1 /* Definitions for expressions designed to be executed on the agent 2 Copyright (C) 1998-2000, 2007-2012 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 3 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, see <http://www.gnu.org/licenses/>. */ 18 19 #ifndef AGENTEXPR_H 20 #define AGENTEXPR_H 21 22 #include "doublest.h" /* For DOUBLEST. */ 23 24 /* It's sometimes useful to be able to debug programs that you can't 25 really stop for more than a fraction of a second. To this end, the 26 user can specify a tracepoint (like a breakpoint, but you don't 27 stop at it), and specify a bunch of expressions to record the 28 values of when that tracepoint is reached. As the program runs, 29 GDB collects the values. At any point (possibly while values are 30 still being collected), the user can display the collected values. 31 32 This is used with remote debugging; we don't really support it on 33 native configurations. 34 35 This means that expressions are being evaluated by the remote agent, 36 which doesn't have any access to the symbol table information, and 37 needs to be small and simple. 38 39 The agent_expr routines and datatypes are a bytecode language 40 designed to be executed by the agent. Agent expressions work in 41 terms of fixed-width values, operators, memory references, and 42 register references. You can evaluate a agent expression just given 43 a bunch of memory and register values to sniff at; you don't need 44 any symbolic information like variable names, types, etc. 45 46 GDB translates source expressions, whose meaning depends on 47 symbolic information, into agent bytecode expressions, whose meaning 48 is independent of symbolic information. This means the agent can 49 evaluate them on the fly without reference to data only available 50 to the host GDB. */ 51 52 53 /* Different kinds of flaws an agent expression might have, as 54 detected by ax_reqs. */ 55 enum agent_flaws 56 { 57 agent_flaw_none = 0, /* code is good */ 58 59 /* There is an invalid instruction in the stream. */ 60 agent_flaw_bad_instruction, 61 62 /* There is an incomplete instruction at the end of the expression. */ 63 agent_flaw_incomplete_instruction, 64 65 /* ax_reqs was unable to prove that every jump target is to a 66 valid offset. Valid offsets are within the bounds of the 67 expression, and to a valid instruction boundary. */ 68 agent_flaw_bad_jump, 69 70 /* ax_reqs was unable to prove to its satisfaction that, for each 71 jump target location, the stack will have the same height whether 72 that location is reached via a jump or by straight execution. */ 73 agent_flaw_height_mismatch, 74 75 /* ax_reqs was unable to prove that every instruction following 76 an unconditional jump was the target of some other jump. */ 77 agent_flaw_hole 78 }; 79 80 /* Agent expression data structures. */ 81 82 /* The type of an element of the agent expression stack. 83 The bytecode operation indicates which element we should access; 84 the value itself has no typing information. GDB generates all 85 bytecode streams, so we don't have to worry about type errors. */ 86 87 union agent_val 88 { 89 LONGEST l; 90 DOUBLEST d; 91 }; 92 93 /* A buffer containing a agent expression. */ 94 struct agent_expr 95 { 96 /* The bytes of the expression. */ 97 unsigned char *buf; 98 99 /* The number of bytecode in the expression. */ 100 int len; 101 102 /* Allocated space available currently. */ 103 int size; 104 105 /* The target architecture assumed to be in effect. */ 106 struct gdbarch *gdbarch; 107 108 /* The address to which the expression applies. */ 109 CORE_ADDR scope; 110 111 /* If the following is not equal to agent_flaw_none, the rest of the 112 information in this structure is suspect. */ 113 enum agent_flaws flaw; 114 115 /* Number of elements left on stack at end; may be negative if expr 116 only consumes elements. */ 117 int final_height; 118 119 /* Maximum and minimum stack height, relative to initial height. */ 120 int max_height, min_height; 121 122 /* Largest `ref' or `const' opcode used, in bits. Zero means the 123 expression has no such instructions. */ 124 int max_data_size; 125 126 /* Bit vector of registers needed. Register R is needed iff 127 128 reg_mask[R / 8] & (1 << (R % 8)) 129 130 is non-zero. Note! You may not assume that this bitmask is long 131 enough to hold bits for all the registers of the machine; the 132 agent expression code has no idea how many registers the machine 133 has. However, the bitmask is reg_mask_len bytes long, so the 134 valid register numbers run from 0 to reg_mask_len * 8 - 1. 135 136 Also note that this mask may contain registers that are needed 137 for the original collection expression to work, but that are 138 not referenced by any bytecode. This could, for example, occur 139 when collecting a local variable allocated to a register; the 140 compiler sets the mask bit and skips generating a bytecode whose 141 result is going to be discarded anyway. 142 */ 143 int reg_mask_len; 144 unsigned char *reg_mask; 145 }; 146 147 /* The actual values of the various bytecode operations. */ 148 149 enum agent_op 150 { 151 #define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \ 152 aop_ ## NAME = VALUE, 153 #include "ax.def" 154 #undef DEFOP 155 aop_last 156 }; 157 158 159 160 /* Functions for building expressions. */ 161 162 /* Allocate a new, empty agent expression. */ 163 extern struct agent_expr *new_agent_expr (struct gdbarch *, CORE_ADDR); 164 165 /* Free a agent expression. */ 166 extern void free_agent_expr (struct agent_expr *); 167 extern struct cleanup *make_cleanup_free_agent_expr (struct agent_expr *); 168 169 /* Append a simple operator OP to EXPR. */ 170 extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP); 171 172 /* Append a pick operator to EXPR. DEPTH is the stack item to pick, 173 with 0 being top of stack. */ 174 extern void ax_pick (struct agent_expr *EXPR, int DEPTH); 175 176 /* Append the floating-point prefix, for the next bytecode. */ 177 #define ax_float(EXPR) (ax_simple ((EXPR), aop_float)) 178 179 /* Append a sign-extension instruction to EXPR, to extend an N-bit value. */ 180 extern void ax_ext (struct agent_expr *EXPR, int N); 181 182 /* Append a zero-extension instruction to EXPR, to extend an N-bit value. */ 183 extern void ax_zero_ext (struct agent_expr *EXPR, int N); 184 185 /* Append a trace_quick instruction to EXPR, to record N bytes. */ 186 extern void ax_trace_quick (struct agent_expr *EXPR, int N); 187 188 /* Append a goto op to EXPR. OP is the actual op (must be aop_goto or 189 aop_if_goto). We assume we don't know the target offset yet, 190 because it's probably a forward branch, so we leave space in EXPR 191 for the target, and return the offset in EXPR of that space, so we 192 can backpatch it once we do know the target offset. Use ax_label 193 to do the backpatching. */ 194 extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP); 195 196 /* Suppose a given call to ax_goto returns some value PATCH. When you 197 know the offset TARGET that goto should jump to, call 198 ax_label (EXPR, PATCH, TARGET) 199 to patch TARGET into the ax_goto instruction. */ 200 extern void ax_label (struct agent_expr *EXPR, int patch, int target); 201 202 /* Assemble code to push a constant on the stack. */ 203 extern void ax_const_l (struct agent_expr *EXPR, LONGEST l); 204 extern void ax_const_d (struct agent_expr *EXPR, LONGEST d); 205 206 /* Assemble code to push the value of register number REG on the 207 stack. */ 208 extern void ax_reg (struct agent_expr *EXPR, int REG); 209 210 /* Add the given register to the register mask of the expression. */ 211 extern void ax_reg_mask (struct agent_expr *ax, int reg); 212 213 /* Assemble code to operate on a trace state variable. */ 214 extern void ax_tsv (struct agent_expr *expr, enum agent_op op, int num); 215 216 217 /* Functions for printing out expressions, and otherwise debugging 218 things. */ 219 220 /* Disassemble the expression EXPR, writing to F. */ 221 extern void ax_print (struct ui_file *f, struct agent_expr * EXPR); 222 223 /* An entry in the opcode map. */ 224 struct aop_map 225 { 226 227 /* The name of the opcode. Null means that this entry is not a 228 valid opcode --- a hole in the opcode space. */ 229 const char *name; 230 231 /* All opcodes take no operands from the bytecode stream, or take 232 unsigned integers of various sizes. If this is a positive number 233 n, then the opcode is followed by an n-byte operand, which should 234 be printed as an unsigned integer. If this is zero, then the 235 opcode takes no operands from the bytecode stream. 236 237 If we get more complicated opcodes in the future, don't add other 238 magic values of this; that's a crock. Add an `enum encoding' 239 field to this, or something like that. */ 240 int op_size; 241 242 /* The size of the data operated upon, in bits, for bytecodes that 243 care about that (ref and const). Zero for all others. */ 244 int data_size; 245 246 /* Number of stack elements consumed, and number produced. */ 247 int consumed, produced; 248 }; 249 250 /* Map of the bytecodes, indexed by bytecode number. */ 251 extern struct aop_map aop_map[]; 252 253 /* Given an agent expression AX, analyze and update its requirements. */ 254 255 extern void ax_reqs (struct agent_expr *ax); 256 257 #endif /* AGENTEXPR_H */ 258