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 complaint (&symfile_complaints, "\
378 bad CFI data; mismatched DW_CFA_restore_state at 0x%s", paddr (fs->pc));
382 xfree (fs->regs.reg);
390 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
391 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
392 fs->cfa_offset = utmp;
393 fs->cfa_how = CFA_REG_OFFSET;
396 case DW_CFA_def_cfa_register:
397 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
398 fs->cfa_how = CFA_REG_OFFSET;
401 case DW_CFA_def_cfa_offset:
402 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_offset);
403 /* cfa_how deliberately not set. */
409 case DW_CFA_def_cfa_expression:
410 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_exp_len);
411 fs->cfa_exp = insn_ptr;
412 fs->cfa_how = CFA_EXP;
413 insn_ptr += fs->cfa_exp_len;
416 case DW_CFA_expression:
417 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
418 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
419 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
420 fs->regs.reg[reg].loc.exp = insn_ptr;
421 fs->regs.reg[reg].exp_len = utmp;
422 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_EXP;
426 case DW_CFA_offset_extended_sf:
427 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
428 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
429 offset *= fs->data_align;
430 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
431 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
432 fs->regs.reg[reg].loc.offset = offset;
435 case DW_CFA_def_cfa_sf:
436 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
437 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
438 fs->cfa_offset = offset * fs->data_align;
439 fs->cfa_how = CFA_REG_OFFSET;
442 case DW_CFA_def_cfa_offset_sf:
443 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
444 fs->cfa_offset = offset * fs->data_align;
445 /* cfa_how deliberately not set. */
448 case DW_CFA_GNU_args_size:
450 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
454 internal_error (__FILE__, __LINE__, "Unknown CFI encountered.");
459 /* Don't allow remember/restore between CIE and FDE programs. */
460 dwarf2_frame_state_free_regs (fs->regs.prev);
461 fs->regs.prev = NULL;
465 /* Architecture-specific operations. */
467 /* Per-architecture data key. */
468 static struct gdbarch_data *dwarf2_frame_data;
470 struct dwarf2_frame_ops
472 /* Pre-initialize the register state REG for register REGNUM. */
473 void (*init_reg) (struct gdbarch *, int, struct dwarf2_frame_state_reg *);
476 /* Default architecture-specific register state initialization
480 dwarf2_frame_default_init_reg (struct gdbarch *gdbarch, int regnum,
481 struct dwarf2_frame_state_reg *reg)
483 /* If we have a register that acts as a program counter, mark it as
484 a destination for the return address. If we have a register that
485 serves as the stack pointer, arrange for it to be filled with the
486 call frame address (CFA). The other registers are marked as
489 We copy the return address to the program counter, since many
490 parts in GDB assume that it is possible to get the return address
491 by unwinding the program counter register. However, on ISA's
492 with a dedicated return address register, the CFI usually only
493 contains information to unwind that return address register.
495 The reason we're treating the stack pointer special here is
496 because in many cases GCC doesn't emit CFI for the stack pointer
497 and implicitly assumes that it is equal to the CFA. This makes
498 some sense since the DWARF specification (version 3, draft 8,
501 "Typically, the CFA is defined to be the value of the stack
502 pointer at the call site in the previous frame (which may be
503 different from its value on entry to the current frame)."
505 However, this isn't true for all platforms supported by GCC
506 (e.g. IBM S/390 and zSeries). Those architectures should provide
507 their own architecture-specific initialization function. */
509 if (regnum == PC_REGNUM)
510 reg->how = DWARF2_FRAME_REG_RA;
511 else if (regnum == SP_REGNUM)
512 reg->how = DWARF2_FRAME_REG_CFA;
515 /* Return a default for the architecture-specific operations. */
518 dwarf2_frame_init (struct obstack *obstack)
520 struct dwarf2_frame_ops *ops;
522 ops = OBSTACK_ZALLOC (obstack, struct dwarf2_frame_ops);
523 ops->init_reg = dwarf2_frame_default_init_reg;
527 /* Set the architecture-specific register state initialization
528 function for GDBARCH to INIT_REG. */
531 dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
532 void (*init_reg) (struct gdbarch *, int,
533 struct dwarf2_frame_state_reg *))
535 struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
537 ops->init_reg = init_reg;
540 /* Pre-initialize the register state REG for register REGNUM. */
543 dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
544 struct dwarf2_frame_state_reg *reg)
546 struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
548 ops->init_reg (gdbarch, regnum, reg);
552 struct dwarf2_frame_cache
554 /* DWARF Call Frame Address. */
557 /* Saved registers, indexed by GDB register number, not by DWARF
559 struct dwarf2_frame_state_reg *reg;
562 static struct dwarf2_frame_cache *
563 dwarf2_frame_cache (struct frame_info *next_frame, void **this_cache)
565 struct cleanup *old_chain;
566 struct gdbarch *gdbarch = get_frame_arch (next_frame);
567 const int num_regs = NUM_REGS + NUM_PSEUDO_REGS;
568 struct dwarf2_frame_cache *cache;
569 struct dwarf2_frame_state *fs;
570 struct dwarf2_fde *fde;
575 /* Allocate a new cache. */
576 cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache);
577 cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg);
579 /* Allocate and initialize the frame state. */
580 fs = XMALLOC (struct dwarf2_frame_state);
581 memset (fs, 0, sizeof (struct dwarf2_frame_state));
582 old_chain = make_cleanup (dwarf2_frame_state_free, fs);
586 Note that if NEXT_FRAME is never supposed to return (i.e. a call
587 to abort), the compiler might optimize away the instruction at
588 NEXT_FRAME's return address. As a result the return address will
589 point at some random instruction, and the CFI for that
590 instruction is probably worthless to us. GCC's unwinder solves
591 this problem by substracting 1 from the return address to get an
592 address in the middle of a presumed call instruction (or the
593 instruction in the associated delay slot). This should only be
594 done for "normal" frames and not for resume-type frames (signal
595 handlers, sentinel frames, dummy frames). The function
596 frame_unwind_address_in_block does just this. It's not clear how
597 reliable the method is though; there is the potential for the
598 register state pre-call being different to that on return. */
599 fs->pc = frame_unwind_address_in_block (next_frame);
601 /* Find the correct FDE. */
602 fde = dwarf2_frame_find_fde (&fs->pc);
603 gdb_assert (fde != NULL);
605 /* Extract any interesting information from the CIE. */
606 fs->data_align = fde->cie->data_alignment_factor;
607 fs->code_align = fde->cie->code_alignment_factor;
608 fs->retaddr_column = fde->cie->return_address_register;
610 /* First decode all the insns in the CIE. */
611 execute_cfa_program (fde->cie->initial_instructions,
612 fde->cie->end, next_frame, fs);
614 /* Save the initialized register set. */
615 fs->initial = fs->regs;
616 fs->initial.reg = dwarf2_frame_state_copy_regs (&fs->regs);
618 /* Then decode the insns in the FDE up to our target PC. */
619 execute_cfa_program (fde->instructions, fde->end, next_frame, fs);
621 /* Caclulate the CFA. */
625 cache->cfa = read_reg (next_frame, fs->cfa_reg);
626 cache->cfa += fs->cfa_offset;
631 execute_stack_op (fs->cfa_exp, fs->cfa_exp_len, next_frame, 0);
635 internal_error (__FILE__, __LINE__, "Unknown CFA rule.");
638 /* Initialize the register state. */
642 for (regnum = 0; regnum < num_regs; regnum++)
643 dwarf2_frame_init_reg (gdbarch, regnum, &cache->reg[regnum]);
646 /* Go through the DWARF2 CFI generated table and save its register
647 location information in the cache. Note that we don't skip the
648 return address column; it's perfectly all right for it to
649 correspond to a real register. If it doesn't correspond to a
650 real register, or if we shouldn't treat it as such,
651 DWARF2_REG_TO_REGNUM should be defined to return a number outside
652 the range [0, NUM_REGS). */
654 int column; /* CFI speak for "register number". */
656 for (column = 0; column < fs->regs.num_regs; column++)
658 /* Use the GDB register number as the destination index. */
659 int regnum = DWARF2_REG_TO_REGNUM (column);
661 /* If there's no corresponding GDB register, ignore it. */
662 if (regnum < 0 || regnum >= num_regs)
665 /* NOTE: cagney/2003-09-05: CFI should specify the disposition
666 of all debug info registers. If it doesn't, complain (but
667 not too loudly). It turns out that GCC assumes that an
668 unspecified register implies "same value" when CFI (draft
669 7) specifies nothing at all. Such a register could equally
670 be interpreted as "undefined". Also note that this check
671 isn't sufficient; it only checks that all registers in the
672 range [0 .. max column] are specified, and won't detect
673 problems when a debug info register falls outside of the
674 table. We need a way of iterating through all the valid
675 DWARF2 register numbers. */
676 if (fs->regs.reg[column].how == DWARF2_FRAME_REG_UNSPECIFIED)
677 complaint (&symfile_complaints,
678 "Incomplete CFI data; unspecified registers at 0x%s",
681 cache->reg[regnum] = fs->regs.reg[column];
685 /* Eliminate any DWARF2_FRAME_REG_RA rules. */
689 for (regnum = 0; regnum < num_regs; regnum++)
691 if (cache->reg[regnum].how == DWARF2_FRAME_REG_RA)
693 struct dwarf2_frame_state_reg *retaddr_reg =
694 &fs->regs.reg[fs->retaddr_column];
696 /* It seems rather bizarre to specify an "empty" column as
697 the return adress column. However, this is exactly
698 what GCC does on some targets. It turns out that GCC
699 assumes that the return address can be found in the
700 register corresponding to the return address column.
701 Incidentally, that's how should treat a return address
702 column specifying "same value" too. */
703 if (fs->retaddr_column < fs->regs.num_regs
704 && retaddr_reg->how != DWARF2_FRAME_REG_UNSPECIFIED
705 && retaddr_reg->how != DWARF2_FRAME_REG_SAME_VALUE)
706 cache->reg[regnum] = *retaddr_reg;
709 cache->reg[regnum].loc.reg = fs->retaddr_column;
710 cache->reg[regnum].how = DWARF2_FRAME_REG_SAVED_REG;
716 do_cleanups (old_chain);
723 dwarf2_frame_this_id (struct frame_info *next_frame, void **this_cache,
724 struct frame_id *this_id)
726 struct dwarf2_frame_cache *cache =
727 dwarf2_frame_cache (next_frame, this_cache);
729 (*this_id) = frame_id_build (cache->cfa, frame_func_unwind (next_frame));
733 dwarf2_frame_prev_register (struct frame_info *next_frame, void **this_cache,
734 int regnum, int *optimizedp,
735 enum lval_type *lvalp, CORE_ADDR *addrp,
736 int *realnump, void *valuep)
738 struct gdbarch *gdbarch = get_frame_arch (next_frame);
739 struct dwarf2_frame_cache *cache =
740 dwarf2_frame_cache (next_frame, this_cache);
742 switch (cache->reg[regnum].how)
744 case DWARF2_FRAME_REG_UNDEFINED:
745 /* If CFI explicitly specified that the value isn't defined,
746 mark it as optimized away; the value isn't available. */
753 /* In some cases, for example %eflags on the i386, we have
754 to provide a sane value, even though this register wasn't
755 saved. Assume we can get it from NEXT_FRAME. */
756 frame_unwind_register (next_frame, regnum, valuep);
760 case DWARF2_FRAME_REG_SAVED_OFFSET:
762 *lvalp = lval_memory;
763 *addrp = cache->cfa + cache->reg[regnum].loc.offset;
767 /* Read the value in from memory. */
768 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
772 case DWARF2_FRAME_REG_SAVED_REG:
774 *lvalp = lval_register;
776 *realnump = DWARF2_REG_TO_REGNUM (cache->reg[regnum].loc.reg);
778 frame_unwind_register (next_frame, (*realnump), valuep);
781 case DWARF2_FRAME_REG_SAVED_EXP:
783 *lvalp = lval_memory;
784 *addrp = execute_stack_op (cache->reg[regnum].loc.exp,
785 cache->reg[regnum].exp_len,
786 next_frame, cache->cfa);
790 /* Read the value in from memory. */
791 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
795 case DWARF2_FRAME_REG_UNSPECIFIED:
796 /* GCC, in its infinite wisdom decided to not provide unwind
797 information for registers that are "same value". Since
798 DWARF2 (3 draft 7) doesn't define such behavior, said
799 registers are actually undefined (which is different to CFI
800 "undefined"). Code above issues a complaint about this.
801 Here just fudge the books, assume GCC, and that the value is
802 more inner on the stack. */
804 *lvalp = lval_register;
808 frame_unwind_register (next_frame, (*realnump), valuep);
811 case DWARF2_FRAME_REG_SAME_VALUE:
813 *lvalp = lval_register;
817 frame_unwind_register (next_frame, (*realnump), valuep);
820 case DWARF2_FRAME_REG_CFA:
827 /* Store the value. */
828 store_typed_address (valuep, builtin_type_void_data_ptr, cache->cfa);
833 internal_error (__FILE__, __LINE__, "Unknown register rule.");
837 static const struct frame_unwind dwarf2_frame_unwind =
840 dwarf2_frame_this_id,
841 dwarf2_frame_prev_register
844 const struct frame_unwind *
845 dwarf2_frame_sniffer (struct frame_info *next_frame)
847 /* Grab an address that is guarenteed to reside somewhere within the
848 function. frame_pc_unwind(), for a no-return next function, can
849 end up returning something past the end of this function's body. */
850 CORE_ADDR block_addr = frame_unwind_address_in_block (next_frame);
851 if (dwarf2_frame_find_fde (&block_addr))
852 return &dwarf2_frame_unwind;
858 /* There is no explicitly defined relationship between the CFA and the
859 location of frame's local variables and arguments/parameters.
860 Therefore, frame base methods on this page should probably only be
861 used as a last resort, just to avoid printing total garbage as a
862 response to the "info frame" command. */
865 dwarf2_frame_base_address (struct frame_info *next_frame, void **this_cache)
867 struct dwarf2_frame_cache *cache =
868 dwarf2_frame_cache (next_frame, this_cache);
873 static const struct frame_base dwarf2_frame_base =
875 &dwarf2_frame_unwind,
876 dwarf2_frame_base_address,
877 dwarf2_frame_base_address,
878 dwarf2_frame_base_address
881 const struct frame_base *
882 dwarf2_frame_base_sniffer (struct frame_info *next_frame)
884 CORE_ADDR pc = frame_pc_unwind (next_frame);
885 if (dwarf2_frame_find_fde (&pc))
886 return &dwarf2_frame_base;
891 /* A minimal decoding of DWARF2 compilation units. We only decode
892 what's needed to get to the call frame information. */
896 /* Keep the bfd convenient. */
899 struct objfile *objfile;
901 /* Linked list of CIEs for this object. */
902 struct dwarf2_cie *cie;
904 /* Pointer to the .debug_frame section loaded into memory. */
905 char *dwarf_frame_buffer;
907 /* Length of the loaded .debug_frame section. */
908 unsigned long dwarf_frame_size;
910 /* Pointer to the .debug_frame section. */
911 asection *dwarf_frame_section;
913 /* Base for DW_EH_PE_datarel encodings. */
916 /* Base for DW_EH_PE_textrel encodings. */
920 const struct objfile_data *dwarf2_frame_objfile_data;
923 read_1_byte (bfd *bfd, char *buf)
925 return bfd_get_8 (abfd, (bfd_byte *) buf);
929 read_4_bytes (bfd *abfd, char *buf)
931 return bfd_get_32 (abfd, (bfd_byte *) buf);
935 read_8_bytes (bfd *abfd, char *buf)
937 return bfd_get_64 (abfd, (bfd_byte *) buf);
941 read_unsigned_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
944 unsigned int num_read;
954 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
957 result |= ((byte & 0x7f) << shift);
962 *bytes_read_ptr = num_read;
968 read_signed_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
972 unsigned int num_read;
981 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
984 result |= ((byte & 0x7f) << shift);
989 if ((shift < 32) && (byte & 0x40))
990 result |= -(1 << shift);
992 *bytes_read_ptr = num_read;
998 read_initial_length (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
1002 result = bfd_get_32 (abfd, (bfd_byte *) buf);
1003 if (result == 0xffffffff)
1005 result = bfd_get_64 (abfd, (bfd_byte *) buf + 4);
1006 *bytes_read_ptr = 12;
1009 *bytes_read_ptr = 4;
1015 /* Pointer encoding helper functions. */
1017 /* GCC supports exception handling based on DWARF2 CFI. However, for
1018 technical reasons, it encodes addresses in its FDE's in a different
1019 way. Several "pointer encodings" are supported. The encoding
1020 that's used for a particular FDE is determined by the 'R'
1021 augmentation in the associated CIE. The argument of this
1022 augmentation is a single byte.
1024 The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
1025 LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether
1026 the address is signed or unsigned. Bits 4, 5 and 6 encode how the
1027 address should be interpreted (absolute, relative to the current
1028 position in the FDE, ...). Bit 7, indicates that the address
1029 should be dereferenced. */
1031 static unsigned char
1032 encoding_for_size (unsigned int size)
1037 return DW_EH_PE_udata2;
1039 return DW_EH_PE_udata4;
1041 return DW_EH_PE_udata8;
1043 internal_error (__FILE__, __LINE__, "Unsupported address size");
1048 size_of_encoded_value (unsigned char encoding)
1050 if (encoding == DW_EH_PE_omit)
1053 switch (encoding & 0x07)
1055 case DW_EH_PE_absptr:
1056 return TYPE_LENGTH (builtin_type_void_data_ptr);
1057 case DW_EH_PE_udata2:
1059 case DW_EH_PE_udata4:
1061 case DW_EH_PE_udata8:
1064 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1069 read_encoded_value (struct comp_unit *unit, unsigned char encoding,
1070 unsigned char *buf, unsigned int *bytes_read_ptr)
1072 int ptr_len = size_of_encoded_value (DW_EH_PE_absptr);
1076 /* GCC currently doesn't generate DW_EH_PE_indirect encodings for
1078 if (encoding & DW_EH_PE_indirect)
1079 internal_error (__FILE__, __LINE__,
1080 "Unsupported encoding: DW_EH_PE_indirect");
1082 *bytes_read_ptr = 0;
1084 switch (encoding & 0x70)
1086 case DW_EH_PE_absptr:
1089 case DW_EH_PE_pcrel:
1090 base = bfd_get_section_vma (unit->bfd, unit->dwarf_frame_section);
1091 base += ((char *) buf - unit->dwarf_frame_buffer);
1093 case DW_EH_PE_datarel:
1096 case DW_EH_PE_textrel:
1099 case DW_EH_PE_funcrel:
1100 /* FIXME: kettenis/20040501: For now just pretend
1101 DW_EH_PE_funcrel is equivalent to DW_EH_PE_absptr. For
1102 reading the initial location of an FDE it should be treated
1103 as such, and currently that's the only place where this code
1107 case DW_EH_PE_aligned:
1109 offset = (char *) buf - unit->dwarf_frame_buffer;
1110 if ((offset % ptr_len) != 0)
1112 *bytes_read_ptr = ptr_len - (offset % ptr_len);
1113 buf += *bytes_read_ptr;
1117 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1120 if ((encoding & 0x07) == 0x00)
1121 encoding |= encoding_for_size (ptr_len);
1123 switch (encoding & 0x0f)
1125 case DW_EH_PE_uleb128:
1128 unsigned char *end_buf = buf + (sizeof (value) + 1) * 8 / 7;
1129 *bytes_read_ptr = read_uleb128 (buf, end_buf, &value) - buf;
1130 return base + value;
1132 case DW_EH_PE_udata2:
1133 *bytes_read_ptr += 2;
1134 return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
1135 case DW_EH_PE_udata4:
1136 *bytes_read_ptr += 4;
1137 return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
1138 case DW_EH_PE_udata8:
1139 *bytes_read_ptr += 8;
1140 return (base + bfd_get_64 (unit->abfd, (bfd_byte *) buf));
1141 case DW_EH_PE_sleb128:
1144 char *end_buf = buf + (sizeof (value) + 1) * 8 / 7;
1145 *bytes_read_ptr = read_sleb128 (buf, end_buf, &value) - buf;
1146 return base + value;
1148 case DW_EH_PE_sdata2:
1149 *bytes_read_ptr += 2;
1150 return (base + bfd_get_signed_16 (unit->abfd, (bfd_byte *) buf));
1151 case DW_EH_PE_sdata4:
1152 *bytes_read_ptr += 4;
1153 return (base + bfd_get_signed_32 (unit->abfd, (bfd_byte *) buf));
1154 case DW_EH_PE_sdata8:
1155 *bytes_read_ptr += 8;
1156 return (base + bfd_get_signed_64 (unit->abfd, (bfd_byte *) buf));
1158 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1163 /* GCC uses a single CIE for all FDEs in a .debug_frame section.
1164 That's why we use a simple linked list here. */
1166 static struct dwarf2_cie *
1167 find_cie (struct comp_unit *unit, ULONGEST cie_pointer)
1169 struct dwarf2_cie *cie = unit->cie;
1173 if (cie->cie_pointer == cie_pointer)
1183 add_cie (struct comp_unit *unit, struct dwarf2_cie *cie)
1185 cie->next = unit->cie;
1189 /* Find the FDE for *PC. Return a pointer to the FDE, and store the
1190 inital location associated with it into *PC. */
1192 static struct dwarf2_fde *
1193 dwarf2_frame_find_fde (CORE_ADDR *pc)
1195 struct objfile *objfile;
1197 ALL_OBJFILES (objfile)
1199 struct dwarf2_fde *fde;
1202 fde = objfile_data (objfile, dwarf2_frame_objfile_data);
1206 gdb_assert (objfile->section_offsets);
1207 offset = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
1211 if (*pc >= fde->initial_location + offset
1212 && *pc < fde->initial_location + offset + fde->address_range)
1214 *pc = fde->initial_location + offset;
1226 add_fde (struct comp_unit *unit, struct dwarf2_fde *fde)
1228 fde->next = objfile_data (unit->objfile, dwarf2_frame_objfile_data);
1229 set_objfile_data (unit->objfile, dwarf2_frame_objfile_data, fde);
1232 #ifdef CC_HAS_LONG_LONG
1233 #define DW64_CIE_ID 0xffffffffffffffffULL
1235 #define DW64_CIE_ID ~0
1238 static char *decode_frame_entry (struct comp_unit *unit, char *start,
1241 /* Decode the next CIE or FDE. Return NULL if invalid input, otherwise
1242 the next byte to be processed. */
1244 decode_frame_entry_1 (struct comp_unit *unit, char *start, int eh_frame_p)
1248 unsigned int bytes_read;
1251 ULONGEST cie_pointer;
1255 length = read_initial_length (unit->abfd, buf, &bytes_read);
1259 /* Are we still within the section? */
1260 if (end > unit->dwarf_frame_buffer + unit->dwarf_frame_size)
1266 /* Distinguish between 32 and 64-bit encoded frame info. */
1267 dwarf64_p = (bytes_read == 12);
1269 /* In a .eh_frame section, zero is used to distinguish CIEs from FDEs. */
1273 cie_id = DW64_CIE_ID;
1279 cie_pointer = read_8_bytes (unit->abfd, buf);
1284 cie_pointer = read_4_bytes (unit->abfd, buf);
1288 if (cie_pointer == cie_id)
1290 /* This is a CIE. */
1291 struct dwarf2_cie *cie;
1293 unsigned int cie_version;
1295 /* Record the offset into the .debug_frame section of this CIE. */
1296 cie_pointer = start - unit->dwarf_frame_buffer;
1298 /* Check whether we've already read it. */
1299 if (find_cie (unit, cie_pointer))
1302 cie = (struct dwarf2_cie *)
1303 obstack_alloc (&unit->objfile->objfile_obstack,
1304 sizeof (struct dwarf2_cie));
1305 cie->initial_instructions = NULL;
1306 cie->cie_pointer = cie_pointer;
1308 /* The encoding for FDE's in a normal .debug_frame section
1309 depends on the target address size. */
1310 cie->encoding = DW_EH_PE_absptr;
1312 /* Check version number. */
1313 cie_version = read_1_byte (unit->abfd, buf);
1314 if (cie_version != 1 && cie_version != 3)
1318 /* Interpret the interesting bits of the augmentation. */
1320 buf = augmentation + strlen (augmentation) + 1;
1322 /* The GCC 2.x "eh" augmentation has a pointer immediately
1323 following the augmentation string, so it must be handled
1325 if (augmentation[0] == 'e' && augmentation[1] == 'h')
1328 buf += TYPE_LENGTH (builtin_type_void_data_ptr);
1332 cie->code_alignment_factor =
1333 read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1336 cie->data_alignment_factor =
1337 read_signed_leb128 (unit->abfd, buf, &bytes_read);
1340 if (cie_version == 1)
1342 cie->return_address_register = read_1_byte (unit->abfd, buf);
1346 cie->return_address_register = read_unsigned_leb128 (unit->abfd, buf,
1350 cie->saw_z_augmentation = (*augmentation == 'z');
1351 if (cie->saw_z_augmentation)
1355 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1359 cie->initial_instructions = buf + length;
1363 while (*augmentation)
1365 /* "L" indicates a byte showing how the LSDA pointer is encoded. */
1366 if (*augmentation == 'L')
1373 /* "R" indicates a byte indicating how FDE addresses are encoded. */
1374 else if (*augmentation == 'R')
1376 cie->encoding = *buf++;
1380 /* "P" indicates a personality routine in the CIE augmentation. */
1381 else if (*augmentation == 'P')
1384 unsigned char encoding = *buf++;
1385 read_encoded_value (unit, encoding, buf, &bytes_read);
1390 /* Otherwise we have an unknown augmentation.
1391 Bail out unless we saw a 'z' prefix. */
1394 if (cie->initial_instructions == NULL)
1397 /* Skip unknown augmentations. */
1398 buf = cie->initial_instructions;
1403 cie->initial_instructions = buf;
1406 add_cie (unit, cie);
1410 /* This is a FDE. */
1411 struct dwarf2_fde *fde;
1413 /* In an .eh_frame section, the CIE pointer is the delta between the
1414 address within the FDE where the CIE pointer is stored and the
1415 address of the CIE. Convert it to an offset into the .eh_frame
1419 cie_pointer = buf - unit->dwarf_frame_buffer - cie_pointer;
1420 cie_pointer -= (dwarf64_p ? 8 : 4);
1423 /* In either case, validate the result is still within the section. */
1424 if (cie_pointer >= unit->dwarf_frame_size)
1427 fde = (struct dwarf2_fde *)
1428 obstack_alloc (&unit->objfile->objfile_obstack,
1429 sizeof (struct dwarf2_fde));
1430 fde->cie = find_cie (unit, cie_pointer);
1431 if (fde->cie == NULL)
1433 decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer,
1435 fde->cie = find_cie (unit, cie_pointer);
1438 gdb_assert (fde->cie != NULL);
1440 fde->initial_location =
1441 read_encoded_value (unit, fde->cie->encoding, buf, &bytes_read);
1444 fde->address_range =
1445 read_encoded_value (unit, fde->cie->encoding & 0x0f, buf, &bytes_read);
1448 /* A 'z' augmentation in the CIE implies the presence of an
1449 augmentation field in the FDE as well. The only thing known
1450 to be in here at present is the LSDA entry for EH. So we
1451 can skip the whole thing. */
1452 if (fde->cie->saw_z_augmentation)
1456 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1457 buf += bytes_read + length;
1462 fde->instructions = buf;
1465 add_fde (unit, fde);
1471 /* Read a CIE or FDE in BUF and decode it. */
1473 decode_frame_entry (struct comp_unit *unit, char *start, int eh_frame_p)
1475 enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;
1478 ptrdiff_t start_offset;
1482 ret = decode_frame_entry_1 (unit, start, eh_frame_p);
1486 /* We have corrupt input data of some form. */
1488 /* ??? Try, weakly, to work around compiler/assembler/linker bugs
1489 and mismatches wrt padding and alignment of debug sections. */
1490 /* Note that there is no requirement in the standard for any
1491 alignment at all in the frame unwind sections. Testing for
1492 alignment before trying to interpret data would be incorrect.
1494 However, GCC traditionally arranged for frame sections to be
1495 sized such that the FDE length and CIE fields happen to be
1496 aligned (in theory, for performance). This, unfortunately,
1497 was done with .align directives, which had the side effect of
1498 forcing the section to be aligned by the linker.
1500 This becomes a problem when you have some other producer that
1501 creates frame sections that are not as strictly aligned. That
1502 produces a hole in the frame info that gets filled by the
1505 The GCC behaviour is arguably a bug, but it's effectively now
1506 part of the ABI, so we're now stuck with it, at least at the
1507 object file level. A smart linker may decide, in the process
1508 of compressing duplicate CIE information, that it can rewrite
1509 the entire output section without this extra padding. */
1511 start_offset = start - unit->dwarf_frame_buffer;
1512 if (workaround < ALIGN4 && (start_offset & 3) != 0)
1514 start += 4 - (start_offset & 3);
1515 workaround = ALIGN4;
1518 if (workaround < ALIGN8 && (start_offset & 7) != 0)
1520 start += 8 - (start_offset & 7);
1521 workaround = ALIGN8;
1525 /* Nothing left to try. Arrange to return as if we've consumed
1526 the entire input section. Hopefully we'll get valid info from
1527 the other of .debug_frame/.eh_frame. */
1529 ret = unit->dwarf_frame_buffer + unit->dwarf_frame_size;
1539 complaint (&symfile_complaints,
1540 "Corrupt data in %s:%s; align 4 workaround apparently succeeded",
1541 unit->dwarf_frame_section->owner->filename,
1542 unit->dwarf_frame_section->name);
1546 complaint (&symfile_complaints,
1547 "Corrupt data in %s:%s; align 8 workaround apparently succeeded",
1548 unit->dwarf_frame_section->owner->filename,
1549 unit->dwarf_frame_section->name);
1553 complaint (&symfile_complaints,
1554 "Corrupt data in %s:%s",
1555 unit->dwarf_frame_section->owner->filename,
1556 unit->dwarf_frame_section->name);
1564 /* FIXME: kettenis/20030504: This still needs to be integrated with
1565 dwarf2read.c in a better way. */
1567 /* Imported from dwarf2read.c. */
1568 extern asection *dwarf_frame_section;
1569 extern asection *dwarf_eh_frame_section;
1571 /* Imported from dwarf2read.c. */
1572 extern char *dwarf2_read_section (struct objfile *objfile, asection *sectp);
1575 dwarf2_build_frame_info (struct objfile *objfile)
1577 struct comp_unit unit;
1580 /* Build a minimal decoding of the DWARF2 compilation unit. */
1581 unit.abfd = objfile->obfd;
1582 unit.objfile = objfile;
1586 /* First add the information from the .eh_frame section. That way,
1587 the FDEs from that section are searched last. */
1588 if (dwarf_eh_frame_section)
1590 asection *got, *txt;
1593 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1594 dwarf_eh_frame_section);
1596 unit.dwarf_frame_size = bfd_get_section_size (dwarf_eh_frame_section);
1597 unit.dwarf_frame_section = dwarf_eh_frame_section;
1599 /* FIXME: kettenis/20030602: This is the DW_EH_PE_datarel base
1600 that is used for the i386/amd64 target, which currently is
1601 the only target in GCC that supports/uses the
1602 DW_EH_PE_datarel encoding. */
1603 got = bfd_get_section_by_name (unit.abfd, ".got");
1605 unit.dbase = got->vma;
1607 /* GCC emits the DW_EH_PE_textrel encoding type on sh and ia64
1609 txt = bfd_get_section_by_name (unit.abfd, ".text");
1611 unit.tbase = txt->vma;
1613 frame_ptr = unit.dwarf_frame_buffer;
1614 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1615 frame_ptr = decode_frame_entry (&unit, frame_ptr, 1);
1618 if (dwarf_frame_section)
1621 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1622 dwarf_frame_section);
1623 unit.dwarf_frame_size = bfd_get_section_size (dwarf_frame_section);
1624 unit.dwarf_frame_section = dwarf_frame_section;
1626 frame_ptr = unit.dwarf_frame_buffer;
1627 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1628 frame_ptr = decode_frame_entry (&unit, frame_ptr, 0);
1632 /* Provide a prototype to silence -Wmissing-prototypes. */
1633 void _initialize_dwarf2_frame (void);
1636 _initialize_dwarf2_frame (void)
1638 dwarf2_frame_data = gdbarch_data_register_pre_init (dwarf2_frame_init);
1639 dwarf2_frame_objfile_data = register_objfile_data ();