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 #elif defined (__arm__)
 276 #define PC_ADJUST -2
 277 #else
 278 #error Unhandled darwin architecture.
 279 #endif
 280
 281 /*---------------------- PPC AIX/PPC Lynx 178/Older Darwin ------------------*/
 282 #elif ((defined (_POWER) && defined (_AIX)) || \
 283        (defined (__powerpc__) && defined (__Lynx__) && !defined(__ELF__)) || \
 284        (defined (__ppc__) && defined (__APPLE__)))
 285
 286 #define USE_GENERIC_UNWINDER
 287
 288 struct layout
 289 {
 290   struct layout *next;
 291   void *pad;
 292   void *return_address;
 293 };
 294
 295 #define FRAME_OFFSET(FP) 0
 296 #define PC_ADJUST -4
 297
 298 /* Eventhough the base PPC ABI states that a toplevel frame entry
 299    should to feature a null backchain, AIX might expose a null return
 300    address instead.  */
 301
 302 /* Then LynxOS-178 features yet another variation, with return_address
 303    == &<entrypoint>, with two possible entry points (one for the main
 304    process and one for threads). Beware that &bla returns the address
 305    of a descriptor when "bla" is a function.  Getting the code address
 306    requires an extra dereference.  */
 307
 308 #if defined (__Lynx__)
 309 extern void __start();  /* process entry point.  */
 310 extern void __runnit(); /* thread entry point.  */
 311 #define EXTRA_STOP_CONDITION(CURRENT)                 \
 312   ((CURRENT)->return_address == *(void**)&__start     \
 313    || (CURRENT)->return_address == *(void**)&__runnit)
 314 #else
 315 #define EXTRA_STOP_CONDITION(CURRENT) (0)
 316 #endif
 317
 318 #define STOP_FRAME(CURRENT, TOP_STACK) \
 319   (((void *) (CURRENT) < (TOP_STACK)) \
 320    || (CURRENT)->return_address == NULL \
 321    || EXTRA_STOP_CONDITION(CURRENT))
 322
 323 /* The PPC ABI has an interesting specificity: the return address saved by a
 324    function is located in it's caller's frame, and the save operation only
 325    takes place if the function performs a call.
 326
 327    To have __gnat_backtrace retrieve its own return address, we then
 328    define ... */
 329
 330 #define FORCE_CALL 1
 331 #define FRAME_LEVEL 1
 332
 333 #define BASE_SKIP 1
 334
 335 /*-------------------- PPC ELF (GNU/Linux & VxWorks) ---------------------*/
 336
 337 #elif (defined (_ARCH_PPC) && defined (__vxworks)) ||  \
 338   (defined (linux) && defined (__powerpc__))
 339
 340 #define USE_GENERIC_UNWINDER
 341
 342 struct layout
 343 {
 344   struct layout *next;
 345   void *return_address;
 346 };
 347
 348 #define FORCE_CALL 1
 349 #define FRAME_LEVEL 1
 350 /* See the PPC AIX case for an explanation of these values.  */
 351
 352 #define FRAME_OFFSET(FP) 0
 353 #define PC_ADJUST -4
 354
 355 /* According to the base PPC ABI, a toplevel frame entry should feature
 356    a null backchain.  What happens at signal handler frontiers isn't so
 357    well specified, so we add a safety guard on top.  */
 358
 359 #define STOP_FRAME(CURRENT, TOP_STACK) \
 360  ((CURRENT)->next == 0 || ((long)(CURRENT)->next % __alignof__(void*)) != 0)
 361
 362 #define BASE_SKIP 1
 363
 364 /*-------------------------- SPARC Solaris -----------------------------*/
 365
 366 #elif defined (sun) && defined (sparc)
 367
 368 #define USE_GENERIC_UNWINDER
 369
 370 /* These definitions are inspired from the Appendix D (Software
 371    Considerations) of the SPARC V8 architecture manual.  */
 372
 373 struct layout
 374 {
 375   struct layout *next;
 376   void *return_address;
 377 };
 378
 379 #ifdef __arch64__
 380 #define STACK_BIAS 2047 /* V9 ABI */
 381 #else
 382 #define STACK_BIAS 0    /* V8 ABI */
 383 #endif
 384
 385 #define FRAME_LEVEL 0
 386 #define FRAME_OFFSET(FP) (14 * sizeof (void*) + (FP ? STACK_BIAS : 0))
 387 #define PC_ADJUST 0
 388 #define STOP_FRAME(CURRENT, TOP_STACK) \
 389   ((CURRENT)->return_address == 0|| (CURRENT)->next == 0 \
 390    || (void *) (CURRENT) < (TOP_STACK))
 391
 392 /* The SPARC register windows need to be flushed before we may access them
 393    from the stack. This is achieved by way of builtin_frame_address only
 394    when the "count" argument is positive, so force at least one such call.  */
 395 #define FETCH_UP_FRAME_ADDRESS
 396
 397 #define BASE_SKIP 2
 398 /* From the frame pointer of frame N, we are accessing the flushed register
 399    window of frame N-1 (positive offset from fp), in which we retrieve the
 400    saved return address. We then end up with our caller's return address.  */
 401
 402 /*------------------------------- x86 ----------------------------------*/
 403
 404 #elif defined (i386)
 405
 406 #if defined (__WIN32)
 407 #include <windows.h>
 408 #define IS_BAD_PTR(ptr) (IsBadCodePtr((FARPROC)ptr))
 409 #elif defined (sun)
 410 #define IS_BAD_PTR(ptr) ((unsigned long)ptr == -1UL)
 411 #else
 412 #define IS_BAD_PTR(ptr) 0
 413 #endif
 414
 415 /* Starting with GCC 4.6, -fomit-frame-pointer is turned on by default for
 416    32-bit x86/Linux as well and DWARF 2 unwind tables are emitted instead.
 417    See the x86-64 case below for the drawbacks with this approach.  */
 418 #if defined (linux) && (__GNUC__ * 10 + __GNUC_MINOR__ > 45)
 419 #define USE_GCC_UNWINDER
 420 #else
 421 #define USE_GENERIC_UNWINDER
 422 #endif
 423
 424 struct layout
 425 {
 426   struct layout *next;
 427   void *return_address;
 428 };
 429
 430 #define FRAME_LEVEL 1
 431 /* builtin_frame_address (1) is expected to work on this target, and (0) might
 432    return the soft stack pointer, which does not designate a location where a
 433    backchain and a return address might be found.  */
 434
 435 #define FRAME_OFFSET(FP) 0
 436 #define PC_ADJUST -2
 437 #define STOP_FRAME(CURRENT, TOP_STACK) \
 438   (IS_BAD_PTR((long)(CURRENT)) \
 439    || IS_BAD_PTR((long)(CURRENT)->return_address) \
 440    || (CURRENT)->return_address == 0 \
 441    || (void *) ((CURRENT)->next) < (TOP_STACK)  \
 442    || (void *) (CURRENT) < (TOP_STACK))
 443
 444 #define BASE_SKIP (1+FRAME_LEVEL)
 445
 446 /* On i386 architecture we check that at the call point we really have a call
 447    insn. Possible call instructions are:
 448
 449    call  addr16        E8 xx xx xx xx
 450    call  reg           FF Dx
 451    call  off(reg)      FF xx xx
 452    lcall addr seg      9A xx xx xx xx xx xx
 453
 454    This check will not catch all cases but it will increase the backtrace
 455    reliability on this architecture.
 456 */
 457
 458 #define VALID_STACK_FRAME(ptr) \
 459    (!IS_BAD_PTR(ptr) \
 460     && (((*((ptr) - 3) & 0xff) == 0xe8) \
 461         || ((*((ptr) - 5) & 0xff) == 0x9a) \
 462         || ((*((ptr) - 1) & 0xff) == 0xff) \
 463         || (((*(ptr) & 0xd0ff) == 0xd0ff))))
 464
 465 /*----------------------------- x86_64 ---------------------------------*/
 466
 467 #elif defined (__x86_64__)
 468
 469 #define USE_GCC_UNWINDER
 470 /* The generic unwinder is not used for this target because it is based
 471    on frame layout assumptions that are not reliable on this target (the
 472    rbp register is very likely used for something else than storing the
 473    frame pointer in optimized code). Hence, we use the GCC unwinder
 474    based on DWARF 2 call frame information, although it has the drawback
 475    of not being able to unwind through frames compiled without DWARF 2
 476    information.
 477 */
 478
 479 #define PC_ADJUST -2
 480 /* The minimum size of call instructions on this architecture is 2 bytes */
 481
 482 /*----------------------------- ia64 ---------------------------------*/
 483
 484 #elif defined (__ia64__) && (defined (linux) || defined (__hpux__))
 485
 486 #define USE_GCC_UNWINDER
 487 /* Use _Unwind_Backtrace driven exceptions on ia64 HP-UX and ia64
 488    GNU/Linux, where _Unwind_Backtrace is provided by the system unwind
 489    library. On HP-UX 11.23 this requires patch PHSS_33352, which adds
 490    _Unwind_Backtrace to the system unwind library. */
 491
 492 #define PC_ADJUST -4
 493
 494
 495 #endif
 496
 497 /*---------------------------------------------------------------------*
 498  *--      The post GCC 3.3 infrastructure based implementation       --*
 499  *---------------------------------------------------------------------*/
 500
 501 #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33)
 502
 503 /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap
 504    path problems, since the included file refers to post 3.3 functions in
 505    libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3
 506    library.  It actually disables the support for backtraces in this compiler
 507    for targets defining USE_GCC_UNWINDER, which is OK since we don't use the
 508    traceback capability in the compiler anyway.
 509
 510    The condition is expressed the way above because we cannot reliably rely on
 511    any other macro from the base compiler when compiling stage1.  */
 512
 513 #include "tb-gcc.c"
 514
 515 /*------------------------------------------------------------------*
 516  *-- The generic implementation based on frame layout assumptions --*
 517  *------------------------------------------------------------------*/
 518
 519 #elif defined (USE_GENERIC_UNWINDER)
 520
 521 #ifndef CURRENT_STACK_FRAME
 522 # define CURRENT_STACK_FRAME  ({ char __csf; &__csf; })
 523 #endif
 524
 525 #ifndef VALID_STACK_FRAME
 526 #define VALID_STACK_FRAME(ptr) 1
 527 #endif
 528
 529 #ifndef MAX
 530 #define MAX(x,y) ((x) > (y) ? (x) : (y))
 531 #endif
 532
 533 #ifndef FORCE_CALL
 534 #define FORCE_CALL 0
 535 #endif
 536
 537 /* Make sure the function is not inlined.  */
 538 static void forced_callee (void) __attribute__ ((noinline));
 539
 540 static void forced_callee (void)
 541 {
 542   /* Make sure the function is not pure.  */
 543   volatile int i __attribute__ ((unused)) = 0;
 544 }
 545
 546 int
 547 __gnat_backtrace (void **array,
 548                   int size,
 549                   void *exclude_min,
 550                   void *exclude_max,
 551                   int skip_frames)
 552 {
 553   struct layout *current;
 554   void *top_frame;
 555   void *top_stack ATTRIBUTE_UNUSED;
 556   int cnt = 0;
 557
 558   if (FORCE_CALL)
 559     forced_callee ();
 560
 561   /* Force a call to builtin_frame_address with a positive argument
 562      if required. This is necessary e.g. on SPARC to have the register
 563      windows flushed before we attempt to access them on the stack.  */
 564 #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0)
 565   __builtin_frame_address (1);
 566 #endif
 567
 568   top_frame = __builtin_frame_address (FRAME_LEVEL);
 569   top_stack = CURRENT_STACK_FRAME;
 570   current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET (0));
 571
 572   /* Skip the number of calls we have been requested to skip, accounting for
 573      the BASE_SKIP parameter.
 574
 575      FRAME_LEVEL is meaningless for the count adjustment. It impacts where we
 576      start retrieving data from, but how many frames "up" we start at is in
 577      BASE_SKIP by definition.  */
 578
 579   skip_frames = MAX (0, skip_frames - BASE_SKIP);
 580
 581   while (cnt < skip_frames)
 582     {
 583       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 584       cnt++;
 585     }
 586
 587   cnt = 0;
 588   while (cnt < size)
 589     {
 590       if (STOP_FRAME (current, top_stack) ||
 591           !VALID_STACK_FRAME(((char *) current->return_address) + PC_ADJUST))
 592         break;
 593
 594       if (current->return_address < exclude_min
 595           || current->return_address > exclude_max)
 596         array[cnt++] = ((char *) current->return_address) + PC_ADJUST;
 597
 598       current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
 599     }
 600
 601   return cnt;
 602 }
 603
 604 #else
 605
 606 /* No target specific implementation and neither USE_GCC_UNWINDER nor
 607    USE_GENERIC_UNWINDER defined.  */
 608
 609 /*------------------------------*
 610  *-- The dummy implementation --*
 611  *------------------------------*/
 612
 613 int
 614 __gnat_backtrace (void **array ATTRIBUTE_UNUSED,
 615                   int size ATTRIBUTE_UNUSED,
 616                   void *exclude_min ATTRIBUTE_UNUSED,
 617                   void *exclude_max ATTRIBUTE_UNUSED,
 618                   int skip_frames ATTRIBUTE_UNUSED)
 619 {
 620   return 0;
 621 }
 622
 623 #endif
 624
 625 #endif
 626
 627 #ifdef __cplusplus
 628 }
 629 #endif