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4c2df51b DJ |
1 | /* DWARF 2 location expression support for GDB. |
2 | Copyright 2003 Free Software Foundation, Inc. | |
3 | Contributed by Daniel Jacobowitz, MontaVista Software, Inc. | |
4 | ||
5 | This file is part of GDB. | |
6 | ||
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. | |
11 | ||
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. | |
16 | ||
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. */ | |
21 | ||
22 | #include "defs.h" | |
23 | #include "ui-out.h" | |
24 | #include "value.h" | |
25 | #include "frame.h" | |
26 | #include "gdbcore.h" | |
27 | #include "target.h" | |
28 | #include "inferior.h" | |
a55cc764 DJ |
29 | #include "ax.h" |
30 | #include "ax-gdb.h" | |
e4adbba9 | 31 | #include "regcache.h" |
4c2df51b DJ |
32 | |
33 | #include "elf/dwarf2.h" | |
34 | #include "dwarf2expr.h" | |
35 | #include "dwarf2loc.h" | |
36 | ||
37 | #include "gdb_string.h" | |
38 | ||
39 | #ifndef DWARF2_REG_TO_REGNUM | |
40 | #define DWARF2_REG_TO_REGNUM(REG) (REG) | |
41 | #endif | |
42 | ||
0d53c4c4 DJ |
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. | |
47 | ||
48 | For now, only return the first matching location expression; there | |
49 | can be more than one in the list. */ | |
50 | ||
51 | static char * | |
52 | find_location_expression (struct dwarf2_loclist_baton *baton, | |
b6b08ebf | 53 | size_t *locexpr_length, CORE_ADDR pc) |
0d53c4c4 DJ |
54 | { |
55 | CORE_ADDR base_address = baton->base_address; | |
56 | CORE_ADDR low, high; | |
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)); | |
60 | ||
61 | loc_ptr = baton->data; | |
62 | buf_end = baton->data + baton->size; | |
63 | ||
64 | while (1) | |
65 | { | |
66 | low = dwarf2_read_address (loc_ptr, buf_end, &length); | |
67 | loc_ptr += length; | |
68 | high = dwarf2_read_address (loc_ptr, buf_end, &length); | |
69 | loc_ptr += length; | |
70 | ||
71 | /* An end-of-list entry. */ | |
72 | if (low == 0 && high == 0) | |
73 | return NULL; | |
74 | ||
75 | /* A base-address-selection entry. */ | |
76 | if ((low & base_mask) == base_mask) | |
77 | { | |
78 | base_address = high; | |
79 | continue; | |
80 | } | |
81 | ||
82 | /* Otherwise, a location expression entry. */ | |
83 | low += base_address; | |
84 | high += base_address; | |
85 | ||
86 | length = extract_unsigned_integer (loc_ptr, 2); | |
87 | loc_ptr += 2; | |
88 | ||
89 | if (pc >= low && pc < high) | |
90 | { | |
91 | *locexpr_length = length; | |
92 | return loc_ptr; | |
93 | } | |
94 | ||
95 | loc_ptr += length; | |
96 | } | |
97 | } | |
98 | ||
4c2df51b DJ |
99 | /* This is the baton used when performing dwarf2 expression |
100 | evaluation. */ | |
101 | struct dwarf_expr_baton | |
102 | { | |
103 | struct frame_info *frame; | |
104 | struct objfile *objfile; | |
105 | }; | |
106 | ||
107 | /* Helper functions for dwarf2_evaluate_loc_desc. */ | |
108 | ||
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. */ | |
112 | static CORE_ADDR | |
61fbb938 | 113 | dwarf_expr_read_reg (void *baton, int dwarf_regnum) |
4c2df51b | 114 | { |
4c2df51b | 115 | struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; |
61fbb938 DJ |
116 | CORE_ADDR result, save_addr; |
117 | enum lval_type lval_type; | |
e4adbba9 DJ |
118 | char *buf; |
119 | int optimized, regnum, realnum, regsize; | |
120 | ||
121 | regnum = DWARF2_REG_TO_REGNUM (dwarf_regnum); | |
122 | regsize = register_size (current_gdbarch, regnum); | |
123 | buf = (char *) alloca (regsize); | |
4c2df51b | 124 | |
61fbb938 DJ |
125 | frame_register (debaton->frame, regnum, &optimized, &lval_type, &save_addr, |
126 | &realnum, buf); | |
af1342ab AC |
127 | /* NOTE: cagney/2003-05-22: This extract is assuming that a DWARF 2 |
128 | address is always unsigned. That may or may not be true. */ | |
129 | result = extract_unsigned_integer (buf, regsize); | |
4c2df51b DJ |
130 | |
131 | return result; | |
132 | } | |
133 | ||
134 | /* Read memory at ADDR (length LEN) into BUF. */ | |
135 | ||
136 | static void | |
137 | dwarf_expr_read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len) | |
138 | { | |
139 | read_memory (addr, buf, len); | |
140 | } | |
141 | ||
142 | /* Using the frame specified in BATON, find the location expression | |
143 | describing the frame base. Return a pointer to it in START and | |
144 | its length in LENGTH. */ | |
145 | static void | |
146 | dwarf_expr_frame_base (void *baton, unsigned char **start, size_t * length) | |
147 | { | |
da62e633 AC |
148 | /* FIXME: cagney/2003-03-26: This code should be using |
149 | get_frame_base_address(), and then implement a dwarf2 specific | |
150 | this_base method. */ | |
4c2df51b | 151 | struct symbol *framefunc; |
4c2df51b | 152 | struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; |
0d53c4c4 | 153 | |
4c2df51b | 154 | framefunc = get_frame_function (debaton->frame); |
0d53c4c4 DJ |
155 | |
156 | if (SYMBOL_LOCATION_FUNCS (framefunc) == &dwarf2_loclist_funcs) | |
157 | { | |
158 | struct dwarf2_loclist_baton *symbaton; | |
159 | symbaton = SYMBOL_LOCATION_BATON (framefunc); | |
160 | *start = find_location_expression (symbaton, length, | |
161 | get_frame_pc (debaton->frame)); | |
162 | } | |
163 | else | |
164 | { | |
165 | struct dwarf2_locexpr_baton *symbaton; | |
166 | symbaton = SYMBOL_LOCATION_BATON (framefunc); | |
167 | *length = symbaton->size; | |
168 | *start = symbaton->data; | |
169 | } | |
170 | ||
171 | if (*start == NULL) | |
172 | error ("Could not find the frame base for \"%s\".", | |
173 | SYMBOL_NATURAL_NAME (framefunc)); | |
4c2df51b DJ |
174 | } |
175 | ||
176 | /* Using the objfile specified in BATON, find the address for the | |
177 | current thread's thread-local storage with offset OFFSET. */ | |
178 | static CORE_ADDR | |
179 | dwarf_expr_tls_address (void *baton, CORE_ADDR offset) | |
180 | { | |
181 | struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; | |
182 | CORE_ADDR addr; | |
183 | ||
184 | if (target_get_thread_local_address_p ()) | |
185 | addr = target_get_thread_local_address (inferior_ptid, | |
186 | debaton->objfile, | |
187 | offset); | |
188 | else | |
189 | error ("Cannot find thread-local variables on this target"); | |
190 | ||
191 | return addr; | |
192 | } | |
193 | ||
194 | /* Evaluate a location description, starting at DATA and with length | |
195 | SIZE, to find the current location of variable VAR in the context | |
196 | of FRAME. */ | |
197 | static struct value * | |
198 | dwarf2_evaluate_loc_desc (struct symbol *var, struct frame_info *frame, | |
199 | unsigned char *data, unsigned short size, | |
200 | struct objfile *objfile) | |
201 | { | |
202 | CORE_ADDR result; | |
203 | struct value *retval; | |
204 | struct dwarf_expr_baton baton; | |
205 | struct dwarf_expr_context *ctx; | |
206 | ||
0d53c4c4 DJ |
207 | if (size == 0) |
208 | { | |
209 | retval = allocate_value (SYMBOL_TYPE (var)); | |
210 | VALUE_LVAL (retval) = not_lval; | |
211 | VALUE_OPTIMIZED_OUT (retval) = 1; | |
212 | } | |
213 | ||
4c2df51b DJ |
214 | baton.frame = frame; |
215 | baton.objfile = objfile; | |
216 | ||
217 | ctx = new_dwarf_expr_context (); | |
218 | ctx->baton = &baton; | |
219 | ctx->read_reg = dwarf_expr_read_reg; | |
220 | ctx->read_mem = dwarf_expr_read_mem; | |
221 | ctx->get_frame_base = dwarf_expr_frame_base; | |
222 | ctx->get_tls_address = dwarf_expr_tls_address; | |
223 | ||
224 | dwarf_expr_eval (ctx, data, size); | |
61fbb938 | 225 | result = dwarf_expr_fetch (ctx, 0); |
4c2df51b DJ |
226 | |
227 | if (ctx->in_reg) | |
051caad9 KB |
228 | { |
229 | int regnum = DWARF2_REG_TO_REGNUM (result); | |
230 | retval = value_from_register (SYMBOL_TYPE (var), regnum, frame); | |
231 | } | |
4c2df51b DJ |
232 | else |
233 | { | |
61fbb938 DJ |
234 | retval = allocate_value (SYMBOL_TYPE (var)); |
235 | VALUE_BFD_SECTION (retval) = SYMBOL_BFD_SECTION (var); | |
236 | ||
4c2df51b DJ |
237 | VALUE_LVAL (retval) = lval_memory; |
238 | VALUE_LAZY (retval) = 1; | |
239 | VALUE_ADDRESS (retval) = result; | |
240 | } | |
241 | ||
242 | free_dwarf_expr_context (ctx); | |
243 | ||
244 | return retval; | |
245 | } | |
246 | ||
247 | ||
248 | ||
249 | ||
250 | \f | |
251 | /* Helper functions and baton for dwarf2_loc_desc_needs_frame. */ | |
252 | ||
253 | struct needs_frame_baton | |
254 | { | |
255 | int needs_frame; | |
256 | }; | |
257 | ||
258 | /* Reads from registers do require a frame. */ | |
259 | static CORE_ADDR | |
61fbb938 | 260 | needs_frame_read_reg (void *baton, int regnum) |
4c2df51b DJ |
261 | { |
262 | struct needs_frame_baton *nf_baton = baton; | |
263 | nf_baton->needs_frame = 1; | |
264 | return 1; | |
265 | } | |
266 | ||
267 | /* Reads from memory do not require a frame. */ | |
268 | static void | |
269 | needs_frame_read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len) | |
270 | { | |
271 | memset (buf, 0, len); | |
272 | } | |
273 | ||
274 | /* Frame-relative accesses do require a frame. */ | |
275 | static void | |
276 | needs_frame_frame_base (void *baton, unsigned char **start, size_t * length) | |
277 | { | |
278 | static char lit0 = DW_OP_lit0; | |
279 | struct needs_frame_baton *nf_baton = baton; | |
280 | ||
281 | *start = &lit0; | |
282 | *length = 1; | |
283 | ||
284 | nf_baton->needs_frame = 1; | |
285 | } | |
286 | ||
287 | /* Thread-local accesses do require a frame. */ | |
288 | static CORE_ADDR | |
289 | needs_frame_tls_address (void *baton, CORE_ADDR offset) | |
290 | { | |
291 | struct needs_frame_baton *nf_baton = baton; | |
292 | nf_baton->needs_frame = 1; | |
293 | return 1; | |
294 | } | |
295 | ||
296 | /* Return non-zero iff the location expression at DATA (length SIZE) | |
297 | requires a frame to evaluate. */ | |
298 | ||
299 | static int | |
300 | dwarf2_loc_desc_needs_frame (unsigned char *data, unsigned short size) | |
301 | { | |
302 | struct needs_frame_baton baton; | |
303 | struct dwarf_expr_context *ctx; | |
304 | ||
305 | baton.needs_frame = 0; | |
306 | ||
307 | ctx = new_dwarf_expr_context (); | |
308 | ctx->baton = &baton; | |
309 | ctx->read_reg = needs_frame_read_reg; | |
310 | ctx->read_mem = needs_frame_read_mem; | |
311 | ctx->get_frame_base = needs_frame_frame_base; | |
312 | ctx->get_tls_address = needs_frame_tls_address; | |
313 | ||
314 | dwarf_expr_eval (ctx, data, size); | |
315 | ||
316 | free_dwarf_expr_context (ctx); | |
317 | ||
318 | return baton.needs_frame; | |
319 | } | |
320 | ||
0d53c4c4 DJ |
321 | static void |
322 | dwarf2_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, | |
323 | struct axs_value * value, unsigned char *data, | |
324 | int size) | |
325 | { | |
326 | if (size == 0) | |
327 | error ("Symbol \"%s\" has been optimized out.", | |
328 | SYMBOL_PRINT_NAME (symbol)); | |
329 | ||
330 | if (size == 1 | |
331 | && data[0] >= DW_OP_reg0 | |
332 | && data[0] <= DW_OP_reg31) | |
333 | { | |
334 | value->kind = axs_lvalue_register; | |
335 | value->u.reg = data[0] - DW_OP_reg0; | |
336 | } | |
337 | else if (data[0] == DW_OP_regx) | |
338 | { | |
339 | ULONGEST reg; | |
340 | read_uleb128 (data + 1, data + size, ®); | |
341 | value->kind = axs_lvalue_register; | |
342 | value->u.reg = reg; | |
343 | } | |
344 | else if (data[0] == DW_OP_fbreg) | |
345 | { | |
346 | /* And this is worse than just minimal; we should honor the frame base | |
347 | as above. */ | |
348 | int frame_reg; | |
349 | LONGEST frame_offset; | |
350 | unsigned char *buf_end; | |
351 | ||
352 | buf_end = read_sleb128 (data + 1, data + size, &frame_offset); | |
353 | if (buf_end != data + size) | |
354 | error ("Unexpected opcode after DW_OP_fbreg for symbol \"%s\".", | |
355 | SYMBOL_PRINT_NAME (symbol)); | |
4c2df51b | 356 | |
0d53c4c4 DJ |
357 | TARGET_VIRTUAL_FRAME_POINTER (ax->scope, &frame_reg, &frame_offset); |
358 | ax_reg (ax, frame_reg); | |
359 | ax_const_l (ax, frame_offset); | |
360 | ax_simple (ax, aop_add); | |
4c2df51b | 361 | |
0d53c4c4 DJ |
362 | ax_const_l (ax, frame_offset); |
363 | ax_simple (ax, aop_add); | |
364 | value->kind = axs_lvalue_memory; | |
365 | } | |
366 | else | |
367 | error ("Unsupported DWARF opcode in the location of \"%s\".", | |
368 | SYMBOL_PRINT_NAME (symbol)); | |
369 | } | |
4c2df51b DJ |
370 | \f |
371 | /* Return the value of SYMBOL in FRAME using the DWARF-2 expression | |
372 | evaluator to calculate the location. */ | |
373 | static struct value * | |
374 | locexpr_read_variable (struct symbol *symbol, struct frame_info *frame) | |
375 | { | |
376 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
377 | struct value *val; | |
378 | val = dwarf2_evaluate_loc_desc (symbol, frame, dlbaton->data, dlbaton->size, | |
379 | dlbaton->objfile); | |
380 | ||
381 | return val; | |
382 | } | |
383 | ||
384 | /* Return non-zero iff we need a frame to evaluate SYMBOL. */ | |
385 | static int | |
386 | locexpr_read_needs_frame (struct symbol *symbol) | |
387 | { | |
388 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
389 | return dwarf2_loc_desc_needs_frame (dlbaton->data, dlbaton->size); | |
390 | } | |
391 | ||
392 | /* Print a natural-language description of SYMBOL to STREAM. */ | |
393 | static int | |
394 | locexpr_describe_location (struct symbol *symbol, struct ui_file *stream) | |
395 | { | |
396 | /* FIXME: be more extensive. */ | |
397 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
398 | ||
399 | if (dlbaton->size == 1 | |
400 | && dlbaton->data[0] >= DW_OP_reg0 | |
401 | && dlbaton->data[0] <= DW_OP_reg31) | |
402 | { | |
403 | int regno = DWARF2_REG_TO_REGNUM (dlbaton->data[0] - DW_OP_reg0); | |
404 | fprintf_filtered (stream, | |
405 | "a variable in register %s", REGISTER_NAME (regno)); | |
406 | return 1; | |
407 | } | |
408 | ||
409 | fprintf_filtered (stream, | |
410 | "a variable with complex or multiple locations (DWARF2)"); | |
411 | return 1; | |
412 | } | |
413 | ||
a55cc764 DJ |
414 | |
415 | /* Describe the location of SYMBOL as an agent value in VALUE, generating | |
416 | any necessary bytecode in AX. | |
417 | ||
418 | NOTE drow/2003-02-26: This function is extremely minimal, because | |
419 | doing it correctly is extremely complicated and there is no | |
420 | publicly available stub with tracepoint support for me to test | |
421 | against. When there is one this function should be revisited. */ | |
422 | ||
0d53c4c4 | 423 | static void |
a55cc764 DJ |
424 | locexpr_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, |
425 | struct axs_value * value) | |
426 | { | |
427 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
428 | ||
0d53c4c4 | 429 | dwarf2_tracepoint_var_ref (symbol, ax, value, dlbaton->data, dlbaton->size); |
a55cc764 DJ |
430 | } |
431 | ||
4c2df51b DJ |
432 | /* The set of location functions used with the DWARF-2 expression |
433 | evaluator. */ | |
434 | struct location_funcs dwarf2_locexpr_funcs = { | |
435 | locexpr_read_variable, | |
436 | locexpr_read_needs_frame, | |
437 | locexpr_describe_location, | |
a55cc764 | 438 | locexpr_tracepoint_var_ref |
4c2df51b | 439 | }; |
0d53c4c4 DJ |
440 | |
441 | ||
442 | /* Wrapper functions for location lists. These generally find | |
443 | the appropriate location expression and call something above. */ | |
444 | ||
445 | /* Return the value of SYMBOL in FRAME using the DWARF-2 expression | |
446 | evaluator to calculate the location. */ | |
447 | static struct value * | |
448 | loclist_read_variable (struct symbol *symbol, struct frame_info *frame) | |
449 | { | |
450 | struct dwarf2_loclist_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
451 | struct value *val; | |
452 | unsigned char *data; | |
b6b08ebf | 453 | size_t size; |
0d53c4c4 DJ |
454 | |
455 | data = find_location_expression (dlbaton, &size, | |
456 | frame ? get_frame_pc (frame) : 0); | |
457 | if (data == NULL) | |
458 | error ("Variable \"%s\" is not available.", SYMBOL_NATURAL_NAME (symbol)); | |
459 | ||
460 | val = dwarf2_evaluate_loc_desc (symbol, frame, data, size, dlbaton->objfile); | |
461 | ||
462 | return val; | |
463 | } | |
464 | ||
465 | /* Return non-zero iff we need a frame to evaluate SYMBOL. */ | |
466 | static int | |
467 | loclist_read_needs_frame (struct symbol *symbol) | |
468 | { | |
469 | /* If there's a location list, then assume we need to have a frame | |
470 | to choose the appropriate location expression. With tracking of | |
471 | global variables this is not necessarily true, but such tracking | |
472 | is disabled in GCC at the moment until we figure out how to | |
473 | represent it. */ | |
474 | ||
475 | return 1; | |
476 | } | |
477 | ||
478 | /* Print a natural-language description of SYMBOL to STREAM. */ | |
479 | static int | |
480 | loclist_describe_location (struct symbol *symbol, struct ui_file *stream) | |
481 | { | |
482 | /* FIXME: Could print the entire list of locations. */ | |
483 | fprintf_filtered (stream, "a variable with multiple locations"); | |
484 | return 1; | |
485 | } | |
486 | ||
487 | /* Describe the location of SYMBOL as an agent value in VALUE, generating | |
488 | any necessary bytecode in AX. */ | |
489 | static void | |
490 | loclist_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, | |
491 | struct axs_value * value) | |
492 | { | |
493 | struct dwarf2_loclist_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
494 | unsigned char *data; | |
b6b08ebf | 495 | size_t size; |
0d53c4c4 DJ |
496 | |
497 | data = find_location_expression (dlbaton, &size, ax->scope); | |
498 | if (data == NULL) | |
499 | error ("Variable \"%s\" is not available.", SYMBOL_NATURAL_NAME (symbol)); | |
500 | ||
501 | dwarf2_tracepoint_var_ref (symbol, ax, value, data, size); | |
502 | } | |
503 | ||
504 | /* The set of location functions used with the DWARF-2 expression | |
505 | evaluator and location lists. */ | |
506 | struct location_funcs dwarf2_loclist_funcs = { | |
507 | loclist_read_variable, | |
508 | loclist_read_needs_frame, | |
509 | loclist_describe_location, | |
510 | loclist_tracepoint_var_ref | |
511 | }; |