1 /* Frame unwinder for frames with DWARF Call Frame Information.
3 Copyright 2003 Free Software Foundation, Inc.
5 Contributed by Mark Kettenis.
7 This file is part of GDB.
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 59 Temple Place - Suite 330,
22 Boston, MA 02111-1307, USA. */
25 #include "dwarf2expr.h"
26 #include "elf/dwarf2.h"
28 #include "frame-base.h"
29 #include "frame-unwind.h"
36 #include "gdb_assert.h"
37 #include "gdb_string.h"
39 #include "complaints.h"
40 #include "dwarf2-frame.h"
42 /* Call Frame Information (CFI). */
44 /* Common Information Entry (CIE). */
48 /* Offset into the .debug_frame section where this CIE was found.
49 Used to identify this CIE. */
52 /* Constant that is factored out of all advance location
54 ULONGEST code_alignment_factor
;
56 /* Constants that is factored out of all offset instructions. */
57 LONGEST data_alignment_factor
;
59 /* Return address column. */
60 ULONGEST return_address_register
;
62 /* Instruction sequence to initialize a register set. */
63 unsigned char *initial_instructions
;
66 /* Encoding of addresses. */
67 unsigned char encoding
;
69 /* True if a 'z' augmentation existed. */
70 unsigned char saw_z_augmentation
;
72 struct dwarf2_cie
*next
;
75 /* Frame Description Entry (FDE). */
79 /* CIE for this FDE. */
80 struct dwarf2_cie
*cie
;
82 /* First location associated with this FDE. */
83 CORE_ADDR initial_location
;
85 /* Number of bytes of program instructions described by this FDE. */
86 CORE_ADDR address_range
;
88 /* Instruction sequence. */
89 unsigned char *instructions
;
92 struct dwarf2_fde
*next
;
95 static struct dwarf2_fde
*dwarf2_frame_find_fde (CORE_ADDR
*pc
);
98 /* Structure describing a frame state. */
102 /* Make certain that 0 maps onto the correct enum value; the
103 corresponding structure is being initialized using memset zero.
104 This indicates that CFI didn't provide any information at all
105 about a register, leaving how to obtain its value totally
109 /* The term "undefined" comes from the DWARF2 CFI spec which this
110 code is moddeling; it indicates that the register's value is
111 "undefined". GCC uses the less formal term "unsaved". Its
112 definition is a combination of REG_UNDEFINED and REG_UNSPECIFIED.
113 The failure to differentiate the two helps explain a few problems
114 with the CFI generated by GCC. */
121 /* These aren't defined by the DWARF2 CFI specification, but are
122 used internally by GDB. */
123 REG_RA
, /* Return Address. */
124 REG_CFA
/* Call Frame Address. */
127 struct dwarf2_frame_state
129 /* Each register save state can be described in terms of a CFA slot,
130 another register, or a location expression. */
131 struct dwarf2_frame_state_reg_info
133 struct dwarf2_frame_state_reg
141 enum dwarf2_reg_rule how
;
145 /* Used to implement DW_CFA_remember_state. */
146 struct dwarf2_frame_state_reg_info
*prev
;
151 unsigned char *cfa_exp
;
158 /* The PC described by the current frame state. */
161 /* Initial register set from the CIE.
162 Used to implement DW_CFA_restore. */
163 struct dwarf2_frame_state_reg_info initial
;
165 /* The information we care about from the CIE. */
168 ULONGEST retaddr_column
;
171 /* Store the length the expression for the CFA in the `cfa_reg' field,
172 which is unused in that case. */
173 #define cfa_exp_len cfa_reg
175 /* Assert that the register set RS is large enough to store NUM_REGS
176 columns. If necessary, enlarge the register set. */
179 dwarf2_frame_state_alloc_regs (struct dwarf2_frame_state_reg_info
*rs
,
182 size_t size
= sizeof (struct dwarf2_frame_state_reg
);
184 if (num_regs
<= rs
->num_regs
)
187 rs
->reg
= (struct dwarf2_frame_state_reg
*)
188 xrealloc (rs
->reg
, num_regs
* size
);
190 /* Initialize newly allocated registers. */
191 memset (rs
->reg
+ rs
->num_regs
, 0, (num_regs
- rs
->num_regs
) * size
);
192 rs
->num_regs
= num_regs
;
195 /* Copy the register columns in register set RS into newly allocated
196 memory and return a pointer to this newly created copy. */
198 static struct dwarf2_frame_state_reg
*
199 dwarf2_frame_state_copy_regs (struct dwarf2_frame_state_reg_info
*rs
)
201 size_t size
= rs
->num_regs
* sizeof (struct dwarf2_frame_state_reg_info
);
202 struct dwarf2_frame_state_reg
*reg
;
204 reg
= (struct dwarf2_frame_state_reg
*) xmalloc (size
);
205 memcpy (reg
, rs
->reg
, size
);
210 /* Release the memory allocated to register set RS. */
213 dwarf2_frame_state_free_regs (struct dwarf2_frame_state_reg_info
*rs
)
217 dwarf2_frame_state_free_regs (rs
->prev
);
224 /* Release the memory allocated to the frame state FS. */
227 dwarf2_frame_state_free (void *p
)
229 struct dwarf2_frame_state
*fs
= p
;
231 dwarf2_frame_state_free_regs (fs
->initial
.prev
);
232 dwarf2_frame_state_free_regs (fs
->regs
.prev
);
233 xfree (fs
->initial
.reg
);
234 xfree (fs
->regs
.reg
);
239 /* Helper functions for execute_stack_op. */
242 read_reg (void *baton
, int reg
)
244 struct frame_info
*next_frame
= (struct frame_info
*) baton
;
248 regnum
= DWARF2_REG_TO_REGNUM (reg
);
250 buf
= (char *) alloca (register_size (current_gdbarch
, regnum
));
251 frame_unwind_register (next_frame
, regnum
, buf
);
252 return extract_typed_address (buf
, builtin_type_void_data_ptr
);
256 read_mem (void *baton
, char *buf
, CORE_ADDR addr
, size_t len
)
258 read_memory (addr
, buf
, len
);
262 no_get_frame_base (void *baton
, unsigned char **start
, size_t *length
)
264 internal_error (__FILE__
, __LINE__
,
265 "Support for DW_OP_fbreg is unimplemented");
269 no_get_tls_address (void *baton
, CORE_ADDR offset
)
271 internal_error (__FILE__
, __LINE__
,
272 "Support for DW_OP_GNU_push_tls_address is unimplemented");
276 execute_stack_op (unsigned char *exp
, ULONGEST len
,
277 struct frame_info
*next_frame
, CORE_ADDR initial
)
279 struct dwarf_expr_context
*ctx
;
282 ctx
= new_dwarf_expr_context ();
283 ctx
->baton
= next_frame
;
284 ctx
->read_reg
= read_reg
;
285 ctx
->read_mem
= read_mem
;
286 ctx
->get_frame_base
= no_get_frame_base
;
287 ctx
->get_tls_address
= no_get_tls_address
;
289 dwarf_expr_push (ctx
, initial
);
290 dwarf_expr_eval (ctx
, exp
, len
);
291 result
= dwarf_expr_fetch (ctx
, 0);
294 result
= read_reg (next_frame
, result
);
296 free_dwarf_expr_context (ctx
);
303 execute_cfa_program (unsigned char *insn_ptr
, unsigned char *insn_end
,
304 struct frame_info
*next_frame
,
305 struct dwarf2_frame_state
*fs
)
307 CORE_ADDR pc
= frame_pc_unwind (next_frame
);
310 while (insn_ptr
< insn_end
&& fs
->pc
<= pc
)
312 unsigned char insn
= *insn_ptr
++;
316 if ((insn
& 0xc0) == DW_CFA_advance_loc
)
317 fs
->pc
+= (insn
& 0x3f) * fs
->code_align
;
318 else if ((insn
& 0xc0) == DW_CFA_offset
)
321 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &utmp
);
322 offset
= utmp
* fs
->data_align
;
323 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
324 fs
->regs
.reg
[reg
].how
= REG_SAVED_OFFSET
;
325 fs
->regs
.reg
[reg
].loc
.offset
= offset
;
327 else if ((insn
& 0xc0) == DW_CFA_restore
)
329 gdb_assert (fs
->initial
.reg
);
331 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
332 fs
->regs
.reg
[reg
] = fs
->initial
.reg
[reg
];
339 fs
->pc
= dwarf2_read_address (insn_ptr
, insn_end
, &bytes_read
);
340 insn_ptr
+= bytes_read
;
343 case DW_CFA_advance_loc1
:
344 utmp
= extract_unsigned_integer (insn_ptr
, 1);
345 fs
->pc
+= utmp
* fs
->code_align
;
348 case DW_CFA_advance_loc2
:
349 utmp
= extract_unsigned_integer (insn_ptr
, 2);
350 fs
->pc
+= utmp
* fs
->code_align
;
353 case DW_CFA_advance_loc4
:
354 utmp
= extract_unsigned_integer (insn_ptr
, 4);
355 fs
->pc
+= utmp
* fs
->code_align
;
359 case DW_CFA_offset_extended
:
360 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, ®
);
361 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &utmp
);
362 offset
= utmp
* fs
->data_align
;
363 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
364 fs
->regs
.reg
[reg
].how
= REG_SAVED_OFFSET
;
365 fs
->regs
.reg
[reg
].loc
.offset
= offset
;
368 case DW_CFA_restore_extended
:
369 gdb_assert (fs
->initial
.reg
);
370 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, ®
);
371 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
372 fs
->regs
.reg
[reg
] = fs
->initial
.reg
[reg
];
375 case DW_CFA_undefined
:
376 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, ®
);
377 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
378 fs
->regs
.reg
[reg
].how
= REG_UNDEFINED
;
381 case DW_CFA_same_value
:
382 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, ®
);
383 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
384 fs
->regs
.reg
[reg
].how
= REG_SAME_VALUE
;
387 case DW_CFA_register
:
388 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, ®
);
389 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &utmp
);
390 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
391 fs
->regs
.reg
[reg
].how
= REG_SAVED_REG
;
392 fs
->regs
.reg
[reg
].loc
.reg
= utmp
;
395 case DW_CFA_remember_state
:
397 struct dwarf2_frame_state_reg_info
*new_rs
;
399 new_rs
= XMALLOC (struct dwarf2_frame_state_reg_info
);
401 fs
->regs
.reg
= dwarf2_frame_state_copy_regs (&fs
->regs
);
402 fs
->regs
.prev
= new_rs
;
406 case DW_CFA_restore_state
:
408 struct dwarf2_frame_state_reg_info
*old_rs
= fs
->regs
.prev
;
412 xfree (fs
->regs
.reg
);
419 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &fs
->cfa_reg
);
420 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &utmp
);
421 fs
->cfa_offset
= utmp
;
422 fs
->cfa_how
= CFA_REG_OFFSET
;
425 case DW_CFA_def_cfa_register
:
426 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &fs
->cfa_reg
);
427 fs
->cfa_how
= CFA_REG_OFFSET
;
430 case DW_CFA_def_cfa_offset
:
431 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &fs
->cfa_offset
);
432 /* cfa_how deliberately not set. */
438 case DW_CFA_def_cfa_expression
:
439 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &fs
->cfa_exp_len
);
440 fs
->cfa_exp
= insn_ptr
;
441 fs
->cfa_how
= CFA_EXP
;
442 insn_ptr
+= fs
->cfa_exp_len
;
445 case DW_CFA_expression
:
446 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, ®
);
447 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
448 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &utmp
);
449 fs
->regs
.reg
[reg
].loc
.exp
= insn_ptr
;
450 fs
->regs
.reg
[reg
].exp_len
= utmp
;
451 fs
->regs
.reg
[reg
].how
= REG_SAVED_EXP
;
455 case DW_CFA_offset_extended_sf
:
456 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, ®
);
457 insn_ptr
= read_sleb128 (insn_ptr
, insn_end
, &offset
);
458 offset
+= fs
->data_align
;
459 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
460 fs
->regs
.reg
[reg
].how
= REG_SAVED_OFFSET
;
461 fs
->regs
.reg
[reg
].loc
.offset
= offset
;
464 case DW_CFA_def_cfa_sf
:
465 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &fs
->cfa_reg
);
466 insn_ptr
= read_sleb128 (insn_ptr
, insn_end
, &offset
);
467 fs
->cfa_offset
= offset
* fs
->data_align
;
468 fs
->cfa_how
= CFA_REG_OFFSET
;
471 case DW_CFA_def_cfa_offset_sf
:
472 insn_ptr
= read_sleb128 (insn_ptr
, insn_end
, &offset
);
473 fs
->cfa_offset
= offset
* fs
->data_align
;
474 /* cfa_how deliberately not set. */
477 case DW_CFA_GNU_args_size
:
479 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &utmp
);
483 internal_error (__FILE__
, __LINE__
, "Unknown CFI encountered.");
488 /* Don't allow remember/restore between CIE and FDE programs. */
489 dwarf2_frame_state_free_regs (fs
->regs
.prev
);
490 fs
->regs
.prev
= NULL
;
493 struct dwarf2_frame_cache
495 /* DWARF Call Frame Address. */
498 /* Saved registers, indexed by GDB register number, not by DWARF
500 struct dwarf2_frame_state_reg
*reg
;
503 static struct dwarf2_frame_cache
*
504 dwarf2_frame_cache (struct frame_info
*next_frame
, void **this_cache
)
506 struct cleanup
*old_chain
;
507 const int num_regs
= NUM_REGS
+ NUM_PSEUDO_REGS
;
508 struct dwarf2_frame_cache
*cache
;
509 struct dwarf2_frame_state
*fs
;
510 struct dwarf2_fde
*fde
;
515 /* Allocate a new cache. */
516 cache
= FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache
);
517 cache
->reg
= FRAME_OBSTACK_CALLOC (num_regs
, struct dwarf2_frame_state_reg
);
519 /* Allocate and initialize the frame state. */
520 fs
= XMALLOC (struct dwarf2_frame_state
);
521 memset (fs
, 0, sizeof (struct dwarf2_frame_state
));
522 old_chain
= make_cleanup (dwarf2_frame_state_free
, fs
);
526 Note that if NEXT_FRAME is never supposed to return (i.e. a call
527 to abort), the compiler might optimize away the instruction at
528 NEXT_FRAME's return address. As a result the return address will
529 point at some random instruction, and the CFI for that
530 instruction is probably worthless to us. GCC's unwinder solves
531 this problem by substracting 1 from the return address to get an
532 address in the middle of a presumed call instruction (or the
533 instruction in the associated delay slot). This should only be
534 done for "normal" frames and not for resume-type frames (signal
535 handlers, sentinel frames, dummy frames). The function
536 frame_unwind_address_in_block does just this. It's not clear how
537 reliable the method is though; there is the potential for the
538 register state pre-call being different to that on return. */
539 fs
->pc
= frame_unwind_address_in_block (next_frame
);
541 /* Find the correct FDE. */
542 fde
= dwarf2_frame_find_fde (&fs
->pc
);
543 gdb_assert (fde
!= NULL
);
545 /* Extract any interesting information from the CIE. */
546 fs
->data_align
= fde
->cie
->data_alignment_factor
;
547 fs
->code_align
= fde
->cie
->code_alignment_factor
;
548 fs
->retaddr_column
= fde
->cie
->return_address_register
;
550 /* First decode all the insns in the CIE. */
551 execute_cfa_program (fde
->cie
->initial_instructions
,
552 fde
->cie
->end
, next_frame
, fs
);
554 /* Save the initialized register set. */
555 fs
->initial
= fs
->regs
;
556 fs
->initial
.reg
= dwarf2_frame_state_copy_regs (&fs
->regs
);
558 /* Then decode the insns in the FDE up to our target PC. */
559 execute_cfa_program (fde
->instructions
, fde
->end
, next_frame
, fs
);
561 /* Caclulate the CFA. */
565 cache
->cfa
= read_reg (next_frame
, fs
->cfa_reg
);
566 cache
->cfa
+= fs
->cfa_offset
;
571 execute_stack_op (fs
->cfa_exp
, fs
->cfa_exp_len
, next_frame
, 0);
575 internal_error (__FILE__
, __LINE__
, "Unknown CFA rule.");
578 /* Initialize the register rules. If we have a register that acts
579 as a program counter, mark it as a destination for the return
580 address. If we have a register that serves as the stack pointer,
581 arrange for it to be filled with the call frame address (CFA).
582 The other registers are marked as unspecified.
584 We copy the return address to the program counter, since many
585 parts in GDB assume that it is possible to get the return address
586 by unwind the program counter register. However, on ISA's with a
587 dedicated return address register, the CFI usually only contains
588 information to unwind that return address register.
590 The reason we're treating the stack pointer special here is
591 because in many cases GCC doesn't emit CFI for the stack pointer
592 and implicitly assumes that it is equal to the CFA. This makes
593 some sense since the DWARF specification (version 3, draft 8,
596 "Typically, the CFA is defined to be the value of the stack
597 pointer at the call site in the previous frame (which may be
598 different from its value on entry to the current frame)."
600 However, this isn't true for all platforms supported by GCC
601 (e.g. IBM S/390 and zSeries). For those targets we should
602 override the defaults given here. */
606 for (regnum
= 0; regnum
< num_regs
; regnum
++)
608 if (regnum
== PC_REGNUM
)
609 cache
->reg
[regnum
].how
= REG_RA
;
610 else if (regnum
== SP_REGNUM
)
611 cache
->reg
[regnum
].how
= REG_CFA
;
613 cache
->reg
[regnum
].how
= REG_UNSPECIFIED
;
617 /* Go through the DWARF2 CFI generated table and save its register
618 location information in the cache. Note that we don't skip the
619 return address column; it's perfectly all right for it to
620 correspond to a real register. If it doesn't correspond to a
621 real register, or if we shouldn't treat it as such,
622 DWARF2_REG_TO_REGNUM should be defined to return a number outside
623 the range [0, NUM_REGS). */
625 int column
; /* CFI speak for "register number". */
627 for (column
= 0; column
< fs
->regs
.num_regs
; column
++)
629 /* Use the GDB register number as the destination index. */
630 int regnum
= DWARF2_REG_TO_REGNUM (column
);
632 /* If there's no corresponding GDB register, ignore it. */
633 if (regnum
< 0 || regnum
>= num_regs
)
636 /* NOTE: cagney/2003-09-05: CFI should specify the disposition
637 of all debug info registers. If it doesn't, complain (but
638 not too loudly). It turns out that GCC assumes that an
639 unspecified register implies "same value" when CFI (draft
640 7) specifies nothing at all. Such a register could equally
641 be interpreted as "undefined". Also note that this check
642 isn't sufficient; it only checks that all registers in the
643 range [0 .. max column] are specified, and won't detect
644 problems when a debug info register falls outside of the
645 table. We need a way of iterating through all the valid
646 DWARF2 register numbers. */
647 if (fs
->regs
.reg
[column
].how
== REG_UNSPECIFIED
)
648 complaint (&symfile_complaints
,
649 "Incomplete CFI data; unspecified registers at 0x%s",
652 cache
->reg
[regnum
] = fs
->regs
.reg
[column
];
656 /* Eliminate any REG_RA rules. */
660 for (regnum
= 0; regnum
< num_regs
; regnum
++)
662 if (cache
->reg
[regnum
].how
== REG_RA
)
664 /* It seems rather bizarre to specify an "empty" column as
665 the return adress column. However, this is exactly
666 what GCC does on some targets. It turns out that GCC
667 assumes that the return address can be found in the
668 register corresponding to the return address column.
669 Incidentally, that's how should treat a return address
670 column specifying "same value" too. */
671 if (fs
->retaddr_column
< fs
->regs
.num_regs
672 && fs
->regs
.reg
[fs
->retaddr_column
].how
!= REG_UNSPECIFIED
673 && fs
->regs
.reg
[fs
->retaddr_column
].how
!= REG_SAME_VALUE
)
674 cache
->reg
[regnum
] = fs
->regs
.reg
[fs
->retaddr_column
];
677 cache
->reg
[regnum
].loc
.reg
= fs
->retaddr_column
;
678 cache
->reg
[regnum
].how
= REG_SAVED_REG
;
684 do_cleanups (old_chain
);
691 dwarf2_frame_this_id (struct frame_info
*next_frame
, void **this_cache
,
692 struct frame_id
*this_id
)
694 struct dwarf2_frame_cache
*cache
=
695 dwarf2_frame_cache (next_frame
, this_cache
);
697 (*this_id
) = frame_id_build (cache
->cfa
, frame_func_unwind (next_frame
));
701 dwarf2_frame_prev_register (struct frame_info
*next_frame
, void **this_cache
,
702 int regnum
, int *optimizedp
,
703 enum lval_type
*lvalp
, CORE_ADDR
*addrp
,
704 int *realnump
, void *valuep
)
706 struct dwarf2_frame_cache
*cache
=
707 dwarf2_frame_cache (next_frame
, this_cache
);
709 switch (cache
->reg
[regnum
].how
)
712 /* If CFI explicitly specified that the value isn't defined,
713 mark it as optimized away; the value isn't available. */
720 /* In some cases, for example %eflags on the i386, we have
721 to provide a sane value, even though this register wasn't
722 saved. Assume we can get it from NEXT_FRAME. */
723 frame_unwind_register (next_frame
, regnum
, valuep
);
727 case REG_SAVED_OFFSET
:
729 *lvalp
= lval_memory
;
730 *addrp
= cache
->cfa
+ cache
->reg
[regnum
].loc
.offset
;
734 /* Read the value in from memory. */
735 read_memory (*addrp
, valuep
,
736 register_size (current_gdbarch
, regnum
));
741 regnum
= DWARF2_REG_TO_REGNUM (cache
->reg
[regnum
].loc
.reg
);
742 frame_register_unwind (next_frame
, regnum
,
743 optimizedp
, lvalp
, addrp
, realnump
, valuep
);
748 *lvalp
= lval_memory
;
749 *addrp
= execute_stack_op (cache
->reg
[regnum
].loc
.exp
,
750 cache
->reg
[regnum
].exp_len
,
751 next_frame
, cache
->cfa
);
755 /* Read the value in from memory. */
756 read_memory (*addrp
, valuep
,
757 register_size (current_gdbarch
, regnum
));
761 case REG_UNSPECIFIED
:
762 /* GCC, in its infinite wisdom decided to not provide unwind
763 information for registers that are "same value". Since
764 DWARF2 (3 draft 7) doesn't define such behavior, said
765 registers are actually undefined (which is different to CFI
766 "undefined"). Code above issues a complaint about this.
767 Here just fudge the books, assume GCC, and that the value is
768 more inner on the stack. */
769 frame_register_unwind (next_frame
, regnum
,
770 optimizedp
, lvalp
, addrp
, realnump
, valuep
);
774 frame_register_unwind (next_frame
, regnum
,
775 optimizedp
, lvalp
, addrp
, realnump
, valuep
);
785 /* Store the value. */
786 store_typed_address (valuep
, builtin_type_void_data_ptr
, cache
->cfa
);
791 internal_error (__FILE__
, __LINE__
, "Unknown register rule.");
795 static const struct frame_unwind dwarf2_frame_unwind
=
798 dwarf2_frame_this_id
,
799 dwarf2_frame_prev_register
802 const struct frame_unwind
*
803 dwarf2_frame_sniffer (struct frame_info
*next_frame
)
805 /* Grab an address that is guarenteed to reside somewhere within the
806 function. frame_pc_unwind(), for a no-return next function, can
807 end up returning something past the end of this function's body. */
808 CORE_ADDR block_addr
= frame_unwind_address_in_block (next_frame
);
809 if (dwarf2_frame_find_fde (&block_addr
))
810 return &dwarf2_frame_unwind
;
816 /* There is no explicitly defined relationship between the CFA and the
817 location of frame's local variables and arguments/parameters.
818 Therefore, frame base methods on this page should probably only be
819 used as a last resort, just to avoid printing total garbage as a
820 response to the "info frame" command. */
823 dwarf2_frame_base_address (struct frame_info
*next_frame
, void **this_cache
)
825 struct dwarf2_frame_cache
*cache
=
826 dwarf2_frame_cache (next_frame
, this_cache
);
831 static const struct frame_base dwarf2_frame_base
=
833 &dwarf2_frame_unwind
,
834 dwarf2_frame_base_address
,
835 dwarf2_frame_base_address
,
836 dwarf2_frame_base_address
839 const struct frame_base
*
840 dwarf2_frame_base_sniffer (struct frame_info
*next_frame
)
842 CORE_ADDR pc
= frame_pc_unwind (next_frame
);
843 if (dwarf2_frame_find_fde (&pc
))
844 return &dwarf2_frame_base
;
849 /* A minimal decoding of DWARF2 compilation units. We only decode
850 what's needed to get to the call frame information. */
854 /* Keep the bfd convenient. */
857 struct objfile
*objfile
;
859 /* Linked list of CIEs for this object. */
860 struct dwarf2_cie
*cie
;
862 /* Address size for this unit - from unit header. */
863 unsigned char addr_size
;
865 /* Pointer to the .debug_frame section loaded into memory. */
866 char *dwarf_frame_buffer
;
868 /* Length of the loaded .debug_frame section. */
869 unsigned long dwarf_frame_size
;
871 /* Pointer to the .debug_frame section. */
872 asection
*dwarf_frame_section
;
874 /* Base for DW_EH_PE_datarel encodings. */
877 /* Base for DW_EH_PE_textrel encodings. */
881 const struct objfile_data
*dwarf2_frame_data
;
884 read_1_byte (bfd
*bfd
, char *buf
)
886 return bfd_get_8 (abfd
, (bfd_byte
*) buf
);
890 read_4_bytes (bfd
*abfd
, char *buf
)
892 return bfd_get_32 (abfd
, (bfd_byte
*) buf
);
896 read_8_bytes (bfd
*abfd
, char *buf
)
898 return bfd_get_64 (abfd
, (bfd_byte
*) buf
);
902 read_unsigned_leb128 (bfd
*abfd
, char *buf
, unsigned int *bytes_read_ptr
)
905 unsigned int num_read
;
915 byte
= bfd_get_8 (abfd
, (bfd_byte
*) buf
);
918 result
|= ((byte
& 0x7f) << shift
);
923 *bytes_read_ptr
= num_read
;
929 read_signed_leb128 (bfd
*abfd
, char *buf
, unsigned int *bytes_read_ptr
)
933 unsigned int num_read
;
942 byte
= bfd_get_8 (abfd
, (bfd_byte
*) buf
);
945 result
|= ((byte
& 0x7f) << shift
);
950 if ((shift
< 32) && (byte
& 0x40))
951 result
|= -(1 << shift
);
953 *bytes_read_ptr
= num_read
;
959 read_initial_length (bfd
*abfd
, char *buf
, unsigned int *bytes_read_ptr
)
963 result
= bfd_get_32 (abfd
, (bfd_byte
*) buf
);
964 if (result
== 0xffffffff)
966 result
= bfd_get_64 (abfd
, (bfd_byte
*) buf
+ 4);
967 *bytes_read_ptr
= 12;
976 /* Pointer encoding helper functions. */
978 /* GCC supports exception handling based on DWARF2 CFI. However, for
979 technical reasons, it encodes addresses in its FDE's in a different
980 way. Several "pointer encodings" are supported. The encoding
981 that's used for a particular FDE is determined by the 'R'
982 augmentation in the associated CIE. The argument of this
983 augmentation is a single byte.
985 The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
986 LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether
987 the address is signed or unsigned. Bits 4, 5 and 6 encode how the
988 address should be interpreted (absolute, relative to the current
989 position in the FDE, ...). Bit 7, indicates that the address
990 should be dereferenced. */
993 encoding_for_size (unsigned int size
)
998 return DW_EH_PE_udata2
;
1000 return DW_EH_PE_udata4
;
1002 return DW_EH_PE_udata8
;
1004 internal_error (__FILE__
, __LINE__
, "Unsupported address size");
1009 size_of_encoded_value (unsigned char encoding
)
1011 if (encoding
== DW_EH_PE_omit
)
1014 switch (encoding
& 0x07)
1016 case DW_EH_PE_absptr
:
1017 return TYPE_LENGTH (builtin_type_void_data_ptr
);
1018 case DW_EH_PE_udata2
:
1020 case DW_EH_PE_udata4
:
1022 case DW_EH_PE_udata8
:
1025 internal_error (__FILE__
, __LINE__
, "Invalid or unsupported encoding");
1030 read_encoded_value (struct comp_unit
*unit
, unsigned char encoding
,
1031 char *buf
, unsigned int *bytes_read_ptr
)
1033 int ptr_len
= size_of_encoded_value (DW_EH_PE_absptr
);
1037 /* GCC currently doesn't generate DW_EH_PE_indirect encodings for
1039 if (encoding
& DW_EH_PE_indirect
)
1040 internal_error (__FILE__
, __LINE__
,
1041 "Unsupported encoding: DW_EH_PE_indirect");
1043 *bytes_read_ptr
= 0;
1045 switch (encoding
& 0x70)
1047 case DW_EH_PE_absptr
:
1050 case DW_EH_PE_pcrel
:
1051 base
= bfd_get_section_vma (unit
->bfd
, unit
->dwarf_frame_section
);
1052 base
+= (buf
- unit
->dwarf_frame_buffer
);
1054 case DW_EH_PE_datarel
:
1057 case DW_EH_PE_textrel
:
1060 case DW_EH_PE_aligned
:
1062 offset
= buf
- unit
->dwarf_frame_buffer
;
1063 if ((offset
% ptr_len
) != 0)
1065 *bytes_read_ptr
= ptr_len
- (offset
% ptr_len
);
1066 buf
+= *bytes_read_ptr
;
1070 internal_error (__FILE__
, __LINE__
, "Invalid or unsupported encoding");
1073 if ((encoding
& 0x0f) == 0x00)
1074 encoding
|= encoding_for_size (ptr_len
);
1076 switch (encoding
& 0x0f)
1078 case DW_EH_PE_udata2
:
1079 *bytes_read_ptr
+= 2;
1080 return (base
+ bfd_get_16 (unit
->abfd
, (bfd_byte
*) buf
));
1081 case DW_EH_PE_udata4
:
1082 *bytes_read_ptr
+= 4;
1083 return (base
+ bfd_get_32 (unit
->abfd
, (bfd_byte
*) buf
));
1084 case DW_EH_PE_udata8
:
1085 *bytes_read_ptr
+= 8;
1086 return (base
+ bfd_get_64 (unit
->abfd
, (bfd_byte
*) buf
));
1087 case DW_EH_PE_sdata2
:
1088 *bytes_read_ptr
+= 2;
1089 return (base
+ bfd_get_signed_16 (unit
->abfd
, (bfd_byte
*) buf
));
1090 case DW_EH_PE_sdata4
:
1091 *bytes_read_ptr
+= 4;
1092 return (base
+ bfd_get_signed_32 (unit
->abfd
, (bfd_byte
*) buf
));
1093 case DW_EH_PE_sdata8
:
1094 *bytes_read_ptr
+= 8;
1095 return (base
+ bfd_get_signed_64 (unit
->abfd
, (bfd_byte
*) buf
));
1097 internal_error (__FILE__
, __LINE__
, "Invalid or unsupported encoding");
1102 /* GCC uses a single CIE for all FDEs in a .debug_frame section.
1103 That's why we use a simple linked list here. */
1105 static struct dwarf2_cie
*
1106 find_cie (struct comp_unit
*unit
, ULONGEST cie_pointer
)
1108 struct dwarf2_cie
*cie
= unit
->cie
;
1112 if (cie
->cie_pointer
== cie_pointer
)
1122 add_cie (struct comp_unit
*unit
, struct dwarf2_cie
*cie
)
1124 cie
->next
= unit
->cie
;
1128 /* Find the FDE for *PC. Return a pointer to the FDE, and store the
1129 inital location associated with it into *PC. */
1131 static struct dwarf2_fde
*
1132 dwarf2_frame_find_fde (CORE_ADDR
*pc
)
1134 struct objfile
*objfile
;
1136 ALL_OBJFILES (objfile
)
1138 struct dwarf2_fde
*fde
;
1141 fde
= objfile_data (objfile
, dwarf2_frame_data
);
1145 gdb_assert (objfile
->section_offsets
);
1146 offset
= ANOFFSET (objfile
->section_offsets
, SECT_OFF_TEXT (objfile
));
1150 if (*pc
>= fde
->initial_location
+ offset
1151 && *pc
< fde
->initial_location
+ offset
+ fde
->address_range
)
1153 *pc
= fde
->initial_location
+ offset
;
1165 add_fde (struct comp_unit
*unit
, struct dwarf2_fde
*fde
)
1167 fde
->next
= objfile_data (unit
->objfile
, dwarf2_frame_data
);
1168 set_objfile_data (unit
->objfile
, dwarf2_frame_data
, fde
);
1171 #ifdef CC_HAS_LONG_LONG
1172 #define DW64_CIE_ID 0xffffffffffffffffULL
1174 #define DW64_CIE_ID ~0
1177 static char *decode_frame_entry (struct comp_unit
*unit
, char *start
,
1180 /* Decode the next CIE or FDE. Return NULL if invalid input, otherwise
1181 the next byte to be processed. */
1183 decode_frame_entry_1 (struct comp_unit
*unit
, char *start
, int eh_frame_p
)
1187 unsigned int bytes_read
;
1190 ULONGEST cie_pointer
;
1194 length
= read_initial_length (unit
->abfd
, buf
, &bytes_read
);
1198 /* Are we still within the section? */
1199 if (end
> unit
->dwarf_frame_buffer
+ unit
->dwarf_frame_size
)
1205 /* Distinguish between 32 and 64-bit encoded frame info. */
1206 dwarf64_p
= (bytes_read
== 12);
1208 /* In a .eh_frame section, zero is used to distinguish CIEs from FDEs. */
1212 cie_id
= DW64_CIE_ID
;
1218 cie_pointer
= read_8_bytes (unit
->abfd
, buf
);
1223 cie_pointer
= read_4_bytes (unit
->abfd
, buf
);
1227 if (cie_pointer
== cie_id
)
1229 /* This is a CIE. */
1230 struct dwarf2_cie
*cie
;
1233 /* Record the offset into the .debug_frame section of this CIE. */
1234 cie_pointer
= start
- unit
->dwarf_frame_buffer
;
1236 /* Check whether we've already read it. */
1237 if (find_cie (unit
, cie_pointer
))
1240 cie
= (struct dwarf2_cie
*)
1241 obstack_alloc (&unit
->objfile
->psymbol_obstack
,
1242 sizeof (struct dwarf2_cie
));
1243 cie
->initial_instructions
= NULL
;
1244 cie
->cie_pointer
= cie_pointer
;
1246 /* The encoding for FDE's in a normal .debug_frame section
1247 depends on the target address size as specified in the
1248 Compilation Unit Header. */
1249 cie
->encoding
= encoding_for_size (unit
->addr_size
);
1251 /* Check version number. */
1252 if (read_1_byte (unit
->abfd
, buf
) != DW_CIE_VERSION
)
1256 /* Interpret the interesting bits of the augmentation. */
1258 buf
= augmentation
+ strlen (augmentation
) + 1;
1260 /* The GCC 2.x "eh" augmentation has a pointer immediately
1261 following the augmentation string, so it must be handled
1263 if (augmentation
[0] == 'e' && augmentation
[1] == 'h')
1266 buf
+= TYPE_LENGTH (builtin_type_void_data_ptr
);
1270 cie
->code_alignment_factor
=
1271 read_unsigned_leb128 (unit
->abfd
, buf
, &bytes_read
);
1274 cie
->data_alignment_factor
=
1275 read_signed_leb128 (unit
->abfd
, buf
, &bytes_read
);
1278 cie
->return_address_register
= read_1_byte (unit
->abfd
, buf
);
1281 cie
->saw_z_augmentation
= (*augmentation
== 'z');
1282 if (cie
->saw_z_augmentation
)
1286 length
= read_unsigned_leb128 (unit
->abfd
, buf
, &bytes_read
);
1290 cie
->initial_instructions
= buf
+ length
;
1294 while (*augmentation
)
1296 /* "L" indicates a byte showing how the LSDA pointer is encoded. */
1297 if (*augmentation
== 'L')
1304 /* "R" indicates a byte indicating how FDE addresses are encoded. */
1305 else if (*augmentation
== 'R')
1307 cie
->encoding
= *buf
++;
1311 /* "P" indicates a personality routine in the CIE augmentation. */
1312 else if (*augmentation
== 'P')
1315 buf
+= size_of_encoded_value (*buf
++);
1319 /* Otherwise we have an unknown augmentation.
1320 Bail out unless we saw a 'z' prefix. */
1323 if (cie
->initial_instructions
== NULL
)
1326 /* Skip unknown augmentations. */
1327 buf
= cie
->initial_instructions
;
1332 cie
->initial_instructions
= buf
;
1335 add_cie (unit
, cie
);
1339 /* This is a FDE. */
1340 struct dwarf2_fde
*fde
;
1342 /* In an .eh_frame section, the CIE pointer is the delta between the
1343 address within the FDE where the CIE pointer is stored and the
1344 address of the CIE. Convert it to an offset into the .eh_frame
1348 cie_pointer
= buf
- unit
->dwarf_frame_buffer
- cie_pointer
;
1349 cie_pointer
-= (dwarf64_p
? 8 : 4);
1352 /* In either case, validate the result is still within the section. */
1353 if (cie_pointer
>= unit
->dwarf_frame_size
)
1356 fde
= (struct dwarf2_fde
*)
1357 obstack_alloc (&unit
->objfile
->psymbol_obstack
,
1358 sizeof (struct dwarf2_fde
));
1359 fde
->cie
= find_cie (unit
, cie_pointer
);
1360 if (fde
->cie
== NULL
)
1362 decode_frame_entry (unit
, unit
->dwarf_frame_buffer
+ cie_pointer
,
1364 fde
->cie
= find_cie (unit
, cie_pointer
);
1367 gdb_assert (fde
->cie
!= NULL
);
1369 fde
->initial_location
=
1370 read_encoded_value (unit
, fde
->cie
->encoding
, buf
, &bytes_read
);
1373 fde
->address_range
=
1374 read_encoded_value (unit
, fde
->cie
->encoding
& 0x0f, buf
, &bytes_read
);
1377 /* A 'z' augmentation in the CIE implies the presence of an
1378 augmentation field in the FDE as well. The only thing known
1379 to be in here at present is the LSDA entry for EH. So we
1380 can skip the whole thing. */
1381 if (fde
->cie
->saw_z_augmentation
)
1385 length
= read_unsigned_leb128 (unit
->abfd
, buf
, &bytes_read
);
1386 buf
+= bytes_read
+ length
;
1391 fde
->instructions
= buf
;
1394 add_fde (unit
, fde
);
1400 /* Read a CIE or FDE in BUF and decode it. */
1402 decode_frame_entry (struct comp_unit
*unit
, char *start
, int eh_frame_p
)
1404 enum { NONE
, ALIGN4
, ALIGN8
, FAIL
} workaround
= NONE
;
1407 ptrdiff_t start_offset
;
1411 ret
= decode_frame_entry_1 (unit
, start
, eh_frame_p
);
1415 /* We have corrupt input data of some form. */
1417 /* ??? Try, weakly, to work around compiler/assembler/linker bugs
1418 and mismatches wrt padding and alignment of debug sections. */
1419 /* Note that there is no requirement in the standard for any
1420 alignment at all in the frame unwind sections. Testing for
1421 alignment before trying to interpret data would be incorrect.
1423 However, GCC traditionally arranged for frame sections to be
1424 sized such that the FDE length and CIE fields happen to be
1425 aligned (in theory, for performance). This, unfortunately,
1426 was done with .align directives, which had the side effect of
1427 forcing the section to be aligned by the linker.
1429 This becomes a problem when you have some other producer that
1430 creates frame sections that are not as strictly aligned. That
1431 produces a hole in the frame info that gets filled by the
1434 The GCC behaviour is arguably a bug, but it's effectively now
1435 part of the ABI, so we're now stuck with it, at least at the
1436 object file level. A smart linker may decide, in the process
1437 of compressing duplicate CIE information, that it can rewrite
1438 the entire output section without this extra padding. */
1440 start_offset
= start
- unit
->dwarf_frame_buffer
;
1441 if (workaround
< ALIGN4
&& (start_offset
& 3) != 0)
1443 start
+= 4 - (start_offset
& 3);
1444 workaround
= ALIGN4
;
1447 if (workaround
< ALIGN8
&& (start_offset
& 7) != 0)
1449 start
+= 8 - (start_offset
& 7);
1450 workaround
= ALIGN8
;
1454 /* Nothing left to try. Arrange to return as if we've consumed
1455 the entire input section. Hopefully we'll get valid info from
1456 the other of .debug_frame/.eh_frame. */
1458 ret
= unit
->dwarf_frame_buffer
+ unit
->dwarf_frame_size
;
1468 complaint (&symfile_complaints
,
1469 "Corrupt data in %s:%s; align 4 workaround apparently succeeded",
1470 unit
->dwarf_frame_section
->owner
->filename
,
1471 unit
->dwarf_frame_section
->name
);
1475 complaint (&symfile_complaints
,
1476 "Corrupt data in %s:%s; align 8 workaround apparently succeeded",
1477 unit
->dwarf_frame_section
->owner
->filename
,
1478 unit
->dwarf_frame_section
->name
);
1482 complaint (&symfile_complaints
,
1483 "Corrupt data in %s:%s",
1484 unit
->dwarf_frame_section
->owner
->filename
,
1485 unit
->dwarf_frame_section
->name
);
1494 /* FIXME: kettenis/20030504: This still needs to be integrated with
1495 dwarf2read.c in a better way. */
1497 /* Imported from dwarf2read.c. */
1498 extern asection
*dwarf_frame_section
;
1499 extern asection
*dwarf_eh_frame_section
;
1501 /* Imported from dwarf2read.c. */
1502 extern char *dwarf2_read_section (struct objfile
*objfile
, asection
*sectp
);
1505 dwarf2_build_frame_info (struct objfile
*objfile
)
1507 struct comp_unit unit
;
1510 /* Build a minimal decoding of the DWARF2 compilation unit. */
1511 unit
.abfd
= objfile
->obfd
;
1512 unit
.objfile
= objfile
;
1513 unit
.addr_size
= objfile
->obfd
->arch_info
->bits_per_address
/ 8;
1517 /* First add the information from the .eh_frame section. That way,
1518 the FDEs from that section are searched last. */
1519 if (dwarf_eh_frame_section
)
1521 asection
*got
, *txt
;
1524 unit
.dwarf_frame_buffer
= dwarf2_read_section (objfile
,
1525 dwarf_eh_frame_section
);
1527 unit
.dwarf_frame_size
1528 = bfd_get_section_size_before_reloc (dwarf_eh_frame_section
);
1529 unit
.dwarf_frame_section
= dwarf_eh_frame_section
;
1531 /* FIXME: kettenis/20030602: This is the DW_EH_PE_datarel base
1532 that is used for the i386/amd64 target, which currently is
1533 the only target in GCC that supports/uses the
1534 DW_EH_PE_datarel encoding. */
1535 got
= bfd_get_section_by_name (unit
.abfd
, ".got");
1537 unit
.dbase
= got
->vma
;
1539 /* GCC emits the DW_EH_PE_textrel encoding type on sh and ia64
1541 txt
= bfd_get_section_by_name (unit
.abfd
, ".text");
1543 unit
.tbase
= txt
->vma
;
1545 frame_ptr
= unit
.dwarf_frame_buffer
;
1546 while (frame_ptr
< unit
.dwarf_frame_buffer
+ unit
.dwarf_frame_size
)
1547 frame_ptr
= decode_frame_entry (&unit
, frame_ptr
, 1);
1550 if (dwarf_frame_section
)
1553 unit
.dwarf_frame_buffer
= dwarf2_read_section (objfile
,
1554 dwarf_frame_section
);
1555 unit
.dwarf_frame_size
1556 = bfd_get_section_size_before_reloc (dwarf_frame_section
);
1557 unit
.dwarf_frame_section
= dwarf_frame_section
;
1559 frame_ptr
= unit
.dwarf_frame_buffer
;
1560 while (frame_ptr
< unit
.dwarf_frame_buffer
+ unit
.dwarf_frame_size
)
1561 frame_ptr
= decode_frame_entry (&unit
, frame_ptr
, 0);
1565 /* Provide a prototype to silence -Wmissing-prototypes. */
1566 void _initialize_dwarf2_frame (void);
1569 _initialize_dwarf2_frame (void)
1571 dwarf2_frame_data
= register_objfile_data ();