1 /* Frame unwinder for frames with DWARF Call Frame Information.
3 Copyright 2003, 2004 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. */
100 struct dwarf2_frame_state
102 /* Each register save state can be described in terms of a CFA slot,
103 another register, or a location expression. */
104 struct dwarf2_frame_state_reg_info
106 struct dwarf2_frame_state_reg *reg;
109 /* Used to implement DW_CFA_remember_state. */
110 struct dwarf2_frame_state_reg_info *prev;
115 unsigned char *cfa_exp;
122 /* The PC described by the current frame state. */
125 /* Initial register set from the CIE.
126 Used to implement DW_CFA_restore. */
127 struct dwarf2_frame_state_reg_info initial;
129 /* The information we care about from the CIE. */
132 ULONGEST retaddr_column;
135 /* Store the length the expression for the CFA in the `cfa_reg' field,
136 which is unused in that case. */
137 #define cfa_exp_len cfa_reg
139 /* Assert that the register set RS is large enough to store NUM_REGS
140 columns. If necessary, enlarge the register set. */
143 dwarf2_frame_state_alloc_regs (struct dwarf2_frame_state_reg_info *rs,
146 size_t size = sizeof (struct dwarf2_frame_state_reg);
148 if (num_regs <= rs->num_regs)
151 rs->reg = (struct dwarf2_frame_state_reg *)
152 xrealloc (rs->reg, num_regs * size);
154 /* Initialize newly allocated registers. */
155 memset (rs->reg + rs->num_regs, 0, (num_regs - rs->num_regs) * size);
156 rs->num_regs = num_regs;
159 /* Copy the register columns in register set RS into newly allocated
160 memory and return a pointer to this newly created copy. */
162 static struct dwarf2_frame_state_reg *
163 dwarf2_frame_state_copy_regs (struct dwarf2_frame_state_reg_info *rs)
165 size_t size = rs->num_regs * sizeof (struct dwarf2_frame_state_reg_info);
166 struct dwarf2_frame_state_reg *reg;
168 reg = (struct dwarf2_frame_state_reg *) xmalloc (size);
169 memcpy (reg, rs->reg, size);
174 /* Release the memory allocated to register set RS. */
177 dwarf2_frame_state_free_regs (struct dwarf2_frame_state_reg_info *rs)
181 dwarf2_frame_state_free_regs (rs->prev);
188 /* Release the memory allocated to the frame state FS. */
191 dwarf2_frame_state_free (void *p)
193 struct dwarf2_frame_state *fs = p;
195 dwarf2_frame_state_free_regs (fs->initial.prev);
196 dwarf2_frame_state_free_regs (fs->regs.prev);
197 xfree (fs->initial.reg);
198 xfree (fs->regs.reg);
203 /* Helper functions for execute_stack_op. */
206 read_reg (void *baton, int reg)
208 struct frame_info *next_frame = (struct frame_info *) baton;
209 struct gdbarch *gdbarch = get_frame_arch (next_frame);
213 regnum = DWARF2_REG_TO_REGNUM (reg);
215 buf = (char *) alloca (register_size (gdbarch, regnum));
216 frame_unwind_register (next_frame, regnum, buf);
217 return extract_typed_address (buf, builtin_type_void_data_ptr);
221 read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len)
223 read_memory (addr, buf, len);
227 no_get_frame_base (void *baton, unsigned char **start, size_t *length)
229 internal_error (__FILE__, __LINE__,
230 "Support for DW_OP_fbreg is unimplemented");
234 no_get_tls_address (void *baton, CORE_ADDR offset)
236 internal_error (__FILE__, __LINE__,
237 "Support for DW_OP_GNU_push_tls_address is unimplemented");
241 execute_stack_op (unsigned char *exp, ULONGEST len,
242 struct frame_info *next_frame, CORE_ADDR initial)
244 struct dwarf_expr_context *ctx;
247 ctx = new_dwarf_expr_context ();
248 ctx->baton = next_frame;
249 ctx->read_reg = read_reg;
250 ctx->read_mem = read_mem;
251 ctx->get_frame_base = no_get_frame_base;
252 ctx->get_tls_address = no_get_tls_address;
254 dwarf_expr_push (ctx, initial);
255 dwarf_expr_eval (ctx, exp, len);
256 result = dwarf_expr_fetch (ctx, 0);
259 result = read_reg (next_frame, result);
261 free_dwarf_expr_context (ctx);
268 execute_cfa_program (unsigned char *insn_ptr, unsigned char *insn_end,
269 struct frame_info *next_frame,
270 struct dwarf2_frame_state *fs)
272 CORE_ADDR pc = frame_pc_unwind (next_frame);
275 while (insn_ptr < insn_end && fs->pc <= pc)
277 unsigned char insn = *insn_ptr++;
281 if ((insn & 0xc0) == DW_CFA_advance_loc)
282 fs->pc += (insn & 0x3f) * fs->code_align;
283 else if ((insn & 0xc0) == DW_CFA_offset)
286 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
287 offset = utmp * fs->data_align;
288 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
289 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
290 fs->regs.reg[reg].loc.offset = offset;
292 else if ((insn & 0xc0) == DW_CFA_restore)
294 gdb_assert (fs->initial.reg);
296 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
297 fs->regs.reg[reg] = fs->initial.reg[reg];
304 fs->pc = dwarf2_read_address (insn_ptr, insn_end, &bytes_read);
305 insn_ptr += bytes_read;
308 case DW_CFA_advance_loc1:
309 utmp = extract_unsigned_integer (insn_ptr, 1);
310 fs->pc += utmp * fs->code_align;
313 case DW_CFA_advance_loc2:
314 utmp = extract_unsigned_integer (insn_ptr, 2);
315 fs->pc += utmp * fs->code_align;
318 case DW_CFA_advance_loc4:
319 utmp = extract_unsigned_integer (insn_ptr, 4);
320 fs->pc += utmp * fs->code_align;
324 case DW_CFA_offset_extended:
325 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
326 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
327 offset = utmp * fs->data_align;
328 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
329 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
330 fs->regs.reg[reg].loc.offset = offset;
333 case DW_CFA_restore_extended:
334 gdb_assert (fs->initial.reg);
335 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
336 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
337 fs->regs.reg[reg] = fs->initial.reg[reg];
340 case DW_CFA_undefined:
341 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
342 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
343 fs->regs.reg[reg].how = DWARF2_FRAME_REG_UNDEFINED;
346 case DW_CFA_same_value:
347 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
348 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
349 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAME_VALUE;
352 case DW_CFA_register:
353 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
354 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
355 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
356 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_REG;
357 fs->regs.reg[reg].loc.reg = utmp;
360 case DW_CFA_remember_state:
362 struct dwarf2_frame_state_reg_info *new_rs;
364 new_rs = XMALLOC (struct dwarf2_frame_state_reg_info);
366 fs->regs.reg = dwarf2_frame_state_copy_regs (&fs->regs);
367 fs->regs.prev = new_rs;
371 case DW_CFA_restore_state:
373 struct dwarf2_frame_state_reg_info *old_rs = fs->regs.prev;
377 xfree (fs->regs.reg);
384 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
385 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
386 fs->cfa_offset = utmp;
387 fs->cfa_how = CFA_REG_OFFSET;
390 case DW_CFA_def_cfa_register:
391 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
392 fs->cfa_how = CFA_REG_OFFSET;
395 case DW_CFA_def_cfa_offset:
396 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_offset);
397 /* cfa_how deliberately not set. */
403 case DW_CFA_def_cfa_expression:
404 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_exp_len);
405 fs->cfa_exp = insn_ptr;
406 fs->cfa_how = CFA_EXP;
407 insn_ptr += fs->cfa_exp_len;
410 case DW_CFA_expression:
411 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
412 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
413 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
414 fs->regs.reg[reg].loc.exp = insn_ptr;
415 fs->regs.reg[reg].exp_len = utmp;
416 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_EXP;
420 case DW_CFA_offset_extended_sf:
421 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
422 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
423 offset += fs->data_align;
424 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
425 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
426 fs->regs.reg[reg].loc.offset = offset;
429 case DW_CFA_def_cfa_sf:
430 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
431 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
432 fs->cfa_offset = offset * fs->data_align;
433 fs->cfa_how = CFA_REG_OFFSET;
436 case DW_CFA_def_cfa_offset_sf:
437 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
438 fs->cfa_offset = offset * fs->data_align;
439 /* cfa_how deliberately not set. */
442 case DW_CFA_GNU_args_size:
444 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
448 internal_error (__FILE__, __LINE__, "Unknown CFI encountered.");
453 /* Don't allow remember/restore between CIE and FDE programs. */
454 dwarf2_frame_state_free_regs (fs->regs.prev);
455 fs->regs.prev = NULL;
459 /* Architecture-specific operations. */
461 /* Per-architecture data key. */
462 static struct gdbarch_data *dwarf2_frame_data;
464 struct dwarf2_frame_ops
466 /* Pre-initialize the register state REG for register REGNUM. */
467 void (*init_reg) (struct gdbarch *, int, struct dwarf2_frame_state_reg *);
470 /* Default architecture-specific register state initialization
474 dwarf2_frame_default_init_reg (struct gdbarch *gdbarch, int regnum,
475 struct dwarf2_frame_state_reg *reg)
477 /* If we have a register that acts as a program counter, mark it as
478 a destination for the return address. If we have a register that
479 serves as the stack pointer, arrange for it to be filled with the
480 call frame address (CFA). The other registers are marked as
483 We copy the return address to the program counter, since many
484 parts in GDB assume that it is possible to get the return address
485 by unwinding the program counter register. However, on ISA's
486 with a dedicated return address register, the CFI usually only
487 contains information to unwind that return address register.
489 The reason we're treating the stack pointer special here is
490 because in many cases GCC doesn't emit CFI for the stack pointer
491 and implicitly assumes that it is equal to the CFA. This makes
492 some sense since the DWARF specification (version 3, draft 8,
495 "Typically, the CFA is defined to be the value of the stack
496 pointer at the call site in the previous frame (which may be
497 different from its value on entry to the current frame)."
499 However, this isn't true for all platforms supported by GCC
500 (e.g. IBM S/390 and zSeries). Those architectures should provide
501 their own architecture-specific initialization function. */
503 if (regnum == PC_REGNUM)
504 reg->how = DWARF2_FRAME_REG_RA;
505 else if (regnum == SP_REGNUM)
506 reg->how = DWARF2_FRAME_REG_CFA;
509 /* Return a default for the architecture-specific operations. */
512 dwarf2_frame_init (struct gdbarch *gdbarch)
514 struct dwarf2_frame_ops *ops;
516 ops = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct dwarf2_frame_ops);
517 ops->init_reg = dwarf2_frame_default_init_reg;
521 /* Set the architecture-specific register state initialization
522 function for GDBARCH to INIT_REG. */
525 dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
526 void (*init_reg) (struct gdbarch *, int,
527 struct dwarf2_frame_state_reg *))
529 struct dwarf2_frame_ops *ops;
531 ops = gdbarch_data (gdbarch, dwarf2_frame_data);
532 ops->init_reg = init_reg;
535 /* Pre-initialize the register state REG for register REGNUM. */
538 dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
539 struct dwarf2_frame_state_reg *reg)
541 struct dwarf2_frame_ops *ops;
543 ops = gdbarch_data (gdbarch, dwarf2_frame_data);
544 ops->init_reg (gdbarch, regnum, reg);
548 struct dwarf2_frame_cache
550 /* DWARF Call Frame Address. */
553 /* Saved registers, indexed by GDB register number, not by DWARF
555 struct dwarf2_frame_state_reg *reg;
558 static struct dwarf2_frame_cache *
559 dwarf2_frame_cache (struct frame_info *next_frame, void **this_cache)
561 struct cleanup *old_chain;
562 struct gdbarch *gdbarch = get_frame_arch (next_frame);
563 const int num_regs = NUM_REGS + NUM_PSEUDO_REGS;
564 struct dwarf2_frame_cache *cache;
565 struct dwarf2_frame_state *fs;
566 struct dwarf2_fde *fde;
571 /* Allocate a new cache. */
572 cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache);
573 cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg);
575 /* Allocate and initialize the frame state. */
576 fs = XMALLOC (struct dwarf2_frame_state);
577 memset (fs, 0, sizeof (struct dwarf2_frame_state));
578 old_chain = make_cleanup (dwarf2_frame_state_free, fs);
582 Note that if NEXT_FRAME is never supposed to return (i.e. a call
583 to abort), the compiler might optimize away the instruction at
584 NEXT_FRAME's return address. As a result the return address will
585 point at some random instruction, and the CFI for that
586 instruction is probably worthless to us. GCC's unwinder solves
587 this problem by substracting 1 from the return address to get an
588 address in the middle of a presumed call instruction (or the
589 instruction in the associated delay slot). This should only be
590 done for "normal" frames and not for resume-type frames (signal
591 handlers, sentinel frames, dummy frames). The function
592 frame_unwind_address_in_block does just this. It's not clear how
593 reliable the method is though; there is the potential for the
594 register state pre-call being different to that on return. */
595 fs->pc = frame_unwind_address_in_block (next_frame);
597 /* Find the correct FDE. */
598 fde = dwarf2_frame_find_fde (&fs->pc);
599 gdb_assert (fde != NULL);
601 /* Extract any interesting information from the CIE. */
602 fs->data_align = fde->cie->data_alignment_factor;
603 fs->code_align = fde->cie->code_alignment_factor;
604 fs->retaddr_column = fde->cie->return_address_register;
606 /* First decode all the insns in the CIE. */
607 execute_cfa_program (fde->cie->initial_instructions,
608 fde->cie->end, next_frame, fs);
610 /* Save the initialized register set. */
611 fs->initial = fs->regs;
612 fs->initial.reg = dwarf2_frame_state_copy_regs (&fs->regs);
614 /* Then decode the insns in the FDE up to our target PC. */
615 execute_cfa_program (fde->instructions, fde->end, next_frame, fs);
617 /* Caclulate the CFA. */
621 cache->cfa = read_reg (next_frame, fs->cfa_reg);
622 cache->cfa += fs->cfa_offset;
627 execute_stack_op (fs->cfa_exp, fs->cfa_exp_len, next_frame, 0);
631 internal_error (__FILE__, __LINE__, "Unknown CFA rule.");
634 /* Initialize the register state. */
638 for (regnum = 0; regnum < num_regs; regnum++)
639 dwarf2_frame_init_reg (gdbarch, regnum, &cache->reg[regnum]);
642 /* Go through the DWARF2 CFI generated table and save its register
643 location information in the cache. Note that we don't skip the
644 return address column; it's perfectly all right for it to
645 correspond to a real register. If it doesn't correspond to a
646 real register, or if we shouldn't treat it as such,
647 DWARF2_REG_TO_REGNUM should be defined to return a number outside
648 the range [0, NUM_REGS). */
650 int column; /* CFI speak for "register number". */
652 for (column = 0; column < fs->regs.num_regs; column++)
654 /* Use the GDB register number as the destination index. */
655 int regnum = DWARF2_REG_TO_REGNUM (column);
657 /* If there's no corresponding GDB register, ignore it. */
658 if (regnum < 0 || regnum >= num_regs)
661 /* NOTE: cagney/2003-09-05: CFI should specify the disposition
662 of all debug info registers. If it doesn't, complain (but
663 not too loudly). It turns out that GCC assumes that an
664 unspecified register implies "same value" when CFI (draft
665 7) specifies nothing at all. Such a register could equally
666 be interpreted as "undefined". Also note that this check
667 isn't sufficient; it only checks that all registers in the
668 range [0 .. max column] are specified, and won't detect
669 problems when a debug info register falls outside of the
670 table. We need a way of iterating through all the valid
671 DWARF2 register numbers. */
672 if (fs->regs.reg[column].how == DWARF2_FRAME_REG_UNSPECIFIED)
673 complaint (&symfile_complaints,
674 "Incomplete CFI data; unspecified registers at 0x%s",
677 cache->reg[regnum] = fs->regs.reg[column];
681 /* Eliminate any DWARF2_FRAME_REG_RA rules. */
685 for (regnum = 0; regnum < num_regs; regnum++)
687 if (cache->reg[regnum].how == DWARF2_FRAME_REG_RA)
689 struct dwarf2_frame_state_reg *retaddr_reg =
690 &fs->regs.reg[fs->retaddr_column];
692 /* It seems rather bizarre to specify an "empty" column as
693 the return adress column. However, this is exactly
694 what GCC does on some targets. It turns out that GCC
695 assumes that the return address can be found in the
696 register corresponding to the return address column.
697 Incidentally, that's how should treat a return address
698 column specifying "same value" too. */
699 if (fs->retaddr_column < fs->regs.num_regs
700 && retaddr_reg->how != DWARF2_FRAME_REG_UNSPECIFIED
701 && retaddr_reg->how != DWARF2_FRAME_REG_SAME_VALUE)
702 cache->reg[regnum] = *retaddr_reg;
705 cache->reg[regnum].loc.reg = fs->retaddr_column;
706 cache->reg[regnum].how = DWARF2_FRAME_REG_SAVED_REG;
712 do_cleanups (old_chain);
719 dwarf2_frame_this_id (struct frame_info *next_frame, void **this_cache,
720 struct frame_id *this_id)
722 struct dwarf2_frame_cache *cache =
723 dwarf2_frame_cache (next_frame, this_cache);
725 (*this_id) = frame_id_build (cache->cfa, frame_func_unwind (next_frame));
729 dwarf2_frame_prev_register (struct frame_info *next_frame, void **this_cache,
730 int regnum, int *optimizedp,
731 enum lval_type *lvalp, CORE_ADDR *addrp,
732 int *realnump, void *valuep)
734 struct gdbarch *gdbarch = get_frame_arch (next_frame);
735 struct dwarf2_frame_cache *cache =
736 dwarf2_frame_cache (next_frame, this_cache);
738 switch (cache->reg[regnum].how)
740 case DWARF2_FRAME_REG_UNDEFINED:
741 /* If CFI explicitly specified that the value isn't defined,
742 mark it as optimized away; the value isn't available. */
749 /* In some cases, for example %eflags on the i386, we have
750 to provide a sane value, even though this register wasn't
751 saved. Assume we can get it from NEXT_FRAME. */
752 frame_unwind_register (next_frame, regnum, valuep);
756 case DWARF2_FRAME_REG_SAVED_OFFSET:
758 *lvalp = lval_memory;
759 *addrp = cache->cfa + cache->reg[regnum].loc.offset;
763 /* Read the value in from memory. */
764 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
768 case DWARF2_FRAME_REG_SAVED_REG:
769 regnum = DWARF2_REG_TO_REGNUM (cache->reg[regnum].loc.reg);
770 frame_register_unwind (next_frame, regnum,
771 optimizedp, lvalp, addrp, realnump, valuep);
774 case DWARF2_FRAME_REG_SAVED_EXP:
776 *lvalp = lval_memory;
777 *addrp = execute_stack_op (cache->reg[regnum].loc.exp,
778 cache->reg[regnum].exp_len,
779 next_frame, cache->cfa);
783 /* Read the value in from memory. */
784 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
788 case DWARF2_FRAME_REG_UNSPECIFIED:
789 /* GCC, in its infinite wisdom decided to not provide unwind
790 information for registers that are "same value". Since
791 DWARF2 (3 draft 7) doesn't define such behavior, said
792 registers are actually undefined (which is different to CFI
793 "undefined"). Code above issues a complaint about this.
794 Here just fudge the books, assume GCC, and that the value is
795 more inner on the stack. */
796 frame_register_unwind (next_frame, regnum,
797 optimizedp, lvalp, addrp, realnump, valuep);
800 case DWARF2_FRAME_REG_SAME_VALUE:
801 frame_register_unwind (next_frame, regnum,
802 optimizedp, lvalp, addrp, realnump, valuep);
805 case DWARF2_FRAME_REG_CFA:
812 /* Store the value. */
813 store_typed_address (valuep, builtin_type_void_data_ptr, cache->cfa);
818 internal_error (__FILE__, __LINE__, "Unknown register rule.");
822 static const struct frame_unwind dwarf2_frame_unwind =
825 dwarf2_frame_this_id,
826 dwarf2_frame_prev_register
829 const struct frame_unwind *
830 dwarf2_frame_sniffer (struct frame_info *next_frame)
832 /* Grab an address that is guarenteed to reside somewhere within the
833 function. frame_pc_unwind(), for a no-return next function, can
834 end up returning something past the end of this function's body. */
835 CORE_ADDR block_addr = frame_unwind_address_in_block (next_frame);
836 if (dwarf2_frame_find_fde (&block_addr))
837 return &dwarf2_frame_unwind;
843 /* There is no explicitly defined relationship between the CFA and the
844 location of frame's local variables and arguments/parameters.
845 Therefore, frame base methods on this page should probably only be
846 used as a last resort, just to avoid printing total garbage as a
847 response to the "info frame" command. */
850 dwarf2_frame_base_address (struct frame_info *next_frame, void **this_cache)
852 struct dwarf2_frame_cache *cache =
853 dwarf2_frame_cache (next_frame, this_cache);
858 static const struct frame_base dwarf2_frame_base =
860 &dwarf2_frame_unwind,
861 dwarf2_frame_base_address,
862 dwarf2_frame_base_address,
863 dwarf2_frame_base_address
866 const struct frame_base *
867 dwarf2_frame_base_sniffer (struct frame_info *next_frame)
869 CORE_ADDR pc = frame_pc_unwind (next_frame);
870 if (dwarf2_frame_find_fde (&pc))
871 return &dwarf2_frame_base;
876 /* A minimal decoding of DWARF2 compilation units. We only decode
877 what's needed to get to the call frame information. */
881 /* Keep the bfd convenient. */
884 struct objfile *objfile;
886 /* Linked list of CIEs for this object. */
887 struct dwarf2_cie *cie;
889 /* Address size for this unit - from unit header. */
890 unsigned char addr_size;
892 /* Pointer to the .debug_frame section loaded into memory. */
893 char *dwarf_frame_buffer;
895 /* Length of the loaded .debug_frame section. */
896 unsigned long dwarf_frame_size;
898 /* Pointer to the .debug_frame section. */
899 asection *dwarf_frame_section;
901 /* Base for DW_EH_PE_datarel encodings. */
904 /* Base for DW_EH_PE_textrel encodings. */
908 const struct objfile_data *dwarf2_frame_objfile_data;
911 read_1_byte (bfd *bfd, char *buf)
913 return bfd_get_8 (abfd, (bfd_byte *) buf);
917 read_4_bytes (bfd *abfd, char *buf)
919 return bfd_get_32 (abfd, (bfd_byte *) buf);
923 read_8_bytes (bfd *abfd, char *buf)
925 return bfd_get_64 (abfd, (bfd_byte *) buf);
929 read_unsigned_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
932 unsigned int num_read;
942 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
945 result |= ((byte & 0x7f) << shift);
950 *bytes_read_ptr = num_read;
956 read_signed_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
960 unsigned int num_read;
969 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
972 result |= ((byte & 0x7f) << shift);
977 if ((shift < 32) && (byte & 0x40))
978 result |= -(1 << shift);
980 *bytes_read_ptr = num_read;
986 read_initial_length (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
990 result = bfd_get_32 (abfd, (bfd_byte *) buf);
991 if (result == 0xffffffff)
993 result = bfd_get_64 (abfd, (bfd_byte *) buf + 4);
994 *bytes_read_ptr = 12;
1003 /* Pointer encoding helper functions. */
1005 /* GCC supports exception handling based on DWARF2 CFI. However, for
1006 technical reasons, it encodes addresses in its FDE's in a different
1007 way. Several "pointer encodings" are supported. The encoding
1008 that's used for a particular FDE is determined by the 'R'
1009 augmentation in the associated CIE. The argument of this
1010 augmentation is a single byte.
1012 The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
1013 LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether
1014 the address is signed or unsigned. Bits 4, 5 and 6 encode how the
1015 address should be interpreted (absolute, relative to the current
1016 position in the FDE, ...). Bit 7, indicates that the address
1017 should be dereferenced. */
1019 static unsigned char
1020 encoding_for_size (unsigned int size)
1025 return DW_EH_PE_udata2;
1027 return DW_EH_PE_udata4;
1029 return DW_EH_PE_udata8;
1031 internal_error (__FILE__, __LINE__, "Unsupported address size");
1036 size_of_encoded_value (unsigned char encoding)
1038 if (encoding == DW_EH_PE_omit)
1041 switch (encoding & 0x07)
1043 case DW_EH_PE_absptr:
1044 return TYPE_LENGTH (builtin_type_void_data_ptr);
1045 case DW_EH_PE_udata2:
1047 case DW_EH_PE_udata4:
1049 case DW_EH_PE_udata8:
1052 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1057 read_encoded_value (struct comp_unit *unit, unsigned char encoding,
1058 char *buf, unsigned int *bytes_read_ptr)
1060 int ptr_len = size_of_encoded_value (DW_EH_PE_absptr);
1064 /* GCC currently doesn't generate DW_EH_PE_indirect encodings for
1066 if (encoding & DW_EH_PE_indirect)
1067 internal_error (__FILE__, __LINE__,
1068 "Unsupported encoding: DW_EH_PE_indirect");
1070 *bytes_read_ptr = 0;
1072 switch (encoding & 0x70)
1074 case DW_EH_PE_absptr:
1077 case DW_EH_PE_pcrel:
1078 base = bfd_get_section_vma (unit->bfd, unit->dwarf_frame_section);
1079 base += (buf - unit->dwarf_frame_buffer);
1081 case DW_EH_PE_datarel:
1084 case DW_EH_PE_textrel:
1087 case DW_EH_PE_aligned:
1089 offset = buf - unit->dwarf_frame_buffer;
1090 if ((offset % ptr_len) != 0)
1092 *bytes_read_ptr = ptr_len - (offset % ptr_len);
1093 buf += *bytes_read_ptr;
1097 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1100 if ((encoding & 0x0f) == 0x00)
1101 encoding |= encoding_for_size (ptr_len);
1103 switch (encoding & 0x0f)
1105 case DW_EH_PE_udata2:
1106 *bytes_read_ptr += 2;
1107 return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
1108 case DW_EH_PE_udata4:
1109 *bytes_read_ptr += 4;
1110 return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
1111 case DW_EH_PE_udata8:
1112 *bytes_read_ptr += 8;
1113 return (base + bfd_get_64 (unit->abfd, (bfd_byte *) buf));
1114 case DW_EH_PE_sdata2:
1115 *bytes_read_ptr += 2;
1116 return (base + bfd_get_signed_16 (unit->abfd, (bfd_byte *) buf));
1117 case DW_EH_PE_sdata4:
1118 *bytes_read_ptr += 4;
1119 return (base + bfd_get_signed_32 (unit->abfd, (bfd_byte *) buf));
1120 case DW_EH_PE_sdata8:
1121 *bytes_read_ptr += 8;
1122 return (base + bfd_get_signed_64 (unit->abfd, (bfd_byte *) buf));
1124 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1129 /* GCC uses a single CIE for all FDEs in a .debug_frame section.
1130 That's why we use a simple linked list here. */
1132 static struct dwarf2_cie *
1133 find_cie (struct comp_unit *unit, ULONGEST cie_pointer)
1135 struct dwarf2_cie *cie = unit->cie;
1139 if (cie->cie_pointer == cie_pointer)
1149 add_cie (struct comp_unit *unit, struct dwarf2_cie *cie)
1151 cie->next = unit->cie;
1155 /* Find the FDE for *PC. Return a pointer to the FDE, and store the
1156 inital location associated with it into *PC. */
1158 static struct dwarf2_fde *
1159 dwarf2_frame_find_fde (CORE_ADDR *pc)
1161 struct objfile *objfile;
1163 ALL_OBJFILES (objfile)
1165 struct dwarf2_fde *fde;
1168 fde = objfile_data (objfile, dwarf2_frame_objfile_data);
1172 gdb_assert (objfile->section_offsets);
1173 offset = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
1177 if (*pc >= fde->initial_location + offset
1178 && *pc < fde->initial_location + offset + fde->address_range)
1180 *pc = fde->initial_location + offset;
1192 add_fde (struct comp_unit *unit, struct dwarf2_fde *fde)
1194 fde->next = objfile_data (unit->objfile, dwarf2_frame_objfile_data);
1195 set_objfile_data (unit->objfile, dwarf2_frame_objfile_data, fde);
1198 #ifdef CC_HAS_LONG_LONG
1199 #define DW64_CIE_ID 0xffffffffffffffffULL
1201 #define DW64_CIE_ID ~0
1204 static char *decode_frame_entry (struct comp_unit *unit, char *start,
1207 /* Decode the next CIE or FDE. Return NULL if invalid input, otherwise
1208 the next byte to be processed. */
1210 decode_frame_entry_1 (struct comp_unit *unit, char *start, int eh_frame_p)
1214 unsigned int bytes_read;
1217 ULONGEST cie_pointer;
1221 length = read_initial_length (unit->abfd, buf, &bytes_read);
1225 /* Are we still within the section? */
1226 if (end > unit->dwarf_frame_buffer + unit->dwarf_frame_size)
1232 /* Distinguish between 32 and 64-bit encoded frame info. */
1233 dwarf64_p = (bytes_read == 12);
1235 /* In a .eh_frame section, zero is used to distinguish CIEs from FDEs. */
1239 cie_id = DW64_CIE_ID;
1245 cie_pointer = read_8_bytes (unit->abfd, buf);
1250 cie_pointer = read_4_bytes (unit->abfd, buf);
1254 if (cie_pointer == cie_id)
1256 /* This is a CIE. */
1257 struct dwarf2_cie *cie;
1260 /* Record the offset into the .debug_frame section of this CIE. */
1261 cie_pointer = start - unit->dwarf_frame_buffer;
1263 /* Check whether we've already read it. */
1264 if (find_cie (unit, cie_pointer))
1267 cie = (struct dwarf2_cie *)
1268 obstack_alloc (&unit->objfile->objfile_obstack,
1269 sizeof (struct dwarf2_cie));
1270 cie->initial_instructions = NULL;
1271 cie->cie_pointer = cie_pointer;
1273 /* The encoding for FDE's in a normal .debug_frame section
1274 depends on the target address size as specified in the
1275 Compilation Unit Header. */
1276 cie->encoding = encoding_for_size (unit->addr_size);
1278 /* Check version number. */
1279 if (read_1_byte (unit->abfd, buf) != DW_CIE_VERSION)
1283 /* Interpret the interesting bits of the augmentation. */
1285 buf = augmentation + strlen (augmentation) + 1;
1287 /* The GCC 2.x "eh" augmentation has a pointer immediately
1288 following the augmentation string, so it must be handled
1290 if (augmentation[0] == 'e' && augmentation[1] == 'h')
1293 buf += TYPE_LENGTH (builtin_type_void_data_ptr);
1297 cie->code_alignment_factor =
1298 read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1301 cie->data_alignment_factor =
1302 read_signed_leb128 (unit->abfd, buf, &bytes_read);
1305 cie->return_address_register = read_1_byte (unit->abfd, buf);
1308 cie->saw_z_augmentation = (*augmentation == 'z');
1309 if (cie->saw_z_augmentation)
1313 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1317 cie->initial_instructions = buf + length;
1321 while (*augmentation)
1323 /* "L" indicates a byte showing how the LSDA pointer is encoded. */
1324 if (*augmentation == 'L')
1331 /* "R" indicates a byte indicating how FDE addresses are encoded. */
1332 else if (*augmentation == 'R')
1334 cie->encoding = *buf++;
1338 /* "P" indicates a personality routine in the CIE augmentation. */
1339 else if (*augmentation == 'P')
1342 buf += size_of_encoded_value (*buf++);
1346 /* Otherwise we have an unknown augmentation.
1347 Bail out unless we saw a 'z' prefix. */
1350 if (cie->initial_instructions == NULL)
1353 /* Skip unknown augmentations. */
1354 buf = cie->initial_instructions;
1359 cie->initial_instructions = buf;
1362 add_cie (unit, cie);
1366 /* This is a FDE. */
1367 struct dwarf2_fde *fde;
1369 /* In an .eh_frame section, the CIE pointer is the delta between the
1370 address within the FDE where the CIE pointer is stored and the
1371 address of the CIE. Convert it to an offset into the .eh_frame
1375 cie_pointer = buf - unit->dwarf_frame_buffer - cie_pointer;
1376 cie_pointer -= (dwarf64_p ? 8 : 4);
1379 /* In either case, validate the result is still within the section. */
1380 if (cie_pointer >= unit->dwarf_frame_size)
1383 fde = (struct dwarf2_fde *)
1384 obstack_alloc (&unit->objfile->objfile_obstack,
1385 sizeof (struct dwarf2_fde));
1386 fde->cie = find_cie (unit, cie_pointer);
1387 if (fde->cie == NULL)
1389 decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer,
1391 fde->cie = find_cie (unit, cie_pointer);
1394 gdb_assert (fde->cie != NULL);
1396 fde->initial_location =
1397 read_encoded_value (unit, fde->cie->encoding, buf, &bytes_read);
1400 fde->address_range =
1401 read_encoded_value (unit, fde->cie->encoding & 0x0f, buf, &bytes_read);
1404 /* A 'z' augmentation in the CIE implies the presence of an
1405 augmentation field in the FDE as well. The only thing known
1406 to be in here at present is the LSDA entry for EH. So we
1407 can skip the whole thing. */
1408 if (fde->cie->saw_z_augmentation)
1412 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1413 buf += bytes_read + length;
1418 fde->instructions = buf;
1421 add_fde (unit, fde);
1427 /* Read a CIE or FDE in BUF and decode it. */
1429 decode_frame_entry (struct comp_unit *unit, char *start, int eh_frame_p)
1431 enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;
1434 ptrdiff_t start_offset;
1438 ret = decode_frame_entry_1 (unit, start, eh_frame_p);
1442 /* We have corrupt input data of some form. */
1444 /* ??? Try, weakly, to work around compiler/assembler/linker bugs
1445 and mismatches wrt padding and alignment of debug sections. */
1446 /* Note that there is no requirement in the standard for any
1447 alignment at all in the frame unwind sections. Testing for
1448 alignment before trying to interpret data would be incorrect.
1450 However, GCC traditionally arranged for frame sections to be
1451 sized such that the FDE length and CIE fields happen to be
1452 aligned (in theory, for performance). This, unfortunately,
1453 was done with .align directives, which had the side effect of
1454 forcing the section to be aligned by the linker.
1456 This becomes a problem when you have some other producer that
1457 creates frame sections that are not as strictly aligned. That
1458 produces a hole in the frame info that gets filled by the
1461 The GCC behaviour is arguably a bug, but it's effectively now
1462 part of the ABI, so we're now stuck with it, at least at the
1463 object file level. A smart linker may decide, in the process
1464 of compressing duplicate CIE information, that it can rewrite
1465 the entire output section without this extra padding. */
1467 start_offset = start - unit->dwarf_frame_buffer;
1468 if (workaround < ALIGN4 && (start_offset & 3) != 0)
1470 start += 4 - (start_offset & 3);
1471 workaround = ALIGN4;
1474 if (workaround < ALIGN8 && (start_offset & 7) != 0)
1476 start += 8 - (start_offset & 7);
1477 workaround = ALIGN8;
1481 /* Nothing left to try. Arrange to return as if we've consumed
1482 the entire input section. Hopefully we'll get valid info from
1483 the other of .debug_frame/.eh_frame. */
1485 ret = unit->dwarf_frame_buffer + unit->dwarf_frame_size;
1495 complaint (&symfile_complaints,
1496 "Corrupt data in %s:%s; align 4 workaround apparently succeeded",
1497 unit->dwarf_frame_section->owner->filename,
1498 unit->dwarf_frame_section->name);
1502 complaint (&symfile_complaints,
1503 "Corrupt data in %s:%s; align 8 workaround apparently succeeded",
1504 unit->dwarf_frame_section->owner->filename,
1505 unit->dwarf_frame_section->name);
1509 complaint (&symfile_complaints,
1510 "Corrupt data in %s:%s",
1511 unit->dwarf_frame_section->owner->filename,
1512 unit->dwarf_frame_section->name);
1520 /* FIXME: kettenis/20030504: This still needs to be integrated with
1521 dwarf2read.c in a better way. */
1523 /* Imported from dwarf2read.c. */
1524 extern asection *dwarf_frame_section;
1525 extern asection *dwarf_eh_frame_section;
1527 /* Imported from dwarf2read.c. */
1528 extern char *dwarf2_read_section (struct objfile *objfile, asection *sectp);
1531 dwarf2_build_frame_info (struct objfile *objfile)
1533 struct comp_unit unit;
1536 /* Build a minimal decoding of the DWARF2 compilation unit. */
1537 unit.abfd = objfile->obfd;
1538 unit.objfile = objfile;
1539 unit.addr_size = objfile->obfd->arch_info->bits_per_address / 8;
1543 /* First add the information from the .eh_frame section. That way,
1544 the FDEs from that section are searched last. */
1545 if (dwarf_eh_frame_section)
1547 asection *got, *txt;
1550 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1551 dwarf_eh_frame_section);
1553 unit.dwarf_frame_size
1554 = bfd_get_section_size_before_reloc (dwarf_eh_frame_section);
1555 unit.dwarf_frame_section = dwarf_eh_frame_section;
1557 /* FIXME: kettenis/20030602: This is the DW_EH_PE_datarel base
1558 that is used for the i386/amd64 target, which currently is
1559 the only target in GCC that supports/uses the
1560 DW_EH_PE_datarel encoding. */
1561 got = bfd_get_section_by_name (unit.abfd, ".got");
1563 unit.dbase = got->vma;
1565 /* GCC emits the DW_EH_PE_textrel encoding type on sh and ia64
1567 txt = bfd_get_section_by_name (unit.abfd, ".text");
1569 unit.tbase = txt->vma;
1571 frame_ptr = unit.dwarf_frame_buffer;
1572 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1573 frame_ptr = decode_frame_entry (&unit, frame_ptr, 1);
1576 if (dwarf_frame_section)
1579 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1580 dwarf_frame_section);
1581 unit.dwarf_frame_size
1582 = bfd_get_section_size_before_reloc (dwarf_frame_section);
1583 unit.dwarf_frame_section = dwarf_frame_section;
1585 frame_ptr = unit.dwarf_frame_buffer;
1586 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1587 frame_ptr = decode_frame_entry (&unit, frame_ptr, 0);
1591 /* Provide a prototype to silence -Wmissing-prototypes. */
1592 void _initialize_dwarf2_frame (void);
1595 _initialize_dwarf2_frame (void)
1597 dwarf2_frame_data = register_gdbarch_data (dwarf2_frame_init);
1598 dwarf2_frame_objfile_data = register_objfile_data ();