gdb/arm-linux-nat.c

   1 /* GNU/Linux on ARM native support.
   2    Copyright 1999 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 "gdb_string.h"
  25
  26 #include <sys/user.h>
  27 #include <sys/ptrace.h>
  28 #include <sys/utsname.h>
  29
  30 extern int arm_apcs_32;
  31
  32 #define         typeNone                0x00
  33 #define         typeSingle              0x01
  34 #define         typeDouble              0x02
  35 #define         typeExtended            0x03
  36 #define         FPWORDS                 28
  37 #define         CPSR_REGNUM             16
  38
  39 typedef union tagFPREG
  40   {
  41     unsigned int fSingle;
  42     unsigned int fDouble[2];
  43     unsigned int fExtended[3];
  44   }
  45 FPREG;
  46
  47 typedef struct tagFPA11
  48   {
  49     FPREG fpreg[8];             /* 8 floating point registers */
  50     unsigned int fpsr;          /* floating point status register */
  51     unsigned int fpcr;          /* floating point control register */
  52     unsigned char fType[8];     /* type of floating point value held in
  53                                    floating point registers.  */
  54     int initflag;               /* NWFPE initialization flag.  */
  55   }
  56 FPA11;
  57
  58 /* The following variables are used to determine the version of the
  59    underlying Linux operating system.  Examples:
  60
  61    Linux 2.0.35                 Linux 2.2.12
  62    os_version = 0x00020023      os_version = 0x0002020c
  63    os_major = 2                 os_major = 2
  64    os_minor = 0                 os_minor = 2
  65    os_release = 35              os_release = 12
  66
  67    Note: os_version = (os_major << 16) | (os_minor << 8) | os_release
  68
  69    These are initialized using get_linux_version() from
  70    _initialize_arm_linux_nat().  */
  71
  72 static unsigned int os_version, os_major, os_minor, os_release;
  73
  74 static void
  75 fetch_nwfpe_single (unsigned int fn, FPA11 * fpa11)
  76 {
  77   unsigned int mem[3];
  78
  79   mem[0] = fpa11->fpreg[fn].fSingle;
  80   mem[1] = 0;
  81   mem[2] = 0;
  82   supply_register (F0_REGNUM + fn, (char *) &mem[0]);
  83 }
  84
  85 static void
  86 fetch_nwfpe_double (unsigned int fn, FPA11 * fpa11)
  87 {
  88   unsigned int mem[3];
  89
  90   mem[0] = fpa11->fpreg[fn].fDouble[1];
  91   mem[1] = fpa11->fpreg[fn].fDouble[0];
  92   mem[2] = 0;
  93   supply_register (F0_REGNUM + fn, (char *) &mem[0]);
  94 }
  95
  96 static void
  97 fetch_nwfpe_none (unsigned int fn)
  98 {
  99   unsigned int mem[3] =
 100   {0, 0, 0};
 101
 102   supply_register (F0_REGNUM + fn, (char *) &mem[0]);
 103 }
 104
 105 static void
 106 fetch_nwfpe_extended (unsigned int fn, FPA11 * fpa11)
 107 {
 108   unsigned int mem[3];
 109
 110   mem[0] = fpa11->fpreg[fn].fExtended[0];       /* sign & exponent */
 111   mem[1] = fpa11->fpreg[fn].fExtended[2];       /* ls bits */
 112   mem[2] = fpa11->fpreg[fn].fExtended[1];       /* ms bits */
 113   supply_register (F0_REGNUM + fn, (char *) &mem[0]);
 114 }
 115
 116 static void
 117 store_nwfpe_single (unsigned int fn, FPA11 * fpa11)
 118 {
 119   unsigned int mem[3];
 120
 121   read_register_gen (F0_REGNUM + fn, (char *) &mem[0]);
 122   fpa11->fpreg[fn].fSingle = mem[0];
 123   fpa11->fType[fn] = typeSingle;
 124 }
 125
 126 static void
 127 store_nwfpe_double (unsigned int fn, FPA11 * fpa11)
 128 {
 129   unsigned int mem[3];
 130
 131   read_register_gen (F0_REGNUM + fn, (char *) &mem[0]);
 132   fpa11->fpreg[fn].fDouble[1] = mem[0];
 133   fpa11->fpreg[fn].fDouble[0] = mem[1];
 134   fpa11->fType[fn] = typeDouble;
 135 }
 136
 137 void
 138 store_nwfpe_extended (unsigned int fn, FPA11 * fpa11)
 139 {
 140   unsigned int mem[3];
 141
 142   read_register_gen (F0_REGNUM + fn, (char *) &mem[0]);
 143   fpa11->fpreg[fn].fExtended[0] = mem[0];       /* sign & exponent */
 144   fpa11->fpreg[fn].fExtended[2] = mem[1];       /* ls bits */
 145   fpa11->fpreg[fn].fExtended[1] = mem[2];       /* ms bits */
 146   fpa11->fType[fn] = typeDouble;
 147 }
 148
 149 /* Get the whole floating point state of the process and store the
 150    floating point stack into registers[].  */
 151
 152 static void
 153 fetch_fpregs (void)
 154 {
 155   int ret, regno;
 156   FPA11 fp;
 157
 158   /* Read the floating point state.  */
 159   ret = ptrace (PT_GETFPREGS, inferior_pid, 0, &fp);
 160   if (ret < 0)
 161     {
 162       warning ("Unable to fetch the floating point state.");
 163       return;
 164     }
 165
 166   /* Fetch fpsr.  */
 167   supply_register (FPS_REGNUM, (char *) &fp.fpsr);
 168
 169   /* Fetch the floating point registers.  */
 170   for (regno = F0_REGNUM; regno <= F7_REGNUM; regno++)
 171     {
 172       int fn = regno - F0_REGNUM;
 173       unsigned int *p = (unsigned int *) &registers[REGISTER_BYTE (regno)];
 174
 175       switch (fp.fType[fn])
 176         {
 177         case typeSingle:
 178           fetch_nwfpe_single (fn, &fp);
 179           break;
 180
 181         case typeDouble:
 182           fetch_nwfpe_double (fn, &fp);
 183           break;
 184
 185         case typeExtended:
 186           fetch_nwfpe_extended (fn, &fp);
 187           break;
 188
 189         default:
 190           fetch_nwfpe_none (fn);
 191         }
 192     }
 193 }
 194
 195 /* Save the whole floating point state of the process using
 196    the contents from registers[].  */
 197
 198 static void
 199 store_fpregs (void)
 200 {
 201   int ret, regno;
 202   FPA11 fp;
 203
 204   /* Store fpsr.  */
 205   if (register_valid[FPS_REGNUM])
 206     read_register_gen (FPS_REGNUM, (char *) &fp.fpsr);
 207
 208   /* Store the floating point registers.  */
 209   for (regno = F0_REGNUM; regno <= F7_REGNUM; regno++)
 210     {
 211       if (register_valid[regno])
 212         {
 213           unsigned int fn = regno - F0_REGNUM;
 214           switch (fp.fType[fn])
 215             {
 216             case typeSingle:
 217               store_nwfpe_single (fn, &fp);
 218               break;
 219
 220             case typeDouble:
 221               store_nwfpe_double (fn, &fp);
 222               break;
 223
 224             case typeExtended:
 225               store_nwfpe_extended (fn, &fp);
 226               break;
 227             }
 228         }
 229     }
 230
 231   ret = ptrace (PTRACE_SETFPREGS, inferior_pid, 0, &fp);
 232   if (ret < 0)
 233     {
 234       warning ("Unable to store floating point state.");
 235       return;
 236     }
 237 }
 238
 239 /* Fetch all general registers of the process and store into
 240    registers[].  */
 241
 242 static void
 243 fetch_regs (void)
 244 {
 245   int ret, regno;
 246   struct pt_regs regs;
 247
 248   ret = ptrace (PTRACE_GETREGS, inferior_pid, 0, &regs);
 249   if (ret < 0)
 250     {
 251       warning ("Unable to fetch general registers.");
 252       return;
 253     }
 254
 255   for (regno = A1_REGNUM; regno < PC_REGNUM; regno++)
 256     supply_register (regno, (char *) &regs.uregs[regno]);
 257
 258   if (arm_apcs_32)
 259     supply_register (PS_REGNUM, (char *) &regs.uregs[CPSR_REGNUM]);
 260   else
 261     supply_register (PS_REGNUM, (char *) &regs.uregs[PC_REGNUM]);
 262
 263   regs.uregs[PC_REGNUM] = ADDR_BITS_REMOVE (regs.uregs[PC_REGNUM]);
 264   supply_register (PC_REGNUM, (char *) &regs.uregs[PC_REGNUM]);
 265 }
 266
 267 /* Store all general registers of the process from the values in
 268    registers[].  */
 269
 270 static void
 271 store_regs (void)
 272 {
 273   int ret, regno;
 274   struct pt_regs regs;
 275
 276   ret = ptrace (PTRACE_GETREGS, inferior_pid, 0, &regs);
 277   if (ret < 0)
 278     {
 279       warning ("Unable to fetch general registers.");
 280       return;
 281     }
 282
 283   for (regno = A1_REGNUM; regno <= PC_REGNUM; regno++)
 284     {
 285       if (register_valid[regno])
 286         read_register_gen (regno, (char *) &regs.uregs[regno]);
 287     }
 288
 289   ret = ptrace (PTRACE_SETREGS, inferior_pid, 0, &regs);
 290
 291   if (ret < 0)
 292     {
 293       warning ("Unable to store general registers.");
 294       return;
 295     }
 296 }
 297
 298 /* Fetch registers from the child process.  Fetch all registers if
 299    regno == -1, otherwise fetch all general registers or all floating
 300    point registers depending upon the value of regno.  */
 301
 302 void
 303 fetch_inferior_registers (int regno)
 304 {
 305   if ((regno < F0_REGNUM) || (regno > FPS_REGNUM))
 306     fetch_regs ();
 307
 308   if (((regno >= F0_REGNUM) && (regno <= FPS_REGNUM)) || (regno == -1))
 309     fetch_fpregs ();
 310 }
 311
 312 /* Store registers back into the inferior.  Store all registers if
 313    regno == -1, otherwise store all general registers or all floating
 314    point registers depending upon the value of regno.  */
 315
 316 void
 317 store_inferior_registers (int regno)
 318 {
 319   if ((regno < F0_REGNUM) || (regno > FPS_REGNUM))
 320     store_regs ();
 321
 322   if (((regno >= F0_REGNUM) && (regno <= FPS_REGNUM)) || (regno == -1))
 323     store_fpregs ();
 324 }
 325
 326 #ifdef GET_LONGJMP_TARGET
 327
 328 /* Figure out where the longjmp will land.  We expect that we have
 329    just entered longjmp and haven't yet altered r0, r1, so the
 330    arguments are still in the registers.  (A1_REGNUM) points at the
 331    jmp_buf structure from which we extract the pc (JB_PC) that we will
 332    land at.  The pc is copied into ADDR.  This routine returns true on
 333    success. */
 334
 335 #define LONGJMP_TARGET_SIZE     sizeof(int)
 336 #define JB_ELEMENT_SIZE         sizeof(int)
 337 #define JB_SL                   18
 338 #define JB_FP                   19
 339 #define JB_SP                   20
 340 #define JB_PC                   21
 341
 342 int
 343 arm_get_longjmp_target (CORE_ADDR * pc)
 344 {
 345   CORE_ADDR jb_addr;
 346   char buf[LONGJMP_TARGET_SIZE];
 347
 348   jb_addr = read_register (A1_REGNUM);
 349
 350   if (target_read_memory (jb_addr + JB_PC * JB_ELEMENT_SIZE, buf,
 351                           LONGJMP_TARGET_SIZE))
 352     return 0;
 353
 354   *pc = extract_address (buf, LONGJMP_TARGET_SIZE);
 355   return 1;
 356 }
 357
 358 #endif /* GET_LONGJMP_TARGET */
 359
 360 /*
 361    Dynamic Linking on ARM Linux
 362    ----------------------------
 363
 364    Note: PLT = procedure linkage table
 365    GOT = global offset table
 366
 367    As much as possible, ELF dynamic linking defers the resolution of
 368    jump/call addresses until the last minute. The technique used is
 369    inspired by the i386 ELF design, and is based on the following
 370    constraints.
 371
 372    1) The calling technique should not force a change in the assembly
 373    code produced for apps; it MAY cause changes in the way assembly
 374    code is produced for position independent code (i.e. shared
 375    libraries).
 376
 377    2) The technique must be such that all executable areas must not be
 378    modified; and any modified areas must not be executed.
 379
 380    To do this, there are three steps involved in a typical jump:
 381
 382    1) in the code
 383    2) through the PLT
 384    3) using a pointer from the GOT
 385
 386    When the executable or library is first loaded, each GOT entry is
 387    initialized to point to the code which implements dynamic name
 388    resolution and code finding.  This is normally a function in the
 389    program interpreter (on ARM Linux this is usually ld-linux.so.2,
 390    but it does not have to be).  On the first invocation, the function
 391    is located and the GOT entry is replaced with the real function
 392    address.  Subsequent calls go through steps 1, 2 and 3 and end up
 393    calling the real code.
 394
 395    1) In the code:
 396
 397    b    function_call
 398    bl   function_call
 399
 400    This is typical ARM code using the 26 bit relative branch or branch
 401    and link instructions.  The target of the instruction
 402    (function_call is usually the address of the function to be called.
 403    In position independent code, the target of the instruction is
 404    actually an entry in the PLT when calling functions in a shared
 405    library.  Note that this call is identical to a normal function
 406    call, only the target differs.
 407
 408    2) In the PLT:
 409
 410    The PLT is a synthetic area, created by the linker. It exists in
 411    both executables and libraries. It is an array of stubs, one per
 412    imported function call. It looks like this:
 413
 414    PLT[0]:
 415    str     lr, [sp, #-4]!       @push the return address (lr)
 416    ldr     lr, [pc, #16]   @load from 6 words ahead
 417    add     lr, pc, lr      @form an address for GOT[0]
 418    ldr     pc, [lr, #8]!   @jump to the contents of that addr
 419
 420    The return address (lr) is pushed on the stack and used for
 421    calculations.  The load on the second line loads the lr with
 422    &GOT[3] - . - 20.  The addition on the third leaves:
 423
 424    lr = (&GOT[3] - . - 20) + (. + 8)
 425    lr = (&GOT[3] - 12)
 426    lr = &GOT[0]
 427
 428    On the fourth line, the pc and lr are both updated, so that:
 429
 430    pc = GOT[2]
 431    lr = &GOT[0] + 8
 432    = &GOT[2]
 433
 434    NOTE: PLT[0] borrows an offset .word from PLT[1]. This is a little
 435    "tight", but allows us to keep all the PLT entries the same size.
 436
 437    PLT[n+1]:
 438    ldr     ip, [pc, #4]    @load offset from gotoff
 439    add     ip, pc, ip      @add the offset to the pc
 440    ldr     pc, [ip]        @jump to that address
 441    gotoff: .word   GOT[n+3] - .
 442
 443    The load on the first line, gets an offset from the fourth word of
 444    the PLT entry.  The add on the second line makes ip = &GOT[n+3],
 445    which contains either a pointer to PLT[0] (the fixup trampoline) or
 446    a pointer to the actual code.
 447
 448    3) In the GOT:
 449
 450    The GOT contains helper pointers for both code (PLT) fixups and
 451    data fixups.  The first 3 entries of the GOT are special. The next
 452    M entries (where M is the number of entries in the PLT) belong to
 453    the PLT fixups. The next D (all remaining) entries belong to
 454    various data fixups. The actual size of the GOT is 3 + M + D.
 455
 456    The GOT is also a synthetic area, created by the linker. It exists
 457    in both executables and libraries.  When the GOT is first
 458    initialized , all the GOT entries relating to PLT fixups are
 459    pointing to code back at PLT[0].
 460
 461    The special entries in the GOT are:
 462
 463    GOT[0] = linked list pointer used by the dynamic loader
 464    GOT[1] = pointer to the reloc table for this module
 465    GOT[2] = pointer to the fixup/resolver code
 466
 467    The first invocation of function call comes through and uses the
 468    fixup/resolver code.  On the entry to the fixup/resolver code:
 469
 470    ip = &GOT[n+3]
 471    lr = &GOT[2]
 472    stack[0] = return address (lr) of the function call
 473    [r0, r1, r2, r3] are still the arguments to the function call
 474
 475    This is enough information for the fixup/resolver code to work
 476    with.  Before the fixup/resolver code returns, it actually calls
 477    the requested function and repairs &GOT[n+3].  */
 478
 479 CORE_ADDR
 480 arm_skip_solib_resolver (CORE_ADDR pc)
 481 {
 482   /* FIXME */
 483   return 0;
 484 }
 485
 486 int
 487 arm_linux_register_u_addr (int blockend, int regnum)
 488 {
 489   return blockend + REGISTER_BYTE (regnum);
 490 }
 491
 492 int
 493 arm_linux_kernel_u_size (void)
 494 {
 495   return (sizeof (struct user));
 496 }
 497
 498 /* Extract from an array REGBUF containing the (raw) register state
 499    a function return value of type TYPE, and copy that, in virtual format,
 500    into VALBUF.  */
 501
 502 void
 503 arm_linux_extract_return_value (struct type *type,
 504                                 char regbuf[REGISTER_BYTES],
 505                                 char *valbuf)
 506 {
 507   /* ScottB: This needs to be looked at to handle the different
 508      floating point emulators on ARM Linux.  Right now the code
 509      assumes that fetch inferior registers does the right thing for
 510      GDB.  I suspect this won't handle NWFPE registers correctly, nor
 511      will the default ARM version (arm_extract_return_value()).  */
 512
 513   int regnum = (TYPE_CODE_FLT == TYPE_CODE (type)) ? F0_REGNUM : A1_REGNUM;
 514   memcpy (valbuf, &regbuf[REGISTER_BYTE (regnum)], TYPE_LENGTH (type));
 515 }
 516
 517 static unsigned int
 518 get_linux_version (unsigned int *vmajor,
 519                    unsigned int *vminor,
 520                    unsigned int *vrelease)
 521 {
 522   struct utsname info;
 523   char *pmajor, *pminor, *prelease, *tail;
 524
 525   if (-1 == uname (&info))
 526     {
 527       warning ("Unable to determine Linux version.");
 528       return -1;
 529     }
 530
 531   pmajor = strtok (info.release, ".");
 532   pminor = strtok (NULL, ".");
 533   prelease = strtok (NULL, ".");
 534
 535   *vmajor = (unsigned int) strtoul (pmajor, &tail, 0);
 536   *vminor = (unsigned int) strtoul (pminor, &tail, 0);
 537   *vrelease = (unsigned int) strtoul (prelease, &tail, 0);
 538
 539   return ((*vmajor << 16) | (*vminor << 8) | *vrelease);
 540 }
 541
 542 void
 543 _initialize_arm_linux_nat (void)
 544 {
 545   os_version = get_linux_version (&os_major, &os_minor, &os_release);
 546 }