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 obstack *obstack)
514 struct dwarf2_frame_ops *ops;
516 ops = OBSTACK_ZALLOC (obstack, 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 = gdbarch_data (gdbarch, dwarf2_frame_data);
531 ops->init_reg = init_reg;
534 /* Pre-initialize the register state REG for register REGNUM. */
537 dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
538 struct dwarf2_frame_state_reg *reg)
540 struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
542 ops->init_reg (gdbarch, regnum, reg);
546 struct dwarf2_frame_cache
548 /* DWARF Call Frame Address. */
551 /* Saved registers, indexed by GDB register number, not by DWARF
553 struct dwarf2_frame_state_reg *reg;
556 static struct dwarf2_frame_cache *
557 dwarf2_frame_cache (struct frame_info *next_frame, void **this_cache)
559 struct cleanup *old_chain;
560 struct gdbarch *gdbarch = get_frame_arch (next_frame);
561 const int num_regs = NUM_REGS + NUM_PSEUDO_REGS;
562 struct dwarf2_frame_cache *cache;
563 struct dwarf2_frame_state *fs;
564 struct dwarf2_fde *fde;
569 /* Allocate a new cache. */
570 cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache);
571 cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg);
573 /* Allocate and initialize the frame state. */
574 fs = XMALLOC (struct dwarf2_frame_state);
575 memset (fs, 0, sizeof (struct dwarf2_frame_state));
576 old_chain = make_cleanup (dwarf2_frame_state_free, fs);
580 Note that if NEXT_FRAME is never supposed to return (i.e. a call
581 to abort), the compiler might optimize away the instruction at
582 NEXT_FRAME's return address. As a result the return address will
583 point at some random instruction, and the CFI for that
584 instruction is probably worthless to us. GCC's unwinder solves
585 this problem by substracting 1 from the return address to get an
586 address in the middle of a presumed call instruction (or the
587 instruction in the associated delay slot). This should only be
588 done for "normal" frames and not for resume-type frames (signal
589 handlers, sentinel frames, dummy frames). The function
590 frame_unwind_address_in_block does just this. It's not clear how
591 reliable the method is though; there is the potential for the
592 register state pre-call being different to that on return. */
593 fs->pc = frame_unwind_address_in_block (next_frame);
595 /* Find the correct FDE. */
596 fde = dwarf2_frame_find_fde (&fs->pc);
597 gdb_assert (fde != NULL);
599 /* Extract any interesting information from the CIE. */
600 fs->data_align = fde->cie->data_alignment_factor;
601 fs->code_align = fde->cie->code_alignment_factor;
602 fs->retaddr_column = fde->cie->return_address_register;
604 /* First decode all the insns in the CIE. */
605 execute_cfa_program (fde->cie->initial_instructions,
606 fde->cie->end, next_frame, fs);
608 /* Save the initialized register set. */
609 fs->initial = fs->regs;
610 fs->initial.reg = dwarf2_frame_state_copy_regs (&fs->regs);
612 /* Then decode the insns in the FDE up to our target PC. */
613 execute_cfa_program (fde->instructions, fde->end, next_frame, fs);
615 /* Caclulate the CFA. */
619 cache->cfa = read_reg (next_frame, fs->cfa_reg);
620 cache->cfa += fs->cfa_offset;
625 execute_stack_op (fs->cfa_exp, fs->cfa_exp_len, next_frame, 0);
629 internal_error (__FILE__, __LINE__, "Unknown CFA rule.");
632 /* Initialize the register state. */
636 for (regnum = 0; regnum < num_regs; regnum++)
637 dwarf2_frame_init_reg (gdbarch, regnum, &cache->reg[regnum]);
640 /* Go through the DWARF2 CFI generated table and save its register
641 location information in the cache. Note that we don't skip the
642 return address column; it's perfectly all right for it to
643 correspond to a real register. If it doesn't correspond to a
644 real register, or if we shouldn't treat it as such,
645 DWARF2_REG_TO_REGNUM should be defined to return a number outside
646 the range [0, NUM_REGS). */
648 int column; /* CFI speak for "register number". */
650 for (column = 0; column < fs->regs.num_regs; column++)
652 /* Use the GDB register number as the destination index. */
653 int regnum = DWARF2_REG_TO_REGNUM (column);
655 /* If there's no corresponding GDB register, ignore it. */
656 if (regnum < 0 || regnum >= num_regs)
659 /* NOTE: cagney/2003-09-05: CFI should specify the disposition
660 of all debug info registers. If it doesn't, complain (but
661 not too loudly). It turns out that GCC assumes that an
662 unspecified register implies "same value" when CFI (draft
663 7) specifies nothing at all. Such a register could equally
664 be interpreted as "undefined". Also note that this check
665 isn't sufficient; it only checks that all registers in the
666 range [0 .. max column] are specified, and won't detect
667 problems when a debug info register falls outside of the
668 table. We need a way of iterating through all the valid
669 DWARF2 register numbers. */
670 if (fs->regs.reg[column].how == DWARF2_FRAME_REG_UNSPECIFIED)
671 complaint (&symfile_complaints,
672 "Incomplete CFI data; unspecified registers at 0x%s",
675 cache->reg[regnum] = fs->regs.reg[column];
679 /* Eliminate any DWARF2_FRAME_REG_RA rules. */
683 for (regnum = 0; regnum < num_regs; regnum++)
685 if (cache->reg[regnum].how == DWARF2_FRAME_REG_RA)
687 struct dwarf2_frame_state_reg *retaddr_reg =
688 &fs->regs.reg[fs->retaddr_column];
690 /* It seems rather bizarre to specify an "empty" column as
691 the return adress column. However, this is exactly
692 what GCC does on some targets. It turns out that GCC
693 assumes that the return address can be found in the
694 register corresponding to the return address column.
695 Incidentally, that's how should treat a return address
696 column specifying "same value" too. */
697 if (fs->retaddr_column < fs->regs.num_regs
698 && retaddr_reg->how != DWARF2_FRAME_REG_UNSPECIFIED
699 && retaddr_reg->how != DWARF2_FRAME_REG_SAME_VALUE)
700 cache->reg[regnum] = *retaddr_reg;
703 cache->reg[regnum].loc.reg = fs->retaddr_column;
704 cache->reg[regnum].how = DWARF2_FRAME_REG_SAVED_REG;
710 do_cleanups (old_chain);
717 dwarf2_frame_this_id (struct frame_info *next_frame, void **this_cache,
718 struct frame_id *this_id)
720 struct dwarf2_frame_cache *cache =
721 dwarf2_frame_cache (next_frame, this_cache);
723 (*this_id) = frame_id_build (cache->cfa, frame_func_unwind (next_frame));
727 dwarf2_frame_prev_register (struct frame_info *next_frame, void **this_cache,
728 int regnum, int *optimizedp,
729 enum lval_type *lvalp, CORE_ADDR *addrp,
730 int *realnump, void *valuep)
732 struct gdbarch *gdbarch = get_frame_arch (next_frame);
733 struct dwarf2_frame_cache *cache =
734 dwarf2_frame_cache (next_frame, this_cache);
736 switch (cache->reg[regnum].how)
738 case DWARF2_FRAME_REG_UNDEFINED:
739 /* If CFI explicitly specified that the value isn't defined,
740 mark it as optimized away; the value isn't available. */
747 /* In some cases, for example %eflags on the i386, we have
748 to provide a sane value, even though this register wasn't
749 saved. Assume we can get it from NEXT_FRAME. */
750 frame_unwind_register (next_frame, regnum, valuep);
754 case DWARF2_FRAME_REG_SAVED_OFFSET:
756 *lvalp = lval_memory;
757 *addrp = cache->cfa + cache->reg[regnum].loc.offset;
761 /* Read the value in from memory. */
762 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
766 case DWARF2_FRAME_REG_SAVED_REG:
767 regnum = DWARF2_REG_TO_REGNUM (cache->reg[regnum].loc.reg);
768 frame_register_unwind (next_frame, regnum,
769 optimizedp, lvalp, addrp, realnump, valuep);
772 case DWARF2_FRAME_REG_SAVED_EXP:
774 *lvalp = lval_memory;
775 *addrp = execute_stack_op (cache->reg[regnum].loc.exp,
776 cache->reg[regnum].exp_len,
777 next_frame, cache->cfa);
781 /* Read the value in from memory. */
782 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
786 case DWARF2_FRAME_REG_UNSPECIFIED:
787 /* GCC, in its infinite wisdom decided to not provide unwind
788 information for registers that are "same value". Since
789 DWARF2 (3 draft 7) doesn't define such behavior, said
790 registers are actually undefined (which is different to CFI
791 "undefined"). Code above issues a complaint about this.
792 Here just fudge the books, assume GCC, and that the value is
793 more inner on the stack. */
794 frame_register_unwind (next_frame, regnum,
795 optimizedp, lvalp, addrp, realnump, valuep);
798 case DWARF2_FRAME_REG_SAME_VALUE:
799 frame_register_unwind (next_frame, regnum,
800 optimizedp, lvalp, addrp, realnump, valuep);
803 case DWARF2_FRAME_REG_CFA:
810 /* Store the value. */
811 store_typed_address (valuep, builtin_type_void_data_ptr, cache->cfa);
816 internal_error (__FILE__, __LINE__, "Unknown register rule.");
820 static const struct frame_unwind dwarf2_frame_unwind =
823 dwarf2_frame_this_id,
824 dwarf2_frame_prev_register
827 const struct frame_unwind *
828 dwarf2_frame_sniffer (struct frame_info *next_frame)
830 /* Grab an address that is guarenteed to reside somewhere within the
831 function. frame_pc_unwind(), for a no-return next function, can
832 end up returning something past the end of this function's body. */
833 CORE_ADDR block_addr = frame_unwind_address_in_block (next_frame);
834 if (dwarf2_frame_find_fde (&block_addr))
835 return &dwarf2_frame_unwind;
841 /* There is no explicitly defined relationship between the CFA and the
842 location of frame's local variables and arguments/parameters.
843 Therefore, frame base methods on this page should probably only be
844 used as a last resort, just to avoid printing total garbage as a
845 response to the "info frame" command. */
848 dwarf2_frame_base_address (struct frame_info *next_frame, void **this_cache)
850 struct dwarf2_frame_cache *cache =
851 dwarf2_frame_cache (next_frame, this_cache);
856 static const struct frame_base dwarf2_frame_base =
858 &dwarf2_frame_unwind,
859 dwarf2_frame_base_address,
860 dwarf2_frame_base_address,
861 dwarf2_frame_base_address
864 const struct frame_base *
865 dwarf2_frame_base_sniffer (struct frame_info *next_frame)
867 CORE_ADDR pc = frame_pc_unwind (next_frame);
868 if (dwarf2_frame_find_fde (&pc))
869 return &dwarf2_frame_base;
874 /* A minimal decoding of DWARF2 compilation units. We only decode
875 what's needed to get to the call frame information. */
879 /* Keep the bfd convenient. */
882 struct objfile *objfile;
884 /* Linked list of CIEs for this object. */
885 struct dwarf2_cie *cie;
887 /* Address size for this unit - from unit header. */
888 unsigned char addr_size;
890 /* Pointer to the .debug_frame section loaded into memory. */
891 char *dwarf_frame_buffer;
893 /* Length of the loaded .debug_frame section. */
894 unsigned long dwarf_frame_size;
896 /* Pointer to the .debug_frame section. */
897 asection *dwarf_frame_section;
899 /* Base for DW_EH_PE_datarel encodings. */
902 /* Base for DW_EH_PE_textrel encodings. */
906 const struct objfile_data *dwarf2_frame_objfile_data;
909 read_1_byte (bfd *bfd, char *buf)
911 return bfd_get_8 (abfd, (bfd_byte *) buf);
915 read_4_bytes (bfd *abfd, char *buf)
917 return bfd_get_32 (abfd, (bfd_byte *) buf);
921 read_8_bytes (bfd *abfd, char *buf)
923 return bfd_get_64 (abfd, (bfd_byte *) buf);
927 read_unsigned_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
930 unsigned int num_read;
940 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
943 result |= ((byte & 0x7f) << shift);
948 *bytes_read_ptr = num_read;
954 read_signed_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
958 unsigned int num_read;
967 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
970 result |= ((byte & 0x7f) << shift);
975 if ((shift < 32) && (byte & 0x40))
976 result |= -(1 << shift);
978 *bytes_read_ptr = num_read;
984 read_initial_length (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
988 result = bfd_get_32 (abfd, (bfd_byte *) buf);
989 if (result == 0xffffffff)
991 result = bfd_get_64 (abfd, (bfd_byte *) buf + 4);
992 *bytes_read_ptr = 12;
1001 /* Pointer encoding helper functions. */
1003 /* GCC supports exception handling based on DWARF2 CFI. However, for
1004 technical reasons, it encodes addresses in its FDE's in a different
1005 way. Several "pointer encodings" are supported. The encoding
1006 that's used for a particular FDE is determined by the 'R'
1007 augmentation in the associated CIE. The argument of this
1008 augmentation is a single byte.
1010 The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
1011 LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether
1012 the address is signed or unsigned. Bits 4, 5 and 6 encode how the
1013 address should be interpreted (absolute, relative to the current
1014 position in the FDE, ...). Bit 7, indicates that the address
1015 should be dereferenced. */
1017 static unsigned char
1018 encoding_for_size (unsigned int size)
1023 return DW_EH_PE_udata2;
1025 return DW_EH_PE_udata4;
1027 return DW_EH_PE_udata8;
1029 internal_error (__FILE__, __LINE__, "Unsupported address size");
1034 size_of_encoded_value (unsigned char encoding)
1036 if (encoding == DW_EH_PE_omit)
1039 switch (encoding & 0x07)
1041 case DW_EH_PE_absptr:
1042 return TYPE_LENGTH (builtin_type_void_data_ptr);
1043 case DW_EH_PE_udata2:
1045 case DW_EH_PE_udata4:
1047 case DW_EH_PE_udata8:
1050 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1055 read_encoded_value (struct comp_unit *unit, unsigned char encoding,
1056 char *buf, unsigned int *bytes_read_ptr)
1058 int ptr_len = size_of_encoded_value (DW_EH_PE_absptr);
1062 /* GCC currently doesn't generate DW_EH_PE_indirect encodings for
1064 if (encoding & DW_EH_PE_indirect)
1065 internal_error (__FILE__, __LINE__,
1066 "Unsupported encoding: DW_EH_PE_indirect");
1068 *bytes_read_ptr = 0;
1070 switch (encoding & 0x70)
1072 case DW_EH_PE_absptr:
1075 case DW_EH_PE_pcrel:
1076 base = bfd_get_section_vma (unit->bfd, unit->dwarf_frame_section);
1077 base += (buf - unit->dwarf_frame_buffer);
1079 case DW_EH_PE_datarel:
1082 case DW_EH_PE_textrel:
1085 case DW_EH_PE_aligned:
1087 offset = buf - unit->dwarf_frame_buffer;
1088 if ((offset % ptr_len) != 0)
1090 *bytes_read_ptr = ptr_len - (offset % ptr_len);
1091 buf += *bytes_read_ptr;
1095 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1098 if ((encoding & 0x0f) == 0x00)
1099 encoding |= encoding_for_size (ptr_len);
1101 switch (encoding & 0x0f)
1103 case DW_EH_PE_udata2:
1104 *bytes_read_ptr += 2;
1105 return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
1106 case DW_EH_PE_udata4:
1107 *bytes_read_ptr += 4;
1108 return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
1109 case DW_EH_PE_udata8:
1110 *bytes_read_ptr += 8;
1111 return (base + bfd_get_64 (unit->abfd, (bfd_byte *) buf));
1112 case DW_EH_PE_sdata2:
1113 *bytes_read_ptr += 2;
1114 return (base + bfd_get_signed_16 (unit->abfd, (bfd_byte *) buf));
1115 case DW_EH_PE_sdata4:
1116 *bytes_read_ptr += 4;
1117 return (base + bfd_get_signed_32 (unit->abfd, (bfd_byte *) buf));
1118 case DW_EH_PE_sdata8:
1119 *bytes_read_ptr += 8;
1120 return (base + bfd_get_signed_64 (unit->abfd, (bfd_byte *) buf));
1122 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1127 /* GCC uses a single CIE for all FDEs in a .debug_frame section.
1128 That's why we use a simple linked list here. */
1130 static struct dwarf2_cie *
1131 find_cie (struct comp_unit *unit, ULONGEST cie_pointer)
1133 struct dwarf2_cie *cie = unit->cie;
1137 if (cie->cie_pointer == cie_pointer)
1147 add_cie (struct comp_unit *unit, struct dwarf2_cie *cie)
1149 cie->next = unit->cie;
1153 /* Find the FDE for *PC. Return a pointer to the FDE, and store the
1154 inital location associated with it into *PC. */
1156 static struct dwarf2_fde *
1157 dwarf2_frame_find_fde (CORE_ADDR *pc)
1159 struct objfile *objfile;
1161 ALL_OBJFILES (objfile)
1163 struct dwarf2_fde *fde;
1166 fde = objfile_data (objfile, dwarf2_frame_objfile_data);
1170 gdb_assert (objfile->section_offsets);
1171 offset = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
1175 if (*pc >= fde->initial_location + offset
1176 && *pc < fde->initial_location + offset + fde->address_range)
1178 *pc = fde->initial_location + offset;
1190 add_fde (struct comp_unit *unit, struct dwarf2_fde *fde)
1192 fde->next = objfile_data (unit->objfile, dwarf2_frame_objfile_data);
1193 set_objfile_data (unit->objfile, dwarf2_frame_objfile_data, fde);
1196 #ifdef CC_HAS_LONG_LONG
1197 #define DW64_CIE_ID 0xffffffffffffffffULL
1199 #define DW64_CIE_ID ~0
1202 static char *decode_frame_entry (struct comp_unit *unit, char *start,
1205 /* Decode the next CIE or FDE. Return NULL if invalid input, otherwise
1206 the next byte to be processed. */
1208 decode_frame_entry_1 (struct comp_unit *unit, char *start, int eh_frame_p)
1212 unsigned int bytes_read;
1215 ULONGEST cie_pointer;
1219 length = read_initial_length (unit->abfd, buf, &bytes_read);
1223 /* Are we still within the section? */
1224 if (end > unit->dwarf_frame_buffer + unit->dwarf_frame_size)
1230 /* Distinguish between 32 and 64-bit encoded frame info. */
1231 dwarf64_p = (bytes_read == 12);
1233 /* In a .eh_frame section, zero is used to distinguish CIEs from FDEs. */
1237 cie_id = DW64_CIE_ID;
1243 cie_pointer = read_8_bytes (unit->abfd, buf);
1248 cie_pointer = read_4_bytes (unit->abfd, buf);
1252 if (cie_pointer == cie_id)
1254 /* This is a CIE. */
1255 struct dwarf2_cie *cie;
1258 /* Record the offset into the .debug_frame section of this CIE. */
1259 cie_pointer = start - unit->dwarf_frame_buffer;
1261 /* Check whether we've already read it. */
1262 if (find_cie (unit, cie_pointer))
1265 cie = (struct dwarf2_cie *)
1266 obstack_alloc (&unit->objfile->objfile_obstack,
1267 sizeof (struct dwarf2_cie));
1268 cie->initial_instructions = NULL;
1269 cie->cie_pointer = cie_pointer;
1271 /* The encoding for FDE's in a normal .debug_frame section
1272 depends on the target address size as specified in the
1273 Compilation Unit Header. */
1274 cie->encoding = encoding_for_size (unit->addr_size);
1276 /* Check version number. */
1277 if (read_1_byte (unit->abfd, buf) != DW_CIE_VERSION)
1281 /* Interpret the interesting bits of the augmentation. */
1283 buf = augmentation + strlen (augmentation) + 1;
1285 /* The GCC 2.x "eh" augmentation has a pointer immediately
1286 following the augmentation string, so it must be handled
1288 if (augmentation[0] == 'e' && augmentation[1] == 'h')
1291 buf += TYPE_LENGTH (builtin_type_void_data_ptr);
1295 cie->code_alignment_factor =
1296 read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1299 cie->data_alignment_factor =
1300 read_signed_leb128 (unit->abfd, buf, &bytes_read);
1303 cie->return_address_register = read_1_byte (unit->abfd, buf);
1306 cie->saw_z_augmentation = (*augmentation == 'z');
1307 if (cie->saw_z_augmentation)
1311 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1315 cie->initial_instructions = buf + length;
1319 while (*augmentation)
1321 /* "L" indicates a byte showing how the LSDA pointer is encoded. */
1322 if (*augmentation == 'L')
1329 /* "R" indicates a byte indicating how FDE addresses are encoded. */
1330 else if (*augmentation == 'R')
1332 cie->encoding = *buf++;
1336 /* "P" indicates a personality routine in the CIE augmentation. */
1337 else if (*augmentation == 'P')
1340 buf += size_of_encoded_value (*buf++);
1344 /* Otherwise we have an unknown augmentation.
1345 Bail out unless we saw a 'z' prefix. */
1348 if (cie->initial_instructions == NULL)
1351 /* Skip unknown augmentations. */
1352 buf = cie->initial_instructions;
1357 cie->initial_instructions = buf;
1360 add_cie (unit, cie);
1364 /* This is a FDE. */
1365 struct dwarf2_fde *fde;
1367 /* In an .eh_frame section, the CIE pointer is the delta between the
1368 address within the FDE where the CIE pointer is stored and the
1369 address of the CIE. Convert it to an offset into the .eh_frame
1373 cie_pointer = buf - unit->dwarf_frame_buffer - cie_pointer;
1374 cie_pointer -= (dwarf64_p ? 8 : 4);
1377 /* In either case, validate the result is still within the section. */
1378 if (cie_pointer >= unit->dwarf_frame_size)
1381 fde = (struct dwarf2_fde *)
1382 obstack_alloc (&unit->objfile->objfile_obstack,
1383 sizeof (struct dwarf2_fde));
1384 fde->cie = find_cie (unit, cie_pointer);
1385 if (fde->cie == NULL)
1387 decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer,
1389 fde->cie = find_cie (unit, cie_pointer);
1392 gdb_assert (fde->cie != NULL);
1394 fde->initial_location =
1395 read_encoded_value (unit, fde->cie->encoding, buf, &bytes_read);
1398 fde->address_range =
1399 read_encoded_value (unit, fde->cie->encoding & 0x0f, buf, &bytes_read);
1402 /* A 'z' augmentation in the CIE implies the presence of an
1403 augmentation field in the FDE as well. The only thing known
1404 to be in here at present is the LSDA entry for EH. So we
1405 can skip the whole thing. */
1406 if (fde->cie->saw_z_augmentation)
1410 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1411 buf += bytes_read + length;
1416 fde->instructions = buf;
1419 add_fde (unit, fde);
1425 /* Read a CIE or FDE in BUF and decode it. */
1427 decode_frame_entry (struct comp_unit *unit, char *start, int eh_frame_p)
1429 enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;
1432 ptrdiff_t start_offset;
1436 ret = decode_frame_entry_1 (unit, start, eh_frame_p);
1440 /* We have corrupt input data of some form. */
1442 /* ??? Try, weakly, to work around compiler/assembler/linker bugs
1443 and mismatches wrt padding and alignment of debug sections. */
1444 /* Note that there is no requirement in the standard for any
1445 alignment at all in the frame unwind sections. Testing for
1446 alignment before trying to interpret data would be incorrect.
1448 However, GCC traditionally arranged for frame sections to be
1449 sized such that the FDE length and CIE fields happen to be
1450 aligned (in theory, for performance). This, unfortunately,
1451 was done with .align directives, which had the side effect of
1452 forcing the section to be aligned by the linker.
1454 This becomes a problem when you have some other producer that
1455 creates frame sections that are not as strictly aligned. That
1456 produces a hole in the frame info that gets filled by the
1459 The GCC behaviour is arguably a bug, but it's effectively now
1460 part of the ABI, so we're now stuck with it, at least at the
1461 object file level. A smart linker may decide, in the process
1462 of compressing duplicate CIE information, that it can rewrite
1463 the entire output section without this extra padding. */
1465 start_offset = start - unit->dwarf_frame_buffer;
1466 if (workaround < ALIGN4 && (start_offset & 3) != 0)
1468 start += 4 - (start_offset & 3);
1469 workaround = ALIGN4;
1472 if (workaround < ALIGN8 && (start_offset & 7) != 0)
1474 start += 8 - (start_offset & 7);
1475 workaround = ALIGN8;
1479 /* Nothing left to try. Arrange to return as if we've consumed
1480 the entire input section. Hopefully we'll get valid info from
1481 the other of .debug_frame/.eh_frame. */
1483 ret = unit->dwarf_frame_buffer + unit->dwarf_frame_size;
1493 complaint (&symfile_complaints,
1494 "Corrupt data in %s:%s; align 4 workaround apparently succeeded",
1495 unit->dwarf_frame_section->owner->filename,
1496 unit->dwarf_frame_section->name);
1500 complaint (&symfile_complaints,
1501 "Corrupt data in %s:%s; align 8 workaround apparently succeeded",
1502 unit->dwarf_frame_section->owner->filename,
1503 unit->dwarf_frame_section->name);
1507 complaint (&symfile_complaints,
1508 "Corrupt data in %s:%s",
1509 unit->dwarf_frame_section->owner->filename,
1510 unit->dwarf_frame_section->name);
1518 /* FIXME: kettenis/20030504: This still needs to be integrated with
1519 dwarf2read.c in a better way. */
1521 /* Imported from dwarf2read.c. */
1522 extern asection *dwarf_frame_section;
1523 extern asection *dwarf_eh_frame_section;
1525 /* Imported from dwarf2read.c. */
1526 extern char *dwarf2_read_section (struct objfile *objfile, asection *sectp);
1529 dwarf2_build_frame_info (struct objfile *objfile)
1531 struct comp_unit unit;
1534 /* Build a minimal decoding of the DWARF2 compilation unit. */
1535 unit.abfd = objfile->obfd;
1536 unit.objfile = objfile;
1537 unit.addr_size = objfile->obfd->arch_info->bits_per_address / 8;
1541 /* First add the information from the .eh_frame section. That way,
1542 the FDEs from that section are searched last. */
1543 if (dwarf_eh_frame_section)
1545 asection *got, *txt;
1548 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1549 dwarf_eh_frame_section);
1551 unit.dwarf_frame_size
1552 = bfd_get_section_size_before_reloc (dwarf_eh_frame_section);
1553 unit.dwarf_frame_section = dwarf_eh_frame_section;
1555 /* FIXME: kettenis/20030602: This is the DW_EH_PE_datarel base
1556 that is used for the i386/amd64 target, which currently is
1557 the only target in GCC that supports/uses the
1558 DW_EH_PE_datarel encoding. */
1559 got = bfd_get_section_by_name (unit.abfd, ".got");
1561 unit.dbase = got->vma;
1563 /* GCC emits the DW_EH_PE_textrel encoding type on sh and ia64
1565 txt = bfd_get_section_by_name (unit.abfd, ".text");
1567 unit.tbase = txt->vma;
1569 frame_ptr = unit.dwarf_frame_buffer;
1570 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1571 frame_ptr = decode_frame_entry (&unit, frame_ptr, 1);
1574 if (dwarf_frame_section)
1577 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1578 dwarf_frame_section);
1579 unit.dwarf_frame_size
1580 = bfd_get_section_size_before_reloc (dwarf_frame_section);
1581 unit.dwarf_frame_section = dwarf_frame_section;
1583 frame_ptr = unit.dwarf_frame_buffer;
1584 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1585 frame_ptr = decode_frame_entry (&unit, frame_ptr, 0);
1589 /* Provide a prototype to silence -Wmissing-prototypes. */
1590 void _initialize_dwarf2_frame (void);
1593 _initialize_dwarf2_frame (void)
1595 dwarf2_frame_data = gdbarch_data_register_pre_init (dwarf2_frame_init);
1596 dwarf2_frame_objfile_data = register_objfile_data ();