gcc/ada/tracebak.c

   1 /****************************************************************************
   2  *                                                                          *
   3  *                         GNAT COMPILER COMPONENTS                         *
   4  *                                                                          *
   5  *                            T R A C E B A C K                             *
   6  *                                                                          *
   7  *                          C Implementation File                           *
   8  *                                                                          *
   9  *                     Copyright (C) 2000-2009, AdaCore                     *
  10  *                                                                          *
  11  * GNAT is free software;  you can  redistribute it  and/or modify it under *
  12  * terms of the  GNU General Public License as published  by the Free Soft- *
  13  * ware  Foundation;  either version 2,  or (at your option) any later ver- *
  14  * sion.  GNAT is distributed in the hope that it will be useful, but WITH- *
  15  * OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY *
  16  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License *
  17  * for  more details.  You should have  received  a copy of the GNU General *
  18  * Public License  distributed with GNAT;  see file COPYING.  If not, write *
  19  * to  the  Free Software Foundation,  51  Franklin  Street,  Fifth  Floor, *
  20  * Boston, MA 02110-1301, USA.                                              *
  21  *                                                                          *
  22  * As a  special  exception,  if you  link  this file  with other  files to *
  23  * produce an executable,  this file does not by itself cause the resulting *
  24  * executable to be covered by the GNU General Public License. This except- *
  25  * ion does not  however invalidate  any other reasons  why the  executable *
  26  * file might be covered by the  GNU Public License.                        *
  27  *                                                                          *
  28  * GNAT was originally developed  by the GNAT team at  New York University. *
  29  * Extensive contributions were provided by Ada Core Technologies Inc.      *
  30  *                                                                          *
  31  ****************************************************************************/
  32
  33 /* This file contains low level support for stack unwinding using GCC intrinsic
  34    functions.
  35    It has been tested on the following configurations:
  36    PowerPC/AiX
  37    PowerPC/Darwin
  38    PowerPC/VxWorks
  39    SPARC/Solaris
  40    i386/GNU/Linux
  41    i386/Solaris
  42    i386/NT
  43    i386/OS2
  44    i386/LynxOS
  45    Alpha/VxWorks
  46    Alpha/VMS
  47 */
  48
  49 #ifdef __alpha_vxworks
  50 #include "vxWorks.h"
  51 #endif
  52
  53 #ifdef IN_RTS
  54 #define POSIX
  55 #include "tconfig.h"
  56 #include "tsystem.h"
  57 #else
  58 #include "config.h"
  59 #include "system.h"
  60 /* We don't want fancy_abort here.  */
  61 #undef abort
  62 #endif
  63
  64 extern int __gnat_backtrace (void **, int, void *, void *, int);
  65
  66 /* The point is to provide an implementation of the __gnat_backtrace function
  67    above, called by the default implementation of the System.Traceback package.
  68
  69    We first have a series of target specific implementations, each included
  70    from a separate C file for readability purposes.
  71
  72    Then come two flavors of a generic implementation: one relying on static
  73    assumptions about the frame layout, and the other one using the GCC EH
  74    infrastructure.  The former uses a whole set of macros and structures which
  75    may be tailored on a per target basis, and is activated as soon as
  76    USE_GENERIC_UNWINDER is defined.  The latter uses a small subset of the
  77    macro definitions and is activated when USE_GCC_UNWINDER is defined. It is
  78    only available post GCC 3.3.
  79
  80    Finally, there is a default dummy implementation, necessary to make the
  81    linker happy on platforms where the feature is not supported, but where the
  82    function is still referenced by the default System.Traceback.  */
  83
  84 #define Lock_Task system__soft_links__lock_task
  85 extern void (*Lock_Task) (void);
  86
  87 #define Unlock_Task system__soft_links__unlock_task
  88 extern void (*Unlock_Task) (void);
  89
  90 /*-------------------------------------*
  91  *-- Target specific implementations --*
  92  *-------------------------------------*/
  93
  94 #if defined (__alpha_vxworks)
  95
  96 #include "tb-alvxw.c"
  97
  98 #elif defined (__ALPHA) && defined (__VMS__)
  99
 100 #include "tb-alvms.c"
 101
 102 #elif defined (__ia64__) && defined (__VMS__)
 103
 104 #include "tb-ivms.c"
 105
 106 #else
 107
 108 /* No target specific implementation.  */
 109
 110 /*----------------------------------------------------------------*
 111  *-- Target specific definitions for the generic implementation --*
 112  *----------------------------------------------------------------*/
 113
 114 /* The stack layout is specified by the target ABI. The "generic" scheme is
 115    based on the following assumption:
 116
 117      The stack layout from some frame pointer is such that the information
 118      required to compute the backtrace is available at static offsets.
 119
 120    For a given frame, the information we are interested in is the saved return
 121    address (somewhere after the call instruction in the caller) and a pointer
 122    to the caller's frame. The former is the base of the call chain information
 123    we store in the tracebacks array. The latter allows us to loop over the
 124    successive frames in the chain.
 125
 126    To initiate the process, we retrieve an initial frame address using the
 127    appropriate GCC builtin (__builtin_frame_address).
 128
 129    This scheme is unfortunately not applicable on every target because the
 130    stack layout is not necessarily regular (static) enough. On targets where
 131    this scheme applies, the implementation relies on the following items:
 132
 133    o struct layout, describing the expected stack data layout relevant to the
 134      information we are interested in,
 135
 136    o FRAME_OFFSET, the offset, from a given frame address or frame pointer
 137      value, at which this layout will be found,
 138
 139    o FRAME_LEVEL, controls how many frames up we get at to start with,
 140      from the initial frame pointer we compute by way of the GCC builtin,
 141
 142      0 is most often the appropriate value. 1 may be necessary on targets
 143      where return addresses are saved by a function in it's caller's frame
 144      (e.g. PPC).
 145
 146    o PC_ADJUST, to account for the difference between a call point (address
 147      of a call instruction), which is what we want in the output array, and
 148      the associated return address, which is what we retrieve from the stack.
 149
 150    o STOP_FRAME, to decide whether we reached the top of the call chain, and
 151      thus if the process shall stop.
 152
 153            :
 154            :                   stack
 155            |             +----------------+
 156            |   +-------->|       :        |
 157            |   |         | (FRAME_OFFSET) |
 158            |   |         |       :        |  (PC_ADJUST)
 159            |   |  layout:| return_address ----------------+
 160            |   |         |     ....       |               |
 161            +---------------  next_frame   |               |
 162                |         |     ....       |               |
 163                |         |                |               |
 164                |         +----------------+               |  +-----+
 165                |         |       :        |<- Base fp     |  |  :  |
 166                |         | (FRAME_OFFSET) | (FRAME_LEVEL) |  |  :  |
 167                |         |       :        |               +--->    | [1]
 168                |  layout:| return_address -------------------->    | [0]
 169                |         |       ...      |  (PC_ADJUST)     +-----+
 170                +----------   next_frame   |                 traceback[]
 171                          |       ...      |
 172                          |                |
 173                          +----------------+
 174
 175    o BASE_SKIP,
 176
 177    Since we inherently deal with return addresses, there is an implicit shift
 178    by at least one for the initial point we are able to observe in the chain.
 179
 180    On some targets (e.g. sparc-solaris), the first return address we can
 181    easily get without special code is even our caller's return address, so
 182    there is a initial shift of two.
 183
 184    BASE_SKIP represents this initial shift, which is the minimal "skip_frames"
 185    value we support. We could add special code for the skip_frames < BASE_SKIP
 186    cases. This is not done currently because there is virtually no situation
 187    in which this would be useful.
 188
 189    Finally, to account for some ABI specificities, a target may (but does
 190    not have to) define:
 191
 192    o FORCE_CALL, to force a call to a dummy function at the very beginning
 193      of the computation. See the PPC AIX target for an example where this
 194      is useful.
 195
 196    o FETCH_UP_FRAME, to force an invocation of __builtin_frame_address with a
 197      positive argument right after a possibly forced call even if FRAME_LEVEL
 198      is 0. See the SPARC Solaris case for an example where this is useful.
 199
 200   */
 201
 202 /*--------------------------- PPC AIX/Darwin ----------------------------*/
 203
 204 #if ((defined (_POWER) && defined (_AIX)) || \
 205 (defined (__ppc__) && defined (__APPLE__)))
 206
 207 #define USE_GENERIC_UNWINDER
 208
 209 struct layout
 210 {
 211   struct layout *next;
 212   void *pad;
 213   void *return_address;
 214 };
 215
 216 #define FRAME_OFFSET(FP) 0
 217 #define PC_ADJUST -4
 218 #define STOP_FRAME(CURRENT, TOP_STACK) ((void *) (CURRENT) < (TOP_STACK))
 219
 220 /* The PPC ABI has an interesting specificity: the return address saved by a
 221    function is located in it's caller's frame, and the save operation only
 222    takes place if the function performs a call.
 223
 224    To have __gnat_backtrace retrieve its own return address, we then
 225    define ... */
 226
 227 #define FORCE_CALL 1
 228 #define FRAME_LEVEL 1
 229
 230 #define BASE_SKIP 1
 231
 232 /*-------------------- PPC ELF (GNU/Linux & VxWorks) ---------------------*/
 233
 234 #elif (defined (_ARCH_PPC) && defined (__vxworks)) ||  \
 235   (defined (linux) && defined (__powerpc__))
 236
 237 #define USE_GENERIC_UNWINDER
 238
 239 struct layout
 240 {
 241   struct layout *next;
 242   void *return_address;
 243 };
 244
 245 #define FORCE_CALL 1
 246 #define FRAME_LEVEL 1
 247 /* See the PPC AIX case for an explanation of these values.  */
 248
 249 #define FRAME_OFFSET(FP) 0
 250 #define PC_ADJUST -4
 251 #define STOP_FRAME(CURRENT, TOP_STACK) ((CURRENT)->next == 0)
 252
 253 #define BASE_SKIP 1
 254
 255 /*-------------------------- SPARC Solaris -----------------------------*/
 256
 257 #elif defined (sun) && defined (sparc)
 258
 259 #define USE_GENERIC_UNWINDER
 260
 261 /* These definitions are inspired from the Appendix D (Software
 262    Considerations) of the SPARC V8 architecture manual.  */
 263
 264 struct layout
 265 {
 266   struct layout *next;
 267   void *return_address;
 268 };
 269
 270 #ifdef __arch64__
 271 #define STACK_BIAS 2047 /* V9 ABI */
 272 #else
 273 #define STACK_BIAS 0    /* V8 ABI */
 274 #endif
 275
 276 #define FRAME_LEVEL 0
 277 #define FRAME_OFFSET(FP) (14 * sizeof (void*) + (FP ? STACK_BIAS : 0))
 278 #define PC_ADJUST 0
 279 #define STOP_FRAME(CURRENT, TOP_STACK) \
 280   ((CURRENT)->return_address == 0|| (CURRENT)->next == 0 \
 281    || (void *) (CURRENT) < (TOP_STACK))
 282
 283 /* The SPARC register windows need to be flushed before we may access them
 284    from the stack. This is achieved by way of builtin_frame_address only
 285    when the "count" argument is positive, so force at least one such call.  */
 286 #define FETCH_UP_FRAME_ADDRESS
 287
 288 #define BASE_SKIP 2
 289 /* From the frame pointer of frame N, we are accessing the flushed register
 290    window of frame N-1 (positive offset from fp), in which we retrieve the
 291    saved return address. We then end up with our caller's return address.  */
 292
 293 /*------------------------------- x86 ----------------------------------*/
 294
 295 #elif defined (i386)
 296
 297 #if defined (__WIN32)
 298 #include <windows.h>
 299 #define IS_BAD_PTR(ptr) (IsBadCodePtr((void *)ptr))
 300 #elif defined (sun)
 301 #define IS_BAD_PTR(ptr) ((unsigned long)ptr == -1UL)
 302 #else
 303 #define IS_BAD_PTR(ptr) 0
 304 #endif
 305
 306 #define USE_GENERIC_UNWINDER
 307
 308 struct layout
 309 {
 310   struct layout *next;
 311   void *return_address;
 312 };
 313
 314 #define FRAME_LEVEL 1
 315 /* builtin_frame_address (1) is expected to work on this target, and (0) might
 316    return the soft stack pointer, which does not designate a location where a
 317    backchain and a return address might be found.  */
 318
 319 #define FRAME_OFFSET(FP) 0
 320 #define PC_ADJUST -2
 321 #define STOP_FRAME(CURRENT, TOP_STACK) \
 322   (IS_BAD_PTR((long)(CURRENT)) \
 323    || IS_BAD_PTR((long)(CURRENT)->return_address) \
 324    || (CURRENT)->return_address == 0|| (CURRENT)->next == 0  \
 325    || (void *) (CURRENT) < (TOP_STACK))
 326
 327 #define BASE_SKIP (1+FRAME_LEVEL)
 328
 329 /* On i386 architecture we check that at the call point we really have a call
 330    insn. Possible call instructions are:
 331
 332    call  addr16        E8 xx xx xx xx
 333    call  reg           FF Dx
 334    call  off(reg)      FF xx xx
 335    lcall addr seg      9A xx xx xx xx xx xx
 336
 337    This check will not catch all cases but it will increase the backtrace
 338    reliability on this architecture.
 339 */
 340
 341 #define VALID_STACK_FRAME(ptr) \
 342    (!IS_BAD_PTR(ptr) \
 343     && (((*((ptr) - 3) & 0xff) == 0xe8) \
 344         || ((*((ptr) - 5) & 0xff) == 0x9a) \
 345         || ((*((ptr) - 1) & 0xff) == 0xff) \
 346         || (((*(ptr) & 0xd0ff) == 0xd0ff))))
 347
 348 /*----------------------------- x86_64 ---------------------------------*/
 349
 350 #elif defined (__x86_64__)
 351
 352 #define USE_GCC_UNWINDER
 353 /* The generic unwinder is not used for this target because it is based
 354    on frame layout assumptions that are not reliable on this target (the
 355    rbp register is very likely used for something else than storing the
 356    frame pointer in optimized code). Hence, we use the GCC unwinder
 357    based on DWARF 2 call frame information, although it has the drawback
 358    of not being able to unwind through frames compiled without DWARF 2
 359    information.
 360 */
 361
 362 #define PC_ADJUST -2
 363 /* The minimum size of call instructions on this architecture is 2 bytes */
 364
 365 /*----------------------------- ia64 ---------------------------------*/
 366
 367 #elif defined (__ia64__) && (defined (linux) || defined (__hpux__))
 368
 369 #define USE_GCC_UNWINDER
 370 /* Use _Unwind_Backtrace driven exceptions on ia64 HP-UX and ia64
 371    GNU/Linux, where _Unwind_Backtrace is provided by the system unwind
 372    library. On HP-UX 11.23 this requires patch PHSS_33352, which adds
 373    _Unwind_Backtrace to the system unwind library. */
 374
 375 #define PC_ADJUST -4
 376
 377
 378 #endif
 379
 380 /*---------------------------------------------------------------------*
 381  *--      The post GCC 3.3 infrastructure based implementation       --*
 382  *---------------------------------------------------------------------*/
 383
 384 #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33)
 385
 386 /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap
 387    path problems, since the included file refers to post 3.3 functions in
 388    libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3
 389    library.  It actually disables the support for backtraces in this compiler
 390    for targets defining USE_GCC_UNWINDER, which is OK since we don't use the
 391    traceback capability in the compiler anyway.
 392
 393    The condition is expressed the way above because we cannot reliably rely on
 394    any other macro from the base compiler when compiling stage1.  */
 395
 396 #include "tb-gcc.c"
 397
 398 /*------------------------------------------------------------------*
 399  *-- The generic implementation based on frame layout assumptions --*
 400  *------------------------------------------------------------------*/
 401
 402 #elif defined (USE_GENERIC_UNWINDER)
 403
 404 #ifndef CURRENT_STACK_FRAME
 405 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
 406 #endif
 407
 408 #ifndef VALID_STACK_FRAME
 409 #define VALID_STACK_FRAME(ptr) 1
 410 #endif
 411
 412 #ifndef MAX
 413 #define MAX(x,y) ((x) > (y) ? (x) : (y))
 414 #endif
 415
 416 #ifndef FORCE_CALL
 417 #define FORCE_CALL 0
 418 #endif
 419
 420 /* Make sure the function is not inlined.  */
 421 static void forced_callee (void) __attribute__ ((noinline));
 422
 423 static void forced_callee (void)
 424 {
 425   /* Make sure the function is not pure.  */
 426   volatile int i __attribute__ ((unused)) = 0;
 427 }
 428
 429 int
 430 __gnat_backtrace (void **array,
 431                   int size,
 432                   void *exclude_min,
 433                   void *exclude_max,
 434                   int skip_frames)
 435 {
 436   struct layout *current;
 437   void *top_frame;
 438   void *top_stack;
 439   int cnt = 0;
 440
 441   if (FORCE_CALL)
 442     forced_callee ();
 443
 444   /* Force a call to builtin_frame_address with a positive argument
 445      if required. This is necessary e.g. on SPARC to have the register
 446      windows flushed before we attempt to access them on the stack.  */
 447 #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0)
 448   __builtin_frame_address (1);
 449 #endif
 450
 451   top_frame = __builtin_frame_address (FRAME_LEVEL);
 452   top_stack = CURRENT_STACK_FRAME;
 453   current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET (0));
 454
 455   /* Skip the number of calls we have been requested to skip, accounting for
 456      the BASE_SKIP parameter.
 457
 458      FRAME_LEVEL is meaningless for the count adjustment. It impacts where we
 459      start retrieving data from, but how many frames "up" we start at is in
 460      BASE_SKIP by definition.  */
 461
 462   skip_frames = MAX (0, skip_frames - BASE_SKIP);
 463
 464   while (cnt < skip_frames)
 465     {
 466       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 467       cnt++;
 468     }
 469
 470   cnt = 0;
 471   while (cnt < size)
 472     {
 473       if (STOP_FRAME (current, top_stack) ||
 474           !VALID_STACK_FRAME((char *)(current->return_address + PC_ADJUST)))
 475         break;
 476
 477       if (current->return_address < exclude_min
 478           || current->return_address > exclude_max)
 479         array[cnt++] = current->return_address + PC_ADJUST;
 480
 481       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 482     }
 483
 484   return cnt;
 485 }
 486
 487 #else
 488
 489 /* No target specific implementation and neither USE_GCC_UNWINDER not
 490    USE_GCC_UNWINDER defined.  */
 491
 492 /*------------------------------*
 493  *-- The dummy implementation --*
 494  *------------------------------*/
 495
 496 int
 497 __gnat_backtrace (void **array ATTRIBUTE_UNUSED,
 498                   int size ATTRIBUTE_UNUSED,
 499                   void *exclude_min ATTRIBUTE_UNUSED,
 500                   void *exclude_max ATTRIBUTE_UNUSED,
 501                   int skip_frames ATTRIBUTE_UNUSED)
 502 {
 503   return 0;
 504 }
 505
 506 #endif
 507
 508 #endif