gcc/ada/tracebak.c

   1 /****************************************************************************
   2  *                                                                          *
   3  *                         GNAT RUN-TIME COMPONENTS                         *
   4  *                                                                          *
   5  *                            T R A C E B A C K                             *
   6  *                                                                          *
   7  *                          C Implementation File                           *
   8  *                                                                          *
   9  *            Copyright (C) 2000-2015, Free Software Foundation, 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 3,  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.                                     *
  17  *                                                                          *
  18  * As a special exception under Section 7 of GPL version 3, you are granted *
  19  * additional permissions described in the GCC Runtime Library Exception,   *
  20  * version 3.1, as published by the Free Software Foundation.               *
  21  *                                                                          *
  22  * You should have received a copy of the GNU General Public License and    *
  23  * a copy of the GCC Runtime Library Exception along with this program;     *
  24  * see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    *
  25  * <http://www.gnu.org/licenses/>.                                          *
  26  *                                                                          *
  27  * GNAT was originally developed  by the GNAT team at  New York University. *
  28  * Extensive contributions were provided by Ada Core Technologies Inc.      *
  29  *                                                                          *
  30  ****************************************************************************/
  31
  32 /* This file contains low level support for stack unwinding using GCC intrinsic
  33    functions.
  34    It has been tested on the following configurations:
  35    PowerPC/AiX
  36    PowerPC/Darwin
  37    PowerPC/VxWorks
  38    PowerPC/LynxOS-178
  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 __cplusplus
  50 extern "C" {
  51 #endif
  52
  53 #ifdef __alpha_vxworks
  54 #include "vxWorks.h"
  55 #endif
  56
  57 #ifdef IN_RTS
  58 #define POSIX
  59 #include "tconfig.h"
  60 #include "tsystem.h"
  61 #else
  62 #include "config.h"
  63 #include "system.h"
  64 /* We don't want fancy_abort here.  */
  65 #undef abort
  66 #endif
  67
  68 extern int __gnat_backtrace (void **, int, void *, void *, int);
  69
  70 /* The point is to provide an implementation of the __gnat_backtrace function
  71    above, called by the default implementation of the System.Traceback package.
  72
  73    We first have a series of target specific implementations, each included
  74    from a separate C file for readability purposes.
  75
  76    Then come two flavors of a generic implementation: one relying on static
  77    assumptions about the frame layout, and the other one using the GCC EH
  78    infrastructure.  The former uses a whole set of macros and structures which
  79    may be tailored on a per target basis, and is activated as soon as
  80    USE_GENERIC_UNWINDER is defined.  The latter uses a small subset of the
  81    macro definitions and is activated when USE_GCC_UNWINDER is defined. It is
  82    only available post GCC 3.3.
  83
  84    Finally, there is a default dummy implementation, necessary to make the
  85    linker happy on platforms where the feature is not supported, but where the
  86    function is still referenced by the default System.Traceback.  */
  87
  88 #define Lock_Task system__soft_links__lock_task
  89 extern void (*Lock_Task) (void);
  90
  91 #define Unlock_Task system__soft_links__unlock_task
  92 extern void (*Unlock_Task) (void);
  93
  94 /*-------------------------------------*
  95  *-- Target specific implementations --*
  96  *-------------------------------------*/
  97
  98 #if defined (_WIN64) && defined (__SEH__)
  99
 100 #include <windows.h>
 101
 102 int
 103 __gnat_backtrace (void **array,
 104                   int size,
 105                   void *exclude_min,
 106                   void *exclude_max,
 107                   int skip_frames)
 108 {
 109   CONTEXT context;
 110   UNWIND_HISTORY_TABLE history;
 111   int i;
 112
 113   /* Get the context.  */
 114   RtlCaptureContext (&context);
 115
 116   /* Setup unwind history table (a cached to speed-up unwinding).  */
 117   memset (&history, 0, sizeof (history));
 118
 119   i = 0;
 120   while (1)
 121     {
 122       PRUNTIME_FUNCTION RuntimeFunction;
 123       KNONVOLATILE_CONTEXT_POINTERS NvContext;
 124       ULONG64 ImageBase;
 125       VOID *HandlerData;
 126       ULONG64 EstablisherFrame;
 127
 128       /* Get function metadata.  */
 129       RuntimeFunction = RtlLookupFunctionEntry
 130         (context.Rip, &ImageBase, &history);
 131
 132       if (!RuntimeFunction)
 133         {
 134           /* In case of failure, assume this is a leaf function.  */
 135           context.Rip = *(ULONG64 *) context.Rsp;
 136           context.Rsp += 8;
 137         }
 138       else
 139         {
 140           /* Unwind.  */
 141           memset (&NvContext, 0, sizeof (KNONVOLATILE_CONTEXT_POINTERS));
 142           RtlVirtualUnwind (0, ImageBase, context.Rip, RuntimeFunction,
 143                             &context, &HandlerData, &EstablisherFrame,
 144                             &NvContext);
 145         }
 146
 147       /* 0 means bottom of the stack.  */
 148       if (context.Rip == 0)
 149         break;
 150
 151       /* Skip frames.  */
 152       if (skip_frames > 1)
 153         {
 154           skip_frames--;
 155           continue;
 156         }
 157       /* Excluded frames.  */
 158       if ((void *)context.Rip >= exclude_min
 159           && (void *)context.Rip <= exclude_max)
 160         continue;
 161
 162       array[i++] = (void *)(context.Rip - 2);
 163       if (i >= size)
 164         break;
 165     }
 166   return i;
 167 }
 168 #else
 169
 170 /* No target specific implementation.  */
 171
 172 /*----------------------------------------------------------------*
 173  *-- Target specific definitions for the generic implementation --*
 174  *----------------------------------------------------------------*/
 175
 176 /* The stack layout is specified by the target ABI. The "generic" scheme is
 177    based on the following assumption:
 178
 179      The stack layout from some frame pointer is such that the information
 180      required to compute the backtrace is available at static offsets.
 181
 182    For a given frame, the information we are interested in is the saved return
 183    address (somewhere after the call instruction in the caller) and a pointer
 184    to the caller's frame. The former is the base of the call chain information
 185    we store in the tracebacks array. The latter allows us to loop over the
 186    successive frames in the chain.
 187
 188    To initiate the process, we retrieve an initial frame address using the
 189    appropriate GCC builtin (__builtin_frame_address).
 190
 191    This scheme is unfortunately not applicable on every target because the
 192    stack layout is not necessarily regular (static) enough. On targets where
 193    this scheme applies, the implementation relies on the following items:
 194
 195    o struct layout, describing the expected stack data layout relevant to the
 196      information we are interested in,
 197
 198    o FRAME_OFFSET, the offset, from a given frame address or frame pointer
 199      value, at which this layout will be found,
 200
 201    o FRAME_LEVEL, controls how many frames up we get at to start with,
 202      from the initial frame pointer we compute by way of the GCC builtin,
 203
 204      0 is most often the appropriate value. 1 may be necessary on targets
 205      where return addresses are saved by a function in it's caller's frame
 206      (e.g. PPC).
 207
 208    o PC_ADJUST, to account for the difference between a call point (address
 209      of a call instruction), which is what we want in the output array, and
 210      the associated return address, which is what we retrieve from the stack.
 211
 212    o STOP_FRAME, to decide whether we reached the top of the call chain, and
 213      thus if the process shall stop.
 214
 215            :
 216            :                   stack
 217            |             +----------------+
 218            |   +-------->|       :        |
 219            |   |         | (FRAME_OFFSET) |
 220            |   |         |       :        |  (PC_ADJUST)
 221            |   |  layout:| return_address ----------------+
 222            |   |         |     ....       |               |
 223            +---------------  next_frame   |               |
 224                |         |     ....       |               |
 225                |         |                |               |
 226                |         +----------------+               |  +-----+
 227                |         |       :        |<- Base fp     |  |  :  |
 228                |         | (FRAME_OFFSET) | (FRAME_LEVEL) |  |  :  |
 229                |         |       :        |               +--->    | [1]
 230                |  layout:| return_address -------------------->    | [0]
 231                |         |       ...      |  (PC_ADJUST)     +-----+
 232                +----------   next_frame   |                 traceback[]
 233                          |       ...      |
 234                          |                |
 235                          +----------------+
 236
 237    o BASE_SKIP,
 238
 239    Since we inherently deal with return addresses, there is an implicit shift
 240    by at least one for the initial point we are able to observe in the chain.
 241
 242    On some targets (e.g. sparc-solaris), the first return address we can
 243    easily get without special code is even our caller's return address, so
 244    there is a initial shift of two.
 245
 246    BASE_SKIP represents this initial shift, which is the minimal "skip_frames"
 247    value we support. We could add special code for the skip_frames < BASE_SKIP
 248    cases. This is not done currently because there is virtually no situation
 249    in which this would be useful.
 250
 251    Finally, to account for some ABI specificities, a target may (but does
 252    not have to) define:
 253
 254    o FORCE_CALL, to force a call to a dummy function at the very beginning
 255      of the computation. See the PPC AIX target for an example where this
 256      is useful.
 257
 258    o FETCH_UP_FRAME, to force an invocation of __builtin_frame_address with a
 259      positive argument right after a possibly forced call even if FRAME_LEVEL
 260      is 0. See the SPARC Solaris case for an example where this is useful.
 261
 262   */
 263
 264 /*------------------- Darwin 8 (OSX 10.4) or newer ----------------------*/
 265 #if defined (__APPLE__) \
 266     && defined (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) \
 267     && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 1040
 268
 269 #define USE_GCC_UNWINDER
 270
 271 #if defined (__i386__) || defined (__x86_64__)
 272 #define PC_ADJUST -2
 273 #elif defined (__ppc__) || defined (__ppc64__)
 274 #define PC_ADJUST -4
 275 #elif defined (__arm__)
 276 #define PC_ADJUST -2
 277 #elif defined (__arm64__)
 278 #define PC_ADJUST -4
 279 #else
 280 #error Unhandled darwin architecture.
 281 #endif
 282
 283 /*---------------------------- x86 *BSD --------------------------------*/
 284
 285 #elif defined (__i386__) &&   \
 286     ( defined (__NetBSD__) || defined (__FreeBSD__) || defined (__OpenBSD__) )
 287
 288 #define USE_GCC_UNWINDER
 289 /* The generic unwinder is not used for this target because the default
 290    implementation doesn't unwind on the BSD platforms.  AMD64 targets use the
 291    gcc unwinder for all platforms, so let's keep i386 consistent with that.
 292 */
 293
 294 #define PC_ADJUST -2
 295 /* The minimum size of call instructions on this architecture is 2 bytes */
 296
 297 /*---------------------- PPC AIX/PPC Lynx 178/Older Darwin ------------------*/
 298 #elif ((defined (_POWER) && defined (_AIX)) || \
 299        (defined (__powerpc__) && defined (__Lynx__) && !defined(__ELF__)) || \
 300        (defined (__ppc__) && defined (__APPLE__)))
 301
 302 #define USE_GENERIC_UNWINDER
 303
 304 struct layout
 305 {
 306   struct layout *next;
 307   void *pad;
 308   void *return_address;
 309 };
 310
 311 #define FRAME_OFFSET(FP) 0
 312 #define PC_ADJUST -4
 313
 314 /* Eventhough the base PPC ABI states that a toplevel frame entry
 315    should to feature a null backchain, AIX might expose a null return
 316    address instead.  */
 317
 318 /* Then LynxOS-178 features yet another variation, with return_address
 319    == &<entrypoint>, with two possible entry points (one for the main
 320    process and one for threads). Beware that &bla returns the address
 321    of a descriptor when "bla" is a function.  Getting the code address
 322    requires an extra dereference.  */
 323
 324 #if defined (__Lynx__)
 325 extern void __start();  /* process entry point.  */
 326 extern void __runnit(); /* thread entry point.  */
 327 #define EXTRA_STOP_CONDITION(CURRENT)                 \
 328   ((CURRENT)->return_address == *(void**)&__start     \
 329    || (CURRENT)->return_address == *(void**)&__runnit)
 330 #else
 331 #define EXTRA_STOP_CONDITION(CURRENT) (0)
 332 #endif
 333
 334 #define STOP_FRAME(CURRENT, TOP_STACK) \
 335   (((void *) (CURRENT) < (TOP_STACK)) \
 336    || (CURRENT)->return_address == NULL \
 337    || EXTRA_STOP_CONDITION(CURRENT))
 338
 339 /* The PPC ABI has an interesting specificity: the return address saved by a
 340    function is located in it's caller's frame, and the save operation only
 341    takes place if the function performs a call.
 342
 343    To have __gnat_backtrace retrieve its own return address, we then
 344    define ... */
 345
 346 #define FORCE_CALL 1
 347 #define FRAME_LEVEL 1
 348
 349 #define BASE_SKIP 1
 350
 351 /*-------------------- PPC ELF (GNU/Linux & VxWorks) ---------------------*/
 352
 353 #elif (defined (_ARCH_PPC) && defined (__vxworks)) ||  \
 354   (defined (__linux__) && defined (__powerpc__))
 355
 356 #define USE_GENERIC_UNWINDER
 357
 358 struct layout
 359 {
 360   struct layout *next;
 361   void *return_address;
 362 };
 363
 364 #define FORCE_CALL 1
 365 #define FRAME_LEVEL 1
 366 /* See the PPC AIX case for an explanation of these values.  */
 367
 368 #define FRAME_OFFSET(FP) 0
 369 #define PC_ADJUST -4
 370
 371 /* According to the base PPC ABI, a toplevel frame entry should feature
 372    a null backchain.  What happens at signal handler frontiers isn't so
 373    well specified, so we add a safety guard on top.  */
 374
 375 #define STOP_FRAME(CURRENT, TOP_STACK) \
 376  ((CURRENT)->next == 0 || ((long)(CURRENT)->next % __alignof__(void*)) != 0)
 377
 378 #define BASE_SKIP 1
 379
 380 /*-------------------------- SPARC Solaris -----------------------------*/
 381
 382 #elif defined (__sun__) && defined (__sparc__)
 383
 384 #define USE_GENERIC_UNWINDER
 385
 386 /* These definitions are inspired from the Appendix D (Software
 387    Considerations) of the SPARC V8 architecture manual.  */
 388
 389 struct layout
 390 {
 391   struct layout *next;
 392   void *return_address;
 393 };
 394
 395 #ifdef __arch64__
 396 #define STACK_BIAS 2047 /* V9 ABI */
 397 #else
 398 #define STACK_BIAS 0    /* V8 ABI */
 399 #endif
 400
 401 #define FRAME_LEVEL 0
 402 #define FRAME_OFFSET(FP) (14 * sizeof (void*) + (FP ? STACK_BIAS : 0))
 403 #define PC_ADJUST 0
 404 #define STOP_FRAME(CURRENT, TOP_STACK) \
 405   ((CURRENT)->return_address == 0|| (CURRENT)->next == 0 \
 406    || (void *) (CURRENT) < (TOP_STACK))
 407
 408 /* The SPARC register windows need to be flushed before we may access them
 409    from the stack. This is achieved by way of builtin_frame_address only
 410    when the "count" argument is positive, so force at least one such call.  */
 411 #define FETCH_UP_FRAME_ADDRESS
 412
 413 #define BASE_SKIP 2
 414 /* From the frame pointer of frame N, we are accessing the flushed register
 415    window of frame N-1 (positive offset from fp), in which we retrieve the
 416    saved return address. We then end up with our caller's return address.  */
 417
 418 /*---------------------------- x86 & x86_64 ---------------------------------*/
 419
 420 #elif defined (__i386__) || defined (__x86_64__)
 421
 422 #if defined (__WIN32)
 423 #include <windows.h>
 424 #define IS_BAD_PTR(ptr) (IsBadCodePtr((FARPROC)ptr))
 425 #elif defined (__sun__)
 426 #define IS_BAD_PTR(ptr) ((unsigned long)ptr == -1UL)
 427 #else
 428 #define IS_BAD_PTR(ptr) 0
 429 #endif
 430
 431 /* Use the dwarf2 unwinder when we expect to have dwarf2 tables at
 432    hand. Backtraces will reliably stop on frames missing such tables,
 433    but our only alternative is the generic unwinder which requires
 434    compilation forcing a frame pointer to be reliable.  */
 435
 436 #if (defined (__x86_64__) || defined (__linux__)) && !defined (__USING_SJLJ_EXCEPTIONS__)
 437 #define USE_GCC_UNWINDER
 438 #else
 439 #define USE_GENERIC_UNWINDER
 440 #endif
 441
 442 struct layout
 443 {
 444   struct layout *next;
 445   void *return_address;
 446 };
 447
 448 #define FRAME_LEVEL 1
 449 /* builtin_frame_address (1) is expected to work on this family of targets,
 450    and (0) might return the soft stack pointer, which does not designate a
 451    location where a backchain and a return address might be found.  */
 452
 453 #define FRAME_OFFSET(FP) 0
 454 #define PC_ADJUST -2
 455 #define STOP_FRAME(CURRENT, TOP_STACK) \
 456   (IS_BAD_PTR((long)(CURRENT)) \
 457    || IS_BAD_PTR((long)(CURRENT)->return_address) \
 458    || (CURRENT)->return_address == 0 \
 459    || (void *) ((CURRENT)->next) < (TOP_STACK)  \
 460    || (void *) (CURRENT) < (TOP_STACK))
 461
 462 #define BASE_SKIP (1+FRAME_LEVEL)
 463
 464 /* On i386 architecture we check that at the call point we really have a call
 465    insn. Possible call instructions are:
 466
 467    call  addr16        E8 xx xx xx xx
 468    call  reg           FF Dx
 469    call  off(reg)      FF xx xx
 470    lcall addr seg      9A xx xx xx xx xx xx
 471
 472    This check will not catch all cases but it will increase the backtrace
 473    reliability on this architecture.
 474 */
 475
 476 #define VALID_STACK_FRAME(ptr) \
 477    (!IS_BAD_PTR(ptr) \
 478     && (((*((ptr) - 3) & 0xff) == 0xe8) \
 479         || ((*((ptr) - 5) & 0xff) == 0x9a) \
 480         || ((*((ptr) - 1) & 0xff) == 0xff) \
 481         || (((*(ptr) & 0xd0ff) == 0xd0ff))))
 482
 483 /*----------------------------- ia64 ---------------------------------*/
 484
 485 #elif defined (__ia64__) && (defined (__linux__) || defined (__hpux__))
 486
 487 #define USE_GCC_UNWINDER
 488 /* Use _Unwind_Backtrace driven exceptions on ia64 HP-UX and ia64
 489    GNU/Linux, where _Unwind_Backtrace is provided by the system unwind
 490    library. On HP-UX 11.23 this requires patch PHSS_33352, which adds
 491    _Unwind_Backtrace to the system unwind library. */
 492
 493 #define PC_ADJUST -4
 494
 495
 496 #endif
 497
 498 /*---------------------------------------------------------------------*
 499  *--      The post GCC 3.3 infrastructure based implementation       --*
 500  *---------------------------------------------------------------------*/
 501
 502 #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33)
 503
 504 /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap
 505    path problems, since the included file refers to post 3.3 functions in
 506    libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3
 507    library.  It actually disables the support for backtraces in this compiler
 508    for targets defining USE_GCC_UNWINDER, which is OK since we don't use the
 509    traceback capability in the compiler anyway.
 510
 511    The condition is expressed the way above because we cannot reliably rely on
 512    any other macro from the base compiler when compiling stage1.  */
 513
 514 #include "tb-gcc.c"
 515
 516 /*------------------------------------------------------------------*
 517  *-- The generic implementation based on frame layout assumptions --*
 518  *------------------------------------------------------------------*/
 519
 520 #elif defined (USE_GENERIC_UNWINDER)
 521
 522 #ifndef CURRENT_STACK_FRAME
 523 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
 524 #endif
 525
 526 #ifndef VALID_STACK_FRAME
 527 #define VALID_STACK_FRAME(ptr) 1
 528 #endif
 529
 530 #ifndef MAX
 531 #define MAX(x,y) ((x) > (y) ? (x) : (y))
 532 #endif
 533
 534 #ifndef FORCE_CALL
 535 #define FORCE_CALL 0
 536 #endif
 537
 538 /* Make sure the function is not inlined.  */
 539 static void forced_callee (void) __attribute__ ((noinline));
 540
 541 static void forced_callee (void)
 542 {
 543   /* Make sure the function is not pure.  */
 544   volatile int i __attribute__ ((unused)) = 0;
 545 }
 546
 547 int
 548 __gnat_backtrace (void **array,
 549                   int size,
 550                   void *exclude_min,
 551                   void *exclude_max,
 552                   int skip_frames)
 553 {
 554   struct layout *current;
 555   void *top_frame;
 556   void *top_stack ATTRIBUTE_UNUSED;
 557   int cnt = 0;
 558
 559   if (FORCE_CALL)
 560     forced_callee ();
 561
 562   /* Force a call to builtin_frame_address with a positive argument
 563      if required. This is necessary e.g. on SPARC to have the register
 564      windows flushed before we attempt to access them on the stack.  */
 565 #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0)
 566   __builtin_frame_address (1);
 567 #endif
 568
 569   top_frame = __builtin_frame_address (FRAME_LEVEL);
 570   top_stack = CURRENT_STACK_FRAME;
 571   current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET (0));
 572
 573   /* Skip the number of calls we have been requested to skip, accounting for
 574      the BASE_SKIP parameter.
 575
 576      FRAME_LEVEL is meaningless for the count adjustment. It impacts where we
 577      start retrieving data from, but how many frames "up" we start at is in
 578      BASE_SKIP by definition.  */
 579
 580   skip_frames = MAX (0, skip_frames - BASE_SKIP);
 581
 582   while (cnt < skip_frames)
 583     {
 584       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 585       cnt++;
 586     }
 587
 588   cnt = 0;
 589   while (cnt < size)
 590     {
 591       if (STOP_FRAME (current, top_stack) ||
 592           !VALID_STACK_FRAME(((char *) current->return_address) + PC_ADJUST))
 593         break;
 594
 595       if (current->return_address < exclude_min
 596           || current->return_address > exclude_max)
 597         array[cnt++] = ((char *) current->return_address) + PC_ADJUST;
 598
 599       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 600     }
 601
 602   return cnt;
 603 }
 604
 605 #else
 606
 607 /* No target specific implementation and neither USE_GCC_UNWINDER nor
 608    USE_GENERIC_UNWINDER defined.  */
 609
 610 /*------------------------------*
 611  *-- The dummy implementation --*
 612  *------------------------------*/
 613
 614 int
 615 __gnat_backtrace (void **array ATTRIBUTE_UNUSED,
 616                   int size ATTRIBUTE_UNUSED,
 617                   void *exclude_min ATTRIBUTE_UNUSED,
 618                   void *exclude_max ATTRIBUTE_UNUSED,
 619                   int skip_frames ATTRIBUTE_UNUSED)
 620 {
 621   return 0;
 622 }
 623
 624 #endif
 625
 626 #endif
 627
 628 #ifdef __cplusplus
 629 }
 630 #endif