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 = 0;
43 retval->stack_allocated = 10;
44 retval->stack = xmalloc (retval->stack_allocated * sizeof (CORE_ADDR));
48 /* Release the memory allocated to CTX. */
51 free_dwarf_expr_context (struct dwarf_expr_context *ctx)
57 /* Expand the memory allocated to CTX's stack to contain at least
58 NEED more elements than are currently used. */
61 dwarf_expr_grow_stack (struct dwarf_expr_context *ctx, size_t need)
63 if (ctx->stack_len + need > ctx->stack_allocated)
65 size_t newlen = ctx->stack_len + need + 10;
66 ctx->stack = xrealloc (ctx->stack,
67 newlen * sizeof (CORE_ADDR));
68 ctx->stack_allocated = newlen;
72 /* Push VALUE onto CTX's stack. */
75 dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value)
77 dwarf_expr_grow_stack (ctx, 1);
78 ctx->stack[ctx->stack_len++] = value;
81 /* Pop the top item off of CTX's stack. */
84 dwarf_expr_pop (struct dwarf_expr_context *ctx)
86 if (ctx->stack_len <= 0)
87 error ("dwarf expression stack underflow");
91 /* Retrieve the N'th item on CTX's stack. */
94 dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n)
96 if (ctx->stack_len < n)
97 error ("Asked for position %d of stack, stack only has %d elements on it\n",
99 return ctx->stack[ctx->stack_len - (1 + n)];
103 /* Evaluate the expression at ADDR (LEN bytes long) using the context
107 dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr,
110 execute_stack_op (ctx, addr, addr + len);
113 /* Decode the unsigned LEB128 constant at BUF into the variable pointed to
114 by R, and return the new value of BUF. Verify that it doesn't extend
118 read_uleb128 (unsigned char *buf, unsigned char *buf_end, ULONGEST * r)
127 error ("read_uleb128: Corrupted DWARF expression.");
130 result |= (byte & 0x7f) << shift;
131 if ((byte & 0x80) == 0)
139 /* Decode the signed LEB128 constant at BUF into the variable pointed to
140 by R, and return the new value of BUF. Verify that it doesn't extend
144 read_sleb128 (unsigned char *buf, unsigned char *buf_end, LONGEST * r)
153 error ("read_sleb128: Corrupted DWARF expression.");
156 result |= (byte & 0x7f) << shift;
158 if ((byte & 0x80) == 0)
161 if (shift < (sizeof (*r) * 8) && (byte & 0x40) != 0)
162 result |= -(1 << shift);
168 /* Read an address from BUF, and verify that it doesn't extend past
169 BUF_END. The address is returned, and *BYTES_READ is set to the
170 number of bytes read from BUF. */
173 dwarf2_read_address (unsigned char *buf, unsigned char *buf_end, int *bytes_read)
177 if (buf_end - buf < TARGET_ADDR_BIT / TARGET_CHAR_BIT)
178 error ("dwarf2_read_address: Corrupted DWARF expression.");
180 *bytes_read = TARGET_ADDR_BIT / TARGET_CHAR_BIT;
181 result = extract_address (buf, TARGET_ADDR_BIT / TARGET_CHAR_BIT);
185 /* Return the type of an address, for unsigned arithmetic. */
188 unsigned_address_type (void)
190 switch (TARGET_ADDR_BIT / TARGET_CHAR_BIT)
193 return builtin_type_uint16;
195 return builtin_type_uint32;
197 return builtin_type_uint64;
199 internal_error (__FILE__, __LINE__,
200 "Unsupported address size.\n");
204 /* Return the type of an address, for signed arithmetic. */
207 signed_address_type (void)
209 switch (TARGET_ADDR_BIT / TARGET_CHAR_BIT)
212 return builtin_type_int16;
214 return builtin_type_int32;
216 return builtin_type_int64;
218 internal_error (__FILE__, __LINE__,
219 "Unsupported address size.\n");
223 /* The engine for the expression evaluator. Using the context in CTX,
224 evaluate the expression between OP_PTR and OP_END. */
227 execute_stack_op (struct dwarf_expr_context *ctx, unsigned char *op_ptr,
228 unsigned char *op_end)
232 while (op_ptr < op_end)
234 enum dwarf_location_atom op = *op_ptr++;
236 ULONGEST uoffset, reg;
274 result = op - DW_OP_lit0;
278 result = dwarf2_read_address (op_ptr, op_end, &bytes_read);
279 op_ptr += bytes_read;
283 result = extract_unsigned_integer (op_ptr, 1);
287 result = extract_signed_integer (op_ptr, 1);
291 result = extract_unsigned_integer (op_ptr, 2);
295 result = extract_signed_integer (op_ptr, 2);
299 result = extract_unsigned_integer (op_ptr, 4);
303 result = extract_signed_integer (op_ptr, 4);
307 result = extract_unsigned_integer (op_ptr, 8);
311 result = extract_signed_integer (op_ptr, 8);
315 op_ptr = read_uleb128 (op_ptr, op_end, &uoffset);
319 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
323 /* The DW_OP_reg operations are required to occur alone in
324 location expressions. */
357 if (op_ptr != op_end && *op_ptr != DW_OP_piece)
358 error ("DWARF-2 expression error: DW_OP_reg operations must be "
359 "used either alone or in conjuction with DW_OP_piece.");
361 result = op - DW_OP_reg0;
367 op_ptr = read_uleb128 (op_ptr, op_end, ®);
368 if (op_ptr != op_end && *op_ptr != DW_OP_piece)
369 error ("DWARF-2 expression error: DW_OP_reg operations must be "
370 "used either alone or in conjuction with DW_OP_piece.");
409 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
410 result = (ctx->read_reg) (ctx->baton, op - DW_OP_breg0);
416 op_ptr = read_uleb128 (op_ptr, op_end, ®);
417 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
418 result = (ctx->read_reg) (ctx->baton, reg);
424 unsigned char *datastart;
426 unsigned int before_stack_len;
428 op_ptr = read_sleb128 (op_ptr, op_end, &offset);
429 /* Rather than create a whole new context, we simply
430 record the stack length before execution, then reset it
431 afterwards, effectively erasing whatever the recursive
433 before_stack_len = ctx->stack_len;
434 /* FIXME: cagney/2003-03-26: This code should be using
435 get_frame_base_address(), and then implement a dwarf2
436 specific this_base method. */
437 (ctx->get_frame_base) (ctx->baton, &datastart, &datalen);
438 dwarf_expr_eval (ctx, datastart, datalen);
439 result = dwarf_expr_fetch (ctx, 0);
441 result = (ctx->read_reg) (ctx->baton, result);
444 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
447 (ctx->read_mem) (ctx->baton, buf, result,
448 TARGET_ADDR_BIT / TARGET_CHAR_BIT);
449 result = dwarf2_read_address (buf,
450 buf + (TARGET_ADDR_BIT
454 result = result + offset;
455 ctx->stack_len = before_stack_len;
460 result = dwarf_expr_fetch (ctx, 0);
464 dwarf_expr_pop (ctx);
469 result = dwarf_expr_fetch (ctx, offset);
473 result = dwarf_expr_fetch (ctx, 1);
478 CORE_ADDR t1, t2, t3;
480 if (ctx->stack_len < 3)
481 error ("Not enough elements for DW_OP_rot. Need 3, have %d\n",
483 t1 = ctx->stack[ctx->stack_len - 1];
484 t2 = ctx->stack[ctx->stack_len - 2];
485 t3 = ctx->stack[ctx->stack_len - 3];
486 ctx->stack[ctx->stack_len - 1] = t2;
487 ctx->stack[ctx->stack_len - 2] = t3;
488 ctx->stack[ctx->stack_len - 3] = t1;
493 case DW_OP_deref_size:
497 case DW_OP_plus_uconst:
498 /* Unary operations. */
499 result = dwarf_expr_fetch (ctx, 0);
500 dwarf_expr_pop (ctx);
506 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
509 (ctx->read_mem) (ctx->baton, buf, result,
510 TARGET_ADDR_BIT / TARGET_CHAR_BIT);
511 result = dwarf2_read_address (buf,
512 buf + (TARGET_ADDR_BIT
518 case DW_OP_deref_size:
520 char *buf = alloca (TARGET_ADDR_BIT / TARGET_CHAR_BIT);
523 (ctx->read_mem) (ctx->baton, buf, result, *op_ptr++);
524 result = dwarf2_read_address (buf,
525 buf + (TARGET_ADDR_BIT
532 if ((signed int) result < 0)
541 case DW_OP_plus_uconst:
542 op_ptr = read_uleb128 (op_ptr, op_end, ®);
566 /* Binary operations. Use the value engine to do computations in
568 CORE_ADDR first, second;
569 enum exp_opcode binop;
570 struct value *val1, *val2;
572 second = dwarf_expr_fetch (ctx, 0);
573 dwarf_expr_pop (ctx);
575 first = dwarf_expr_fetch (ctx, 1);
576 dwarf_expr_pop (ctx);
578 val1 = value_from_longest (unsigned_address_type (), first);
579 val2 = value_from_longest (unsigned_address_type (), second);
584 binop = BINOP_BITWISE_AND;
598 binop = BINOP_BITWISE_IOR;
610 val1 = value_from_longest (signed_address_type (), first);
613 binop = BINOP_BITWISE_XOR;
631 binop = BINOP_NOTEQUAL;
634 internal_error (__FILE__, __LINE__,
635 "Can't be reached.");
637 result = value_as_long (value_binop (val1, val2, binop));
641 case DW_OP_GNU_push_tls_address:
642 result = dwarf_expr_fetch (ctx, 0);
643 dwarf_expr_pop (ctx);
644 result = (ctx->get_tls_address) (ctx->baton, result);
648 offset = extract_signed_integer (op_ptr, 2);
654 offset = extract_signed_integer (op_ptr, 2);
656 if (dwarf_expr_fetch (ctx, 0) != 0)
658 dwarf_expr_pop (ctx);
665 error ("Unhandled dwarf expression opcode");
668 /* Most things push a result value. */
669 dwarf_expr_push (ctx, result);