1 /****************************************************************************
3 * GNAT COMPILER COMPONENTS *
7 * C Implementation File *
9 * Copyright (C) 2000-2011, Free Software Foundation, Inc. *
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 2, 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. See the GNU General Public License *
17 * for more details. You should have received a copy of the GNU General *
18 * Public License distributed with GNAT; see file COPYING. If not, write *
19 * to the Free Software Foundation, 51 Franklin Street, Fifth Floor, *
20 * Boston, MA 02110-1301, USA. *
22 * As a special exception, if you link this file with other files to *
23 * produce an executable, this file does not by itself cause the resulting *
24 * executable to be covered by the GNU General Public License. This except- *
25 * ion does not however invalidate any other reasons why the executable *
26 * file might be covered by the GNU Public License. *
28 * GNAT was originally developed by the GNAT team at New York University. *
29 * Extensive contributions were provided by Ada Core Technologies Inc. *
31 ****************************************************************************/
33 /* This file contains low level support for stack unwinding using GCC intrinsic
35 It has been tested on the following configurations:
53 #ifdef __alpha_vxworks
64 /* We don't want fancy_abort here. */
68 extern int __gnat_backtrace (void **, int, void *, void *, int);
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.
73 We first have a series of target specific implementations, each included
74 from a separate C file for readability purposes.
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.
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. */
88 #define Lock_Task system__soft_links__lock_task
89 extern void (*Lock_Task) (void);
91 #define Unlock_Task system__soft_links__unlock_task
92 extern void (*Unlock_Task) (void);
94 /*-------------------------------------*
95 *-- Target specific implementations --*
96 *-------------------------------------*/
98 #if defined (__alpha_vxworks)
100 #include "tb-alvxw.c"
102 #elif defined (__ALPHA) && defined (__VMS__)
104 #include "tb-alvms.c"
106 #elif defined (__ia64__) && defined (__VMS__)
112 /* No target specific implementation. */
114 /*----------------------------------------------------------------*
115 *-- Target specific definitions for the generic implementation --*
116 *----------------------------------------------------------------*/
118 /* The stack layout is specified by the target ABI. The "generic" scheme is
119 based on the following assumption:
121 The stack layout from some frame pointer is such that the information
122 required to compute the backtrace is available at static offsets.
124 For a given frame, the information we are interested in is the saved return
125 address (somewhere after the call instruction in the caller) and a pointer
126 to the caller's frame. The former is the base of the call chain information
127 we store in the tracebacks array. The latter allows us to loop over the
128 successive frames in the chain.
130 To initiate the process, we retrieve an initial frame address using the
131 appropriate GCC builtin (__builtin_frame_address).
133 This scheme is unfortunately not applicable on every target because the
134 stack layout is not necessarily regular (static) enough. On targets where
135 this scheme applies, the implementation relies on the following items:
137 o struct layout, describing the expected stack data layout relevant to the
138 information we are interested in,
140 o FRAME_OFFSET, the offset, from a given frame address or frame pointer
141 value, at which this layout will be found,
143 o FRAME_LEVEL, controls how many frames up we get at to start with,
144 from the initial frame pointer we compute by way of the GCC builtin,
146 0 is most often the appropriate value. 1 may be necessary on targets
147 where return addresses are saved by a function in it's caller's frame
150 o PC_ADJUST, to account for the difference between a call point (address
151 of a call instruction), which is what we want in the output array, and
152 the associated return address, which is what we retrieve from the stack.
154 o STOP_FRAME, to decide whether we reached the top of the call chain, and
155 thus if the process shall stop.
161 | | | (FRAME_OFFSET) |
162 | | | : | (PC_ADJUST)
163 | | layout:| return_address ----------------+
165 +--------------- next_frame | |
168 | +----------------+ | +-----+
169 | | : |<- Base fp | | : |
170 | | (FRAME_OFFSET) | (FRAME_LEVEL) | | : |
172 | layout:| return_address --------------------> | [0]
173 | | ... | (PC_ADJUST) +-----+
174 +---------- next_frame | traceback[]
181 Since we inherently deal with return addresses, there is an implicit shift
182 by at least one for the initial point we are able to observe in the chain.
184 On some targets (e.g. sparc-solaris), the first return address we can
185 easily get without special code is even our caller's return address, so
186 there is a initial shift of two.
188 BASE_SKIP represents this initial shift, which is the minimal "skip_frames"
189 value we support. We could add special code for the skip_frames < BASE_SKIP
190 cases. This is not done currently because there is virtually no situation
191 in which this would be useful.
193 Finally, to account for some ABI specificities, a target may (but does
196 o FORCE_CALL, to force a call to a dummy function at the very beginning
197 of the computation. See the PPC AIX target for an example where this
200 o FETCH_UP_FRAME, to force an invocation of __builtin_frame_address with a
201 positive argument right after a possibly forced call even if FRAME_LEVEL
202 is 0. See the SPARC Solaris case for an example where this is useful.
206 /*--------------------------- PPC AIX/Darwin ----------------------------*/
208 #if ((defined (_POWER) && defined (_AIX)) || \
209 (defined (__ppc__) && defined (__APPLE__)))
211 #define USE_GENERIC_UNWINDER
217 void *return_address;
220 #define FRAME_OFFSET(FP) 0
222 #define STOP_FRAME(CURRENT, TOP_STACK) ((void *) (CURRENT) < (TOP_STACK))
224 /* The PPC ABI has an interesting specificity: the return address saved by a
225 function is located in it's caller's frame, and the save operation only
226 takes place if the function performs a call.
228 To have __gnat_backtrace retrieve its own return address, we then
232 #define FRAME_LEVEL 1
236 /*-------------------- PPC ELF (GNU/Linux & VxWorks) ---------------------*/
238 #elif (defined (_ARCH_PPC) && defined (__vxworks)) || \
239 (defined (linux) && defined (__powerpc__))
241 #define USE_GENERIC_UNWINDER
246 void *return_address;
250 #define FRAME_LEVEL 1
251 /* See the PPC AIX case for an explanation of these values. */
253 #define FRAME_OFFSET(FP) 0
255 #define STOP_FRAME(CURRENT, TOP_STACK) ((CURRENT)->next == 0)
259 /*-------------------------- SPARC Solaris -----------------------------*/
261 #elif defined (sun) && defined (sparc)
263 #define USE_GENERIC_UNWINDER
265 /* These definitions are inspired from the Appendix D (Software
266 Considerations) of the SPARC V8 architecture manual. */
271 void *return_address;
275 #define STACK_BIAS 2047 /* V9 ABI */
277 #define STACK_BIAS 0 /* V8 ABI */
280 #define FRAME_LEVEL 0
281 #define FRAME_OFFSET(FP) (14 * sizeof (void*) + (FP ? STACK_BIAS : 0))
283 #define STOP_FRAME(CURRENT, TOP_STACK) \
284 ((CURRENT)->return_address == 0|| (CURRENT)->next == 0 \
285 || (void *) (CURRENT) < (TOP_STACK))
287 /* The SPARC register windows need to be flushed before we may access them
288 from the stack. This is achieved by way of builtin_frame_address only
289 when the "count" argument is positive, so force at least one such call. */
290 #define FETCH_UP_FRAME_ADDRESS
293 /* From the frame pointer of frame N, we are accessing the flushed register
294 window of frame N-1 (positive offset from fp), in which we retrieve the
295 saved return address. We then end up with our caller's return address. */
297 /*------------------------------- x86 ----------------------------------*/
301 #if defined (__WIN32)
303 #define IS_BAD_PTR(ptr) (IsBadCodePtr((void *)ptr))
305 #define IS_BAD_PTR(ptr) ((unsigned long)ptr == -1UL)
307 #define IS_BAD_PTR(ptr) 0
310 /* Starting with GCC 4.6, -fomit-frame-pointer is turned on by default for
311 32-bit x86/Linux as well and DWARF 2 unwind tables are emitted instead.
312 See the x86-64 case below for the drawbacks with this approach. */
313 #if defined (linux) && (__GNUC__ * 10 + __GNUC_MINOR__ > 45)
314 #define USE_GCC_UNWINDER
316 #define USE_GENERIC_UNWINDER
322 void *return_address;
325 #define FRAME_LEVEL 1
326 /* builtin_frame_address (1) is expected to work on this target, and (0) might
327 return the soft stack pointer, which does not designate a location where a
328 backchain and a return address might be found. */
330 #define FRAME_OFFSET(FP) 0
332 #define STOP_FRAME(CURRENT, TOP_STACK) \
333 (IS_BAD_PTR((long)(CURRENT)) \
334 || IS_BAD_PTR((long)(CURRENT)->return_address) \
335 || (CURRENT)->return_address == 0|| (CURRENT)->next == 0 \
336 || (void *) (CURRENT) < (TOP_STACK))
338 #define BASE_SKIP (1+FRAME_LEVEL)
340 /* On i386 architecture we check that at the call point we really have a call
341 insn. Possible call instructions are:
343 call addr16 E8 xx xx xx xx
345 call off(reg) FF xx xx
346 lcall addr seg 9A xx xx xx xx xx xx
348 This check will not catch all cases but it will increase the backtrace
349 reliability on this architecture.
352 #define VALID_STACK_FRAME(ptr) \
354 && (((*((ptr) - 3) & 0xff) == 0xe8) \
355 || ((*((ptr) - 5) & 0xff) == 0x9a) \
356 || ((*((ptr) - 1) & 0xff) == 0xff) \
357 || (((*(ptr) & 0xd0ff) == 0xd0ff))))
359 /*----------------------------- x86_64 ---------------------------------*/
361 #elif defined (__x86_64__)
363 #define USE_GCC_UNWINDER
364 /* The generic unwinder is not used for this target because it is based
365 on frame layout assumptions that are not reliable on this target (the
366 rbp register is very likely used for something else than storing the
367 frame pointer in optimized code). Hence, we use the GCC unwinder
368 based on DWARF 2 call frame information, although it has the drawback
369 of not being able to unwind through frames compiled without DWARF 2
374 /* The minimum size of call instructions on this architecture is 2 bytes */
376 /*----------------------------- ia64 ---------------------------------*/
378 #elif defined (__ia64__) && (defined (linux) || defined (__hpux__))
380 #define USE_GCC_UNWINDER
381 /* Use _Unwind_Backtrace driven exceptions on ia64 HP-UX and ia64
382 GNU/Linux, where _Unwind_Backtrace is provided by the system unwind
383 library. On HP-UX 11.23 this requires patch PHSS_33352, which adds
384 _Unwind_Backtrace to the system unwind library. */
391 /*---------------------------------------------------------------------*
392 *-- The post GCC 3.3 infrastructure based implementation --*
393 *---------------------------------------------------------------------*/
395 #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33)
397 /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap
398 path problems, since the included file refers to post 3.3 functions in
399 libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3
400 library. It actually disables the support for backtraces in this compiler
401 for targets defining USE_GCC_UNWINDER, which is OK since we don't use the
402 traceback capability in the compiler anyway.
404 The condition is expressed the way above because we cannot reliably rely on
405 any other macro from the base compiler when compiling stage1. */
409 /*------------------------------------------------------------------*
410 *-- The generic implementation based on frame layout assumptions --*
411 *------------------------------------------------------------------*/
413 #elif defined (USE_GENERIC_UNWINDER)
415 #ifndef CURRENT_STACK_FRAME
416 # define CURRENT_STACK_FRAME ({ char __csf; &__csf; })
419 #ifndef VALID_STACK_FRAME
420 #define VALID_STACK_FRAME(ptr) 1
424 #define MAX(x,y) ((x) > (y) ? (x) : (y))
431 /* Make sure the function is not inlined. */
432 static void forced_callee (void) __attribute__ ((noinline));
434 static void forced_callee (void)
436 /* Make sure the function is not pure. */
437 volatile int i __attribute__ ((unused)) = 0;
441 __gnat_backtrace (void **array,
447 struct layout *current;
449 void *top_stack ATTRIBUTE_UNUSED;
455 /* Force a call to builtin_frame_address with a positive argument
456 if required. This is necessary e.g. on SPARC to have the register
457 windows flushed before we attempt to access them on the stack. */
458 #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0)
459 __builtin_frame_address (1);
462 top_frame = __builtin_frame_address (FRAME_LEVEL);
463 top_stack = CURRENT_STACK_FRAME;
464 current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET (0));
466 /* Skip the number of calls we have been requested to skip, accounting for
467 the BASE_SKIP parameter.
469 FRAME_LEVEL is meaningless for the count adjustment. It impacts where we
470 start retrieving data from, but how many frames "up" we start at is in
471 BASE_SKIP by definition. */
473 skip_frames = MAX (0, skip_frames - BASE_SKIP);
475 while (cnt < skip_frames)
477 current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
484 if (STOP_FRAME (current, top_stack) ||
485 !VALID_STACK_FRAME(((char *) current->return_address) + PC_ADJUST))
488 if (current->return_address < exclude_min
489 || current->return_address > exclude_max)
490 array[cnt++] = ((char *) current->return_address) + PC_ADJUST;
492 current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
500 /* No target specific implementation and neither USE_GCC_UNWINDER nor
501 USE_GENERIC_UNWINDER defined. */
503 /*------------------------------*
504 *-- The dummy implementation --*
505 *------------------------------*/
508 __gnat_backtrace (void **array ATTRIBUTE_UNUSED,
509 int size ATTRIBUTE_UNUSED,
510 void *exclude_min ATTRIBUTE_UNUSED,
511 void *exclude_max ATTRIBUTE_UNUSED,
512 int skip_frames ATTRIBUTE_UNUSED)