gdb/arm-linux-nat.c

   1 /* GNU/Linux on ARM native support.
   2    Copyright (C) 1999, 2000, 2001, 2002, 2004, 2005, 2006, 2007, 2008, 2009,
   3    2010, 2011 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "inferior.h"
  22 #include "gdbcore.h"
  23 #include "gdb_string.h"
  24 #include "regcache.h"
  25 #include "target.h"
  26 #include "linux-nat.h"
  27 #include "target-descriptions.h"
  28 #include "auxv.h"
  29
  30 #include "arm-tdep.h"
  31 #include "arm-linux-tdep.h"
  32
  33 #include <elf/common.h>
  34 #include <sys/user.h>
  35 #include <sys/ptrace.h>
  36 #include <sys/utsname.h>
  37 #include <sys/procfs.h>
  38
  39 /* Prototypes for supply_gregset etc.  */
  40 #include "gregset.h"
  41
  42 /* Defines ps_err_e, struct ps_prochandle.  */
  43 #include "gdb_proc_service.h"
  44
  45 #include "features/arm-with-iwmmxt.c"
  46 #include "features/arm-with-vfpv2.c"
  47 #include "features/arm-with-vfpv3.c"
  48 #include "features/arm-with-neon.c"
  49
  50 #ifndef PTRACE_GET_THREAD_AREA
  51 #define PTRACE_GET_THREAD_AREA 22
  52 #endif
  53
  54 #ifndef PTRACE_GETWMMXREGS
  55 #define PTRACE_GETWMMXREGS 18
  56 #define PTRACE_SETWMMXREGS 19
  57 #endif
  58
  59 #ifndef PTRACE_GETVFPREGS
  60 #define PTRACE_GETVFPREGS 27
  61 #define PTRACE_SETVFPREGS 28
  62 #endif
  63
  64 /* These are in <asm/elf.h> in current kernels.  */
  65 #define HWCAP_VFP       64
  66 #define HWCAP_IWMMXT    512
  67 #define HWCAP_NEON      4096
  68 #define HWCAP_VFPv3     8192
  69 #define HWCAP_VFPv3D16  16384
  70
  71 /* A flag for whether the WMMX registers are available.  */
  72 static int arm_linux_has_wmmx_registers;
  73
  74 /* The number of 64-bit VFP registers we have (expect this to be 0,
  75    16, or 32).  */
  76 static int arm_linux_vfp_register_count;
  77
  78 extern int arm_apcs_32;
  79
  80 /* The following variables are used to determine the version of the
  81    underlying GNU/Linux operating system.  Examples:
  82
  83    GNU/Linux 2.0.35             GNU/Linux 2.2.12
  84    os_version = 0x00020023      os_version = 0x0002020c
  85    os_major = 2                 os_major = 2
  86    os_minor = 0                 os_minor = 2
  87    os_release = 35              os_release = 12
  88
  89    Note: os_version = (os_major << 16) | (os_minor << 8) | os_release
  90
  91    These are initialized using get_linux_version() from
  92    _initialize_arm_linux_nat().  */
  93
  94 static unsigned int os_version, os_major, os_minor, os_release;
  95
  96 /* On GNU/Linux, threads are implemented as pseudo-processes, in which
  97    case we may be tracing more than one process at a time.  In that
  98    case, inferior_ptid will contain the main process ID and the
  99    individual thread (process) ID.  get_thread_id () is used to get
 100    the thread id if it's available, and the process id otherwise.  */
 101
 102 int
 103 get_thread_id (ptid_t ptid)
 104 {
 105   int tid = TIDGET (ptid);
 106   if (0 == tid)
 107     tid = PIDGET (ptid);
 108   return tid;
 109 }
 110
 111 #define GET_THREAD_ID(PTID)     get_thread_id (PTID)
 112
 113 /* Get the value of a particular register from the floating point
 114    state of the process and store it into regcache.  */
 115
 116 static void
 117 fetch_fpregister (struct regcache *regcache, int regno)
 118 {
 119   int ret, tid;
 120   gdb_byte fp[ARM_LINUX_SIZEOF_NWFPE];
 121
 122   /* Get the thread id for the ptrace call.  */
 123   tid = GET_THREAD_ID (inferior_ptid);
 124
 125   /* Read the floating point state.  */
 126   ret = ptrace (PT_GETFPREGS, tid, 0, fp);
 127   if (ret < 0)
 128     {
 129       warning (_("Unable to fetch floating point register."));
 130       return;
 131     }
 132
 133   /* Fetch fpsr.  */
 134   if (ARM_FPS_REGNUM == regno)
 135     regcache_raw_supply (regcache, ARM_FPS_REGNUM,
 136                          fp + NWFPE_FPSR_OFFSET);
 137
 138   /* Fetch the floating point register.  */
 139   if (regno >= ARM_F0_REGNUM && regno <= ARM_F7_REGNUM)
 140     supply_nwfpe_register (regcache, regno, fp);
 141 }
 142
 143 /* Get the whole floating point state of the process and store it
 144    into regcache.  */
 145
 146 static void
 147 fetch_fpregs (struct regcache *regcache)
 148 {
 149   int ret, regno, tid;
 150   gdb_byte fp[ARM_LINUX_SIZEOF_NWFPE];
 151
 152   /* Get the thread id for the ptrace call.  */
 153   tid = GET_THREAD_ID (inferior_ptid);
 154
 155   /* Read the floating point state.  */
 156   ret = ptrace (PT_GETFPREGS, tid, 0, fp);
 157   if (ret < 0)
 158     {
 159       warning (_("Unable to fetch the floating point registers."));
 160       return;
 161     }
 162
 163   /* Fetch fpsr.  */
 164   regcache_raw_supply (regcache, ARM_FPS_REGNUM,
 165                        fp + NWFPE_FPSR_OFFSET);
 166
 167   /* Fetch the floating point registers.  */
 168   for (regno = ARM_F0_REGNUM; regno <= ARM_F7_REGNUM; regno++)
 169     supply_nwfpe_register (regcache, regno, fp);
 170 }
 171
 172 /* Save a particular register into the floating point state of the
 173    process using the contents from regcache.  */
 174
 175 static void
 176 store_fpregister (const struct regcache *regcache, int regno)
 177 {
 178   int ret, tid;
 179   gdb_byte fp[ARM_LINUX_SIZEOF_NWFPE];
 180
 181   /* Get the thread id for the ptrace call.  */
 182   tid = GET_THREAD_ID (inferior_ptid);
 183
 184   /* Read the floating point state.  */
 185   ret = ptrace (PT_GETFPREGS, tid, 0, fp);
 186   if (ret < 0)
 187     {
 188       warning (_("Unable to fetch the floating point registers."));
 189       return;
 190     }
 191
 192   /* Store fpsr.  */
 193   if (ARM_FPS_REGNUM == regno && regcache_valid_p (regcache, ARM_FPS_REGNUM))
 194     regcache_raw_collect (regcache, ARM_FPS_REGNUM, fp + NWFPE_FPSR_OFFSET);
 195
 196   /* Store the floating point register.  */
 197   if (regno >= ARM_F0_REGNUM && regno <= ARM_F7_REGNUM)
 198     collect_nwfpe_register (regcache, regno, fp);
 199
 200   ret = ptrace (PTRACE_SETFPREGS, tid, 0, fp);
 201   if (ret < 0)
 202     {
 203       warning (_("Unable to store floating point register."));
 204       return;
 205     }
 206 }
 207
 208 /* Save the whole floating point state of the process using
 209    the contents from regcache.  */
 210
 211 static void
 212 store_fpregs (const struct regcache *regcache)
 213 {
 214   int ret, regno, tid;
 215   gdb_byte fp[ARM_LINUX_SIZEOF_NWFPE];
 216
 217   /* Get the thread id for the ptrace call.  */
 218   tid = GET_THREAD_ID (inferior_ptid);
 219
 220   /* Read the floating point state.  */
 221   ret = ptrace (PT_GETFPREGS, tid, 0, fp);
 222   if (ret < 0)
 223     {
 224       warning (_("Unable to fetch the floating point registers."));
 225       return;
 226     }
 227
 228   /* Store fpsr.  */
 229   if (regcache_valid_p (regcache, ARM_FPS_REGNUM))
 230     regcache_raw_collect (regcache, ARM_FPS_REGNUM, fp + NWFPE_FPSR_OFFSET);
 231
 232   /* Store the floating point registers.  */
 233   for (regno = ARM_F0_REGNUM; regno <= ARM_F7_REGNUM; regno++)
 234     if (regcache_valid_p (regcache, regno))
 235       collect_nwfpe_register (regcache, regno, fp);
 236
 237   ret = ptrace (PTRACE_SETFPREGS, tid, 0, fp);
 238   if (ret < 0)
 239     {
 240       warning (_("Unable to store floating point registers."));
 241       return;
 242     }
 243 }
 244
 245 /* Fetch a general register of the process and store into
 246    regcache.  */
 247
 248 static void
 249 fetch_register (struct regcache *regcache, int regno)
 250 {
 251   int ret, tid;
 252   elf_gregset_t regs;
 253
 254   /* Get the thread id for the ptrace call.  */
 255   tid = GET_THREAD_ID (inferior_ptid);
 256
 257   ret = ptrace (PTRACE_GETREGS, tid, 0, &regs);
 258   if (ret < 0)
 259     {
 260       warning (_("Unable to fetch general register."));
 261       return;
 262     }
 263
 264   if (regno >= ARM_A1_REGNUM && regno < ARM_PC_REGNUM)
 265     regcache_raw_supply (regcache, regno, (char *) &regs[regno]);
 266
 267   if (ARM_PS_REGNUM == regno)
 268     {
 269       if (arm_apcs_32)
 270         regcache_raw_supply (regcache, ARM_PS_REGNUM,
 271                              (char *) &regs[ARM_CPSR_GREGNUM]);
 272       else
 273         regcache_raw_supply (regcache, ARM_PS_REGNUM,
 274                              (char *) &regs[ARM_PC_REGNUM]);
 275     }
 276
 277   if (ARM_PC_REGNUM == regno)
 278     {
 279       regs[ARM_PC_REGNUM] = gdbarch_addr_bits_remove
 280                               (get_regcache_arch (regcache),
 281                                regs[ARM_PC_REGNUM]);
 282       regcache_raw_supply (regcache, ARM_PC_REGNUM,
 283                            (char *) &regs[ARM_PC_REGNUM]);
 284     }
 285 }
 286
 287 /* Fetch all general registers of the process and store into
 288    regcache.  */
 289
 290 static void
 291 fetch_regs (struct regcache *regcache)
 292 {
 293   int ret, regno, tid;
 294   elf_gregset_t regs;
 295
 296   /* Get the thread id for the ptrace call.  */
 297   tid = GET_THREAD_ID (inferior_ptid);
 298
 299   ret = ptrace (PTRACE_GETREGS, tid, 0, &regs);
 300   if (ret < 0)
 301     {
 302       warning (_("Unable to fetch general registers."));
 303       return;
 304     }
 305
 306   for (regno = ARM_A1_REGNUM; regno < ARM_PC_REGNUM; regno++)
 307     regcache_raw_supply (regcache, regno, (char *) &regs[regno]);
 308
 309   if (arm_apcs_32)
 310     regcache_raw_supply (regcache, ARM_PS_REGNUM,
 311                          (char *) &regs[ARM_CPSR_GREGNUM]);
 312   else
 313     regcache_raw_supply (regcache, ARM_PS_REGNUM,
 314                          (char *) &regs[ARM_PC_REGNUM]);
 315
 316   regs[ARM_PC_REGNUM] = gdbarch_addr_bits_remove
 317                           (get_regcache_arch (regcache), regs[ARM_PC_REGNUM]);
 318   regcache_raw_supply (regcache, ARM_PC_REGNUM,
 319                        (char *) &regs[ARM_PC_REGNUM]);
 320 }
 321
 322 /* Store all general registers of the process from the values in
 323    regcache.  */
 324
 325 static void
 326 store_register (const struct regcache *regcache, int regno)
 327 {
 328   int ret, tid;
 329   elf_gregset_t regs;
 330
 331   if (!regcache_valid_p (regcache, regno))
 332     return;
 333
 334   /* Get the thread id for the ptrace call.  */
 335   tid = GET_THREAD_ID (inferior_ptid);
 336
 337   /* Get the general registers from the process.  */
 338   ret = ptrace (PTRACE_GETREGS, tid, 0, &regs);
 339   if (ret < 0)
 340     {
 341       warning (_("Unable to fetch general registers."));
 342       return;
 343     }
 344
 345   if (regno >= ARM_A1_REGNUM && regno <= ARM_PC_REGNUM)
 346     regcache_raw_collect (regcache, regno, (char *) &regs[regno]);
 347   else if (arm_apcs_32 && regno == ARM_PS_REGNUM)
 348     regcache_raw_collect (regcache, regno,
 349                          (char *) &regs[ARM_CPSR_GREGNUM]);
 350   else if (!arm_apcs_32 && regno == ARM_PS_REGNUM)
 351     regcache_raw_collect (regcache, ARM_PC_REGNUM,
 352                          (char *) &regs[ARM_PC_REGNUM]);
 353
 354   ret = ptrace (PTRACE_SETREGS, tid, 0, &regs);
 355   if (ret < 0)
 356     {
 357       warning (_("Unable to store general register."));
 358       return;
 359     }
 360 }
 361
 362 static void
 363 store_regs (const struct regcache *regcache)
 364 {
 365   int ret, regno, tid;
 366   elf_gregset_t regs;
 367
 368   /* Get the thread id for the ptrace call.  */
 369   tid = GET_THREAD_ID (inferior_ptid);
 370
 371   /* Fetch the general registers.  */
 372   ret = ptrace (PTRACE_GETREGS, tid, 0, &regs);
 373   if (ret < 0)
 374     {
 375       warning (_("Unable to fetch general registers."));
 376       return;
 377     }
 378
 379   for (regno = ARM_A1_REGNUM; regno <= ARM_PC_REGNUM; regno++)
 380     {
 381       if (regcache_valid_p (regcache, regno))
 382         regcache_raw_collect (regcache, regno, (char *) &regs[regno]);
 383     }
 384
 385   if (arm_apcs_32 && regcache_valid_p (regcache, ARM_PS_REGNUM))
 386     regcache_raw_collect (regcache, ARM_PS_REGNUM,
 387                          (char *) &regs[ARM_CPSR_GREGNUM]);
 388
 389   ret = ptrace (PTRACE_SETREGS, tid, 0, &regs);
 390
 391   if (ret < 0)
 392     {
 393       warning (_("Unable to store general registers."));
 394       return;
 395     }
 396 }
 397
 398 /* Fetch all WMMX registers of the process and store into
 399    regcache.  */
 400
 401 #define IWMMXT_REGS_SIZE (16 * 8 + 6 * 4)
 402
 403 static void
 404 fetch_wmmx_regs (struct regcache *regcache)
 405 {
 406   char regbuf[IWMMXT_REGS_SIZE];
 407   int ret, regno, tid;
 408
 409   /* Get the thread id for the ptrace call.  */
 410   tid = GET_THREAD_ID (inferior_ptid);
 411
 412   ret = ptrace (PTRACE_GETWMMXREGS, tid, 0, regbuf);
 413   if (ret < 0)
 414     {
 415       warning (_("Unable to fetch WMMX registers."));
 416       return;
 417     }
 418
 419   for (regno = 0; regno < 16; regno++)
 420     regcache_raw_supply (regcache, regno + ARM_WR0_REGNUM,
 421                          &regbuf[regno * 8]);
 422
 423   for (regno = 0; regno < 2; regno++)
 424     regcache_raw_supply (regcache, regno + ARM_WCSSF_REGNUM,
 425                          &regbuf[16 * 8 + regno * 4]);
 426
 427   for (regno = 0; regno < 4; regno++)
 428     regcache_raw_supply (regcache, regno + ARM_WCGR0_REGNUM,
 429                          &regbuf[16 * 8 + 2 * 4 + regno * 4]);
 430 }
 431
 432 static void
 433 store_wmmx_regs (const struct regcache *regcache)
 434 {
 435   char regbuf[IWMMXT_REGS_SIZE];
 436   int ret, regno, tid;
 437
 438   /* Get the thread id for the ptrace call.  */
 439   tid = GET_THREAD_ID (inferior_ptid);
 440
 441   ret = ptrace (PTRACE_GETWMMXREGS, tid, 0, regbuf);
 442   if (ret < 0)
 443     {
 444       warning (_("Unable to fetch WMMX registers."));
 445       return;
 446     }
 447
 448   for (regno = 0; regno < 16; regno++)
 449     if (regcache_valid_p (regcache, regno + ARM_WR0_REGNUM))
 450       regcache_raw_collect (regcache, regno + ARM_WR0_REGNUM,
 451                             &regbuf[regno * 8]);
 452
 453   for (regno = 0; regno < 2; regno++)
 454     if (regcache_valid_p (regcache, regno + ARM_WCSSF_REGNUM))
 455       regcache_raw_collect (regcache, regno + ARM_WCSSF_REGNUM,
 456                             &regbuf[16 * 8 + regno * 4]);
 457
 458   for (regno = 0; regno < 4; regno++)
 459     if (regcache_valid_p (regcache, regno + ARM_WCGR0_REGNUM))
 460       regcache_raw_collect (regcache, regno + ARM_WCGR0_REGNUM,
 461                             &regbuf[16 * 8 + 2 * 4 + regno * 4]);
 462
 463   ret = ptrace (PTRACE_SETWMMXREGS, tid, 0, regbuf);
 464
 465   if (ret < 0)
 466     {
 467       warning (_("Unable to store WMMX registers."));
 468       return;
 469     }
 470 }
 471
 472 /* Fetch and store VFP Registers.  The kernel object has space for 32
 473    64-bit registers, and the FPSCR.  This is even when on a VFPv2 or
 474    VFPv3D16 target.  */
 475 #define VFP_REGS_SIZE (32 * 8 + 4)
 476
 477 static void
 478 fetch_vfp_regs (struct regcache *regcache)
 479 {
 480   char regbuf[VFP_REGS_SIZE];
 481   int ret, regno, tid;
 482
 483   /* Get the thread id for the ptrace call.  */
 484   tid = GET_THREAD_ID (inferior_ptid);
 485
 486   ret = ptrace (PTRACE_GETVFPREGS, tid, 0, regbuf);
 487   if (ret < 0)
 488     {
 489       warning (_("Unable to fetch VFP registers."));
 490       return;
 491     }
 492
 493   for (regno = 0; regno < arm_linux_vfp_register_count; regno++)
 494     regcache_raw_supply (regcache, regno + ARM_D0_REGNUM,
 495                          (char *) regbuf + regno * 8);
 496
 497   regcache_raw_supply (regcache, ARM_FPSCR_REGNUM,
 498                        (char *) regbuf + 32 * 8);
 499 }
 500
 501 static void
 502 store_vfp_regs (const struct regcache *regcache)
 503 {
 504   char regbuf[VFP_REGS_SIZE];
 505   int ret, regno, tid;
 506
 507   /* Get the thread id for the ptrace call.  */
 508   tid = GET_THREAD_ID (inferior_ptid);
 509
 510   ret = ptrace (PTRACE_GETVFPREGS, tid, 0, regbuf);
 511   if (ret < 0)
 512     {
 513       warning (_("Unable to fetch VFP registers (for update)."));
 514       return;
 515     }
 516
 517   for (regno = 0; regno < arm_linux_vfp_register_count; regno++)
 518     regcache_raw_collect (regcache, regno + ARM_D0_REGNUM,
 519                           (char *) regbuf + regno * 8);
 520
 521   regcache_raw_collect (regcache, ARM_FPSCR_REGNUM,
 522                         (char *) regbuf + 32 * 8);
 523
 524   ret = ptrace (PTRACE_SETVFPREGS, tid, 0, regbuf);
 525
 526   if (ret < 0)
 527     {
 528       warning (_("Unable to store VFP registers."));
 529       return;
 530     }
 531 }
 532
 533 /* Fetch registers from the child process.  Fetch all registers if
 534    regno == -1, otherwise fetch all general registers or all floating
 535    point registers depending upon the value of regno.  */
 536
 537 static void
 538 arm_linux_fetch_inferior_registers (struct target_ops *ops,
 539                                     struct regcache *regcache, int regno)
 540 {
 541   if (-1 == regno)
 542     {
 543       fetch_regs (regcache);
 544       fetch_fpregs (regcache);
 545       if (arm_linux_has_wmmx_registers)
 546         fetch_wmmx_regs (regcache);
 547       if (arm_linux_vfp_register_count > 0)
 548         fetch_vfp_regs (regcache);
 549     }
 550   else
 551     {
 552       if (regno < ARM_F0_REGNUM || regno == ARM_PS_REGNUM)
 553         fetch_register (regcache, regno);
 554       else if (regno >= ARM_F0_REGNUM && regno <= ARM_FPS_REGNUM)
 555         fetch_fpregister (regcache, regno);
 556       else if (arm_linux_has_wmmx_registers
 557                && regno >= ARM_WR0_REGNUM && regno <= ARM_WCGR7_REGNUM)
 558         fetch_wmmx_regs (regcache);
 559       else if (arm_linux_vfp_register_count > 0
 560                && regno >= ARM_D0_REGNUM
 561                && regno <= ARM_D0_REGNUM + arm_linux_vfp_register_count)
 562         fetch_vfp_regs (regcache);
 563     }
 564 }
 565
 566 /* Store registers back into the inferior.  Store all registers if
 567    regno == -1, otherwise store all general registers or all floating
 568    point registers depending upon the value of regno.  */
 569
 570 static void
 571 arm_linux_store_inferior_registers (struct target_ops *ops,
 572                                     struct regcache *regcache, int regno)
 573 {
 574   if (-1 == regno)
 575     {
 576       store_regs (regcache);
 577       store_fpregs (regcache);
 578       if (arm_linux_has_wmmx_registers)
 579         store_wmmx_regs (regcache);
 580       if (arm_linux_vfp_register_count > 0)
 581         store_vfp_regs (regcache);
 582     }
 583   else
 584     {
 585       if (regno < ARM_F0_REGNUM || regno == ARM_PS_REGNUM)
 586         store_register (regcache, regno);
 587       else if ((regno >= ARM_F0_REGNUM) && (regno <= ARM_FPS_REGNUM))
 588         store_fpregister (regcache, regno);
 589       else if (arm_linux_has_wmmx_registers
 590                && regno >= ARM_WR0_REGNUM && regno <= ARM_WCGR7_REGNUM)
 591         store_wmmx_regs (regcache);
 592       else if (arm_linux_vfp_register_count > 0
 593                && regno >= ARM_D0_REGNUM
 594                && regno <= ARM_D0_REGNUM + arm_linux_vfp_register_count)
 595         store_vfp_regs (regcache);
 596     }
 597 }
 598
 599 /* Wrapper functions for the standard regset handling, used by
 600    thread debugging.  */
 601
 602 void
 603 fill_gregset (const struct regcache *regcache,
 604               gdb_gregset_t *gregsetp, int regno)
 605 {
 606   arm_linux_collect_gregset (NULL, regcache, regno, gregsetp, 0);
 607 }
 608
 609 void
 610 supply_gregset (struct regcache *regcache, const gdb_gregset_t *gregsetp)
 611 {
 612   arm_linux_supply_gregset (NULL, regcache, -1, gregsetp, 0);
 613 }
 614
 615 void
 616 fill_fpregset (const struct regcache *regcache,
 617                gdb_fpregset_t *fpregsetp, int regno)
 618 {
 619   arm_linux_collect_nwfpe (NULL, regcache, regno, fpregsetp, 0);
 620 }
 621
 622 /* Fill GDB's register array with the floating-point register values
 623    in *fpregsetp.  */
 624
 625 void
 626 supply_fpregset (struct regcache *regcache, const gdb_fpregset_t *fpregsetp)
 627 {
 628   arm_linux_supply_nwfpe (NULL, regcache, -1, fpregsetp, 0);
 629 }
 630
 631 /* Fetch the thread-local storage pointer for libthread_db.  */
 632
 633 ps_err_e
 634 ps_get_thread_area (const struct ps_prochandle *ph,
 635                     lwpid_t lwpid, int idx, void **base)
 636 {
 637   if (ptrace (PTRACE_GET_THREAD_AREA, lwpid, NULL, base) != 0)
 638     return PS_ERR;
 639
 640   /* IDX is the bias from the thread pointer to the beginning of the
 641      thread descriptor.  It has to be subtracted due to implementation
 642      quirks in libthread_db.  */
 643   *base = (void *) ((char *)*base - idx);
 644
 645   return PS_OK;
 646 }
 647
 648 static unsigned int
 649 get_linux_version (unsigned int *vmajor,
 650                    unsigned int *vminor,
 651                    unsigned int *vrelease)
 652 {
 653   struct utsname info;
 654   char *pmajor, *pminor, *prelease, *tail;
 655
 656   if (-1 == uname (&info))
 657     {
 658       warning (_("Unable to determine GNU/Linux version."));
 659       return -1;
 660     }
 661
 662   pmajor = strtok (info.release, ".");
 663   pminor = strtok (NULL, ".");
 664   prelease = strtok (NULL, ".");
 665
 666   *vmajor = (unsigned int) strtoul (pmajor, &tail, 0);
 667   *vminor = (unsigned int) strtoul (pminor, &tail, 0);
 668   *vrelease = (unsigned int) strtoul (prelease, &tail, 0);
 669
 670   return ((*vmajor << 16) | (*vminor << 8) | *vrelease);
 671 }
 672
 673 static const struct target_desc *
 674 arm_linux_read_description (struct target_ops *ops)
 675 {
 676   CORE_ADDR arm_hwcap = 0;
 677   arm_linux_has_wmmx_registers = 0;
 678   arm_linux_vfp_register_count = 0;
 679
 680   if (target_auxv_search (ops, AT_HWCAP, &arm_hwcap) != 1)
 681     {
 682       return NULL;
 683     }
 684
 685   if (arm_hwcap & HWCAP_IWMMXT)
 686     {
 687       arm_linux_has_wmmx_registers = 1;
 688       if (tdesc_arm_with_iwmmxt == NULL)
 689         initialize_tdesc_arm_with_iwmmxt ();
 690       return tdesc_arm_with_iwmmxt;
 691     }
 692
 693   if (arm_hwcap & HWCAP_VFP)
 694     {
 695       int pid;
 696       char *buf;
 697       const struct target_desc * result = NULL;
 698
 699       /* NEON implies VFPv3-D32 or no-VFP unit.  Say that we only support
 700          Neon with VFPv3-D32.  */
 701       if (arm_hwcap & HWCAP_NEON)
 702         {
 703           arm_linux_vfp_register_count = 32;
 704           if (tdesc_arm_with_neon == NULL)
 705             initialize_tdesc_arm_with_neon ();
 706           result = tdesc_arm_with_neon;
 707         }
 708       else if ((arm_hwcap & (HWCAP_VFPv3 | HWCAP_VFPv3D16)) == HWCAP_VFPv3)
 709         {
 710           arm_linux_vfp_register_count = 32;
 711           if (tdesc_arm_with_vfpv3 == NULL)
 712             initialize_tdesc_arm_with_vfpv3 ();
 713           result = tdesc_arm_with_vfpv3;
 714         }
 715       else
 716         {
 717           arm_linux_vfp_register_count = 16;
 718           if (tdesc_arm_with_vfpv2 == NULL)
 719             initialize_tdesc_arm_with_vfpv2 ();
 720           result = tdesc_arm_with_vfpv2;
 721         }
 722
 723       /* Now make sure that the kernel supports reading these
 724          registers.  Support was added in 2.6.30.  */
 725       pid = GET_LWP (inferior_ptid);
 726       errno = 0;
 727       buf = alloca (VFP_REGS_SIZE);
 728       if (ptrace (PTRACE_GETVFPREGS, pid, 0, buf) < 0
 729           && errno == EIO)
 730         result = NULL;
 731
 732       return result;
 733     }
 734
 735   return NULL;
 736 }
 737
 738 void _initialize_arm_linux_nat (void);
 739
 740 void
 741 _initialize_arm_linux_nat (void)
 742 {
 743   struct target_ops *t;
 744
 745   os_version = get_linux_version (&os_major, &os_minor, &os_release);
 746
 747   /* Fill in the generic GNU/Linux methods.  */
 748   t = linux_target ();
 749
 750   /* Add our register access methods.  */
 751   t->to_fetch_registers = arm_linux_fetch_inferior_registers;
 752   t->to_store_registers = arm_linux_store_inferior_registers;
 753
 754   t->to_read_description = arm_linux_read_description;
 755
 756   /* Register the target.  */
 757   linux_nat_add_target (t);
 758 }