1 /* DWARF 2 Expression Evaluator.
3 Copyright (C) 2001-2022 Free Software Foundation, Inc.
5 Contributed by Daniel Berlin <dan@dberlin.org>.
7 This file is part of GDB.
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.
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.
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/>. */
22 #if !defined (DWARF2EXPR_H)
28 struct dwarf2_per_objfile
;
30 /* The location of a value. */
31 enum dwarf_value_location
33 /* The piece is in memory.
34 The value on the dwarf stack is its address. */
37 /* The piece is in a register.
38 The value on the dwarf stack is the register number. */
41 /* The piece is on the dwarf stack. */
44 /* The piece is a literal. */
47 /* The piece was optimized out. */
48 DWARF_VALUE_OPTIMIZED_OUT
,
50 /* The piece is an implicit pointer. */
51 DWARF_VALUE_IMPLICIT_POINTER
54 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece. */
55 struct dwarf_expr_piece
57 enum dwarf_value_location location
;
63 /* This piece's address, for DWARF_VALUE_MEMORY pieces. */
65 /* Non-zero if the piece is known to be in memory and on
66 the program's stack. */
70 /* The piece's register number, for DWARF_VALUE_REGISTER pieces. */
73 /* The piece's literal value, for DWARF_VALUE_STACK pieces. */
78 /* A pointer to the data making up this piece,
79 for DWARF_VALUE_LITERAL pieces. */
81 /* The length of the available data. */
85 /* Used for DWARF_VALUE_IMPLICIT_POINTER. */
88 /* The referent DIE from DW_OP_implicit_pointer. */
89 sect_offset die_sect_off
;
90 /* The byte offset into the resulting data. */
95 /* The length of the piece, in bits. */
97 /* The piece offset, in bits. */
101 /* The dwarf expression stack. */
103 struct dwarf_stack_value
105 dwarf_stack_value (struct value
*value_
, int in_stack_memory_
)
106 : value (value_
), in_stack_memory (in_stack_memory_
)
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". */
115 bool in_stack_memory
;
118 /* The expression evaluator works with a dwarf_expr_context, describing
119 its current state and its callbacks. */
120 struct dwarf_expr_context
122 dwarf_expr_context (dwarf2_per_objfile
*per_objfile
,
124 virtual ~dwarf_expr_context () = default;
126 void push_address (CORE_ADDR value
, bool in_stack_memory
);
128 /* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU
131 AS_LVAL defines if the returned struct value is expected to be a
132 value (false) or a location description (true).
134 TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET describe the expected struct
135 value representation of the evaluation result.
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
*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);
147 /* The stack of values. */
148 std::vector
<dwarf_stack_value
> m_stack
;
150 /* Target address size in bytes. */
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. */
156 int m_recursion_depth
= 0, m_max_recursion_depth
= 0x100;
158 /* Location of the value. */
159 dwarf_value_location m_location
= DWARF_VALUE_MEMORY
;
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. */
165 const gdb_byte
*m_data
= nullptr;
167 /* Initialization status of variable: Non-zero if variable has been
168 initialized; zero otherwise. */
169 int m_initialized
= 0;
171 /* A vector of pieces.
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.
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.
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
;
195 /* We evaluate the expression in the context of this objfile. */
196 dwarf2_per_objfile
*m_per_objfile
;
198 /* Frame information used for the evaluation. */
199 frame_info
*m_frame
= nullptr;
201 /* Compilation unit used for the evaluation. */
202 dwarf2_per_cu_data
*m_per_cu
= nullptr;
204 /* Property address info used for the evaluation. */
205 const struct property_addr_info
*m_addr_info
= nullptr;
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
);
214 struct value
*fetch (int n
);
215 CORE_ADDR
fetch_address (int n
);
216 bool fetch_in_stack_memory (int n
);
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
);
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
);
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
);
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
240 void dwarf_call (cu_offset die_cu_off
);
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
246 void push_dwarf_reg_entry_value (call_site_parameter_kind kind
,
247 call_site_parameter_u kind_u
,
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
);
257 /* Return the value of register number REG (a DWARF register number),
258 read as an address in a given FRAME. */
259 CORE_ADDR
read_addr_from_reg (frame_info
*frame
, int reg
);
261 void dwarf_expr_require_composition (const gdb_byte
*, const gdb_byte
*,
264 int dwarf_block_to_dwarf_reg (const gdb_byte
*buf
, const gdb_byte
*buf_end
);
266 int dwarf_block_to_dwarf_reg_deref (const gdb_byte
*buf
,
267 const gdb_byte
*buf_end
,
268 CORE_ADDR
*deref_size_return
);
270 int dwarf_block_to_fb_offset (const gdb_byte
*buf
, const gdb_byte
*buf_end
,
271 CORE_ADDR
*fb_offset_return
);
273 int dwarf_block_to_sp_offset (struct gdbarch
*gdbarch
, const gdb_byte
*buf
,
274 const gdb_byte
*buf_end
,
275 CORE_ADDR
*sp_offset_return
);
277 /* Wrappers around the leb128 reader routines to simplify them for our
280 static inline const gdb_byte
*
281 gdb_read_uleb128 (const gdb_byte
*buf
, const gdb_byte
*buf_end
,
284 size_t bytes_read
= read_uleb128_to_uint64 (buf
, buf_end
, r
);
288 return buf
+ bytes_read
;
291 static inline const gdb_byte
*
292 gdb_read_sleb128 (const gdb_byte
*buf
, const gdb_byte
*buf_end
,
295 size_t bytes_read
= read_sleb128_to_int64 (buf
, buf_end
, r
);
299 return buf
+ bytes_read
;
302 static inline const gdb_byte
*
303 gdb_skip_leb128 (const gdb_byte
*buf
, const gdb_byte
*buf_end
)
305 size_t bytes_read
= skip_leb128 (buf
, buf_end
);
309 return buf
+ bytes_read
;
312 extern const gdb_byte
*safe_read_uleb128 (const gdb_byte
*buf
,
313 const gdb_byte
*buf_end
,
316 extern const gdb_byte
*safe_read_sleb128 (const gdb_byte
*buf
,
317 const gdb_byte
*buf_end
,
320 extern const gdb_byte
*safe_skip_leb128 (const gdb_byte
*buf
,
321 const gdb_byte
*buf_end
);
323 #endif /* dwarf2expr.h */