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c906108c | 1 | /* Definitions for expressions designed to be executed on the agent |
1d506c26 | 2 | Copyright (C) 1998-2024 Free Software Foundation, Inc. |
c906108c | 3 | |
c5aa993b | 4 | This file is part of GDB. |
c906108c | 5 | |
c5aa993b JM |
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 | |
a9762ec7 | 8 | the Free Software Foundation; either version 3 of the License, or |
c5aa993b | 9 | (at your option) any later version. |
c906108c | 10 | |
c5aa993b JM |
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. | |
c906108c | 15 | |
c5aa993b | 16 | You should have received a copy of the GNU General Public License |
a9762ec7 | 17 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
c906108c | 18 | |
1a5c2598 TT |
19 | #ifndef AX_H |
20 | #define AX_H | |
c906108c SS |
21 | |
22 | /* It's sometimes useful to be able to debug programs that you can't | |
23 | really stop for more than a fraction of a second. To this end, the | |
24 | user can specify a tracepoint (like a breakpoint, but you don't | |
25 | stop at it), and specify a bunch of expressions to record the | |
26 | values of when that tracepoint is reached. As the program runs, | |
27 | GDB collects the values. At any point (possibly while values are | |
28 | still being collected), the user can display the collected values. | |
29 | ||
30 | This is used with remote debugging; we don't really support it on | |
31 | native configurations. | |
32 | ||
33 | This means that expressions are being evaluated by the remote agent, | |
34 | which doesn't have any access to the symbol table information, and | |
35 | needs to be small and simple. | |
36 | ||
37 | The agent_expr routines and datatypes are a bytecode language | |
38 | designed to be executed by the agent. Agent expressions work in | |
39 | terms of fixed-width values, operators, memory references, and | |
40 | register references. You can evaluate a agent expression just given | |
41 | a bunch of memory and register values to sniff at; you don't need | |
42 | any symbolic information like variable names, types, etc. | |
43 | ||
44 | GDB translates source expressions, whose meaning depends on | |
45 | symbolic information, into agent bytecode expressions, whose meaning | |
46 | is independent of symbolic information. This means the agent can | |
47 | evaluate them on the fly without reference to data only available | |
48 | to the host GDB. */ | |
c906108c | 49 | \f |
c5aa993b | 50 | |
35c9c7ba SS |
51 | /* Different kinds of flaws an agent expression might have, as |
52 | detected by ax_reqs. */ | |
53 | enum agent_flaws | |
54 | { | |
55 | agent_flaw_none = 0, /* code is good */ | |
56 | ||
57 | /* There is an invalid instruction in the stream. */ | |
58 | agent_flaw_bad_instruction, | |
59 | ||
60 | /* There is an incomplete instruction at the end of the expression. */ | |
61 | agent_flaw_incomplete_instruction, | |
62 | ||
63 | /* ax_reqs was unable to prove that every jump target is to a | |
64 | valid offset. Valid offsets are within the bounds of the | |
65 | expression, and to a valid instruction boundary. */ | |
66 | agent_flaw_bad_jump, | |
67 | ||
68 | /* ax_reqs was unable to prove to its satisfaction that, for each | |
69 | jump target location, the stack will have the same height whether | |
70 | that location is reached via a jump or by straight execution. */ | |
71 | agent_flaw_height_mismatch, | |
72 | ||
73 | /* ax_reqs was unable to prove that every instruction following | |
74 | an unconditional jump was the target of some other jump. */ | |
75 | agent_flaw_hole | |
76 | }; | |
77 | ||
c906108c SS |
78 | /* Agent expression data structures. */ |
79 | ||
c906108c | 80 | /* A buffer containing a agent expression. */ |
c5aa993b JM |
81 | struct agent_expr |
82 | { | |
833177a4 | 83 | /* Construct an empty agent expression. */ |
b0b5ba6b TT |
84 | agent_expr (struct gdbarch *gdbarch, CORE_ADDR scope) |
85 | : gdbarch (gdbarch), | |
da25448d | 86 | scope (scope) |
b0b5ba6b | 87 | { } |
833177a4 | 88 | |
35c9c7ba | 89 | /* The bytes of the expression. */ |
6f96f485 | 90 | gdb::byte_vector buf; |
35c9c7ba SS |
91 | |
92 | /* The target architecture assumed to be in effect. */ | |
93 | struct gdbarch *gdbarch; | |
94 | ||
95 | /* The address to which the expression applies. */ | |
c5aa993b | 96 | CORE_ADDR scope; |
c906108c | 97 | |
35c9c7ba SS |
98 | /* If the following is not equal to agent_flaw_none, the rest of the |
99 | information in this structure is suspect. */ | |
100 | enum agent_flaws flaw; | |
101 | ||
102 | /* Number of elements left on stack at end; may be negative if expr | |
103 | only consumes elements. */ | |
104 | int final_height; | |
105 | ||
106 | /* Maximum and minimum stack height, relative to initial height. */ | |
107 | int max_height, min_height; | |
108 | ||
109 | /* Largest `ref' or `const' opcode used, in bits. Zero means the | |
110 | expression has no such instructions. */ | |
111 | int max_data_size; | |
112 | ||
113 | /* Bit vector of registers needed. Register R is needed iff | |
a2bbca9f TT |
114 | reg_mask[R] is non-zero. Note! You may not assume that this |
115 | bitmask is long enough to hold bits for all the registers of | |
116 | the machine; the agent expression code has no idea how many | |
117 | registers the machine has. | |
35c9c7ba SS |
118 | |
119 | Also note that this mask may contain registers that are needed | |
120 | for the original collection expression to work, but that are | |
121 | not referenced by any bytecode. This could, for example, occur | |
122 | when collecting a local variable allocated to a register; the | |
123 | compiler sets the mask bit and skips generating a bytecode whose | |
124 | result is going to be discarded anyway. | |
125 | */ | |
a2bbca9f | 126 | std::vector<bool> reg_mask; |
92bc6a20 TT |
127 | |
128 | /* For the data tracing facility, we need to insert `trace' bytecodes | |
129 | before each data fetch; this records all the memory that the | |
130 | expression touches in the course of evaluation, so that memory will | |
131 | be available when the user later tries to evaluate the expression | |
132 | in GDB. | |
133 | ||
da25448d | 134 | Setting the flag 'tracing' to true enables the code that |
92bc6a20 TT |
135 | emits the trace bytecodes at the appropriate points. */ |
136 | ||
da25448d | 137 | bool tracing = false; |
92bc6a20 TT |
138 | |
139 | /* This indicates that pointers to chars should get an added | |
140 | tracenz bytecode to record nonzero bytes, up to a length that | |
141 | is the value of trace_string. */ | |
142 | ||
b0b5ba6b | 143 | int trace_string = 0; |
35c9c7ba | 144 | }; |
c906108c | 145 | |
833177a4 | 146 | /* An agent_expr owning pointer. */ |
6c73cd95 | 147 | typedef std::unique_ptr<agent_expr> agent_expr_up; |
833177a4 | 148 | |
94d5e490 | 149 | /* The actual values of the various bytecode operations. */ |
c906108c | 150 | |
c5aa993b JM |
151 | enum agent_op |
152 | { | |
94d5e490 TT |
153 | #define DEFOP(NAME, SIZE, DATA_SIZE, CONSUMED, PRODUCED, VALUE) \ |
154 | aop_ ## NAME = VALUE, | |
268a13a5 | 155 | #include "gdbsupport/ax.def" |
94d5e490 | 156 | #undef DEFOP |
c5aa993b JM |
157 | }; |
158 | \f | |
c906108c SS |
159 | |
160 | ||
c906108c SS |
161 | /* Functions for building expressions. */ |
162 | ||
70b8286a SM |
163 | /* Append a raw byte to EXPR. */ |
164 | extern void ax_raw_byte (struct agent_expr *expr, gdb_byte byte); | |
165 | ||
c906108c | 166 | /* Append a simple operator OP to EXPR. */ |
a14ed312 | 167 | extern void ax_simple (struct agent_expr *EXPR, enum agent_op OP); |
c906108c | 168 | |
c7f96d2b TT |
169 | /* Append a pick operator to EXPR. DEPTH is the stack item to pick, |
170 | with 0 being top of stack. */ | |
171 | extern void ax_pick (struct agent_expr *EXPR, int DEPTH); | |
172 | ||
c906108c SS |
173 | /* Append the floating-point prefix, for the next bytecode. */ |
174 | #define ax_float(EXPR) (ax_simple ((EXPR), aop_float)) | |
175 | ||
176 | /* Append a sign-extension instruction to EXPR, to extend an N-bit value. */ | |
a14ed312 | 177 | extern void ax_ext (struct agent_expr *EXPR, int N); |
c906108c SS |
178 | |
179 | /* Append a zero-extension instruction to EXPR, to extend an N-bit value. */ | |
a14ed312 | 180 | extern void ax_zero_ext (struct agent_expr *EXPR, int N); |
c906108c SS |
181 | |
182 | /* Append a trace_quick instruction to EXPR, to record N bytes. */ | |
a14ed312 | 183 | extern void ax_trace_quick (struct agent_expr *EXPR, int N); |
c906108c SS |
184 | |
185 | /* Append a goto op to EXPR. OP is the actual op (must be aop_goto or | |
186 | aop_if_goto). We assume we don't know the target offset yet, | |
187 | because it's probably a forward branch, so we leave space in EXPR | |
188 | for the target, and return the offset in EXPR of that space, so we | |
189 | can backpatch it once we do know the target offset. Use ax_label | |
190 | to do the backpatching. */ | |
a14ed312 | 191 | extern int ax_goto (struct agent_expr *EXPR, enum agent_op OP); |
c906108c SS |
192 | |
193 | /* Suppose a given call to ax_goto returns some value PATCH. When you | |
194 | know the offset TARGET that goto should jump to, call | |
c5aa993b | 195 | ax_label (EXPR, PATCH, TARGET) |
c906108c | 196 | to patch TARGET into the ax_goto instruction. */ |
a14ed312 | 197 | extern void ax_label (struct agent_expr *EXPR, int patch, int target); |
c906108c SS |
198 | |
199 | /* Assemble code to push a constant on the stack. */ | |
a14ed312 KB |
200 | extern void ax_const_l (struct agent_expr *EXPR, LONGEST l); |
201 | extern void ax_const_d (struct agent_expr *EXPR, LONGEST d); | |
c906108c SS |
202 | |
203 | /* Assemble code to push the value of register number REG on the | |
204 | stack. */ | |
a14ed312 | 205 | extern void ax_reg (struct agent_expr *EXPR, int REG); |
f61e138d | 206 | |
35c9c7ba SS |
207 | /* Add the given register to the register mask of the expression. */ |
208 | extern void ax_reg_mask (struct agent_expr *ax, int reg); | |
209 | ||
f61e138d SS |
210 | /* Assemble code to operate on a trace state variable. */ |
211 | extern void ax_tsv (struct agent_expr *expr, enum agent_op op, int num); | |
d3ce09f5 SS |
212 | |
213 | /* Append a string to the bytecode stream. */ | |
741d92cf | 214 | extern void ax_string (struct agent_expr *x, const char *str, int slen); |
c906108c | 215 | \f |
c5aa993b | 216 | |
c906108c SS |
217 | /* Functions for printing out expressions, and otherwise debugging |
218 | things. */ | |
219 | ||
220 | /* Disassemble the expression EXPR, writing to F. */ | |
d9fcf2fb | 221 | extern void ax_print (struct ui_file *f, struct agent_expr * EXPR); |
c906108c | 222 | |
35c9c7ba | 223 | /* Given an agent expression AX, analyze and update its requirements. */ |
c906108c | 224 | |
35c9c7ba | 225 | extern void ax_reqs (struct agent_expr *ax); |
c906108c | 226 | |
1a5c2598 | 227 | #endif /* AX_H */ |