1 /* Dwarf2 Expression Evaluator
2 Copyright 2001, 2002, 2003 Free Software Foundation, Inc.
3 Contributed by Daniel Berlin (dan@dberlin.org)
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
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU 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. */
27 #include "elf/dwarf2.h"
28 #include "dwarf2expr.h"
30 /* Local prototypes. */
32 static void execute_stack_op (struct dwarf_expr_context *,
33 unsigned char *, unsigned char *);
35 /* Create a new context for the expression evaluator. */
37 struct dwarf_expr_context *
38 new_dwarf_expr_context (void)
40 struct dwarf_expr_context *retval;
41 retval = xcalloc (1, sizeof (struct dwarf_expr_context));
42 retval->stack_len = 10;
43 retval->stack = xmalloc (10 * sizeof (CORE_ADDR));
47 /* Release the memory allocated to CTX. */
50 free_dwarf_expr_context (struct dwarf_expr_context *ctx)
56 /* Expand the memory allocated to CTX's stack to contain at least
57 NEED more elements than are currently used. */
60 dwarf_expr_grow_stack (struct dwarf_expr_context *ctx, size_t need)
62 if (ctx->stack_len + need > ctx->stack_allocated)
64 size_t templen = ctx->stack_len * 2;
65 while (templen < (ctx->stack_len + need))
67 ctx->stack = xrealloc (ctx->stack,
68 templen * sizeof (CORE_ADDR));
69 ctx->stack_allocated = templen;
73 /* Push VALUE onto CTX's stack. */
76 dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value)
78 dwarf_expr_grow_stack (ctx, 1);
79 ctx->stack[ctx->stack_len++] = value;
82 /* Pop the top item off of CTX's stack. */
85 dwarf_expr_pop (struct dwarf_expr_context *ctx)
87 if (ctx->stack_len <= 0)
88 error ("dwarf expression stack underflow");
92 /* Retrieve the N'th item on CTX's stack. */
95 dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n)
97 if (ctx->stack_len < n)
98 error ("Asked for position %d of stack, stack only has %d elements on it\n",
100 return ctx->stack[ctx->stack_len - (1 + n)];
104 /* Evaluate the expression at ADDR (LEN bytes long) using the context
108 dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
111 execute_stack_op (ctx, addr, addr + len);
114 /* Decode the unsigned LEB128 constant at BUF into the variable pointed to
115 by R, and return the new value of BUF. Verify that it doesn't extend
119 read_uleb128 (unsigned char *buf, unsigned char *buf_end, ULONGEST * r)
128 error ("read_uleb128: Corrupted DWARF expression.");
131 result |= (byte & 0x7f) << shift;
132 if ((byte & 0x80) == 0)
140 /* Decode the signed LEB128 constant at BUF into the variable pointed to
141 by R, and return the new value of BUF. Verify that it doesn't extend
145 read_sleb128 (unsigned char *buf, unsigned char *buf_end, LONGEST * r)
154 error ("read_sleb128: Corrupted DWARF expression.");
157 result |= (byte & 0x7f) << shift;
159 if ((byte & 0x80) == 0)
162 if (shift < (sizeof (*r) * 8) && (byte & 0x40) != 0)
163 result |= -(1 << shift);
169 /* Read an address from BUF, and verify that it doesn't extend past
170 BUF_END. The address is returned, and *BYTES_READ is set to the
171 number of bytes read from BUF. */
174 dwarf2_read_address (unsigned char *buf, unsigned char *buf_end, int *bytes_read)
178 if (buf_end - buf < TARGET_ADDR_BIT / TARGET_CHAR_BIT)
179 error ("dwarf2_read_address: Corrupted DWARF expression.");
181 *bytes_read = TARGET_ADDR_BIT / TARGET_CHAR_BIT;
182 result = extract_address (buf, TARGET_ADDR_BIT / TARGET_CHAR_BIT);
186 /* Return the type of an address, for unsigned arithmetic. */
189 unsigned_address_type (void)
191 switch (TARGET_ADDR_BIT / TARGET_CHAR_BIT)
194 return builtin_type_uint16;
196 return builtin_type_uint32;
198 return builtin_type_uint64;
200 internal_error (__FILE__, __LINE__,
201 "Unsupported address size.\n");
205 /* Return the type of an address, for signed arithmetic. */
208 signed_address_type (void)
210 switch (TARGET_ADDR_BIT / TARGET_CHAR_BIT)
213 return builtin_type_int16;
215 return builtin_type_int32;
217 return builtin_type_int64;
219 internal_error (__FILE__, __LINE__,
220 "Unsupported address size.\n");
224 /* The engine for the expression evaluator. Using the context in CTX,
225 evaluate the expression between OP_PTR and OP_END. */
228 execute_stack_op (struct dwarf_expr_context *ctx, unsigned char *op_ptr,
229 unsigned char *op_end)
231 while (op_ptr < op_end)
233 enum dwarf_location_atom op = *op_ptr++;
235 ULONGEST uoffset, reg;
275 result = op - DW_OP_lit0;
279 result = dwarf2_read_address (op_ptr, op_end, &bytes_read);
280 op_ptr += bytes_read;
284 result = extract_unsigned_integer (op_ptr, 1);
288 result = extract_signed_integer (op_ptr, 1);
292 result = extract_unsigned_integer (op_ptr, 2);
296 result = extract_signed_integer (op_ptr, 2);
300 result = extract_unsigned_integer (op_ptr, 4);
304 result = extract_signed_integer (op_ptr, 4);
308 result = extract_unsigned_integer (op_ptr, 8);
312 result = extract_signed_integer (op_ptr, 8);
316 op_ptr = read_uleb128 (op_ptr, op_end, &uoffset);
320 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
324 /* The DW_OP_reg operations are required to occur alone in
325 location expressions. */
358 /* NOTE: in the presence of DW_OP_piece this check is incorrect. */
359 if (op_ptr != op_end)
360 error ("DWARF-2 expression error: DW_OP_reg operations must be "
363 result = op - DW_OP_reg0;
369 op_ptr = read_uleb128 (op_ptr, op_end, ®);
370 if (op_ptr != op_end)
371 error ("DWARF-2 expression error: DW_OP_reg operations must be "
411 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
412 result = (ctx->read_reg) (ctx->baton, op - DW_OP_breg0);
418 op_ptr = read_uleb128 (op_ptr, op_end, ®);
419 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
420 result = (ctx->read_reg) (ctx->baton, reg);
426 unsigned char *datastart;
428 unsigned int before_stack_len;
430 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
431 /* Rather than create a whole new context, we simply
432 record the stack length before execution, then reset it
433 afterwards, effectively erasing whatever the recursive
435 before_stack_len = ctx->stack_len;
436 /* FIXME: cagney/2003-03-26: This code should be using
437 get_frame_base_address(), and then implement a dwarf2
438 specific this_base method. */
439 (ctx->get_frame_base) (ctx->baton, &datastart, &datalen);
440 dwarf_expr_eval (ctx, datastart, datalen);
441 result = dwarf_expr_fetch (ctx, 0);
443 result = (ctx->read_reg) (ctx->baton, result);
446 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
449 (ctx->read_mem) (ctx->baton, buf, result,
450 TARGET_ADDR_BIT / TARGET_CHAR_BIT);
451 result = dwarf2_read_address (buf,
452 buf + (TARGET_ADDR_BIT
456 result = result + offset;
457 ctx->stack_len = before_stack_len;
462 result = dwarf_expr_fetch (ctx, 0);
466 dwarf_expr_pop (ctx);
471 result = dwarf_expr_fetch (ctx, offset);
475 result = dwarf_expr_fetch (ctx, 1);
480 CORE_ADDR t1, t2, t3;
482 if (ctx->stack_len < 3)
483 error ("Not enough elements for DW_OP_rot. Need 3, have %d\n",
485 t1 = ctx->stack[ctx->stack_len - 1];
486 t2 = ctx->stack[ctx->stack_len - 2];
487 t3 = ctx->stack[ctx->stack_len - 3];
488 ctx->stack[ctx->stack_len - 1] = t2;
489 ctx->stack[ctx->stack_len - 2] = t3;
490 ctx->stack[ctx->stack_len - 3] = t1;
495 case DW_OP_deref_size:
499 case DW_OP_plus_uconst:
500 /* Unary operations. */
501 result = dwarf_expr_fetch (ctx, 0);
502 dwarf_expr_pop (ctx);
508 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
511 (ctx->read_mem) (ctx->baton, buf, result,
512 TARGET_ADDR_BIT / TARGET_CHAR_BIT);
513 result = dwarf2_read_address (buf,
514 buf + (TARGET_ADDR_BIT
520 case DW_OP_deref_size:
522 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
525 (ctx->read_mem) (ctx->baton, buf, result, *op_ptr++);
526 result = dwarf2_read_address (buf,
527 buf + (TARGET_ADDR_BIT
534 if ((signed int) result < 0)
543 case DW_OP_plus_uconst:
544 op_ptr = read_uleb128 (op_ptr, op_end, ®);
568 /* Binary operations. Use the value engine to do computations in
570 CORE_ADDR first, second;
571 enum exp_opcode binop;
572 struct value *val1, *val2;
574 second = dwarf_expr_fetch (ctx, 0);
575 dwarf_expr_pop (ctx);
577 first = dwarf_expr_fetch (ctx, 1);
578 dwarf_expr_pop (ctx);
580 val1 = value_from_longest (unsigned_address_type (), first);
581 val2 = value_from_longest (unsigned_address_type (), second);
586 binop = BINOP_BITWISE_AND;
600 binop = BINOP_BITWISE_IOR;
612 val1 = value_from_longest (signed_address_type (), first);
615 binop = BINOP_BITWISE_XOR;
633 binop = BINOP_NOTEQUAL;
636 internal_error (__FILE__, __LINE__,
637 "Can't be reached.");
639 result = value_as_long (value_binop (val1, val2, binop));
643 case DW_OP_GNU_push_tls_address:
644 result = dwarf_expr_fetch (ctx, 0);
645 dwarf_expr_pop (ctx);
646 result = (ctx->get_tls_address) (ctx->baton, result);
650 offset = extract_signed_integer (op_ptr, 2);
656 offset = extract_signed_integer (op_ptr, 2);
658 if (dwarf_expr_fetch (ctx, 0) != 0)
660 dwarf_expr_pop (ctx);
667 error ("Unhandled dwarf expression opcode");
670 /* Most things push a result value. */
671 dwarf_expr_push (ctx, result);