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/* Definitions for expressions designed to be executed on the agent

   Copyright (C) 1998, 1999, 2000, 2007, 2008, 2009, 2010

   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 3 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, see <http://www.gnu.org/licenses/>.  */

#ifndef AGENTEXPR_H

#define AGENTEXPR_H

#include "doublest.h"           /* For DOUBLEST.  */

/* 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.  */

/* Different kinds of flaws an agent expression might have, as

   detected by ax_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,

    /* ax_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,

    /* ax_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,

    /* ax_reqs was unable to prove that every instruction following

       an unconditional jump was the target of some other jump.  */

    agent_flaw_hole

  };

/* 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

  {

    /* The bytes of the expression.  */

    unsigned char *buf;

    /* The number of bytecode in the expression.  */

    int len;

    /* Allocated space available currently.  */

    int size;

    /* The target architecture assumed to be in effect.  */

    struct gdbarch *gdbarch;

    /* The address to which the expression applies.  */

    CORE_ADDR scope;

    /* 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 needed.  Register R is needed 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.

       Also note that this mask may contain registers that are needed

       for the original collection expression to work, but that are

       not referenced by any bytecode.  This could, for example, occur

       when collecting a local variable allocated to a register; the

       compiler sets the mask bit and skips generating a bytecode whose

       result is going to be discarded anyway.

    */

    int reg_mask_len;

    unsigned char *reg_mask;

  };

/* 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_getv = 0x2c,

    aop_setv = 0x2d,

    aop_tracev = 0x2e,

    aop_trace16 = 0x30,

    aop_last

  };

/* Functions for building expressions.  */

/* Allocate a new, empty agent expression.  */

extern struct agent_expr *new_agent_expr (struct gdbarch *, CORE_ADDR);

/* Free a agent expression.  */

extern void free_agent_expr (struct agent_expr *);

extern struct cleanup *make_cleanup_free_agent_expr (struct agent_expr *);

/* Append a simple operator OP to EXPR.  */

extern void ax_simple (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 (struct agent_expr *EXPR, int N);

/* Append a zero-extension instruction to EXPR, to extend an N-bit value.  */

extern void ax_zero_ext (struct agent_expr *EXPR, int N);

/* Append a trace_quick instruction to EXPR, to record N bytes.  */

extern void ax_trace_quick (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 (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 (struct agent_expr *EXPR, int patch, int target);

/* Assemble code to push a constant on the stack.  */

extern void ax_const_l (struct agent_expr *EXPR, LONGEST l);

extern void ax_const_d (struct agent_expr *EXPR, LONGEST d);

/* Assemble code to push the value of register number REG on the

   stack.  */

extern void ax_reg (struct agent_expr *EXPR, int REG);

/* Add the given register to the register mask of the expression.  */

extern void ax_reg_mask (struct agent_expr *ax, int reg);

/* Assemble code to operate on a trace state variable.  */

extern void ax_tsv (struct agent_expr *expr, enum agent_op op, int num);

/* Functions for printing out expressions, and otherwise debugging

   things.  */

/* Disassemble the expression EXPR, writing to F.  */

extern void ax_print (struct ui_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[];

/* Given an agent expression AX, analyze and update its requirements.  */

extern void ax_reqs (struct agent_expr *ax);

#endif /* AGENTEXPR_H */