRAMP (insn0, insn1))
 642     return 2;
 643
 644   return 0;
 645 }
 646
 647 /* Offset to saved PC in sigcontext, from <asm/sigcontext.h>.  */
 648 #define SIGCONTEXT_PC_OFFSET 26
 649
 650 /* Offset to saved PC in ucontext, from <asm/ucontext.h>.  */
 651 #define UCONTEXT_PC_OFFSET 88
 652
 653 /* Get saved user PC for sigtramp from sigcontext or ucontext.  */
 654
 655 static CORE_ADDR
 656 m68k_linux_sigtramp_saved_pc (struct frame_info *frame)
 657 {
 658   CORE_ADDR sigcontext_addr;
 659   char buf[TARGET_PTR_BIT / TARGET_CHAR_BIT];
 660   int ptrbytes = TARGET_PTR_BIT / TARGET_CHAR_BIT;
 661   int sigcontext_offs = (2 * TARGET_INT_BIT) / TARGET_CHAR_BIT;
 662
 663   /* Get sigcontext address, it is the third parameter on the stack.  */
 664   if (frame->next)
 665     sigcontext_addr = read_memory_integer (FRAME_ARGS_ADDRESS (frame->next)
 666                                            + FRAME_ARGS_SKIP
 667                                            + sigcontext_offs,
 668                                            ptrbytes);
 669   else
 670     sigcontext_addr = read_memory_integer (read_register (SP_REGNUM)
 671                                            + sigcontext_offs,
 672                                            ptrbytes);
 673
 674   /* Don't cause a memory_error when accessing sigcontext in case the
 675      stack layout has changed or the stack is corrupt.  */
 676   if (m68k_linux_in_sigtramp (frame->pc) == 2)
 677     target_read_memory (sigcontext_addr + UCONTEXT_PC_OFFSET, buf, ptrbytes);
 678   else
 679     target_read_memory (sigcontext_addr + SIGCONTEXT_PC_OFFSET, buf, ptrbytes);
 680   return extract_unsigned_integer (buf, ptrbytes);
 681 }
 682
 683 /* Return the saved program counter for FRAME.  */
 684
 685 CORE_ADDR
 686 m68k_linux_frame_saved_pc (struct frame_info *frame)
 687 {
 688   if (frame->signal_handler_caller)
 689     return m68k_linux_sigtramp_saved_pc (frame);
 690
 691   return read_memory_integer (frame->frame + 4, 4);
 692 }
 693 \f
 694 /* Register that we are able to handle GNU/Linux ELF core file
 695    formats.  */
 696
 697 static struct core_fns linux_elf_core_fns =
 698 {
 699   bfd_target_elf_flavour,               /* core_flavour */
 700   default_check_format,                 /* check_format */
 701   default_core_sniffer,                 /* core_sniffer */
 702   fetch_core_registers,                 /* core_read_registers */
 703   NULL                                  /* next */
 704 };
 705
 706 void
 707 _initialize_m68k_linux_nat ()
 708 {
 709   add_core_fns (&linux_elf_core_fns);
 710 }