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authorStan Shebs <shebs@codesourcery.com>1999-04-16 01:35:26 +0000
committerStan Shebs <shebs@codesourcery.com>1999-04-16 01:35:26 +0000
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treea0015aa5cedc19ccbab307251353a41722a3ae13 /gdb/ax.h
parentcd946cff9ede3f30935803403f06f6ed30cad136 (diff)
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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 */