gdb/ax.h

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