gdb/ax.h

   1 /* Definitions for expressions designed to be executed on the agent
   2    Copyright (C) 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., 51 Franklin Street, Fifth Floor,
  19    Boston, MA 02110-1301, 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 \f
  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 \f
 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 \f
 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 */