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 /* $Id$ */
  21
  22 #ifndef AGENTEXPR_H
  23 #define AGENTEXPR_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 \f
  54 /* Agent expression data structures.  */
  55
  56 /* The type of an element of the agent expression stack.
  57    The bytecode operation indicates which element we should access;
  58    the value itself has no typing information.  GDB generates all
  59    bytecode streams, so we don't have to worry about type errors.  */
  60
  61 union agent_val {
  62   LONGEST l;
  63   DOUBLEST d;
  64 };
  65
  66 /* A buffer containing a agent expression.  */
  67 struct agent_expr {
  68   unsigned char *buf;
  69   int len;                      /* number of characters used */
  70   int size;                     /* allocated size */
  71   CORE_ADDR scope;
  72 };
  73
  74
  75
  76
  77 /* The actual values of the various bytecode operations.
  78
  79    Other independent implementations of the agent bytecode engine will
  80    rely on the exact values of these enums, and may not be recompiled
  81    when we change this table.  The numeric values should remain fixed
  82    whenever possible.  Thus, we assign them values explicitly here (to
  83    allow gaps to form safely), and the disassembly table in
  84    agentexpr.h behaves like an opcode map.  If you want to see them
  85    grouped logically, see doc/agentexpr.texi.  */
  86
  87 enum agent_op {
  88   aop_float = 0x01,
  89   aop_add = 0x02,
  90   aop_sub = 0x03,
  91   aop_mul = 0x04,
  92   aop_div_signed = 0x05,
  93   aop_div_unsigned = 0x06,
  94   aop_rem_signed = 0x07,
  95   aop_rem_unsigned = 0x08,
  96   aop_lsh = 0x09,
  97   aop_rsh_signed = 0x0a,
  98   aop_rsh_unsigned = 0x0b,
  99   aop_trace = 0x0c,
 100   aop_trace_quick = 0x0d,
 101   aop_log_not = 0x0e,
 102   aop_bit_and = 0x0f,
 103   aop_bit_or = 0x10,
 104   aop_bit_xor = 0x11,
 105   aop_bit_not = 0x12,
 106   aop_equal = 0x13,
 107   aop_less_signed = 0x14,
 108   aop_less_unsigned = 0x15,
 109   aop_ext = 0x16,
 110   aop_ref8 = 0x17,
 111   aop_ref16 = 0x18,
 112   aop_ref32 = 0x19,
 113   aop_ref64 = 0x1a,
 114   aop_ref_float = 0x1b,
 115   aop_ref_double = 0x1c,
 116   aop_ref_long_double = 0x1d,
 117   aop_l_to_d = 0x1e,
 118   aop_d_to_l = 0x1f,
 119   aop_if_goto = 0x20,
 120   aop_goto = 0x21,
 121   aop_const8 = 0x22,
 122   aop_const16 = 0x23,
 123   aop_const32 = 0x24,
 124   aop_const64 = 0x25,
 125   aop_reg = 0x26,
 126   aop_end = 0x27,
 127   aop_dup = 0x28,
 128   aop_pop = 0x29,
 129   aop_zero_ext = 0x2a,
 130   aop_swap = 0x2b,
 131   aop_trace16 = 0x30,
 132   aop_last
 133 };
 134
 135
 136 \f
 137 /* Functions for building expressions.  */
 138
 139 /* Allocate a new, empty agent expression.  */
 140 extern struct agent_expr *new_agent_expr PARAMS ((CORE_ADDR));
 141
 142 /* Free a agent expression.  */
 143 extern void free_agent_expr PARAMS ((struct agent_expr *));
 144
 145 /* Append a simple operator OP to EXPR.  */
 146 extern void ax_simple PARAMS ((struct agent_expr *EXPR, enum agent_op OP));
 147
 148 /* Append the floating-point prefix, for the next bytecode.  */
 149 #define ax_float(EXPR) (ax_simple ((EXPR), aop_float))
 150
 151 /* Append a sign-extension instruction to EXPR, to extend an N-bit value.  */
 152 extern void ax_ext PARAMS ((struct agent_expr *EXPR, int N));
 153
 154 /* Append a zero-extension instruction to EXPR, to extend an N-bit value.  */
 155 extern void ax_zero_ext PARAMS ((struct agent_expr *EXPR, int N));
 156
 157 /* Append a trace_quick instruction to EXPR, to record N bytes.  */
 158 extern void ax_trace_quick PARAMS ((struct agent_expr *EXPR, int N));
 159
 160 /* Append a goto op to EXPR.  OP is the actual op (must be aop_goto or
 161    aop_if_goto).  We assume we don't know the target offset yet,
 162    because it's probably a forward branch, so we leave space in EXPR
 163    for the target, and return the offset in EXPR of that space, so we
 164    can backpatch it once we do know the target offset.  Use ax_label
 165    to do the backpatching.  */
 166 extern int ax_goto PARAMS ((struct agent_expr *EXPR, enum agent_op OP));
 167
 168 /* Suppose a given call to ax_goto returns some value PATCH.  When you
 169    know the offset TARGET that goto should jump to, call
 170         ax_label (EXPR, PATCH, TARGET)
 171    to patch TARGET into the ax_goto instruction.  */
 172 extern void ax_label PARAMS ((struct agent_expr *EXPR, int patch, int target));
 173
 174 /* Assemble code to push a constant on the stack.  */
 175 extern void ax_const_l PARAMS ((struct agent_expr *EXPR, LONGEST l));
 176 extern void ax_const_d PARAMS ((struct agent_expr *EXPR, LONGEST d));
 177
 178 /* Assemble code to push the value of register number REG on the
 179    stack.  */
 180 extern void ax_reg PARAMS ((struct agent_expr *EXPR, int REG));
 181
 182 \f
 183 /* Functions for printing out expressions, and otherwise debugging
 184    things.  */
 185
 186 /* Disassemble the expression EXPR, writing to F.  */
 187 extern void ax_print PARAMS ((GDB_FILE *f, struct agent_expr *EXPR));
 188
 189 /* An entry in the opcode map.  */
 190 struct aop_map {
 191
 192   /* The name of the opcode.  Null means that this entry is not a
 193      valid opcode --- a hole in the opcode space.  */
 194   char *name;
 195
 196   /* All opcodes take no operands from the bytecode stream, or take
 197      unsigned integers of various sizes.  If this is a positive number
 198      n, then the opcode is followed by an n-byte operand, which should
 199      be printed as an unsigned integer.  If this is zero, then the
 200      opcode takes no operands from the bytecode stream.
 201
 202      If we get more complicated opcodes in the future, don't add other
 203      magic values of this; that's a crock.  Add an `enum encoding'
 204      field to this, or something like that.  */
 205   int op_size;
 206
 207   /* The size of the data operated upon, in bits, for bytecodes that
 208      care about that (ref and const).  Zero for all others.  */
 209   int data_size;
 210
 211   /* Number of stack elements consumed, and number produced.  */
 212   int consumed, produced;
 213 };
 214
 215 /* Map of the bytecodes, indexed by bytecode number.  */
 216 extern struct aop_map aop_map[];
 217
 218 /* Different kinds of flaws an agent expression might have, as
 219    detected by agent_reqs.  */
 220 enum agent_flaws {
 221   agent_flaw_none = 0,          /* code is good */
 222
 223   /* There is an invalid instruction in the stream.  */
 224   agent_flaw_bad_instruction,
 225
 226   /* There is an incomplete instruction at the end of the expression.  */
 227   agent_flaw_incomplete_instruction,
 228
 229   /* agent_reqs was unable to prove that every jump target is to a
 230      valid offset.  Valid offsets are within the bounds of the
 231      expression, and to a valid instruction boundary.  */
 232   agent_flaw_bad_jump,
 233
 234   /* agent_reqs was unable to prove to its satisfaction that, for each
 235      jump target location, the stack will have the same height whether
 236      that location is reached via a jump or by straight execution.  */
 237   agent_flaw_height_mismatch,
 238
 239   /* agent_reqs was unable to prove that every instruction following
 240      an unconditional jump was the target of some other jump.  */
 241   agent_flaw_hole
 242 };
 243
 244 /* Structure describing the requirements of a bytecode expression.  */
 245 struct agent_reqs {
 246
 247   /* If the following is not equal to agent_flaw_none, the rest of the
 248      information in this structure is suspect.  */
 249   enum agent_flaws flaw;
 250
 251   /* Number of elements left on stack at end; may be negative if expr
 252      only consumes elements.  */
 253   int final_height;
 254
 255   /* Maximum and minimum stack height, relative to initial height.  */
 256   int max_height, min_height;
 257
 258   /* Largest `ref' or `const' opcode used, in bits.  Zero means the
 259      expression has no such instructions.  */
 260   int max_data_size;
 261
 262   /* Bit vector of registers used.  Register R is used iff
 263
 264         reg_mask[R / 8] & (1 << (R % 8))
 265
 266      is non-zero.  Note!  You may not assume that this bitmask is long
 267      enough to hold bits for all the registers of the machine; the
 268      agent expression code has no idea how many registers the machine
 269      has.  However, the bitmask is reg_mask_len bytes long, so the
 270      valid register numbers run from 0 to reg_mask_len * 8 - 1.
 271
 272      We're assuming eight-bit bytes.  So sue me.
 273
 274      The caller should free reg_list when done.  */
 275   int reg_mask_len;
 276   unsigned char *reg_mask;
 277 };
 278
 279
 280 /* Given an agent expression AX, fill in an agent_reqs structure REQS
 281    describing it.  */
 282 extern void ax_reqs PARAMS ((struct agent_expr *ax,
 283                              struct agent_reqs *reqs));
 284
 285 #endif /* AGENTEXPR_H */