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) 2000-2014, 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 #else
 276 #error Unhandled darwin architecture.
 277 #endif
 278
 279 /*---------------------- PPC AIX/PPC Lynx 178/Older Darwin ------------------*/
 280 #elif ((defined (_POWER) && defined (_AIX)) || \
 281        (defined (__powerpc__) && defined (__Lynx__) && !defined(__ELF__)) || \
 282        (defined (__ppc__) && defined (__APPLE__)))
 283
 284 #define USE_GENERIC_UNWINDER
 285
 286 struct layout
 287 {
 288   struct layout *next;
 289   void *pad;
 290   void *return_address;
 291 };
 292
 293 #define FRAME_OFFSET(FP) 0
 294 #define PC_ADJUST -4
 295
 296 /* Eventhough the base PPC ABI states that a toplevel frame entry
 297    should to feature a null backchain, AIX might expose a null return
 298    address instead.  */
 299
 300 /* Then LynxOS-178 features yet another variation, with return_address
 301    == &<entrypoint>, with two possible entry points (one for the main
 302    process and one for threads). Beware that &bla returns the address
 303    of a descriptor when "bla" is a function.  Getting the code address
 304    requires an extra dereference.  */
 305
 306 #if defined (__Lynx__)
 307 extern void __start();  /* process entry point.  */
 308 extern void __runnit(); /* thread entry point.  */
 309 #define EXTRA_STOP_CONDITION(CURRENT)                 \
 310   ((CURRENT)->return_address == *(void**)&__start     \
 311    || (CURRENT)->return_address == *(void**)&__runnit)
 312 #else
 313 #define EXTRA_STOP_CONDITION(CURRENT) (0)
 314 #endif
 315
 316 #define STOP_FRAME(CURRENT, TOP_STACK) \
 317   (((void *) (CURRENT) < (TOP_STACK)) \
 318    || (CURRENT)->return_address == NULL \
 319    || EXTRA_STOP_CONDITION(CURRENT))
 320
 321 /* The PPC ABI has an interesting specificity: the return address saved by a
 322    function is located in it's caller's frame, and the save operation only
 323    takes place if the function performs a call.
 324
 325    To have __gnat_backtrace retrieve its own return address, we then
 326    define ... */
 327
 328 #define FORCE_CALL 1
 329 #define FRAME_LEVEL 1
 330
 331 #define BASE_SKIP 1
 332
 333 /*-------------------- PPC ELF (GNU/Linux & VxWorks) ---------------------*/
 334
 335 #elif (defined (_ARCH_PPC) && defined (__vxworks)) ||  \
 336   (defined (linux) && defined (__powerpc__))
 337
 338 #define USE_GENERIC_UNWINDER
 339
 340 struct layout
 341 {
 342   struct layout *next;
 343   void *return_address;
 344 };
 345
 346 #define FORCE_CALL 1
 347 #define FRAME_LEVEL 1
 348 /* See the PPC AIX case for an explanation of these values.  */
 349
 350 #define FRAME_OFFSET(FP) 0
 351 #define PC_ADJUST -4
 352
 353 /* According to the base PPC ABI, a toplevel frame entry should feature
 354    a null backchain.  What happens at signal handler frontiers isn't so
 355    well specified, so we add a safety guard on top.  */
 356
 357 #define STOP_FRAME(CURRENT, TOP_STACK) \
 358  ((CURRENT)->next == 0 || ((long)(CURRENT)->next % __alignof__(void*)) != 0)
 359
 360 #define BASE_SKIP 1
 361
 362 /*-------------------------- SPARC Solaris -----------------------------*/
 363
 364 #elif defined (sun) && defined (sparc)
 365
 366 #define USE_GENERIC_UNWINDER
 367
 368 /* These definitions are inspired from the Appendix D (Software
 369    Considerations) of the SPARC V8 architecture manual.  */
 370
 371 struct layout
 372 {
 373   struct layout *next;
 374   void *return_address;
 375 };
 376
 377 #ifdef __arch64__
 378 #define STACK_BIAS 2047 /* V9 ABI */
 379 #else
 380 #define STACK_BIAS 0    /* V8 ABI */
 381 #endif
 382
 383 #define FRAME_LEVEL 0
 384 #define FRAME_OFFSET(FP) (14 * sizeof (void*) + (FP ? STACK_BIAS : 0))
 385 #define PC_ADJUST 0
 386 #define STOP_FRAME(CURRENT, TOP_STACK) \
 387   ((CURRENT)->return_address == 0|| (CURRENT)->next == 0 \
 388    || (void *) (CURRENT) < (TOP_STACK))
 389
 390 /* The SPARC register windows need to be flushed before we may access them
 391    from the stack. This is achieved by way of builtin_frame_address only
 392    when the "count" argument is positive, so force at least one such call.  */
 393 #define FETCH_UP_FRAME_ADDRESS
 394
 395 #define BASE_SKIP 2
 396 /* From the frame pointer of frame N, we are accessing the flushed register
 397    window of frame N-1 (positive offset from fp), in which we retrieve the
 398    saved return address. We then end up with our caller's return address.  */
 399
 400 /*------------------------------- x86 ----------------------------------*/
 401
 402 #elif defined (i386)
 403
 404 #if defined (__WIN32)
 405 #include <windows.h>
 406 #define IS_BAD_PTR(ptr) (IsBadCodePtr((FARPROC)ptr))
 407 #elif defined (sun)
 408 #define IS_BAD_PTR(ptr) ((unsigned long)ptr == -1UL)
 409 #else
 410 #define IS_BAD_PTR(ptr) 0
 411 #endif
 412
 413 /* Starting with GCC 4.6, -fomit-frame-pointer is turned on by default for
 414    32-bit x86/Linux as well and DWARF 2 unwind tables are emitted instead.
 415    See the x86-64 case below for the drawbacks with this approach.  */
 416 #if defined (linux) && (__GNUC__ * 10 + __GNUC_MINOR__ > 45)
 417 #define USE_GCC_UNWINDER
 418 #else
 419 #define USE_GENERIC_UNWINDER
 420 #endif
 421
 422 struct layout
 423 {
 424   struct layout *next;
 425   void *return_address;
 426 };
 427
 428 #define FRAME_LEVEL 1
 429 /* builtin_frame_address (1) is expected to work on this target, and (0) might
 430    return the soft stack pointer, which does not designate a location where a
 431    backchain and a return address might be found.  */
 432
 433 #define FRAME_OFFSET(FP) 0
 434 #define PC_ADJUST -2
 435 #define STOP_FRAME(CURRENT, TOP_STACK) \
 436   (IS_BAD_PTR((long)(CURRENT)) \
 437    || IS_BAD_PTR((long)(CURRENT)->return_address) \
 438    || (CURRENT)->return_address == 0 \
 439    || (void *) ((CURRENT)->next) < (TOP_STACK)  \
 440    || (void *) (CURRENT) < (TOP_STACK))
 441
 442 #define BASE_SKIP (1+FRAME_LEVEL)
 443
 444 /* On i386 architecture we check that at the call point we really have a call
 445    insn. Possible call instructions are:
 446
 447    call  addr16        E8 xx xx xx xx
 448    call  reg           FF Dx
 449    call  off(reg)      FF xx xx
 450    lcall addr seg      9A xx xx xx xx xx xx
 451
 452    This check will not catch all cases but it will increase the backtrace
 453    reliability on this architecture.
 454 */
 455
 456 #define VALID_STACK_FRAME(ptr) \
 457    (!IS_BAD_PTR(ptr) \
 458     && (((*((ptr) - 3) & 0xff) == 0xe8) \
 459         || ((*((ptr) - 5) & 0xff) == 0x9a) \
 460         || ((*((ptr) - 1) & 0xff) == 0xff) \
 461         || (((*(ptr) & 0xd0ff) == 0xd0ff))))
 462
 463 /*----------------------------- x86_64 ---------------------------------*/
 464
 465 #elif defined (__x86_64__)
 466
 467 #define USE_GCC_UNWINDER
 468 /* The generic unwinder is not used for this target because it is based
 469    on frame layout assumptions that are not reliable on this target (the
 470    rbp register is very likely used for something else than storing the
 471    frame pointer in optimized code). Hence, we use the GCC unwinder
 472    based on DWARF 2 call frame information, although it has the drawback
 473    of not being able to unwind through frames compiled without DWARF 2
 474    information.
 475 */
 476
 477 #define PC_ADJUST -2
 478 /* The minimum size of call instructions on this architecture is 2 bytes */
 479
 480 /*----------------------------- ia64 ---------------------------------*/
 481
 482 #elif defined (__ia64__) && (defined (linux) || defined (__hpux__))
 483
 484 #define USE_GCC_UNWINDER
 485 /* Use _Unwind_Backtrace driven exceptions on ia64 HP-UX and ia64
 486    GNU/Linux, where _Unwind_Backtrace is provided by the system unwind
 487    library. On HP-UX 11.23 this requires patch PHSS_33352, which adds
 488    _Unwind_Backtrace to the system unwind library. */
 489
 490 #define PC_ADJUST -4
 491
 492
 493 #endif
 494
 495 /*---------------------------------------------------------------------*
 496  *--      The post GCC 3.3 infrastructure based implementation       --*
 497  *---------------------------------------------------------------------*/
 498
 499 #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33)
 500
 501 /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap
 502    path problems, since the included file refers to post 3.3 functions in
 503    libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3
 504    library.  It actually disables the support for backtraces in this compiler
 505    for targets defining USE_GCC_UNWINDER, which is OK since we don't use the
 506    traceback capability in the compiler anyway.
 507
 508    The condition is expressed the way above because we cannot reliably rely on
 509    any other macro from the base compiler when compiling stage1.  */
 510
 511 #include "tb-gcc.c"
 512
 513 /*------------------------------------------------------------------*
 514  *-- The generic implementation based on frame layout assumptions --*
 515  *------------------------------------------------------------------*/
 516
 517 #elif defined (USE_GENERIC_UNWINDER)
 518
 519 #ifndef CURRENT_STACK_FRAME
 520 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
 521 #endif
 522
 523 #ifndef VALID_STACK_FRAME
 524 #define VALID_STACK_FRAME(ptr) 1
 525 #endif
 526
 527 #ifndef MAX
 528 #define MAX(x,y) ((x) > (y) ? (x) : (y))
 529 #endif
 530
 531 #ifndef FORCE_CALL
 532 #define FORCE_CALL 0
 533 #endif
 534
 535 /* Make sure the function is not inlined.  */
 536 static void forced_callee (void) __attribute__ ((noinline));
 537
 538 static void forced_callee (void)
 539 {
 540   /* Make sure the function is not pure.  */
 541   volatile int i __attribute__ ((unused)) = 0;
 542 }
 543
 544 int
 545 __gnat_backtrace (void **array,
 546                   int size,
 547                   void *exclude_min,
 548                   void *exclude_max,
 549                   int skip_frames)
 550 {
 551   struct layout *current;
 552   void *top_frame;
 553   void *top_stack ATTRIBUTE_UNUSED;
 554   int cnt = 0;
 555
 556   if (FORCE_CALL)
 557     forced_callee ();
 558
 559   /* Force a call to builtin_frame_address with a positive argument
 560      if required. This is necessary e.g. on SPARC to have the register
 561      windows flushed before we attempt to access them on the stack.  */
 562 #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0)
 563   __builtin_frame_address (1);
 564 #endif
 565
 566   top_frame = __builtin_frame_address (FRAME_LEVEL);
 567   top_stack = CURRENT_STACK_FRAME;
 568   current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET (0));
 569
 570   /* Skip the number of calls we have been requested to skip, accounting for
 571      the BASE_SKIP parameter.
 572
 573      FRAME_LEVEL is meaningless for the count adjustment. It impacts where we
 574      start retrieving data from, but how many frames "up" we start at is in
 575      BASE_SKIP by definition.  */
 576
 577   skip_frames = MAX (0, skip_frames - BASE_SKIP);
 578
 579   while (cnt < skip_frames)
 580     {
 581       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 582       cnt++;
 583     }
 584
 585   cnt = 0;
 586   while (cnt < size)
 587     {
 588       if (STOP_FRAME (current, top_stack) ||
 589           !VALID_STACK_FRAME(((char *) current->return_address) + PC_ADJUST))
 590         break;
 591
 592       if (current->return_address < exclude_min
 593           || current->return_address > exclude_max)
 594         array[cnt++] = ((char *) current->return_address) + PC_ADJUST;
 595
 596       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 597     }
 598
 599   return cnt;
 600 }
 601
 602 #else
 603
 604 /* No target specific implementation and neither USE_GCC_UNWINDER nor
 605    USE_GENERIC_UNWINDER defined.  */
 606
 607 /*------------------------------*
 608  *-- The dummy implementation --*
 609  *------------------------------*/
 610
 611 int
 612 __gnat_backtrace (void **array ATTRIBUTE_UNUSED,
 613                   int size ATTRIBUTE_UNUSED,
 614                   void *exclude_min ATTRIBUTE_UNUSED,
 615                   void *exclude_max ATTRIBUTE_UNUSED,
 616                   int skip_frames ATTRIBUTE_UNUSED)
 617 {
 618   return 0;
 619 }
 620
 621 #endif
 622
 623 #endif
 624
 625 #ifdef __cplusplus
 626 }
 627 #endif