ax.h revision 1.3
1/* Definitions for expressions designed to be executed on the agent 2 Copyright (C) 1998-2015 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#include "vec.h" 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/* Different kinds of flaws an agent expression might have, as 55 detected by ax_reqs. */ 56enum agent_flaws 57 { 58 agent_flaw_none = 0, /* code is good */ 59 60 /* There is an invalid instruction in the stream. */ 61 agent_flaw_bad_instruction, 62 63 /* There is an incomplete instruction at the end of the expression. */ 64 agent_flaw_incomplete_instruction, 65 66 /* ax_reqs was unable to prove that every jump target is to a 67 valid offset. Valid offsets are within the bounds of the 68 expression, and to a valid instruction boundary. */ 69 agent_flaw_bad_jump, 70 71 /* ax_reqs was unable to prove to its satisfaction that, for each 72 jump target location, the stack will have the same height whether 73 that location is reached via a jump or by straight execution. */ 74 agent_flaw_height_mismatch, 75 76 /* ax_reqs was unable to prove that every instruction following 77 an unconditional jump was the target of some other jump. */ 78 agent_flaw_hole 79 }; 80 81/* Agent expression data structures. */ 82 83/* The type of an element of the agent expression stack. 84 The bytecode operation indicates which element we should access; 85 the value itself has no typing information. GDB generates all 86 bytecode streams, so we don't have to worry about type errors. */ 87 88union agent_val 89 { 90 LONGEST l; 91 DOUBLEST d; 92 }; 93 94/* A buffer containing a agent expression. */ 95struct agent_expr 96 { 97 /* The bytes of the expression. */ 98 unsigned char *buf; 99 100 /* The number of bytecode in the expression. */ 101 int len; 102 103 /* Allocated space available currently. */ 104 int size; 105 106 /* The target architecture assumed to be in effect. */ 107 struct gdbarch *gdbarch; 108 109 /* The address to which the expression applies. */ 110 CORE_ADDR scope; 111 112 /* If the following is not equal to agent_flaw_none, the rest of the 113 information in this structure is suspect. */ 114 enum agent_flaws flaw; 115 116 /* Number of elements left on stack at end; may be negative if expr 117 only consumes elements. */ 118 int final_height; 119 120 /* Maximum and minimum stack height, relative to initial height. */ 121 int max_height, min_height; 122 123 /* Largest `ref' or `const' opcode used, in bits. Zero means the 124 expression has no such instructions. */ 125 int max_data_size; 126 127 /* Bit vector of registers needed. Register R is needed iff 128 129 reg_mask[R / 8] & (1 << (R % 8)) 130 131 is non-zero. Note! You may not assume that this bitmask is long 132 enough to hold bits for all the registers of the machine; the 133 agent expression code has no idea how many registers the machine 134 has. However, the bitmask is reg_mask_len bytes long, so the 135 valid register numbers run from 0 to reg_mask_len * 8 - 1. 136 137 Also note that this mask may contain registers that are needed 138 for the original collection expression to work, but that are 139 not referenced by any bytecode. This could, for example, occur 140 when collecting a local variable allocated to a register; the 141 compiler sets the mask bit and skips generating a bytecode whose 142 result is going to be discarded anyway. 143 */ 144 int reg_mask_len; 145 unsigned char *reg_mask; 146 147 /* For the data tracing facility, we need to insert `trace' bytecodes 148 before each data fetch; this records all the memory that the 149 expression touches in the course of evaluation, so that memory will 150 be available when the user later tries to evaluate the expression 151 in GDB. 152 153 Setting the flag 'tracing' to non-zero enables the code that 154 emits the trace bytecodes at the appropriate points. */ 155 156 unsigned int tracing : 1; 157 158 /* This indicates that pointers to chars should get an added 159 tracenz bytecode to record nonzero bytes, up to a length that 160 is the value of trace_string. */ 161 162 int trace_string; 163 }; 164 165/* Pointer to an agent_expr structure. */ 166typedef struct agent_expr *agent_expr_p; 167 168/* Vector of pointers to agent expressions. */ 169DEF_VEC_P (agent_expr_p); 170 171/* The actual values of the various bytecode operations. */ 172 173enum agent_op 174 { 175#define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \ 176 aop_ ## NAME = VALUE, 177#include "ax.def" 178#undef DEFOP 179 aop_last 180 }; 181 182 183 184/* Functions for building expressions. */ 185 186/* Allocate a new, empty agent expression. */ 187extern struct agent_expr *new_agent_expr (struct gdbarch *, CORE_ADDR); 188 189/* Free a agent expression. */ 190extern void free_agent_expr (struct agent_expr *); 191extern struct cleanup *make_cleanup_free_agent_expr (struct agent_expr *); 192 193/* Append a simple operator OP to EXPR. */ 194extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP); 195 196/* Append a pick operator to EXPR. DEPTH is the stack item to pick, 197 with 0 being top of stack. */ 198extern void ax_pick (struct agent_expr *EXPR, int DEPTH); 199 200/* Append the floating-point prefix, for the next bytecode. */ 201#define ax_float(EXPR) (ax_simple ((EXPR), aop_float)) 202 203/* Append a sign-extension instruction to EXPR, to extend an N-bit value. */ 204extern void ax_ext (struct agent_expr *EXPR, int N); 205 206/* Append a zero-extension instruction to EXPR, to extend an N-bit value. */ 207extern void ax_zero_ext (struct agent_expr *EXPR, int N); 208 209/* Append a trace_quick instruction to EXPR, to record N bytes. */ 210extern void ax_trace_quick (struct agent_expr *EXPR, int N); 211 212/* Append a goto op to EXPR. OP is the actual op (must be aop_goto or 213 aop_if_goto). We assume we don't know the target offset yet, 214 because it's probably a forward branch, so we leave space in EXPR 215 for the target, and return the offset in EXPR of that space, so we 216 can backpatch it once we do know the target offset. Use ax_label 217 to do the backpatching. */ 218extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP); 219 220/* Suppose a given call to ax_goto returns some value PATCH. When you 221 know the offset TARGET that goto should jump to, call 222 ax_label (EXPR, PATCH, TARGET) 223 to patch TARGET into the ax_goto instruction. */ 224extern void ax_label (struct agent_expr *EXPR, int patch, int target); 225 226/* Assemble code to push a constant on the stack. */ 227extern void ax_const_l (struct agent_expr *EXPR, LONGEST l); 228extern void ax_const_d (struct agent_expr *EXPR, LONGEST d); 229 230/* Assemble code to push the value of register number REG on the 231 stack. */ 232extern void ax_reg (struct agent_expr *EXPR, int REG); 233 234/* Add the given register to the register mask of the expression. */ 235extern void ax_reg_mask (struct agent_expr *ax, int reg); 236 237/* Assemble code to operate on a trace state variable. */ 238extern void ax_tsv (struct agent_expr *expr, enum agent_op op, int num); 239 240/* Append a string to the bytecode stream. */ 241extern void ax_string (struct agent_expr *x, const char *str, int slen); 242 243 244/* Functions for printing out expressions, and otherwise debugging 245 things. */ 246 247/* Disassemble the expression EXPR, writing to F. */ 248extern void ax_print (struct ui_file *f, struct agent_expr * EXPR); 249 250/* An entry in the opcode map. */ 251struct aop_map 252 { 253 254 /* The name of the opcode. Null means that this entry is not a 255 valid opcode --- a hole in the opcode space. */ 256 const char *name; 257 258 /* All opcodes take no operands from the bytecode stream, or take 259 unsigned integers of various sizes. If this is a positive number 260 n, then the opcode is followed by an n-byte operand, which should 261 be printed as an unsigned integer. If this is zero, then the 262 opcode takes no operands from the bytecode stream. 263 264 If we get more complicated opcodes in the future, don't add other 265 magic values of this; that's a crock. Add an `enum encoding' 266 field to this, or something like that. */ 267 int op_size; 268 269 /* The size of the data operated upon, in bits, for bytecodes that 270 care about that (ref and const). Zero for all others. */ 271 int data_size; 272 273 /* Number of stack elements consumed, and number produced. */ 274 int consumed, produced; 275 }; 276 277/* Map of the bytecodes, indexed by bytecode number. */ 278extern struct aop_map aop_map[]; 279 280/* Given an agent expression AX, analyze and update its requirements. */ 281 282extern void ax_reqs (struct agent_expr *ax); 283 284#endif /* AGENTEXPR_H */ 285