1 /* Definitions for expressions designed to be executed on the agent 2 Copyright 1998, 1999, 2000 Free Software Foundation, Inc. 3 4 This file is part of GDB. 5 6 This program is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by 8 the Free Software Foundation; either version 2 of the License, or 9 (at your option) any later version. 10 11 This program is distributed in the hope that it will be useful, 12 but WITHOUT ANY WARRANTY; without even the implied warranty of 13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 GNU General Public License for more details. 15 16 You should have received a copy of the GNU General Public License 17 along with this program; if not, write to the Free Software 18 Foundation, Inc., 59 Temple Place - Suite 330, 19 Boston, MA 02111-1307, USA. */ 20 21 #ifndef AGENTEXPR_H 22 #define AGENTEXPR_H 23 24 #include "doublest.h" /* For DOUBLEST. */ 25 26 /* It's sometimes useful to be able to debug programs that you can't 27 really stop for more than a fraction of a second. To this end, the 28 user can specify a tracepoint (like a breakpoint, but you don't 29 stop at it), and specify a bunch of expressions to record the 30 values of when that tracepoint is reached. As the program runs, 31 GDB collects the values. At any point (possibly while values are 32 still being collected), the user can display the collected values. 33 34 This is used with remote debugging; we don't really support it on 35 native configurations. 36 37 This means that expressions are being evaluated by the remote agent, 38 which doesn't have any access to the symbol table information, and 39 needs to be small and simple. 40 41 The agent_expr routines and datatypes are a bytecode language 42 designed to be executed by the agent. Agent expressions work in 43 terms of fixed-width values, operators, memory references, and 44 register references. You can evaluate a agent expression just given 45 a bunch of memory and register values to sniff at; you don't need 46 any symbolic information like variable names, types, etc. 47 48 GDB translates source expressions, whose meaning depends on 49 symbolic information, into agent bytecode expressions, whose meaning 50 is independent of symbolic information. This means the agent can 51 evaluate them on the fly without reference to data only available 52 to the host GDB. */ 53 54 55 /* Agent expression data structures. */ 56 57 /* The type of an element of the agent expression stack. 58 The bytecode operation indicates which element we should access; 59 the value itself has no typing information. GDB generates all 60 bytecode streams, so we don't have to worry about type errors. */ 61 62 union agent_val 63 { 64 LONGEST l; 65 DOUBLEST d; 66 }; 67 68 /* A buffer containing a agent expression. */ 69 struct agent_expr 70 { 71 unsigned char *buf; 72 int len; /* number of characters used */ 73 int size; /* allocated size */ 74 CORE_ADDR scope; 75 }; 76 77 78 79 80 /* The actual values of the various bytecode operations. 81 82 Other independent implementations of the agent bytecode engine will 83 rely on the exact values of these enums, and may not be recompiled 84 when we change this table. The numeric values should remain fixed 85 whenever possible. Thus, we assign them values explicitly here (to 86 allow gaps to form safely), and the disassembly table in 87 agentexpr.h behaves like an opcode map. If you want to see them 88 grouped logically, see doc/agentexpr.texi. */ 89 90 enum agent_op 91 { 92 aop_float = 0x01, 93 aop_add = 0x02, 94 aop_sub = 0x03, 95 aop_mul = 0x04, 96 aop_div_signed = 0x05, 97 aop_div_unsigned = 0x06, 98 aop_rem_signed = 0x07, 99 aop_rem_unsigned = 0x08, 100 aop_lsh = 0x09, 101 aop_rsh_signed = 0x0a, 102 aop_rsh_unsigned = 0x0b, 103 aop_trace = 0x0c, 104 aop_trace_quick = 0x0d, 105 aop_log_not = 0x0e, 106 aop_bit_and = 0x0f, 107 aop_bit_or = 0x10, 108 aop_bit_xor = 0x11, 109 aop_bit_not = 0x12, 110 aop_equal = 0x13, 111 aop_less_signed = 0x14, 112 aop_less_unsigned = 0x15, 113 aop_ext = 0x16, 114 aop_ref8 = 0x17, 115 aop_ref16 = 0x18, 116 aop_ref32 = 0x19, 117 aop_ref64 = 0x1a, 118 aop_ref_float = 0x1b, 119 aop_ref_double = 0x1c, 120 aop_ref_long_double = 0x1d, 121 aop_l_to_d = 0x1e, 122 aop_d_to_l = 0x1f, 123 aop_if_goto = 0x20, 124 aop_goto = 0x21, 125 aop_const8 = 0x22, 126 aop_const16 = 0x23, 127 aop_const32 = 0x24, 128 aop_const64 = 0x25, 129 aop_reg = 0x26, 130 aop_end = 0x27, 131 aop_dup = 0x28, 132 aop_pop = 0x29, 133 aop_zero_ext = 0x2a, 134 aop_swap = 0x2b, 135 aop_trace16 = 0x30, 136 aop_last 137 }; 138 139 140 141 /* Functions for building expressions. */ 142 143 /* Allocate a new, empty agent expression. */ 144 extern struct agent_expr *new_agent_expr (CORE_ADDR); 145 146 /* Free a agent expression. */ 147 extern void free_agent_expr (struct agent_expr *); 148 extern struct cleanup *make_cleanup_free_agent_expr (struct agent_expr *); 149 150 /* Append a simple operator OP to EXPR. */ 151 extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP); 152 153 /* Append the floating-point prefix, for the next bytecode. */ 154 #define ax_float(EXPR) (ax_simple ((EXPR), aop_float)) 155 156 /* Append a sign-extension instruction to EXPR, to extend an N-bit value. */ 157 extern void ax_ext (struct agent_expr *EXPR, int N); 158 159 /* Append a zero-extension instruction to EXPR, to extend an N-bit value. */ 160 extern void ax_zero_ext (struct agent_expr *EXPR, int N); 161 162 /* Append a trace_quick instruction to EXPR, to record N bytes. */ 163 extern void ax_trace_quick (struct agent_expr *EXPR, int N); 164 165 /* Append a goto op to EXPR. OP is the actual op (must be aop_goto or 166 aop_if_goto). We assume we don't know the target offset yet, 167 because it's probably a forward branch, so we leave space in EXPR 168 for the target, and return the offset in EXPR of that space, so we 169 can backpatch it once we do know the target offset. Use ax_label 170 to do the backpatching. */ 171 extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP); 172 173 /* Suppose a given call to ax_goto returns some value PATCH. When you 174 know the offset TARGET that goto should jump to, call 175 ax_label (EXPR, PATCH, TARGET) 176 to patch TARGET into the ax_goto instruction. */ 177 extern void ax_label (struct agent_expr *EXPR, int patch, int target); 178 179 /* Assemble code to push a constant on the stack. */ 180 extern void ax_const_l (struct agent_expr *EXPR, LONGEST l); 181 extern void ax_const_d (struct agent_expr *EXPR, LONGEST d); 182 183 /* Assemble code to push the value of register number REG on the 184 stack. */ 185 extern void ax_reg (struct agent_expr *EXPR, int REG); 186 187 188 /* Functions for printing out expressions, and otherwise debugging 189 things. */ 190 191 /* Disassemble the expression EXPR, writing to F. */ 192 extern void ax_print (struct ui_file *f, struct agent_expr * EXPR); 193 194 /* An entry in the opcode map. */ 195 struct aop_map 196 { 197 198 /* The name of the opcode. Null means that this entry is not a 199 valid opcode --- a hole in the opcode space. */ 200 char *name; 201 202 /* All opcodes take no operands from the bytecode stream, or take 203 unsigned integers of various sizes. If this is a positive number 204 n, then the opcode is followed by an n-byte operand, which should 205 be printed as an unsigned integer. If this is zero, then the 206 opcode takes no operands from the bytecode stream. 207 208 If we get more complicated opcodes in the future, don't add other 209 magic values of this; that's a crock. Add an `enum encoding' 210 field to this, or something like that. */ 211 int op_size; 212 213 /* The size of the data operated upon, in bits, for bytecodes that 214 care about that (ref and const). Zero for all others. */ 215 int data_size; 216 217 /* Number of stack elements consumed, and number produced. */ 218 int consumed, produced; 219 }; 220 221 /* Map of the bytecodes, indexed by bytecode number. */ 222 extern struct aop_map aop_map[]; 223 224 /* Different kinds of flaws an agent expression might have, as 225 detected by agent_reqs. */ 226 enum agent_flaws 227 { 228 agent_flaw_none = 0, /* code is good */ 229 230 /* There is an invalid instruction in the stream. */ 231 agent_flaw_bad_instruction, 232 233 /* There is an incomplete instruction at the end of the expression. */ 234 agent_flaw_incomplete_instruction, 235 236 /* agent_reqs was unable to prove that every jump target is to a 237 valid offset. Valid offsets are within the bounds of the 238 expression, and to a valid instruction boundary. */ 239 agent_flaw_bad_jump, 240 241 /* agent_reqs was unable to prove to its satisfaction that, for each 242 jump target location, the stack will have the same height whether 243 that location is reached via a jump or by straight execution. */ 244 agent_flaw_height_mismatch, 245 246 /* agent_reqs was unable to prove that every instruction following 247 an unconditional jump was the target of some other jump. */ 248 agent_flaw_hole 249 }; 250 251 /* Structure describing the requirements of a bytecode expression. */ 252 struct agent_reqs 253 { 254 255 /* If the following is not equal to agent_flaw_none, the rest of the 256 information in this structure is suspect. */ 257 enum agent_flaws flaw; 258 259 /* Number of elements left on stack at end; may be negative if expr 260 only consumes elements. */ 261 int final_height; 262 263 /* Maximum and minimum stack height, relative to initial height. */ 264 int max_height, min_height; 265 266 /* Largest `ref' or `const' opcode used, in bits. Zero means the 267 expression has no such instructions. */ 268 int max_data_size; 269 270 /* Bit vector of registers used. Register R is used iff 271 272 reg_mask[R / 8] & (1 << (R % 8)) 273 274 is non-zero. Note! You may not assume that this bitmask is long 275 enough to hold bits for all the registers of the machine; the 276 agent expression code has no idea how many registers the machine 277 has. However, the bitmask is reg_mask_len bytes long, so the 278 valid register numbers run from 0 to reg_mask_len * 8 - 1. 279 280 We're assuming eight-bit bytes. So sue me. 281 282 The caller should free reg_list when done. */ 283 int reg_mask_len; 284 unsigned char *reg_mask; 285 }; 286 287 288 /* Given an agent expression AX, fill in an agent_reqs structure REQS 289 describing it. */ 290 extern void ax_reqs (struct agent_expr *ax, struct agent_reqs *reqs); 291 292 #endif /* AGENTEXPR_H */ 293