1 /* DWARF 2 Expression Evaluator.
3 Copyright (C) 2001-2016 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 /* The location of a value. */
29 enum dwarf_value_location
31 /* The piece is in memory.
32 The value on the dwarf stack is its address. */
35 /* The piece is in a register.
36 The value on the dwarf stack is the register number. */
39 /* The piece is on the dwarf stack. */
42 /* The piece is a literal. */
45 /* The piece was optimized out. */
46 DWARF_VALUE_OPTIMIZED_OUT,
48 /* The piece is an implicit pointer. */
49 DWARF_VALUE_IMPLICIT_POINTER
52 /* The dwarf expression stack. */
54 struct dwarf_stack_value
58 /* Non-zero if the piece is in memory and is known to be
59 on the program's stack. It is always ok to set this to zero.
60 This is used, for example, to optimize memory access from the target.
61 It can vastly speed up backtraces on long latency connections when
62 "set stack-cache on". */
66 /* The expression evaluator works with a dwarf_expr_context, describing
67 its current state and its callbacks. */
68 struct dwarf_expr_context
70 dwarf_expr_context ();
71 virtual ~dwarf_expr_context ();
73 void push_address (CORE_ADDR value, int in_stack_memory);
74 void eval (const gdb_byte *addr, size_t len);
75 struct value *fetch (int n);
76 CORE_ADDR fetch_address (int n);
77 int fetch_in_stack_memory (int n);
79 /* The stack of values, allocated with xmalloc. */
80 struct dwarf_stack_value *stack;
82 /* The number of values currently pushed on the stack, and the
83 number of elements allocated to the stack. */
84 int stack_len, stack_allocated;
86 /* Target architecture to use for address operations. */
87 struct gdbarch *gdbarch;
89 /* Target address size in bytes. */
92 /* DW_FORM_ref_addr size in bytes. If -1 DWARF is executed from a frame
93 context and operations depending on DW_FORM_ref_addr are not allowed. */
96 /* Offset used to relocate DW_OP_addr and DW_OP_GNU_addr_index arguments. */
99 /* The current depth of dwarf expression recursion, via DW_OP_call*,
100 DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
101 depth we'll tolerate before raising an error. */
102 int recursion_depth, max_recursion_depth;
104 /* Location of the value. */
105 enum dwarf_value_location location;
107 /* For DWARF_VALUE_LITERAL, the current literal value's length and
108 data. For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
109 target DIE of sect_offset kind. */
111 const gdb_byte *data;
113 /* Initialization status of variable: Non-zero if variable has been
114 initialized; zero otherwise. */
117 /* An array of pieces. PIECES points to its first element;
118 NUM_PIECES is its length.
120 Each time DW_OP_piece is executed, we add a new element to the
121 end of this array, recording the current top of the stack, the
122 current location, and the size given as the operand to
123 DW_OP_piece. We then pop the top value from the stack, reset the
124 location, and resume evaluation.
126 The Dwarf spec doesn't say whether DW_OP_piece pops the top value
127 from the stack. We do, ensuring that clients of this interface
128 expecting to see a value left on the top of the stack (say, code
129 evaluating frame base expressions or CFA's specified with
130 DW_CFA_def_cfa_expression) will get an error if the expression
131 actually marks all the values it computes as pieces.
133 If an expression never uses DW_OP_piece, num_pieces will be zero.
134 (It would be nice to present these cases as expressions yielding
135 a single piece, so that callers need not distinguish between the
136 no-DW_OP_piece and one-DW_OP_piece cases. But expressions with
137 no DW_OP_piece operations have no value to place in a piece's
138 'size' field; the size comes from the surrounding data. So the
139 two cases need to be handled separately.) */
141 struct dwarf_expr_piece *pieces;
143 /* Return the value of register number REGNUM (a DWARF register number),
144 read as an address. */
145 virtual CORE_ADDR read_addr_from_reg (int regnum) = 0;
147 /* Return a value of type TYPE, stored in register number REGNUM
148 of the frame associated to the given BATON.
150 REGNUM is a DWARF register number. */
151 virtual struct value *get_reg_value (struct type *type, int regnum) = 0;
153 /* Read LENGTH bytes at ADDR into BUF. */
154 virtual void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length) = 0;
156 /* Return the location expression for the frame base attribute, in
157 START and LENGTH. The result must be live until the current
158 expression evaluation is complete. */
159 virtual void get_frame_base (const gdb_byte **start, size_t *length) = 0;
161 /* Return the CFA for the frame. */
162 virtual CORE_ADDR get_frame_cfa () = 0;
164 /* Return the PC for the frame. */
165 virtual CORE_ADDR get_frame_pc ()
167 error (_("%s is invalid in this context"), "DW_OP_GNU_implicit_pointer");
170 /* Return the thread-local storage address for
171 DW_OP_GNU_push_tls_address or DW_OP_form_tls_address. */
172 virtual CORE_ADDR get_tls_address (CORE_ADDR offset) = 0;
174 /* Execute DW_AT_location expression for the DWARF expression
175 subroutine in the DIE at DIE_OFFSET in the CU. Do not touch
176 STACK while it being passed to and returned from the called DWARF
178 virtual void dwarf_call (cu_offset die_offset) = 0;
180 /* Return the base type given by the indicated DIE. This can throw
181 an exception if the DIE is invalid or does not represent a base
182 type. If can also be NULL in the special case where the
183 callbacks are not performing evaluation, and thus it is
184 meaningful to substitute a stub type of the correct size. */
185 virtual struct type *impl_get_base_type (cu_offset die)
187 /* Anything will do. */
188 return builtin_type (this->gdbarch)->builtin_int;
191 /* Push on DWARF stack an entry evaluated for DW_TAG_GNU_call_site's
192 parameter matching KIND and KIND_U at the caller of specified BATON.
193 If DEREF_SIZE is not -1 then use DW_AT_GNU_call_site_data_value instead of
194 DW_AT_GNU_call_site_value. */
195 virtual void push_dwarf_reg_entry_value (enum call_site_parameter_kind kind,
196 union call_site_parameter_u kind_u,
199 /* Return the address indexed by DW_OP_GNU_addr_index.
200 This can throw an exception if the index is out of range. */
201 virtual CORE_ADDR get_addr_index (unsigned int index) = 0;
203 /* Return the `object address' for DW_OP_push_object_address. */
204 virtual CORE_ADDR get_object_address () = 0;
208 struct type *address_type () const;
209 void grow_stack (size_t need);
210 void push (struct value *value, int in_stack_memory);
211 int stack_empty_p () const;
212 void add_piece (ULONGEST size, ULONGEST offset);
213 struct type *get_base_type (cu_offset die, int size);
214 void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
219 /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece. */
220 struct dwarf_expr_piece
222 enum dwarf_value_location location;
228 /* This piece's address, for DWARF_VALUE_MEMORY pieces. */
230 /* Non-zero if the piece is known to be in memory and on
231 the program's stack. */
235 /* The piece's register number, for DWARF_VALUE_REGISTER pieces. */
238 /* The piece's literal value, for DWARF_VALUE_STACK pieces. */
243 /* A pointer to the data making up this piece,
244 for DWARF_VALUE_LITERAL pieces. */
245 const gdb_byte *data;
246 /* The length of the available data. */
250 /* Used for DWARF_VALUE_IMPLICIT_POINTER. */
253 /* The referent DIE from DW_OP_GNU_implicit_pointer. */
255 /* The byte offset into the resulting data. */
260 /* The length of the piece, in bits. */
262 /* The piece offset, in bits. */
266 void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
269 int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
271 int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
272 const gdb_byte *buf_end,
273 CORE_ADDR *deref_size_return);
275 int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
276 CORE_ADDR *fb_offset_return);
278 int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
279 const gdb_byte *buf_end,
280 CORE_ADDR *sp_offset_return);
282 /* Wrappers around the leb128 reader routines to simplify them for our
285 static inline const gdb_byte *
286 gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
289 size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
293 return buf + bytes_read;
296 static inline const gdb_byte *
297 gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
300 size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
304 return buf + bytes_read;
307 static inline const gdb_byte *
308 gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
310 size_t bytes_read = skip_leb128 (buf, buf_end);
314 return buf + bytes_read;
317 extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
318 const gdb_byte *buf_end,
321 extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
322 const gdb_byte *buf_end,
325 extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
326 const gdb_byte *buf_end);
328 #endif /* dwarf2expr.h */