1 /* DWARF 2 location expression support for GDB.
3 Copyright (C) 2003, 2005 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);
207 baton
.objfile
= objfile
;
209 ctx
= new_dwarf_expr_context ();
211 ctx
->read_reg
= dwarf_expr_read_reg
;
212 ctx
->read_mem
= dwarf_expr_read_mem
;
213 ctx
->get_frame_base
= dwarf_expr_frame_base
;
214 ctx
->get_tls_address
= dwarf_expr_tls_address
;
216 dwarf_expr_eval (ctx
, data
, size
);
217 if (ctx
->num_pieces
> 0)
223 retval
= allocate_value (SYMBOL_TYPE (var
));
224 contents
= value_contents_raw (retval
);
225 for (i
= 0; i
< ctx
->num_pieces
; i
++)
227 struct dwarf_expr_piece
*p
= &ctx
->pieces
[i
];
230 bfd_byte regval
[MAX_REGISTER_SIZE
];
231 int gdb_regnum
= DWARF2_REG_TO_REGNUM (p
->value
);
232 get_frame_register (frame
, gdb_regnum
, regval
);
233 memcpy (contents
+ offset
, regval
, p
->size
);
235 else /* In memory? */
237 read_memory (p
->value
, contents
+ offset
, p
->size
);
242 else if (ctx
->in_reg
)
244 CORE_ADDR dwarf_regnum
= dwarf_expr_fetch (ctx
, 0);
245 int gdb_regnum
= DWARF2_REG_TO_REGNUM (dwarf_regnum
);
246 retval
= value_from_register (SYMBOL_TYPE (var
), gdb_regnum
, frame
);
250 CORE_ADDR address
= dwarf_expr_fetch (ctx
, 0);
252 retval
= allocate_value (SYMBOL_TYPE (var
));
253 VALUE_LVAL (retval
) = lval_memory
;
254 set_value_lazy (retval
, 1);
255 VALUE_ADDRESS (retval
) = address
;
258 free_dwarf_expr_context (ctx
);
267 /* Helper functions and baton for dwarf2_loc_desc_needs_frame. */
269 struct needs_frame_baton
274 /* Reads from registers do require a frame. */
276 needs_frame_read_reg (void *baton
, int regnum
)
278 struct needs_frame_baton
*nf_baton
= baton
;
279 nf_baton
->needs_frame
= 1;
283 /* Reads from memory do not require a frame. */
285 needs_frame_read_mem (void *baton
, gdb_byte
*buf
, CORE_ADDR addr
, size_t len
)
287 memset (buf
, 0, len
);
290 /* Frame-relative accesses do require a frame. */
292 needs_frame_frame_base (void *baton
, gdb_byte
**start
, size_t * length
)
294 static gdb_byte lit0
= DW_OP_lit0
;
295 struct needs_frame_baton
*nf_baton
= baton
;
300 nf_baton
->needs_frame
= 1;
303 /* Thread-local accesses do require a frame. */
305 needs_frame_tls_address (void *baton
, CORE_ADDR offset
)
307 struct needs_frame_baton
*nf_baton
= baton
;
308 nf_baton
->needs_frame
= 1;
312 /* Return non-zero iff the location expression at DATA (length SIZE)
313 requires a frame to evaluate. */
316 dwarf2_loc_desc_needs_frame (gdb_byte
*data
, unsigned short size
)
318 struct needs_frame_baton baton
;
319 struct dwarf_expr_context
*ctx
;
322 baton
.needs_frame
= 0;
324 ctx
= new_dwarf_expr_context ();
326 ctx
->read_reg
= needs_frame_read_reg
;
327 ctx
->read_mem
= needs_frame_read_mem
;
328 ctx
->get_frame_base
= needs_frame_frame_base
;
329 ctx
->get_tls_address
= needs_frame_tls_address
;
331 dwarf_expr_eval (ctx
, data
, size
);
333 in_reg
= ctx
->in_reg
;
335 if (ctx
->num_pieces
> 0)
339 /* If the location has several pieces, and any of them are in
340 registers, then we will need a frame to fetch them from. */
341 for (i
= 0; i
< ctx
->num_pieces
; i
++)
342 if (ctx
->pieces
[i
].in_reg
)
346 free_dwarf_expr_context (ctx
);
348 return baton
.needs_frame
|| in_reg
;
352 dwarf2_tracepoint_var_ref (struct symbol
*symbol
, struct agent_expr
*ax
,
353 struct axs_value
*value
, gdb_byte
*data
,
357 error (_("Symbol \"%s\" has been optimized out."),
358 SYMBOL_PRINT_NAME (symbol
));
361 && data
[0] >= DW_OP_reg0
362 && data
[0] <= DW_OP_reg31
)
364 value
->kind
= axs_lvalue_register
;
365 value
->u
.reg
= data
[0] - DW_OP_reg0
;
367 else if (data
[0] == DW_OP_regx
)
370 read_uleb128 (data
+ 1, data
+ size
, ®
);
371 value
->kind
= axs_lvalue_register
;
374 else if (data
[0] == DW_OP_fbreg
)
376 /* And this is worse than just minimal; we should honor the frame base
379 LONGEST frame_offset
;
382 buf_end
= read_sleb128 (data
+ 1, data
+ size
, &frame_offset
);
383 if (buf_end
!= data
+ size
)
384 error (_("Unexpected opcode after DW_OP_fbreg for symbol \"%s\"."),
385 SYMBOL_PRINT_NAME (symbol
));
387 TARGET_VIRTUAL_FRAME_POINTER (ax
->scope
, &frame_reg
, &frame_offset
);
388 ax_reg (ax
, frame_reg
);
389 ax_const_l (ax
, frame_offset
);
390 ax_simple (ax
, aop_add
);
392 value
->kind
= axs_lvalue_memory
;
394 else if (data
[0] >= DW_OP_breg0
395 && data
[0] <= DW_OP_breg31
)
401 reg
= data
[0] - DW_OP_breg0
;
402 buf_end
= read_sleb128 (data
+ 1, data
+ size
, &offset
);
403 if (buf_end
!= data
+ size
)
404 error (_("Unexpected opcode after DW_OP_breg%u for symbol \"%s\"."),
405 reg
, SYMBOL_PRINT_NAME (symbol
));
408 ax_const_l (ax
, offset
);
409 ax_simple (ax
, aop_add
);
411 value
->kind
= axs_lvalue_memory
;
414 error (_("Unsupported DWARF opcode 0x%x in the location of \"%s\"."),
415 data
[0], SYMBOL_PRINT_NAME (symbol
));
418 /* Return the value of SYMBOL in FRAME using the DWARF-2 expression
419 evaluator to calculate the location. */
420 static struct value
*
421 locexpr_read_variable (struct symbol
*symbol
, struct frame_info
*frame
)
423 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
425 val
= dwarf2_evaluate_loc_desc (symbol
, frame
, dlbaton
->data
, dlbaton
->size
,
431 /* Return non-zero iff we need a frame to evaluate SYMBOL. */
433 locexpr_read_needs_frame (struct symbol
*symbol
)
435 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
436 return dwarf2_loc_desc_needs_frame (dlbaton
->data
, dlbaton
->size
);
439 /* Print a natural-language description of SYMBOL to STREAM. */
441 locexpr_describe_location (struct symbol
*symbol
, struct ui_file
*stream
)
443 /* FIXME: be more extensive. */
444 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
446 if (dlbaton
->size
== 1
447 && dlbaton
->data
[0] >= DW_OP_reg0
448 && dlbaton
->data
[0] <= DW_OP_reg31
)
450 int regno
= DWARF2_REG_TO_REGNUM (dlbaton
->data
[0] - DW_OP_reg0
);
451 fprintf_filtered (stream
,
452 "a variable in register %s", REGISTER_NAME (regno
));
456 /* The location expression for a TLS variable looks like this (on a
459 DW_AT_location : 10 byte block: 3 4 0 0 0 0 0 0 0 e0
460 (DW_OP_addr: 4; DW_OP_GNU_push_tls_address)
462 0x3 is the encoding for DW_OP_addr, which has an operand as long
463 as the size of an address on the target machine (here is 8
464 bytes). 0xe0 is the encoding for DW_OP_GNU_push_tls_address.
465 The operand represents the offset at which the variable is within
466 the thread local storage. */
468 if (dlbaton
->size
> 1
469 && dlbaton
->data
[dlbaton
->size
- 1] == DW_OP_GNU_push_tls_address
)
470 if (dlbaton
->data
[0] == DW_OP_addr
)
473 CORE_ADDR offset
= dwarf2_read_address (&dlbaton
->data
[1],
474 &dlbaton
->data
[dlbaton
->size
- 1],
476 fprintf_filtered (stream
,
477 "a thread-local variable at offset %s in the "
478 "thread-local storage for `%s'",
479 paddr_nz (offset
), dlbaton
->objfile
->name
);
484 fprintf_filtered (stream
,
485 "a variable with complex or multiple locations (DWARF2)");
490 /* Describe the location of SYMBOL as an agent value in VALUE, generating
491 any necessary bytecode in AX.
493 NOTE drow/2003-02-26: This function is extremely minimal, because
494 doing it correctly is extremely complicated and there is no
495 publicly available stub with tracepoint support for me to test
496 against. When there is one this function should be revisited. */
499 locexpr_tracepoint_var_ref (struct symbol
* symbol
, struct agent_expr
* ax
,
500 struct axs_value
* value
)
502 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
504 dwarf2_tracepoint_var_ref (symbol
, ax
, value
, dlbaton
->data
, dlbaton
->size
);
507 /* The set of location functions used with the DWARF-2 expression
509 const struct symbol_ops dwarf2_locexpr_funcs
= {
510 locexpr_read_variable
,
511 locexpr_read_needs_frame
,
512 locexpr_describe_location
,
513 locexpr_tracepoint_var_ref
517 /* Wrapper functions for location lists. These generally find
518 the appropriate location expression and call something above. */
520 /* Return the value of SYMBOL in FRAME using the DWARF-2 expression
521 evaluator to calculate the location. */
522 static struct value
*
523 loclist_read_variable (struct symbol
*symbol
, struct frame_info
*frame
)
525 struct dwarf2_loclist_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
530 data
= find_location_expression (dlbaton
, &size
,
531 frame
? get_frame_address_in_block (frame
)
535 val
= allocate_value (SYMBOL_TYPE (symbol
));
536 VALUE_LVAL (val
) = not_lval
;
537 set_value_optimized_out (val
, 1);
540 val
= dwarf2_evaluate_loc_desc (symbol
, frame
, data
, size
,
546 /* Return non-zero iff we need a frame to evaluate SYMBOL. */
548 loclist_read_needs_frame (struct symbol
*symbol
)
550 /* If there's a location list, then assume we need to have a frame
551 to choose the appropriate location expression. With tracking of
552 global variables this is not necessarily true, but such tracking
553 is disabled in GCC at the moment until we figure out how to
559 /* Print a natural-language description of SYMBOL to STREAM. */
561 loclist_describe_location (struct symbol
*symbol
, struct ui_file
*stream
)
563 /* FIXME: Could print the entire list of locations. */
564 fprintf_filtered (stream
, "a variable with multiple locations");
568 /* Describe the location of SYMBOL as an agent value in VALUE, generating
569 any necessary bytecode in AX. */
571 loclist_tracepoint_var_ref (struct symbol
* symbol
, struct agent_expr
* ax
,
572 struct axs_value
* value
)
574 struct dwarf2_loclist_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
578 data
= find_location_expression (dlbaton
, &size
, ax
->scope
);
580 error (_("Variable \"%s\" is not available."), SYMBOL_NATURAL_NAME (symbol
));
582 dwarf2_tracepoint_var_ref (symbol
, ax
, value
, data
, size
);
585 /* The set of location functions used with the DWARF-2 expression
586 evaluator and location lists. */
587 const struct symbol_ops dwarf2_loclist_funcs
= {
588 loclist_read_variable
,
589 loclist_read_needs_frame
,
590 loclist_describe_location
,
591 loclist_tracepoint_var_ref