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292 lines
10 KiB
C
292 lines
10 KiB
C
/* Definitions for expressions designed to be executed on the agent
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Copyright (C) 1998, 1999, 2000, 2007, 2008, 2009
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Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef AGENTEXPR_H
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#define AGENTEXPR_H
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#include "doublest.h" /* For DOUBLEST. */
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/* It's sometimes useful to be able to debug programs that you can't
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really stop for more than a fraction of a second. To this end, the
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user can specify a tracepoint (like a breakpoint, but you don't
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stop at it), and specify a bunch of expressions to record the
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values of when that tracepoint is reached. As the program runs,
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GDB collects the values. At any point (possibly while values are
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still being collected), the user can display the collected values.
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This is used with remote debugging; we don't really support it on
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native configurations.
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This means that expressions are being evaluated by the remote agent,
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which doesn't have any access to the symbol table information, and
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needs to be small and simple.
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The agent_expr routines and datatypes are a bytecode language
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designed to be executed by the agent. Agent expressions work in
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terms of fixed-width values, operators, memory references, and
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register references. You can evaluate a agent expression just given
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a bunch of memory and register values to sniff at; you don't need
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any symbolic information like variable names, types, etc.
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GDB translates source expressions, whose meaning depends on
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symbolic information, into agent bytecode expressions, whose meaning
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is independent of symbolic information. This means the agent can
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evaluate them on the fly without reference to data only available
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to the host GDB. */
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/* Agent expression data structures. */
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/* The type of an element of the agent expression stack.
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The bytecode operation indicates which element we should access;
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the value itself has no typing information. GDB generates all
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bytecode streams, so we don't have to worry about type errors. */
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union agent_val
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{
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LONGEST l;
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DOUBLEST d;
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};
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/* A buffer containing a agent expression. */
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struct agent_expr
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{
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unsigned char *buf;
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int len; /* number of characters used */
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int size; /* allocated size */
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CORE_ADDR scope;
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};
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/* The actual values of the various bytecode operations.
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Other independent implementations of the agent bytecode engine will
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rely on the exact values of these enums, and may not be recompiled
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when we change this table. The numeric values should remain fixed
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whenever possible. Thus, we assign them values explicitly here (to
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allow gaps to form safely), and the disassembly table in
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agentexpr.h behaves like an opcode map. If you want to see them
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grouped logically, see doc/agentexpr.texi. */
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enum agent_op
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{
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aop_float = 0x01,
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aop_add = 0x02,
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aop_sub = 0x03,
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aop_mul = 0x04,
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aop_div_signed = 0x05,
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aop_div_unsigned = 0x06,
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aop_rem_signed = 0x07,
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aop_rem_unsigned = 0x08,
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aop_lsh = 0x09,
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aop_rsh_signed = 0x0a,
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aop_rsh_unsigned = 0x0b,
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aop_trace = 0x0c,
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aop_trace_quick = 0x0d,
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aop_log_not = 0x0e,
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aop_bit_and = 0x0f,
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aop_bit_or = 0x10,
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aop_bit_xor = 0x11,
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aop_bit_not = 0x12,
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aop_equal = 0x13,
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aop_less_signed = 0x14,
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aop_less_unsigned = 0x15,
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aop_ext = 0x16,
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aop_ref8 = 0x17,
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aop_ref16 = 0x18,
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aop_ref32 = 0x19,
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aop_ref64 = 0x1a,
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aop_ref_float = 0x1b,
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aop_ref_double = 0x1c,
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aop_ref_long_double = 0x1d,
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aop_l_to_d = 0x1e,
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aop_d_to_l = 0x1f,
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aop_if_goto = 0x20,
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aop_goto = 0x21,
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aop_const8 = 0x22,
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aop_const16 = 0x23,
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aop_const32 = 0x24,
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aop_const64 = 0x25,
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aop_reg = 0x26,
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aop_end = 0x27,
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aop_dup = 0x28,
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aop_pop = 0x29,
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aop_zero_ext = 0x2a,
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aop_swap = 0x2b,
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aop_trace16 = 0x30,
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aop_last
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};
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/* Functions for building expressions. */
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/* Allocate a new, empty agent expression. */
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extern struct agent_expr *new_agent_expr (CORE_ADDR);
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/* Free a agent expression. */
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extern void free_agent_expr (struct agent_expr *);
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extern struct cleanup *make_cleanup_free_agent_expr (struct agent_expr *);
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/* Append a simple operator OP to EXPR. */
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extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP);
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/* Append the floating-point prefix, for the next bytecode. */
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#define ax_float(EXPR) (ax_simple ((EXPR), aop_float))
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/* Append a sign-extension instruction to EXPR, to extend an N-bit value. */
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extern void ax_ext (struct agent_expr *EXPR, int N);
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/* Append a zero-extension instruction to EXPR, to extend an N-bit value. */
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extern void ax_zero_ext (struct agent_expr *EXPR, int N);
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/* Append a trace_quick instruction to EXPR, to record N bytes. */
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extern void ax_trace_quick (struct agent_expr *EXPR, int N);
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/* Append a goto op to EXPR. OP is the actual op (must be aop_goto or
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aop_if_goto). We assume we don't know the target offset yet,
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because it's probably a forward branch, so we leave space in EXPR
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for the target, and return the offset in EXPR of that space, so we
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can backpatch it once we do know the target offset. Use ax_label
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to do the backpatching. */
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extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP);
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/* Suppose a given call to ax_goto returns some value PATCH. When you
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know the offset TARGET that goto should jump to, call
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ax_label (EXPR, PATCH, TARGET)
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to patch TARGET into the ax_goto instruction. */
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extern void ax_label (struct agent_expr *EXPR, int patch, int target);
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/* Assemble code to push a constant on the stack. */
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extern void ax_const_l (struct agent_expr *EXPR, LONGEST l);
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extern void ax_const_d (struct agent_expr *EXPR, LONGEST d);
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/* Assemble code to push the value of register number REG on the
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stack. */
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extern void ax_reg (struct agent_expr *EXPR, int REG);
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/* Functions for printing out expressions, and otherwise debugging
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things. */
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/* Disassemble the expression EXPR, writing to F. */
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extern void ax_print (struct ui_file *f, struct agent_expr * EXPR);
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/* An entry in the opcode map. */
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struct aop_map
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{
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/* The name of the opcode. Null means that this entry is not a
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valid opcode --- a hole in the opcode space. */
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char *name;
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/* All opcodes take no operands from the bytecode stream, or take
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unsigned integers of various sizes. If this is a positive number
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n, then the opcode is followed by an n-byte operand, which should
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be printed as an unsigned integer. If this is zero, then the
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opcode takes no operands from the bytecode stream.
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If we get more complicated opcodes in the future, don't add other
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magic values of this; that's a crock. Add an `enum encoding'
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field to this, or something like that. */
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int op_size;
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/* The size of the data operated upon, in bits, for bytecodes that
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care about that (ref and const). Zero for all others. */
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int data_size;
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/* Number of stack elements consumed, and number produced. */
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int consumed, produced;
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};
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/* Map of the bytecodes, indexed by bytecode number. */
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extern struct aop_map aop_map[];
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/* Different kinds of flaws an agent expression might have, as
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detected by agent_reqs. */
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enum agent_flaws
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{
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agent_flaw_none = 0, /* code is good */
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/* There is an invalid instruction in the stream. */
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agent_flaw_bad_instruction,
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/* There is an incomplete instruction at the end of the expression. */
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agent_flaw_incomplete_instruction,
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/* agent_reqs was unable to prove that every jump target is to a
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valid offset. Valid offsets are within the bounds of the
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expression, and to a valid instruction boundary. */
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agent_flaw_bad_jump,
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/* agent_reqs was unable to prove to its satisfaction that, for each
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jump target location, the stack will have the same height whether
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that location is reached via a jump or by straight execution. */
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agent_flaw_height_mismatch,
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/* agent_reqs was unable to prove that every instruction following
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an unconditional jump was the target of some other jump. */
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agent_flaw_hole
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};
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/* Structure describing the requirements of a bytecode expression. */
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struct agent_reqs
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{
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/* If the following is not equal to agent_flaw_none, the rest of the
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information in this structure is suspect. */
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enum agent_flaws flaw;
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/* Number of elements left on stack at end; may be negative if expr
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only consumes elements. */
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int final_height;
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/* Maximum and minimum stack height, relative to initial height. */
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int max_height, min_height;
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/* Largest `ref' or `const' opcode used, in bits. Zero means the
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expression has no such instructions. */
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int max_data_size;
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/* Bit vector of registers used. Register R is used iff
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reg_mask[R / 8] & (1 << (R % 8))
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is non-zero. Note! You may not assume that this bitmask is long
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enough to hold bits for all the registers of the machine; the
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agent expression code has no idea how many registers the machine
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has. However, the bitmask is reg_mask_len bytes long, so the
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valid register numbers run from 0 to reg_mask_len * 8 - 1.
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We're assuming eight-bit bytes. So sue me.
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The caller should free reg_list when done. */
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int reg_mask_len;
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unsigned char *reg_mask;
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};
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/* Given an agent expression AX, fill in an agent_reqs structure REQS
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describing it. */
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extern void ax_reqs (struct agent_expr *ax, struct agent_reqs *reqs);
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#endif /* AGENTEXPR_H */
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