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expr.h
Go to the documentation of this file.
1/* DWARF 2 Expression Evaluator.
2
3 Copyright (C) 2001-2023 Free Software Foundation, Inc.
4
5 Contributed by Daniel Berlin <dan@dberlin.org>.
6
7 This file is part of GDB.
8
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3 of the License, or
12 (at your option) any later version.
13
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
18
19 You should have received a copy of the GNU General Public License
20 along with this program. If not, see <http://www.gnu.org/licenses/>. */
21
22#if !defined (DWARF2EXPR_H)
23#define DWARF2EXPR_H
24
25#include "leb128.h"
26#include "dwarf2/call-site.h"
27
29
30/* The location of a value. */
32{
33 /* The piece is in memory.
34 The value on the dwarf stack is its address. */
36
37 /* The piece is in a register.
38 The value on the dwarf stack is the register number. */
40
41 /* The piece is on the dwarf stack. */
43
44 /* The piece is a literal. */
46
47 /* The piece was optimized out. */
49
50 /* The piece is an implicit pointer. */
52};
53
54/* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece. */
56{
58
59 union
60 {
61 struct
62 {
63 /* This piece's address, for DWARF_VALUE_MEMORY pieces. */
64 CORE_ADDR addr;
65 /* Non-zero if the piece is known to be in memory and on
66 the program's stack. */
68 } mem;
69
70 /* The piece's register number, for DWARF_VALUE_REGISTER pieces. */
71 int regno;
72
73 /* The piece's literal value, for DWARF_VALUE_STACK pieces. */
74 struct value *value;
75
76 struct
77 {
78 /* A pointer to the data making up this piece,
79 for DWARF_VALUE_LITERAL pieces. */
80 const gdb_byte *data;
81 /* The length of the available data. */
82 ULONGEST length;
84
85 /* Used for DWARF_VALUE_IMPLICIT_POINTER. */
86 struct
87 {
88 /* The referent DIE from DW_OP_implicit_pointer. */
89 sect_offset die_sect_off;
90 /* The byte offset into the resulting data. */
91 LONGEST offset;
92 } ptr;
93 } v;
94
95 /* The length of the piece, in bits. */
96 ULONGEST size;
97 /* The piece offset, in bits. */
98 ULONGEST offset;
99};
100
101/* The dwarf expression stack. */
102
104{
105 dwarf_stack_value (struct value *value_, int in_stack_memory_)
106 : value (value_), in_stack_memory (in_stack_memory_)
107 {}
108
109 struct value *value;
110
111 /* True if the piece is in memory and is known to be on the program's stack.
112 It is always ok to set this to zero. This is used, for example, to
113 optimize memory access from the target. It can vastly speed up backtraces
114 on long latency connections when "set stack-cache on". */
116};
117
118/* The expression evaluator works with a dwarf_expr_context, describing
119 its current state and its callbacks. */
121{
123 int addr_size);
124 virtual ~dwarf_expr_context () = default;
125
126 void push_address (CORE_ADDR value, bool in_stack_memory);
127
128 /* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU
129 and FRAME context.
130
131 AS_LVAL defines if the returned struct value is expected to be a
132 value (false) or a location description (true).
133
134 TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET describe the expected struct
135 value representation of the evaluation result.
136
137 The ADDR_INFO property can be specified to override the range of
138 memory addresses with the passed in buffer. */
139 value *evaluate (const gdb_byte *addr, size_t len, bool as_lval,
140 dwarf2_per_cu_data *per_cu, frame_info_ptr frame,
141 const struct property_addr_info *addr_info = nullptr,
142 struct type *type = nullptr,
143 struct type *subobj_type = nullptr,
144 LONGEST subobj_offset = 0);
145
146private:
147 /* The stack of values. */
148 std::vector<dwarf_stack_value> m_stack;
149
150 /* Target address size in bytes. */
151 int m_addr_size = 0;
152
153 /* The current depth of dwarf expression recursion, via DW_OP_call*,
154 DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
155 depth we'll tolerate before raising an error. */
157
158 /* Location of the value. */
160
161 /* For DWARF_VALUE_LITERAL, the current literal value's length and
162 data. For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
163 target DIE of sect_offset kind. */
164 ULONGEST m_len = 0;
165 const gdb_byte *m_data = nullptr;
166
167 /* Initialization status of variable: True if variable has been
168 initialized; false otherwise. */
169 bool m_initialized = false;
170
171 /* A vector of pieces.
172
173 Each time DW_OP_piece is executed, we add a new element to the
174 end of this array, recording the current top of the stack, the
175 current location, and the size given as the operand to
176 DW_OP_piece. We then pop the top value from the stack, reset the
177 location, and resume evaluation.
178
179 The Dwarf spec doesn't say whether DW_OP_piece pops the top value
180 from the stack. We do, ensuring that clients of this interface
181 expecting to see a value left on the top of the stack (say, code
182 evaluating frame base expressions or CFA's specified with
183 DW_CFA_def_cfa_expression) will get an error if the expression
184 actually marks all the values it computes as pieces.
185
186 If an expression never uses DW_OP_piece, num_pieces will be zero.
187 (It would be nice to present these cases as expressions yielding
188 a single piece, so that callers need not distinguish between the
189 no-DW_OP_piece and one-DW_OP_piece cases. But expressions with
190 no DW_OP_piece operations have no value to place in a piece's
191 'size' field; the size comes from the surrounding data. So the
192 two cases need to be handled separately.) */
193 std::vector<dwarf_expr_piece> m_pieces;
194
195 /* We evaluate the expression in the context of this objfile. */
197
198 /* Frame information used for the evaluation. */
200
201 /* Compilation unit used for the evaluation. */
203
204 /* Property address info used for the evaluation. */
205 const struct property_addr_info *m_addr_info = nullptr;
206
207 void eval (const gdb_byte *addr, size_t len);
208 struct type *address_type () const;
209 void push (struct value *value, bool in_stack_memory);
210 bool stack_empty_p () const;
211 void add_piece (ULONGEST size, ULONGEST offset);
212 void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
213 void pop ();
214 struct value *fetch (int n);
215 CORE_ADDR fetch_address (int n);
216 bool fetch_in_stack_memory (int n);
217
218 /* Fetch the result of the expression evaluation in a form of
219 a struct value, where TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET
220 describe the source level representation of that result.
221 AS_LVAL defines if the fetched struct value is expected to
222 be a value or a location description. */
223 value *fetch_result (struct type *type, struct type *subobj_type,
224 LONGEST subobj_offset, bool as_lval);
225
226 /* Return the location expression for the frame base attribute, in
227 START and LENGTH. The result must be live until the current
228 expression evaluation is complete. */
229 void get_frame_base (const gdb_byte **start, size_t *length);
230
231 /* Return the base type given by the indicated DIE at DIE_CU_OFF.
232 This can throw an exception if the DIE is invalid or does not
233 represent a base type. */
234 struct type *get_base_type (cu_offset die_cu_off);
235
236 /* Execute DW_AT_location expression for the DWARF expression
237 subroutine in the DIE at DIE_CU_OFF in the CU. Do not touch
238 STACK while it being passed to and returned from the called DWARF
239 subroutine. */
240 void dwarf_call (cu_offset die_cu_off);
241
242 /* Push on DWARF stack an entry evaluated for DW_TAG_call_site's
243 parameter matching KIND and KIND_U at the caller of specified BATON.
244 If DEREF_SIZE is not -1 then use DW_AT_call_data_value instead of
245 DW_AT_call_value. */
248 int deref_size);
249
250 /* Read LENGTH bytes at ADDR into BUF. This method also handles the
251 case where a caller of the evaluator passes in some data,
252 but with the address being 0. In this situation, we arrange for
253 memory reads to come from the passed-in buffer. */
254 void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length);
255};
256
257/* Return the value of register number REG (a DWARF register number),
258 read as an address in a given FRAME. */
259CORE_ADDR read_addr_from_reg (frame_info_ptr frame, int reg);
260
261void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
262 const char *);
263
264int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
265
266int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
267 const gdb_byte *buf_end,
268 CORE_ADDR *deref_size_return);
269
270int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
271 CORE_ADDR *fb_offset_return);
272
273int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
274 const gdb_byte *buf_end,
275 CORE_ADDR *sp_offset_return);
276
277/* Wrappers around the leb128 reader routines to simplify them for our
278 purposes. */
279
280static inline const gdb_byte *
281gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
282 uint64_t *r)
283{
284 size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
285
286 if (bytes_read == 0)
287 return NULL;
288 return buf + bytes_read;
289}
290
291static inline const gdb_byte *
292gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
293 int64_t *r)
294{
295 size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
296
297 if (bytes_read == 0)
298 return NULL;
299 return buf + bytes_read;
300}
301
302static inline const gdb_byte *
303gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
304{
305 size_t bytes_read = skip_leb128 (buf, buf_end);
306
307 if (bytes_read == 0)
308 return NULL;
309 return buf + bytes_read;
310}
311
312extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
313 const gdb_byte *buf_end,
314 uint64_t *r);
315
316extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
317 const gdb_byte *buf_end,
318 int64_t *r);
319
320extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
321 const gdb_byte *buf_end);
322
323#endif /* DWARF2EXPR_H */
call_site_parameter_kind
Definition call-site.h:36
static const gdb_byte * gdb_read_uleb128(const gdb_byte *buf, const gdb_byte *buf_end, uint64_t *r)
Definition expr.h:281
const gdb_byte * safe_skip_leb128(const gdb_byte *buf, const gdb_byte *buf_end)
Definition expr.c:1281
dwarf_value_location
Definition expr.h:32
@ DWARF_VALUE_STACK
Definition expr.h:42
@ DWARF_VALUE_LITERAL
Definition expr.h:45
@ DWARF_VALUE_IMPLICIT_POINTER
Definition expr.h:51
@ DWARF_VALUE_REGISTER
Definition expr.h:39
@ DWARF_VALUE_OPTIMIZED_OUT
Definition expr.h:48
@ DWARF_VALUE_MEMORY
Definition expr.h:35
void dwarf_expr_require_composition(const gdb_byte *, const gdb_byte *, const char *)
Definition expr.c:1295
static const gdb_byte * gdb_read_sleb128(const gdb_byte *buf, const gdb_byte *buf_end, int64_t *r)
Definition expr.h:292
int dwarf_block_to_dwarf_reg_deref(const gdb_byte *buf, const gdb_byte *buf_end, CORE_ADDR *deref_size_return)
Definition expr.c:1367
const gdb_byte * safe_read_sleb128(const gdb_byte *buf, const gdb_byte *buf_end, int64_t *r)
Definition expr.c:1271
static const gdb_byte * gdb_skip_leb128(const gdb_byte *buf, const gdb_byte *buf_end)
Definition expr.h:303
int dwarf_block_to_sp_offset(struct gdbarch *gdbarch, const gdb_byte *buf, const gdb_byte *buf_end, CORE_ADDR *sp_offset_return)
Definition expr.c:1453
CORE_ADDR read_addr_from_reg(frame_info_ptr frame, int reg)
Definition expr.c:81
const gdb_byte * safe_read_uleb128(const gdb_byte *buf, const gdb_byte *buf_end, uint64_t *r)
Definition expr.c:1259
int dwarf_block_to_fb_offset(const gdb_byte *buf, const gdb_byte *buf_end, CORE_ADDR *fb_offset_return)
Definition expr.c:1426
int dwarf_block_to_dwarf_reg(const gdb_byte *buf, const gdb_byte *buf_end)
Definition expr.c:1324
size_t size
Definition go32-nat.c:239
void execute_stack_op(const gdb_byte *op_ptr, const gdb_byte *op_end)
Definition expr.c:1494
std::vector< dwarf_stack_value > m_stack
Definition expr.h:148
const struct property_addr_info * m_addr_info
Definition expr.h:205
void eval(const gdb_byte *addr, size_t len)
Definition expr.c:1245
struct value * fetch(int n)
Definition expr.c:759
const gdb_byte * m_data
Definition expr.h:165
ULONGEST m_len
Definition expr.h:164
void push_address(CORE_ADDR value, bool in_stack_memory)
Definition expr.c:740
std::vector< dwarf_expr_piece > m_pieces
Definition expr.h:193
bool stack_empty_p() const
Definition expr.c:1194
dwarf_expr_context(dwarf2_per_objfile *per_objfile, int addr_size)
Definition expr.c:722
frame_info_ptr m_frame
Definition expr.h:199
struct type * address_type() const
Definition expr.c:691
value * evaluate(const gdb_byte *addr, size_t len, bool as_lval, dwarf2_per_cu_data *per_cu, frame_info_ptr frame, const struct property_addr_info *addr_info=nullptr, struct type *type=nullptr, struct type *subobj_type=nullptr, LONGEST subobj_offset=0)
Definition expr.c:1078
CORE_ADDR fetch_address(int n)
Definition expr.c:1150
struct type * get_base_type(cu_offset die_cu_off)
Definition expr.c:799
void push(struct value *value, bool in_stack_memory)
Definition expr.c:732
void dwarf_call(cu_offset die_cu_off)
Definition expr.c:816
int m_recursion_depth
Definition expr.h:156
int m_max_recursion_depth
Definition expr.h:156
dwarf_value_location m_location
Definition expr.h:159
dwarf2_per_cu_data * m_per_cu
Definition expr.h:202
bool fetch_in_stack_memory(int n)
Definition expr.c:1182
void push_dwarf_reg_entry_value(call_site_parameter_kind kind, call_site_parameter_u kind_u, int deref_size)
Definition expr.c:866
dwarf2_per_objfile * m_per_objfile
Definition expr.h:196
value * fetch_result(struct type *type, struct type *subobj_type, LONGEST subobj_offset, bool as_lval)
Definition expr.c:914
bool m_initialized
Definition expr.h:169
virtual ~dwarf_expr_context()=default
void get_frame_base(const gdb_byte **start, size_t *length)
Definition expr.c:771
void read_mem(gdb_byte *buf, CORE_ADDR addr, size_t length)
Definition expr.c:841
void add_piece(ULONGEST size, ULONGEST offset)
Definition expr.c:1201
struct dwarf_expr_piece::@42::@43 mem
enum dwarf_value_location location
Definition expr.h:57
ULONGEST length
Definition expr.h:82
const gdb_byte * data
Definition expr.h:80
struct dwarf_expr_piece::@42::@45 ptr
ULONGEST offset
Definition expr.h:98
bool in_stack_memory
Definition expr.h:67
struct value * value
Definition expr.h:74
sect_offset die_sect_off
Definition expr.h:89
union dwarf_expr_piece::@42 v
ULONGEST size
Definition expr.h:96
struct dwarf_expr_piece::@42::@44 literal
LONGEST offset
Definition expr.h:91
CORE_ADDR addr
Definition expr.h:64
bool in_stack_memory
Definition expr.h:115
dwarf_stack_value(struct value *value_, int in_stack_memory_)
Definition expr.h:105
struct value * value
Definition expr.h:109
Definition value.h:130