1 /* Definitions for expressions designed to be executed on the agent
2 Copyright (C) 1998-2016 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 3 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, see <http://www.gnu.org/licenses/>. */
22 #include "doublest.h" /* For DOUBLEST. */
25 /* It's sometimes useful to be able to debug programs that you can't
26 really stop for more than a fraction of a second. To this end, the
27 user can specify a tracepoint (like a breakpoint, but you don't
28 stop at it), and specify a bunch of expressions to record the
29 values of when that tracepoint is reached. As the program runs,
30 GDB collects the values. At any point (possibly while values are
31 still being collected), the user can display the collected values.
33 This is used with remote debugging; we don't really support it on
34 native configurations.
36 This means that expressions are being evaluated by the remote agent,
37 which doesn't have any access to the symbol table information, and
38 needs to be small and simple.
40 The agent_expr routines and datatypes are a bytecode language
41 designed to be executed by the agent. Agent expressions work in
42 terms of fixed-width values, operators, memory references, and
43 register references. You can evaluate a agent expression just given
44 a bunch of memory and register values to sniff at; you don't need
45 any symbolic information like variable names, types, etc.
47 GDB translates source expressions, whose meaning depends on
48 symbolic information, into agent bytecode expressions, whose meaning
49 is independent of symbolic information. This means the agent can
50 evaluate them on the fly without reference to data only available
54 /* Different kinds of flaws an agent expression might have, as
55 detected by ax_reqs. */
58 agent_flaw_none = 0, /* code is good */
60 /* There is an invalid instruction in the stream. */
61 agent_flaw_bad_instruction,
63 /* There is an incomplete instruction at the end of the expression. */
64 agent_flaw_incomplete_instruction,
66 /* ax_reqs was unable to prove that every jump target is to a
67 valid offset. Valid offsets are within the bounds of the
68 expression, and to a valid instruction boundary. */
71 /* ax_reqs was unable to prove to its satisfaction that, for each
72 jump target location, the stack will have the same height whether
73 that location is reached via a jump or by straight execution. */
74 agent_flaw_height_mismatch,
76 /* ax_reqs was unable to prove that every instruction following
77 an unconditional jump was the target of some other jump. */
81 /* Agent expression data structures. */
83 /* The type of an element of the agent expression stack.
84 The bytecode operation indicates which element we should access;
85 the value itself has no typing information. GDB generates all
86 bytecode streams, so we don't have to worry about type errors. */
94 /* A buffer containing a agent expression. */
97 /* Construct an empty agent expression. */
98 explicit agent_expr (struct gdbarch *gdbarch, CORE_ADDR scope);
102 /* The bytes of the expression. */
105 /* The number of bytecode in the expression. */
108 /* Allocated space available currently. */
111 /* The target architecture assumed to be in effect. */
112 struct gdbarch *gdbarch;
114 /* The address to which the expression applies. */
117 /* If the following is not equal to agent_flaw_none, the rest of the
118 information in this structure is suspect. */
119 enum agent_flaws flaw;
121 /* Number of elements left on stack at end; may be negative if expr
122 only consumes elements. */
125 /* Maximum and minimum stack height, relative to initial height. */
126 int max_height, min_height;
128 /* Largest `ref' or `const' opcode used, in bits. Zero means the
129 expression has no such instructions. */
132 /* Bit vector of registers needed. Register R is needed iff
134 reg_mask[R / 8] & (1 << (R % 8))
136 is non-zero. Note! You may not assume that this bitmask is long
137 enough to hold bits for all the registers of the machine; the
138 agent expression code has no idea how many registers the machine
139 has. However, the bitmask is reg_mask_len bytes long, so the
140 valid register numbers run from 0 to reg_mask_len * 8 - 1.
142 Also note that this mask may contain registers that are needed
143 for the original collection expression to work, but that are
144 not referenced by any bytecode. This could, for example, occur
145 when collecting a local variable allocated to a register; the
146 compiler sets the mask bit and skips generating a bytecode whose
147 result is going to be discarded anyway.
150 unsigned char *reg_mask;
152 /* For the data tracing facility, we need to insert `trace' bytecodes
153 before each data fetch; this records all the memory that the
154 expression touches in the course of evaluation, so that memory will
155 be available when the user later tries to evaluate the expression
158 Setting the flag 'tracing' to non-zero enables the code that
159 emits the trace bytecodes at the appropriate points. */
161 unsigned int tracing : 1;
163 /* This indicates that pointers to chars should get an added
164 tracenz bytecode to record nonzero bytes, up to a length that
165 is the value of trace_string. */
170 /* An agent_expr owning pointer. */
171 typedef gdb::unique_ptr<agent_expr> agent_expr_up;
173 /* The actual values of the various bytecode operations. */
177 #define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \
178 aop_ ## NAME = VALUE,
186 /* Functions for building expressions. */
188 /* Append a raw byte to EXPR. */
189 extern void ax_raw_byte (struct agent_expr *expr, gdb_byte byte);
191 /* Append a simple operator OP to EXPR. */
192 extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP);
194 /* Append a pick operator to EXPR. DEPTH is the stack item to pick,
195 with 0 being top of stack. */
196 extern void ax_pick (struct agent_expr *EXPR, int DEPTH);
198 /* Append the floating-point prefix, for the next bytecode. */
199 #define ax_float(EXPR) (ax_simple ((EXPR), aop_float))
201 /* Append a sign-extension instruction to EXPR, to extend an N-bit value. */
202 extern void ax_ext (struct agent_expr *EXPR, int N);
204 /* Append a zero-extension instruction to EXPR, to extend an N-bit value. */
205 extern void ax_zero_ext (struct agent_expr *EXPR, int N);
207 /* Append a trace_quick instruction to EXPR, to record N bytes. */
208 extern void ax_trace_quick (struct agent_expr *EXPR, int N);
210 /* Append a goto op to EXPR. OP is the actual op (must be aop_goto or
211 aop_if_goto). We assume we don't know the target offset yet,
212 because it's probably a forward branch, so we leave space in EXPR
213 for the target, and return the offset in EXPR of that space, so we
214 can backpatch it once we do know the target offset. Use ax_label
215 to do the backpatching. */
216 extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP);
218 /* Suppose a given call to ax_goto returns some value PATCH. When you
219 know the offset TARGET that goto should jump to, call
220 ax_label (EXPR, PATCH, TARGET)
221 to patch TARGET into the ax_goto instruction. */
222 extern void ax_label (struct agent_expr *EXPR, int patch, int target);
224 /* Assemble code to push a constant on the stack. */
225 extern void ax_const_l (struct agent_expr *EXPR, LONGEST l);
226 extern void ax_const_d (struct agent_expr *EXPR, LONGEST d);
228 /* Assemble code to push the value of register number REG on the
230 extern void ax_reg (struct agent_expr *EXPR, int REG);
232 /* Add the given register to the register mask of the expression. */
233 extern void ax_reg_mask (struct agent_expr *ax, int reg);
235 /* Assemble code to operate on a trace state variable. */
236 extern void ax_tsv (struct agent_expr *expr, enum agent_op op, int num);
238 /* Append a string to the bytecode stream. */
239 extern void ax_string (struct agent_expr *x, const char *str, int slen);
242 /* Functions for printing out expressions, and otherwise debugging
245 /* Disassemble the expression EXPR, writing to F. */
246 extern void ax_print (struct ui_file *f, struct agent_expr * EXPR);
248 /* An entry in the opcode map. */
252 /* The name of the opcode. Null means that this entry is not a
253 valid opcode --- a hole in the opcode space. */
256 /* All opcodes take no operands from the bytecode stream, or take
257 unsigned integers of various sizes. If this is a positive number
258 n, then the opcode is followed by an n-byte operand, which should
259 be printed as an unsigned integer. If this is zero, then the
260 opcode takes no operands from the bytecode stream.
262 If we get more complicated opcodes in the future, don't add other
263 magic values of this; that's a crock. Add an `enum encoding'
264 field to this, or something like that. */
267 /* The size of the data operated upon, in bits, for bytecodes that
268 care about that (ref and const). Zero for all others. */
271 /* Number of stack elements consumed, and number produced. */
272 int consumed, produced;
275 /* Map of the bytecodes, indexed by bytecode number. */
276 extern struct aop_map aop_map[];
278 /* Given an agent expression AX, analyze and update its requirements. */
280 extern void ax_reqs (struct agent_expr *ax);
282 #endif /* AGENTEXPR_H */