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+/* Definitions for expressions designed to be executed on the agent
+   Copyright 1998 Free Software Foundation, Inc.
+
+This file is part of GDB.
+
+This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
+
+/* $Id$ */
+
+#ifndef AGENTEXPR_H
+#define AGENTEXPR_H
+
+/* It's sometimes useful to be able to debug programs that you can't
+   really stop for more than a fraction of a second.  To this end, the
+   user can specify a tracepoint (like a breakpoint, but you don't
+   stop at it), and specify a bunch of expressions to record the
+   values of when that tracepoint is reached.  As the program runs,
+   GDB collects the values.  At any point (possibly while values are
+   still being collected), the user can display the collected values.
+
+   This is used with remote debugging; we don't really support it on
+   native configurations.
+
+   This means that expressions are being evaluated by the remote agent,
+   which doesn't have any access to the symbol table information, and
+   needs to be small and simple.
+
+   The agent_expr routines and datatypes are a bytecode language
+   designed to be executed by the agent.  Agent expressions work in
+   terms of fixed-width values, operators, memory references, and
+   register references.  You can evaluate a agent expression just given
+   a bunch of memory and register values to sniff at; you don't need
+   any symbolic information like variable names, types, etc.
+
+   GDB translates source expressions, whose meaning depends on
+   symbolic information, into agent bytecode expressions, whose meaning
+   is independent of symbolic information.  This means the agent can
+   evaluate them on the fly without reference to data only available
+   to the host GDB.  */
+
+
+/* Agent expression data structures.  */
+
+/* The type of an element of the agent expression stack.
+   The bytecode operation indicates which element we should access;
+   the value itself has no typing information.  GDB generates all
+   bytecode streams, so we don't have to worry about type errors.  */
+
+union agent_val {
+  LONGEST l;
+  DOUBLEST d;
+};
+
+/* A buffer containing a agent expression.  */
+struct agent_expr {
+  unsigned char *buf;
+  int len;			/* number of characters used */
+  int size;			/* allocated size */
+  CORE_ADDR scope;
+};
+
+
+
+
+/* The actual values of the various bytecode operations.
+
+   Other independent implementations of the agent bytecode engine will
+   rely on the exact values of these enums, and may not be recompiled
+   when we change this table.  The numeric values should remain fixed
+   whenever possible.  Thus, we assign them values explicitly here (to
+   allow gaps to form safely), and the disassembly table in
+   agentexpr.h behaves like an opcode map.  If you want to see them
+   grouped logically, see doc/agentexpr.texi.  */
+
+enum agent_op {
+  aop_float = 0x01,
+  aop_add = 0x02,
+  aop_sub = 0x03,
+  aop_mul = 0x04,
+  aop_div_signed = 0x05,
+  aop_div_unsigned = 0x06,
+  aop_rem_signed = 0x07,
+  aop_rem_unsigned = 0x08,
+  aop_lsh = 0x09,
+  aop_rsh_signed = 0x0a,
+  aop_rsh_unsigned = 0x0b,
+  aop_trace = 0x0c,
+  aop_trace_quick = 0x0d,
+  aop_log_not = 0x0e,
+  aop_bit_and = 0x0f,
+  aop_bit_or = 0x10,
+  aop_bit_xor = 0x11,
+  aop_bit_not = 0x12,
+  aop_equal = 0x13,
+  aop_less_signed = 0x14,
+  aop_less_unsigned = 0x15,
+  aop_ext = 0x16,
+  aop_ref8 = 0x17,
+  aop_ref16 = 0x18,
+  aop_ref32 = 0x19,
+  aop_ref64 = 0x1a,
+  aop_ref_float = 0x1b,
+  aop_ref_double = 0x1c,
+  aop_ref_long_double = 0x1d,
+  aop_l_to_d = 0x1e,
+  aop_d_to_l = 0x1f,
+  aop_if_goto = 0x20,
+  aop_goto = 0x21,
+  aop_const8 = 0x22,
+  aop_const16 = 0x23,
+  aop_const32 = 0x24,
+  aop_const64 = 0x25,
+  aop_reg = 0x26,
+  aop_end = 0x27,
+  aop_dup = 0x28,
+  aop_pop = 0x29,
+  aop_zero_ext = 0x2a,
+  aop_swap = 0x2b,
+  aop_trace16 = 0x30,
+  aop_last
+};
+
+
+
+/* Functions for building expressions.  */
+
+/* Allocate a new, empty agent expression.  */
+extern struct agent_expr *new_agent_expr PARAMS ((CORE_ADDR));
+
+/* Free a agent expression.  */
+extern void free_agent_expr PARAMS ((struct agent_expr *));
+
+/* Append a simple operator OP to EXPR.  */
+extern void ax_simple PARAMS ((struct agent_expr *EXPR, enum agent_op OP));
+
+/* Append the floating-point prefix, for the next bytecode.  */
+#define ax_float(EXPR) (ax_simple ((EXPR), aop_float))
+
+/* Append a sign-extension instruction to EXPR, to extend an N-bit value.  */
+extern void ax_ext PARAMS ((struct agent_expr *EXPR, int N));
+
+/* Append a zero-extension instruction to EXPR, to extend an N-bit value.  */
+extern void ax_zero_ext PARAMS ((struct agent_expr *EXPR, int N));
+
+/* Append a trace_quick instruction to EXPR, to record N bytes.  */
+extern void ax_trace_quick PARAMS ((struct agent_expr *EXPR, int N));
+
+/* Append a goto op to EXPR.  OP is the actual op (must be aop_goto or
+   aop_if_goto).  We assume we don't know the target offset yet,
+   because it's probably a forward branch, so we leave space in EXPR
+   for the target, and return the offset in EXPR of that space, so we
+   can backpatch it once we do know the target offset.  Use ax_label
+   to do the backpatching.  */
+extern int ax_goto PARAMS ((struct agent_expr *EXPR, enum agent_op OP));
+
+/* Suppose a given call to ax_goto returns some value PATCH.  When you
+   know the offset TARGET that goto should jump to, call
+	ax_label (EXPR, PATCH, TARGET)
+   to patch TARGET into the ax_goto instruction.  */
+extern void ax_label PARAMS ((struct agent_expr *EXPR, int patch, int target));
+
+/* Assemble code to push a constant on the stack.  */
+extern void ax_const_l PARAMS ((struct agent_expr *EXPR, LONGEST l));
+extern void ax_const_d PARAMS ((struct agent_expr *EXPR, LONGEST d));
+
+/* Assemble code to push the value of register number REG on the
+   stack.  */
+extern void ax_reg PARAMS ((struct agent_expr *EXPR, int REG));
+
+
+/* Functions for printing out expressions, and otherwise debugging
+   things.  */
+
+/* Disassemble the expression EXPR, writing to F.  */
+extern void ax_print PARAMS ((GDB_FILE *f, struct agent_expr *EXPR));
+
+/* An entry in the opcode map.  */
+struct aop_map {
+
+  /* The name of the opcode.  Null means that this entry is not a
+     valid opcode --- a hole in the opcode space.  */
+  char *name;
+
+  /* All opcodes take no operands from the bytecode stream, or take
+     unsigned integers of various sizes.  If this is a positive number
+     n, then the opcode is followed by an n-byte operand, which should
+     be printed as an unsigned integer.  If this is zero, then the
+     opcode takes no operands from the bytecode stream.
+
+     If we get more complicated opcodes in the future, don't add other
+     magic values of this; that's a crock.  Add an `enum encoding'
+     field to this, or something like that.  */
+  int op_size;
+
+  /* The size of the data operated upon, in bits, for bytecodes that
+     care about that (ref and const).  Zero for all others.  */
+  int data_size;
+
+  /* Number of stack elements consumed, and number produced.  */
+  int consumed, produced;
+};
+
+/* Map of the bytecodes, indexed by bytecode number.  */
+extern struct aop_map aop_map[];
+
+/* Different kinds of flaws an agent expression might have, as
+   detected by agent_reqs.  */
+enum agent_flaws {
+  agent_flaw_none = 0,		/* code is good */
+
+  /* There is an invalid instruction in the stream.  */
+  agent_flaw_bad_instruction,
+
+  /* There is an incomplete instruction at the end of the expression.  */
+  agent_flaw_incomplete_instruction,
+
+  /* agent_reqs was unable to prove that every jump target is to a
+     valid offset.  Valid offsets are within the bounds of the
+     expression, and to a valid instruction boundary.  */
+  agent_flaw_bad_jump,
+
+  /* agent_reqs was unable to prove to its satisfaction that, for each
+     jump target location, the stack will have the same height whether
+     that location is reached via a jump or by straight execution.  */
+  agent_flaw_height_mismatch,
+
+  /* agent_reqs was unable to prove that every instruction following
+     an unconditional jump was the target of some other jump.  */
+  agent_flaw_hole
+};
+
+/* Structure describing the requirements of a bytecode expression.  */
+struct agent_reqs {
+
+  /* If the following is not equal to agent_flaw_none, the rest of the
+     information in this structure is suspect.  */
+  enum agent_flaws flaw;
+
+  /* Number of elements left on stack at end; may be negative if expr
+     only consumes elements.  */
+  int final_height;
+
+  /* Maximum and minimum stack height, relative to initial height.  */
+  int max_height, min_height;
+
+  /* Largest `ref' or `const' opcode used, in bits.  Zero means the
+     expression has no such instructions.  */
+  int max_data_size;
+
+  /* Bit vector of registers used.  Register R is used iff
+  
+	reg_mask[R / 8] & (1 << (R % 8))
+
+     is non-zero.  Note!  You may not assume that this bitmask is long
+     enough to hold bits for all the registers of the machine; the
+     agent expression code has no idea how many registers the machine
+     has.  However, the bitmask is reg_mask_len bytes long, so the
+     valid register numbers run from 0 to reg_mask_len * 8 - 1.  
+
+     We're assuming eight-bit bytes.  So sue me.
+
+     The caller should free reg_list when done.  */
+  int reg_mask_len;
+  unsigned char *reg_mask;
+};
+
+
+/* Given an agent expression AX, fill in an agent_reqs structure REQS
+   describing it.  */
+extern void ax_reqs PARAMS ((struct agent_expr *ax,
+			     struct agent_reqs *reqs));
+
+#endif /* AGENTEXPR_H */