1 /* DWARF 2 location expression support for GDB.
3 Copyright (C) 2003, 2005, 2007 Free Software Foundation, Inc.
5 Contributed by Daniel Jacobowitz, MontaVista Software, Inc.
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 (at
12 your option) any later version.
14 This program is distributed in the hope that it will be useful, but
15 WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 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., 51 Franklin Street, Fifth Floor,
22 Boston, MA 02110-1301, USA. */
35 #include "exceptions.h"
37 #include "elf/dwarf2.h"
38 #include "dwarf2expr.h"
39 #include "dwarf2loc.h"
41 #include "gdb_string.h"
43 #ifndef DWARF2_REG_TO_REGNUM
44 #define DWARF2_REG_TO_REGNUM(REG) (REG)
47 /* A helper function for dealing with location lists. Given a
48 symbol baton (BATON) and a pc value (PC), find the appropriate
49 location expression, set *LOCEXPR_LENGTH, and return a pointer
50 to the beginning of the expression. Returns NULL on failure.
52 For now, only return the first matching location expression; there
53 can be more than one in the list. */
56 find_location_expression (struct dwarf2_loclist_baton
*baton
,
57 size_t *locexpr_length
, CORE_ADDR pc
)
60 gdb_byte
*loc_ptr
, *buf_end
;
62 unsigned int addr_size
= TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
;
63 CORE_ADDR base_mask
= ~(~(CORE_ADDR
)1 << (addr_size
* 8 - 1));
64 /* Adjust base_address for relocatable objects. */
65 CORE_ADDR base_offset
= ANOFFSET (baton
->objfile
->section_offsets
,
66 SECT_OFF_TEXT (baton
->objfile
));
67 CORE_ADDR base_address
= baton
->base_address
+ base_offset
;
69 loc_ptr
= baton
->data
;
70 buf_end
= baton
->data
+ baton
->size
;
74 low
= dwarf2_read_address (loc_ptr
, buf_end
, &length
);
76 high
= dwarf2_read_address (loc_ptr
, buf_end
, &length
);
79 /* An end-of-list entry. */
80 if (low
== 0 && high
== 0)
83 /* A base-address-selection entry. */
84 if ((low
& base_mask
) == base_mask
)
90 /* Otherwise, a location expression entry. */
94 length
= extract_unsigned_integer (loc_ptr
, 2);
97 if (pc
>= low
&& pc
< high
)
99 *locexpr_length
= length
;
107 /* This is the baton used when performing dwarf2 expression
109 struct dwarf_expr_baton
111 struct frame_info
*frame
;
112 struct objfile
*objfile
;
115 /* Helper functions for dwarf2_evaluate_loc_desc. */
117 /* Using the frame specified in BATON, return the value of register
118 REGNUM, treated as a pointer. */
120 dwarf_expr_read_reg (void *baton
, int dwarf_regnum
)
122 struct dwarf_expr_baton
*debaton
= (struct dwarf_expr_baton
*) baton
;
126 regnum
= DWARF2_REG_TO_REGNUM (dwarf_regnum
);
127 result
= address_from_register (builtin_type_void_data_ptr
,
128 regnum
, debaton
->frame
);
132 /* Read memory at ADDR (length LEN) into BUF. */
135 dwarf_expr_read_mem (void *baton
, gdb_byte
*buf
, CORE_ADDR addr
, size_t len
)
137 read_memory (addr
, buf
, len
);
140 /* Using the frame specified in BATON, find the location expression
141 describing the frame base. Return a pointer to it in START and
142 its length in LENGTH. */
144 dwarf_expr_frame_base (void *baton
, gdb_byte
**start
, size_t * length
)
146 /* FIXME: cagney/2003-03-26: This code should be using
147 get_frame_base_address(), and then implement a dwarf2 specific
149 struct symbol
*framefunc
;
150 struct dwarf_expr_baton
*debaton
= (struct dwarf_expr_baton
*) baton
;
152 framefunc
= get_frame_function (debaton
->frame
);
154 if (SYMBOL_OPS (framefunc
) == &dwarf2_loclist_funcs
)
156 struct dwarf2_loclist_baton
*symbaton
;
157 struct frame_info
*frame
= debaton
->frame
;
159 symbaton
= SYMBOL_LOCATION_BATON (framefunc
);
160 *start
= find_location_expression (symbaton
, length
,
161 get_frame_address_in_block (frame
));
165 struct dwarf2_locexpr_baton
*symbaton
;
166 symbaton
= SYMBOL_LOCATION_BATON (framefunc
);
167 *length
= symbaton
->size
;
168 *start
= symbaton
->data
;
172 error (_("Could not find the frame base for \"%s\"."),
173 SYMBOL_NATURAL_NAME (framefunc
));
176 /* Using the objfile specified in BATON, find the address for the
177 current thread's thread-local storage with offset OFFSET. */
179 dwarf_expr_tls_address (void *baton
, CORE_ADDR offset
)
181 struct dwarf_expr_baton
*debaton
= (struct dwarf_expr_baton
*) baton
;
183 return target_translate_tls_address (debaton
->objfile
, offset
);
186 /* Evaluate a location description, starting at DATA and with length
187 SIZE, to find the current location of variable VAR in the context
189 static struct value
*
190 dwarf2_evaluate_loc_desc (struct symbol
*var
, struct frame_info
*frame
,
191 gdb_byte
*data
, unsigned short size
,
192 struct objfile
*objfile
)
194 struct gdbarch
*arch
= get_frame_arch (frame
);
195 struct value
*retval
;
196 struct dwarf_expr_baton baton
;
197 struct dwarf_expr_context
*ctx
;
201 retval
= allocate_value (SYMBOL_TYPE (var
));
202 VALUE_LVAL (retval
) = not_lval
;
203 set_value_optimized_out (retval
, 1);
208 baton
.objfile
= objfile
;
210 ctx
= new_dwarf_expr_context ();
212 ctx
->read_reg
= dwarf_expr_read_reg
;
213 ctx
->read_mem
= dwarf_expr_read_mem
;
214 ctx
->get_frame_base
= dwarf_expr_frame_base
;
215 ctx
->get_tls_address
= dwarf_expr_tls_address
;
217 dwarf_expr_eval (ctx
, data
, size
);
218 if (ctx
->num_pieces
> 0)
224 retval
= allocate_value (SYMBOL_TYPE (var
));
225 contents
= value_contents_raw (retval
);
226 for (i
= 0; i
< ctx
->num_pieces
; i
++)
228 struct dwarf_expr_piece
*p
= &ctx
->pieces
[i
];
231 bfd_byte regval
[MAX_REGISTER_SIZE
];
232 int gdb_regnum
= DWARF2_REG_TO_REGNUM (p
->value
);
233 get_frame_register (frame
, gdb_regnum
, regval
);
234 memcpy (contents
+ offset
, regval
, p
->size
);
236 else /* In memory? */
238 read_memory (p
->value
, contents
+ offset
, p
->size
);
243 else if (ctx
->in_reg
)
245 CORE_ADDR dwarf_regnum
= dwarf_expr_fetch (ctx
, 0);
246 int gdb_regnum
= DWARF2_REG_TO_REGNUM (dwarf_regnum
);
247 retval
= value_from_register (SYMBOL_TYPE (var
), gdb_regnum
, frame
);
251 CORE_ADDR address
= dwarf_expr_fetch (ctx
, 0);
253 retval
= allocate_value (SYMBOL_TYPE (var
));
254 VALUE_LVAL (retval
) = lval_memory
;
255 set_value_lazy (retval
, 1);
256 VALUE_ADDRESS (retval
) = address
;
259 free_dwarf_expr_context (ctx
);
268 /* Helper functions and baton for dwarf2_loc_desc_needs_frame. */
270 struct needs_frame_baton
275 /* Reads from registers do require a frame. */
277 needs_frame_read_reg (void *baton
, int regnum
)
279 struct needs_frame_baton
*nf_baton
= baton
;
280 nf_baton
->needs_frame
= 1;
284 /* Reads from memory do not require a frame. */
286 needs_frame_read_mem (void *baton
, gdb_byte
*buf
, CORE_ADDR addr
, size_t len
)
288 memset (buf
, 0, len
);
291 /* Frame-relative accesses do require a frame. */
293 needs_frame_frame_base (void *baton
, gdb_byte
**start
, size_t * length
)
295 static gdb_byte lit0
= DW_OP_lit0
;
296 struct needs_frame_baton
*nf_baton
= baton
;
301 nf_baton
->needs_frame
= 1;
304 /* Thread-local accesses do require a frame. */
306 needs_frame_tls_address (void *baton
, CORE_ADDR offset
)
308 struct needs_frame_baton
*nf_baton
= baton
;
309 nf_baton
->needs_frame
= 1;
313 /* Return non-zero iff the location expression at DATA (length SIZE)
314 requires a frame to evaluate. */
317 dwarf2_loc_desc_needs_frame (gdb_byte
*data
, unsigned short size
)
319 struct needs_frame_baton baton
;
320 struct dwarf_expr_context
*ctx
;
323 baton
.needs_frame
= 0;
325 ctx
= new_dwarf_expr_context ();
327 ctx
->read_reg
= needs_frame_read_reg
;
328 ctx
->read_mem
= needs_frame_read_mem
;
329 ctx
->get_frame_base
= needs_frame_frame_base
;
330 ctx
->get_tls_address
= needs_frame_tls_address
;
332 dwarf_expr_eval (ctx
, data
, size
);
334 in_reg
= ctx
->in_reg
;
336 if (ctx
->num_pieces
> 0)
340 /* If the location has several pieces, and any of them are in
341 registers, then we will need a frame to fetch them from. */
342 for (i
= 0; i
< ctx
->num_pieces
; i
++)
343 if (ctx
->pieces
[i
].in_reg
)
347 free_dwarf_expr_context (ctx
);
349 return baton
.needs_frame
|| in_reg
;
353 dwarf2_tracepoint_var_ref (struct symbol
*symbol
, struct agent_expr
*ax
,
354 struct axs_value
*value
, gdb_byte
*data
,
358 error (_("Symbol \"%s\" has been optimized out."),
359 SYMBOL_PRINT_NAME (symbol
));
362 && data
[0] >= DW_OP_reg0
363 && data
[0] <= DW_OP_reg31
)
365 value
->kind
= axs_lvalue_register
;
366 value
->u
.reg
= data
[0] - DW_OP_reg0
;
368 else if (data
[0] == DW_OP_regx
)
371 read_uleb128 (data
+ 1, data
+ size
, ®
);
372 value
->kind
= axs_lvalue_register
;
375 else if (data
[0] == DW_OP_fbreg
)
377 /* And this is worse than just minimal; we should honor the frame base
380 LONGEST frame_offset
;
383 buf_end
= read_sleb128 (data
+ 1, data
+ size
, &frame_offset
);
384 if (buf_end
!= data
+ size
)
385 error (_("Unexpected opcode after DW_OP_fbreg for symbol \"%s\"."),
386 SYMBOL_PRINT_NAME (symbol
));
388 TARGET_VIRTUAL_FRAME_POINTER (ax
->scope
, &frame_reg
, &frame_offset
);
389 ax_reg (ax
, frame_reg
);
390 ax_const_l (ax
, frame_offset
);
391 ax_simple (ax
, aop_add
);
393 value
->kind
= axs_lvalue_memory
;
395 else if (data
[0] >= DW_OP_breg0
396 && data
[0] <= DW_OP_breg31
)
402 reg
= data
[0] - DW_OP_breg0
;
403 buf_end
= read_sleb128 (data
+ 1, data
+ size
, &offset
);
404 if (buf_end
!= data
+ size
)
405 error (_("Unexpected opcode after DW_OP_breg%u for symbol \"%s\"."),
406 reg
, SYMBOL_PRINT_NAME (symbol
));
409 ax_const_l (ax
, offset
);
410 ax_simple (ax
, aop_add
);
412 value
->kind
= axs_lvalue_memory
;
415 error (_("Unsupported DWARF opcode 0x%x in the location of \"%s\"."),
416 data
[0], SYMBOL_PRINT_NAME (symbol
));
419 /* Return the value of SYMBOL in FRAME using the DWARF-2 expression
420 evaluator to calculate the location. */
421 static struct value
*
422 locexpr_read_variable (struct symbol
*symbol
, struct frame_info
*frame
)
424 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
426 val
= dwarf2_evaluate_loc_desc (symbol
, frame
, dlbaton
->data
, dlbaton
->size
,
432 /* Return non-zero iff we need a frame to evaluate SYMBOL. */
434 locexpr_read_needs_frame (struct symbol
*symbol
)
436 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
437 return dwarf2_loc_desc_needs_frame (dlbaton
->data
, dlbaton
->size
);
440 /* Print a natural-language description of SYMBOL to STREAM. */
442 locexpr_describe_location (struct symbol
*symbol
, struct ui_file
*stream
)
444 /* FIXME: be more extensive. */
445 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
447 if (dlbaton
->size
== 1
448 && dlbaton
->data
[0] >= DW_OP_reg0
449 && dlbaton
->data
[0] <= DW_OP_reg31
)
451 int regno
= DWARF2_REG_TO_REGNUM (dlbaton
->data
[0] - DW_OP_reg0
);
452 fprintf_filtered (stream
,
453 "a variable in register %s", REGISTER_NAME (regno
));
457 /* The location expression for a TLS variable looks like this (on a
460 DW_AT_location : 10 byte block: 3 4 0 0 0 0 0 0 0 e0
461 (DW_OP_addr: 4; DW_OP_GNU_push_tls_address)
463 0x3 is the encoding for DW_OP_addr, which has an operand as long
464 as the size of an address on the target machine (here is 8
465 bytes). 0xe0 is the encoding for DW_OP_GNU_push_tls_address.
466 The operand represents the offset at which the variable is within
467 the thread local storage. */
469 if (dlbaton
->size
> 1
470 && dlbaton
->data
[dlbaton
->size
- 1] == DW_OP_GNU_push_tls_address
)
471 if (dlbaton
->data
[0] == DW_OP_addr
)
474 CORE_ADDR offset
= dwarf2_read_address (&dlbaton
->data
[1],
475 &dlbaton
->data
[dlbaton
->size
- 1],
477 fprintf_filtered (stream
,
478 "a thread-local variable at offset %s in the "
479 "thread-local storage for `%s'",
480 paddr_nz (offset
), dlbaton
->objfile
->name
);
485 fprintf_filtered (stream
,
486 "a variable with complex or multiple locations (DWARF2)");
491 /* Describe the location of SYMBOL as an agent value in VALUE, generating
492 any necessary bytecode in AX.
494 NOTE drow/2003-02-26: This function is extremely minimal, because
495 doing it correctly is extremely complicated and there is no
496 publicly available stub with tracepoint support for me to test
497 against. When there is one this function should be revisited. */
500 locexpr_tracepoint_var_ref (struct symbol
* symbol
, struct agent_expr
* ax
,
501 struct axs_value
* value
)
503 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
505 dwarf2_tracepoint_var_ref (symbol
, ax
, value
, dlbaton
->data
, dlbaton
->size
);
508 /* The set of location functions used with the DWARF-2 expression
510 const struct symbol_ops dwarf2_locexpr_funcs
= {
511 locexpr_read_variable
,
512 locexpr_read_needs_frame
,
513 locexpr_describe_location
,
514 locexpr_tracepoint_var_ref
518 /* Wrapper functions for location lists. These generally find
519 the appropriate location expression and call something above. */
521 /* Return the value of SYMBOL in FRAME using the DWARF-2 expression
522 evaluator to calculate the location. */
523 static struct value
*
524 loclist_read_variable (struct symbol
*symbol
, struct frame_info
*frame
)
526 struct dwarf2_loclist_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
531 data
= find_location_expression (dlbaton
, &size
,
532 frame
? get_frame_address_in_block (frame
)
536 val
= allocate_value (SYMBOL_TYPE (symbol
));
537 VALUE_LVAL (val
) = not_lval
;
538 set_value_optimized_out (val
, 1);
541 val
= dwarf2_evaluate_loc_desc (symbol
, frame
, data
, size
,
547 /* Return non-zero iff we need a frame to evaluate SYMBOL. */
549 loclist_read_needs_frame (struct symbol
*symbol
)
551 /* If there's a location list, then assume we need to have a frame
552 to choose the appropriate location expression. With tracking of
553 global variables this is not necessarily true, but such tracking
554 is disabled in GCC at the moment until we figure out how to
560 /* Print a natural-language description of SYMBOL to STREAM. */
562 loclist_describe_location (struct symbol
*symbol
, struct ui_file
*stream
)
564 /* FIXME: Could print the entire list of locations. */
565 fprintf_filtered (stream
, "a variable with multiple locations");
569 /* Describe the location of SYMBOL as an agent value in VALUE, generating
570 any necessary bytecode in AX. */
572 loclist_tracepoint_var_ref (struct symbol
* symbol
, struct agent_expr
* ax
,
573 struct axs_value
* value
)
575 struct dwarf2_loclist_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
579 data
= find_location_expression (dlbaton
, &size
, ax
->scope
);
581 error (_("Variable \"%s\" is not available."), SYMBOL_NATURAL_NAME (symbol
));
583 dwarf2_tracepoint_var_ref (symbol
, ax
, value
, data
, size
);
586 /* The set of location functions used with the DWARF-2 expression
587 evaluator and location lists. */
588 const struct symbol_ops dwarf2_loclist_funcs
= {
589 loclist_read_variable
,
590 loclist_read_needs_frame
,
591 loclist_describe_location
,
592 loclist_tracepoint_var_ref