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) 2000-2005 Ada Core Technologies, Inc.            *
  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/VxWorks
  38    Sparc/Solaris
  39    i386/GNU/Linux
  40    i386/Solaris
  41    i386/NT
  42    i386/OS2
  43    i386/LynxOS
  44    Alpha/VxWorks
  45    Alpha/VMS
  46 */
  47
  48 #ifdef __alpha_vxworks
  49 #include "vxWorks.h"
  50 #endif
  51
  52 #ifdef IN_RTS
  53 #define POSIX
  54 #include "tconfig.h"
  55 #include "tsystem.h"
  56 #else
  57 #include "config.h"
  58 #include "system.h"
  59 #endif
  60
  61 extern int __gnat_backtrace (void **, int, void *, void *, int);
  62
  63 /* The point is to provide an implementation of the __gnat_backtrace function
  64    above, called by the default implementation of the System.Traceback package.
  65
  66    We first have a series of target specific implementations, each included
  67    from a separate C file for readability purposes.
  68
  69    Then come two flavors of a generic implementation: one relying on static
  70    assumptions about the frame layout, and the other one using the GCC EH
  71    infrastructure.  The former uses a whole set of macros and structures which
  72    may be tailored on a per target basis, and is activated as soon as
  73    USE_GENERIC_UNWINDER is defined.  The latter uses a small subset of the
  74    macro definitions and is activated when USE_GCC_UNWINDER is defined. It is
  75    only available post GCC 3.3.
  76
  77    Finally, there is a default dummy implementation, necessary to make the
  78    linker happy on platforms where the feature is not supported, but where the
  79    function is still referenced by the default System.Traceback.  */
  80
  81 #define Lock_Task system__soft_links__lock_task
  82 extern void (*Lock_Task) (void);
  83
  84 #define Unlock_Task system__soft_links__unlock_task
  85 extern void (*Unlock_Task) (void);
  86
  87 /*-------------------------------------*
  88  *-- Target specific implementations --*
  89  *-------------------------------------*/
  90
  91 #if defined (__alpha_vxworks)
  92
  93 #include "tb-alvxw.c"
  94
  95 #elif defined (__ALPHA) && defined (__VMS__)
  96
  97 #include "tb-alvms.c"
  98
  99 #else
 100 /* No target specific implementation.  */
 101
 102 /*----------------------------------------------------------------*
 103  *-- Target specific definitions for the generic implementation --*
 104  *----------------------------------------------------------------*/
 105
 106 /* The stack layout is specified by the target ABI. The "generic" scheme is
 107    based on the following assumption:
 108
 109      The stack layout from some frame pointer is such that the information
 110      required to compute the backtrace is available at static offsets.
 111
 112    For a given frame, the information we are interested in is the saved return
 113    address (somewhere after the call instruction in the caller) and a pointer
 114    to the caller's frame. The former is the base of the call chain information
 115    we store in the tracebacks array. The latter allows us to loop over the
 116    successive frames in the chain.
 117
 118    To initiate the process, we retrieve an initial frame pointer using the
 119    appropriate GCC builtin (__builtin_frame_address).
 120
 121    This scheme is unfortunately not applicable on every target because the
 122    stack layout is not necessarily regular (static) enough. On targets where
 123    this scheme applies, the implementation relies on the following items:
 124
 125    o struct layout, describing the expected stack data layout relevant to the
 126      information we are interested in,
 127
 128    o FRAME_OFFSET, the offset, from a given frame pointer, at which this
 129      layout will be found,
 130
 131    o FRAME_LEVEL, controls how many frames up we get at to start with,
 132      from the initial frame pointer we compute by way of the GCC builtin,
 133
 134      0 is most often the appropriate value. 1 may be necessary on targets
 135      where return addresses are saved by a function in it's caller's frame
 136      (e.g. PPC).
 137
 138    o PC_ADJUST, to account for the difference between a call point (address
 139      of a call instruction), which is what we want in the output array, and
 140      the associated return address, which is what we retrieve from the stack.
 141
 142    o STOP_FRAME, to decide wether we reached the top of the call chain, and
 143      thus if the process shall stop.
 144
 145            :
 146            :                   stack
 147            |             +----------------+
 148            |   +-------->|       :        |
 149            |   |         | (FRAME_OFFSET) |
 150            |   |         |       :        |  (PC_ADJUST)
 151            |   |  layout:| return_address ----------------+
 152            |   |         |     ....       |               |
 153            +---------------  next_frame   |               |
 154                |         |     ....       |               |
 155                |         |                |               |
 156                |         +----------------+               |  +-----+
 157                |         |       :        |<- Base fp     |  |  :  |
 158                |         | (FRAME_OFFSET) | (FRAME_LEVEL) |  |  :  |
 159                |         |       :        |               +--->    | [1]
 160                |  layout:| return_address -------------------->    | [0]
 161                |         |       ...      |  (PC_ADJUST)     +-----+
 162                +----------   next_frame   |                 traceback[]
 163                          |       ...      |
 164                          |                |
 165                          +----------------+
 166
 167    o BASE_SKIP,
 168
 169    Since we inherently deal with return addresses, there is an implicit shift
 170    by at least one for the initial point we are able to observe in the chain.
 171
 172    On some targets (e.g. sparc-solaris), the first return address we can
 173    easily get without special code is even our caller's return address, so
 174    there is a initial shift of two.
 175
 176    BASE_SKIP represents this initial shift, which is the minimal "skip_frames"
 177    value we support. We could add special code for the skip_frames < BASE_SKIP
 178    cases. This is not done currently because there is virtually no situation
 179    in which this would be useful.
 180
 181    Finally, to account for some ABI specificities, a target may (but does
 182    not have to) define:
 183
 184    o FORCE_CALL, to force a call to a dummy function at the very beginning
 185      of the computation. See the PPC AIX target for an example where this
 186      is useful.
 187
 188    o FETCH_UP_FRAME, to force an invocation of __builtin_frame_address with a
 189      positive argument right after a possibly forced call even if FRAME_LEVEL
 190      is 0. See the Sparc Solaris case for an example where this is useful.
 191
 192   */
 193
 194 /*--------------------------- PPC AIX/Darwin ----------------------------*/
 195
 196 #if (defined (__ppc__) && ((defined (_AIX) || defined (__APPLE__))))
 197
 198 #define USE_GENERIC_UNWINDER
 199
 200 struct layout
 201 {
 202   struct layout *next;
 203   void *pad;
 204   void *return_address;
 205 };
 206
 207 #define FRAME_OFFSET 0
 208 #define PC_ADJUST -4
 209 #define STOP_FRAME(CURRENT, TOP_STACK) ((void *) (CURRENT) < (TOP_STACK))
 210
 211 /* The PPC ABI has an interesting specificity: the return address saved by a
 212    function is located in it's caller's frame, and the save operation only
 213    takes place if the function performs a call.
 214
 215    To have __gnat_backtrace retrieve its own return address, we then
 216    define ... */
 217
 218 #define FORCE_CALL
 219 #define FRAME_LEVEL 1
 220
 221 #define BASE_SKIP 1
 222
 223 /*---------------------------- PPC VxWorks------------------------------*/
 224
 225 #elif defined (_ARCH_PPC) && defined (__vxworks)
 226
 227 #define USE_GENERIC_UNWINDER
 228
 229 struct layout
 230 {
 231   struct layout *next;
 232   void *return_address;
 233 };
 234
 235 #define FORCE_CALL
 236 #define FRAME_LEVEL 1
 237 /* See the PPC AIX case for an explanation of these values.  */
 238
 239 #define FRAME_OFFSET 0
 240 #define PC_ADJUST -4
 241 #define STOP_FRAME(CURRENT, TOP_STACK) ((CURRENT)->next == 0)
 242
 243 #define BASE_SKIP 1
 244
 245 /*-------------------------- SPARC Solaris -----------------------------*/
 246
 247 #elif defined (sun) && defined (sparc)
 248
 249 #define USE_GENERIC_UNWINDER
 250
 251 /* These definitions are inspired from the Appendix D (Software
 252    Considerations) of the SPARC V8 architecture manual.  */
 253
 254 struct layout
 255 {
 256   struct layout *next;
 257   void *return_address;
 258 };
 259
 260 #ifdef __arch64__
 261 #define STACK_BIAS 2047 /* V9 ABI */
 262 #else
 263 #define STACK_BIAS 0    /* V8 ABI */
 264 #endif
 265
 266 #define FRAME_LEVEL 0
 267 #define FRAME_OFFSET (14 * sizeof (void*) + STACK_BIAS)
 268 #define PC_ADJUST 0
 269 #define STOP_FRAME(CURRENT, TOP_STACK) \
 270   ((CURRENT)->return_address == 0|| (CURRENT)->next == 0 \
 271    || (void *) (CURRENT) < (TOP_STACK))
 272
 273 /* The sparc register windows need to be flushed before we may access them
 274    from the stack. This is achieved by way of builtin_frame_address only
 275    when the "count" argument is positive, so force at least one such call.  */
 276 #define FETCH_UP_FRAME_ADDRESS
 277
 278 #define BASE_SKIP 2
 279 /* From the frame pointer of frame N, we are accessing the flushed register
 280    window of frame N-1 (positive offset from fp), in which we retrieve the
 281    saved return address. We then end up with our caller's return address.  */
 282
 283 /*------------------------------- x86 ----------------------------------*/
 284
 285 #elif defined (i386)
 286
 287 #ifdef __WIN32
 288 #include <windows.h>
 289 #define IS_BAD_PTR(ptr) (IsBadCodePtr((void *)ptr))
 290 #else
 291 #define IS_BAD_PTR(ptr) 0
 292 #endif
 293
 294 #define USE_GENERIC_UNWINDER
 295
 296 struct layout
 297 {
 298   struct layout *next;
 299   void *return_address;
 300 };
 301
 302 #define LOWEST_ADDR 0
 303 #define FRAME_LEVEL 0
 304 #define FRAME_OFFSET 0
 305 #define PC_ADJUST -2
 306 #define STOP_FRAME(CURRENT, TOP_STACK) \
 307   (IS_BAD_PTR((long)(CURRENT)->return_address) \
 308    || (unsigned int)(CURRENT)->return_address < LOWEST_ADDR \
 309    || (CURRENT)->return_address == 0|| (CURRENT)->next == 0  \
 310    || (void *) (CURRENT) < (TOP_STACK))
 311
 312 #define BASE_SKIP 1
 313
 314 /* On i386 architecture we check that at the call point we really have a call
 315    insn. Possible call instructions are:
 316
 317    call  addr16        E8 xx xx xx xx
 318    call  reg           FF Dx
 319    call  off(reg)      FF xx xx
 320    lcall addr seg      9A xx xx xx xx xx xx
 321
 322    This check will not catch all cases but it will increase the backtrace
 323    reliability on this architecture.
 324 */
 325
 326 #define VALID_STACK_FRAME(ptr) \
 327    (!IS_BAD_PTR(ptr) \
 328     && (((*((ptr) - 3) & 0xff) == 0xe8) \
 329         || ((*((ptr) - 5) & 0xff) == 0x9a) \
 330         || ((*((ptr) - 1) & 0xff) == 0xff) \
 331         || (((*(ptr) & 0xd0ff) == 0xd0ff))))
 332
 333 /*----------------------------- x86_64 ---------------------------------*/
 334
 335 #elif defined (__x86_64__)
 336
 337 #define USE_GCC_UNWINDER
 338 /* The generic unwinder is not used for this target because it is based
 339    on frame layout assumptions that are not reliable on this target (the
 340    rbp register is very likely used for something else than storing the
 341    frame pointer in optimized code). Hence, we use the GCC unwinder
 342    based on DWARF 2 call frame information, although it has the drawback
 343    of not being able to unwind through frames compiled without DWARF 2
 344    information.
 345 */
 346
 347 #define PC_ADJUST -2
 348 /* The minimum size of call instructions on this architecture is 2 bytes */
 349
 350 /*----------------------------- ia64 ---------------------------------*/
 351
 352 #elif defined (__ia64__) && !defined (USE_LIBUNWIND_EXCEPTIONS)
 353
 354 #define USE_GCC_UNWINDER
 355
 356 #define PC_ADJUST -16
 357 /* Every call on ia64 is part of a 128 bit bundle, so an adjustment of
 358    minus 16 bytes from the point of return finds the address of the
 359    previous bundle. */
 360
 361 #endif
 362
 363 /*---------------------------------------------------------------------*
 364  *--      The post GCC 3.3 infrastructure based implementation       --*
 365  *---------------------------------------------------------------------*/
 366
 367 #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33)
 368
 369 /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap
 370    path problems, since the included file refers to post 3.3 functions in
 371    libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3
 372    library.  It actually disables the support for backtraces in this compiler
 373    for targets defining USE_GCC_UNWINDER, which is OK since we don't use the
 374    traceback capability in the compiler anyway.
 375
 376    The condition is expressed the way above because we cannot reliably rely on
 377    any other macro from the base compiler when compiling stage1.  */
 378
 379 #include "tb-gcc.c"
 380
 381 /*------------------------------------------------------------------*
 382  *-- The generic implementation based on frame layout assumptions --*
 383  *------------------------------------------------------------------*/
 384
 385 #elif defined (USE_GENERIC_UNWINDER)
 386
 387 #ifndef CURRENT_STACK_FRAME
 388 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
 389 #endif
 390
 391 #ifndef VALID_STACK_FRAME
 392 #define VALID_STACK_FRAME(ptr) 1
 393 #endif
 394
 395 #ifndef MAX
 396 #define MAX(x,y) ((x) > (y) ? (x) : (y))
 397 #endif
 398
 399 /* Define a dummy function to call if FORCE_CALL is defined.  Don't
 400    define it otherwise, as this could lead to "defined but not used"
 401    warnings.  */
 402 #if defined (FORCE_CALL)
 403 static void forced_callee () {}
 404 #endif
 405
 406 int
 407 __gnat_backtrace (void **array,
 408                   int size,
 409                   void *exclude_min,
 410                   void *exclude_max,
 411                   int skip_frames)
 412 {
 413   struct layout *current;
 414   void *top_frame;
 415   void *top_stack;
 416   int cnt = 0;
 417
 418   /* Honor FORCE_CALL when defined.  */
 419 #if defined (FORCE_CALL)
 420   forced_callee ();
 421 #endif
 422
 423   /* Force a call to builtin_frame_address with a positive argument
 424      if required. This is necessary e.g. on sparc to have the register
 425      windows flushed before we attempt to access them on the stack.  */
 426 #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0)
 427   __builtin_frame_address (1);
 428 #endif
 429
 430   top_frame = __builtin_frame_address (FRAME_LEVEL);
 431   top_stack = CURRENT_STACK_FRAME;
 432   current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET);
 433
 434   /* Skip the number of calls we have been requested to skip, accounting for
 435      the BASE_SKIP parameter.
 436
 437      FRAME_LEVEL is meaningless for the count adjustment. It impacts where we
 438      start retrieving data from, but how many frames "up" we start at is in
 439      BASE_SKIP by definition.  */
 440
 441   skip_frames = MAX (0, skip_frames - BASE_SKIP);
 442
 443   while (cnt < skip_frames)
 444     {
 445       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET);
 446       cnt++;
 447     }
 448
 449   cnt = 0;
 450   while (cnt < size)
 451     {
 452       if (STOP_FRAME (current, top_stack) ||
 453           !VALID_STACK_FRAME((char *)(current->return_address + PC_ADJUST)))
 454         break;
 455
 456       if (current->return_address < exclude_min
 457           || current->return_address > exclude_max)
 458         array[cnt++] = current->return_address + PC_ADJUST;
 459
 460       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET);
 461     }
 462
 463   return cnt;
 464 }
 465
 466 #else
 467
 468 /* No target specific implementation and neither USE_GCC_UNWINDER not
 469    USE_GCC_UNWINDER defined.  */
 470
 471 /*------------------------------*
 472  *-- The dummy implementation --*
 473  *------------------------------*/
 474
 475 int
 476 __gnat_backtrace (array, size, exclude_min, exclude_max, skip_frames)
 477      void **array ATTRIBUTE_UNUSED;
 478      int size ATTRIBUTE_UNUSED;
 479      void *exclude_min ATTRIBUTE_UNUSED;
 480      void *exclude_max ATTRIBUTE_UNUSED;
 481      int skip_frames ATTRIBUTE_UNUSED;
 482 {
 483   return 0;
 484 }
 485
 486 #endif
 487
 488 #endif