1 /* Definitions for expressions designed to be executed on the agent
2 Copyright 1998 Free Software Foundation, Inc.
4 This file is part of GDB.
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.
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.
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. */
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.
32 This is used with remote debugging; we don't really support it on
33 native configurations.
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.
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.
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
53 /* Agent expression data structures. */
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. */
66 /* A buffer containing a agent expression. */
70 int len
; /* number of characters used */
71 int size
; /* allocated size */
78 /* The actual values of the various bytecode operations.
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. */
94 aop_div_signed
= 0x05,
95 aop_div_unsigned
= 0x06,
96 aop_rem_signed
= 0x07,
97 aop_rem_unsigned
= 0x08,
99 aop_rsh_signed
= 0x0a,
100 aop_rsh_unsigned
= 0x0b,
102 aop_trace_quick
= 0x0d,
109 aop_less_signed
= 0x14,
110 aop_less_unsigned
= 0x15,
116 aop_ref_float
= 0x1b,
117 aop_ref_double
= 0x1c,
118 aop_ref_long_double
= 0x1d,
139 /* Functions for building expressions. */
141 /* Allocate a new, empty agent expression. */
142 extern struct agent_expr
*new_agent_expr
PARAMS ((CORE_ADDR
));
144 /* Free a agent expression. */
145 extern void free_agent_expr
PARAMS ((struct agent_expr
*));
147 /* Append a simple operator OP to EXPR. */
148 extern void ax_simple
PARAMS ((struct agent_expr
* EXPR
, enum agent_op OP
));
150 /* Append the floating-point prefix, for the next bytecode. */
151 #define ax_float(EXPR) (ax_simple ((EXPR), aop_float))
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
));
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
));
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
));
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
));
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
));
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
));
180 /* Assemble code to push the value of register number REG on the
182 extern void ax_reg
PARAMS ((struct agent_expr
* EXPR
, int REG
));
185 /* Functions for printing out expressions, and otherwise debugging
188 /* Disassemble the expression EXPR, writing to F. */
189 extern void ax_print
PARAMS ((GDB_FILE
* f
, struct agent_expr
* EXPR
));
191 /* An entry in the opcode map. */
195 /* The name of the opcode. Null means that this entry is not a
196 valid opcode --- a hole in the opcode space. */
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.
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. */
210 /* The size of the data operated upon, in bits, for bytecodes that
211 care about that (ref and const). Zero for all others. */
214 /* Number of stack elements consumed, and number produced. */
215 int consumed
, produced
;
218 /* Map of the bytecodes, indexed by bytecode number. */
219 extern struct aop_map aop_map
[];
221 /* Different kinds of flaws an agent expression might have, as
222 detected by agent_reqs. */
225 agent_flaw_none
= 0, /* code is good */
227 /* There is an invalid instruction in the stream. */
228 agent_flaw_bad_instruction
,
230 /* There is an incomplete instruction at the end of the expression. */
231 agent_flaw_incomplete_instruction
,
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. */
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
,
243 /* agent_reqs was unable to prove that every instruction following
244 an unconditional jump was the target of some other jump. */
248 /* Structure describing the requirements of a bytecode expression. */
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
;
256 /* Number of elements left on stack at end; may be negative if expr
257 only consumes elements. */
260 /* Maximum and minimum stack height, relative to initial height. */
261 int max_height
, min_height
;
263 /* Largest `ref' or `const' opcode used, in bits. Zero means the
264 expression has no such instructions. */
267 /* Bit vector of registers used. Register R is used iff
269 reg_mask[R / 8] & (1 << (R % 8))
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.
277 We're assuming eight-bit bytes. So sue me.
279 The caller should free reg_list when done. */
281 unsigned char *reg_mask
;
285 /* Given an agent expression AX, fill in an agent_reqs structure REQS
287 extern void ax_reqs
PARAMS ((struct agent_expr
* ax
,
288 struct agent_reqs
* reqs
));
290 #endif /* AGENTEXPR_H */