1 /* Frame unwinder for frames with DWARF Call Frame Information.
3 Copyright 2003, 2004 Free Software Foundation, Inc.
5 Contributed by Mark Kettenis.
7 This file is part of GDB.
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 2 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with this program; if not, write to the Free Software
21 Foundation, Inc., 59 Temple Place - Suite 330,
22 Boston, MA 02111-1307, USA. */
25 #include "dwarf2expr.h"
26 #include "elf/dwarf2.h"
28 #include "frame-base.h"
29 #include "frame-unwind.h"
36 #include "gdb_assert.h"
37 #include "gdb_string.h"
39 #include "complaints.h"
40 #include "dwarf2-frame.h"
42 /* Call Frame Information (CFI). */
44 /* Common Information Entry (CIE). */
48 /* Offset into the .debug_frame section where this CIE was found.
49 Used to identify this CIE. */
52 /* Constant that is factored out of all advance location
54 ULONGEST code_alignment_factor;
56 /* Constants that is factored out of all offset instructions. */
57 LONGEST data_alignment_factor;
59 /* Return address column. */
60 ULONGEST return_address_register;
62 /* Instruction sequence to initialize a register set. */
63 unsigned char *initial_instructions;
66 /* Encoding of addresses. */
67 unsigned char encoding;
69 /* True if a 'z' augmentation existed. */
70 unsigned char saw_z_augmentation;
72 struct dwarf2_cie *next;
75 /* Frame Description Entry (FDE). */
79 /* CIE for this FDE. */
80 struct dwarf2_cie *cie;
82 /* First location associated with this FDE. */
83 CORE_ADDR initial_location;
85 /* Number of bytes of program instructions described by this FDE. */
86 CORE_ADDR address_range;
88 /* Instruction sequence. */
89 unsigned char *instructions;
92 struct dwarf2_fde *next;
95 static struct dwarf2_fde *dwarf2_frame_find_fde (CORE_ADDR *pc);
98 /* Structure describing a frame state. */
100 struct dwarf2_frame_state
102 /* Each register save state can be described in terms of a CFA slot,
103 another register, or a location expression. */
104 struct dwarf2_frame_state_reg_info
106 struct dwarf2_frame_state_reg *reg;
109 /* Used to implement DW_CFA_remember_state. */
110 struct dwarf2_frame_state_reg_info *prev;
115 unsigned char *cfa_exp;
122 /* The PC described by the current frame state. */
125 /* Initial register set from the CIE.
126 Used to implement DW_CFA_restore. */
127 struct dwarf2_frame_state_reg_info initial;
129 /* The information we care about from the CIE. */
132 ULONGEST retaddr_column;
135 /* Store the length the expression for the CFA in the `cfa_reg' field,
136 which is unused in that case. */
137 #define cfa_exp_len cfa_reg
139 /* Assert that the register set RS is large enough to store NUM_REGS
140 columns. If necessary, enlarge the register set. */
143 dwarf2_frame_state_alloc_regs (struct dwarf2_frame_state_reg_info *rs,
146 size_t size = sizeof (struct dwarf2_frame_state_reg);
148 if (num_regs <= rs->num_regs)
151 rs->reg = (struct dwarf2_frame_state_reg *)
152 xrealloc (rs->reg, num_regs * size);
154 /* Initialize newly allocated registers. */
155 memset (rs->reg + rs->num_regs, 0, (num_regs - rs->num_regs) * size);
156 rs->num_regs = num_regs;
159 /* Copy the register columns in register set RS into newly allocated
160 memory and return a pointer to this newly created copy. */
162 static struct dwarf2_frame_state_reg *
163 dwarf2_frame_state_copy_regs (struct dwarf2_frame_state_reg_info *rs)
165 size_t size = rs->num_regs * sizeof (struct dwarf2_frame_state_reg_info);
166 struct dwarf2_frame_state_reg *reg;
168 reg = (struct dwarf2_frame_state_reg *) xmalloc (size);
169 memcpy (reg, rs->reg, size);
174 /* Release the memory allocated to register set RS. */
177 dwarf2_frame_state_free_regs (struct dwarf2_frame_state_reg_info *rs)
181 dwarf2_frame_state_free_regs (rs->prev);
188 /* Release the memory allocated to the frame state FS. */
191 dwarf2_frame_state_free (void *p)
193 struct dwarf2_frame_state *fs = p;
195 dwarf2_frame_state_free_regs (fs->initial.prev);
196 dwarf2_frame_state_free_regs (fs->regs.prev);
197 xfree (fs->initial.reg);
198 xfree (fs->regs.reg);
203 /* Helper functions for execute_stack_op. */
206 read_reg (void *baton, int reg)
208 struct frame_info *next_frame = (struct frame_info *) baton;
209 struct gdbarch *gdbarch = get_frame_arch (next_frame);
213 regnum = DWARF2_REG_TO_REGNUM (reg);
215 buf = (char *) alloca (register_size (gdbarch, regnum));
216 frame_unwind_register (next_frame, regnum, buf);
217 return extract_typed_address (buf, builtin_type_void_data_ptr);
221 read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len)
223 read_memory (addr, buf, len);
227 no_get_frame_base (void *baton, unsigned char **start, size_t *length)
229 internal_error (__FILE__, __LINE__,
230 "Support for DW_OP_fbreg is unimplemented");
234 no_get_tls_address (void *baton, CORE_ADDR offset)
236 internal_error (__FILE__, __LINE__,
237 "Support for DW_OP_GNU_push_tls_address is unimplemented");
241 execute_stack_op (unsigned char *exp, ULONGEST len,
242 struct frame_info *next_frame, CORE_ADDR initial)
244 struct dwarf_expr_context *ctx;
247 ctx = new_dwarf_expr_context ();
248 ctx->baton = next_frame;
249 ctx->read_reg = read_reg;
250 ctx->read_mem = read_mem;
251 ctx->get_frame_base = no_get_frame_base;
252 ctx->get_tls_address = no_get_tls_address;
254 dwarf_expr_push (ctx, initial);
255 dwarf_expr_eval (ctx, exp, len);
256 result = dwarf_expr_fetch (ctx, 0);
259 result = read_reg (next_frame, result);
261 free_dwarf_expr_context (ctx);
268 execute_cfa_program (unsigned char *insn_ptr, unsigned char *insn_end,
269 struct frame_info *next_frame,
270 struct dwarf2_frame_state *fs)
272 CORE_ADDR pc = frame_pc_unwind (next_frame);
275 while (insn_ptr < insn_end && fs->pc <= pc)
277 unsigned char insn = *insn_ptr++;
281 if ((insn & 0xc0) == DW_CFA_advance_loc)
282 fs->pc += (insn & 0x3f) * fs->code_align;
283 else if ((insn & 0xc0) == DW_CFA_offset)
286 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
287 offset = utmp * fs->data_align;
288 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
289 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
290 fs->regs.reg[reg].loc.offset = offset;
292 else if ((insn & 0xc0) == DW_CFA_restore)
294 gdb_assert (fs->initial.reg);
296 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
297 fs->regs.reg[reg] = fs->initial.reg[reg];
304 fs->pc = dwarf2_read_address (insn_ptr, insn_end, &bytes_read);
305 insn_ptr += bytes_read;
308 case DW_CFA_advance_loc1:
309 utmp = extract_unsigned_integer (insn_ptr, 1);
310 fs->pc += utmp * fs->code_align;
313 case DW_CFA_advance_loc2:
314 utmp = extract_unsigned_integer (insn_ptr, 2);
315 fs->pc += utmp * fs->code_align;
318 case DW_CFA_advance_loc4:
319 utmp = extract_unsigned_integer (insn_ptr, 4);
320 fs->pc += utmp * fs->code_align;
324 case DW_CFA_offset_extended:
325 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
326 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
327 offset = utmp * fs->data_align;
328 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
329 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
330 fs->regs.reg[reg].loc.offset = offset;
333 case DW_CFA_restore_extended:
334 gdb_assert (fs->initial.reg);
335 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
336 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
337 fs->regs.reg[reg] = fs->initial.reg[reg];
340 case DW_CFA_undefined:
341 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
342 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
343 fs->regs.reg[reg].how = DWARF2_FRAME_REG_UNDEFINED;
346 case DW_CFA_same_value:
347 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
348 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
349 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAME_VALUE;
352 case DW_CFA_register:
353 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
354 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
355 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
356 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_REG;
357 fs->regs.reg[reg].loc.reg = utmp;
360 case DW_CFA_remember_state:
362 struct dwarf2_frame_state_reg_info *new_rs;
364 new_rs = XMALLOC (struct dwarf2_frame_state_reg_info);
366 fs->regs.reg = dwarf2_frame_state_copy_regs (&fs->regs);
367 fs->regs.prev = new_rs;
371 case DW_CFA_restore_state:
373 struct dwarf2_frame_state_reg_info *old_rs = fs->regs.prev;
377 xfree (fs->regs.reg);
384 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
385 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
386 fs->cfa_offset = utmp;
387 fs->cfa_how = CFA_REG_OFFSET;
390 case DW_CFA_def_cfa_register:
391 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
392 fs->cfa_how = CFA_REG_OFFSET;
395 case DW_CFA_def_cfa_offset:
396 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_offset);
397 /* cfa_how deliberately not set. */
403 case DW_CFA_def_cfa_expression:
404 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_exp_len);
405 fs->cfa_exp = insn_ptr;
406 fs->cfa_how = CFA_EXP;
407 insn_ptr += fs->cfa_exp_len;
410 case DW_CFA_expression:
411 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
412 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
413 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
414 fs->regs.reg[reg].loc.exp = insn_ptr;
415 fs->regs.reg[reg].exp_len = utmp;
416 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_EXP;
420 case DW_CFA_offset_extended_sf:
421 insn_ptr = read_uleb128 (insn_ptr, insn_end, ®);
422 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
423 offset += fs->data_align;
424 dwarf2_frame_state_alloc_regs (&fs->regs, reg + 1);
425 fs->regs.reg[reg].how = DWARF2_FRAME_REG_SAVED_OFFSET;
426 fs->regs.reg[reg].loc.offset = offset;
429 case DW_CFA_def_cfa_sf:
430 insn_ptr = read_uleb128 (insn_ptr, insn_end, &fs->cfa_reg);
431 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
432 fs->cfa_offset = offset * fs->data_align;
433 fs->cfa_how = CFA_REG_OFFSET;
436 case DW_CFA_def_cfa_offset_sf:
437 insn_ptr = read_sleb128 (insn_ptr, insn_end, &offset);
438 fs->cfa_offset = offset * fs->data_align;
439 /* cfa_how deliberately not set. */
442 case DW_CFA_GNU_args_size:
444 insn_ptr = read_uleb128 (insn_ptr, insn_end, &utmp);
448 internal_error (__FILE__, __LINE__, "Unknown CFI encountered.");
453 /* Don't allow remember/restore between CIE and FDE programs. */
454 dwarf2_frame_state_free_regs (fs->regs.prev);
455 fs->regs.prev = NULL;
459 /* Architecture-specific operations. */
461 /* Per-architecture data key. */
462 static struct gdbarch_data *dwarf2_frame_data;
464 struct dwarf2_frame_ops
466 /* Pre-initialize the register state REG for register REGNUM. */
467 void (*init_reg) (struct gdbarch *, int, struct dwarf2_frame_state_reg *);
470 /* Default architecture-specific register state initialization
474 dwarf2_frame_default_init_reg (struct gdbarch *gdbarch, int regnum,
475 struct dwarf2_frame_state_reg *reg)
477 /* If we have a register that acts as a program counter, mark it as
478 a destination for the return address. If we have a register that
479 serves as the stack pointer, arrange for it to be filled with the
480 call frame address (CFA). The other registers are marked as
483 We copy the return address to the program counter, since many
484 parts in GDB assume that it is possible to get the return address
485 by unwinding the program counter register. However, on ISA's
486 with a dedicated return address register, the CFI usually only
487 contains information to unwind that return address register.
489 The reason we're treating the stack pointer special here is
490 because in many cases GCC doesn't emit CFI for the stack pointer
491 and implicitly assumes that it is equal to the CFA. This makes
492 some sense since the DWARF specification (version 3, draft 8,
495 "Typically, the CFA is defined to be the value of the stack
496 pointer at the call site in the previous frame (which may be
497 different from its value on entry to the current frame)."
499 However, this isn't true for all platforms supported by GCC
500 (e.g. IBM S/390 and zSeries). Those architectures should provide
501 their own architecture-specific initialization function. */
503 if (regnum == PC_REGNUM)
504 reg->how = DWARF2_FRAME_REG_RA;
505 else if (regnum == SP_REGNUM)
506 reg->how = DWARF2_FRAME_REG_CFA;
509 /* Return a default for the architecture-specific operations. */
512 dwarf2_frame_init (struct gdbarch *gdbarch)
514 struct dwarf2_frame_ops *ops;
516 ops = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct dwarf2_frame_ops);
517 ops->init_reg = dwarf2_frame_default_init_reg;
521 static struct dwarf2_frame_ops *
522 dwarf2_frame_ops (struct gdbarch *gdbarch)
524 struct dwarf2_frame_ops *ops = gdbarch_data (gdbarch, dwarf2_frame_data);
527 /* ULGH, called during architecture initialization. Patch
529 ops = dwarf2_frame_init (gdbarch);
530 set_gdbarch_data (gdbarch, dwarf2_frame_data, ops);
535 /* Set the architecture-specific register state initialization
536 function for GDBARCH to INIT_REG. */
539 dwarf2_frame_set_init_reg (struct gdbarch *gdbarch,
540 void (*init_reg) (struct gdbarch *, int,
541 struct dwarf2_frame_state_reg *))
543 struct dwarf2_frame_ops *ops;
545 ops = dwarf2_frame_ops (gdbarch);
546 ops->init_reg = init_reg;
549 /* Pre-initialize the register state REG for register REGNUM. */
552 dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
553 struct dwarf2_frame_state_reg *reg)
555 struct dwarf2_frame_ops *ops;
557 ops = dwarf2_frame_ops (gdbarch);
558 ops->init_reg (gdbarch, regnum, reg);
562 struct dwarf2_frame_cache
564 /* DWARF Call Frame Address. */
567 /* Saved registers, indexed by GDB register number, not by DWARF
569 struct dwarf2_frame_state_reg *reg;
572 static struct dwarf2_frame_cache *
573 dwarf2_frame_cache (struct frame_info *next_frame, void **this_cache)
575 struct cleanup *old_chain;
576 struct gdbarch *gdbarch = get_frame_arch (next_frame);
577 const int num_regs = NUM_REGS + NUM_PSEUDO_REGS;
578 struct dwarf2_frame_cache *cache;
579 struct dwarf2_frame_state *fs;
580 struct dwarf2_fde *fde;
585 /* Allocate a new cache. */
586 cache = FRAME_OBSTACK_ZALLOC (struct dwarf2_frame_cache);
587 cache->reg = FRAME_OBSTACK_CALLOC (num_regs, struct dwarf2_frame_state_reg);
589 /* Allocate and initialize the frame state. */
590 fs = XMALLOC (struct dwarf2_frame_state);
591 memset (fs, 0, sizeof (struct dwarf2_frame_state));
592 old_chain = make_cleanup (dwarf2_frame_state_free, fs);
596 Note that if NEXT_FRAME is never supposed to return (i.e. a call
597 to abort), the compiler might optimize away the instruction at
598 NEXT_FRAME's return address. As a result the return address will
599 point at some random instruction, and the CFI for that
600 instruction is probably worthless to us. GCC's unwinder solves
601 this problem by substracting 1 from the return address to get an
602 address in the middle of a presumed call instruction (or the
603 instruction in the associated delay slot). This should only be
604 done for "normal" frames and not for resume-type frames (signal
605 handlers, sentinel frames, dummy frames). The function
606 frame_unwind_address_in_block does just this. It's not clear how
607 reliable the method is though; there is the potential for the
608 register state pre-call being different to that on return. */
609 fs->pc = frame_unwind_address_in_block (next_frame);
611 /* Find the correct FDE. */
612 fde = dwarf2_frame_find_fde (&fs->pc);
613 gdb_assert (fde != NULL);
615 /* Extract any interesting information from the CIE. */
616 fs->data_align = fde->cie->data_alignment_factor;
617 fs->code_align = fde->cie->code_alignment_factor;
618 fs->retaddr_column = fde->cie->return_address_register;
620 /* First decode all the insns in the CIE. */
621 execute_cfa_program (fde->cie->initial_instructions,
622 fde->cie->end, next_frame, fs);
624 /* Save the initialized register set. */
625 fs->initial = fs->regs;
626 fs->initial.reg = dwarf2_frame_state_copy_regs (&fs->regs);
628 /* Then decode the insns in the FDE up to our target PC. */
629 execute_cfa_program (fde->instructions, fde->end, next_frame, fs);
631 /* Caclulate the CFA. */
635 cache->cfa = read_reg (next_frame, fs->cfa_reg);
636 cache->cfa += fs->cfa_offset;
641 execute_stack_op (fs->cfa_exp, fs->cfa_exp_len, next_frame, 0);
645 internal_error (__FILE__, __LINE__, "Unknown CFA rule.");
648 /* Initialize the register state. */
652 for (regnum = 0; regnum < num_regs; regnum++)
653 dwarf2_frame_init_reg (gdbarch, regnum, &cache->reg[regnum]);
656 /* Go through the DWARF2 CFI generated table and save its register
657 location information in the cache. Note that we don't skip the
658 return address column; it's perfectly all right for it to
659 correspond to a real register. If it doesn't correspond to a
660 real register, or if we shouldn't treat it as such,
661 DWARF2_REG_TO_REGNUM should be defined to return a number outside
662 the range [0, NUM_REGS). */
664 int column; /* CFI speak for "register number". */
666 for (column = 0; column < fs->regs.num_regs; column++)
668 /* Use the GDB register number as the destination index. */
669 int regnum = DWARF2_REG_TO_REGNUM (column);
671 /* If there's no corresponding GDB register, ignore it. */
672 if (regnum < 0 || regnum >= num_regs)
675 /* NOTE: cagney/2003-09-05: CFI should specify the disposition
676 of all debug info registers. If it doesn't, complain (but
677 not too loudly). It turns out that GCC assumes that an
678 unspecified register implies "same value" when CFI (draft
679 7) specifies nothing at all. Such a register could equally
680 be interpreted as "undefined". Also note that this check
681 isn't sufficient; it only checks that all registers in the
682 range [0 .. max column] are specified, and won't detect
683 problems when a debug info register falls outside of the
684 table. We need a way of iterating through all the valid
685 DWARF2 register numbers. */
686 if (fs->regs.reg[column].how == DWARF2_FRAME_REG_UNSPECIFIED)
687 complaint (&symfile_complaints,
688 "Incomplete CFI data; unspecified registers at 0x%s",
691 cache->reg[regnum] = fs->regs.reg[column];
695 /* Eliminate any DWARF2_FRAME_REG_RA rules. */
699 for (regnum = 0; regnum < num_regs; regnum++)
701 if (cache->reg[regnum].how == DWARF2_FRAME_REG_RA)
703 struct dwarf2_frame_state_reg *retaddr_reg =
704 &fs->regs.reg[fs->retaddr_column];
706 /* It seems rather bizarre to specify an "empty" column as
707 the return adress column. However, this is exactly
708 what GCC does on some targets. It turns out that GCC
709 assumes that the return address can be found in the
710 register corresponding to the return address column.
711 Incidentally, that's how should treat a return address
712 column specifying "same value" too. */
713 if (fs->retaddr_column < fs->regs.num_regs
714 && retaddr_reg->how != DWARF2_FRAME_REG_UNSPECIFIED
715 && retaddr_reg->how != DWARF2_FRAME_REG_SAME_VALUE)
716 cache->reg[regnum] = *retaddr_reg;
719 cache->reg[regnum].loc.reg = fs->retaddr_column;
720 cache->reg[regnum].how = DWARF2_FRAME_REG_SAVED_REG;
726 do_cleanups (old_chain);
733 dwarf2_frame_this_id (struct frame_info *next_frame, void **this_cache,
734 struct frame_id *this_id)
736 struct dwarf2_frame_cache *cache =
737 dwarf2_frame_cache (next_frame, this_cache);
739 (*this_id) = frame_id_build (cache->cfa, frame_func_unwind (next_frame));
743 dwarf2_frame_prev_register (struct frame_info *next_frame, void **this_cache,
744 int regnum, int *optimizedp,
745 enum lval_type *lvalp, CORE_ADDR *addrp,
746 int *realnump, void *valuep)
748 struct gdbarch *gdbarch = get_frame_arch (next_frame);
749 struct dwarf2_frame_cache *cache =
750 dwarf2_frame_cache (next_frame, this_cache);
752 switch (cache->reg[regnum].how)
754 case DWARF2_FRAME_REG_UNDEFINED:
755 /* If CFI explicitly specified that the value isn't defined,
756 mark it as optimized away; the value isn't available. */
763 /* In some cases, for example %eflags on the i386, we have
764 to provide a sane value, even though this register wasn't
765 saved. Assume we can get it from NEXT_FRAME. */
766 frame_unwind_register (next_frame, regnum, valuep);
770 case DWARF2_FRAME_REG_SAVED_OFFSET:
772 *lvalp = lval_memory;
773 *addrp = cache->cfa + cache->reg[regnum].loc.offset;
777 /* Read the value in from memory. */
778 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
782 case DWARF2_FRAME_REG_SAVED_REG:
783 regnum = DWARF2_REG_TO_REGNUM (cache->reg[regnum].loc.reg);
784 frame_register_unwind (next_frame, regnum,
785 optimizedp, lvalp, addrp, realnump, valuep);
788 case DWARF2_FRAME_REG_SAVED_EXP:
790 *lvalp = lval_memory;
791 *addrp = execute_stack_op (cache->reg[regnum].loc.exp,
792 cache->reg[regnum].exp_len,
793 next_frame, cache->cfa);
797 /* Read the value in from memory. */
798 read_memory (*addrp, valuep, register_size (gdbarch, regnum));
802 case DWARF2_FRAME_REG_UNSPECIFIED:
803 /* GCC, in its infinite wisdom decided to not provide unwind
804 information for registers that are "same value". Since
805 DWARF2 (3 draft 7) doesn't define such behavior, said
806 registers are actually undefined (which is different to CFI
807 "undefined"). Code above issues a complaint about this.
808 Here just fudge the books, assume GCC, and that the value is
809 more inner on the stack. */
810 frame_register_unwind (next_frame, regnum,
811 optimizedp, lvalp, addrp, realnump, valuep);
814 case DWARF2_FRAME_REG_SAME_VALUE:
815 frame_register_unwind (next_frame, regnum,
816 optimizedp, lvalp, addrp, realnump, valuep);
819 case DWARF2_FRAME_REG_CFA:
826 /* Store the value. */
827 store_typed_address (valuep, builtin_type_void_data_ptr, cache->cfa);
832 internal_error (__FILE__, __LINE__, "Unknown register rule.");
836 static const struct frame_unwind dwarf2_frame_unwind =
839 dwarf2_frame_this_id,
840 dwarf2_frame_prev_register
843 const struct frame_unwind *
844 dwarf2_frame_sniffer (struct frame_info *next_frame)
846 /* Grab an address that is guarenteed to reside somewhere within the
847 function. frame_pc_unwind(), for a no-return next function, can
848 end up returning something past the end of this function's body. */
849 CORE_ADDR block_addr = frame_unwind_address_in_block (next_frame);
850 if (dwarf2_frame_find_fde (&block_addr))
851 return &dwarf2_frame_unwind;
857 /* There is no explicitly defined relationship between the CFA and the
858 location of frame's local variables and arguments/parameters.
859 Therefore, frame base methods on this page should probably only be
860 used as a last resort, just to avoid printing total garbage as a
861 response to the "info frame" command. */
864 dwarf2_frame_base_address (struct frame_info *next_frame, void **this_cache)
866 struct dwarf2_frame_cache *cache =
867 dwarf2_frame_cache (next_frame, this_cache);
872 static const struct frame_base dwarf2_frame_base =
874 &dwarf2_frame_unwind,
875 dwarf2_frame_base_address,
876 dwarf2_frame_base_address,
877 dwarf2_frame_base_address
880 const struct frame_base *
881 dwarf2_frame_base_sniffer (struct frame_info *next_frame)
883 CORE_ADDR pc = frame_pc_unwind (next_frame);
884 if (dwarf2_frame_find_fde (&pc))
885 return &dwarf2_frame_base;
890 /* A minimal decoding of DWARF2 compilation units. We only decode
891 what's needed to get to the call frame information. */
895 /* Keep the bfd convenient. */
898 struct objfile *objfile;
900 /* Linked list of CIEs for this object. */
901 struct dwarf2_cie *cie;
903 /* Address size for this unit - from unit header. */
904 unsigned char addr_size;
906 /* Pointer to the .debug_frame section loaded into memory. */
907 char *dwarf_frame_buffer;
909 /* Length of the loaded .debug_frame section. */
910 unsigned long dwarf_frame_size;
912 /* Pointer to the .debug_frame section. */
913 asection *dwarf_frame_section;
915 /* Base for DW_EH_PE_datarel encodings. */
918 /* Base for DW_EH_PE_textrel encodings. */
922 const struct objfile_data *dwarf2_frame_objfile_data;
925 read_1_byte (bfd *bfd, char *buf)
927 return bfd_get_8 (abfd, (bfd_byte *) buf);
931 read_4_bytes (bfd *abfd, char *buf)
933 return bfd_get_32 (abfd, (bfd_byte *) buf);
937 read_8_bytes (bfd *abfd, char *buf)
939 return bfd_get_64 (abfd, (bfd_byte *) buf);
943 read_unsigned_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
946 unsigned int num_read;
956 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
959 result |= ((byte & 0x7f) << shift);
964 *bytes_read_ptr = num_read;
970 read_signed_leb128 (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
974 unsigned int num_read;
983 byte = bfd_get_8 (abfd, (bfd_byte *) buf);
986 result |= ((byte & 0x7f) << shift);
991 if ((shift < 32) && (byte & 0x40))
992 result |= -(1 << shift);
994 *bytes_read_ptr = num_read;
1000 read_initial_length (bfd *abfd, char *buf, unsigned int *bytes_read_ptr)
1004 result = bfd_get_32 (abfd, (bfd_byte *) buf);
1005 if (result == 0xffffffff)
1007 result = bfd_get_64 (abfd, (bfd_byte *) buf + 4);
1008 *bytes_read_ptr = 12;
1011 *bytes_read_ptr = 4;
1017 /* Pointer encoding helper functions. */
1019 /* GCC supports exception handling based on DWARF2 CFI. However, for
1020 technical reasons, it encodes addresses in its FDE's in a different
1021 way. Several "pointer encodings" are supported. The encoding
1022 that's used for a particular FDE is determined by the 'R'
1023 augmentation in the associated CIE. The argument of this
1024 augmentation is a single byte.
1026 The address can be encoded as 2 bytes, 4 bytes, 8 bytes, or as a
1027 LEB128. This is encoded in bits 0, 1 and 2. Bit 3 encodes whether
1028 the address is signed or unsigned. Bits 4, 5 and 6 encode how the
1029 address should be interpreted (absolute, relative to the current
1030 position in the FDE, ...). Bit 7, indicates that the address
1031 should be dereferenced. */
1033 static unsigned char
1034 encoding_for_size (unsigned int size)
1039 return DW_EH_PE_udata2;
1041 return DW_EH_PE_udata4;
1043 return DW_EH_PE_udata8;
1045 internal_error (__FILE__, __LINE__, "Unsupported address size");
1050 size_of_encoded_value (unsigned char encoding)
1052 if (encoding == DW_EH_PE_omit)
1055 switch (encoding & 0x07)
1057 case DW_EH_PE_absptr:
1058 return TYPE_LENGTH (builtin_type_void_data_ptr);
1059 case DW_EH_PE_udata2:
1061 case DW_EH_PE_udata4:
1063 case DW_EH_PE_udata8:
1066 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1071 read_encoded_value (struct comp_unit *unit, unsigned char encoding,
1072 char *buf, unsigned int *bytes_read_ptr)
1074 int ptr_len = size_of_encoded_value (DW_EH_PE_absptr);
1078 /* GCC currently doesn't generate DW_EH_PE_indirect encodings for
1080 if (encoding & DW_EH_PE_indirect)
1081 internal_error (__FILE__, __LINE__,
1082 "Unsupported encoding: DW_EH_PE_indirect");
1084 *bytes_read_ptr = 0;
1086 switch (encoding & 0x70)
1088 case DW_EH_PE_absptr:
1091 case DW_EH_PE_pcrel:
1092 base = bfd_get_section_vma (unit->bfd, unit->dwarf_frame_section);
1093 base += (buf - unit->dwarf_frame_buffer);
1095 case DW_EH_PE_datarel:
1098 case DW_EH_PE_textrel:
1101 case DW_EH_PE_funcrel:
1102 /* FIXME: kettenis/20040501: For now just pretend
1103 DW_EH_PE_funcrel is equivalent to DW_EH_PE_absptr. For
1104 reading the initial location of an FDE it should be treated
1105 as such, and currently that's the only place where this code
1109 case DW_EH_PE_aligned:
1111 offset = buf - unit->dwarf_frame_buffer;
1112 if ((offset % ptr_len) != 0)
1114 *bytes_read_ptr = ptr_len - (offset % ptr_len);
1115 buf += *bytes_read_ptr;
1119 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1122 if ((encoding & 0x0f) == 0x00)
1123 encoding |= encoding_for_size (ptr_len);
1125 switch (encoding & 0x0f)
1127 case DW_EH_PE_udata2:
1128 *bytes_read_ptr += 2;
1129 return (base + bfd_get_16 (unit->abfd, (bfd_byte *) buf));
1130 case DW_EH_PE_udata4:
1131 *bytes_read_ptr += 4;
1132 return (base + bfd_get_32 (unit->abfd, (bfd_byte *) buf));
1133 case DW_EH_PE_udata8:
1134 *bytes_read_ptr += 8;
1135 return (base + bfd_get_64 (unit->abfd, (bfd_byte *) buf));
1136 case DW_EH_PE_sdata2:
1137 *bytes_read_ptr += 2;
1138 return (base + bfd_get_signed_16 (unit->abfd, (bfd_byte *) buf));
1139 case DW_EH_PE_sdata4:
1140 *bytes_read_ptr += 4;
1141 return (base + bfd_get_signed_32 (unit->abfd, (bfd_byte *) buf));
1142 case DW_EH_PE_sdata8:
1143 *bytes_read_ptr += 8;
1144 return (base + bfd_get_signed_64 (unit->abfd, (bfd_byte *) buf));
1146 internal_error (__FILE__, __LINE__, "Invalid or unsupported encoding");
1151 /* GCC uses a single CIE for all FDEs in a .debug_frame section.
1152 That's why we use a simple linked list here. */
1154 static struct dwarf2_cie *
1155 find_cie (struct comp_unit *unit, ULONGEST cie_pointer)
1157 struct dwarf2_cie *cie = unit->cie;
1161 if (cie->cie_pointer == cie_pointer)
1171 add_cie (struct comp_unit *unit, struct dwarf2_cie *cie)
1173 cie->next = unit->cie;
1177 /* Find the FDE for *PC. Return a pointer to the FDE, and store the
1178 inital location associated with it into *PC. */
1180 static struct dwarf2_fde *
1181 dwarf2_frame_find_fde (CORE_ADDR *pc)
1183 struct objfile *objfile;
1185 ALL_OBJFILES (objfile)
1187 struct dwarf2_fde *fde;
1190 fde = objfile_data (objfile, dwarf2_frame_objfile_data);
1194 gdb_assert (objfile->section_offsets);
1195 offset = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
1199 if (*pc >= fde->initial_location + offset
1200 && *pc < fde->initial_location + offset + fde->address_range)
1202 *pc = fde->initial_location + offset;
1214 add_fde (struct comp_unit *unit, struct dwarf2_fde *fde)
1216 fde->next = objfile_data (unit->objfile, dwarf2_frame_objfile_data);
1217 set_objfile_data (unit->objfile, dwarf2_frame_objfile_data, fde);
1220 #ifdef CC_HAS_LONG_LONG
1221 #define DW64_CIE_ID 0xffffffffffffffffULL
1223 #define DW64_CIE_ID ~0
1226 static char *decode_frame_entry (struct comp_unit *unit, char *start,
1229 /* Decode the next CIE or FDE. Return NULL if invalid input, otherwise
1230 the next byte to be processed. */
1232 decode_frame_entry_1 (struct comp_unit *unit, char *start, int eh_frame_p)
1236 unsigned int bytes_read;
1239 ULONGEST cie_pointer;
1243 length = read_initial_length (unit->abfd, buf, &bytes_read);
1247 /* Are we still within the section? */
1248 if (end > unit->dwarf_frame_buffer + unit->dwarf_frame_size)
1254 /* Distinguish between 32 and 64-bit encoded frame info. */
1255 dwarf64_p = (bytes_read == 12);
1257 /* In a .eh_frame section, zero is used to distinguish CIEs from FDEs. */
1261 cie_id = DW64_CIE_ID;
1267 cie_pointer = read_8_bytes (unit->abfd, buf);
1272 cie_pointer = read_4_bytes (unit->abfd, buf);
1276 if (cie_pointer == cie_id)
1278 /* This is a CIE. */
1279 struct dwarf2_cie *cie;
1282 /* Record the offset into the .debug_frame section of this CIE. */
1283 cie_pointer = start - unit->dwarf_frame_buffer;
1285 /* Check whether we've already read it. */
1286 if (find_cie (unit, cie_pointer))
1289 cie = (struct dwarf2_cie *)
1290 obstack_alloc (&unit->objfile->objfile_obstack,
1291 sizeof (struct dwarf2_cie));
1292 cie->initial_instructions = NULL;
1293 cie->cie_pointer = cie_pointer;
1295 /* The encoding for FDE's in a normal .debug_frame section
1296 depends on the target address size as specified in the
1297 Compilation Unit Header. */
1298 cie->encoding = encoding_for_size (unit->addr_size);
1300 /* Check version number. */
1301 if (read_1_byte (unit->abfd, buf) != DW_CIE_VERSION)
1305 /* Interpret the interesting bits of the augmentation. */
1307 buf = augmentation + strlen (augmentation) + 1;
1309 /* The GCC 2.x "eh" augmentation has a pointer immediately
1310 following the augmentation string, so it must be handled
1312 if (augmentation[0] == 'e' && augmentation[1] == 'h')
1315 buf += TYPE_LENGTH (builtin_type_void_data_ptr);
1319 cie->code_alignment_factor =
1320 read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1323 cie->data_alignment_factor =
1324 read_signed_leb128 (unit->abfd, buf, &bytes_read);
1327 cie->return_address_register = read_1_byte (unit->abfd, buf);
1330 cie->saw_z_augmentation = (*augmentation == 'z');
1331 if (cie->saw_z_augmentation)
1335 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1339 cie->initial_instructions = buf + length;
1343 while (*augmentation)
1345 /* "L" indicates a byte showing how the LSDA pointer is encoded. */
1346 if (*augmentation == 'L')
1353 /* "R" indicates a byte indicating how FDE addresses are encoded. */
1354 else if (*augmentation == 'R')
1356 cie->encoding = *buf++;
1360 /* "P" indicates a personality routine in the CIE augmentation. */
1361 else if (*augmentation == 'P')
1364 buf += size_of_encoded_value (*buf++);
1368 /* Otherwise we have an unknown augmentation.
1369 Bail out unless we saw a 'z' prefix. */
1372 if (cie->initial_instructions == NULL)
1375 /* Skip unknown augmentations. */
1376 buf = cie->initial_instructions;
1381 cie->initial_instructions = buf;
1384 add_cie (unit, cie);
1388 /* This is a FDE. */
1389 struct dwarf2_fde *fde;
1391 /* In an .eh_frame section, the CIE pointer is the delta between the
1392 address within the FDE where the CIE pointer is stored and the
1393 address of the CIE. Convert it to an offset into the .eh_frame
1397 cie_pointer = buf - unit->dwarf_frame_buffer - cie_pointer;
1398 cie_pointer -= (dwarf64_p ? 8 : 4);
1401 /* In either case, validate the result is still within the section. */
1402 if (cie_pointer >= unit->dwarf_frame_size)
1405 fde = (struct dwarf2_fde *)
1406 obstack_alloc (&unit->objfile->objfile_obstack,
1407 sizeof (struct dwarf2_fde));
1408 fde->cie = find_cie (unit, cie_pointer);
1409 if (fde->cie == NULL)
1411 decode_frame_entry (unit, unit->dwarf_frame_buffer + cie_pointer,
1413 fde->cie = find_cie (unit, cie_pointer);
1416 gdb_assert (fde->cie != NULL);
1418 fde->initial_location =
1419 read_encoded_value (unit, fde->cie->encoding, buf, &bytes_read);
1422 fde->address_range =
1423 read_encoded_value (unit, fde->cie->encoding & 0x0f, buf, &bytes_read);
1426 /* A 'z' augmentation in the CIE implies the presence of an
1427 augmentation field in the FDE as well. The only thing known
1428 to be in here at present is the LSDA entry for EH. So we
1429 can skip the whole thing. */
1430 if (fde->cie->saw_z_augmentation)
1434 length = read_unsigned_leb128 (unit->abfd, buf, &bytes_read);
1435 buf += bytes_read + length;
1440 fde->instructions = buf;
1443 add_fde (unit, fde);
1449 /* Read a CIE or FDE in BUF and decode it. */
1451 decode_frame_entry (struct comp_unit *unit, char *start, int eh_frame_p)
1453 enum { NONE, ALIGN4, ALIGN8, FAIL } workaround = NONE;
1456 ptrdiff_t start_offset;
1460 ret = decode_frame_entry_1 (unit, start, eh_frame_p);
1464 /* We have corrupt input data of some form. */
1466 /* ??? Try, weakly, to work around compiler/assembler/linker bugs
1467 and mismatches wrt padding and alignment of debug sections. */
1468 /* Note that there is no requirement in the standard for any
1469 alignment at all in the frame unwind sections. Testing for
1470 alignment before trying to interpret data would be incorrect.
1472 However, GCC traditionally arranged for frame sections to be
1473 sized such that the FDE length and CIE fields happen to be
1474 aligned (in theory, for performance). This, unfortunately,
1475 was done with .align directives, which had the side effect of
1476 forcing the section to be aligned by the linker.
1478 This becomes a problem when you have some other producer that
1479 creates frame sections that are not as strictly aligned. That
1480 produces a hole in the frame info that gets filled by the
1483 The GCC behaviour is arguably a bug, but it's effectively now
1484 part of the ABI, so we're now stuck with it, at least at the
1485 object file level. A smart linker may decide, in the process
1486 of compressing duplicate CIE information, that it can rewrite
1487 the entire output section without this extra padding. */
1489 start_offset = start - unit->dwarf_frame_buffer;
1490 if (workaround < ALIGN4 && (start_offset & 3) != 0)
1492 start += 4 - (start_offset & 3);
1493 workaround = ALIGN4;
1496 if (workaround < ALIGN8 && (start_offset & 7) != 0)
1498 start += 8 - (start_offset & 7);
1499 workaround = ALIGN8;
1503 /* Nothing left to try. Arrange to return as if we've consumed
1504 the entire input section. Hopefully we'll get valid info from
1505 the other of .debug_frame/.eh_frame. */
1507 ret = unit->dwarf_frame_buffer + unit->dwarf_frame_size;
1517 complaint (&symfile_complaints,
1518 "Corrupt data in %s:%s; align 4 workaround apparently succeeded",
1519 unit->dwarf_frame_section->owner->filename,
1520 unit->dwarf_frame_section->name);
1524 complaint (&symfile_complaints,
1525 "Corrupt data in %s:%s; align 8 workaround apparently succeeded",
1526 unit->dwarf_frame_section->owner->filename,
1527 unit->dwarf_frame_section->name);
1531 complaint (&symfile_complaints,
1532 "Corrupt data in %s:%s",
1533 unit->dwarf_frame_section->owner->filename,
1534 unit->dwarf_frame_section->name);
1542 /* FIXME: kettenis/20030504: This still needs to be integrated with
1543 dwarf2read.c in a better way. */
1545 /* Imported from dwarf2read.c. */
1546 extern asection *dwarf_frame_section;
1547 extern asection *dwarf_eh_frame_section;
1549 /* Imported from dwarf2read.c. */
1550 extern char *dwarf2_read_section (struct objfile *objfile, asection *sectp);
1553 dwarf2_build_frame_info (struct objfile *objfile)
1555 struct comp_unit unit;
1558 /* Build a minimal decoding of the DWARF2 compilation unit. */
1559 unit.abfd = objfile->obfd;
1560 unit.objfile = objfile;
1561 unit.addr_size = objfile->obfd->arch_info->bits_per_address / 8;
1565 /* First add the information from the .eh_frame section. That way,
1566 the FDEs from that section are searched last. */
1567 if (dwarf_eh_frame_section)
1569 asection *got, *txt;
1572 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1573 dwarf_eh_frame_section);
1575 unit.dwarf_frame_size
1576 = bfd_get_section_size (dwarf_eh_frame_section);
1577 unit.dwarf_frame_section = dwarf_eh_frame_section;
1579 /* FIXME: kettenis/20030602: This is the DW_EH_PE_datarel base
1580 that is used for the i386/amd64 target, which currently is
1581 the only target in GCC that supports/uses the
1582 DW_EH_PE_datarel encoding. */
1583 got = bfd_get_section_by_name (unit.abfd, ".got");
1585 unit.dbase = got->vma;
1587 /* GCC emits the DW_EH_PE_textrel encoding type on sh and ia64
1589 txt = bfd_get_section_by_name (unit.abfd, ".text");
1591 unit.tbase = txt->vma;
1593 frame_ptr = unit.dwarf_frame_buffer;
1594 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1595 frame_ptr = decode_frame_entry (&unit, frame_ptr, 1);
1598 if (dwarf_frame_section)
1601 unit.dwarf_frame_buffer = dwarf2_read_section (objfile,
1602 dwarf_frame_section);
1603 unit.dwarf_frame_size
1604 = bfd_get_section_size (dwarf_frame_section);
1605 unit.dwarf_frame_section = dwarf_frame_section;
1607 frame_ptr = unit.dwarf_frame_buffer;
1608 while (frame_ptr < unit.dwarf_frame_buffer + unit.dwarf_frame_size)
1609 frame_ptr = decode_frame_entry (&unit, frame_ptr, 0);
1613 /* Provide a prototype to silence -Wmissing-prototypes. */
1614 void _initialize_dwarf2_frame (void);
1617 _initialize_dwarf2_frame (void)
1619 dwarf2_frame_data = register_gdbarch_data (dwarf2_frame_init);
1620 dwarf2_frame_objfile_data = register_objfile_data ();