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- /* DWARF 2 Expression Evaluator.
- Copyright (C) 2001-2022 Free Software Foundation, Inc.
- Contributed by Daniel Berlin <dan@dberlin.org>.
- This file is part of GDB.
- This program is free software; you can redistribute it and/or modify
- it under the terms of the GNU General Public License as published by
- the Free Software Foundation; either version 3 of the License, or
- (at your option) any later version.
- This program is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- GNU General Public License for more details.
- You should have received a copy of the GNU General Public License
- along with this program. If not, see <http://www.gnu.org/licenses/>. */
- #if !defined (DWARF2EXPR_H)
- #define DWARF2EXPR_H
- #include "leb128.h"
- #include "gdbtypes.h"
- struct dwarf2_per_objfile;
- /* The location of a value. */
- enum dwarf_value_location
- {
- /* The piece is in memory.
- The value on the dwarf stack is its address. */
- DWARF_VALUE_MEMORY,
- /* The piece is in a register.
- The value on the dwarf stack is the register number. */
- DWARF_VALUE_REGISTER,
- /* The piece is on the dwarf stack. */
- DWARF_VALUE_STACK,
- /* The piece is a literal. */
- DWARF_VALUE_LITERAL,
- /* The piece was optimized out. */
- DWARF_VALUE_OPTIMIZED_OUT,
- /* The piece is an implicit pointer. */
- DWARF_VALUE_IMPLICIT_POINTER
- };
- /* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece. */
- struct dwarf_expr_piece
- {
- enum dwarf_value_location location;
- union
- {
- struct
- {
- /* This piece's address, for DWARF_VALUE_MEMORY pieces. */
- CORE_ADDR addr;
- /* Non-zero if the piece is known to be in memory and on
- the program's stack. */
- bool in_stack_memory;
- } mem;
- /* The piece's register number, for DWARF_VALUE_REGISTER pieces. */
- int regno;
- /* The piece's literal value, for DWARF_VALUE_STACK pieces. */
- struct value *value;
- struct
- {
- /* A pointer to the data making up this piece,
- for DWARF_VALUE_LITERAL pieces. */
- const gdb_byte *data;
- /* The length of the available data. */
- ULONGEST length;
- } literal;
- /* Used for DWARF_VALUE_IMPLICIT_POINTER. */
- struct
- {
- /* The referent DIE from DW_OP_implicit_pointer. */
- sect_offset die_sect_off;
- /* The byte offset into the resulting data. */
- LONGEST offset;
- } ptr;
- } v;
- /* The length of the piece, in bits. */
- ULONGEST size;
- /* The piece offset, in bits. */
- ULONGEST offset;
- };
- /* The dwarf expression stack. */
- struct dwarf_stack_value
- {
- dwarf_stack_value (struct value *value_, int in_stack_memory_)
- : value (value_), in_stack_memory (in_stack_memory_)
- {}
- struct value *value;
- /* True if the piece is in memory and is known to be on the program's stack.
- It is always ok to set this to zero. This is used, for example, to
- optimize memory access from the target. It can vastly speed up backtraces
- on long latency connections when "set stack-cache on". */
- bool in_stack_memory;
- };
- /* The expression evaluator works with a dwarf_expr_context, describing
- its current state and its callbacks. */
- struct dwarf_expr_context
- {
- dwarf_expr_context (dwarf2_per_objfile *per_objfile,
- int addr_size);
- virtual ~dwarf_expr_context () = default;
- void push_address (CORE_ADDR value, bool in_stack_memory);
- /* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU
- and FRAME context.
- AS_LVAL defines if the returned struct value is expected to be a
- value (false) or a location description (true).
- TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET describe the expected struct
- value representation of the evaluation result.
- The ADDR_INFO property can be specified to override the range of
- memory addresses with the passed in buffer. */
- value *evaluate (const gdb_byte *addr, size_t len, bool as_lval,
- dwarf2_per_cu_data *per_cu, frame_info *frame,
- const struct property_addr_info *addr_info = nullptr,
- struct type *type = nullptr,
- struct type *subobj_type = nullptr,
- LONGEST subobj_offset = 0);
- private:
- /* The stack of values. */
- std::vector<dwarf_stack_value> m_stack;
- /* Target address size in bytes. */
- int m_addr_size = 0;
- /* The current depth of dwarf expression recursion, via DW_OP_call*,
- DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
- depth we'll tolerate before raising an error. */
- int m_recursion_depth = 0, m_max_recursion_depth = 0x100;
- /* Location of the value. */
- dwarf_value_location m_location = DWARF_VALUE_MEMORY;
- /* For DWARF_VALUE_LITERAL, the current literal value's length and
- data. For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
- target DIE of sect_offset kind. */
- ULONGEST m_len = 0;
- const gdb_byte *m_data = nullptr;
- /* Initialization status of variable: Non-zero if variable has been
- initialized; zero otherwise. */
- int m_initialized = 0;
- /* A vector of pieces.
- Each time DW_OP_piece is executed, we add a new element to the
- end of this array, recording the current top of the stack, the
- current location, and the size given as the operand to
- DW_OP_piece. We then pop the top value from the stack, reset the
- location, and resume evaluation.
- The Dwarf spec doesn't say whether DW_OP_piece pops the top value
- from the stack. We do, ensuring that clients of this interface
- expecting to see a value left on the top of the stack (say, code
- evaluating frame base expressions or CFA's specified with
- DW_CFA_def_cfa_expression) will get an error if the expression
- actually marks all the values it computes as pieces.
- If an expression never uses DW_OP_piece, num_pieces will be zero.
- (It would be nice to present these cases as expressions yielding
- a single piece, so that callers need not distinguish between the
- no-DW_OP_piece and one-DW_OP_piece cases. But expressions with
- no DW_OP_piece operations have no value to place in a piece's
- 'size' field; the size comes from the surrounding data. So the
- two cases need to be handled separately.) */
- std::vector<dwarf_expr_piece> m_pieces;
- /* We evaluate the expression in the context of this objfile. */
- dwarf2_per_objfile *m_per_objfile;
- /* Frame information used for the evaluation. */
- frame_info *m_frame = nullptr;
- /* Compilation unit used for the evaluation. */
- dwarf2_per_cu_data *m_per_cu = nullptr;
- /* Property address info used for the evaluation. */
- const struct property_addr_info *m_addr_info = nullptr;
- void eval (const gdb_byte *addr, size_t len);
- struct type *address_type () const;
- void push (struct value *value, bool in_stack_memory);
- bool stack_empty_p () const;
- void add_piece (ULONGEST size, ULONGEST offset);
- void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
- void pop ();
- struct value *fetch (int n);
- CORE_ADDR fetch_address (int n);
- bool fetch_in_stack_memory (int n);
- /* Fetch the result of the expression evaluation in a form of
- a struct value, where TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET
- describe the source level representation of that result.
- AS_LVAL defines if the fetched struct value is expected to
- be a value or a location description. */
- value *fetch_result (struct type *type, struct type *subobj_type,
- LONGEST subobj_offset, bool as_lval);
- /* Return the location expression for the frame base attribute, in
- START and LENGTH. The result must be live until the current
- expression evaluation is complete. */
- void get_frame_base (const gdb_byte **start, size_t *length);
- /* Return the base type given by the indicated DIE at DIE_CU_OFF.
- This can throw an exception if the DIE is invalid or does not
- represent a base type. */
- struct type *get_base_type (cu_offset die_cu_off);
- /* Execute DW_AT_location expression for the DWARF expression
- subroutine in the DIE at DIE_CU_OFF in the CU. Do not touch
- STACK while it being passed to and returned from the called DWARF
- subroutine. */
- void dwarf_call (cu_offset die_cu_off);
- /* Push on DWARF stack an entry evaluated for DW_TAG_call_site's
- parameter matching KIND and KIND_U at the caller of specified BATON.
- If DEREF_SIZE is not -1 then use DW_AT_call_data_value instead of
- DW_AT_call_value. */
- void push_dwarf_reg_entry_value (call_site_parameter_kind kind,
- call_site_parameter_u kind_u,
- int deref_size);
- /* Read LENGTH bytes at ADDR into BUF. This method also handles the
- case where a caller of the evaluator passes in some data,
- but with the address being 0. In this situation, we arrange for
- memory reads to come from the passed-in buffer. */
- void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length);
- };
- /* Return the value of register number REG (a DWARF register number),
- read as an address in a given FRAME. */
- CORE_ADDR read_addr_from_reg (frame_info *frame, int reg);
- void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
- const char *);
- int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
- int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
- const gdb_byte *buf_end,
- CORE_ADDR *deref_size_return);
- int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
- CORE_ADDR *fb_offset_return);
- int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
- const gdb_byte *buf_end,
- CORE_ADDR *sp_offset_return);
- /* Wrappers around the leb128 reader routines to simplify them for our
- purposes. */
- static inline const gdb_byte *
- gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
- uint64_t *r)
- {
- size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
- if (bytes_read == 0)
- return NULL;
- return buf + bytes_read;
- }
- static inline const gdb_byte *
- gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
- int64_t *r)
- {
- size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
- if (bytes_read == 0)
- return NULL;
- return buf + bytes_read;
- }
- static inline const gdb_byte *
- gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
- {
- size_t bytes_read = skip_leb128 (buf, buf_end);
- if (bytes_read == 0)
- return NULL;
- return buf + bytes_read;
- }
- extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
- const gdb_byte *buf_end,
- uint64_t *r);
- extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
- const gdb_byte *buf_end,
- int64_t *r);
- extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
- const gdb_byte *buf_end);
- #endif /* DWARF2EXPR_H */
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