1 /* DWARF 2 location expression support for GDB.
2 Copyright 2003 Free Software Foundation, Inc.
3 Contributed by Daniel Jacobowitz, MontaVista Software, Inc.
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 2 of the License, or (at
10 your option) any later version.
12 This program is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place - Suite 330,
20 Boston, MA 02111-1307, USA. */
33 #include "elf/dwarf2.h"
34 #include "dwarf2expr.h"
35 #include "dwarf2loc.h"
37 #include "gdb_string.h"
39 #ifndef DWARF2_REG_TO_REGNUM
40 #define DWARF2_REG_TO_REGNUM(REG) (REG)
43 /* A helper function for dealing with location lists. Given a
44 symbol baton (BATON) and a pc value (PC), find the appropriate
45 location expression, set *LOCEXPR_LENGTH, and return a pointer
46 to the beginning of the expression. Returns NULL on failure.
48 For now, only return the first matching location expression; there
49 can be more than one in the list. */
52 find_location_expression (struct dwarf2_loclist_baton
*baton
,
53 int *locexpr_length
, CORE_ADDR pc
)
55 CORE_ADDR base_address
= baton
->base_address
;
57 char *loc_ptr
, *buf_end
;
58 unsigned int addr_size
= TARGET_ADDR_BIT
/ TARGET_CHAR_BIT
, length
;
59 CORE_ADDR base_mask
= ~(~(CORE_ADDR
)1 << (addr_size
* 8 - 1));
61 loc_ptr
= baton
->data
;
62 buf_end
= baton
->data
+ baton
->size
;
66 low
= dwarf2_read_address (loc_ptr
, buf_end
, &length
);
68 high
= dwarf2_read_address (loc_ptr
, buf_end
, &length
);
71 /* An end-of-list entry. */
72 if (low
== 0 && high
== 0)
75 /* A base-address-selection entry. */
76 if ((low
& base_mask
) == base_mask
)
82 /* Otherwise, a location expression entry. */
86 length
= extract_unsigned_integer (loc_ptr
, 2);
89 if (pc
>= low
&& pc
< high
)
91 *locexpr_length
= length
;
99 /* This is the baton used when performing dwarf2 expression
101 struct dwarf_expr_baton
103 struct frame_info
*frame
;
104 struct objfile
*objfile
;
107 /* Helper functions for dwarf2_evaluate_loc_desc. */
109 /* Using the frame specified in BATON, read register REGNUM. The lval
110 type will be returned in LVALP, and for lval_memory the register
111 save address will be returned in ADDRP. */
113 dwarf_expr_read_reg (void *baton
, int dwarf_regnum
)
115 struct dwarf_expr_baton
*debaton
= (struct dwarf_expr_baton
*) baton
;
116 CORE_ADDR result
, save_addr
;
117 enum lval_type lval_type
;
119 int optimized
, regnum
, realnum
, regsize
;
121 regnum
= DWARF2_REG_TO_REGNUM (dwarf_regnum
);
122 regsize
= register_size (current_gdbarch
, regnum
);
123 buf
= (char *) alloca (regsize
);
125 frame_register (debaton
->frame
, regnum
, &optimized
, &lval_type
, &save_addr
,
127 result
= extract_address (buf
, regsize
);
132 /* Read memory at ADDR (length LEN) into BUF. */
135 dwarf_expr_read_mem (void *baton
, char *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
, unsigned char **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_LOCATION_FUNCS (framefunc
) == &dwarf2_loclist_funcs
)
156 struct dwarf2_loclist_baton
*symbaton
;
157 symbaton
= SYMBOL_LOCATION_BATON (framefunc
);
158 *start
= find_location_expression (symbaton
, length
,
159 get_frame_pc (debaton
->frame
));
163 struct dwarf2_locexpr_baton
*symbaton
;
164 symbaton
= SYMBOL_LOCATION_BATON (framefunc
);
165 *length
= symbaton
->size
;
166 *start
= symbaton
->data
;
170 error ("Could not find the frame base for \"%s\".",
171 SYMBOL_NATURAL_NAME (framefunc
));
174 /* Using the objfile specified in BATON, find the address for the
175 current thread's thread-local storage with offset OFFSET. */
177 dwarf_expr_tls_address (void *baton
, CORE_ADDR offset
)
179 struct dwarf_expr_baton
*debaton
= (struct dwarf_expr_baton
*) baton
;
182 if (target_get_thread_local_address_p ())
183 addr
= target_get_thread_local_address (inferior_ptid
,
187 error ("Cannot find thread-local variables on this target");
192 /* Evaluate a location description, starting at DATA and with length
193 SIZE, to find the current location of variable VAR in the context
195 static struct value
*
196 dwarf2_evaluate_loc_desc (struct symbol
*var
, struct frame_info
*frame
,
197 unsigned char *data
, unsigned short size
,
198 struct objfile
*objfile
)
201 struct value
*retval
;
202 struct dwarf_expr_baton baton
;
203 struct dwarf_expr_context
*ctx
;
207 retval
= allocate_value (SYMBOL_TYPE (var
));
208 VALUE_LVAL (retval
) = not_lval
;
209 VALUE_OPTIMIZED_OUT (retval
) = 1;
213 baton
.objfile
= objfile
;
215 ctx
= new_dwarf_expr_context ();
217 ctx
->read_reg
= dwarf_expr_read_reg
;
218 ctx
->read_mem
= dwarf_expr_read_mem
;
219 ctx
->get_frame_base
= dwarf_expr_frame_base
;
220 ctx
->get_tls_address
= dwarf_expr_tls_address
;
222 dwarf_expr_eval (ctx
, data
, size
);
223 result
= dwarf_expr_fetch (ctx
, 0);
227 int regnum
= DWARF2_REG_TO_REGNUM (result
);
228 retval
= value_from_register (SYMBOL_TYPE (var
), regnum
, frame
);
232 retval
= allocate_value (SYMBOL_TYPE (var
));
233 VALUE_BFD_SECTION (retval
) = SYMBOL_BFD_SECTION (var
);
235 VALUE_LVAL (retval
) = lval_memory
;
236 VALUE_LAZY (retval
) = 1;
237 VALUE_ADDRESS (retval
) = result
;
240 free_dwarf_expr_context (ctx
);
249 /* Helper functions and baton for dwarf2_loc_desc_needs_frame. */
251 struct needs_frame_baton
256 /* Reads from registers do require a frame. */
258 needs_frame_read_reg (void *baton
, int regnum
)
260 struct needs_frame_baton
*nf_baton
= baton
;
261 nf_baton
->needs_frame
= 1;
265 /* Reads from memory do not require a frame. */
267 needs_frame_read_mem (void *baton
, char *buf
, CORE_ADDR addr
, size_t len
)
269 memset (buf
, 0, len
);
272 /* Frame-relative accesses do require a frame. */
274 needs_frame_frame_base (void *baton
, unsigned char **start
, size_t * length
)
276 static char lit0
= DW_OP_lit0
;
277 struct needs_frame_baton
*nf_baton
= baton
;
282 nf_baton
->needs_frame
= 1;
285 /* Thread-local accesses do require a frame. */
287 needs_frame_tls_address (void *baton
, CORE_ADDR offset
)
289 struct needs_frame_baton
*nf_baton
= baton
;
290 nf_baton
->needs_frame
= 1;
294 /* Return non-zero iff the location expression at DATA (length SIZE)
295 requires a frame to evaluate. */
298 dwarf2_loc_desc_needs_frame (unsigned char *data
, unsigned short size
)
300 struct needs_frame_baton baton
;
301 struct dwarf_expr_context
*ctx
;
303 baton
.needs_frame
= 0;
305 ctx
= new_dwarf_expr_context ();
307 ctx
->read_reg
= needs_frame_read_reg
;
308 ctx
->read_mem
= needs_frame_read_mem
;
309 ctx
->get_frame_base
= needs_frame_frame_base
;
310 ctx
->get_tls_address
= needs_frame_tls_address
;
312 dwarf_expr_eval (ctx
, data
, size
);
314 free_dwarf_expr_context (ctx
);
316 return baton
.needs_frame
;
320 dwarf2_tracepoint_var_ref (struct symbol
* symbol
, struct agent_expr
* ax
,
321 struct axs_value
* value
, unsigned char *data
,
325 error ("Symbol \"%s\" has been optimized out.",
326 SYMBOL_PRINT_NAME (symbol
));
329 && data
[0] >= DW_OP_reg0
330 && data
[0] <= DW_OP_reg31
)
332 value
->kind
= axs_lvalue_register
;
333 value
->u
.reg
= data
[0] - DW_OP_reg0
;
335 else if (data
[0] == DW_OP_regx
)
338 read_uleb128 (data
+ 1, data
+ size
, ®
);
339 value
->kind
= axs_lvalue_register
;
342 else if (data
[0] == DW_OP_fbreg
)
344 /* And this is worse than just minimal; we should honor the frame base
347 LONGEST frame_offset
;
348 unsigned char *buf_end
;
350 buf_end
= read_sleb128 (data
+ 1, data
+ size
, &frame_offset
);
351 if (buf_end
!= data
+ size
)
352 error ("Unexpected opcode after DW_OP_fbreg for symbol \"%s\".",
353 SYMBOL_PRINT_NAME (symbol
));
355 TARGET_VIRTUAL_FRAME_POINTER (ax
->scope
, &frame_reg
, &frame_offset
);
356 ax_reg (ax
, frame_reg
);
357 ax_const_l (ax
, frame_offset
);
358 ax_simple (ax
, aop_add
);
360 ax_const_l (ax
, frame_offset
);
361 ax_simple (ax
, aop_add
);
362 value
->kind
= axs_lvalue_memory
;
365 error ("Unsupported DWARF opcode in the location of \"%s\".",
366 SYMBOL_PRINT_NAME (symbol
));
369 /* Return the value of SYMBOL in FRAME using the DWARF-2 expression
370 evaluator to calculate the location. */
371 static struct value
*
372 locexpr_read_variable (struct symbol
*symbol
, struct frame_info
*frame
)
374 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
376 val
= dwarf2_evaluate_loc_desc (symbol
, frame
, dlbaton
->data
, dlbaton
->size
,
382 /* Return non-zero iff we need a frame to evaluate SYMBOL. */
384 locexpr_read_needs_frame (struct symbol
*symbol
)
386 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
387 return dwarf2_loc_desc_needs_frame (dlbaton
->data
, dlbaton
->size
);
390 /* Print a natural-language description of SYMBOL to STREAM. */
392 locexpr_describe_location (struct symbol
*symbol
, struct ui_file
*stream
)
394 /* FIXME: be more extensive. */
395 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
397 if (dlbaton
->size
== 1
398 && dlbaton
->data
[0] >= DW_OP_reg0
399 && dlbaton
->data
[0] <= DW_OP_reg31
)
401 int regno
= DWARF2_REG_TO_REGNUM (dlbaton
->data
[0] - DW_OP_reg0
);
402 fprintf_filtered (stream
,
403 "a variable in register %s", REGISTER_NAME (regno
));
407 fprintf_filtered (stream
,
408 "a variable with complex or multiple locations (DWARF2)");
413 /* Describe the location of SYMBOL as an agent value in VALUE, generating
414 any necessary bytecode in AX.
416 NOTE drow/2003-02-26: This function is extremely minimal, because
417 doing it correctly is extremely complicated and there is no
418 publicly available stub with tracepoint support for me to test
419 against. When there is one this function should be revisited. */
422 locexpr_tracepoint_var_ref (struct symbol
* symbol
, struct agent_expr
* ax
,
423 struct axs_value
* value
)
425 struct dwarf2_locexpr_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
427 dwarf2_tracepoint_var_ref (symbol
, ax
, value
, dlbaton
->data
, dlbaton
->size
);
430 /* The set of location functions used with the DWARF-2 expression
432 struct location_funcs dwarf2_locexpr_funcs
= {
433 locexpr_read_variable
,
434 locexpr_read_needs_frame
,
435 locexpr_describe_location
,
436 locexpr_tracepoint_var_ref
440 /* Wrapper functions for location lists. These generally find
441 the appropriate location expression and call something above. */
443 /* Return the value of SYMBOL in FRAME using the DWARF-2 expression
444 evaluator to calculate the location. */
445 static struct value
*
446 loclist_read_variable (struct symbol
*symbol
, struct frame_info
*frame
)
448 struct dwarf2_loclist_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
453 data
= find_location_expression (dlbaton
, &size
,
454 frame
? get_frame_pc (frame
) : 0);
456 error ("Variable \"%s\" is not available.", SYMBOL_NATURAL_NAME (symbol
));
458 val
= dwarf2_evaluate_loc_desc (symbol
, frame
, data
, size
, dlbaton
->objfile
);
463 /* Return non-zero iff we need a frame to evaluate SYMBOL. */
465 loclist_read_needs_frame (struct symbol
*symbol
)
467 /* If there's a location list, then assume we need to have a frame
468 to choose the appropriate location expression. With tracking of
469 global variables this is not necessarily true, but such tracking
470 is disabled in GCC at the moment until we figure out how to
476 /* Print a natural-language description of SYMBOL to STREAM. */
478 loclist_describe_location (struct symbol
*symbol
, struct ui_file
*stream
)
480 /* FIXME: Could print the entire list of locations. */
481 fprintf_filtered (stream
, "a variable with multiple locations");
485 /* Describe the location of SYMBOL as an agent value in VALUE, generating
486 any necessary bytecode in AX. */
488 loclist_tracepoint_var_ref (struct symbol
* symbol
, struct agent_expr
* ax
,
489 struct axs_value
* value
)
491 struct dwarf2_loclist_baton
*dlbaton
= SYMBOL_LOCATION_BATON (symbol
);
495 data
= find_location_expression (dlbaton
, &size
, ax
->scope
);
497 error ("Variable \"%s\" is not available.", SYMBOL_NATURAL_NAME (symbol
));
499 dwarf2_tracepoint_var_ref (symbol
, ax
, value
, data
, size
);
502 /* The set of location functions used with the DWARF-2 expression
503 evaluator and location lists. */
504 struct location_funcs dwarf2_loclist_funcs
= {
505 loclist_read_variable
,
506 loclist_read_needs_frame
,
507 loclist_describe_location
,
508 loclist_tracepoint_var_ref