1 /* Definitions for expressions designed to be executed on the agent 2 Copyright (C) 1998, 1999, 2000, 2007, 2008, 2009 3 Free Software Foundation, 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 3 of the License, or 10 (at your option) any later version. 11 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. 16 17 You should have received a copy of the GNU General Public License 18 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 19 20 #ifndef AGENTEXPR_H 21 #define AGENTEXPR_H 22 23 #include "doublest.h" /* For DOUBLEST. */ 24 25 /* It's sometimes useful to be able to debug programs that you can't 26 really stop for more than a fraction of a second. To this end, the 27 user can specify a tracepoint (like a breakpoint, but you don't 28 stop at it), and specify a bunch of expressions to record the 29 values of when that tracepoint is reached. As the program runs, 30 GDB collects the values. At any point (possibly while values are 31 still being collected), the user can display the collected values. 32 33 This is used with remote debugging; we don't really support it on 34 native configurations. 35 36 This means that expressions are being evaluated by the remote agent, 37 which doesn't have any access to the symbol table information, and 38 needs to be small and simple. 39 40 The agent_expr routines and datatypes are a bytecode language 41 designed to be executed by the agent. Agent expressions work in 42 terms of fixed-width values, operators, memory references, and 43 register references. You can evaluate a agent expression just given 44 a bunch of memory and register values to sniff at; you don't need 45 any symbolic information like variable names, types, etc. 46 47 GDB translates source expressions, whose meaning depends on 48 symbolic information, into agent bytecode expressions, whose meaning 49 is independent of symbolic information. This means the agent can 50 evaluate them on the fly without reference to data only available 51 to the host GDB. */ 52 53 54 /* Agent expression data structures. */ 55 56 /* The type of an element of the agent expression stack. 57 The bytecode operation indicates which element we should access; 58 the value itself has no typing information. GDB generates all 59 bytecode streams, so we don't have to worry about type errors. */ 60 61 union agent_val 62 { 63 LONGEST l; 64 DOUBLEST d; 65 }; 66 67 /* A buffer containing a agent expression. */ 68 struct agent_expr 69 { 70 unsigned char *buf; 71 int len; /* number of characters used */ 72 int size; /* allocated size */ 73 CORE_ADDR scope; 74 }; 75 76 77 78 79 /* The actual values of the various bytecode operations. 80 81 Other independent implementations of the agent bytecode engine will 82 rely on the exact values of these enums, and may not be recompiled 83 when we change this table. The numeric values should remain fixed 84 whenever possible. Thus, we assign them values explicitly here (to 85 allow gaps to form safely), and the disassembly table in 86 agentexpr.h behaves like an opcode map. If you want to see them 87 grouped logically, see doc/agentexpr.texi. */ 88 89 enum agent_op 90 { 91 aop_float = 0x01, 92 aop_add = 0x02, 93 aop_sub = 0x03, 94 aop_mul = 0x04, 95 aop_div_signed = 0x05, 96 aop_div_unsigned = 0x06, 97 aop_rem_signed = 0x07, 98 aop_rem_unsigned = 0x08, 99 aop_lsh = 0x09, 100 aop_rsh_signed = 0x0a, 101 aop_rsh_unsigned = 0x0b, 102 aop_trace = 0x0c, 103 aop_trace_quick = 0x0d, 104 aop_log_not = 0x0e, 105 aop_bit_and = 0x0f, 106 aop_bit_or = 0x10, 107 aop_bit_xor = 0x11, 108 aop_bit_not = 0x12, 109 aop_equal = 0x13, 110 aop_less_signed = 0x14, 111 aop_less_unsigned = 0x15, 112 aop_ext = 0x16, 113 aop_ref8 = 0x17, 114 aop_ref16 = 0x18, 115 aop_ref32 = 0x19, 116 aop_ref64 = 0x1a, 117 aop_ref_float = 0x1b, 118 aop_ref_double = 0x1c, 119 aop_ref_long_double = 0x1d, 120 aop_l_to_d = 0x1e, 121 aop_d_to_l = 0x1f, 122 aop_if_goto = 0x20, 123 aop_goto = 0x21, 124 aop_const8 = 0x22, 125 aop_const16 = 0x23, 126 aop_const32 = 0x24, 127 aop_const64 = 0x25, 128 aop_reg = 0x26, 129 aop_end = 0x27, 130 aop_dup = 0x28, 131 aop_pop = 0x29, 132 aop_zero_ext = 0x2a, 133 aop_swap = 0x2b, 134 aop_trace16 = 0x30, 135 aop_last 136 }; 137 138 139 140 /* Functions for building expressions. */ 141 142 /* Allocate a new, empty agent expression. */ 143 extern struct agent_expr *new_agent_expr (CORE_ADDR); 144 145 /* Free a agent expression. */ 146 extern void free_agent_expr (struct agent_expr *); 147 extern struct cleanup *make_cleanup_free_agent_expr (struct agent_expr *); 148 149 /* Append a simple operator OP to EXPR. */ 150 extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP); 151 152 /* Append the floating-point prefix, for the next bytecode. */ 153 #define ax_float(EXPR) (ax_simple ((EXPR), aop_float)) 154 155 /* Append a sign-extension instruction to EXPR, to extend an N-bit value. */ 156 extern void ax_ext (struct agent_expr *EXPR, int N); 157 158 /* Append a zero-extension instruction to EXPR, to extend an N-bit value. */ 159 extern void ax_zero_ext (struct agent_expr *EXPR, int N); 160 161 /* Append a trace_quick instruction to EXPR, to record N bytes. */ 162 extern void ax_trace_quick (struct agent_expr *EXPR, int N); 163 164 /* Append a goto op to EXPR. OP is the actual op (must be aop_goto or 165 aop_if_goto). We assume we don't know the target offset yet, 166 because it's probably a forward branch, so we leave space in EXPR 167 for the target, and return the offset in EXPR of that space, so we 168 can backpatch it once we do know the target offset. Use ax_label 169 to do the backpatching. */ 170 extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP); 171 172 /* Suppose a given call to ax_goto returns some value PATCH. When you 173 know the offset TARGET that goto should jump to, call 174 ax_label (EXPR, PATCH, TARGET) 175 to patch TARGET into the ax_goto instruction. */ 176 extern void ax_label (struct agent_expr *EXPR, int patch, int target); 177 178 /* Assemble code to push a constant on the stack. */ 179 extern void ax_const_l (struct agent_expr *EXPR, LONGEST l); 180 extern void ax_const_d (struct agent_expr *EXPR, LONGEST d); 181 182 /* Assemble code to push the value of register number REG on the 183 stack. */ 184 extern void ax_reg (struct agent_expr *EXPR, int REG); 185 186 187 /* Functions for printing out expressions, and otherwise debugging 188 things. */ 189 190 /* Disassemble the expression EXPR, writing to F. */ 191 extern void ax_print (struct ui_file *f, struct agent_expr * EXPR); 192 193 /* An entry in the opcode map. */ 194 struct aop_map 195 { 196 197 /* The name of the opcode. Null means that this entry is not a 198 valid opcode --- a hole in the opcode space. */ 199 char *name; 200 201 /* All opcodes take no operands from the bytecode stream, or take 202 unsigned integers of various sizes. If this is a positive number 203 n, then the opcode is followed by an n-byte operand, which should 204 be printed as an unsigned integer. If this is zero, then the 205 opcode takes no operands from the bytecode stream. 206 207 If we get more complicated opcodes in the future, don't add other 208 magic values of this; that's a crock. Add an `enum encoding' 209 field to this, or something like that. */ 210 int op_size; 211 212 /* The size of the data operated upon, in bits, for bytecodes that 213 care about that (ref and const). Zero for all others. */ 214 int data_size; 215 216 /* Number of stack elements consumed, and number produced. */ 217 int consumed, produced; 218 }; 219 220 /* Map of the bytecodes, indexed by bytecode number. */ 221 extern struct aop_map aop_map[]; 222 223 /* Different kinds of flaws an agent expression might have, as 224 detected by agent_reqs. */ 225 enum agent_flaws 226 { 227 agent_flaw_none = 0, /* code is good */ 228 229 /* There is an invalid instruction in the stream. */ 230 agent_flaw_bad_instruction, 231 232 /* There is an incomplete instruction at the end of the expression. */ 233 agent_flaw_incomplete_instruction, 234 235 /* agent_reqs was unable to prove that every jump target is to a 236 valid offset. Valid offsets are within the bounds of the 237 expression, and to a valid instruction boundary. */ 238 agent_flaw_bad_jump, 239 240 /* agent_reqs was unable to prove to its satisfaction that, for each 241 jump target location, the stack will have the same height whether 242 that location is reached via a jump or by straight execution. */ 243 agent_flaw_height_mismatch, 244 245 /* agent_reqs was unable to prove that every instruction following 246 an unconditional jump was the target of some other jump. */ 247 agent_flaw_hole 248 }; 249 250 /* Structure describing the requirements of a bytecode expression. */ 251 struct agent_reqs 252 { 253 254 /* If the following is not equal to agent_flaw_none, the rest of the 255 information in this structure is suspect. */ 256 enum agent_flaws flaw; 257 258 /* Number of elements left on stack at end; may be negative if expr 259 only consumes elements. */ 260 int final_height; 261 262 /* Maximum and minimum stack height, relative to initial height. */ 263 int max_height, min_height; 264 265 /* Largest `ref' or `const' opcode used, in bits. Zero means the 266 expression has no such instructions. */ 267 int max_data_size; 268 269 /* Bit vector of registers used. Register R is used iff 270 271 reg_mask[R / 8] & (1 << (R % 8)) 272 273 is non-zero. Note! You may not assume that this bitmask is long 274 enough to hold bits for all the registers of the machine; the 275 agent expression code has no idea how many registers the machine 276 has. However, the bitmask is reg_mask_len bytes long, so the 277 valid register numbers run from 0 to reg_mask_len * 8 - 1. 278 279 We're assuming eight-bit bytes. So sue me. 280 281 The caller should free reg_list when done. */ 282 int reg_mask_len; 283 unsigned char *reg_mask; 284 }; 285 286 287 /* Given an agent expression AX, fill in an agent_reqs structure REQS 288 describing it. */ 289 extern void ax_reqs (struct agent_expr *ax, struct agent_reqs *reqs); 290 291 #endif /* AGENTEXPR_H */ 292