1/* Definitions for expressions designed to be executed on the agent
2   Copyright 1998, 1999, 2000 Free Software Foundation, Inc.
3
4   This file is part of GDB.
5
6   This program is free software; you can redistribute it and/or modify
7   it under the terms of the GNU General Public License as published by
8   the Free Software Foundation; either version 2 of the License, or
9   (at your option) any later version.
10
11   This program is distributed in the hope that it will be useful,
12   but WITHOUT ANY WARRANTY; without even the implied warranty of
13   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14   GNU General Public License for more details.
15
16   You should have received a copy of the GNU General Public License
17   along with this program; if not, write to the Free Software
18   Foundation, Inc., 59 Temple Place - Suite 330,
19   Boston, MA 02111-1307, USA.  */
20
21#ifndef AGENTEXPR_H
22#define AGENTEXPR_H
23
24#include "doublest.h"		/* For DOUBLEST.  */
25
26/* It's sometimes useful to be able to debug programs that you can't
27   really stop for more than a fraction of a second.  To this end, the
28   user can specify a tracepoint (like a breakpoint, but you don't
29   stop at it), and specify a bunch of expressions to record the
30   values of when that tracepoint is reached.  As the program runs,
31   GDB collects the values.  At any point (possibly while values are
32   still being collected), the user can display the collected values.
33
34   This is used with remote debugging; we don't really support it on
35   native configurations.
36
37   This means that expressions are being evaluated by the remote agent,
38   which doesn't have any access to the symbol table information, and
39   needs to be small and simple.
40
41   The agent_expr routines and datatypes are a bytecode language
42   designed to be executed by the agent.  Agent expressions work in
43   terms of fixed-width values, operators, memory references, and
44   register references.  You can evaluate a agent expression just given
45   a bunch of memory and register values to sniff at; you don't need
46   any symbolic information like variable names, types, etc.
47
48   GDB translates source expressions, whose meaning depends on
49   symbolic information, into agent bytecode expressions, whose meaning
50   is independent of symbolic information.  This means the agent can
51   evaluate them on the fly without reference to data only available
52   to the host GDB.  */
53
54
55/* Agent expression data structures.  */
56
57/* The type of an element of the agent expression stack.
58   The bytecode operation indicates which element we should access;
59   the value itself has no typing information.  GDB generates all
60   bytecode streams, so we don't have to worry about type errors.  */
61
62union agent_val
63  {
64    LONGEST l;
65    DOUBLEST d;
66  };
67
68/* A buffer containing a agent expression.  */
69struct agent_expr
70  {
71    unsigned char *buf;
72    int len;			/* number of characters used */
73    int size;			/* allocated size */
74    CORE_ADDR scope;
75  };
76
77
78
79
80/* The actual values of the various bytecode operations.
81
82   Other independent implementations of the agent bytecode engine will
83   rely on the exact values of these enums, and may not be recompiled
84   when we change this table.  The numeric values should remain fixed
85   whenever possible.  Thus, we assign them values explicitly here (to
86   allow gaps to form safely), and the disassembly table in
87   agentexpr.h behaves like an opcode map.  If you want to see them
88   grouped logically, see doc/agentexpr.texi.  */
89
90enum agent_op
91  {
92    aop_float = 0x01,
93    aop_add = 0x02,
94    aop_sub = 0x03,
95    aop_mul = 0x04,
96    aop_div_signed = 0x05,
97    aop_div_unsigned = 0x06,
98    aop_rem_signed = 0x07,
99    aop_rem_unsigned = 0x08,
100    aop_lsh = 0x09,
101    aop_rsh_signed = 0x0a,
102    aop_rsh_unsigned = 0x0b,
103    aop_trace = 0x0c,
104    aop_trace_quick = 0x0d,
105    aop_log_not = 0x0e,
106    aop_bit_and = 0x0f,
107    aop_bit_or = 0x10,
108    aop_bit_xor = 0x11,
109    aop_bit_not = 0x12,
110    aop_equal = 0x13,
111    aop_less_signed = 0x14,
112    aop_less_unsigned = 0x15,
113    aop_ext = 0x16,
114    aop_ref8 = 0x17,
115    aop_ref16 = 0x18,
116    aop_ref32 = 0x19,
117    aop_ref64 = 0x1a,
118    aop_ref_float = 0x1b,
119    aop_ref_double = 0x1c,
120    aop_ref_long_double = 0x1d,
121    aop_l_to_d = 0x1e,
122    aop_d_to_l = 0x1f,
123    aop_if_goto = 0x20,
124    aop_goto = 0x21,
125    aop_const8 = 0x22,
126    aop_const16 = 0x23,
127    aop_const32 = 0x24,
128    aop_const64 = 0x25,
129    aop_reg = 0x26,
130    aop_end = 0x27,
131    aop_dup = 0x28,
132    aop_pop = 0x29,
133    aop_zero_ext = 0x2a,
134    aop_swap = 0x2b,
135    aop_trace16 = 0x30,
136    aop_last
137  };
138
139
140
141/* Functions for building expressions.  */
142
143/* Allocate a new, empty agent expression.  */
144extern struct agent_expr *new_agent_expr (CORE_ADDR);
145
146/* Free a agent expression.  */
147extern void free_agent_expr (struct agent_expr *);
148extern struct cleanup *make_cleanup_free_agent_expr (struct agent_expr *);
149
150/* Append a simple operator OP to EXPR.  */
151extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP);
152
153/* Append the floating-point prefix, for the next bytecode.  */
154#define ax_float(EXPR) (ax_simple ((EXPR), aop_float))
155
156/* Append a sign-extension instruction to EXPR, to extend an N-bit value.  */
157extern void ax_ext (struct agent_expr *EXPR, int N);
158
159/* Append a zero-extension instruction to EXPR, to extend an N-bit value.  */
160extern void ax_zero_ext (struct agent_expr *EXPR, int N);
161
162/* Append a trace_quick instruction to EXPR, to record N bytes.  */
163extern void ax_trace_quick (struct agent_expr *EXPR, int N);
164
165/* Append a goto op to EXPR.  OP is the actual op (must be aop_goto or
166   aop_if_goto).  We assume we don't know the target offset yet,
167   because it's probably a forward branch, so we leave space in EXPR
168   for the target, and return the offset in EXPR of that space, so we
169   can backpatch it once we do know the target offset.  Use ax_label
170   to do the backpatching.  */
171extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP);
172
173/* Suppose a given call to ax_goto returns some value PATCH.  When you
174   know the offset TARGET that goto should jump to, call
175   ax_label (EXPR, PATCH, TARGET)
176   to patch TARGET into the ax_goto instruction.  */
177extern void ax_label (struct agent_expr *EXPR, int patch, int target);
178
179/* Assemble code to push a constant on the stack.  */
180extern void ax_const_l (struct agent_expr *EXPR, LONGEST l);
181extern void ax_const_d (struct agent_expr *EXPR, LONGEST d);
182
183/* Assemble code to push the value of register number REG on the
184   stack.  */
185extern void ax_reg (struct agent_expr *EXPR, int REG);
186
187
188/* Functions for printing out expressions, and otherwise debugging
189   things.  */
190
191/* Disassemble the expression EXPR, writing to F.  */
192extern void ax_print (struct ui_file *f, struct agent_expr * EXPR);
193
194/* An entry in the opcode map.  */
195struct aop_map
196  {
197
198    /* The name of the opcode.  Null means that this entry is not a
199       valid opcode --- a hole in the opcode space.  */
200    char *name;
201
202    /* All opcodes take no operands from the bytecode stream, or take
203       unsigned integers of various sizes.  If this is a positive number
204       n, then the opcode is followed by an n-byte operand, which should
205       be printed as an unsigned integer.  If this is zero, then the
206       opcode takes no operands from the bytecode stream.
207
208       If we get more complicated opcodes in the future, don't add other
209       magic values of this; that's a crock.  Add an `enum encoding'
210       field to this, or something like that.  */
211    int op_size;
212
213    /* The size of the data operated upon, in bits, for bytecodes that
214       care about that (ref and const).  Zero for all others.  */
215    int data_size;
216
217    /* Number of stack elements consumed, and number produced.  */
218    int consumed, produced;
219  };
220
221/* Map of the bytecodes, indexed by bytecode number.  */
222extern struct aop_map aop_map[];
223
224/* Different kinds of flaws an agent expression might have, as
225   detected by agent_reqs.  */
226enum agent_flaws
227  {
228    agent_flaw_none = 0,	/* code is good */
229
230    /* There is an invalid instruction in the stream.  */
231    agent_flaw_bad_instruction,
232
233    /* There is an incomplete instruction at the end of the expression.  */
234    agent_flaw_incomplete_instruction,
235
236    /* agent_reqs was unable to prove that every jump target is to a
237       valid offset.  Valid offsets are within the bounds of the
238       expression, and to a valid instruction boundary.  */
239    agent_flaw_bad_jump,
240
241    /* agent_reqs was unable to prove to its satisfaction that, for each
242       jump target location, the stack will have the same height whether
243       that location is reached via a jump or by straight execution.  */
244    agent_flaw_height_mismatch,
245
246    /* agent_reqs was unable to prove that every instruction following
247       an unconditional jump was the target of some other jump.  */
248    agent_flaw_hole
249  };
250
251/* Structure describing the requirements of a bytecode expression.  */
252struct agent_reqs
253  {
254
255    /* If the following is not equal to agent_flaw_none, the rest of the
256       information in this structure is suspect.  */
257    enum agent_flaws flaw;
258
259    /* Number of elements left on stack at end; may be negative if expr
260       only consumes elements.  */
261    int final_height;
262
263    /* Maximum and minimum stack height, relative to initial height.  */
264    int max_height, min_height;
265
266    /* Largest `ref' or `const' opcode used, in bits.  Zero means the
267       expression has no such instructions.  */
268    int max_data_size;
269
270    /* Bit vector of registers used.  Register R is used iff
271
272       reg_mask[R / 8] & (1 << (R % 8))
273
274       is non-zero.  Note!  You may not assume that this bitmask is long
275       enough to hold bits for all the registers of the machine; the
276       agent expression code has no idea how many registers the machine
277       has.  However, the bitmask is reg_mask_len bytes long, so the
278       valid register numbers run from 0 to reg_mask_len * 8 - 1.
279
280       We're assuming eight-bit bytes.  So sue me.
281
282       The caller should free reg_list when done.  */
283    int reg_mask_len;
284    unsigned char *reg_mask;
285  };
286
287
288/* Given an agent expression AX, fill in an agent_reqs structure REQS
289   describing it.  */
290extern void ax_reqs (struct agent_expr *ax, struct agent_reqs *reqs);
291
292#endif /* AGENTEXPR_H */
293