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/* Definitions for expressions designed to be executed on the agent
Copyright 1998, 1999, 2000 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. */
#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. */
/* 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 (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);
/* 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[];
/* 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 (struct agent_expr *ax, struct agent_reqs *reqs);
#endif /* AGENTEXPR_H */