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)
678 if (cache->reg[regnum].how == DWARF2_FRAME_REG_UNSPECIFIED)
679 complaint (&symfile_complaints, "\
680 incomplete CFI data; unspecified registers (e.g., %s) at 0x%s",
681 gdbarch_register_name (gdbarch, regnum),
685 cache->reg[regnum] = fs->regs.reg[column];
689 /* Eliminate any DWARF2_FRAME_REG_RA rules. */
693 for (regnum = 0; regnum < num_regs; regnum++)
695 if (cache->reg[regnum].how == DWARF2_FRAME_REG_RA)
697 struct dwarf2_frame_state_reg *retaddr_reg =
698 &fs->regs.reg[fs->retaddr_column];
700 /* It seems rather bizarre to specify an "empty" column as
701 the return adress column. However, this is exactly
702 what GCC does on some targets. It turns out that GCC
703 assumes that the return address can be found in the
704 register corresponding to the return address column.
705 Incidentally, that's how should treat a return address
706 column specifying "same value" too. */
707 if (fs->retaddr_column < fs->regs.num_regs
708 && retaddr_reg->how != DWARF2_FRAME_REG_UNSPECIFIED
709 && retaddr_reg->how != DWARF2_FRAME_REG_SAME_VALUE)
710 cache->reg[regnum] = *retaddr_reg;
713 cache->reg[regnum].loc.reg = fs->retaddr_column;
714 cache->reg[regnum].how = DWARF2_FRAME_REG_SAVED_REG;
720 do_cleanups (old_chain);
727 dwarf2_frame_this_id (struct frame_info *next_frame, void **this_cache,
728 struct frame_id *this_id)
730 struct dwarf2_frame_cache *cache =
731 dwarf2_frame_cache (next_frame, this_cache);
733 (*this_id) = frame_id_build (cache->cfa, frame_func_unwind (next_frame));
737 dwarf2_frame_prev_register (struct frame_info *next_frame, void **this_cache,
738 int regnum, int *optimizedp,
739 enum lval_type *lvalp, CORE_ADDR *addrp,
740 int *realnump, void *valuep)
742 struct gdbarch *gdbarch = get_frame_arch (next_frame);
743 struct dwarf2_frame_cache *cache =
744 dwarf2_frame_cache (next_frame, this_cache);
746 switch (cache->reg[regnum].how)
748 case DWARF2_FRAME_REG_UNDEFINED:
749 /* If CFI explicitly specified that the value isn't defined,
750 mark it as optimized away; the value isn't available. */
757 /* In some cases, for example %eflags on the i386, we have
758 to provide a sane value, even though this register wasn't
759 saved. Assume we can get it from NEXT_FRAME. */
760 frame_unwind_register (next_frame, regnum, valuep);
764 case DWARF2_FRAME_REG_SAVED_OFFSET:
766 *lvalp = lval_memory;
767 *addrp = cache->cfa + cache->reg[regnum].loc.offset;
771 /* Read the value in from memory. */
772 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
776 case DWARF2_FRAME_REG_SAVED_REG:
778 *lvalp = lval_register;
780 *realnump = DWARF2_REG_TO_REGNUM (cache->reg[regnum].loc.reg);
782 frame_unwind_register (next_frame, (*realnump), valuep);
785 case DWARF2_FRAME_REG_SAVED_EXP:
787 *lvalp = lval_memory;
788 *addrp = execute_stack_op (cache->reg[regnum].loc.exp,
789 cache->reg[regnum].exp_len,
790 next_frame, cache->cfa);
794 /* Read the value in from memory. */
795 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
799 case DWARF2_FRAME_REG_UNSPECIFIED:
800 /* GCC, in its infinite wisdom decided to not provide unwind
801 information for registers that are "same value". Since
802 DWARF2 (3 draft 7) doesn't define such behavior, said
803 registers are actually undefined (which is different to CFI
804 "undefined"). Code above issues a complaint about this.
805 Here just fudge the books, assume GCC, and that the value is
806 more inner on the stack. */
808 *lvalp = lval_register;
812 frame_unwind_register (next_frame, (*realnump), valuep);
815 case DWARF2_FRAME_REG_SAME_VALUE:
817 *lvalp = lval_register;
821 frame_unwind_register (next_frame, (*realnump), valuep);
824 case DWARF2_FRAME_REG_CFA:
831 /* Store the value. */
832 store_typed_address (valuep, builtin_type_void_data_ptr, cache->cfa);
837 internal_error (__FILE__, __LINE__, "Unknown register rule.");
841 static const struct frame_unwind dwarf2_frame_unwind =
844 dwarf2_frame_this_id,
845 dwarf2_frame_prev_register
848 const struct frame_unwind *
849 dwarf2_frame_sniffer (struct frame_info *next_frame)
851 /* Grab an address that is guarenteed to reside somewhere within the
852 function. frame_pc_unwind(), for a no-return next function, can
853 end up returning something past the end of this function's body. */
854 CORE_ADDR block_addr = frame_unwind_address_in_block (next_frame);
855 if (dwarf2_frame_find_fde (&block_addr))
856 return &dwarf2_frame_unwind;
862 /* There is no explicitly defined relationship between the CFA and the
863 location of frame's local variables and arguments/parameters.
864 Therefore, frame base methods on this page should probably only be
865 used as a last resort, just to avoid printing total garbage as a
866 response to the "info frame" command. */
869 dwarf2_frame_base_address (struct frame_info *next_frame, void **this_cache)
871 struct dwarf2_frame_cache *cache =
872 dwarf2_frame_cache (next_frame, this_cache);
877 static const struct frame_base dwarf2_frame_base =
879 &dwarf2_frame_unwind,
880 dwarf2_frame_base_address,
881 dwarf2_frame_base_address,
882 dwarf2_frame_base_address
885 const struct frame_base *
886 dwarf2_frame_base_sniffer (struct frame_info *next_frame)
888 CORE_ADDR pc = frame_pc_unwind (next_frame);
889 if (dwarf2_frame_find_fde (&pc))
890 return &dwarf2_frame_base;
895 /* A minimal decoding of DWARF2 compilation units. We only decode
896 what's needed to get to the call frame information. */
900 /* Keep the bfd convenient. */
903 struct objfile *objfile;
905 /* Linked list of CIEs for this object. */
906 struct dwarf2_cie *cie;
908 /* Pointer to the .debug_frame section loaded into memory. */
909 char *dwarf_frame_buffer;
911 /* Length of the loaded .debug_frame section. */
912 unsigned long dwarf_frame_size;
914 /* Pointer to the .debug_frame section. */
915 asection *dwarf_frame_section;
917 /* Base for DW_EH_PE_datarel encodings. */
920 /* Base for DW_EH_PE_textrel encodings. */
924 const struct objfile_data *dwarf2_frame_objfile_data;
927 read_1_byte (bfd *bfd, char *buf)
929 return bfd_get_8 (abfd, (bfd_byte *) buf);
933 read_4_bytes (bfd *abfd, char *buf)
935 return bfd_get_32 (abfd, (bfd_byte *) buf);
939 read_8_bytes (bfd *abfd, char *buf)
941 return bfd_get_64 (abfd, (bfd_byte *) buf);
945 read_unsigned_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
948 unsigned int num_read;
958 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
961 result |= ((byte & 0x7f) << shift);
966 *bytes_read_ptr = num_read;
972 read_signed_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
976 unsigned int num_read;
985 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
988 result |= ((byte & 0x7f) << shift);
993 if ((shift < 32) && (byte & 0x40))
994 result |= -(1 << shift);
996 *bytes_read_ptr = num_read;
1002 read_initial_length (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
1006 result = bfd_get_32 (abfd, (bfd_byte *) buf);
1007 if (result == 0xffffffff)
1009 result = bfd_get_64 (abfd, (bfd_byte *) buf + 4);
1010 *bytes_read_ptr = 12;
1013 *bytes_read_ptr = 4;
1019 /* Pointer encoding helper functions. */
1021 /* GCC supports exception handling based on DWARF2 CFI. However, for
1022 technical reasons, it encodes addresses in its FDE's in a different
1023 way. Several "pointer encodings" are supported. The encoding
1024 that's used for a particular FDE is determined by the 'R'
1025 augmentation in the associated CIE. The argument of this
1026 augmentation is a single byte.
1028 The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
1029 LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether
1030 the address is signed or unsigned. Bits 4, 5 and 6 encode how the
1031 address should be interpreted (absolute, relative to the current
1032 position in the FDE, ...). Bit 7, indicates that the address
1033 should be dereferenced. */
1035 static unsigned char
1036 encoding_for_size (unsigned int size)
1041 return DW_EH_PE_udata2;
1043 return DW_EH_PE_udata4;
1045 return DW_EH_PE_udata8;
1047 internal_error (__FILE__, __LINE__, "Unsupported address size");
1052 size_of_encoded_value (unsigned char encoding)
1054 if (encoding == DW_EH_PE_omit)
1057 switch (encoding & 0x07)
1059 case DW_EH_PE_absptr:
1060 return TYPE_LENGTH (builtin_type_void_data_ptr);
1061 case DW_EH_PE_udata2:
1063 case DW_EH_PE_udata4:
1065 case DW_EH_PE_udata8:
1068 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1073 read_encoded_value (struct comp_unit *unit, unsigned char encoding,
1074 unsigned char *buf, unsigned int *bytes_read_ptr)
1076 int ptr_len = size_of_encoded_value (DW_EH_PE_absptr);
1080 /* GCC currently doesn't generate DW_EH_PE_indirect encodings for
1082 if (encoding & DW_EH_PE_indirect)
1083 internal_error (__FILE__, __LINE__,
1084 "Unsupported encoding: DW_EH_PE_indirect");
1086 *bytes_read_ptr = 0;
1088 switch (encoding & 0x70)
1090 case DW_EH_PE_absptr:
1093 case DW_EH_PE_pcrel:
1094 base = bfd_get_section_vma (unit->bfd, unit->dwarf_frame_section);
1095 base += ((char *) buf - unit->dwarf_frame_buffer);
1097 case DW_EH_PE_datarel:
1100 case DW_EH_PE_textrel:
1103 case DW_EH_PE_funcrel:
1104 /* FIXME: kettenis/20040501: For now just pretend
1105 DW_EH_PE_funcrel is equivalent to DW_EH_PE_absptr. For
1106 reading the initial location of an FDE it should be treated
1107 as such, and currently that's the only place where this code
1111 case DW_EH_PE_aligned:
1113 offset = (char *) buf - unit->dwarf_frame_buffer;
1114 if ((offset % ptr_len) != 0)
1116 *bytes_read_ptr = ptr_len - (offset % ptr_len);
1117 buf += *bytes_read_ptr;
1121 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1124 if ((encoding & 0x07) == 0x00)
1125 encoding |= encoding_for_size (ptr_len);
1127 switch (encoding & 0x0f)
1129 case DW_EH_PE_uleb128:
1132 unsigned char *end_buf = buf + (sizeof (value) + 1) * 8 / 7;
1133 *bytes_read_ptr = read_uleb128 (buf, end_buf, &value) - buf;
1134 return base + value;
1136 case DW_EH_PE_udata2:
1137 *bytes_read_ptr += 2;
1138 return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
1139 case DW_EH_PE_udata4:
1140 *bytes_read_ptr += 4;
1141 return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
1142 case DW_EH_PE_udata8:
1143 *bytes_read_ptr += 8;
1144 return (base + bfd_get_64 (unit->abfd, (bfd_byte *) buf));
1145 case DW_EH_PE_sleb128:
1148 char *end_buf = buf + (sizeof (value) + 1) * 8 / 7;
1149 *bytes_read_ptr = read_sleb128 (buf, end_buf, &value) - buf;
1150 return base + value;
1152 case DW_EH_PE_sdata2:
1153 *bytes_read_ptr += 2;
1154 return (base + bfd_get_signed_16 (unit->abfd, (bfd_byte *) buf));
1155 case DW_EH_PE_sdata4:
1156 *bytes_read_ptr += 4;
1157 return (base + bfd_get_signed_32 (unit->abfd, (bfd_byte *) buf));
1158 case DW_EH_PE_sdata8:
1159 *bytes_read_ptr += 8;
1160 return (base + bfd_get_signed_64 (unit->abfd, (bfd_byte *) buf));
1162 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1167 /* GCC uses a single CIE for all FDEs in a .debug_frame section.
1168 That's why we use a simple linked list here. */
1170 static struct dwarf2_cie *
1171 find_cie (struct comp_unit *unit, ULONGEST cie_pointer)
1173 struct dwarf2_cie *cie = unit->cie;
1177 if (cie->cie_pointer == cie_pointer)
1187 add_cie (struct comp_unit *unit, struct dwarf2_cie *cie)
1189 cie->next = unit->cie;
1193 /* Find the FDE for *PC. Return a pointer to the FDE, and store the
1194 inital location associated with it into *PC. */
1196 static struct dwarf2_fde *
1197 dwarf2_frame_find_fde (CORE_ADDR *pc)
1199 struct objfile *objfile;
1201 ALL_OBJFILES (objfile)
1203 struct dwarf2_fde *fde;
1206 fde = objfile_data (objfile, dwarf2_frame_objfile_data);
1210 gdb_assert (objfile->section_offsets);
1211 offset = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
1215 if (*pc >= fde->initial_location + offset
1216 && *pc < fde->initial_location + offset + fde->address_range)
1218 *pc = fde->initial_location + offset;
1230 add_fde (struct comp_unit *unit, struct dwarf2_fde *fde)
1232 fde->next = objfile_data (unit->objfile, dwarf2_frame_objfile_data);
1233 set_objfile_data (unit->objfile, dwarf2_frame_objfile_data, fde);
1236 #ifdef CC_HAS_LONG_LONG
1237 #define DW64_CIE_ID 0xffffffffffffffffULL
1239 #define DW64_CIE_ID ~0
1242 static char *decode_frame_entry (struct comp_unit *unit, char *start,
1245 /* Decode the next CIE or FDE. Return NULL if invalid input, otherwise
1246 the next byte to be processed. */
1248 decode_frame_entry_1 (struct comp_unit *unit, char *start, int eh_frame_p)
1252 unsigned int bytes_read;
1255 ULONGEST cie_pointer;
1259 length = read_initial_length (unit->abfd, buf, &bytes_read);
1263 /* Are we still within the section? */
1264 if (end > unit->dwarf_frame_buffer + unit->dwarf_frame_size)
1270 /* Distinguish between 32 and 64-bit encoded frame info. */
1271 dwarf64_p = (bytes_read == 12);
1273 /* In a .eh_frame section, zero is used to distinguish CIEs from FDEs. */
1277 cie_id = DW64_CIE_ID;
1283 cie_pointer = read_8_bytes (unit->abfd, buf);
1288 cie_pointer = read_4_bytes (unit->abfd, buf);
1292 if (cie_pointer == cie_id)
1294 /* This is a CIE. */
1295 struct dwarf2_cie *cie;
1297 unsigned int cie_version;
1299 /* Record the offset into the .debug_frame section of this CIE. */
1300 cie_pointer = start - unit->dwarf_frame_buffer;
1302 /* Check whether we've already read it. */
1303 if (find_cie (unit, cie_pointer))
1306 cie = (struct dwarf2_cie *)
1307 obstack_alloc (&unit->objfile->objfile_obstack,
1308 sizeof (struct dwarf2_cie));
1309 cie->initial_instructions = NULL;
1310 cie->cie_pointer = cie_pointer;
1312 /* The encoding for FDE's in a normal .debug_frame section
1313 depends on the target address size. */
1314 cie->encoding = DW_EH_PE_absptr;
1316 /* Check version number. */
1317 cie_version = read_1_byte (unit->abfd, buf);
1318 if (cie_version != 1 && cie_version != 3)
1322 /* Interpret the interesting bits of the augmentation. */
1324 buf = augmentation + strlen (augmentation) + 1;
1326 /* The GCC 2.x "eh" augmentation has a pointer immediately
1327 following the augmentation string, so it must be handled
1329 if (augmentation[0] == 'e' && augmentation[1] == 'h')
1332 buf += TYPE_LENGTH (builtin_type_void_data_ptr);
1336 cie->code_alignment_factor =
1337 read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1340 cie->data_alignment_factor =
1341 read_signed_leb128 (unit->abfd, buf, &bytes_read);
1344 if (cie_version == 1)
1346 cie->return_address_register = read_1_byte (unit->abfd, buf);
1350 cie->return_address_register = read_unsigned_leb128 (unit->abfd, buf,
1354 cie->saw_z_augmentation = (*augmentation == 'z');
1355 if (cie->saw_z_augmentation)
1359 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1363 cie->initial_instructions = buf + length;
1367 while (*augmentation)
1369 /* "L" indicates a byte showing how the LSDA pointer is encoded. */
1370 if (*augmentation == 'L')
1377 /* "R" indicates a byte indicating how FDE addresses are encoded. */
1378 else if (*augmentation == 'R')
1380 cie->encoding = *buf++;
1384 /* "P" indicates a personality routine in the CIE augmentation. */
1385 else if (*augmentation == 'P')
1387 /* Skip. Avoid indirection since we throw away the result. */
1388 unsigned char encoding = (*buf++) & ~DW_EH_PE_indirect;
1389 read_encoded_value (unit, encoding, buf, &bytes_read);
1394 /* Otherwise we have an unknown augmentation.
1395 Bail out unless we saw a 'z' prefix. */
1398 if (cie->initial_instructions == NULL)
1401 /* Skip unknown augmentations. */
1402 buf = cie->initial_instructions;
1407 cie->initial_instructions = buf;
1410 add_cie (unit, cie);
1414 /* This is a FDE. */
1415 struct dwarf2_fde *fde;
1417 /* In an .eh_frame section, the CIE pointer is the delta between the
1418 address within the FDE where the CIE pointer is stored and the
1419 address of the CIE. Convert it to an offset into the .eh_frame
1423 cie_pointer = buf - unit->dwarf_frame_buffer - cie_pointer;
1424 cie_pointer -= (dwarf64_p ? 8 : 4);
1427 /* In either case, validate the result is still within the section. */
1428 if (cie_pointer >= unit->dwarf_frame_size)
1431 fde = (struct dwarf2_fde *)
1432 obstack_alloc (&unit->objfile->objfile_obstack,
1433 sizeof (struct dwarf2_fde));
1434 fde->cie = find_cie (unit, cie_pointer);
1435 if (fde->cie == NULL)
1437 decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer,
1439 fde->cie = find_cie (unit, cie_pointer);
1442 gdb_assert (fde->cie != NULL);
1444 fde->initial_location =
1445 read_encoded_value (unit, fde->cie->encoding, buf, &bytes_read);
1448 fde->address_range =
1449 read_encoded_value (unit, fde->cie->encoding & 0x0f, buf, &bytes_read);
1452 /* A 'z' augmentation in the CIE implies the presence of an
1453 augmentation field in the FDE as well. The only thing known
1454 to be in here at present is the LSDA entry for EH. So we
1455 can skip the whole thing. */
1456 if (fde->cie->saw_z_augmentation)
1460 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1461 buf += bytes_read + length;
1466 fde->instructions = buf;
1469 add_fde (unit, fde);
1475 /* Read a CIE or FDE in BUF and decode it. */
1477 decode_frame_entry (struct comp_unit *unit, char *start, int eh_frame_p)
1479 enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;
1482 ptrdiff_t start_offset;
1486 ret = decode_frame_entry_1 (unit, start, eh_frame_p);
1490 /* We have corrupt input data of some form. */
1492 /* ??? Try, weakly, to work around compiler/assembler/linker bugs
1493 and mismatches wrt padding and alignment of debug sections. */
1494 /* Note that there is no requirement in the standard for any
1495 alignment at all in the frame unwind sections. Testing for
1496 alignment before trying to interpret data would be incorrect.
1498 However, GCC traditionally arranged for frame sections to be
1499 sized such that the FDE length and CIE fields happen to be
1500 aligned (in theory, for performance). This, unfortunately,
1501 was done with .align directives, which had the side effect of
1502 forcing the section to be aligned by the linker.
1504 This becomes a problem when you have some other producer that
1505 creates frame sections that are not as strictly aligned. That
1506 produces a hole in the frame info that gets filled by the
1509 The GCC behaviour is arguably a bug, but it's effectively now
1510 part of the ABI, so we're now stuck with it, at least at the
1511 object file level. A smart linker may decide, in the process
1512 of compressing duplicate CIE information, that it can rewrite
1513 the entire output section without this extra padding. */
1515 start_offset = start - unit->dwarf_frame_buffer;
1516 if (workaround < ALIGN4 && (start_offset & 3) != 0)
1518 start += 4 - (start_offset & 3);
1519 workaround = ALIGN4;
1522 if (workaround < ALIGN8 && (start_offset & 7) != 0)
1524 start += 8 - (start_offset & 7);
1525 workaround = ALIGN8;
1529 /* Nothing left to try. Arrange to return as if we've consumed
1530 the entire input section. Hopefully we'll get valid info from
1531 the other of .debug_frame/.eh_frame. */
1533 ret = unit->dwarf_frame_buffer + unit->dwarf_frame_size;
1543 complaint (&symfile_complaints,
1544 "Corrupt data in %s:%s; align 4 workaround apparently succeeded",
1545 unit->dwarf_frame_section->owner->filename,
1546 unit->dwarf_frame_section->name);
1550 complaint (&symfile_complaints,
1551 "Corrupt data in %s:%s; align 8 workaround apparently succeeded",
1552 unit->dwarf_frame_section->owner->filename,
1553 unit->dwarf_frame_section->name);
1557 complaint (&symfile_complaints,
1558 "Corrupt data in %s:%s",
1559 unit->dwarf_frame_section->owner->filename,
1560 unit->dwarf_frame_section->name);
1568 /* FIXME: kettenis/20030504: This still needs to be integrated with
1569 dwarf2read.c in a better way. */
1571 /* Imported from dwarf2read.c. */
1572 extern asection *dwarf_frame_section;
1573 extern asection *dwarf_eh_frame_section;
1575 /* Imported from dwarf2read.c. */
1576 extern char *dwarf2_read_section (struct objfile *objfile, asection *sectp);
1579 dwarf2_build_frame_info (struct objfile *objfile)
1581 struct comp_unit unit;
1584 /* Build a minimal decoding of the DWARF2 compilation unit. */
1585 unit.abfd = objfile->obfd;
1586 unit.objfile = objfile;
1590 /* First add the information from the .eh_frame section. That way,
1591 the FDEs from that section are searched last. */
1592 if (dwarf_eh_frame_section)
1594 asection *got, *txt;
1597 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1598 dwarf_eh_frame_section);
1600 unit.dwarf_frame_size = bfd_get_section_size (dwarf_eh_frame_section);
1601 unit.dwarf_frame_section = dwarf_eh_frame_section;
1603 /* FIXME: kettenis/20030602: This is the DW_EH_PE_datarel base
1604 that is used for the i386/amd64 target, which currently is
1605 the only target in GCC that supports/uses the
1606 DW_EH_PE_datarel encoding. */
1607 got = bfd_get_section_by_name (unit.abfd, ".got");
1609 unit.dbase = got->vma;
1611 /* GCC emits the DW_EH_PE_textrel encoding type on sh and ia64
1613 txt = bfd_get_section_by_name (unit.abfd, ".text");
1615 unit.tbase = txt->vma;
1617 frame_ptr = unit.dwarf_frame_buffer;
1618 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1619 frame_ptr = decode_frame_entry (&unit, frame_ptr, 1);
1622 if (dwarf_frame_section)
1625 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1626 dwarf_frame_section);
1627 unit.dwarf_frame_size = bfd_get_section_size (dwarf_frame_section);
1628 unit.dwarf_frame_section = dwarf_frame_section;
1630 frame_ptr = unit.dwarf_frame_buffer;
1631 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1632 frame_ptr = decode_frame_entry (&unit, frame_ptr, 0);
1636 /* Provide a prototype to silence -Wmissing-prototypes. */
1637 void _initialize_dwarf2_frame (void);
1640 _initialize_dwarf2_frame (void)
1642 dwarf2_frame_data = gdbarch_data_register_pre_init (dwarf2_frame_init);
1643 dwarf2_frame_objfile_data = register_objfile_data ();