1 /****************************************************************************
3 * GNAT RUN-TIME 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 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. *
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. *
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/>. *
27 * GNAT was originally developed by the GNAT team at New York University. *
28 * Extensive contributions were provided by Ada Core Technologies Inc. *
30 ****************************************************************************/
32 /* This file contains low level support for stack unwinding using GCC intrinsic
34 It has been tested on the following configurations:
52 #ifdef __alpha_vxworks
63 /* We don't want fancy_abort here. */
67 extern int __gnat_backtrace (void **, int, void *, void *, int);
69 /* The point is to provide an implementation of the __gnat_backtrace function
70 above, called by the default implementation of the System.Traceback package.
72 We first have a series of target specific implementations, each included
73 from a separate C file for readability purposes.
75 Then come two flavors of a generic implementation: one relying on static
76 assumptions about the frame layout, and the other one using the GCC EH
77 infrastructure. The former uses a whole set of macros and structures which
78 may be tailored on a per target basis, and is activated as soon as
79 USE_GENERIC_UNWINDER is defined. The latter uses a small subset of the
80 macro definitions and is activated when USE_GCC_UNWINDER is defined. It is
81 only available post GCC 3.3.
83 Finally, there is a default dummy implementation, necessary to make the
84 linker happy on platforms where the feature is not supported, but where the
85 function is still referenced by the default System.Traceback. */
87 #define Lock_Task system__soft_links__lock_task
88 extern void (*Lock_Task) (void);
90 #define Unlock_Task system__soft_links__unlock_task
91 extern void (*Unlock_Task) (void);
93 /*-------------------------------------*
94 *-- Target specific implementations --*
95 *-------------------------------------*/
97 #if defined (__alpha_vxworks)
101 #elif defined (__ALPHA) && defined (__VMS__)
103 #include "tb-alvms.c"
105 #elif defined (__ia64__) && defined (__VMS__)
111 /* No target specific implementation. */
113 /*----------------------------------------------------------------*
114 *-- Target specific definitions for the generic implementation --*
115 *----------------------------------------------------------------*/
117 /* The stack layout is specified by the target ABI. The "generic" scheme is
118 based on the following assumption:
120 The stack layout from some frame pointer is such that the information
121 required to compute the backtrace is available at static offsets.
123 For a given frame, the information we are interested in is the saved return
124 address (somewhere after the call instruction in the caller) and a pointer
125 to the caller's frame. The former is the base of the call chain information
126 we store in the tracebacks array. The latter allows us to loop over the
127 successive frames in the chain.
129 To initiate the process, we retrieve an initial frame address using the
130 appropriate GCC builtin (__builtin_frame_address).
132 This scheme is unfortunately not applicable on every target because the
133 stack layout is not necessarily regular (static) enough. On targets where
134 this scheme applies, the implementation relies on the following items:
136 o struct layout, describing the expected stack data layout relevant to the
137 information we are interested in,
139 o FRAME_OFFSET, the offset, from a given frame address or frame pointer
140 value, at which this layout will be found,
142 o FRAME_LEVEL, controls how many frames up we get at to start with,
143 from the initial frame pointer we compute by way of the GCC builtin,
145 0 is most often the appropriate value. 1 may be necessary on targets
146 where return addresses are saved by a function in it's caller's frame
149 o PC_ADJUST, to account for the difference between a call point (address
150 of a call instruction), which is what we want in the output array, and
151 the associated return address, which is what we retrieve from the stack.
153 o STOP_FRAME, to decide whether we reached the top of the call chain, and
154 thus if the process shall stop.
160 | | | (FRAME_OFFSET) |
161 | | | : | (PC_ADJUST)
162 | | layout:| return_address ----------------+
164 +--------------- next_frame | |
167 | +----------------+ | +-----+
168 | | : |<- Base fp | | : |
169 | | (FRAME_OFFSET) | (FRAME_LEVEL) | | : |
171 | layout:| return_address --------------------> | [0]
172 | | ... | (PC_ADJUST) +-----+
173 +---------- next_frame | traceback[]
180 Since we inherently deal with return addresses, there is an implicit shift
181 by at least one for the initial point we are able to observe in the chain.
183 On some targets (e.g. sparc-solaris), the first return address we can
184 easily get without special code is even our caller's return address, so
185 there is a initial shift of two.
187 BASE_SKIP represents this initial shift, which is the minimal "skip_frames"
188 value we support. We could add special code for the skip_frames < BASE_SKIP
189 cases. This is not done currently because there is virtually no situation
190 in which this would be useful.
192 Finally, to account for some ABI specificities, a target may (but does
195 o FORCE_CALL, to force a call to a dummy function at the very beginning
196 of the computation. See the PPC AIX target for an example where this
199 o FETCH_UP_FRAME, to force an invocation of __builtin_frame_address with a
200 positive argument right after a possibly forced call even if FRAME_LEVEL
201 is 0. See the SPARC Solaris case for an example where this is useful.
205 /*------------------- Darwin 8 (OSX 10.4) or newer ----------------------*/
206 #if defined (__APPLE__) \
207 && defined (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) \
208 && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 1040
210 #define USE_GCC_UNWINDER
212 #if defined (__i386__) || defined (__x86_64__)
214 #elif defined (__ppc__) || defined (__ppc64__)
217 #error Unhandled darwin architecture.
220 /*------------------------ PPC AIX/Older Darwin -------------------------*/
221 #elif ((defined (_POWER) && defined (_AIX)) || \
222 (defined (__ppc__) && defined (__APPLE__)))
224 #define USE_GENERIC_UNWINDER
230 void *return_address;
233 #define FRAME_OFFSET(FP) 0
236 /* Eventhough the base PPC ABI states that a toplevel frame entry
237 should to feature a null backchain, AIX might expose a null return
240 #define STOP_FRAME(CURRENT, TOP_STACK) \
241 (((void *) (CURRENT) < (TOP_STACK)) \
242 || (CURRENT)->return_address == NULL)
244 /* The PPC ABI has an interesting specificity: the return address saved by a
245 function is located in it's caller's frame, and the save operation only
246 takes place if the function performs a call.
248 To have __gnat_backtrace retrieve its own return address, we then
252 #define FRAME_LEVEL 1
256 /*-------------------- PPC ELF (GNU/Linux & VxWorks) ---------------------*/
258 #elif (defined (_ARCH_PPC) && defined (__vxworks)) || \
259 (defined (linux) && defined (__powerpc__))
261 #define USE_GENERIC_UNWINDER
266 void *return_address;
270 #define FRAME_LEVEL 1
271 /* See the PPC AIX case for an explanation of these values. */
273 #define FRAME_OFFSET(FP) 0
276 /* According to the base PPC ABI, a toplevel frame entry should feature
277 a null backchain. What happens at signal handler frontiers isn't so
278 well specified, so we add a safety guard on top. */
280 #define STOP_FRAME(CURRENT, TOP_STACK) \
281 ((CURRENT)->next == 0 || ((long)(CURRENT)->next % __alignof__(void*)) != 0)
285 /*-------------------------- SPARC Solaris -----------------------------*/
287 #elif defined (sun) && defined (sparc)
289 #define USE_GENERIC_UNWINDER
291 /* These definitions are inspired from the Appendix D (Software
292 Considerations) of the SPARC V8 architecture manual. */
297 void *return_address;
301 #define STACK_BIAS 2047 /* V9 ABI */
303 #define STACK_BIAS 0 /* V8 ABI */
306 #define FRAME_LEVEL 0
307 #define FRAME_OFFSET(FP) (14 * sizeof (void*) + (FP ? STACK_BIAS : 0))
309 #define STOP_FRAME(CURRENT, TOP_STACK) \
310 ((CURRENT)->return_address == 0|| (CURRENT)->next == 0 \
311 || (void *) (CURRENT) < (TOP_STACK))
313 /* The SPARC register windows need to be flushed before we may access them
314 from the stack. This is achieved by way of builtin_frame_address only
315 when the "count" argument is positive, so force at least one such call. */
316 #define FETCH_UP_FRAME_ADDRESS
319 /* From the frame pointer of frame N, we are accessing the flushed register
320 window of frame N-1 (positive offset from fp), in which we retrieve the
321 saved return address. We then end up with our caller's return address. */
323 /*------------------------------- x86 ----------------------------------*/
327 #if defined (__WIN32)
329 #define IS_BAD_PTR(ptr) (IsBadCodePtr((FARPROC)ptr))
331 #define IS_BAD_PTR(ptr) ((unsigned long)ptr == -1UL)
333 #define IS_BAD_PTR(ptr) 0
336 /* Starting with GCC 4.6, -fomit-frame-pointer is turned on by default for
337 32-bit x86/Linux as well and DWARF 2 unwind tables are emitted instead.
338 See the x86-64 case below for the drawbacks with this approach. */
339 #if defined (linux) && (__GNUC__ * 10 + __GNUC_MINOR__ > 45)
340 #define USE_GCC_UNWINDER
342 #define USE_GENERIC_UNWINDER
348 void *return_address;
351 #define FRAME_LEVEL 1
352 /* builtin_frame_address (1) is expected to work on this target, and (0) might
353 return the soft stack pointer, which does not designate a location where a
354 backchain and a return address might be found. */
356 #define FRAME_OFFSET(FP) 0
358 #define STOP_FRAME(CURRENT, TOP_STACK) \
359 (IS_BAD_PTR((long)(CURRENT)) \
360 || IS_BAD_PTR((long)(CURRENT)->return_address) \
361 || (CURRENT)->return_address == 0 \
362 || (void *) ((CURRENT)->next) < (TOP_STACK) \
363 || (void *) (CURRENT) < (TOP_STACK))
365 #define BASE_SKIP (1+FRAME_LEVEL)
367 /* On i386 architecture we check that at the call point we really have a call
368 insn. Possible call instructions are:
370 call addr16 E8 xx xx xx xx
372 call off(reg) FF xx xx
373 lcall addr seg 9A xx xx xx xx xx xx
375 This check will not catch all cases but it will increase the backtrace
376 reliability on this architecture.
379 #define VALID_STACK_FRAME(ptr) \
381 && (((*((ptr) - 3) & 0xff) == 0xe8) \
382 || ((*((ptr) - 5) & 0xff) == 0x9a) \
383 || ((*((ptr) - 1) & 0xff) == 0xff) \
384 || (((*(ptr) & 0xd0ff) == 0xd0ff))))
386 /*----------------------------- x86_64 ---------------------------------*/
388 #elif defined (__x86_64__)
390 #define USE_GCC_UNWINDER
391 /* The generic unwinder is not used for this target because it is based
392 on frame layout assumptions that are not reliable on this target (the
393 rbp register is very likely used for something else than storing the
394 frame pointer in optimized code). Hence, we use the GCC unwinder
395 based on DWARF 2 call frame information, although it has the drawback
396 of not being able to unwind through frames compiled without DWARF 2
401 /* The minimum size of call instructions on this architecture is 2 bytes */
403 /*----------------------------- ia64 ---------------------------------*/
405 #elif defined (__ia64__) && (defined (linux) || defined (__hpux__))
407 #define USE_GCC_UNWINDER
408 /* Use _Unwind_Backtrace driven exceptions on ia64 HP-UX and ia64
409 GNU/Linux, where _Unwind_Backtrace is provided by the system unwind
410 library. On HP-UX 11.23 this requires patch PHSS_33352, which adds
411 _Unwind_Backtrace to the system unwind library. */
418 /*---------------------------------------------------------------------*
419 *-- The post GCC 3.3 infrastructure based implementation --*
420 *---------------------------------------------------------------------*/
422 #if defined (USE_GCC_UNWINDER) && (__GNUC__ * 10 + __GNUC_MINOR__ > 33)
424 /* Conditioning the inclusion on the GCC version is useful to avoid bootstrap
425 path problems, since the included file refers to post 3.3 functions in
426 libgcc, and the stage1 compiler is unlikely to be linked against a post 3.3
427 library. It actually disables the support for backtraces in this compiler
428 for targets defining USE_GCC_UNWINDER, which is OK since we don't use the
429 traceback capability in the compiler anyway.
431 The condition is expressed the way above because we cannot reliably rely on
432 any other macro from the base compiler when compiling stage1. */
436 /*------------------------------------------------------------------*
437 *-- The generic implementation based on frame layout assumptions --*
438 *------------------------------------------------------------------*/
440 #elif defined (USE_GENERIC_UNWINDER)
442 #ifndef CURRENT_STACK_FRAME
443 # define CURRENT_STACK_FRAME ({ char __csf; &__csf; })
446 #ifndef VALID_STACK_FRAME
447 #define VALID_STACK_FRAME(ptr) 1
451 #define MAX(x,y) ((x) > (y) ? (x) : (y))
458 /* Make sure the function is not inlined. */
459 static void forced_callee (void) __attribute__ ((noinline));
461 static void forced_callee (void)
463 /* Make sure the function is not pure. */
464 volatile int i __attribute__ ((unused)) = 0;
468 __gnat_backtrace (void **array,
474 struct layout *current;
476 void *top_stack ATTRIBUTE_UNUSED;
482 /* Force a call to builtin_frame_address with a positive argument
483 if required. This is necessary e.g. on SPARC to have the register
484 windows flushed before we attempt to access them on the stack. */
485 #if defined (FETCH_UP_FRAME_ADDRESS) && (FRAME_LEVEL == 0)
486 __builtin_frame_address (1);
489 top_frame = __builtin_frame_address (FRAME_LEVEL);
490 top_stack = CURRENT_STACK_FRAME;
491 current = (struct layout *) ((size_t) top_frame + FRAME_OFFSET (0));
493 /* Skip the number of calls we have been requested to skip, accounting for
494 the BASE_SKIP parameter.
496 FRAME_LEVEL is meaningless for the count adjustment. It impacts where we
497 start retrieving data from, but how many frames "up" we start at is in
498 BASE_SKIP by definition. */
500 skip_frames = MAX (0, skip_frames - BASE_SKIP);
502 while (cnt < skip_frames)
504 current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
511 if (STOP_FRAME (current, top_stack) ||
512 !VALID_STACK_FRAME(((char *) current->return_address) + PC_ADJUST))
515 if (current->return_address < exclude_min
516 || current->return_address > exclude_max)
517 array[cnt++] = ((char *) current->return_address) + PC_ADJUST;
519 current = (struct layout *) ((size_t) current->next + FRAME_OFFSET (1));
527 /* No target specific implementation and neither USE_GCC_UNWINDER nor
528 USE_GENERIC_UNWINDER defined. */
530 /*------------------------------*
531 *-- The dummy implementation --*
532 *------------------------------*/
535 __gnat_backtrace (void **array ATTRIBUTE_UNUSED,
536 int size ATTRIBUTE_UNUSED,
537 void *exclude_min ATTRIBUTE_UNUSED,
538 void *exclude_max ATTRIBUTE_UNUSED,
539 int skip_frames ATTRIBUTE_UNUSED)