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1 /* Definitions for expressions designed to be executed on the agent
2  Copyright (C) 1998-2015 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 3 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, see <http://www.gnu.org/licenses/>. */
18 
19 #ifndef AGENTEXPR_H
20 #define AGENTEXPR_H
21 
22 #include "doublest.h" /* For DOUBLEST. */
23 #include "vec.h"
24 
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.
32 
33  This is used with remote debugging; we don't really support it on
34  native configurations.
35 
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.
39 
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.
46 
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
51  to the host GDB. */
52 
53 
54 /* Different kinds of flaws an agent expression might have, as
55  detected by ax_reqs. */
57  {
58  agent_flaw_none = 0, /* code is good */
59 
60  /* There is an invalid instruction in the stream. */
62 
63  /* There is an incomplete instruction at the end of the expression. */
65 
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. */
70 
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. */
75 
76  /* ax_reqs was unable to prove that every instruction following
77  an unconditional jump was the target of some other jump. */
79  };
80 
81 /* Agent expression data structures. */
82 
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. */
87 
88 union agent_val
89  {
92  };
93 
94 /* A buffer containing a agent expression. */
95 struct agent_expr
96  {
97  /* The bytes of the expression. */
98  unsigned char *buf;
99 
100  /* The number of bytecode in the expression. */
101  int len;
102 
103  /* Allocated space available currently. */
104  int size;
105 
106  /* The target architecture assumed to be in effect. */
107  struct gdbarch *gdbarch;
108 
109  /* The address to which the expression applies. */
111 
112  /* If the following is not equal to agent_flaw_none, the rest of the
113  information in this structure is suspect. */
115 
116  /* Number of elements left on stack at end; may be negative if expr
117  only consumes elements. */
119 
120  /* Maximum and minimum stack height, relative to initial height. */
122 
123  /* Largest `ref' or `const' opcode used, in bits. Zero means the
124  expression has no such instructions. */
126 
127  /* Bit vector of registers needed. Register R is needed iff
128 
129  reg_mask[R / 8] & (1 << (R % 8))
130 
131  is non-zero. Note! You may not assume that this bitmask is long
132  enough to hold bits for all the registers of the machine; the
133  agent expression code has no idea how many registers the machine
134  has. However, the bitmask is reg_mask_len bytes long, so the
135  valid register numbers run from 0 to reg_mask_len * 8 - 1.
136 
137  Also note that this mask may contain registers that are needed
138  for the original collection expression to work, but that are
139  not referenced by any bytecode. This could, for example, occur
140  when collecting a local variable allocated to a register; the
141  compiler sets the mask bit and skips generating a bytecode whose
142  result is going to be discarded anyway.
143  */
145  unsigned char *reg_mask;
146 
147  /* For the data tracing facility, we need to insert `trace' bytecodes
148  before each data fetch; this records all the memory that the
149  expression touches in the course of evaluation, so that memory will
150  be available when the user later tries to evaluate the expression
151  in GDB.
152 
153  Setting the flag 'tracing' to non-zero enables the code that
154  emits the trace bytecodes at the appropriate points. */
155 
156  unsigned int tracing : 1;
157 
158  /* This indicates that pointers to chars should get an added
159  tracenz bytecode to record nonzero bytes, up to a length that
160  is the value of trace_string. */
161 
163  };
164 
165 /* Pointer to an agent_expr structure. */
166 typedef struct agent_expr *agent_expr_p;
167 
168 /* Vector of pointers to agent expressions. */
169 DEF_VEC_P (agent_expr_p);
170 
171 /* The actual values of the various bytecode operations. */
172 
174  {
175 #define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \
176  aop_ ## NAME = VALUE,
177 #include "ax.def"
178 #undef DEFOP
179  aop_last
180  };
181 
182 
183 
184 /* Functions for building expressions. */
185 
186 /* Allocate a new, empty agent expression. */
187 extern struct agent_expr *new_agent_expr (struct gdbarch *, CORE_ADDR);
188 
189 /* Free a agent expression. */
190 extern void free_agent_expr (struct agent_expr *);
191 extern struct cleanup *make_cleanup_free_agent_expr (struct agent_expr *);
192 
193 /* Append a simple operator OP to EXPR. */
194 extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP);
195 
196 /* Append a pick operator to EXPR. DEPTH is the stack item to pick,
197  with 0 being top of stack. */
198 extern void ax_pick (struct agent_expr *EXPR, int DEPTH);
199 
200 /* Append the floating-point prefix, for the next bytecode. */
201 #define ax_float(EXPR) (ax_simple ((EXPR), aop_float))
202 
203 /* Append a sign-extension instruction to EXPR, to extend an N-bit value. */
204 extern void ax_ext (struct agent_expr *EXPR, int N);
205 
206 /* Append a zero-extension instruction to EXPR, to extend an N-bit value. */
207 extern void ax_zero_ext (struct agent_expr *EXPR, int N);
208 
209 /* Append a trace_quick instruction to EXPR, to record N bytes. */
210 extern void ax_trace_quick (struct agent_expr *EXPR, int N);
211 
212 /* Append a goto op to EXPR. OP is the actual op (must be aop_goto or
213  aop_if_goto). We assume we don't know the target offset yet,
214  because it's probably a forward branch, so we leave space in EXPR
215  for the target, and return the offset in EXPR of that space, so we
216  can backpatch it once we do know the target offset. Use ax_label
217  to do the backpatching. */
218 extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP);
219 
220 /* Suppose a given call to ax_goto returns some value PATCH. When you
221  know the offset TARGET that goto should jump to, call
222  ax_label (EXPR, PATCH, TARGET)
223  to patch TARGET into the ax_goto instruction. */
224 extern void ax_label (struct agent_expr *EXPR, int patch, int target);
225 
226 /* Assemble code to push a constant on the stack. */
227 extern void ax_const_l (struct agent_expr *EXPR, LONGEST l);
228 extern void ax_const_d (struct agent_expr *EXPR, LONGEST d);
229 
230 /* Assemble code to push the value of register number REG on the
231  stack. */
232 extern void ax_reg (struct agent_expr *EXPR, int REG);
233 
234 /* Add the given register to the register mask of the expression. */
235 extern void ax_reg_mask (struct agent_expr *ax, int reg);
236 
237 /* Assemble code to operate on a trace state variable. */
238 extern void ax_tsv (struct agent_expr *expr, enum agent_op op, int num);
239 
240 /* Append a string to the bytecode stream. */
241 extern void ax_string (struct agent_expr *x, const char *str, int slen);
242 
243 
244 /* Functions for printing out expressions, and otherwise debugging
245  things. */
246 
247 /* Disassemble the expression EXPR, writing to F. */
248 extern void ax_print (struct ui_file *f, struct agent_expr * EXPR);
249 
250 /* An entry in the opcode map. */
251 struct aop_map
252  {
253 
254  /* The name of the opcode. Null means that this entry is not a
255  valid opcode --- a hole in the opcode space. */
256  const char *name;
257 
258  /* All opcodes take no operands from the bytecode stream, or take
259  unsigned integers of various sizes. If this is a positive number
260  n, then the opcode is followed by an n-byte operand, which should
261  be printed as an unsigned integer. If this is zero, then the
262  opcode takes no operands from the bytecode stream.
263 
264  If we get more complicated opcodes in the future, don't add other
265  magic values of this; that's a crock. Add an `enum encoding'
266  field to this, or something like that. */
267  int op_size;
268 
269  /* The size of the data operated upon, in bits, for bytecodes that
270  care about that (ref and const). Zero for all others. */
272 
273  /* Number of stack elements consumed, and number produced. */
275  };
276 
277 /* Map of the bytecodes, indexed by bytecode number. */
278 extern struct aop_map aop_map[];
279 
280 /* Given an agent expression AX, analyze and update its requirements. */
281 
282 extern void ax_reqs (struct agent_expr *ax);
283 
284 #endif /* AGENTEXPR_H */
int final_height
Definition: ax.h:118
agent_flaws
Definition: ax.h:56
Definition: ax.h:88
LONGEST l
Definition: ax.h:90
bfd_vma CORE_ADDR
Definition: common-types.h:41
void ax_reg(struct agent_expr *EXPR, int REG)
Definition: ax-general.c:290
void free_agent_expr(struct agent_expr *)
Definition: ax-general.c:67
void ax_simple(struct agent_expr *EXPR, enum agent_op OP)
Definition: ax-general.c:140
unsigned char * reg_mask
Definition: ax.h:145
void ax_print(struct ui_file *f, struct agent_expr *EXPR)
Definition: ax-general.c:376
Definition: ax.h:277
int ax_goto(struct agent_expr *EXPR, enum agent_op OP)
Definition: ax-general.c:216
Definition: ax.h:95
int produced
Definition: ax.h:274
int max_height
Definition: ax.h:121
struct gdbarch * gdbarch
Definition: ax.h:107
enum agent_flaws flaw
Definition: ax.h:114
int trace_string
Definition: ax.h:162
Definition: expression.h:74
void ax_trace_quick(struct agent_expr *EXPR, int N)
Definition: ax-general.c:196
Definition: ax.h:251
unsigned int tracing
Definition: ax.h:156
void ax_tsv(struct agent_expr *expr, enum agent_op op, int num)
Definition: ax-general.c:320
double DOUBLEST
Definition: doublest.h:24
void ax_pick(struct agent_expr *EXPR, int DEPTH)
Definition: ax-general.c:150
void ax_const_l(struct agent_expr *EXPR, LONGEST l)
Definition: ax-general.c:245
agent_op
Definition: ax.h:173
DEF_VEC_P(agent_expr_p)
void ax_const_d(struct agent_expr *EXPR, LONGEST d)
Definition: ax-general.c:279
int min_height
Definition: ax.h:121
void ax_label(struct agent_expr *EXPR, int patch, int target)
Definition: ax-general.c:231
struct agent_expr * new_agent_expr(struct gdbarch *, CORE_ADDR)
Definition: ax-general.c:42
void ax_ext(struct agent_expr *EXPR, int N)
Definition: ax-general.c:180
Definition: regdef.h:22
DOUBLEST d
Definition: ax.h:91
void ax_reqs(struct agent_expr *ax)
Definition: ax-general.c:477
void ax_zero_ext(struct agent_expr *EXPR, int N)
Definition: ax-general.c:188
struct agent_expr * agent_expr_p
Definition: ax.h:166
int data_size
Definition: ax.h:271
const char * name
Definition: ax.h:256
int len
Definition: ax.h:101
int op_size
Definition: ax.h:267
struct cleanup * make_cleanup_free_agent_expr(struct agent_expr *)
Definition: ax-general.c:81
void ax_string(struct agent_expr *x, const char *str, int slen)
Definition: ax-general.c:341
unsigned char * buf
Definition: ax.h:98
int reg_mask_len
Definition: ax.h:144
int consumed
Definition: ax.h:274
void ax_reg_mask(struct agent_expr *ax, int reg)
Definition: ax-general.c:438
int max_data_size
Definition: ax.h:125
long long LONGEST
Definition: common-types.h:52
CORE_ADDR scope
Definition: ax.h:110
int size
Definition: ax.h:104