drgn/libdrgn/dwarf_info.h
Omar Sandoval f4af9b5b1d libdrgn: set default number of OpenMP threads without hyperthreads
In commit c4a122ead6 ("libdrgn: dwarf_info: scalably index all DIEs
per name"), I noted that indexing the Linux kernel was slower with 80
threads than with 8. After experimenting on multiple systems, I
determined that the slowdown was because of hyperthreading; limiting the
number of threads to the number of cores (not hyperthreads) was usually
faster, and never slower.

Unfortunately, OpenMP doesn't have a convenient way to express this, so
we have to parse sysfs and explicitly specify the number of threads
ourselves.

Compared to commit c4a122ead6 ("libdrgn: dwarf_info: scalably index
all DIEs per name"), this makes indexing the large C++ application half
a second faster, and the Linux kernel 70 ms faster, all while using less
resources.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2023-08-18 08:33:56 -07:00

364 lines
12 KiB
C

// Copyright (c) Meta Platforms, Inc. and affiliates.
// SPDX-License-Identifier: LGPL-2.1-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 "hash_table.h"
#include "vector.h"
struct drgn_debug_info;
struct drgn_elf_file;
struct drgn_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_dwarf_cfi::cies. */
size_t cie;
const char *instructions;
size_t instructions_size;
};
/** DWARF Call Frame Information. */
struct drgn_dwarf_cfi {
/** 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_dwarf_cfi::fdes. */
size_t num_fdes;
};
/** DWARF debugging information for a @ref drgn_module. */
struct drgn_module_dwarf_info {
/** Call Frame Information from .debug_frame. */
struct drgn_dwarf_cfi debug_frame;
/** Call Frame Information from .eh_frame. */
struct drgn_dwarf_cfi eh_frame;
/** 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;
};
void drgn_module_dwarf_info_deinit(struct drgn_module *module);
DEFINE_VECTOR_TYPE(drgn_dwarf_index_die_vector, uintptr_t,
vector_inline_minimal, uint32_t);
DEFINE_HASH_MAP_TYPE(drgn_dwarf_index_die_map, struct nstring,
struct drgn_dwarf_index_die_vector);
DEFINE_HASH_TABLE_TYPE(drgn_namespace_table,
struct drgn_namespace_dwarf_index *);
/* DWARF tags that act as namespaces. */
#define DRGN_DWARF_INDEX_NAMESPACE_TAGS \
X(structure_type) \
X(class_type) \
X(union_type) \
X(namespace)
/* DWARF tags that we index. */
#define DRGN_DWARF_INDEX_TAGS \
/* \
* These must be first for a few places where we only care about \
* namespace-like tags (e.g., drgn_namespace_dwarf_index::dies_indexed).\
*/ \
DRGN_DWARF_INDEX_NAMESPACE_TAGS \
X(enumeration_type) \
X(typedef) \
X(enumerator) \
X(subprogram) \
X(variable) \
X(base_type)
enum drgn_dwarf_index_tag {
#define X(name) DRGN_DWARF_INDEX_##name,
DRGN_DWARF_INDEX_TAGS
#undef X
};
#define X(_) + 1
enum { DRGN_DWARF_INDEX_NUM_NAMESPACE_TAGS = DRGN_DWARF_INDEX_NAMESPACE_TAGS };
enum { DRGN_DWARF_INDEX_NUM_TAGS = DRGN_DWARF_INDEX_TAGS };
#undef X
_Static_assert(DRGN_DWARF_INDEX_base_type == DRGN_DWARF_INDEX_NUM_TAGS - 1,
"base_type must be last");
enum { DRGN_DWARF_INDEX_MAP_SIZE = DRGN_DWARF_INDEX_NUM_TAGS - 1 };
/**
* DWARF information for a namespace or nested definitions in a class, struct,
* or union.
*/
struct drgn_namespace_dwarf_index {
/** Debugging information cache that owns this index. */
struct drgn_debug_info *dbinfo;
/** (Null-terminated) name of this namespace. */
const char *name;
/** Length of @ref name. */
size_t name_len;
/** Parent namespace, or @c NULL if it is the global namespace. */
struct drgn_namespace_dwarf_index *parent;
/** Children namespaces indexed by name. */
struct drgn_namespace_table children;
/**
* Mapping for each @ref drgn_dwarf_index_tag from name to a list of
* matching DIE addresses.
*
* This has a few quirks:
*
* - `base_type` DIEs are in @ref drgn_dwarf_info::base_types, not here.
* - `enumerator` entries store the addresses of the parent
* `enumeration_type` DIEs instead.
* - `namespace` entries also include the addresses of `class_type`,
* `structure_type`, and `union_type` DIEs that have children and
* `DW_AT_declaration`. This is because class, struct, and union
* declaration DIEs can contain nested definitions, so we want to
* index the children of those declarations, but we don't want to
* encounter the declarations when looking for the actual type.
* - Otherwise, this does not include DIEs with `DW_AT_declaration`.
*/
struct drgn_dwarf_index_die_map map[DRGN_DWARF_INDEX_MAP_SIZE];
/**
* Number of CUs that were indexed the last time that this namespace was
* indexed.
*/
size_t cus_indexed;
/**
* Number of DIEs for each namespace-like tag in the parent's index that
* were indexed the last time that this namespace was indexed.
*/
uint32_t dies_indexed[DRGN_DWARF_INDEX_NUM_NAMESPACE_TAGS];
/** Saved error from a previous index. */
struct drgn_error *saved_err;
};
/** 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_base_type_map, struct nstring, uintptr_t);
DEFINE_HASH_MAP_TYPE(drgn_dwarf_specification_map, uintptr_t, uintptr_t);
DEFINE_VECTOR_TYPE(drgn_dwarf_index_cu_vector, struct drgn_dwarf_index_cu);
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 {
/** Global namespace index. */
struct drgn_namespace_dwarf_index global;
/**
* Mapping from name to `DW_TAG_base_type` DIE address with that name.
*
* Unlike user-defined types and variables, there can only be one base
* type with a given name in the entire program, so we don't store them
* in a @ref drgn_dwarf_index_die_map.
*/
struct drgn_dwarf_base_type_map base_types;
/**
* Map from the address of a (usually non-defining) DIE to the address
* of a DIE with a DW_AT_specification attribute that references it.
* This is used to resolve DIEs with DW_AT_declaration to their
* definition.
*/
struct drgn_dwarf_specification_map specifications;
/** Indexed compilation units. */
struct drgn_dwarf_index_cu_vector index_cus;
/**
* 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);
/**
* State tracked while indexing new DWARF information in a @ref drgn_dwarf_info.
*/
struct drgn_dwarf_index_state {
struct drgn_debug_info *dbinfo;
/** Per-thread arrays of CUs to be indexed. */
struct drgn_dwarf_index_cu_vector *cus;
};
/**
* Initialize state for indexing new DWARF information.
*
* @return @c true on success, @c false on failure to allocate memory.
*/
bool drgn_dwarf_index_state_init(struct drgn_dwarf_index_state *state,
struct drgn_debug_info *dbinfo);
/** Deinitialize state for indexing new DWARF information. */
void drgn_dwarf_index_state_deinit(struct drgn_dwarf_index_state *state);
/** Read a @ref drgn_module to index its DWARF information. */
struct drgn_error *
drgn_dwarf_index_read_module(struct drgn_dwarf_index_state *state,
struct drgn_module *module);
/**
* Index new DWARF information.
*
* This should be called once all modules have been read with @ref
* drgn_dwarf_index_read_module() to finish indexing those modules.
*/
struct drgn_error *
drgn_dwarf_info_update_index(struct drgn_dwarf_index_state *state);
/**
* Find the DWARF DIEs in a @ref drgn_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_module_find_dwarf_scopes(struct drgn_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)));
/**
* Get an array of names of `DW_TAG_variable` and `DW_TAG_formal_parameter` DIEs
* in local scopes.
*
* @param[out] names_ret Returned array of names. On success, must be freed with
* @c free(). The individual strings should not be freed.
* @param[out] count_ret Returned number of names in @p names_ret.
*/
struct drgn_error *drgn_dwarf_scopes_names(Dwarf_Die *scopes,
size_t num_scopes,
const char ***names_ret,
size_t *count_ret);
/**
* 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_elf_file *file, 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_module_find_dwarf_cfi(struct drgn_module *module, uint64_t pc,
struct drgn_cfi_row **row_ret, bool *interrupted_ret,
drgn_register_number *ret_addr_regno_ret);
struct drgn_error *
drgn_module_find_eh_cfi(struct drgn_module *module, uint64_t 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,
struct drgn_elf_file *file,
const struct drgn_cfi_rule *rule,
const struct drgn_register_state *regs,
void *buf, size_t size);
/** @} */
#endif /* DRGN_DEBUG_INFO_DWARF_H */