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Change DWARF stack to use new dwarf_entry classes

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To replace existing DWARF stack element (dwarf_stack_value) with
dwarf_entry class based objects, a support for conversion between
struct value and the new classes is needed. The reason for this is
that dwarf_entry based classes are not designed to be visible outside
the expr.c file. This makes the DWARF expression evaluator more self
contained. This can be beneficial if there is ever a need to have a
DWARF support in gdbserver.

Once the conversion support is added, the current DWARF stack element
can easily be swapped out.

gdb/ChangeLog:

	* dwarf2/expr.c (dwarf_value_equal_op): New function.
	(dwarf_value_less_op): New function.
	(struct piece_closure): Change to use dwarf_entry based
	classes.
	(allocate_piece_closure): Change to use dwarf_entry based
	classes.
	(rw_pieced_value): Change to use dwarf_entry based classes.
	(check_pieced_synthetic_pointer): Change to use dwarf_entry
	based classes.
	(check_synthetic_pointer_location): New function.
	(indirect_pieced_value): Change to use dwarf_entry based
	classes.
	(indirect_from_location): New function.
	(coerce_pieced_ref): Change to use dwarf_entry based classes.
	(free_pieced_value_closure): Change to use dwarf_entry based
	classes.
	(dwarf_expr_context::~dwarf_expr_context): Instantiate
	dwarf_entry_factory object.
	(dwarf_expr_context::push): Change to use dwarf_entry based
	classes.
	(dwarf_expr_context::push_address): Change to use dwarf_entry
	based classes.
	(dwarf_expr_context::fetch): Change to use dwarf_entry based
	classes.
	(dwarf_expr_context::read_mem): Remove method.
	(dwarf_expr_context::fetch_result): Change to use dwarf_entry
	based classes.
	(dwarf_expr_context::dwarf_entry_deref): New method.
	(dwarf_expr_context::gdb_value_to_dwarf_entry): New method.
	(dwarf_expr_context::dwarf_entry_to_gdb_value): New method.
	(dwarf_expr_context::fetch_address): Change to use dwarf_entry
	based classes.
	(dwarf_expr_context::fetch_in_stack_memory): Change to use
	dwarf_entry based classes.
	(dwarf_expr_context::add_piece): Change to use dwarf_entry based
	classes.
	(dwarf_expr_context::execute_stack_op): Change to use dwarf_entry
	based classes.
	* dwarf2/expr.h (class dwarf_entry): New declaration.
	(class dwarf_entry_factory): New declaration.
	(enum dwarf_value_location): Remove enumeration.
	(struct dwarf_expr_piece): Remove structure.
	(struct dwarf_stack_value): Remove structure.
	(struct dwarf_expr_context): Change to use dwarf_entry based
	classes. Add dwarf_entry_factory object.

Change-Id: I828c9b087c8ab3f57d9b208b360bcf5688810586
This commit is contained in:
Zoran Zaric
2020-12-07 19:00:22 +00:00
committed by Simon Marchi
parent 7200429a72
commit bedecfcbea
2 changed files with 909 additions and 1009 deletions
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1691
gdb/dwarf2/expr.c
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227
gdb/dwarf2/expr.h
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@@ -25,109 +25,28 @@
#include "leb128.h"
#include "gdbtypes.h"
class dwarf_entry;
class dwarf_entry_factory;
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
{
/* We should ever only pass in the PER_OBJFILE, while the ADDR_SIZE
/* Create a new context for the expression evaluator.
We should ever only pass in the PER_OBJFILE and the ADDR_SIZE
information should be retrievable from there. The PER_OBJFILE
contains a pointer to the PER_BFD information anyway and the
address size information must be the same for the whole BFD. */
dwarf_expr_context (struct dwarf2_per_objfile *per_objfile,
int addr_size);
virtual ~dwarf_expr_context () = default;
void push_address (CORE_ADDR value, bool in_stack_memory);
/* Destroy dwarf entry factory object. */
virtual ~dwarf_expr_context ();
/* Push ADDR onto the stack. */
void push_address (CORE_ADDR addr, bool in_stack_memory);
/* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU
FRAME context. AS_LVAL defines if the returned struct value is
@@ -146,7 +65,7 @@ struct dwarf_expr_context
private:
/* The stack of values. */
std::vector<dwarf_stack_value> stack;
std::vector<dwarf_entry *> stack;
/* Target architecture to use for address operations. */
struct gdbarch *gdbarch;
@@ -154,8 +73,9 @@ private:
/* Target address size in bytes. */
int addr_size;
/* DW_FORM_ref_addr size in bytes. If -1 DWARF is executed from a frame
context and operations depending on DW_FORM_ref_addr are not allowed. */
/* DW_FORM_ref_addr size in bytes. If -1 DWARF is executed
from a frame context and operations depending on DW_FORM_ref_addr
are not allowed. */
int ref_addr_size;
/* The current depth of dwarf expression recursion, via DW_OP_call*,
@@ -163,43 +83,6 @@ private:
depth we'll tolerate before raising an error. */
int recursion_depth, max_recursion_depth;
/* Location of the value. */
enum dwarf_value_location location;
/* 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 len;
const gdb_byte *data;
/* Initialization status of variable: Non-zero if variable has been
initialized; zero otherwise. */
int initialized;
/* 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> pieces;
/* We evaluate the expression in the context of this objfile. */
dwarf2_per_objfile *per_objfile;
@@ -212,16 +95,40 @@ private:
/* Property address info used for the evaluation. */
const struct property_addr_info *addr_info;
/* Factory in charge of the dwarf entry's life cycle. */
dwarf_entry_factory *entry_factory;
/* Evaluate the expression at ADDR (LEN bytes long). */
void eval (const gdb_byte *addr, size_t len);
/* Return the type used for DWARF operations where the type is
unspecified in the DWARF spec. Only certain sizes are
supported. */
struct type *address_type () const;
void push (struct value *value, bool in_stack_memory);
/* Push ENTRY onto the stack. */
void push (dwarf_entry *value);
/* Return true if the expression stack is empty. */
bool stack_empty_p () const;
void add_piece (ULONGEST size, ULONGEST offset);
/* Pop a top element of the stack and add as a composite piece.
If the fallowing top element of the stack is a composite
location description, the piece will be added to it. Otherwise
a new composite location description will be created and
the piece will be added to that composite. */
dwarf_entry *add_piece (ULONGEST bit_size, ULONGEST bit_offset);
/* The engine for the expression evaluator. Using the context in this
object, evaluate the expression between OP_PTR and OP_END. */
void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
/* Pop the top item off of the stack. */
void pop ();
struct value *fetch (int n);
CORE_ADDR fetch_address (int n);
bool fetch_in_stack_memory (int n);
/* Retrieve the N'th item on the stack. */
dwarf_entry *fetch (int n);
/* Fetch the result of the expression evaluation in a form of
a struct value, where TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET
@@ -251,13 +158,36 @@ private:
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. */
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 (enum call_site_parameter_kind kind,
union call_site_parameter_u kind_u,
int deref_size);
void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length);
/* Apply dereference operation on the DWARF ENTRY. In the case of a
value entry, the entry will be implicitly converted to the
appropriate location description before the operation is applied.
If the SIZE is specified, it must be equal or smaller then the
TYPE type size. If SIZE is smaller then the type size, the value
will be zero extended to the difference. */
dwarf_entry* dwarf_entry_deref (dwarf_entry *entry, struct type *type,
size_t size = 0);
/* Convert struct value to the matching DWARF entry representation.
Used for non-standard DW_OP_GNU_variable_value operation
support. */
dwarf_entry *gdb_value_to_dwarf_entry (struct value *value);
/* Convert DWARF entry to the matching struct value representation
of the given TYPE type. SUBOBJ_TYPE information if specified, will
be used for more precise description of the source variable type
information. Where SUBOBJ_OFFSET defines an offset into the DWARF
entry contents. */
struct value *dwarf_entry_to_gdb_value (dwarf_entry *entry,
struct type *type,
struct type *subobj_type = nullptr,
LONGEST subobj_offset = 0);
};
/* Return the address type used of the GDBARCH architecture and
@@ -268,18 +198,32 @@ struct type *address_type (struct gdbarch *gdbarch, int addr_size);
read as an address in a given FRAME. */
CORE_ADDR read_addr_from_reg (struct frame_info *, int);
/* Check that the current operator is either at the end of an
expression, or that it is followed by a composition operator or by
DW_OP_GNU_uninit (which should terminate the expression). */
void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
const char *);
/* If <BUF..BUF_END] contains DW_FORM_block* with single DW_OP_reg* return the
DWARF register number. Otherwise return -1. */
int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
/* If <BUF..BUF_END] contains DW_FORM_block* with just DW_OP_breg*(0) and
DW_OP_deref* return the DWARF register number. Otherwise return -1.
DEREF_SIZE_RETURN contains -1 for DW_OP_deref; otherwise it contains the
size from DW_OP_deref_size. */
int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
const gdb_byte *buf_end,
CORE_ADDR *deref_size_return);
/* If <BUF..BUF_END] contains DW_FORM_block* with single DW_OP_fbreg(X) fill
in FB_OFFSET_RETURN with the X offset and return 1. Otherwise return 0. */
int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
CORE_ADDR *fb_offset_return);
/* If <BUF..BUF_END] contains DW_FORM_block* with single DW_OP_bregSP(X) fill
in SP_OFFSET_RETURN with the X offset and return 1. Otherwise return 0.
The matched SP register number depends on GDBARCH. */
int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
const gdb_byte *buf_end,
CORE_ADDR *sp_offset_return);
@@ -319,14 +263,17 @@ gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
return buf + bytes_read;
}
/* Helper to read a uleb128 value or throw an error. */
extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
const gdb_byte *buf_end,
uint64_t *r);
/* Helper to read a sleb128 value or throw an error. */
extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
const gdb_byte *buf_end,
int64_t *r);
/* Helper to skip a leb128 value or throw an error. */
extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
const gdb_byte *buf_end);