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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, | |
53 | int *locexpr_length, CORE_ADDR pc) | |
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); | |
e4adbba9 | 127 | result = extract_address (buf, regsize); |
4c2df51b DJ |
128 | |
129 | return result; | |
130 | } | |
131 | ||
132 | /* Read memory at ADDR (length LEN) into BUF. */ | |
133 | ||
134 | static void | |
135 | dwarf_expr_read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len) | |
136 | { | |
137 | read_memory (addr, buf, len); | |
138 | } | |
139 | ||
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. */ | |
143 | static void | |
144 | dwarf_expr_frame_base (void *baton, unsigned char **start, size_t * length) | |
145 | { | |
da62e633 AC |
146 | /* FIXME: cagney/2003-03-26: This code should be using |
147 | get_frame_base_address(), and then implement a dwarf2 specific | |
148 | this_base method. */ | |
4c2df51b | 149 | struct symbol *framefunc; |
4c2df51b | 150 | struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; |
0d53c4c4 | 151 | |
4c2df51b | 152 | framefunc = get_frame_function (debaton->frame); |
0d53c4c4 DJ |
153 | |
154 | if (SYMBOL_LOCATION_FUNCS (framefunc) == &dwarf2_loclist_funcs) | |
155 | { | |
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)); | |
160 | } | |
161 | else | |
162 | { | |
163 | struct dwarf2_locexpr_baton *symbaton; | |
164 | symbaton = SYMBOL_LOCATION_BATON (framefunc); | |
165 | *length = symbaton->size; | |
166 | *start = symbaton->data; | |
167 | } | |
168 | ||
169 | if (*start == NULL) | |
170 | error ("Could not find the frame base for \"%s\".", | |
171 | SYMBOL_NATURAL_NAME (framefunc)); | |
4c2df51b DJ |
172 | } |
173 | ||
174 | /* Using the objfile specified in BATON, find the address for the | |
175 | current thread's thread-local storage with offset OFFSET. */ | |
176 | static CORE_ADDR | |
177 | dwarf_expr_tls_address (void *baton, CORE_ADDR offset) | |
178 | { | |
179 | struct dwarf_expr_baton *debaton = (struct dwarf_expr_baton *) baton; | |
180 | CORE_ADDR addr; | |
181 | ||
182 | if (target_get_thread_local_address_p ()) | |
183 | addr = target_get_thread_local_address (inferior_ptid, | |
184 | debaton->objfile, | |
185 | offset); | |
186 | else | |
187 | error ("Cannot find thread-local variables on this target"); | |
188 | ||
189 | return addr; | |
190 | } | |
191 | ||
192 | /* Evaluate a location description, starting at DATA and with length | |
193 | SIZE, to find the current location of variable VAR in the context | |
194 | of FRAME. */ | |
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) | |
199 | { | |
200 | CORE_ADDR result; | |
201 | struct value *retval; | |
202 | struct dwarf_expr_baton baton; | |
203 | struct dwarf_expr_context *ctx; | |
204 | ||
0d53c4c4 DJ |
205 | if (size == 0) |
206 | { | |
207 | retval = allocate_value (SYMBOL_TYPE (var)); | |
208 | VALUE_LVAL (retval) = not_lval; | |
209 | VALUE_OPTIMIZED_OUT (retval) = 1; | |
210 | } | |
211 | ||
4c2df51b DJ |
212 | baton.frame = frame; |
213 | baton.objfile = objfile; | |
214 | ||
215 | ctx = new_dwarf_expr_context (); | |
216 | ctx->baton = &baton; | |
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; | |
221 | ||
222 | dwarf_expr_eval (ctx, data, size); | |
61fbb938 | 223 | result = dwarf_expr_fetch (ctx, 0); |
4c2df51b DJ |
224 | |
225 | if (ctx->in_reg) | |
61fbb938 | 226 | retval = value_from_register (SYMBOL_TYPE (var), result, frame); |
4c2df51b DJ |
227 | else |
228 | { | |
61fbb938 DJ |
229 | retval = allocate_value (SYMBOL_TYPE (var)); |
230 | VALUE_BFD_SECTION (retval) = SYMBOL_BFD_SECTION (var); | |
231 | ||
4c2df51b DJ |
232 | VALUE_LVAL (retval) = lval_memory; |
233 | VALUE_LAZY (retval) = 1; | |
234 | VALUE_ADDRESS (retval) = result; | |
235 | } | |
236 | ||
237 | free_dwarf_expr_context (ctx); | |
238 | ||
239 | return retval; | |
240 | } | |
241 | ||
242 | ||
243 | ||
244 | ||
245 | \f | |
246 | /* Helper functions and baton for dwarf2_loc_desc_needs_frame. */ | |
247 | ||
248 | struct needs_frame_baton | |
249 | { | |
250 | int needs_frame; | |
251 | }; | |
252 | ||
253 | /* Reads from registers do require a frame. */ | |
254 | static CORE_ADDR | |
61fbb938 | 255 | needs_frame_read_reg (void *baton, int regnum) |
4c2df51b DJ |
256 | { |
257 | struct needs_frame_baton *nf_baton = baton; | |
258 | nf_baton->needs_frame = 1; | |
259 | return 1; | |
260 | } | |
261 | ||
262 | /* Reads from memory do not require a frame. */ | |
263 | static void | |
264 | needs_frame_read_mem (void *baton, char *buf, CORE_ADDR addr, size_t len) | |
265 | { | |
266 | memset (buf, 0, len); | |
267 | } | |
268 | ||
269 | /* Frame-relative accesses do require a frame. */ | |
270 | static void | |
271 | needs_frame_frame_base (void *baton, unsigned char **start, size_t * length) | |
272 | { | |
273 | static char lit0 = DW_OP_lit0; | |
274 | struct needs_frame_baton *nf_baton = baton; | |
275 | ||
276 | *start = &lit0; | |
277 | *length = 1; | |
278 | ||
279 | nf_baton->needs_frame = 1; | |
280 | } | |
281 | ||
282 | /* Thread-local accesses do require a frame. */ | |
283 | static CORE_ADDR | |
284 | needs_frame_tls_address (void *baton, CORE_ADDR offset) | |
285 | { | |
286 | struct needs_frame_baton *nf_baton = baton; | |
287 | nf_baton->needs_frame = 1; | |
288 | return 1; | |
289 | } | |
290 | ||
291 | /* Return non-zero iff the location expression at DATA (length SIZE) | |
292 | requires a frame to evaluate. */ | |
293 | ||
294 | static int | |
295 | dwarf2_loc_desc_needs_frame (unsigned char *data, unsigned short size) | |
296 | { | |
297 | struct needs_frame_baton baton; | |
298 | struct dwarf_expr_context *ctx; | |
299 | ||
300 | baton.needs_frame = 0; | |
301 | ||
302 | ctx = new_dwarf_expr_context (); | |
303 | ctx->baton = &baton; | |
304 | ctx->read_reg = needs_frame_read_reg; | |
305 | ctx->read_mem = needs_frame_read_mem; | |
306 | ctx->get_frame_base = needs_frame_frame_base; | |
307 | ctx->get_tls_address = needs_frame_tls_address; | |
308 | ||
309 | dwarf_expr_eval (ctx, data, size); | |
310 | ||
311 | free_dwarf_expr_context (ctx); | |
312 | ||
313 | return baton.needs_frame; | |
314 | } | |
315 | ||
0d53c4c4 DJ |
316 | static void |
317 | dwarf2_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, | |
318 | struct axs_value * value, unsigned char *data, | |
319 | int size) | |
320 | { | |
321 | if (size == 0) | |
322 | error ("Symbol \"%s\" has been optimized out.", | |
323 | SYMBOL_PRINT_NAME (symbol)); | |
324 | ||
325 | if (size == 1 | |
326 | && data[0] >= DW_OP_reg0 | |
327 | && data[0] <= DW_OP_reg31) | |
328 | { | |
329 | value->kind = axs_lvalue_register; | |
330 | value->u.reg = data[0] - DW_OP_reg0; | |
331 | } | |
332 | else if (data[0] == DW_OP_regx) | |
333 | { | |
334 | ULONGEST reg; | |
335 | read_uleb128 (data + 1, data + size, ®); | |
336 | value->kind = axs_lvalue_register; | |
337 | value->u.reg = reg; | |
338 | } | |
339 | else if (data[0] == DW_OP_fbreg) | |
340 | { | |
341 | /* And this is worse than just minimal; we should honor the frame base | |
342 | as above. */ | |
343 | int frame_reg; | |
344 | LONGEST frame_offset; | |
345 | unsigned char *buf_end; | |
346 | ||
347 | buf_end = read_sleb128 (data + 1, data + size, &frame_offset); | |
348 | if (buf_end != data + size) | |
349 | error ("Unexpected opcode after DW_OP_fbreg for symbol \"%s\".", | |
350 | SYMBOL_PRINT_NAME (symbol)); | |
4c2df51b | 351 | |
0d53c4c4 DJ |
352 | TARGET_VIRTUAL_FRAME_POINTER (ax->scope, &frame_reg, &frame_offset); |
353 | ax_reg (ax, frame_reg); | |
354 | ax_const_l (ax, frame_offset); | |
355 | ax_simple (ax, aop_add); | |
4c2df51b | 356 | |
0d53c4c4 DJ |
357 | ax_const_l (ax, frame_offset); |
358 | ax_simple (ax, aop_add); | |
359 | value->kind = axs_lvalue_memory; | |
360 | } | |
361 | else | |
362 | error ("Unsupported DWARF opcode in the location of \"%s\".", | |
363 | SYMBOL_PRINT_NAME (symbol)); | |
364 | } | |
4c2df51b DJ |
365 | \f |
366 | /* Return the value of SYMBOL in FRAME using the DWARF-2 expression | |
367 | evaluator to calculate the location. */ | |
368 | static struct value * | |
369 | locexpr_read_variable (struct symbol *symbol, struct frame_info *frame) | |
370 | { | |
371 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
372 | struct value *val; | |
373 | val = dwarf2_evaluate_loc_desc (symbol, frame, dlbaton->data, dlbaton->size, | |
374 | dlbaton->objfile); | |
375 | ||
376 | return val; | |
377 | } | |
378 | ||
379 | /* Return non-zero iff we need a frame to evaluate SYMBOL. */ | |
380 | static int | |
381 | locexpr_read_needs_frame (struct symbol *symbol) | |
382 | { | |
383 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
384 | return dwarf2_loc_desc_needs_frame (dlbaton->data, dlbaton->size); | |
385 | } | |
386 | ||
387 | /* Print a natural-language description of SYMBOL to STREAM. */ | |
388 | static int | |
389 | locexpr_describe_location (struct symbol *symbol, struct ui_file *stream) | |
390 | { | |
391 | /* FIXME: be more extensive. */ | |
392 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
393 | ||
394 | if (dlbaton->size == 1 | |
395 | && dlbaton->data[0] >= DW_OP_reg0 | |
396 | && dlbaton->data[0] <= DW_OP_reg31) | |
397 | { | |
398 | int regno = DWARF2_REG_TO_REGNUM (dlbaton->data[0] - DW_OP_reg0); | |
399 | fprintf_filtered (stream, | |
400 | "a variable in register %s", REGISTER_NAME (regno)); | |
401 | return 1; | |
402 | } | |
403 | ||
404 | fprintf_filtered (stream, | |
405 | "a variable with complex or multiple locations (DWARF2)"); | |
406 | return 1; | |
407 | } | |
408 | ||
a55cc764 DJ |
409 | |
410 | /* Describe the location of SYMBOL as an agent value in VALUE, generating | |
411 | any necessary bytecode in AX. | |
412 | ||
413 | NOTE drow/2003-02-26: This function is extremely minimal, because | |
414 | doing it correctly is extremely complicated and there is no | |
415 | publicly available stub with tracepoint support for me to test | |
416 | against. When there is one this function should be revisited. */ | |
417 | ||
0d53c4c4 | 418 | static void |
a55cc764 DJ |
419 | locexpr_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, |
420 | struct axs_value * value) | |
421 | { | |
422 | struct dwarf2_locexpr_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
423 | ||
0d53c4c4 | 424 | dwarf2_tracepoint_var_ref (symbol, ax, value, dlbaton->data, dlbaton->size); |
a55cc764 DJ |
425 | } |
426 | ||
4c2df51b DJ |
427 | /* The set of location functions used with the DWARF-2 expression |
428 | evaluator. */ | |
429 | struct location_funcs dwarf2_locexpr_funcs = { | |
430 | locexpr_read_variable, | |
431 | locexpr_read_needs_frame, | |
432 | locexpr_describe_location, | |
a55cc764 | 433 | locexpr_tracepoint_var_ref |
4c2df51b | 434 | }; |
0d53c4c4 DJ |
435 | |
436 | ||
437 | /* Wrapper functions for location lists. These generally find | |
438 | the appropriate location expression and call something above. */ | |
439 | ||
440 | /* Return the value of SYMBOL in FRAME using the DWARF-2 expression | |
441 | evaluator to calculate the location. */ | |
442 | static struct value * | |
443 | loclist_read_variable (struct symbol *symbol, struct frame_info *frame) | |
444 | { | |
445 | struct dwarf2_loclist_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
446 | struct value *val; | |
447 | unsigned char *data; | |
448 | int size; | |
449 | ||
450 | data = find_location_expression (dlbaton, &size, | |
451 | frame ? get_frame_pc (frame) : 0); | |
452 | if (data == NULL) | |
453 | error ("Variable \"%s\" is not available.", SYMBOL_NATURAL_NAME (symbol)); | |
454 | ||
455 | val = dwarf2_evaluate_loc_desc (symbol, frame, data, size, dlbaton->objfile); | |
456 | ||
457 | return val; | |
458 | } | |
459 | ||
460 | /* Return non-zero iff we need a frame to evaluate SYMBOL. */ | |
461 | static int | |
462 | loclist_read_needs_frame (struct symbol *symbol) | |
463 | { | |
464 | /* If there's a location list, then assume we need to have a frame | |
465 | to choose the appropriate location expression. With tracking of | |
466 | global variables this is not necessarily true, but such tracking | |
467 | is disabled in GCC at the moment until we figure out how to | |
468 | represent it. */ | |
469 | ||
470 | return 1; | |
471 | } | |
472 | ||
473 | /* Print a natural-language description of SYMBOL to STREAM. */ | |
474 | static int | |
475 | loclist_describe_location (struct symbol *symbol, struct ui_file *stream) | |
476 | { | |
477 | /* FIXME: Could print the entire list of locations. */ | |
478 | fprintf_filtered (stream, "a variable with multiple locations"); | |
479 | return 1; | |
480 | } | |
481 | ||
482 | /* Describe the location of SYMBOL as an agent value in VALUE, generating | |
483 | any necessary bytecode in AX. */ | |
484 | static void | |
485 | loclist_tracepoint_var_ref (struct symbol * symbol, struct agent_expr * ax, | |
486 | struct axs_value * value) | |
487 | { | |
488 | struct dwarf2_loclist_baton *dlbaton = SYMBOL_LOCATION_BATON (symbol); | |
489 | unsigned char *data; | |
490 | int size; | |
491 | ||
492 | data = find_location_expression (dlbaton, &size, ax->scope); | |
493 | if (data == NULL) | |
494 | error ("Variable \"%s\" is not available.", SYMBOL_NATURAL_NAME (symbol)); | |
495 | ||
496 | dwarf2_tracepoint_var_ref (symbol, ax, value, data, size); | |
497 | } | |
498 | ||
499 | /* The set of location functions used with the DWARF-2 expression | |
500 | evaluator and location lists. */ | |
501 | struct location_funcs dwarf2_loclist_funcs = { | |
502 | loclist_read_variable, | |
503 | loclist_read_needs_frame, | |
504 | loclist_describe_location, | |
505 | loclist_tracepoint_var_ref | |
506 | }; |