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) 2000-2008, 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 #ifdef __WIN32
 298 #include <windows.h>
 299 #define IS_BAD_PTR(ptr) (IsBadCodePtr((void *)ptr))
 300 #else
 301 #define IS_BAD_PTR(ptr) 0
 302 #endif
 303
 304 #define USE_GENERIC_UNWINDER
 305
 306 struct layout
 307 {
 308   struct layout *next;
 309   void *return_address;
 310 };
 311
 312 #define FRAME_LEVEL 1
 313 /* builtin_frame_address (1) is expected to work on this target, and (0) might
 314    return the soft stack pointer, which does not designate a location where a
 315    backchain and a return address might be found.  */
 316
 317 #define FRAME_OFFSET(FP) 0
 318 #define PC_ADJUST -2
 319 #define STOP_FRAME(CURRENT, TOP_STACK) \
 320   (IS_BAD_PTR((long)(CURRENT)) \
 321    || IS_BAD_PTR((long)(CURRENT)->return_address) \
 322    || (CURRENT)->return_address == 0|| (CURRENT)->next == 0  \
 323    || (void *) (CURRENT) < (TOP_STACK))
 324
 325 #define BASE_SKIP (1+FRAME_LEVEL)
 326
 327 /* On i386 architecture we check that at the call point we really have a call
 328    insn. Possible call instructions are:
 329
 330    call  addr16        E8 xx xx xx xx
 331    call  reg           FF Dx
 332    call  off(reg)      FF xx xx
 333    lcall addr seg      9A xx xx xx xx xx xx
 334
 335    This check will not catch all cases but it will increase the backtrace
 336    reliability on this architecture.
 337 */
 338
 339 #define VALID_STACK_FRAME(ptr) \
 340    (!IS_BAD_PTR(ptr) \
 341     && (((*((ptr) - 3) & 0xff) == 0xe8) \
 342         || ((*((ptr) - 5) & 0xff) == 0x9a) \
 343         || ((*((ptr) - 1) & 0xff) == 0xff) \
 344         || (((*(ptr) & 0xd0ff) == 0xd0ff))))
 345
 346 /*----------------------------- x86_64 ---------------------------------*/
 347
 348 #elif defined (__x86_64__)
 349
 350 #define USE_GCC_UNWINDER
 351 /* The generic unwinder is not used for this target because it is based
 352    on frame layout assumptions that are not reliable on this target (the
 353    rbp register is very likely used for something else than storing the
 354    frame pointer in optimized code). Hence, we use the GCC unwinder
 355    based on DWARF 2 call frame information, although it has the drawback
 356    of not being able to unwind through frames compiled without DWARF 2
 357    information.
 358 */
 359
 360 #define PC_ADJUST -2
 361 /* The minimum size of call instructions on this architecture is 2 bytes */
 362
 363 /*----------------------------- ia64 ---------------------------------*/
 364
 365 #elif defined (__ia64__) && (defined (linux) || defined (__hpux__))
 366
 367 #define USE_GCC_UNWINDER
 368 /* Use _Unwind_Backtrace driven exceptions on ia64 HP-UX and ia64
 369    GNU/Linux, where _Unwind_Backtrace is provided by the system unwind
 370    library. On HP-UX 11.23 this requires patch PHSS_33352, which adds
 371    _Unwind_Backtrace to the system unwind library. */
 372
 373 #define PC_ADJUST -4
 374
 375
 376 #endif
 377
 378 /*---------------------------------------------------------------------*
 379  *--      The post GCC 3.3 infrastructure based implementation       --*
 380  *---------------------------------------------------------------------*/
 381
 382 #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33)
 383
 384 /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap
 385    path problems, since the included file refers to post 3.3 functions in
 386    libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3
 387    library.  It actually disables the support for backtraces in this compiler
 388    for targets defining USE_GCC_UNWINDER, which is OK since we don't use the
 389    traceback capability in the compiler anyway.
 390
 391    The condition is expressed the way above because we cannot reliably rely on
 392    any other macro from the base compiler when compiling stage1.  */
 393
 394 #include "tb-gcc.c"
 395
 396 /*------------------------------------------------------------------*
 397  *-- The generic implementation based on frame layout assumptions --*
 398  *------------------------------------------------------------------*/
 399
 400 #elif defined (USE_GENERIC_UNWINDER)
 401
 402 #ifndef CURRENT_STACK_FRAME
 403 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
 404 #endif
 405
 406 #ifndef VALID_STACK_FRAME
 407 #define VALID_STACK_FRAME(ptr) 1
 408 #endif
 409
 410 #ifndef MAX
 411 #define MAX(x,y) ((x) > (y) ? (x) : (y))
 412 #endif
 413
 414 #ifndef FORCE_CALL
 415 #define FORCE_CALL 0
 416 #endif
 417
 418 /* Make sure the function is not inlined.  */
 419 static void forced_callee (void) __attribute__ ((noinline));
 420
 421 static void forced_callee (void)
 422 {
 423   /* Make sure the function is not pure.  */
 424   volatile int i __attribute__ ((unused)) = 0;
 425 }
 426
 427 int
 428 __gnat_backtrace (void **array,
 429                   int size,
 430                   void *exclude_min,
 431                   void *exclude_max,
 432                   int skip_frames)
 433 {
 434   struct layout *current;
 435   void *top_frame;
 436   void *top_stack;
 437   int cnt = 0;
 438
 439   if (FORCE_CALL)
 440     forced_callee ();
 441
 442   /* Force a call to builtin_frame_address with a positive argument
 443      if required. This is necessary e.g. on SPARC to have the register
 444      windows flushed before we attempt to access them on the stack.  */
 445 #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0)
 446   __builtin_frame_address (1);
 447 #endif
 448
 449   top_frame = __builtin_frame_address (FRAME_LEVEL);
 450   top_stack = CURRENT_STACK_FRAME;
 451   current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET (0));
 452
 453   /* Skip the number of calls we have been requested to skip, accounting for
 454      the BASE_SKIP parameter.
 455
 456      FRAME_LEVEL is meaningless for the count adjustment. It impacts where we
 457      start retrieving data from, but how many frames "up" we start at is in
 458      BASE_SKIP by definition.  */
 459
 460   skip_frames = MAX (0, skip_frames - BASE_SKIP);
 461
 462   while (cnt < skip_frames)
 463     {
 464       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 465       cnt++;
 466     }
 467
 468   cnt = 0;
 469   while (cnt < size)
 470     {
 471       if (STOP_FRAME (current, top_stack) ||
 472           !VALID_STACK_FRAME((char *)(current->return_address + PC_ADJUST)))
 473         break;
 474
 475       if (current->return_address < exclude_min
 476           || current->return_address > exclude_max)
 477         array[cnt++] = current->return_address + PC_ADJUST;
 478
 479       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 480     }
 481
 482   return cnt;
 483 }
 484
 485 #else
 486
 487 /* No target specific implementation and neither USE_GCC_UNWINDER not
 488    USE_GCC_UNWINDER defined.  */
 489
 490 /*------------------------------*
 491  *-- The dummy implementation --*
 492  *------------------------------*/
 493
 494 int
 495 __gnat_backtrace (array, size, exclude_min, exclude_max, skip_frames)
 496      void **array ATTRIBUTE_UNUSED;
 497      int size ATTRIBUTE_UNUSED;
 498      void *exclude_min ATTRIBUTE_UNUSED;
 499      void *exclude_max ATTRIBUTE_UNUSED;
 500      int skip_frames ATTRIBUTE_UNUSED;
 501 {
 502   return 0;
 503 }
 504
 505 #endif
 506
 507 #endif