1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . T R A C E B A C K --
11 -- Copyright (C) 1999-2002 Ada Core Technologies, Inc. --
13 -- GNAT is free software; you can redistribute it and/or modify it under --
14 -- terms of the GNU General Public License as published by the Free Soft- --
15 -- ware Foundation; either version 2, or (at your option) any later ver- --
16 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
17 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
18 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
19 -- for more details. You should have received a copy of the GNU General --
20 -- Public License distributed with GNAT; see file COPYING. If not, write --
21 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
22 -- MA 02111-1307, USA. --
24 -- As a special exception, if other files instantiate generics from this --
25 -- unit, or you link this unit with other files to produce an executable, --
26 -- this unit does not by itself cause the resulting executable to be --
27 -- covered by the GNU General Public License. This exception does not --
28 -- however invalidate any other reasons why the executable file might be --
29 -- covered by the GNU Public License. --
31 -- GNAT was originally developed by the GNAT team at New York University. --
32 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
34 ------------------------------------------------------------------------------
36 with Ada
.Unchecked_Conversion
;
38 package body System
.Traceback
is
40 -- This package implements the backtracing facility by way of a dedicated
41 -- HP library for stack unwinding described in the "Runtime Architecture
44 pragma Linker_Options
("/usr/lib/libcl.a");
46 -- The library basically offers services to fetch information about a
47 -- "previous" frame based on information about a "current" one.
49 type Current_Frame_Descriptor
is record
50 cur_fsz
: Address
; -- Frame size of current routine.
51 cur_sp
: Address
; -- The current value of stack pointer.
52 cur_rls
: Address
; -- PC-space of the caller.
53 cur_rlo
: Address
; -- PC-offset of the caller.
54 cur_dp
: Address
; -- Data Pointer of the current routine.
55 top_rp
: Address
; -- Initial value of RP.
56 top_mrp
: Address
; -- Initial value of MRP.
57 top_sr0
: Address
; -- Initial value of sr0.
58 top_sr4
: Address
; -- Initial value of sr4.
59 top_r3
: Address
; -- Initial value of gr3.
60 cur_r19
: Address
; -- GR19 value of the calling routine.
61 top_r4
: Address
; -- Initial value of gr4.
62 dummy
: Address
; -- Reserved.
63 out_rlo
: Address
; -- PC-offset of the caller after get_previous.
66 type Previous_Frame_Descriptor
is record
67 prev_fsz
: Address
; -- frame size of calling routine.
68 prev_sp
: Address
; -- SP of calling routine.
69 prev_rls
: Address
; -- PC_space of calling routine's caller.
70 prev_rlo
: Address
; -- PC_offset of calling routine's caller.
71 prev_dp
: Address
; -- DP of calling routine.
72 udescr0
: Address
; -- low word of calling routine's unwind desc.
73 udescr1
: Address
; -- high word of calling routine's unwind desc.
74 ustart
: Address
; -- start of the unwind region.
75 uend
: Address
; -- end of the unwind region.
76 uw_index
: Address
; -- index into the unwind table.
77 prev_r19
: Address
; -- GR19 value of the caller's caller.
78 top_r3
: Address
; -- Caller's initial gr3.
79 top_r4
: Address
; -- Caller's initial gr4.
82 -- Provide useful shortcuts for the names
84 subtype CFD
is Current_Frame_Descriptor
;
85 subtype PFD
is Previous_Frame_Descriptor
;
87 -- Frames with dynamic stack allocation are handled using the associated
88 -- frame pointer, but HP compilers and GCC setup this pointer differently.
89 -- HP compilers set it to point at the top (highest address) of the static
90 -- part of the frame, wheras GCC sets it to point at the bottom of this
91 -- region. We have to fake the unwinder to compensate for this difference,
92 -- for which we'll need to access some subprograms unwind descriptors.
94 type Bits_2_Value
is mod 2 ** 2;
95 for Bits_2_Value
'Size use 2;
97 type Bits_4_Value
is mod 2 ** 4;
98 for Bits_4_Value
'Size use 4;
100 type Bits_5_Value
is mod 2 ** 5;
101 for Bits_5_Value
'Size use 5;
103 type Bits_27_Value
is mod 2 ** 27;
104 for Bits_27_Value
'Size use 27;
106 type Unwind_Descriptor
is record
107 cannot_unwind
: Boolean;
109 mcode_save_restore
: Boolean;
110 region_desc
: Bits_2_Value
;
113 entry_fr
: Bits_4_Value
;
114 entry_gr
: Bits_5_Value
;
116 args_stored
: Boolean;
117 variable_frame
: Boolean;
118 separate_package_body
: Boolean;
119 frame_extension_mcode
: Boolean;
121 stack_overflow_check
: Boolean;
122 two_steps_sp_adjust
: Boolean;
123 sr4_export
: Boolean;
126 cxx_try_catch
: Boolean;
127 sched_entry_seq
: Boolean;
136 hpe_interrupt_marker
: Boolean;
137 hpux_interrupt_marker
: Boolean;
138 large_frame
: Boolean;
139 alloca_frame
: Boolean;
142 frame_size
: Bits_27_Value
;
145 for Unwind_Descriptor
'Size use 64;
147 for Unwind_Descriptor
use record
148 cannot_unwind
at 0 range 0 .. 0;
149 mcode
at 0 range 1 .. 1;
150 mcode_save_restore
at 0 range 2 .. 2;
151 region_desc
at 0 range 3 .. 4;
152 reserved0
at 0 range 5 .. 5;
153 entry_sr
at 0 range 6 .. 6;
154 entry_fr
at 0 range 7 .. 10;
156 entry_gr
at 1 range 3 .. 7;
158 args_stored
at 2 range 0 .. 0;
159 variable_frame
at 2 range 1 .. 1;
160 separate_package_body
at 2 range 2 .. 2;
161 frame_extension_mcode
at 2 range 3 .. 3;
162 stack_overflow_check
at 2 range 4 .. 4;
163 two_steps_sp_adjust
at 2 range 5 .. 5;
164 sr4_export
at 2 range 6 .. 6;
165 cxx_info
at 2 range 7 .. 7;
167 cxx_try_catch
at 3 range 0 .. 0;
168 sched_entry_seq
at 3 range 1 .. 1;
169 reserved1
at 3 range 2 .. 2;
170 save_sp
at 3 range 3 .. 3;
171 save_rp
at 3 range 4 .. 4;
172 save_mrp
at 3 range 5 .. 5;
173 save_r19
at 3 range 6 .. 6;
174 cleanups
at 3 range 7 .. 7;
176 hpe_interrupt_marker
at 4 range 0 .. 0;
177 hpux_interrupt_marker
at 4 range 1 .. 1;
178 large_frame
at 4 range 2 .. 2;
179 alloca_frame
at 4 range 3 .. 3;
181 reserved2
at 4 range 4 .. 4;
182 frame_size
at 4 range 5 .. 31;
185 subtype UWD
is Unwind_Descriptor
;
186 type UWD_Ptr
is access all UWD
;
188 function To_UWD_Access
is new Ada
.Unchecked_Conversion
(Address
, UWD_Ptr
);
190 -- The descriptor associated with a given code location is retrieved
191 -- using functions imported from the HP library, requiring the definition
192 -- of additional structures.
194 type Unwind_Table_Region
is record
195 Table_Start
: Address
;
198 -- An Unwind Table region, which is a memory area containing Unwind
201 subtype UWT
is Unwind_Table_Region
;
203 -- The subprograms imported below are provided by the HP library
205 function U_get_unwind_table
return UWT
;
206 pragma Import
(C
, U_get_unwind_table
, "U_get_unwind_table");
207 -- Get the unwind table region associated with the current executable.
208 -- This function is actually documented as having an argument, but which
209 -- is only used for the MPE/iX targets.
211 function U_get_shLib_unwind_table
(r19
: Address
) return UWT
;
212 pragma Import
(C
, U_get_shLib_unwind_table
, "U_get_shLib_unw_tbl");
213 -- Return the unwind table region associated with a possible shared
214 -- library, as determined by the provided r19 value.
216 function U_get_shLib_text_addr
(r19
: Address
) return Address
;
217 pragma Import
(C
, U_get_shLib_text_addr
, "U_get_shLib_text_addr");
218 -- Return the address at which the code for a shared library begins, or
219 -- -1 if the value provided for r19 does not identify shared library code.
221 function U_get_unwind_entry
224 Table_Start
: Address
;
227 pragma Import
(C
, U_get_unwind_entry
, "U_get_unwind_entry");
228 -- Given the bounds of an unwind table, return the address of the
229 -- unwind descriptor associated with a code location/space. In the case
230 -- of shared library code, the offset from the beginning of the library
231 -- is expected as Pc.
233 procedure U_init_frame_record
(Frame
: access CFD
);
234 pragma Import
(C
, U_init_frame_record
, "U_init_frame_record");
236 procedure U_prep_frame_rec_for_unwind
(Frame
: access CFD
);
237 pragma Import
(C
, U_prep_frame_rec_for_unwind
,
238 "U_prep_frame_rec_for_unwind");
240 -- Fetch the description data of the frame in which these two procedures
243 function U_get_u_rlo
(Cur
: access CFD
; Prev
: access PFD
) return Integer;
244 pragma Import
(C
, U_get_u_rlo
, "U_IS_STUB_OR_CALLX");
245 -- From a complete current frame with a return location possibly located
246 -- into a linker generated stub, and basic information about the previous
247 -- frame, place the first non stub return location into the current frame.
248 -- Return -1 if something went wrong during the computation.
250 function U_is_shared_pc
(rlo
: Address
; r19
: Address
) return Address
;
251 pragma Import
(C
, U_is_shared_pc
, "U_is_shared_pc");
252 -- Return 0 if the provided return location does not correspond to code
253 -- in a shared library, or something non null otherwise.
255 function U_get_previous_frame_x
256 (current_frame
: access CFD
;
257 previous_frame
: access PFD
;
258 previous_size
: Integer)
260 pragma Import
(C
, U_get_previous_frame_x
, "U_get_previous_frame_x");
261 -- Fetch the data describing the "previous" frame relatively to the
262 -- "current" one. "previous_size" should be the size of the "previous"
263 -- frame descriptor provided.
265 -- The library provides a simpler interface without the size parameter
266 -- but it is not usable when frames with dynamically allocated space are
273 function C_Call_Chain
274 (Traceback
: System
.Address
;
281 Call_Chain
(Traceback
, Max_Len
, Val
);
290 (Traceback
: System
.Address
;
293 Exclude_Min
: System
.Address
:= System
.Null_Address
;
294 Exclude_Max
: System
.Address
:= System
.Null_Address
)
296 type Tracebacks_Array
is array (1 .. Max_Len
) of System
.Address
;
297 pragma Suppress_Initialization
(Tracebacks_Array
);
299 -- The code location returned by the unwinder is a return location but
300 -- what we need is a call point. Under HP-UX call instructions are 4
301 -- bytes long and the return point they specify is 4 bytes beyond the
302 -- next instruction because of the delay slot.
304 Call_Size
: constant := 4;
305 DSlot_Size
: constant := 4;
306 Rlo_Offset
: constant := Call_Size
+ DSlot_Size
;
308 -- Moreover, the return point is passed via a register which two least
309 -- significant bits specify a privilege level that we will have to mask.
311 Priv_Mask
: constant := 16#
00000003#
;
314 Code
: System
.Address
;
316 Pop_Success
: Boolean;
317 Trace
: Tracebacks_Array
;
318 for Trace
'Address use Traceback
;
320 -- The backtracing process needs a set of subprograms :
322 function UWD_For_RLO_Of
(Frame
: access CFD
) return UWD_Ptr
;
323 -- Return an access to the unwind descriptor for the caller of
324 -- a given frame, using only the provided return location.
326 function UWD_For_Caller_Of
(Frame
: access CFD
) return UWD_Ptr
;
327 -- Return an access to the unwind descriptor for the user code caller
328 -- of a given frame, or null if the information is not available.
330 function Pop_Frame
(Frame
: access CFD
) return Boolean;
331 -- Update the provided machine state structure so that it reflects
332 -- the state one call frame "above" the initial one.
334 -- Return True if the operation has been successful, False otherwise.
335 -- Failure typically occurs when the top of the call stack has been
338 function Prepare_For_Unwind_Of
(Frame
: access CFD
) return Boolean;
339 -- Perform the necessary adaptations to the machine state before
340 -- calling the unwinder. Currently used for the specific case of
341 -- dynamically sized previous frames.
343 -- Return True if everything went fine, or False otherwise.
345 Program_UWT
: constant UWT
:= U_get_unwind_table
;
351 function Pop_Frame
(Frame
: access CFD
) return Boolean is
352 Up_Frame
: aliased PFD
;
353 State_Ready
: Boolean;
356 -- Check/adapt the state before calling the unwinder and return
357 -- if anything went wrong.
359 State_Ready
:= Prepare_For_Unwind_Of
(Frame
);
361 if not State_Ready
then
365 -- Now, safely call the unwinder and use the results.
367 if U_get_previous_frame_x
(Frame
,
374 -- In case a stub is on the way, the usual previous return location
375 -- (the one in prev_rlo) is the one in the stub and the "real" one
376 -- is placed in the "current" record, so let's take this one into
379 Frame
.out_rlo
:= Frame
.cur_rlo
;
381 Frame
.cur_fsz
:= Up_Frame
.prev_fsz
;
382 Frame
.cur_sp
:= Up_Frame
.prev_sp
;
383 Frame
.cur_rls
:= Up_Frame
.prev_rls
;
384 Frame
.cur_rlo
:= Up_Frame
.prev_rlo
;
385 Frame
.cur_dp
:= Up_Frame
.prev_dp
;
386 Frame
.cur_r19
:= Up_Frame
.prev_r19
;
387 Frame
.top_r3
:= Up_Frame
.top_r3
;
388 Frame
.top_r4
:= Up_Frame
.top_r4
;
393 ---------------------------------
394 -- Prepare_State_For_Unwind_Of --
395 ---------------------------------
397 function Prepare_For_Unwind_Of
(Frame
: access CFD
) return Boolean
399 Caller_UWD
: UWD_Ptr
;
400 FP_Adjustment
: Integer;
403 -- No need to bother doing anything if the stack is already fully
406 if Frame
.cur_rlo
= 0 then
410 -- When ALLOCA_FRAME is set in an unwind descriptor, the unwinder
411 -- uses the value provided in current.top_r3 or current.top_r4 as
412 -- a frame pointer to compute the size of the frame. What decides
413 -- between r3 or r4 is the unwind descriptor LARGE_FRAME bit, with
414 -- r4 chosen if the bit is set.
416 -- The size computed by the unwinder is STATIC_PART + (SP - FP),
417 -- which is correct with HP's frame pointer convention, but not
418 -- with GCC's one since we end up with the static part accounted
421 -- We have to compute r4 when it is required because the unwinder
422 -- has looked for it at a place where it was not if we went through
425 -- The size of the static part of a frame can be found in the
426 -- associated unwind descriptor.
428 Caller_UWD
:= UWD_For_Caller_Of
(Frame
);
430 -- If we cannot get it, we are unable to compute the potentially
431 -- necessary adjustments. We'd better not try to go on then.
433 if Caller_UWD
= null then
437 -- If the caller frame is a GCC one, r3 is its frame pointer and
438 -- points to the bottom of the frame. The value to provide for r4
439 -- can then be computed directly from the one of r3, compensating
440 -- for the static part of the frame.
442 -- If the caller frame is an HP one, r3 is used to locate the
443 -- previous frame marker, that is it also points to the bottom of
444 -- the frame (this is why r3 cannot be used as the frame pointer in
445 -- the HP sense for large frames). The value to provide for r4 can
446 -- then also be computed from the one of r3 with the compensation
447 -- for the static part of the frame.
449 FP_Adjustment
:= Integer (Caller_UWD
.frame_size
* 8);
450 Frame
.top_r4
:= Address
(Integer (Frame
.top_r3
) + FP_Adjustment
);
453 end Prepare_For_Unwind_Of
;
455 -----------------------
456 -- UWD_For_Caller_Of --
457 -----------------------
459 function UWD_For_Caller_Of
(Frame
: access CFD
) return UWD_Ptr
461 UWD_Access
: UWD_Ptr
;
464 -- First try the most direct path, using the return location data
465 -- associated with the frame.
467 UWD_Access
:= UWD_For_RLO_Of
(Frame
);
469 if UWD_Access
/= null then
473 -- If we did not get a result, we might face an in-stub return
474 -- address. In this case U_get_previous_frame can tell us what the
475 -- first not-in-stub return point is. We cannot call it directly,
476 -- though, because we haven't computed the potentially necessary
477 -- frame pointer adjustments, which might lead to SEGV in some
478 -- circumstances. Instead, we directly call the libcl routine which
479 -- is called by U_get_previous_frame and which only requires few
480 -- information. Take care, however, that the information is provided
481 -- in the "current" argument, so we need to work on a copy to avoid
482 -- disturbing our caller.
485 U_Current
: aliased CFD
:= Frame
.all;
486 U_Previous
: aliased PFD
;
489 U_Previous
.prev_dp
:= U_Current
.cur_dp
;
490 U_Previous
.prev_rls
:= U_Current
.cur_rls
;
491 U_Previous
.prev_sp
:= U_Current
.cur_sp
- U_Current
.cur_fsz
;
493 if U_get_u_rlo
(U_Current
'Access, U_Previous
'Access) /= -1 then
494 UWD_Access
:= UWD_For_RLO_Of
(U_Current
'Access);
499 end UWD_For_Caller_Of
;
505 function UWD_For_RLO_Of
(Frame
: access CFD
) return UWD_Ptr
507 UWD_Address
: Address
;
509 -- The addresses returned by the library point to full descriptors
510 -- including the frame information bits but also the applicable PC
511 -- range. We need to account for this.
513 Frame_Info_Offset
: constant := 8;
516 -- First try to locate the descriptor in the program's unwind table.
518 UWD_Address
:= U_get_unwind_entry
(Frame
.cur_rlo
,
520 Program_UWT
.Table_Start
,
521 Program_UWT
.Table_End
);
523 -- If we did not get it, we might have a frame from code in a
524 -- stub or shared library. For code in stub we would have to
525 -- compute the first non-stub return location but this is not
526 -- the role of this subprogram, so let's just try to see if we
527 -- can get a result from the tables in shared libraries.
530 and then U_is_shared_pc
(Frame
.cur_rlo
, Frame
.cur_r19
) /= 0
533 Shlib_UWT
: UWT
:= U_get_shLib_unwind_table
(Frame
.cur_r19
);
534 Shlib_Start
: Address
:= U_get_shLib_text_addr
(Frame
.cur_r19
);
535 Rlo_Offset
: Address
:= Frame
.cur_rlo
- Shlib_Start
;
538 UWD_Address
:= U_get_unwind_entry
(Rlo_Offset
,
540 Shlib_UWT
.Table_Start
,
541 Shlib_UWT
.Table_End
);
545 if UWD_Address
/= -1 then
546 return To_UWD_Access
(UWD_Address
+ Frame_Info_Offset
);
552 -- Start of processing for Call_Chain
555 -- Fetch the state for this subprogram's frame and pop it so that the
556 -- backtrace starts at the right point for our caller, that is at its
559 U_init_frame_record
(Frame
'Access);
563 U_prep_frame_rec_for_unwind
(Frame
'Access);
565 Pop_Success
:= Pop_Frame
(Frame
'Access);
567 -- Loop popping frames and storing locations until either a problem
568 -- occurs, or the top of the call chain is reached, or the provided
572 -- We have to test some conditions against the return location
573 -- as it is returned, so get it as is first.
575 Code
:= Frame
.out_rlo
;
577 exit when not Pop_Success
or else Code
= 0 or else J
= Max_Len
+ 1;
579 -- Compute the call point from the retrieved return location :
580 -- Mask the privilege bits and account for the delta between the
581 -- call site and the return point.
583 Code
:= (Code
and not Priv_Mask
) - Rlo_Offset
;
585 if Code
< Exclude_Min
or else Code
> Exclude_Max
then
590 Pop_Success
:= Pop_Frame
(Frame
'Access);
596 end System
.Traceback
;