1 /* DWARF 2 Expression Evaluator.
2
3 Copyright (C) 2001-2020 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 "gdbtypes.h"
27
28 struct dwarf2_per_objfile;
29
30 /* The location of a value. */
31 enum dwarf_value_location
32 {
33 /* The piece is in memory.
34 The value on the dwarf stack is its address. */
35 DWARF_VALUE_MEMORY,
36
37 /* The piece is in a register.
38 The value on the dwarf stack is the register number. */
39 DWARF_VALUE_REGISTER,
40
41 /* The piece is on the dwarf stack. */
42 DWARF_VALUE_STACK,
43
44 /* The piece is a literal. */
45 DWARF_VALUE_LITERAL,
46
47 /* The piece was optimized out. */
48 DWARF_VALUE_OPTIMIZED_OUT,
49
50 /* The piece is an implicit pointer. */
51 DWARF_VALUE_IMPLICIT_POINTER
52 };
53
54 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece. */
55 struct dwarf_expr_piece
56 {
57 enum dwarf_value_location location;
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. */
67 bool in_stack_memory;
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;
83 } literal;
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
103 struct dwarf_stack_value
104 {
dwarf_stack_valuedwarf_stack_value105 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". */
115 bool in_stack_memory;
116 };
117
118 /* The expression evaluator works with a dwarf_expr_context, describing
119 its current state and its callbacks. */
120 struct dwarf_expr_context
121 {
122 dwarf_expr_context (dwarf2_per_objfile *per_objfile);
123 virtual ~dwarf_expr_context () = default;
124
125 void push_address (CORE_ADDR value, bool in_stack_memory);
126 void eval (const gdb_byte *addr, size_t len);
127 struct value *fetch (int n);
128 CORE_ADDR fetch_address (int n);
129 bool fetch_in_stack_memory (int n);
130
131 /* The stack of values. */
132 std::vector<dwarf_stack_value> stack;
133
134 /* Target architecture to use for address operations. */
135 struct gdbarch *gdbarch;
136
137 /* Target address size in bytes. */
138 int addr_size;
139
140 /* DW_FORM_ref_addr size in bytes. If -1 DWARF is executed from a frame
141 context and operations depending on DW_FORM_ref_addr are not allowed. */
142 int ref_addr_size;
143
144 /* The current depth of dwarf expression recursion, via DW_OP_call*,
145 DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
146 depth we'll tolerate before raising an error. */
147 int recursion_depth, max_recursion_depth;
148
149 /* Location of the value. */
150 enum dwarf_value_location location;
151
152 /* For DWARF_VALUE_LITERAL, the current literal value's length and
153 data. For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
154 target DIE of sect_offset kind. */
155 ULONGEST len;
156 const gdb_byte *data;
157
158 /* Initialization status of variable: Non-zero if variable has been
159 initialized; zero otherwise. */
160 int initialized;
161
162 /* A vector of pieces.
163
164 Each time DW_OP_piece is executed, we add a new element to the
165 end of this array, recording the current top of the stack, the
166 current location, and the size given as the operand to
167 DW_OP_piece. We then pop the top value from the stack, reset the
168 location, and resume evaluation.
169
170 The Dwarf spec doesn't say whether DW_OP_piece pops the top value
171 from the stack. We do, ensuring that clients of this interface
172 expecting to see a value left on the top of the stack (say, code
173 evaluating frame base expressions or CFA's specified with
174 DW_CFA_def_cfa_expression) will get an error if the expression
175 actually marks all the values it computes as pieces.
176
177 If an expression never uses DW_OP_piece, num_pieces will be zero.
178 (It would be nice to present these cases as expressions yielding
179 a single piece, so that callers need not distinguish between the
180 no-DW_OP_piece and one-DW_OP_piece cases. But expressions with
181 no DW_OP_piece operations have no value to place in a piece's
182 'size' field; the size comes from the surrounding data. So the
183 two cases need to be handled separately.) */
184 std::vector<dwarf_expr_piece> pieces;
185
186 /* We evaluate the expression in the context of this objfile. */
187 dwarf2_per_objfile *per_objfile;
188
189 /* Return the value of register number REGNUM (a DWARF register number),
190 read as an address. */
191 virtual CORE_ADDR read_addr_from_reg (int regnum) = 0;
192
193 /* Return a value of type TYPE, stored in register number REGNUM
194 of the frame associated to the given BATON.
195
196 REGNUM is a DWARF register number. */
197 virtual struct value *get_reg_value (struct type *type, int regnum) = 0;
198
199 /* Read LENGTH bytes at ADDR into BUF. */
200 virtual void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length) = 0;
201
202 /* Return the location expression for the frame base attribute, in
203 START and LENGTH. The result must be live until the current
204 expression evaluation is complete. */
205 virtual void get_frame_base (const gdb_byte **start, size_t *length) = 0;
206
207 /* Return the CFA for the frame. */
208 virtual CORE_ADDR get_frame_cfa () = 0;
209
210 /* Return the PC for the frame. */
get_frame_pcdwarf_expr_context211 virtual CORE_ADDR get_frame_pc ()
212 {
213 error (_("%s is invalid in this context"), "DW_OP_implicit_pointer");
214 }
215
216 /* Return the thread-local storage address for
217 DW_OP_GNU_push_tls_address or DW_OP_form_tls_address. */
218 virtual CORE_ADDR get_tls_address (CORE_ADDR offset) = 0;
219
220 /* Execute DW_AT_location expression for the DWARF expression
221 subroutine in the DIE at DIE_CU_OFF in the CU. Do not touch
222 STACK while it being passed to and returned from the called DWARF
223 subroutine. */
224 virtual void dwarf_call (cu_offset die_cu_off) = 0;
225
226 /* Execute "variable value" operation on the DIE at SECT_OFF. */
227 virtual struct value *dwarf_variable_value (sect_offset sect_off) = 0;
228
229 /* Return the base type given by the indicated DIE at DIE_CU_OFF.
230 This can throw an exception if the DIE is invalid or does not
231 represent a base type. SIZE is non-zero if this function should
232 verify that the resulting type has the correct size. */
get_base_typedwarf_expr_context233 virtual struct type *get_base_type (cu_offset die_cu_off, int size)
234 {
235 /* Anything will do. */
236 return builtin_type (this->gdbarch)->builtin_int;
237 }
238
239 /* Push on DWARF stack an entry evaluated for DW_TAG_call_site's
240 parameter matching KIND and KIND_U at the caller of specified BATON.
241 If DEREF_SIZE is not -1 then use DW_AT_call_data_value instead of
242 DW_AT_call_value. */
243 virtual void push_dwarf_reg_entry_value (enum call_site_parameter_kind kind,
244 union call_site_parameter_u kind_u,
245 int deref_size) = 0;
246
247 /* Return the address indexed by DW_OP_addrx or DW_OP_GNU_addr_index.
248 This can throw an exception if the index is out of range. */
249 virtual CORE_ADDR get_addr_index (unsigned int index) = 0;
250
251 /* Return the `object address' for DW_OP_push_object_address. */
252 virtual CORE_ADDR get_object_address () = 0;
253
254 private:
255
256 struct type *address_type () const;
257 void push (struct value *value, bool in_stack_memory);
258 bool stack_empty_p () const;
259 void add_piece (ULONGEST size, ULONGEST offset);
260 void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
261 void pop ();
262 };
263
264 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
265 const char *);
266
267 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
268
269 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
270 const gdb_byte *buf_end,
271 CORE_ADDR *deref_size_return);
272
273 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
274 CORE_ADDR *fb_offset_return);
275
276 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
277 const gdb_byte *buf_end,
278 CORE_ADDR *sp_offset_return);
279
280 /* Wrappers around the leb128 reader routines to simplify them for our
281 purposes. */
282
283 static inline const gdb_byte *
gdb_read_uleb128(const gdb_byte * buf,const gdb_byte * buf_end,uint64_t * r)284 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
285 uint64_t *r)
286 {
287 size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
288
289 if (bytes_read == 0)
290 return NULL;
291 return buf + bytes_read;
292 }
293
294 static inline const gdb_byte *
gdb_read_sleb128(const gdb_byte * buf,const gdb_byte * buf_end,int64_t * r)295 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
296 int64_t *r)
297 {
298 size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
299
300 if (bytes_read == 0)
301 return NULL;
302 return buf + bytes_read;
303 }
304
305 static inline const gdb_byte *
gdb_skip_leb128(const gdb_byte * buf,const gdb_byte * buf_end)306 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
307 {
308 size_t bytes_read = skip_leb128 (buf, buf_end);
309
310 if (bytes_read == 0)
311 return NULL;
312 return buf + bytes_read;
313 }
314
315 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
316 const gdb_byte *buf_end,
317 uint64_t *r);
318
319 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
320 const gdb_byte *buf_end,
321 int64_t *r);
322
323 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
324 const gdb_byte *buf_end);
325
326 #endif /* dwarf2expr.h */
327