1 /* DWARF 2 Expression Evaluator. 2 3 Copyright (C) 2001, 2002, 2003, 2005, 2007, 2008, 2009 4 Free Software Foundation, Inc. 5 6 Contributed by Daniel Berlin <dan@dberlin.org>. 7 8 This file is part of GDB. 9 10 This program is free software; you can redistribute it and/or modify 11 it under the terms of the GNU General Public License as published by 12 the Free Software Foundation; either version 3 of the License, or 13 (at your option) any later version. 14 15 This program is distributed in the hope that it will be useful, 16 but WITHOUT ANY WARRANTY; without even the implied warranty of 17 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 18 GNU General Public License for more details. 19 20 You should have received a copy of the GNU General Public License 21 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 22 23 #if !defined (DWARF2EXPR_H) 24 #define DWARF2EXPR_H 25 26 /* The location of a value. */ 27 enum dwarf_value_location 28 { 29 /* The piece is in memory. 30 The value on the dwarf stack is its address. */ 31 DWARF_VALUE_MEMORY, 32 33 /* The piece is in a register. 34 The value on the dwarf stack is the register number. */ 35 DWARF_VALUE_REGISTER, 36 37 /* The piece is on the dwarf stack. */ 38 DWARF_VALUE_STACK, 39 40 /* The piece is a literal. */ 41 DWARF_VALUE_LITERAL 42 }; 43 44 /* The dwarf expression stack. */ 45 46 struct dwarf_stack_value 47 { 48 CORE_ADDR value; 49 50 /* Non-zero if the piece is in memory and is known to be 51 on the program's stack. It is always ok to set this to zero. 52 This is used, for example, to optimize memory access from the target. 53 It can vastly speed up backtraces on long latency connections when 54 "set stack-cache on". */ 55 int in_stack_memory; 56 }; 57 58 /* The expression evaluator works with a dwarf_expr_context, describing 59 its current state and its callbacks. */ 60 struct dwarf_expr_context 61 { 62 /* The stack of values, allocated with xmalloc. */ 63 struct dwarf_stack_value *stack; 64 65 /* The number of values currently pushed on the stack, and the 66 number of elements allocated to the stack. */ 67 int stack_len, stack_allocated; 68 69 /* Target architecture to use for address operations. */ 70 struct gdbarch *gdbarch; 71 72 /* Target address size in bytes. */ 73 int addr_size; 74 75 /* An opaque argument provided by the caller, which will be passed 76 to all of the callback functions. */ 77 void *baton; 78 79 /* Return the value of register number REGNUM. */ 80 CORE_ADDR (*read_reg) (void *baton, int regnum); 81 82 /* Read LENGTH bytes at ADDR into BUF. */ 83 void (*read_mem) (void *baton, gdb_byte *buf, CORE_ADDR addr, size_t length); 84 85 /* Return the location expression for the frame base attribute, in 86 START and LENGTH. The result must be live until the current 87 expression evaluation is complete. */ 88 void (*get_frame_base) (void *baton, gdb_byte **start, size_t *length); 89 90 /* Return the CFA for the frame. */ 91 CORE_ADDR (*get_frame_cfa) (void *baton); 92 93 /* Return the thread-local storage address for 94 DW_OP_GNU_push_tls_address. */ 95 CORE_ADDR (*get_tls_address) (void *baton, CORE_ADDR offset); 96 97 #if 0 98 /* Not yet implemented. */ 99 100 /* Return the location expression for the dwarf expression 101 subroutine in the die at OFFSET in the current compilation unit. 102 The result must be live until the current expression evaluation 103 is complete. */ 104 unsigned char *(*get_subr) (void *baton, off_t offset, size_t *length); 105 106 /* Return the `object address' for DW_OP_push_object_address. */ 107 CORE_ADDR (*get_object_address) (void *baton); 108 #endif 109 110 /* The current depth of dwarf expression recursion, via DW_OP_call*, 111 DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum 112 depth we'll tolerate before raising an error. */ 113 int recursion_depth, max_recursion_depth; 114 115 /* Location of the value. */ 116 enum dwarf_value_location location; 117 118 /* For VALUE_LITERAL, a the current literal value's length and 119 data. */ 120 ULONGEST len; 121 gdb_byte *data; 122 123 /* Initialization status of variable: Non-zero if variable has been 124 initialized; zero otherwise. */ 125 int initialized; 126 127 /* An array of pieces. PIECES points to its first element; 128 NUM_PIECES is its length. 129 130 Each time DW_OP_piece is executed, we add a new element to the 131 end of this array, recording the current top of the stack, the 132 current location, and the size given as the operand to 133 DW_OP_piece. We then pop the top value from the stack, reset the 134 location, and resume evaluation. 135 136 The Dwarf spec doesn't say whether DW_OP_piece pops the top value 137 from the stack. We do, ensuring that clients of this interface 138 expecting to see a value left on the top of the stack (say, code 139 evaluating frame base expressions or CFA's specified with 140 DW_CFA_def_cfa_expression) will get an error if the expression 141 actually marks all the values it computes as pieces. 142 143 If an expression never uses DW_OP_piece, num_pieces will be zero. 144 (It would be nice to present these cases as expressions yielding 145 a single piece, so that callers need not distinguish between the 146 no-DW_OP_piece and one-DW_OP_piece cases. But expressions with 147 no DW_OP_piece operations have no value to place in a piece's 148 'size' field; the size comes from the surrounding data. So the 149 two cases need to be handled separately.) */ 150 int num_pieces; 151 struct dwarf_expr_piece *pieces; 152 }; 153 154 155 /* A piece of an object, as recorded by DW_OP_piece. */ 156 struct dwarf_expr_piece 157 { 158 enum dwarf_value_location location; 159 160 union 161 { 162 struct 163 { 164 /* This piece's address or register number. */ 165 CORE_ADDR value; 166 /* Non-zero if the piece is known to be in memory and on 167 the program's stack. */ 168 int in_stack_memory; 169 } expr; 170 171 struct 172 { 173 /* A pointer to the data making up this piece, for literal 174 pieces. */ 175 gdb_byte *data; 176 /* The length of the available data. */ 177 ULONGEST length; 178 } literal; 179 } v; 180 181 /* The length of the piece, in bytes. */ 182 ULONGEST size; 183 }; 184 185 struct dwarf_expr_context *new_dwarf_expr_context (void); 186 void free_dwarf_expr_context (struct dwarf_expr_context *ctx); 187 struct cleanup * 188 make_cleanup_free_dwarf_expr_context (struct dwarf_expr_context *ctx); 189 190 void dwarf_expr_push (struct dwarf_expr_context *ctx, CORE_ADDR value, 191 int in_stack_memory); 192 void dwarf_expr_pop (struct dwarf_expr_context *ctx); 193 void dwarf_expr_eval (struct dwarf_expr_context *ctx, unsigned char *addr, 194 size_t len); 195 CORE_ADDR dwarf_expr_fetch (struct dwarf_expr_context *ctx, int n); 196 int dwarf_expr_fetch_in_stack_memory (struct dwarf_expr_context *ctx, int n); 197 198 199 gdb_byte *read_uleb128 (gdb_byte *buf, gdb_byte *buf_end, ULONGEST * r); 200 gdb_byte *read_sleb128 (gdb_byte *buf, gdb_byte *buf_end, LONGEST * r); 201 CORE_ADDR dwarf2_read_address (struct gdbarch *gdbarch, gdb_byte *buf, 202 gdb_byte *buf_end, int addr_size); 203 204 #endif /* dwarf2expr.h */ 205