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. */
435 case DW_CFA_def_cfa_expression
:
436 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &fs
->cfa_exp_len
);
437 fs
->cfa_exp
= insn_ptr
;
438 fs
->cfa_how
= CFA_EXP
;
439 insn_ptr
+= fs
->cfa_exp_len
;
442 case DW_CFA_expression
:
443 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, ®
);
444 dwarf2_frame_state_alloc_regs (&fs
->regs
, reg
+ 1);
445 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &utmp
);
446 fs
->regs
.reg
[reg
].loc
.exp
= insn_ptr
;
447 fs
->regs
.reg
[reg
].exp_len
= utmp
;
448 fs
->regs
.reg
[reg
].how
= REG_SAVED_EXP
;
455 case DW_CFA_GNU_args_size
:
457 insn_ptr
= read_uleb128 (insn_ptr
, insn_end
, &utmp
);
461 internal_error (__FILE__
, __LINE__
, "Unknown CFI encountered.");
466 /* Don't allow remember/restore between CIE and FDE programs. */
467 dwarf2_frame_state_free_regs (fs
->regs
.prev
);
468 fs
->regs
.prev
= NULL
;
471 struct dwarf2_frame_cache
473 /* DWARF Call Frame Address. */
476 /* Saved registers, indexed by GDB register number, not by DWARF
478 struct dwarf2_frame_state_reg
*reg
;
481 static struct dwarf2_frame_cache
*
482 dwarf2_frame_cache (struct frame_info
*next_frame
, void **this_cache
)
484 struct cleanup
*old_chain
;
485 const int num_regs
= NUM_REGS
+ NUM_PSEUDO_REGS
;
486 struct dwarf2_frame_cache
*cache
;
487 struct dwarf2_frame_state
*fs
;
488 struct dwarf2_fde
*fde
;
493 /* Allocate a new cache. */
494 cache
= FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache
);
495 cache
->reg
= FRAME_OBSTACK_CALLOC (num_regs
, struct dwarf2_frame_state_reg
);
497 /* Allocate and initialize the frame state. */
498 fs
= XMALLOC (struct dwarf2_frame_state
);
499 memset (fs
, 0, sizeof (struct dwarf2_frame_state
));
500 old_chain
= make_cleanup (dwarf2_frame_state_free
, fs
);
504 Note that if NEXT_FRAME is never supposed to return (i.e. a call
505 to abort), the compiler might optimize away the instruction at
506 NEXT_FRAME's return address. As a result the return address will
507 point at some random instruction, and the CFI for that
508 instruction is probably worthless to us. GCC's unwinder solves
509 this problem by substracting 1 from the return address to get an
510 address in the middle of a presumed call instruction (or the
511 instruction in the associated delay slot). This should only be
512 done for "normal" frames and not for resume-type frames (signal
513 handlers, sentinel frames, dummy frames). The function
514 frame_unwind_address_in_block does just this. It's not clear how
515 reliable the method is though; there is the potential for the
516 register state pre-call being different to that on return. */
517 fs
->pc
= frame_unwind_address_in_block (next_frame
);
519 /* Find the correct FDE. */
520 fde
= dwarf2_frame_find_fde (&fs
->pc
);
521 gdb_assert (fde
!= NULL
);
523 /* Extract any interesting information from the CIE. */
524 fs
->data_align
= fde
->cie
->data_alignment_factor
;
525 fs
->code_align
= fde
->cie
->code_alignment_factor
;
526 fs
->retaddr_column
= fde
->cie
->return_address_register
;
528 /* First decode all the insns in the CIE. */
529 execute_cfa_program (fde
->cie
->initial_instructions
,
530 fde
->cie
->end
, next_frame
, fs
);
532 /* Save the initialized register set. */
533 fs
->initial
= fs
->regs
;
534 fs
->initial
.reg
= dwarf2_frame_state_copy_regs (&fs
->regs
);
536 /* Then decode the insns in the FDE up to our target PC. */
537 execute_cfa_program (fde
->instructions
, fde
->end
, next_frame
, fs
);
539 /* Caclulate the CFA. */
543 cache
->cfa
= read_reg (next_frame
, fs
->cfa_reg
);
544 cache
->cfa
+= fs
->cfa_offset
;
549 execute_stack_op (fs
->cfa_exp
, fs
->cfa_exp_len
, next_frame
, 0);
553 internal_error (__FILE__
, __LINE__
, "Unknown CFA rule.");
556 /* Initialize the register rules. If we have a register that acts
557 as a program counter, mark it as a destination for the return
558 address. If we have a register that serves as the stack pointer,
559 arrange for it to be filled with the call frame address (CFA).
560 The other registers are marked as unspecified.
562 We copy the return address to the program counter, since many
563 parts in GDB assume that it is possible to get the return address
564 by unwind the program counter register. However, on ISA's with a
565 dedicated return address register, the CFI usually only contains
566 information to unwind that return address register.
568 The reason we're treating the stack pointer special here is
569 because in many cases GCC doesn't emit CFI for the stack pointer
570 and implicitly assumes that it is equal to the CFA. This makes
571 some sense since the DWARF specification (version 3, draft 8,
574 "Typically, the CFA is defined to be the value of the stack
575 pointer at the call site in the previous frame (which may be
576 different from its value on entry to the current frame)."
578 However, this isn't true for all platforms supported by GCC
579 (e.g. IBM S/390 and zSeries). For those targets we should
580 override the defaults given here. */
584 for (regnum
= 0; regnum
< num_regs
; regnum
++)
586 if (regnum
== PC_REGNUM
)
587 cache
->reg
[regnum
].how
= REG_RA
;
588 else if (regnum
== SP_REGNUM
)
589 cache
->reg
[regnum
].how
= REG_CFA
;
591 cache
->reg
[regnum
].how
= REG_UNSPECIFIED
;
595 /* Go through the DWARF2 CFI generated table and save its register
596 location information in the cache. Note that we don't skip the
597 return address column; it's perfectly all right for it to
598 correspond to a real register. If it doesn't correspond to a
599 real register, or if we shouldn't treat it as such,
600 DWARF2_REG_TO_REGNUM should be defined to return a number outside
601 the range [0, NUM_REGS). */
603 int column
; /* CFI speak for "register number". */
605 for (column
= 0; column
< fs
->regs
.num_regs
; column
++)
607 /* Use the GDB register number as the destination index. */
608 int regnum
= DWARF2_REG_TO_REGNUM (column
);
610 /* If there's no corresponding GDB register, ignore it. */
611 if (regnum
< 0 || regnum
>= num_regs
)
614 /* NOTE: cagney/2003-09-05: CFI should specify the disposition
615 of all debug info registers. If it doesn't, complain (but
616 not too loudly). It turns out that GCC assumes that an
617 unspecified register implies "same value" when CFI (draft
618 7) specifies nothing at all. Such a register could equally
619 be interpreted as "undefined". Also note that this check
620 isn't sufficient; it only checks that all registers in the
621 range [0 .. max column] are specified, and won't detect
622 problems when a debug info register falls outside of the
623 table. We need a way of iterating through all the valid
624 DWARF2 register numbers. */
625 if (fs
->regs
.reg
[column
].how
== REG_UNSPECIFIED
)
626 complaint (&symfile_complaints
,
627 "Incomplete CFI data; unspecified registers at 0x%s",
630 cache
->reg
[regnum
] = fs
->regs
.reg
[column
];
634 /* Eliminate any REG_RA rules. */
638 for (regnum
= 0; regnum
< num_regs
; regnum
++)
640 if (cache
->reg
[regnum
].how
== REG_RA
)
642 if (fs
->retaddr_column
< fs
->regs
.num_regs
)
643 cache
->reg
[regnum
] = fs
->regs
.reg
[fs
->retaddr_column
];
646 /* It turns out that GCC assumes that if the return
647 address column is "empty" the return address can be
648 found in the register corresponding to the return
650 cache
->reg
[regnum
].loc
.reg
= fs
->retaddr_column
;
651 cache
->reg
[regnum
].how
= REG_SAVED_REG
;
657 do_cleanups (old_chain
);
664 dwarf2_frame_this_id (struct frame_info
*next_frame
, void **this_cache
,
665 struct frame_id
*this_id
)
667 struct dwarf2_frame_cache
*cache
=
668 dwarf2_frame_cache (next_frame
, this_cache
);
670 (*this_id
) = frame_id_build (cache
->cfa
, frame_func_unwind (next_frame
));
674 dwarf2_frame_prev_register (struct frame_info
*next_frame
, void **this_cache
,
675 int regnum
, int *optimizedp
,
676 enum lval_type
*lvalp
, CORE_ADDR
*addrp
,
677 int *realnump
, void *valuep
)
679 struct dwarf2_frame_cache
*cache
=
680 dwarf2_frame_cache (next_frame
, this_cache
);
682 switch (cache
->reg
[regnum
].how
)
685 /* If CFI explicitly specified that the value isn't defined,
686 mark it as optimized away; the value isn't available. */
693 /* In some cases, for example %eflags on the i386, we have
694 to provide a sane value, even though this register wasn't
695 saved. Assume we can get it from NEXT_FRAME. */
696 frame_unwind_register (next_frame
, regnum
, valuep
);
700 case REG_SAVED_OFFSET
:
702 *lvalp
= lval_memory
;
703 *addrp
= cache
->cfa
+ cache
->reg
[regnum
].loc
.offset
;
707 /* Read the value in from memory. */
708 read_memory (*addrp
, valuep
,
709 register_size (current_gdbarch
, regnum
));
714 regnum
= DWARF2_REG_TO_REGNUM (cache
->reg
[regnum
].loc
.reg
);
715 frame_register_unwind (next_frame
, regnum
,
716 optimizedp
, lvalp
, addrp
, realnump
, valuep
);
721 *lvalp
= lval_memory
;
722 *addrp
= execute_stack_op (cache
->reg
[regnum
].loc
.exp
,
723 cache
->reg
[regnum
].exp_len
,
724 next_frame
, cache
->cfa
);
728 /* Read the value in from memory. */
729 read_memory (*addrp
, valuep
,
730 register_size (current_gdbarch
, regnum
));
734 case REG_UNSPECIFIED
:
735 /* GCC, in its infinite wisdom decided to not provide unwind
736 information for registers that are "same value". Since
737 DWARF2 (3 draft 7) doesn't define such behavior, said
738 registers are actually undefined (which is different to CFI
739 "undefined"). Code above issues a complaint about this.
740 Here just fudge the books, assume GCC, and that the value is
741 more inner on the stack. */
742 frame_register_unwind (next_frame
, regnum
,
743 optimizedp
, lvalp
, addrp
, realnump
, valuep
);
747 frame_register_unwind (next_frame
, regnum
,
748 optimizedp
, lvalp
, addrp
, realnump
, valuep
);
758 /* Store the value. */
759 store_typed_address (valuep
, builtin_type_void_data_ptr
, cache
->cfa
);
764 internal_error (__FILE__
, __LINE__
, "Unknown register rule.");
768 static const struct frame_unwind dwarf2_frame_unwind
=
771 dwarf2_frame_this_id
,
772 dwarf2_frame_prev_register
775 const struct frame_unwind
*
776 dwarf2_frame_sniffer (struct frame_info
*next_frame
)
778 /* Grab an address that is guarenteed to reside somewhere within the
779 function. frame_pc_unwind(), for a no-return next function, can
780 end up returning something past the end of this function's body. */
781 CORE_ADDR block_addr
= frame_unwind_address_in_block (next_frame
);
782 if (dwarf2_frame_find_fde (&block_addr
))
783 return &dwarf2_frame_unwind
;
789 /* There is no explicitly defined relationship between the CFA and the
790 location of frame's local variables and arguments/parameters.
791 Therefore, frame base methods on this page should probably only be
792 used as a last resort, just to avoid printing total garbage as a
793 response to the "info frame" command. */
796 dwarf2_frame_base_address (struct frame_info
*next_frame
, void **this_cache
)
798 struct dwarf2_frame_cache
*cache
=
799 dwarf2_frame_cache (next_frame
, this_cache
);
804 static const struct frame_base dwarf2_frame_base
=
806 &dwarf2_frame_unwind
,
807 dwarf2_frame_base_address
,
808 dwarf2_frame_base_address
,
809 dwarf2_frame_base_address
812 const struct frame_base
*
813 dwarf2_frame_base_sniffer (struct frame_info
*next_frame
)
815 CORE_ADDR pc
= frame_pc_unwind (next_frame
);
816 if (dwarf2_frame_find_fde (&pc
))
817 return &dwarf2_frame_base
;
822 /* A minimal decoding of DWARF2 compilation units. We only decode
823 what's needed to get to the call frame information. */
827 /* Keep the bfd convenient. */
830 struct objfile
*objfile
;
832 /* Linked list of CIEs for this object. */
833 struct dwarf2_cie
*cie
;
835 /* Address size for this unit - from unit header. */
836 unsigned char addr_size
;
838 /* Pointer to the .debug_frame section loaded into memory. */
839 char *dwarf_frame_buffer
;
841 /* Length of the loaded .debug_frame section. */
842 unsigned long dwarf_frame_size
;
844 /* Pointer to the .debug_frame section. */
845 asection
*dwarf_frame_section
;
847 /* Base for DW_EH_PE_datarel encodings. */
850 /* Base for DW_EH_PE_textrel encodings. */
854 const struct objfile_data
*dwarf2_frame_data
;
857 read_1_byte (bfd
*bfd
, char *buf
)
859 return bfd_get_8 (abfd
, (bfd_byte
*) buf
);
863 read_4_bytes (bfd
*abfd
, char *buf
)
865 return bfd_get_32 (abfd
, (bfd_byte
*) buf
);
869 read_8_bytes (bfd
*abfd
, char *buf
)
871 return bfd_get_64 (abfd
, (bfd_byte
*) buf
);
875 read_unsigned_leb128 (bfd
*abfd
, char *buf
, unsigned int *bytes_read_ptr
)
878 unsigned int num_read
;
888 byte
= bfd_get_8 (abfd
, (bfd_byte
*) buf
);
891 result
|= ((byte
& 0x7f) << shift
);
896 *bytes_read_ptr
= num_read
;
902 read_signed_leb128 (bfd
*abfd
, char *buf
, unsigned int *bytes_read_ptr
)
906 unsigned int num_read
;
915 byte
= bfd_get_8 (abfd
, (bfd_byte
*) buf
);
918 result
|= ((byte
& 0x7f) << shift
);
923 if ((shift
< 32) && (byte
& 0x40))
924 result
|= -(1 << shift
);
926 *bytes_read_ptr
= num_read
;
932 read_initial_length (bfd
*abfd
, char *buf
, unsigned int *bytes_read_ptr
)
936 result
= bfd_get_32 (abfd
, (bfd_byte
*) buf
);
937 if (result
== 0xffffffff)
939 result
= bfd_get_64 (abfd
, (bfd_byte
*) buf
+ 4);
940 *bytes_read_ptr
= 12;
949 /* Pointer encoding helper functions. */
951 /* GCC supports exception handling based on DWARF2 CFI. However, for
952 technical reasons, it encodes addresses in its FDE's in a different
953 way. Several "pointer encodings" are supported. The encoding
954 that's used for a particular FDE is determined by the 'R'
955 augmentation in the associated CIE. The argument of this
956 augmentation is a single byte.
958 The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
959 LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether
960 the address is signed or unsigned. Bits 4, 5 and 6 encode how the
961 address should be interpreted (absolute, relative to the current
962 position in the FDE, ...). Bit 7, indicates that the address
963 should be dereferenced. */
966 encoding_for_size (unsigned int size
)
971 return DW_EH_PE_udata2
;
973 return DW_EH_PE_udata4
;
975 return DW_EH_PE_udata8
;
977 internal_error (__FILE__
, __LINE__
, "Unsupported address size");
982 size_of_encoded_value (unsigned char encoding
)
984 if (encoding
== DW_EH_PE_omit
)
987 switch (encoding
& 0x07)
989 case DW_EH_PE_absptr
:
990 return TYPE_LENGTH (builtin_type_void_data_ptr
);
991 case DW_EH_PE_udata2
:
993 case DW_EH_PE_udata4
:
995 case DW_EH_PE_udata8
:
998 internal_error (__FILE__
, __LINE__
, "Invalid or unsupported encoding");
1003 read_encoded_value (struct comp_unit
*unit
, unsigned char encoding
,
1004 char *buf
, unsigned int *bytes_read_ptr
)
1006 int ptr_len
= size_of_encoded_value (DW_EH_PE_absptr
);
1010 /* GCC currently doesn't generate DW_EH_PE_indirect encodings for
1012 if (encoding
& DW_EH_PE_indirect
)
1013 internal_error (__FILE__
, __LINE__
,
1014 "Unsupported encoding: DW_EH_PE_indirect");
1016 *bytes_read_ptr
= 0;
1018 switch (encoding
& 0x70)
1020 case DW_EH_PE_absptr
:
1023 case DW_EH_PE_pcrel
:
1024 base
= bfd_get_section_vma (unit
->bfd
, unit
->dwarf_frame_section
);
1025 base
+= (buf
- unit
->dwarf_frame_buffer
);
1027 case DW_EH_PE_datarel
:
1030 case DW_EH_PE_textrel
:
1033 case DW_EH_PE_aligned
:
1035 offset
= buf
- unit
->dwarf_frame_buffer
;
1036 if ((offset
% ptr_len
) != 0)
1038 *bytes_read_ptr
= ptr_len
- (offset
% ptr_len
);
1039 buf
+= *bytes_read_ptr
;
1043 internal_error (__FILE__
, __LINE__
, "Invalid or unsupported encoding");
1046 if ((encoding
& 0x0f) == 0x00)
1047 encoding
|= encoding_for_size (ptr_len
);
1049 switch (encoding
& 0x0f)
1051 case DW_EH_PE_udata2
:
1052 *bytes_read_ptr
+= 2;
1053 return (base
+ bfd_get_16 (unit
->abfd
, (bfd_byte
*) buf
));
1054 case DW_EH_PE_udata4
:
1055 *bytes_read_ptr
+= 4;
1056 return (base
+ bfd_get_32 (unit
->abfd
, (bfd_byte
*) buf
));
1057 case DW_EH_PE_udata8
:
1058 *bytes_read_ptr
+= 8;
1059 return (base
+ bfd_get_64 (unit
->abfd
, (bfd_byte
*) buf
));
1060 case DW_EH_PE_sdata2
:
1061 *bytes_read_ptr
+= 2;
1062 return (base
+ bfd_get_signed_16 (unit
->abfd
, (bfd_byte
*) buf
));
1063 case DW_EH_PE_sdata4
:
1064 *bytes_read_ptr
+= 4;
1065 return (base
+ bfd_get_signed_32 (unit
->abfd
, (bfd_byte
*) buf
));
1066 case DW_EH_PE_sdata8
:
1067 *bytes_read_ptr
+= 8;
1068 return (base
+ bfd_get_signed_64 (unit
->abfd
, (bfd_byte
*) buf
));
1070 internal_error (__FILE__
, __LINE__
, "Invalid or unsupported encoding");
1075 /* GCC uses a single CIE for all FDEs in a .debug_frame section.
1076 That's why we use a simple linked list here. */
1078 static struct dwarf2_cie
*
1079 find_cie (struct comp_unit
*unit
, ULONGEST cie_pointer
)
1081 struct dwarf2_cie
*cie
= unit
->cie
;
1085 if (cie
->cie_pointer
== cie_pointer
)
1095 add_cie (struct comp_unit
*unit
, struct dwarf2_cie
*cie
)
1097 cie
->next
= unit
->cie
;
1101 /* Find the FDE for *PC. Return a pointer to the FDE, and store the
1102 inital location associated with it into *PC. */
1104 static struct dwarf2_fde
*
1105 dwarf2_frame_find_fde (CORE_ADDR
*pc
)
1107 struct objfile
*objfile
;
1109 ALL_OBJFILES (objfile
)
1111 struct dwarf2_fde
*fde
;
1114 fde
= objfile_data (objfile
, dwarf2_frame_data
);
1118 gdb_assert (objfile
->section_offsets
);
1119 offset
= ANOFFSET (objfile
->section_offsets
, SECT_OFF_TEXT (objfile
));
1123 if (*pc
>= fde
->initial_location
+ offset
1124 && *pc
< fde
->initial_location
+ offset
+ fde
->address_range
)
1126 *pc
= fde
->initial_location
+ offset
;
1138 add_fde (struct comp_unit
*unit
, struct dwarf2_fde
*fde
)
1140 fde
->next
= objfile_data (unit
->objfile
, dwarf2_frame_data
);
1141 set_objfile_data (unit
->objfile
, dwarf2_frame_data
, fde
);
1144 #ifdef CC_HAS_LONG_LONG
1145 #define DW64_CIE_ID 0xffffffffffffffffULL
1147 #define DW64_CIE_ID ~0
1150 static char *decode_frame_entry (struct comp_unit
*unit
, char *start
,
1153 /* Decode the next CIE or FDE. Return NULL if invalid input, otherwise
1154 the next byte to be processed. */
1156 decode_frame_entry_1 (struct comp_unit
*unit
, char *start
, int eh_frame_p
)
1160 unsigned int bytes_read
;
1163 ULONGEST cie_pointer
;
1167 length
= read_initial_length (unit
->abfd
, buf
, &bytes_read
);
1171 /* Are we still within the section? */
1172 if (end
> unit
->dwarf_frame_buffer
+ unit
->dwarf_frame_size
)
1178 /* Distinguish between 32 and 64-bit encoded frame info. */
1179 dwarf64_p
= (bytes_read
== 12);
1181 /* In a .eh_frame section, zero is used to distinguish CIEs from FDEs. */
1185 cie_id
= DW64_CIE_ID
;
1191 cie_pointer
= read_8_bytes (unit
->abfd
, buf
);
1196 cie_pointer
= read_4_bytes (unit
->abfd
, buf
);
1200 if (cie_pointer
== cie_id
)
1202 /* This is a CIE. */
1203 struct dwarf2_cie
*cie
;
1206 /* Record the offset into the .debug_frame section of this CIE. */
1207 cie_pointer
= start
- unit
->dwarf_frame_buffer
;
1209 /* Check whether we've already read it. */
1210 if (find_cie (unit
, cie_pointer
))
1213 cie
= (struct dwarf2_cie
*)
1214 obstack_alloc (&unit
->objfile
->psymbol_obstack
,
1215 sizeof (struct dwarf2_cie
));
1216 cie
->initial_instructions
= NULL
;
1217 cie
->cie_pointer
= cie_pointer
;
1219 /* The encoding for FDE's in a normal .debug_frame section
1220 depends on the target address size as specified in the
1221 Compilation Unit Header. */
1222 cie
->encoding
= encoding_for_size (unit
->addr_size
);
1224 /* Check version number. */
1225 if (read_1_byte (unit
->abfd
, buf
) != DW_CIE_VERSION
)
1229 /* Interpret the interesting bits of the augmentation. */
1231 buf
= augmentation
+ strlen (augmentation
) + 1;
1233 /* The GCC 2.x "eh" augmentation has a pointer immediately
1234 following the augmentation string, so it must be handled
1236 if (augmentation
[0] == 'e' && augmentation
[1] == 'h')
1239 buf
+= TYPE_LENGTH (builtin_type_void_data_ptr
);
1243 cie
->code_alignment_factor
=
1244 read_unsigned_leb128 (unit
->abfd
, buf
, &bytes_read
);
1247 cie
->data_alignment_factor
=
1248 read_signed_leb128 (unit
->abfd
, buf
, &bytes_read
);
1251 cie
->return_address_register
= read_1_byte (unit
->abfd
, buf
);
1254 cie
->saw_z_augmentation
= (*augmentation
== 'z');
1255 if (cie
->saw_z_augmentation
)
1259 length
= read_unsigned_leb128 (unit
->abfd
, buf
, &bytes_read
);
1263 cie
->initial_instructions
= buf
+ length
;
1267 while (*augmentation
)
1269 /* "L" indicates a byte showing how the LSDA pointer is encoded. */
1270 if (*augmentation
== 'L')
1277 /* "R" indicates a byte indicating how FDE addresses are encoded. */
1278 else if (*augmentation
== 'R')
1280 cie
->encoding
= *buf
++;
1284 /* "P" indicates a personality routine in the CIE augmentation. */
1285 else if (*augmentation
== 'P')
1288 buf
+= size_of_encoded_value (*buf
++);
1292 /* Otherwise we have an unknown augmentation.
1293 Bail out unless we saw a 'z' prefix. */
1296 if (cie
->initial_instructions
== NULL
)
1299 /* Skip unknown augmentations. */
1300 buf
= cie
->initial_instructions
;
1305 cie
->initial_instructions
= buf
;
1308 add_cie (unit
, cie
);
1312 /* This is a FDE. */
1313 struct dwarf2_fde
*fde
;
1315 /* In an .eh_frame section, the CIE pointer is the delta between the
1316 address within the FDE where the CIE pointer is stored and the
1317 address of the CIE. Convert it to an offset into the .eh_frame
1321 cie_pointer
= buf
- unit
->dwarf_frame_buffer
- cie_pointer
;
1322 cie_pointer
-= (dwarf64_p
? 8 : 4);
1325 /* In either case, validate the result is still within the section. */
1326 if (cie_pointer
>= unit
->dwarf_frame_size
)
1329 fde
= (struct dwarf2_fde
*)
1330 obstack_alloc (&unit
->objfile
->psymbol_obstack
,
1331 sizeof (struct dwarf2_fde
));
1332 fde
->cie
= find_cie (unit
, cie_pointer
);
1333 if (fde
->cie
== NULL
)
1335 decode_frame_entry (unit
, unit
->dwarf_frame_buffer
+ cie_pointer
,
1337 fde
->cie
= find_cie (unit
, cie_pointer
);
1340 gdb_assert (fde
->cie
!= NULL
);
1342 fde
->initial_location
=
1343 read_encoded_value (unit
, fde
->cie
->encoding
, buf
, &bytes_read
);
1346 fde
->address_range
=
1347 read_encoded_value (unit
, fde
->cie
->encoding
& 0x0f, buf
, &bytes_read
);
1350 /* A 'z' augmentation in the CIE implies the presence of an
1351 augmentation field in the FDE as well. The only thing known
1352 to be in here at present is the LSDA entry for EH. So we
1353 can skip the whole thing. */
1354 if (fde
->cie
->saw_z_augmentation
)
1358 length
= read_unsigned_leb128 (unit
->abfd
, buf
, &bytes_read
);
1359 buf
+= bytes_read
+ length
;
1364 fde
->instructions
= buf
;
1367 add_fde (unit
, fde
);
1373 /* Read a CIE or FDE in BUF and decode it. */
1375 decode_frame_entry (struct comp_unit
*unit
, char *start
, int eh_frame_p
)
1377 enum { NONE
, ALIGN4
, ALIGN8
, FAIL
} workaround
= NONE
;
1380 ptrdiff_t start_offset
;
1384 ret
= decode_frame_entry_1 (unit
, start
, eh_frame_p
);
1388 /* We have corrupt input data of some form. */
1390 /* ??? Try, weakly, to work around compiler/assembler/linker bugs
1391 and mismatches wrt padding and alignment of debug sections. */
1392 /* Note that there is no requirement in the standard for any
1393 alignment at all in the frame unwind sections. Testing for
1394 alignment before trying to interpret data would be incorrect.
1396 However, GCC traditionally arranged for frame sections to be
1397 sized such that the FDE length and CIE fields happen to be
1398 aligned (in theory, for performance). This, unfortunately,
1399 was done with .align directives, which had the side effect of
1400 forcing the section to be aligned by the linker.
1402 This becomes a problem when you have some other producer that
1403 creates frame sections that are not as strictly aligned. That
1404 produces a hole in the frame info that gets filled by the
1407 The GCC behaviour is arguably a bug, but it's effectively now
1408 part of the ABI, so we're now stuck with it, at least at the
1409 object file level. A smart linker may decide, in the process
1410 of compressing duplicate CIE information, that it can rewrite
1411 the entire output section without this extra padding. */
1413 start_offset
= start
- unit
->dwarf_frame_buffer
;
1414 if (workaround
< ALIGN4
&& (start_offset
& 3) != 0)
1416 start
+= 4 - (start_offset
& 3);
1417 workaround
= ALIGN4
;
1420 if (workaround
< ALIGN8
&& (start_offset
& 7) != 0)
1422 start
+= 8 - (start_offset
& 7);
1423 workaround
= ALIGN8
;
1427 /* Nothing left to try. Arrange to return as if we've consumed
1428 the entire input section. Hopefully we'll get valid info from
1429 the other of .debug_frame/.eh_frame. */
1431 ret
= unit
->dwarf_frame_buffer
+ unit
->dwarf_frame_size
;
1441 complaint (&symfile_complaints
,
1442 "Corrupt data in %s:%s; align 4 workaround apparently succeeded",
1443 unit
->dwarf_frame_section
->owner
->filename
,
1444 unit
->dwarf_frame_section
->name
);
1448 complaint (&symfile_complaints
,
1449 "Corrupt data in %s:%s; align 8 workaround apparently succeeded",
1450 unit
->dwarf_frame_section
->owner
->filename
,
1451 unit
->dwarf_frame_section
->name
);
1455 complaint (&symfile_complaints
,
1456 "Corrupt data in %s:%s",
1457 unit
->dwarf_frame_section
->owner
->filename
,
1458 unit
->dwarf_frame_section
->name
);
1467 /* FIXME: kettenis/20030504: This still needs to be integrated with
1468 dwarf2read.c in a better way. */
1470 /* Imported from dwarf2read.c. */
1471 extern asection
*dwarf_frame_section
;
1472 extern asection
*dwarf_eh_frame_section
;
1474 /* Imported from dwarf2read.c. */
1475 extern char *dwarf2_read_section (struct objfile
*objfile
, asection
*sectp
);
1478 dwarf2_build_frame_info (struct objfile
*objfile
)
1480 struct comp_unit unit
;
1483 /* Build a minimal decoding of the DWARF2 compilation unit. */
1484 unit
.abfd
= objfile
->obfd
;
1485 unit
.objfile
= objfile
;
1486 unit
.addr_size
= objfile
->obfd
->arch_info
->bits_per_address
/ 8;
1490 /* First add the information from the .eh_frame section. That way,
1491 the FDEs from that section are searched last. */
1492 if (dwarf_eh_frame_section
)
1494 asection
*got
, *txt
;
1497 unit
.dwarf_frame_buffer
= dwarf2_read_section (objfile
,
1498 dwarf_eh_frame_section
);
1500 unit
.dwarf_frame_size
1501 = bfd_get_section_size_before_reloc (dwarf_eh_frame_section
);
1502 unit
.dwarf_frame_section
= dwarf_eh_frame_section
;
1504 /* FIXME: kettenis/20030602: This is the DW_EH_PE_datarel base
1505 that is used for the i386/amd64 target, which currently is
1506 the only target in GCC that supports/uses the
1507 DW_EH_PE_datarel encoding. */
1508 got
= bfd_get_section_by_name (unit
.abfd
, ".got");
1510 unit
.dbase
= got
->vma
;
1512 /* GCC emits the DW_EH_PE_textrel encoding type on sh and ia64
1514 txt
= bfd_get_section_by_name (unit
.abfd
, ".text");
1516 unit
.tbase
= txt
->vma
;
1518 frame_ptr
= unit
.dwarf_frame_buffer
;
1519 while (frame_ptr
< unit
.dwarf_frame_buffer
+ unit
.dwarf_frame_size
)
1520 frame_ptr
= decode_frame_entry (&unit
, frame_ptr
, 1);
1523 if (dwarf_frame_section
)
1526 unit
.dwarf_frame_buffer
= dwarf2_read_section (objfile
,
1527 dwarf_frame_section
);
1528 unit
.dwarf_frame_size
1529 = bfd_get_section_size_before_reloc (dwarf_frame_section
);
1530 unit
.dwarf_frame_section
= dwarf_frame_section
;
1532 frame_ptr
= unit
.dwarf_frame_buffer
;
1533 while (frame_ptr
< unit
.dwarf_frame_buffer
+ unit
.dwarf_frame_size
)
1534 frame_ptr
= decode_frame_entry (&unit
, frame_ptr
, 0);
1538 /* Provide a prototype to silence -Wmissing-prototypes. */
1539 void _initialize_dwarf2_frame (void);
1542 _initialize_dwarf2_frame (void)
1544 dwarf2_frame_data
= register_objfile_data ();