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