drgn/libdrgn/dwarf_info.h

// Copyright (c) Facebook, Inc. and its affiliates.
// SPDX-License-Identifier: GPL-3.0-or-later

/**
 * @file
 *
 * DWARF and .eh_frame support.
 *
 * See @ref DebugInfo.
 */

#ifndef DRGN_DEBUG_INFO_DWARF_H
#define DRGN_DEBUG_INFO_DWARF_H

/**
 * @ingroup DebugInfo
 *
 * @{
 */

#include <elfutils/libdw.h>

#include "cfi.h"
#include "drgn.h"
#include "dwarf_index.h"
#include "hash_table.h"

struct drgn_debug_info;
struct drgn_debug_info_module;
struct drgn_register_state;

/** DWARF Frame Description Entry. */
struct drgn_dwarf_fde {
	uint64_t initial_location;
	uint64_t address_range;
	/* CIE for this FDE as an index into drgn_debug_info_module::cies. */
	size_t cie;
	const char *instructions;
	size_t instructions_size;
};

/** DWARF debugging information for a @ref drgn_debug_info_module. */
struct drgn_dwarf_module_info {
	/** Base for `DW_EH_PE_pcrel`. */
	uint64_t pcrel_base;
	/** Base for `DW_EH_PE_textrel`. */
	uint64_t textrel_base;
	/** Base for `DW_EH_PE_datarel`. */
	uint64_t datarel_base;
	/** Array of DWARF Common Information Entries. */
	struct drgn_dwarf_cie *cies;
	/**
	 * Array of DWARF Frame Description Entries sorted by initial_location.
	 */
	struct drgn_dwarf_fde *fdes;
	/** Number of elements in @ref drgn_debug_info_module::fdes. */
	size_t num_fdes;
};

void drgn_dwarf_module_info_deinit(struct drgn_debug_info_module *module);

/** Cached type in a @ref drgn_debug_info. */
struct drgn_dwarf_type {
	struct drgn_type *type;
	enum drgn_qualifiers qualifiers;
	/**
	 * Whether this is an incomplete array type or a typedef of one.
	 *
	 * This is used to work around a GCC bug; see @ref
	 * drgn_type_from_dwarf_internal().
	 */
	bool is_incomplete_array;
};

DEFINE_HASH_MAP_TYPE(drgn_dwarf_type_map, const void *, struct drgn_dwarf_type)

/** DWARF debugging information for a program/@ref drgn_debug_info. */
struct drgn_dwarf_info {
	/** Index of DWARF debugging information. */
	struct drgn_dwarf_index index;

	/**
	 * Cache of parsed types.
	 *
	 * The key is the address of the DIE (@c Dwarf_Die::addr). The value is
	 * a @ref drgn_dwarf_type.
	 */
	struct drgn_dwarf_type_map types;
	/**
	 * Cache of parsed types which appear to be incomplete array types but
	 * can't be.
	 *
	 * See @ref drgn_type_from_dwarf_internal().
	 */
	struct drgn_dwarf_type_map cant_be_incomplete_array_types;

	/** Current parsing recursion depth. */
	int depth;
};

void drgn_dwarf_info_init(struct drgn_debug_info *dbinfo);
void drgn_dwarf_info_deinit(struct drgn_debug_info *dbinfo);

/**
 * Find the DWARF DIEs in a @ref drgn_debug_info_module for the scope containing
 * a given program counter.
 *
 * @param[in] module Module containing @p pc.
 * @param[in] pc Program counter.
 * @param[out] bias_ret Returned difference between addresses in the loaded
 * module and addresses in the returned DIEs.
 * @param[out] dies_ret Returned DIEs. `(*dies_ret)[*length_ret - 1]` is the
 * innermost DIE containing @p pc, `(*dies_ret)[*length_ret - 2]` is its parent
 * (which may not contain @p pc itself), `(*dies_ret)[*length_ret - 3]` is its
 * grandparent, etc. Must be freed with @c free().
 * @param[out] length_ret Returned length of @p dies_ret.
 */
struct drgn_error *
drgn_debug_info_module_find_dwarf_scopes(struct drgn_debug_info_module *module,
					 uint64_t pc, uint64_t *bias_ret,
					 Dwarf_Die **dies_ret,
					 size_t *length_ret)
	__attribute__((__nonnull__(1, 3, 4, 5)));

/**
 * Find the ancestors of a DWARF DIE.
 *
 * This finds the parent, grandparent, etc., of a DWARF DIE in the tree of DIEs.
 *
 * @param[in] module Module containing @p die.
 * @param[in] die DIE to find.
 * @param[out] dies_ret Returned DIEs. `(*dies_ret)[*length_ret]` is the DIE,
 * `(*dies_ret)[*length_ret - 1]` is its parent, `(*dies_ret)[*length_ret - 2]`
 * is its grandparent, etc., and `(*dies_ret)[0]` is the top-level unit DIE.
 * @param[out] length_ret Returned number of ancestors in @p dies_ret.
 */
struct drgn_error *drgn_find_die_ancestors(Dwarf_Die *die, Dwarf_Die **dies_ret,
					  size_t *length_ret)
	__attribute__((__nonnull__(2, 3)));

/**
 * Find an object DIE in an array of DWARF scopes.
 *
 * @param[in] scopes Array of scopes, from outermost to innermost.
 * @param[in] num_scopes Number of scopes in @p scopes.
 * @param[out] die_ret Returned object DIE.
 * @param[out] type_ret If @p die_ret is a `DW_TAG_enumerator` DIE, its parent.
 * Otherwise, undefined.
 */
struct drgn_error *drgn_find_in_dwarf_scopes(Dwarf_Die *scopes,
					     size_t num_scopes,
					     const char *name,
					     Dwarf_Die *die_ret,
					     Dwarf_Die *type_ret);

/**
 * Create a @ref drgn_object from a `Dwarf_Die`.
 *
 * @param[in] die Object DIE (e.g., `DW_TAG_subprogram`, `DW_TAG_variable`,
 * `DW_TAG_formal_parameter`, `DW_TAG_enumerator`,
 * `DW_TAG_template_value_parameter`).
 * @param[in] type_die DIE of object's type. If @c NULL, use the `DW_AT_type`
 * attribute of @p die. If @p die is a `DW_TAG_enumerator` DIE, this should be
 * its parent.
 * @param[in] function_die DIE of current function. @c NULL if not in function
 * context.
 * @param[in] regs Registers of current stack frame. @c NULL if not in stack
 * frame context.
 * @param[out] ret Returned object.
 */
struct drgn_error *
drgn_object_from_dwarf(struct drgn_debug_info *dbinfo,
		       struct drgn_debug_info_module *module,
		       Dwarf_Die *die, Dwarf_Die *type_die,
		       Dwarf_Die *function_die,
		       const struct drgn_register_state *regs,
		       struct drgn_object *ret);

struct drgn_error *
drgn_debug_info_find_dwarf_cfi(struct drgn_debug_info_module *module,
			       uint64_t unbiased_pc,
			       struct drgn_cfi_row **row_ret,
			       bool *interrupted_ret,
			       drgn_register_number *ret_addr_regno_ret);

struct drgn_error *
drgn_eval_cfi_dwarf_expression(struct drgn_program *prog,
			       const struct drgn_cfi_rule *rule,
			       const struct drgn_register_state *regs,
			       void *buf, size_t size);

/** @} */

#endif /* DRGN_DEBUG_INFO_DWARF_H */