gcc/ada/5htraceb.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                     S Y S T E M . T R A C E B A C K                      --
   6 --                             (HP/UX Version)                              --
   7 --                                                                          --
   8 --                                 B o d y                                  --
   9 --                                                                          --
  10 --                            $Revision: 1.10 $
  11 --                                                                          --
  12 --           Copyright (C) 1999-2001 Ada Core Technologies, Inc.            --
  13 --                                                                          --
  14 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  15 -- terms of the  GNU General Public License as published  by the Free Soft- --
  16 -- ware  Foundation;  either version 2,  or (at your option) any later ver- --
  17 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  18 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  19 -- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
  20 -- for  more details.  You should have  received  a copy of the GNU General --
  21 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  22 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  23 -- MA 02111-1307, USA.                                                      --
  24 --                                                                          --
  25 -- As a special exception,  if other files  instantiate  generics from this --
  26 -- unit, or you link  this unit with other files  to produce an executable, --
  27 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  28 -- covered  by the  GNU  General  Public  License.  This exception does not --
  29 -- however invalidate  any other reasons why  the executable file  might be --
  30 -- covered by the  GNU Public License.                                      --
  31 --                                                                          --
  32 -- GNAT was originally developed  by the GNAT team at  New York University. --
  33 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  34 --                                                                          --
  35 ------------------------------------------------------------------------------
  36
  37 with Ada.Unchecked_Conversion;
  38
  39 package body System.Traceback is
  40
  41    --  This package implements the backtracing facility by way of a dedicated
  42    --  HP library for stack unwinding described in the "Runtime Architecture
  43    --  Document".
  44
  45    pragma Linker_Options ("/usr/lib/libcl.a");
  46
  47    --  The library basically offers services to fetch information about a
  48    --  "previous" frame based on information about a "current" one.
  49
  50    type Current_Frame_Descriptor is record
  51       cur_fsz : Address;  --  Frame size of current routine.
  52       cur_sp  : Address;  --  The current value of stack pointer.
  53       cur_rls : Address;  --  PC-space of the caller.
  54       cur_rlo : Address;  --  PC-offset of the caller.
  55       cur_dp  : Address;  --  Data Pointer of the current routine.
  56       top_rp  : Address;  --  Initial value of RP.
  57       top_mrp : Address;  --  Initial value of MRP.
  58       top_sr0 : Address;  --  Initial value of sr0.
  59       top_sr4 : Address;  --  Initial value of sr4.
  60       top_r3  : Address;  --  Initial value of gr3.
  61       cur_r19 : Address;  --  GR19 value of the calling routine.
  62       top_r4  : Address;  --  Initial value of gr4.
  63       dummy   : Address;  --  Reserved.
  64       out_rlo : Address;  --  PC-offset of the caller after get_previous.
  65    end record;
  66
  67    type Previous_Frame_Descriptor is record
  68       prev_fsz : Address;  --  frame size of calling routine.
  69       prev_sp  : Address;  --  SP of calling routine.
  70       prev_rls : Address;  --  PC_space of calling routine's caller.
  71       prev_rlo : Address;  --  PC_offset of calling routine's caller.
  72       prev_dp  : Address;  --  DP of calling routine.
  73       udescr0  : Address;  --  low word of calling routine's unwind desc.
  74       udescr1  : Address;  --  high word of calling routine's unwind desc.
  75       ustart   : Address;  --  start of the unwind region.
  76       uend     : Address;  --  end of the unwind region.
  77       uw_index : Address;  --  index into the unwind table.
  78       prev_r19 : Address;  --  GR19 value of the caller's caller.
  79       top_r3   : Address;  --  Caller's initial gr3.
  80       top_r4   : Address;  --  Caller's initial gr4.
  81    end record;
  82
  83    --  Provide useful shortcuts for the names
  84
  85    subtype CFD is Current_Frame_Descriptor;
  86    subtype PFD is Previous_Frame_Descriptor;
  87
  88    --  Frames with dynamic stack allocation are handled using the associated
  89    --  frame pointer, but HP compilers and GCC setup this pointer differently.
  90    --  HP compilers set it to point at the top (highest address) of the static
  91    --  part of the frame, wheras GCC sets it to point at the bottom of this
  92    --  region. We have to fake the unwinder to compensate for this difference,
  93    --  for which we'll need to access some subprograms unwind descriptors.
  94
  95    type Bits_2_Value is mod 2 ** 2;
  96    for Bits_2_Value'Size use 2;
  97
  98    type Bits_4_Value  is mod 2 ** 4;
  99    for Bits_4_Value'Size use 4;
 100
 101    type Bits_5_Value  is mod 2 ** 5;
 102    for Bits_5_Value'Size use 5;
 103
 104    type Bits_27_Value is mod 2 ** 27;
 105    for Bits_27_Value'Size use 27;
 106
 107    type Unwind_Descriptor is record
 108       cannot_unwind         : Boolean;
 109       mcode                 : Boolean;
 110       mcode_save_restore    : Boolean;
 111       region_desc           : Bits_2_Value;
 112       reserved0             : Boolean;
 113       entry_sr              : Boolean;
 114       entry_fr              : Bits_4_Value;
 115       entry_gr              : Bits_5_Value;
 116
 117       args_stored           : Boolean;
 118       variable_frame        : Boolean;
 119       separate_package_body : Boolean;
 120       frame_extension_mcode : Boolean;
 121
 122       stack_overflow_check  : Boolean;
 123       two_steps_sp_adjust   : Boolean;
 124       sr4_export            : Boolean;
 125       cxx_info              : Boolean;
 126
 127       cxx_try_catch         : Boolean;
 128       sched_entry_seq       : Boolean;
 129       reserved1             : Boolean;
 130       save_sp               : Boolean;
 131
 132       save_rp               : Boolean;
 133       save_mrp              : Boolean;
 134       save_r19              : Boolean;
 135       cleanups              : Boolean;
 136
 137       hpe_interrupt_marker  : Boolean;
 138       hpux_interrupt_marker : Boolean;
 139       large_frame           : Boolean;
 140       alloca_frame          : Boolean;
 141
 142       reserved2             : Boolean;
 143       frame_size            : Bits_27_Value;
 144    end record;
 145
 146    for Unwind_Descriptor'Size use 64;
 147
 148    for Unwind_Descriptor use record
 149       cannot_unwind         at 0 range 0 .. 0;
 150       mcode                 at 0 range 1 .. 1;
 151       mcode_save_restore    at 0 range 2 .. 2;
 152       region_desc           at 0 range 3 .. 4;
 153       reserved0             at 0 range 5 .. 5;
 154       entry_sr              at 0 range 6 .. 6;
 155       entry_fr              at 0 range 7 .. 10;
 156
 157       entry_gr              at 1 range 3 .. 7;
 158
 159       args_stored           at 2 range 0 .. 0;
 160       variable_frame        at 2 range 1 .. 1;
 161       separate_package_body at 2 range 2 .. 2;
 162       frame_extension_mcode at 2 range 3 .. 3;
 163       stack_overflow_check  at 2 range 4 .. 4;
 164       two_steps_sp_adjust   at 2 range 5 .. 5;
 165       sr4_export            at 2 range 6 .. 6;
 166       cxx_info              at 2 range 7 .. 7;
 167
 168       cxx_try_catch         at 3 range 0 .. 0;
 169       sched_entry_seq       at 3 range 1 .. 1;
 170       reserved1             at 3 range 2 .. 2;
 171       save_sp               at 3 range 3 .. 3;
 172       save_rp               at 3 range 4 .. 4;
 173       save_mrp              at 3 range 5 .. 5;
 174       save_r19              at 3 range 6 .. 6;
 175       cleanups              at 3 range 7 .. 7;
 176
 177       hpe_interrupt_marker  at 4 range 0 .. 0;
 178       hpux_interrupt_marker at 4 range 1 .. 1;
 179       large_frame           at 4 range 2 .. 2;
 180       alloca_frame          at 4 range 3 .. 3;
 181
 182       reserved2             at 4 range 4 .. 4;
 183       frame_size            at 4 range 5 .. 31;
 184    end record;
 185
 186    subtype UWD is Unwind_Descriptor;
 187    type UWD_Ptr is access all UWD;
 188
 189    function To_UWD_Access is new Ada.Unchecked_Conversion (Address, UWD_Ptr);
 190
 191    --  The descriptor associated with a given code location is retrieved
 192    --  using functions imported from the HP library, requiring the definition
 193    --  of additional structures.
 194
 195    type Unwind_Table_Region is record
 196       Table_Start : Address;
 197       Table_End   : Address;
 198    end record;
 199    --  An Unwind Table region, which is a memory area containing Unwind
 200    --  Descriptors.
 201
 202    subtype UWT is Unwind_Table_Region;
 203    type UWT_Ptr is access all UWT;
 204
 205    function To_UWT_Address is new Ada.Unchecked_Conversion (UWT_Ptr, Address);
 206
 207    --  The subprograms imported below are provided by the HP library
 208
 209    function U_get_unwind_table return UWT;
 210    pragma Import (C, U_get_unwind_table, "U_get_unwind_table");
 211    --  Get the unwind table region associated with the current executable.
 212    --  This function is actually documented as having an argument, but which
 213    --  is only used for the MPE/iX targets.
 214
 215    function U_get_shLib_unwind_table (r19 : Address) return UWT;
 216    pragma Import (C, U_get_shLib_unwind_table, "U_get_shLib_unw_tbl");
 217    --  Return the unwind table region associated with a possible shared
 218    --  library, as determined by the provided r19 value.
 219
 220    function U_get_shLib_text_addr (r19 : Address) return Address;
 221    pragma Import (C, U_get_shLib_text_addr, "U_get_shLib_text_addr");
 222    --  Return the address at which the code for a shared library begins, or
 223    --  -1 if the value provided for r19 does not identify shared library code.
 224
 225    function U_get_unwind_entry
 226      (Pc          : Address;
 227       Space       : Address;
 228       Table_Start : Address;
 229       Table_End   : Address)
 230       return        Address;
 231    pragma Import (C, U_get_unwind_entry, "U_get_unwind_entry");
 232    --  Given the bounds of an unwind table, return the address of the
 233    --  unwind descriptor associated with a code location/space. In the case
 234    --  of shared library code, the offset from the beginning of the library
 235    --  is expected as Pc.
 236
 237    procedure U_init_frame_record (Frame : access CFD);
 238    pragma Import (C, U_init_frame_record, "U_init_frame_record");
 239
 240    procedure U_prep_frame_rec_for_unwind (Frame : access CFD);
 241    pragma Import (C, U_prep_frame_rec_for_unwind,
 242                     "U_prep_frame_rec_for_unwind");
 243
 244    --  Fetch the description data of the frame in which these two procedures
 245    --  are called.
 246
 247    function U_get_u_rlo (Cur : access CFD; Prev : access PFD) return Integer;
 248    pragma Import (C, U_get_u_rlo, "U_IS_STUB_OR_CALLX");
 249    --  From a complete current frame with a return location possibly located
 250    --  into a linker generated stub, and basic information about the previous
 251    --  frame, place the first non stub return location into the current frame.
 252    --  Return -1 if something went wrong during the computation.
 253
 254    function U_is_shared_pc (rlo : Address; r19 : Address) return Address;
 255    pragma Import (C, U_is_shared_pc, "U_is_shared_pc");
 256    --  Return 0 if the provided return location does not correspond to code
 257    --  in a shared library, or something non null otherwise.
 258
 259    function U_get_previous_frame_x
 260      (current_frame  : access CFD;
 261       previous_frame : access PFD;
 262       previous_size  : Integer)
 263       return           Integer;
 264    pragma Import (C, U_get_previous_frame_x, "U_get_previous_frame_x");
 265    --  Fetch the data describing the "previous" frame relatively to the
 266    --  "current" one. "previous_size" should be the size of the "previous"
 267    --  frame descriptor provided.
 268    --
 269    --  The library provides a simpler interface without the size parameter
 270    --  but it is not usable when frames with dynamically allocated space are
 271    --  on the way.
 272
 273    ------------------
 274    -- C_Call_Chain --
 275    ------------------
 276
 277    function C_Call_Chain
 278      (Traceback   : System.Address;
 279       Max_Len     : Natural)
 280       return        Natural
 281    is
 282       Val : Natural;
 283
 284    begin
 285       Call_Chain (Traceback, Max_Len, Val);
 286       return Val;
 287    end C_Call_Chain;
 288
 289    ----------------
 290    -- Call_Chain --
 291    ----------------
 292
 293    procedure Call_Chain
 294      (Traceback   : System.Address;
 295       Max_Len     : Natural;
 296       Len         : out Natural;
 297       Exclude_Min : System.Address := System.Null_Address;
 298       Exclude_Max : System.Address := System.Null_Address)
 299    is
 300       type Tracebacks_Array is array (1 .. Max_Len) of System.Address;
 301       pragma Suppress_Initialization (Tracebacks_Array);
 302
 303       --  The code location returned by the unwinder is a return location but
 304       --  what we need is a call point. Under HP-UX call instructions are 4
 305       --  bytes long and the return point they specify is 4 bytes beyond the
 306       --  next instruction because of the delay slot.
 307
 308       Call_Size  : constant := 4;
 309       DSlot_Size : constant := 4;
 310       Rlo_Offset : constant := Call_Size + DSlot_Size;
 311
 312       --  Moreover, the return point is passed via a register which two least
 313       --  significant bits specify a privilege level that we will have to mask.
 314
 315       Priv_Mask  : constant := 16#00000003#;
 316
 317       Frame       : aliased CFD;
 318       Code        : System.Address;
 319       J           : Natural := 1;
 320       Pop_Success : Boolean;
 321       Trace       : Tracebacks_Array;
 322       for Trace'Address use Traceback;
 323
 324       --  The backtracing process needs a set of subprograms :
 325
 326       function UWD_For_RLO_Of (Frame : access CFD) return UWD_Ptr;
 327       --  Return an access to the unwind descriptor for the caller of
 328       --  a given frame, using only the provided return location.
 329
 330       function UWD_For_Caller_Of (Frame : access CFD) return UWD_Ptr;
 331       --  Return an access to the unwind descriptor for the user code caller
 332       --  of a given frame, or null if the information is not available.
 333
 334       function Pop_Frame (Frame : access CFD) return Boolean;
 335       --  Update the provided machine state structure so that it reflects
 336       --  the state one call frame "above" the initial one.
 337       --
 338       --  Return True if the operation has been successful, False otherwise.
 339       --  Failure typically occurs when the top of the call stack has been
 340       --  reached.
 341
 342       function Prepare_For_Unwind_Of (Frame : access CFD) return Boolean;
 343       --  Perform the necessary adaptations to the machine state before
 344       --  calling the unwinder. Currently used for the specific case of
 345       --  dynamically sized previous frames.
 346       --
 347       --  Return True if everything went fine, or False otherwise.
 348
 349       Program_UWT : constant UWT := U_get_unwind_table;
 350
 351       ---------------
 352       -- Pop_Frame --
 353       ---------------
 354
 355       function Pop_Frame (Frame : access CFD) return Boolean is
 356          Up_Frame    : aliased PFD;
 357          State_Ready : Boolean;
 358
 359       begin
 360          --  Check/adapt the state before calling the unwinder and return
 361          --  if anything went wrong.
 362
 363          State_Ready := Prepare_For_Unwind_Of (Frame);
 364
 365          if not State_Ready then
 366             return False;
 367          end if;
 368
 369          --  Now, safely call the unwinder and use the results.
 370
 371          if U_get_previous_frame_x (Frame,
 372                                     Up_Frame'Access,
 373                                     Up_Frame'Size) /= 0
 374          then
 375             return False;
 376          end if;
 377
 378          --  In case a stub is on the way, the usual previous return location
 379          --  (the one in prev_rlo) is the one in the stub and the "real" one
 380          --  is placed in the "current" record, so let's take this one into
 381          --  account.
 382
 383          Frame.out_rlo := Frame.cur_rlo;
 384
 385          Frame.cur_fsz := Up_Frame.prev_fsz;
 386          Frame.cur_sp  := Up_Frame.prev_sp;
 387          Frame.cur_rls := Up_Frame.prev_rls;
 388          Frame.cur_rlo := Up_Frame.prev_rlo;
 389          Frame.cur_dp  := Up_Frame.prev_dp;
 390          Frame.cur_r19 := Up_Frame.prev_r19;
 391          Frame.top_r3  := Up_Frame.top_r3;
 392          Frame.top_r4  := Up_Frame.top_r4;
 393
 394          return True;
 395       end Pop_Frame;
 396
 397       ---------------------------------
 398       -- Prepare_State_For_Unwind_Of --
 399       ---------------------------------
 400
 401       function Prepare_For_Unwind_Of (Frame : access CFD) return Boolean
 402       is
 403          Caller_UWD    : UWD_Ptr;
 404          FP_Adjustment : Integer;
 405
 406       begin
 407          --  No need to bother doing anything if the stack is already fully
 408          --  unwound.
 409
 410          if Frame.cur_rlo = 0 then
 411             return False;
 412          end if;
 413
 414          --  When ALLOCA_FRAME is set in an unwind descriptor, the unwinder
 415          --  uses the value provided in current.top_r3 or current.top_r4 as
 416          --  a frame pointer to compute the size of the frame. What decides
 417          --  between r3 or r4 is the unwind descriptor LARGE_FRAME bit, with
 418          --  r4 chosen if the bit is set.
 419
 420          --  The size computed by the unwinder is STATIC_PART + (SP - FP),
 421          --  which is correct with HP's frame pointer convention, but not
 422          --  with GCC's one since we end up with the static part accounted
 423          --  for twice.
 424
 425          --  We have to compute r4 when it is required because the unwinder
 426          --  has looked for it at a place where it was not if we went through
 427          --  GCC frames.
 428
 429          --  The size of the static part of a frame can be found in the
 430          --  associated unwind descriptor.
 431
 432          Caller_UWD := UWD_For_Caller_Of (Frame);
 433
 434          --  If we cannot get it, we are unable to compute the potentially
 435          --  necessary adjustments. We'd better not try to go on then.
 436
 437          if Caller_UWD = null then
 438             return False;
 439          end if;
 440
 441          --  If the caller frame is a GCC one, r3 is its frame pointer and
 442          --  points to the bottom of the frame. The value to provide for r4
 443          --  can then be computed directly from the one of r3, compensating
 444          --  for the static part of the frame.
 445
 446          --  If the caller frame is an HP one, r3 is used to locate the
 447          --  previous frame marker, that is it also points to the bottom of
 448          --  the frame (this is why r3 cannot be used as the frame pointer in
 449          --  the HP sense for large frames). The value to provide for r4 can
 450          --  then also be computed from the one of r3 with the compensation
 451          --  for the static part of the frame.
 452
 453          FP_Adjustment := Integer (Caller_UWD.frame_size * 8);
 454          Frame.top_r4  := Address (Integer (Frame.top_r3) + FP_Adjustment);
 455
 456          return True;
 457       end Prepare_For_Unwind_Of;
 458
 459       -----------------------
 460       -- UWD_For_Caller_Of --
 461       -----------------------
 462
 463       function UWD_For_Caller_Of (Frame : access CFD) return UWD_Ptr
 464       is
 465          UWD_Access : UWD_Ptr;
 466
 467       begin
 468          --  First try the most direct path, using the return location data
 469          --  associated with the frame.
 470
 471          UWD_Access := UWD_For_RLO_Of (Frame);
 472
 473          if UWD_Access /= null then
 474             return UWD_Access;
 475          end if;
 476
 477          --  If we did not get a result, we might face an in-stub return
 478          --  address. In this case U_get_previous_frame can tell us what the
 479          --  first not-in-stub return point is. We cannot call it directly,
 480          --  though, because we haven't computed the potentially necessary
 481          --  frame pointer adjustments, which might lead to SEGV in some
 482          --  circumstances. Instead, we directly call the libcl routine which
 483          --  is called by U_get_previous_frame and which only requires few
 484          --  information. Take care, however, that the information is provided
 485          --  in the "current" argument, so we need to work on a copy to avoid
 486          --  disturbing our caller.
 487
 488          declare
 489             U_Current  : aliased CFD := Frame.all;
 490             U_Previous : aliased PFD;
 491
 492          begin
 493             U_Previous.prev_dp  := U_Current.cur_dp;
 494             U_Previous.prev_rls := U_Current.cur_rls;
 495             U_Previous.prev_sp  := U_Current.cur_sp - U_Current.cur_fsz;
 496
 497             if U_get_u_rlo (U_Current'Access, U_Previous'Access) /= -1 then
 498                UWD_Access := UWD_For_RLO_Of (U_Current'Access);
 499             end if;
 500          end;
 501
 502          return UWD_Access;
 503       end UWD_For_Caller_Of;
 504
 505       --------------------
 506       -- UWD_For_RLO_Of --
 507       --------------------
 508
 509       function UWD_For_RLO_Of (Frame : access CFD) return UWD_Ptr
 510       is
 511          UWD_Address : Address;
 512
 513          --  The addresses returned by the library point to full descriptors
 514          --  including the frame information bits but also the applicable PC
 515          --  range. We need to account for this.
 516
 517          Frame_Info_Offset  : constant := 8;
 518
 519       begin
 520          --  First try to locate the descriptor in the program's unwind table.
 521
 522          UWD_Address := U_get_unwind_entry (Frame.cur_rlo,
 523                                             Frame.cur_rls,
 524                                             Program_UWT.Table_Start,
 525                                             Program_UWT.Table_End);
 526
 527          --  If we did not get it, we might have a frame from code in a
 528          --  stub or shared library. For code in stub we would have to
 529          --  compute the first non-stub return location but this is not
 530          --  the role of this subprogram, so let's just try to see if we
 531          --  can get a result from the tables in shared libraries.
 532
 533          if UWD_Address = -1
 534            and then U_is_shared_pc (Frame.cur_rlo, Frame.cur_r19) /= 0
 535          then
 536             declare
 537                Shlib_UWT   : UWT := U_get_shLib_unwind_table (Frame.cur_r19);
 538                Shlib_Start : Address := U_get_shLib_text_addr (Frame.cur_r19);
 539                Rlo_Offset  : Address := Frame.cur_rlo - Shlib_Start;
 540
 541             begin
 542                UWD_Address := U_get_unwind_entry (Rlo_Offset,
 543                                                   Frame.cur_rls,
 544                                                   Shlib_UWT.Table_Start,
 545                                                   Shlib_UWT.Table_End);
 546             end;
 547          end if;
 548
 549          if UWD_Address /= -1 then
 550             return To_UWD_Access (UWD_Address + Frame_Info_Offset);
 551          else
 552             return null;
 553          end if;
 554       end UWD_For_RLO_Of;
 555
 556    --  Start of processing for Call_Chain
 557
 558    begin
 559       --  Fetch the state for this subprogram's frame and pop it so that the
 560       --  backtrace starts at the right point for our caller, that is at its
 561       --  own frame.
 562
 563       U_init_frame_record (Frame'Access);
 564       Frame.top_sr0 := 0;
 565       Frame.top_sr4 := 0;
 566
 567       U_prep_frame_rec_for_unwind (Frame'Access);
 568
 569       Pop_Success := Pop_Frame (Frame'Access);
 570
 571       --  Loop popping frames and storing locations until either a problem
 572       --  occurs, or the top of the call chain is reached, or the provided
 573       --  array is full.
 574
 575       loop
 576          --  We have to test some conditions against the return location
 577          --  as it is returned, so get it as is first.
 578
 579          Code := Frame.out_rlo;
 580
 581          exit when not Pop_Success or else Code = 0 or else J = Max_Len + 1;
 582
 583          --  Compute the call point from the retrieved return location :
 584          --  Mask the privilege bits and account for the delta between the
 585          --  call site and the return point.
 586
 587          Code := (Code and not Priv_Mask) - Rlo_Offset;
 588
 589          if Code < Exclude_Min or else Code > Exclude_Max then
 590             Trace (J) := Code;
 591             J := J + 1;
 592          end if;
 593
 594          Pop_Success := Pop_Frame (Frame'Access);
 595       end loop;
 596
 597       Len := J - 1;
 598    end Call_Chain;
 599
 600 end System.Traceback;
 601